High Glucose–Enhanced Mesangial Cell Extracellular Signal–Regulated Protein Kinase Activation and 1(IV) Collagen Expression in Response to Endothelin-1 Role of Specific Protein Kinase C Isozymes

High glucose (HG) stimulates glomerular mesangial cell (MC) expression of extracellular matrix, a process involving protein kinase C (PKC) isozymes and enhanced signaling by autocrine peptides such as endothelin-1 (ET-1). The purpose of this study was to identify the specific PKC isozymes mediating the effects of HG on MC extracellular signal–regulated protein kinase (ERK1/2) signaling and 1(IV) collagen expression in response to ET-1. HG (30 mmol/l for 72 h) enhanced ET-1–stimulated 1(IV) collagen mRNA expression from 1.2 0.1–fold to 1.9 0.2–fold (P < 0.05 vs. normal glucose [NG] ET-1), and the effect was significantly reduced by Calphostin C or the MEK (mitogenactivated protein kinase kinase) inhibitor PD98059. In transiently transfected MCs, dominant-negative (DN)– PKC, , or inhibited ET-1 activation of ERK1/2. Likewise, downstream of ERK1/2, ET-1 stimulated Elk1–driven GAL4 luciferase activity to 11 1–fold (P < 0.002 vs. NG ET-1) in HG, and DN-PKC– , – , or – attenuated this response to NG levels. HG enhanced ET-1–stimulated intracellular 1(IV) collagen protein expression, assessed by confocal immunofluorescence imaging, showed that individual DN–PKC, , , as well as DN–PKCand , attenuated the response. Thus, HG-enhanced ET-1 stimulation of 1(IV) collagen expression requires PKC, , and to act through an ERK1/2-dependent pathway and via PKCand , which are independent of ERK1/2. Diabetes 50:2376–2383, 2001