Abstract-Dietary obesity is associated with type 2 diabetes and cardiovascular diseases, although the underlying mechanism is unknown. This study was undertaken to elucidate the role of angiotensin II and apoptosis signal regulating kinase-1 (ASK1) in obesity/diabetes-associated cardiovascular complications and hepatic steatosis. Mice fed a high-fat diet were treated with olmesartan, an angiotensin II type 1 receptor blocker, to elucidate the role of angiotensin II in diabetic mice. Treatment of mice fed a high-fat diet with olmesartan markedly suppressed cardiac inflammation and fibrosis, as well as vascular endothelial dysfunction and remodeling, induced by obesity/diabetes. Moreover, olmesartan suppressed the disruption of the vascular endothelial NO synthase dimer in diabetic mice. Olmesartan also significantly prevented hepatic steatosis and fibrosis in diabetic mice. These beneficial effects of olmesartan on diabetic mice were associated with the attenuation of ASK1 activation in these mice. ASK1-deficient mice and wild-type mice were compared, regarding the effects of a high-fat diet. A comparison between ASK1-deficient and wild-type mice showed that ASK1 deficiency attenuated cardiac inflammation and fibrosis, as well as vascular endothelial dysfunction and remodeling induced by obesity/diabetes. The amelioration of vascular endothelial impairment by ASK1 deficiency was attributed to the prevention of endothelial NO synthase dimer disruption. ASK1 deficiency also significantly lessened hepatic steatosis in diabetic mice. In conclusion, our work provided the evidence that ASK1 is significantly activated in diet-induced diabetic mice and contributes to cardiovascular diseases and hepatic steatosis in diabetic mice. Moreover, the beneficial effects of angiotensin II inhibition on dietary diabetic mice seem to be mediated by the inhibition of ASK1 activation. Key Words: diabetes Ⅲ obesity Ⅲ angiotensin Ⅲ ASK1 Ⅲ reactive oxygen species Ⅲ vascular endothelial function Ⅲ cardiac injury O besity, particularly dietary obesity, is associated with type 2 diabetes 1 and an increased risk of cardiovascular diseases. 2-5 However, the underlying mechanism is poorly understood. Accumulating experimental and clinical evidence indicate that the renin-angiotensin system is involved not only in hypertension but also in various cardiovascular diseases. 6 Furthermore, emerging experimental and clinical data support the notion that the renin-angiotensin system participates in the pathophysiology of obesity and type 2 diabetes, 7-13 although the underlying mechanism remains to be elucidated.Reactive oxygen species (ROS) are supposed to be involved in obesity, 14 -17 insulin resistance, diabetes, 1,18 and cardiovascular diseases. 19,20 Apoptosis signal regulating kinase-1 (ASK1), one of the mitogen-activated protein kinase kinase kinases, is markedly activated by ROS and plays a critical role in a variety of cellular responses induced by ROS, including cell apoptosis, growth, differentiation, gene expression, etc. 21-23 Previous...

Objective-This work was undertaken to investigate comparative effect of AT1 receptor blocker (ARB), 3-hydroxy-3-methylglutaryl (HMG) coenzymeA (CoA) reductase inhibitor (statin), and their combination on vascular injury of salt-sensitive hypertension. Methods and Results-Salt-loaded Dahl salt-sensitive hypertensive rats (DS rats) were treated with (1) vehicle, (2) hydralazine (5 mg/kg/d), (3) olmesartan (0.5 mg/kg/d), (4) pravastatin (100 mg/kg/d), and (5) combined olmesartan and pravastatin for 4 weeks. Olmesartan or pravastatin significantly and comparably improved vascular endotheliumdependent relaxation to acetylcholine, coronary arterial remodeling, and eNOS activity of DS rats. Olmesartan prevented vascular eNOS dimer disruption or the downregulation of dihydrofolate reductase (DHFR) more than pravastatin, whereas Akt phosphorylation was enhanced by pravastatin but not olmesartan, indicating differential pleiotropic effects between olmesartan and pravastatin. Add-on pravastatin significantly enhanced the improvement of vascular endothelial dysfunction and remodeling by olmesartan in DS rats. Moreover, pravastatin enhanced the increase in eNOS activity by olmesartan, being associated with additive effects of pravastatin on phosphorylation of Akt and eNOS. Conclusions-Olmesartan and pravastatin exerted beneficial vascular effects in salt-sensitive hypertension, via differential pleiotropic effects. Pravastatin enhanced vascular protective effects of olmesartan. Thus, the combination of ARB with statin may be the potential therapeutic strategy for vascular diseases of salt-sensitive hypertension. Key Words: eNOS dimers Ⅲ DHFR Ⅲ oxidative stress Ⅲ vascular injury Ⅲ combined ARB and statin A ccumulating evidence indicates that renin-angiotensin system (RAS) plays a crucial role in the pathophysiology of cardiovascular diseases in hypertension, and that RAS blockers, including angiotensin-converting enzyme inhibitors and AT1 receptor blockers (ARB), are the useful therapeutic agents for hypertensive cardiovascular diseases. 1 As hypertension is often accompanied by dyslipidemia in the same patients, their treatment frequently involves the combination of RAS blockers with 3-hydroxy-3-methylglutaryl coenzymeA (HMG-CoA) reductase inhibitors (statins), potent inhibitors of cholesterol biosynthesis. Clinical evidence show that statins improve endothelial dysfunction and reduce the incidence of atherosclerotic events, 2-5 and these vascular protective effects by statins are at least partially attributed to their pleiotropic vascular effects beyond lowering of plasma cholesterol. 4 -6 However, the difference in vascular pleiotropic effects between RAS blockers and statins remains to be fully understood. Moreover, the significance and the advantage of their combination therapy in hypertension, particularly salt-sensitive hypertension, are not defined.Clinically, salt-sensitive hypertensive patients are more prone to cardiovascular diseases than their salt-insensitive counterparts. 7,8 Therefore, it is a key clinical is...

Abstract-The effect of pioglitazone, a peroxisome proliferator-activated receptor ␥ agonist, on hypertensive cardiovascular injury is unknown. We examined the effect of pioglitazone on hypertensive cardiovascular injury and the significance of combination of pioglitazone with angiotensin type 1 receptor blocker. Stroke-prone spontaneously hypertensive rats (SHRSP) were orally given pioglitazone, candesartan, or combined pioglitazone and candesartan for 4 weeks to compare their effects on cardiovasucular injury. Pioglitazone, without lowering blood pressure, significantly suppressed cardiac inflammation and fibrosis and reduced vascular endothelial dysfunction, and these beneficial effects were associated with the reduction of superoxide by inhibition of cardiovascular NADPH oxidase. Thus, pioglitazone protects against hypertensive cardiovascular injury, by inhibiting reactive oxygen species (ROS). Combination of pioglitazone and candesartan suppressed cardiac hypertrophy, inflammation, and interstitial fibrosis of SHRSP to a greater extent than either monotherapy, and reduced vascular endothelial dysfunction of SHRSP more than either monotherapy. Furthermore, more beneficial effects of their combination on cardiovascular injury were associated with more reduction of NADPH oxidase-mediated cardiovascular ROS. To elucidate the underlying molecular mechanism, we examined cardiovascular NADPH oxidase subunits. Pioglitazone monotherapy significantly attenuated cardiovascular p22 phox and Rac1 in SHRSP, whereas pioglitazone combined with candesartan more attenuated p22 phox and significantly reduced Nox1. Thus, additive suppression of cardiovascular NADPH oxidase by the combination was attributed to its additive attenuation of p22 phox and Nox1 protein levels. In conclusion, we showed that pioglitazone protected against hypertensive cardiovascular damage, and the combination of pioglitazone and candesartan exerted more beneficial effects on hypertensive cardiovascular injury by more suppressing ROS. (Hypertension. 2008;51:296-301.) Key Words: cardiac remodeling Ⅲ endothelium Ⅲ hypertension Ⅲ reactive oxygen species Ⅲ inflammation Ⅲ peroxisome proliferator-activated receptor ␥ Ⅲ AT1 receptor H ypertension is frequently accompanied by type 2 diabetes in the same patients, and hence, many hypertensive patients are subjected to the combination therapy of antihypertensive drug and antidiabetic drug. Pioglitazone is a peroxisome proliferator-activated receptor ␥ (PPAR-␥) agonist 1 and is a useful therapeutic drug for type 2 diabetes, by improving insulin resistance. A growing body of experimental 2-5 and clinical 6 -9 evidence indicate that pioglitazone has beneficial pleiotropic effects on cardiovascular diseases, independently of the improvement of insulin resistance and glycemic control. However, the potential pleiotropic effects of pioglitazone on cardiovascular diseases in hypertension are not clear.Among antihypertensive drugs, an angiotensin type 1 (AT 1 ) receptor blocker (ARB) has been established to exert favorabl...

Objective-The mechanism and role of angiotensin II-induced vascular endothelial injury is unclear. We examined the molecular mechanism of angiotensin (AII)-induced vascular endothelial injury and its significance for hypertensive diastolic heart failure. Methods and Results-We compared the effect of valsartan and amlodipine on Dahl salt-sensitive hypertensive rats (DS rats).Valsartan improved vascular endothelial dysfunction of DS rats more than amlodipine, by inhibiting endothelial apoptosis and eNOS uncoupling more. Moreover, valsartan inhibited vascular apoptosis signal-regulating kinase 1 (ASK1) more than amlodipine. Thus, AT1 receptor contributed to vascular endothelial apoptosis, eNOS uncoupling, and ASK1 activation of DS rats. Using ASK1 Ϫ/Ϫ mice, we examined the causative role of ASK1 in endothelial apoptosis and eNOS uncoupling. AII infusion in wild-type mice markedly caused vascular endothelial apoptosis and eNOS uncoupling accompanied by vascular endothelial dysfunction, whereas these effects of AII were absent in ASK1 Ϫ/Ϫ mice. Therefore, ASK1 participated in AII-induced vascular endothelial apoptosis and eNOS uncoupling. Using tetrahydrobiopterin, we found that eNOS uncoupling was involved in vascular endothelial dysfunction in DS rats with established diastolic heart failure. Conclusion-AII-induced vascular endothelial apoptosis and eNOS uncoupling were mediated by ASK1 and contributed to vascular injury in diastolic heart failure of salt-sensitive hypertension. Key Words: angiotensin Ⅲ endothelium Ⅲ heart failure Ⅲ nitric oxide Ⅲ signal transduction S alt-sensitive hypertensive patients are more prone to cardiovascular diseases than their salt-insensitive counterparts. 1,2 Therefore, it is a clinically important issue to determine the mechanism and the therapeutic strategy of cardiovascular diseases in salt-sensitive hypertension. Vascular endothelial function plays a key role in the pathophysiology 3,4 and the prognosis 5-7 of cardiovascular diseases, including atherosclerosis, ischemic heart disease, and heart failure. However, the detailed molecular mechanism and the pathological significance of vascular endothelial dysfunction in salt-sensitive hypertension are unknown.Apoptosis signal-regulating kinase 1 (ASK1), a mitogenactivated protein kinase kinase kinase, has been identified as a proapoptotic signaling molecule. 8 -11 ASK1 is activated in response to a variety of stress stimuli, such as reactive oxygen species (ROS), angiotensin II (AII), or cytokines, etc. Accumulating in vitro evidence indicates that ASK1 participates in not only apoptosis but also various cellular responses, including cell differentiation and growth, or gene expression. Previously, we have shown that ASK1 is responsible for cardiac hypertrophy and fibrosis, 12 vascular intimal hyperplasia, 13 and ischemia-induced angiogenesis. 14 Furthermore, other investigators have also reported that ASK1 is implicated in cardiac myocyte death and remodeling induced by ischemia. 15,16 However, the role of ASK1 in vascular endotheli...