Using a translational approach with an ST-segment myocardial infarction (STEMI) cohort and mouse model of myocardial infarction, we highlighted the role of the secreted IL-6 and MCP-1 cytokines and the STAT3 pathway in heart macrophage recruitment and activation. Cardiac myocytes secrete IL-6 and MCP-1 in response to hypoxic stress, leading to a recruitment and/or polarization of anti-inflammatory macrophages via the STAT3 pathway. In our preclinical model of myocardial infarction, neutralization of IL-6 and MCP-1 or STAT3 pathway reduced infarct size. Together, our data demonstrate that anti-inflammatory macrophages can be deleterious in the acute phase of STEMI.

Gasoline exposure has been widely reported in the literature as being toxic to human health. However, the exact underlying molecular mechanisms triggered by its inhalation have not been thoroughly investigated. We herein present a model of sub‐chronic, static gasoline vapor inhalation in adult female C57BL/6 mice. Animals were exposed daily to either gasoline vapors (0.86 g/animal/90 min) or ambient air for 5 days/week over 7 consecutive weeks. At the end of the study period, toxic and molecular mechanisms underlying the inflammatory, oxidative, and apoptotic effects triggered by gasoline vapors, were examined in the lungs and liver of gasoline‐exposed (GE) mice.

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Mitochondrial diseases are genetic disorders that lead to impaired mitochondrial function, resulting in exercise intolerance and muscle weakness. In patients, muscle fatigue due to defects in mitochondrial oxidative capacities commonly precedes muscle weakness. In mice, deletion of the fast-twitch skeletal muscle-specific Tfam gene (Tfam KO) leads to a deficit in respiratory chain activity, severe muscle weakness and early death. Here, we performed a time-course study of mitochondrial and muscular dysfunctions in 11-and 14-week-old Tfam KO mice, i.e. before and when mice are about to enter the terminal stage, respectively. Although force in the unfatigued state was reduced in Tfam KO mice compared to control littermates (wild type) only at 14 weeks, during repeated submaximal contractions fatigue was faster at both ages. During fatiguing stimulation, total phosphocreatine breakdown was larger in Tfam KO muscle than in wild-type muscle at both ages, whereas phosphocreatine consumption was faster only at 14 weeks. In conclusion, the Tfam KO mouse model represents a reliable model of lethal mitochondrial myopathy in which impaired mitochondrial energy production and premature fatigue occur before muscle weakness and early death.

Ghrelin has a key role in modulating energy metabolism and weight gain. The present study aimed at studying the potential role of ghrelin in the development and/or exacerbation of organ damage in a mouse model of diet-induced obesity. Adult mice were fed one of two diets for 20 weeks: standard high carbohydrate (HC) or high-fat high-sugar (HFHS). Starting week 17, the animals were given regular intraperitoneal ghrelin (160 µg/kg) or saline injections Abdominal fat, serum creatinine, and glucose levels, as well as kidney, liver and heart weight and pathology were assessed. Ghrelin-injected mice showed significant organ damage, which was more exacerbated in HFHS-fed animals. While the HFHS diet was associated with significant liver damage, ghrelin administration did not reverse it. Interestingly, ghrelin administration induced moderate kidney damage and significantly affected the heart by increasing perivascular and myocardium fibrosis, steatosis as well as inflammation. Moreover, serum creatinine levels were higher in the animal group injected with ghrelin. Ghrelin administration was associated with increased functional and structural organ damage, regardless of diet. The present study provides novel evidence of multi-organ physiologic alterations secondary to ghrelin administration.

Following a prolonged exposure to hypoxia–reoxygenation, a partial disruption of the ER-mitochondria tethering by mitofusin 2 (MFN2) knock-down decreases the Ca2+ transfer between the two organelles limits mitochondrial Ca2+ overload and prevents the Ca2+-dependent opening of the mitochondrial permeability transition pore, i.e., limits cardiomyocyte cell death. The impact of the metabolic changes resulting from the alteration of this Ca2+crosstalk on the tolerance to hypoxia–reoxygenation injury remains partial and fragmented between different field of expertise. >In this study, we report that MFN2 loss of function results in a metabolic switch driven by major modifications in energy production by mitochondria. During hypoxia, mitochondria maintain their ATP concentration and, concomitantly, the inner membrane potential by importing cytosolic ATP into mitochondria through an overexpressed ANT2 protein and by decreasing the expression and activity of the ATP hydrolase via IF1. This adaptation further blunts the detrimental hyperpolarisation of the inner mitochondrial membrane (IMM) upon re-oxygenation. These metabolic changes play an important role to attenuate cell death during a prolonged hypoxia–reoxygenation challenge.

The signal transducer and activator of transcription 3, STAT3, transfers cellular signals from the plasma membrane to the nucleus, acting as a signaling molecule and a transcription factor. Reports proposed an additional non-canonical role of STAT3 that could regulate the activity of complexes I and II of the electron transport chain and the opening of the mitochondrial permeability transition pore (PTP) after ischemia-reperfusion in various cell types. The native expression of STAT3 in heart mitochondria, together with a direct versus an indirect transcriptional role in mitochondrial functions, have been recently questioned. The objective of the present study was to investigate the cellular distribution of STAT3 in mouse adult cardiomyocytes under basal and stress conditions, along with assessing its presence and activity in cardiac mitochondria using structural and functional approaches. The analysis of the spatial distribution of STAT3 signal in the cardiomyocytes interestingly showed that it is transversely distributed along the T-tubules and in the nucleus. This distribution was neither affected by hypoxia nor by hypoxia/re‑oxygenation conditions. Focusing on the mitochondrial STAT3 localization, our results suggest that serine-phosphorylated STAT3 (PS727-STAT3) and total STAT3 are detected in crude but not in pure mitochondria of mouse adult cardiomyocytes, under basal and ischemia-reperfusion conditions. The inhibition of STAT3, with a pre-validated non-toxic Stattic dose, had no significant effects on mitochondrial respiration, but a weak effect on the calcium retention capacity. Overall, our results exclusively reveal a unique cellular distribution of STAT3 in mouse adult cardiomyocytes, along the T-tubules and in nucleus, under different conditions. They also challenge the expression and activity of STAT3 in mitochondria of these cells under basal conditions and following ischemia-reperfusion. In addition, our results underline technical methods, complemental to cell fractionation, to evaluate STAT3 roles during hypoxia-reoxygenation and at the interface between nucleus and endoplasmic reticulum.

Cardioprotection methods have been developed to protect the heart against deleterious effects of ischemia reperfusion (IR), among them, postconditioning (PC) was shown to decrease infarct size (IS). Thus, it was shown that deacetylation, a post-translational modification, was crucial for PC success. Our lab recently shown that modification on acetylation level of cyclophilin D (CypD) by sirtuin 3 (SIRT3), a mitochondrial deacetylase, modifies the efficiency of ischemic-postconditionning (IPC). Indeed, it was shown that in absence of SIRT3, CypD is hyperacetylated leading to mPTP opening and cell death and inefficacy of IPC. Moreover, numerous studies have linked the lack of SIRT3 with aging associated pathologies. The goal of this study was to decipher the impact of CypD deacetylation mediated by SIRT3 in PC in the aging context. We submitted young (2 months) and old (≤ 12 months) mice, WT and SIRT3 KO, to IR and IPC. IS were quantified, and mitochondrial protein acetylation was evaluated. In parallel, basal mitochondrial functions and protein acetylation were assessed, as well as deacetylase activity, to estimate the impact of aging. Our results enlightened the importance of SIRT3 for PC success in young mice (25% IS reduction), that is lost in the old mice. We reported no more modification of the acetylation profile neither after IR or IPC in old mice. Moreover, we quantified a significant decrease in deacetylase activity with age (25%), associated to a significant decrease in NAD+ content (60%) with no basal mitochondrial function modification in old mice that could be associated to the loss of IPC efficiency. In accordance with what we demonstrated in young mice, the failure of IPC in old mice could be explained by a lack of CypD deacetylation following IPC stimulus, linked with an alteration of the deacetylase mitochondrial activity associated to a significant decrease in NAD+ mitochondrial content.