Differential Regulation of Angiotensin II-induced Expression of Connective Tissue Growth Factor by Protein Kinase C Isoforms in the Myocardium

Abstract

Protein kinase C (PKC) and angiotensin II (AngII) can regulate cardiac function in pathological conditions such as in diabetes or ischemic heart disease. We have reported that expression of connective tissue growth factor (CTGF) is increased in the myocardium of diabetic mice. Now we showed that the increase in CTGF expression in cardiac tissues of streptozotocin-induced diabetic rats was reversed by captopril and islet cell transplantation. Infusion of AngII in rats increased CTGF mRNA expression by 15-fold, which was completely inhibited by co-infusion with AT1 receptor antagonist, candesartan. Similarly, incubation of cultured cardiomyocytes with AngII increased CTGF mRNA expression by 2-fold, which was blocked by candesartan and a general PKC inhibitor, GF109203X. The role of PKC isoform-dependent action was further studied using adenoviral vector-mediated gene transfer of dominant negative (dn) PKC or wild type PKC isoforms. Expression of dnPKC␣, -⑀, and -isoforms suppressed AngII-induced CTGF expression in cardiomyocytes. In contrast, expression of dominant negative PKC␦ significantly increased AngII-induced CTGF expression, whereas expression of wild type PKC␦ inhibited this induction. This inhibitory effect was further confirmed in the myocardium of transgenic mice with cardiomyocyte-specific overexpression of PKC␦ (␦Tg mice). Thus, AngII can regulate CTGF expression in cardiomyocytes through a PKC activation-mediated pathway in an isoform-selective manner both in physiological and diabetic states and may contribute to the development of cardiac fibrosis in diabetic cardiomyopathy.

Diacylglycerol Kinase .ZETA.Rescues G.ALPHA.q-Induced Heart Failure in Transgenic Mice

“…In contrast, the combination of G q and the PKC inhibitor peptide in double transgenic mice improved systolic and diastolic function. 40,41 In the present study, PKC activity was increased in G q-TG mice, as previously reported, 8 but translocation of PKC was significantly attenuated in G q/ DGK -TG mice. These data are consistent with our previous studies reporting that inhibition of PKC translocation by DGK attenuated fibrosis in the noninfarct area after myocardial infarction 28 and that caused by pressure overload.…”

Effects of Insulin Replacements, Inhibitors of Angiotensin, and PKCβ's Actions to Normalize Cardiac Gene Expression and Fuel Metabolism in Diabetic Rats

“…Similarly, inhibition of ACE has been shown to reduce interstitial and perivascular fibrosis in hearts of diabetic rats (46). These new findings suggest that PKC activation could contribute to the increase in stiffness of the myocardium induced by diabetes or angiotensin II, possibly by increasing the expressions of transforming growth factor-␤ or connective tissue growth factor as previously reported (11,22,46).…”

“…Cardiomyocyte culture experiment. Neonatal rat cardiomyocytes (NRCM) were harvested from 1-to 2-day-old rats and plated to ϳ100% confluency in Dulbecco's modified Eagle's medium (DMEM)/F12 medium with 5.5 mmol/l glucose and 5% horse serum on to gelatin-coated dishes for gene expression studies or Nunclon ⌬ polystyrene culture tubes (NalgeNunc, Roskilde, Denmark) for glucose oxidation assays (22,23). Sixteen hours after plating, culture media were replaced with DMEM/F12 plus 5.5 mmol/l glucose without serum.…”

Fli1 and Ets1 Have Distinct Roles in Connective Tissue Growth Factor/CCN2 Gene Regulation and Induction of the Profibrotic Gene Program

“…It was shown that stimulation of CCN2 gene expression by TGF-␤ required activation of both Smad and ERK signaling pathways (26). Additional pathways implicated in CCN2 gene regulation include small GTPase Rho and protein kinase C (27,28). Whereas the regulation of CCN2 occurs primarily at the level of transcription, with the exception of TGF-␤/Smad3 signaling, little is known about the nature of the transcription factors mediating regulation of the CCN2 gene in response to various stimuli.…”