Dipyridamole inhibits human peritoneal mesothelial cell proliferation in vitro and attenuates rat peritoneal fibrosis in vivo

Prevention or treatment of peritoneal fibrosing syndrome has become an important issue in patients on continuous ambulatory peritoneal dialysis (CAPD). Recent evidence has suggested that mesothelial stem cell proliferation and matrix over-production predispose the development of peritoneal fibrosis. We investigated whether pentoxifylline (PTX) affects human peritoneal mesothelial cell (HPMC) growth and collagen synthesis. HPMC was cultured from human omentum by an enzymic disaggregation method. Cell proliferation was assayed using a methyltetrazolium uptake method. Cell cycle analysis was performed by flow cytometry. Collagen synthesis was measured by 3H-proline incorporation into pepsin-resistant, salt-precipitated collagen. Prostaglandins and cAMP were determined by enzyme immunoassay. Northern blot analysis was used to determine mRNA expression. Our data show that PTX inhibited serum-stimulated HPMC growth and collagen synthesis in a dose-dependent manner. Cell cycle analysis showed that PTX arrested the HPMCs in the G1 phase. PTX decreased the procollagen alpha1 (I) mRNA expression either stimulated by serum or transforming growth factor-beta (TGF-beta). PTX did not alter prostaglandins synthesis but dose-dependently increased intracellular cAMP level. PTX, the same as 3-isobutyl-l-methylxanthine, could potentiate prostaglandin E1 (PGE1) increased cAMP levels of HPMC. The antimitogenic and antifibrogenic effects of PTX on HPMC were reversed by N-[2]-((p-Bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide (H-89). Therefore, the mechanism of these effects may be due to the phospodiesterase inhibitory property of PTX. These data suggest that PTX may have a role in treating peritoneal fibrosing syndrome.

Background: Many glomerular diseases are associated with mesangial cell proliferation and the accumulation of extracellular matrix. At present, there are, however, few treatments which can inhibit these processes. The current study assessed the effects of the anti-platelet and putative anti-proliferative drug dipyridamole (DP) on the growth of human mesangial cells in vitro and their production of the extracellular matrix protein, fibronectin. Methods: Human mesangial cell proliferation, both intrinsic and stimulated by platelet-derived growth factor, was assessed using 3 H-thymidine incorporation and an MTT proliferation assay. A sandwich enzyme-linked immunosorbent assay was used to study the effects of DP on fibronectin synthesis, again in cells stimulated by transforming growth factor beta 1 and in unstimulated cells. Results: At concentrations compatible with the serum levels found in subjects consuming standard dosages, DP significantly inhibited the growth of human mesangial cells in vitro in a dose-dependent fashion. DP also abrogated the mitogenic effects of platelet-derived growth factor. It had no significant effects on the synthesis of fibronectin by these cells (either spontaneous or induced by transforming growth factor beta 1). There was no evidence of cytotoxicity. Conclusion: These data suggest that DP may have a therapeutic role in proliferative glomerulonephritis and possibly other diseases characterized by cell proliferation.