Formation of reactive oxygen metabolites in rat mesangial cells (mc) is selectively suppressed by rol1pram, inhibitor of camp phosphodiesterase isozymeiv (PDE-IV)

Reactive oxygen metabolites play an important role in glomerular injury and perhaps also in signal transduction. In previous study we found that rolipram, a PDE-IV inhibitor, suppressed ROM generation in the whole rat glomeruli. Because MC play a major role in several types of immunoinflammatory glomerular injury, we investigated the effect of selective PDE isozyme inhibitors upon ROM generation by MC, which contain PDE isozymes type HI and IV. ROM generation by MC was measured by a microfluorometric assay using 2',5'-dichlorofluorescein diacetate as a probe and was stimulated by serum-opsonized zymozan (STZ). STZ-increased fluorescence was inhibited by the ROM scavengers Superoxide dismutase and dimethylthiourea. Although either 10 iiM rolipram or cilostamide (PDE-UI inhibitor) increased activity of protein kinase A (PKA) in situ (+ 59% and +37% respectively) to similar degree, only rolipram suppressed ROM generation by -33%, while cilostamide caused no inhibition. Suppression of ROM generation by rolipram was similar to the cAMPincreasing agent forskolin (-41%) and the PKA activator dibutyryl cAMP (-43%). These findings suggest that a cAMP-signaling pathway specifically linked to PDE-IV regulates ROM generation in MC, as opposed to PDE-1II, which regulates proliferation in these cells (J. Clin. Inv. 96:401, 1995). These results indicate that different PDE isozymes are involved with regulation of different processes in MC and also that MC contribute substantially to ROM generation by glomeruli.