Inhibition of glomerular cell apoptosis by heparin

Heparin, the multifunctional glycosaminoglycan, has been considered a therapeutic agent for glomerular diseases. Although a number of biological properties are postulated to explain its therapeutic utility, it is unknown whether heparin affects cell survival in the glomerulus. In this report, we investigated the effect of heparin on apoptosis of glomerular cells.

Cultured rat mesangial cells were pretreated with heparin or heparan sulfate proteoglycan (HSPG) and were exposed to proapoptotic stimuli. To examine an effect of heparin on spontaneous apoptosis that occurs in explanted glomeruli, isolated rat glomeruli were incubated in the presence or absence of heparin. Apoptosis was evaluated by Hoechst 33258 staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, and agarose gel electrophoresis to detect DNA fragmentation. The effect of heparin on activator protein 1 (AP-1), a crucial mediator for oxidant-induced apoptosis, was examined by Northern blot analysis and a reporter assay.

Heparin and HSPG inhibited apoptosis of mesangial cells triggered by hydrogen peroxide. It was associated with blunted expression of c-fos/c-jun mRNAs and suppression of AP-1 activation. The cytoprotective effect of heparin was also observed in other cell types and in apoptosis triggered by different stimuli. That is, (a) heparin inhibited mesangial cell apoptosis induced by staurosporine, pyrrolidine dithiocarbamate, and ultraviolet light, and (b) heparin suppressed oxidant-induced apoptosis of NRK49F fibroblasts and Madin-Darby canine kidney epithelial cells. Furthermore, heparin attenuated spontaneous apoptosis of podocytes in explanted glomeruli.

These results indicate the novel potential of heparin as an inhibitor of apoptosis in several cell types, including glomerular cells.