Suppression of Type I Collagen Gene Expression by Prostaglandins in Fibroblasts Is Mediated at the Transcriptional Level

Abstract

Background: Tissues undergoing a chronic inflammatory process, such as the synovium in rheumatoid arthritis, are characterized by the infiltration of lymphocytes of different subsets and activation of monocyte/macrophages. Interleukin-1 (IL-1), a monocyte/ macrophage product that stimulates synovial fibroblasts to produce matrix metalloproteinases (MMPs), prostaglandins, and other cytokines, also has profound effects on the synthesis of extracellular matrix components such as type I collagen. In previous studies, we have shown that synovial fibroblasts and chondrocytes isolated from human joint tissues are particularly sensitive to prostaglandins, which modulate the effects of IL-1 on collagen gene expression in an autocrine manner. Materials and Methods: BALBc/3T3 fibroblasts were treated with IL-1 and prostaglandins in the absence and presence of indomethacin to inhibit endogenous prostaglandin biosynthesis. Collagen synthesis was analyzed by SDS-PAGE as [ 3 H]prolinelabeled, secreted proteins, and prostaglandin production and cyclic adenosine 3',5'-cyclic monophosphate (camp) content were assayed. The expression of type I collagen gene (Col1a1) promoter-reporter gene constructs was examined in transient transfection experiments, and the binding of nuclear factors to the Col1a1 promoter region spanning Ϫ222 bpրϩ116 bp was analyzed by DNase I footprinting and electrophoretic mobility shift (EMSA) assays. Results: IL-1 increased the synthesis of type I and type III collagens in BALBc/3T3 fibroblasts; greater increases were observed when IL-1-stimulated synthesis of PGE 2 was blocked by indomethacin. Transient transfection experiments demonstrated dose-dependent inhibition of theϪ222 bp Col1a1 promoter by exogenously added prostaglandins with the order of potency of PGF 2 ␣ Ͼ PGE 2 Ͼ PGE 1. DNase I footprinting showed increased protection, which extended from the region immediately upstream of the TATA box, owing to the binding of nuclear factors from PGE 2-or PGE 1-treated BALBc/3T3 cells. EMSA analysis showed zinc-dependent differences in the binding of nuclear factors from untreated and prostaglandin-treated cells to the Ϫ84 bpրϪ29 bp region of the Col1a1 promoter. Conclusions: These results show that the inhibition of Col1a1 expression by IL-1 in fibroblasts is mediated by prostaglandins at the transcriptional level and suggest that PGE-responsive factors may interact directly or indirectly with basal regulatory elements in the proximal promoter region of the Col1a1 gene.

Pivotal role of connective tissue growth factor in lung fibrosis: MAPK‐dependent transcriptional activation of type I collagen

“…In an early report, Riquet and colleagues suggested that prostaglandins suppress type I collagen expression at the transcriptional level, and speculated that this effect may be mediated through cis-acting elements in sequences adjoining the CCAAT box (40). This hypothesis supports our findings, since prostaglandins stimulate cAMP signaling pathways, which are thought to regulate transcriptional activity through cAMP response elements (CREs).…”

An Essential Role for Fibronectin Extra Type III Domain A in Pulmonary Fibrosis

“…For example, EDA 2/2 cells, in response to TGF-b1 stimulation, may be capable of greater production of antifibrotic molecules, such as prostaglandin E 2 or IFN-g, which would have a net effect of preventing collagen up-regulation. In support of these possibilities, Riquet and colleagues (29) and our own group (30) have shown that prostaglandin E 2 is a potent suppressor of both a-SMA and collagen I expression at the gene and protein level, even in the face of active TGF-b1 stimulation. Similarly, Jaffe and colleagues have shown that murine fibroblasts infected with adenovirus encoding murine IFN-g results in a selective inhibition of procollagen I mRNA and secretion of total collagen compared with uninfected cells (31).…”

The Achilles Tendinopathy: Pathogenesis Review

“…Among the disease mediators, for example, it has been observed that repetitive mechanical stretching increases prostaglandin E2 (PGE2) concentrations in human patellar tendon fibroblasts [98] . PGE2 is a potent inhibitor of type I collagen synthesis and it has recently been shown that it has catabolic effects on tendon structure, decreasing proliferation and collagen production in human patellar tendon fibroblasts [99] . Other mediators of inflammation and vascular perfusion were found to be stimulated by exercise, such as bradykinin, adenosine, interleukin-6 and thromboxane [100] .…”