Acetylcholine inhibits tumor necrosis factor α activated endoplasmic reticulum apoptotic pathway via EGFR-PI3K signaling in cardiomyocytes.

Previous findings have shown that acetylcholine (ACh) decreased hypoxia-induced tumor necrosis factor alpha (TNF α) production, thus protected against cardiomyocyte injury. However, whether and how ACh affects TNF α-induced endoplasmic reticulum (ER) stress and cell apoptosis remain poorly defined. This study was aimed at determining the effect of ACh in H9c2 cells after TNF α stimulation. Presence of ER stress was verified using the ER stress protein markers glucose regulatory protein 78 (GRP78) and C/EBP homologous protein (CHOP). Cell apoptosis was shown by caspase-3 activation and terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling. Exogenously administered ACh significantly decreased these TNF α-induced changes. Moreover, when the cells were exposed to nonspecific muscarinic receptor (M AChR) inhibitor atropine, methoctramine (M2 AChR inhibitor) or the epidermal growth factor receptor (EGFR) inhibitor AG1478, the cardioprotection elicited by ACh was diminished. Furthermore, the above effects were also blocked by M2 AChR or EGFR siRNA, indicating that EGFR transactivation by M2 AChR may be the major pathway responsible for the benefits of ACh. In addition, LY294002, a phosphatidylinositol-3-kinase (PI3K) inhibitor, displayed the similar trends as AG1478, suggesting that PI3K/Akt signaling may be the downstream of EGFR in ACh-elicited anti-apoptotic property. Together, these data indicate that EGFR-PI3K/Akt signaling is involved in M2 AChR-mediated ER apoptotic pathway suppression and the subsequent survival of H9c2 cardiomyocytes. We have identified a novel pathway underlying the cardioprotection afforded by ACh.

Aerobic interval training protects against myocardial infarction-induced oxidative injury by enhancing antioxidase system and mitochondrial biosynthesis.

1. Aerobic interval training (AIT) exerts beneficial effects on cardiovascular disease. However, its cardioprotective mechanisms are not fully understood. The aim of the present study was to evaluate AIT-mediated anti-oxidation by focusing on anti-oxidase and mitochondrial biogenesis in rats after myocardial infarction (MI). 2. Sprague-Dawley rats were divided into three groups: (i) a sham-operated control (CON); (ii) an MI group; and (iii) an MI + AIT group. Myocardial microstructure and function, markers of oxidative stress, mitochondrial anti-oxidase, Phase II enzymes and mitochondrial biogenesis were assessed. In addition, levels of nuclear factor-erythroid 2-related factor (Nrf2) and phosphorylated (p-) AMP-activated protein kinase (AMPK) were determined. The anti-oxidative gene sirtuin 3 (SIRT3) and the prosurvival phosphatidylinositol-3 kinase (PI3-K)-protein kinase B (Akt) signalling cascade were also evaluated. 3. Compared with CON, there was noticeable microstructure injury, cardiac dysfunction and oxidative damage in rats after MI. In addition, decreased mitochondrial anti-oxidase content, Phase II enzyme (except heme oxygenase-1) expression and mitochondrial biogenesis were observed in the post-MI rats as well as reduced protein levels of the regulators Nrf2 and p-AMPK and suppression of SIRT3 levels and PI3-K/Akt signalling. These detrimental modifications were considerably ameliorated by AIT, as evidenced by increases in anti-oxidase, mitochondrial biogenesis, Nrf2 and AMPK phosphorylation, as well as SIRT3 upregulation and PI3-K/Akt signalling activation. Moreover, PI3-K inhibitor-LY294002 (20 mg/kg) treatment partly attenuated AIT-elicited increases in Nrf2 levels and AMPK phosphorylation. 4. Based on these results, we conclude that AIT effectively alleviates MI-induced oxidative injury, which may be closely correlated with activation of the anti-oxidase system and mitochondrial biosynthesis. Increased SIRT3 expression and activation of PI3-K/Akt signalling may play key roles in AIT-mediated anti-oxidation. These results open up new avenues for exercise intervention therapies for MI patients.

Aerobic interval training attenuates mitochondrial dysfunction in rats post-myocardial infarction: roles of mitochondrial network dynamics.

Aerobic interval training (AIT) can favorably affect cardiovascular diseases. However, the effects of AIT on post-myocardial infarction (MI)-associated mitochondrial dysfunctions remain unclear. In this study, we investigated the protective effects of AIT on myocardial mitochondria in post-MI rats by focusing on mitochondrial dynamics (fusion and fission). Mitochondrial respiratory functions (as measured by the respiratory control ratio (RCR) and the ratio of ADP to oxygen consumption (P/O)); complex activities; dynamic proteins (mitofusin (mfn) 1/2, type 1 optic atrophy (OPA1) and dynamin-related protein1 (DRP1)); nuclear peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α); and the oxidative signaling of extracellular signal-regulated kinase (ERK) 1/2, c-Jun NH2-terminal protein kinase (JNK) and P53 were observed. Post-MI rats exhibited mitochondrial dysfunction and adverse mitochondrial network dynamics (reduced fusion and increased fission), which was associated with activated ERK1/2-JNK-P53 signaling and decreased nuclear PGC-1α. After AIT, MI-associated mitochondrial dysfunction was improved (elevated RCR and P/O and enhanced complex I, III and IV activities); in addition, increased fusion (mfn2 and OPA1), decreased fission (DRP1), elevated nuclear PGC-1α and inactivation of the ERK1/2-JNK-P53 signaling were observed. These data demonstrate that AIT may restore the post-MI mitochondrial function by inhibiting dynamics pathological remodeling, which may be associated with inactivation of ERK1/2-JNK-P53 signaling and increase in nuclear PGC-1α expression.

Amlodipine ameliorates endothelial dysfunction in mesenteric arteries from spontaneously hypertensive rats.

1. Endothelial dysfunction plays a critical role in the development and progression or pathogenesis of hypertension. Amlodipine, a calcium channel blocker, is an effective antihypertensive agent. We investigated the effects of amlodipine on endothelial dysfunction in mesenteric arteries from spontaneously hypertensive rats (SHR). 2. Eight-week-old SHR were treated with amlodipine (10 mg/kg per day) for 8 weeks. Control SHR and Wistar-Kyoto (WKY) rats were treated with saline. Systolic blood pressure (SBP) was measured by the tail-cuff method. Isometric tension changes of isolated mesenteric arterial rings were recorded continuously by a myograph system. Serum contents of malondialdehyde (MDA) and total nitrate/nitrite (NO(x) ) were determined. Vascular superoxide anion production was analysed with dihydroethidium (DHE) fluorescence. 3. The contractile responses to KCl and phenylephrine were greater in untreated SHR than in WKY. Acetylcholine (ACh)-induced relaxation was significantly impaired in untreated SHR. Amlodipine treatment reduced the contractions and improved relaxation to ACh. In WKY, relaxation to ACh was inhibited by N(G) -nitro-l-arginine methyl ester (l-NAME) and not changed by ascorbic acid. In untreated SHR, the response to ACh was unaffected by l-NAME, whereas it was improved by ascorbic acid. Amlodipine restored the inhibitory effect of l-NAME on ACh-induced relaxation, but ascorbic acid no longer exerted its facilitating effect. Amlodipine prevented the rise in SBP and ameliorated abnormalities in serum MDA and NO in untreated SHR. DHE assay showed an increased intravascular superoxide generation in untreated SHR, which was abrogated by amlodipine. 4. Treatment of SHR with amlodipine resulted in amelioration of endothelial dysfunction by anti-oxidant activity and improvement in NO availability.

[Alterations in aortic vasomotor function in rats with chronic heart failure and its mechanism].

The aim of the present study was to investigate the alterations in thoracic aortic vasomotor function in rats with chronic heart failure (CHF) post myocardial infarction (MI), and then explored the possible mechanism of pathological changes. Male Sprague-Dawley rats were divided into sham and CHF groups randomly. The CHF model group of rats was generated by ligating the left anterior descending artery. In sham-operated rats the ligation was placed but not tightened. A total of 20 rats underwent either sham-operated (n=8) or surgery for MI (n=12). All sham-operated rats survived the surgical procedure and the post-surgical period, whereas total mortality among MI-rats was 25% (3 out of 12). Only MI-rats with infarct-size >30% of the left ventricle (LV) were included for analysis (8 out of 9). Ten weeks after surgery, rats were anaesthetized for hemodynamic measurements, which contains systolic pressure, diastolic pressure, left ventricular systolic pressure (LVSP), left ventricular end diastolic pressure (LVEDP), LV+dp/dt(max) and LV-dp/dt(max). After that hearts were rapidly excised and weighed. Myocardial infarct size was determined by triphenyltetrazolium chloride (TTC) staining method. Isolated thoracic artery ring preparations were studied in a wire-myograph. The arterial constrictive responses to KCl, CaCl2, phenylephrine (PE), and caffeine and the arterial diastolic responses to acetylcholine (ACh) were recorded by the Multi Myograph System. To explore the possible mechanism, nitric oxide synthase (NOS) inhibitor N-nitrl-L-arginine methylester (L-NAME) and non-selective cyclooxygenase (COX) inhibitor indomethacin (Indo) were used. The results obtained were as follows: (1) CHF group showed an increased contraction response to KCl (5-100 mmol/L) and PE (1x10(-8)-3x10(-4) mol/L), and a reduced endothelium-dependent relaxation response to ACh (1x10(-12)-1x10(-4) mol/L) compared with those observed in sham group (P<0.01, P<0.05); (2) In the presence of L-NAME (1 mmol/L), the endothelium-dependent cumulative contractions to ACh (1x10(-7)-1x 10(-4) mol/L) was significantly enhanced in CHF group (P<0.05), and this effect was reversed by pretreatment with Indo (10 mumol/L); (3) In CHF group, the vessels incubated with Indo (10 mumol/L) showed an increased vasodilation induced by ACh (1x10(-12)-1x10(-4) mol/L) (P<0.05); (4) In the Ca(2+)-free K-H solution, calcium-dependent contraction curves induced by CaCl2 (1x10(-4)-3x10(-2) mol/L) in CHF group significantly shifted to the left compared with sham group (P<0.05); while the vascular contraction induced by caffeine (30 mmol/L) had no significant changes. These findings suggest that thoracic arteries of rats with CHF have endothelial dysfunction, and the contribution of endothelial dilation and contraction was significantly altered in CHF rats. The mechanism could be partly associated with the increased endothelium-dependent contracting factors by COX pathway, or the increased extracellular Ca(2+) influx through voltage-operated channels, thus leading to elevated vasoconstriction.