We have recently reported that angiotensin II (Ang II)-induced mitogen-activated protein kinase (MAPK) activation is mainly mediated by Ca 2؉ -dependent activation of a protein tyrosine kinase through G q -coupled Ang II type 1 receptor in cultured rat vascular smooth muscle cells (VSMC). In the present study, we found Ang II rapidly induced the tyrosine phosphorylation of the epidermal growth factor (EGF) receptor and its association with Shc and Grb2. These reactions were inhibited by the EGF receptor kinase inhibitor, AG1478. The Ang II-induced phosphorylation of the EGF receptor was mimicked by a Ca 2؉ ionophore and completely inhibited by an intracellular Ca 2؉ chelator. Thus, AG1478 abolished the MAPK activation induced by Ang II, a Ca 2؉ ionophore as well as EGF but not by a phorbol ester or platelet-derived growth factor-BB in the VSMC. Moreover, Ang II induced association of EGF receptor with catalytically active c-Src. This reaction was not affected by AG1478. These data indicate that Ang II induces Ca 2؉ -dependent transactivation of the EGF receptor which serves as a scaffold for pre-activated c-Src and for downstream adaptors, leading to MAPK activation in VSMC.

The growth-promoting effect of mechanical stress on vascular smooth muscle cells (VSMCs) has been implicated in the progress of vascular disease in hypertension. Extracellular signal-regulated kinases (ERKs) have been implicated in cellular responses, such as vascular remodeling, induced by mechanical stretch. However, it remains to be determined how mechanical stretch activates ERKs. The cytoskeleton seems the most likely candidate for force transmission into the interior of the cell. Therefore, we examined (1) whether the cytoskeleton involves mechanical stretch-induced signaling, (2) whether Rho is activated by stretch, and (3) whether Rho mediates the stretch-induced signaling in rat cultured VSMCs. Mechanical stretch activated ERKs, with a peak response observed at 20 minutes, followed by a significant increase in DNA synthesis. Treatment with the ERK kinase-1 inhibitor, PD98059, inhibited the stretch-induced increase in DNA synthesis. Cytochalasin D, which selectively disrupts the network of actin filaments, markedly inhibited stretch-induced ERK activation. In the control state, RhoA was observed predominantly in the cytosolic fraction, but it was translocated in part to the particulate fraction in response to mechanical stretch. Botulinum C3 exoenzyme, which inactivates Rho p21 (known to participate in the reorganization of the actin cytoskeleton), attenuated stretch-induced ERK activation. Inhibition of Rho kinase (p160ROCK) also suppressed stretch-induced ERK activation dose dependently. Our results suggest that mechanotransduction in VSMCs is dependent on intact actin filaments, that Rho is activated by stretch, and that Rho/p160ROCK mediates stretch-induced ERK activation and vascular hyperplasia.

Abstract-Angiotensin II (Ang II) is now believed to play a critical role in the pathogenesis of hypertrophy and/or hyperplasia of vascular smooth muscle cells (VSMCs). Several G i -and G q -coupled receptors, including the Ang II type 1 (AT 1 ) receptor, activate Rho and Rho-associated kinase in Swiss 3T3 cells and cardiac myocytes. However, little is known about the role of Rho-kinase in Ang II-induced vascular hypertrophy in VSMCs. In the present study, we explored the role of Rho and Rho-kinase in Ang II-induced protein synthesis in VSMCs. In unstimulated cells, RhoA was observed predominantly in the cytosolic fraction, but it was translocated in part to the particulate fraction in response to Ang II (100 nmol/L). This effect was completely blocked by the AT 1 receptor blocker candesartan but not by the Ang II type 2 (AT 2 ) receptor antagonist PD123319. Botulinum C 3 exoenzyme, which inactivated RhoA, attenuated Ang II-induced [ 3 H]leucine incorporation. The specific Rho-kinase inhibitor, Y-27632, dose-dependently abolished Ang II-induced protein synthesis and also suppressed Ang II-induced c-fos mRNA expression. On the other hand, Y-27632 had no effect on Ang II-stimulated phosphorylation of p70 S6 kinase and extracellular signal-regulated kinase 1/2, which are reported to be involved in Ang II-induced protein synthesis, nor had it any effect on the Ang II-induced phosphorylation of PHAS-I, a heat-and acid-stable eIF-4E-binding protein. The phosphorylation of PHAS-I is regulating for translation initiation. These observations suggest that the Rho, Rho-kinase, and c-fos pathways may play a role in Ang II-induced hypertrophic changes of VSMCs through a novel pathway. Key Words: angiotensin II Ⅲ hypertrophy Ⅲ G proteins P revious studies have reported that medial thickening, at least in large conduit vessels, is due in part to increased vascular smooth muscle cell (VSMC) mass, which occurs primarily by enlargement or hypertrophy of preexisting VSMCs, with little or no change in the number of VSMCs. 1,2 There is clear evidence implicating a role for angiotensin II (Ang II) in the mediation of VSMC hypertrophy during chronic hypertension. For instance, angiotensin-converting enzyme inhibitors and Ang II receptor blockers have been shown to be highly effective in inhibiting the development of VSMC medial hypertrophy in a variety of hypertensive animal models. 3,4 Importantly, the effects of angiotensinconverting enzyme inhibitors or Ang II antagonists do not appear to be due simply to blood pressure lowering, because other antihypertensive drugs were not as efficacious in blocking hypertrophy despite equipotent reductions in blood pressure. Consistent with in vivo studies, several laboratories have shown that Ang II stimulates increased protein synthesis and cellular hypertrophy in cultured VSMCs by stimulating Ang II type 1 (AT 1 ) receptors. The mechanism of this pathway is not clear and seems to be complex. 5,6 There has been considerable interest in identifying the mechanism and cellular signaling pathways w...

Abstract-PYK2, a recently identified Ca 2ϩ -sensitive tyrosine kinase, has been implicated in extracellular signal-regulated kinase (ERK) activation via several G protein-coupled receptors. We have reported that angiotensin II (Ang II) induces Ca 2ϩ -dependent transactivation of the epidermal growth factor receptor (EGFR) which serves as a scaffold for preactivated c-Src and downstream adaptors (Shc/Grb2), leading to ERK activation in cultured rat vascular smooth muscle cells (VSMC). Herein we demonstrate the involvement of PYK2 in this cascade. Ang II rapidly induced tyrosine phosphorylation of PYK2, whose effect was completely inhibited by an AT 1 receptor antagonist and an intracellular Ca 2ϩ chelator. A Ca 2ϩ ionophore also induced PYK2 tyrosine phosphorylation to a level comparable with that by Ang II, whereas phorbol ester-induced phosphorylation was less than that by Ang II. Moreover, PYK2 formed a complex coprecipitable with catalytically active c-Src after Ang II stimulation. Although a selective EGFR kinase inhibitor completely abolished Ang II-induced recruitment of Grb2 to EGFR and markedly attenuated Ang II-induced ERK activation, it had no effect on Ang II-induced PYK2 tyrosine phosphorylation or its association with c-Src and Grb2. These data suggest that the AT 1 receptor uses Ca 2ϩ -dependent PYK2 to activate c-Src, thereby leading to EGFR transactivation, which preponderantly recruits Grb2 in rat VSMC.

Abstract-Angiotensin II (Ang II) stimulates the release of prostaglandins (PGs) in various cells and tissues. Recently, cyclooxygenase-2 (COX-2) emerged as a new key regulator for PG synthesis. In the present study, we investigated whether Ang II regulates COX-2 expression in cultured rat vascular smooth muscle cells (VSMCs). Ang II markedly increased the expression of COX-2 mRNA in a time-and dose-dependent manner. This effect was completely blocked by the Ang II type 1 receptor antagonist losartan but not by the Ang II type 2 receptor antagonist PD123319. The p42/44 mitogen-activated protein kinase (MAPK) kinase-1 inhibitor PD98059 and the p38 MAPK inhibitor SB203580 significantly suppressed Ang II-induced COX-2 mRNA and protein expression. Ang II did not increase transcription of the COX-2 gene, as examined with a COX-2 promoter/luciferase chimeric plasmid construct. Instead, it suppressed the degradation of COX-2 mRNA. PD98059 and SB203580 markedly enhanced the decay of COX-2 mRNA induced by Ang II, implying that p42/44 and p38 MAPK activated by Ang II play a role in the regulation of COX-2 through stabilization of its mRNA. The COX-2-specific inhibitor NS-398 attenuated Ang II-stimulated DNA and protein synthesis, as well as PGE 2 production by VSMCs. These results suggest that Ang II regulates COX-2 expression and PG production and modulates cell proliferation through MAPK-mediated signaling pathways in rat VSMCs.

Our results suggest that subsets of T cell populations and their function may be reduced in human obesity, and that this may be related, at least in part, to the elevated TNF-alpha production. Furthermore, this T cell dysfunction can be recovered by adequate weight reduction.

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Aim:We previously reported that glycemic control deteriorated in patients receiving atorvastatin, which is useful for the treatment of hypercholesterolemia in patients with type 2 diabetes. Pitavastatin has a strong lipid-lowering effect, comparable to that of atorvastatin, but it is unknown whether pitavastatin has an adverse influence on glycemic control. The aim of this study was to examine. The effects of three different statins (pravastatin, atorvastatin, and pitavastatin) on blood glucose and HbA1c levels in diabetic patients. Methods: We retrospectively compared glycemic control between groups receiving atorvastatin (10 mg/day, group A, n 99), pravastatin (10 mg/day, group Pr, n 85), and pitavastatin (2 mg/day, group Pi, n 95) from the start of treatment until 3 months later. Patients were excluded if the dosage of their antidiabetic drugs was changed, if their drug therapy was altered within 3 months before starting statin therapy, or if events occurred that could affect glycemic control such as hospitalization. Results: The subjects available for analysis were 74 patients from group A, 71 patients from group Pr, and 74 patients from group Pi. Arbitrary blood glucose levels increased from 147 51 mg/dL (mean SD) to 176 69 mg/dL in group A, but only changed minimally from 136 31 to 134 32 mg/dL in group Pr and from 155 53 to 154 51 mg/dL in group Pi. HbA1c increased from 7.0 1.1% to 7.4 1.2% in group A, while it was 6.9 0.9% versus 6.9 1.0% in group Pr, and 7.3 1.0% versus 7.2 1.0% in group Pi. There was no correlation between LDL-C and HbA1c (the change from baseline to 3 months) in any of the groups. Conclusion: The glycemic parameters only increased significantly in group A, suggesting that pitavastatin and pravastatin did not have an adverse influence on glycemic control in type 2 diabetic patients. J Atheroscler