Cell Biology of the Mitochondrion

Ferroptosis-Driven Nanotherapeutics to Reverse Drug Resistance in Tumor Microenvironment

Ferroptosis, characterized by iron-dependent lipid reactive oxygen species (ROS) accumulation, is non-apoptotic programmed cell death highly relevant to tumor development. It was found to manipulate oncogenes and resistant mutations of cancer cells via lipid metabolism pathways converging on phospholipid glutathione peroxidase (GPX4) that squanders lipid peroxides (L-OOH) to block the iron-mediated reactions of peroxides, thus rendering resistant cancer cells vulnerable to ferroptotic cell death. By accumulating ROS and lipid peroxidation (LPO) products to lethal levels in tumor microenvironment (TME), ferroptosis-driven nanotherapeutics show a superior ability of eradicating aggressive malignancies than traditional therapeutic modalities, especially for the drug-resistant tumors with high metastasis tendency. Moreover, Fenton reaction, inhibition of GPX-4, and exogenous regulation of LPO are three major therapeutic strategies to induce ferroptosis in cancer cells, which were generally applied in ferroptosis-driven nanotherapeutics. In this review, we elaborate current trends of ferroptosis-driven nanotherapeutics to reverse drug resistance of tumors in anticancer fields at the intersection of cancer biology, materials science, and chemistry. Finally, their challenges and perspectives toward feasible translational studies are spotlighted, which would ignite the hope of anti-resistant cancer treatment.

UPRmt activation improves pathological alterations in cellular models of mitochondrial diseases

Background

Mitochondrial diseases represent one of the most common groups of genetic diseases. With a prevalence greater than 1 in 5000 adults, such diseases still lack effective treatment. Current therapies are purely palliative and, in most cases, insufficient. Novel approaches to compensate and, if possible, revert mitochondrial dysfunction must be developed.

Results

In this study, we tackled the issue using as a model fibroblasts from a patient bearing a mutation in the GFM1 gene, which is involved in mitochondrial protein synthesis. Mutant GFM1 fibroblasts could not survive in galactose restrictive medium for more than 3 days, making them the perfect screening platform to test several compounds. Tetracycline enabled mutant GFM1 fibroblasts survival under nutritional stress. Here we demonstrate that tetracycline upregulates the mitochondrial Unfolded Protein Response (UPR^mt), a compensatory pathway regulating mitochondrial proteostasis. We additionally report that activation of UPR^mt improves mutant GFM1 cellular bioenergetics and partially restores mitochondrial protein expression.

Conclusions

Overall, we provide compelling evidence to propose the activation of intrinsic cellular compensatory mechanisms as promising therapeutic strategy for mitochondrial diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02331-8.

Dietary Supplements and Natural Products: An Update on Their Clinical Effectiveness and Molecular Mechanisms of Action During Accelerated Biological Aging

Accelerated biological aging, which involves the gradual decline of organ or tissue functions and the distortion of physiological processes, underlies several human diseases. Away from the earlier free radical concept, telomere attrition, cellular senescence, proteostasis loss, mitochondrial dysfunction, stem cell exhaustion, and epigenetic and genomic alterations have emerged as biological hallmarks of aging. Moreover, nutrient-sensing metabolic pathways are critical to an organism’s ability to sense and respond to nutrient levels. Pharmaceutical, genetic, and nutritional interventions reverting physiological declines by targeting nutrient-sensing metabolic pathways can promote healthy aging and increase lifespan. On this basis, biological aging hallmarks and nutrient-sensing dependent and independent pathways represent evolving drug targets for many age-linked diseases. Here, we discuss and update the scientific community on contemporary advances in how dietary supplements and natural products beneficially revert accelerated biological aging processes to retrograde human aging and age-dependent human diseases, both from the clinical and preclinical studies point-of-view. Overall, our review suggests that dietary/natural products increase healthspan—rather than lifespan—effectively minimizing the period of frailty at the end of life. However, real-world setting clinical trials and basic studies on dietary supplements and natural products are further required to decisively demonstrate whether dietary/natural products could promote human lifespan.

Nuclear microRNAs may regulate mitochondrial gene expression following effluent exposure in darter (Etheostoma) species

Wastewater effluent is a metabolic stressor to aquatic organisms, though the mechanisms regulating metabolic rate in fish are not fully understood. Changes in metabolism may be regulated by microRNA (miRNA), small RNA molecules that post-transcriptionally regulate target mRNA translation in fish. Nuclear encoded miRNA are present in mammalian mitochondria where they regulate translation of mitochondrial genes, namely subunits for oxidative phosphorylation complexes; though this mechanism has not been identified in fish. This study aimed to identify if miRNA are present in darter (Etheostoma spp.) mitochondria, and if the metabolic stress occurring in darters in the Grand River, Waterloo, is partly regulated by miRNAs supressing translation of target mitochondrial genes. Three species of darters (E. caeruleum; E. nigrum; E. flabellare) were collected from upstream and downstream of the Waterloo wastewater treatment plant, and qPCR analysis confirmed the presence of four miRNA bioinformatically predicted to target mitochondrial mRNAs within the mitochondria, namely let-7a, miR-1, miR-122 and miR-20. E. caeruleum collected from downstream had lower cytochrome c oxidase activity, with a respective higher miR-1 abundance in the mitochondria, while E. nigrum had both a higher miR-20 abundance and cytochrome c oxidase activity downstream. E. flabellare was the only species that exhibited a lower miR-122 abundance downstream, despite no difference in cytochrome c oxidase activity between sites. Overall, this study confirmed the presence of miRNA within the mitochondria of daters, predicted a relationship between miR-1, and miR-20 abundance and cytochrome c oxidase activity, and identified one sex-specific miRNA, miR-20.

Mitochondrial Dysfunction in Cardiovascular Diseases: Potential Targets for Treatment

Cardiovascular diseases (CVDs) are serious public health issues and are responsible for nearly one-third of global deaths. Mitochondrial dysfunction is accountable for the development of most CVDs. Mitochondria produce adenosine triphosphate through oxidative phosphorylation and inevitably generate reactive oxygen species (ROS). Excessive ROS causes mitochondrial dysfunction and cell death. Mitochondria can protect against these damages via the regulation of mitochondrial homeostasis. In recent years, mitochondria-targeted therapy for CVDs has attracted increasing attention. Various studies have confirmed that clinical drugs (β-blockers, angiotensin-converting enzyme inhibitors/angiotensin receptor-II blockers) against CVDs have mitochondrial protective functions. An increasing number of cardiac mitochondrial targets have shown their cardioprotective effects in experimental and clinical studies. Here, we briefly introduce the mechanisms of mitochondrial dysfunction and summarize the progression of mitochondrial targets against CVDs, which may provide ideas for experimental studies and clinical trials.

Remodeling Osteoarthritic Articular Cartilage under Hypoxic Conditions

Osteoarthritis (OA) is one of the leading joint diseases induced by abnormalities or inflammation in the synovial membrane and articular cartilage, causing severe pain and disability. Along with the cartilage malfunction, imbalanced oxygen uptake occurs, changing chondrocytes into type I collagen- and type X collagen-producing dedifferentiated cells, contributing to OA progression. However, mounting evidence suggests treating OA by inducing a hypoxic environment in the articular cartilage, targeting the inhibition of several OA-related pathways to bring chondrocytes into a normal state. This review discusses the implications of OA-diseased articular cartilage on chondrocyte phenotypes and turnover and debates the hypoxic mechanism of action. Furthermore, this review highlights the new understanding of OA, provided by tissue engineering and a regenerative medicine experimental design, modeling the disease into diverse 2D and 3D structures and investigating hypoxia and hypoxia-inducing biomolecules and potential cell therapies. This review also reports the mechanism of hypoxic regulation and highlights the importance of activating and stabilizing the hypoxia-inducible factor and related molecules to protect chondrocytes from mitochondrial dysfunction and apoptosis occurring under the influence of OA.

Mitochondrial Fusion, Fission, and Mitophagy in Cardiac Diseases: Challenges and Therapeutic Opportunities

Significance: Mitochondria play a critical role in the physiology of the heart by controlling cardiac metabolism, function, and remodeling. Accumulation of fragmented and damaged mitochondria is a hallmark of cardiac diseases. Recent Advances: Disruption of quality control systems that maintain mitochondrial number, size, and shape through fission/fusion balance and mitophagy results in dysfunctional mitochondria, defective mitochondrial segregation, impaired cardiac bioenergetics, and excessive oxidative stress. Critical Issues: Pharmacological tools that improve the cardiac pool of healthy mitochondria through inhibition of excessive mitochondrial fission, boosting mitochondrial fusion, or increasing the clearance of damaged mitochondria have emerged as promising approaches to improve the prognosis of heart diseases. Future Directions: There is a reasonable amount of preclinical evidence supporting the effectiveness of molecules targeting mitochondrial fission and fusion to treat cardiac diseases. The current and future challenges are turning these lead molecules into treatments. Clinical studies focusing on acute (i.e., myocardial infarction) and chronic (i.e., heart failure) cardiac diseases are needed to validate the effectiveness of such strategies in improving mitochondrial morphology, metabolism, and cardiac function. Antioxid. Redox Signal. 36, 844-863.

NADH dehydrogenase subunit 1/4/5 promotes survival of acute myeloid leukemia by mediating specific oxidative phosphorylation

Acute myeloid leukemia (AML) is a type of hematological malignancy caused by uncontrolled clonal proliferation of hematopoietic stem cells. The special energy metabolism mode of AML relying on oxidative phosphorylation is different from the traditional ‘Warburg effect’. However, its mechanism is not clear. In the present study, it was demonstrated that the mRNA expression levels of NADH dehydrogenase subunit 1, 4 and 5 (ND1, ND4 and ND5) were upregulated in AML samples from The Cancer Genome Atlas database using the limma package in the R programming language. Reverse transcription-quantitative PCR and ELISA were used to verify the upregulation of ND1, ND4 and ND5 in clinical samples. Pan-cancer analysis revealed that the expression of ND1 was upregulated only in AML, ND2 was upregulated only in AML and thymoma, and ND4 was upregulated only in AML and kidney chromophobe. In the present study, it was demonstrated that silencing of ND1/4/5 could inhibit the proliferation of AML cells in transplanted tumor of nude mice. Additionally, it was found that oxidative phosphorylation and energy metabolism of AML cells were decreased after silencing of ND1/4/5. In conclusion, the present study suggested that ND1/4/5 may be involved in the regulation of oxidative phosphorylation metabolism in AML as a potential cancer-promoting factor.

Revisiting the role of melatonin in human melanocyte physiology: A skin context perspective

The evolutionarily ancient methoxyindoleamine, melatonin, has long perplexed investigators by its versatility of functions and mechanisms of action, which include the regulation of vertebrate pigmentation. Although first discovered through its potent skin-lightening effects in amphibians, melatonin's role in human skin and hair follicle pigmentation and its impact on melanocyte physiology remain unclear. Synthesizing our limited current understanding of this role, we specifically examine its impact on melanogenesis, oxidative biology, mitochondrial function, melanocyte senescence, and pigmentation-related clock gene activity, with emphasis on human skin, yet without ignoring instructive pointers from nonhuman species. Given the strict dependence of melanocyte functions on the epithelial microenvironment, we underscore that melanocyte responses to melatonin are best interrogated in a physiological tissue context. Current evidence suggests that melatonin and some of its metabolites inhibit both, melanogenesis (via reducing tyrosinase activity) and melanocyte proliferation by stimulating melatonin membrane receptors (MT1, MT2). We discuss whether putative melanogenesis-inhibitory effects of melatonin may occur via activation of Nrf2-mediated PI3K/AKT signaling, estrogen receptor-mediated and/or melanocortin-1 receptor- and cAMP-dependent signaling, and/or via melatonin-regulated changes in peripheral clock genes that regulate human melanogenesis, namely Bmal1 and Per1. Melatonin and its metabolites also accumulate in melanocytes where they exert net cyto- and senescence-protective as well as antioxidative effects by operating as free radical scavengers, stimulating the synthesis and activity of ROS scavenging enzymes and other antioxidants, promoting DNA repair, and enhancing mitochondrial function. We argue that it is clinically and biologically important to definitively clarify whether melanocyte cell culture-based observations translate into melatonin-induced pigmentary changes in a physiological tissue context, that is, in human epidermis and hair follicles ex vivo, and are confirmed by clinical trial results. After defining major open questions in this field, we close by suggesting how to begin answering them in clinically relevant, currently available preclinical in situ research models.

Tryptophan Alleviates Acute Heat Stress-Induced Impairment of Antioxidant Status and Mitochondrial Function in Broilers

Heat stress has been considered as a critical risk factor for decreasing performance and causing oxidative stress in broilers. The tryptophan (TRP) derivative 5-hydroxytryptophan has been reported to protect membrane fluidity in broilers suffering from oxidative stress. Therefore, this experiment was conducted to investigate the effects of dietary TRP supplementation on antioxidant status and mitochondrial function-related genes expressions in broilers exposed to acute heat stress (34 ± 1°C, 24 h). Female Arbor Acres broilers (19-d-old, n = 180) were randomly assigned to 1 of 3 treatments. Broilers were fed a basal diet and in the thermoneutral conditions (TN, 23 ± 1°C) was considered as the TN group. Broilers were fed a basal diet and exposed to acute heat stress (HS, 34 ± 1°C) was regarded as the HS group. Broilers were fed a basal diet supplemented with 0.18% L-tryptophan and under HS conditions was treated as the HS + TRP groups. Heat stress led to increased malondialdehyde (MDA) concentration (P < 0.05), while it elevated catalase (CAT), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and total antioxidant capacity activities (T-AOC) (P < 0.05) compared with the TN group. Nevertheless, compared with the HS group, TRP supplementation increased SOD activity (P < 0.05). The effects of acute heat stress were associated with increased mRNA abundance for redox-related genes (P < 0.05), and reduced mRNA levels for mitochondrial function-related genes (P < 0.05). Notably, the effects of acute heat stress on mitochondrial function-related genes expressions were reversed by TRP treatment. Collectively, dietary 0.18% TRP supplementation beneficially protects against acute heat stress-induced oxidation stress and mitochondrial dysfunction by regulating antioxidant states and increasing mitochondrial function-related genes expressions in broilers.

Mitonuclear Mismatch is Associated With Increased Male Frequency, Outcrossing, and Male Sperm Size in Experimentally-Evolved C. elegans

We provide a partial test of the mitonuclear sex hypothesis with the first controlled study of how male frequencies and rates of outcrossing evolve in response to mitonuclear mismatch by allowing replicate lineages of C. elegans nematodes containing either mitochondrial or nuclear mutations of electron transport chain (ETC) genes to evolve under three sexual systems: facultatively outcrossing (wildtype), obligately selfing, and obligately outcrossing. Among facultatively outcrossing lines, we found evolution of increased male frequency in at least one replicate line of all four ETC mutant backgrounds tested—nuclear isp-1, mitochondrial cox-1 and ctb-1, and an isp-1 IV; ctb-1M mitonuclear double mutant—and confirmed for a single line set (cox-1) that increased male frequency also resulted in successful outcrossing. We previously found the same result for lines evolved from another nuclear ETC mutant, gas-1. For several lines in the current experiment, however, male frequency declined to wildtype levels (near 0%) in later generations. Male frequency did not change in lines evolved from a wildtype control strain. Additional phenotypic assays of lines evolved from the mitochondrial cox-1 mutant indicated that evolution of high male frequency was accompanied by evolution of increased male sperm size and mating success with tester females, but that it did not translate into increased mating success with coevolved hermaphrodites. Rather, hermaphrodites’ self-crossed reproductive fitness increased, consistent with sexually antagonistic coevolution. In accordance with evolutionary theory, males and sexual outcrossing may be most beneficial to populations evolving from a state of low ancestral fitness (gas-1, as previously reported) and less beneficial or deleterious to those evolving from a state of higher ancestral fitness (cox-1). In support of this idea, the obligately outcrossing fog-2 V; cox-1 M lines exhibited no fitness evolution compared to their ancestor, while facultatively outcrossing lines showed slight upward evolution of fitness, and all but one of the obligately selfing xol-1 X; cox-1 M lines evolved substantially increased fitness—even beyond wildtype levels. This work provides a foundation to directly test the effect of reproductive mode on the evolutionary dynamics of mitonuclear genomes, as well as whether compensatory mutations (nuclear or mitochondrial) can rescue populations from mitochondrial dysfunction.

Overexpression of cytosolic long noncoding RNA cytb protects against pressure-overload-induced heart failure via sponging microRNA-103-3p

Long noncoding RNAs (lncRNAs) play crucial roles in cardiovascular diseases. To date, only limited studies have reported the role of mitochondria-derived lncRNAs in heart failure (HF). In the current study, recombinant adeno-associated virus 9 was used to manipulate lncRNA cytb (lnccytb) expression in vivo. Fluorescence in situ hybridization (FISH) assay was used to determine the location of lnccytb, while microRNA (miRNA) sequencing and bioinformatics analyses were applied to identify the downstream targets. The competitive endogenous RNA (ceRNA) function of lnccytb was evaluated by biotin-coupled miRNA pull-down assays and luciferase reporter assays. Results showed that lnccytb expression was decreased in the heart of mice with transverse aortic constriction (TAC), as well as in the heart and plasma of patients with HF. FISH assay and absolute RNA quantification via real-time reverse transcription PCR suggested that the reduction of the lnccytb transcripts mainly occurred in the cytosol. Upregulation of cytosolic lnccytb attenuated cardiac dysfunction in TAC mice. Moreover, overexpression of cytosolic lnccytb in cardiomyocytes alleviated isoprenaline-induced reactive oxidative species (ROS) production and hypertrophy. Mechanistically, lnccytb acted as a ceRNA via sponging miR-103-3p, ultimately mitigating the suppression of PTEN by miR-103-3p. In summary, we demonstrated that the overexpression of cytosolic lnccytb could ameliorate HF.

Mitochondria Related Cell Death Modalities and Disease

Mitochondria are well known as the centre of energy metabolism in eukaryotic cells. However, they can not only generate ATP through the tricarboxylic acid cycle and oxidative phosphorylation but also control the mode of cell death through various mechanisms, especially regulated cell death (RCD), such as apoptosis, mitophagy, NETosis, pyroptosis, necroptosis, entosis, parthanatos, ferroptosis, alkaliptosis, autosis, clockophagy and oxeiptosis. These mitochondria-associated modes of cell death can lead to a variety of diseases. During cell growth, these modes of cell death are programmed, meaning that they can be induced or predicted. Mitochondria-based treatments have been shown to be effective in many trials. Therefore, mitochondria have great potential for the treatment of many diseases. In this review, we discuss how mitochondria are involved in modes of cell death, as well as basic research and the latest clinical progress in related fields. We also detail a variety of organ system diseases related to mitochondria, including nervous system diseases, cardiovascular diseases, digestive system diseases, respiratory diseases, endocrine diseases, urinary system diseases and cancer. We highlight the role that mitochondria play in these diseases and suggest possible therapeutic directions as well as pressing issues that need to be addressed today. Because of the key role of mitochondria in cell death, a comprehensive understanding of mitochondria can help provide more effective strategies for clinical treatment.

Effect of blueberry extract on energetic metabolism, levels of brain-derived neurotrophic factor, and Ca2+-ATPase activity in the hippocampus and cerebral cortex of rats submitted to ketamine-induced mania-like behavior

Bipolar disorder (BD) is a psychiatric disease characterized by mood episodes. Blueberry is rich in bioactive compounds and shows excellent therapeutic potential against chronic diseases. The aim of this study was to evaluate the effects of blueberry extract on behavior, energetic metabolism, Ca²⁺-ATPase activity, and levels of brain-derived neurotrophic factor (BDNF) in the cerebral cortex and hippocampus of rats submitted to an animal model of mania induced by ketamine. Vehicle, lithium (45 mg/kg, twice a day), or blueberry extract (200 mg/kg), was orally administered to Wistar rats for 14 days. Ketamine (25 mg/kg) or vehicle was administered intraperitoneally, once a day, between the 8th and 14th day. On the 15th day, animals received ketamine or vehicle and were subjected to the open field test. Our results demonstrated that the administration of lithium and blueberry extract prevented ketamine-induced hyperlocomotion (P < 0.01). Blueberry extract attenuated the ketamine-induced reduction in the activity of complex I in the cerebral cortex (P < 0.05). Additionally, the administration of ketamine reduced the activities of complexes I and IV (P < 0.05) and citrate synthase in the hippocampus (P < 0.01). However, blueberry extract attenuated the inhibition in the activity of complex IV (P < 0.01). Furthermore, ketamine reduced the Ca²⁺-ATPase activity in the cerebral cortex and hippocampus (P < 0.05); however, blueberry extract prevented the change in the cerebral cortex (P < 0.05). There were no significant alterations in the levels of BDNF (P > 0.05). In conclusion, this suggested that the blueberry extract can serve as a potential therapeutic strategy for studies searching for novel therapeutic alternatives for BD patients.

A comprehensive review of 1,2,4-triazole fungicide toxicity in zebrafish (Danio rerio): A mitochondrial and metabolic perspective

In this critical review, we synthesize data from peer-reviewed literature reporting on triazole fungicide exposures in the zebrafish model. Based on their mode of action in plants (potent inhibitors of ergosterol synthesis), we focused attention on mechanisms related to cellular, lipid, and steroid metabolism. Evidence from several studies reveals that zebrafish exposed to triazoles present with impaired mitochondrial oxidative phosphorylation and oxidative stress, as well as dysregulation of lipid metabolism. Such metabolic disruptions are expected to underscore developmental delays, deformity, and aberrant locomotor activity and behaviors often observed following exposure. We begin by summarizing physiological and behavioral effects observed with triazole fungicide exposure in zebrafish. We then discuss mechanisms that may underlie adverse apical effects, focusing on mitochondrial bioenergetics and metabolism. Using computational approaches, we also identify novel biomarkers of triazole fungicide exposure. Extracting and analyzing data contained in the Comparative Toxicogenomics Database (CTD) revealed that transcriptional signatures responsive to different triazoles are related to metabolism of lipids and lipoproteins, biological oxidations, and fatty acid, triacylglycerol, and ketone body metabolism among other processes. Pathway and sub-network analysis identified several transcripts that are responsive in organisms exposed to triazole fungicides, several of which include lipid-related genes. Knowledge gaps and recommendations for future investigations include; (1) targeted metabolomics for metabolites in glycolysis, Krebs cycle, and the electron transport chain; (2) additional studies conducted at environmentally relevant concentrations to characterize the potential for endocrine disruption, given that studies point to altered cholesterol (precursor for steroid hormones), as well as altered estrogen receptor alpha and thyroid hormone expression; (3) studies into the potential role for lipid peroxidation and oxidation of lipid biomolecules as a mechanism of triazole-induced toxicity, given the strong evidence for oxidative damage in zebrafish following exposure to triazole fungicides.

Therapeutic Interventions to Mitigate Mitochondrial Dysfunction and Oxidative Stress–Induced Damage in Patients with Bipolar Disorder

Bipolar disorder (BD) is characterized by mood changes, including recurrent manic, hypomanic, and depressive episodes, which may involve mixed symptoms. Despite the progress in neurobiological research, the pathophysiology of BD has not been extensively described to date. Progress in the understanding of the neurobiology driving BD could help facilitate the discovery of therapeutic targets and biomarkers for its early detection. Oxidative stress (OS), which damages biomolecules and causes mitochondrial and dopamine system dysfunctions, is a persistent finding in patients with BD. Inflammation and immune dysfunction might also play a role in BD pathophysiology. Specific nutrient supplements (nutraceuticals) may target neurobiological pathways suggested to be perturbed in BD, such as inflammation, mitochondrial dysfunction, and OS. Consequently, nutraceuticals may be used in the adjunctive treatment of BD. This paper summarizes the possible roles of OS, mitochondrial dysfunction, and immune system dysregulation in the onset of BD. It then discusses OS-mitigating strategies that may serve as therapeutic interventions for BD. It also analyzes the relationship between diet and BD as well as the use of nutritional interventions in the treatment of BD. In addition, it addresses the use of lithium therapy; novel antipsychotic agents, including clozapine, olanzapine, risperidone, cariprazine, and quetiapine; and anti-inflammatory agents to treat BD. Furthermore, it reviews the efficacy of the most used therapies for BD, such as cognitive–behavioral therapy, bright light therapy, imagery-focused cognitive therapy, and electroconvulsive therapy. A better understanding of the roles of OS, mitochondrial dysfunction, and inflammation in the pathogenesis of bipolar disorder, along with a stronger elucidation of the therapeutic functions of antioxidants, antipsychotics, anti-inflammatory agents, lithium therapy, and light therapies, may lead to improved strategies for the treatment and prevention of bipolar disorder.

Redox Homeostasis in Well-differentiated Primary Human Nasal Epithelial Cells

Oxidative stress (OS) in the airway epithelium is associated with inflammation, cell damage, and mitochondrial dysfunction that may initiate or worsen respiratory disease. Redox regulation maintains the equilibrium of pro-oxidant/antioxidant reactions but can be disturbed by environmental exposures. The mechanism(s) underlying the induction and impact of OS on airway epithelium and how these influences on respiratory disease is poorly understood. The aim of this study was to develop a stress response model in primary human nasal epithelial cells (NECs) grown at the air-liquid interface (ALI) into a well-differentiated epithelium and to use this model to investigate the mechanisms underlying OS. Hydrogen peroxide (H₂O₂) was used to induce acute OS and the responses were measured with trans epithelial electrical resistance (TEER), membrane permeability, cell death (LDH release), mitochondrial reactive oxygen species (mtROS) generation, redox status (GSH/GSSG ratio), cellular ATP, and signaling pathways (SIRT1, FOXO3, p53, p21, PINK1, PARKIN, NRF2). Following 25 mM (sensitive) or 50mM (resistant) H₂O₂ exposure, cell integrity decreased (p<0.05), GSH/GSSG ratio reduced (p<0.05), and ATP production declined by 83% (p<0.05) in the sensitive and 55% (p<0.05) in the resistant group; mtROS production increased 3.4-fold (p<0.001). Significant inter-individual differences between healthy humans with regards to susceptibility to OS, and differential activation of various pathways (FOXO3, PARKIN) were observed. These intra-individual differences in susceptibility to OS may be attributed to resistant individuals having more mitochondria or greater mitochondrial function.

BMP-2 promotes osteogenic differentiation of mesenchymal stem cells by enhancing mitochondrial activity

OBJECTIVES

Mesenchymal stem cells (MSCs) have become seed cells and basic elements for bone regeneration and bone tissue engineering. The aim of the present study was to investigate the roles and mechanisms of bone morphogenetic protein 2 (BMP-2) on osteogenic differentiation of MSCs.

METHODS

Primary MSCs were isolated from the femur and tibia bone of rats and then transfected with BMP-2 and PGC-1α adenovirus vectors. Alkaline phosphatase (ALP) activity and alizarin red staining were used to measure osteogenic differentiation of MSCs. Real-time PCR and western blot assays were performed to assess osteogenic differentiation-related proteins levels. The activities of mitochondrial respiratory chain complexes I and II and mitochondrial fluorescence intensity were used to explore mitochondria status during osteogenic differentiation of MSCs.

RESULTS

We found that the ability of BMP-2 overexpressed (OE) group osteogenic differentiation was significantly improved, compared with the negative control (NC) group. The results also indicated that BMP-2 can promote the activity of mitochondria. We further used the gain- and loss-of-function approaches to demonstrate that BMP-2 promotes mitochondrial activity by up-regulating PGC-1α to promote osteogenic differentiation of MSCs.

CONCLUSIONS

These results explored the important role of BMP-2 in the osteoblast differentiation of MSCs from a new perspective, providing a theoretical and experimental basis for bone defect and repair.

Agmatine mitigates palmitate (PA)-induced mitochondrial and metabolic dysfunction in microvascular endothelial cells

Agmatine is an arginine metabolite that has neuroprotective capacity. Recently, it has been found to ameliorate atherosclerosis progression in rabbits. However, further molecular mechanisms of its anti-atherosclerotic properties remain unclear. High plasma levels of free fatty acids (FFAs) are an important risk factor for atherosclerosis due to their detrimental effects on vascular endothelial cells (ECs). Here, we used palmitate (PA), a kind of FFA, to induce endothelial dysfunction in human microvascular endothelial cells (HMECs) to determine the possible biological functions of agmatine. We found that PA caused ECs dysfunction in HMEC-1 cells, decreased cell viability, and elevated lactate dehydrogenase (LDH) release which could be reversed by agmatine treatment. Agmatine also improved the nitric oxide (NO) production and endothelial nitric oxide synthase (eNOS) activity in PA-induced HMEC-1 cells. The PA-caused mitochondrial dysfunction of HMEC-1 cells was diminished after agmatine treatment, as proven by the increased intracellular Adenosine Triphosphate (ATP) level, decreased mitochondrial reactive oxygen species (ROS) level, and increased mitochondrial oxygen consumption rate (OCR). Further, agmatine could alleviate PA-caused lipid accumulation with increased levels of Triglyceride (TG) and total cholesterol (TC) in HMEC-1 cells. Furthermore, Western blot analysis revealed that agmatine administration markedly decreased the expression levels of phosphorylated-AMP-activated protein kinase α (p-AMPKα), p-protein kinase B (p-AKT), and p-eNOS in PA-induced HMEC-1 cells. Inhibition of AMPK by compound C reversed the protective effects of agmatine on PA-induced HMEC-1 cells. Taken together, we hypothesize that agmatine mitigated PA-induced HMEC-1 cell dysfunction by alleviating mitochondrial and metabolic dysfunction via the AMPK/PI3K/Akt/eNOS signaling pathway.

Molecular Mechanisms and Regulation of Mammalian Mitophagy

Mitochondria in the cell are the center for energy production, essential biomolecule synthesis, and cell fate determination. Moreover, the mitochondrial functional versatility enables cells to adapt to the changes in cellular environment and various stresses. In the process of discharging its cellular duties, mitochondria face multiple types of challenges, such as oxidative stress, protein-related challenges (import, folding, and degradation) and mitochondrial DNA damage. They mitigate all these challenges with robust quality control mechanisms which include antioxidant defenses, proteostasis systems (chaperones and proteases) and mitochondrial biogenesis. Failure of these quality control mechanisms leaves mitochondria as terminally damaged, which then have to be promptly cleared from the cells before they become a threat to cell survival. Such damaged mitochondria are degraded by a selective form of autophagy called mitophagy. Rigorous research in the field has identified multiple types of mitophagy processes based on targeting signals on damaged or superfluous mitochondria. In this review, we provide an in-depth overview of mammalian mitophagy and its importance in human health and diseases. We also attempted to highlight the future area of investigation in the field of mitophagy.

Immune Metabolism of IL-4-Activated B Cells and Th2 Cells in the Context of Allergic Diseases

Over the last decades, the frequency of allergic disorders has steadily increased. Immunologically, allergies are caused by abnormal immune responses directed against otherwise harmless antigens derived from our environment. Two of the main cell types driving allergic sensitization and inflammation are IgE-producing plasma cells and Th2 cells. The acute activation of T and B cells, their differentiation into effector cells, as well as the formation of immunological memory are paralleled by distinct changes in cellular metabolism. Understanding the functional consequences of these metabolic changes is the focus of a new research field termed "immune metabolism". Currently, the contribution of metabolic changes in T and B cells to either the development or maintenance of allergies is not completely understood. Therefore, this mini review will introduce the fundamentals of energy metabolism, its connection to immune metabolism, and subsequently focus on the metabolic phenotypes of IL-4-activated B cells and Th2 cells.

Mitochondrial genome of the critically endangered Baer's Pochard, Aythya baeri, and its phylogenetic relationship with other Anatidae species

Historically, the diving duck, Baer’s Pochard (Aythya baeri) was widely distributed in East and South Asia, but according to a recent estimate, its global population is now less than 1000 individuals. To date, the mitochondrial genome of A. baeri has not been deposited and is not available in GenBank. Therefore, we aimed to sequence the complete mitochondrial genome of this species. The genome was 16,623 bp in length, double stranded, circular in shape, and contained 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one non-coding control region. Many structural and compositional similarities were discovered between A. baeri and the other three Aythya mitochondrial genomes. Among 13 protein-coding genes of the four Aythya species, the fastest-evolving gene was ATP8 while the slowest-evolving gene was COII. Furthermore, the phylogenetic tree of Anatidae based on Bayesian inference and maximum likelihood methods showed that the relationships among 15 genera of the Anatidae family were as follows: Dendrocygna was an early diverging lineage that was fairly distant from the other ingroup taxa; Cygnus, Branta, and Anser were clustered into one branch that corresponded to the Anserinae subfamily; and Aythya, Asarcornis, Netta, Anas, Mareca, Mergus, Lophodytes, Bucephala, Tadorna, Cairina, and Aix were clustered into another branch that corresponded to the Anatinae subfamily. Our target species and three other Aythya species formed a monophyletic group. These results provide new mitogenomic information to support further phylogenetic and taxonomic studies and genetic conservation of Anatidae species.

Effects of Pesticides on Longevity and Bioenergetics in Invertebrates-The Impact of Polyphenolic Metabolites

Environmentally hazardous substances such as pesticides are gaining increasing interest in agricultural and nutritional research. This study aims to investigate the impact of these compounds on the healthspan and mitochondrial functions in an invertebrate in vivo model and in vitro in SH-SY5Y neuroblastoma cells, and to investigate the potential of polyphenolic metabolites to compensate for potential impacts. Wild-type nematodes (Caenorhabditis elegans, N2) were treated with pesticides such as pyraclostrobin (Pyr), glyphosate (Gly), or fluopyram (Fluo). The lifespans of the nematodes under heat stress conditions (37 °C) were determined, and the chemotaxis was assayed. Energetic metabolites, including adenosine triphosphate (ATP), lactate, and pyruvate, were analyzed in lysates of nematodes and cells. Genetic expression patterns of several genes associated with lifespan determination and mitochondrial parameters were assessed via qRT-PCR. After incubation with environmentally hazardous substances, nematodes were incubated with a pre-fermented polyphenol mixture (Rechtsregulat^®Bio, RR) or protocatechuic acid (PCA) to determine heat stress resistance. Treatment with Pyr, Glyph and Fluo leads to dose-dependently decreased heat stress resistance, which was significantly improved by RR and PCA. The chemotaxes of the nematodes were not affected by pesticides. ATP levels were not significantly altered by the pesticides, except for Pyr, which increased ATP levels after 48 h leads. The gene expression of healthspan and mitochondria-associated genes were diversely affected by the pesticides, while Pyr led to an overall decrease of mRNA levels. Over time, the treatment of nematodes leads to a recovery of the nematodes on the mitochondrial level but not on stress resistance on gene expression. Fermented extracts of fruits and vegetables and phenolic metabolites such as PCA seem to have the potential to recover the vitality of C. elegans after damage caused by pesticides.

Quantitative high-confidence human mitochondrial proteome and its dynamics in cellular context

Mitochondria are key organelles for cellular energetics, metabolism, signaling, and quality control and have been linked to various diseases. Different views exist on the composition of the human mitochondrial proteome. We classified >8,000 proteins in mitochondrial preparations of human cells and defined a mitochondrial high-confidence proteome of >1,100 proteins (MitoCoP). We identified interactors of translocases, respiratory chain, and ATP synthase assembly factors. The abundance of MitoCoP proteins covers six orders of magnitude and amounts to 7% of the cellular proteome with the chaperones HSP60-HSP10 being the most abundant mitochondrial proteins. MitoCoP dynamics spans three orders of magnitudes, with half-lives from hours to months, and suggests a rapid regulation of biosynthesis and assembly processes. 460 MitoCoP genes are linked to human diseases with a strong prevalence for the central nervous system and metabolism. MitoCoP will provide a high-confidence resource for placing dynamics, functions, and dysfunctions of mitochondria into the cellular context.

Quality Control Mechanisms of Mitochondria: Another Important Target for Treatment of Peripheral Neuropathy

Mitochondria provide energy for various cellular activities and are involved in the regulating of several physiological and pathological processes. Mitochondria constitute a dynamic network regulated by numerous quality control mechanisms; for example, division is necessary for mitochondria to develop, and fusion dilutes toxins produced by the mitochondria. Mitophagy removes damaged mitochondria. The etiologies of peripheral neuropathy include congenital and acquired diseases, and the pathogenesis varies; however, oxidative stress caused by mitochondrial damage is the accepted pathogenesis of peripheral neuropathy. Regulation and control of mitochondrial quality might point the way toward potential treatments for peripheral neuropathy. This article will review mitochondrial quality control mechanisms, their involvement in peripheral nerve diseases, and their potential therapeutic role.

Optimization of different intensities of exercise preconditioning in protecting exhausted exercise induced heart injury in rats

This study was to optimize the exercise preconditioning (EP) intensity in protecting from exhaustive exercise-induced cardiac injury (EECI). A total of 98 male Sprague-Dawley rats were divided into 7 groups (n ​= ​14): the control group (C), the exhaustive exercise group (EE) and the EP ​+ ​EE groups, which include the V10 (53.0%˙O_2max), V15 (58.4%˙O_2max), V20 (67.0%˙O_2max), V26 (74.0%˙O_2max) and V30 (80.0%˙O_2max) groups. Except the C group, the other groups were subjected to treadmill running. The serum contents of N terminal pro B type natriuretic peptide (NT-proBNP) and cardiac troponin I (cTn-I) were detected by the enzyme-linked immunosorbent assay method, ECG was recorded, heart function was detected by pressure volume catheter and the activities of mitochondrial electron transfer pathway (ET pathway) complexes I, Ⅱ and IV were measured by high-resolution respiration instrument. Compared to the EE group, the EP groups have shown decrease of NT-proBNP and cTn-I, improvement of mitochondrial respiratory function and cardiac function. Compared to other EP groups, the V26 group has shown significant decrease of myocardial enzymes and improvement of mitochondrial function. The correlation analysis showed the EP effect was proportional to EP intensity in the range of 53.0%˙O_2max-74.0%˙O_2max. High intensity and long duration of exhaustive exercise caused cardiac injury and EP could decrease serum level of NT-proBNP and cTn-I, improve electrical derangement and the left ventricular function, and raise the activities of ET pathway complexes I, Ⅱ and IV. The protection of EP on EECI was improved as the EP intensity was increased from 53.0%˙O_2max to 74.0%˙O_2max and when EP intensity was 74.0%˙O_2max, the effect was the most obvious among all the setting EP groups.

Immune metabolism in allergies, does it matter?-A review of immune metabolic basics and adaptations associated with the activation of innate immune cells in allergy

Type I allergies are pathological, type 2 inflammatory immune responses against otherwise harmless environmental allergens that arise from complex interactions between different types of immune cells. Activated immune cells undergo extensive changes in phenotype and function to fulfill their effector functions. Hereby, activation, differentiation, proliferation, migration, and mounting of effector responses require metabolic reprogramming. While the metabolic changes associated with activation of dendritic cells, macrophages, and T cells are extensively studied, data about the metabolic phenotypes of the other cell types critically involved in allergic responses (epithelial cells, eosinophils, basophils, mast cells, and ILC2s) are rather limited. This review briefly covers the basics of cellular energy metabolism and its connection to immune cell function. In addition, it summarizes the current state of knowledge in terms of dendritic cell and macrophage metabolism and subsequently focuses on the metabolic changes associated with activation of epithelial cells, eosinophils, basophils, mast cells, as well as ILC2s in allergy. Interestingly, the innate key cell types in allergic inflammation were reported to change their metabolic phenotype during activation, shifting to either glycolysis (epithelial cells, M1 macrophages, DCs, eosinophils, basophils, acutely activated mast cells), oxidative phosphorylation (M2 macrophages, longer term activated mast cells), or fatty acid oxidation (ILC2s). Therefore, immune metabolism is of relevance in allergic diseases and its connection to immune cell effector function needs to be considered to better understand induction and maintenance of allergic responses. Further progress in this field will likely improve both our understanding of disease pathology and enable new treatment targets/strategies.

Clinical Characteristics of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, a maternally inherited mitochondrial disorder, is characterized by its genetic, biochemical and clinical complexity. The most common mutation associated with MELAS syndrome is the mtDNA A3243G mutation in the MT-TL1 gene encoding the mitochondrial tRNA-leu(UUR), which results in impaired mitochondrial translation and protein synthesis involving the mitochondrial electron transport chain complex subunits, leading to impaired mitochondrial energy production. Angiopathy, either alone or in combination with nitric oxide (NO) deficiency, further contributes to multi-organ involvement in MELAS syndrome. Management for MELAS syndrome is amostly symptomatic multidisciplinary approach. In this article, we review the clinical presentations, pathogenic mechanisms and options for management of MELAS syndrome.

TFB2M activates aerobic glycolysis in hepatocellular carcinoma cells through the NAD+ /SIRT3/HIF-1α signaling

BACKGROUND AND AIM

Increased aerobic glycolysis has been well-known as a hallmark of cancer, which is closely related to mitochondrial dysfunction. TFB2M (mitochondrial transcription factor B2) is a core mitochondrial transcription factor, which has been shown by us to play an oncogenic role in hepatocellular carcinoma (HCC). However, whether TFB2M contributes to the aerobic glycolysis in HCC cells remains unexplored.

METHODS

The role and underlying molecular mechanisms of TFB2M in the regulation of aerobic glycolysis in HCC cells were systematically investigated by in vitro cell glucose metabolism and metabolomics analyses. Besides, the effects of TFB2M-regulated aerobic glycolysis in the growth and metastasis of HCC cells were also explored.

RESULTS

Here, we show that TFB2M markedly enhanced the reprogramming of glucose metabolism from oxidative phosphorylation to aerobic glycolysis mainly through two mechanisms. On the one hand, TFB2M increased the expressions of glycolytic genes GAPDH, LDHA, GLUT1, and HK2. On the other hand, TFB2M decreased the expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), a critical regulator of mitochondrial respiration. Mechanistically, TFB2M regulates the upregulation of glycolytic genes and downregulation of PGC-1α mainly through NAD⁺ /SIRT3/HIF-1α signaling. Additionally, we found that TFBM2 promoted the progression of HCC cells through HIF-1α-regulated reprogramming of glucose metabolism.

CONCLUSIONS

Our findings indicate that TFB2M serves as a critical glucose metabolic reprogramming mechanism in tumorigenesis, which could be used as potential therapeutic target in HCC.

Therapeutic Interaction of Apatinib and Chidamide in T-Cell Acute Lymphoblastic Leukemia through Interference with Mitochondria Associated Biogenesis and Intrinsic Apoptosis

T-cell acute lymphoblastic leukemia (T-ALL) shows poor clinical outcome and has limited therapeutic options, indicating that new treatment approaches for this disease are urgently required. Our previous study demonstrated that apatinib, an orally selective VEGFR-2 antagonist, is highly effective in T-ALL. Additionally, chidamide, a histone deacetylase inhibitor, has proven to be cytotoxic against T-ALL in preclinical and clinical settings. However, whether the therapeutic interaction of apatinib and chidamide in T-ALL remains unknown. In this study, apatinib and chidamide acted additively to decrease cell viability and induce apoptosis in T-ALL in vitro. Notably, compared with apatinib or chidamide alone, the combinational regimen was more efficient in abrogating the leukemia burden in the spleen and bone marrow of T-ALL patient-derived xenograft (PDX) models. Mechanistically, the additive antileukemia effect of apatinib and chidamide was associated with suppression of mitochondrial respiration and downregulation of the abundance levels of several rate-limiting enzymes that are involved in the citric acid cycle and oxidative phosphorylation (OXPHOS). In addition, apatinib enhanced the antileukemia effect of chidamide on T-ALL via activation of the mitochondria-mediated apoptosis pathway and impediment of mitochondrial biogenesis. Taken together, the study provides a potential role for apatinib in combination with chidamide in the management of T-ALL and warrants further clinical evaluations of this combination in patients with T-ALL.

Anoxia-induced mitophagy in the yeast Kluyveromyces marxianus

Kluyveromyces marxianus is a thermotolerant, ethanol-producing yeast that requires oxygen for efficient ethanol fermentation. Under anaerobic conditions, glucose consumption and ethanol production are retarded, suggesting that oxygen affects the metabolic state of K. marxianus. Mitochondria require oxygen to function, and their forms and number vary according to environmental conditions. In this study, the effect of anoxia on mitochondrial behavior in K. marxianus was examined. Under aerobic growth conditions, mitochondria-targeted GFP exhibited a tubular and dotted localization, representing a typical mitochondrial morphology, but under anaerobic conditions, GFP localized in vacuoles, suggesting that mitophagy occurs under anaerobic conditions. To confirm mitophagy induction, the ATG32, ATG8, ATG11 and ATG19 genes were disrupted. Vacuolar localization of mitochondria-targeted GFP under anaerobic conditions was interrupted in the Δatg32 and Δatg8 strains but not the Δatg11 and Δatg19 strains. Electron microscopy revealed mitochondria-like membrane components in the vacuoles of wild-type cells grown under anaerobic conditions. Quantitative analyses using mitochondria-targeted Pho8 demonstrated that mitophagy was induced in K. marxianus by anoxia but not nitrogen starvation. To the best of our knowledge, this is the first demonstration of anoxia-induced mitophagy in yeasts.

Mitochondrial Biogenesis, Mitochondrial Dynamics, and Mitophagy in the Maturation of Cardiomyocytes

Pluripotent stem cells (PSCs) can undergo unlimited self-renewal and can differentiate into all the cell types present in our body, including cardiomyocytes. Therefore, PSCs can be an excellent source of cardiomyocytes for future regenerative medicine and medical research studies. However, cardiomyocytes obtained from PSC differentiation culture are regarded as immature structurally, electrophysiologically, metabolically, and functionally. Mitochondria are organelles responsible for various cellular functions such as energy metabolism, different catabolic and anabolic processes, calcium fluxes, and various signaling pathways. Cells can respond to cellular needs to increase the mitochondrial mass by mitochondrial biogenesis. On the other hand, cells can also degrade mitochondria through mitophagy. Mitochondria are also dynamic organelles that undergo continuous fusion and fission events. In this review, we aim to summarize previous findings on the changes of mitochondrial biogenesis, mitophagy, and mitochondrial dynamics during the maturation of cardiomyocytes. In addition, we intend to summarize whether changes in these processes would affect the maturation of cardiomyocytes. Lastly, we aim to discuss unanswered questions in the field and to provide insights for the possible strategies of enhancing the maturation of PSC-derived cardiomyocytes.

Mitochondrial disease, mitophagy, and cellular distress in methylmalonic acidemia

Mitochondria—the intracellular powerhouse in which nutrients are converted into energy in the form of ATP or heat—are highly dynamic, double-membraned organelles that harness a plethora of cellular functions that sustain energy metabolism and homeostasis. Exciting new discoveries now indicate that the maintenance of this ever changing and functionally pleiotropic organelle is particularly relevant in terminally differentiated cells that are highly dependent on aerobic metabolism. Given the central role in maintaining metabolic and physiological homeostasis, dysregulation of the mitochondrial network might therefore confer a potentially devastating vulnerability to high-energy requiring cell types, contributing to a broad variety of hereditary and acquired diseases. In this Review, we highlight the biological functions of mitochondria-localized enzymes from the perspective of understanding—and potentially reversing—the pathophysiology of inherited disorders affecting the homeostasis of the mitochondrial network and cellular metabolism. Using methylmalonic acidemia as a paradigm of complex mitochondrial dysfunction, we discuss how mitochondrial directed-signaling circuitries govern the homeostasis and physiology of specialized cell types and how these may be disturbed in disease. This Review also provides a critical analysis of affected tissues, potential molecular mechanisms, and novel cellular and animal models of methylmalonic acidemia which are being used to develop new therapeutic options for this disease. These insights might ultimately lead to new therapeutics, not only for methylmalonic acidemia, but also for other currently intractable mitochondrial diseases, potentially transforming our ability to regulate homeostasis and health.

Dynamin-related protein 1 regulates substrate oxidation in skeletal muscle by stabilizing cellular and mitochondrial calcium dynamics

Mitochondria undergo continuous cycles of fission and fusion to promote inheritance, regulate quality control, and mitigate organelle stress. More recently, this process of mitochondrial dynamics has been demonstrated to be highly sensitive to nutrient supply, ultimately conferring bioenergetic plasticity to the organelle. However, whether regulators of mitochondrial dynamics play a causative role in nutrient regulation remains unclear. In this study, we generated a cellular loss-of-function model for dynamin-related protein 1 (DRP1), the primary regulator of outer membrane mitochondrial fission. Loss of DRP1 (shDRP1) resulted in extensive ultrastructural and functional remodeling of mitochondria, characterized by pleomorphic enlargement, increased electron density of the matrix, and defective NADH and succinate oxidation. Despite increased mitochondrial size and volume, shDRP1 cells exhibited reduced cellular glucose uptake and mitochondrial fatty acid oxidation. Untargeted transcriptomic profiling revealed severe downregulation of genes required for cellular and mitochondrial calcium homeostasis, which was coupled to loss of ATP-stimulated calcium flux and impaired substrate oxidation stimulated by exogenous calcium. The insights obtained herein suggest that DRP1 regulates substrate oxidation by altering whole-cell and mitochondrial calcium dynamics. These findings are relevant to the targetability of mitochondrial fission and have clinical relevance in the identification of treatments for fission-related pathologies such as hereditary neuropathies, inborn errors in metabolism, cancer, and chronic diseases.

Dietary calcium supplementation promotes the accumulation of intramuscular fat

BACKGROUND

In the livestock industry, intramuscular fat content is a key factor affecting meat quality. Many studies have shown that dietary calcium supplementation is closely related to lipid metabolism. However, few studies have examined the relationship between dietary calcium supplementation and intramuscular fat accumulation.

METHODS

Here, we used C2C12 cells, C57BL/6 mice (n = 8) and three-way cross-breeding pigs (Duroc×Landrace×Large white) (n = 10) to study the effect of calcium addition on intramuscular fat accumulation. In vitro, we used calcium chloride to adjust the calcium levels in the medium (2 mmol/L or 3 mmol/L). Then we measured various indicators. In vivo, calcium carbonate was used to regulate calcium levels in feeds (Mice: 0.5% calcium or 1.2% calcium) (Pigs: 0.9% calcium or 1.5% calcium). Then we tested the mice gastrocnemius muscle triglyceride content, pig longissimus dorsi muscle meat quality and lipidomics.

RESULTS

In vitro, calcium addition (3 mmol/L) had no significant effect on cell proliferation, but promoted the differentiation of C2C12 cells into slow-twitch fibers. Calcium supplementation increased triglyceride accumulation in C2C12 cells. Calcium addition increased the number of mitochondria and also increased the calcium level in the mitochondria and reduced the of key enzymes activity involved in β-oxidation such as acyl-coenzyme A dehydrogenase. Decreasing mitochondrial calcium level can alleviate lipid accumulation induced by calcium addition. In addition, calcium addition also reduced the glycolytic capacity and glycolytic conversion rate of C2C12 cells. In vivo, dietary calcium supplementation (1.2%) promoted the accumulation of triglycerides in the gastrocnemius muscle of mice. Dietary calcium supplementation (1.5%) had no effect on pig weight, but significantly improved the flesh color of the longissimus dorsi muscle, reduced the backfat thickness and increased intramuscular fat content in pigs. Besides, calcium addition had no effect on longissimus dorsi pH, electrical conductivity and shear force.

CONCLUSIONS

These results suggest that calcium addition promotes intramuscular fat accumulation by inhibiting the oxidation of fatty acids. These findings provide a new tool for increasing intramuscular fat content and an economical strategy for improving meat quality.

Directed evolution predicts cytochrome b G37V target site modification as probable adaptive mechanism towards the QiI fungicide fenpicoxamid in Zymoseptoria tritici

Acquired resistance is a threat to antifungal efficacy in medicine and agriculture. The diversity of possible resistance mechanisms and highly adaptive traits of pathogens make it difficult to predict evolutionary outcomes of treatments. We used directed evolution as an approach to assess the resistance risk to the new fungicide fenpicoxamid in the wheat pathogenic fungus Zymoseptoria tritici. Fenpicoxamid inhibits complex III of the respiratory chain at the ubiquinone reduction site (Qi site) of the mitochondrially encoded cytochrome b, a different site than the widely used strobilurins which inhibit the same complex at the ubiquinol oxidation site (Q_o site). We identified the G37V change within the cytochrome b Q_i site as the most likely resistance mechanism to be selected in Z. tritici. This change triggered high fenpicoxamid resistance and halved the enzymatic activity of cytochrome b, despite no significant penalty for in vitro growth. We identified negative cross-resistance between isolates harbouring G37V or G143A, a Q_o site change previously selected by strobilurins. Double mutants were less resistant to both QiIs and quinone outside inhibitors compared to single mutants. This work is a proof of concept that experimental evolution can be used to predict adaptation to fungicides and provides new perspectives for the management of QiIs.

Non-alcoholic fatty liver disease in mice with hepatocyte-specific deletion of mitochondrial fission factor

AIMS/HYPOTHESIS

Mitochondria are highly dynamic organelles continuously undergoing fission and fusion, referred to as mitochondrial dynamics, to adapt to nutritional demands. Evidence suggests that impaired mitochondrial dynamics leads to metabolic abnormalities such as non-alcoholic steatohepatitis (NASH) phenotypes. However, how mitochondrial dynamics are involved in the development of NASH is poorly understood. This study aimed to elucidate the role of mitochondrial fission factor (MFF) in the development of NASH.

METHODS

We created mice with hepatocyte-specific deletion of MFF (MffLiKO). MffLiKO mice fed normal chow diet (NCD) or high-fat diet (HFD) were evaluated for metabolic variables and their livers were examined by histological analysis. To elucidate the mechanism of development of NASH, we examined the expression of genes related to endoplasmic reticulum (ER) stress and lipid metabolism, and the secretion of triacylglycerol (TG) using the liver and primary hepatocytes isolated from MffLiKO and control mice.

RESULTS

MffLiKO mice showed aberrant mitochondrial morphologies with no obvious NASH phenotypes during NCD, while they developed full-blown NASH phenotypes in response to HFD. Expression of genes related to ER stress was markedly upregulated in the liver from MffLiKO mice. In addition, expression of genes related to hepatic TG secretion was downregulated, with reduced hepatic TG secretion in MffLiKO mice in vivo and in primary cultures of MFF-deficient hepatocytes in vitro. Furthermore, thapsigargin-induced ER stress suppressed TG secretion in primary hepatocytes isolated from control mice.

CONCLUSIONS/INTERPRETATION

We demonstrated that ablation of MFF in liver provoked ER stress and reduced hepatic TG secretion in vivo and in vitro. Moreover, MffLiKO mice were more susceptible to HFD-induced NASH phenotype than control mice, partly because of ER stress-induced apoptosis of hepatocytes and suppression of TG secretion from hepatocytes. This study provides evidence for the role of mitochondrial fission in the development of NASH.

Down the Iron Path: Mitochondrial Iron Homeostasis and Beyond

Cellular iron homeostasis and mitochondrial iron homeostasis are interdependent. Mitochondria must import iron to form iron–sulfur clusters and heme, and to incorporate these cofactors along with iron ions into mitochondrial proteins that support essential functions, including cellular respiration. In turn, mitochondria supply the cell with heme and enable the biogenesis of cytosolic and nuclear proteins containing iron–sulfur clusters. Impairment in cellular or mitochondrial iron homeostasis is deleterious and can result in numerous human diseases. Due to its reactivity, iron is stored and trafficked through the body, intracellularly, and within mitochondria via carefully orchestrated processes. Here, we focus on describing the processes of and components involved in mitochondrial iron trafficking and storage, as well as mitochondrial iron–sulfur cluster biogenesis and heme biosynthesis. Recent findings and the most pressing topics for future research are highlighted.

The medicinal chemistry of mitochondrial dysfunction: a critical overview of efforts to modulate mitochondrial health

Mitochondria are subcellular organelles that perform a variety of critical biological functions, including ATP production and acting as hubs of immune and apoptotic signalling. Mitochondrial dysfunction has been extensively linked to the pathology of multiple neurodegenerative disorders, resulting in significant investment from the drug discovery community. Despite extensive efforts, there remains no disease modifying therapies for neurodegenerative disorders. This manuscript aims to review the compounds historically used to modulate the mitochondrial network through the lens of modern medicinal chemistry, and to offer a perspective on the evidence that relevant exposure was achieved in a representative model and that exposure was likely to result in target binding and engagement of pharmacology. We hope this manuscript will aid the community in identifying those targets and mechanisms which have been convincingly (in)validated with high quality chemical matter, and those for which an opportunity exists to explore in greater depth.

Mitochondrial DNA in innate immune responses against infectious diseases

Mitochondrial DNA (mtDNA) can initiate an innate immune response when mislocalized in a compartment other than the mitochondrial matrix. mtDNA plays significant roles in regulating mitochondrial dynamics as well as mitochondrial unfolded protein response (UPR). The mislocalized extra-mtDNA can elicit innate immune response via cGAS-STING (cyclic GMP-AMP synthase-stimulator of interferon genes) pathway, inducing the expression of the interferon-stimulated genes (ISGs). Also, cytosolic damaged mtDNA is cleared up by various pathways which are responsible for participating in the activation of inflammatory responses. Four pathways of extra-mitochondrial mtDNA clearance are highlighted in this review - the inflammasome activation mechanism, neutrophil extracellular traps formation, recognition by Toll-like receptor 9 and transfer of mtDNA between cells packaged into extracellular vesicles. Anomalies in these pathways are associated with various diseases. We posit our review in the present pandemic situation and discuss how mtDNA elicits innate immune responses against different viruses and bacteria. This review gives a comprehensive picture of the role of extra-mitochondrial mtDNA in infectious diseases and speculates that research towards its understanding would help establish its therapeutic potential.

Mitochondrion as a Selective Target for the Treatment of Atherosclerosis: Role of Mitochondrial DNA Mutations and Defective Mitophagy in the Pathogenesis of Atherosclerosis and Chronic Inflammation

BACKGROUND

Atherosclerosis is a chronic inflammatory condition that affects different arteries in the human body and often leads to severe neurological complications, such as stroke and its sequelae. Affected blood vessels develop atherosclerotic lesions in the form of focal thickening of the intimal layer, so called atherosclerotic plaques.

OBJECTIVES

Despite the high priority of atherosclerosis research for global health and the numerous preclinical and clinical studies conducted, currently, there is no effective pharmacological treatment that directly impacts atherosclerotic plaques. Many knowledge gaps exist in our understanding of the mechanisms of plaque formation. In this review, we discuss the role of mitochondria in different cell types involved in atherogenesis and provide information about mtDNA mutations associated with the disease.

RESULTS

Mitochondria of blood and arterial wall cells appear to be one of the important factors in disease initiation and development. Significant experimental evidence connects oxidative stress associated with mitochondrial dysfunction and vascular disease. Moreover, mitochondrial DNA (mtDNA) deletions and mutations are being considered as potential disease markers. Further study of mtDNA damage and associated dysfunction may open new perspectives for atherosclerosis treatment.

CONCLUSION

Mitochondria can be considered as important disease-modifying factors in several chronic pathologies. Deletions and mutations of mtDNA may be used as potential disease markers. Mitochondria-targeting antioxidant therapies appear to be promising for the development of treatment of atherosclerosis and other diseases associated with oxidative stress and chronic inflammation.

Ethylene glycol butyl ether deteriorates oocyte quality via impairing mitochondrial function

Ethylene glycol butyl ether (EGBE) is a ubiquitous environmental pollutant that is commonly used in maquillage, industrial, and household products. EGBE has been shown to cause blood toxicity, carcinogenicity, and organ malformations. However, little is known about the impact of EGBE on the female reproductive system, especially oocyte quality. Here, we reported that EGBE influenced oocyte quality by showing the disturbed oocyte meiotic capacity, fertilization potential, and early embryonic development competency. Specifically, EGBE exposure impaired spindle/chromosome structure, microtubule stability, and actin polymerization to result in the oocyte maturation arrest and aneuploidy. In addition, EGBE exposure compromised the dynamics of cortical granules and their component ovastacin, leading to the failure of sperm binding and fertilization. Last, single-cell transcriptome analysis revealed that EGBE-induced oocyte deterioration was caused by mitochondrial dysfunction, which led to the accumulation of ROS and occurrence of apoptosis. Altogether, our study illustrates that mitochondrial dysfunction and redox perturbation is the major cause of the poor quality of oocytes exposed to EGBE.

Mitochondrial Function Are Disturbed in the Presence of the Anticancer Drug, 3-Bromopyruvate

3-bromopuryvate (3-BP) is a compound with unique antitumor activity. It has a selective action against tumor cells that exhibit the Warburg effect. It has been proven that the action of 3-BP is pleiotropic: it acts on proteins, glycolytic enzymes, reduces the amount of ATP, induces the formation of ROS (reactive oxygen species), and induces nuclear DNA damage. Mitochondria are important organelles for the proper functioning of the cell. The production of cellular energy (ATP), the proper functioning of the respiratory chain, or participation in the production of amino acids are one of the many functions of mitochondria. Here, for the first time, we show on the yeast model that 3-BP acts in the eukaryotic cell also by influence on mitochondria and that agents inhibiting mitochondrial function can potentially be used in cancer therapy with 3-BP. We show that cells with functional mitochondria are more resistant to 3-BP than rho⁰ cells. Using an MTT assay (a colorimetric assay for assessing cell metabolic activity), we demonstrated that 3-BP decreased mitochondrial activity in yeast in a dose-dependent manner. 3-BP induces mitochondrial-dependent ROS generation which results in ∆sod2, ∆por1, or ∆gpx1 mutant sensitivity to 3-BP. Probably due to ROS mtDNA lesions rise during 3-BP treatment. Our findings may have a significant impact on the therapy with 3-BP.

Zwitterion-Based Hydrogen Sulfide Nanomotors Induce Multiple Acidosis in Tumor Cells by Destroying Tumor Metabolic Symbiosis

Destruction of tumor metabolism symbiosis is an attractive cancer treatment method which targets tumor cells with little harm to normal cells. Yet, a single intervention strategy and poor penetration of the drug in tumor tissue result in limited effect. Herein, we propose a zero-waste zwitterion-based hydrogen sulfide (H₂ S)-driven nanomotor based on the basic principle of reaction in human body. When loaded with monocarboxylic acid transporter inhibitor α-cyano-4-hydroxycinnamic acid (α-CHCA), the nanomotor can move in tumor microenvironment and induce multiple acidosis of tumor cells and inhibit tumor growth through the synergistic effect of motion effect, driving force H₂ S and α-CHCA. Given the good biosafety of the substrate and driving gas of this kind of nanomotor, as well as the limited variety of nanomotors currently available to move in the tumor microenvironment, this kind of nanomotor may provide a competitive candidate for the active drug delivery system of cancer treatment.

Repeated Aconitine Treatment Induced the Remodeling of Mitochondrial Function via AMPK-OPA1-ATP5A1 Pathway

Aconitine is attracting increasing attention for its unique positive inotropic effect on the cardiovascular system, but underlying molecular mechanisms are still not fully understood. The cardiotonic effect always requires abundant energy supplement, which is mainly related to mitochondrial function. And OPA1 has been documented to play a critical role in mitochondrial morphology and energy metabolism in cardiomyocytes. Hence, this study was designed to investigate the potential role of OPA1-mediated regulation of energy metabolism in the positive inotropic effect caused by repeated aconitine treatment and the possible mechanism involved. Our results showed that repeated treatment with low-doses (0-10 μM) of aconitine for 7 days did not induce detectable cytotoxicity and enhanced myocardial contraction in Neonatal Rat Ventricular Myocytes (NRVMs). Also, we first identified that no more than 5 μM of aconitine triggered an obvious perturbation of mitochondrial homeostasis in cardiomyocytes by accelerating mitochondrial fusion, biogenesis, and Parkin-mediated mitophagy, followed by the increase in mitochondrial function and the cellular ATP content, both of which were identified to be related to the upregulation of ATP synthase α-subunit (ATP5A1). Besides, with compound C (CC), an inhibitor of AMPK, could reverse aconitine-increased the content of phosphor-AMPK, OPA1, and ATP5A1, and the following mitochondrial function. In conclusion, this study first demonstrated that repeated aconitine treatment could cause the remodeling of mitochondrial function via the AMPK-OPA1-ATP5A1 pathway and provide a possible explanation for the energy metabolism associated with cardiotonic effect induced by medicinal plants containing aconitine.

Chlorogenic Acid Ameliorates Damage Induced by Fluorene-9-Bisphenol in Porcine Sertoli Cells

4,4′-(9-Fluorenylidene) diphenol (BPFL, also known as BHPF and fluorene-9-bisphenol) is a novel bisphenol A substitute that is used in the plastics industry as an organic synthesis intermediate and is a potential endocrine disruptor. However, the deleterious effects of BPFL on porcine Sertoli cells (SCs) and the possible underlying mechanisms are still unclear. Chlorogenic acid (CA) is a free radical scavenger in the cellular antioxidant system that prevents oxidative damage and apoptosis. In the present research, we found that BPFL induced impairments in porcine SCs in a dose-dependent manner and that CA protected porcine SCs against BPFL exposure-induced impairments. Cell viability, proliferation and apoptosis assay results revealed that BPFL exposure could inhibit porcine SC proliferation and induce apoptosis, while CA supplementation ameliorated the effects of BPFL. Further analysis revealed that BPFL exposure induced oxidative stress, mitochondrial membrane potential dysfunction and DNA damage accumulation. Transcriptome analysis and further real-time quantitative PCR and Western blot results showed that BPFL exposure induced endoplasmic reticulum stress and apoptosis. Supplementation with CA dramatically ameliorated these phenotypes in BPFL-exposed porcine SCs. Overall, the present research reveals the possible underlying mechanisms by which BPFL exposure induced impairments and CA supplementation protected against these impairments in porcine SCs.

Dysfunctional mitochondria as critical players in the inflammation of autoimmune diseases: Potential role in Sjögren's syndrome

Relevant reviews highlight the association between dysfunctional mitochondria and inflammation, but few studies address the contribution of mitochondria and mitochondria-endoplasmic reticulum (ER) contact sites (MERCs) to cellular homeostasis and inflammatory signaling. The present review outlines the important role of mitochondria in cellular homeostasis and how dysfunctional mitochondrion can release and misplace mitochondrial components (cardiolipin, mitochondrial DNA (mtDNA), and mitochondrial formylated peptides) through multiple mechanisms. These components can act as damage-associated molecular patterns (DAMPs) and induce an inflammatory response via pattern recognition receptors (PRRs). Accumulation of damaged ROS-generating mitochondria, accompanied by the release of mitochondrial DAMPs, can activate PRRs such as the NLRP3 inflammasome, TLR9, cGAS/STING, and ZBP1. This process would explain the chronic inflammation that is observed in autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), type I diabetes (T1D), and Sjögren's syndrome. This review also provides a comprehensive overview of the importance of MERCs to mitochondrial function and morphology, cellular homeostasis, and the inflammatory response. MERCs play an important role in calcium homeostasis by mediating the transfer of calcium from the ER to the mitochondria and thereby facilitating the production of ATP. They also contribute to the synthesis and transfer of phospholipids, protein folding in the ER, mitochondrial fission, mitochondrial fusion, initiation of autophagosome formation, regulation of cell death/survival signaling, and regulation of immune responses. Therefore, alterations within MERCs could increase inflammatory signaling, modulate ER stress responses, cell homeostasis, and ultimately, the cell fate. This study shows severe ultrastructural alterations of mitochondria in salivary gland cells from Sjögren's syndrome patients for the first time, which could trigger alterations in cellular bioenergetics. This finding could explain symptoms such as fatigue and malfunction of the salivary glands in Sjögren's syndrome patients, which would contribute to the chronic inflammatory pathology of the disease. However, this is only a first step in solving this complex puzzle, and several other important factors such as changes in mitochondrial morphology, functionality, and their important contacts with other organelles require further in-depth study. Future work should focus on detecting the key milestones that are related to inflammation in patients with autoimmune diseases, such as Sjögren´s syndrome.

Physical activity counteracted associations of exposure to mixture of air pollutants with mitochondrial DNA copy number among rural Chinese adults

BACKGROUND

Exposure to single air pollutant and physical activity (PA) were associated with an altered mitochondrial DNA copy number (mtDNA-CN). However, studies on the interactive effects of single or a mixture of air pollutants and PA on mtDNA-CN were limited.

METHODS

A total of 2707 Chinese adults were obtained from the Henan Rural Cohort Study. Spatiotemporal models were used to estimate particulate matter (PMs) (PM with an aerodynamic diameter ≤ 1.0 μm (PM₁), ≤2.5 μm (PM_2.5) or ≤ 10 μm (PM₁₀)) and nitrogen dioxide (NO₂) concentrations. Relative mtDNA-CN was measured by quantitative real-time polymerase chain reaction. Linear regression and quantile g-computation models were applied to examine associations of single or mixture of air pollutants with relative mtDNA-CN. The interactive effects of single or mixture of air pollutants and PA on relative mtDNA-CN were visualized by using Interaction plots.

RESULTS

Each 1 μg/m³ increment in PM₁, PM_2.5, PM₁₀ or NO₂ was associated with a 5.11% (95% confidence interval: 3.71%, 6.53%), 6.77% (4.81%, 8.76%), 3.05% (2.22%, 3.87%) or 4.99% (3.45%, 6.55%) increase in relative mtDNA-CN. Each one-quartile increment in mixture of the four air pollutants was related to a 0.053 (0.032, 0.075) increase in relative mtDNA-CN. Negative interaction effects of single or mixture of air pollutants and PA on relative mtDNA-CN were observed.

CONCLUSIONS

The positive associations of single or mixture of air pollutants with relative mtDNA-CN were counteracted by PA at certain levels, implying that PA may be a costless and effective approach to decrease negative effects of air pollution on mtDNA-CN.