Function and regulation of the divisome for mitochondrial fission

Functionally conserved inner mitochondrial membrane proteins CCDC51 and Mdm33 demarcate a subset of fission events

While extensive work has examined the mechanisms of mitochondrial fission, it remains unclear whether internal mitochondrial proteins in metazoans play a direct role in the process. Previously, the yeast inner membrane protein Mdm33 was shown to be required for normal mitochondrial morphology and has been hypothesized to be involved in mitochondrial fission. However, it is unknown whether Mdm33 plays a direct role, and it is not thought to have a mammalian homolog. Here, we use a bioinformatic approach to identify a structural ortholog of Mdm33 in humans, CCDC51 (also called MITOK), whose depletion phenocopies loss of Mdm33. We find that knockdown of CCDC51 also leads to reduced rates of mitochondrial fission. Further, we spatially and temporally resolve Mdm33 and CCDC51 to a subset of mitochondrial fission events. Finally, we show that CCDC51 overexpression promotes its spatial association with Drp1 and induces mitochondrial fragmentation, suggesting it is a positive effector of mitochondrial fission. Together, our data reveal that Mdm33 and CCDC51 are functionally conserved and suggest that internal mitochondrial proteins are directly involved in at least a subset of mitochondrial fission events in human cells.

Plant-derived compounds as potential neuroprotective agents in Parkinson's disease

OBJECTIVES

Current Parkinson's disease (PD) medications treat symptoms; none can slow down or arrest the disease progression. Disease-modifying therapies for PD remain an urgent unmet clinical need. This review was designed to summarize recent findings regarding to the efficacy of phytochemicals in the treatment of PD and their underlying mechanisms.

METHODS

A literature search was performed using PubMed databases from inception until January 2024.

RESULTS

We first review the role of oxidative stress in PD and phytochemical-based antioxidant therapy. We then summarize recent work on neuroinflammation in the pathogenesis of PD, as well as preclinical data supporting anti-inflammatory efficacy in treating or preventing the disease. We last evaluate evidence for brain mitochondrial dysfunction in PD, together with the phytochemicals that protect mitochondrial function in preclinical model of PD. Furthermore, we discussed possible reasons for failures of preclinical-to-clinical translation for neuroprotective therapeutics.

CONCLUSIONS

There is now extensive evidence from preclinical studies that neuroprotective phytochemicals as promising candidate drugs for PD are needed to translate from the laboratory to the clinic.

Depleting chemoresponsive mitochondrial fission mediator DRP1 does not mitigate sarcoma resistance

Specific patterns of mitochondrial dynamics have been repeatedly reported to promote drug resistance in cancer. However, whether targeting mitochondrial fission- and fusion-related proteins could be leveraged to combat multidrug-resistant pediatric sarcomas is poorly understood. Here, we demonstrated that the expression and activation of the mitochondrial fission mediator DRP1 are affected by chemotherapy exposure in common pediatric sarcomas, namely, rhabdomyosarcoma and osteosarcoma. Unexpectedly, decreasing DRP1 activity through stable DRP1 knockdown neither attenuated sarcoma drug resistance nor affected growth rate or mitochondrial network morphology. The minimal impact on sarcoma cell physiology, along with the up-regulation of fission adaptor proteins (MFF and FIS1) detected in rhabdomyosarcoma cells, suggests an alternative DRP1-independent mitochondrial fission mechanism that may efficiently compensate for the lack of DRP1 activity. By exploring the upstream mitophagy and mitochondrial fission regulator, AMPKα1, we found that markedly reduced AMPKα1 levels are sufficient to maintain AMPK signaling capacity without affecting chemosensitivity. Collectively, our findings challenge the direct involvement of DRP1 in pediatric sarcoma drug resistance and highlight the complexity of yet-to-be-characterized noncanonical regulators of mitochondrial dynamics.

Pathological roles of mitochondrial dysfunction in endothelial cells during the cerebral no-reflow phenomenon: A review

Emergency intravascular interventional therapy is the most effective approach to rapidly restore blood flow and manage occlusion of major blood vessels during the initial phase of acute ischemic stroke. Nevertheless, several patients continue to experience ineffective reperfusion or cerebral no-reflow phenomenon, that is, hypoperfusion of cerebral blood supply after treatment. This is primarily attributed to downstream microcirculation disturbance. As integral components of the cerebral microvascular structure, endothelial cells (ECs) attach importance to regulating microcirculatory blood flow. Unlike neurons and microglia, ECs harbor a relatively low abundance of mitochondria, acting as key sensors of environmental and cellular stress in regulating the viability, structural integrity, and function of ECs rather than generating energy. Mitochondria dysfunction including increased mitochondrial reactive oxygen species levels and disturbed mitochondrial dynamics causes endothelial injury, further causing microcirculation disturbance involved in the cerebral no-reflow phenomenon. Therefore, this review aims to discuss the role of mitochondrial changes in regulating the role of ECs and cerebral microcirculation blood flow during I/R injury. The outcomes of the review will provide promising potential therapeutic targets for future prevention and effective improvement of the cerebral no-reflow phenomenon.

The mitochondrial long non-coding RNA lncMtloop regulates mitochondrial transcription and suppresses Alzheimer's disease

Maintaining mitochondrial homeostasis is crucial for cell survival and organismal health, as evidenced by the links between mitochondrial dysfunction and various diseases, including Alzheimer's disease (AD). Here, we report that lncMtDloop, a non-coding RNA of unknown function encoded within the D-loop region of the mitochondrial genome, maintains mitochondrial RNA levels and function with age. lncMtDloop expression is decreased in the brains of both human AD patients and 3xTg AD mouse models. Furthermore, lncMtDloop binds to mitochondrial transcription factor A (TFAM), facilitates TFAM recruitment to mtDNA promoters, and increases mitochondrial transcription. To allow lncMtDloop transport into mitochondria via the PNPASE-dependent trafficking pathway, we fused the 3'UTR localization sequence of mitochondrial ribosomal protein S12 (MRPS12) to its terminal end, generating a specified stem-loop structure. Introducing this allotropic lncMtDloop into AD model mice significantly improved mitochondrial function and morphology, and ameliorated AD-like pathology and behavioral deficits of AD model mice. Taken together, these data provide insights into lncMtDloop as a regulator of mitochondrial transcription and its contribution to Alzheimer's pathogenesis.

Mitochondrial dysfunction induced by ambient fine particulate matter and potential mechanisms

Air pollution is one of the major environmental threats contributing to the global burden of disease. Among diverse air pollutants, fine particulate matter (PM2.5) poses a significant adverse health impact and causes multi-system damage. As a highly dynamic organelle, mitochondria are essential for cellular energy metabolism and vital for cellular homeostasis and body fitness. Moreover, mitochondria are vulnerable to external insults and common targets for PM2.5-induced cellular damage. The resultant impairment of mitochondrial structure and function initiates the pathogenesis of diverse human diseases. This review mainly summarizes the in vivo and in vitro findings of PM2.5-induced mitochondrial dysfunction and its implication in PM2.5-induced health effects. Furthermore, recent advances toward the underlying mechanisms of PM2.5 and its components-induced mitochondrial dysfunction are also discussed, with an attempt to provide insights into the toxicity of PM2.5 and basic information for devising appropriate intervention strategies.

SUMOylation modulates mitochondrial dynamics in an in vitro rotenone model of Parkinson's disease

SUMOylation is a post-translational modification essential for various biological processes. SUMO proteins bind to target substrates in a three-step enzymatic pathway, which is rapidly reversible by the action of specific proteases, known as SENPs. Studies have shown that SUMOylation is dysregulated in several human disorders, including neurodegenerative diseases that are characterized by the progressive loss of neurons, mitochondrial dysfunction, deficits in autophagy, and oxidative stress. Considering the potential neuroprotective roles of SUMOylation, the aim of this study was to investigate the effects of SENP3 knockdown in H4 neuroglioma cells exposed to rotenone, an in vitro model of cytotoxicity that mimics dopaminergic loss in Parkinson's disease (PD). The current data show that SENP3 knockdown increases SUMO-2/3 conjugates, which is accompanied by reduced levels of the mitochondrial fission protein Drp1 and increased levels of the mitochondrial fusion protein OPA1. Of high interest, SENP3 knockdown prevented rotenone-induced superoxide production and cellular death. Taken together, these findings highlight the importance of SUMOylation in maintaining mitochondrial homeostasis and the neuroprotective potential of this modification in PD.

Epithelial mitochondrial fission-mediated PANoptosis is crucial for ulcerative colitis and its inhibition by saquinavir through Drp1

Ulcerative colitis (UC) is characterized by increased cell death in intestinal epithelial cell (IEC), which compromises gut barrier function and activates inflammation. Aberrant mitochondrial dynamics have been implicated in various forms of cell death, but it is currently unclear if they play a role in IEC death and colitis pathogenesis. This study aims to investigate the contribution of aberrant mitochondrial dynamics to colitis progression using cellular models, animal models, and clinical samples. The results revealed that IEC in mice with Dextran sulfate sodium salt (DSS)-induced colitis exhibited dynamin-related protein 1 (Drp1)-mediated mitochondrial fission and Z-DNA binding protein 1 (ZBP1)-dependent PANoptosis, which is a combination of apoptosis, necroptosis, and pyroptosis. However, these processes and the pathogenesis of DSS-induced colitis were significantly attenuated in IEC-specific Drp1 heterozygous knockout mice. Importantly, ZBP1-PANoptosis and Drp1-mediated mitochondrial fission were observed in IEC of UC patients, exhibiting a positive correlation with disease severity. Mechanistically, hyperactivated mitochondrial fission induced mitochondrial reactive oxygen species production leading to PANoptosis through ZBP1 sulfenylation at Cys327 independently of its Zα domain. Saquinavir, an FDA-approved drug identified through in-silico screening alongside in vivo and in vitro experiments, inhibits mitochondrial fission thereby enhancing therapeutic efficacy in mice with colitis.

Bag2 protects against doxorubicin-induced cardiotoxicity by maintaining Pink1-mediated mitophagy

The clinical application of Doxorubicin (DOX) is limited due to its cardiotoxicity. Mitophagy dysfunction is the primary cause of DOX-induced cardiotoxicity (DIC). However, the precise mechanism by which DOX regulates mitophagy remains elusive. Bag2 (BCL2-associated athanogene 2) is a cochaperone implicated in multiple pathological states. The aim of this study was to investigate the potential cardio-protective effects of Bag2 in DIC. C57BL/6 mice and AC16 cells were used to establish DIC model. The expression of Bag2 were measured by western blotting and immunohistochemical. The effects of Bag2 on DIC were assessed through functional gain and loss experiments. Through in vitro and in vivo experiments, we found that Bag2 expression was significantly reduced after DOX treatment. Both Bag2 knockdown and DOX administration resulted in apoptosis, mitochondrial dysfunction, and impaired mitophagy. Conversely, Bag2 overexpression exerted protective effects against these phenotypes induced by DOX stimulation. Mechanistically, Bag2 maintained mitophagy activation by binding to Pink1 and protecting it from proteasome-dependent degradation, thereby preserving mitochondrial function and protecting against myocardial lesions. Our findings suggest that Bag2 may serve as a promising therapeutic target for the treatment of DIC.

Procyanidin C1 ameliorates acidic pH stress induced nucleus pulposus degeneration through SIRT3/FOXO3-mediated mitochondrial dynamics

Intervertebral disc degeneration (IVDD) is a common cause of low back pain. Procyanidin C1 (PCC1) has been demonstrated to exert a protective effect on nucleus pulposus (NP) cells, and therefore, plays a critical role in the prevention and therapy of IVDD. Clarifying the pathophysiological characteristics and molecular mechanisms of IVDD may be helpful in establishing novel preventive and therapeutic strategies. This study aimed to investigate the probable mechanisms underlying the protection against acidic pH stress induced human NP cell injury. In vitro, acidic pH stress induced degeneration, mitochondrial dynamics imbalance, mitophagy, and mitochondria-mediated apoptosis in NP cells, all of which were ameliorated by PCC1. Autophagy inhibition partially eliminated the protective effects of PCC1 on mitochondrial homeostasis in NP cells. Moreover, PCC1 activated the sirtuin 3 (SIRT3)/forkhead box O3 (FOXO3) signaling pathway, a pivotal signaling pathway involved in the regulation of mitochondrial homeostasis in NP cells. In vivo, PCC1 ameliorated IVDD in a rat model and preserved the extracellular matrix of NP cells. Consequently, the protective effects of PCC1 on NP cells may inhibit IVDD progression via regulation of the SIRT3/FOXO3 signaling pathway. Therefore, regulation of the SIRT3/FOXO3 signaling pathway may be a novel preventive and therapeutic strategy for IVDD.

Mitochondrial structure and function: A new direction for the targeted treatment of chronic liver disease with Chinese herbal medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Excessive fat accumulation, biological clock dysregulation, viral infections, and sustained inflammatory responses can lead to liver inflammation, fibrosis, and cancer, thus promoting the development of chronic liver disease. A comprehensive understanding of the etiological factors leading to chronic liver disease and the intrinsic mechanisms influencing its onset and progression can aid in identifying potential targets for targeted therapy. Mitochondria, as key organelles that maintain the metabolic homeostasis of the liver, provide an important foundation for exploring therapeutic targets for chronic liver disease. Recent studies have shown that active ingredients in herbal medicines and their natural products can modulate chronic liver disease by influencing the structure and function of mitochondria. Therefore, studying how Chinese herbs target mitochondrial structure and function to treat chronic liver diseases is of great significance.

AIM OF THE STUDY

Investigating the prospects of herbal medicine the Lens of chronic liver disease based on mitochondrial structure and function.

MATERIALS AND METHODS

A computerized search of PubMed was conducted using the keywords "mitochondrial structure", "mitochondrial function", "mitochondria and chronic liver disease", "botanicals, mitochondria and chronic liver disease".Data from the Web of Science and Science Direct databases were also included. The research findings regarding herbal medicines targeting mitochondrial structure and function for the treatment of chronic liver disease are summarized.

RESULTS

A computerized search of PubMed using the keywords "mitochondrial structure", "mitochondrial function", "mitochondria and chronic liver disease", "phytopharmaceuticals, mitochondria, and chronic liver disease", as well as the Web of Science and Science Direct databases was conducted to summarize information on studies of mitochondrial structure- and function-based Chinese herbal medicines for the treatment of chronic liver disease and to suggest that the effects of herbal medicines on mitochondrial division and fusion.The study suggested that there is much room for research on the influence of Chinese herbs on mitochondrial division and fusion.

CONCLUSIONS

Targeting mitochondrial structure and function is crucial for herbal medicine to combat chronic liver disease.

HSP90 N-terminal inhibition promotes mitochondria-derived vesicles related metastasis by reducing TFEB transcription via decreased HSP90AA1-HCFC1 interaction in liver cancer

Cancer cells compensate with increasing mitochondria-derived vesicles (MDVs) to maintain mitochondrial homeostasis, when canonical MAP1LC3B/LC3B (microtubule associated protein 1 light chain 3 beta)-mediated mitophagy is lacking. MDVs promote the transport of mitochondrial components into extracellular vesicles (EVs) and induce tumor metastasis. Although HSP90 (heat shock protein 90) chaperones hundreds of client proteins and its inhibitors suppress tumors, HSP90 inhibitors-related chemotherapy is associated with unexpected metastasis. Herein, we find that HSP90 inhibitor causes mitochondrial damage but stimulates the low LC3-induced MDVs and the release of MDVs-derived EVs. However, why LC3 decreases and what is the transcriptional regulatory mechanism of MDVs formation under HSP90 inhibition remain unknown. Because TFEB (transcription factor EB) is the most important mitophagy transcription factor, and the HSP90 client HCFC1 (host cell factor C1) regulates TFEB transcription, there should be a hidden connection between TFEB, HCFC1 and HSP90 in MDVs formation. Our results support the idea that HSP90 N-terminal inhibition reduces TFEB transcription via decreased HSP90AA1-HCFC1 interaction, which prevents HCFC1 from binding to the TFEB proximal promoter region. Decreased TFEB transcription and consequently reduced LC3, ultimately promoted MDVs formation. Blocking MDVs formation with the microtubule inhibitor nocodazole (NOC) activates the HCFC1-TFEB-LC3 axis, weakens HSP90 inhibitors-induced MDVs and the release of MDVs-derived EVs, inhibits the growth of tumor cell spheres and primary liver tumors, and reduces the extravasation of cancer cells to secondary metastatic sites. Taken together, these data suggest that combination therapy should be used to reduce the metastatic risk of low TFEB-triggered-MDVs formation caused by HSP90 inhibitors.Abbreviation: ACIs: ATP-competitive inhibitors; BaFA1: bafilomycin A1; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; ChIP: chromatin immunoprecipitation; CHX: cycloheximide; CTD: C-terminal domain; EVs: extracellular vesicles; HCFC1: host cell factor C1; HSP90: heat shock protein 90; ILVs: intralumenal vesicles; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MD: middle domain; MDVs: mitochondria-derived vesicles; MQC: mitochondrial quality control; ΔΨm: mitochondrial membrane potential; MVBs: multivesicular bodies; NB: novobiocin; TEM: transmission electron microscopy; TFEB: transcription factor EB; TFs: transcription factors. NOC: nocodazole; NTD: N-terminal nucleotide binding domain; OCR: oxygen consumption rate; RFP: red fluorescent protein; ROS: reactive oxygen species; STA9090: Ganetespib; VPS35: VPS35 retromer complex component.

The Emerging Role of Brain Mitochondria in Fear and Anxiety

The functional complexity of brain circuits underlies the broad spectrum of behaviors, cognitive functions, and their associated disorders. Mitochondria, traditionally known for their role in cellular energy metabolism, are increasingly recognized as central to brain function and behavior. This review examines how mitochondria are pivotal in linking cellular energy processes with the functioning of neural circuits that govern fear and anxiety. Following an introductory section in which we summarize current knowledge about fear and anxiety neural circuits, we provide a brief summary of mitochondria fundamental roles (e.g., from energy production and calcium buffering to their involvement in reactive oxygen species (ROS) generation, mitochondrial dynamics, and signaling), particularly emphasizing their contribution to synaptic plasticity, neurodevelopment, and stress response mechanisms. The review's core focuses on the current state of knowledge regarding how mitochondrial function and dysfunction impact the neural substrates of fear and anxiety. Furthermore, we explore the implications of mitochondrial alterations in the context of posttraumatic stress disorder (PTSD) and anxiety disorders, underscoring the potential of mitochondrial pathways as new therapeutic targets. Integrating insights from genetic, biochemical, neurobiological, behavioral, and clinical studies, we propose a model in which mitochondrial function is critical for regulating the neural circuits that underpin fear and anxiety behaviors, highlighting how mitochondrial dysfunction can lead to their pathological manifestations. This integration emphasizes the potential for developing novel treatments targeting the biological roots of fear, anxiety, and related disorders. By merging mitochondrial biology with behavioral and circuit neuroscience, we enrich our neurobiological understanding of fear and anxiety, uncovering promising avenues for therapeutic intervention.

Mitochondrial dysfunction is a key link involved in the pathogenesis of sick sinus syndrome: a review

Sick sinus syndrome (SSS) is a grave medical condition that can precipitate sudden death. The pathogenesis of SSS remains incompletely understood. Existing research postulates that the fundamental mechanism involves increased fibrosis of the sinoatrial node and its surrounding tissues, as well as disturbances in the coupled-clock system, comprising the membrane clock and the Ca2+ clock. Mitochondrial dysfunction exacerbates regional tissue fibrosis and disrupts the functioning of both the membrane and calcium clocks. This plays a crucial role in the underlying pathophysiology of SSS, including mitochondrial energy metabolism disorders, mitochondrial oxidative stress damage, calcium overload, and mitochondrial quality control disorders. Elucidating the mitochondrial mechanisms involved in the pathophysiology of SSS and further investigating the disease's mechanisms is of great significance.

Targeting TGR5 to mitigate liver fibrosis: Inhibition of hepatic stellate cell activation through modulation of mitochondrial fission

Chronic hepatitis B virus (HBV) infection continues to be a prominent cause of liver fibrosis and end-stage liver disease in China, necessitating the development of effective therapeutic strategies. This study investigated the potential of targeting TGR5 to alleviate liver fibrosis by impeding the activation of hepatic stellate cells (HSCs), which play a pivotal role in fibrotic progression. Using the human hepatic stellate cell line LX-2 overexpressing hepatitis B virus X protein (HBX), this study revealed that TGR5 activation through INT-777 inhibits HBX-induced LX-2 cell activation, thereby ameliorating liver fibrosis, which is associated with the attenuation of mitochondrial fission and introduces a novel regulatory pathway in liver fibrosis. Additional experiments with mitochondrial fission inducers and inhibitors confirm the crucial role of mitochondrial dynamics in TGR5-mediated effects. In vivo studies using TGR5 knockout mice substantiate these findings, demonstrating exacerbated fibrosis in the absence of TGR5 and its alleviation with the mitochondrial fission inhibitor Mdivi-1. Overall, this study provides insights into TGR5-mediated regulation of liver fibrosis through the modulation of mitochondrial fission in HSCs, suggesting potential therapeutic strategies for liver fibrosis intervention.

The Large GTPase Guanylate-Binding Protein-1 (GBP-1) Promotes Mitochondrial Fission in Glioblastoma

Glioblastomas (aka Glioblastoma multiformes (GBMs)) are the most deadly of the adult brain tumors. Even with aggressive treatment, the prognosis is extremely poor. The large GTPase Guanylate-Binding Protein-1 (GBP-1) contributes to the poor prognosis of GBM by promoting migration and invasion. GBP-1 is substantially localized to the cytosolic side of the outer membrane of mitochondria in GBM cells. Because mitochondrial dynamics, particularly mitochondrial fission, can drive cell migration and invasion, the potential interactions between GBP-1 and mitochondrial dynamin-related protein 1 (Drp1) were explored. Drp1 is the major driver of mitochondrial fission. While GBP-1 and Drp1 both had punctate distributions within the cytoplasm and localized to regions of the cytoplasmic side of the plasma membrane of GBM cells, the proteins were only molecularly co-localized at the mitochondria. Subcellular fractionation showed that the presence of elevated GBP-1 promoted the movement of Drp1 from the cytosol to the mitochondria. The migration of U251 cells treated with the Drp1 inhibitor, Mdivi-1, was less inhibited in the cells with elevated GBP-1. Elevated GBP-1 in GBM cells resulted in shorter and wider mitochondria, most likely from mitochondrial fission. Mitochondrial fission can drive several important cellular processes, including cell migration, invasion, and metastasis.

Molecular mechanisms of mitochondrial dynamics

Mitochondria not only synthesize energy required for cellular functions but are also involved in numerous cellular pathways including apoptosis, calcium homoeostasis, inflammation and immunity. Mitochondria are dynamic organelles that undergo cycles of fission and fusion, and these transitions between fragmented and hyperfused networks ensure mitochondrial function, enabling adaptations to metabolic changes or cellular stress. Defects in mitochondrial morphology have been associated with numerous diseases, highlighting the importance of elucidating the molecular mechanisms regulating mitochondrial morphology. Here, we discuss recent structural insights into the assembly and mechanism of action of the core mitochondrial dynamics proteins, such as the dynamin-related protein 1 (DRP1) that controls division, and the mitofusins (MFN1 and MFN2) and optic atrophy 1 (OPA1) driving membrane fusion. Furthermore, we provide an updated view of the complex interplay between different proteins, lipids and organelles during the processes of mitochondrial membrane fusion and fission. Overall, we aim to present a valuable framework reflecting current perspectives on how mitochondrial membrane remodelling is regulated.

A review: Polysaccharides targeting mitochondria to improve obesity

Polysaccharides are one of the most important and widely used bioactive components of natural products, which can be used to treat metabolic diseases. Natural polysaccharides (NPs) have been the subject of much study and research in the field of treating obesity in recent years. Studies in the past have demonstrated that mitochondria are important for the initiation, progression, and management of obesity. Additionally, NPs have the ability to improve mitochondrial dysfunction via a variety of mechanisms. This review summarized the relationship between the structure of NPs and their anti-obesity activity, focusing on the anti-obesity effects of these compounds at the mitochondrial level. We discussed the association between the structure and anti-obesity action of NPs, including molecular weight, monosaccharide composition, glycosidic linkage, conformation and extraction methods. Furthermore, NPs can demonstrate a range of functions in adipose tissue, including but not limited to improving the mitochondrial oxidative respiratory chain, inhibiting oxidative stress, and maintaining mitochondrial mass homeostasis. The purpose of this work is to acquire a thorough understanding of the function that mitochondria play in the anti-obesity effects of NPs and to offer fresh insights for the investigation of how NPs prevent obesity and the creation of natural anti-obesity medications.

Atg44/Mdi1/mitofissin facilitates Dnm1-mediated mitochondrial fission

Mitochondria undergo fission and fusion, and their coordinated balance is crucial for maintaining mitochondrial homeostasis. In yeast, the dynamin-related protein Dnm1 is a mitochondrial fission factor acting from outside the mitochondria. We recently reported the mitochondrial intermembrane space protein Atg44/mitofissin/Mdi1/Mco8 as a novel fission factor, but the relationship between Atg44 and Dnm1 remains elusive. Here, we show that Atg44 is required to complete Dnm1-mediated mitochondrial fission under homeostatic conditions. Atg44-deficient cells often exhibit enlarged mitochondria with accumulated Dnm1 and rosary-like mitochondria with Dnm1 foci at constriction sites. These mitochondrial constriction sites retain the continuity of both the outer and inner membranes within an extremely confined space, indicating that Dnm1 is unable to complete mitochondrial fission without Atg44. Moreover, accumulated Atg44 proteins are observed at mitochondrial constriction sites. These findings suggest that Atg44 and Dnm1 cooperatively execute mitochondrial fission from inside and outside the mitochondria, respectively.Abbreviation: ATG: autophagy related; CLEM: correlative light and electron microscopy; EM: electron microscopy; ER: endoplasmic reticulum; ERMES: endoplasmic reticulum-mitochondria encounter structure; GA: glutaraldehyde; GFP: green fluorescent protein; GTP: guanosine triphosphate: IMM: inner mitochondrial membrane; IMS: intermembrane space; OMM: outer mitochondrial membrane; PB: phosphate buffer; PBS: phosphate-buffered saline; PFA: paraformaldehyde; RFP: red fluorescent protein; WT: wild type.

Spinster homolog 2/S1P signaling ameliorates macrophage inflammatory response to bacterial infections by balancing PGE2 production

BACKGROUND

Mitochondria play a crucial role in shaping the macrophage inflammatory response during bacterial infections. Spinster homolog 2 (Spns2), responsible for sphingosine-1-phosphate (S1P) secretion, acts as a key regulator of mitochondrial dynamics in macrophages. However, the link between Spns2/S1P signaling and mitochondrial functions remains unclear.

METHODS

Peritoneal macrophages were isolated from both wild-type and Spns2 knockout rats, followed by non-targeted metabolomics and RNA sequencing analysis to identify the potential mediators through which Spns2/S1P signaling influences the mitochondrial functions in macrophages. Various agonists and antagonists were used to modulate the activation of Spns2/S1P signaling and its downstream pathways, with the underlying mechanisms elucidated through western blotting. Mitochondrial functions were assessed using flow cytometry and oxygen consumption assays, as well as morphological analysis. The impact on inflammatory response was validated through both in vitro and in vivo sepsis models, with the specific role of macrophage-expressed Spns2 in sepsis evaluated using Spns2flox/floxLyz2-Cre mice. Additionally, the regulation of mitochondrial functions by Spns2/S1P signaling was confirmed using THP-1 cells, a human monocyte-derived macrophage model.

RESULTS

In this study, we unveil prostaglandin E2 (PGE2) as a pivotal mediator involved in Spns2/S1P-mitochondrial communication. Spns2/S1P signaling suppresses PGE2 production to support malate-aspartate shuttle activity. Conversely, excessive PGE2 resulting from Spns2 deficiency impairs mitochondrial respiration, leading to intracellular lactate accumulation and increased reactive oxygen species (ROS) generation through E-type prostanoid receptor 4 activation. The overactive lactate-ROS axis contributes to the early-phase hyperinflammation during infections. Prolonged exposure to elevated PGE2 due to Spns2 deficiency culminates in subsequent immunosuppression, underscoring the dual roles of PGE2 in inflammation throughout infections. The regulation of PGE2 production by Spns2/S1P signaling appears to depend on the coordinated activation of multiple S1P receptors rather than any single one.

CONCLUSIONS

These findings emphasize PGE2 as a key effector of Spns2/S1P signaling on mitochondrial dynamics in macrophages, elucidating the mechanisms through which Spns2/S1P signaling balances both early hyperinflammation and subsequent immunosuppression during bacterial infections.

Comparative evaluation of cigarette smoke and a heated tobacco product on microglial toxicity, oxidative stress and inflammatory response

BACKGROUND

Tobacco smoking is the leading cause of preventable death and disease worldwide, with over 8 million annual deaths attributed to cigarette smoking. This study investigates the impact of cigarette smoke and heated tobacco products (HTPs) on microglial function, focusing on toxicological profiles, inflammatory responses, and oxidative stress using ISO standard and clinically relevant conditions of exposure.

METHODS

We assessed cell viability, reactive oxygen species (ROS) production, lipid peroxidation, mitochondrial function, unfolded protein response, and inflammation in human microglial cells (HMC3) exposed to cigarette smoke, HTP aerosol or nicotine.

RESULTS

Our findings show that cigarette smoke significantly reduces microglial viability, increases ROS formation, induces lipid peroxidation, and reduces intracellular glutathione levels. Cigarette smoke also alters the expression of genes involved in mitochondrial dynamics and biogenesis, leading to mitochondrial dysfunction. Additionally, cigarette smoke impairs the unfolded protein response, activates the NF-κB pathway, and induces a pro-inflammatory state characterized by increased TNF and IL-18 expression. Furthermore, cigarette smoke causes DNA damage and decreases the expression of the aging marker Klotho β. In contrast, HTP, exhibited a lesser degree of microglial toxicity, with reduced ROS production, lipid peroxidation, and mitochondrial dysfunction compared to conventional cigarettes.

CONCLUSION

These results highlight the differential toxicological profile of cigarette smoke and HTP on microglial cells, suggesting a potential harm reduction strategy for neurodegenerative disease for smokers unwilling or unable to quit.

Visualizing Mitochondrial Membrane Potential with FRET Probes: Integrating Fluorescence Intensity Ratio and Lifetime Imaging

Mitochondrial membrane potential (MMP) is crucial for mitochondrial function and serves as a key indicator of cellular health and metabolic activity. Traditional lipophilic cationic fluorescence intensity probes are unavoidably influenced by probe concentration, laser intensity, and photobleaching, limiting their accuracy. To address these issues, we designed and synthesized a pair of fluorescence molecules, OR-C8 and SiR-BA, based on the Förster Resonance Energy Transfer (FRET) mechanism, for dual-modality visualization of MMP. OR-C8 anchors to the inner mitochondrial membrane through strong hydrophobic interactions, while SiR-BA is expelled from mitochondria when MMP decreases, thereby regulating the FRET process. During MMP reduction, the fluorescence intensity and lifetime of OR-C8 increase, while the fluorescence intensity of SiR-BA decreases. By combining changes in fluorescence intensity ratio and fluorescence lifetime, dual-modality visualization of MMP was achieved. This method not only accurately reflects MMP changes but also provides a novel tool for in-depth studies of mitochondrial function and related disease mechanisms, offering significant potential for advancing mitochondrial research and therapeutic development.

Mitochondrial Dynamics and mRNA Translation: A Local Synaptic Tale

Mitochondria are dynamic organelles that can adjust and respond to different stimuli within a cell. This plastic ability allows them to effectively coordinate several cellular functions in cells and becomes particularly relevant in highly complex cells such as neurons. An imbalance in mitochondrial dynamics can disrupt mitochondrial function, leading to abnormal cellular function and ultimately to a range of diseases, including neurodegenerative disorders. Regulation of mRNA transport and local translation inside neurons is crucial for maintaining the proteome of distal mitochondria, which is vital for energy production and synaptic function. A significant portion of the axonal transcriptome is dedicated to mRNAs for mitochondrial proteins, emphasizing the importance of local translation in sustaining mitochondrial function in areas far from the cell body. In neurons, local translation and the regulation of mRNAs encoding mitochondrial-shaping proteins could be essential for synaptic plasticity and neuronal health. The dynamics of these mRNAs, including their transport and local translation, may influence the morphology and function of mitochondria, thereby affecting the overall energy status and responsiveness of synapses. Comprehending the mitochondria-related mRNA regulation and local translation, as well as its influence on mitochondrial morphology near the synapses will help to better understand neuronal physiology and neurological diseases where mitochondrial dysfunction and impaired synaptic plasticity play a central role.

Mechanism study of YangJing ZhongYu decoction on regulating mitochondrial dynamics of ovarian granular cells and improving diminished ovarian reserve

OBJECTIVE

Diminished ovarian reserve (DOR) encompasses both reproductive and endocrine disorders, resulting in a decline in female fertility. This paper explored the mechanism of Yangjing Zhongyu Decoction (YJZYD) regulating mitochondrial dynamics of ovarian granulosa cells (GCs) to improve DOR.

METHODS

DOR patients were treated with YJZYD, with ovarian volume (OV), antral follicle count (AFC), and endometrial thickness (EMT) detected. C57BL/6 female mice were treated by cyclophosphamide (Cy) intraperitoneal injection and YJZYD solution daily gavage, with serum anti-Mullerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) levels determined. Ovarian GCs (KGN) were interfered with 4-Hydroperoxy-Cyclophosphamide (4-HC) and treated with the MAPK/ERK pathway inhibitor or activator.

RESULTS

DOR patients showed increased levels of serum AMH, E2, OV, AFC and EMT, while reduced FSH and LH levels after YJZYD treatment. After Cy induction, DOR mice exhibited irregular estrous cycles, diminished serum AMH and E2 levels, elevated FSH and LH levels, reduced follicle number and atresia follicle number, disorderly arranged GCs, and severe interstitial fibrosis. After 4-HC treatment, KGN proliferation and Bcl-2, MFN1, and MFN2 were suppressed, while apoptotic rate, Bax, Cleaved-caspase-3, and p-Drp1 (Ser616) levels, and mitochondrial fission and quantity increased. YJZYD promoted 4-HC-treated KGN proliferation, boosted mitochondrial fusion, and inhibited apoptosis and mitochondrial fission via the MAPK/ERK pathway.

CONCLUSION

YJZYD promoted ovarian GC proliferation and mitochondrial fusion, suppressed cell apoptosis and mitochondrial fission, and effectively improved DOR in mice by activating the MAPK/ERK pathway, providing a theoretical basis for the clinical application value of YJZYD in DOR treatment.

Silencing of PCK1 mitigates the proliferation and migration of vascular smooth muscle cells and vascular intimal hyperplasia by suppressing STAT3/DRP1-mediated mitochondrial fission

The pathological proliferation and migration of vascular smooth muscle cells (VSMCs) are key processes during vascular neointimal hyperplasia (NIH) and restenosis. Phosphoenolpyruvate carboxy kinase 1 (PCK1) is closely related to a variety of malignant proliferative diseases. However, the role of PCK1 in VSMCs has rarely been investigated. This study aims to examine the role of PCK1 in the proliferation and migration of VSMCs and vascular NIH after injury. In vivo, extensive NIH and increased expression of PCK1 within the neointima are observed in injured arteries. Interestingly, the administration of adeno-associated virus-9 (AAV-9) carrying Pck1 short hairpin RNA (sh Pck1) significantly attenuates NIH and stenosis of the vascular lumen. In vitro, Pck1 small interfering RNA (si Pck1)-induced PCK1 silencing inhibits VSMC proliferation and migration. Additionally, silencing of PCK1 leads to reduced expression of dynamin-related protein 1 (DRP1) and attenuated mitochondrial fission. Lentivirus-mediated DRP1 overexpression markedly reverses the inhibitory effects of PCK1 silencing on VSMC proliferation, migration, and mitochondrial fission. Finally, PCK1 inhibition attenuates the phosphorylation of signal transducer and activator of transcription 3 (STAT3). Activation of STAT3 abolishes the suppressive effects of PCK1 silencing on DRP1 expression, mitochondrial fission, proliferation, and migration in VSMCs. In conclusion, PCK1 inhibition attenuates the mitochondrial fission, proliferation, and migration of VSMCs by inhibiting the STAT3/DRP1 axis, thereby suppressing vascular NIH and restenosis.

Dual-Modality Imaging with a Zwitterionic Fluorescent Probe for Reversible Monitoring of Mitochondrial Membrane Potential Dynamics

Traditional fluorescence intensity-based probes face challenges in accurately measuring mitochondrial membrane potential (MMP) due to intramolecular fluorescence quenching. In this work, we introduce a novel approach by incorporating quenching moieties within the zwitterionic probe to eliminate self-quenching interference, thus, enabling real-time and precise visualization of reversible MMP changes. We synthesized a zwitterionic fluorescent probe consisting of silicon-rhodamine (SiR) that was hydroxyl-substituted on the bay position of perylene diimides (PDIs) connected via a polyethylene glycol (PEG) linker. The lipophilic cationic SiR facilitates the entry of the PDI into the mitochondria, where the alkaline pH environment (pH = 8.0) ionizes the hydroxyl to a negatively charged species, affecting the quenching efficiency of SiR depending on the distance between the PDI and SiR moieties regulated by the MMP. The rigid aromatic ring of the PDI and strong hydrophobic interactions with the lipid bilayer, along with the inhibitory effect of the negatively charged hydroxyl on internalization, ensure the retention of PDI within the mitochondria. As the MMP decreases, SiR shifts outward, reducing quenching by phenolic anions and restoring fluorescence. Conversely, as the MMP increases, SiR moves inward, intensifying quenching by phenolic ions and reducing fluorescence, enabling reversible visualization monitoring of the MMP. This strategy overcomes the limitations of traditional intensity-based probes, providing a new avenue for reversible monitoring of the MMP.

Altered Endoplasmic Reticulum Integrity and Organelle Interactions in Living Cells Expressing INF2 Variants

The cytoskeleton mediates fundamental cellular processes by organizing inter-organelle interactions. Pathogenic variants of inverted formin 2 (INF2) CAAX isoform, an actin assembly factor that is predominantly expressed in the endoplasmic reticulum (ER), are linked to focal segmental glomerulosclerosis (FSGS) and Charcot-Marie-Tooth (CMT) neuropathy. To investigate how pathogenic INF2 variants alter ER integrity, we used high-resolution live imaging of HeLa cells. Cells expressing wild-type (WT) INF2 showed a predominant tubular ER with perinuclear clustering. Cells expressing INF2 FSGS variants that cause mild and intermediate disease induced more sheet-like ER, a pattern similar to that seen for cells expressing WT-INF2 that were treated with actin and microtubule (MT) inhibitors. Dual CMT-FSGS INF2 variants led to more severe ER dysmorphism, with a diffuse, fragmented ER and coarse INF2 aggregates. Proper organization of both F-actin and MT was needed to modulate the tubule vs. sheet conformation balance, while MT arrays regulated spatial expansion of tubular ER in the cell periphery. Pathogenic INF2 variants also induced mitochondria fragmentation and dysregulated mitochondria distribution. Such mitochondrial abnormalities were more prominent for cells expressing CMT-FSGS compared to those with FSGS variants, indicating that the severity of the dysfunction is linked to the degree of cytoskeletal disorganization. Our observations suggest that pathogenic INF2 variants disrupt ER continuity by altering interactions between the ER and the cytoskeleton that in turn impairs inter-organelle communication, especially at ER-mitochondria contact sites. ER continuity defects may be a common disease mechanism involved in both peripheral neuropathy and glomerulopathy.

Cdc42 deletion yielded enamel defects by disrupting mitochondria and producing reactive oxygen species in dental epithelium

Developmental defects of enamel are common due to genetic and environmental factors before and after birth. Cdc42, a Rho family small GTPase, regulates prenatal tooth development in mice. However, its role in postnatal tooth development, especially enamel formation, remains elusive. Here, we investigated Cdc42 functions in mouse enamel development and tooth repair after birth. Cdc42 showed highly dynamic temporospatial patterns in the developing incisors, with robust expression in ameloblast and odontoblast layers. Strikingly, epithelium-specific Cdc42 deletion resulted in enamel defects in incisors. Ameloblast differentiation was inhibited, and hypomineralization of enamel was observed upon epithelial Cdc42 deletion. Proteomic analysis showed that abnormal mitochondrial components, phosphotransferase activity, and ion channel regulator activity occurred in the Cdc42 mutant dental epithelium. Reactive oxygen species accumulation was detected in the mutant mice, suggesting that abnormal oxidative stress occurred after Cdc42 depletion. Moreover, Cdc42 mutant mice showed delayed tooth repair and generated less calcified enamel. Mitochondrial dysfunction and abnormal oxygen consumption were evidenced by reduced Apool and Timm8a1 expression, increased Atp5j2 levels, and reactive oxygen species overproduction in the mutant repair epithelium. Epithelium-specific Cdc42 deletion attenuated ERK1/2 signaling in the labial cervical loop. Aberrant Sox2 expression in the mutant labial cervical loop after clipping might lead to delayed tooth repair. These findings suggested that mitochondrial dysfunction, up-regulated oxidative stress, and abnormal ion channel activity may be among multiple factors responsible for the observed enamel defects in Cdc42 mutant incisors. Overall, Cdc42 exerts multidimensional and pivotal roles in enamel development and is particularly required for ameloblast differentiation and enamel matrix formation.

Ciprofloxacin Accelerates Angiotensin-II-Induced Vascular Smooth Muscle Cells Senescence Through Modulating AMPK/ROS pathway in Aortic Aneurysm and Dissection

Aortic aneurysm and dissection (AAD) is a cardiovascular disease that poses a severe threat to life and has high morbidity and mortality rates. Clinical and animal-based studies have irrefutably shown that fluoroquinolones, a commonly prescribed antibiotic for treating infections, significantly increase the risk of AAD. Despite this, the precise mechanism by which fluoroquinolones cause AAD remains unclear. Therefore, this study aims to investigate the molecular mechanism and role of Ciprofloxacin definitively-a type of fluoroquinolone antibiotic-in the progression of AAD. Aortic transcriptome data were collected from GEO datasets to detect the genes and pathways expressed differently between healthy donors and AAD patients. Human primary Vascular Smooth Muscle Cells (VSMCs) were isolated from the aorta. After 72 h of exposure to 110ug/ml Ciprofloxacin or 100 nmol/L AngII, either or combined, the senescent cells were identified through SA-β-gal staining. MitoTracker staining was used to examine the morphology of mitochondria in each group. Cellular Reactive Oxygen Species (ROS) levels were measured using MitoSox and DCFH-DA staining. Western blot assay was performed to detect the protein expression level. We conducted an analysis of transcriptome data from both healthy donors and patients with AAD and found that there were significant changes in cellular senescence-related signaling pathways in the latter group. We then isolated and identified human primary VSMCs from healthy donors (control-VSMCs) and patients' (AAD-VSMCs) aortic tissue, respectively. We found that VSMCs from patients exhibited senescent phenotype as compared to control-VSMCs. The higher levels of p21 and p16 and elevated SA-β-gal activity demonstrated this. We also found that pretreatment with Ciprofloxacin promoted angiotensin-II-induced cellular senescence in control-VSMCs. This was evidenced by increased SA-β-gal activity, decreased cell proliferation, and elevation of p21 and p16 protein levels. Additionally, we found that Angiotensin-II (AngII) induced VSMC senescence by promoting ROS generation. We used DCFH-DA and mitoSOX staining to identify that Ciprofloxacin and AngII pretreatment further elevated ROS levels than the vehicle or alone group. Furthermore, JC-1 staining showed that mitochondrial membrane potential significantly declined in the Ciprofloxacin and AngII combination group compared to others. Compared to the other three groups, pretreatment of Ciprofloxacin plus AngII could further induce mitochondrial fission, demonstrated by mitoTracker staining and western blotting assay. Mechanistically, we found that Ciprofloxacin impaired the balance of mitochondrial fission and fusion dynamics in VSMCs by suppressing the phosphorylation of AMPK signaling. This caused mitochondrial dysfunction and ROS generation, thereby elevating AngII-induced cellular senescence. However, treatment with the AMPK activator partially alleviated those effects. Our data indicate that Ciprofloxacin may accelerate AngII-induced VSMC senescence through modulating AMPK/ROS signaling and, subsequently, hasten the progression of AAD.

Role of Excessive Mitochondrial Fission in Seawater Immersion Aggravated Hemorrhagic Shock-Induced Cardiac Dysfunction and the Protective Effect of Mitochondrial Division Inhibitor-1

Aims: Seawater immersion significantly aggravated organ dysfunction following hemorrhagic shock, leading to higher mortality rate. However, the effective treatment is still unavailable in clinic. Mitochondria were involved in the onset and development of multiple organ function disorders; whether mitochondria participate in the cardiac dysfunction following seawater immersion combined with hemorrhagic shock remains poorly understood. Hence, we investigated the role and possible mechanism of mitochondria in seawater immersion combined with hemorrhage shock-induced cardiac dysfunction. Results: Mitochondrial fission protein dynamin-related protein 1 (Drp1) was activated and translocated from the cytoplasm to mitochondria in the heart following seawater immersion combined with hemorrhagic shock, leading to excessive mitochondrial fission. Excessive mitochondrial fission disrupted mitochondrial function and structure and activated mitophagy and apoptosis. At the same time, excessive mitochondrial fission resulted in disturbance of myocardial structure and hemodynamic disorders and ultimately provoked multiple organ dysfunction and high mortality. Further studies showed that the mitochondrial division inhibitor mitochondrial division inhibitor-1 can significantly reverse Drp1 mitochondrial translocation and inhibit mitochondrial fragmentation, reactive oxygen species (ROS) accumulation, mitophagy, and apoptosis and then protect circulation and vital organ functions, prolonging animal survival. Innovation: Our findings indicate that Drp1-mediated mitochondrial fission could be a novel therapeutic targets for the treatment of seawater immersion combined with hemorrhagic shock. Conclusion: Drp1 mitochondrial translocation played an important role in the cardiac dysfunction after seawater immersion combined with hemorrhage shock. Drp1-mediated excessive mitochondrial fission leads to cardiac dysfunction due to the mitochondrial structure and bioenergetics impairment.

GPRASP2 deficiency contributes to apoptosis in the spiral ganglion cells via the AMPK/DRP1 signaling pathway

G protein-coupled receptor-associated sorting protein 2 (GPRASP2) deficiency has been implicated in immunological inflammation, cancers, and neurological disorders. Our previous work revealed that the pathogenic mutation in GPRASP2 was responsible for X-linked recessive syndromic hearing loss (SHL). Given the specific high expression of GPRASP2 in the spiral ganglion, GPRASP2 likely contributes to the maintenance and functionality of neurons, potentially playing a role in synaptic transmission. The impact of GPRASP2 deficiency on spiral ganglion cells (SGCs) and their underlying pathogenic mechanisms will be investigated in this study. The primary culture of SGCs obtained from mouse cochleae was treated with Gprasp2-targeting short hairpin RNA (Gprasp2-shRNA) via lentivirus infection. The results showed that GPRASP2 deficiency enhanced SGCs apoptosis and decreased cell viability. Meanwhile, a significant abnormality of mitochondrial morphology and decreased membrane potential were observed in GPRASP2-deficient SGCs. These effects could be mitigated by treatment with the mitochondrial division inhibitor 1 (Mdivi-1). In addition to enhancing SGCs apoptosis and decreasing cell viability, GPRASP2 deficiency also inhibited the development of SGCs in mouse cochlear explant culture. Our study further revealed that this deficiency resulted in increased phosphorylation of AMPK and activation of the AMPK/DRP1 pathway, promoting SGCs apoptosis. These findings provide insight into the pathogenic mechanisms by which GPRASP2 deficiency is implicated in auditory dysfunction.

SIRT6 prevent chronic cerebral hypoperfusion induced cognitive impairment by remodeling mitochondrial dynamics in a STAT5-PGAM5-Drp1 dependent manner

Vascular dementia (VaD) is a prevalent form of dementia resulting from chronic cerebral hypoperfusion (CCH). However, the pathogenic mechanisms of VaD and corresponding therapeutic strategies are not well understood. Sirtuin 6 (SIRT6) has been implicated in various biological processes, including cellular metabolism, DNA repair, redox homeostasis, and aging. Nevertheless, its functional relevance in VaD remains unexplored. In this study, we utilized a bilateral common carotid artery stenosis (BCAS) mouse model of VaD to investigate the role of SIRT6. We detected a significant decrease in neuronal SIRT6 protein expression following CCH. Intriguingly, neuron-specific ablation of Sirt6 in mice exacerbated neuronal damage and cognitive deficits after CCH. Conversely, treatment with MDL-800, an agonist of SIRT6, effectively mitigated neuronal loss and facilitated neurological recovery. Mechanistically, SIRT6 inhibited excessive mitochondrial fission by suppressing the CCH-induced STAT5-PGAM5-Drp1 signaling cascade. Additionally, the gene expression of monocyte SIRT6 in patients with asymptomatic carotid stenosis showed a correlation with cognitive outcomes, suggesting translational implications in human subjects. Our findings provide the first evidence that SIRT6 prevents cognitive impairment induced by CCH, and mechanistically, this protection is achieved through the remodeling of mitochondrial dynamics in a STAT5-PGAM5-Drp1-dependent manner.

ML335 inhibits TWIK2 channel-mediated potassium efflux and attenuates mitochondrial damage in MSU crystal-induced inflammation

BACKGROUND

Activation of the NLRP3 inflammasome is critical in the inflammatory response to gout. Potassium ion (K+) efflux mediated by the TWIK2 channel is an important upstream mechanism for NLRP3 inflammasome activation. Therefore, the TWIK2 channel may be a promising therapeutic target for MSU crystal-induced inflammation. In the present study, we investigated the effect of ML335, a known K2P channel modulator, on MSU crystal-induced inflammatory responses and its underlying molecular mechanisms.

METHODS

By molecular docking, we calculated the binding energies and inhibition constants of five K2P channel modulators (Hydroxychloroquine, Fluoxetine, DCPIB, ML365 and ML335) with TWIK2. Intracellular potassium ion concentration and mitochondrial function were assessed by flow cytometry. The interaction between MARCH5 and SIRT3 was demonstrated by immunoprecipitation and Western blotting assay. MSU suspensions were injected into mouse paw and peritoneal cavity to induce acute gout model.

RESULTS

ML335 has the highest binding energy and the lowest inhibition constant with TWIK2 in the five calculated K2P channel modulators. In comparison, among these five compounds, ML335 efficiently inhibited the release of IL-1β from MSU crystal-treated BMDMs. ML335 decreased MSU crystal-induced K+ efflux mainly dependent on TWIK2 channel. More importantly, ML335 can effectively inhibit the expression of the mitochondrial E3 ubiquitin ligase MARCH5 induced by MSU crystals, and MARCH5 can interact with the SIRT3 protein. ML335 blocked MSU crystal-induced ubiquitination of SIRT3 protein by MARCH5. In addition, ML335 improved mitochondrial dynamics homeostasis and mitochondrial function by inhibiting MARCH5 protein expression. ML335 attenuated the inflammatory response induced by MSU crystals in vivo and in vitro.

CONCLUSION

Inhibition of TWIK2-mediated K+ efflux by ML335 alleviated mitochondrial injury via suppressing March5 expression, suggesting that ML335 may be an effective candidate for the future treatment of gout.

MCU inhibition protects against intestinal ischemia‒reperfusion by inhibiting Drp1-dependent mitochondrial fission

Intestinal ischemia‒reperfusion (IIR) injury is a common complication of surgery, but clear molecular insights and valuable therapeutic targets are lacking. Mitochondrial calcium overload is an early sign of various diseases and is considered a vital factor in ischemia‒reperfusion injury. The mitochondrial calcium uniporter (MCU), which is located on the inner mitochondrial membrane, is the primary mediator of calcium ion entry into the mitochondria. However, the specific mechanism of MCU in IIR injury remains to be clarified. In this study, we generated an IIR model using C57BL/6 mice and Caco-2 cells and found increases in the calcium levels and MCU expression following IIR injury. The specific inhibition of MCU markedly attenuated IIR injury. Moreover, MCU knockdown alleviates mitochondrial dysfunction by reducing oxidative stress and apoptosis. Mechanistically, MCU knockdown substantially reduced the translocation of Drp1 and thus its binding to Fis1 receptors, resulting in decreased mitochondrial fission. Taken together, our findings demonstrated that MCU is a novel upstream regulator of Drp1 in ischemia‒reperfusion and represents a predictive and therapeutic target for IIR.

Role of dynamin-related protein 1-dependent mitochondrial fission in drug-induced toxicity

Dynamin-related protein 1 (DRP1) is an essential controller of mitochondrial fission whose activity is tightly controlled to ensure balanced mitochondrial dynamics and maintain internal cellular homeostasis. Growing evidence suggests that DRP1-dependent mitochondrial fission plays a role in drug-induced toxicity (DIT). Therefore, understanding the molecular mechanisms underlying DIT and the precise regulation of DRP1 function will inform the development of potential therapeutic treatments for DIT. This review comprehensively summarizes the diverse DITs and their potential mechanism associated with DRP1-dependent mitochondrial fission and discusses in vivo and in vitro model studies of toxicity protection targeting DRP1.

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.

Presenilin2 D439A Mutation Induces Dysfunction of Mitochondrial Fusion/Fission Dynamics and Abnormal Regulation of GTPase Activity

Alzheimer's disease (AD) is an age-related progressive neurodegenerative disease, and approximately 10% of AD cases are early-onset familial AD (EOFAD), which is mainly linked to point mutations in genes encoding presenilins (PS1 and PS2). Mutations in PS2 are extremely rare and have not received enough attention. Recently, studies have found that Rho GTPase activity is closely related to the pathogenesis of AD. In this study, we used transcriptome sequencing in PS2 siRNA-transfected SH-SY5Y cells and found a group of differentially expressed genes (DEGs) related to the regulation of GTPase activity. Among those DEGs, the most significantly downregulated was Rho guanine nucleotide exchange factor 5 (ARHGEF5). GTPase activity in PS2 siRNA-transfected cells was significantly decreased. Then, we found that the expression of ARHGEF5 and the GTPase activity of Mitochondrial Rho GTPase 2 (Miro2) in PS2 D439A mutant SH-SY5Y cells were significantly decreased. We found for the first time that PS2 can bind to Miro2, and the PS2 D439A mutation reduced the binding between PS2 and Miro2, reduced the expression of Miro2, and resulted in an imbalance in mitochondrial fusion/fission dynamics. In conclusion, PS2 gene knockdown may participate in the pathogenesis of AD through the regulation of GTPase activity. The imbalance in mitochondrial dynamics mediated by the PS2 D439A mutation through regulation of the expression and GTPase activity of Miro2 may be a potential pathogenic mechanism of AD.

Mitochondrial endogenous substance transport-inspired nanomaterials for mitochondria-targeted gene delivery

Mitochondrial genome (mtDNA) independent of nuclear gene is a set of double-stranded circular DNA that encodes 13 proteins, 2 ribosomal RNAs and 22 mitochondrial transfer RNAs, all of which play vital roles in functions as well as behaviors of mitochondria. Mutations in mtDNA result in various mitochondrial disorders without available cures. However, the manipulation of mtDNA via the mitochondria-targeted gene delivery faces formidable barriers, particularly owing to the mitochondrial double membrane. Given the fact that there are various transport channels on the mitochondrial membrane used to transfer a variety of endogenous substances to maintain the normal functions of mitochondria, mitochondrial endogenous substance transport-inspired nanomaterials have been proposed for mitochondria-targeted gene delivery. In this review, we summarize mitochondria-targeted gene delivery systems based on different mitochondrial endogenous substance transport pathways. These are categorized into mitochondrial steroid hormones import pathways-inspired nanomaterials, protein import pathways-inspired nanomaterials and other mitochondria-targeted gene delivery nanomaterials. We also review the applications and challenges involved in current mitochondrial gene editing systems. This review delves into the approaches of mitochondria-targeted gene delivery, providing details on the design of mitochondria-targeted delivery systems and the limitations regarding the various technologies. Despite the progress in this field is currently slow, the ongoing exploration of mitochondrial endogenous substance transport and mitochondrial biological phenomena may act as a crucial breakthrough in the targeted delivery of gene into mitochondria and even the manipulation of mtDNA.

A Systematic Review and Developmental Perspective on Origin of CMS Genes in Crops

Cytoplasmic male sterility (CMS) arises from the incompatibility between the nucleus and cytoplasm as typical representatives of the chimeric structures in the mitochondrial genome (mitogenome), which has been extensively applied for hybrid seed production in various crops. The frequent occurrence of chimeric mitochondrial genes leading to CMS is consistent with the mitochondrial DNA (mtDNA) evolution. The sequence conservation resulting from faithfully maternal inheritance and the chimeric structure caused by frequent sequence recombination have been defined as two major features of the mitogenome. However, when and how these chimeric mitochondrial genes appear in the context of the highly conserved reproduction of mitochondria is an enigma. This review, therefore, presents the critical view of the research on CMS in plants to elucidate the mechanisms of this phenomenon. Generally, distant hybridization is the main mechanism to generate an original CMS source in natural populations and in breeding. Mitochondria and mitogenomes show pleomorphic and dynamic changes at key stages of the life cycle. The promitochondria in dry seeds develop into fully functioning mitochondria during seed imbibition, followed by massive mitochondria or mitogenome fusion and fission in the germination stage along with changes in the mtDNA structure and quantity. The mitogenome stability is controlled by nuclear loci, such as the nuclear gene Msh1. Its suppression leads to the rearrangement of mtDNA and the production of heritable CMS genes. An abundant recombination of mtDNA is also often found in distant hybrids and somatic/cybrid hybrids. Since mtDNA recombination is ubiquitous in distant hybridization, we put forward a hypothesis that the original CMS genes originated from mtDNA recombination during the germination of the hybrid seeds produced from distant hybridizations to solve the nucleo-cytoplasmic incompatibility resulting from the allogenic nuclear genome during seed germination.

Hexokinase 1 forms rings that regulate mitochondrial fission during energy stress

Metabolic enzymes can adapt during energy stress, but the consequences of these adaptations remain understudied. Here, we discovered that hexokinase 1 (HK1), a key glycolytic enzyme, forms rings around mitochondria during energy stress. These HK1-rings constrict mitochondria at contact sites with the endoplasmic reticulum (ER) and mitochondrial dynamics protein (MiD51). HK1-rings prevent mitochondrial fission by displacing the dynamin-related protein 1 (Drp1) from mitochondrial fission factor (Mff) and mitochondrial fission 1 protein (Fis1). The disassembly of HK1-rings during energy restoration correlated with mitochondrial fission. Mechanistically, we identified that the lack of ATP and glucose-6-phosphate (G6P) promotes the formation of HK1-rings. Mutations that affect the formation of HK1-rings showed that HK1-rings rewire cellular metabolism toward increased TCA cycle activity. Our findings highlight that HK1 is an energy stress sensor that regulates the shape, connectivity, and metabolic activity of mitochondria. Thus, the formation of HK1-rings may affect mitochondrial function in energy-stress-related pathologies.

SETD3 is a mechanosensitive enzyme that methylates actin on His73 to regulate mitochondrial dynamics and function

Mitochondria, which act as sensors of metabolic homeostasis and metabolite signaling, form a dynamic intracellular network that continuously changes shape, size and localization to respond to localized cellular energy demands. Mitochondrial dynamics and function depend on interactions with the F-actin cytoskeleton that are poorly understood. Here, we show that SET domain protein 3 (SETD3), a recently described actin histidine methyltransferase, directly methylates actin at histidine-73 and enhances F-actin polymerization on mitochondria. SETD3 is a mechano-sensitive enzyme that is localized on the outer mitochondrial membrane and promotes actin polymerization around mitochondria. SETD3 loss of function leads to diminished F-actin around mitochondria and a decrease in mitochondrial branch length, branch number and mitochondrial movement. Our functional analysis revealed that SETD3 is required for oxidative phosphorylation, and mitochondrial complex I assembly and function. Our data further indicate that SETD3 regulates F-actin formation around mitochondria and is essential for maintaining mitochondrial morphology, movement and function. Finally, we discovered that SETD3 levels are regulated by extracellular matrix (ECM) stiffness and regulate mitochondrial shape in response to changes in ECM stiffness. These findings provide new insight into the mechanism for F-actin polymerization around mitochondria.

An aggregated mitochondrial distribution in preimplantation embryos disrupts nuclear morphology, function, and developmental potential

A dispersed cytoplasmic distribution of mitochondria is a hallmark of normal cellular organization. Here, we have utilized the expression of exogenous Trak2 in mouse oocytes and embryos to disrupt the dispersed distribution of mitochondria by driving them into a large cytoplasmic aggregate. Our findings reveal that aggregated mitochondria have minimal impact on asymmetric meiotic cell divisions of the oocyte. In contrast, aggregated mitochondria during the first mitotic division result in daughter cells with unequal sizes and increased micronuclei. Further, in two-cell embryos, microtubule-mediated centering properties of the mitochondrial aggregate prevent nuclear centration, distort nuclear shape, and inhibit DNA synthesis and the onset of embryonic transcription. These findings demonstrate the motor protein-mediated distribution of mitochondria throughout the cytoplasm is highly regulated and is an essential feature of cytoplasmic organization to ensure optimal cell function.

Development and Application of Cationic Nile Blue Probes in Live-Cell Super-Resolution Imaging and Specific Targeting to Mitochondria

Mitochondria are essential organelles involved in various metabolic processes in eukaryotes. The imaging, targeting, and investigation of cell death mechanisms related to mitochondria have garnered significant interest. Small-molecule fluorescent probes have proven to be robust tools for utilizing light to advance the study of mitochondrial biology. In this study, we present the rational design of cationic Nile blue probes carrying a permanent positive charge for these purposes. The cationic Nile blue probes exhibit excellent mitochondrial permeability, unique solvatochromism, and resistance to oxidation. We observed weaker fluorescence in aqueous solutions compared to lipophilic solvents, thereby minimizing background fluorescence in the cytoplasm. Additionally, we achieved photoredox switching of the cationic Nile blue probes under mild conditions. This enabled us to demonstrate their application for the first time in single-molecule localization microscopy of mitochondria, allowing us to observe mitochondrial fission and fusion behaviors. Compared to conventional cyanine fluorophores, this class of dyes demonstrated prolonged resistance to photobleaching, likely due to their antioxidation properties. Furthermore, we extended the application of cationic Nile blue probes to the mitochondria-specific delivery of taxanes, facilitating the study of direct interactions between the drug and organelles. Our approach to triggering cell death without reliance on microtubule binding provides valuable insights into anticancer drug research and drug-resistance mechanisms.

Reconstituting membrane fission using a high content and throughput assay

Protein-mediated membrane fission has been analyzed both in bulk and at the single event resolution. Studies on membrane fission in vitro using tethers have provided fundamental insights into the process but are low in throughput. In recent years, supported membrane template (SMrT) have emerged as a facile and convenient assay system for membrane fission. SMrTs provide useful information on intermediates in the pathway to fission and are therefore high in content. They are also high in throughput because numerous fission events can be monitored in a single experiment. This review discusses the utility of SMrTs in providing insights into fission pathways and its adaptation to annotate membrane fission functions in proteins.

Systemic phospho-defective and phospho-mimetic Drp1 mice exhibit normal growth and development with altered anxiety-like behavior

Mitochondrial division controls the size, distribution, and turnover of this essential organelle. A dynamin-related GTPase, Drp1, drives membrane division as a force-generating mechano-chemical enzyme. Drp1 is regulated by multiple mechanisms, including phosphorylation at two primary sites: serine 579 and serine 600. While previous studies in cell culture systems have shown that Drp1 S579 phosphorylation promotes mitochondrial division, its physiological functions remained unclear. Here, we generated phospho-mimetic Drp1 S579D and phospho-defective Drp1 S579R mice using the CRISPR-Cas system. Both mouse models exhibited normal growth, development, and breeding. We found that Drp1 is highly phosphorylated at S579 in brain neurons. Notably, the Drp1 S579D mice showed decreased anxiety-like behaviors, whereas the Drp1 S579R mice displayed increased anxiety-like behaviors. These findings suggest a critical role for Drp1 S579 phosphorylation in brain function. The Drp1 S579D and S579R mice thus offer valuable in vivo models for specific analysis of Drp1 S579 phosphorylation.

Research progress on the role of mitochondria in the process of hepatic ischemia-reperfusion injury

During liver ischemia-reperfusion injury, existing mechanisms involved oxidative stress, calcium overload, and the activation of inflammatory responses involve mitochondrial injury. Mitochondrial autophagy, a process that maintains the normal physiological activity of mitochondria, promotes cellular metabolism, improves cellular function, and facilitates organelle renewal. Mitochondrial autophagy is involved in oxidative stress and apoptosis, of which the PINK1-Parkin pathway is a major regulatory pathway, and the deletion of PINK1 and Parkin increases mitochondrial damage, reactive oxygen species production, and inflammatory response, playing an important role in mitochondrial quality regulation. In addition, proper mitochondrial permeability translational cycle regulation can help maintain mitochondrial stability and mitigate hepatocyte death during ischemia-reperfusion injury. This mechanism is also closely related to oxidative stress, calcium overload, and the aforementioned autophagy pathway, all of which leads to the augmentation of the mitochondrial membrane permeability transition pore opening and cause apoptosis. Moreover, the release of mitochondrial DNA (mtDNA) due to oxidative stress further aggravates mitochondrial function impairment. Mitochondrial fission and fusion are non-negligible processes required to maintain the dynamic renewal of mitochondria and are essential to the dynamic stability of these organelles. The Bcl-2 protein family also plays an important regulatory role in the mitochondrial apoptosis signaling pathway. A series of complex mechanisms work together to cause hepatic ischemia-reperfusion injury (HIRI). This article reviews the role of mitochondria in HIRI, hoping to provide new therapeutic clues for alleviating HIRI in clinical practice.

Hydrogen alleviates impaired lung epithelial barrier in acute respiratory distress syndrome via inhibiting Drp1-mediated mitochondrial fission through the Trx1 pathway

Acute respiratory distress syndrome (ARDS) is an acute and severe clinical complication lacking effective therapeutic interventions. The disruption of the lung epithelial barrier plays a crucial role in ARDS pathogenesis. Recent studies have proposed the involvement of abnormal mitochondrial dynamics mediated by dynamin-related protein 1 (Drp1) in the mechanism of impaired epithelial barrier in ARDS. Hydrogen is an anti-oxidative stress molecule that regulates mitochondrial function via multiple signaling pathways. Our previous study confirmed that hydrogen modulated oxidative stress and attenuated acute pulmonary edema in ARDS by upregulating thioredoxin 1 (Trx1) expression, but the exact mechanism remains unclear. This study aimed to investigate the effects of hydrogen on mitochondrial dynamics both in vivo and in vitro. Our study revealed that hydrogen inhibited lipopolysaccharide (LPS)-induced phosphorylation of Drp1 (at Ser616), suppressed Drp1-mediated mitochondrial fission, alleviated epithelial tight junction damage and cell apoptosis, and improved the integrity of the epithelial barrier. This process was associated with the upregulation of Trx1 in lung epithelial tissues of ARDS mice by hydrogen. In addition, hydrogen treatment reduced the production of reactive oxygen species in LPS-induced airway epithelial cells (AECs) and increased the mitochondrial membrane potential, indicating that the mitochondrial dysfunction was restored. Then, the expression of tight junction proteins occludin and zonula occludens 1 was upregulated, and apoptosis in AECs was alleviated. Remarkably, the protective effects of hydrogen on the mitochondrial and epithelial barrier were eliminated after applying the Trx1 inhibitor PX-12. The results showed that hydrogen significantly inhibited the cell apoptosis and the disruption of epithelial tight junctions, maintaining the integrity of the epithelial barrier in mice of ARDS. This might be related to the inhibition of Drp1-mediated mitochondrial fission through the Trx1 pathway. The findings of this study provided a new theoretical basis for the application of hydrogen in the clinical treatment of ARDS.

Super-resolution microscopies, technological breakthrough to decipher mitochondrial structure and dynamic

Mitochondria are complex organelles with an outer membrane enveloping a second inner membrane that creates a vast matrix space partitioned by pockets or cristae that join the peripheral inner membrane with several thin junctions. Several micrometres long, mitochondria are generally close to 300 nm in diameter, with membrane layers separated by a few tens of nanometres. Ultrastructural data from electron microscopy revealed the structure of these mitochondria, while conventional optical microscopy revealed their extraordinary dynamics through fusion, fission, and migration processes but its limited resolution power restricted the possibility to go further. By overcoming the limits of light diffraction, Super-Resolution Microscopy (SRM) now offers the potential to establish the links between the ultrastructure and remodelling of mitochondrial membranes, leading to major advances in our understanding of mitochondria's structure-function. Here we review the contributions of SRM imaging to our understanding of the relationship between mitochondrial structure and function. What are the hopes for these new imaging approaches which are particularly important for mitochondrial pathologies?

Transcriptomic analysis reveals molecular characterization and immune landscape of PANoptosis-related genes in atherosclerosis

BACKGROUND

Atherosclerosis is a chronic inflammatory disease characterized by abnormal lipid deposition in the arteries. Programmed cell death is involved in the inflammatory response of atherosclerosis, but PANoptosis, as a new form of programmed cell death, is still unclear in atherosclerosis. This study explored the key PANoptosis-related genes involved in atherosclerosis and their potential mechanisms through bioinformatics analysis.

METHODS

We evaluated differentially expressed genes (DEGs) and immune infiltration landscape in atherosclerosis using microarray datasets and bioinformatics analysis. By intersecting PANoptosis-related genes from the GeneCards database with DEGs, we obtained a set of PANoptosis-related genes in atherosclerosis (PANoDEGs). Functional enrichment analysis of PANoDEGs was performed and protein-protein interaction (PPI) network of PANoDEGs was established. The machine learning algorithms were used to identify the key PANoDEGs closely linked to atherosclerosis. Receiver operating characteristic (ROC) analysis was used to assess the diagnostic potency of key PANoDEGs. CIBERSORT was used to analyze the immune infiltration patterns in atherosclerosis, and the Spearman method was used to study the relationship between key PANoDEGs and immune infiltration abundance. The single gene enrichment analysis of key PANoDEGs was investigated by GSEA. The transcription factors and target miRNAs of key PANoDEGs were predicted by Cytoscape and online database, respectively. The expression of key PANoDEGs was validated through animal and cell experiments.

RESULTS

PANoDEGs in atherosclerosis were significantly enriched in apoptotic process, pyroptosis, necroptosis, cytosolic DNA-sensing pathway, NOD-like receptor signaling pathway, lipid and atherosclerosis. Four key PANoDEGs (ZBP1, SNHG6, DNM1L, and AIM2) were found to be closely related to atherosclerosis. The ROC curve analysis demonstrated that the key PANoDEGs had a strong diagnostic potential in distinguishing atherosclerotic samples from control samples. Immune cell infiltration analysis revealed that the proportion of initial B cells, plasma cells, CD4 memory resting T cells, and M1 macrophages was significantly higher in atherosclerotic tissues compared to normal tissues. Spearman analysis showed that key PANoDEGs showed strong correlations with immune cells such as T cells, macrophages, plasma cells, and mast cells. The regulatory networks of the four key PANoDEGs were established. The expression of key PANoDEGs was verified in further cell and animal experiments.

CONCLUSIONS

This study evaluated the expression changes of PANoptosis-related genes in atherosclerosis, providing a reference direction for the study of PANoptosis in atherosclerosis and offering potential new avenues for further understanding the pathogenesis and treatment strategies of atherosclerosis.