Heart failure in patients is associated with downregulation of mitochondrial quality control genes.

BACKGROUND: Mitochondrial dysfunction is one of key factors causing heart failure. We performed a comprehensive analysis of expression of mitochondrial quality control (MQC) genes in heart failure. METHODS: Myocardial samples were obtained from patients with ischemic and dilated cardiomyopathy in a terminal stage of heart failure and donors without heart disease. Using quantitative real-time PCR, we analysed a total of 45 MQC genes belonging to mitochondrial biogenesis, fusion-fission balance, mitochondrial unfolded protein response (UPRmt), translocase of the inner membrane (TIM) and mitophagy. Protein expression was analysed by ELISA and immunohistochemistry. RESULTS: The following genes were downregulated in ischemic and dilated cardiomyopathy: COX1, NRF1, TFAM, SIRT1, MTOR, MFF, DNM1L, DDIT3, UBL5, HSPA9, HSPE1, YME1L, LONP1, SPG7, HTRA2, OMA1, TIMM23, TIMM17A, TIMM17B, TIMM44, PAM16, TIMM22, TIMM9, TIMM10, PINK1, PARK2, ROTH1, PARL, FUNDC1, BNIP3, BNIP3L, TPCN2, LAMP2, MAP1LC3A and BECN1. Moreover, MT-ATP8, MFN2, EIF2AK4 and ULK1 were downregulated in heart failure from dilated, but not ischemic cardiomyopathy. VDAC1 and JUN were only genes that exhibited significantly different expression between ischemic and dilated cardiomyopathy. Expression of PPARGC1, OPA1, JUN, CEBPB, EIF2A, HSPD1, TIMM50 and TPCN1 was not significantly different between control and any form of heart failure. TOMM20 and COX proteins were downregulated in ICM and DCM. CONCLUSIONS: Heart failure in patients with ischemic and dilated cardiomyopathy is associated with downregulation of large number of UPRmt, mitophagy, TIM and fusion-fission balance genes. This indicates multiple defects in MQC and represents one of potential mechanisms underlying mitochondrial dysfunction in patients with heart failure.

Isoflurane protects cardiomyocytes and mitochondria by immediate and cytosol-independent action at reperfusion.

BACKGROUND AND PURPOSE: The volatile anaesthetic isoflurane protects the heart from ischaemia and reperfusion (I/R) injury when applied at the onset of reperfusion [anaesthetic postconditioning (APoC)]. However, the mechanism of APoC-mediated protection is unknown. In this study, we examined the effect of APoC on mitochondrial bioenergetics, mitochondrial matrix pH (pH(m)) and cytosolic pH (pH(i)), and intracellular Ca(2+). EXPERIMENTAL APPROACH: Cardiac mitochondria from Wistar rats were isolated after in vivo I/R with or without APoC (1.4%-vol isoflurane, 1 minimum alveolar concentration), and mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential (DeltaPsi(m)), and oxygen consumption were assessed. In isolated cardiomyocytes and isolated mitochondria I/R injury was produced in vitro, with or without APoC (0.5 mM isoflurane). Intracellular Ca(2+), pH(m), pH(i) and DeltaPsi(m) were monitored with SNARF-1, TMRE and fluo-4, respectively. Myocyte survival was assessed when APoC was induced at pH 7.4 and 7.8. In isolated mitochondria oxygen consumption and ATP synthesis were measured. KEY RESULTS: In vivo APoC protected against mPTP opening, slowed mitochondrial respiration and depolarized mitochondria. APoC decreased the number of hypercontracted cardiomyocytes at pH 7.4, but not at pH 7.8. APoC attenuated intracellular Ca(2+) accumulation, maintained lower pH(m), and preserved DeltaPsi(m) during reoxygenation. Isoflurane did not affect the regulation of cytosolic pH. In mitochondria, APoC preserved ATP production rate and respiration. CONCLUSIONS AND IMPLICATIONS: At reperfusion, APoC inhibited mitochondrial respiration, depolarized mitochondria and acidified pH(m). These events may lead to inhibition of mPTP opening and, consequently, to preserved DeltaPsi(m) and ATP synthesis. This reduces intracellular Ca(2+) overload and cell death.

Accelerated inactivation of cardiac L-type calcium channels triggered by anaesthetic-induced preconditioning.

BACKGROUND AND PURPOSE: Cardioprotection against ischaemia by anaesthetic-induced preconditioning (APC) is well established. However, the mechanism underlying Ca(2+) overload attenuation by APC is unknown. The effects of APC by isoflurane on the cardiac L-type Ca channel were investigated. EXPERIMENTAL APPROACH: In a model of in vivo APC, Wistar rats were exposed to isoflurane (1.4%), delivered via a vaporizer in an enclosure, prior to thoracotomy. The Dahl S rats were similarly preconditioned to determine strain-dependent effects. Whole-cell patch clamp using cardiac ventricular myocytes was used to determine the L-type Ca(2+) current (I(Ca,L)) characteristics and calmodulin (CaM) levels were determined by Western blot analysis. Cytosolic Ca(2+) levels were monitored using fluo-4-AM. Action potential (AP) simulations examined the effects of APC. KEY RESULTS: In Wistar rats, APC significantly accelerated I(Ca,L) inactivation kinetics. This was abolished when external Ca(2+) was replaced with Ba(2+), suggesting that Ca(2+)-dependent inactivation of I(Ca,L) was modulated by APC. Expression levels of CaM, a determinant of I(Ca,L) inactivation, were not affected. Attenuation of cytosolic Ca(2+) accumulation following oxidative stress was observed in the APC group. Simulations showed that the accelerated inactivation of I(Ca,L) resulted in a shortening of the AP duration. The Dahl S rat strain was resistant to APC and changes in I(Ca,L) inactivation were not observed in cardiomyocytes prepared from these rats. CONCLUSIONS AND IMPLICATIONS: APC triggered persistent changes in the inactivation of cardiac L-type Ca channels. This can potentially lead to a reduction in Ca(2+) influx and attenuation of Ca(2+) overload during ischaemia/reperfusion.