Perindopril effects on angiotensin I elimination in lung after experimental myocardial injury induced by intracoronary microembolization in rats

Effect of metoprolol on myocardial apoptosis after coronary microembolization in rats

BACKGROUND

Coronary microembolization (CME) is a serious complication following percutaneous coronary intervention (PCI) in patients with acute coronary syndromes. The use of metoprolol before PCI can significantly protect ischemic myocardium from myocardial damage, but the function of metoprolol in the treatment of CME is not entirely clear. This study was to explore the effect and significance of metoprolol on myocardial apoptosis and caspase-3 activation after CME in rats.

METHODS

Thirty rats were randomly divided into three groups including sham-operation (control group), CME plus saline (CME group), CME plus metoprolol (metoprolol group), 10 rats for each group. The CME group was induced by injecting 3 000 polyethylene microspheres (42 μm) into the left ventricle during a 10-second occlusion of the ascending aorta; the control group was injected with physiological saline instead of microembolization ball; the metoprolol or saline group was given three intravenous bolus injections before CME. Echocardiography, TUNEL staining, and Western blotting were used to evaluate cardiac function, proportion of apoptotic cells and activation of caspase-3 respectively at 6 hours after operation.

RESULTS

Echocardiographic parameters displayed that the metoprolol group improved cardiac function significantly compared with the CME group (P<0.05). The myocardial apoptotic rate of the CME group as well as the contents of activated caspase-3 increased significantly (P<0.05), both of which were ameliorated significantly by metoprolol treatment (P<0.05).

CONCLUSIONS

This study demonstrates that metoprolol can protect the myocardium during CME in rats by inhibiting apoptosis and improving cardiac function. These results suggest that the inhibition of apoptosis can be a potential therapeutic strategy for the treatment of CME.

Effect of atorvastatin (Lipitor) on myocardial apoptosis and caspase-8 activation following coronary microembolization

We determined the effect of atorvastatin on myocardial apoptosis and caspase-8 activation following coronary microembolization (CME) in a rat model. For this, 50 rats were randomly and equally divided into CME; sham-operated (control); atorvastatin lavage; gastric lavage control; and caspase-8 inhibitor (CHO) groups. In CME animals, a microembolization ball was injected through the left ventricle. Sham animals were injected with normal saline (NS). Atorvastatin group received atorvastatin gastric lavage once-a-day, 1 week before surgery. Gastric lavage controls had similar lavage with NS. CHO group was i.p-injected (CHO: 10 mg/kg) 30 min before surgery. Cardiac indices in each group were determined by echocardiography 6-h postoperatively. TUNEL assay and western blot were used for myocardial apoptosis and expression of caspases-3/-8, respectively. Echocardiography data show that left ventricular ejection fraction (LVEF) in CME group was significantly decreased (P < 0.05) compared with sham controls. Besides, left ventricular fractional shortening (FS) and cardiac output (CO) were also decreased with an increase in left ventricular end-diastolic dimension (LVEDd). Atorvastatin and CHO animals had significantly improved (P < 0.05) cardiac function compared with CME group. Myocardial apoptosis and activation levels of caspases-3/-8 were significantly increased (P < 0.05) compared with sham; myocardial apoptosis and activation levels of caspases-3/-8 were significantly decreased (P < 0.05) in atorvastatin and CHO groups compared with CME group. In conclusion, atorvastatin pretreatment suppressed post-CME myocardial apoptosis and improved cardiac function through the blockade of a myocardial death receptor-mediated apoptotic pathway.

Beta blocker metoprolol protects against contractile dysfunction in rats after coronary microembolization by regulating expression of myocardial inflammatory cytokines

AIMS

To examine the effects of metoprolol on expression of myocardial inflammatory cytokines and myocardial function in rats following coronary microembolization (CME).

MAIN METHODS

Male rats were randomly assigned to receive either sham-operation (control group), CME plus saline (CME group), or CME plus metoprolol (metoprolol group). CME was induced by injecting 3000 polyethylene microspheres (42 μm) into the left ventricle during a 10-second occlusion of the ascending aorta. Metoprolol (2.5mg/kg) or saline was administered as three intravenous bolus injections after CME. At 3h, 6h, 12h, 24h and 4 weeks after CME, myocardial function was measured with echocardiography; and the mRNA and protein levels of tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10) and interleukin 1-β (IL-1β) were determined.

KEY FINDINGS

Induced CME led to markedly higher mRNA and protein levels of TNF-α, IL-1β and IL-10 at 3, 6, 12, and 24h, as well as reduced left ventricular function, compared to the control group. Metoprolol administration reduced TNF-α and IL-1β levels, but increased IL-10 levels at 3, 6, 12, and 24h compared to the CME group. Moreover, metoprolol treatment resulted in significantly improved left ventricular function at 12h, 24h and 4 weeks, but afforded no cardiac protection at 3h and 12h, compared to the CME group.

SIGNIFICANCE

Higher levels of TNF-α and IL-1β in rats following CME are associated with the development of myocardial contractile dysfunction. Metoprolol-conferred protection against progressive contractile dysfunction following CME may be mediated by its anti-inflammation potential.

Endothelin-converting enzyme inhibition in the rat model of acute heart failure: heart function and neurohormonal activation

Endothelin-1 (ET-1) has been implicated in many cardiovascular diseases, including acute heart failure (AHF) due to myocardial ischemia. Previously we described the oral endothelin-converting enzyme (ECE) inhibitor, PP36, and in this study, we investigated its cardioprotective effect in more detail, and examined the role of PP36 in the neurohormonal activation in rats that had been subjected to acute myocardial ischemia due to the microsphere embolization of coronary microcirculation. PP36 treatment (3.5 x 10(-5) M/kg/day) led to a significant fourfold decrease in hypertensive response when big-ET-1 was administered to healthy, conscious rats. ECE inhibition did not affect mortality during the first 48 hours after ischemia initiation. Systemic hemodynamic, heart function, and neurohormonal activation were analyzed in the healthy control group, the AHF group, and the AHF+PP36 group two days after AHF induction. In conscious rats in the AHF+PP36 group, mean arterial pressure (MAP) was restored and became similar to that of the MAP of the control group. In anesthetized rats, in the AHF+PP36 group, MAP was not restored and was 22% lower than the MAP of the control group. Myocardial contractility was partially restored and cardiac relaxation significantly improved after PP36 application. Further analysis of cardiac output and peripheral resistance in anesthetized rats revealed no differences between the AHF group and the AHF+PP36 group. There were no differences in plasma ET-1 concentration, serum angiotensin converting enzyme activity, and in the adrenal glands' catecholamine content between the AHF group and the AHF+PP36 group. However, rats in the AHF+PP36 group demonstrated a 60% decrease in cardiac endothelial nitric oxide synthase (eNOS) protein expression, and a 56% reduction of myocardial norepinephrine release, when compared with the AHF group's animals. These results suggest that PP36 can preserve heart function during the recovery from acute ischemic injury, and may modulate the cardiac norepinephrine release and eNOS protein level.