Role of Protein Kinase C on the Expression of Platelet-Derived Growth Factor and Endothelin-1 in the Retina of Diabetic Rats and Cultured Retinal Capillary Pericytes

Role of Protein Kinase C on the Expression of Platelet-Derived Growth Factor and Endothelin-1 in the Retina of Diabetic Rats and Cultured Retinal Capillary Pericytes Tamotsu Yokota 1 , Ronald C. Ma 1 , Joong-Yeol Park 1 , Keiji Isshiki 1 , Konstantinos B. Sotiropoulos 1 , Ravi K. Rauniyar 1 , Karin E. Bornfeldt 2 and George L. King 1 1 Research Division, Joslin Diabetes Center, Harvard Medical School, Boston, Massachusetts 2 Department of Pathology, School of Medicine University of Washington, Seattle, Washington Abstract Increased expression of endothelin-1 (ET-1) is associated with diabetic retinopathy and vasculopathy, although the molecular explanation has not been defined. The effects of high glucose and protein kinase C (PKC) activation on platelet-derived growth factor (PDGF)-BB and of ET-1 expression in the retina of streptozotocin (STZ)-induced diabetic rats and bovine retinal pericytes (BRPC) were examined. In 4-week diabetic rats, PDGF-B and prepro-ET-1 (ppET-1) mRNA levels increased significantly by 2.8- and 1.9-fold, respectively, as quantified by RT-PCR. Treatment with PKC-β isoform–specific inhibitor (LY333531) or insulin normalized retinal ET-1 and PDGF-B expression. In BRPC, high glucose levels increased ppET-1 and PDGF-B mRNA expression by 1.7- and 1.9-fold, respectively. The addition of PDGF-BB but not PDGF-AA increased expression of ppET-1 and vascular endothelial growth factor mRNA by 1.6- and 2.1-fold, respectively, with both inhibited by AG1296, a selective PDGF receptor kinase inhibitor. A general PKC inhibitor, GF109203X, suppressed PDGF-BB’s induction of ET-1 mRNA. Thus, increased ET-1 expression in diabetic retina could be due to increased expression of PDGF-BB, mediated via PDGF-β receptors in part by PKC activation. The novel demonstration of elevated expression of PDGF-B and its induction by PKC activation identifies a potential new molecular step in the pathogenesis of diabetic retinopathy. Footnotes Address correspondence and reprint requests to George L. King, Joslin Diabetes Center, Section on Vascular Cell Biology, One Joslin Place, Boston, MA 02215. E-mail: george.king{at}joslin.harvard.edu . Received for publication 24 May 2002 and accepted in revised form 18 November 2002. G.L.K. is a consultant for Lilly on the PKC project.. BRPC, bovine retinal pericytes; DMEM, Dulbecco’s modified Eagle’s medium; ET-1, endothelin-1; FBS, fetal bovine serum; MAPK, mitogen-activated protein kinase; PDGF, platelet-derived growth factor;