No abstract

Cardiac hypertrophy is the main cause of heart failure and sudden death in patients. But the pathogenesis is unclear. Angiotensin II may contribute to cardiac hypertrophy in response to pressure overload. In angiotensin II‐treated cardiomyocytes, there is a larger cross‐sectional area, more apoptosis cells, and a reduction of irisin expression. An increase in P62, an autophagy flux index, as well as LC3II, were observed in cardiomyocytes after angiotensin II‐induced injury. Surprisely, irisin supplementation increased LC3II expression and decreased P62 expression, consisted of results of RFP‐GFP‐LC3B adenovirus transfection, and reduced cardiomyocyte apoptosis, meanwhile, the protection of irisin was reversed by the autophagy inhibitor 3‐methyladenine. In animal experiments, overexpression of irisin reduced cardiomyocyte apoptosis and alleviated myocardial hypertrophy caused by pressure overload. The above results indicate that irisin‐induced protective autophagy and alleviated the apoptosis signaling pathway in cardiomyocytes, consequently reducing cardiomyocyte apoptosis after angiotensin II‐induced injury. Hence, increasing irisin expression may be a new way to improve cardiac function and quality of life in patients with cardiac hypertrophy.

Endoplasmic reticulum stress (ERS) is usually involved in tumor development and progression, and anticancer agents have recently been recognized to induce ERS. Cucurbitacin‐I showed a potent anticancer action by inducing apoptosis through the inhibition of signal transducer and activator of transcription 3 pathway and triggering autophagic cell death. It is not known whether ERS mediates the cancer cell death induced by cucurbitacin‐I. Here, we investigated the role of ERS in cucurbitacin‐I‐treated SKOV3 ovarian cancer cells and PANC‐1 pancreatic cancer cells. We confirmed that cucurbitacin‐I caused cell death and stirred excessive ERS levels by activating inositol requiring enzyme 1α (IRE1α) and protein kinase R‐like endoplasmic reticulum kinase (PERK), as well as PERK downstream factors, including IRE1α and C/EBP homologous protein, but not activating transcription factor 6 (ATF6α) pathway, which was in parallel with the increased Bax and caspase‐12‐dependent ERS‐associated apoptosis, autophagy and autophagy flux levels and caspase‐independent nonapoptotic cell death. Furthermore, 4‐phenylbutyrate, an ERS inhibitor, suppressed cucurbitacin‐I‐induced apoptosis, autophagy, autophagy flux, and autophagic cell death. Simultaneously, there are positive correlations among ERS and cucurbitacin‐I‐induced reactive oxygen species and Ca 2+. Our results suggested that cucurbitacin‐I‐induced cancer cell death through the excessive ERS and CHOP‐Bax and caspase‐12‐dependent ERS‐associated apoptosis, as well as ERS‐dependent autophagy, autophagy flux, and caspase‐independent nonapoptotic cell death. These novel signaling insights may be useful for developing new, effective anticancer strategies in oncotherapy.

No abstract

Sirt6, a class III NAD + -dependent deacetylase of the sirtuin family, is a highly speci c H3 deacetylase and plays important roles in regulating cellular growth and death. The induction of oxidative stress and death are the crucial mechanisms involved in cardiomyocyte damage and cardiac dysfunction in doxorubicininduced cardiotoxocity, but the regulatory role of Sirt6 in the fate of DOX-impaired cardiomyocytes is poorly understood. In this study, we exposed heterozygous Sirt6 knockout (Sirt6 +/− ) mice and their littermates as well as cultured neonatal rat cardiomyocytes to DOX, then investigated how Sirt6 mitigates oxidative stress and myocardial injury in the DOX-treated myocardium. Sirt6 partial knockout or silencing worsened myocardial damage, cardiac remodeling, and oxidative stress in mice or cultured cardiomyocytes with DOX challenge. Cardiomyocytes infected with adenoviral constructs encoding Sirt6 showed reversal of this DOX-induced damage. Intriguingly, Sirt6 reduced oxidative stress injury by upregulating endogenous antioxidant levels, interacted with oxidative stress-stirred p53, and acted as a co-repressor of p53 in nuclei. Sirt6 was recruited by p53 to the promoter regions of the target genes Fas and FasL and further suppressed p53 transcription activity by reducing histone acetylation. Sirt6 inhibited Fas/FasL signaling and attenuated both Fas-FADD-caspase-8 apoptotic and Fas-RIP3 necrotic pathways. These results suggest that Sirt6 protects the heart against DOX-induced cardiotoxity by upregulating endogenous antioxidants, as well as suppressing oxidative stress and cell death signaling pathways dependent on ROS-stirred p53 transcriptional activation, thus reducing Fas-FasL-mediated apoptosis and necrosis.