Cellular fibronectin, which contains an alternatively spliced exon encoding type III repeat extra domain A (EDA), is produced in response to tissue injury. Fragments of fibronectin have been implicated in physiological and pathological processes, especially tissue remodeling associated with inflammation. Because EDAcontaining fibronectin fragments produce cellular responses similar to those provoked by bacterial lipopolysaccharide (LPS), we examined the ability of recombinant EDA to activate Toll-like receptor 4 (TLR4), the signaling receptor stimulated by LPS. We found that recombinant EDA, but not other recombinant fibronectin domains, activates human TLR4 expressed in a cell type (HEK 293 cells) that normally lacks this Toll-like receptor. EDA stimulation of TLR4 was dependent upon co-expression of MD-2, a TLR4 accessory protein. Unlike LPS, the activity of EDA was heat-sensitive and persisted in the presence of the LPS-binding antibiotic polymyxin B and a potent LPS antagonist, E5564, which completely suppressed LPS activation of TLR4. These observations provided a mechanism by which EDA-containing fibronectin fragments promote expression of genes involved in the inflammatory response.

The process of cervical ripening has been likened to an inflammatory reaction associated with the catabolism of cervical extracellular matrix by enzymes released from infiltrating leukocytes. We hypothesized that smooth muscle cells in the cervix also participate in this process and that pro-inflammatory cytokines act on cervical smooth muscle cells (CSMC) to provoke the expression of matrix-degrading enzymes. We treated primary cultures of human CSMC with tumor necrosis factor-␣ (TNF-␣) and examined expression of the elastinolytic enzyme , cathepsin S, the collagen metabolizing matrix metalloproteinases (MMP)-1 , -3 , -9 , and the tissue inhibitor of metalloproteinase (TIMP)-1 and -2. A time course analysis revealed that 10 ng/ml of TNF-␣ induced cathepsin S, MMP-1 , -3 , and -9 mRNA expression with the maximal response observed after 24 -48 hours. TNF-␣ induced cathepsin S , MMP-1 , -3 , and -9 mRNA expression in a dose-dependent manner: the maximal effect was observed at a concentration of 10 ng/ml , with appreciable increases observed at concentrations of 0.1 to 1.0 ng/ml. In contrast , TIMP-1 and -2 mRNAs were not significantly increased by TNF-␣ treatment. Interleukin-1␤ produced a pattern of gene expression in the CSMC similar to that observed following TNF-␣ treatment. Western blot analysis and zymography confirmed the induction of proMMP-1 , -3 , and -9 in response to TNF-␣, but MMP-2 immunoreactivity and zymographic activity were unaffected. TNF-␣ increased secretion of procathepsin S , but did not affect TIMP-1 and reduced TIMP-2 production. We conclude that CSMC are targets of pro-inflammatory cytokines, which induce a repertoire of enzymes capable of degrading the cervical extracellular matrix. The induction of these enzymes may facilitate the normal ripening of the cervix at term and participate in the The human cervix is composed primarily of connective tissue consisting mainly of fibrillar collagens, elastin, and glycosaminoglycans.

No abstract

Immediately before parturition the cervix undergoes striking changes in structure (ripening) that facilitate dilatation and effacement. Cervical ripening shares many features in common with inflammation-associated tissue remodeling, making it a valuable process to explore with respect to the biochemical events in extracellular matrix restructuring. Cervical ripening can be pharmacologically induced with prostaglandin E(2) (PGE(2)). Among the biochemical changes in the cervix at parturition is a marked increase in the hyaluronic acid (HA) content. HA and HA-binding proteins have been implicated in tissue hydration, release of collagenase, and leukocyte migration, but their roles in cervical ripening have not been explored. In the present study we examined the ability of PGE(2) to induce expression of the HA-binding protein, tumor necrosis factor-stimulated gene (TSG)-6, in human cervical smooth muscle cells (hCSMCs) and compared the PGE(2) response to that of tumor necrosis factor-alpha (TNF-alpha), an established inducer of TSG-6. TNF-alpha stimulated TSG-6 mRNA accumulation in a dose- and time-dependent manner, with the maximal response observed at 10 ng/ml after 6 hours of incubation. PGE(2) stimulated TSG-6 mRNA expression, but the magnitude of response was substantially less than that produced by TNF-alpha, and it was maximal only after 24 hours of incubation. Quantitative real-time polymerase chain reaction was performed to assess the induction of TSG-6 mRNA and nascent transcripts at 24 hours of treatment. Induction of TSG-6 mRNA and nascent transcripts in response to 10 micromol/L of PGE(2) was 5.7-fold and 6.3-fold greater than control values, respectively, whereas TNF-alpha (10 ng/ml) induced TSG-6 mRNA and nascent transcripts by 80-fold and 134-fold, respectively. TNF-alpha and PGE(2) stimulated secretion of TSG-6 into the culture medium as detected by Western blotting. The effects of PGE(2) on secretion of TSG-6 were delayed compared to TNF-alpha. A 1.3-kb fragment of the human TSG-6 proximal promoter drove luciferase expression in transfected hCSMCs. PGE(2) increased TSG-6 promoter activity 1.75-fold. Paradoxically, TNF-alpha reduced TSG-6 promoter activity by 50%. We conclude that hCSMCs express the hyaladherin TSG-6; that TSG-6 expression in these cells is regulated by PGE(2) as well as proinflammatory cytokines; responses of hCSMCs to TNF-alpha and PGE(2) are distinct in terms of magnitude and the time course; and PGE(2) and TNF-alpha exert different effects on the TSG-6 proximal promoter.