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BACKGROUND/AIM: In addition to its cholesterol-lowering effect, atorvastatin (ATV) has been thought to have multiple cardiovascular benefits, including anti-inflammatory and anti-apoptotic properties. The present study was undertaken to determine whether ATV pretreatment could attenuate myocardial apoptosis and inflammation and improve cardiac function in a swine model of coronary microembolization (CME). METHODS: Twenty-four swine were randomly and equally divided into a sham-operated (control) group, CME group, and CME plus ATV group. Swine CME was induced by intracoronary injection of inert plastic microspheres (diameter 42 µm) into the left anterior descending coronary, with or without pretreatment of ATV. Echocardiographic measurements, a pathological examination, terminal deoxynucleotidyl transferase-mediated nick end labeling staining, and Western blotting were performed to assess the functional, morphological, and molecular effects in CME. RESULTS: The expression levels of caspase 3 and tumor necrosis factor-α (TNF-α) were aberrantly upregulated in cardiomyocytes following CME. Downregulation of caspase 3 and TNF-α with ATV pretreatment was associated with improved cardiac function and attenuated serum cardiac troponin I (cTnI) and high-sensitivity C-reactive protein. In addition, through a Pearson correlation analysis, the left ventricular ejection fraction negatively correlated with caspase 3, TNF-α, and cTnI. CONCLUSION: This study demonstrated that ATV pretreatment could significantly inhibit CME-induced myocardial apoptosis and inflammation and improve cardiac function. The data generated from this study provide a rationale for the development of myocardial apoptosis and inflammation-based therapeutic strategies for CME-induced myocardial injury.

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BACKGROUND: Cardiomyocyte apoptosis by coronary microembolization (CME) contributes to myocardial dysfunction, in which mitochondrial pathway and death receptor pathway are activated. Lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1) is a membrane protein involved in apoptosis. The study aimed to explore the role of LOX-1 in the activation of these 2 major apoptotic pathways. METHODS: Twenty Bama miniature swine were randomized into 4 groups (n = 5 per group). The groups were Sham, CME, LOX-1 small-interfering RNA (siRNA), and control siRNA. Microspheres were injected into the left anterior descending artery of swine to establish CME model. Twelve hours after operation, cardiac function, serum c-troponin I level, microinfarct, and apoptotic index were examined. The levels of LOX-1, Bcl-2, Bax, cytochrome c as well as cleaved caspase 9, -8, and -3 were detected. RESULTS: Myocardial dysfunction, enhanced serum c-troponin I, microinfarct, and apoptosis were induced following CME. Moreover, CME induced increased expression of LOX-1, Bax, cytochrome c, cleaved caspase 9, -8, and -3 as well as decreased Bcl-2 expression levels. The LOX-1 siRNA reversed these effects by CME except cleaved caspase 8 expression, while the control siRNA had no effect. CONCLUSION: Coronary microembolization induces cardiomyocyte apoptosis via the LOX-1-dependent mitochondrial pathway and caspase 8-dependent pathway.

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BACKGROUND: Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a membrane protein associated with apoptosis. Endoplasmic reticulum (ER) stress-induced apoptosis has been determined in several cardiovascular diseases. Mitogen-activated protein kinase (MAPK) signalling is involved in apoptosis. The aim of this study was to investigate whether LOX-1, ER stress, and MAPKs play a role in cardiomyocyte apoptosis after coronary microembolization (CME) and the exact mechanisms involved. METHODS: Thirty swine were randomized into the following groups (n = 5 per group): sham, CME, CME + LOX-1 small-interfering RNA (siRNA), CME + control siRNA, CME + JNK inhibitor, and CME + p38 inhibitor. The CME model was established by injecting microspheres into the left anterior descending (LAD) artery, whereas swine in the sham group received normal saline instead. Twelve hours after the sham operation or CME, cardiac function, serum c-troponin I level, microinfarcts, and apoptotic index were determined. Relative expression levels of LOX-1, ER stress markers (glucose-regulated protein 78 [GRP 78], C/EBP homologous protein [CHOP], and cleaved caspase-12), cleaved caspase-3, c-Jun NH2-terminal protein kinases (JNK), p38, and extracellular signal-related protein kinases (ERK1/2) were measured. RESULTS: CME induced cardiac dysfunction, microinfarction, increased serum c-troponin I levels, and cardiomyocyte apoptosis. Additionally, the expression of LOX-1, ER stress markers, and cleaved caspase-3, and the phosphorylation of JNK, p38, and ERK1/2 were all enhanced. LOX-1 siRNA inhibited these effects except the phosphorylation of ERK1/2. Pretreatment with a JNK inhibitor or a p38 inhibitor attenuated the expression of ER stress markers and apoptosis. CONCLUSIONS: Our results indicated that CME induced cardiomyocyte apoptosis through the LOX-1-dependent ER stress pathway, in which the phosphorylation of JNK and p38 were involved. This might provide a new approach for the prevention and treatment of CME.

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OBJECTIVE: To investigate the effects of metoprolol on cardiomyocyte apoptosis and caspase-8 activation after coronary microembolization(CME) in rats. METHODS: Adult rats were randomly assigned into CME group (intraventricular injection of 3000 microspheres with 42 µm in diameter), sham-operated group (0.1 ml saline) and CME plus metoprolol group (pretreatment with 3 bolus metoprolol 2.5 mg/kg intravenous injection at 10 minutes interval at 30 minutes before microspheres injection, n = 15, each group). Cardiac function was evaluated by echocardiography at 6 hours post various treatments. Cardiomyocyte apoptosis was detected with TUNEL staining and the expression of caspase-3 and caspase-8 was detected with Western blot analysis. RESULTS: Compared with sham-operated group, LVEF (72.68% ± 3.26% vs. 82.64% ± 3.43%, P < 0.05), fractional shortening (FS) (37.46% ± 2.38% vs. 42.85% ± 3.25%) and cardiac output (CO) [(0.101 ± 0.006) L/min vs. (0.162 ± 0.008) L/min] were significantly reduced while left ventricular end-diastolic diameter (LVEDd) [(6.22 ± 0.17) mm vs. (5.18 ± 0.43) mm] was significantly increased in CME group (all P < 0.05). Cardiac function [LVEF:73.94% ± 4.22%, FS:38.53% ± 2.03%, CO:(0.120 ± 0.012) L/min, LVEDd:(6.18 ± 0.27) mm] was similar in CME plus metoprolol group compared to CME group (all P > 0.05). The cardiomyocytes apoptosis rates (3.19% ± 1.23% vs. 0.18% ± 0.10%) and the levels of activated caspase-3 and caspase-8 proteins were significantly increased in CME group than in sham-operated group (all P < 0.05). The cardiomyocyte apoptosis rate (1.32% ± 0.28%) and the levels of activated caspase-3 and caspase-8 proteins were significantly lower in CME plus metoprolol group than in CME group (all P < 0.05). CONCLUSIONS: Metoprolol pretreatment reduced post-CME myocardial apoptosis possibly through downregulating death receptor-mediated apoptotic pathway.

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