Atorvastatin Attenuates Metabolic Remodeling in Ischemic Myocardium through the Downregulation of UCP2 Expression

Abstract

Uncoupling protein 2 (UCP2) is primarily expressed in the myocardium and is closely related to myocardial ischemia/reperfusion injury and myocardial metabolism. To explore the effects and the mechanisms of UCP2 on atorvastatin-mediated myocardium protection, the rat model of myocardial ischemia was established by ligation of the left anterior descending coronary arteries (LADs). The rats were divided into the sham operation (SO) group, myocardial infarction (MI) group and MI-atorvastatin group. The study that atorvastatin reduced myocardial remodeling and improved the disturbed myocardial energy metabolism after MI. Furthermore, the mechanisms of myocardial metabolic remodeling affected by atorvastatin were explored. The atorvastatin group showed a significantly decreased expression of UCP2 mRNA and protein. Furthermore, the primary rat cardiomyocytes were cultured and treated with angiotensin II (Ang II) to induce cardiomyocyte hypertrophy. The results showed that in the atorvastatin group, the surface area of the cardiomyocytes, the total protein content per unit of cells, and the expression of the UCP2 protein were significantly decreased. These data suggested that atorvastatin significantly attenuated the myocardial remodeling by downregulating the expression of UCP2 that was found to improve the myocardial energy metabolism, inhibit myocardial hypertrophy, and eventually reduce myocardial remodeling.

Keywords: atorvastatin; heart failure; metabolic remodeling; uncoupling proteins-2.

Figure 1

Atorvastatin suppressed HF in the rat with MI. (A) Hemodynamic index, including ±dP/dtmax, LVEDP, and LVSP. (B) Increased LVMI is a major indicator to determine the existence of left ventricular hypertrophy or left ventricular remodeling. The LVMI is equal to the left ventricular weight divided by the body weight (LVW/BW). (C) Representative images of hearts. Four weeks after drug administration, the heart was removed, and tissue sections stained with H&E (×200 magnification) or scanned by electron microscope (×20,000 magnification). +dP/dtmax, maximal rate of rise in the blood pressure in the ventricular chamber; -dp/dtmax, maximal rate of decline in the blood pressure in the ventricular chamber; LVEDP, left ventricular end diastolic pressure; LVSP, left ventricular systolic pressure. Data were presented as mean ± SD. *P < 0.05, **P < 0.01 vs. SO group; ^#P < 0.05, ^##P < 0.01 vs. MI group.

Figure 2

Atorvastatin might attenuate deleterious ventricular remodeling by affecting energy metabolism in cardiomyocytes. (A) The serum lactate levels and FFA concentrations. (B) Levels of ATP in myocardial tissue. The levels of ATP were detected by ELISA. (C) ATPase activities in the serum and the erythrocyte membrane. Na+-K+-ATPase activities, Ca2+-Mg2+-ATPase activities, and erythrocyte membrane ATPase activities were detected by colorimetry. The data are presented as the means ± SD. **P < 0.01 vs. SO group; #P < 0.05, ##P < 0.01 vs. MI group.

Figure 3

Atorvastatin affects energy metabolism in cardiomyocytes after HF via downregulation of UCP2 expression. (A) The expression of UCP2 mRNA by qRT-PCR. The total RNA of non-infarcted left ventricular tissue was extracted using TRIzol, and qRT-PCR was performed to determine the levels of UCP2 mRNA. The data are presented as the means ± SD. **P < 0.01 vs. SO group; #P < 0.05, ##P < 0.01 vs. MI group. (B) The expression of UCP2 in rat cardiac tissues by immunohistochemistry (×200 magnification). (C) Western blotting was performed to determine the expression of the UCP2 protein. Protein extract was prepared from myocardial tissue, separated by SDS-PAGE, and immunoblotted sequentially using the anti-UCP2 antibody. The graph shows the densitometric quantification of the UCP2 protein relative to β-actin that was as an internal control. The data are presented as the means ± SD. **P < 0.01 vs. SO group; ^#P < 0.05, ^##P < 0.01 vs. MI group.

Figure 4

Atorvastatin inhibited Ang II-induced cardiomyocyte hypertrophy through the downregulation of UCP2 expression. (A) Cell surface area measurement. Inverted phase contrast microscope was used to obtain the cardiomyocyte images at ×100 magnification. The surface area of a minimum of 25 cells per treatment group was measured and averaged to generate one N value. The data are presented as the means ± SD. **P < 0.01 vs. control group, ^##P < 0.01 vs. Ang II group. (B) Total protein content per unit of cells. The protein extracts from cardiomyocytes were prepared, and the total protein content per unit cells calculates. The data are presented as the means ± SD. **P < 0.01 vs. control group, ^##P < 0.01 vs. Ang II group. (C) Western blotting was performed to determine the UCP2 expression. Proteins were extracted from cardiomyocytes, separated by SDS-PAGE, and immunoblotted sequentially using the anti-UCP2 antibody. The graph shows the result of densitometric quantification of the UCP2 protein relative to β-actin utilized as an internal control. The data are presented as the means ± SD. **P < 0.01 vs. control group; #P < 0.05, ##P 0.01 vs. Ang II group.