HS regulated the acetylation level and activities of enzymes in fatty acid oxidation and glucose oxidation in cardiac tissues of db/db mice. Exogenous HS decreased mitochondrial acetylation level through upregulating the expression and activity of SIRT3 in vivo and in vitro. HS induced a switch in cardiac energy substrate utilization from fatty acid oxidation to glucose.

Diabetic cardiomyopathy (DCM) is a serious complication of diabetes. Hydrogen sulphide (H2S), a newly found gaseous signalling molecule, has an important role in many regulatory functions. The purpose of this study is to investigate the effects of exogenous H2S on autophagy and its possible mechanism in DCM induced by type II diabetes (T2DCM). In this study, we found that sodium hydrosulphide (NaHS) attenuated the augment in left ventricular (LV) mass and increased LV volume, decreased reactive oxygen species (ROS) production and ameliorated H2S production in the hearts of db/db mice. NaHS facilitated autophagosome content degradation, reduced the expression of P62 (a known substrate of autophagy) and increased the expression of microtubule-associated protein 1 light chain 3 II. It also increased the expression of autophagy-related protein 7 (ATG7) and Beclin1 in db/db mouse hearts. NaHS increased the expression of Kelch-like ECH-associated protein 1 (Keap-1) and reduced the ubiquitylation level in the hearts of db/db mice. 1,4-Dithiothreitol, an inhibitor of disulphide bonds, increased the ubiquitylation level of Keap-1, suppressed the expression of Keap-1 and abolished the effects of NaHS on ubiquitin aggregate clearance and ROS production in H9C2 cells treated with high glucose and palmitate. Overall, we concluded that exogenous H2S promoted ubiquitin aggregate clearance via autophagy, which might exert its antioxidative effect in db/db mouse myocardia. Moreover, exogenous H2S increased Keap-1 expression by suppressing its ubiquitylation, which might have an important role in ubiquitin aggregate clearance via autophagy. Our findings provide new insight into the mechanisms responsible for the antioxidative effects of H2S in the context of T2DCM.

Communication between the SR (sarcoplasmic reticulum, SR) and mitochondria is important for cell survival and apoptosis. The SR supplies Ca2+ directly to mitochondria via inositol 1,4,5-trisphosphate receptors (IP3Rs) at close contacts between the two organelles referred to as mitochondrion-associated ER membrane (MAM). Although it has been demonstrated that CaR (calcium sensing receptor) activation is involved in intracellular calcium overload during hypoxia/reoxygenation (H/Re), the role of CaR activation in the cardiomyocyte apoptotic pathway remains unclear. We postulated that CaR activation plays a role in the regulation of SR-mitochondrial inter-organelle Ca2+ signaling, causing apoptosis during H/Re. To investigate the above hypothesis, cultured cardiomyocytes were subjected to H/Re. We examined the distribution of IP3Rs in cardiomyocytes via immunofluorescence and Western blotting and found that type 3 IP3Rs were located in the SR. [Ca2+]i, [Ca2+]m and [Ca2+]SR were determined using Fluo-4, x-rhod-1 and Fluo 5N, respectively, and the mitochondrial membrane potential was detected with JC-1 during reoxygenation using laser confocal microscopy. We found that activation of CaR reduced [Ca2+]SR, increased [Ca2+]i and [Ca2+]m and decreased the mitochondrial membrane potential during reoxygenation. We found that the activation of CaR caused the cleavage of BAP31, thus generating the pro-apoptotic p20 fragment, which induced the release of cytochrome c from mitochondria and the translocation of bak/bax to mitochondria. Taken together, these results reveal that CaR activation causes Ca2+ release from the SR into the mitochondria through IP3Rs and induces cardiomyocyte apoptosis during hypoxia/reoxygenation.

Ischaemia-reperfusion injury (IRI) is the predominant cause of acute kidney injury. Nevertheless, the underlying molecular mechanisms are still unclear. The current study investigated the effects of nicorandil on ATP-sensitive potassium (K_ATP) channels and the potential signal transduction pathway(s) in a rat kidney IRI model and in cultured tubular HK-2 cells subjected to oxygen and glucose deprivation/reoxygenation (OGD/R) injury. The standard procedure for IRI was performed in newborn rat kidneys. Pretreatment with nicorandil (10 mg/kg) 2 h prior to induction of IRI improved renal function, attenuated tubule damage, and prevented apoptosis of tubule cells, infiltration of neutrophils and macrophages, and production of inflammatory cytokines interleukin (IL)-6, IL-17 and tumour necrosis factor-a. Ischaemia-reperfusion-induced reduction of K_IR6.2 was restored to normal levels by nicorandil. The activation of the phosphoinositide-3-kinase (PI3K)-Akt-nuclear factor (NF)-κB axis was detected in this rat kidney IRI model, which was blocked by nicorandil. The renoprotection of nicorandil against IRI was abolished by its inhibitor glibenclamide (1 mg/kg). Similar results were obtained in OGD/R-damaged HK-2 cells. Taken together, our findings demonstrated the specific renoprotective role of nicorandil in the newborn rat IRI kidney by decreasing the production of inflammatory cytokines, and restoring the expression of K_IR6.2 potentially through the PI3K-Akt-NF-κB axis.

The calcium-sensing receptor (CaR) is a G protein-coupled receptor. The CaR stimulation elicits phospholipase C-mediated inositol triphosphate formation, leading to an elevation in the level of intracellular calcium released from endoplasmic reticulum (ER). Depletion of ER Ca 2+ leads to ER stress, which is thought to induce apoptosis. Intracellular calcium overload-induced apoptosis in cardiac myocytes during hypoxia-reoxygenation (H ⁄ Re) has been demonstrated. However, the links between CaR, ER stress and apoptosis during H ⁄ Re are unclear. This study hypothesized that the CaR could induce apoptosis in neonatal rat cardiomyocytes during H ⁄ Re via the ER stress pathway. Neonatal rat cardiomyocytes were subjected to 3 hr of hypoxia, followed by 6 hr of reoxygenation. CaR expression was elevated and the number of apoptotic cells was significantly increased, as shown by transferase-mediated dUTP nick end-labelling, with exposure to CaCl 2 , a CaR activator, during H ⁄ Re. The intracellular calcium concentration was significantly elevated and the Ca 2+ concentration in the ER was dramatically decreased during H ⁄ Re with CaCl 2 ; both intracellular and ER calcium concentrations were detected by laser confocal microscopy. Expression of GRP78 (glucose-regulated protein 78), the cleavage products of ATF6 (activating transcription factor 6), phospho-PERK [pancreatic ER kinase (PKR)-like ER kinase], the activated fragments of caspase-12, and phospho-JNK (c-Jun NH 2 -terminal kinase) were increased following exposure to CaCl 2 during H ⁄ Re. Our results confirmed that the activated CaR can induce cardiomyocyte apoptosis via ER stress-associated apoptotic pathways during H ⁄ Re.Reperfusion after ischaemia induces a sequence of events ultimately leading to cellular damage and organ dysfunction. Apoptosis has been confirmed in myocardium after ischaemia ⁄ reperfusion. The mechanisms of apoptosis in cardiac ischaemia-reperfusion are diverse, likely involving many subcellular organelles, such as the endoplasmic reticulum (ER) and mitochondria [1,2] The calcium-sensing receptor (CaR) belongs to the family of type-III G protein-coupled receptors. The CaR stimulation elicits phospholipase C (PLC)-mediated inositol triphosphate (IP 3 ) formation, leading to an elevation in [Ca 2+ ]i [5,6]. In our previous study using isolated hearts, we found that ischaemia-reperfusion induced the activation of CaR, leading to excessive accumulation of intracellular calcium [7]. A number of studies have demonstrated that uncontrolled Ca 2+ leakage from the ER induces ER-dependent apoptosis [8][9][10]. We therefore hypothesized that CaRmediated cardiomyocyte apoptosis may be related to ER stress-associated apoptotic pathways during hypoxia-reoxygenation (H ⁄ Re). Materials and MethodsHeart preparations. Male Wistar rats, weighing 250 € 20 g, were purchased from the Animal Center of Harbin Medical University and treated in accordance with the Guide for Care and Use of Laboratory Animals published by the China National Institutes o...