Thermal treatment attenuates neointimal thickening with enhanced expression of heat-shock protein 72 and suppression of oxidative stress.

BACKGROUND: The beneficial effects of thermal therapy have been reported in several cardiovascular diseases. However, it is unknown whether the thermal treatment has some beneficial roles against the development of atherosclerosis. METHODS AND RESULTS: The inflammatory arterial lesion was introduced by placement of a polyethylene cuff on femoral arteries of male Sprague-Dawley rats for 4 weeks. Thermal-treated group underwent daily bathing in 41 degrees C hot water for 15 minutes. Neointimal thickening along with immunohistochemical expression of heat-shock proteins (HSPs), monocyte chemoattractant protein-1 (MCP-1), and NADPH oxidase were compared with those of a thermally untreated (Control) group. Morphometric analysis demonstrated a significant suppression of neointimal thickening in thermal-treated group compared with the Control group (intimal/medial area ratios, 0.01+/-0.01 versus 0.31+/-0.04, P<0.01). Expression of MCP-1 and infiltration of ED-positive cells were enhanced in the adventitial layer of Control. More importantly, expression of HSP72 in media was enhanced by thermal treatment. Expression of p22-phox, the major membrane subunit of NADPH oxidase, and MCP-1 was augmented in cuff-injured adventitia of the Control but not the thermal-treated groups. CONCLUSIONS: Thermal treatment significantly attenuated infiltration of inflammatory cells in adventitia and suppressed neointimal thickening in cuff-injured arteries with the enhancement of HSP72 expression and suppression of oxidative stress.

Impaired glutathione redox system paradoxically suppresses angiotensin II-induced vascular remodeling.

BACKGROUND: Angiotensin II (AII) plays a central role in vascular remodeling via oxidative stress. However, the interaction between AII and reduced glutathione (GSH) redox status in cardiovascular remodeling remains unknown. METHODS: In vivo: The cuff-induced vascular injury model was applied to Sprague Dawley rats. Then we administered saline or a GSH inhibitor, buthionine sulfoximine (BSO, 30 mmol/L in drinking water) for a week, subsequently administered 4 more weeks by osmotic pump with saline or AII (200 ng/kg/minute) to the rats. In vitro: Incorporation of bromodeoxyuridine (BrdU) was measured to determine DNA synthesis in cultured rat vascular smooth muscle cells (VSMCs). RESULTS: BSO reduced whole blood GSH levels. Systolic blood pressure was increased up to 215 ± 4 mmHg by AII at 4 weeks (p<0.01), which was not affected by BSO. Superoxide production in vascular wall was increased by AII and BSO alone, and was markedly enhanced by AII+BSO. The left ventricular weight to body weight ratio was significantly increased in AII and AII+BSO as compared to controls (2.52 ± 0.08, 2.50 ± 0.09 and 2.10 ± 0.07 mg/g respectively, p<0.05). Surprisingly, the co-treatment of BSO totally abolished these morphological changes. Although the vascular circumferential wall stress was well compensated in AII, significantly increased in AII+BSO. The anti-single-stranded DNA staining revealed increasing apoptotic cells in the neointima of injured arteries in BSO groups. BrdU incorporation in cultured VSMCs with AII was increased dose-dependently. Furthermore it was totally abolished by BSO and was reversed by GSH monoethyl ester. CONCLUSIONS: We demonstrated that a vast oxidative stress in impaired GSH redox system totally abolished AII-induced vascular, not cardiac remodeling via enhancement of apoptosis in the neointima and suppression of cell growth in the media. The drastic suppression of remodeling may result in fragile vasculature intolerable to mechanical stress by AII.

Ischemic preconditioning enhances scavenging activity of reactive oxygen species and diminishes transmural difference of infarct size.

Reactive oxygen species (ROS) enhance myocardial ischemia-reperfusion (I/R) injury. Ischemic preconditioning (PC) provides potent cardioprotective effects in I/R. However, it has not been elucidated whether PC diminishes ROS stress in I/R and whether PC protects the myocardium from ROS stress transmurally and homogeneously. Isolated rabbit hearts perfused with Krebs-Henseleit buffer underwent 30 min of ischemia and 60 min of reperfusion. Hemodynamic changes and myocardial damage extent were analyzed in four groups. The control group underwent I/R alone. The H2O2 group underwent I/R with H2O2 infusion (50 microM) in the first minute of reperfusion to enhance oxidative stress. The PC and H2O2+PC groups underwent 5 min of PC before control and H2O2 protocols, respectively. Extracted myocardial DNA was analyzed for 8-hydroxydeoxyguanosine (8-OHdG), an indicator of oxidative DNA damage, with the use of the HPLC-electrochemical detection method. Glutathione peroxidase (GPX) activity and the reduced form of GSH were measured by spectrophotometric assays. The myocardial infarct size was significantly reduced in the PC group (19 +/- 2%) compared with the control group (37 +/- 4%; P < 0.05), particularly in the subendocardium. H2O2 transmurally increased the infarct size by 59 +/- 4% (P < 0.05), which was significantly diminished in the H2O2+PC group (31 +/- 4%; P < 0.01). The GSH levels, but not GPX activity, were well preserved transmurally in protocols with PC. The 8-OHdG levels were significantly decreased in PC and were significantly enhanced in H2O2 (P < 0.01). These changes in oxidative DNA damage were effectively diminished by PC. In conclusion, PC enhanced the scavenging activity of GSH against ROS transmurally, reduced myocardial damage, particularly in the subendocardium, and diminished the transmural difference in myocardial infarct size.

Unequal effects of renin-angiotensin system inhibitors in acute cardiac dysfunction induced by isoproterenol.

Several clinical trials have demonstrated that angiotensin-converting enzyme inhibitor (ACEI) and angiotensin II type 1 receptor blocker (ARB) are equally effective in the treatment of chronic heart failure. However, this has not been confirmed for acute cardiac dysfunction. We examined whether ACEI or ARB prevents isoproterenol-induced acute left ventricular (LV) dysfunction in dogs. LV dysfunction induced by a large dose of isoproterenol (1 microg.kg(-1).min(-1), 3-h infusion) was compared in dogs treated with ACEI (temocaprilat) or ARB (olmesartan). Atrial pacing induced a constant heart rate and use of adjustable aortic banding provided a nearly constant afterload. LV systolic function (LV dP/dt, fractional shortening, and ejection fraction) and diastolic function (tau and LV end-diastolic pressure) were significantly deteriorated after isoproterenol infusion. The LV dysfunction was almost totally prevented by ARB but was only partially prevented by ACEI. The partial effect of ACEI was complemented by cotreatment with HOE-140, a bradykinin B2 receptor antagonist. At baseline, the response to low doses of isoproterenol was significantly attenuated by ACEI but not by ARB, and the ACEI-induced attenuation was totally abolished by cotreatment with HOE-140. The response to isoproterenol was significantly attenuated after 3 h of excess isoproterenol loading, and it was almost completely preserved by ARB but not by ACEI. In conclusion, acute LV dysfunction and beta-adrenergic desensitization induced by excess isoproterenol administration were almost totally prevented by ARB but only partially prevented by ACEI. These differences were attributable at least in part to bradykinin pathways activated by ACEI administration in acute LV dysfunction.