Mitochondrial quality control by the Pink1/Parkin system

The Role of Endothelial Cell Mitophagy in Age-Related Cardiovascular Diseases

Aging is a major risk factor for cardiovascular diseases (CVD), and mitochondrial autophagy impairment is considered a significant physiological change associated with aging. Endothelial cells play a crucial role in maintaining vascular homeostasis and function, participating in various physiological processes such as regulating vascular tone, coagulation, angiogenesis, and inflammatory responses. As aging progresses, mitochondrial autophagy impairment in endothelial cells worsens, leading to the development of numerous cardiovascular diseases. Therefore, regulating mitochondrial autophagy in endothelial cells is vital for preventing and treating age-related cardiovascular diseases. However, there is currently a lack of systematic reviews in this area. To address this gap, we have written this review to provide new research and therapeutic strategies for managing aging and age-related cardiovascular diseases.

Sesamin alleviates lipid accumulation induced by oleic acid via PINK1/Parkin-mediated mitophagy in HepG2 cells

Sesamin, a special compound present in sesame and sesame oil, has been reported a role in regulating lipid metabolism, while the underlying mechanisms remain unclear. Autophagy has been reported associated with lipid metabolism and regarded as a key modulator in liver steatosis. The present work aimed to investigate whether sesamin could exert its protective effects against lipid accumulation via modulating autophagy in HepG2 cells stimulated with oleic acid (OA). Cell viability was evaluated using the CCK-8 method, and triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein, cholesterol (LDL-C), alanine aminotransferase (ALT), along with aspartate aminotransferase (AST) were assessed by oil red O staining, transmission electron microscopy (TEM), and biochemical kits to investigate the lipid-lowering effects of sesamin. Differentially expressed genes were screened by RNA sequencing and validated using real-time quantitative PCR and Western blot. Autophagy and mitophagy related molecules were analyzed employing TEM, Western blot, and immunofluorescence. The data shows that in HepG2 cells stimulated by OA, sesamin reduces levels of TG, TC, LDL-C, ALT, and AST while elevating HDL-C, alleviates the lipid accumulation and improves fatty acid metabolism through modulating the levels of fat metabolism related genes including PCSK9, FABP1, CD36, and SOX4. Sesamin restores the suppressed autophagy in HepG2 cells caused by OA, which could be blocked by autophagy inhibitors. This indicates that sesamin improves fatty acid metabolism by enhancing autophagy levels, thereby mitigating the intracellular lipid accumulation. Furthermore, sesamin significantly enhances the mitophagy and improves mitochondrial homeostasis via activating the PINK/Parkin pathway. These data suggest that sesamin alleviates the excessive lipid accumulation in HepG2 caused by OA by restoring the impaired mitophagy via the PINK1/Parkin pathway, probably playing a preventive or therapeutic role in hepatic steatosis.

Liraglutide ameliorates delirium-like behaviors of aged mice undergoing cardiac surgery by mitigating microglia activation via promoting mitophagy

OBJECTIVE

Postoperative delirium (POD) is a prevalent complication in cardiac surgery patients, particularly the elderly, with neuroinflammation posited as a crucial contributing factor. We investigated the prophylactic effects of liraglutide, a GLP-1 analog, on delirium-like behaviors in aged mice undergoing cardiac surgery and explored the underlying mechanisms focusing on neuroinflammation, mitochondrial dysfunction, and synaptic plasticity.

METHODS

Using a cardiac ischemia-reperfusion animal model to mimic cardiac surgery, we assessed delirium-like behaviors, microglial activation, NLRP3 inflammasome activation, mitophagy, synaptic engulfment, and synaptic plasticity.

RESULTS

Cardiac surgery triggered delirium-like behaviors, concomitant with heightened microglial and NLRP3 inflammasome activation and impaired mitochondrial function and synaptic plasticity. Pretreatment with liraglutide ameliorated these adverse outcomes. Mechanistically, liraglutide enhanced mitophagy, thereby inhibiting NLRP3 inflammasome activation and subsequent microglial activation. Furthermore, liraglutide counteracted surgery-induced synaptic loss and impairment of synaptic plasticity.

CONCLUSION

Liraglutide exerts protective effects against delirium-like behaviors in aged mice post-cardiac surgery, potentially through bolstering microglia mitophagy, curtailing neuroinflammation, and preserving synaptic integrity. This highlights the potential of liraglutide as a promising perioperative strategy for delirium prevention in cardiac surgery patients.

Comprehensive overview of the role of mitochondrial dysfunction in the pathogenesis of acute kidney ischemia-reperfusion injury: a narrative review

Acute kidney ischemia-reperfusion (IR) injury is a life-threatening condition that predisposes individuals to chronic kidney disease. Since the kidney is one of the most energy-demanding organs in the human body and mitochondria are the powerhouse of cells, mitochondrial dysfunction plays a central role in the pathogenesis of IR-induced acute kidney injury. Mitochondrial dysfunction causes a reduction in adenosine triphosphate production, loss of mitochondrial dynamics (represented by persistent fragmentation), and impaired mitophagy. Furthermore, the pathological accumulation of succinate resulting from fumarate reduction under oxygen deprivation (ischemia) in the reverse flux of the Krebs cycle can eventually lead to a burst of reactive oxygen species driven by reverse electron transfer during the reperfusion phase. Accumulating evidence indicates that improving mitochondrial function, biogenesis, and dynamics, and normalizing metabolic reprogramming within the mitochondria have the potential to preserve kidney function during IR injury and prevent progression to chronic kidney disease. In this review, we summarize recent advances in understanding the detrimental role of metabolic reprogramming and mitochondrial dysfunction in IR injury and explore potential therapeutic strategies for treating kidney IR injury.

Targeting mitochondrial Ca2+ uptake for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rare adult-onset neurodegenerative disease characterized by progressive motor neuron (MN) loss, muscle denervation and paralysis. Over the past several decades, researchers have made tremendous efforts to understand the pathogenic mechanisms underpinning ALS, with much yet to be resolved. ALS is described as a non-cell autonomous condition with pathology detected in both MNs and non-neuronal cells, such as glial cells and skeletal muscle. Studies in ALS patient and animal models reveal ubiquitous abnormalities in mitochondrial structure and function, and disturbance of intracellular calcium homeostasis in various tissue types, suggesting a pivotal role of aberrant mitochondrial calcium uptake and dysfunctional calcium signalling cascades in ALS pathogenesis. Calcium signalling and mitochondrial dysfunction are intricately related to the manifestation of cell death contributing to MN loss and skeletal muscle dysfunction. In this review, we discuss the potential contribution of intracellular calcium signalling, particularly mitochondrial calcium uptake, in ALS pathogenesis. Functional consequences of excessive mitochondrial calcium uptake and possible therapeutic strategies targeting mitochondrial calcium uptake or the mitochondrial calcium uniporter, the main channel mediating mitochondrial calcium influx, are also discussed.

Role of PTEN-Induced Protein Kinase 1 as a Mitochondrial Dysfunction Regulator in Cardiovascular Disease Pathogenesis

Cardiovascular disease (CVD) remains a global health challenge, primarily due to atherosclerosis, which leads to conditions such as coronary artery disease, cerebrovascular disease, and peripheral arterial disease. Mitochondrial dysfunction initiates endothelial dysfunction, a key contributor to CVD pathogenesis, as well as triggers the accumulation of reactive oxygen species (ROS), energy stress, and cell death in endothelial cells, which are crucial for atherosclerosis development. This review explores the role of PTEN-induced protein kinase 1 (PINK1) in mitochondrial quality control, focusing on its significance in cardiovascular health. PINK1 plays a pivotal role in mitophagy (selective removal of damaged mitochondria), contributing to the prevention of CVD progression. PINK1-mediated mitophagy also affects the maintenance of cardiomyocyte homeostasis in ischemic heart disease, thus mitigating mitochondrial dysfunction and oxidative stress, as well as regulates endothelial health in atherosclerosis through influencing ROS levels and inflammatory response. We also investigated the role of PINK1 in vascular smooth muscle cells, emphasizing on its role in apoptosis and atherosclerosis. Dysfunctional mitophagy in these cells accelerates cellular senescence and contributes to adverse effects including plaque rupture and inflammation. Mitophagy has also been explored as a potential therapeutic target for vascular calcification, a representative lesion in atherosclerosis, with a focus on lactate-induced mechanisms. Finally, we highlight the current research and clinical trials targeting mitophagy as a therapeutic avenue for CVD.

Role of autophagy in skin photoaging: A narrative review

As the largest organ of the human body, the skin serves as the primary barrier against external damage. The continuous increase in human activities and environmental pollution has resulted in the ongoing depletion of the ozone layer. Excessive exposure to ultraviolet (UV) radiation enhances the impact of external factors on the skin, leading to photoaging. Photoaging causes physical and psychological damage to the human body. The prevention and management of photoaging have attracted increased attention in recent years. Despite significant progress in understanding and mitigating UV-induced photoaging, the precise mechanisms through which autophagy contributes to the prevention of photoaging remain unclear. Given the important role of autophagy in repairing UV-induced DNA damage and scavenging oxidized lipids, autophagy is considered a novel strategy for preventing the occurrence of photoaging and other UV light-induced skin diseases. This review aims to elucidate the biochemical and clinical features of photoaging, the relationship of skin photoaging and chronological aging, the mechanisms underlying skin photoaging and autophagy, and the role of autophagy in skin photoaging.

Morin suppresses mTORc1/IRE-1α/JNK and IP3R-VDAC-1 pathways: Crucial mechanisms in apoptosis and mitophagy inhibition in experimental Huntington's disease, supported by in silico molecular docking simulations

AIMS

Endoplasmic reticulum stress (ERS) with aberrant mitochondrial-ER contact (MERC), mitophagy, and apoptosis are interconnected determinants in neurodegenerative diseases. Previously, we proved the potential of Morin hydrate (MH), a potent antioxidant flavonoid, to mitigate Huntington's disease (HD)-3-nitropropionic acid (3-NP) model by modulating glutamate/calpain/Kidins220/BDNF trajectory. Extending our work, we aimed to evaluate its impact on combating the ERS/MERC, mitophagy, and apoptosis.

METHODS

Rats were subjected to 3-NP for 14 days and post-treated with MH and/or the ERS inducer WAG-4S for 7 days. Disease progression was assessed by gross inspection and striatal biochemical, histopathological, immunohistochemical, and transmission electron microscopical (TEM) examinations. A molecular docking study was attained to explore MH binding to mTOR, JNK, the kinase domain of IRE1-α, and IP3R.

KEY FINDINGS

MH decreased weight loss and motor dysfunction using open field and rotarod tests. It halted HD degenerative striatal neurons and nucleus/mitochondria ultra-microscopic alterations reflecting neuroprotection. Mechanistically, MH deactivated striatal mTOR/IRE1-α/XBP1s&JNK/IP3R, PINK1/Ubiquitin/Mfn2, and cytochrome c/caspase-3 signaling pathways, besides enhancing p-PGC-1α and p-VDAC1. WAG-4S was able to ameliorate all effects initiated by MH to different extents. Molecular docking simulations revealed promising binding patterns of MH and hence its potential inhibition of the studied proteins, especially mTOR, IP3R, and JNK.

SIGNIFICANCE

MH alleviated HD-associated ERS, MERC, mitophagy, and apoptosis. This is mainly achieved by combating the mTOR/IRE1-α signaling, IP3R/VDAC hub, PINK1/Ubiquitin/Mfn2, and cytochrome c/caspase 3 axis to be worsened by WAG-4S. Molecular docking simulations showed the promising binding of MH to mTOR and JNK as novel identified targets.

Advancements in Genetic and Biochemical Insights: Unraveling the Etiopathogenesis of Neurodegeneration in Parkinson's Disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative movement disorder worldwide, which is primarily characterized by motor impairments. Even though multiple hypotheses have been proposed over the decades that explain the pathogenesis of PD, presently, there are no cures or promising preventive therapies for PD. This could be attributed to the intricate pathophysiology of PD and the poorly understood molecular mechanism. To address these challenges comprehensively, a thorough disease model is imperative for a nuanced understanding of PD's underlying pathogenic mechanisms. This review offers a detailed analysis of the current state of knowledge regarding the molecular mechanisms underlying the pathogenesis of PD, with a particular emphasis on the roles played by gene-based factors in the disease's development and progression. This study includes an extensive discussion of the proteins and mutations of primary genes that are linked to PD, including α-synuclein, GBA1, LRRK2, VPS35, PINK1, DJ-1, and Parkin. Further, this review explores plausible mechanisms for DAergic neural loss, non-motor and non-dopaminergic pathologies, and the risk factors associated with PD. The present study will encourage the related research fields to understand better and analyze the current status of the biochemical mechanisms of PD, which might contribute to the design and development of efficacious and safe treatment strategies for PD in future endeavors.

Mitochondrial quality control in health and cardiovascular diseases

Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

Reactive nitrogen species as therapeutic targets for autophagy/mitophagy modulation to relieve neurodegeneration in multiple sclerosis: Potential application for drug discovery

Multiple sclerosis (MS) is a neuroinflammatory disease with limited therapeutic effects, eventually developing into handicap. Seeking novel therapeutic strategies for MS is timely important. Active autophagy/mitophagy could mediate neurodegeneration, while its roles in MS remain controversial. To elucidate the exact roles of autophagy/mitophagy and reveal its in-depth regulatory mechanisms, we conduct a systematic literature study and analyze the factors that might be responsible for divergent results obtained. The dynamic change levels of autophagy/mitophagy appear to be a determining factor for final neuron fate during MS pathology. Excessive neuronal autophagy/mitophagy contributes to neurodegeneration after disease onset at the active MS phase. Reactive nitrogen species (RNS) serve as key regulators for redox-related modifications and participate in autophagy/mitophagy modulation in MS. Nitric oxide (•NO) and peroxynitrite (ONOO-), two representative RNS, could nitrate or nitrosate Drp1/parkin/PINK1 pathway, activating excessive mitophagy and aggravating neuronal injury. Targeting RNS-mediated excessive autophagy/mitophagy could be a promising strategy for developing novel anti-MS drugs. In this review, we highlight the important roles of RNS-mediated autophagy/mitophagy in neuronal injury and review the potential therapeutic compounds with the bioactivities of inhibiting RNS-mediated autophagy/mitophagy activation and attenuating MS progression. Overall, we conclude that reactive nitrogen species could be promising therapeutic targets to regulate autophagy/mitophagy for multiple sclerosis treatment.

The Analgesia Effect of Aucubin on CFA-Induced Inflammatory Pain by Inhibiting Glial Cells Activation-Mediated Inflammatory Response via Activating Mitophagy

BACKGROUND

Inflammatory pain, characterized by sustained nociceptive hypersensitivity, represents one of the most prevalent conditions in both daily life and clinical settings. Aucubin, a natural plant iridoid glycoside, possesses potent biological effects, encompassing anti-inflammatory, antioxidant, and neuroprotective properties. However, its impact on inflammatory pain remains unclear. The aim of this study is to investigate the therapeutic effects and underlying mechanism of aucubin in addressing inflammatory pain induced by complete Freund's adjuvant (CFA).

METHODS

The CFA-induced inflammatory pain model was employed to assess whether aucubin exerts analgesic effects and its potential mechanisms. Behavioral tests evaluated mechanical and thermal hyperalgesia as well as anxiety-like behaviors in mice. The activation of spinal glial cells and the expression of pro-inflammatory cytokines were examined to evaluate neuroinflammation. Additionally, RNA sequencing was utilized for the identification of differentially expressed genes (DEGs). Molecular biology experiments were conducted to determine the levels of the PINK1 gene and autophagy-related genes, along with PINK1 distribution in neural cells. Furthermore, mitophagy induced by carbonyl cyanide m-chlorophenylhydrazone (CCCP) was employed to examine the roles of PINK1 and mitophagy in pain processing.

RESULTS

Aucubin significantly ameliorated pain and anxiety-like behaviors induced by CFA in mice and reduced spinal inflammation. RNA sequencing indicated PINK1 as a pivotal gene, and aucubin treatment led to a significant downregulation of PINK1 expression. Further GO and KEGG analyses suggested the involvement of mitochondrial function in the therapeutic regulation of aucubin. Western blotting revealed that aucubin markedly decreased PINK1, Parkin, and p62 levels while increasing LC3B expression. Immunofluorescence showed the predominant co-localization of PINK1 with neuronal cells. Moreover, CCCP-induced mitophagy alleviated mechanical and thermal hyperalgesia caused by CFA and reversed CFA-induced mitochondrial dysfunction.

CONCLUSIONS

In summary, our data suggest that aucubin effectively alleviates CFA-induced inflammatory pain, potentially through triggering the PINK1 pathway, promoting mitophagy, and suppressing inflammation. These results provide a novel theoretical foundation for addressing the treatment of inflammatory pain.

Autophagy in Parkinson's Disease

Parkinson's disease (PD) is a devastating disease associated with accumulation of α-synuclein (α-Syn) within dopaminergic neurons, leading to neuronal death. PD is characterized by both motor and non-motor clinical symptoms. Several studies indicate that autophagy, an important intracellular degradation pathway, may be involved in different neurodegenerative diseases including PD. The autophagic process mediates the degradation of protein aggregates, damaged and unneeded proteins, and organelles, allowing their clearance, and thereby maintaining cell homeostasis. Impaired autophagy may cause the accumulation of abnormal proteins. Incomplete or impaired autophagy may explain the neurotoxic accumulation of protein aggregates in several neurodegenerative diseases including PD. Indeed, studies have suggested the contribution of impaired autophagy to α-Syn accumulation, the death of dopaminergic neurons, and neuroinflammation. In this review, we summarize the recent literature on the involvement of autophagy in PD pathogenesis.

Thrap3 promotes nonalcoholic fatty liver disease by suppressing AMPK-mediated autophagy

Autophagy functions in cellular quality control and metabolic regulation. Dysregulation of autophagy is one of the major pathogenic factors contributing to the progression of nonalcoholic fatty liver disease (NAFLD). Autophagy is involved in the breakdown of intracellular lipids and the maintenance of healthy mitochondria in NAFLD. However, the mechanisms underlying autophagy dysregulation in NAFLD remain unclear. Here, we demonstrate that the hepatic expression level of Thrap3 was significantly increased in NAFLD conditions. Liver-specific Thrap3 knockout improved lipid accumulation and metabolic properties in a high-fat diet (HFD)-induced NAFLD model. Furthermore, Thrap3 deficiency enhanced autophagy and mitochondrial function. Interestingly, Thrap3 knockout increased the cytosolic translocation of AMPK from the nucleus and enhanced its activation through physical interaction. The translocation of AMPK was regulated by direct binding with AMPK and the C-terminal domain of Thrap3. Our results indicate a role for Thrap3 in NAFLD progression and suggest that Thrap3 is a potential target for NAFLD treatment.

Glaucomatous optic neuropathy: Mitochondrial dynamics, dysfunction and protection in retinal ganglion cells

Glaucoma is a leading cause of irreversible blindness worldwide and is characterized by a slow, progressive, and multifactorial degeneration of retinal ganglion cells (RGCs) and their axons, resulting in vision loss. Despite its high prevalence in individuals 60 years of age and older, the causing factors contributing to glaucoma progression are currently not well characterized. Intraocular pressure (IOP) is the only proven treatable risk factor. However, lowering IOP is insufficient for preventing disease progression. One of the significant interests in glaucoma pathogenesis is understanding the structural and functional impairment of mitochondria in RGCs and their axons and synapses. Glaucomatous risk factors such as IOP elevation, aging, genetic variation, neuroinflammation, neurotrophic factor deprivation, and vascular dysregulation, are potential inducers for mitochondrial dysfunction in glaucoma. Because oxidative phosphorylation stress-mediated mitochondrial dysfunction is associated with structural and functional impairment of mitochondria in glaucomatous RGCs, understanding the underlying mechanisms and relationship between structural and functional alterations in mitochondria would be beneficial to developing mitochondria-related neuroprotection in RGCs and their axons and synapses against glaucomatous neurodegeneration. Here, we review the current studies focusing on mitochondrial dynamics-based structural and functional alterations in the mitochondria of glaucomatous RGCs and therapeutic strategies to protect RGCs against glaucomatous neurodegeneration.

Role of A-Kinase Anchoring Protein 1 in Retinal Ganglion Cells: Neurodegeneration and Neuroprotection

A-Kinase anchoring protein 1 (AKAP1) is a multifunctional mitochondrial scaffold protein that regulates mitochondrial dynamics, bioenergetics, and calcium homeostasis by anchoring several proteins, including protein kinase A, to the outer mitochondrial membrane. Glaucoma is a complex, multifactorial disease characterized by a slow and progressive degeneration of the optic nerve and retinal ganglion cells (RGCs), ultimately resulting in vision loss. Impairment of the mitochondrial network and function is linked to glaucomatous neurodegeneration. Loss of AKAP1 induces dynamin-related protein 1 dephosphorylation-mediated mitochondrial fragmentation and loss of RGCs. Elevated intraocular pressure triggers a significant reduction in AKAP1 protein expression in the glaucomatous retina. Amplification of AKAP1 expression protects RGCs from oxidative stress. Hence, modulation of AKAP1 could be considered a potential therapeutic target for neuroprotective intervention in glaucoma and other mitochondria-associated optic neuropathies. This review covers the current research on the role of AKAP1 in the maintenance of mitochondrial dynamics, bioenergetics, and mitophagy in RGCs and provides a scientific basis to identify and develop new therapeutic strategies that could protect RGCs and their axons in glaucoma.

The mitophagy receptor BNIP3 is critical for the regulation of metabolic homeostasis and mitochondrial function in the nucleus pulposus cells of the intervertebral disc

The contribution of mitochondria to the metabolic function of hypoxic NP cells has been overlooked. We have shown that NP cells contain networked mitochondria and that mitochondrial translocation of BNIP3 mediates hypoxia-induced mitophagy. However, whether BNIP3 also plays a role in governing mitochondrial function and metabolism in hypoxic NP cells is not known. BNIP3 knockdown altered mitochondrial morphology, and number, and increased mitophagy. Interestingly, BNIP3 deficiency in NP cells reduced glycolytic capacity reflected by lower production of lactate/H+ and lower ATP production rate. Widely targeted metabolic profiling and flux analysis using 1-2-13C-glucose showed that the BNIP3 loss resulted in redirection of glycolytic flux into pentose phosphate and hexosamine biosynthesis as well as pyruvate resulting in increased TCA flux. An overall reduction in one-carbon metabolism was noted suggesting reduced biosynthesis. U13C-glutamine flux analysis showed preservation of glutamine utilization to maintain TCA intermediates. The transcriptomic analysis of the BNIP3-deficient cells showed dysregulation of cellular functions including membrane and cytoskeletal integrity, ECM-growth factor signaling, and protein quality control with an overall increase in themes related to angiogenesis and innate immune response. Importantly, we observed strong thematic similarities with the transcriptome of a subset of human degenerative samples. Last, we noted increased autophagic flux, decreased disc height index and aberrant COL10A1/collagen X expression, signs of early disc degeneration in young adult bnip3 knockout mice. These results suggested that in addition to mitophagy regulation, BNIP3 plays a role in maintaining mitochondrial function and metabolism, and dysregulation of mitochondrial homeostasis could promote disc degeneration.Abbreviations: ECAR extracellular acidification rate; HIF hypoxia inducible factor; MFA metabolic flux analysis; NP nucleus pulposus; OCR oxygen consumption rate; ShBnip3 short-hairpin Bnip3.

PINK1-PRKN mediated mitophagy: differences between in vitro and in vivo models

Mitophagy is a key intracellular process that selectively removes damaged mitochondria to prevent their accumulation that can cause neuronal degeneration. During mitophagy, PINK1 (PTEN induced kinase 1), a serine/threonine kinase, works with PRKN/parkin, an E3 ubiquitin ligase, to target damaged mitochondria to the lysosome for degradation. Mutations in the PINK1 and PRKN genes cause early-onset Parkinson disease that is also associated with mitochondrial dysfunction. There are a large number of reports indicating the critical role of PINK1 in mitophagy. However, most of these findings were obtained from in vitro experiments with exogenous PINK1 expression and acute damage of mitochondria by toxins. Recent studies using novel animal models suggest that PINK1-PRKN can also function independent of mitochondria. In this review, we highlight the major differences between in vitro and in vivo models for investigating PINK1 and discuss the potential mechanisms underlying these differences with the aim of understanding how PINK1 functions under different circumstances.Abbreviations: AAV: adeno-associated viruses;AD: Alzheimer disease; CCCP: carbonyl cyanidem-chlorophenyl hydrazone; HD: Huntington disease; MPTP: 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine; MTS: mitochondrial targeting sequence; PD: Parkinson diseases; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; ROS: reactive oxygen species; UIM, ubiquitin interacting motif.

Tactics with Prebiotics for the Treatment of Metabolic Dysfunction-Associated Fatty Liver Disease via the Improvement of Mitophagy

Mitophagy/autophagy plays a protective role in various forms of liver damage, by renovating cellular metabolism linking to sustain liver homeostasis. A characterized pathway for mitophagy is the phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)/Parkin-dependent signaling pathway. In particular, PINK1-mediated mitophagy could play an indispensable role in improving the metabolic dysfunction-associated fatty liver disease (MAFLD) which could precede to steatohepatitis (NASH), fibrosis, and hepatocellular carcinoma. In addition, the PI3K/AKT/mTOR pathway might regulate the various characteristics of cellular homeostasis including energy metabolism, cell proliferation, and/or cell protection. Therefore, targeting mitophagy with the alteration of PI3K/AKT/mTOR or PINK1/Parkin-dependent signaling to eliminate impaired mitochondria might be an attractive strategy for the treatment of MAFLD. In particular, the efficacy of prebiotics for the treatment of MAFLD has been suggested to be useful via the modulation of the PI3K/AKT/mTOR/AMPK pathway. Additionally, several edible phytochemicals could activate mitophagy for the improvement of mitochondrial damages, which could also be a promising option to treat MAFLD with providing liver protection. Here, the potential therapeutics with several phytochemicals has been discussed for the treatment of MAFLD. Tactics with a viewpoint of prospective probiotics might contribute to the development of therapeutic interventions.

Ginsenoside Rg1 Protects against Cardiac Remodeling in Heart Failure via SIRT1/PINK1/Parkin-Mediated Mitophagy

Adverse cardiac remodeling may lead to the development and progression of heart failure, which is lack of effective clinical treatment. Ginsenoside Rg1 (GRg1), a primary ingredient of Panax ginseng, protects against diverse cardiovascular disease, but its effects on cardiac remodeling remain unclear. Thus, we investigated the protective effect and mechanism of GRg1 on cardiac remodeling after myocardial infarction. GRg1 significantly ameliorated cardiac remodeling in mice with left anterior descending coronary artery ligation, reflected by reduced left ventricular dilation and decreased cardiac fibrosis, accompanied by improved cardiac function. Mechanistically, GRg1 considerably increased mitophagosomes formation, ameliorated cardiac mitochondria damage, and enhanced SIRT1/PINK1/Parkin-mediated mitophagy during cardiac remodeling. Consistently, GRg1 increased cell viability and attenuated apoptosis and fibrotic responses in H₂ O₂ -treated H9c2 cells by promoting the SIRT1/PINK1/Parkin axis. Furthermore, SIRT1-specific inhibitor (EX527) or the use of small interfering RNA against Parkin abolished the protective effect of GRg1 in vitro. These findings reveal a novel mechanism of GRg1 alleviating cardiac remodeling via enhancing SIRT1/PINK1/Parkin-mediated mitophagy.

Mitochondria in Cell-Based Therapy for Stroke

Despite a relatively developed understanding of the pathophysiology underlying primary and secondary mechanisms of cell death after ischemic injury, there are few established treatments to improve stroke prognoses. A major contributor to secondary cell death is mitochondrial dysfunction. Recent advancements in cell-based therapies suggest that stem cells may be revolutionary for treating stroke, and the reestablishment of mitochondrial integrity may underlie these therapeutic benefits. In fact, functioning mitochondria are imperative for reducing oxidative damage and neuroinflammation following stroke and reperfusion injury. In this review, we will discuss the role of mitochondria in establishing the anti-oxidative effects of stem cell therapies for stroke.

The Novel Role of Mitochondrial Citrate Synthase and Citrate in the Pathophysiology of Alzheimer's Disease

Citrate synthase is a key mitochondrial enzyme that utilizes acetyl-CoA and oxaloacetate to form citrate in the mitochondrial membrane, which participates in energy production in the TCA cycle and linked to the electron transport chain. Citrate transports through a citrate malate pump and synthesizes acetyl-CoA and acetylcholine (ACh) in neuronal cytoplasm. In a mature brain, acetyl-CoA is mainly utilized for ACh synthesis and is responsible for memory and cognition. Studies have shown low citrate synthase in different regions of brain in Alzheimer's disease (AD) patients, which reduces mitochondrial citrate, cellular bioenergetics, neurocytoplasmic citrate, acetyl-CoA, and ACh synthesis. Reduced citrate mediated low energy favors amyloid-β (Aβ) aggregation. Citrate inhibits Aβ25-35 and Aβ1-40 aggregation in vitro. Hence, citrate can be a better therapeutic option for AD by improving cellular energy and ACh synthesis, and inhibiting Aβ aggregation, which prevents tau hyperphosphorylation and glycogen synthase kinase-3 beta. Therefore, we need clinical studies if citrate reverses Aβ deposition by balancing mitochondrial energy pathway and neurocytoplasmic ACh production. Furthermore, in AD's silent phase pathophysiology, when neuronal cells are highly active, they shift ATP utilization from oxidative phosphorylation to glycolysis and prevent excessive generation of hydrogen peroxide and reactive oxygen species (oxidative stress) as neuroprotective action, which upregulates glucose transporter-3 (GLUT3) and pyruvate dehydrogenase kinase-3 (PDK3). PDK3 inhibits pyruvate dehydrogenase, which decreases mitochondrial-acetyl-CoA, citrate, and cellular bioenergetics, and decreases neurocytoplasmic citrate, acetyl-CoA, and ACh formation, thus initiating AD pathophysiology. Therefore, GLUT3 and PDK3 can be biomarkers for silent phase of AD.

Qing-Re-Xiao-Zheng-Yi-Qi formula relieves kidney damage and activates mitophagy in diabetic kidney disease

Introduction: Qing-Re-Xiao-Zheng-Yi-Qi Formula is an effective prescription in diabetic kidney disease treatment, we have confirmed the efficacy of Qing-Re-Xiao-Zheng therapy in diabetic kidney disease through clinical trials. In this study, we investigated the mechanisms of Qing-Re-Xiao-Zheng-Yi-Qi Formula in the treatment of diabetic kidney disease. Methods: We used Vanquish UHPLC^TM to analyze the chemical profiling of Qing-Re-Xiao-Zheng-Yi-Qi Formula freeze-dried powder. We constructed diabetic kidney disease rat models induced by unilateral nephrectomy and high-dose streptozocin injection. We examined blood urea nitrogen, serum creatinine, serum glucose, total cholesterol, triglyceride, serum total protein, albumin, alanine aminotransferase, aspartate aminotransferase and 24 h urinary total protein in diabetic kidney disease rats. The renal pathological changes were observed by HE, Masson, PAS stanning and transmission electron microscopy. The levels of fibrosis-related proteins and mitophagy-related proteins were detected by western blot analysis. We also conducted an immunofluorescence co-localization analysis on podocytes to further investigate the effect of Qing-Re-Xiao-Zheng-Yi-Qi Formula treatment on mitophagy. Results: A total of 27 constituents in Qing-Re-Xiao-Zheng-Yi-Qi Formula were tentatively identified. We found PINK1/Parkin-mediated mitophagy was inhibited in diabetic kidney disease. Qing-Re-Xiao-Zheng-Yi-Qi Formula treatment could raise body weight and reduce renal index, reduce proteinuria, improve glycolipid metabolic disorders, ameliorate renal fibrosis, and reduce the expression of Col Ⅳ and TGF-β1 in diabetic kidney disease rats. Qing-Re-Xiao-Zheng-Yi-Qi Formula treatment could also increase the expression of nephrin, activate mitophagy and protect podocytes in diabetic kidney disease rats and high glucose cultured podocytes. Conclusion: PINK1/Parkin-mediated mitophagy was inhibited in diabetic kidney disease, and Qing-Re-Xiao-Zheng-Yi-Qi Formula treatment could not only ameliorate pathological damage, but also promote mitophagy to protect podocytes in diabetic kidney disease.

Selenium improved mitochondrial quality and energy supply in the liver of high-fat diet-fed grass carp (Ctenopharyngodon idella) after heat stress

This study aims to explore the effects of dietary selenium on hepatic mitochondrial quality and energy supply of grass carp (Ctenopharyngodon idella) fed with high-fat diet (HFD) after heat stress (HS). Grass carp were fed with HFD, and HFD contained 0.3 mg/kg nano-selenium for 10 weeks, thereafter exposed to HS from 26 to 34 °C, and named the HFD + HS (control) group and the HFD + Se + HS group, respectively. The results show that selenium significantly prompted the growth, increased glutathione peroxidase (GPX) activity, but reduced malondialdehyde (MDA) content in the liver and the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the serum of grass carp fed with HFD after HS. Further, selenium alleviated mitochondrial damage and increased the number of mitochondrial DNA copies in the liver of the grass carp fed with HFD after HS. And selenium also maintained mitochondrial homeostasis by upregulating the expression of mitochondrial quality control-related genes (pgc-1α, nrf1/2, tfam, opa1, mfn1/2, and drp1), mitophagy-related genes (beclin1, atg5, atg12, pink1, and parkin), and the protein expression of parkin and LC3-II/I in the liver of grass carp. Finally, selenium reduced the triglyceride (TG) level and increased the free fatty acid (FFA) level and adenosine triphosphate (ATP) production in the liver of grass carp fed with HFD after HS. In conclusion, dietary selenium alleviated liver damage and improved liver mitochondrial quality and ATP production by increasing liver antioxidant capacity and promoting liver mitochondrial quality in grass carp fed with HFD after HS, which help grass carp to resist these two stressors.

Cell Biology of Parkin: Clues to the Development of New Therapeutics for Parkinson's Disease

Parkinson's disease is the second most prevalent neurodegenerative disease and contributes significantly to morbidity globally. Currently, no disease-modifying therapies exist to combat this disorder. Insights from the molecular and cellular pathobiology of the disease seems to indicate promising therapeutic targets. The parkin protein has been extensively studied for its role in autosomal recessive Parkinson's disease and, more recently, its role in sporadic Parkinson's disease. Parkin is an E3 ubiquitin ligase that plays a prominent role in mitochondrial quality control, mitochondrial-dependent cell death pathways, and other diverse functions. Understanding the numerous roles of parkin has introduced many new possibilities for therapeutic modalities in treating both autosomal recessive Parkinson's disease and sporadic Parkinson's disease. In this article, we review parkin biology with an emphasis on mitochondrial-related functions and propose novel, potentially disease-modifying therapeutic approaches for treating this debilitating condition.

Potential Diets to Improve Mitochondrial Activity in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease, the pathogenesis of which is based on alternations in the mitochondria of motor neurons, causing their progressive death. A growing body of evidence shows that more efficient mitophagy could prevent and/or treat this disorder by suppressing mitochondrial dysfunction-induced oxidative stress and inflammation. Mitophagy has been considered one of the main mechanisms responsible for mitochondrial quality control. Since ALS is characterized by enormous oxidative stress, several edible phytochemicals that can activate mitophagy to remove damaged mitochondria could be considered a promising option to treat ALS by providing neuroprotection. Therefore, it is of great significance to explore the mechanisms of mitophagy in ALS and to understand the effects and/or molecular mechanisms of phytochemical action, which could translate into a treatment for neurodegenerative diseases, including ALS.

Purine nucleoside phosphorylase as a target to treat age-associated lower urinary tract dysfunction

The lower urinary tract (LUT), including the bladder, urethra and external striated muscle, becomes dysfunctional with age; consequently, many older individuals suffer from lower urinary tract disorders (LUTDs). By compromising urine storage and voiding, LUTDs degrade quality of life for millions of individuals worldwide. Treatments for LUTDs have been disappointing, frustrating both patients and their physicians; however, emerging evidence suggests that partial inhibition of the enzyme purine nucleoside phosphorylase (PNPase) with 8-aminoguanine (an endogenous PNPase inhibitor that moderately reduces PNPase activity) reverses age-associated defects in the LUT and restores the LUT to that of a younger state. Thus, 8-aminoguanine improves LUT biochemistry, structure and function by rebalancing the LUT purine metabolome, making 8-aminoguanine a novel potential treatment for LUTDs.

Research progress on the relationship between mitochondrial function and heart failure: A bibliometric study from 2002 to 2021

Heart failure is one of the major public health problems in the world. In recent years, more and more attention has been paid to the relationship between heart failure and mitochondrial function. In the past 2 decades, a growing number of research papers in this field have been published. This study conducted a bibliometric analysis of the published literature on the relationship between MF and HF in the past 20 years by utilizing Microsoft Excel 2019, Biblio metric analysis platform, WoSCC database, VosViewer and Citespace. The results show that the papers have increased year by year and China and the United States are the leading countries in this field, as well as the countries with the most cooperation and exchanges. University of california system is the research institution with the greatest impacts on research results, and Yip H.K. is the author with more papers. The American Journal of Physiology-heart and Circulatory Physiology is probably the most popular magazine. At present, most of the published articles on mitochondria and HF are cited from internationally influential journals. The research focus includes oxidative stress, metabolic dysfunction, mitochondrial Ca²⁺ homeostasis imbalance, mitochondrial quality control and mitochondrial dysfunction mediated by inflammation in the pathogenesis of HF. Targeted regulating of mitochondria will be the keynote of future research on prevention and treatment of HF.

A Peptide HEPFYGNEGALR from Apostichopus japonicus Alleviates Acute Alcoholic Liver Injury by Enhancing Antioxidant Response in Male C57BL/6J Mice

Liver-related disease caused by alcohol is a frequent disorder of the hepatic tract. Heavy consumption of alcohol in a short period causes oxidative damage to the liver. Sea cucumber is abundant in nutrients and its various extracts have been studied for antioxidant properties. One peptide was isolated and identified from Apostichopus japonicus in our recent study. We investigated the benefits of the peptide in a model of acute ethanol-induced male C57BL/6J mice. Dietary intake of the peptide could attenuate hepatomegaly, hepatitis and the accumulation of lipid droplets, and increase antioxidant enzyme activities in mice with acute alcoholic liver injury. The results indicated that a 20 mg/kg peptide supplement could activate the Nrf2/HO-1 pathway and block the nuclear translocation of NF-κB to alleviate oxidative stress and inflammation. In addition, the preventive effects of peptide supplementation may be related to autophagy. This study suggests that dietary supplementation with a sea cucumber-derived peptide is one of the potential candidates to alleviate acute alcoholic liver injury.

The relationship of alpha-synuclein to mitochondrial dynamics and quality control

Maintenance of mitochondrial health is essential for neuronal survival and relies upon dynamic changes in the mitochondrial network and effective mitochondrial quality control mechanisms including the mitochondrial-derived vesicle pathway and mitophagy. Mitochondrial dysfunction has been implicated in driving the pathology of several neurodegenerative diseases, including Parkinson’s disease (PD) where dopaminergic neurons in the substantia nigra are selectively degenerated. In addition, many genes with PD-associated mutations have defined functions in organelle quality control, indicating that dysregulation in mitochondrial quality control may represent a key element of pathology. The most well-characterized aspect of PD pathology relates to alpha-synuclein; an aggregation-prone protein that forms intracellular Lewy-body inclusions. Details of how alpha-synuclein exerts its toxicity in PD is not completely known, however, dysfunctional mitochondria have been observed in both PD patients and models of alpha-synuclein pathology. Accordingly, an association between alpha-synuclein and mitochondrial function has been established. This relates to alpha-synuclein’s role in mitochondrial transport, dynamics, and quality control. Despite these relationships, there is limited research defining the direct mechanisms linking alpha-synuclein to mitochondrial dynamics and quality control. In this review, we will discuss the current literature addressing this association and provide insight into the proposed mechanisms promoting these functional relationships. We will also consider some of the alternative mechanisms linking alpha-synuclein with mitochondrial dynamics and speculate what the relationship between alpha-synuclein and mitochondria might mean both physiologically and in relation to PD.

Aging-Associated Changes in Oxidative Stress Negatively Impacts the Urinary Bladder Urothelium

PURPOSE

Lower urinary tract symptoms are known to significantly increase with age, negatively impacting quality of life and self-reliance. The urothelium fulfills crucial tasks, serving as a barrier protecting the underlying bladder tissue from the harsh chemical composition of urine, and exhibits signaling properties via the release of mediators within the bladder wall that affect bladder functioning. Aging is associated with detrimental changes in cellular health, in part by increasing oxidative stress in the bladder mucosa, and more specifically the urothelium. This, in turn, may impact urothelial mitochondrial health and bioenergetics.

METHODS

We collected mucosal tissue samples from both young (3-4 months old) and aged (25-30 months old) rats. Tissue was evaluated for p21-Arc, nitrotyrosine, and cytochrome C expression by western immunoblotting. Urothelial cells were cultured for single-cell imaging to analyze basal levels of reactive oxygen species and the mitochondrial membrane potential. Mitochondrial bioenergetics and cellular respiration were investigated by the Seahorse assay, and measurements of adenosine triphosphate release were made using the luciferin-luciferase assay.

RESULTS

Aging was associated with a significant increase in biomarkers of cellular senescence, oxidative stress, and basal levels of reactive oxygen species. The mitochondrial membrane potential was significantly lower in urothelial cell cultures from aged animals, and cultures from aged animals showed a significant decrease in mitochondrial bioenergetics.

CONCLUSION

Aging-related increases in oxidative stress and excessive reactive oxygen species may be contributing factors underlying lower urinary tract symptoms in older adults. The mechanisms outlined in this study could be utilized to identify novel pharmaceutical targets to improve aging-associated bladder dysfunction.

PINK1/Parkin-mediated mitophagy in cardiovascular disease: From pathogenesis to novel therapy

Cardiovascular disease(CVD)is one of the predominant causes of death and morbidity. Mitochondria play a key role in maintaining cardiac energy metabolism. However, mitochondrial dysfunction leads to excessive production of ROS, resulting in oxidative damage to cardiomyocytes and contributing to a variety of cardiovascular diseases. In such a case, the clearance of impaired mitochondria is necessary. Currently, most studies have indicated an essential role for mitophagy in maintaining cardiac homeostasis and regulating CVD-related metabolic transition. Recent studies have implicated that PTEN-induced putative kinase 1 (PINK1)/Parkin-mediated mitophagy has been implicated in maintaining cardiomyocyte homeostasis. Here, we discuss the physiological and pathological roles of PINK1/Parkin-mediated mitophagy in the cardiovascular system, as well as potential therapeutic strategies based on PINK1/Parkin-mediated mitophagy modulation, which are of great significance for the prevention and treatment of cardiovascular diseases.

PTEN-induced kinase 1 deficiency alters albumin permeability and insulin signaling in podocytes

Alterations of insulin signaling in diabetes are associated with podocyte injury, proteinuria, and renal failure. Insulin stimulates glucose transport to cells and regulates other intracellular processes that are linked to cellular bioenergetics, such as autophagy, gluconeogenesis, fatty acid metabolism, and mitochondrial homeostasis. The dysfunction of mitochondrial dynamics, including mitochondrial fusion, fission, and mitophagy, has been observed in high glucose-treated podocytes and renal cells from patients with diabetes. Previous studies showed that prolonged hyperglycemia is associated with the development of insulin resistance in podocytes, and high glucose-treated podocytes exhibit an increase in mitochondrial fission and decrease in markers of mitophagy. In the present study, we found that deficiency of the main mitophagy protein PTEN-induced kinase 1 (PINK1) significantly increased albumin permeability and hampered glucose uptake to podocytes. We suggest that PINK1 inhibition impairs the insulin signaling pathway, in which lower levels of phosphorylated Akt and membrane fractions of the insulin receptor and glucose transporter-4 were observed. Moreover, PINK1-depleted podocytes exhibited lower podocin and nephrin expression, thus identifying a potential mechanism whereby albumin leakage increases under hyperglycemic conditions when mitophagy is inhibited. In conclusion, we found that PINK1 plays an essential role in insulin signaling and the maintenance of proper permeability in podocytes. Therefore, PINK1 may be a potential therapeutic target for the treatment or prevention of diabetic nephropathy.

Dictyophora Polysaccharide Attenuates As-Mediated PINK1/Parkin Pathway-Induced Mitophagy in L-02 Cell through Scavenging ROS

Arsenic (As) is common in the human living environment and a certain amount of exposure to As can lead to liver damage; this toxic effect has been proved to be closely related to intracellular PINK1/Parkin pathway-mediated mitophagy. Dictyophora is an edible fungus that extracts polysaccharides with antioxidant and hepatoprotective effects. In the present study, we demonstrated that As induced the onset of mitophagy in hepatocytes by stimulating cellular production of ROS to activate PINK1/Parkin, and the extent of damage increased with increased As-induced toxicity. Dictyophora polysaccharide (DIP) has the ability to scavenge intracellular ROS, which can inhibit oxidative stress injury and inhibit the PINK/Parkin pathway through its receptors or efficacious proteins, thus preventing mitochondrial autophagy and alleviating the hepatotoxicity of As. In conclusion, our results indicate that DIP can reduce As-induced PINK1/Parkin pathway-mediated hepatic mitophagy through scavenging ROS and exert hepatoprotective effects, providing experimental data and theoretical basis for the development of medicinal value of Dictyophora as a dual-use food and medicinal fungus.

Transcription Factor Movement and Exercise-Induced Mitochondrial Biogenesis in Human Skeletal Muscle: Current Knowledge and Future Perspectives

In response to exercise, the oxidative capacity of mitochondria within skeletal muscle increases through the coordinated expression of mitochondrial proteins in a process termed mitochondrial biogenesis. Controlling the expression of mitochondrial proteins are transcription factors-a group of proteins that regulate messenger RNA transcription from DNA in the nucleus and mitochondria. To fulfil other functions or to limit gene expression, transcription factors are often localised away from DNA to different subcellular compartments and undergo rapid movement or accumulation only when required. Although many transcription factors involved in exercise-induced mitochondrial biogenesis have been identified, numerous conflicting findings and gaps exist within our knowledge of their subcellular movement. This review aims to summarise and provide a critical analysis of the published literature regarding the exercise-induced movement of transcription factors involved in mitochondria biogenesis in skeletal muscle.

Neurodegenerative Disorders and the Current State, Pathophysiology, and Management of Parkinson's Disease

In the last few decades, major knowledge has been gained about pathophysiological aspects and molecular pathways behind Parkinson's Disease (PD). Based on neurotoxicological studies and postmortem investigations, there is a general concept of how environmental toxicants (neurotoxins, pesticides, insecticides) and genetic factors (genetic mutations in PD-associated proteins) cause depletion of dopamine from substantia nigra pars compacta region of the midbrain and modulate cellular processes leading to the pathogenesis of PD. α-Synuclein, a neuronal protein accumulation in oligomeric form, called protofibrils, is associated with cellular dysfunction and neuronal death, thus possibly contributing to PD propagation. With advances made in identifying loci that contribute to PD, molecular pathways involved in disease pathogenesis are now clear, and introducing therapeutic strategy at the right time may delay the progression. Biomarkers for PD have helped monitor PD progression; therefore, personalized therapeutic strategies can be facilitated. In order to further improve PD diagnostic and prognostic accuracy, independent validation of biomarkers is required.

Podocyte Bioenergetics in the Development of Diabetic Nephropathy: The Role of Mitochondria

Diabetic nephropathy (DN) is the leading cause of kidney failure, with an increasing incidence worldwide. Mitochondrial dysfunction is known to occur in DN and has been implicated in the underlying pathogenesis of disease. These complex organelles have an array of important cellular functions and involvement in signaling pathways, and understanding the intricacies of these responses in health, as well as how they are damaged in disease, is likely to highlight novel therapeutic avenues. A key cell type damaged early in DN is the podocyte, and increasing studies have focused on investigating the role of mitochondria in podocyte injury. This review will summarize what is known about podocyte mitochondrial dynamics in DN, with a particular focus on bioenergetic pathways, highlighting key studies in this field and potential opportunities to target, enhance or protect podocyte mitochondrial function in the treatment of DN.

Role of Mitochondrial Protein Import in Age-Related Neurodegenerative and Cardiovascular Diseases

Mitochondria play a critical role in providing energy, maintaining cellular metabolism, and regulating cell survival and death. To carry out these crucial functions, mitochondria employ more than 1500 proteins, distributed between two membranes and two aqueous compartments. An extensive network of dedicated proteins is engaged in importing and sorting these nuclear-encoded proteins into their designated mitochondrial compartments. Defects in this fundamental system are related to a variety of pathologies, particularly engaging the most energy-demanding tissues. In this review, we summarize the state-of-the-art knowledge about the mitochondrial protein import machinery and describe the known interrelation of its failure with age-related neurodegenerative and cardiovascular diseases.

PINK1 deficiency impairs osteoblast differentiation through aberrant mitochondrial homeostasis

Background

PTEN-induced kinase 1 (PINK1) is a serine/threonine-protein kinase in mitochondria that is critical for mitochondrial quality control. PINK1 triggers mitophagy, a selective autophagy of mitochondria, and is involved in mitochondrial regeneration. Although increments of mitochondrial biogenesis and activity are known to be crucial during differentiation, data regarding the specific role of PINK1 in osteogenic maturation and bone remodeling are limited.

Methods

We adopted an ovariectomy model in female wildtype and Pink1^−/− mice. Ovariectomized mice were analyzed using micro-CT, H&E staining, Masson’s trichrome staining. RT-PCR, western blot, immunofluorescence, alkaline phosphatase, and alizarin red staining were performed to assess the expression of PINK1 and osteogenic markers in silencing of PINK1 MC3T3-E1 cells. Clinical relevance of PINK1 expression levels was determined via qRT-PCR analysis in normal and osteoporosis patients.

Results

A significant decrease in bone mass and collagen deposition was observed in the femurs of Pink1^−/− mice after ovariectomy. Ex vivo, differentiation of osteoblasts was inhibited upon Pink1 downregulation, accompanied by impaired mitochondrial homeostasis, increased mitochondrial reactive oxygen species production, and defects in mitochondrial calcium handling. Furthermore, PINK1 expression was reduced in bones from patients with osteoporosis, which supports the practical role of PINK1 in human bone disease.

Conclusions

In this study, we demonstrated that activation of PINK1 is a requisite in osteoblasts during differentiation, which is related to mitochondrial quality control and low reactive oxygen species production. Enhancing PINK1 activity might be a possible treatment target in bone diseases as it can promote a healthy pool of functional mitochondria in osteoblasts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02656-4.

Mitochondrial Quality Control in the Maintenance of Cardiovascular Homeostasis: The Roles and Interregulation of UPS, Mitochondrial Dynamics and Mitophagy

Maintenance of normal function of mitochondria is vital to the fate and health of cardiomyocytes. Mitochondrial quality control (MQC) mechanisms are essential in governing mitochondrial integrity and function. The ubiquitin-proteasome system (UPS), mitochondrial dynamics, and mitophagy are three major components of MQC. With the progress of research, our understanding of MQC mechanisms continues to deepen. Gradually, we realize that the three MQC mechanisms are not independent of each other. To the contrary, there are crosstalk among the mechanisms, which can make them interact with each other and cooperate well, forming a triangle interplay. Briefly, the UPS system can regulate the level of mitochondrial dynamic proteins and mitophagy receptors. In the process of Parkin-dependent mitophagy, the UPS is also widely activated, performing critical roles. Mitochondrial dynamics have a profound influence on mitophagy. In this review, we provide new processes of the three major MQC mechanisms in the background of cardiomyocytes and delve into the relationship between them.

Inflammatory injury and mitophagy of the brain in chicken exposed to Cr(VI)

The aim of this study is to determine whether Cr(VI) can induce inflammatory injury in chicken brain and influence mitophagy and related mechanisms. A total of 120 hyline brown chickens (1 day old, 20±3g) were selected and randomly divided into four groups and given different doses of Cr(VI) (0, 10, 30, and 50 mg/kg) every day at 45 days. Results showed that excessive intake of Cr(VI) led to increased tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) levels and decreased interferon-gamma (IF-γ) level. Cr(VI) increased the production of mitochondrial reactive oxygen species (ROS) in chicken brain cells, causing the decline of mitochondrial membrane potential (MMP) and formation of autophagosomes for mitophagy. In addition, Cr(VI) promoted the translocation of Parkin to the mitochondrial outer membrane, increased LC3-II protein level, and inhibited p62 and TOM20 protein expression. In conclusion, excessive Cr(VI) intake can induce inflammatory injury and mitophagy in chicken brain.

Protective effects of melatonin on the white matter damage of neonatal rats by regulating NLRP3 inflammasome activity

OBJECTIVE

The aim of the study was to investigate the protective effects and relevant mechanisms of melatonin on the white matter damage (WMD) caused by endotoxin and ischemic hypoxia in neonatal rats.

METHODS

Seventy-two female neonatal rats (postnatal day 3) were randomly divided into the sham, melatonin-treated, and control groups (n = 24 for each group). The periventricular white matter was collected to evaluate the WMD and apoptosis. In addition, the reactive oxygen species (ROS) level was measured. The expression levels of nucleotide-binding domain-like receptor protein 3 (NLRP3), interleukin (IL)-1β, IL-18, pink1, parkin, Toll-like receptor (TLR)-4, and nuclear factor (NF)-κB were detected.

RESULTS

Hematoxylin and eosin and terminal-deoxynucleoitidyl transferase mediated nick end labeling staining showed that the WMD, as well as cell degeneration, necrosis, and apoptosis in the control group, were more severe than those in the melatonin-treated group. Endotoxin and ischemic hypoxia upregulated the expression of NLRP3 and downstream inflammatory factors such as IL-1β and IL-18, which could be reversed by melatonin treatment. Melatonin increased mitochondrial autophagy marker (pink1 and parkin) expression in the white matter and reduced ROS production. Moreover, melatonin-reduced TLR4 and NF-κB expression.

CONCLUSIONS

Melatonin can inhibit the hyperactivity of NLRP3 inflammasomes by enhancing mitochondrial autophagy and inhibiting TLR4/NF-κB pathway activity. Thus, melatonin may be a promising treatment for alleviating the WMD caused by endotoxin and ischemic hypoxia in neonatal rats.

Autophagy and ALS: mechanistic insights and therapeutic implications

Mechanisms of protein homeostasis are crucial for overseeing the clearance of misfolded and toxic proteins over the lifetime of an organism, thereby ensuring the health of neurons and other cells of the central nervous system. The highly conserved pathway of autophagy is particularly necessary for preventing and counteracting pathogenic insults that may lead to neurodegeneration. In line with this, mutations in genes that encode essential autophagy factors result in impaired autophagy and lead to neurodegenerative conditions such as amyotrophic lateral sclerosis (ALS). However, the mechanistic details underlying the neuroprotective role of autophagy, neuronal resistance to autophagy induction, and the neuron-specific effects of autophagy-impairing mutations remain incompletely defined. Further, the manner and extent to which non-cell autonomous effects of autophagy dysfunction contribute to ALS pathogenesis are not fully understood. Here, we review the current understanding of the interplay between autophagy and ALS pathogenesis by providing an overview of critical steps in the autophagy pathway, with special focus on pivotal factors impaired by ALS-causing mutations, their physiologic effects on autophagy in disease models, and the cell type-specific mechanisms regulating autophagy in non-neuronal cells which, when impaired, can contribute to neurodegeneration. This review thereby provides a framework not only to guide further investigations of neuronal autophagy but also to refine therapeutic strategies for ALS and related neurodegenerative diseases.Abbreviations: ALS: amyotrophic lateral sclerosis; Atg: autophagy-related; CHMP2B: charged multivesicular body protein 2B; DPR: dipeptide repeat; FTD: frontotemporal dementia; iPSC: induced pluripotent stem cell; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; PINK1: PTEN induced kinase 1; RNP: ribonuclear protein; sALS: sporadic ALS; SPHK1: sphingosine kinase 1; TARDBP/TDP-43: TAR DNA binding protein; TBK1: TANK-binding kinase 1; TFEB: transcription factor EB; ULK: unc-51 like autophagy activating kinase; UPR: unfolded protein response; UPS: ubiquitin-proteasome system; VCP: valosin containing protein.

The Role of Mitophagy in Regulating Cell Death

Mitochondria are multifaceted organelles that serve to power critical cellular functions, including act as power generators of the cell, buffer cytosolic calcium overload, production of reactive oxygen species, and modulating cell survival. The structure and the cellular location of mitochondria are critical for their function and depend on highly regulated activities such as mitochondrial quality control (MQC) mechanisms. The MQC is regulated by several sets of processes: mitochondrial biogenesis, mitochondrial fusion and fission, mitophagy, and other mitochondrial proteostasis mechanisms such as mitochondrial unfolded protein response (mtUPR) or mitochondrial-derived vesicles (MDVs). These processes are important for the maintenance of mitochondrial homeostasis, and alterations in the mitochondrial function and signaling are known to contribute to the dysregulation of cell death pathways. Recent studies have uncovered regulatory mechanisms that control the activity of the key components for mitophagy. In this review, we discuss how mitophagy is controlled and how mitophagy impinges on health and disease through regulating cell death.

The cell biology of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder resulting from the death of dopamine neurons in the substantia nigra pars compacta. Our understanding of PD biology has been enriched by the identification of genes involved in its rare, inheritable forms, termed PARK genes. These genes encode proteins including α-syn, LRRK2, VPS35, parkin, PINK1, and DJ1, which can cause monogenetic PD when mutated. Investigating the cellular functions of these proteins has been instrumental in identifying signaling pathways that mediate pathology in PD and neuroprotective mechanisms active during homeostatic and pathological conditions. It is now evident that many PD-associated proteins perform multiple functions in PD-associated signaling pathways in neurons. Furthermore, several PARK proteins contribute to non-cell-autonomous mechanisms of neuron death, such as neuroinflammation. A comprehensive understanding of cell-autonomous and non-cell-autonomous pathways involved in PD is essential for developing therapeutics that may slow or halt its progression.

VDAC1 promotes cardiomyocyte autophagy in anoxia/reoxygenation injury via the PINK1/Parkin pathway

Ischemia/reperfusion (I/R) is a well-known injury to the myocardium, but the mechanism involved remains elusive. In addition to the well-accepted apoptosis theory, autophagy was recently found to be involved in the process, exerting a dual role as protection in ischemia and detriment in reperfusion. Activation of autophagy is mediated by mitochondrial permeability transition pore (MPTP) opening during reperfusion. In our previous study, we showed that MPTP opening is regulated by VDAC1, a channel protein located in the outer membrane of mitochondria. Thus, upregulation of VDAC1 expression is a possible trigger to cardiomyocyte autophagy via an unclear pathway. Here, we established an anoxia/reoxygenation (A/R) model in vitro to simulate the I/R process in vivo. At the end of A/R treatment, VDAC1, Beclin 1, and LC3-II/I were upregulated, and autophagic vacuoles were increased in cardiomyocytes, which showed a connection of VDAC1 and autophagy development. These variations also led to ROS burst, mitochondrial dysfunction, and aggravated apoptosis. Knockdown of VDAC1 by RNAi could alleviate the above-mentioned cellular damages. Additionally, the expression of PINK1 and Parkin was enhanced after A/R injury. Furthermore, Parkin was recruited to mitochondria from the cytosol, which suggested that the PINK1/Parkin autophagic pathway was activated during A/R. Nevertheless, the PINK1/Parkin pathway was effectively inhibited when VDAC1 was knocked-down. Taken together, the A/R-induced cardiomyocyte injury was mediated by VDAC1 upregulation, which led to cell autophagy via the PINK1/Parkin pathway, and finally aggravated apoptosis.

Intracellular AIBP (Apolipoprotein A-I Binding Protein) Regulates Oxidized LDL (Low-Density Lipoprotein)-Induced Mitophagy in Macrophages

OBJECTIVE

Atherosclerotic lesions are often characterized by accumulation of OxLDL (oxidized low-density lipoprotein), which is associated with vascular inflammation and lesion vulnerability to rupture. Extracellular AIBP (apolipoprotein A-I binding protein; encoded by APOA1BP gene), when secreted, promotes cholesterol efflux and regulates lipid rafts dynamics, but its role as an intracellular protein in mammalian cells remains unknown. The aim of this work was to determine the function of intracellular AIBP in macrophages exposed to OxLDL and in atherosclerotic lesions. Approach and Results: Using a novel monoclonal antibody against human and mouse AIBP, which are highly homologous, we demonstrated robust AIBP expression in human and mouse atherosclerotic lesions. We observed significantly reduced autophagy in bone marrow-derived macrophages, isolated from Apoa1bp-/- compared with wild-type mice, which were exposed to OxLDL. In atherosclerotic lesions from Apoa1bp-/- mice subjected to Ldlr knockdown and fed a Western diet, autophagy was reduced, whereas apoptosis was increased, when compared with that in wild-type mice. AIBP expression was necessary for efficient control of reactive oxygen species and cell death and for mitochondria quality control in macrophages exposed to OxLDL. Mitochondria-localized AIBP, via its N-terminal domain, associated with E3 ubiquitin-protein ligase PARK2 (Parkin), MFN (mitofusin)1, and MFN2, but not BNIP3 (Bcl2/adenovirus E1B 19-kDa-interacting protein-3), and regulated ubiquitination of MFN1 and MFN2, key components of mitophagy.

CONCLUSIONS

These data suggest that intracellular AIBP is a new regulator of autophagy in macrophages. Mitochondria-localized AIBP augments mitophagy and participates in mitochondria quality control, protecting macrophages against cell death in the context of atherosclerosis.

OMA1-An integral membrane protease?

OMA1 is a mitochondrial protease. Among its substrates are DELE1, a signaling peptide, which can elicit the integrated stress response, as well as the membrane-shaping dynamin-related GTPase OPA1, which can drive mitochondrial outer membrane permeabilization. OMA1 is dormant under physiological conditions but rapidly activated upon mitochondrial stress, such as loss of membrane potential or excessive reactive oxygen species. Accordingly, OMA1 was found to be activated in a number of disease conditions, including cancer and neurodegeneration. OMA1 has a predicted transmembrane domain and is believed to be tethered to the mitochondrial inner membrane. Yet, its structure has not been resolved and its context-dependent regulation remains obscure. Here, I review the literature with focus on OMA1's biochemistry. I provide a good homology model of OMA1's active site with a root-mean-square deviation of 0.9 Å and a DALI Z-score of 19.8. And I build a case for OMA1 actually being an integral membrane protease based on OMA1's role in the generation of small signaling peptides, its functional overlap with PARL, and OMA1's homology with ZMPSTE24. The refined understanding of this important enzyme can help with the design of tool compounds and development of chemical probes in the future.

MCTR3 reduces LPS-induced acute lung injury in mice via the ALX/PINK1 signaling pathway

Acute lung injury (ALI), a common respiratory distress syndrome in the intensive care unit (ICU), is mainly caused by severe infection and shock. Epithelial and capillary endothelial cell injury, interstitial edema and inflammatory cell infiltration are the main pathological changes observed in ALI animal models. Maresin conjugates in tissue regeneration (MCTR) are a new family of anti-inflammatory proteins. MCTR3 is a key enhancer of the host response, that promotes tissue regeneration and reduces infection; however, its role and mechanism in ALI are still unclear. The purpose of our research was to assess the protective effects of MCTR3 against ALI and its underlying mechanism. The work in this study was conducted in a murine model and the pulmonary epithelial cell line MLE-12. In vivo, MCTR3 (2 ng/g) was given 2 h after lipopolysaccharide (LPS) injection. We found that the treatment of mice with LPS-induced ALI with MCTR3 significantly reduced the cell number and protein levels in the bronchoalveolar lavage fluid (BALF); decreased the production of inflammatory cytokines; alleviated oxidative stress and cell apoptosis, consequently decreased lung injury; and restored pulmonary function. These protective effects of MCTR3 were dependent on down-regulation of the PTEN-induced putative kinase 1 (PINK1) pathway. Additionally, in MLE-12 cells stimulated with LPS, MCTR3 inhibited cell death, inflammatory cytokine levels and oxidative stress via the ALX/PINK1 signaling pathway. Thus, we conclude that MCTR3 protected against LPS-induced ALI partly through inactivation of the ALX/PINK1 mediated mitophagy pathway.