Aim: Berberine (BBR), an isoquinoline-derived alkaloid isolated from Rhizoma coptidis, exerts cardioprotective effects. Because endoplasmic reticulum (ER) stress plays a pivotal role in myocardial ischemia/reperfusion (MI/R)-induced apoptosis, it was interesting to examine whether the protective effects of BBR resulted from modulating ER stress levels during MI/R injury, and to define the signaling mechanisms in this process. Methods: Male rats were treated with BBR (200 mg·kg -1 ·d -1 , ig) for 2 weeks, and then subjected to MI/R surgery. Cardiac dimensions and function were assessed using echocardiography. Myocardial infarct size and apoptosis was examined. Total serum LDH levels and CK activities, superoxide production, MDA levels and the antioxidant SOD activities in heart tissue were determined. An in vitro study was performed on cultured rat embryonic myocardium-derived cells H9C2 exposed to simulated ischemia/reperfusion (SIR). The expression of apoptotic, ER stress-related and signaling proteins were assessed using Western blot analyses. Results: Pretreatment with BBR significantly reduced MI/R-induced myocardial infarct size, improved cardiac function, and suppressed myocardial apoptosis and oxidative damage. Furthermore, pretreatment with BBR suppressed MI/R-induced ER stress, evidenced by down-regulating the phosphorylation levels of myocardial PERK and eIF2α and the expression of ATF4 and CHOP in heart tissues. Pretreatment with BBR also activated the JAK2/STAT3 signaling pathway in heart tissues, and co-treatment with AG490, a specific JAK2/STAT3 inhibitor, blocked not only the protective effects of BBR, but also the inhibition of BBR on MI/R-induced ER stress. In H9C2 cells, treatment with BBR (50 μmol/L) markedly reduced SIR-induced cell apoptosis, oxidative stress and ER stress, which were abolished by transfection with JAK2 siRNA. Conclusion: BBR ameliorates MI/R injury in rats by activating the AK2/STAT3 signaling pathway and attenuating ER stress-induced apoptosis.Keywords: berberine; myocardial ischemia/reperfusion injury; apoptosis; ER stress; oxidative stress; JAK2/STAT3; AG490 Acta Pharmacologica Sinica (2016) 37: 354-367; doi: 10.1038/aps.2015 published online 25 Jan 2016 Original Article # These authors contributed equally to this work. * To whom correspondence should be addressed. E-mail yunwangww@163.com (Yun WANG);shiqiangyu210@126.com (Shi-qiang YU) Received 2015-08-26 Accepted 2015-11-20 IntroductionIschemic heart disease remains the leading cause of mortality and disability worldwide. Although timely reperfusion therapy is the primary treatment, reperfusion itself results in major cardiac damage, commonly referred to as myocardial ischemia/reperfusion (MI/R) injury [1,2] . The endoplasmic reticulum (ER) is a multifunctional organelle in eukaryotic cells, which participates in the biosynthesis and folding of proteins. MI/R injury is known to result in the accumulation of unfolded proteins in the ER, which causes a severe unfolded protein response (UPR). Persistent UPR eventually ...

Diabetes mellitus (DM) increases myocardial oxidative stress and endoplasmic reticulum (ER) stress. Melatonin confers cardioprotective effect by suppressing oxidative damage. However, the effect and mechanism of melatonin on myocardial ischemia-reperfusion (MI/R) injury in type 2 diabetic state are still unknown. In this study, we developed high-fat diet-fed streptozotocin (HFD-STZ) rat, a well-known type 2 diabetic model, to evaluate the effect of melatonin on MI/R injury with a focus on silent information regulator 1 (SIRT1) signaling, oxidative stress, and PERK/eIF2α/ATF4-mediated ER stress. HFD-STZ treated rats were exposed to melatonin treatment in the presence or the absence of sirtinol (a SIRT1 inhibitor) and subjected to MI/R surgery. Compared with nondiabetic animals, type 2 diabetic rats exhibited significantly decreased myocardial SIRT1 signaling, increased apoptosis, enhanced oxidative stress, and ER stress. Additionally, further reduced SIRT1 signaling, aggravated oxidative damage, and ER stress were found in diabetic animals subjected to MI/R surgery. Melatonin markedly reduced MI/R injury by improving cardiac functional recovery and decreasing myocardial apoptosis in type 2 diabetic animals. Melatonin treatment up-regulated SIRT1 expression, reduced oxidative damage, and suppressed PERK/eIF2α/ATF4 signaling. However, these effects were all attenuated by SIRT1 inhibition. Melatonin also protected high glucose/high fat cultured H9C2 cardiomyocytes against simulated ischemia-reperfusion injury-induced ER stress by activating SIRT1 signaling while SIRT1 siRNA blunted this action. Taken together, our study demonstrates that reduced cardiac SIRT1 signaling in type 2 diabetic state aggravates MI/R injury. Melatonin ameliorates reperfusion-induced oxidative stress and ER stress via activation of SIRT1 signaling, thus reducing MI/R damage and improving cardiac function.

Berberine (BBR) confers cardioprotective effect against myocardial ischemia reperfusion injury (MI/RI). Activation of Notch1/Hairy and enhancer of split 1 (Hes1) signaling also reduces MI/RI. We hypothesize that BBR may protect against MI/RI by modulating Notch1/Hes1-Phosphatase and tensin homolog deleted on chromosome ten (PTEN)/Akt signaling. In this study, male Sprague-Dawley rats were exposed to BBR treatment (200 mg/kg/d) for 2 weeks and then subjected to MI/RI. BBR significantly improved cardiac function recovery and decreased myocardial apoptosis, infarct size, serum creatine kinase and lactate dehydrogenase levels. Furthermore, in cultured H9c2 cardiomyocytes, BBR (50 μmol/L) attenuated simulated ischemia/reperfusion-induced myocardial apoptosis. Both in vivo and in vitro study showed that BBR treatment up-regulates Notch1 intracellular domain, Hes1, Bcl-2 expression and p-Akt/Akt ratio, down-regulates Bax Caspase-3 and cleaved Caspase-3 expression. However, the anti-apoptotic effect conferred by BBR was blocked by Notch1 siRNA, Hes1 siRNA or LY294002 (the specific inhibitor of Akt signaling) in the cultured cardiomyocytes. In summary, our results demonstrate that BBR treatment attenuates MI/RI by modulating Notch1/Hes1-PTEN/Akt signaling.

Berberine (BBR) exerts potential protective effect against myocardial ischemia/reperfusion (MI/R) injury. Activation of silent information regulator 1 (SIRT1) signaling attenuates MI/R injury by reducing oxidative damage and inflammation response. This study investigated the antioxidative and anti-inflammatory effects of BBR treatment in MI/R condition and elucidated its potential mechanisms. Sprague-Dawley rats were treated with BBR in the absence or presence of the SIRT1 inhibitor sirtinol (Stnl) and then subjected to MI/R injury. BBR conferred cardioprotective effects by improving postischemic cardiac function, decreasing infarct size, reducing apoptotic index, diminishing serum creatine kinase and lactate dehydrogenase levels, upregulating SIRT1, Bcl-2 expressions, and downregulating Bax and caspase-3 expressions. Stnl attenuated these effects by inhibiting SIRT1 signaling. BBR treatment also reduced myocardium superoxide generation, gp91phox expression, malondialdehyde (MDA) level, and cardiac inflammatory markers and increased myocardium superoxide dismutase (SOD) level. However, these effects were also inhibited by Stnl. Consistently, BBR conferred similar antioxidative and anti-inflammatory effects against simulated ischemia reperfusion injury in cultured H9C2 cardiomyocytes. SIRT1 siRNA administration also abolished these effects. In summary, our results demonstrate that BBR significantly improves post-MI/R cardiac function recovery and reduces infarct size against MI/R injury possibly due to its strong antioxidative and anti-inflammatory activity. Additionally, SIRT1 signaling plays a key role in this process.

Melatonin confers profound protective effect against myocardial ischemia-reperfusion injury (MI/RI). Activation of Notch1/Hairy and enhancer of split 1 (Hes1) signaling also ameliorates MI/RI. We hypothesize that melatonin attenuates MI/RI-induced oxidative damage by activating Notch1/Hes1 signaling pathway with phosphatase and tensin homolog deleted on chromosome 10 (Pten)/Akt acting as the downstream signaling pathway in a melatonin membrane receptor-dependent manner. Male Sprague Dawley rats were treated with melatonin (10 mg/kg/day) for 4 wk and then subjected to MI/R surgery. Melatonin significantly improved cardiac function and decreased myocardial apoptosis and oxidative damage. Furthermore, in cultured H9C2 cardiomyocytes, melatonin (100 μmol/L) attenuated simulated ischemia-reperfusion (SIR)-induced myocardial apoptosis and oxidative damage. Both in vivo and in vitro study demonstrated that melatonin treatment increased Notch1, Notch1 intracellular domain (NICD), Hes1, Bcl-2 expressions, and p-Akt/Akt ratio and decreased Pten, Bax, and caspase-3 expressions. However, these protective effects conferred by melatonin were blocked by DAPT (the specific inhibitor of Notch1 signaling), luzindole (the antagonist of melatonin membrane receptors), Notch1 siRNA, or Hes1 siRNA administration. In summary, our study demonstrates that melatonin treatment protects against MI/RI by modulating Notch1/Hes1 signaling in a receptor-dependent manner and Pten/Akt signaling pathways are key downstream mediators.

BackgroundOver the last two or three decades, the pace of development of treatments for osteosarcoma tends has been slow. Novel effective therapies for osteosarcoma are still lacking. Previously, we reported that tumor-suppressing STF cDNA 3 (TSSC3) functions as an imprinted tumor suppressor gene in osteosarcoma; however, the underlying mechanism by which TSSC3 suppresses the tumorigenesis and metastasis remain unclear.MethodsWe investigated the dynamic expression patterns of TSSC3 and autophagy-related proteins (autophagy related 5 (ATG5) and P62) in 33 human benign bone tumors and 58 osteosarcoma tissues using immunohistochemistry. We further investigated the correlations between TSSC3 and autophagy in osteosarcoma using western blotting and transmission electronic microscopy. CCK-8, Edu, and clone formation assays; wound healing and Transwell assays; PCR; immunohistochemistry; immunofluorescence; and western blotting were used to investigated the responses in TSSC3-overexpressing osteosarcoma cell lines, and in xenografts and metastasis in vivo models, with or without autophagy deficiency caused by chloroquine or ATG5 silencing.ResultsWe found that ATG5 expression correlated positively with TSSC3 expression in human osteosarcoma tissues. We demonstrated that TSSC3 was an independent prognostic marker for overall survival in osteosarcoma, and positive ATG5 expression associated with positive TSSC3 expression suggested a favorable prognosis for patients. Then, we showed that TSSC3 overexpression enhanced autophagy via inactivating the Src-mediated PI3K/Akt/mTOR pathway in osteosarcoma. Further results suggested autophagy contributed to TSSC3-induced suppression of tumorigenesis and metastasis in osteosarcoma in vitro and in vivo models.ConclusionsOur findings highlighted, for the first time, the importance of autophagy as an underlying mechanism in TSSC3-induced antitumor effects in osteosarcoma. We also revealed that TSSC3-associated positive ATG5 expression might be a potential predictor of favorable prognosis in patients with osteosarcoma.Electronic supplementary materialThe online version of this article (10.1186/s13046-018-0856-6) contains supplementary material, which is available to authorized users.

Stress hyperglycemia is commonly observed in patients suffering from ischemic heart disease. It not only worsens cardiovascular prognosis but also attenuates the efficacies of various cardioprotective agents. This study aimed to investigate the protective effect of melatonin against myocardial ischemia-reperfusion (MI/R) injury in acute hyperglycemic state with a focus on Notch1/Hes1/Akt signaling and intracellular thioredoxin (Trx) system. Sprague Dawley rats were subjected to MI/R surgery and high-glucose (HG, 500 g/L) infusion (4 mL/kg/h) to induce temporary hyperglycemia. Rats were treated with or without melatonin (10 mg/kg/d) during the operation. Furthermore, HG (33 mmol/L)-incubated H9c2 cardiomyoblasts were treated in the presence or absence of luzindole (a competitive melatonin receptor antagonist), DAPT (a γ-secretase inhibitor), LY294002 (a PI3-kinase/Akt inhibitor), or thioredoxin-interacting protein (Txnip) adenoviral vectors. We found that acute hyperglycemia aggravated MI/R injury by suppressing Notch1/Hes1/Akt signaling and intracellular Trx activity. Melatonin treatment effectively ameliorated MI/R injury by reducing infarct size, myocardial apoptosis, and oxidative stress. Moreover, melatonin also markedly enhanced Notch1/Hes1/Akt signaling and rescued intracellular Trx system by upregulating Notch1, N1ICD, Hes1, and p-Akt expressions, increasing Trx activity, and downregulating Txnip expression. However, these effects were blunted by luzindole, DAPT, or LY294002. Additionally, Txnip overexpression not only decreased Trx activity, but also attenuated the cytoprotective effect of melatonin. We conclude that impaired Notch1 signaling aggravates MI/R injury in acute hyperglycemic state. Melatonin rescues Trx system by reducing Txnip expression via Notch1/Hes1/Akt signaling in a membrane receptor-dependent manner. Its role as a prophylactic/therapeutic drug deserves further clinical study.

Recently, we demonstrated that melatonin reduced protein kinase RNA (PKR)-like ER kinase (PERK)-eukaryotic initiation factor 2 alpha (eIF2α)-activating transcription factor-4 (ATF4)-mediated myocardial endoplasmic reticulum (ER) stress and apoptosis during myocardial ischemia-reperfusion (MI/R) injury. However, the underlying mechanisms are still not clear. Myocardial reperfusion injury salvage kinase (RISK) pathway as well as survivor activating factor enhancement (SAFE) pathway are two pivotal intrinsic pro-survival signaling cascades. In this study, we performed in vivo and in vitro experiment to investigate the ameliorative effect of melatonin on ER stress with a focus on RISK and SAFE pathways interaction. Male C57Bl/6 mice received melatonin (300 μg/25 g/day, 3 days before MI/R surgery; 300 μg/25 g, 25 min before the onset of ischemia) pre-treatment with or without the administration of LY294002 (a PI3K/Akt inhibitor), U0126 (an ERK1/2 inhibitor) or AG490 (a STAT3 pathway inhibitor). H9c2 cells were pre-treated with melatonin (100 μM, 8 h) in the presence or absence of LY294002, U0126 or AG490. Compared with the I/R-injured group, melatonin effectively reduced myocardial apoptosis, oxidative stress and improved cardiac function. In addition, melatonin pre-treatment also increased the phosphorylation of Akt, GSK-3β, ERK1/2 and STAT3 and reduced PERK-eIF2α-ATF4-mediated ER stress. However, these effects were blocked by LY294002, U0126 or AG490. Additionally, either LY294002 or U0126 treatment could inhibit STAT3 phosphorylation, whereas AG490 administration also reduced both Akt and ERK1/2 phosphorylation, indicating an interplay exists between RISK and SAFE pathways in melatonin's cardioprotective effect. In summary, our study demonstrates that RISK and SAFE pathways mediate the cardioprotective effect of melatonin against MI/R injury. Melatonin pre-treatment attenuates PERK-eIF2α-ATF4-mediated ER stress and apoptosis during MI/R injury via RISK and SAFE pathways interaction.