Mitochondrial sodium/calcium exchanger (NCLX) regulates basal and starvation-induced autophagy through calcium signaling.

Mitochondria shape intracellular Ca2+ signaling through the concerted activity of Ca2+ uptake via mitochondrial calcium uniporters and efflux by Na+ /Ca2+ exchangers (NCLX). Here, we describe a novel relationship among NCLX, intracellular Ca2+ , and autophagic activity. Conditions that stimulate autophagy in vivo and in vitro, such as caloric restriction and nutrient deprivation, upregulate NCLX expression in hepatic tissue and cells. Conversely, knockdown of NCLX impairs basal and starvation-induced autophagy. Similarly, acute inhibition of NCLX activity by CGP 37157 affects bulk and endoplasmic reticulum autophagy (ER-phagy) without significant impacts on mitophagy. Mechanistically, CGP 37157 inhibited the formation of FIP200 puncta and downstream autophagosome biogenesis. Inhibition of NCLX caused decreased cytosolic Ca2+ levels, and intracellular Ca2+ chelation similarly suppressed autophagy. Furthermore, chelation did not exhibit an additive effect on NCLX inhibition of autophagy, demonstrating that mitochondrial Ca2+ efflux regulates autophagy through the modulation of Ca2+ signaling. Collectively, our results show that the mitochondrial Ca2+ extrusion pathway through NCLX is an important regulatory node linking nutrient restriction and autophagy regulation.

Metabolic dysfunction induced by HFD + L-NAME preferentially affects hippocampal mitochondria, impacting spatial memory in rats.

High-fat diet-induced metabolic changes are not restricted to the onset of cardiovascular diseases, but also include effects on brain functions related to learning and memory. This study aimed to evaluate mitochondrial markers and function, as well as cognitive function, in a rat model of metabolic dysfunction. Eight-week-old male Wistar rats were subjected to either a control diet or a two-hit protocol combining a high fat diet (HFD) with the nitric oxide synthase inhibitor L-NAME in the drinking water. HFD plus L-NAME induced obesity, hypertension, and increased serum cholesterol. These rats exhibited bioenergetic dysfunction in the hippocampus, characterized by decreased oxygen (O2) consumption related to ATP production, with no changes in H2O2 production. Furthermore, OPA1 protein expression was upregulated in the hippocampus of HFD + L-NAME rats, with no alterations in other morphology-related proteins. Consistently, HFD + L-NAME rats showed disruption of performance in the Morris Water Maze Reference Memory test. The neocortex did not exhibit either bioenergetic changes or alterations in H2O2 production. Calcium uptake rate and retention capacity in the neocortex of HFD + L-NAME rats were not altered. Our results indicate that hippocampal mitochondrial bioenergetic function is disturbed in rats exposed to a HFD plus L-NAME, thus disrupting spatial learning, whereas neocortical function remains unaffected.

Goldilocks calcium concentrations and the regulation of oxidative phosphorylation: Too much, too little, or just right.

Calcium (Ca2+) is a key regulator in diverse intracellular signaling pathways and has long been implicated in metabolic control and mitochondrial function. Mitochondria can actively take up large amounts of Ca2+, thereby acting as important intracellular Ca2+ buffers and affecting cytosolic Ca2+ transients. Excessive mitochondrial matrix Ca2+ is known to be deleterious due to opening of the mitochondrial permeability transition pore (mPTP) and consequent membrane potential dissipation, leading to mitochondrial swelling, rupture, and cell death. Moderate Ca2+ within the organelle, on the other hand, can directly or indirectly activate mitochondrial matrix enzymes, possibly impacting on ATP production. Here, we aimed to determine in a quantitative manner if extra- or intramitochondrial Ca2+ modulates oxidative phosphorylation in mouse liver mitochondria and intact hepatocyte cell lines. To do so, we monitored the effects of more modest versus supraphysiological increases in cytosolic and mitochondrial Ca2+ on oxygen consumption rates. Isolated mitochondria present increased respiratory control ratios (a measure of oxidative phosphorylation efficiency) when incubated with low (2.4 ± 0.6 µM) and medium (22.0 ± 2.4 µM) Ca2+ concentrations in the presence of complex I-linked substrates pyruvate plus malate and α-ketoglutarate, respectively, but not complex II-linked succinate. In intact cells, both low and high cytosolic Ca2+ led to decreased respiratory rates, while ideal rates were present under physiological conditions. High Ca2+ decreased mitochondrial respiration in a substrate-dependent manner, mediated by mPTP. Overall, our results uncover a Goldilocks effect of Ca2+ on liver mitochondria, with specific "just right" concentrations that activate oxidative phosphorylation.

Mitochondrial Ca2+ handling as a cell signaling hub: lessons from astrocyte function.

Astrocytes are a heterogenous population of macroglial cells spread throughout the central nervous system with diverse functions, expression signatures, and intricate morphologies. Their subcellular compartments contain a distinct range of mitochondria, with functional microdomains exhibiting widespread activities, such as controlling local metabolism and Ca2+ signaling. Ca2+ is an ion of utmost importance, both physiologically and pathologically, and participates in critical central nervous system processes, including synaptic plasticity, neuron-astrocyte integration, excitotoxicity, and mitochondrial physiology and metabolism. The mitochondrial Ca2+ handling system is formed by the mitochondrial Ca2+ uniporter complex (MCUc), which mediates Ca2+ influx, and the mitochondrial Na+/Ca2+ exchanger (NCLX), responsible for most mitochondrial Ca2+ efflux, as well as additional components, including the mitochondrial permeability transition pore (mtPTP). Over the last decades, mitochondrial Ca2+ handling has been shown to be key for brain homeostasis, acting centrally in physiopathological processes such as astrogliosis, astrocyte-neuron activity integration, energy metabolism control, and neurodegeneration. In this review, we discuss the current state of knowledge regarding the mitochondrial Ca2+ handling system molecular composition, highlighting its impact on astrocytic homeostasis.

Mitochondrial sodium/calcium exchanger NCLX regulates glycolysis in astrocytes, impacting on cognitive performance.

Intracellular Ca2+ concentrations are strictly controlled by plasma membrane transporters, the endoplasmic reticulum, and mitochondria, in which Ca2+ uptake is mediated by the mitochondrial calcium uniporter complex (MCUc), while efflux occurs mainly through the mitochondrial Na+ /Ca2+ exchanger (NCLX). RNAseq database repository searches led us to identify the Nclx transcript as highly enriched in astrocytes when compared with neurons. To assess the role of NCLX in mouse primary culture astrocytes, we inhibited its function both pharmacologically or genetically. This resulted in re-shaping of cytosolic Ca2+ signaling and a metabolic shift that increased glycolytic flux and lactate secretion in a Ca2+ -dependent manner. Interestingly, in vivo genetic deletion of NCLX in hippocampal astrocytes improved cognitive performance in behavioral tasks, whereas hippocampal neuron-specific deletion of NCLX impaired cognitive performance. These results unveil a role for NCLX as a novel modulator of astrocytic glucose metabolism, impacting on cognition.

Changes in mitochondrial morphology modulate LPS-induced loss of calcium homeostasis in BV-2 microglial cells.

Microglial activation involves both fragmentation of the mitochondrial network and changes in cellular Ca2+ homeostasis, but possible modifications in mitochondrial calcium uptake have never been described in this context. Here we report that activated microglial BV-2 cells have impaired mitochondrial calcium uptake, including lower calcium retention capacity and calcium uptake rates. These changes were not dependent on altered expression of the mitochondrial calcium uniporter. Respiratory capacity and the inner membrane potential, key determinants of mitochondrial calcium uptake, are both decreased in activated microglial BV-2 cells. Modified mitochondrial calcium uptake correlates with impaired cellular calcium signaling, including reduced ER calcium stores, and decreased replenishment by store operated calcium entry (SOCE). Induction of mitochondrial fragmentation through Mfn2 knockdown in control cells mimicked this effect, while inhibiting LPS-induced mitochondrial fragmentation by a dominant negative form of Drp1 prevented it. Overall, our results show that mitochondrial fragmentation induced by LPS promotes altered Ca2+ homeostasis in microglial cells, a new aspect of microglial activation that could be a key feature in the inflammatory role of these cells.

Double coronary thrombosis in a patient with Behçet's disease.

Behçet's disease is a chronic relapsing multisystem autoinflammatory condition, in which cardiac involvement is rare, but among the most life-threatening complications. Treatment is largely empirical, and is aimed at suppressing vasculitis. In this role glucocorticoids and colchicine are frequently used. We present the case of a 42-year-old male with previously diagnosed Behçet's disease presenting to our emergency department with an anterior-inferior STEMI. He presented combined thrombosis of the distal anterior descending coronary artery and proximal right coronary artery, and was treated with sequential primary percutaneous coronary interventions and implantation of drug-eluting stents, but required two interventions due to high thrombotic load. His clinical course during hospitalization was good, with no systolic dysfunction at discharge. During follow-up, he has so far had no new cardiovascular events.

Neurological disorders and mitochondria.

The brain is highly dependent on mitochondrial energy metabolism. As a result, mitochondrial dysfunction is a central aspect of many adult-onset neurological diseases, including stroke, ALS, Alzheimer's, Huntington's, and Parkinson's diseases. We review here how different mitochondrial functions, including oxidative phosphorylation, mitochondrial dynamics, oxidant generation, cell death regulation, Ca2+ homeostasis, and proteostasis are involved in these disorders.

Mitochondrial morphology regulates organellar Ca2+ uptake and changes cellular Ca2+ homeostasis.

Changes in mitochondrial size and shape have been implicated in several physiologic processes, but their role in mitochondrial Ca2+ uptake regulation and overall cellular Ca2+ homeostasis is largely unknown. Here we show that modulating mitochondrial dynamics toward increased fusion through expression of a dominant negative (DN) form of the fission protein [dynamin-related protein 1 (DRP1)] markedly increased both mitochondrial Ca2+ retention capacity and Ca2+ uptake rates in permeabilized C2C12 cells. Similar results were seen using the pharmacological fusion-promoting M1 molecule. Conversely, promoting a fission phenotype through the knockdown of the fusion protein mitofusin (MFN)-2 strongly reduced the mitochondrial Ca2+ uptake speed and capacity in these cells. These changes were not dependent on modifications in mitochondrial calcium uniporter expression, inner membrane potentials, or the mitochondrial permeability transition. Implications of mitochondrial morphology modulation on cellular calcium homeostasis were measured in intact cells; mitochondrial fission promoted lower basal cellular calcium levels and lower endoplasmic reticulum (ER) calcium stores, as indicated by depletion with thapsigargin. Indeed, mitochondrial fission was associated with ER stress. Additionally, the calcium-replenishing process of store-operated calcium entry was impaired in MFN2 knockdown cells, whereas DRP1-DN-promoted fusion resulted in faster cytosolic Ca2+ increase rates. Overall, our results show a novel role for mitochondrial morphology in the regulation of mitochondrial Ca2+ uptake, which impacts cellular Ca2+ homeostasis.-Kowaltowski, A. J., Menezes-Filho, S. L., Assali, E. A., Gonçalves, I. G., Cabral-Costa, J. V., Abreu, P., Miller, N., Nolasco, P., Laurindo, F. R. M., Bruni-Cardoso, A., Shirihai, O. Mitochondrial morphology regulates organellar Ca2+ uptake and changes cellular Ca2+ homeostasis.

Intermittent fasting uncovers and rescues cognitive phenotypes in PTEN neuronal haploinsufficient mice.

Phosphatase and tensin homolog (PTEN) is an important protein with key modulatory functions in cell growth and survival. PTEN is crucial during embryogenesis and plays a key role in the central nervous system (CNS), where it directly modulates neuronal development and synaptic plasticity. Loss of PTEN signaling function is associated with cognitive deficits and synaptic plasticity impairment. Accordingly, Pten mutations have a strong link with autism spectrum disorder. In this study, neuronal Pten haploinsufficient male mice were subjected to a long-term environmental intervention - intermittent fasting (IF) - and then evaluated for alterations in exploratory, anxiety and learning and memory behaviors. Although no significant effects on spatial memory were observed, mutant mice showed impaired contextual fear memory in the passive avoidance test - an outcome that was effectively rescued by IF. In this study, we demonstrated that IF modulation, in addition to its rescue of the memory deficit, was also required to uncover behavioral phenotypes otherwise hidden in this neuronal Pten haploinsufficiency model.

skn-1 is required for interneuron sensory integration and foraging behavior in Caenorhabditis elegans.

Nrf2/skn-1, a transcription factor known to mediate adaptive responses of cells to stress, also regulates energy metabolism in response to changes in nutrient availability. The ability to locate food sources depends upon chemosensation. Here we show that Nrf2/skn-1 is expressed in olfactory interneurons, and is required for proper integration of multiple food-related sensory cues in Caenorhabditis elegans. Compared to wild type worms, skn-1 mutants fail to perceive that food density is limiting, and display altered chemo- and thermotactic responses. These behavioral deficits are associated with aberrant AIY interneuron morphology and migration in skn-1 mutants. Both skn-1-dependent AIY autonomous and non-autonomous mechanisms regulate the neural circuitry underlying multisensory integration of environmental cues related to energy acquisition.

Acute Heart Failure Registry: Risk Assessment Model in Decompensated Heart Failure / Registro de Insuficiência Cardíaca Aguda: Modelo de Avaliação de Risco na Insuficiência Cardíaca Descompensada

Abstract Background: Heart failure (HF) is a highly prevalent syndrome. Although the long-term prognostic factors have been identified in chronic HF, this information is scarcer with respect to patients with acute HF. despite available data in the literature on long-term prognostic factors in chronic HF, data on acute HF patients are more scarce. Objectives: To develop a predictor of unfavorable prognostic events in patients hospitalized for acute HF syndromes, and to characterize a group at higher risk regarding their clinical characteristics, treatment and outcomes. Methods: cohort study of 600 patients admitted for acute HF, defined according to the European Society of Cardiology criteria. Primary endpoint for score derivation was defined as all-cause mortality and / or rehospitalization for HF at 12 months. For score validation, the following endpoints were used: all-cause mortality and / or readmission for HF at 6, 12 and 24 months. The exclusion criteria were: high output HF; patients with acute myocardial infraction, acute myocarditis, infectious endocarditis, pulmonary infection, pulmonary artery hypertension and severe mitral stenosis. Results: 505 patients were included, and prognostic predicting factors at 12 months were identified. One or two points were assigned according to the odds ratio (OR) obtained (p < 0.05). After the total score value was determined, a 4-point cut-off was determined for each ROC curve at 12 months. Two groups were formed according to the number of points, group A < 4 points, and group B = 4 points. Group B was composed of older patients, with higher number of comorbidities and predictors of the combined endpoint at 6, 12 and 24 months, as linearly represented in the survival curves (Log rank). Conclusions: This risk score enabled the identification of a group with worse prognosis at 12 months.

Resumo Fundamento: A insuficiência cardíaca (IC) é uma síndrome de elevada prevalência. Apesar de existir na literatura informação relativa aos fatores prognósticos a longo prazo na IC crônica, esta é mais escassa no que diz respeito aos pacientes com IC aguda. Objetivos: Desenvolver um score preditor de eventos prognósticos desfavoráveis em doentes admitidos com síndromes de IC aguda e caracterizar um grupo de maior risco quanto às suas características clínicas, terapêutica e resultados. Métodos: Estudo de coorte de 600 doentes internados com IC aguda, definida de acordo com os critérios da Sociedade Europeia de Cardiologia. O endpoint primário para a derivação do score foi definido como mortalidade de qualquer causa e/ou reinternação por IC aos 12 meses. Para a validação do score, foram utilizados como endpoints: mortalidade de qualquer causa e/ou reinternação por IC aos 6, 12 e 24 meses. Os critérios de exclusão foram: IC de alto débito, pacientes com infarto agudo do miocárdio, miocardite aguda, endocardite infeciosa, infeção pulmonar, hipertensão arterial pulmonar e estenose mitral grave. Resultados: Foram incluídos 505 doentes e identificados preditores prognósticos aos 12 meses. Atribuíram-se 1 ou 2 pontos (p.) de acordo com os odds ratio (OR) obtidos (p < 0,05). Após a determinação do valor de score total, foi estabelecido um cut-off de 4 pontos por curva ROC. Constituíram-se 2 grupos de acordo com a pontuação, grupo A < 4 p. versus grupo B = 4 p. O grupo B era constituído por idosos, com maior número de comorbidades e preditor de endpoint combinado aos 6, 12 e 24 meses traduzido linearmente nas curvas de sobrevida (Log rank). Conclusões: Este score de risco permitiu identificar um grupo com pior prognóstico aos 12 meses.

The Role of Steroid Hormones in the Modulation of Neuroinflammation by Dietary Interventions.

Steroid hormones, such as sex hormones and glucocorticoids, have been demonstrated to play a role in different cellular processes in the central nervous system, ranging from neurodevelopment to neurodegeneration. Environmental factors, such as calorie intake or fasting frequency, may also impact on such processes, indicating the importance of external factors in the development and preservation of a healthy brain. The hypothalamic-pituitary-adrenal axis and glucocorticoid activity play a role in neurodegenerative processes, including in disorders such as in Alzheimer's and Parkinson's diseases. Sex hormones have also been shown to modulate cognitive functioning. Inflammation is a common feature in neurodegenerative disorders, and sex hormones/glucocorticoids can act to regulate inflammatory processes. Intermittent fasting can protect the brain against cognitive decline that is induced by an inflammatory stimulus. On the other hand, obesity increases susceptibility to inflammation, while metabolic syndromes, such as diabetes, are associated with neurodegeneration. Consequently, given that gonadal and/or adrenal steroids may significantly impact the pathophysiology of neurodegeneration, via their effect on inflammatory processes, this review focuses on how environmental factors, such as calorie intake and intermittent fasting, acting through their modulation of steroid hormones, impact on inflammation that contributes to cognitive and neurodegenerative processes.

Acute Heart Failure Registry: Risk Assessment Model in Decompensated Heart Failure.

BACKGROUND: Heart failure (HF) is a highly prevalent syndrome. Although the long-term prognostic factors have been identified in chronic HF, this information is scarcer with respect to patients with acute HF. despite available data in the literature on long-term prognostic factors in chronic HF, data on acute HF patients are more scarce. OBJECTIVES: To develop a predictor of unfavorable prognostic events in patients hospitalized for acute HF syndromes, and to characterize a group at higher risk regarding their clinical characteristics, treatment and outcomes. METHODS: cohort study of 600 patients admitted for acute HF, defined according to the European Society of Cardiology criteria. Primary endpoint for score derivation was defined as all-cause mortality and / or rehospitalization for HF at 12 months. For score validation, the following endpoints were used: all-cause mortality and / or readmission for HF at 6, 12 and 24 months. The exclusion criteria were: high output HF; patients with acute myocardial infraction, acute myocarditis, infectious endocarditis, pulmonary infection, pulmonary artery hypertension and severe mitral stenosis. RESULTS: 505 patients were included, and prognostic predicting factors at 12 months were identified. One or two points were assigned according to the odds ratio (OR) obtained (p < 0.05). After the total score value was determined, a 4-point cut-off was determined for each ROC curve at 12 months. Two groups were formed according to the number of points, group A < 4 points, and group B = 4 points. Group B was composed of older patients, with higher number of comorbidities and predictors of the combined endpoint at 6, 12 and 24 months, as linearly represented in the survival curves (Log rank). CONCLUSIONS: This risk score enabled the identification of a group with worse prognosis at 12 months.

Longevity Pathways (mTOR, SIRT, Insulin/IGF-1) as Key Modulatory Targets on Aging and Neurodegeneration.

Recent data from epidemiologic studies have shown that the majority of the public health costs are related to age-related disorders, and most of these diseases can lead to neuronal death. The specific signaling mechanisms underpinning neurodegeneration and aging are incompletely understood. Much work has been directed to the search for the etiology of neurodegeneration and aging and to new therapeutic strategies, including not only drugs but also non-pharmacological approaches, such as physical exercise and low-calorie dietary intake. The most important processes in aging-associated conditions, including neurodegeneration, include the mammalian (or mechanistic target of rapamycin (mTOR, sirtuin (SIRT and insulin/insulin growth factor 1 signaling (IIS pathways. These longevity pathways are involved in an array of different processes, including metabolism, cognition, stress response and brain plasticity. In this review we focus on the current advances involving the mTOR, SIRT and IIS longevity pathways during the course of healthy aging processes and neurodegenerative diseases, bringing new insights in the form of a better understanding of the signaling mechanisms underpinning neurodegeneration and how these differ from physiological normal aging processes. This also provides new targets for the therapeutic management and/or prevention of these devastating age-related disorders.

Hypertrophic cardiomyopathy associated with left ventricular noncompaction cardiomyopathy and coronary fistulae: a case report. One genotype, three phenotypes?

The authors present a rare case of hypertrophic cardiomyopathy associated with left ventricular noncompaction cardiomyopathy and coronary artery-left ventricular fistulae in a 42-year-old woman presenting with non-ST-elevation myocardial infarction. Coronary angiography, transthoracic echocardiography and cardiac magnetic resonance revealed the structural abnormalities of the left ventricle and the coronary tree.

[Description of a new mutation in a female patient with Fabry disease]. / Mutação de novo causadora de doença de Fabry em paciente do sexo feminino.

Fabry disease is caused by intracellular accumulation of glycosphingolipids in various tissues, secondary to mutations in the GLA gene (Xq22). Classically described as affecting hemizygous males with no residual alpha-galactosidase A activity, it is now known to affect both sexes, with later and less severe manifestations in females. The manifestations of this disease are systemic: neurological, cutaneous (angiokeratomas), renal, cardiovascular (left ventricular hypertrophy, valve thickening or rhythm disturbances), cochlear-vestibular, and cerebrovascular. In the absence of treatment there is progressive damage to vital organs with renal failure, stroke, heart failure or rhythm perturbations, leading to severe impairment of quality of life as well as reduced life expectancy. We describe the case of a female patient with a history of cryptogenic ischemic stroke at the age of 38 years and chronic renal failure with proteinuria, who presented to the emergency room with atrial fibrillation. The echocardiogram revealed concentric left ventricular hypertrophy, diastolic dysfunction and decreased longitudinal strain in the basal septum. In the context of a screening protocol, she was diagnosed with Fabry disease and a previously undescribed mutation was identified.

[Severe left ventricular outflow tract obstruction as a complication of mitral valve repair: case report]. / Obstrução grave do tracto de saída do ventrículo esquerdo como complicação de valvuloplastia mitral: a propósito de um caso clínico.

Systolic anterior motion (SAM) is a postoperative complication of mitral valve repair, with an incidence of 5 to 10%. Early recognition of the signs and symptoms of SAM is essential for the management of these patients. This article focuses on the pathophysiology and dynamics of SAM and the treatment strategies described in the literature. The authors present a case study and echocardiographic images illustrating the clinical relevance of the mechanism involved, in order to clarify whether surgical reintervention is necessary.