help button home button
AJRCMB
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Lama, V.
Right arrow Articles by Peters-Golden, M.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Lama, V.
Right arrow Articles by Peters-Golden, M.
American Journal of Respiratory Cell and Molecular Biology. Vol. 27, pp. 752-758, 2002
© 2002 American Thoracic Society
DOI: 10.1165/rcmb.4857

Prostaglandin E2 Synthesis and Suppression of Fibroblast Proliferation by Alveolar Epithelial Cells Is Cyclooxygenase-2–Dependent

Vibha Lama, Bethany B. Moore, Paul Christensen, Galen B. Toews and Marc Peters-Golden

Division of Pulmonary and Critical Care Medicine, University of Michigan Health System; and Department of Veterans Affairs Medical Center, Ann Arbor, Michigan

Address correspondence to: Marc Peters-Golden, M.D., 6301 MSRB III, 1150 W. Medical Center Drive, Ann Arbor, MI 48109-0642. E-mail: petersm{at}umich.edu


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Alveolar epithelial cells (AECs) may influence neighboring fibroblasts by the elaboration of prostaglandin E2 (PGE2). This prostanoid can be synthesized via "constitutive" cyclooxygenase (COX)-1 and "inducible" COX-2 enzyme isoforms. We compared AECs isolated from wild-type (WT), COX-1 knockout (KO), and COX-2 KO mice to determine the contribution of COX isoforms to AEC PGE2 synthesis and capacity for suppression of fibroblast proliferation in co-cultures. WT AECs constitutively expressed both COX-1 and COX-2 isoforms by immunoblot analysis. COX-1 KO cells and WT cells comparably augmented PGE2 synthesis following incubation with lipopolysaccharide or interleukin-1, whereas COX-2 KO cells were unable to do so. Surprisingly, however, constitutive generation of PGE2 was also dramatically reduced only in COX-2 KO cells. When co-cultured with WT murine lung fibroblasts, AECs from WT and COX-1 KO animals suppressed serum-induced fibroblast proliferation, whereas COX-2-deficient AECs caused a modest enhancement in fibroblast proliferation. These results indicate that PGE2 synthetic capacity in AECs is predominantly COX-2–dependent under both basal and stimulated conditions. They also demonstrate conclusively that AECs can modulate fibroblast function by the elaboration of suppressive prostanoids. These alterations in AEC phenotype likely contribute to the propensity for pulmonary fibrosis observed in COX-2–deficient mice.

Abbreviations: alveolar epithelial cell, AEC • cyclooxygenase, COX • Dulbecco's modified Eagle's medium, DMEM • interleukin-1, IL-1 • knockout, KO • lipopolysaccharide, LPS • prostaglandin E2, PGE2 • prostacyclin, PGI2 • wild type, WT


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Fibrosis of the distal lung represents the culmination of a series of pathophysiologic responses to injury. These responses include injury to or loss of alveolar epithelial cells (AECs), accumulation and activation of chronic inflammatory cells, and fibroblast proliferation, as well as deposition of extracellular matrix proteins such as collagen. Fibrotic lung disease occurs in a variety of settings. These include certain occupational exposures, systemic collagen-vascular diseases, and after acute lung injury, but the most common form is idiopathic pulmonary fibrosis. A substantial amount of research has focused on the mechanisms by which fibroblasts are activated by proinflammatory signals in these disorders, and standard therapy has consisted of anti-inflammatory corticosteroids and immunosuppressive agents. However, the disappointing efficacy of such agents demands new pathophysiologic paradigms and new therapeutic approaches for fibrotic lung disease (1, 2).

There is a growing appreciation that fibrosis reflects inadequate generation of suppressive signals that ordinarily control fibroblast responses. The possibility that AECs are an important source of such suppressive signals is suggested by: (i) the intercellular communications (footprocesses) extending from AECs to interstitial fibroblasts that can be observed microscopically (3, 4); (ii) observations in animal models that a failure of AEC proliferation or differentiation is a central determinant of fibrotic, rather than reparative, responses to injury (5, 6); and (iii) the ability of AECs to effect inhibition of fibroblast proliferation in co-cultures (7, 8). Indeed, it has recently been suggested that pulmonary fibrosis is an "epithelial-fibroblastic disease" (2).

A growing body of evidence supports the possibility that prostaglandin E2 (PGE2) is a key mediator of the suppressive effects of AECs on fibroblasts. First, PGE2 is a potent inhibitor of fibroblast functions, including migration (9), proliferation (10, 11), and collagen synthesis (12, 13). Second, the conclusion that PGE2 is a relevant endogenous anti-fibrotic mediator is supported by the finding that mice rendered prostaglandin-deficient by either pharmacologic (14) or genetic (15) disruption of cyclooxygenase (COX) (also termed prostaglandin synthase) enzymes exhibit an exaggerated fibrotic response to the intrapulmonary administration of bleomycin. Third, PGE2 is the major arachidonic acid metabolite of AECs from rats (16, 17) and humans (18), and these cells have a prodigious capacity for PGE2 synthesis. Fourth, suppressive effects of AEC-derived conditioned medium on fibroblast proliferation have been reported to be inhibitable by the COX inhibitor, indomethacin (7).

COX, the initial and rate-limiting enzyme in the metabolism of arachidonic acid to prostanoids, is encoded by two distinct genes. In most cells and tissues, COX-1 is constitutively expressed, whereas COX-2 is only expressed when induced by inflammatory or mitogenic stimuli (19). Pulmonary epithelium appears to represent an exception to this usual pattern, because both airway epithelial cells (20–22) and AECs (22) have been shown to express both COX isoforms constitutively. However, the relative contributions of these two isoforms to AEC production of PGE2 are not known.

In the present study, we sought to address this question by examining PGE2 production under basal and stimulated conditions in AECs isolated from COX-1 and COX-2 knockout (KO) mice. We also determined the functional consequences of such metabolic abnormalities by investigating the ability of AECs of both genotypes to suppress the proliferation of normal, wild-type (WT) fibroblasts. Unexpectedly, our results demonstrate that, even under basal conditions, COX-2 is the major source of PGE2 mediating the antifibrotic effects of AECs.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Mice
COX-1 (23) and COX-2 (24) KO mice and their littermate WT controls were a generous gift of Dr. Robert Langenbach, National Institute of Environmental Health Sciences, Research Triangle Park, NC. Mice were generation 15–20, bred on a C57Bl6/129 hybrid background. Mice were 5–7 mo of age at the time of study. For experiments in Figure 1 and 2, WT C57Bl/6 mice (Jackson Laboratories, Bar Harbor, ME) were used. Mice were housed under specific pathogen-free conditions in enclosed filter top cages, and clean water and food were given ad libitum. The University Committee on the Use and Care of Animals approved these experiments.



View larger version (23K):
[in this window]
[in a new window]
  		Figure 1. Alveolar epithelial cell inhibition of fibroblast proliferation is prostanoid-dependent. (A) Fibroblasts isolated from WT C57Bl/6 mouse lungs were plated at 5,000 cells/well in the presence of medium (Fib alone), the reversible COX inhibitor indomethacin (5 µM) (Fib + Indo), in the presence of 50,000 C57Bl/6 AECs (Fib + AEC), or in the presence of AECs and indomethacin (Fib + AEC + Indo). Cells were cultured alone or together for 48 h total with [3H]thymidine included for the last 16 h of culture. Proliferation is expressed as a percentage of the level observed in fibroblasts alone (taken as 100%). Data represent mean ± SEM from n = 6 replicates per condition in one experiment which is representative of two. P < 0.05 for Fib + Indo compared with Fib Alone as well as for Fib + AEC compared with Fib Alone. (B) Fibroblasts and AECs were isolated from C57Bl/6 mice as described above. AECs were pretreated for 30 min with (ASA/AEC) or without (AEC) the irreversible COX inhibitor aspirin (100 µM) before washing and the addition of fibroblasts in the presence (open bars) or absence (filled bars) of 100 nM exogenous PGE2. Data are presented as a percentage of proliferation exhibited by fibroblasts alone, and represent mean ± SEM from n = 4–6 replicate wells/condition in one experiment which is representative of two. P = 0.001 for Fib Alone versus Fib + AECs, for Fib + AECs versus Fib + ASA/AECs, and for Fib Alone versus Fib Alone + PGE2. P = 0.004 for Fib + AECs versus Fib + AECs + PGE2. P = 0.0002 for Fib + ASA/AECs versus Fib + ASA/AECs + PGE2.

 


View larger version (43K):
[in this window]
[in a new window]
  		Figure 2. Purified alveolar epithelial cells express both COX-1 and COX-2 constitutively. AECs were purified from WT C57Bl/6 mice as described in MATERIALS AND METHODS and 1 x 106 AECs were plated onto fibronectin-coated 35-mm dishes. Once adhered, cells were scraped into lysis buffer and analyzed by Western blot for expression of COX-1 and COX-2. Both isoforms are present in unstimulated AECs at the correct molecular size ({bsim} 72 kD).

 
AEC Purification
Type II AECs were isolated from mice using the method of Corti and coworkers (25). Following anesthesia and heparinization, the mouse was exsanguinated and the pulmonary vasculature was perfused via the right ventricle with 0.9% NaCl until the effluent was free of blood. The trachea was cannulated with 20-gauge tubing and the lungs were filled with 1–2 ml of Dispase (Worthington). Subsequently, 0.45 ml of low melting point agarose was infused via the trachea and the lungs were placed in iced PBS for 2 min to harden the agarose. The lungs were placed in 2 ml Dispase and incubated for 45 min at 24°C. Subsequently the lung tissue was teased from the airways and minced in Dulbecco's modified Eagle's medium (DMEM) with 0.01% DNase. The lung mince was gently swirled for 10 min, and passed successively through 100-, 40-, and 25-µm nylon mesh filters. The cell suspension was collected by centrifugation and incubated with biotinylated antibodies (anti-CD32 and anti-CD45) recognizing bone marrow–derived cells. The cell suspension was incubated with streptavidin-coated magnetic particles, then was placed in a magnetic tube separator for removal of the bone marrow–derived cells. Mesenchymal cells were removed by overnight adherence in a petri dish. The nonadherent AECs were then plated either at 50,000 cells/well on fibronectin-coated 96-well plates (for PGE2 analysis and for co-culture with fibroblasts), or at 106 cells per fibronectin-coated 35 mm plate for immunoblot analysis. Cells were maintained in DMEM with penicillin/streptomycin and 10% fetal calf serum at 37°C in 5% CO2. The final adherent population included only 4% nonepithelial cells at Day 2 in culture by intermediate filament staining.

Immunoblot Analysis
Untreated AECs at Day 2 in culture were detached by scraping into ice-cold lysis buffer (50 mM Tris-HCl, 25 mM KCl, 1 mM dithiothreitol, 0.5 mM phenylmethylsulfonyl fluoride, 1 mM leupeptin, pH 7.4)and lysates prepared by sonication. Approximately 15 µg of total cellular protein (determined by a modified Coomassie Blue dye binding assay [Pierce Chemicals, Rockford, IL]) were subjected to SDS-polyacrylamide gel electrophoresis under reducing conditions. Rainbow molecular weight markers as well as standards for COX-1 and COX-2 were run in parallel. After overnight transfer to nitrocellulose membranes, membranes were incubated overnight with anti–COX-1 antiserum (1:5,000 dilution) (26) or anti–COX-2 antiserum (1:10,000 dilution; Cayman Chemical Co., Ann Arbor, MI), followed by peroxidase-conjugated goat anti-rabbit IgG (1:5,000). Proteins of interest were detected using the ECL enhanced chemiluminescence method (Amersham Pharmacia Biotech, Piscataway, NJ).

Determination of PGE2 Synthesis
AECs were adhered by culturing as described above for 24 h, after which the wells were washed three times with PBS. Cells were then cultured for an additional 24 h with fresh serum-containing medium in the absence or presence of interleukin-1 (IL-1) (10 ng/ml) or lipopolysaccharide (LPS) (10 µg/ml). Culture supernatants were stored at -20°C for eventual quantitation of the predominant COX product, PGE2. This was accomplished using a highly sensitive and specific enzyme immunoassay kit from Cayman Chemicals.

Fibroblast Purification
Lungs of WT mice were perfused via the right ventricle with 5 ml 0.9% NaCl and removed using aseptic conditions. Lungs were minced with scissors in DMEM containing 10% fetal calf serum. One minced lung was placed in 10 ml of medium in 100 cm2 tissue culture plates. Fibroblasts were allowed to grow out of the minced tissue, and when cells reached 70% confluence they were passaged following trypsinization. Fibroblasts were grown for 10–20 d (2–3 passages) before being used and were always used before passage 6.

AEC-Fibroblast Co-Cultures and Fibroblast Proliferation Assays
AECs were isolated as described and cultured on fibronectin-coated wells for 2 d. After washing three times, fresh DMEM with 10% fetal calf-serum containing 5,000 fibroblasts was added to each well of AECs, or to wells without AECs. Fibroblasts were cultured in the presence or absence of AECs for 24–48 h. In some experiments, co-cultures were incubated with the reversible isoform-nonselective COX inhibitor indomethacin (5 µM). In others, AECs were pretreated for 30 min with the irreversible isoform-nonselective COX inhibitor aspirin (100 µM) before washing the drug away and adding aspirin-untreated fibroblasts. [3H]thymidine (specific acitivity 5.0 Ci/mmol; Amersham) was then added at 10 µCi/well, and cells were allowed to grow for 16 more hours. Cells were harvested onto glass fiber filters with a cell harvester and radioactivity on filters was determined in the presence of scintillation fluid using a ß scintillation counter. As purified AEC grow very poorly in culture and incorporate minimal quantities of [3H]thymidine, this technique measures fibroblast proliferation in co-cultures (27, 28).

Data Analysis
Data are presented as mean values ± SEM. Statistical significance was analyzed using the InStat 2.01 program (Graphpad Software) on a Power Macintosh G3. Significance was assessed with a Student's t test for comparisons of two groups, or with ANOVA and a post hoc Bonferroni test for three or more groups. P < 0.05 was considered significant.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
COX-Dependent Suppression of Fibroblast Proliferation by Normal Murine AECs
Proliferation of normal lung fibroblasts in response to serum was examined in fibroblast-only cultures and in fibroblast-AEC co-cultures derived from C57Bl/6 mice. 5,000 fibroblasts alone incorporated {bsim} 25,000 cpm [3H]thymidine; for comparison, incorporation of [3H]thymidine by cultures of 50,000 AECs alone averaged {bsim} 1,200 cpm (data not shown). Thus, [3H]thymidine incorporation in co-cultures is largely a reflection of fibroblast proliferation. Proliferation of fibroblasts was increased in the presence of the reversible COX inhibitor, indomethacin (5 µM), indicating that fibroblast-derived prostaglandin(s) (most likely PGE2) suppressed proliferation (Figure 1A). By contrast, proliferation was reduced when these cells were co-cultured with normal AECs. The addition of indomethacin to co-cultures completely abolished any suppressive effects of AECs on fibroblast proliferation. Although this finding demonstrated a COX dependency to AEC suppression, it failed to discern whether the suppressive prostanoid was generated by AECs or by fibroblasts in co-cultures. This is an important limitation, because it has recently been suggested that AECs act in this regard by stimulating fibroblast PGE2 production (8).

In an effort to focus on the AEC as a potential source of suppressive prostanoids, we utilized two different strategies. First, we pretreated normal AECs with the irreversible COX inhibitor aspirin, before washing it away and adding untreated fibroblasts. In these co-cultures, the fibroblast-suppressive capacity of aspirin-pretreated AECs was significantly less than that of untreated AECs (Figure 1B). This unambiguously identifies the AEC as an important source of suppressive prostanoids. We next sought to determine if the addition of exogenous PGE2 could restore the AEC suppressive activity. PGE2 (100 nM) was added to fibroblasts alone, as well as to co-cultures comprised of untreated and aspirin-pretreated AECs. As also shown in Figure 1B, exogenous PGE2 significantly reduced fibroblast proliferation under all experimental conditions. Of note, it substantially (but incompletely) restored the impaired suppressive capacity of aspirin-pretreated AECs. These data emphasize the importance of AECs themselves as a source of PGE2 acting as a mediator of fibroblast suppression. As a second strategy, we sought to characterize the COX isoform expression in WT AECs and to study PGE2 production as well as fibroblast suppression by COX KO AECs.

COX Isoform Expression in WT Murine AECs
Immunohistochemical staining of sections of normal mouse lung have indicated the presence of both COX-1 and COX-2 in AECs (22). To assess basal COX isoform expression in isolated AECs from WT mice, unstimulated cells were harvested at Day 2 in culture and lysates were subjected to immunoblot analysis. Using isoform-specific antibodies, both COX-1 and COX-2 were indeed detected under these basal conditions at the expected molecular weight of {bsim} 72 kD (Figure 2).

PGE2 Generation by WT and COX KO AECs
Cumulative PGE2 synthesis and secretion over 24 h by cultured AECs were examined under both basal conditions and in response to IL-1 and LPS, agonists known to induce COX-2 expression in a variety of cell types (29, 30) (Figure 3). WT cells constitutively elaborated substantial quantities of PGE2, and output increased further in response to IL-1 or LPS. Surprisingly, COX-1 KO cells exhibited a similar constitutive PGE2 output as did WT cells. As expected, COX-1 KO AECs were also capable of upregulating PGE2 synthesis in response to IL-1 or LPS, implying an intact inducibility of COX-2. In fact, the increment in PGE2 synthesis in response to IL-1 and LPS exceeded that of WT AECs. In contrast, AECs from COX-2 KO mice manifested a dramatic impairment in constitutive PGE2 elaboration and were entirely incapable of upregulating PGE2 synthesis in response to agonists. These data demonstrate that, although they express both COX isoforms, murine AECs depend almost exclusively on COX-2 for PGE2 generation under both constitutive and stimulated conditions.



View larger version (30K):
[in this window]
[in a new window]
  		Figure 3. COX-2 KO, but not COX-1 KO alveolar epithelial cells are deficient in the production of PGE2. AECs were purified from COX-1 KO, COX-2 KO, or littermate control (WT) mice as described in MATERIALS AND METHODS and plated on fibronectin-coated wells in the presence of medium alone (dotted bars), IL-1ß (10 ng/ml; hatched bars) or LPS (10 µg/ml; filled bars). Cells were cultured in the presence of the additives for 24 h before cell-free supernatants were collected and analyzed for PGE2 levels using a highly specific enzyme immunoassay technique. Data represent mean ± SEM from n = 4–6 replicates per condition from one experiment which is representative of two. There was no statistical difference in the PGE2 levels elaborated by either WT or COX-1 KO AECs (top panel). In contrast, the COX-2 AECs were profoundly deficient in PGE2 production (P = <0.0001) compared with WT AECs (bottom panel).

 
Effects of AEC Genotype on Proliferation of WT Fibroblasts in Co-Culture
We next determined whether the genotype of the AEC had any effect on the ability to suppress fibroblast proliferation (Figure 4). As compared with [3H]thymidine incorporation by fibroblast-only cultures, incorporation in the presence of AECs from WT mice was reduced by {bsim} 40–60%. AECs from COX-1 KO mice, previously shown (Figure 3) to have intact basal PGE2 synthetic capacity, effected a similar degree of inhibition of fibroblast proliferation. However, AECs from COX-2 KO mice, which exhibited a profound impairment in basal PGE2 synthetic capacity (Figure 3), were incapable of effecting any inhibition of fibroblast proliferation. In fact, a modest but significant enhancement of fibroblast proliferation, as compared with fibroblast-only cultures, was seen in co-cultures containing COX-2 KO AECs. These data demonstrate that COX-2 is primarily responsible for the capacity of AECs to suppress fibroblast proliferation in co-culture.



View larger version (30K):
[in this window]
[in a new window]
  		Figure 4. COX-2 KO AECs are unable to inhibit fibroblast proliferation. AECs were isolated from COX-1 KO, COX-2 KO, or littermate control (WT) mice and plated at 5 x 104 cells/well on fibronectin-coated 96-well plates. Following adherence, AECs were washed and complete medium containing 5,000 WT fibroblasts was added to control wells, and to wells containing AECs. Cells were co-cultured for 48 h and [3H]thymidine was added for the last 16 h of culture. Data are presented as a percentage of the fibroblast proliferation determined in the absence of AECs (100%). Data represent mean ± SEM from n = 6 replicate wells per condition from one experiment which is representative of two. In the top panel, both COX-1 KO (P = 0.004) and WT AECs (P = 0.04) significantly suppressed fibroblast proliferation as compared with fibroblasts alone. In the bottom panel, WT AECs suppressed fibroblast proliferation (P = 0.001), whereas COX-2 KO AECs increased (P = 0.01) fibroblast proliferation.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
Following injury, dysregulated interactions between AECs and fibroblasts are thought to drive the lung's response toward fibrosis, rather than repair. It has been observed in animal models that a fibrotic response to lung injury often correlates with a failure of AEC proliferation and/or differentiation, implying that repair requires AECs to suppress fibroblast activation (2, 5, 6). In the present investigation, we have used a genetic approach to determine the importance of prostaglandins derived from the COX pathway of arachidonic acid metabolism in the ability of AECs to suppress fibroblast proliferation. Using AECs from COX isoform KO mice has two advantages over a pharmacologic approach. First, the addition of pharmacologic inhibitors to co-cultures, as employed in Figure 1A, would inhibit COX in both cell types. As AECs have been reported to have the capacity to inhibit fibroblast proliferation by stimulating fibroblast PGE2 synthesis (8), the effects of an inhibitor in co-culture could reflect its actions on either AEC or fibroblast COX. Second, COX inhibitors are recognized to possess a variety of biologic actions that may be independent of COX (31). Our data conclusively show that the capacity of murine AECs to suppress fibroblast proliferation is related to their own capacity for the synthesis of PGE2. Moreover, studies with AECs derived from both COX-1 and COX-2 KO mice demonstrate the novel finding that COX-2 is the predominant COX isoform responsible for both PGE2 generation and inhibition of fibroblast proliferation by AECs.

PGE2 is a good candidate to serve as an endogenous, AEC-derived inhibitor of fibroblast function. PGE2 has been shown to inhibit fibroblast migration (9), fibroblast proliferation in response to various mitogens (10, 11), and fibroblast expression of platelet-derived growth factor receptors (32). In addition, this prostanoid inhibits collagen gene expression (33, 34) and collagen protein synthesis (12, 13) and promotes collagen degradation (35). These actions are thought to be mediated by ligation of PGE2 receptors coupled to activation of adenyl cyclase, with subsequent increases in intracellular cyclic AMP (36). The major AA metabolites of rat (16) and human (18) AECs are PGE2 followed by prostacyclin (PGI2). PGI2 also signals via activation of adenyl cyclase, and it too has been reported to inhibit fibroblast proliferation (37). Thus, both PGE2 and PGI2 secreted by AECs could contribute to the suppressive effects observed in this study, and the precise contributions of each remain to be elucidated.

It has recently been reported that COX-2 KO mice developed an exaggerated fibrotic response to bleomycin (15). Although this observation clearly suggests an important in vivo role for COX-2 in the suppression of fibrogenesis, it was somewhat surprising given the presence of an intact COX-1 enzyme in these animals. Abundant PGE2 synthesis has been observed in pulmonary fibroblasts from COX-2 KO animals (38). Our results demonstrating that this is not the case for isolated AECs suggest that the AEC is likely to be a critical COX-2–dependent cellular source of suppressive PGE2 in vivo following lung injury.

The fact that COX-2 is induced at sites of injury or inflammation has widely been assumed to indicate a proinflammatory role for the products of this enzyme. Although this assumption is undoubtedly true in certain circumstances (39), an alternative possibility is that COX-2 induction at such sites may serve as a means to generate anti-inflammatory and antifibrotic mediators and thus counterbalance the effects of the inciting injury. A protective role for COX-2 expression has been suggested in several animal models of disease, including not only bleomycin-induced pulmonary fibrosis (15), as mentioned above, but also antigen-induced airway inflammation (40), doxorubicin-induced cardiac injury (41), acetominophen-induced liver injury (42), carrageenin-induced pleurisy (43), and dextran sulfate–induced colitis (44). COX-2–derived products with potential protective actions include PGE2 and PGI2, as well as prostaglandin derivatives that are ligands for peroxisome proliferator-activated receptor-{gamma}.

Though originally thought to be a strictly inducible gene, COX-2 is now recognized to be constitutively expressed in particular cells and tissues. These include certain regions of the kidneys (45) and brain (46), vascular endothelium (47), and airway epithelium (20–22). Immunohistochemical staining for COX-2 in normal murine lung has identified COX-2 expression in AECs (22); our investigation provides verification of this finding by demonstrating constitutive COX-2 in isolated AECs as determined by immunoblot analysis. In both airway epithelial cells in vitro (20, 21) and vascular endothelium in vivo (47), basal prostaglandin synthesis was largely suppressible by COX-2–selective pharmacologic inhibitors, even though these cells expressed both COX isoforms. Our data are the first to demonstrate a similar phenomenon using cells from animals with a targeted deletion in COX-2. The mechanism(s) underlying the metabolic preeminence of COX-2 over COX-1 in these cells is not known, but could relate to differences in enzyme kinetics between the two isoforms (48) or to differences in their coupling to upstream phospholipases (49) or downstream terminal prostaglandin synthases (such as PGE synthase) (50, 51).

Our data extend previous in situ observations that AECs constitutively express COX-2, and demonstrate, moreover, that COX-2 is the isoform largely responsible for the generation of antifibrotic PGE2 by these cells. It is important to recognize that the milieu of an injured lung includes a variety of proinflammatory cytokines and growth factors that are themselves capable of inducing COX-2 expression. We and others have previously reported a defect in COX-2 inducibility in response to proinflammatory and mitogenic substances in pulmonary fibroblasts from patients with idiopathic pulmonary fibrosis (29, 52, 53). This defect would be expected to impair the autocrine generation of PGE2 by fibroblasts, contributing to dysregulated fibroblast activation. In a similar manner, a lack of inducibility of COX-2 in AECs, as modeled by the COX-2 KO AECs used in the studies reported herein, would represent an impairment in the paracrine generation of PGE2, which would likewise contribute to fibroblast dysregulation. Although it is unknown if lung injury impairs expression of COX-2 in AECs, it has been shown to impair certain other AEC functions such as expression of granulocyte-macrophage colony-stimulating factor (54) and alveolar fluid clearance (55). Furthermore, deficient expression of COX-2 and/or PGE2 synthetic capacity has been identified in airway epithelium in humans or animals with airway injury and obstruction (56, 57). It is apparent that a relative deficiency of AEC-derived COX-2, whether due to epithelial cell loss or dysfunction, would promote fibrogenesis, as was modeled in the present study using co-cultures containing COX-2–deficient AECs.

In conclusion, our data provide novel insights into the importance of COX-2 for PGE2 generation by AECs and the importance of COX-2–derived PGE2 for the capacity of AECs to suppress fibroblast proliferation. Ascertaining the in vivo significance of these observations in determining whether lung injury results in repair or fibrosis will require further investigation.


   Acknowledgments
 
The authors gratefully acknowledge the provision of KO and littermate WT mice used in this study by Dr. Robert Langenbach, National Institute for Environmental Health Sciences. The technical assistance of Susan Phare, Ming Du, and Carol Wilke are also acknowledged. This work was supported by NIH Specialized Center of Research in Fibrotic Lung Disease, P50 HL56402.

Received in original form March 8, 2002

Received in final form July 29, 2002


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Mason, R., M. Schwarz, G. Hunninghake, and R. Musson. 1999. NHLBI Workshop Summary. Pharmacological therapy for idiopathic pulmonary fibrosis: past, present, and future. Am. J. Respir. Crit. Care Med. 160:1771–1777.[Free Full Text]
  2. Selman, M., T. King, Jr., and A. Pardo. 2001. Idiopathic pulmonary fibrosis: prevailing and evolving hypotheses about its pathogenesis and implications for therapy. Ann. Intern. Med. 134:136–151.[Abstract/Free Full Text]
  3. Brody, A., P. Soler, F. Basset, W. Haschek, and H. Witschi. 1981. Epithelial-mesenchymal associations of cells in human pulmonary fibrosis and in BHT-oxygen-induced fibrosis in mice. Exp. Lung Res. 2:207–220.[Medline]
  4. Kawanami, O., V. Ferrans, and R. Crystal. 1982. Structure of alveolar epithelial cells in patients with fibrotic lung disorders. Lab. Invest. 46:39–53.[Medline]
  5. Haschek, W., and H. Witschi. 1979. Pulmonary fibrosis: a possible mechanism. Toxicol. Appl. Pharmacol. 51:475–487.[Medline]
  6. Adamson, I., L. Young, and D. Bowden. 1988. Relationship of alveolar epithelial injury and repair to the induction of pulmonary fibrosis. Am. J. Pathol. 130:377–386.[Abstract]
  7. Klien, J. H., and I. Y. R. Adamson. 1989. Fibroblast inhibition and prostaglandin secretion by alveolar epithelial cells exposed to silica. Lab. Invest. 60:808–813.[Medline]
  8. Pan, T., R. Mason, J. Westcott, and J. Shannon. 2001. Rat alveolar type II cells inhibit lung fibroblast proliferation in vitro. Am. J. Respir. Cell Mol. Biol. 25:353–361.[Abstract/Free Full Text]
  9. Kohyama, T., R. Ertl, V. Valenti, J. Spurzem, M. Kawamoto, Y. Nakamura, T. Veys, L. Alegra, D. Romberger, and S. Rennard. 2001. Prostaglandin E2 inhibits fibroblast chemotaxis. Am. J. Physiol. Lung Cell. Mol. Physiol. 281:L1257–L1263.[Abstract/Free Full Text]
  10. Bitterman, P., M. Wewers, S. Rennard, S. Adelberg, and R. Crystal. 1986. Modulation of alveolar macrophage-driven fibroblast proliferation by alternative macrophage mediators. J. Clin. Invest. 77:700–708.
  11. Elias, J., M. Rossman, R. Zurier, and R. Daniele. 1985. Human alveolar macrophage inhibition of lung fibroblast growth: a prostaglandin-dependent process. Am. Rev. Respir. Dis. 131:94–99.[Medline]
  12. Korn, J., P. Halushka, and E. Leroy. 1980. Mononuclear cell modulation of connective tissue function: suppression of fibroblast growth by stimulation of endogenous prostaglandin production. J. Clin. Invest. 65:543–554.
  13. Goldstein, R., and P. Polgar. 1982. The effect and interaction of bradykinin and prostaglandins on protein and collagen production by lung fibroblasts. J. Biol. Chem. 257:8630–8633.[Abstract/Free Full Text]
  14. Moore, B., M. Coffey, P. Christensen, S. Sitterding, R. Ngan, C. Wilke, R. McDonald, S. Phare, M. Peters-Golden, R. Paine, and G. Toews. 2000. GM-CSF regulates bleomycin-induced pulmonary fibrosis via a prostaglandin-dependent mechanism. J. Immunol. 165:4032–4039.[Abstract/Free Full Text]
  15. Keerthisingam, C., R. Jenkins, N. Harrison, N. Hernandez-Rodriguez, H. Booth, G. Laurent, S. Hart, M. Foster, and R. McAnulty. 2001. Cyclooxygenase-2 deficiency results in a loss of the anti-proliferative response to transforming growth factor-ß in human fibrotic lung fibroblasts and promotes bleomycin-induced fibrosis in mice. Am. J. Pathol. 158:1411–1422.[Abstract/Free Full Text]
  16. Chauncey, J., M. Peters-Golden, and R. Simon. 1988. Arachidonic acid metabolism by rat alveolar epithelial cells. Lab. Invest. 58:133–140.[Medline]
  17. Cott, G., J. Westcott, and N. Voelkel. 1990. Prostaglandin and leukotriene production by alveolar type II cells in vitro. Am. J. Physiol. (Lung Cell Mol. Physiol.) 258:L179–L187.[Abstract/Free Full Text]
  18. van Overveld, F. J., P. G. Jorens, W. A. De Backer, M. Rampart, L. Bossaert, and P. A. Vermeire. 1992. Release of arachidonic acid metabolites from isolated human alveolar type II cells. Prostaglandins 44:101–110.[Medline]
  19. Dubois, R., S. Abramson, L. Crofford, R. Gupta, L. Simon, L. Van De Putte, and P. Lipsky. 1998. Cyclooxygenase in biology and disease. FASEB J. 12:1063–1073.[Abstract/Free Full Text]
  20. Asano, K., C. Lilly, and J. Drazen. 1996. Prostaglandin G/H synthase-2 is the constitutive and dominant isoform in cultured human lung epithelial cells. Am. J. Physiol. 271:L126–L131.[Abstract/Free Full Text]
  21. Walenga, R., M. Kester, E. Coroneos, S. Butcher, R. Dwivdi, and C. Statt. 1996. Constitutive expression of prostaglandin endoperoxide G/H synthetase (PGHS)-2 but not PGHS-1 in human tracheal epithelial cells in vitro. Prostaglandins 52:341–359.[Medline]
  22. Wardlaw, S., T. March, and S. Belinsky. 2000. Cyclooxygenase-2 expression is abundant in alveolar type II cells in lung cancer-sensitive mouse strains and in premalignant lesions. Carcinogenesis 21:1371–1377.[Abstract/Free Full Text]
  23. Langenbach, R., S. Morham, H. Tiano, C. Loftin, B. Ghanayem, P. Chulada, J. Mahler, C. Lee, E. Goulding, K. Kluckman, H. Sim, and O. Smithies. 1995. Prostaglandin synthase 1 gene disruption in mice reduces arachidonic acid-induced inflammation and indomethacin-induced gastric ulceration. Cell 83:483–492.[Medline]
  24. Morham, S., R. Langenbach, C. Loftin, H. Tiano, N. Vouloumanos, J. Jennette, J. Mahler, K. Kluckman, A. Ledford, C. Lee, and O. Smithies. 1995. Prostaglandin synthase 2 gene disruption causes severe renal pathology in the mouse. Cell 83:473–482.[Medline]
  25. Corti, M., A. Brody, and J. Harrison. 1996. Isolation and primary culture of murine alveolar type II cells. Am. J. Respir. Cell Mol. Biol. 14:309–315.[Abstract]
  26. Smith, W., and T. Rollins. 1982. Characteristics of rabbit anti-PGH synthase antibodies and use in immunochemistry. Methods Enzymol. 86:213–222.[Medline]
  27. Leslie, C., K. McCormick-Shannon, R. Mason, and J. Shannon. 1993. Proliferation of rat alveolar epithelial cells in low density primary culture. Am. J. Respir. Cell Mol. Biol. 9:64–72.
  28. Young, L., and I. Adamson. 1993. Epithelial-fibroblast interactions in bleomycin-induced lung injury and repair. Environ. Health Perspect. 101:56–61.[Medline]
  29. Wilborn, J., L. Crofford, M. Burdick, S. Kunkel, R. Strieter, and M. Peters-Golden. 1995. Fibroblasts isolated from patients with idiopathic pulmonary fibrosis have a diminished capacity to synthesize prostaglandin E2 and to express cyclooxygenase-2. J. Clin. Invest. 95:1861–1868.
  30. Lin, C., S. Sheu, H. Lee, Y. Ho, W. Lee, W. Ko, and J. Sheu. 2000. Involvement of protein kinase C-gamma in IL-1 beta-induced cyclooxygenase-2 expression in human pulmonary epithelial cells. Mol. Pharmacol. 57:36–43.[Abstract/Free Full Text]
  31. Lehmann, J., J. Lenhard, B. Oliver, G. Ringold, and S. Kliewer. 1997. Peroxisome proliferator-activated receptors {alpha} and {gamma} are activated by indomethacin and other non-steroidal anti-inflammatory drugs. J. Biol. Chem. 272:3406–3410.[Abstract/Free Full Text]
  32. Boyle, J., P. Lindroos, A. Rice, L. Zhang, D. Zeldin, and J. Bonner. 1999. Prostaglandin E2 counteracts interleukin-1ß-stimulated upregulation of platelet-derived growth factor {alpha}-receptor on rat pulmonary myofibroblasts. Am. J. Respir. Cell Mol. Biol. 20:433–440.[Abstract/Free Full Text]
  33. Ricupero, D., D. Rishikof, P. Kuang, C. Poliks, and R. Goldstein. 1999. Regulation of connective tissue growth factor expression by prostaglandin E2. Am. J. Physiol. 277:L1165–L1171.[Abstract/Free Full Text]
  34. Riquet, F., W. Lai, J. Birkhead, L. Suen, G. Karsenty, and M. Goldring. 2000. Suppression of type I collagen gene expression by prostaglandins in fibroblasts is mediated at the transcriptional level. Mol. Med. 6:705–719.[Medline]
  35. Baum, B., S. Moss, R. Breul, and R. Crystal. 1980. Effect of cyclic AMP an the intracellular degradation of newly synthesized collagen. J. Biol. Chem. 255:2843–2847.[Abstract/Free Full Text]
  36. Saltzman, L., J. Moss, R. Berg, B. Hom, and R. Crystal. 1982. Modulation of collagen production by fibroblasts: effects of chronic exposure to agonists that increase intracellular cyclic AMP. Biochem. J. 204:25–30.[Medline]
  37. Stratton, R., X. Shiwen, G. Martini, A. Holmes, A. Leask, T. Haberberger, G. Martin, C. Black, and D. Abraham. 2001. Iloprost suppresses connective tissue growth factor production in fibroblasts and in the skin of scleroderma patients. J. Clin. Invest. 108:241–250.[Medline]
  38. Kirtikara, K., S. G. Morham, R. Raghow, S. J. Laulederkind, T. Kanekura, S. Goorha, and L. R. Ballou. 1998. Compensatory prostaglandin E2 biosynthesis in cyclooxygenase 1 or 2 null cells. J. Exp. Med. 187:517–523.[Abstract/Free Full Text]
  39. Wollin, L., S. Uhlig, R. Nusing, and A. Wendel. 2001. Granulocyte-macrophage colony-stimulating factor amplifies lipopolysaccharide-induced bronchoconstriction by a neutrophil- and cyclooxygenase 2-dependent mechanism. Am. J. Respir. Crit. Care Med. 163:443–450.[Abstract/Free Full Text]
  40. Gavett, S., S. Madison, P. Chulada, P. Scarborough, W. Qu, J. Boyle, H. Tiano, C. Lee, R. Langenbach, V. Roggli, and D. Zeldin. 1999. Allergic lung responses are increased in prostaglandin H synthase-deficient mice. J. Clin. Invest. 104:721–732.[Medline]
  41. Dowd, N., M. Scully, S. Adderley, A. Cunningham, and D. Fitzgerald. 2001. Inhibition of cyclooxygenase-2 aggravates doxorubicin-mediated cardiac injury in vivo. J. Clin. Invest. 108:585–590.[Medline]
  42. Reilly, T., J. Brady, M. Marchick, M. Bourdi, J. George, M. Radonovich, C. Pise-Masison, and L. Pohl. 2001. A protective role for cyclooxygenase-2 in drug-induced liver injury in mice. Chem. Res. Toxicol. 14:1620–1628.[Medline]
  43. Gilroy, D., P. Colville-Nash, D. Willis, J. Chivers, J. Paul-Clark, and D. Willoughby. 1999. Inducible cyclooxygenase may have anti-inflammatory properties. Nat. Med. 5:698–701.[Medline]
  44. Morteau, O., S. Morham, R. Sellon, L. Dieleman, R. Langenbach, O. Smithies, and R. Sartor. 2000. Impaired mucosal defense to acute colonic injury in mice lacking cyclooxygenase-1 or cyclooxygenase-2. J. Clin. Invest. 105:469–478.[Medline]
  45. Harris, R., J. McKanna, Y. Akai, H. Jacobson, R. Dubois, and M. Breyer. 1994. Cyclooxygenase-2 is associated with the macula densa of rat kidney and increases with salt restriction. J. Clin. Invest. 94:2504–2510.
  46. Yamagata, K., K. Andreasson, W. Kaufmann, C. Barnes, and P. Worley. 1993. Expression of a mitogen-inducible cyclooxygenase in brain neurons: regulation by synaptic activity and glucocorticoids. Neuron 11:371–386.[Medline]
  47. McAdam, B., F. Catella-Lawson, I. Mardini, S. Kapoor, J. Lawson, and G. FitzGerald. 1999. Systemic biosynthesis of prostacyclin by cyclooxygenase (COX)-2: the human pharmacology of a selective inhibitor of COX-2. Proc. Natl. Acad. Sci. USA 96:272–277.[Abstract/Free Full Text]
  48. Penglis, P., L. Cleland, M. Demasi, G. Caughey, and M. James. 2000. Differential regulation of prostaglandin E2 and thromboxane A2 production in human monocytes: implications for the use of cyclooxygenase inhibitors. J. Immunol. 165:1605–1611.[Abstract/Free Full Text]
  49. Reddy, S., and H. Herschman. 1997. Prostaglandin synthase-1 and prostaglandin synthase-2 are coupled to distinct phospholipases for the generation of prostaglandin D2 in activated mast cells. J. Biol. Chem. 272:3231–3237.[Abstract/Free Full Text]
  50. Naraba, H., M. Murakami, H. Matsumoto, S. Shimbara, A. Ueno, I. Kudo, and S. Oh-ishi. 1998. Segregated coupling of phospholipases A2, cyclooxygenases, and terminal prostanoid synthases in different phases of prostanoid biosynthesis in rat peritoneal macrophages. J. Immunol. 160:2974–2982.[Abstract/Free Full Text]
  51. Brock, T., R. McNish, and M. Peters-Golden. 1999. Arachidonic acid is preferentially metabolized by cyclooxygenase-2 to prostacyclin and prostaglandin E2. J. Biol. Chem. 274:11660–11666.[Abstract/Free Full Text]
  52. McAnulty, R., N. Hernandez-Rodriguez, S. Mutsaers, R. Coker, and G. Laurent. 1997. Indomethacin suppresses the anti-proliferative effects of transforming growth factor-beta isoforms on fibroblast cell cultures. Biochem. J. 321:639–643.
  53. Vancheri, C., M. Sortino, V. Tomaselli, C. Mastruzzo, F. Condorelli, G. Bellistri, M. Pistorio, P. Canonico, and N. Crimi. 2000. Different expression of TNF-{alpha} receptors and prostaglandin E2 production in normal and fibrotic lung fibroblasts. Am. J. Respir. Cell Mol. Biol. 22:628–634.[Abstract/Free Full Text]
  54. Christensen, P., M. Bailie, R. Goodman, A. O'Brien, G. Toews, and R. I. Paine. 2000. Role of diminished epithelial GM-CSF in the pathogenesis of bleomycin-induced pulmonary fibrosis. Am. J. Physiol. Lung Cell. Mol. Physiol. 279:L487–L495.[Abstract/Free Full Text]
  55. Frank, J., J. Gutierrez, K. Jones, L. Allen, L. Dobbs, and M. Matthay. 2002. Low tidal volume reduces epithelial and endothelial injury in acid-injured rat lungs. Am. J. Respir. Crit. Care Med. 165:242–249.[Abstract/Free Full Text]
  56. Gray, P., F. Derksen, R. Broadstone, N. Robinson, and M. Peters-Golden. 1992. Decreased airway mucosal PGE2 production during airway obstruction in an animal model of asthma. Am. Rev. Respir. Dis. 146:586–591.[Medline]
  57. Picado, C., J. Fernandez-Morata, M. Juan, J. Roca-Ferrer, M. Fuentes, A. Xaubet, and J. Mullol. 1999. Cyclooxygenase-2 mRNA is downexpressed in nasal polyps from aspirin-sensitive asthmatics. Am. J. Respir. Crit. Care Med. 160:291–296.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
Y. H. Lee, Y. J. Suzuki, A. J. Griffin, and R. M. Day
Hepatocyte growth factor regulates cyclooxygenase-2 expression via {beta}-catenin, Akt, and p42/p44 MAPK in human bronchial epithelial cells
Am J Physiol Lung Cell Mol Physiol, April 1, 2008; 294(4): L778 - L786.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
K. E. White, Q. Ding, B. B. Moore, M. Peters-Golden, L. B. Ware, M. A. Matthay, and M. A. Olman
Prostaglandin E2 Mediates IL-1 -Related Fibroblast Mitogenic Effects in Acute Lung Injury through Differential Utilization of Prostanoid Receptors
J. Immunol., January 1, 2008; 180(1): 637 - 646.
[Abstract] [Full Text] [PDF]

Home page
 J. Pharmacol. Exp. Ther.Home page
E. Carrier, I. Brochu, A. J. de Brum-Fernandes, and P. D'Orleans-Juste
The Inducible Nitric-Oxide Synthase Modulates Endothelin-1-Dependent Release of Prostacyclin and Inhibition of Platelet Aggregation ex Vivo in the Mouse
J. Pharmacol. Exp. Ther., December 1, 2007; 323(3): 972 - 978.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
S. Huang, S. H. Wettlaufer, C. Hogaboam, D. M. Aronoff, and M. Peters-Golden
Prostaglandin E2 inhibits collagen expression and proliferation in patient-derived normal lung fibroblasts via E prostanoid 2 receptor and cAMP signaling
Am J Physiol Lung Cell Mol Physiol, February 1, 2007; 292(2): L405 - L413.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Cell Physiol.Home page
J. P. Meng, S. Ceryak, Z. Aratsu, L. Jones, L. Epstein, and B. Bouscarel
Biphasic regulation by bile acids of dermal fibroblast proliferation through regulation of cAMP production and COX-2 expression level
Am J Physiol Cell Physiol, September 1, 2006; 291(3): C546 - C554.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Cell Mol. Bio.Home page
B. B. Moore, L. Murray, A. Das, C. A. Wilke, A. B. Herrygers, and G. B. Toews
The Role of CCL12 in the Recruitment of Fibrocytes and Lung Fibrosis
Am. J. Respir. Cell Mol. Biol., August 1, 2006; 35(2): 175 - 181.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
R. J. Soberman and P. Christmas
Revisiting prostacyclin: new directions in pulmonary fibrosis and inflammation
Am J Physiol Lung Cell Mol Physiol, August 1, 2006; 291(2): L142 - L143.
[Full Text] [PDF]

Home page
 ThoraxHome page
M Molina-Molina, A Serrano-Mollar, O Bulbena, L Fernandez-Zabalegui, D Closa, A Marin-Arguedas, A Torrego, J Mullol, C Picado, and A Xaubet
Losartan attenuates bleomycin induced lung fibrosis by increasing prostaglandin E2 synthesis
Thorax, July 1, 2006; 61(7): 604 - 610.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
G. Y. Park and J. W. Christman
Involvement of cyclooxygenase-2 and prostaglandins in the molecular pathogenesis of inflammatory lung diseases
Am J Physiol Lung Cell Mol Physiol, May 1, 2006; 290(5): L797 - L805.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Crit. Care Med.Home page
A. Prasse, D. V. Pechkovsky, G. B. Toews, W. Jungraithmayr, F. Kollert, T. Goldmann, E. Vollmer, J. Muller-Quernheim, and G. Zissel
A Vicious Circle of Alveolar Macrophages and Fibroblasts Perpetuates Pulmonary Fibrosis via CCL18
Am. J. Respir. Crit. Care Med., April 1, 2006; 173(7): 781 - 792.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
J. Portnoy, T. Pan, C. A. Dinarello, J. M. Shannon, J. Y. Westcott, L. Zhang, and R. J. Mason
Alveolar type II cells inhibit fibroblast proliferation: role of IL-1{alpha}
Am J Physiol Lung Cell Mol Physiol, February 1, 2006; 290(2): L307 - L316.
[Abstract] [Full Text] [PDF]

Home page
 Proc Am Thorac SocHome page
M. Selman and A. Pardo
Role of epithelial cells in idiopathic pulmonary fibrosis: from innocent targets to serial killers.
Proceedings of the ATS, January 1, 2006; 3(4): 364 - 372.
[Abstract] [Full Text] [PDF]

Home page
 J. Immunol.Home page
B. B. Moore, M. N. Ballinger, E. S. White, M. E. Green, A. B. Herrygers, C. A. Wilke, G. B. Toews, and M. Peters-Golden
Bleomycin-Induced E Prostanoid Receptor Changes Alter Fibroblast Responses to Prostaglandin E2
J. Immunol., May 1, 2005; 174(9): 5644 - 5649.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Cell Mol. Bio.Home page
E. S. White, R. G. Atrasz, E. G. Dickie, D. M. Aronoff, V. Stambolic, T. W. Mak, B. B. Moore, and M. Peters-Golden
Prostaglandin E2 Inhibits Fibroblast Migration by E-Prostanoid 2 Receptor-Mediated Increase in PTEN Activity
Am. J. Respir. Cell Mol. Biol., February 1, 2005; 32(2): 135 - 141.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Pathol.Home page
R. J. Hodges, R. G. Jenkins, C. P.D. Wheeler-Jones, D. M. Copeman, S. E. Bottoms, G. J. Bellingan, C. B. Nanthakumar, G. J. Laurent, S. L. Hart, M. L. Foster, et al.
Severity of Lung Injury in Cyclooxygenase-2-Deficient Mice Is Dependent on Reduced Prostaglandin E2 Production
Am. J. Pathol., November 1, 2004; 165(5): 1663 - 1676.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Crit. Care Med.Home page
M. Peters-Golden
When Defenses against Fibroproliferation Fail: Spotlight on an Axis of Prophylaxis
Am. J. Respir. Crit. Care Med., November 15, 2003; 168(10): 1141 - 1142.
[Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
R. P. Charbeneau, P. J. Christensen, C. J. Chrisman, R. Paine III, G. B. Toews, M. Peters-Golden, and B. B. Moore
Impaired synthesis of prostaglandin E2 by lung fibroblasts and alveolar epithelial cells from GM-CSF-/- mice: implications for fibroproliferation
Am J Physiol Lung Cell Mol Physiol, June 1, 2003; 284(6): L1103 - L1111.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Physiol. Lung Cell. Mol. Physiol.Home page
B. B. Moore, M. Peters-Golden, P. J. Christensen, V. Lama, W. A. Kuziel, R. Paine III, and G. B. Toews
Alveolar epithelial cell inhibition of fibroblast proliferation is regulated by MCP-1/CCR2 and mediated by PGE2
Am J Physiol Lung Cell Mol Physiol, February 1, 2003; 284(2): L342 - L349.
[Abstract] [Full Text] [PDF]

<
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow