Transforming growth factor beta-1 (TGF-β1) plays a critical role in progression of cardiac fibrosis, which may involve intracellular calcium change. We examined effects of efonidipine, a dual T-type and L-type calcium channel blocker (CCB), on TGF-β1–induced fibrotic changes in neonatal rat cardiac fibroblast. T-type and L-type calcium channel mRNAs were highly expressed in cultured cardiac fibroblasts. TGF-β1 (5 ng/mL) significantly increased Smad2 phosphorylation and [3H]-leucine incorporation, which were attenuated by pretreatment with efonidipine (10 μM). Neither R(−)efonidipine (10 μM), selective T-type CCB, nor nifedipine (10 μM), selective L-type CCB, efficaciously inhibited both TGF-β1–induced Smad2 phosphorylation and [3H]-leucine incorporation. However, both were markedly attenuated by combination of R(−)efonidipine and nifedipine, EDTA, or calcium-free medium. Pretreatment with Smad2 siRNA significantly attenuated [3H]-leucine incorporation induced by TGF-β1. These data suggest that efonidipine elicits inhibitory effects on TGF-β1– and Smad2-dependent protein synthesis through both T-type and L-type calcium channel–blocking actions in cardiac fibroblasts.

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Angiotensin II (AngII) stimulates vascular smooth muscle cell (VSMC) proliferation; however, the effect of AngII on cell proliferation in the presence of mechanical force is not clear. We investigated the mechanism of AngII-induced cell proliferation mediated by mechanical stretch in VSMCs of both normotensive and hypertensive rats. VSMCs obtained from the thoracic aortas of 8-week-old Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were stretched by a Flex culture system. Mechanical stretch significantly upregulated protein expression of AngII type 1 (AT 1 ) receptor, epidermal growth factor (EGF) receptor and mitogen-activated protein kinase phosphatase-1 in both SHR and WKY VSMCs; however, there was no significant difference in these changes between the cells from SHR and WKY. Mechanical stretch attenuated AngII-induced phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, ERK kinase (MEK) and EGF receptor; it also attenuated [ 3 H] thymidine incorporation and cell proliferation in VSMC of WKY. In contrast, the effects of AngII were augmented by mechanical stretch in VSMC of SHR. AngII-induced ERK 1/2 phosphorylation and cell proliferation in SHR were inhibited by pretreatment with an AT 1 receptor blocker, candesartan and an inhibitor of MEK, PD98059. Moreover, pretreatment with an EGF receptor tyrosine kinase inhibitor, AG1478, also blocked upregulation of AngII-induced ERK 1/2 phosphorylation induced by stretch in SHR VSMCs. This study demonstrates that mechanical stretch augments SHR VSMC proliferation through an AT 1 /EGF receptor/ERK-dependent pathway. These findings may provide new insights into the signaling mechanisms whereby AngII exerts its growth-promoting effects on vasculature in a hypertensive state.

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Afferent renal nerves (ARNs) convey signals generated by physiological changes in the kidney to the central nervous system. The aim of this study was to determine whether ARNs contribute to cardiovascular regulation through central renin-angiotensin system (RAS)-dependent pathways. Blood pressure and renal sympathetic nerve activity (RSNA) were monitored during elevations in pelvic pressure in anesthetized Wistar-Kyoto Izm (WKY) rats and spontaneously hypertensive Izm rats (SHRs). In both groups of rats, blood pressure and RSNA were significantly increased in response to elevations in renal pelvic pressure in a pressure-dependent fashion, which were prevented by renal denervation. Injection of an angiotensin II type I receptor blocker (CV-11974, 10 lg) into the intracerebroventricular region significantly suppressed the vasopressor and sympathoexcitatory responses to the increases in pelvic pressure in both WKY rats and SHRs, although these inhibitory effects of CV-11974 in SHRs appeared to be weaker than in WKY rats. These results indicate that signals transmitted by ARNs have an important role in the control of systemic hemodynamics through regulating central RAS-mediated changes in sympathetic nerve activity.