CHARACTERIZATION OF PROTEIN-KINASE-C BETA-ISOFORM ACTIVATION ON THE GENE-EXPRESSION OF TRANSFORMING GROWTH-FACTOR-BETA, EXTRACELLULAR-MATRIX COMPONENTS, AND PROSTANOIDS IN THE GLOMERULI OF DIABETIC RATS

Induction of protein kinase C (PKC) pathway in the vascular tissues by hyperglycemia has been associated with many of the cellular changes o bserved in the complications of diabetes. Recently, we have reported t hat the use of a novel, orally effective specific inhibitor of PKC bet a isoform (LY333531) normalized many of the early retinal and renal he modynamics in rat models of diabetes, In the present study, we have ch aracterized a spectrum of biochemical and molecular abnormalities asso ciated with chronic changes induced by glucose or diabetes in the cult ured mesangial cells and renal glomeruli that can be prevented by LY33 3531, Hyperglycemia increased diacylglycerol (DAG) level in cultured m esangial cells exposed to high concentrations of glucose and activated PKC alpha and beta 1 isoforms in the renal glomeruli of diabetic rats . The addition of PKC beta selective inhibitor (LY333531) to cultured mesangial cells inhibited activated PKC activities by high glucose wit hout lowering DAG levels and LY333531 given orally in diabetic rats sp ecifically inhibited the activation of PKC beta 1 isoform without decr easing PKC alpha isoform activation, Glucose-induced increases in arac hidonic acid release, prostaglandin E-2 production, and inhibition of Na+-K+ ATPase activities in the cultured mesangial cells were complete ly prevented by the addition of LY333531, Oral feeding of LY333531 pre vented the increased mRNA expression of TGF-beta 1 and extracellular m atrix components such as fibronectin and alpha 1(IV) collagen in the g lomeruli of diabetic rats in parallel with inhibition of glomerular PK C activity, These results suggest that the activation of PKC, predomin ately the beta isoform by hyperglycemia in the mesangial cells and glo meruli can partly contribute to early renal dysfunctions by alteration of prostaglandin production and Na+-K+ ATPase activity as well as the chronic pathological changes by the overexpression of TGF-beta 1 and extracellular matrix components genes.