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Aims: Transforming growth factor β (TGF‐β) signalling is one of the critical pathways in fibroblast activation, and several drugs targeting the TGF‐β/Smad signalling pathway in heart failure with cardiac fibrosis are being tested in clinical trials. Some caveolins and cavins, which are components of caveolae on the plasma membrane, are known for their association with the regulation of TGF‐β signalling. Cavin‐2 is particularly abundant in fibroblasts; however, the detailed association between Cavin‐2 and cardiac fibrosis is still unclear. We tried to clarify the involvement and role of Cavin‐2 in fibroblasts and cardiac fibrosis. Methods and results: To clarify the role of Cavin‐2 in cardiac fibrosis, we performed transverse aortic constriction (TAC) operations on four types of mice: wild‐type (WT), Cavin‐2 null (Cavin‐2 KO), Cavin‐2flox/flox, and activated fibroblast‐specific Cavin‐2 conditional knockout (Postn‐Cre/Cavin‐2flox/flox, Cavin‐2 cKO) mice. We collected mouse embryonic fibroblasts (MEFs) from WT and Cavin‐2 KO mice and investigated the effect of Cavin‐2 in fibroblast trans‐differentiation into myofibroblasts and associated TGF‐β signalling. Four weeks after TAC, cardiac fibrotic areas in both the Cavin‐2 KO and the Cavin‐2 cKO mice were significantly decreased compared with each control group (WT 8.04 ± 1.58% vs. Cavin‐2 KO 0.40 ± 0.03%, P < 0.01; Cavin‐2flox/flox, 7.19 ± 0.50% vs. Cavin‐2 cKO 0.88 ± 0.44%, P < 0.01). Fibrosis‐associated mRNA expression (Col1a1, Ctgf, and Col3) was significantly attenuated in the Cavin‐2 KO mice after TAC. α1 type I collagen deposition and non‐vascular αSMA‐positive cells (WT 43.5 ± 2.4% vs. Cavin‐2 KO 25.4 ± 3.2%, P < 0.01) were reduced in the heart of the Cavin‐2 cKO mice after TAC operation. The levels of αSMA protein (0.36‐fold, P < 0.05) and fibrosis‐associated mRNA expression (Col1a1, 0.69‐fold, P < 0.01; Ctgf, 0.27‐fold, P < 0.01; Col3, 0.60‐fold, P < 0.01) were decreased in the Cavin‐2 KO MEFs compared with the WT MEFs. On the other hand, αSMA protein levels were higher in the Cavin‐2 overexpressed MEFs compared with the control MEFs (2.40‐fold, P < 0.01). TGF‐β1‐induced Smad2 phosphorylation was attenuated in the Cavin‐2 KO MEFs compared with WT MEFs (0.60‐fold, P < 0.01). Heat shock protein 90 protein levels were significantly reduced in the Cavin‐2 KO MEFs compared with the WT MEFs (0.69‐fold, P < 0.01). Conclusions: Cavin‐2 loss suppressed fibroblast trans‐differentiation into myofibroblasts through the TGF‐β/Smad signalling. The loss of Cavin‐2 in cardiac fibroblasts suppresses cardiac fibrosis and may maintain cardiac function. [ABSTRACT FROM AUTHOR]

Aims: Cardiac ischaemia/reperfusion (I/R) injury remains a critical issue in the therapeutic management of ischaemic heart failure. Although mild hypothermia has a protective effect on cardiac I/R injury, more rapid and safe methods that can obtain similar results to hypothermia therapy are required. 2‐Methyl‐2‐thiazoline (2MT), an innate fear inducer, causes mild hypothermia resulting in resistance to critical hypoxia in cutaneous or cerebral I/R injury. The aim of this study is to demonstrate the protective effect of systemically administered 2MT on cardiac I/R injury and to elucidate the mechanism underlying this effect. Methods and results: A single subcutaneous injection of 2MT (50 mg/kg) was given prior to reperfusion of the I/R injured 10 week‐old male mouse heart and its efficacy was evaluated 24 h after the ligation of the left anterior descending coronary artery. 2MT preserved left ventricular systolic function following I/R injury (ejection fraction, %: control 37.9 ± 6.7, 2MT 54.1 ± 6.4, P < 0.01). 2MT also decreased infarct size (infarct size/ischaemic area at risk, %: control 48.3 ± 12.1, 2MT 25.6 ± 4.2, P < 0.05) and serum cardiac troponin levels (ng/mL: control 8.9 ± 1.1, 2MT 1.9 ± 0.1, P < 0.01) after I/R. Moreover, 2MT reduced the oxidative stress‐exposed area within the heart (%: control 25.3 ± 4.7, 2MT 10.8 ± 1.4, P < 0.01). These results were supported by microarray analysis of the mouse hearts. 2MT induced a transient, mild decrease in core body temperature (°C: −2.4 ± 1.4), which gradually recovered over several hours. Metabolome analysis of the mouse hearts suggested that 2MT minimized energy metabolism towards suppressing oxidative stress. Furthermore, 18F‐fluorodeoxyglucose‐positron emission tomography/computed tomography imaging revealed that 2MT reduced the activity of brown adipose tissue (standardized uptake value: control 24.3 ± 6.4, 2MT 18.4 ± 5.8, P < 0.05). 2MT also inhibited mitochondrial respiration and glycolysis in rat cardiomyoblasts. Conclusions: We identified the cardioprotective effect of systemically administered 2MT on cardiac I/R injury by sparing energy metabolism with reversible hypothermia. Our results highlight the potential of drug‐induced hypothermia therapy as an adjunct to coronary intervention in severe ischaemic heart disease. [ABSTRACT FROM AUTHOR]

Background Ischemia/reperfusion (I/R) injury is a critical issue in the development of treatment strategies for ischemic heart disease. MURC (muscle-restricted coiled-coil protein)/Cavin-4 (caveolae-associated protein 4), which is a component of caveolae, is involved in the pathophysiology of dilated cardiomyopathy and cardiac hypertrophy. However, the role of MURC in cardiac I/R injury remains unknown. Methods and Results The systems network genomic analysis based on PC-corr network inference on microarray data between wild-type and MURC knockout mouse hearts predicted a network of discriminating genes associated with reactive oxygen species. To demonstrate the prediction, we analyzed I/R-injured mouse hearts. MURC deletion decreased infarct size and preserved heart contraction with reactive oxygen species-related molecule EGR1 (early growth response protein 1) and DDIT4 (DNA-damage-inducible transcript 4) suppression in I/R-injured hearts. Because PC-corr network inference integrated with a protein-protein interaction network prediction also showed that MURC is involved in the apoptotic pathway, we confirmed the upregulation of STAT3 (signal transducer and activator of transcription 3) and BCL2 (B-cell lymphoma 2) and the inactivation of caspase 3 in I/R-injured hearts of MURC knockout mice compared with those of wild-type mice. STAT3 inhibitor canceled the cardioprotective effect of MURC deletion in I/R-injured hearts. In cardiomyocytes exposed to hydrogen peroxide, MURC overexpression promoted apoptosis and MURC knockdown inhibited apoptosis. STAT3 inhibitor canceled the antiapoptotic effect of MURC knockdown in cardiomyocytes. Conclusions Our findings, obtained by prediction from systems network genomic analysis followed by experimental validation, suggested that MURC modulates cardiac I/R injury through the regulation of reactive oxygen species-induced cell death and STAT3-meditated antiapoptosis. Functional inhibition of MURC may be effective in reducing cardiac I/R injury.