EXOGENOUS NITRIC-OXIDE INHIBITS MESANGIAL CELL-ADHESION TO EXTRACELLULAR-MATRIX COMPONENTS

Interactions of mesangial cells (MCs) with components of the extracell ular matrix (ECM) profoundly influence the MC phenotype, such as attac hment, contraction, migration, survival and proliferation. Here, we in vestigated the effects of exogenous nitric oxide (NO) on the process o f MC adhesion to ECM molecules. Incubation of rat MCs with the NO dono r S-nitroso-N-acetylpenicillamine (SNAP) dose-and time-dependently inh ibited MC adhesion and spreading on various ECM substrata, being more pronounced on collagen type I than on collagen type IV, laminin or fib ronectin. In contrast, SNAP did not inhibit MC adhesion to L-polylysin e-coated plates. The inhibitory effects of SNAP were reduced by hemogl obin and enhanced by superoxide dismutase. The anti-adhesive action of SNAP was mimicked not only by other NO donors but also by 8-bromo-cGM P, and significantly reversed by the soluble guanylate cyclase inhibit or 1H-[1,2,4] oxadiazolo[4,3,-alpha]quinoxalin-1-one (ODQ). Moreover, SNAP and 8-bromo-cGMP decreased the adhesion-induced phosphorylation o f focal adhesion kinase (pp125(FAK)). In the presence of SNAP or 8-bro mo-cGMP, adherent MCs exhibited disturbed organization of alpha-actin filaments and reduced numbers of focal adhesions, as shown by immunocy tochemistry. In additional experiments with adherent MCs, it was found that exposure to SNAP or 8-bromo-cGMP for 12 and 24 hours induced det achment of MCs. The results indicate that exogenous NO interferes with the establishment and maintenance of MC adhesion to ECM components. T his inhibitory NO effect is mediated predominantly by cGMP-signaling. Disturbance of MC attachment to ECM molecules could represent an impor tant mechanism by which NO affects MC behavior in vitro and in vivo.