The anticancer therapy of doxorubicin (Dox) has been limited by its acute and chronic cardiotoxicity. In addition to a causative role of oxidative stress, autophagy appears to play an important role in the regulation of Dox-induced cardiotoxicity. However, the underlying mechanisms remain unclear. Accordingly, we explored a role of nuclear factor erythroid-2 related factor 2 (Nrf2) in Dox-induced cardiomyopathy with a focus on myocardial oxidative stress and autophagic activity. In wild type (WT) mice, a single intraperitoneal injection of 25 mg/kg Dox rapidly induced cardiomyocyte necrosis and cardiac dysfunction, which were associated with oxidative stress, impaired autophagy, and accumulated polyubiquitinated protein aggregates. However, these Dox-induced adverse effects were exaggerated in Nrf2 knockout (Nrf2−/−) mice. In cultured cardiomyocytes, overexpression of Nrf2 increased the steady levels of LC3-II, ameliorated Dox-induced impairment of autophagic flux and accumulation of ubiquitinated protein aggregates, and suppressed Dox-induced cytotoxicity, whereas knockdown of Nrf2 exerted opposite effects. Moreover, the exaggerated adverse effects in Dox-intoxicated Nrf2 depleted cardiomyocytes were dramatically attenuated by forced activation of autophagy via overexpression of autophagy related gene 5 (Atg5). Thus, these results suggest that Nrf2 is likely an endogenous suppressor of Dox-induced cardiotoxicity by controlling both oxidative stress and autophagy in the heart.

The conserved cylindromatosis (CYLD) codes for a deubiquitinating enzyme and is a crucial regulator of diverse cellular processes such as immune responses, inflammation, death, and proliferation. It directly regulates multiple key signaling cascades, such as the Nuclear Factor kappa B [NF-kB] and the Mitogen-Activated Protein Kinase (MAPK) pathways, by its catalytic activity on polyubiquitinated key intermediates. Several lines of emerging evidence have linked CYLD to the pathogenesis of various maladies, including cancer, poor infection control, lung fibrosis, neural development, and now cardiovascular dysfunction. While CYLD-mediated signaling is cell type and stimuli specific, the activity of CYLD is tightly controlled by phosphorylation and other regulators such as Snail. This review explores a broad selection of current and past literature regarding CYLD’s expression, function and regulation with emerging reports on its role in cardiovascular disease.

Nuclear factor erythroid-2 related factor 2 (Nrf2) is a master transcription factor that controls the basal and inducible expression of a battery of antioxidant genes and other cytoprotective phase II detoxifying enzymes. While knockout of Nrf2 exaggerates cardiac pathological remodeling and dysfunction in diverse pathological settings, pharmacological activation of Nrf2 protects against cardiomyocyte injury and cardiac dysfunction. In contrast, there is also a concern that the chronic activation of Nrf2 secondary to oxidative stress is a contributing mechanism for the reductive stress-mediated heart failure. However, a direct link between cardiac specific activation of Nrf2 and cardiac protection or dysfunction in vivo remains to be established. Therefore, we investigated the effect of cardiomyocyte-specific transgenic activation of Nrf2 (Nrf2ctg) on cardiac pathological remodeling and dysfunction. We found that the cardiomyocyte-specific activation of Nrf2 suppressed myocardial oxidative stress as well as cardiac apoptosis, fibrosis, hypertrophy, and dysfunction in a setting of sustained pressure overload induced by transverse aortic arch constriction (TAC) in mice. Notably, the constitutive activation of Nrf2 increased the steady level of autophagosomes while decreasing the ubiquitinated protein aggregates in the heart after TAC. Nrf2 gene gain- and loss-of-function approaches revealed that Nrf2 enhances autophagosome formation and autophagic flux in cardiomyocytes. Unexpectedly, while Nrf2 minimally regulated apoptosis, it suppressed significantly the proteotoxic necrosis in cardiomyocytes. In addition, Nrf2 attenuated the proteocytotoxicity presumably via enhancing autophagy-mediated clearance of ubiquitinated protein aggregates in cardiomyocytes. Taken together, we demonstrated for the first time that cardiac specific activation of Nrf2 suppresses cardiac maladaptive remodeling and dysfunction most likely by enhancing autophagic clearance of toxic protein aggregates in the heart.

Exercise offers short-term and long-term health benefits, including an increased metabolic rate and energy expenditure in myocardium. The newly-discovered exercise-induced myokine, irisin, stimulates conversion of white into brown adipocytes as well as increased mitochondrial biogenesis and energy expenditure. Remarkably, irisin is highly expressed in myocardium, but its physiological effects in the heart are unknown. The objective of this work is to investigate irisin’s potential multifaceted effects on cardiomyoblasts and myocardium. For this purpose, H9C2 cells were treated with recombinant irisin produced in yeast cells (r-irisin) and in HEK293 cells (hr-irisin) for examining its effects on cell proliferation by MTT [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and on gene transcription profiles by qRT-PCR. R-irisin and hr-irisin both inhibited cell proliferation and activated genes related to cardiomyocyte metabolic function and differentiation, including myocardin, follistatin, smooth muscle actin, and nuclear respiratory factor-1. Signal transduction pathways affected by r-irisin in H9C2 cells and C57BL/6 mice were examined by detecting phosphorylation of PI3K-AKT, p38, ERK or STAT3. We also measured intracellular Ca2+ signaling and mitochondrial thermogenesis and energy expenditure in r-irisin-treated H9C2 cells. The results showed that r-irisin, in a certain concentration rage, could activate PI3K-AKT and intracellular Ca2+ signaling and increase cellular oxygen consumption in H9C2 cells. Our study also suggests the existence of irisin-specific receptor on the membrane of H9C2 cells. In conclusion, irisin in a certain concentration rage increased myocardial cell metabolism, inhibited cell proliferation and promoted cell differentiation. These effects might be mediated through PI3K-AKT and Ca2+ signaling, which are known to activate expression of exercise-related genes such as follistatin and myocardin. This work supports the value of exercise, which promotes irisin release.

Two distinct subtypes of angiotensin (Ang) II receptors, type 1 (AT(1)) and type 2 (AT(2)), have been identified. Vascular smooth muscle cells (VSMCs) usually express AT(1) receptor. To elucidate the direct effects of the AT(2) receptor on the AT(1) receptor in VSMCs, we transfected AT(2) receptor gene into cultured rat VSMCs. Overexpression of AT(2) receptor significantly decreased expression of AT(1a) receptor at both the mRNA and protein levels in the presence and absence of Ang II in VSMCs. Overexpression of AT(2) receptor increased expression of bradykinin and inducible NO in the presence and absence of Ang II in VSMCs. Bradykinin B(2) receptor antagonist HOE-140 and NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) inhibited the decreases in AT(1a) receptor expression by the overexpression of AT(2) receptor in VSMCs. L-Arginine augmented the decrease in AT(1a) receptor expression. Overexpression of AT(2) receptor suppressed basal DNA synthesis and proliferation of VSMCs and abolished response of DNA synthesis to Ang II in VSMCs. Our results demonstrate that overexpression of the AT(2) receptor downregulates AT(1a) receptor expression in rat VSMCs in a ligand-independent manner that is mediated by the bradykinin/NO pathway. Downregulation of AT(1a) receptor is a novel mechanism by which the AT(2) receptor regulates growth and metabolism of VSMCs.