Luteolin alleviates post-infarction cardiac dysfunction by up-regulating autophagy through Mst1 inhibition.

Myocardial infarction (MI), which is characterized by chamber dilation and LV dysfunction, is associated with substantially higher mortality. We investigated the effects and underlying mechanisms of Luteolin on post-infarction cardiac dysfunction. Myocardial infarction was constructed by left anterior descending coronary artery ligation. In vitro, cultured neonatal cardiomyocytes subjected to simulated MI were used to probe mechanism. Luteolin significantly improved cardiac function, decreased cardiac enzyme and inflammatory cytokines release after MI. Enhanced autophagic flux as indicated by more autophagosomes puncta, less accumulation of aggresomes and P62 in the neonatal cardiomyocytes after hypoxia was observed in the Luteolin pre-treatment group. Western blot analysis also demonstrated that Luteolin up-regulated autophagy in the cardiomyocytes subjected to simulated MI injury. Furthermore, Luteolin increased mitochondrial membrane potential, adenosine triphosphate content, citrate synthase activity and complexes I/II/III/IV/V activities in the cardiomyocytes subjected to simulated MI injury. Interestingly, mammalian sterile 20-like kinase 1 (Mst1) knockout abolished the protective effects of Luteolin administration. Luteolin enhances cardiac function, reduces cardiac enzyme and inflammatory markers release after MI. The protective effects of Luteolin are associated with up-regulation of autophagy and improvement of mitochondrial biogenesis through Mst1 inhibition.

Myocardial protective effect of extracellular superoxide dismutase gene modified bone marrow mesenchymal stromal cells on infarcted mice hearts.

AIM: Extracellular superoxide dismutase (ecSOD) is a unique scavenger of superoxide anions and a promising target of gene therapy for ischemia/reperfusion injury (I/R). However, conventional gene therapies have limitation in effectiveness and efficiency. This study aimed to investigate the protective effects of ecSOD gene modified bone marrow mesenchymal stromal cells (BMSCs) on cardiac function improvement in mice infarcted heart. METHODS & RESULTS: BMSCs were isolated from Fluc(+) transgenic mice (Tg FVB[Fluc(+)]) and transfected by adenovirus combined with human ecSOD gene. ELISA was performed to determine ecSOD protein level. Female syngeneic FVB mice were randomized into 5 groups: (1) Sham group (sham); (2) MI group (MI); (3) MI+BMSCs group (BMSC); (4) MI+BMSCs-vector group (BMSC-vector); (5) MI+ BMSCs-ecSOD group (BMSC-ecSOD). MI was accomplished by ligation of the left anterior descending artery. BMSCs (2 x 10(6)) were injected into the border zone of infarction. In vivo bioluminescence imaging (BLI) was performed to monitor transplanted BMSCs viability. Echocardiography and histological staining revealed that BMSCs-ecSOD significantly reduced myocardial infarction size and improved cardiac function. Lucigenin chemiluminescence, DHE and TUNEL staining demonstrated that BMSCs-ecSOD delivery reduced ROS level and cell apoptosis both in vivo and in vitro. Western blot assay revealed that ecSOD supplementation increased FoxO3a phosphorylation in cardiomyocytes. Moreover, quantitative real-time PCR showed that pro-apoptotic factors (bim and bax) were decreased while the anti-apoptotic factor mir-21 expression was increased after ecSOD intervention. CONCLUSION: Intra-myocardial transplantation of adenovirus-ecSOD transfected BMSCs could exert potential cardiac protection against MI, which may be partly through reduction of oxidative stress and improvement of BMSCs survival.

Impaired mitochondrial biogenesis due to dysfunctional adiponectin-AMPK-PGC-1α signaling contributing to increased vulnerability in diabetic heart.

Impaired mitochondrial biogenesis causes skeletal muscle damage in diabetes. However, whether and how mitochondrial biogenesis is impaired in the diabetic heart remains largely unknown. Whether adiponectin (APN), a potent cardioprotective molecule, regulates cardiac mitochondrial function has also not been previously investigated. In this study, electron microscopy revealed significant mitochondrial disorders in ob/ob cardiomyocytes, including mitochondrial swelling and cristae disorientation and breakage. Moreover, mitochondrial biogenesis of ob/ob cardiomyocytes is significantly impaired, as evidenced by reduced Ppargc-1a/Nrf-1/Tfam mRNA levels, mitochondrial DNA content, ATP content, citrate synthase activity, complexes I/III/V activity, AMPK phosphorylation, and increased PGC-1α acetylation. Since APN is an upstream activator of AMPK and APN plasma levels are significantly reduced in ob/ob mice, we further tested the hypothesis that reduced APN in ob/ob mice is causatively related to mitochondrial biogenesis impairment. One week of APN treatment of ob/ob mice activated AMPK, reduced PGC-1α acetylation, increased mitochondrial biogenesis, and attenuated mitochondrial disorders. In contrast, knocking out APN inhibited AMPK-PGC-1α signaling and impaired both mitochondrial biogenesis and function. The ob/ob mice exhibited lower survival rates and exacerbated myocardial injury after MI, when compared to controls. APN supplementation improved mitochondrial biogenesis and attenuated MI injury, an effect that was almost completely abrogated by the AMPK inhibitor compound C. In high glucose/high fat treated neonatal rat ventricular myocytes, siRNA-mediated knockdown of PGC-1α blocked gAd-enhanced mitochondrial biogenesis and function and attenuated protection against hypoxia/reoxygenation injury. In conclusion, hypoadiponectinemia impaired AMPK-PGC-1α signaling, resulting in dysfunctional mitochondrial biogenesis that constitutes a novel mechanism for rendering diabetic hearts more vulnerable to enhanced MI injury.

Rosuvastatin enhances the therapeutic efficacy of adipose-derived mesenchymal stem cells for myocardial infarction via PI3K/Akt and MEK/ERK pathways.

The poor viability of transplanted stem cells hampers their therapeutic efficacy for treatment of myocardial infarction. The aim of this study was to investigate whether rosuvastatin improved survival of adipose-derived mesenchymal stem cells (AD-MSCs) after transplantation into infarcted hearts. AD-MSCs isolated from Tg(Fluc-egfp) mice which constitutively express both firefly luciferase (Fluc) and enhanced green fluorescent protein were transplanted into infarcted hearts with or without rosuvastatin administration. Longitudinal in vivo bioluminescence imaging and histological staining revealed that rosuvastatin enhanced the survival of engrafted AD-MSCs. Furthermore, combined therapy of AD-MSC and rosuvastatin reduced fibrosis, decreased cardiomyocyte apoptosis, and preserved heart function. AD-MSCs were then subjected to hypoxia and serum deprivation injury in vitro to mimic the ischemic environment. Rosuvastatin (10(-6) mmol/L) enhanced the viability and paracrine effect of AD-MSCs, and decreased their apoptotic rate. Western blotting revealed that rosuvastatin supplementation increased Akt and ERK phosphorylation, which resulted in FoxO3a phosphorylation and nuclear export. In addition, rosuvastatin administration decreased the pro-apoptotic proteins Bim and Bax, and increased the anti-apoptotic proteins Bcl-xL and Bcl-2. Furthermore, these effects were abolished by PI3K inhibitor LY294002 and MEK1/2 inhibitor U0126. This study demonstrates that rosuvastatin may improve the survival of engrafted AD-MSCs at least in part through the PI3K/Akt and MEK/ERK1/2 signaling pathways. Combination therapy with rosuvastatin and AD-MSCs has a synergetic effect on improving myocardial function after infarction.

Pulsed magnetic field induces angiogenesis and improves cardiac function of surgically induced infarcted myocardium in Sprague-Dawley rats.

OBJECTIVE: It was the aim of this study to investigate the impact of pulsed magnetic field (PMF) on ischemic myocardium, though it has been reported that PMF treatment is a safe and effective method to facilitate bone and cutaneous wound healing. METHODS: In this report, we describe a study in which 10 Hz 4 mT PMF and 15 Hz 6 mT PMF was used to treat rats with myocardial infarction (MI). RESULTS: After 28 days of treatment, the rats treated with 15 Hz 6 mT PMF exhibited decreased left ventricular end-diastolic pressure and accelerated maximum dp/dt of left ventricular pressure when compared with the untreated MI and the MI + 10 Hz 4 mT groups. Additionally, capillary density was increased and infarction area size was decreased in the MI + 15 Hz 6 mT group. Furthermore, the plasma vascular endothelial growth factor concentration and the protein expression of vascular endothelial growth factor receptor 2 in myocardial tissue were increased in rats of the MI + 15 Hz 6 mT group. CONCLUSION: This study shows that 15 Hz 6 mT PMF promotes myocardial angiogenesis and improves cardiac function after MI in rats. This suggests that there is a potential use for some PMF signal strengths in ischemic myocardial disease.

Nitrative inactivation of thioredoxin-1 increases vulnerability of diabetic hearts to ischemia/reperfusion injury.

Hyperglycemia (HG) significantly increases mortality after myocardial infarction (MI) in patients with and without established diabetes. The specific underlying mechanism remains unknown. The present study attempted to determine whether nitrative inactivation of thioredoxin-1 (Trx-1) may contribute to the exaggerated myocardial ischemia/reperfusion (I/R) injury observed in the hyperglycemic condition. Diabetes was induced by multiple intraperitoneal injections of low-dose streptozotocin (STZ) in mice. After 30 min ischemia by slip-knot ligature of the left anterior descending coronary artery, the myocardium was reperfused for 3h after knot release (for apoptosis, Trx-1-activity, and -nitration determination) or 24h (for cardiac function and infarct size determination). At 10 min before reperfusion, diabetic mice were randomized to receive vehicle, EUK134 (a peroxynitrite scavenger), recombinant human Trx-1 (rhTrx-1), or SIN-1 (a peroxynitrite donor) nitrated Trx-1 (N-Trx-1) administration. Diabetes intensified I/R-induced myocardial injury, evidenced by further enlarged infarct size, increased apoptosis, and decreased cardiac function in diabetic mice. Trx-1 nitrative inactivation was elevated in the diabetic heart before I/R and was further amplified after I/R. Treatment with EUK134 or rhTrx-1, but not N-Trx-1, before reperfusion significantly reduced Trx-1 nitration, preserved Trx-1 activity, attenuated apoptosis, reduced infarct size, and improved cardiac function in diabetic mice. Taken together, our results demonstrated that HG increased cardiac vulnerability to I/R injury by enhancing nitrative inactivation of Trx-1, suggesting that blockade of Trx-1 nitration, or supplementation of exogenous rhTrx-1, might represent novel therapies to attenuate cardiac injury after MI in diabetic patients.

High glucose sensitizes adult cardiomyocytes to ischaemia/reperfusion injury through nitrative thioredoxin inactivation.

AIMS: Ischaemic cardiac injury is significantly increased in diabetic patients, but its underlying mechanisms remain incompletely understood. The current study attempted to identify new molecular mechanisms potentially contributive to hyperglycaemic-exaggeration of myocardial ischaemic injury. METHODS AND RESULTS: Adult mouse cardiomyocytes were cultured in normal-glucose (NG, 5.5 mM) or high-glucose (HG, 25 mM) medium. Twelve hours after NG or HG pre-culture, cardiomyocytes were subjected to 3 h of simulated ischaemia (SI), followed by 3 h of reperfusion (R) in NG medium. Prior to and after SI/R, the following were determined: cardiomyocyte death and apoptosis, sustained oxidative/nitrative stress and thioredoxin (Trx) activity, expression, and nitration. Compared with NG-cultured cardiomyocytes, 12 h HG culture significantly increased superoxide and peroxynitrite production, increased Trx-1 nitration, and reduced Trx activity (P < 0.01). Despite being subject to identical SI/R procedures and conditions, cells pre-cultured in HG sustained greater injury, evidenced by elevated lactate dehydrogenase release and caspase-3 activation (P < 0.01). Moreover, SI/R induced greater superoxide/peroxynitrite overproduction and greater Trx-1 nitration and inactivation in HG pre-cultured cardiomyocytes than in NG pre-cultured cardiomyocytes. Finally, the supplementation of human Trx-1, superoxide scavenger, or peroxynitrite decomposition catalyst in HG pre-cultured cells reduced Trx-1 nitration, preserved Trx-1 activity, and normalized SI/R injury to levels observed in NG pre-cultured cardiomyocytes. CONCLUSION: High glucose sensitized cardiomyocytes to ischaemia/reperfusion injury through nitrative Trx-1 inactivation. Interventions restoring Trx-1 activity in the diabetic heart may represent novel therapies attenuating cardiac injury in diabetic patients.

Tanshinone IIA: a new activator of human cardiac KCNQ1/KCNE1 (I(Ks)) potassium channels.

Tanshinone IIA, one of the main active components from Chinese herb Danshen, is widely used to treat cardiovascular diseases including arrhythmia in Asian countries especially in China. However, the mechanisms underlying its anti-arrythmia effects are not clear. In this study we investigate the effects of tanshinone IIA on human KCNQ1/KCNE1 potassium channels (I(Ks)), human ether-a-go-go-related gene potassium channels (hERG), Kv1.5 potassium channels, inward rectifier potassium channels (I(K1)) expressed in HEK 293 cells using patch clamp technique. Tanshinone IIA potently and reversibly enhanced the amplitude of I(Ks) in a concentration dependent manner with an EC(50) of 64.5 microM, accelerated the activation rate of I(Ks) channels, decelerated their deactivation and shifted the voltage dependence of I(Ks) activation to negative direction. Isoproteronol, a stimulator of beta-adrenergic receptor, at 1 microM and sodium nitroprusside (SNP), a NO donor, at 1 mM, had no significant effects on the enhancement of I(Ks) by 30 microM tanshinone IIA. N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H89), a selective protein kinase A inhibitor, at 0.1 microM and 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one (ODQ), a selective nitric oxide-sensitive guanylyl cyclase inhibitor, at 10 microM, also had no significant effects on the enhancement of I(Ks) by 30 microM tanshinone IIA. Tanshinone IIA did not affect expressed hERG channels, Kv1.5 channels and I(K1) channels. These results indicate that tanshinone IIA directly and specifically activate human cardiac KCNQ1/KCNE1 potassium channels (I(Ks)) in HEK 293 cell through affecting the channels' kinetics.