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Mitochondria are the major cellular energy‐producing organelles and intracellular source of reactive oxygen species. These organelles are responsible for driving cell life and death through mitochondrial network structure homeostasis, which is determined by a balance of fission and fusion. Recent advances revealed that a number of components of the fission and fusion machinery, including dynamin‐related protein 1 (Drp1), mitofusin1/2 (Mfn1/2) and Optic atrophy 1 (OPA1), that have been implicated in mitochondrial shape changes are indispensible for autophagy, apoptosis and necroptosis. Drp1 is the main regulator of mitochondrial fission and has become a key point of contention. The controversy focuses on whether Drp1 is directly involved in the regulation of cell death and, if involved, whether is it a stimulator or a negative regulator of cell death. Here, we examine the relevance of the homeostasis of the mitochondrial network structure in 3 different types of cell death, including autophagy, apoptosis and necroptosis. Furthermore, a variety of cancers often exhibit a fragmented mitochondrial phenotype. Thus, the fragmented ratio can reflect tumor progression that predicts prognosis and therapeutic response. In addition, we investigate whether the targeting of the mitochondrial fission protein Drp1 could be a novel therapeutic approach. Here, we examine the relevance of the homeostasis of the mitochondrial network structure in 3 different types of cell death, including autophagy, apoptosis and necroptosis. Furthermore, a variety of cancers often exhibit a fragmented mitochondrial phenotype. Targeting the mitochondrial fission protein Drp1or other shaping proteins is becoming a topic of interest. Further studies are needed to understand the differential effects of oncogenic signaling pathways on mitochondrial dynamics and to identify additional new signaling axes that regulate mitochondrial network structure homeostasis.

Objectives High‐mobility group box‐1 (HMGB1) and aberrant mitochondrial fission mediated by excessive activation of GTPase dynamin‐related protein 1 (Drp1) have been found to be elevated in patients with pulmonary arterial hypertension (PAH) and critically implicated in PAH pathogenesis. However, it remains unknown whether Drp1‐mediated mitochondrial fission and which downstream targets of mitochondrial fission mediate HMGB1‐induced pulmonary arterial smooth muscle cells (PASMCs) proliferation and migration leading to vascular remodelling in PAH. This study aims to address these issues. Methods Primary cultured PASMCs were obtained from male Sprague‐Dawley (SD) rats. We detected RNA levels by qRT‐PCR, protein levels by Western blotting, cell proliferation by Cell Counting Kit‐8 (CCK‐8) and EdU incorporation assays, migration by wound healing and transwell assays. SD rats were injected with monocrotaline (MCT) to establish PAH. Hemodynamic parameters were measured by closed‐chest right heart catheterization. Results HMGB1 increased Drp1 phosphorylation and Drp1‐dependent mitochondrial fragmentation through extracellular signal‐regulated kinases 1/2 (ERK1/2) signalling activation, and subsequently triggered autophagy activation, which further led to bone morphogenetic protein receptor 2 (BMPR2) lysosomal degradation and inhibitor of DNA binding 1 (Id1) downregulation, and eventually promoted PASMCs proliferation/migration. Inhibition of ERK1/2 cascade, knockdown of Drp1 or suppression of autophagy restored HMGB1‐induced reductions of BMPR2 and Id1, and diminished HMGB1‐induced PASMCs proliferation/migration. In addition, pharmacological inhibition of HMGB1 by glycyrrhizin, suppression of mitochondrial fission by Mdivi‐1 or blockage of autophagy by chloroquine prevented PAH development in MCT‐induced rats PAH model. Conclusions HMGB1 promotes PASMCs proliferation/migration and pulmonary vascular remodelling by activating ERK1/2/Drp1/Autophagy/BMPR2/Id1 axis, suggesting that this cascade might be a potential novel target for management of PAH. The molecular mechanisms underlying HMGB1‐induced pulmonary vascular remodelling in PAH. HMGB1 increases Drp1 phosphorylation and Drp1‐dependent mitochondrial fission through activation of ERK1/2 signaling pathway, and subsequently stimulates autophagy activation, which further lead to BMPR2 lysosomal degradation and Id1 downregulation, and ultimately promotes PASMCs proliferation/migration and pulmonary vascular remodeling in PAH.

Bioenergetic failure and oxidative stress are common pathological hallmarks of amyotrophic lateral sclerosis (ALS), but whether these could be targeted effectively for novel therapeutic intervention needs to be determined. One of the reported contributors to ALS pathology is mitochondrial dysfunction associated with excessive mitochondrial fission and fragmentation, which is predominantly mediated by Drp1 hyperactivation. Here, we determined whether inhibition of excessive fission by inhibiting Drp1/Fis1 interaction affects disease progression. We observed mitochondrial excessive fragmentation and dysfunction in several familial forms of ALS patient‐derived fibroblasts as well as in cultured motor neurons expressing SOD1 mutant. In both cell models, inhibition of Drp1/Fis1 interaction by a selective peptide inhibitor, P110, led to a significant reduction in reactive oxygen species levels, and to improvement in mitochondrial structure and functions. Sustained treatment of mice expressing G93A SOD1 mutation with P110, beginning at the onset of disease symptoms at day 90, produced an improvement in motor performance and survival, suggesting that Drp1 hyperactivation may be an attractive target in the treatment of ALS patients. Synopsis Drp1 hyperactivation has been associated with neurodegenerative diseases, like amyotrophic lateral sclerosis (ALS). P110, an inhibitor of the mitochondrial fission protein Drp1, is shown to reduce the detrimental effects of mitochondrial dysfunction and ameliorate symptoms in an ALS mouse model. P110 suppresses mitochondrial dysfunction in patient‐derived fibroblasts, SOD1 G93A NSC‐34 cells and in ALS model mice. P110 reduces muscular mitochondrial pathology and oxidative stress in ALS model mice. P110 enhances motor activity in ALS model mice. Drugs that improve mitochondrial function, such as P110, may provide benefits for patients with motor neuron diseases that show mitochondrial defects. Graphical Abstract Drp1 hyperactivation has been associated with neurodegenerative diseases, like amyotrophic lateral sclerosis (ALS). P110, an inhibitor of the mitochondrial fission protein Drp1, is shown to reduce the detrimental effects of mitochondrial dysfunction and ameliorate symptoms in an ALS mouse model.

Mitochondrial fission plays a role in cardiovascular calcification. Melatonin has previously been shown to protect against cardiovascular disease, so this study sought to explore whether it attenuates vascular calcification by regulating mitochondrial fission via the AMP‐activated protein kinase/dynamin‐related protein 1 (AMPK/Drp1) signalling pathway. The effects of melatonin on vascular calcification were investigated in vascular smooth muscle cells (VSMCs). Calcium deposits were visualized by Alizarin red staining, while calcium content and alkaline phosphatase (ALP) activity were used to evaluate osteogenic differentiation. Western blots were used to measure the expression of runt‐related transcription factor 2 (Runx2), Drp1 and cleaved caspase 3. Melatonin markedly reduced calcium deposition and ALP activity. Runx2 and cleaved caspase 3 were down‐regulated, Drp1 was reduced in response to melatonin, and this was accompanied by decreased apoptosis. Melatonin also reduced levels of mitochondrial superoxide, reversed β‐glycerophosphate (β‐GP)‐induced ΔΨm dissipation and decreased mitochondrial fragmentation. The effects of melatonin in β‐GP‐treated VSMCs were similar to those of mitochondrial division inhibitor 1. Melatonin significantly activated the expression of AMPK and decreased Drp1 expression. Treatment with compound C ablated the observed benefits of melatonin treatment. These findings indicate that melatonin protects VSMCs against calcification by inhibiting mitochondrial fission via the AMPK/Drp1 pathway.

Opposing mitochondrial fission and fusion reactions determine the shape and interconnectivity of mitochondria. Dynamin‐related protein 1 (Drp1) is an ancient mechanoenzyme that uses GTP hydrolysis to power the constriction and division of mitochondria. Although Drp1‐mediated mitochondrial fragmentation is recognized as an early event in the apoptotic programme, acute regulation of Drp1 activity is poorly understood. Here, we identify a crucial phosphorylation site that is conserved in all metazoan Drp1 orthologues. Ser 656 is phosphorylated by cyclic AMP‐dependent protein kinase and dephosphorylated by calcineurin, and its phosphorylation state is controlled by sympathetic tone, calcium levels and cell viability. Pseudophosphorylation of Drp1 by mutation of Ser 656 to aspartic acid leads to the elongation of mitochondria and confers resistance to various pro‐apoptotic insults. Conversely, the constitutively dephosphorylated Ser656Ala mutant Drp1 promotes mitochondrial fragmentation and increases cell vulnerability. Thus, Drp1 phosphorylation at Ser 656 provides a mechanism for the integration of cAMP and calcium signals in the control of mitochondrial shape, apoptosis and other aspects of mitochondrial function.

Despite extensive progress in the knowledge and understanding of cardiovascular diseases and significant advances in pharmacological treatments and procedural interventions, cardiovascular diseases (CVD) remain the leading cause of death globally. Mitochondrial dynamics refers to the repetitive cycle of fission and fusion of the mitochondrial network. Fission and fusion balance regulate mitochondrial shape and influence physiology, quality and homeostasis. Mitophagy is a process that eliminates aberrant mitochondria. Melatonin (Mel) is a pineal‐synthesized hormone with a range of pharmacological properties. Numerous nonclinical trials have demonstrated that Mel provides cardioprotection against ischemia/reperfusion, cardiomyopathies, atherosclerosis and cardiotoxicity. Recently, interest has grown in how mitochondrial dynamics contribute to melatonin cardioprotective effects. This review assesses the literature on the protective effects of Mel against CVD via the regulation of mitochondrial dynamics and mitophagy in both in‐vivo and in‐vitro studies. The signalling pathways underlying its cardioprotective effects were reviewed. Mel modulated mitochondrial dynamics and mitophagy proteins by upregulation of mitofusin, inhibition of DRP1 and regulation of mitophagy‐related proteins. The evidence supports a significant role of Mel in mitochondrial dynamics and mitophagy quality control in CVD.

[Cu(ttpy‐tpp)Br2]Br (abbreviated as CTB) is a novel mitochondrion‐targeting copper(II) complex synthesized by our research group, which contains tri‐phenyl‐phosphonium (TPP) groups as its lipophilic property. In this study, we explored how CTB affects mitochondrial functions and exerts its anti‐tumour activity. Multiple functional and molecular analyses including Seahorse XF Bioanalyzer Platform, Western blot, immunofluorescence analysis, co‐immunoprecipitation and transmission electron microscopy were used to elucidate the underlying mechanisms. Human hepatoma cells were subcutaneously injected into right armpit of male nude mice for evaluating the effects of CTB in vivo. We discovered that CTB inhibited aerobic glycolysis and cell acidification by impairing the activity of HK2 in hepatoma cells, accompanied by dissociation of HK2 from mitochondria. The modification of HK2 not only led to the complete dissipation of mitochondrial membrane potential (MMP) but also promoted the opening of mitochondrial permeability transition pore (mPTP), contributing to the activation of mitophagy. In addition, CTB co‐ordinately promoted dynamin‐related protein 1 (Drp1) recruitment in mitochondria to induce mitochondrial fission. Our findings established a previously unrecognized role for copper complex in aerobic glycolysis of tumour cells, revealing the interaction between mitochondrial HK2‐mediated mitophagy and Drp1‐regulated mitochondrial fission.

Introduction Skin is susceptible to senescence‐associated secretory phenotype (SASP) and inflamm‐ageing partly owing to the degeneration of mitochondria. AdipoRon (AR) has protective effects on mitochondria in metabolic diseases such as diabetes. We explored the role of AR on mitochondria damage induced by skin inflamm‐ageing and its underlying mechanism. Methods Western blot, immunofluorescence and TUNEL staining were used to detect inflammatory factors and apoptosis during skin ageing. Transmission electron microscopy, ATP determination kit, CellLight Mitochondria GFP (Mito‐GFP), mitochondrial stress test, MitoSOX and JC‐1 staining were used to detect mitochondrial changes. Western blot was applied to explore the underlying mechanism. Flow cytometry, scratch test, Sulforhodamine B assay and wound healing test were used to detect the effects of AR on cell apoptosis, migration and proliferation. Results AR attenuated inflammatory factors and apoptosis that increased in aged skin, and improved mitochondrial morphology and function. This process at least partly depended on the suppression of dynamin‐related protein 1 (Drp1)‐mediated excessive mitochondrial division. More specifically, AR up‐regulated the phosphorylation of Drp1 at Serine 637 by activating AMP‐activated protein kinase (AMPK), thereby inhibiting the mitochondrial translocation of Drp1. Moreover, AR reduced mitochondrial fragmentation and the production of superoxide, preserved the membrane potential and permeability of mitochondria and accelerated wound healing in aged skin. Conclusion AR rescues the mitochondria in aged skin by suppressing its excessive division mediated by Drp1. AdipoRon can effectively activate the AMPK pathway and reverse the down‐regulation of the phosphorylation level of Drp1 at serine 637 in epidermal stem cells (ESCs) under the inflammatory environment, thus attenuate excessive mitochondrial translocation of Drp1. The repression of the mitochondrial fragments by AdipoRon protected the morphology and function of mitochondria under inflammation, thus contributed to an alleviated ROS and inflammation levels, and ultimately improved proliferation and migration of ESCs and wound healing in aged skin.

Mitochondrial dysfunction contributes to various inflammatory‐related diseases by triggering the release of inflammatory molecules. Targeting mitochondrial dysfunction is emerging as a promising avenue for treating inflammatory diseases. Here, it is demonstrated that dietary plant‐derived mitochondria (P‐Mit) are capable of rescuing the lung macrophage mitochondrial (M‐Mit) dysfunction in lipopolysaccharide (LPS)‐induced mouse acute lung injury (ALI). Specifically, oral administration of dietary onion‐derived mitochondria (O‐Mit) can travel from the gut to the lungs in ALI mice, where preferentially uptake by lung macrophage mediated by the interaction between O‐Mit phosphatic acid (PA) and macrophage complement C3b/C4b receptor 1 Like (CR1L), followed by fusing with murine M‐Mit and by reprograming the M‐Mit energy metabolism in the lungs of ALI mice. Further evidence suggests that O‐Mit enriches methyl 3,4‐dihydroxybenzoate (MDHB) inhibits M‐Mit NADH dehydrogenase subunit 1 (ND1) gene expression in the epigenetic process, which represses LPS‐induced complex I‐related oxidative stress activation and excessive mitochondrial fission via modulating dynamin‐related protein 1 (DRP1) phosphorylation and cardiolipin peroxidation in M‐Mit, eventually rescues the LPS‐induced ALI. Given LPS‐induced mouse model of ALI is widely used to study human ALI and acute respiratory distress syndrome, this finding provides a clinical potential for the treatment of human ALI via edible P‐Mit. Proposed model of orally administered onion mitochondria (O‐Mit) uptake by lung macrophages and fuse with macrophage mitochondria (M‐Mit). This fusion reprograms the metabolism of dysfunctional M‐Mit in lipopolysaccharide‐induced murine acute lung injury by modulating dynamin‐related protein 1 (DRP1) phosphorylation and cardiolipin peroxidation, thereby alleviating lung inflammation. These findings reveal a previously unexplored strategy using plant mitochondria in mitochondrial transfer therapy.

Peroxisomes are highly dynamic and responsive organelles, which can adjust their morphology, number, intracellular position, and metabolic functions according to cellular needs. Peroxisome multiplication in mammalian cells involves the concerted action of the membrane-shaping protein PEX11β and division proteins, such as the membrane adaptors FIS1 and MFF, which recruit the fission GTPase DRP1 to the peroxisomal membrane. The latter proteins are also involved in mitochondrial division. Patients with loss of DRP1, MFF or PEX11β function have been identified, showing abnormalities in peroxisomal (and, for the shared proteins, mitochondrial) dynamics as well as developmental and neurological defects, whereas the metabolic functions of the organelles are often unaffected. Here, we provide a timely update on peroxisomal membrane dynamics with a particular focus on peroxisome formation by membrane growth and division. We address the function of PEX11β in these processes, as well as the role of peroxisome–ER contacts in lipid transfer for peroxisomal membrane expansion. Furthermore, we summarize the clinical phenotypes and pathophysiology of patients with defects in the key division proteins DRP1, MFF, and PEX11β as well as in the peroxisome–ER tether ACBD5. Potential therapeutic strategies for these rare disorders with limited treatment options are discussed.