Role of cellular bioenergetics in smooth muscle cell proliferation induced by platelet-derived growth factor

Biomarkers of mitochondrial dysfunction in autism spectrum disorder: A systematic review and meta-analysis

Autism spectrum disorder (ASD) is a neurodevelopmental disorder affecting 1 in 36 children and is associated with physiological abnormalities, most notably mitochondrial dysfunction, at least in a subset of individuals. This systematic review and meta-analysis discovered 204 relevant articles which evaluated biomarkers of mitochondrial dysfunction in ASD individuals. Significant elevations (all p < 0.01) in the prevalence of lactate (17%), pyruvate (41%), alanine (15%) and creatine kinase (9%) were found in ASD. Individuals with ASD had significant differences (all p < 0.01) with moderate to large effect sizes (Cohen's d' ≥ 0.6) compared to controls in mean pyruvate, lactate-to-pyruvate ratio, ATP, and creatine kinase. Some studies found abnormal TCA cycle metabolites associated with ASD. Thirteen controlled studies reported mitochondrial DNA (mtDNA) deletions or variations in the ASD group in blood, peripheral blood mononuclear cells, lymphocytes, leucocytes, granulocytes, and brain. Meta-analyses discovered significant differences (p < 0.01) in copy number of mtDNA overall and in ND1, ND4 and CytB genes. Four studies linked specific mtDNA haplogroups to ASD. A series of studies found a subgroup of ASD with elevated mitochondrial respiration which was associated with increased sensitivity of the mitochondria to physiological stressors and neurodevelopmental regression. Lactate, pyruvate, lactate-to-pyruvate ratio, carnitine, and acyl-carnitines were associated with clinical features such as delays in language, social interaction, cognition, motor skills, and with repetitive behaviors and gastrointestinal symptoms, although not all studies found an association. Lactate, carnitine, acyl-carnitines, ATP, CoQ10, as well as mtDNA variants, heteroplasmy, haplogroups and copy number were associated with ASD severity. Variability was found across biomarker studies primarily due to differences in collection and processing techniques as well as the intrinsic heterogeneity of the ASD population. Several studies reported alterations in mitochondrial metabolism in mothers of children with ASD and in neonates who develop ASD. Treatments targeting mitochondria, particularly carnitine and ubiquinol, appear beneficial in ASD. The link between mitochondrial dysfunction in ASD and common physiological abnormalities in individuals with ASD including gastrointestinal disorders, oxidative stress, and immune dysfunction is outlined. Several subtypes of mitochondrial dysfunction in ASD are discussed, including one related to neurodevelopmental regression, another related to alterations in microbiome metabolites, and another related to elevations in acyl-carnitines. Mechanisms linking abnormal mitochondrial function with alterations in prenatal brain development and postnatal brain function are outlined. Given the multisystem complexity of some individuals with ASD, this review presents evidence for the mitochondria being central to ASD by contributing to abnormalities in brain development, cognition, and comorbidities such as immune and gastrointestinal dysfunction as well as neurodevelopmental regression. A diagnostic approach to identify mitochondrial dysfunction in ASD is outlined. From this evidence, it is clear that many individuals with ASD have alterations in mitochondrial function which may need to be addressed in order to achieve optimal clinical outcomes. The fact that alterations in mitochondrial metabolism may be found during pregnancy and early in the life of individuals who eventually develop ASD provides promise for early life predictive biomarkers of ASD. Further studies may improve the understanding of the role of the mitochondria in ASD by better defining subgroups and understanding the molecular mechanisms driving some of the unique changes found in mitochondrial function in those with ASD.

Bergenin alleviates proliferative arterial diseases by modulating glucose metabolism in vascular smooth muscle cells

BACKGROUND

Vascular smooth muscle cell (VSMC) proliferation and phenotypic switching are key mechanisms in the development of proliferative arterial diseases. Notably, reprogramming of the glucose metabolism pattern in VSMCs plays an important role in this process.

PURPOSE

The aim of this study is to investigate the therapeutic potential and the mechanism underlying the effect of bergenin, an active compound found in Bergenia, in proliferative arterial diseases.

METHODS

The effect of bergenin on proliferative arterial disease was evaluated using platelet-derived growth factor (PDGF)-stimulated VSMCs and a mouse model of carotid artery ligation. VSMC proliferation and phenotypic switching were evaluated in vitro using cell counting kit-8, 5-ethynyl-2-deoxyuridine incorporation, scratch, and transwell assays. Carotid artery neointimal hyperplasia was evaluated in vivo using hematoxylin and eosin staining and immunofluorescence. The expression of proliferation and VSMC contractile phenotype markers was evaluated using PCR and western blotting.

RESULTS

Bergenin treatment inhibited PDGF-induced VSMC proliferation and phenotypic switching and reduced neointimal hyperplasia in the carotid artery ligation model. Additionally, bergenin partially reversed the PDGF-induced Warburg-like glucose metabolism pattern in VSMCs. RNA-sequencing data revealed that bergenin treatment significantly upregulated Ndufs2, an essential subunit of mitochondrial complex I. Ndufs2 knockdown attenuated the inhibitory effect of bergenin on PDGF-induced VSMC proliferation and phenotypic switching, and suppressed neointimal hyperplasia in vivo. Conversely, Ndufs2 overexpression enhanced the protective effect of bergenin. Moreover, Ndufs2 knockdown abrogated the effects of bergenin on the regulation of glucose metabolism in VSMCs.

CONCLUSION

These findings suggest that bergenin is effective in alleviating proliferative arterial diseases. The reversal of the Warburg-like glucose metabolism pattern in VSMCs during proliferation and phenotypic switching may underlie this therapeutic mechanism.

Heterogeneous distribution of mitochondria and succinate dehydrogenase activity in human airway smooth muscle cells

Succinate dehydrogenase (SDH) is a key mitochondrial enzyme involved in the tricarboxylic acid cycle, where it facilitates the oxidation of succinate to fumarate, and is coupled to the reduction of ubiquinone in the electron transport chain as Complex II. Previously, we developed a confocal-based quantitative histochemical technique to determine the maximum velocity of the SDH reaction (SDHmax) in single cells and observed that SDHmax corresponds with mitochondrial volume density. In addition, mitochondrial volume and motility varied within different compartments of human airway smooth muscle (hASM) cells. Therefore, we hypothesize that the SDH activity varies relative to the intracellular mitochondrial volume within hASM cells. Using 3D confocal imaging of labeled mitochondria and a concentric shell method for analysis, we quantified mitochondrial volume density, mitochondrial complexity index, and SDHmax relative to the distance from the nuclear membrane. The mitochondria within individual hASM cells were more filamentous in the immediate perinuclear region and were more fragmented in the distal parts of the cell. Within each shell, SDHmax also corresponded to mitochondrial volume density, where both peaked in the perinuclear region and decreased in more distal parts of the cell. Additionally, when normalized to mitochondrial volume, SDHmax was lower in the perinuclear region when compared to the distal parts of the cell. In summary, our results demonstrate that SDHmax measures differences in SDH activity within different cellular compartments. Importantly, our data indicate that mitochondria within individual cells are morphologically heterogeneous, and their distribution varies substantially within different cellular compartments, with distinct functional properties.

Vitamin E Attenuates Red-Light-Mediated Vasodilation: The Benefits of a Mild Oxidative Stress

Red light (670 nm) energy controls vasodilation via the formation of a transferable endothelium-derived nitric oxide (NO)-precursor-containing substance, its intracellular traffic, and exocytosis. Here we investigated the underlying mechanistic effect of oxidative stress on light-mediated vasodilation by using pressure myography on dissected murine arteries and immunofluorescence on endothelial cells. Treatment with antioxidants Trolox and catalase decreased vessel dilation. In the presence of catalase, a lower number of exosomes were detected in the vessel bath. Light exposure resulted in increased cellular free radical levels. Mitochondrial reactive oxygen species were also more abundant but did not alter cellular ATP production. Red light enhanced the co-localization of late exosome marker CD63 and cellular S-nitrosoprotein to a greater extent than high glucose, suggesting that a mild oxidative stress favors the localization of NO precursor in late exosomes. Exocytosis regulating protein Rab11 was more abundant after irradiation. Our findings conclude that red-light-induced gentle oxidative stress facilitates the dilation of blood vessels, most likely through empowering the traffic of vasodilatory substances. Application of antioxidants disfavors this mechanism.

Dysregulated cellular metabolism in atherosclerosis: mediators and therapeutic opportunities

Accumulating evidence over the past decades has revealed an intricate relationship between dysregulation of cellular metabolism and the progression of atherosclerotic cardiovascular disease. However, an integrated understanding of dysregulated cellular metabolism in atherosclerotic cardiovascular disease and its potential value as a therapeutic target is missing. In this Review, we (1) summarize recent advances concerning the role of metabolic dysregulation during atherosclerosis progression in lesional cells, including endothelial cells, vascular smooth muscle cells, macrophages and T cells; (2) explore the complexity of metabolic cross-talk between these lesional cells; (3) highlight emerging technologies that promise to illuminate unknown aspects of metabolism in atherosclerosis; and (4) suggest strategies for targeting these underexplored metabolic alterations to mitigate atherosclerosis progression and stabilize rupture-prone atheromas with a potential new generation of cardiovascular therapeutics.

Bioenergetic signatures of neurodevelopmental regression

Background: Studies have linked autism spectrum disorder (ASD) to physiological abnormalities including mitochondrial dysfunction. Mitochondrial dysfunction may be linked to a subset of children with ASD who have neurodevelopmental regression (NDR). We have developed a cell model of ASD which demonstrates a unique mitochondrial profile with mitochondrial respiration higher than normal and sensitive to physiological stress. We have previously shown similar mitochondrial profiles in individuals with ASD and NDR. Methods: Twenty-six ASD individuals without a history of NDR (ASD-NoNDR) and 15 ASD individuals with a history of NDR (ASD-NDR) were recruited from 34 families. From these families, 30 mothers, 17 fathers and 5 typically developing (TD) siblings participated. Mitochondrial respiration was measured in peripheral blood mononuclear cells (PBMCs) with the Seahorse 96 XF Analyzer. PBMCs were exposed to various levels of physiological stress for 1 h prior to the assay using 2,3-dimethoxy-1,4-napthoquinone. Results: ASD-NDR children were found to have higher respiratory rates with mitochondria that were more sensitive to physiological stress as compared to ASD-NoNDR children, similar to our cellular model of NDR. Differences in mitochondrial respiration between ASD-NDR and TD siblings were similar to the differences between ASD-NDR and ASD-NoNDR children. Interesting, parents of children with ASD and NDR demonstrated patterns of mitochondrial respiration similar to their children such that parents of children with ASD and NDR demonstrated elevated respiratory rates with mitochondria that were more sensitive to physiological stress. In addition, sex differences were seen in ASD children and parents. Age effects in parents suggested that mitochondria of older parents were more sensitive to physiological stress. Conclusion: This study provides further evidence that children with ASD and NDR may have a unique type of mitochondrial physiology that may make them susceptible to physiological stressors. Identifying these children early in life before NDR occurs and providing treatment to protect mitochondrial physiology may protect children from experiencing NDR. The fact that parents also demonstrate mitochondrial respiration patterns similar to their children implies that this unique change in mitochondrial physiology may be a heritable factor (genetic or epigenetic), a result of shared environment, or both.

Nanopore long-read RNA sequencing reveals functional alternative splicing variants in human vascular smooth muscle cells

Vascular smooth muscle cells (VSMCs) are the major contributor to vascular repair and remodeling, which showed high level of phenotypic plasticity. Abnormalities in VSMC plasticity can lead to multiple cardiovascular diseases, wherein alternative splicing plays important roles. However, alternative splicing variants in VSMC plasticity are not fully understood. Here we systematically characterized the long-read transcriptome and their dysregulation in  human aortic smooth muscle cells (HASMCs) by employing the Oxford Nanopore Technologies long-read RNA sequencing in HASMCs that are separately treated with platelet-derived growth factor, transforming growth factor, and hsa-miR-221-3P transfection. Our analysis reveals frequent alternative splicing events and thousands of unannotated transcripts generated from alternative splicing. HASMCs treated with different factors exhibit distinct transcriptional reprogramming modulated by alternative splicing. We also found that unannotated transcripts produce different open reading frames compared to the annotated transcripts. Finally, we experimentally validated the unannotated transcript derived from gene CISD1, namely CISD1-u, which plays a role in the phenotypic switch of HASMCs. Our study characterizes the phenotypic modulation of HASMCs from an insight of long-read transcriptome, which would promote the understanding and the manipulation of HASMC plasticity in cardiovascular diseases.

Cell-Based Measurement of Mitochondrial Function in Human Airway Smooth Muscle Cells

Cellular mitochondrial function can be assessed using high-resolution respirometry that measures the O2 consumption rate (OCR) across a number of cells. However, a direct measurement of cellular mitochondrial function provides valuable information and physiological insight. In the present study, we used a quantitative histochemical technique to measure the activity of succinate dehydrogenase (SDH), a key enzyme located in the inner mitochondrial membrane, which participates in both the tricarboxylic acid (TCA) cycle and electron transport chain (ETC) as Complex II. In this study, we determine the maximum velocity of the SDH reaction (SDHmax) in individual human airway smooth muscle (hASM) cells. To measure SDHmax, hASM cells were exposed to a solution containing 80 mM succinate and 1.5 mM nitroblue tetrazolium (NBT, reaction indicator). As the reaction proceeded, the change in optical density (OD) due to the reduction of NBT to its diformazan (peak absorbance wavelength of 570 nm) was measured using a confocal microscope with the pathlength for light absorbance tightly controlled. SDHmax was determined during the linear period of the SDH reaction and expressed as mmol fumarate/liter of cell/min. We determine that this technique is rigorous and reproducible, and reliable for the measurement of mitochondrial function in individual cells.

Glycolysis and de novo fatty acid synthesis cooperatively regulate pathological vascular smooth muscle cell phenotypic switching and neointimal hyperplasia

Switching of vascular smooth muscle cells (VSMCs) from a contractile phenotype to a dedifferentiated (proliferative) phenotype contributes to neointima formation, which has been demonstrated to possess a tumor-like nature. Dysregulated glucose and lipid metabolism is recognized as a hallmark of tumors but has not thoroughly been elucidated in neointima formation. Here, we investigated the cooperative role of glycolysis and fatty acid synthesis in vascular injury-induced VSMC dedifferentiation and neointima formation. We found that the expression of hypoxia-inducible factor-1α (HIF-1α) and its target 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3), a critical glycolytic enzyme, were induced in the neointimal VSMCs of human stenotic carotid arteries and wire-injured mouse carotid arteries. HIF-1α overexpression led to elevated glycolysis and resulted in a decreased contractile phenotype while promoting VSMC proliferation and activation of the mechanistic target of rapamycin complex 1 (mTORC1). Conversely, silencing Pfkfb3 had the opposite effects. Mechanistic studies demonstrated that glycolysis generates acetyl coenzyme A to fuel de novo fatty acid synthesis and mTORC1 activation. Whole-transcriptome sequencing analysis confirmed the increased expression of PFKFB3 and fatty acid synthetase (FASN) in dedifferentiated VSMCs. More importantly, FASN upregulation was observed in neointimal VSMCs of human stenotic carotid arteries. Finally, interfering with PFKFB3 or FASN suppressed vascular injury-induced mTORC1 activation, VSMC dedifferentiation, and neointima formation. Together, this study demonstrated that PFKFB3-mediated glycolytic reprogramming and FASN-mediated lipid metabolic reprogramming are distinctive features of VSMC phenotypic switching and could be potential therapeutic targets for treating vascular diseases with neointima formation. © 2023 The Pathological Society of Great Britain and Ireland.

β-cell-selective inhibition of DNA damage response signaling by nitric oxide is associated with an attenuation in glucose uptake

Nitric oxide (NO) plays a dual role in regulating DNA damage response (DDR) signaling in pancreatic β-cells. As a genotoxic agent, NO activates two types of DDR signaling; however, when produced at micromolar levels by the inducible isoform of NO synthase, NO inhibits DDR signaling and DDR-induced apoptosis in a β-cell-selective manner. DDR signaling inhibition by NO correlates with mitochondrial oxidative metabolism inhibition and decreases in ATP and NAD+. Unlike most cell types, β-cells do not compensate for impaired mitochondrial oxidation by increasing glycolytic flux, and this metabolic inflexibility leads to a decrease in ATP and NAD+. Here, we used multiple analytical approaches to determine changes in intermediary metabolites in β-cells and non-β-cells treated with NO or complex I inhibitor rotenone. In addition to ATP and NAD+, glycolytic and tricarboxylic acid cycle intermediates as well as NADPH are significantly decreased in β-cells treated with NO or rotenone. Consistent with glucose-6-phosphate residing at the metabolic branchpoint for glycolysis and the pentose phosphate pathway (NADPH), we show that mitochondrial oxidation inhibitors limit glucose uptake in a β-cell-selective manner. Our findings indicate that the β-cell-selective inhibition of DDR signaling by NO is associated with a decrease in ATP to levels that fall significantly below the KM for ATP of glucokinase (glucose uptake) and suggest that this action places the β-cell in a state of suspended animation where it is metabolically inert until NO is removed, and metabolic function can be restored.

PVT1/miR-145-5p/HK2 modulates vascular smooth muscle cells phenotype switch via glycolysis: The new perspective on the spiral artery remodeling

INTRODUCTION

Vascular smooth muscle cells (VSMC) switched from a contractile phenotype to a synthetic phenotype during the decidual spiral artery (SPAs) remodeling process. The lncRNA plasmacytoma variant translocation 1 (PVT1) and glucose metabolism have been found to regulate the VSMC phenotype switch. This study aimed to analyze the dynamic expression of PVT1 and glycolytic key enzymes hexokinase2 (HK2) at different remodeling stages in early human pregnancy and elucidate the underlying mechanism of the PVT1/miR-145-5p/HK2 axis involved in the spiral artery remodeling.

METHODS

qRT-PCR, Western blot (WB) analysis, Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were used to detect the expression and localization of PVT1 and HK2 in decidual tissue. HA-VSMCs were transfected with specific siRNA, shRNA and plasmids to regulate corresponding genes. Extracellular lactate, cellular ATP, ROS, and intracellular NADPH levels were measured using the corresponding assay kits. Migration was measured by wound-healing and Transwell assays. Contractile phenotypic markers α-SMA, MYH11 with calponin and synthetic phenotypic markers OPN and vimentin were detected by WB. The PDC model was used to detect the degree of spiral arterial remodeling.

RESULTS

PVT1 and HK2 were upregulated with gestational age (GA) increasing in decidual tissue during the early pregnancy. HK2 regulated the glycolytic activity and VSMC phenotype switch in vitro. PVT1 regulated the glycolytic activity and VSMC phenotype switch through HK2. PVT1 played a ceRNA role in regulating HK2 expression by sponging miR-145-5p. PVT1 and HK2 influenced spiral artery remodeling in the PDC model.

DISCUSSION

PVT1 and HK2 were upregulated, and miR-145-5p was downregulated in decidua with the GA increasing. Meanwhile, the PVT1/miR-145-5p/HK2 axis may be involved in regulating the phenotypic switch and migratory capacity of VSMCs by affecting glycolysis in decidual SPAs remodeling.

Oncometabolism: A Paradigm for the Metabolic Remodeling of the Failing Heart

Heart failure is associated with profound alterations in cardiac intermediary metabolism. One of the prevailing hypotheses is that metabolic remodeling leads to a mismatch between cardiac energy (ATP) production and demand, thereby impairing cardiac function. However, even after decades of research, the relevance of metabolic remodeling in the pathogenesis of heart failure has remained elusive. Here we propose that cardiac metabolic remodeling should be looked upon from more perspectives than the mere production of ATP needed for cardiac contraction and relaxation. Recently, advances in cancer research have revealed that the metabolic rewiring of cancer cells, often coined as oncometabolism, directly impacts cellular phenotype and function. Accordingly, it is well feasible that the rewiring of cardiac cellular metabolism during the development of heart failure serves similar functions. In this review, we reflect on the influence of principal metabolic pathways on cellular phenotype as originally described in cancer cells and discuss their potential relevance for cardiac pathogenesis. We discuss current knowledge of metabolism-driven phenotypical alterations in the different cell types of the heart and evaluate their impact on cardiac pathogenesis and therapy.

Metabolomic Signatures of Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) is associated with many variations in metabolism, but the ex-act correlates of these metabolic disturbances with behavior and development and their links to other core metabolic disruptions are understudied. In this study, large-scale targeted LC-MS/MS metabolomic analysis was conducted on fasting morning plasma samples from 57 children with ASD (29 with neurodevelopmental regression, NDR) and 37 healthy controls of similar age and gender. Linear model determined the metabolic signatures of ASD with and without NDR, measures of behavior and neurodevelopment, as well as markers of oxidative stress, inflammation, redox, methylation, and mitochondrial metabolism. MetaboAnalyst ver 5.0 (the Wishart Research Group at the University of Alberta, Edmonton, Canada) identified the pathways associated with altered metabolic signatures. Differences in histidine and glutathione metabolism as well as aromatic amino acid (AAA) biosynthesis differentiated ASD from controls. NDR was associated with disruption in nicotinamide and energy metabolism. Sleep and neurodevelopment were associated with energy metabolism while neurodevelopment was also associated with purine metabolism and aminoacyl-tRNA biosynthesis. While behavior was as-sociated with some of the same pathways as neurodevelopment, it was also associated with alternations in neurotransmitter metabolism. Alterations in methylation was associated with aminoacyl-tRNA biosynthesis and branched chain amino acid (BCAA) and nicotinamide metabolism. Alterations in glutathione metabolism was associated with changes in glycine, serine and threonine, BCAA and AAA metabolism. Markers of oxidative stress and inflammation were as-sociated with energy metabolism and aminoacyl-tRNA biosynthesis. Alterations in mitochondrial metabolism was associated with alterations in energy metabolism and L-glutamine. Using behavioral and biochemical markers, this study finds convergent disturbances in specific metabolic pathways with ASD, particularly changes in energy, nicotinamide, neurotransmitters, and BCAA, as well as aminoacyl-tRNA biosynthesis.

DN200434 Inhibits Vascular Smooth Muscle Cell Proliferation and Prevents Neointima Formation in Mice after Carotid Artery Ligation

BACKGRUOUND

Excessive proliferation and migration of vascular smooth muscle cells (VSMCs), which contributes to the development of occlusive vascular diseases, requires elevated mitochondrial oxidative phosphorylation to meet the increased requirements for energy and anabolic precursors. Therefore, therapeutic strategies based on blockade of mitochondrial oxidative phosphorylation are considered promising for treatment of occlusive vascular diseases. Here, we investigated whether DN200434, an orally available estrogen receptor-related gamma inverse agonist, inhibits proliferation and migration of VSMCs and neointima formation by suppressing mitochondrial oxidative phosphorylation.

METHODS

VSMCs were isolated from the thoracic aortas of 4-week-old Sprague-Dawley rats. Oxidative phosphorylation and the cell cycle were analyzed in fetal bovine serum (FBS)- or platelet-derived growth factor (PDGF)-stimulated VSMCs using a Seahorse XF-24 analyzer and flow cytometry, respectively. A model of neointimal hyperplasia was generated by ligating the left common carotid artery in male C57BL/6J mice.

RESULTS

DN200434 inhibited mitochondrial respiration and mammalian target of rapamycin complex 1 activity and consequently suppressed FBS- or PDGF-stimulated proliferation and migration of VSMCs and cell cycle progression. Furthermore, DN200434 reduced carotid artery ligation-induced neointima formation in mice.

CONCLUSION

Our data suggest that DN200434 is a therapeutic option to prevent the progression of atherosclerosis.

Role of glycolysis in the development of atherosclerosis

Atherosclerosis is a chronic inflammatory vascular disease associated with atherosclerotic plaques and endothelial dysfunction, inflammation, and plaque formation. Glycolysis is a conservative and rigorous biological process that decomposes glucose into pyruvate. Its function is to provide the body with energy and intermediate products required for life activities. However, abnormalities in glycolytic flux during the progression of atherosclerosis accelerate disease progression. Here, we review the role of glycolysis in the development of atherosclerosis to provide new ideas for developing novel anti-atherosclerosis strategies.

Diversification of Potassium Currents in Excitable Cells via Kvβ Proteins

Excitable cells of the nervous and cardiovascular systems depend on an assortment of plasmalemmal potassium channels to control diverse cellular functions. Voltage-gated potassium (Kv) channels are central to the feedback control of membrane excitability in these processes due to their activation by depolarized membrane potentials permitting K⁺ efflux. Accordingly, Kv currents are differentially controlled not only by numerous cellular signaling paradigms that influence channel abundance and shape voltage sensitivity, but also by heteromeric configurations of channel complexes. In this context, we discuss the current knowledge related to how intracellular Kvβ proteins interacting with pore complexes of Shaker-related Kv1 channels may establish a modifiable link between excitability and metabolic state. Past studies in heterologous systems have indicated roles for Kvβ proteins in regulating channel stability, trafficking, subcellular targeting, and gating. More recent works identifying potential in vivo physiologic roles are considered in light of these earlier studies and key gaps in knowledge to be addressed by future research are described.

The Atypical Cadherin FAT1 Limits Mitochondrial Respiration and Proliferation of Vascular Smooth Muscle Cells

Smooth muscle cells contribute to cardiovascular disease, the leading cause of death worldwide. The capacity of these cells to undergo phenotypic switching in mature arteries of the systemic circulation underlies their pathogenic role in atherosclerosis and restenosis, among other vascular diseases. Growth factors and cytokines, extracellular matrix components, regulation of gene expression, neuronal influences, and mechanical forces contribute to smooth muscle cell phenotypic switching. Comparatively little is known about cell metabolism in this process. Studies of cancer and endothelial cell biology have highlighted the importance of cellular metabolic processes for phenotypic transitions that accompany tumor growth and angiogenesis. However, the understanding of cell metabolism during smooth muscle cell phenotypic modulation is incipient. Studies of the atypical cadherin FAT1, which is strongly upregulated in smooth muscle cells in response to arterial injury, suggest that it has important and distinctive functions in this context, mediating control of both smooth muscle cell mitochondrial metabolism and cell proliferation. Here we review the progress made in understanding how FAT1 affects the smooth muscle cell phenotype, highlighting the significance of FAT1 as a processed protein and unexpected regulator of mitochondrial respiration. These mechanisms suggest how a transmembrane protein may relay signals from the extracellular milieu to mitochondria to control metabolic activity during smooth muscle cell phenotypic switching.

Inhibition of PIKfyve Ameliorates the Proliferation and Migration of Vascular Smooth Muscle Cells and Vascular Intima Hyperplasia By Reducing mTORC1 Activity

ABSTRACT

This study was designed to investigate the role and mechanism of PIKfyve in the proliferation and migration of vascular smooth muscle cells (VSMCs) and vascular intima hyperplasia. We first observed increased protein levels of PIKfyve, phospho (p)-S6 Ribosomal Protein (S6)Ser235/236, p-4EBP1Thr37/46 in VSMCs after 24 hours of platelet-derived growth factor (PDGF)-BB treatment. By using cell counting kit-8 assay, Ki-67 immunofluorescence staining and wound healing assay, we found that PIKfyve inhibition ameliorated the enhanced activity of VSMC proliferation and migration induced by PDGF-BB. Silencing PIKfyve also suppressed the phosphorylation of S6 and 4EBP1 (2 major effectors of mammalian target of rapamycin complex 1), glucose consumption, activity of hexokinase, and LDH in PDGF-BB-challenged VSMCs. After rescuing the phosphorylation of S6 and 4EBP1 by silencing Tsc1, the suppressive effects of PIKfyve inhibition on glucose utilization, proliferation, and migration in VSMCs were abolished. The animal model of vascular restenosis was established in C57BL/6J mice by wire injury. We found the expression of PIKfyve was increased in carotid artery at day 28 after injury. Reducing the activity of PIKfyve alleviated vascular neointima hyperplasia after injury. In conclusion, targeting PIKfyve might be a novel effective method to reduce the proliferation and migration of VSMCs and vascular restenosis by affecting mammalian target of rapamycin complex 1-mediated glucose utilization.

Platelet-derived microvesicles regulate vascular smooth muscle cell energy metabolism via PRKAA after intimal injury

Vascular intimal injury initiates various cardiovascular disease processes. Exposure to subendothelial collagen can cause platelet activation, leading to platelet-derived microvesicles (aPMVs) secretion. In addition, vascular smooth muscle cells (VSMCs) exposed to large amounts of aPMVs undergo abnormal energy metabolism, they proliferate excessively and migrate after the loss of endothelium, eventually contributing to neointimal hyperplasia. However, the roles of aPMVs in VSMC energy metabolism are still unknown. Carotid artery intimal injury model indicated platelets adhered to injured blood vessels. In vitro, p-Pka content was increased in aPMVs. aPMVs significantly changed VSMC glycolysis and oxidative phosphorylation, and promoted VSMC migration and proliferation by upregulating p-PRKAA/p-FoxO1. Compound C, an inhibitor of PRKAA, effectively reversed the cell function and energy metabolism triggered by aPMVs in vitro and neointimal formation in vivo. Our data show that aPMVs can affect VSMC energy metabolism through the Pka/PRKAA/FoxO1 signaling pathway and ultimately affect VSMC function, indicating that VSMC metabolic phenotype shifted by aPMVs can be considered a potential target for the inhibition of hyperplasia and providing a new perspective for regulating the abnormal activity of VSMCs after injury.

Time dependent changes in the bioenergetics of peripheral blood mononuclear cells: processing time, collection tubes and cryopreservation effects

OBJECTIVES

Bioenergetic measurements in peripheral blood mononuclear cells (PBMCs) using high-throughput respirometry is a promising minimally invasive approach to studying mitochondrial function in humans. However, optimal methods for collecting PBMCs are not well studied.

METHODS

Bioenergetics and viability were measured across processing delays, tube type and cryopreservation.

RESULTS

Storage of collection tubes on dry ice resulted in unrecoverable samples and using the Cell Preparation Tube (CPT^TM) significantly reduced viability. Thus, storage in Sodium Citrate (NaC) and ethylenediaminetetraacetic acid (EDTA) tubes were studied in detail. Cell viability decreased by 0.5% for each hour the samples remained on wet ice prior to processing while cryopreservation decreased viability by 9.6% with viability remaining stable for about one month in liquid nitrogen. Adenosine triphosphate linked respiration (ALR) and proton-leak respiration (PLR) changed minimally while maximal respiratory capacity (MRC) and reserve capacity (RC) decreased markedly with collection tubes stored on wet ice over 24 hrs. Changes in respiratory parameters were more modest over the first 8 hours. Manipulations to replace media did not attenuate changes in respiratory parameters. Cryopreservation decreased ALR, MRC and RC by 17.20, 95.30 and 54.92 pmol/min, respectively and increased PLR by 2.65 pmol/min. PLR, MRC and RC changed moderately during the first month in liquid nitrogen for freshly frozen PBMCs.

CONCLUSIONS

Our results suggest that bioenergetics in PBMCs vary based on the processing time from specimen collection and preservation method. Changes in bioenergetics can be minimized by processing samples with a minimal time delay. Changes in viability are minimal and may not correspond to changes in bioenergetics.

Myeloid ecotropic viral integration site-1 inhibition promotes apoptosis, suppresses proliferation of acute myeloid leukemia cells, accentuates the effects of anticancer drugs

To investigate the effects of myeloid ecotropic viral integration site-1 (MEIS1) on the proliferation and apoptosis of acute myeloid leukemia (AML) cells and the anticancer effects of the drug, we screened Kasumi-6, KG-1, and Kasumi-1 cells using quantitative reverse transcription polymerase chain reaction. Kasumi-6 and Kasumi-1 cells were subjected to human antigen R (HuR)-mediated interference (IV). Hexokinase 2 (HK2) expression and phosphorylation of protein kinase B (p-AKT) and mammalian target of rapamycin (p-mTOR) were observed with Western blotting. Cell proliferation was assessed using Cell Counting Kit-8, apoptosis was examined using Hoechst 33,258 staining, and glucose uptake was detected with a colorimetric biochemical assay kit. We found that, among the three cell lines tested, MEIS1 expression was highest in Kasumi-1 cells, which were therefore selected for subsequent experiments. Kasumi-1 cells receiving IV showed significantly decreased proliferation (p < 0.05) and increased apoptosis compared to the control group. Compared with the controls, IV significantly increased the expression of HK2, p-AKT, p-mTOR, multidrug resistance-associated protein 1 and P-glycoprotein (P < 0.05), but decreased glucose uptake. Treatment with adriamycin, daunorubicin and imatinib resulted in a progressive increase in inhibition of cell proliferation, with the IV group showing the highest inhibition rate among the three groups (P < 0.05). Thus, inhibition of MEIS1 activity promoted apoptosis, inhibited the proliferation of Kasumi-1 and Kasumi-6 cells, and increaseed the anticancer effect of the drugs, suggesting that inhibition of MEIS1 may be a potential strategy for the treatment of AML.

LDHA mediated degradation of extracellular matrix is a potential target for the treatment of aortic dissection

Aortic dissection (AD) is a disease with high mortality and lacks effective drug treatment. Recent studies have shown that the development of AD is closely related to glucose metabolism. Lactate dehydrogenase A (LDHA) is a key glycolytic enzyme and plays an important role in cardiovascular disease. However, the role of LDHA in the progression of AD remains to be elucidated. Here, we found that the level of LDHA was significantly elevated in AD patients and the mouse model established by BAPN combined with Ang II. In vitro, the knockdown of LDHA reduced the growth of human aortic vascular smooth muscle cells (HAVSMCs), glucose consumption, and lactate production induced by PDGF-BB. The overexpression of LDHA in HAVSMCs promoted the transformation of HAVSMCs from contractile phenotype to synthetic phenotype, and increased the expression of MMP2/9. Mechanistically, LDHA promoted MMP2/9 expression through the LDHA-NDRG3-ERK1/2-MMP2/9 pathway. In vivo, Oxamate, LDH and lactate inhibitor, reduced the degradation of elastic fibers and collagen deposition, inhibited the phenotypic transformation of HAVSMCs from contractile phenotype to synthetic phenotype, reduced the expression of NDRG3, p-ERK1/2, and MMP2/9, and delayed the progression of AD. To sum up, the increase of LDHA promotes the production of MMP2/9, stimulates the degradation of extracellular matrix (ECM), and promoted the transformation of HAVSMCs from contractile phenotype to synthetic phenotype. Oxamate reduced the progression of AD in mice. LDHA may be a therapeutic target for AD.

Regulation of reactive oxygen species in the pathogenesis of matrix vesicles induced calcification of recipient vascular smooth muscle cells

INTRODUCTION

Increased oxidative stress is associated with vascular calcification in patients with chronic kidney disease (CKD). We have previously demonstrated that cellular-derived matrix vesicles (MV), but not media-derived MV, are endocytosed in the presence of phosphorus by recipient normal rat vascular smooth muscle cells (VSMC) and induce calcification through ERK1/2 and [Ca²⁺]_i signaling. We hypothesized that these changes were mediated by increased reactive oxygen species (ROS) production.

METHODS

MV were co-cultured with recipient VSMC in the presence of high phosphorus and ROS production and cell signaling assessed.

RESULTS

The results demonstrated MV endocytosis led to increased ROS production in recipient VSMC with no increase in mitochondrial oxygen consumption or oxidative phosphorylation (OXPHOS), indicating the ROS was not from the mitochondria. The use of inhibitors demonstrated that endocytosis of these MV by VSMC led to a signaling cascade in the cytoplasm beginning with ERK1/2 signaling, then increased [Ca²⁺]_i and stimulation of ROS production, mediated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX)1/4. Media-derived MV did not induce this cascade, indicating endocytosis itself was not a factor. Furthermore, inhibition of either ERK1/2 activation or [Ca²⁺]_i reduced vascular calcification.

CONCLUSION

We conclude that endocytosis of pro-mineralizing MV can induce a series of signaling events in normal VSMC that culminate in generation of ROS via activation of NOX1/4. Understanding these pathways will allow the development of future targeted therapeutics.

Inhibitory Effect of a Glutamine Antagonist on Proliferation and Migration of VSMCs via Simultaneous Attenuation of Glycolysis and Oxidative Phosphorylation

Excessive proliferation and migration of vascular smooth muscle cells (VSMCs) contribute to the development of atherosclerosis and restenosis. Glycolysis and glutaminolysis are increased in rapidly proliferating VSMCs to support their increased energy requirements and biomass production. Thus, it is essential to develop new pharmacological tools that regulate metabolic reprogramming in VSMCs for treatment of atherosclerosis. The effects of 6-diazo-5-oxo-L-norleucine (DON), a glutamine antagonist, have been broadly investigated in highly proliferative cells; however, it is unclear whether DON inhibits proliferation of VSMCs and neointima formation. Here, we investigated the effects of DON on neointima formation in vivo as well as proliferation and migration of VSMCs in vitro. DON simultaneously inhibited FBS- or PDGF-stimulated glycolysis and glutaminolysis as well as mammalian target of rapamycin complex I activity in growth factor-stimulated VSMCs, and thereby suppressed their proliferation and migration. Furthermore, a DON-derived prodrug, named JHU-083, significantly attenuated carotid artery ligation-induced neointima formation in mice. Our results suggest that treatment with a glutamine antagonist is a promising approach to prevent progression of atherosclerosis and restenosis.

Smooth Muscle Cell-Specific PKM2 (Pyruvate Kinase Muscle 2) Promotes Smooth Muscle Cell Phenotypic Switching and Neointimal Hyperplasia

[Figure: see text].

Prenatal air pollution influences neurodevelopment and behavior in autism spectrum disorder by modulating mitochondrial physiology

We investigate the role of the mitochondrion, an organelle highly sensitive to environmental agents, in the influence of prenatal air pollution exposure on neurodevelopment and behavior in 96 children with autism spectrum disorder (ASD) [45 with neurodevelopmental regression (NDR); 76% Male; mean (SD) age 10 y 9 m (3 y 9 m)]. Mitochondrial function was assessed using the Seahorse XFe96 in fresh peripheral blood mononuclear cells. Second and third trimester average and maximal daily exposure to fine air particulate matter of diameter ≤2.5 µm (PM2.5) was obtained from the Environmental Protection Agency's Air Quality System. Neurodevelopment was measured using the Vineland Adaptive Behavior Scale 2nd edition and behavior was assessed using the Aberrant Behavior Checklist and Social Responsiveness Scale. Prenatal PM2.5 exposure influenced mitochondrial respiration during childhood, but this relationship was different for those with (r = 0.25-0.40) and without (r = -0.07 to -0.19) NDR. Mediation analysis found that mitochondrial respiration linked to energy production accounted for 25% (SD = 2%) and 10% (SD = 2%) of the effect of average prenatal PM2.5 exposure on neurodevelopment and behavioral symptoms, respectively. Structural equation models estimated that PM2.5 and mitochondrial respiration accounted for 34% (SD = 4%) and 36% (SD = 3%) of the effect on neurodevelopment, respectively, and that behavior was indirectly influenced by mitochondrial respiration through neurodevelopment but directly influenced by prenatal PM2.5. Our results suggest that prenatal exposure to PM2.5 disrupts neurodevelopment and behavior through complex mechanisms, including long-term changes in mitochondrial respiration and that patterns of early development need to be considered when studying the influence of environmental agents on neurodevelopmental outcomes.

Luteolin Ameliorates Experimental Pulmonary Arterial Hypertension via Suppressing Hippo-YAP/PI3K/AKT Signaling Pathway

Luteolin is a flavonoid compound with a variety of pharmacological effects. In this study, we explored the effects of luteolin on monocrotaline (MCT) induced rat pulmonary arterial hypertension (PAH) and underlying mechanisms. A rat PAH model was generated through MCT injection. In this model, luteolin improved pulmonary vascular remodeling and right ventricular hypertrophy, meanwhile, luteolin could inhibit the proliferation and migration of pulmonary artery smooth muscle cells induced by platelet-derived growth factor-BB (PDGF-BB) in a dose-dependent manner. Moreover, our results showed that luteolin could downregulate the expression of LATS1 and YAP, decrease YAP nuclear localization, reduce the expression of PI3K, and thereby restrain the phosphorylation of AKT induced by PDGF-BB. In conclusion, luteolin ameliorated experimental PAH, which was at least partly mediated through suppressing HIPPO-YAP/PI3K/AKT signaling pathway. Therefore, luteolin might become a promising candidate for treatment of PAH.

Nitric Oxide Circumvents Virus-Mediated Metabolic Regulation during Human Cytomegalovirus Infection

Nitric oxide is a versatile and critical effector molecule that can modulate many cellular functions. Although recognized as a regulator of infections, the inhibitory mechanism of nitric oxide against human cytomegalovirus (HCMV) replication remains elusive. We demonstrate that nitric oxide attenuates viral replication by interfering with HCMV-mediated modulation of several cellular processes. Nitric oxide exposure reduced HCMV genome synthesis and infectious viral progeny with cell-type-dependent differences observed. Mitochondrial respiration was severely reduced in both uninfected and HCMV-infected cells during exposure with little impact on ATP levels indicating changes in cellular metabolism. Metabolomics identified significantly altered small molecules in multiple pathways during nitric oxide exposure including nucleotide biosynthesis, tricarboxylic acid (TCA) cycle, and glutamine metabolism. Glutathione metabolites were increased coinciding with a reduction in the glutathione precursor glutamine. This shift was accompanied by increased antioxidant enzymes. Glutamine deprivation mimicked defects in HCMV replication and mitochondrial respiration observed during nitric oxide exposure. These data suggest that nitric oxide limits glutaminolysis by shuttling glutamine to glutathione synthesis. In addition, lipid intermediates were severely altered, which likely contributes to the observed increase in defective viral particles. Nitric oxide disrupts multiple cellular processes, and we had limited success in rescuing replication defects by supplementing with metabolic intermediates. Our studies indicate that nitric oxide attenuation of HCMV is multifactorial with interference in viral manipulation of cellular metabolism playing a central role.IMPORTANCE Human cytomegalovirus is a prevalent pathogen that can cause serious disease in patients with compromised immune systems, including transplant patients and during congenital infection. HCMV lytic replication likely occurs in localized sites of infection with immune cells infiltrating and releasing nitric oxide with other effector molecules. This nonspecific immune response results in both uninfected and infected cells exposed to high levels of nitric oxide. The absence of nitric oxide synthase has been associated with lethal HCMV infection. We demonstrate that nitric oxide inhibition of HCMV replication is multifactorial and cell type dependent. Our results indicate that nitric oxide controls replication by interfering with viral modulation of cellular metabolism while also affecting proliferation and mitochondrial respiration of neighboring uninfected cells. These studies identify the mechanism and contribution of nitric oxide during immune control of HCMV infection and provide insight into its role in other viral infections.

Metabolic adaptations of cells at the vascular-immune interface during atherosclerosis

Metabolic reprogramming is a physiological cellular adaptation to intracellular and extracellular stimuli that couples to cell polarization and function in multiple cellular subsets. Pathological conditions associated to nutrients overload, such as dyslipidaemia, may disturb cellular metabolic homeostasis and, in turn, affect cellular response and activation, thus contributing to disease progression. At the vascular/immune interface, the site of atherosclerotic plaque development, many of these changes occur. Here, an intimate interaction between endothelial cells (ECs), vascular smooth muscle cells (VSMCs) and immune cells, mainly monocytes/macrophages and lymphocytes, dictates physiological versus pathological response. Furthermore, atherogenic stimuli trigger metabolic adaptations both at systemic and cellular level that affect the EC layer barrier integrity, VSMC proliferation and migration, monocyte infiltration, macrophage polarization, lymphocyte T and B activation. Rewiring cellular metabolism by repurposing “metabolic drugs” might represent a pharmacological approach to modulate cell activation at the vascular immune interface thus contributing to control the immunometabolic response in the context of cardiovascular diseases.

Mitochondrial spare respiratory capacity: Mechanisms, regulation, and significance in non-transformed and cancer cells

Mitochondrial metabolism must constantly adapt to stress conditions in order to maintain bioenergetic levels related to cellular functions. This absence of proper adaptation can be seen in a wide array of conditions, including cancer. Metabolic adaptation calls on mitochondrial function and draws on the mitochondrial reserve to meet increasing needs. Among mitochondrial respiratory parameters, the spare respiratory capacity (SRC) represents a particularly robust functional parameter to evaluate mitochondrial reserve. We provide an overview of potential SRC mechanisms and regulation with a focus on its particular significance in cancer cells.

Metabolism of vascular smooth muscle cells in vascular diseases

Vascular smooth muscle cells (VSMCs) are the fundamental component of the medial layer of arteries and are essential for arterial physiology and pathology. It is becoming increasingly clear that VSMCs can alter their metabolism to fulfill the bioenergetic and biosynthetic requirements. During vascular injury, VSMCs switch from a quiescent "contractile" phenotype to a highly migratory and proliferative "synthetic" phenotype. Recent studies have found that the phenotype switching of VSMCs is driven by a metabolic switch. Metabolic pathways, including aerobic glycolysis, fatty acid oxidation, and amino acid metabolism, have distinct, indispensable roles in normal and dysfunctional vasculature. VSMCs metabolism is also related to the metabolism of endothelial cells. In the present review, we present a brief overview of VSMCs metabolism and how it regulates the progression of several vascular diseases, including atherosclerosis, systemic hypertension, diabetes, pulmonary hypertension, vascular calcification, and aneurysms, and the effect of the risk factors for vascular disease (aging, cigarette smoking, and excessive alcohol drinking) on VSMC metabolism to clarify the role of VSMCs metabolism in the key pathological process.

Early life metal exposure dysregulates cellular bioenergetics in children with regressive autism spectrum disorder

Neurodevelopmental regression (NDR) is a subtype of autism spectrum disorder (ASD) that manifests as loss of previously acquired developmental milestones. Early life dysregulation of nutritional metals and/or exposure to toxic metals have been associated with ASD, but the underlying biological mechanisms by which metals influence neurodevelopment remain unclear. We hypothesize that metals influences neurodevelopment through dysregulation of bioenergetics. Prenatal and early postnatal metal exposures were measured using validated tooth-matrix biomarkers in 27 ASD cases (13 with NDR) and 7 typically-developing (TD) controls. Mitochondrial respiration and glycolysis were measured in peripheral blood mononuclear cells using the Seahorse XF96. Children with ASD demonstrated lower prenatal and postnatal Copper (Cu) and prenatal Nickel concentrations and Copper-to-Zinc (Cu/Zn) ratio as compared with TD children. Children with ASD and NDR showed greater metal-related disruption of cellular bioenergetics than children with ASD without NDR. For children with ASD and NDR mitochondrial respiration decreased as prenatal Manganese concentration increased and increased as prenatal Zinc concentration increased; glycolysis decreased with increased exposure to prenatal Manganese and Lead and postnatal Manganese. For children with ASD without a history of NDR, glycolysis increased with increased postnatal exposure to Tin. Language and communication scores in children with ASD were positively related to prenatal Cu exposure and Cu/Zn ratio. This study suggests that prenatal nutritional metals may be important for neurodevelopment in children with ASD, and that exposure to toxic metals and differences in nutritional metal exposures is associated with dysregulation of cellular bioenergetics, particularly in the NDR subtype of ASD.

Impact of β-glycerophosphate on the bioenergetic profile of vascular smooth muscle cells

Abstract

In chronic kidney disease, hyperphosphatemia is a key pathological factor promoting medial vascular calcification, a common complication associated with cardiovascular events and mortality. This active pathophysiological process involves osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs) via complex intracellular mechanisms that are still incompletely understood. Little is known about the effects of phosphate on the bioenergetic profile of VSMCs during the onset of this process. Therefore, the present study explored the effects of the phosphate donor β-glycerophosphate on cellular bioenergetics of VSMCs. Mitochondrial and glycolytic functions were determined utilizing extracellular flux analysis in primary human aortic VSMCs following exposure to β-glycerophosphate. In VSMCs, β-glycerophosphate increased basal respiration, mitochondrial ATP production as well as proton leak and decreased spare respiratory capacity and coupling efficiency, but did not modify non-mitochondrial or maximal respiration. β-Glycerophosphate-treated VSMCs had higher ability to increase mitochondrial glutamine and long-chain fatty acid usage as oxidation substrates to meet their energy demand. β-Glycerophosphate did not modify glycolytic function or basal and glycolytic proton efflux rate. In contrast, β-glycerophosphate increased non-glycolytic acidification. β-Glycerophosphate-treated VSMCs had a more oxidative and less glycolytic phenotype, but a reduced ability to respond to stressed conditions via mitochondrial respiration. Moreover, compounds targeting components of mitochondrial respiration modulated β-glycerophosphate-induced oxidative stress, osteo-/chondrogenic signalling and mineralization of VSMCs. In conclusion, β-glycerophosphate modifies key parameters of mitochondrial function and cellular bioenergetics in VSMCs that may contribute to the onset of phenotypical transdifferentiation and calcification. These observations advance the understanding of the role of energy metabolism in VSMC physiology and pathophysiology of vascular calcification during hyperphosphatemia.

Key messages

β-Glycerophosphate modifies key parameters of mitochondrial respiration in VSMCs.

β-Glycerophosphate induces changes in mitochondrial fuel choice in VSMCs.

β-Glycerophosphate promotes a more oxidative and less glycolytic phenotype of VSMCs.

β-Glycerophosphate triggers mitochondrial-dependent oxidative stress in VSMCs.

Bioenergetics impact β-glycerophosphate-induced VSMC calcification.

Electronic supplementary material

The online version of this article (10.1007/s00109-020-01925-8) contains supplementary material, which is available to authorized users.

Developmental regression and mitochondrial function in children with autism

BACKGROUND

Developmental regression (DR) occurs in about one-third of children with Autism Spectrum Disorder (ASD) yet it is poorly understood. Current evidence suggests that mitochondrial function in not normal in many children with ASD. However, the relationship between mitochondrial function and DR has not been well-studied in ASD.

METHODS

This cross-sectional study of 32 children, 2 to 8 years old with ASD, with (n = 11) and without (n = 12) DR, and non-ASD controls (n = 9) compared mitochondrial respiration and mtDNA damage and copy number between groups and their relation to standardized measures of ASD severity.

RESULTS

Individuals with ASD demonstrated lower ND1, ND4, and CYTB copy number (Ps < 0.01) as compared to controls. Children with ASD and DR had higher maximal oxygen consumption rate (Ps < 0.02), maximal respiratory capacity (P < 0.05), and reserve capacity (P = 0.01) than those with ASD without DR. Coupling Efficiency and Maximal Respiratory Capacity were associated with disruptive behaviors but these relationships were different for those with and without DR. Higher ND1 copy number was associated with better behavior.

CONCLUSIONS

This study suggests that individuals with ASD and DR may represent a unique metabolic endophenotype with distinct abnormalities in respiratory function that may put their mitochondria in a state of vulnerability. This may allow physiological stress to trigger mitochondrial decompensation as is seen clinically as DR. Since mitochondrial function was found to be related to ASD symptoms, the mitochondria could be a potential target for novel therapeutics. Additionally, identifying those with vulnerable mitochondrial before DR could result in prevention of ASD.

Metabolic Stress

Mitochondria regulate major aspects of cell function by producing ATP, contributing to Ca²⁺ signaling, influencing redox potential, and controlling levels of reactive oxygen species. In this review, we will discuss recent findings that illustrate how mitochondrial respiration, Ca²⁺ handling, and production of reactive oxygen species affect vascular smooth muscle cell function during neointima formation. We will review mitochondrial fission/fusion as fundamental mechanisms for smooth muscle proliferation, migration, and metabolism and examine the role of mitochondrial mobility in cell migration. In addition, we will summarize novel aspects by which mitochondria regulate apoptosis.

PKM2-dependent glycolysis promotes the proliferation and migration of vascular smooth muscle cells during atherosclerosis

Increased glycolysis is involved in the proliferation and migration of vascular smooth muscle cells (VSMCs). Pyruvate kinase isoform M2 (PKM2), a key rate-limiting enzyme in glycolysis, accelerates the proliferation and migration of tumor cells. Although the intracellular mechanisms associated with oxidized low-density lipoprotein (oxLDL)-stimulated VSMC proliferation and migration have been extensively explored, it is still unclear whether oxLDL promotes the proliferation and migration of VSMCs by enhancing PKM2-dependent glycolysis. In the present study, we detected PKM2 expression and pyruvate kinase activity in oxLDL-treated VSMCs and explored the regulation of PKM2 in oxLDL-treated VSMCs and apoE-/- mice. The results showed that PKM2 expression in VSMCs was higher in the intima than in the media in plaques from atherosclerotic rabbits. Moreover, PKM2 level in VSMCs was increased during atherosclerosis progression in apoE-/- mice. Both PKM2 expression and pyruvate kinase activity were found to be upregulated by oxLDL stimulation in VSMCs. Shikonin (SKN), a specific inhibitor of PKM2, was found to inhibit the oxLDL-induced proliferation and migration in VSMCs, in addition to delaying the atherosclerosis progression in apoE-/- mice. More importantly, oxLDL increased glucose uptake, ATP and lactate production, and the extracellular acidification rate in VSMCs, which could be reversed by SKN. Meanwhile, oxygen consumption rate was unchanged after oxLDL stimulation, suggesting that glycolysis is the main contributor to the energy supply in oxLDL-treated VSMCs. Our results suggest that oxLDL induces VSMC proliferation and migration by upregulating PKM2-dependent glycolysis, thereby contributing to the atherosclerosis progression. Thus, targeting PKM2-dependent glycolysis might provide a novel therapeutic approach for the treatment of atherosclerosis.

The Role of Metabolic Flexibility in the Regulation of the DNA Damage Response by Nitric Oxide

In this report, we show that nitric oxide suppresses DNA damage response (DDR) signaling in the pancreatic β-cell line INS 832/13 and rat islets by inhibiting intermediary metabolism. Nitric oxide is known to inhibit complex IV of the electron transport chain and aconitase of the Krebs cycle. Non-β cells compensate by increasing glycolytic metabolism to maintain ATP levels; however, β cells lack this metabolic flexibility, resulting in a nitric oxide-dependent decrease in ATP and NAD+ Like nitric oxide, mitochondrial toxins inhibit DDR signaling in β cells by a mechanism that is associated with a decrease in ATP. Non-β cells compensate for the effects of mitochondrial toxins with an adaptive shift to glycolytic ATP generation that allows for DDR signaling. Forcing non-β cells to derive ATP via mitochondrial respiration (replacing glucose with galactose in the medium) and glucose deprivation sensitizes these cells to nitric oxide-mediated inhibition of DDR signaling. These findings indicate that metabolic flexibility is necessary to maintain DDR signaling under conditions in which mitochondrial oxidative metabolism is inhibited and support the inhibition of oxidative metabolism (decreased ATP) as one protective mechanism by which nitric oxide attenuates DDR-dependent β-cell apoptosis.

Activation of anti-oxidant of curcumin pyrazole derivatives through preservation of mitochondria function and Nrf2 signaling pathway

Oxidative stress is an important cause of neurodegenerative diseases. Antioxidant is an potential important method to treat such diseases. The aim of this study is to discover new and effective antioxidants and their mechanism. The neuroprotective effect of six curcumin pyrozole compounds were first evaluated on sodium nitroprusside (SNP) - induced PC12 cell injury by testing cell viability and LDH release. The results showed that four compounds (C1-C4) have more significant protective effects compared to curcumin and edaravone. Furthermore, compounds C1-C4 can attenuate the intracellular ROS, and compound C3 is the most effective one which can preservate the mitochondria function by inhibiting the mitochondrial membrane potential loss and enhance nuclear translocation of Nrf2 in PC12 cell. These results indicated that C3 may be a potential candidate drug for treating neurodegenerative diseases.

Mechanisms of Trained Innate Immunity in oxLDL Primed Human Coronary Smooth Muscle Cells

Objective: Damage and pathogen associated molecular patterns such as oxidized low-density lipoprotein (oxLDL) or bacillus Calmette-Guerin (BCG) vaccine can induce long term pro-inflammatory priming in monocytes and macrophages due to metabolic and epigenetic reprogramming—an emerging new concept called trained innate immunity. Vascular smooth muscle cells express pattern recognition receptors involved in trained innate immunity in monocytes. Here we investigated whether the mechanisms of trained innate immunity also control a proinflammatory phenotype in human coronary smooth muscle cells.

Methods: Human coronary smooth muscle cells were primed with oxLDL or BCG for 24 h. After a resting time of 4 to 7 days, the cells were restimulated with either PAM3cys4, LPS or TNFα and cytokine production or mRNA expression were measured. Then, mechanisms of monocyte trained innate immunity were analyzed in smooth muscle cells, including receptors, intracellular pathways as well as metabolic and epigenetic reprogramming.

Results: Priming with oxLDL or BCG lead to a significantly increased production of IL6, IL8 and MCP-1 following restimulation. OxLDL priming had little effect on the expression of macrophage or SMC marker genes. Proinflammatory priming of smooth muscle cells induced mTOR-HIF1α-signaling and could be blocked by mTOR-, TLR2-, and TLR4-inhibition. Finally, metabolic and epigenetic mechanisms of trained innate immunity in monocytes could be replicated in smooth muscle cells, including increased glucose consumption, lactate production, responsiveness to 6-fluoromevalonate and mevalonate treatment and inhibition of priming by the histone methyltransferase inhibitor methylthioadenosine (MTA).

Conclusion: We demonstrate for the first time that mechanisms of the so called trained innate immunity control a proinflammatory phenotype in non-immune cells of the vascular wall. Our findings warrant further research into the specificity of trained innate immunity as an immune cell response as well as the mechanisms of vascular smooth muscle cells inflammation.

Pyruvate Treatment Restores the Effectiveness of Chemotherapeutic Agents in Human Colon Adenocarcinoma and Pleural Mesothelioma Cells

Emerging evidence supports the idea that a dysfunction in cell metabolism could sustain a resistant phenotype in cancer cells. As the success of chemotherapeutic agents is often questioned by the occurrence of multidrug resistance (MDR), a multiple cross-resistance towards different anti-cancer drugs represent a major obstacle to cancer treatment. The present study has clarified the involvement of the carbon metabolites in a more aggressive tumor colon adenocarcinoma phenotype and in a chemoresistant mesothelioma, and the role of pyruvate treatment in the reversion of the potentially related resistance. For the first time, we have shown that human colon adenocarcinoma cells (HT29) and its chemoresistant counterpart (HT29-dx) displayed different carbon metabolism: HT29-dx cells had a higher glucose consumption compared to HT29 cells, whereas human malignant mesothelioma (HMM) cells showed a lower glucose consumption compared to HT29 cells, accompanied by a lower pyruvate production and, consequently, a higher production of lactate. When treated with pyruvate, both HT29-dx and HMM cells exhibited a re-established accumulation of doxorubicin and a lower survival ability, a decreased activity of multidrug resistance protein 1 (MRP1) and a restored mitochondrial respiratory chain function, improving the effectiveness of the chemotherapeutic agents in these resistant cancer cells.

Clinical and Molecular Characteristics of Mitochondrial Dysfunction in Autism Spectrum Disorder

Autism spectrum disorder (ASD) affects ~ 2% of children in the United States. The etiology of ASD likely involves environmental factors triggering physiological abnormalities in genetically sensitive individuals. One of these major physiological abnormalities is mitochondrial dysfunction, which may affect a significant subset of children with ASD. Here we systematically review the literature on human studies of mitochondrial dysfunction related to ASD. Clinical aspects of mitochondrial dysfunction in ASD include unusual neurodevelopmental regression, especially if triggered by an inflammatory event, gastrointestinal symptoms, seizures, motor delays, fatigue and lethargy. Traditional biomarkers of mitochondrial disease are widely reported to be abnormal in ASD, but appear non-specific. Newer biomarkers include buccal cell enzymology, biomarkers of fatty acid metabolism, non-mitochondrial enzyme function, apoptosis markers and mitochondrial antibodies. Many genetic abnormalities are associated with mitochondrial dysfunction in ASD, including chromosomal abnormalities, mitochondrial DNA mutations and large-scale deletions, and mutations in both mitochondrial and non-mitochondrial nuclear genes. Mitochondrial dysfunction has been described in immune and buccal cells, fibroblasts, muscle and gastrointestinal tissue and the brains of individuals with ASD. Several environmental factors, including toxicants, microbiome metabolites and an oxidized microenvironment are shown to modulate mitochondrial function in ASD tissues. Investigations of treatments for mitochondrial dysfunction in ASD are promising but preliminary. The etiology of mitochondrial dysfunction and how to define it in ASD is currently unclear. However, preliminary evidence suggests that the mitochondria may be a fruitful target for treatment and prevention of ASD. Further research is needed to better understand the role of mitochondrial dysfunction in the pathophysiology of ASD.

Redox control of vascular smooth muscle cell function and plasticity

Vascular smooth muscle cells (SMC) play a major role in vascular diseases, such as atherosclerosis and hypertension. It has long been established in vitro that contractile SMC can phenotypically switch to function as proliferative and/or migratory cells in response to stimulation by oxidative stress, growth factors, and inflammatory cytokines. Reactive oxygen species (ROS) are oxidative stressors implicated in driving vascular diseases, shifting cell bioenergetics, and increasing SMC proliferation, migration, and apoptosis. In this review, we summarize our current knowledge of how disruptions to redox balance can functionally change SMC and how this may influence vascular disease pathogenesis. Specifically, we focus on our current understanding of the role of vascular nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) 1, 4, and 5 in SMC function. We also review the evidence implicating mitochondrial fission in SMC phenotypic transitions and mitochondrial fusion in maintenance of SMC homeostasis. Finally, we discuss the importance of the redox regulation of the soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway as a potential oxidative and therapeutic target for regulating SMC function.

Alpha-enolase regulates the malignant phenotype of pulmonary artery smooth muscle cells via the AMPK-Akt pathway

The molecular mechanisms underlying the metabolic shift toward increased glycolysis observed in pulmonary artery smooth muscle cells (PASMC) during the pathogenesis of pulmonary arterial hypertension (PAH) are not fully understood. Here we show that the glycolytic enzyme α-enolase (ENO1) regulates the metabolic reprogramming and malignant phenotype of PASMC. We show that ENO1 levels are elevated in patients with associated PAH and in animal models of hypoxic pulmonary hypertension (HPH). The silencing or inhibition of ENO1 decreases PASMC proliferation and de-differentiation, and induces PASMC apoptosis, whereas the overexpression of ENO1 promotes a synthetic, de- differentiated, and apoptotic-resistant phenotype via the AMPK-Akt pathway. The suppression of ENO1 prevents the hypoxia-induced metabolic shift from mitochondrial respiration to glycolysis in PASMC. Finally, we find that pharmacological inhibition of ENO1 reverses HPH in mice and rats, suggesting ENO1 as a regulator of pathogenic metabolic reprogramming in HPH.

Reversal of the Warburg effect with DCA in PDGF‑treated human PASMC is potentiated by pyruvate dehydrogenase kinase‑1 inhibition mediated through blocking Akt/GSK‑3β signalling

There is accumulating evidence indicating that the growth inhibitory effect of dichloroacetate (DCA) on pulmonary arterial smooth muscle cells (PASMCs) may be associated with the reversal of the Warburg effect and initiation of the mitochondria-dependent apoptotic pathway. Previous studies indicated that platelet-derived growth factor (PDGF) promoted the Warburg effect and resulted in apoptotic resistance of PASMCs, which was attributed to activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signalling pathway. However, the mechanism underlying the pro-apoptotic effect of DCA on PDGF-treated PASMCs has not been thoroughly elucidated, and the effect of the Akt/glycogen synthase kinase-3β (GSK-3β) pathway inhibition concomitant with the effect of DCA on PASMC proliferation remains unclear. The growth of human PASMCs and the lactate concentration in extracellular medium of PASMCs were detected by Cell Counting Kit-8 assays and a Lactate Colorimetric Assay kit, respectively. Cell apoptosis was evaluated by fluorescence activated cell sorting. The mitochondrial membrane potential (ΔΨm) was assessed with 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazol-carbocy-anine iodide assays. The expression levels of phosphorylated Akt and GSK-3β, pyruvate dehydrogenase, cleaved caspase-3, pyruvate dehydrogenase kinase-1 (PDK-1), hypoxia inducible factor-1α (HIF-1α) and hexokinase-2 (HK-2) were measured with western blot analysis. Confocal analyses were employed to determine HK-2 co-localisation with the mitochondria. The results indicated that DCA inhibited human PASMC proliferation in a dose-dependent manner. DCA at 10 mM promoted apoptosis and the upregulation of activated caspase-3 in PASMCs pre-treated with 20 ng/ml PDGF-homeodimer BB (BB). Treatment with 5 µM LY294002 produced minimal anti-proliferative effects on human PASMCs and barely induced cellular apoptosis and caspase-3 activation. However, co-administration of 10 mM DCA with LY294002 significantly decreased the cell proliferation index and induced cell apoptosis and caspase-3 activation. The combined administration of LY294002 with DCA significantly decreased lactate concentration, promoted the depolarisation of the ΔΨm and repressed HIF-1α upregulation and HK-2 activation in PASMCs treated with PDGF, which was attributed to the potentiation of DCA-induced PDK-1 inhibition by LY294002 via blockade of the Akt/GSK-3β/HIF-1α signalling pathway. In conclusion, inhibition of the Akt/GSK-3β pathway improved the pro-apoptotic effect of DCA on human PASMCs, which may be attributed to a reversal of the Warburg effect by blocking the mutual interaction between HIF-1α and PDK-1, consequently downregulating HK-2. Therefore, combinatory treatment with DCA and PI3K inhibitors may represent a novel therapeutic strategy for the reversal of apoptosis resistance exhibited by PASMCs as a result of mitochondrial bioenergetic abnormalities, as well as the treatment of pulmonary vascular remodelling in pulmonary arterial hypertension.

Metabolomic analysis of longissimus from underperforming piglets relative to piglets with normal preweaning growth

Background

Recent increases in intra-litter variability in weaning weight have raised swine production costs. A contributor to this variability is the normal birth weight pig that grows at a slower rate than littermates of similar birth weight. The goal of this study was to interrogate biochemical profiles manifested in skeletal muscle originating from slow growing (SG) and faster growing littermates (control), with the aim of identifying differences in metabolic pathway utilization between skeletal muscle of the SG pig relative to its littermates. Samples of longissimus muscle from littermate pairs of pigs were collected at 21 d of age for metabolomic analysis (Metabolon, Inc., Durham, NC).

Results

Birth weights did not differ between littermate pairs of SG and Control pigs (P > 0.05). Weaning weights differed by 1.51 ± 0.19 kg (P < 0.001). Random forest (RF) analysis was effective at segregating the metabolome of muscle samples by growth rate, resulting in a predictive accuracy of 81% versus random segregation (50%). Decreases in sugars in the pentose phosphate pathway (PPP) in the longissimus of SG pigs were detected (P < 0.05). Decreases were also apparent in glycolytic intermediates (glycerol-3-phosphate and lactate) and key glycolysis-derived intermediates (glucose-6-phosphate and fructose-6-phosphate; P < 0.05). SG pigs had increased levels of phospholipids, lysolipids, diacylglycerols, and sphingolipids (P < 0.05). Pathway analysis identified a cluster of molecules associated with muscle and collagen/extracellular matrix breakdown that are increased in the SG pig (glutamate, 3-methylhistidine and hydroxylated proline moieties; P < 0.05). Nicotinate metabolism was altered in SG pigs, resulting in a 78% decrease in the nicotinamide adenine dinucleotide pool (P < 0.05).

Conclusions

These metabolomic data provide the first evidence for biochemical mechanisms that should be investigated to determine if they have a potential role in the slow growth in some normal birth weight piglets that contribute to increased intra-litter variability in weaning weights and provides essential information and potential targets for the development of nutritional intervention strategies.

Electronic supplementary material

The online version of this article (10.1186/s40104-018-0251-3) contains supplementary material, which is available to authorized users.

Vascular smooth muscle cell proliferation as a therapeutic target. Part 1: molecular targets and pathways

Cardiovascular diseases are a major cause of human death worldwide. Excessive proliferation of vascular smooth muscle cells contributes to the etiology of such diseases, including atherosclerosis, restenosis, and pulmonary hypertension. The control of vascular cell proliferation is complex and encompasses interactions of many regulatory molecules and signaling pathways. Herein, we recapitulated the importance of signaling cascades relevant for the regulation of vascular cell proliferation. Detailed understanding of the mechanism underlying this process is essential for the identification of new lead compounds (e.g., natural products) for vascular therapies.

Small-Vessel Vasculopathy Due to Aberrant Autophagy in LAMP-2 Deficiency

Lysosomal associated membrane protein 2 (LAMP2) is physiologically implicated in autophagy. A genetic LAMP2 defect causes Danon disease, which consists of two major phenotypes of myopathy and cardiomyopathy. In addition, arteriopathy may manifest on rare occasions but the pathological basis remains unknown. We encountered two Danon families that developed small-vessel vasculopathy in the coronary or cerebral arteries. To investigate the underlying mechanisms, we characterized the biological features of LAMP-2–deficient mice and cultured cells. LAMP-2–deficient mice at 9–24 months of age showed medial thickening with luminal stenosis due to proliferation of vascular smooth muscle cells (VSMC) in muscular arteries. Ultrastructural analysis of VSMC revealed various autophagic vacuoles scattered throughout the cytoplasm, suggesting impaired autophagy of long-lived metabolites and degraded organelles (i.e., mitochondria). The VSMC in Lamp2 null mice expressed more vimentin but less α-smooth muscle actin (α-SMA), indicating a switch from contractile to synthetic phenotype. Silencing of LAMP2 in cultured human brain VSMC showed the same phenotypic transition with mitochondrial fragmentation, enhanced mitochondrial respiration, and overproduction of reactive oxygen species (ROS). These findings indicate that LAMP-2 deficiency leads to arterial medial hypertrophy with the phenotypic conversion of VSMC, resulting from age-dependent accumulation of cellular waste generated by aberrant autophagy.

Impaired mitochondrial respiration in human carotid plaque atherosclerosis: A potential role for Pink1 in vascular smooth muscle cell energetics

BACKGROUND AND AIMS

DNA damage and mitochondrial dysfunction are thought to play an essential role in ageing and the energetic decline of vascular smooth muscle cells (VSMCs) essential for maintaining plaque integrity. We aimed to better understand VSMCs and identify potentially useful compensatory pathways that could extend their lifespan. Moreover, we wanted to assess if defects in mitochondrial respiration exist in human atherosclerotic plaques and to identify the appropriate markers that may reflect a switch in VSMC energy metabolism.

METHODS

Human plaque tissue and cells were assessed for composition and evidence of DNA damage, repair capacity and mitochondrial dysfunction. Fresh plaque tissue was evaluated using high resolution oxygen respirometry to assess oxidative metabolism. Recruitment and processing of the mitochondrial regulator of autophagy Pink1 kinase was investigated in combination with transcriptional and protein markers associated with a potential switch to a more glycolytic metabolism.

RESULTS

Human VSMC have increased nuclear (nDNA) and mitochondrial (mtDNA) damage and reduced repair capacity. A subset of VSMCs within plaque cap had decreased oxidative phosphorylation and expression of Pink1 kinase. Plaque cells demonstrated increased glycolytic activity in response to loss of mitochondrial function. A potential compensatory glycolytic program may act as energetic switch via AMP kinase (AMPK) and hexokinase 2 (Hex2).

CONCLUSIONS

We have identified a subset of plaque VSMCs required for plaque stability that have increased mitochondrial dysfunction and decreased oxidative phosphorylation. Pink1 kinase may initiate a cellular response to promote a compensatory glycolytic program associated with upregulation of AMPK and Hex2.

Decreased Sirtuin Deacetylase Activity in LRRK2 G2019S iPSC-Derived Dopaminergic Neurons

Mitochondrial changes have long been implicated in the pathogenesis of Parkinson's disease (PD). The glycine to serine mutation (G2019S) in leucine-rich repeat kinase 2 (LRRK2) is the most common genetic cause for PD and has been shown to impair mitochondrial function and morphology in multiple model systems. We analyzed mitochondrial function in LRRK2 G2019S induced pluripotent stem cell (iPSC)-derived neurons to determine whether the G2019S mutation elicits similar mitochondrial deficits among central and peripheral nervous system neuron subtypes. LRRK2 G2019S iPSC-derived dopaminergic neuron cultures displayed unique abnormalities in mitochondrial distribution and trafficking, which corresponded to reduced sirtuin deacetylase activity and nicotinamide adenine dinucleotide levels despite increased sirtuin levels. These data indicate that mitochondrial deficits in the context of LRRK2 G2019S are not a global phenomenon and point to distinct sirtuin and bioenergetic deficiencies intrinsic to dopaminergic neurons, which may underlie dopaminergic neuron loss in PD.

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LRRK2 G2019S iPSC-derived dopaminergic neurons have unique mitochondrial defects

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LRRK2 G2019S dopaminergic neurons have increased sirtuin levels but reduced activity

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LRRK2 G2019S dopaminergic neurons have reduced NAD⁺ levels compared with other neurons

A thermal gradient modulates the oxidative metabolism and growth of human keratinocytes

During their spatial and differentiative progression, keratinocytes face a thermal gradient, from 37 °C in the proliferating basal layer to 32 °C found in skin surface. In our study, we hypothesized that this difference in temperature must be balanced by increasing the heat produced during respiratory activity. We demonstrated that at 33 °C human primary keratinocytes and HaCaT cells raised mitochondrial energy metabolism, but not glycolytic activity. At 33 °C, the increased mitochondrial ATP synthesis was associated with a strong induction of the modulator of the respiratory chain estrogen receptor β, whereas uncoupling protein 1 expression was not changed. The enhanced mitochondrial oxidative metabolism was accompanied by a remarkable reduction in proliferation. These results suggest that environmental temperature can modulate the energy metabolism and proliferation of human keratinocytes.