Angiotensin II Induces Connective Tissue Growth Factor Gene Expression via Calcineurin-Dependent Pathways

Abstract

Connective tissue growth factor (CTGF) is a polypeptide implicated in the extracellular matrix synthesis.Previous studies have provided evidence that angiotensin II (Ang II) promotes collagen synthesis and regulates collagen degradation. We investigated whether or not CTGF mediates the profibrotic effects of Ang II in the heart and kidneys and the role of calcineurin-dependent pathways in CTGF gene regulation. In transgenic rats harboring human renin and angiotensinogen genes, Ang II induced an age-dependent increase in myocardial CTGF expression, which was 3.5-fold greater compared to normotensive Sprague Dawley (SD) rats. CTGF overexpression correlated closely with the Ang II-induced rise in blood pressure. CTGF mRNA and protein were located predominantly in areas with leukocyte infiltration, myocardial, and vascular lesions and co-localized with TGF␤ 1 , collagen I, and collagen III mRNA expressions. Ang II induced CTGF mRNA and protein to a lesser extent in the kidneys, predominantly in glomeruli, arterioles, and in the interstitium with ample inflammation. However, no expression was found in the right ventricle or pulmonary arteries. Blockade of calcineurin activity by cyclosporine A completely normalized Ang II-induced CTGF overexpression in heart and kidney, suppressed the inflammatory response, and mitigated Ang II-induced cell proliferation and apoptosis. In contrast, blockade of mTOR (target of rapamycin) pathway by everolimus, further increased the expression of CTGF even though everolimus ameliorated cell proliferation and T-cellmediated inflammation. Our findings provide evidence that CTGF mediates Ang II-induced fibrosis in the heart and kidneys via blood pressure and cal-

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

“…The effect of AngII is mediated through the activation of AT1R, since candesartan, a selective AT1R blocker, inhibited CTGF induction by AngII both in vivo and in vitro. Previously, Finckenberg et al (24) has reported that hypertensive transgenic rats carrying the renin-angiotensinogen transgene have elevated CTGF expression in the myocardium, presumably via a calcineurin-mediated pathway. However, the above study was not able to distinguish whether this is due to AngII action through hypertension or a direct action on cardiomyocytes.…”

“…Among the multiple signaling pathways that are known to mediate AngII action, protein kinase C (PKC) has been shown to be activated in cardiomyocytes, although the specificities of the various PKC isoforms to propagate AngII effects are yet to be determined (21)(22)(23). AngII has been shown to increase the expression of CTGF in vivo, potentially through a calcineurin-mediated pathway (16,24). The regulation of CTGF expression by PKC activation has not been fully characterized except for studies showing that phorbol 12-myristate 13-acetate (PMA), an analogue of DAG and activator of conventional and novel PKC isoforms, can suppress CTGF expression in cultured fibroblasts (25).…”

Sustained cardiomyocyte apoptosis and left ventricular remodelling after myocardial infarction in experimental diabetes

“…Connective tissue growth factor (CTGF) was determined immunohistochemically with an anti-CTGF antibody (Abcam, Cambridge, UK) as a primary antibody. Each sample was scored from 0 to 4 according to the CTGF intensity in stained sections [10]. Cardiac weights are presented relative to rat body weight (mg/g).…”

Phase 1 Study of Anti-CTGF Monoclonal Antibody in Patients with Diabetes and Microalbuminuria

“…Numerous glomerular, tubulointerstitial, and vascular cells types can produce CTGF, and many factors associated with the diabetic condition can stimulate CTGF expression, including hypertension, hyperglycemia, and hyperlipidemia (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24).…”