Mitochondrial Quality Control Mechanisms Research Articles

Mitochondrial dysfunction in acute kidney injury.

Acute kidney injury (AKI) is a systemic clinical syndrome increasing morbidity and mortality worldwide in recent years. Renal tubular epithelial cells (TECs) death caused by mitochondrial dysfunction is one of the pathogeneses. The imbalance of mitochondrial quality control is the main cause of mitochondrial dysfunction. Mitochondrial quality control plays a crucial role in AKI. Mitochondrial quality control mechanisms are involved in regulating mitochondrial integrity and function, including antioxidant defense, mitochondrial quality control, mitochondrial DNA (mtDNA) repair, mitochondrial dynamics, mitophagy, and mitochondrial biogenesis. Currently, many studies have used mitochondrial dysfunction as a targeted therapeutic strategy for AKI. Therefore, this review aims to present the latest research advancements on mitochondrial dysfunction in AKI, providing a valuable reference and theoretical foundation for clinical prevention and treatment of this condition, ultimately enhancing patient prognosis.

Mitochondrial quality control in alcohol-associated liver disease.

Excessive alcohol consumption is a leading cause of alcohol-associated liver disease (ALD), a significant global health concern with limited therapeutic options. Understanding the key factors contributing to ALD pathogenesis is crucial for identifying potential therapeutic targets. Central to ALD pathogenesis is the intricate interplay between alcohol metabolism and cellular processes, particularly involving mitochondria. Mitochondria are essential organelles in the liver, critical for energy production and metabolic functions. However, they are particularly vulnerable to alcohol-induced damage due to their involvement in alcohol metabolism. Alcohol disrupts mitochondrial function, impairing ATP production and triggering oxidative stress, which leads to cellular damage and inflammation. Mitochondrial quality control mechanisms, including biogenesis, dynamics, and mitophagy, are crucial for maintaining optimal mitochondrial function. Chronic alcohol consumption disrupts mitochondrial quality control checkpoints, leading to mitochondrial dysfunction that impairs fatty acid oxidation and contributes to hepatic steatosis in ALD. Moreover, alcohol promotes the accumulation of damaged mitochondria and the release of proinflammatory components, exacerbating liver damage and inflammation. Preserving mitochondrial health presents a promising therapeutic approach to mitigate ALD progression. In this review, we provide a comprehensive overview of the effects of alcohol on mitochondrial function and quality control mechanisms, highlighting their role in ALD pathogenesis. Understanding these mechanisms may pave the way for the development of novel therapeutic interventions for ALD.

Mitochondrial Bioenergetics Deficiency in cisd-1 Mutants is Linked to AMPK-Mediated Lipid Metabolism

BackgroundCISD-1 is a mitochondrial iron-sulfate [2Fe-2S] protein known to be associated with various human diseases, including cancer and diabetes. Previously, we demonstrated that CISD-1 deficiency in worms lowers glucose and ATP levels. In this study, we further explored how worms compensate for lower ATP levels by analyzing changes in cytoplasmic and mitochondrial iron content, AMPK activities, and total lipid profiles. Materials and MethodsExpression levels of CISD-1 and CISD-1::GFP fusion proteins in wild-type worms (N2), cisd-1-deletion mutants (tm4993 and syb923) and GFP insertion transgenic worms (PHX953 and SJL40) were examined by western blot. Fluorescence microscopy analyzed CISD-1::GFP pattern in PHX953 embryos and adults, and lipid droplet sizes in N2, cisd-1, aak-2 and aak-2;cisd-1 worms. Total and mitochondrial iron content, electron transport complex profiles, and AMPK activity were investigated in tm4993 and syb923 mutants. mRNA levels of mitochondrial β-oxidation genes, acs-2, cpt-5, and ech-1, were quantified by RT-qPCR in various genetic worm strains. Lipidomic analyses were performed in N2 and cisd-1(tm4993) worms. ResultsDefects in cisd-1 lead to an imbalance in iron transport and cause proton leak, resulting in lower ATP production by interrupting the mitochondrial electron transport chain. We identified a signaling pathway that links ATP deficiency-induced AMPK (AMP activated protein kinase) activation to the expression of genes that facilitate lipolysis via β-oxidation. ConclusionOur data provide a functional coordination between CISD-1 and AMPK constitutes a mitochondrial bioenergetics quality control mechanism that provides compensatory energy resources.

The Worsening of Myocardial Ischemia-Reperfusion Injury in Uremic Cardiomyopathy is Further Aggravated by PM2.5 Exposure: Mitochondria Serve as the Central Focus of Pathology.

Uremic cardiomyopathy (UC) represents a complex syndrome characterized by different cardiac complications, including systolic and diastolic dysfunction, left ventricular hypertrophy, and diffuse fibrosis, potentially culminating in myocardial infarction (MI). Revascularization procedures are often necessary for MI management and can induce ischemia reperfusion injury (IR). Despite this clinical relevance, the role of fine particulate matter (PM2.5) in UC pathology and the underlying subcellular mechanisms governing this pathology remains poorly understood. Hence, we investigate the impact of PM2.5 exposure on UC susceptibility to IR injury. Using a rat model of adenine-induced chronic kidney disease (CKD), the animals were exposed to PM2.5 at 250µg/m3 for 3h daily over 21days. Subsequently, hearts were isolated and subjected to 30min of ischemia followed by 60min of reperfusion to induce IR injury. UC hearts exposed to PM2.5 followed by IR induction (Adenine + PM_IR) exhibited significantly impaired cardiac function and increased cardiac injury (increased infarct size and apoptosis). Analysis at the subcellular level revealed reduced mitochondrial copy number, impaired mitochondrial bioenergetics, decreased expression of PGC1-α (a key regulator of mitochondrial biogenesis), and compromised mitochondrial quality control mechanisms. Additionally, increased mitochondrial oxidative stress and perturbation of the PI3K/AKT/AMPK signaling axis were evident. Our findings therefore collectively indicate that UC myocardium when exposed to PM2.5 is more vulnerable to IR-induced injury, primarily due to severe mitochondrial impairment.

The Protective Effects of Mcl-1 on Mitochondrial Damage and Oxidative Stress in Imiquimod-Induced Cancer Cell Death.

Mitochondria, vital organelles that generate ATP, determine cell fate. Dysfunctional and damaged mitochondria are fragmented and removed through mitophagy, a mitochondrial quality control mechanism. The FDA-approved drug IMQ, a synthetic agonist of Toll-like receptor 7, exhibits antitumor activity against various skin malignancies. We previously reported that IMQ promptly reduced the level of the antiapoptotic Mcl-1 protein and that Mcl-1 overexpression attenuated IMQ-triggered apoptosis in skin cancer cells. Furthermore, IMQ profoundly disrupted mitochondrial function, promoted mitochondrial fragmentation, induced mitophagy, and caused cell death by generating high levels of ROS. However, whether Mcl-1 protects mitochondria from IMQ treatment is still unknown. In this study, we demonstrated that Mcl-1 overexpression induced resistance to IMQ-induced apoptosis and reduced both IMQ-induced ROS generation and oxidative stress in cancer cells. Mcl-1 overexpression maintained mitochondrial function and integrity and prevented mitophagy in IMQ-treated cancer cells. Furthermore, IL-6 protected against IMQ-induced apoptosis by increasing Mcl-1 expression and attenuating IMQ-induced mitochondrial fragmentation. Mcl-1 overexpression ameliorates IMQ-induced ROS generation and mitochondrial fragmentation, thereby increasing mitochondrial stability and ultimately attenuating IMQ-induced cell death. Investigating the roles of Mcl-1 in mitochondria is a potential strategy for cancer therapy development.

BNIP3-mediated mitophagy attenuates hypoxic-ischemic brain damage in neonatal rats by inhibiting ferroptosis through P62-KEAP1-NRF2 pathway activation to maintain iron and redox homeostasis.

As a major contributor to neonatal death and neurological sequelae, hypoxic-ischemic encephalopathy (HIE) lacks a viable medication for treatment. Oxidative stress induced by hypoxic-ischemic brain damage (HIBD) predisposes neurons to ferroptosis due to the fact that neonates accumulate high levels of polyunsaturated fatty acids for their brain developmental needs but their antioxidant capacity is immature. Ferroptosis is a form of cell death caused by excessive accumulation of iron-dependent lipid peroxidation and is closely associated with mitochondria. Mitophagy is a type of mitochondrial quality control mechanism that degrades damaged mitochondria and maintains cellular homeostasis. In this study we employed mitophagy agonists and inhibitors to explore the mechanisms by which mitophagy exerted ferroptosis resistance in a neonatal rat HIE model. Seven-days-old neonatal rats were subjected to ligation of the right common carotid artery, followed by exposure to hypoxia for 2 h. The neonatal rats were treated with a mitophagy activator Tat-SPK2 peptide (0.5, 1 mg/kg, i.p.) 1 h before hypoxia, or in combination with mitochondrial division inhibitor-1 (Mdivi-1, 20 mg/kg, i.p.), and ferroptosis inhibitor Ferrostatin-1 (Fer-1) (2 mg/kg, i.p.) at the end of the hypoxia period. The regulation of ferroptosis by mitophagy was also investigated in primary cortical neurons or PC12 cells in vitro subjected to 4 or 6 h of OGD followed by 24 h of reperfusion. We showed that HIBD induced mitochondrial damage, ROS overproduction, intracellular iron accumulation, lipid peroxidation and ferroptosis, which were significantly reduced by the pretreatment with Tat-SPK2 peptide, and aggravated by the treatment with Mdivi-1 or BNIP3 knockdown. Ferroptosis inhibitors Fer-1 and deferoxamine B (DFO) reversed the accumulation of iron and lipid peroxides caused by Mdivi-1, hence reducing ferroptosis triggered by HI. We demonstrated that Tat-SPK2 peptide-activated BNIP3-mediated mitophagy did not alleviate neuronal ferroptosis through the GPX4-GSH pathway. BNIP3-mediated mitophagy drove the P62-KEAP1-NRF2 pathway, which conferred ferroptosis resistance by maintaining iron and redox homeostasis via the regulation of FTH1, HO-1, and DHODH/FSP1-CoQ10-NADH. This study may provide a new perspective and a therapeutic drug for the treatment of neonatal HIE.

Phosphoglycerate mutase 5 exacerbates alcoholic cardiomyopathy in male mice by inducing prohibitin-2 dephosphorylation and impairing mitochondrial quality control.

The induction of mitochondrial quality control (MQC) mechanisms is essential for the re-establishment of mitochondrial homeostasis and cellular bioenergetics during periods of stress. Although MQC activation has cardioprotective effects in various cardiovascular diseases, its precise role and regulatory mechanisms in alcoholic cardiomyopathy (ACM) remain incompletely understood. We explored whether two mitochondria-related proteins, phosphoglycerate mutase 5 (Pgam5) and prohibitin 2 (Phb2), influence MQC in male mice during ACM. Myocardial Pgam5 expression was upregulated in a male mouse model of ACM. Notably, following ACM induction, heart dysfunction was markedly reversed in male cardiomyocyte-specific Pgam5 knockout (Pgam5cKO) mice. Meanwhile, in alcohol-treated male mouse-derived neonatal cardiomyocytes, Pgam5 depletion preserved cell survival and restored mitochondrial dynamics, mitophagy, mitochondrial biogenesis and the mitochondrial unfolded protein response (mtUPR). We further found that in alcohol-treated cardiomyocyte, Pgam5 binds Phb2 and induces its dephosphorylation at Ser91. Alternative transduction of phospho-mimetic (Phb2S91D) and phospho-defective (Phb2S9A) Phb2 mutants attenuated and enhanced, respectively, alcohol-related mitochondrial dysfunction in cardiomyocytes. Moreover, transgenic male mice expressing Phb2S91D were resistant to alcohol-induced heart dysfunction. We conclude that ACM-induced Pgam5 upregulation results in Pgam5-dependent Phb2S91 dephosphorylation, leading to MQC destabilisation and mitochondrial dysfunction in heart. Therefore, modulating the Pgam5/Phb2 interaction could potentially offer a novel therapeutic strategy for ACM in male mice. Pgam5 knockout attenuates alcohol-induced cardiac histopathology and heart dysfunction in male mice. Pgam5 KO reduces alcohol-induced myocardial inflammation, lipid peroxidation and metabolic dysfunction in male mice. Pgam5 depletion protects mitochondrial function in alcohol-exposed male mouse cardiomyocytes. Pgam5 depletion normalises MQC in ACM. EtOH impairs MQC through inducing Phb2 dephosphorylation at Ser91. Pgam5 interacts with Phb2 and induces Phb2 dephosphorylation. Transgenic mice expressing a Ser91 phospho-mimetic Phb2 mutant are resistant to ACM.

Mitochondria as therapeutic targets in assisted reproduction.

Mitochondria are essential organelles with specialized functions, which play crucial roles in energy production, calcium homeostasis, and programmed cell death. In oocytes, mitochondrial populations are inherited maternally and are vital for developmental competence. Dysfunction in mitochondrial quality control mechanisms can lead to reproductive failure. Due to their central role in oocyte and embryo development, mitochondria have been investigated as potential diagnostic and therapeutic targets in assisted reproduction. Pharmacological agents that target mitochondrial function and show promise in improving assisted reproduction outcomes include antioxidant coenzyme Q10 and mitoquinone, mammalian target of rapamycin signaling pathway inhibitor rapamycin, and nicotinamide mononucleotide. Mitochondrial replacement therapies (MRTs) offer solutions for infertility and mitochondrial disorders. Autologous germline mitochondrial energy transfer initially showed promise but failed to demonstrate significant benefits in clinical trials. Maternal spindle transfer (MST) and pronuclear transfer hold potential for preventing mitochondrial disease transmission and improving oocyte quality. Clinical trials of MST have shown promising outcomes, but larger studies are needed to confirm safety and efficacy. However, ethical and legislative challenges complicate the widespread implementation of MRTs.

Mitochondrial Quality Control in Ovarian Function: From Mechanisms to Therapeutic Strategies.

Mitochondrial quality control plays a critical role in cytogenetic development by regulating various cell-death pathways and modulating the release of reactive oxygen species (ROS). Dysregulated mitochondrial quality control can lead to a broad spectrum of diseases, including reproductive disorders, particularly female infertility. Ovarian insufficiency is a significant contributor to female infertility, given its high prevalence, complex pathogenesis, and profound impact on women's health. Understanding the pathogenesis of ovarian insufficiency and devising treatment strategies based on this understanding are crucial. Oocytes and granulosa cells (GCs) are the primary ovarian cell types, with GCs regulated by oocytes, fulfilling their specific energy requirements prior to ovulation. Dysregulation of mitochondrial quality control through gene knockout or external stimuli can precipitate apoptosis, inflammatory responses, or ferroptosis in both oocytes and GCs, exacerbating ovarian insufficiency. This review aimed to delineate the regulatory mechanisms of mitochondrial quality control in GCs and oocytes during ovarian development. This study highlights the adverse consequences of dysregulated mitochondrial quality control on GCs and oocyte development and proposes therapeutic interventions for ovarian insufficiency based on mitochondrial quality control. These insights provide a foundation for future clinical approaches for treating ovarian insufficiency.

Low-intensity pulsed ultrasound improves myocardial ischaemia‒reperfusion injury via migrasome-mediated mitocytosis.

During myocardial ischaemia‒reperfusion injury (MIRI), the accumulation of damaged mitochondria could pose serious threats to the heart. The migrasomes, newly discovered mitocytosis-mediating organelles, selectively remove damaged mitochondria to provide mitochondrial quality control. Here, we utilised low-intensity pulsed ultrasound (LIPUS) on MIRI mice model and demonstrated that LIPUS reduced the infarcted area and improved cardiac dysfunction. Additionally, we found that LIPUS alleviated MIRI-induced mitochondrial dysfunction. We provided new evidence that LIPUS mechanical stimulation facilitated damaged mitochondrial excretion via migrasome-dependent mitocytosis. Inhibition the formation of migrasomes abolished the protective effect of LIPUS on MIRI. Mechanistically, LIPUS induced the formation of migrasomes by evoking the RhoA/Myosin II/F-actin pathway. Meanwhile, F-actin activated YAP nuclear translocation to transcriptionally activate the mitochondrial motor protein KIF5B and Drp1, which are indispensable for LIPUS-induced mitocytosis. These results revealed that LIPUS activates mitocytosis, a migrasome-dependent mitochondrial quality control mechanism, to protect against MIRI, underlining LIPUS as a safe and potentially non-invasive treatment for MIRI.

Elimination of damaged mitochondria during UVB-induced senescence is orchestrated by NIX-dependent mitophagy.

Skin aging is the result of two types of aging, "intrinsic aging" an inevitable consequence of physiologic and genetically determined changes and "extrinsic aging," which is dependent on external factors such as exposure to sunlight, smoking, and dietary habits. UVB causes skin injury through the generation of free radicals and other oxidative byproducts, also contributing to DNA damage. Appearance and accumulation of senescent cells in the skin are considered one of the hallmarks of aging in this tissue. Mitochondria play an important role for the development of cellular senescence, in particular stress-induced senescence of human cells. However, many aspects of mitochondrial physiology relevant to cellular senescence and extrinsic skin aging remain to be unraveled. Here, we demonstrate that mitochondria damaged by UVB irradiation of human dermal fibroblasts (HDF) are eliminated by NIX-dependent mitophagy and that this process is important for cell survival under these conditions. Additionally, UVB-irradiation of human dermal fibroblasts (HDF) induces the shedding of extracellular vesicles (EVs), and this process is significantly enhanced in UVB-irradiated NIX-depleted cells. Our findings establish NIX as the main mitophagy receptor in the process of UVB-induced senescence and suggest the release of EVs as an alternative mechanism of mitochondrial quality control in HDF.

Investigating the temporal link between PM2.5 exposure and acceleration of myocardial ischemia reperfusion injury: Emphasizing the hazardous presence of metals in inhaled air

Exposure to PM2.5 is widely acknowledged to induce cardiotoxic effects, leading to decreased myocardial tolerance to revascularization procedures and subsequent ischemia reperfusion injury (IR). However, the temporal relationship between PM2.5 exposure and vulnerability to IR, along with the underlying mechanisms, remains unclear and is the focus of this study. Female Wistar rats were exposed to PM2.5 at a concentration of 250 μg/m³ for 3 h daily over varying durations (7, 14, and 21 days), followed by IR induction. Our results demonstrated a significant increase in cardiac injury, as evidenced by increased infarct size and elevated cardiac injury markers, starting from day 14 of PM2.5 exposure, accompanied by declined cardiac function. These adverse effects were associated with apoptosis and impaired mitochondrial function, including reduced bioenergetics, mitochondrial DNA copy number and quality control mechanisms, along with inactivation of the PI3K/AKT/AMPK signalling pathways. Furthermore, analysis of myocardial tissue revealed elevated metal accumulation, particularly within mitochondria. Chelation of PM2.5 -associated metals using EDTA significantly mitigated the toxic effects on cardiac IR pathology, as confirmed in both rat myocardium and H9c2 cells. These findings suggest that metals in PM2.5 play a crucial role in inducing cardiotoxicity, impairing myocardial resilience to stress through mitochondrial accumulation and dysfunction.

Cardiomyocyte Derived Extracellular Mitochondria in Inflammatory Response During Oxidative Stress

Increased production of reactive oxygen species (ROS) occurs in a variety of disease states. Elevated oxidative stress often co-exists with inflammatory response. A burst of ROS production due to myocardial ischemia or infarction causes damage to the mitochondria, tissue injury and inflammation. The mitochondria have evolved with quality control mechanisms to maintain the homeostasis for energy metabolism, and to control cell death. We have found secretion of mitochondria as a novel mechanism of mitochondrial quality control and for cell-cell communication. Sublethal doses of H2O2 cause an increased release of mitochondria from cardiomyocytes to the extracellular space. Extracellular mitochondria (EM) appear to be smaller with an average diameter of 524.67±54.69nm (control) and 563.27±41.82nm (H2O2 treated cells), compared to the corresponding intracellular mitochondria (IM) having an average diameter of 1192±256.50nm and 818.37±62.74 nm. LC-MS/MS based proteomics showed an increased levels of peroxiredoxins and several respiratory chain proteins in the EM from stressed cells. However, metabolomics did not reveal significant changes in the EM metabolites collected from control or stressed cells. Both have reduced NAD, ATP, ADP, or AMP but increased nicotinamide, lactate, and a number of amino acids compared to the IM. Inhibiting ceramide synthesis, a sphingolipid derivative, reduced the number of EM released from oxidatively stressed cardiomyocytes, indicating a role of lipids in regulating mitochondrial release. Functionally, EM from oxidatively stressed cardiomyocytes caused activation of M1 and M2 macrophages, as measured by cytokine markers TNFα and CD163. Our data have unveiled a novel mechanism of oxidative stress response and secretion of the extracellular mitochondria as a vehicle for initiation of inflammatory response. NIH R01 GM125212, R01 GM126165, Holsclaw Endowment and the University of Arizona College of Pharmacy start-up fund. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Role of mitochondria in renal ischemia-reperfusion injury.

Acute kidney injury (AKI) induced by renal ischemia-reperfusion injury (IRI) has a high morbidity and mortality, representing a worldwide problem. The kidney is an essential organ of metabolism that has high blood perfusion and is the second most mitochondria-rich organ after the heart because of the high ATP demands of its essential functions of nutrient reabsorption, acid-base and electrolyte balance, and hemodynamics. Thus, these energy-intensive cells are particularly vulnerable to mitochondrial dysfunction. As the bulk of glomerular ultrafiltrate reabsorption by proximal tubules occurs via active transport, the mitochondria of proximal tubules must be equipped for detecting and responding to fluctuations in energy availability to guarantee efficient basal metabolism. Any insults to mitochondrial quality control mechanisms may lead to biological disruption, blocking the clearance of damaged mitochondria and resulting in morphological change and tissue dysfunction. Extensive research has shown that mitochondria have pivotal roles in acute kidney disease, so in this article, we discuss the role of mitochondria, their dynamics and mitophagy in renal ischemia-reperfusion injury.

SIRT1-activating butein inhibits arecoline-induced mitochondrial dysfunction through PGC1α and MTP18 in oral cancer

BackgroundMitochondrial dysfunction associated with mitochondrial DNA mutations, enzyme defects, generation of ROS, and altered oxidative homeostasis is known to induce oral carcinogenesis during exposure to arecoline. Butein, a natural small molecule from Butea monosperma, possesses anti-inflammatory, anti-diabetic, and anti-cancer effects. However, the role of butein in the mitochondrial quality control mechanism has not been illuminated clearly. PurposeThis study aimed to explore the role of butein in preserving mitochondrial quality control during arecoline-induced mitochondrial dysfunction in oral cancer to curtail the early onset of carcinogenesis. MethodsCell viability was evaluated by MTT assay. The relative protein expressions were determined by western blotting. Immunofluorescence and confocal imaging were used to analyze the relative fluorescence and co-localization of proteins. Respective siRNAs were used to examine the knockdown-based studies. ResultsButein, in the presence of arecoline, significantly caused a decrease in mitochondrial hyperpolarization and ROS levels in oral cancer cells. Mechanistically, we found an increase in COXIV, TOM20, and PGC1α expression during butein treatment, and inhibition of PGC1α blunted mitochondrial biogenesis and decreased the mitochondrial pool. Moreover, the fission protein MTP18, and its molecular partners DRP1 and MFF were dose-dependently increased during butein treatment to maintain mitochondria mass. In addition, we also found increased expression of various mitophagy proteins, including PINK1, Parkin, and LC3 during butein treatment, suggesting the clearance of damaged mitochondria to maintain a healthy mitochondrial pool. Interestingly, butein increased the activity of SIRT1 to enhance the functional mitochondrial pool, and inhibition of SIRT1 found to reduce the mitochondrial levels, as evident from the decrease in the expression of PGC1α and MTP18 in oral cancer cells. ConclusionOur study proved that SIRT1 maintains a functional mitochondrial pool through PGC1α and MTP18 for biogenesis and fission of mitochondria during arecoline exposure and could decrease the risk of mitochondria dysfunctionality associated with the onset of oral carcinogenesis.

Loss of FoxO1 activates an alternate mechanism of mitochondrial quality control for healthy adipose browning.

Browning of white adipose tissue is hallmarked by increased mitochondrial density and metabolic improvements. However, it remains largely unknown how mitochondrial turnover and quality control are regulated during adipose browning. In the present study, we found that mice lacking adipocyte FoxO1, a transcription factor that regulates autophagy, adopted an alternate mechanism of mitophagy to maintain mitochondrial turnover and quality control during adipose browning. Post-developmental deletion of adipocyte FoxO1 (adO1KO) suppressed Bnip3 but activated Fundc1/Drp1/OPA1 cascade, concurrent with up-regulation of Atg7 and CTSL. In addition, mitochondrial biogenesis was stimulated via the Pgc1α/Tfam pathway in adO1KO mice. These changes were associated with enhanced mitochondrial homeostasis and metabolic health (e.g., improved glucose tolerance and insulin sensitivity). By contrast, silencing Fundc1 or Pgc1α reversed the changes induced by silencing FoxO1, which impaired mitochondrial quality control and function. Ablation of Atg7 suppressed mitochondrial turnover and function, causing metabolic disorder (e.g., impaired glucose tolerance and insulin sensitivity), regardless of elevated markers of adipose browning. Consistently, suppression of autophagy via CTSL by high-fat diet was associated with a reversal of adO1KO-induced benefits. Our data reveal a unique role of FoxO1 in coordinating mitophagy receptors (Bnip3 and Fundc1) for a fine-tuned mitochondrial turnover and quality control, underscoring autophagic clearance of mitochondria as a prerequisite for healthy browning of adipose tissue.

Defects of mitochondria-lysosomes communication induce secretion of mitochondria-derived vesicles and drive chemoresistance in ovarian cancer cells

BackgroundAmong the mechanisms of mitochondrial quality control (MQC), generation of mitochondria-derived vesicles (MDVs) is a process to avoid complete failure of mitochondria determining lysosomal degradation of mitochondrial damaged proteins. In this context, RAB7, a late endocytic small GTPase, controls delivery of MDVs to late endosomes for subsequent lysosomal degradation. We previously demonstrated that RAB7 has a pivotal role in response to cisplatin (CDDP) regulating resistance to the drug by extracellular vesicle (EVs) secretion.MethodsWestern blot and immunofluorescence analysis were used to analyze structure and function of endosomes and lysosomes in CDDP chemosensitive and chemoresistant ovarian cancer cell lines. EVs were purified from chemosensitive and chemoresistant cells by ultracentrifugation or immunoisolation to analyze their mitochondrial DNA and protein content. Treatment with cyanide m-chlorophenylhydrazone (CCCP) and RAB7 modulation were used, respectively, to understand the role of mitochondrial and late endosomal/lysosomal alterations on MDV secretion. Using conditioned media from chemoresistant cells the effect of MDVs on the viability after CDDP treatment was determined. Seahorse assays and immunofluorescence analysis were used to study the biochemical role of MDVs and the uptake and intracellular localization of MDVs, respectively.ResultsWe observed that CDDP-chemoresistant cells are characterized by increased MDV secretion, impairment of late endocytic traffic, RAB7 downregulation, an increase of RAB7 in EVs, compared to chemosensitive cells, and downregulation of the TFEB-mTOR pathway overseeing lysosomal and mitochondrial biogenesis and turnover. We established that MDVs can be secreted rather than delivered to lysosomes and are able to deliver CDDP outside the cells. We showed increased secretion of MDVs by chemoresistant cells ultimately caused by the extrusion of RAB7 in EVs, resulting in a dramatic drop in its intracellular content, as a novel mechanism to regulate RAB7 levels. We demonstrated that MDVs purified from chemoresistant cells induce chemoresistance in RAB7-modulated process, and, after uptake from recipient cells, MDVs localize to mitochondria and slow down mitochondrial activity.ConclusionsDysfunctional MQC in chemoresistant cells determines a block in lysosomal degradation of MDVs and their consequent secretion, suggesting that MQC is not able to eliminate damaged mitochondria whose components are secreted becoming effectors and potential markers of chemoresistance.

Tom20 gates PINK1 activity and mediates its tethering of the TOM and TIM23 translocases upon mitochondrial stress

Mutations in PTEN-induced putative kinase 1 (PINK1) cause autosomal recessive early-onset Parkinson's disease (PD). PINK1 is a Ser/Thr kinase that regulates mitochondrial quality control by triggering mitophagy mediated by the ubiquitin (Ub) ligase Parkin. Upon mitochondrial damage, PINK1 accumulates on the outer mitochondrial membrane forming a high-molecular-weight complex with the translocase of the outer membrane (TOM). PINK1 then phosphorylates Ub, which enables recruitment and activation of Parkin followed by autophagic clearance of the damaged mitochondrion. Thus, Parkin-dependent mitophagy hinges on the stable accumulation of PINK1 on the TOM complex. Yet, the mechanism linking mitochondrial stressors to PINK1 accumulation and whether the translocases of the inner membrane (TIMs) are also involved remain unclear. Herein, we demonstrate that mitochondrial stress induces the formation of a PINK1-TOM-TIM23 supercomplex in human cultured cell lines, dopamine neurons, and midbrain organoids. Moreover, we show that PINK1 is required to stably tether the TOM to TIM23 complexes in response to stress such that the supercomplex fails to accumulate in cells lacking PINK1. This tethering is dependent on an interaction between the PINK1 N-terminal-C-terminal extension module and the cytosolic domain of the Tom20 subunit of the TOM complex, the disruption of which, by either designer or PD-associated PINK1 mutations, inhibits downstream mitophagy. Together, the findings provide key insight into how PINK1 interfaces with the mitochondrial import machinery, with important implications for the mechanisms of mitochondrial quality control and PD pathogenesis.

Role of the mitophagy-apoptosis axis in the pathogenesis of polycystic ovarian syndrome.

Polycystic ovary syndrome (PCOS) is a common endocrine disorder characterized by menstrual irregularities, androgen excess, and polycystic ovarian morphology, but its pathogenesis remains largely unknown. This review focuses on how androgen excess influences the molecular basis of energy metabolism, mitochondrial function, and mitophagy in granulosa cells and oocytes, summarizes our current understanding of the pathogenesis of PCOS, and discuss perspectives on future research directions. A search of PubMed and Google Scholar databases were used to identify relevant studies for this narrative literature review. Female offspring born of pregnant animals exposed to androgens recapitulates the PCOS phenotype. Abnormal mitochondrial morphology, altered expression of genes related to glycolysis, mitochondrial biogenesis, fission/fusion dynamics, and mitophagy have been identified in PCOS patients and androgenic animal models. Androgen excess causes uncoupling of the electron transport chain and depletion of the cellular adenosine 5'-triphosphate pool, indicating further impairment of mitochondrial function. A shift toward mitochondrial fission restores mitochondrial quality control mechanisms. However, prolonged mitochondrial fission disrupts autophagy/mitophagy induction due to loss of compensatory reserve for mitochondrial biogenesis. Disruption of compensatory mechanisms that mediate the quality control switch from mitophagy to apoptosis may cause a disease phenotype. Furthermore, genetic predisposition, altered expression of genes related to glycolysis and oxidative phosphorylation, or a combination of these factors may also contribute to the development of PCOS. In conclusion, fetuses exposed to a hyperandrogenemic intrauterine environment may cause the PCOS phenotype possibly through disruption of the compensatory regulation of the mitophagy-apoptosis axis.

Mitochondrial quality control alterations and placenta-related disorders.

Mitochondria are ubiquitous in eukaryotic cells. Normal maintenance of function is the premise and basis for various physiological activities. Mitochondrial dysfunction is commonly observed in a wide range of pathological conditions, such as neurodegenerative, metabolic, cardiovascular, and various diseases related to foetal growth and development. The placenta is a highly energy-dependent organ that acts as an intermediary between the mother and foetus and functions to maintain foetal growth and development. Recent studies have demonstrated that mitochondrial dysfunction is associated with placental disorders. Defects in mitochondrial quality control mechanisms may lead to preeclampsia and foetal growth restriction. In this review, we address the quality control mechanisms of mitochondria and the relevant pathologies of mitochondrial dysfunction in placenta-related diseases, such as preeclampsia and foetal growth restriction. This review also investigates the relation between mitochondrial dysfunction and placental disorders.