RESUMEN
Proper control of the mitochondrial Ca2+ uniporter's pore (MCU) is required to allow Ca2+-dependent activation of oxidative metabolism and to avoid mitochondrial Ca2+ overload and cell death. The MCU's gatekeeping and cooperative activation is mediated by the Ca2+-sensing MICU1 protein, which has been proposed to form dimeric complexes anchored to the EMRE scaffold of MCU. We unexpectedly find that MICU1 suppresses inhibition of MCU by ruthenium red/Ru360, which bind to MCU's DIME motif, the selectivity filter. This led us to recognize in MICU1's sequence a putative DIME interacting domain (DID), which is required for both gatekeeping and cooperative activation of MCU and for cell survival. Thus, we propose that MICU1 has to interact with the D-ring formed by the DIME domains in MCU to control the uniporter.
Asunto(s)
Canales de Calcio/metabolismo , Proteínas de Unión al Calcio/metabolismo , Calcio/metabolismo , Proteínas de Transporte de Catión/metabolismo , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Proteínas de Transporte de Membrana Mitocondrial/metabolismo , Compuestos de Rutenio/farmacología , Animales , Proteínas de Unión al Calcio/genética , Proteínas de Transporte de Catión/genética , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Células HEK293 , Hepatocitos/efectos de los fármacos , Hepatocitos/metabolismo , Humanos , Masculino , Potencial de la Membrana Mitocondrial , Ratones , Ratones Noqueados , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/metabolismo , Proteínas de Transporte de Membrana Mitocondrial/genéticaRESUMEN
Mitochondrial Ca2+ uptake is mediated by the mitochondrial uniporter complex (mtCU) that includes a tetramer of the pore-forming subunit, MCU, a scaffold protein, EMRE, and the EF-hand regulatory subunit, MICU1 either homodimerized or heterodimerized with MICU2/3. MICU1 has been proposed to regulate Ca2+ uptake via the mtCU by physically occluding the pore and preventing Ca2+ flux at resting cytoplasmic [Ca2+] (free calcium concentration) and to increase Ca2+ flux at high [Ca2+] due to cooperative activation of MICUs EF-hands. However, mtCU and MICU1 functioning when its EF-hands are unoccupied by Ca2+ is poorly studied due to technical limitations. To overcome this barrier, we have studied the mtCU in divalent-free conditions by assessing the Ru265-sensitive Na+ influx using fluorescence-based measurement of mitochondrial matrix [Na+] (free sodium concentration) rise and the ensuing depolarization and swelling. We show an increase in all these measures of Na+ uptake in MICU1KO cells as compared to wild-type (WT) and rescued MICU1KO HEK cells. However, mitochondria in WT cells and MICU1 stable-rescued cells still allowed some Ru265-sensitive Na+ influx that was prevented by MICU1 in excess upon acute overexpression. Thus, MICU1 restricts the cation flux across the mtCU in the absence of Ca2+, but even in cells with high endogenous MICU1 expression such as HEK, some mtCU seem to lack MICU1-dependent gating. We also show rearrangement of the mtCU and altered number of functional channels in MICU1KO and different rescues, and loss of MICU1 during mitoplast preparation, that together might have obscured the pore-blocking function of MICU1 in divalent-free conditions in previous studies.
Asunto(s)
Canales de Calcio , Proteínas de Transporte de Membrana Mitocondrial , Proteínas de Transporte de Membrana Mitocondrial/metabolismo , Canales de Calcio/metabolismo , Mitocondrias/metabolismo , Transporte Biológico , Calcio/metabolismo , Proteínas de Unión al Calcio/metabolismoRESUMEN
BACKGROUND: Type 2 diabetes (T2D) is a frequent comorbidity encountered in patients with severe aortic stenosis (AS), leading to an adverse left ventricular (LV) remodeling and dysfunction. Metabolic alterations have been suggested as contributors of the deleterious effect of T2D on LV remodeling and function in patients with severe AS, but so far, the underlying mechanisms remain unclear. Mitochondria play a central role in the regulation of cardiac energy metabolism. OBJECTIVES: We aimed to explore the mitochondrial alterations associated with the deleterious effect of T2D on LV remodeling and function in patients with AS, preserved ejection fraction, and no additional heart disease. METHODS: We combined an in-depth clinical, biological and echocardiography phenotype of patients with severe AS, with (n = 34) or without (n = 50) T2D, referred for a valve replacement, with transcriptomic and histological analyses of an intra-operative myocardial LV biopsy. RESULTS: T2D patients had similar AS severity but displayed worse cardiac remodeling, systolic and diastolic function than non-diabetics. RNAseq analysis identified 1029 significantly differentially expressed genes. Functional enrichment analysis revealed several T2D-specific upregulated pathways despite comorbidity adjustment, gathering regulation of inflammation, extracellular matrix organization, endothelial function/angiogenesis, and adaptation to cardiac hypertrophy. Downregulated gene sets independently associated with T2D were related to mitochondrial respiratory chain organization/function and mitochondrial organization. Generation of causal networks suggested a reduced Ca2+ signaling up to the mitochondria, with the measured gene remodeling of the mitochondrial Ca2+ uniporter in favor of enhanced uptake. Histological analyses supported a greater cardiomyocyte hypertrophy and a decreased proximity between the mitochondrial VDAC porin and the reticular IP3-receptor in T2D. CONCLUSIONS: Our data support a crucial role for mitochondrial Ca2+ signaling in T2D-induced cardiac dysfunction in severe AS patients, from a structural reticulum-mitochondria Ca2+ uncoupling to a mitochondrial gene remodeling. Thus, our findings open a new therapeutic avenue to be tested in animal models and further human cardiac biopsies in order to propose new treatments for T2D patients suffering from AS. TRIAL REGISTRATION: URL: https://www. CLINICALTRIALS: gov ; Unique Identifier: NCT01862237.
Asunto(s)
Estenosis de la Válvula Aórtica , Señalización del Calcio , Diabetes Mellitus Tipo 2 , Perfilación de la Expresión Génica , Mitocondrias Cardíacas , Índice de Severidad de la Enfermedad , Transcriptoma , Función Ventricular Izquierda , Remodelación Ventricular , Humanos , Estenosis de la Válvula Aórtica/metabolismo , Estenosis de la Válvula Aórtica/genética , Estenosis de la Válvula Aórtica/fisiopatología , Estenosis de la Válvula Aórtica/diagnóstico por imagen , Estenosis de la Válvula Aórtica/cirugía , Estenosis de la Válvula Aórtica/patología , Masculino , Mitocondrias Cardíacas/metabolismo , Mitocondrias Cardíacas/patología , Femenino , Anciano , Diabetes Mellitus Tipo 2/genética , Diabetes Mellitus Tipo 2/metabolismo , Diabetes Mellitus Tipo 2/complicaciones , Persona de Mediana Edad , Anciano de 80 o más Años , Disfunción Ventricular Izquierda/fisiopatología , Disfunción Ventricular Izquierda/genética , Disfunción Ventricular Izquierda/metabolismo , Disfunción Ventricular Izquierda/diagnóstico por imagenRESUMEN
BACKGROUND & AIMS: Hepatic insulin resistance in obesity and type 2 diabetes was recently associated with endoplasmic reticulum (ER)-mitochondria miscommunication. These contact sites (mitochondria-associated membranes: MAMs) are highly dynamic and involved in many functions; however, whether MAM dysfunction plays a causal role in hepatic insulin resistance and steatosis is not clear. Thus, we aimed to determine whether and how organelle miscommunication plays a role in the onset and progression of hepatic metabolic impairment. METHODS: We analyzed hepatic ER-mitochondria interactions and calcium exchange in a time-dependent and reversible manner in mice with diet-induced obesity. Additionally, we used recombinant adenovirus to express a specific organelle spacer or linker in mouse livers, to determine the causal impact of MAM dysfunction on hepatic metabolic alterations. RESULTS: Disruption of ER-mitochondria interactions and calcium exchange is an early event preceding hepatic insulin resistance and steatosis in mice with diet-induced obesity. Interestingly, an 8-week reversal diet concomitantly reversed hepatic organelle miscommunication and insulin resistance in obese mice. Mechanistically, disrupting structural and functional ER-mitochondria interactions through the hepatic overexpression of the organelle spacer FATE1 was sufficient to impair hepatic insulin action and glucose homeostasis. In addition, FATE1-mediated organelle miscommunication disrupted lipid-related mitochondrial oxidative metabolism and induced hepatic steatosis. Conversely, reinforcement of ER-mitochondria interactions through hepatic expression of a synthetic linker prevented diet-induced glucose intolerance after 4 weeks' overnutrition. Importantly, ER-mitochondria miscommunication was confirmed in the liver of obese patients with type 2 diabetes, and correlated with glycemia, HbA1c and HOMA-IR index. CONCLUSIONS: ER-mitochondria miscommunication is an early causal trigger of hepatic insulin resistance and steatosis, and can be reversed by switching to a healthy diet. Thus, targeting MAMs could help to restore metabolic homeostasis. LAY SUMMARY: The literature suggests that interactions between the endoplasmic reticulum and mitochondria could play a role in hepatic insulin resistance and steatosis during chronic obesity. In the present study, we reappraised the time-dependent regulation of hepatic endoplasmic reticulum-mitochondria interactions and calcium exchange, investigating reversibility and causality, in mice with diet-induced obesity. We also assessed the relevance of our findings to humans. We show that organelle miscommunication is an early causal trigger of hepatic insulin resistance and steatosis that can be improved by nutritional strategies.
Asunto(s)
Diabetes Mellitus Tipo 2 , Hígado Graso , Resistencia a la Insulina , Hepatopatías , Animales , Calcio/metabolismo , Comunicación , Proteínas de Unión al ADN/metabolismo , Diabetes Mellitus Tipo 2/etiología , Diabetes Mellitus Tipo 2/metabolismo , Retículo Endoplásmico/metabolismo , Hígado Graso/etiología , Hígado Graso/metabolismo , Glucosa/metabolismo , Humanos , Hígado/metabolismo , Hepatopatías/metabolismo , Ratones , Mitocondrias/metabolismo , Obesidad/complicaciones , Obesidad/metabolismo , Factores de Transcripción/metabolismoRESUMEN
Diabetic cardiomyopathy (DCM) is a leading complication in type 2 diabetes patients. Recently, we have shown that the reticulum-mitochondria Ca2+ uncoupling is an early and reversible trigger of the cardiac dysfunction in a diet-induced mouse model of DCM. Metformin is a first-line antidiabetic drug with recognized cardioprotective effect in myocardial infarction. Whether metformin could prevent the progression of DCM remains not well understood. We therefore investigated the effect of a chronic 6-week metformin treatment on the reticulum-mitochondria Ca2+ coupling and the cardiac function in our high-fat high-sucrose diet (HFHSD) mouse model of DCM. Although metformin rescued the glycemic regulation in the HFHSD mice, it did not preserve the reticulum-mitochondria Ca2+ coupling either structurally or functionally. Metformin also did not prevent the progression towards cardiac dysfunction, i.e., cardiac hypertrophy and strain dysfunction. In summary, despite its cardioprotective role, metformin is not sufficient to delay the progression to early DCM.
Asunto(s)
Diabetes Mellitus Tipo 2 , Cardiomiopatías Diabéticas , Insuficiencia Cardíaca , Metformina , Animales , Diabetes Mellitus Tipo 2/complicaciones , Diabetes Mellitus Tipo 2/tratamiento farmacológico , Cardiomiopatías Diabéticas/tratamiento farmacológico , Cardiomiopatías Diabéticas/etiología , Modelos Animales de Enfermedad , Insuficiencia Cardíaca/complicaciones , Insuficiencia Cardíaca/etiología , Humanos , Metformina/farmacología , Metformina/uso terapéutico , Ratones , Volumen SistólicoRESUMEN
Mitochondrial Ca2+ uptake has long been considered crucial for meeting the fluctuating energy demands of cells in the heart and other tissues. Increases in mitochondrial matrix [Ca2+] drive mitochondrial ATP production via stimulation of Ca2+-sensitive dehydrogenases. Mitochondria-targeted sensors have revealed mitochondrial matrix [Ca2+] rises that closely follow the cytoplasmic [Ca2+] signals in many paradigms. Mitochondrial Ca2+ uptake is mediated by the Ca2+ uniporter (mtCU). Pharmacological manipulation of the mtCU is potentially key to understanding its physiological significance, but no specific, cell-permeable inhibitors were identified. In the past decade, as the molecular identity of the mtCU was brought to light, efforts have focused on genetic targeting. However, in the cells/animals that are able to survive impaired mtCU function, robust compensatory changes were found in the mtCU as well as other mechanisms. Thus, the discovery, through chemical library screens on normal and mtCU-deficient cells, of new small-molecule inhibitors with improved cell permeability and specificity might offer a better chance to test the relevance of mitochondrial Ca2+ uptake. Success with the development of small molecule mtCU inhibitors is also expected to have clinical impact, considering the growing evidence for the role of mitochondrial Ca2+ uptake in a variety of diseases, including heart attack, stroke and various neurodegenerative disorders. Here, we review the progress in pharmacological targeting of mtCU and illustrate the challenges in this field using data obtained with MCU-i11, a new small molecule inhibitor.
Asunto(s)
Canales de Calcio/metabolismo , Animales , Calcio/metabolismo , Canales de Calcio/genética , Marcación de Gen , Humanos , Modelos Biológicos , Preparaciones Farmacéuticas/metabolismoRESUMEN
Cardiovascular diseases remain the leading cause of death worldwide. Although major therapeutic progress has been made during the past decades, a better understanding of the underlying mechanisms will certainly help to improve patient's prognosis. In vitro models, particularly adult mouse cardiomyocytes, have been largely used; however, their fragility and large size are major obstacles to the use of flow cytometry. Conventional techniques, such as cell imaging, require the use of large numbers of animals and are time consuming. Here, we described a new, simple, and rapid one-day protocol using living adult mouse cardiomyocytes in suspension exposed to hypoxia-reoxygenation that allows a multilabeling analysis by flow cytometry. Several parameters can be measured by fluorescent probes labeling to assess cell viability (propidium iodide, calcein-AM, and Sytox Green), mitochondrial membrane potential [DilC1(5) and TMRM], reactive oxygen species production (MitoSOX Red), and mitochondrial mass (MitoTracker Deep Red). We address the robustness and sensitivity of our model using a cardioprotective agent, cyclosporine A. Overall, our new experimental set-up offers a high-speed quantitative multilabeling analysis of adult mouse cardiomyocytes exposed to hypoxia-reoxygenation. Our model might be interesting to investigate other cellular stresses (oxidative and inflammation) or to perform pharmacological screening.
Asunto(s)
Hipoxia de la Célula/fisiología , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/fisiología , Oxígeno/metabolismo , Animales , Cardiotónicos/farmacología , Hipoxia de la Célula/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/fisiología , Citometría de Flujo/métodos , Masculino , Potencial de la Membrana Mitocondrial/efectos de los fármacos , Potencial de la Membrana Mitocondrial/fisiología , Ratones , Ratones Endogámicos C57BL , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Mitocondrias/fisiología , Daño por Reperfusión Miocárdica/tratamiento farmacológico , Daño por Reperfusión Miocárdica/inmunología , Daño por Reperfusión Miocárdica/fisiopatología , Miocitos Cardíacos/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Estrés Oxidativo/fisiología , Especies Reactivas de Oxígeno/metabolismoRESUMEN
Type 2 diabetic cardiomyopathy features Ca2+ signaling abnormalities, notably an altered mitochondrial Ca2+ handling. We here aimed to study if it might be due to a dysregulation of either the whole Ca2+ homeostasis, the reticulum-mitochondrial Ca2+ coupling, and/or the mitochondrial Ca2+ entry through the uniporter. Following a 16-week high-fat high-sucrose diet (HFHSD), mice developed cardiac insulin resistance, fibrosis, hypertrophy, lipid accumulation, and diastolic dysfunction when compared to standard diet. Ultrastructural and proteomic analyses of cardiac reticulum-mitochondria interface revealed tighter interactions not compatible with Ca2+ transport in HFHSD cardiomyocytes. Intramyocardial adenoviral injections of Ca2+ sensors were performed to measure Ca2+ fluxes in freshly isolated adult cardiomyocytes and to analyze the direct effects of in vivo type 2 diabetes on cardiomyocyte function. HFHSD resulted in a decreased IP3R-VDAC interaction and a reduced IP3-stimulated Ca2+ transfer to mitochondria, with no changes in reticular Ca2+ level, cytosolic Ca2+ transients, and mitochondrial Ca2+ uniporter function. Disruption of organelle Ca2+ exchange was associated with decreased mitochondrial bioenergetics and reduced cell contraction, which was rescued by an adenovirus-mediated expression of a reticulum-mitochondria linker. An 8-week diet reversal was able to restore cardiac insulin signaling, Ca2+ transfer, and cardiac function in HFHSD mice. Therefore, our study demonstrates that the reticulum-mitochondria Ca2+ miscoupling may play an early and reversible role in the development of diabetic cardiomyopathy by disrupting primarily the mitochondrial bioenergetics. A diet reversal, by counteracting the MAM-induced mitochondrial Ca2+ dysfunction, might contribute to restore normal cardiac function and prevent the exacerbation of diabetic cardiomyopathy.
Asunto(s)
Señalización del Calcio , Calcio/metabolismo , Cardiomiopatías Diabéticas/metabolismo , Retículo Endoplásmico/metabolismo , Mitocondrias Cardíacas/metabolismo , Miocitos Cardíacos/metabolismo , Animales , Canales de Calcio/metabolismo , Diabetes Mellitus Experimental/complicaciones , Diabetes Mellitus Tipo 2/complicaciones , Cardiomiopatías Diabéticas/dietoterapia , Cardiomiopatías Diabéticas/etiología , Cardiomiopatías Diabéticas/patología , Dieta Alta en Grasa , Sacarosa en la Dieta , Retículo Endoplásmico/patología , Metabolismo Energético , Acoplamiento Excitación-Contracción , Inositol 1,4,5-Trifosfato/metabolismo , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Resistencia a la Insulina , Masculino , Ratones Endogámicos C57BL , Mitocondrias Cardíacas/patología , Proteínas Mitocondriales/metabolismo , Miocitos Cardíacos/patología , Canal Aniónico 1 Dependiente del Voltaje/metabolismoRESUMEN
Ischemia/reperfusion (I/R) injury is mediated in large part by opening of the mitochondrial permeability transition pore (PTP). Consequently, inhibitors of the PTP hold great promise for the treatment of a variety of cardiovascular disorders. At present, PTP inhibition is obtained only through the use of drugs (e.g. cyclosporine A, CsA) targeting cyclophilin D (CyPD) which is a key modulator, but not a structural component of the PTP. This limitation might explain controversial findings in clinical studies. Therefore, we investigated the protective effects against I/R injury of small-molecule inhibitors of the PTP (63 and TR002) that do not target CyPD. Both compounds exhibited a dose-dependent inhibition of PTP opening in isolated mitochondria and were more potent than CsA. Notably, PTP inhibition was observed also in mitochondria devoid of CyPD. Compounds 63 and TR002 prevented PTP opening and mitochondrial depolarization induced by Ca2+ overload and by reactive oxygen species in neonatal rat ventricular myocytes (NRVMs). Remarkably, both compounds prevented cell death, contractile dysfunction and sarcomeric derangement induced by anoxia/reoxygenation injury in NRVMs at sub-micromolar concentrations, and were more potent than CsA. Cardioprotection was observed also in adult mouse ventricular myocytes and human iPSc-derived cardiomyocytes, as well as ex vivo in perfused hearts. Thus, this study demonstrates that 63 and TR002 represent novel cardioprotective agents that inhibit PTP opening independent of CyPD targeting.
Asunto(s)
Cardiotónicos/uso terapéutico , Poro de Transición de la Permeabilidad Mitocondrial/antagonistas & inhibidores , Daño por Reperfusión Miocárdica/tratamiento farmacológico , Bibliotecas de Moléculas Pequeñas/uso terapéutico , Animales , Cardiotónicos/farmacología , Línea Celular , Células Cultivadas , Humanos , Ratones Endogámicos C57BL , Mitocondrias Cardíacas/efectos de los fármacos , Mitocondrias Cardíacas/metabolismo , Mitocondrias Cardíacas/patología , Poro de Transición de la Permeabilidad Mitocondrial/metabolismo , Daño por Reperfusión Miocárdica/metabolismo , Daño por Reperfusión Miocárdica/patología , Miocitos Cardíacos/efectos de los fármacos , Ratas Sprague-Dawley , Ratas Wistar , Bibliotecas de Moléculas Pequeñas/farmacologíaRESUMEN
Mitochondrial fusion is thought to be important for supporting cardiac contractility, but is hardly detectable in cultured cardiomyocytes and is difficult to directly evaluate in the heart. We overcame this obstacle through in vivo adenoviral transduction with matrix-targeted photoactivatable GFP and confocal microscopy. Imaging in whole rat hearts indicated mitochondrial network formation and fusion activity in ventricular cardiomyocytes. Promptly after isolation, cardiomyocytes showed extensive mitochondrial connectivity and fusion, which decayed in culture (at 24-48 h). Fusion manifested both as rapid content mixing events between adjacent organelles and slower events between both neighboring and distant mitochondria. Loss of fusion in culture likely results from the decline in calcium oscillations/contractile activity and mitofusin 1 (Mfn1), because (i) verapamil suppressed both contraction and mitochondrial fusion, (ii) after spontaneous contraction or short-term field stimulation fusion activity increased in cardiomyocytes, and (iii) ryanodine receptor-2-mediated calcium oscillations increased fusion activity in HEK293 cells and complementing changes occurred in Mfn1. Weakened cardiac contractility in vivo in alcoholic animals is also associated with depressed mitochondrial fusion. Thus, attenuated mitochondrial fusion might contribute to the pathogenesis of cardiomyopathy.
Asunto(s)
Señalización del Calcio/fisiología , Mitocondrias Cardíacas/fisiología , Dinámicas Mitocondriales/fisiología , Contracción Miocárdica/fisiología , Animales , Línea Celular , Genes Reporteros , Vectores Genéticos , Humanos , Proteínas Luminiscentes/análisis , Proteínas Luminiscentes/genética , Masculino , Microscopía Confocal , Mitocondrias Cardíacas/ultraestructura , Ratas , Ratas Sprague-Dawley , Transducción GenéticaRESUMEN
Calcium (Ca2+) release from the endoplasmic reticulum plays an important role in many cell-fate defining cellular processes. Traditionally, this Ca2+ release was associated with the ER Ca2+ release channels, inositol 1,4,5triphosphate receptor (IP3R) and ryanodine receptor (RyR). Lately, however, other calcium conductances have been found to be intracellularly localized and to participate in cell fate regulation. Nonetheless, molecular identity and functional properties of the ER Ca2+ release mechanisms associated with multiple diseases, e.g. prostate cancer, remain unknown. Here we identify a new family of transient receptor potential melastatine 8 (TRPM8) channel isoforms as functional ER Ca2+ release channels expressed in mitochondria-associated ER membranes (MAMs). These TRPM8 isoforms exhibit an unconventional structure with 4 transmembrane domains (TMs) instead of 6 TMs characteristic of the TRP channel archetype. We show that these 4TM-TRPM8 isoforms form functional channels in the ER and participate in regulation of the steady-state Ca2+ concentration ([Ca2+]) in mitochondria and the ER. Thus, our study identifies 4TM-TRPM8 isoforms as ER Ca2+ release mechanism distinct from classical Ca2+ release channels.
Asunto(s)
Calcio/metabolismo , Retículo Endoplásmico/metabolismo , Mitocondrias/metabolismo , Neoplasias de la Próstata/metabolismo , Canales Catiónicos TRPM/genética , Canales Catiónicos TRPM/metabolismo , Anciano , Empalme Alternativo , Línea Celular Tumoral , Células Epiteliales/citología , Células Epiteliales/metabolismo , Regulación Neoplásica de la Expresión Génica , Humanos , Masculino , Persona de Mediana Edad , Próstata/citología , Próstata/metabolismo , Neoplasias de la Próstata/genética , Dominios Proteicos , Canales Catiónicos TRPM/químicaRESUMEN
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/reoxygenation 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.
Asunto(s)
Miocitos Cardíacos/metabolismo , Factor de Transcripción STAT3/metabolismo , Aminofilina/metabolismo , Animales , Atropina/metabolismo , Encéfalo/metabolismo , Línea Celular , Combinación de Medicamentos , Hígado/metabolismo , Masculino , Espectrometría de Masas , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Mitocondrias Cardíacas/metabolismo , Daño por Reperfusión Miocárdica/metabolismo , Nitroglicerina/metabolismo , Fosforilación Oxidativa , Papaverina/metabolismo , Fenobarbital/metabolismo , Ratas , Transducción de Señal/fisiologíaRESUMEN
AIMS/HYPOTHESIS: Mitochondria-associated endoplasmic reticulum membranes (MAMs) are regions of the endoplasmic reticulum (ER) tethered to mitochondria and controlling calcium (Ca(2+)) transfer between both organelles through the complex formed between the voltage-dependent anion channel, glucose-regulated protein 75 and inositol 1,4,5-triphosphate receptor (IP3R). We recently identified cyclophilin D (CYPD) as a new partner of this complex and demonstrated a new role for MAMs in the control of insulin's action in the liver. Here, we report on the mechanisms by which disruption of MAM integrity induces hepatic insulin resistance in CypD (also known as Ppif)-knockout (KO) mice. METHODS: We used either in vitro pharmacological and genetic inhibition of CYPD in HuH7 cells or in vivo loss of CYPD in mice to investigate ER-mitochondria interactions, inter-organelle Ca(2+) exchange, organelle homeostasis and insulin action. RESULTS: Pharmacological and genetic inhibition of CYPD concomitantly reduced ER-mitochondria interactions, inhibited inter-organelle Ca(2+) exchange, induced ER stress and altered insulin signalling in HuH7 cells. In addition, histamine-stimulated Ca(2+) transfer from ER to mitochondria was blunted in isolated hepatocytes of CypD-KO mice and this was associated with an increase in ER calcium store. Interestingly, disruption of inter-organelle Ca(2+) transfer was associated with ER stress, mitochondrial dysfunction, lipid accumulation, activation of c-Jun N-terminal kinase (JNK) and protein kinase C (PKC)ε and insulin resistance in liver of CypD-KO mice. Finally, CYPD-related alterations of insulin signalling were mediated by activation of PKCε rather than JNK in HuH7 cells. CONCLUSIONS/INTERPRETATION: Disruption of IP3R-mediated Ca(2+) signalling in the liver of CypD-KO mice leads to hepatic insulin resistance through disruption of organelle interaction and function, increase in lipid accumulation and activation of PKCε. Modulation of ER-mitochondria Ca(2+) exchange may thus provide an exciting new avenue for treating hepatic insulin resistance.
Asunto(s)
Calcio/metabolismo , Retículo Endoplásmico/metabolismo , Resistencia a la Insulina/fisiología , Mitocondrias/metabolismo , Animales , Línea Celular , Peptidil-Prolil Isomerasa F , Ciclofilinas/genética , Ciclofilinas/metabolismo , Hepatocitos/metabolismo , Humanos , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Hígado/metabolismo , Masculino , Ratones , Ratones NoqueadosRESUMEN
BACKGROUND: Under physiological conditions, Ca(2+) transfer from the endoplasmic reticulum (ER) to mitochondria might occur at least in part at contact points between the 2 organelles and involves the VDAC1/Grp75/IP3R1 complex. Accumulation of Ca(2+) into the mitochondrial matrix may activate the mitochondrial chaperone cyclophilin D (CypD) and trigger permeability transition pore opening, whose role in ischemia/reperfusion injury is well recognized. We questioned here whether the transfer of Ca(2+) from ER to mitochondria might play a role in cardiomyocyte death after hypoxia-reoxygenation. METHODS AND RESULTS: We report that CypD interacts with the VDAC1/Grp75/IP3R1 complex in cardiomyocytes. Genetic or pharmacological inhibition of CypD in both H9c2 cardiomyoblasts and adult cardiomyocytes decreased the Ca(2+) transfer from ER to mitochondria through IP3R under normoxic conditions. During hypoxia-reoxygenation, the interaction between CypD and the IP3R1 Ca(2+) channeling complex increased concomitantly with mitochondrial Ca(2+) content. Inhibition of either CypD, IP3R1, or Grp75 decreased protein interaction within the complex, attenuated mitochondrial Ca(2+) overload, and protected cells from hypoxia-reoxygenation. Genetic or pharmacological inhibition of CypD provided a similar effect in adult mice cardiomyocytes. Disruption of ER-mitochondria interaction via the downregulation of Mfn2 similarly reduced the interaction between CypD and the IP3R1 complex and protected against hypoxia-reoxygenation injury. CONCLUSIONS: Our data (1) point to a new role of CypD at the ER-mitochondria interface and (2) suggest that decreasing ER-mitochondria interaction at reperfusion can protect cardiomyocytes against lethal reperfusion injury through the reduction of mitochondrial Ca(2+) overload via the CypD/VDAC1/Grp75/IP3R1 complex.
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Señalización del Calcio/fisiología , Hipoxia de la Célula/fisiología , Retículo Endoplásmico/fisiología , Mitocondrias Cardíacas/fisiología , Miocitos Cardíacos/patología , Oxígeno/toxicidad , Animales , Línea Celular , Células Cultivadas/metabolismo , Peptidil-Prolil Isomerasa F , Ciclofilinas/deficiencia , Ciclofilinas/genética , Ciclofilinas/fisiología , Proteínas HSP70 de Choque Térmico/fisiología , Técnicas In Vitro , Receptores de Inositol 1,4,5-Trifosfato/fisiología , Membranas Intracelulares/fisiología , Masculino , Proteínas de la Membrana/fisiología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Complejos Multiproteicos , Daño por Reperfusión Miocárdica/prevención & control , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/metabolismo , Miocitos Cardíacos/ultraestructura , Técnicas de Placa-Clamp , Distribución Aleatoria , Ratas , Canal Aniónico 1 Dependiente del Voltaje/fisiologíaRESUMEN
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.
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Background: The immune system, composed of organs, tissues, cells, and proteins, is the key to protecting the body from external biological attacks and inflammation. The latter occurs in several pathologies, such as cancers, type 1 diabetes, and human immunodeficiency virus infection. Immunophenotyping by flow cytometry is the method of choice for diagnosing these pathologies. Under inflammatory conditions, the peripheral blood mononuclear cells (PBMCs) are partially activated and generate intracellular pathways involving Ca2+-dependent signaling cascades leading to transcription factor expression. Ca2+ signaling is typically studied by microscopy in cell lines but can present some limitations to explore human PBMCs, where flow cytometry can be a good alternative. Objective: In this review, we dived into the research field of inflammation and Ca2+ signaling in PBMCs. We aimed to investigate the structure and evolution of this field in a physio-pathological context, and then we focused our review on flow cytometry analysis of Ca2+ fluxes in PBMCs. Methods: From 1984 to 2022, 3865 articles on inflammation and Ca2+ signaling in PBMCs were published, according to The Clarivate Web of Science (WOS) database used in this review. A bibliometric study was designed for this collection and consisted of a co-citation and bibliographic coupling analysis. Results: The co-citation analysis was performed on 133 articles: 4 clusters highlighted the global context of Ca2+ homeostasis, including chemical probe development, identification of the leading players in Ca2+ signaling, and the link with chemokine production in immune cell function. Next, the bibliographic coupling analysis combined 998 articles in 8 clusters. This analysis outlined the mechanisms of PBMC activation, from signal integration to cellular response. Further explorations of the bibliographic coupling network, focusing on flow cytometry, revealed 21 articles measuring cytosolic Ca2+ in PBMCs, with only 5 since 2016. This final query showed that Ca2+ signaling analysis in human PBMCs using flow cytometry is still underdeveloped and investigates mainly the cytosolic Ca2+ compartment. Conclusion: Our review uncovers remaining knowledge gaps of intracellular players involved in Ca2+ signaling in PBMCs, such as reticulum and mitochondria, and presents flow cytometry as a solid option to supplement gold-standard microscopy studies.
Asunto(s)
Leucocitos Mononucleares , Transducción de Señal , Humanos , Leucocitos Mononucleares/metabolismo , Citometría de Flujo/métodos , Línea Celular , Inflamación/metabolismoRESUMEN
Mitochondrial Ca2+ homeostasis loses its control in many diseases and might provide therapeutic targets. Mitochondrial Ca2+ uptake is mediated by the uniporter channel (mtCU), formed by MCU and is regulated by the Ca2+-sensing gatekeeper, MICU1, which shows tissue-specific stoichiometry. An important gap in knowledge is the molecular mechanism of the mtCU activators and inhibitors. We report that all pharmacological activators of the mtCU (spermine, kaempferol, SB202190) act in a MICU1-dependent manner, likely by binding to MICU1 and preventing MICU1's gatekeeping activity. These agents also sensitized the mtCU to inhibition by Ru265 and enhanced the Mn2+-induced cytotoxicity as previously seen with MICU1 deletion. Thus, MCU gating by MICU1 is the target of mtCU agonists and is a barrier for inhibitors like RuRed/Ru360/Ru265. The varying MICU1:MCU ratios result in different outcomes for both mtCU agonists and antagonists in different tissues, which is relevant for both pre-clinical research and therapeutic efforts.
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Canales de Calcio , Proteínas de Transporte de Membrana Mitocondrial , Proteínas de Transporte de Membrana Mitocondrial/metabolismo , Canales de Calcio/metabolismo , Mitocondrias/metabolismo , Transporte Biológico , Calcio/metabolismoRESUMEN
Despite advances in cardioprotection, new therapeutic strategies capable of preventing ischemia-reperfusion injury of patients are still needed. Here, we discover that sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA2) phosphorylation at serine 663 is a clinical and pathophysiological event of cardiac function. Indeed, the phosphorylation level of SERCA2 at serine 663 is increased in ischemic hearts of patients and mouse. Analyses on different human cell lines indicate that preventing serine 663 phosphorylation significantly increases SERCA2 activity and protects against cell death, by counteracting cytosolic and mitochondrial Ca2+ overload. By identifying the phosphorylation level of SERCA2 at serine 663 as an essential regulator of SERCA2 activity, Ca2+ homeostasis and infarct size, these data contribute to a more comprehensive understanding of the excitation/contraction coupling of cardiomyocytes and establish the pathophysiological role and the therapeutic potential of SERCA2 modulation in acute myocardial infarction, based on the hotspot phosphorylation level of SERCA2 at serine 663 residue.
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Infarto del Miocardio , Miocardio , Animales , Humanos , Ratones , Calcio/metabolismo , Homeostasis , Infarto del Miocardio/metabolismo , Miocardio/metabolismo , Miocitos Cardíacos/metabolismo , Fosforilación , Retículo Sarcoplasmático/metabolismo , ATPasas Transportadoras de Calcio del Retículo Sarcoplásmico/metabolismoRESUMEN
Long COVID has become a world-wide, non-communicable epidemic, caused by long-lasting multiorgan symptoms that endure for weeks or months after SARS-CoV-2 infection has already subsided. This scientific document aims to provide insight into the possible causes and therapeutic options available for the cardiovascular manifestations of long COVID. In addition to chronic fatigue, which is a common symptom of long COVID, patients may present with chest pain, ECG abnormalities, postural orthostatic tachycardia, or newly developed supraventricular or ventricular arrhythmias. Imaging of the heart and vessels has provided evidence of chronic, post-infectious perimyocarditis with consequent left or right ventricular failure, arterial wall inflammation, or microthrombosis in certain patient populations. Better understanding of the underlying cellular and molecular mechanisms of long COVID will aid in the development of effective treatment strategies for its cardiovascular manifestations. A number of mechanisms have been proposed, including those involving direct effects on the myocardium, microthrombotic damage to vessels or endothelium, or persistent inflammation. Unfortunately, existing circulating biomarkers, coagulation, and inflammatory markers, are not highly predictive for either the presence or outcome of long COVID when measured 3 months after SARS-CoV-2 infection. Further studies are needed to understand underlying mechanisms, identify specific biomarkers, and guide future preventive strategies or treatments to address long COVID and its cardiovascular sequelae.
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COVID-19 , Cardiopatías , Humanos , Síndrome Post Agudo de COVID-19 , SARS-CoV-2 , Corazón , Miocardio , Prueba de COVID-19RESUMEN
The potent lipid mediator sphingosine-1-phosphate (S1P) regulates diverse physiological processes by binding to 5 specific GPCRs, although it also has intracellular targets. Here, we demonstrate that S1P, produced in the mitochondria mainly by sphingosine kinase 2 (SphK2), binds with high affinity and specificity to prohibitin 2 (PHB2), a highly conserved protein that regulates mitochondrial assembly and function. In contrast, S1P did not bind to the closely related protein PHB1, which forms large, multimeric complexes with PHB2. In mitochondria from SphK2-null mice, a new aberrant band of cytochrome-c oxidase was detected by blue native PAGE, and interaction between subunit IV of cytochrome-c oxidase and PHB2 was greatly reduced. Moreover, depletion of SphK2 or PHB2 led to a dysfunction in mitochondrial respiration through cytochrome-c oxidase. Our data point to a new action of S1P in mitochondria and suggest that interaction of S1P with homomeric PHB2 is important for cytochrome-c oxidase assembly and mitochondrial respiration.