HEPARIN SELECTIVELY INHIBITS SYNTHESIS OF TISSUE-TYPE PLASMINOGEN-ACTIVATOR AND MATRIX DEPOSITION OF PLASMINOGEN-ACTIVATOR INHIBITOR-1 BY HUMAN MESANGIAL CELLS

BACKGROUND: Mesangial changes in a variety of pathologic conditions in volve mesangial cell proliferation and mesangial matrix remodelling. H eparin has been shown to prevent these processes in vivo. In vitro, he parin interferes with cell growth, proto-oncogene expression, synthesi s of specific proteins, and extracellular matrix composition. In some cell types, it seems to interact with intracellular protein kinase C-d ependent pathways. The effect of heparin on the mesangial plasminogen activating system (tissue type plasminogen activator, t-PA, and plasmi nogen activator inhibitor type 1, PAI-1), which is thought to be invol ved in matrix remodelling, has not been previously reported. EXPERIMEN TAL DESIGN: Cultured human mesangial cells were stimulated by 10% feta l calf serum (FCS) or 16 nM phorbol myristate acetate (PMA) in the pre sence or absence of anticoagulant or nonanticoagulant heparins. Cell p roliferation, synthesis of t-PA and PAI-1, cell morphology, and PAI-1 matrix deposition were studied using cell counting, [H-3]thymidine inc orporation, specific t-PA and PAI-1 enzyme-linked immunosorbent assay, Northern blot analysis, light microscopy, immunofluorescence and immu nogold silver staining with combined bright-field and epipolarization microscopy. RESULTS: Heparin partially inhibited FCS-stimulated cell g rowth but not PMA-induced thymidine incorporation. FCS and PMA stimula ted t-PA (p < 0.05 and p < 0,01, respectively) and PAI-1 synthesis (p < 0.05 and p < 0.01 respectively). Heparin selectively and partially i nhibited FCS-stimulated t-PA, but not PAI-1 synthesis. It has no effec t on PMA-stimulated t-PA or PAI-1 synthesis but prevented cell shape-c hanges induced by PMA, suggesting that heparin inhibits some but not a ll protein kinase C (PKC)-dependent effects and that heparin block in t-PA synthesis is distal to PHC activation. Heparin decreased PAI-1 ma trix accumulation. Similar results were observed with anticoagulant an d nonanticoagulant heparin fragments. CONCLUSIONS: In human mesangial cells, anticoagulant and nonanticoagulant heparin exert an antiprolife rative effect and may prevent mesangial matrix changes by decreasing F CS-stimulated t-PA synthesis and PAI-1 deposition in the matrix. Hepar in is able to inhibit PKC-dependent cell shape changes but not PKC-dep endent t-PA or PAI-1 synthesis. It also inhibits PKC-independent cell proliferation and t-PA synthesis. These results suggest multiple intra cellular sites of action for heparin, unrelated or distal to PRC activ ation.