Impaired Mitochondrial Function Research Articles

Melatonin mitigates PNMC-induced disruption of spindle assembly and mitochondrial function in mouse Oocytes

3-methyl-4-nitrophenol (PNMC), a degradation product of organophosphorus insecticides and a byproduct of fuel combustion, exerting endocrine-disrupting effects. However, its impact on the meiotic process of oocytes remains unclear. In the present study, we investigated the effects of PNMC on meiotic maturation of mouse oocytes in vitro and related mechanisms. Morphologically, PNMC-exposure affected germinal vesicle breakdown (GVBD) and polar body extrusion (PBE) in mouse oocytes. Proteomic analysis suggested that PNMC-exposure altered oocyte protein expression that are associated with cytoskeleton, mitochondrial function and oxidative stress. Further studies demonstrated that PNMC-exposure disrupted spindle assembly and chromosome alignment, caused sustained activation of spindle assembly checkpoint (SAC), and arrested meiosis in oocytes. Specifically, PNMC-exposure interfered with the function of microtubule organizing centers (MTOCs) by significantly reducing phosphorylated mitogen activated protein kinase (p-MAPK) expression and disrupting the localization of Pericentrin and p-Aurora A, leading to spindle assembly failure. Besides, PNMC-exposure also increased α-tubulin acetylation, decreased microtubule stability. Moreover, PNMC-exposure impaired mitochondrial function, evidenced by abnormal mitochondrial distribution, decreased mitochondrial membrane potential and ATP levels, release of Cytochrome C into the cytoplasm, and elevated ROS levels. As a result, exposure to PNMC caused DNA damage and early apoptosis in oocytes. Fortunately, melatonin was able to promote oocyte maturation by removing the excessive ROS and enhancing mitochondrial function. These results highlight the adverse effects of PNMC on meiotic maturation, and underscore the protective role of melatonin against PNMC-induced damage.

Liver and Pancreatic Toxicity of Endocrine-Disruptive Chemicals: Focus on Mitochondrial Dysfunction and Oxidative Stress

In recent years, the worldwide epidemic of metabolic diseases, namely obesity, metabolic syndrome, diabetes and metabolic-associated fatty liver disease (MAFLD) has been strongly associated with constant exposure to endocrine-disruptive chemicals (EDCs), in particular, the ones able to disrupt various metabolic pathways. EDCs have a negative impact on several human tissues/systems, including metabolically active organs, such as the liver and pancreas. Among their deleterious effects, EDCs induce mitochondrial dysfunction and oxidative stress, which are also the major pathophysiological mechanisms underlying metabolic diseases. In this narrative review, we delve into the current literature on EDC toxicity effects on the liver and pancreatic tissues in terms of impaired mitochondrial function and redox homeostasis.

Neuronal A2A receptor exacerbates synapse loss and memory deficits in APP/PS1 mice.

Early pathological upregulation of adenosine A2A receptors (A2ARs), one of the caffeine targets, by neurons is thought to be involved in the development of synaptic and memory deficits in Alzheimer's disease (AD) but mechanisms remain ill-defined. To tackle this question, we promoted a neuronal upregulation of A2AR in the hippocampus of APP/PS1 mice developing AD-like amyloidogenesis. Our findings revealed that the early upregulation of A2AR in the presence of an ongoing amyloid pathology exacerbates memory impairments of APP/PS1 mice. These behavioural changes were not linked to major change in the development of amyloid pathology but rather associated with increased phosphorylated tau at neuritic plaques. Moreover, proteomic and transcriptomic analyses coupled with quantitative immunofluorescence studies indicated that neuronal upregulation of the receptor promoted both neuronal and non-neuronal autonomous alterations, i.e. enhanced neuroinflammatory response but also loss of excitatory synapses and impaired neuronal mitochondrial function, presumably accounting for the detrimental effect on memory. Overall, our results provide compelling evidence that neuronal A2AR dysfunction, as seen in the brain of patients, contributes to amyloid-related pathogenesis and underscores the potential of A2AR as a relevant therapeutic target for mitigating cognitive impairments in this neurodegenerative disorder.

Astrocyte Mitochondria Are a Sensitive Target of PCB52 and its Human-Relevant Metabolites.

Polychlorinated biphenyls (PCBs) are industrial chemicals that are ubiquitously found in the environment. Exposure to these compounds has been associated with neurotoxic outcomes; however, the underlying mechanisms for such outcomes remain to be fully understood. Recent studies have shown that astrocytes, the most abundant glial cell type in the brain, are susceptible to PCB exposure as well as exposure to human-relevant metabolites of PCBs. Astrocytes are critical for maintaining healthy brain function due to their unique functional attributes and positioning within the neuronal networks in the brain. In this study, we assessed the toxicity of PCB52, one of the most abundantly found PCB congeners in outdoor and indoor air, and two of its human-relevant metabolites, on astrocyte mitochondria. We exposed C6 cells, an astrocyte cell line, to PCB52 or its human-relevant metabolites and found that all the compounds showed increased toxicity in galactose-containing media compared to that in the glucose-containing media, indicating the involvement of mitochondria in observed toxicity. Additionally, we also found increased oxidative stress upon exposure to PCB52 metabolites. All three compounds caused a loss of mitochondrial membrane potential, distinct changes in the mitochondrial structure, and impaired mitochondrial function. The hydroxylated metabolite 4-OH-PCB52 likely functions as an uncoupler of mitochondria. This is the first study to report the adverse effects of exposure to PCB52 and its human-relevant metabolites on the mitochondrial structure and function in astrocytes.

X chromosome dosage drives statin-induced dysglycemia and mitochondrial dysfunction

Statin drugs lower blood cholesterol levels for cardiovascular disease prevention. Women are more likely than men to experience adverse statin effects, particularly new-onset diabetes (NOD) and muscle weakness. Here we find that impaired glucose homeostasis and muscle weakness in statin-treated female mice are associated with reduced levels of the omega-3 fatty acid, docosahexaenoic acid (DHA), impaired redox tone, and reduced mitochondrial respiration. Statin adverse effects are prevented in females by administering fish oil as a source of DHA, by reducing dosage of the X chromosome or the Kdm5c gene, which escapes X chromosome inactivation and is normally expressed at higher levels in females than males. As seen in female mice, we find that women experience more severe reductions than men in DHA levels after statin administration, and that DHA levels are inversely correlated with glucose levels. Furthermore, induced pluripotent stem cells from women who developed NOD exhibit impaired mitochondrial function when treated with statin, whereas cells from men do not. These studies identify X chromosome dosage as a genetic risk factor for statin adverse effects and suggest DHA supplementation as a preventive co-therapy.

Emamectin benzoate exposure induced carp kidney injury by triggering mitochondrial oxidative stress to accelerate ferroptosis and autophagy

Emamectin benzoate (EMB), commonly used as an insecticide in fishery production, inevitably leaves residual chemicals in aquatic environments. High-level EMB exposure can cause severe damage to multiple systems of marine animals, potentially through mechanisms involving severe mitochondrial damage and oxidative stress. However, it is not clear yet how EMB exposure at a certain level can cause damage to fish kidney tissue. In this study, we exposed carps to an aquatic environment containing 2.4 μg/L of EMB and cultured carp kidney cells in vitro, established a cell model exposed to EMB. Our findings revealed that EMB exposure resulted in severe kidney tissue damage in carp and compromised the viability of grass carp kidney cells (CIK cells). By RNA-seq analysis, EMB exposure led to significant differences in mitochondrial homeostasis, response to ROS, ferroptosis, and autophagy signals in carp kidney tissue. Mechanistically, EMB exposure induced mitochondrial oxidative stress by promoting the generation of mitochondrial superoxide and reducing the activity of antioxidant enzymes. Additionally, EMB exposure triggered loss of mitochondrial membrane potential, an imbalance in mitochondrial fusion/division homeostasis, and dysfunction in oxidative phosphorylation, ultimately impairing ATP synthesis. Notably, EMB exposure also accelerated excessive autophagy and ferroptosis of cells by contributing to the formation of lipid peroxides and autophagosomes, and the deposition of Fe2+. However, N-acetyl-L-cysteine (NAC) treatment alleviated the damage and death of CIK cells by inhibiting oxidative stress. Overall, our study demonstrated that EMB exposure induced mitochondrial oxidative stress, impaired mitochondrial homeostasis, and function, promoted autophagy and ferroptosis of kidney cells, and ultimately led to kidney tissue damage in carp. Our research enhanced the toxicological understanding on EMB exposure and provides a model reference for comparative medicine.

Identification of the central role of RNA polymerase mitochondrial for angiogenesis

Mitochondria are central to endothelial cell activation and angiogenesis, with the RNA polymerase mitochondrial (POLRMT) serving as a key protein in regulating mitochondrial transcription and oxidative phosphorylation. In our study, we examined the impact of POLRMT on angiogenesis and found that its silencing or knockout (KO) in human umbilical vein endothelial cells (HUVECs) and other endothelial cells resulted in robust anti-angiogenic effects, impeding cell proliferation, migration, and capillary tube formation. Depletion of POLRMT led to impaired mitochondrial function, characterized by mitochondrial depolarization, oxidative stress, lipid oxidation, DNA damage, and reduced ATP production, along with significant apoptosis activation. Conversely, overexpressing POLRMT promoted angiogenic activity in the endothelial cells. In vivo experiments demonstrated that endothelial knockdown of POLRMT, by intravitreous injection of endothelial specific POLRMT shRNA adeno-associated virus, inhibited retinal angiogenesis. In addition, inhibiting POLRMT with a first-in-class inhibitor IMT1 exerted significant anti-angiogenic impact in vitro and in vivo. Significantly elevated expression of POLRMT was observed in the retinal tissues of streptozotocin-induced diabetic retinopathy (DR) mice. POLRMT endothelial knockdown inhibited pathological retinal angiogenesis and mitigated retinal ganglion cell (RGC) degeneration in DR mice. At last, POLRMT expression exhibited a substantial increase in the retinal proliferative membrane tissues of human DR patients. These findings collectively establish the indispensable role of POLRMT in angiogenesis, both in vitro and in vivo.

Shiitake mushroom powder supplementation increase antioxidative activity in dogs.

The prevalence of age-related diseases, including obesity (a lipid metabolism disorder), increases with the increase in a dog's lifespan. Most of age-related diseases are associated with oxidative stress by excessive production of reactive oxygen species (ROS) from impaired mitochondrial functions. Safe and effective supplements with antioxidative and anti-inflammatory activities are required to prevent obesity and associated complications. Shiitake mushroom exhibit various functions including antioxidant activity. We investigated the effect of shiitake powder supplementation in healthy dogs. Shiitake powder was supplemented at a dose of 800 mg/kg body weight/day for 4 weeks. The dose was set as 0.60-0.65 mg/kg/day of eritadenine, a hypocholesterolemic factor. The body weight and body condition score of the dogs did not change after shiitake supplementation. In contrast, plasma total cholesterol concentrations decreased and superoxide dismutase activity and leukocyte sirtuin1 mRNA expression increased significantly in the dogs that received the supplement. Oral administration of shiitake powder increased antioxidative activity. The supplement may be useful in ameliorating the signs of age-related diseases, including obesity, in dogs.

Lipopeptides from Bacillus tequilensis EA-CB0015 and cinnamon extract decrease the bioenergetic response of Fusarium oxysporum f. sp. cubense

AbstractLipopeptides (LPs) from B. tequilensis EA-CB0015 have antifungal activity against Fusarium species. Specifically, against F. oxysporum f. sp. cubense (Foc), the cause of Fusarium wilt of banana. Cinnamon (CN) extract is also known for its inhibitory activity against the Fusarium genus. The main goal of this research was to determine whether the effect of LPs and CN extract or their combination against a Foc isolate is related to an impairment of mitochondrial function. Our results show that biomass decreased by 74% (p < 0.0001) and 84% (p < 0.0001) when cultures were treated with 128 ppm LPs and 152.5 ppm CN extract, respectively. In parallel, we found a pronounced impairment of the bioenergetic response. That is, the routine oxygen consumption rate diminished by 55% (p = 0.0148) and 38% (p < 0.0001), respectively. Moreover, the ATP-linked respiratory rate decreased by 63% (p = 0.0461) and 44% (p = 0.0005), while the FCCP-simulated respiratory rate by 63% (p = 0.0255) and 45% (p = 0.0002). Therefore, our data suggest that the altered bioenergetic response observed in cultures of Foc treated with LPs or CN is mainly caused by an impairment of the activity of the respiratory complexes. On the other hand, biomass production was reduced by 80% (p < 0.0001) when cultures were treated with a mixture comprising only 10% LPs and 40% CN extract. Furthermore, ATP-linked and FCCP-stimulated respiratory rates decreased by 62% (p = 0.0024) and 68% (p < 0.0001), respectively under the same conditions. A potentially synergistic antifungal effect of cyclic LPs with a CN extract is suggested. Graphical Abstract

Potential mechanisms of aortic medial degeneration promoted by co-exposure to microplastics and lead

Microplastics (MPs) have attracted widespread attention because they can lead to combined toxicity by adsorbing heavy metals from the environment. Exposure to lead (Pb), a frequently adsorbed heavy metal by MPs, is common. In the current study, the coexistence of MPs and Pb was assessed in human samples. Then, mice were used as models to examine how co-exposure to MPs and Pb promotes aortic medial degeneration. The results showed that MPs and Pb co-exposure were detected in patients with aortic disease. In mice, MPs and Pb co-exposure promoted the damage of elastic fibers, loss of vascular smooth muscle cells (VSMCs), and release of inflammatory factors. In vitro cell models revealed that co-exposure to MPs and Pb induced excessive reactive oxygen species generation, impaired mitochondrial function, and triggered PANoptosome assembly in VSMCs. These events led to PANoptosis and inflammation through the cAMP/PKA-ROS signaling pathway. However, the use of the PKA activator 8-Br-cAMP or mitochondrial ROS scavenger Mito-TEMPO improved, mitochondrial function in VSMCs, reduced cell death, and inhibited inflammatory factor release. Taken together, the present study provided novel insights into the combined toxicity of MPs and Pb co-exposure on the aorta.

Piracetam reduces oxidative stress and mitochondrial function impairment in an in vitro model of vascular dementia.

Vascular dementia (VaD) is the most common cause of dementia in older adults. Due to the lack of effective treatment options, there is an urgent need to find an effective pharmaceutical compound to combat VaD. Piracetam has been reported to improve impaired cognitive function in a variety of conditions in both human and animal models. However, the role and mechanism of Piracetam in VaD remain unclear. Therefore this study aimed to elucidate the effect of Piracetam on a cellular model of VaD in vitro. We found that Piracetam enhanced the growth of OGD-stimulated SH-SY5Y cells. In addition, Piracetam inhibited the oxidative stress of OGD-stimulated SH-SY5Y cells. Further, Piracetam improved mitochondrial function of OGD-stimulated SH-SY5Y cells. Mechanistically, Piracetam inhibited the PI3K/Akt/mTOR pathway in OGD-stimulated SH-SY5Y cells. Collectively, Piracetam improved oxidative stress and mitochondrial dysfunction of OGD-stimulated SH-SY5Y cells through PI3K/Akt/mTOR axis. Hence, Piracetam has the potential to serve as a promising drug of VaD.

Perfluorooctanoic acid triggers premature ovarian insufficiency by impairing NAD+ synthesis and mitochondrial function in adult zebrafish.

High-dose perfluorooctanoic acid (PFOA) impairs oocyte maturation and offspring quality. However, the physiological concentrations of PFOA in follicular fluids of patients with premature ovarian insufficiency (POI) were detected at lower levels, thus the relationship between physiological PFOA and reproductive disorders remains elusive. Here, we investigated whether physiological PFOA exposure affects gonad function in adult zebrafish. Physiological PFOA exposure resulted in POI-like phenotypes in adult females, which exhibited decreased spawning frequency, reduced number of ovulated eggs, abnormal gonadal index, and aberrant embryonic mortality. Meanwhile, oocytes from PFOA-exposed zebrafish showed mitochondrial disintegration and diminished mitochondrial membrane potential (MMP). Unlike the high-dose treated oocytes exhibiting high reactive oxygen species (ROS) levels and excessive apoptosis, physiological PFOA reduced the ROS levels and did not trigger apoptosis. Interestingly, physiological PFOA exposure would not affect testis function, indicating specific toxicity in females. Mechanistically, PFOA suppressed the NAD+ biosynthesis and impaired mitochondrial function in oocytes, thus disrupting oocyte maturation and ovarian fertility. Nicotinamide mononucleotide (NMN), a precursor for NAD+ biosynthesis, alleviated the PFOA-induced toxic effects in oocytes and improved the oocyte maturation and fertility upon PFOA exposure. Our findings discover new insights into PFOA-induced reproductive toxicity and provide NMN as a potential drug for POI therapy.

Apolipoprotein O modulates cholesterol metabolism via NRF2/CYB5R3 independent of LDL receptor

Apolipoprotein O (APOO) plays a critical intracellular role in regulating lipid metabolism. Here, we investigated the roles of APOO in metabolism and atherogenesis in mice. Hepatic APOO expression was increased in response to hyperlipidemia but was inhibited after simvastatin treatment. Using a novel APOO global knockout (Apoo−/−) model, it was found that APOO depletion aggravated diet-induced obesity and elevated plasma cholesterol levels. Upon crossing with low-density lipoprotein receptor (LDLR) and apolipoprotein E (APOE) knockout hyperlipidemic mouse models, Apoo−/−Apoe−/− and Apoo−/−Ldlr−/− mice exhibited elevated plasma cholesterol levels, with more severe atherosclerotic lesions than littermate controls. This indicated the effects of APOO on cholesterol metabolism independent of LDLR and APOE. Moreover, APOO deficiency reduced cholesterol excretion through bile and feces while decreasing phospholipid unsaturation by inhibiting NRF2 and CYB5R3. Restoration of CYB5R3 expression in vivo by adeno-associated virus (AAV) injection reversed the reduced degree of phospholipid unsaturation while decreasing blood cholesterol levels. This represents the first in vivo experimental validation of the role of APOO in plasma cholesterol metabolism independent of LDLR and elucidates a previously unrecognized cholesterol metabolism pathway involving NRF2/CYB5R3. APOO may be a metabolic regulator of total-body cholesterol homeostasis and a target for atherosclerosis management.Apolipoprotein O (APOO) regulates plasma cholesterol levels and atherosclerosis through a pathway involving CYB5R3 that regulates biliary and fecal cholesterol excretion, independently of the LDL receptor. In addition, down-regulation of APOO may lead to impaired mitochondrial function, which in turn aggravates diet-induced obesity and fat accumulation.

Alcohol exposure during pregnancy induces cardiac mitochondrial damage in offspring mice.

Prenatal alcohol exposure (PAE) has been linked to congenital heart disease and fetal alcohol syndrome. The heart primarily relies on mitochondria to generate energy, so impaired mitochondrial function due to alcohol exposure can significantly affect cardiac development and function. Our study aimed to investigate the impact of PAE on myocardial and mitochondrial functions in offspring mice. We administered 30% alcohol (3 g/kg) to pregnant C57BL/6 mice during the second trimester. We assessed cardiac function by transthoracic echocardiography, observed myocardial structure and fibrosis through staining tests and electron transmission microscopy, and detected cardiomyocyte apoptosis with dUTP nick end labeling assay and real-time quantitative PCR. Additionally, we measured the reactive oxygen species content, ATP level, and mitochondrial DNA copy number in myocardial mitochondria. Mitochondrial damage was evaluated by assessing the level of mitochondrial membrane potential and the opening degree of mitochondrial permeability transition pores. Our findings revealed that PAE caused cardiac systolic dysfunction, ventricular enlargement, thinned ventricular wall, cardiac fibrosis in the myocardium, scattered loss of cardiomyocytes, and disordered arrangement of myocardial myotomes in the offspring. Furthermore, we observed a significant increase in mitochondrial reactive oxygen species content, a decrease in mitochondrial membrane potential, ATP level, and mitochondrial DNA copy number, and sustained opening of mitochondrial permeability transition pores in the heart tissues of the offspring. These results indicated that PAE had adverse effects on the cardiac structure and function of the newborn mice and could trigger oxidative stress in their myocardia and contribute to mitochondrial dysfunction.

Impaired cardiac mitochondrial bioenergetics contribute to loss of cardiac function, in a porcine multiple risk factor model

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Dutch CardioVascular Alliance (an initiative with support of the Dutch Heart Foundation) Grant 2020B008 RECONNEXT, and the German Center for Cardiovascular Research (DZHK; 81Z0600207) Background Heart failure with preserved ejection fraction lacks targeted therapies, due to insufficient understanding of pathogenesis. A multiple comorbidity swine model (MCS) was developed by exposure to three risk factors for six months including diabetes (streptozotocin), chronic kidney disease (renal embolization), and an unhealthy diet (high-fat, high salt diet). An additional risk factor ovariectomy was added on top of the MCS model (MCS+). MCS and MCS+ presented with left ventricular diastolic dysfunction, oxidative stress, coronary microvascular dysfunction and inflammation. Furthermore, myocardial oxygen consumption was increased given the same level of cardiac work (Fig. A), suggesting an impairment in myocardial mitochondrial function. Using a combined-omics approach, the purpose of this study is to unravel alterations in gene expression and proteome abundance regarding mitochondrial function in MCS swine. Methods 15 MCS, 4 MCS+ and 10 healthy control female swine were included in the study. Proteome analysis and single nuclei RNA sequencing, were performed on frozen MCS left ventricle myocardial samples. Cardiac mitochondrial function was measured by an O2k-FlouRespirometer ex vivo in MCS+ swine versus control. Results Proteome analysis showed a reduced abundance of proteins involved in branched-chain amino acid (BCAA) catabolism (Fig. B). Single nuclei RNA sequencing of a subgroup of the same animals demonstrated a downregulation of these genes specifically in cardiomyocyte subpopulations. BCAA can act as a source of ATP via oxidative phosphorylation and can modulate mitochondrial substrate utilisation, and impair mitochondrial function, resulting in increased mitochondrial production of reactive oxygen species (ROS). Mitochondrial function was measured in fresh myocardial tissue, using pyruvate/malate/glutamate as substrate. Low mitochondrial respiratory sensitivity to ADP was observed 26±2.5 in MCS+ vs 43.6±1.5 pmol/(s*mg tissue) in healthy control, reflecting low oxidative capacity. Moreover, the respiratory rate after uncoupling by FCCP was reduced in MCS+ versus healthy control (73.6±11.7 vs 118.4±15.6 pmol/(s*mg tissue). These findings are consistent with our data in the MCS swine and indicate impaired BCAA in the myocardium of animals with comorbidities, which is associated with increased ROS levels (8-isoprostane 12.9±0.8 pg/mg protein in MCS vs 10.3±0.5 in healthy animals) and impaired myocardial efficiency during exercise (Fig. A). Conclusion A combined omics approach suggested an alteration in cardiac mitochondria. Respiratory analyses showed impaired mitochondrial bioenergetics and increased oxidative stress, which can contribute to diastolic dysfunction.

Biochemical and molecular determinants of the subclinical inflammatory mechanisms in Rett syndrome

To date, Rett syndrome (RTT), a genetic disorder mainly caused by mutations in the X-linked MECP2 gene, is increasingly considered a broad-spectrum pathology, instead of just a neurodevelopmental disease, due to the multitude of peripheral co-morbidities and the compromised metabolic pathways, affecting the patients. The altered molecular processes include an impaired mitochondrial function, a perturbed redox homeostasis, a chronic subclinical inflammation and an improper cholesterol metabolism.The persistent subclinical inflammatory condition was first defined ten years ago, as a previously unrecognized feature of RTT, playing a role in the pathology progress and modulation of phenotypical severity. In light of this, the present work aims at reviewing the current knowledge on the chronic inflammatory status and the altered immune/inflammatory functions in RTT, as well as investigating the emerging mechanisms underlying this condition with a special focus on the latest findings about inflammasome system, autoimmunity responses and intestinal micro- and mycobiota. On these bases, although further research is needed, future therapeutic strategies able to re-establish an adequate immune/inflammatory response could represent potential approaches for RTT patients.

Exposure to urban particulate matter (UPM) impairs mitochondrial dynamics in BV2 cells, triggering a mitochondrial biogenesis response.

World Health Organisation data suggest that up to 99% of the global population are exposed to air pollutants above recommended levels. Impacts to health range from increased risk of stroke and cardiovascular disease to chronic respiratory conditions, and air pollution may contribute to over 7 million premature deaths a year. Additionally, mounting evidence suggests that in utero or early life exposure to particulate matter (PM) in ambient air pollution increases the risk of neurodevelopmental impairment with obvious lifelong consequences. Identifying brain-specific cellular targets of PM is vital for determining its long-term consequences. We previously established that microglial-like BV2 cells were particularly sensitive to urban (U)PM-induced damage including reactive oxygen species production, which was abrogated by a mitochondrially targeted antioxidant. Here we extend those studies to find that UPM treatment causes a rapid impairment of mitochondrial function and increased mitochondrial fragmentation. However, there is a subsequent restoration of mitochondrial and therefore cell health occurring concomitantly with upregulated measures of mitochondrial biogenesis and mitochondrial load. Our data highlight that protecting mitochondrial function may represent a valuable mechanism to offset the effects of UPM exposure in the neonatal brain. KEY POINTS: Air pollution represents a growing risk to long-term health especially in early life, and the CNS is emerging a target for airborne particulate matter (PM). We previously showed that microglial-like BV2 cells were vulnerable to urban (U)PM exposure, which impaired cell survival and promoted reactive oxygen species production. Here we find that, following UPM exposure, BV2 mitochondrial membrane potential is rapidly reduced, concomitant with decreased cellular bioenergetics and increased mitochondrial fission. However, markers of mitochondrial biogenesis and mitochondrial mass are subsequently induced, which may represent a cellular mitigation strategy. As mitochondria are more vulnerable in the developing brain, exposure to air pollution may represent a greater risk to lifelong health in this cohort; conversely, promoting mitochondrial integrity may offset these risks.

Distinct epigenetic modulation of differentially expressed genes in the adult mouse brain following prenatal exposure to low-dose bisphenol A.

Bisphenol A (BPA) is a common component in the manufacture of daily plastic consumer goods. Recent studies have suggested that prenatal exposure to BPA can increase the susceptibility of offspring to mental illness, although the underlying mechanisms remain unclear. In this study, we performed transcriptomic and epigenomic profiling in the adult mouse brain following prenatal exposure to low-dose BPA. We observed a sex-specific transcriptional dysregulation in the cortex, with more significant differentially expressed genes was observed in adult cortex from male offspring. Moreover, the upregulated genes primarily influenced neuronal functions, while the downregulated genes were significantly associated with energy metabolism pathways. More evidence supporting impaired mitochondrial function included a decreased ATP level and a reduced number of mitochondria in the cortical neuron of the BPA group. We further investigated the higher-order chromatin regulatory patterns of DEGs by incorporating published Hi-C data. Interestingly, we found that upregulated genes exhibited more distal interactions with multiple enhancers, while downregulated genes displayed relatively short-range interactions among adjacent genes. Our data further revealed decreased H3K9me3 signal on the distal enhancers of upregulated genes, whereas increased DNA methylation and H3K27me3 signals on the promoters of downregulated genes. In summary, our study provides compelling evidence for the potential health risks associated with prenatal exposure to BPA, and uncovers sex-specific transcriptional changes with a complex interplay of multiple epigenetic mechanisms.

Targeting the mitochondrial protein YME1L to inhibit osteosarcoma cell growth in vitro and in vivo

Exploring novel diagnostic and therapeutic biomarkers is extremely important for osteosarcoma. YME1 Like 1 ATPase (YME1L), locating in the mitochondrial inner membrane, is key in regulating mitochondrial plasticity and metabolic activity. Its expression and potential functions in osteosarcoma are studied in the present study. We show that YME1L mRNA and protein expression is significantly elevated in osteosarcoma tissues derived from different human patients. Moreover, its expression is upregulated in various primary and immortalized osteosarcoma cells. The Cancer Genome Atlas database results revealed that YME1L overexpression was correlated with poor overall survival and poor disease-specific survival in sarcoma patients. In primary and immortalized osteosarcoma cells, silencing of YME1L through lentiviral shRNA robustly inhibited cell viability, proliferation, and migration. Moreover, cell cycle arrest and apoptosis were detected in YME1L-silenced osteosarcoma cells. YME1L silencing impaired mitochondrial functions in osteosarcoma cells, causing mitochondrial depolarization, oxidative injury, lipid peroxidation and DNA damage as well as mitochondrial respiratory chain complex I activity inhibition and ATP depletion. Contrarily, forced YME1L overexpression exerted pro-cancerous activity and strengthened primary osteosarcoma cell proliferation and migration. YME1L is important for Akt-S6K activation in osteosarcoma cells. Phosphorylation of Akt and S6K was inhibited after YME1L silencing in primary osteosarcoma cells, but was strengthened with YME1L overexpression. Restoring Akt-mTOR activation by S473D constitutively active Akt1 mitigated YME1L shRNA-induced anti-osteosarcoma cell activity. Lastly, intratumoral injection of YME1L shRNA adeno-associated virus inhibited subcutaneous osteosarcoma xenograft growth in nude mice. YME1L depletion, mitochondrial dysfunction, oxidative injury, Akt-S6K inactivation, and apoptosis were detected in YME1L shRNA-treated osteosarcoma xenografts. Together, overexpressed YME1L promotes osteosarcoma cell growth, possibly by maintaining mitochondrial function and Akt-mTOR activation.

The integrated stress response promotes neural stem cell survival under conditions of mitochondrial dysfunction in neurodegeneration.

Impaired mitochondrial function is a hallmark of aging and a major contributor to neurodegenerative diseases. We have shown that disrupted mitochondrial dynamics typically found in aging alters the fate of neural stem cells (NSCs) leading to impairments in learning and memory. At present, little is known regarding the mechanisms by which neural stem and progenitor cells survive and adapt to mitochondrial dysfunction. Using Opa1-inducible knockout as a model of aging and neurodegeneration, we identify a decline in neurogenesis due to impaired stem cell activation and progenitor proliferation, which can be rescued by the mitigation of oxidative stress through hypoxia. Through sc-RNA-seq, we identify the ATF4 pathway as a critical mechanism underlying cellular adaptation to metabolic stress. ATF4 knockdown in Opa1-deficient NSCs accelerates cell death, while the increased expression of ATF4 enhances proliferation and survival. Using a Slc7a11 mutant, an ATF4 target, we show that ATF4-mediated glutathione production plays a critical role in maintaining NSC survival and function under stress conditions. Together, we show that the activation of the integrated stress response (ISR) pathway enables NSCs to adapt to metabolic stress due to mitochondrial dysfunction and metabolic stress and may serve as a therapeutic target to enhance NSC survival and function in aging and neurodegeneration.