| Objective:We hypothesized that both CaMKII and ROS plays an important role in the PAR in cardiac hypertrophy which induced by sustained-βAR-stimulation. There may be a certain relationship between CaMKII and ROS. Therefore, in this study, thiol antioxidant N-acetylcysteine (NAC) was applied to carry out the experimental antioxidative treatment in order to observe the histological changes and CaMKII and NOX4expression of myocardium of ISO-stimulated rats and to investigate the roles and relationship of oxidative stress and CaMKII in sustained-beta AR-stimulated cardiac hypertrophy in rats.Methods:Healthy male Wistar rats (body weight from180-200g) were randomly separated into4groups:control (CTRL), ISO treated (ISO), control with NAC supplement (CTRL+NAC) and ISO treated with NAC supplement group (ISO+NAC) with6rats in each group. ISO treated method:the rats from ISO and ISO+NAC groups receive intraperitoneal injection of ISO for3mg/kg/d; rats from CTRL and CTRL+NAC groups receive intraperitoneal injection of Physiological Saline with the same volume of ISO. NAC supplement method:the rats from CTRL+NAC and ISO+NAC groups drink water with15g/L NAC freely everyday. Systolic blood pressure (SBP) was measured in awake rats with the tail-cuff method every week for two weeks. HW/BW and HE staining was used for the detection of myocardial hypertrophy. Myocardial mitocondrial ROS levels were measured by DCF fluorometry. The expression of activated-CaMKII (p-CaMKⅡ/CaMKⅡ) and NOX4was determined by Western Blot analysis.Results:(1) ISO treatment for2weeks significantly increase the ratio of HW/BW [(4.23±0.19vs2.82±0.04)mg/g, P<0.05], and the myocyte cross-sectional area detected by HE stain[(1422.40±48.35vs784.30±22.08)μm2,P<0.05]; NAC treatment significantly decrease the ISO-stimulated increase of HW/BW [(3.54±0.10vs4.23±0.19) mg/g, P<0.05] and cross-sectional area[(994.90±48.03vs 1422.40±48.35)μm2, P<0.05].(2) Cardiac mitocondrial ROS levels were significantly enhanced by ISO treatment in rats from ISO group compared with CTRL rats[(0.50±0.04vs0.26±0.02)u/s.m, P<0.05]; NAC supplement markedly reduce the excess mitocondrial ROS production by ISO stimulation[(0.27±0.01vs0.50±0.04) u/s.m, P<0.05].(3) The expression of NOX4is consistent with the changes of mitocondrial ROS, and was significantly upregulated in ISO treated rats compared with CTRL rats; NAC supplement effectively reverse the upregulation of NOX4protein expression (P<0.05)induced by ISO.(4) The activated-CaMKII (p-CaMKII/CaMKII) was also significantly upregulate by ISO stimulation to1.6times to CTRL; NAC supplement effectively suppress the upregulated activated-CaMKII expression(P<0.05).(5) SBP showed no difference among four groups of rats. Rats from ISO group showed a significant decrease in heart rate compared to rats from CTRL group [(297±11vs370±3)mmHg, P<0.05]; No significant difference of heart rate was found between rats from ISO+NAC and ISO group.(6) There was no significant difference of the detected index between rats from CTRL+NAC and CTRL group.Conclusion:These results suggest that both oxidative stress and CaMKII play important roles in sustained-pAR-stimulated cardiac hypertrophy and the two factor may have close relationship with each other. NAC may decrease the level of oxidative stress by suppressing both NADPH oxidase and mitocondria, and downregulate the expression of activated-CaMKII, therefore effectively ameliorate the pathologic cardiac hypertrophy mediated by sustained βAR activation. |
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