Calcium Transport and Signaling in Mitochondria

ZLN005, a PGC-1α agonist, delays photoreceptor degeneration by enhancing mitochondrial biogenesis in a murine model of retinitis pigmentosa

Retinitis pigmentosa (RP) is a hereditary neurodegenerative disease characterized by the degeneration of photoreceptors caused by mutations in various genes. Increasing evidence suggests that mitochondrial biogenesis plays a critical role in many neurodegenerative diseases. This study investigated the role of mitochondrial biogenesis in rd1 mice, a widely recognized model of RP. Male C57BL/6 mice and age-matched rd1 mice were used for in vivo experiments, while H2O2 was employed on 661w cells to establish an in vitro model. Our findings revealed that mitochondrial biogenesis and the regulatory PGC-1α/NRF-1/TFAM pathway were significantly downregulated in rd1 mice. Treatment with ZLN005, a PGC-1α agonist, markedly improved visual function in rd1 mice and alleviated thinning of the retinal outer nuclear layer. Additionally, ZLN005 enhanced mitochondrial biogenesis and restored mitochondrial function in photoreceptors. Further analysis in vitro confirmed that ZLN005 rescued photoreceptor degeneration by promoting mitochondrial biogenesis through the PGC-1α/NRF-1/TFAM pathway. In summary, our results highlight the critical role of mitochondrial biogenesis and the PGC-1α/NRF-1/TFAM pathway in the progression of RP. This offers a potential strategy to delay photoreceptor degeneration in RP by maintaining mitochondrial function and could be combined with existing therapies for improving treatment outcomes through synergistic pathways.

Silica Nanoparticles Induce SH-SY5Y Cells Death Via PARP and Caspase Signaling Pathways

A growing stream of research indicates that exposure to Silica nanoparticles (SiNPs) can cause nervous system damage, leading to the occurrence of neurodegenerative diseases such as Alzheimer's disease. However, the specific mechanism by which SiNPs cause neuroblast injury remains unclear and requires further research. This study established an in vitro experimental model of SH-SY5Y cells exposed to SiNPs and observed cell growth through an inverted fluorescence microscope. Cell viability was measured using an MTT assay. The intracellular ROS and Ca2+ levels were detected by flow cytometry. Cell apoptosis was observed using both Hoechst33342 staining and TUNEL staining. The activities of SOD and ATPase and the content of ATP in the cells were tested by biochemical methods. The genes including parp-1, aif, par, ucp2, vdac and prdx3 were explored using quantitative real-time PCR. The expressions of PARP, AIF, PAR, Caspase-3, Caspase-9 and Cyt C proteins were evaluated by Western Blot. The immunofluorescence technique was used to observe the distribution of Parthanatos-related proteins induced by SiNPs. The results showed that SiNPs reduced cell survival rate, induced excessive ROS and Ca2+ overload, decreased SOD activity, ATPase activity, intracellular and mitochondrial ATP content, increased the expression of mitochondrial function and PARP pathway related genes, as well as PARP and Caspase pathway protein expression, ultimately inducing cell apoptosis. As a further test of the roles of PARP and Caspase pathways in SiNPs induced SH-SY5Y cells death, we selected the PARP inhibitor Olaparib and Caspase inhibitor Z-VAD, and the above effects were significantly improved after treatment with the inhibitors. Conclusively, this study confirmed that SiNPs can generate excessive ROS production in SH-SY5Y cells, alter mitochondrial function, and induce cell death through Parthanatos and caspase dependent apoptotic pathways, which can coexist and interact with each other.

TAB2 deficiency induces dilated cardiomyopathy by promoting mitochondrial calcium overload in human iPSC-derived cardiomyocytes

BACKGROUND

TGF-β-activated kinase 1 binding protein 2 (TAB2) is an intermediary protein that links Tumor necrosis factor receptor 1 (TNFR1) and other receptor signals to the TGF-β-activated kinase 1 (TAK1) signaling complex. TAB2 frameshift mutations have been linked to dilated cardiomyopathy (DCM), while the exact mechanism needs further investigation.

METHODS

In this study, we generated a TAB2 compound heterozygous knockout cell line in induced pluripotent stem cells (iPSCs) derived from a healthy individual using CRISPR/Cas9 technology. IPSCs are not species-dependent, are readily accessible, and raise fewer ethical concerns.

RESULTS

TAB2 disruption had no impact on the cardiac differentiation of iPSCs and led to confirmed TAB2 deficiency in human iPSC-derived cardiomyocytes (hiPSC-CMs). TAB2-deficient hiPSC-CMs were found to develop phenotypic features of DCM, such as distorted sarcomeric ultrastructure, decreased contractility and energy production, and mitochondrial damage at day 30 post differentiation. Paradoxically, TAB2 knockout cell lines showed abnormal calcium handling after 40 days, later than reduced contractility, suggesting that the main cause of impaired contractility was abnormal energy production due to mitochondrial damage. As early as day 25, TAB2 knockout cardiomyocytes showed significant mitochondrial calcium overload, which can lead to mitochondrial damage. Furthermore, TAB2 knockout activated receptor-interacting protein kinase 1 (RIPK1), leading to an increase in mitochondrial calcium uniporter (MCU) expression, thereby augmenting the uptake of mitochondrial calcium ions. Finally, the application of the RIPK1 inhibitor Nec-1s prevents the progression of these phenotypes.

CONCLUSIONS

In summary, TAB2 abatement cardiomyocytes mimic dilated cardiomyopathy in vitro. This finding emphasizes the importance of using a human model to study the underlying mechanisms of this specific disease. More importantly, the discovery of a unique pathogenic pathway introduces a new notion for the future management of dilated cardiomyopathy.

Mitochondria-Targeted Biomaterials-Regulating Macrophage Polarization Opens New Perspectives for Disease Treatment

Macrophage immunotherapy is an emerging therapeutic approach designed for modulating the immune response to alleviate disease symptoms. The balance between pro-inflammatory and anti-inflammatory macrophages plays a pivotal role in the progression of inflammatory diseases. Mitochondria, often referred to as the "power plants" of the cell, are essential organelles responsible for critical functions such as energy metabolism, material synthesis, and signal transduction. The functional state of mitochondria is closely linked to macrophage polarization, prompting interest in therapeutic strategies that target mitochondria to regulate this process. To this end, biomaterials with excellent targeting capabilities and effective therapeutic properties have been developed to influence mitochondrial function and regulate macrophage polarization. However, a comprehensive summary of biomaterial-driven modulation of mitochondrial function to control macrophage phenotypes is still lacking. This review highlights the critical role of mitochondrial function in macrophage polarization and discusses therapeutic strategies mediated by biomaterials, including mitochondria-targeted biomaterials. Finally, the prospects and challenges of the use of these biomaterials in disease modulation have been explored, emphasizing their potential to be translated to the clinic. It is anticipated that this review will serve as a valuable resource for materials scientists and clinicians in the development of next-generation mitochondria-targeted biomaterials.

Mitochondria and its epigenetic dynamics: Insight into synaptic regulation and synaptopathies

Mitochondria, the cellular powerhouses, are pivotal to neuronal function and health, particularly through their role in regulating synaptic structure and function. Spine reprogramming, which underlies synapse development, depends heavily on mitochondrial dynamics-such as biogenesis, fission, fusion, and mitophagy as well as functions including ATP production, calcium (Ca2+) regulation, and retrograde signaling. Mitochondria supply the energy necessary for assisting synapse development and plasticity, while also regulating intracellular Ca2+ homeostasis to prevent excitotoxicity and support synaptic neurotransmission. Additionally, the dynamic processes of mitochondria ensure mitochondrial quality and adaptability, which are essential for maintaining effective synaptic activity. Emerging evidence highlights the significant role of epigenetic modifications in regulating mitochondrial dynamics and function. Epigenetic changes influence gene expression, which in turn affects mitochondrial activity, ensuring coordinated responses necessary for synapse development. Furthermore, metabolic changes within mitochondria can impact the epigenetic machinery, thereby modulating gene expression patterns that support synaptic integrity. Altered epigenetic regulation affecting mitochondrial dynamics and functions is linked to several neurological disorders, including Amyotrophic Lateral Sclerosis, Huntington's, Alzheimer's, and Parkinson's diseases, emphasizing its crucial function. The review delves into the molecular machinery involved in mitochondrial dynamics, ATP and Ca2+ regulation, highlighting the role of key proteins that facilitate the processes. Additionally, it also shed light on the emerging epigenetic factors influencing these regulations. It provides a thorough summary on the current understanding of the role of mitochondria in synapse development and emphasizes the importance of both molecular and epigenetic mechanisms in maintaining synaptic integrity.

β-asarone relieves Parkinson's disease through reducing intracellular Ca2+ in PINK1 mutant Drosophila melanogaster

β-asarone, an effective volatile oil component of Acorus chinensis, has been found to hold beneficial effects on Parkinson's disease (PD), but its mechanism remains incompletely understood. Drosophila melanogaster with PTEN induced kinase 1 (PINK1) mutations, a prototype PD model, was used in this study. We found that calcium chelation profoundly alleviated a spectrum of PD symptoms. Whereas, calcium supplementation made the case worse, suggesting accumulated calcium contributes to progression of PD. β-asarone administration decreased Ca2+ level in PD flies, accompanied by alleviated behavioral and neural defects. Further study demonstrated that β-asarone downregulated L-type Ca2+ channels (Dmca1D), which was increased in PD flies. Besides, β-asarone decreased expression of 1,4,5 - trisphosphate receptor (Itpr), which is responsible for calcium release from endoplasmic reticulum (ER). Knockdown of either Dmca1D or Itpr specifically in dopaminergic neurons alleviated behavioral and neural defects in PD flies. While overexpression of Itpr aggravated PD symptoms. The results indicated that increased intracellular calcium influx and release triggers dysregulation of calcium homeostasis in PD flies. And β-asarone prevents PD by restoring Ca2+ homeostasis. Overall, the study demonstrated that β-asarone can serve as a new prospective medication against PD or other diseases associated with dysregulation of Ca2+ homeostasis.

Apoptosis and its role in postmortem meat tenderness: A comprehensive review

Tenderness is considered a crucial attribute of postmortem meat quality, directly influencing consumers' preferences and industrial economic benefits. The degradation of myofibrillar proteins by endogenous enzymes within muscle fibers is believed to be the most effective pathway for meat tenderization. After animals are slaughtered and exsanguinated, there is a significant accumulation of reactive oxygen species (ROS), and a dramatic depletion of adenosine triphosphate (ATP) in muscle, leading to inevitable cell death. Caspases are activated in postmortem muscle cells, which disrupt the cell structure and improve meat tenderness through protein hydrolysis. In this review, we systematically summarized the three primary types of cell death studied in postmortem muscle: apoptosis, autophagy and necrosis. Furthermore, we emphasized the molecular mechanisms of apoptosis and its corresponding apoptotic pathways (mitochondrial apoptosis, death receptors, and endoplasmic reticulum stress) that affect meat tenderness during muscle conversion to meat. Additionally, factors affecting apoptosis were comprehensively discussed, such as ROS, heat shock proteins, calcium (Ca2+)/calpains, and Bcl-2 family proteins. Finally, this comprehensive review of existing research reveals that apoptosis is mainly mediated by the mitochondrial pathway. This ultimately leads to myofibrillar proteins degradation through caspase activation, improving meat tenderness. This review summarizes the research progress on postmortem muscle apoptosis and its molecular mechanisms in meat tenderization. We hope this will enhance understanding of postmortem meat tenderness and provide a theoretical basis for meat tenderization techniques development in the future.

Skeletal muscle adaptations and post-exertional malaise in long COVID

When acute SARS-CoV-2 infections cause symptoms that persist longer than 3 months, this condition is termed long COVID. Symptoms experienced by patients often include myalgia, fatigue, brain fog, cognitive impairments, and post-exertional malaise (PEM), which is the worsening of symptoms following mental or physical exertion. There is little consensus on the pathophysiology of exercise-induced PEM and skeletal-muscle-related symptoms. In this opinion article we highlight intrinsic mitochondrial dysfunction, endothelial abnormalities, and a muscle fiber type shift towards a more glycolytic phenotype as main contributors to the reduced exercise capacity in long COVID. The mechanistic trigger for physical exercise to induce PEM is unknown, but rapid skeletal muscle tissue damage and intramuscular infiltration of immune cells contribute to PEM-related symptoms.

A fully automated morphological analysis of yeast mitochondria from wide-field fluorescence images

Mitochondrial morphology is an important parameter of cellular fitness. Although many approaches are available for assessing mitochondrial morphology in mammalian cells, only a few technically demanding and laborious methods are available for yeast cells. A robust, fully automated and user-friendly approach that would allow (1) segmentation of tubular and spherical mitochondria in the yeast Saccharomyces cerevisiae from conventional wide-field fluorescence images and (2) quantitative assessment of mitochondrial morphology is lacking. To address this, we compared Global thresholding segmentation with deep learning MitoSegNet segmentation, which we retrained on yeast cells. The deep learning model outperformed the Global thresholding segmentation. We applied it to segment mitochondria in strain lacking the MMI1/TMA19 gene encoding an ortholog of the human TCTP protein. Next, we performed a quantitative evaluation of segmented mitochondria by analyses available in ImageJ/Fiji and by MitoA analysis available in the MitoSegNet toolbox. By monitoring a wide range of morphological parameters, we described a novel mitochondrial phenotype of the mmi1Δ strain after its exposure to oxidative stress compared to that of the wild-type strain. The retrained deep learning model, all macros applied to run the analyses, as well as the detailed procedure are now available at https://github.com/LMCF-IMG/Morphology_Yeast_Mitochondria .

Di-(2-ethylhexyl) phthalate induces prepubertal testicular injury through MAM-related mitochondrial calcium overload in Leydig and Sertoli cell apoptosis

As one of the most prevalent environmental endocrine disruptors, di-(2-ethylhexyl) phthalate (DEHP) is known for its significant developmental toxicity to the male reproductive system in humans and mice. Prepubertal exposure to DEHP has been shown to cause testicular damage, but the underlying mechanisms require further investigation. To investigate this effect, prepubertal mice were exposed to 100, 250 or 500 mg/kg body weight (bw) of DEHP for 14 days, which resulted in impaired histological structure and increased apoptosis of the testes. RNA sequencing (RNA-seq) of testicular tissue suggested that DEHP led to injury in Leydig and Sertoli cells. To further elucidate these mechanisms, we conducted experiments using immature mouse Leydig (TM3) and Sertoli (TM4) cells, and exposed them to 200 μM mono-(2-ethylhexyl) phthalate (MEHP), the primary metabolite of DEHP, for 24 h. We found that MEHP exposure induced oxidative stress injury and promoted cell apoptosis, and that cotreatment with N-acetylcysteine partially reversed these injuries. Given the close association between oxidative stress and mitochondrial calcium levels, we demonstrated that MEHP exposure disrupted mitochondria and increased mitochondrial calcium levels. In addition, MEHP exposure facilitated the formation of mitochondria-associated endoplasmic reticulum membranes (MAMs), upregulated protein expression and enhanced the interactions of the IP3R3-Grp75-VDAC1 complex. Furthermore, inhibition of calcium transfer in the IP3R3-Grp75-VDAC1-MCU axis relieved MEHP-induced mitochondrial injury, oxidative stress and apoptosis in TM3 and TM4 cells. This study highlights the importance of MAM-mediated mitochondrial calcium overload and the subsequent apoptosis of Leydig and Sertoli cells as pivotal factors contributing to testicular injury induced by prepubertal exposure to DEHP.

Liver knockout of MCU leads to greater dysregulation of lipid metabolism in MAFLD

Metabolic-associated fatty liver disease (MAFLD) is a common chronic condition that poses a significant threat to human health. Mitochondrial dysfunction, particularly involving the mitochondrial Ca2+ uniporter (MCU), plays a key role in its pathogenesis. This study aimed to investigate the impact of the MCU gene on hepatic lipid metabolism in mice fed a high-fat diet. Using MCU knockout and wild-type mice, subjected to either a high-fat or normal diet for 14 weeks, we observed notable Steatosis and liver weight gain in MCU-deficient mice. Liver function markers, serum triglycerides, very low-density lipoprotein (VLDL) levels, and ApoB protein expression were all significantly elevated. Mechanistic studies revealed that MCU deletion led to mitochondrial dysfunction, increased oxidative stress. These findings highlight the critical role of the MCU gene in maintaining hepatic lipid balance and suggest its potential as a therapeutic target for managing nonalcoholic fatty liver disease.

Mitotic ER-mitochondria contact enhances mitochondrial Ca2+ influx to promote cell division

Cell division is tightly regulated and requires an expanded energy supply. However, how this energy is generated remains unclear. Here, we establish a correlation between two mitochondrial Ca2+ influx events and ATP production during mitosis. While both events promote ATP production during mitosis, the second event, the Ca2+ influx surge, is substantial. To facilitate this Ca2+ influx surge, the lamin B receptor (LBR) organizes a mitosis-specific endoplasmic reticulum (ER)-mitochondrial contact site (ERMCS), creating a rapid Ca2+ transport pathway. LBR acts as a tether, connecting the ER Ca2+ release channel IP3R with the mitochondrial VDAC2. Depletion of LBR disrupts the Ca2+ influx surge, reduces ATP production, and postpones the metaphase-anaphase transition and subsequent cell division. These findings provide insight into the mechanisms underlying mitotic energy production and supply required for cell proliferation.

Neuroprotective treatment with the nitrone compound OKN-007 mitigates age-related muscle weakness in aging mice

Despite the universal impact of sarcopenia on compromised health and quality of life in the elderly, promising pharmaceutical approaches that can effectively mitigate loss of muscle and function during aging have been limited. Our group and others have reported impairments in peripheral motor neurons and loss of muscle innervation as initiating factors in sarcopenia, contributing to mitochondrial dysfunction and elevated oxidative stress in muscle. We recently reported a reduction in α motor neuron loss in aging mice in response to the compound OKN-007, a proposed antioxidant and anti-inflammatory agent. In the current study, we asked whether OKN-007 treatment in wildtype male mice for 8-9 months beginning at 16 months of age can also protect muscle mass and function. At 25 months of age, we observed a reduction in the loss of whole-body lean mass, a reduced loss of innervation at the neuromuscular junction and well-preserved neuromuscular junction morphology in OKN-007 treated mice versus age matched wildtype untreated mice. The loss in muscle force generation in aging mice (~ 25%) is significantly improved with OKN-007 treatment. In contrast, OKN-007 treatment provided no protection in loss of muscle mass in aging mice. Mitochondrial function was improved by OKN-007 treatment, consistent with its potential antioxidative properties. Together, these exciting findings are the first to demonstrate that interventions through neuroprotection can be an effective therapy to counter aging-related muscle dysfunction.

Mitochondrial Extracellular Vesicles: A Promising Avenue for Diagnosing and Treating Lung Diseases

Mitochondria, pivotal organelles governing cellular biosynthesis, energy metabolism, and signal transduction, maintain dynamic equilibrium through processes such as biogenesis, fusion, fission, and mitophagy. Growing evidence implicates mitochondrial dysfunction in a spectrum of respiratory diseases including acute lung injury/acute respiratory distress syndrome, bronchial asthma, pulmonary fibrosis, chronic obstructive pulmonary disease, and lung cancer. Consequently, identifying methods capable of ameliorating damaged mitochondrial function is crucial for the treatment of pulmonary diseases. Extracellular vesicles (EVs), nanosized membrane vesicles released by cells into the extracellular space, facilitate intercellular communication by transferring bioactive substances or signals between cells or organs. Recent studies have identified abundant mitochondrial components within specific subsets of EVs, termed mitochondrial extracellular vesicles (mitoEVs), whose contents and compositions vary with disease progression. Moreover, mitoEVs have demonstrated reparative mitochondrial functions in injured recipient cells. However, a comprehensive understanding of mitoEVs is currently lacking, limiting their clinical translation prospects. This Review explores the biogenesis, classification, functional mitochondrial cargo, and biological effects of mitoEVs, with a focus on their role in pulmonary diseases. Emphasis is placed on their potential as biological markers and innovative therapeutic strategies in pulmonary diseases, offering fresh insights for mechanistic studies and drug development in various pulmonary disorders.

Focus on the role of calcium signaling in ferroptosis: a potential therapeutic strategy for sepsis-induced acute lung injury

By engaging in redox processes, ferroptosis plays a crucial role in sepsis-induced acute lung injury (ALI). Although iron stimulates calcium signaling through the stimulation of redox-sensitive calcium pathways, the function of calcium signals in the physiological process of ferroptosis in septic ALI remains unidentified. Iron homeostasis disequilibrium in ferroptosis is frequently accompanied by aberrant calcium signaling. Intracellular calcium overflow can be a symptom of dysregulation of the cellular redox state, which is characterized by iron overload during the early phase of ferroptosis. This can lead to disruptions in calcium homeostasis and calcium signaling. The mechanisms controlling iron homeostasis and ferroptosis are reviewed here, along with their significance in sepsis-induced acute lung injury, and the potential role of calcium signaling in these processes is clarified. We propose that the development of septic acute lung injury is a combined process involving the bidirectional interaction between iron homeostasis and calcium signaling. Our goal is to raise awareness about the pathophysiology of sepsis-induced acute lung injury and investigate the relationship between these mechanisms and ferroptosis. We also aimed to develop calcium-antagonistic therapies that target ferroptosis in septic ALI and improve the quality of survival for patients suffering from acute lung injury.

A new perspective on liver diseases: Focusing on the mitochondria-associated endoplasmic reticulum membranes

The pathogenesis of liver diseases is multifaceted and intricate, posing a persistent global public health challenge with limited therapeutic options. Therefore, further research into liver diseases is imperative for better comprehension and advancement in treatment strategies. Numerous studies have confirmed the endoplasmic reticulum (ER) and mitochondria as key organelles driving liver diseases. Notably, the mitochondrial-associated ER membranes (MAMs) establish a physical and functional connection between the ER and mitochondria, highlighting the importance of inter-organelle communication in maintaining their functional homeostasis. This review delves into the intricate architecture and regulative mechanism of the integrated MAM that facilitate the physiological transfer of signals and substances between organelles. Additionally, we also provide a detailed overview regarding the varied pathogenic roles of malfunctioning MAM in liver diseases, focusing on its involvement in the progression of ER stress and mitochondrial dysfunction, the regulation of mitochondrial dynamics and Ca2+ transfer, as well as the disruption of lipid and glucose homeostasis. Furthermore, the current challenges and prospects associated with MAM in liver disease research are thoroughly discussed. In conclusion, elucidating the specific structure and function of MAM in different liver diseases may pave the way for novel therapeutic strategies.

The interplay between mitochondrial dynamics and autophagy: From a key homeostatic mechanism to a driver of pathology

The complex relationship between mitochondrial dynamics and autophagy illustrates how two cellular housekeeping processes are intimately linked, illuminating fundamental principles of cellular homeostasis and shedding light on disparate pathological conditions including several neurodegenerative disorders. Here we review the basic tenets of mitochondrial dynamics i.e., the concerted balance between fusion and fission of the organelle, and its interplay with macroautophagy and selective mitochondrial autophagy, also dubbed mitophagy, in the maintenance of mitochondrial quality control and ultimately in cell viability. We illustrate how conditions of altered mitochondrial dynamics reverberate on autophagy and vice versa. Finally, we illustrate how altered interplay between these two key cellular processes participates in the pathogenesis of human disorders affecting multiple organs and systems.

Vascular endothelial cells of Mongolian gerbils are resistant to cholesterol-induced mitochondrial dysfunction and oxidative damage

Atherosclerosis is essentially the leading factor behind occurrences of cardiovascular diseases (CVDs)-associated incidents, while mitochondrial dysfunction is also the main cause of atherosclerosis. The present study conducted a comparative analysis of mitochondrial function-related indicators in cholesterol-induced vascular endothelial cells (VECs) from Mongolian gerbils, Sprague-Dawley (SD) rats and humans. It reported that the inhibitory effect of cholesterol treatment on the viability of Mongolian gerbil VECs was markedly lower than the other two types of VECs at the same concentration. Following cholesterol treatment, mitochondrial DNA copy numbers, reactive oxygen species level, calcium concentration and mitochondrial membrane potential of Mongolian gerbil VECs did not change markedly. These results suggested that the function of mitochondria in the VECs of Mongolian gerbil is normal. Additionally, cholesterol treatment also did not alter the levels of superoxide dismutase, glutathione peroxidase, ATP, NADH-CoQ reductase and cytochrome c oxidase in Mongolian gerbil VECs. It was hypothesized that the VECs of Mongolian gerbils have certain resistance to oxidative damage induced by cholesterol. In brief, the present study demonstrated that VECs of Mongolian gerbils are resistant to cholesterol-induced mitochondrial dysfunction and oxidative damage. The aforementioned findings establish a theoretical foundation for the advancement of innovative strategies in the prevention and treatment of atherosclerosis.

Products of oxidative and non-oxidative metabolism of L-arginine as potential regulators of Ca2+ transport in mitochondria of uterine smooth muscle

Mitochondria play a crucial role in maintaining Ca2+ homeostasis in cells. Due to the critical regulatory role of the products of oxidative and non-oxidative metabolism of L-arginine, it is essential to clarify their effect on Ca2+ transport in smooth muscle mitochondria. Experiments were performed on the uterine myocytes of rats and isolated mitochondria. The possibility of NO synthesis by mitochondria was demonstrated by confocal microscopy and spectrofluorimetry methods using the NO-sensitive fluorescent probe DAF-FM and Mitotracker Orange CM-H2TMRos. It was shown that 50 μM L-arginine stimulates the energy-dependent accumulation of Ca2+ in mitochondria using the fluorescent probe Fluo-4 AM. A similar effect occurred when using nitric oxide donors 100 μM SNP, SNAP, and sodium nitrite (SN) directly. The stimulating effect was eliminated in the presence of the NO scavenger C-PTIO. Nitric oxide reduces the electrical potential in mitochondria without causing them to swell. The stimulatory effect of spermine on the accumulation of Ca2+ by mitochondria is attributed to the enhancement of NO synthesis, which was demonstrated with the use of C-PTIO, NO-synthase inhibitors (100 μM NA and L-NAME), as well as by direct monitoring of NO synthesis fluorescent probe DAF-FM. A conclusion was drawn about the potential regulatory effect of the product of the oxidative metabolism of L-arginine - NO on the transport of Ca2+ in the mitochondria of the myometrium, as well as the corresponding effect of the product of non-oxidative metabolism -spermine by increasing the synthesis of NO in these subcellular structures.

Elevated concentrations of amyloid-β oligomers and their proapoptotic effects on age-related cataract

Recently, amyloid-β oligomers (AβOs) have been studied as the primary pathogenic substances in Alzheimer's disease (AD). Our previous study revealed that the Aβ expression level is closely related to ARC progression. Here, we demonstrated that the accumulation of AβOs in the lens epithelium of age-related cataract (ARC) patients increased during ARC progression and that this alteration was consistent with the changes in mitochondrial function, oxidative stress, and cellular apoptosis. In vitro, human lens epithelial cells (HLECs) treated with AβOs exhibited Ca2+ dyshomeostasis, impaired mitochondrial function, elevated oxidative stress levels, and increased apoptosis. Moreover, the proapoptotic effect of AβOs was alleviated after the uptake of mitochondrial Ca2+ was inhibited. These results establish that AβOs may promote HLEC apoptosis by inducing mitochondrial Ca2+ overload, thus preliminarily revealing the possible association between the accumulation of AβOs and other pathological processes in ARC.

The Emerging Role of the Mitochondrial Respiratory Chain in Skeletal Aging

Maintenance of mitochondrial homeostasis is crucial for ensuring healthy mitochondria and normal cellular function. This process is primarily responsible for regulating processes that include mitochondrial OXPHOS, which generates ATP, as well as mitochondrial oxidative stress, apoptosis, calcium homeostasis, and mitophagy. Bone mesenchymal stem cells express factors that aid in bone formation and vascular growth. Positive regulation of hematopoietic stem cells in the bone marrow affects the differentiation of osteoclasts. Furthermore, the metabolic regulation of cells that play fundamental roles in various regions of the bone, as well as interactions within the bone microenvironment, actively participates in regulating bone integrity and aging. The maintenance of cellular homeostasis is dependent on the regulation of intracellular organelles, thus understanding the impact of mitochondrial functional changes on overall bone metabolism is crucially important. Recent studies have revealed that mitochondrial homeostasis can lead to morphological and functional abnormalities in senescent cells, particularly in the context of bone diseases. Mitochondrial dysfunction in skeletal diseases results in abnormal metabolism of bone-associated cells and a secondary dysregulated microenvironment within bone tissue. This imbalance in the oxidative system and immune disruption in the bone microenvironment ultimately leads to bone dysplasia. In this review, we examine the latest developments in mitochondrial respiratory chain regulation and its impacts on maintenance of bone health. Specifically, we explored whether enhancing mitochondrial function can reduce the occurrence of bone cell deterioration and improve bone metabolism. These findings offer prospects for developing bone remodeling biology strategies to treat age-related degenerative diseases.

Selenium represses microRNA-202-5p/MICU1 aixs to attenuate mercuric chloride-induced kidney ferroptosis

Mercuric chloride (HgCl2) is a nephrotoxic contaminant that is widely present in the environment. Selenium (Se) can effectively antagonize the biological toxicity caused by heavy metals. Here, in vivo and in vitro models of Se antagonism to HgCl2-induced nephrotoxicity in chickens were established, with the aim of exploring the specific mechanism. Morphological observation and kidney function analysis showed that Se alleviated HgCl2-induced kidney tissue injury and cytotoxicity. The results showed that ferroptosis was the primary mechanism for the toxicity of HgCl2, as indicated by iron overload and lipid peroxidation. On the one hand, Se significantly prevented HgCl2-induced iron overload. On the other hand, Se alleviated the intracellular reactive oxygen species (ROS) levels caused by HgCl2. Subsequently, we focused on the sources of ROS during HgCl2-induced ferroptosis. Mechanically, Se reduced ROS overproduction induced by HgCl2 through mitochondrial calcium uniporter (MCU)/mitochondrial calcium uptake 1 (MICU1)-mediated mitochondrial calcium ion (Ca2+) overload. Furthermore, a dual luciferase reporter assay demonstrated that MICU1 was the direct target of miR-202-5p. Overall, Se represses miR-202-5p/MICU1 axis to attenuate HgCl2-induced kidney ferroptosis.

Plasma proteins and persistent postsurgical pelvic pain among adolescents and young adults with endometriosis

BACKGROUND

Noninvasive biomarkers that predict surgical treatment response would inform personalized treatments and provide insight into potential biologic pathways underlying endometriosis-associated pain and symptom progression.

OBJECTIVE

To use plasma proteins in relation to the persistence of pelvic pain following laparoscopic surgery in predominantly adolescents and young adults with endometriosis using a multiplex aptamer-based proteomics biomarker discovery platform.

STUDY DESIGN

We conducted a prospective analysis including 142 participants with laparoscopically-confirmed endometriosis from the Women's Health Study: From Adolescence to Adulthood observational longitudinal cohort with study enrollment from 2012-2018. Biologic samples and patient data were collected with modified World Endometriosis Research Foundation Endometriosis Phenome and Biobanking Harmonization Project tools. In blood collected before laparoscopic ablation or excision of endometriosis, we simultaneously measured 1305 plasma protein levels, including markers for immunity, angiogenesis, and inflammation, using SomaScan. Worsening or persistent postsurgical pelvic pain was defined as having newly developed, persistent (ie, stable), or worsening severity, frequency, or persistent life interference of dysmenorrhea or acyclic pelvic pain at 1-year postsurgery compared with presurgery. We calculated odds ratios and 95% confidence intervals using logistic regression adjusted for age, body mass index, fasting status, and hormone use at blood draw. We applied Ingenuity Pathway Analysis and STRING analysis to identify pathophysiologic pathways and protein interactions.

RESULTS

The median age at blood draw was 17 years (interquartile range, 15-19 years), and most participants were White (90%). All had superficial peritoneal lesions only and were treated by excision or ablation. One-year postsurgery, pelvic pain worsened or persisted for 76 (54%) of these participants with endometriosis, whereas pelvic pain improved for 66 (46%). We identified 83 proteins associated with worsening or persistent pelvic pain 1-year postsurgery (nominal P<.05). Compared with those with improved pelvic pain 1-year postsurgery, those with worsening or persistent pelvic pain had higher plasma levels of CD63 antigen (odds ratio, 2.98 [95% confidence interval, 1.44-6.19]) and CD47 (odds ratio, 2.68 [95% confidence interval, 1.28-5.61]), but lower levels of Sonic Hedgehog protein (odds ratio, 0.55 [95% confidence interval, 0.36-0.84]) in presurgical blood. Pathways related to cell migration were up-regulated, and pathways related to angiogenesis were down-regulated in those with worsening or persistent postsurgical pelvic pain compared with those with improved pain. When we examined the change in protein levels from presurgery to postsurgery and its subsequent risk of worsening or persistent postsurgical pain at 1-year follow-up, we observed increasing levels of Sonic Hedgehog protein from presurgery to postsurgery was associated with a 4-fold increase in the risk of postsurgical pain (odds ratio [quartile 4 vs 1], 3.86 [1.04-14.33]).

CONCLUSION

Using an aptamer-based proteomics platform, we identified plasma proteins and pathways associated with worsening or persistent pelvic pain postsurgical treatment of endometriosis among adolescents and young adults that may aid in risk stratification of individuals with endometriosis.

Toward understanding the cellular control of vertebrate mineralization: The potential role of mitochondria

This review examines the possible role of mitochondria in maintaining calcium and phosphate ion homeostasis and participating in the mineralization of bone, cartilage and other vertebrate hard tissues. The paper builds on the known structural features of mitochondria and the documented observations in these tissues that the organelles contain calcium phosphate granules. Such deposits in mitochondria putatively form to buffer excessively high cytosolic calcium ion concentrations and prevent metabolic deficits and even cell death. While mitochondria protect cytosolic enzyme systems through this buffering capacity, the accumulation of calcium ions by mitochondria promotes the activity of enzymes of the tricarboxylic acid (TCA/Krebs) cycle, increases oxidative phosphorylation and ATP synthesis, and leads to changes in intramitochondrial pH. These pH alterations influence ion solubility and possibly the transitions and composition in the mineral phase structure of the granules. Based on these considerations, mitochondria are proposed to support the mineralization process by providing a mobile store of calcium and phosphate ions, in smaller cluster or larger granule form, while maintaining critical cellular activities. The rise in the mitochondrial calcium level also increases the generation of citrate and other TCA cycle intermediates that contribute to cell function and the development of extracellular mineral. This paper suggests that another key role of the mitochondrion, along with the effects just noted, is to supply phosphate ions, derived from the breakdown of ATP, to endolysosomes and autophagic vesicles originating in the endoplasmic reticulum and Golgi and at the plasma membrane. These many separate but interdependent mitochondrial functions emphasize the critical importance of this organelle in the cellular control of vertebrate mineralization.

Deficiency of IQCH causes male infertility in humans and mice

IQ motif-containing proteins can be recognized by calmodulin (CaM) and are essential for many biological processes. However, the role of IQ motif-containing proteins in spermatogenesis is largely unknown. In this study, we identified a loss-of-function mutation in the novel gene IQ motif-containing H (IQCH) in a Chinese family with male infertility characterized by a cracked flagellar axoneme and abnormal mitochondrial structure. To verify the function of IQCH, Iqch knockout (KO) mice were generated via CRISPR-Cas9 technology. As expected, the Iqch KO male mice exhibited impaired fertility, which was related to deficient acrosome activity and abnormal structures of the axoneme and mitochondria, mirroring the patient phenotypes. Mechanistically, IQCH can bind to CaM and subsequently regulate the expression of RNA-binding proteins (especially HNRPAB), which are indispensable for spermatogenesis. Overall, this study revealed the function of IQCH, expanded the role of IQ motif-containing proteins in reproductive processes, and provided important guidance for genetic counseling and genetic diagnosis of male infertility.

A novel protein CYTB-187AA encoded by the mitochondrial gene CYTB modulates mammalian early development

The mitochondrial genome transcribes 13 mRNAs coding for well-known proteins essential for oxidative phosphorylation. We demonstrate here that cytochrome b (CYTB), the only mitochondrial-DNA-encoded transcript among complex III, also encodes an unrecognized 187-amino-acid-long protein, CYTB-187AA, using the standard genetic code of cytosolic ribosomes rather than the mitochondrial genetic code. After validating the existence of this mtDNA-encoded protein arising from cytosolic translation (mPACT) using mass spectrometry and antibodies, we show that CYTB-187AA is mainly localized in the mitochondrial matrix and promotes the pluripotent state in primed-to-naive transition by interacting with solute carrier family 25 member 3 (SLC25A3) to modulate ATP production. We further generated a transgenic knockin mouse model of CYTB-187AA silencing and found that reduction of CYTB-187AA impairs females' fertility by decreasing the number of ovarian follicles. For the first time, we uncovered the novel mPACT pattern of a mitochondrial mRNA and demonstrated the physiological function of this 14th protein encoded by mtDNA.

Mitochondrial redox state, bioenergetics, and calcium transport in caloric restriction: A metabolic nexus

Mitochondria congregate central reactions in energy metabolism, many of which involve electron transfer. As such, they are expected to both respond to changes in nutrient supply and demand and also provide signals that integrate energy metabolism intracellularly. In this review, we discuss how mitochondrial bioenergetics and reactive oxygen species production is impacted by dietary interventions that change nutrient availability and impact on aging, such as calorie restriction. We also discuss how dietary interventions alter mitochondrial Ca2+ transport, regulating both mitochondrial and cytosolic processes modulated by this ion. Overall, a plethora of literature data support the idea that mitochondrial oxidants and calcium transport act as integrating signals coordinating the response to changes in nutritional supply and demand in cells, tissues, and animals.

Novel insights into STIM1's role in store-operated calcium entry and its implications for T-cell mediated inflammation in trigeminal neuralgia

This investigation aims to elucidate the novel role of Stromal Interaction Molecule 1 (STIM1) in modulating store-operated calcium entry (SOCE) and its subsequent impact on inflammatory cytokine release in T lymphocytes, thereby advancing our understanding of trigeminal neuralgia (TN) pathogenesis. Employing the Gene Expression Omnibus (GEO) database, we extracted microarray data pertinent to TN to identify differentially expressed genes (DEGs). A subsequent comparison with SOCE-related genes from the Genecards database helped pinpoint potential target genes. The STRING database facilitated protein-protein interaction (PPI) analysis to spotlight STIM1 as a gene of interest in TN. Through histological staining, transmission electron microscopy (TEM), and behavioral assessments, we probed STIM1's pathological effects on TN in rat models. Additionally, we examined STIM1's influence on the SOCE pathway in trigeminal ganglion cells using techniques like calcium content measurement, patch clamp electrophysiology, and STIM1- ORAI1 co-localization studies. Changes in the expression of inflammatory markers (TNF-α, IL-1β, IL-6) in T cells were quantified using Western blot (WB) and enzyme-linked immunosorbent assay (ELISA) in vitro, while immunohistochemistry and flow cytometry were applied in vivo to assess these cytokines and T cell count alterations. Our bioinformatic approach highlighted STIM1's significant overexpression in TN patients, underscoring its pivotal role in TN's etiology and progression. Experimental findings from both in vitro and in vivo studies corroborated STIM1's regulatory influence on the SOCE pathway. Furthermore, STIM1 was shown to mediate SOCE-induced inflammatory cytokine release in T lymphocytes, a critical factor in TN development. Supportive evidence from histological, ultrastructural, and behavioral analyses reinforced the link between STIM1-mediated SOCE and T lymphocyte-driven inflammation in TN pathogenesis. This study presents novel evidence that STIM1 is a key regulator of SOCE and inflammatory cytokine release in T lymphocytes, contributing significantly to the pathogenesis of trigeminal neuralgia. Our findings not only deepen the understanding of TN's molecular underpinnings but also potentially open new avenues for targeted therapeutic strategies.

3-MCPD Induces Renal Cell Pyroptosis and Inflammation by Inhibiting ESCRT-III-Mediated Cell Repair and Mitophagy

3-Monochloropropane-1,2-diol (3-MCPD) is a chloropropyl alcohol contaminant mainly from the thermal processing of food and could affect kidneys. Pyroptosis is programmed cell death mediated by inflammasomes and gasdermins, and excessive cellular pyroptosis and inflammation can lead to tissue injury. In the present study, we found that 3-MCPD increased lactate dehydrogenase (LDH) levels in vitro and in vivo, increased the protein expression of NOD-like receptor family pyrin domain containing 3 (NLRP3), N-terminal domain of GSDMD (GSDMD-N), and cleaved caspase-1 and promoted the release of interleukin-1β (IL-1β) and interleukin-18 (IL-18), which induced renal cell pyroptosis and inflammation. Mechanistic studies indicated that the addition of N-acetylcysteine (NAC), a ROS scavenger, inhibited NLRP3 activation and attenuated pyroptosis. Furthermore, we revealed that 3-MCPD induced ROS accumulation by inhibiting ESCRT-III-mediated mitophagy. These results were further validated by the overexpression of charged multivesicular body protein 4B (CHMP4B), a key subunit of ESCRT-III, and the addition of the mitophagy activator carbonyl cyanide m-chlorophenylhydrazone (CCCP) and rapamycin (Rapa). Thus, our results showed that 3-MCPD could induce mitochondrial damage and produce ROS. 3-MCPD suppressed mitophagy, leading to the accumulation of damaged mitochondria and ROS, thereby activating NLRP3 and pyroptosis. Meanwhile, 3-MCPD-mediated suppression of ESCRT-III hindered the repair of GSDMD-induced cell membrane rupture, which further caused the occurrence of pyroptosis. Our findings provide new perspectives for studying the mechanisms underlying 3-MCPD-induced renal injury.

Biological sex impacts oxidative stress in skeletal muscle in a porcine heat stress model

Oxidative stress contributes to heat stress (HS)-mediated alterations in skeletal muscle; however, the extent to which biological sex mediates oxidative stress during HS remains unknown. We hypothesized muscle from males would be more resistant to oxidative stress caused by HS than muscle from females. To address this, male and female pigs were housed in thermoneutral conditions (TN; 20.8 ± 1.6°C; 62.0 ± 4.7% relative humidity; n = 8/sex) or subjected to HS (39.4 ± 0.6°C; 33.7 ± 6.3% relative humidity) for 1 (HS1; n = 8/sex) or 7 days (HS7; n = 8/sex) followed by collection of the oxidative portion of the semitendinosus. Although HS increased muscle temperature, by 7 days, muscle from heat-stressed females was cooler than muscle from heat-stressed males (0.3°C; P < 0.05). Relative protein abundance of 4-hydroxynonenal (4-HNE)-modified proteins increased in HS1 females compared with TN (P = 0.05). Furthermore, malondialdehyde (MDA)-modified proteins and 8-hydroxy-2'-deoxyguanosine (8-OHdG) concentration, a DNA damage marker, was increased in HS7 females compared with TN females (P = 0.05). Enzymatic activities of catalase and superoxide dismutase (SOD) remained similar between groups; however, glutathione peroxidase (GPX) activity decreased in HS7 females compared with TN and HS1 females (P ≤ 0.03) and HS7 males (P = 0.02). Notably, HS increased skeletal muscle Ca2+ deposition (P = 0.05) and was greater in HS1 females compared with TN females (P < 0.05). Heat stress increased sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA)2a protein abundance (P < 0.01); however, Ca2+ ATPase activity remained similar between groups. Overall, despite having lower muscle temperature, muscle from heat-stressed females had increased markers of oxidative stress and calcium deposition than muscle from males following identical environmental exposure.NEW & NOTEWORTHY Heat stress is a global threat to human health and agricultural production. We demonstrated that following 7 days of heat stress, skeletal muscle from females was more susceptible to oxidative stress than muscle from males in a porcine model, despite cooler muscle temperatures. The vulnerability to heat stress-induced oxidative stress in females may be driven, at least in part, by decreased antioxidant capacity and calcium dysregulation.

4-(Benzyloxy)phenol-induced p53 exhibits antimycobacterial response triggering phagosome-lysosome fusion through ROS-dependent intracellular Ca2+ pathway in THP-1 cells

Drug-resistant tuberculosis (TB) outbreak has emerged as a global public health crisis. Therefore, new and innovative therapeutic options like host-directed therapies (HDTs) through novel modulators are urgently required to overcome the challenges associated with TB. In the present study, we have investigated the anti-mycobacterial effect of 4-(Benzyloxy)phenol. Cell-viability assay asserted that 50 μM of 4-(Benzyloxy)phenol was not cytotoxic to phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 (dTHP-1) cells. It was observed that 4-(Benzyloxy)phenol activates p53 expression by hindering its association with KDM1A. Increased ROS, intracellular Ca2+ and phagosome-lysosome fusion, were also observed upon 4-(Benzyloxy)phenol treatment. 4-(Benzyloxy)phenol mediated killing of intracellular mycobacteria was abrogated in the presence of specific inhibitors of ROS, Ca2+ and phagosome-lysosome fusion like NAC, BAPTA-AM, and W7, respectively. We further demonstrate that 4-(Benzyloxy)phenol mediated enhanced ROS production is mediated by acetylation of p53. Blocking of p53 acetylation by Pifithrin-α (PFT- α) enhanced intracellular mycobacterial growth by blocking the mycobactericidal effect of 4-(Benzyloxy)phenol. Altogether, the results showed that 4-(Benzyloxy)phenol executed its anti-mycobacterial effect by modulating p53-mediated ROS production to regulate phagosome-lysosome fusion through Ca2+ production.

Elevated intracellular Ca2+ functions downstream of mitodysfunction to induce Wallerian-like degeneration and necroptosis in organophosphorus-induced delayed neuropathy

Neurotoxic organophosphorus compounds can induce a type of delayed neuropathy in humans and sensitive animals, known as organophosphorus-induced delayed neuropathy (OPIDN). OPIDN is characterized by axonal degeneration akin to Wallerian-like degeneration, which is thought to be caused by increased intra-axonal Ca2+ concentrations. This study was designed to investigate that deregulated cytosolic Ca2+ may function downstream of mitodysfunction in activating Wallerian-like degeneration and necroptosis in OPIDN. Adult hens were administrated a single dosage of 750 mg/kg tri-ortho-cresyl phosphate (TOCP), and then sacrificed at 1 day, 5 day, 10 day and 21 day post-exposure, respectively. Sciatic nerves and spinal cords were examined for pathological changes and proteins expression related to Wallerian-like degeneration and necroptosis. In vitro experiments using differentiated neuro-2a (N2a) cells were conducted to investigate the relationship among mitochondrial dysfunction, Ca2+ influx, axonal degeneration, and necroptosis. The cells were co-administered with the Ca2+-chelator BAPTA-AM, the TRPA1 channel inhibitor HC030031, the RIPK1 inhibitor Necrostatin-1, and the mitochondrial-targeted antioxidant MitoQ along with TOCP. Results demonstrated an increase in cytosolic calcium concentration and key proteins associated with Wallerian degeneration and necroptosis in both in vivo and in vitro models after TOCP exposure. Moreover, co-administration with BATPA-AM or HC030031 significantly attenuated the loss of NMNAT2 and STMN2 in N2a cells, as well as the upregulation of SARM1, RIPK1 and p-MLKL. In contrast, Necrostatin-1 treatment only inhibited the TOCP-induced elevation of p-MLKL. Notably, pharmacological protection of mitochondrial function with MitoQ effectively alleviated the increase in intracellular Ca2+ following TOCP and mitigated axonal degeneration and necroptosis in N2a cells, supporting mitochondrial dysfunction as an upstream event of the intracellular Ca2+ imbalance and neuronal damage in OPIDN. These findings suggest that mitochondrial dysfunction post-TOCP intoxication leads to an elevated intracellular Ca2+ concentration, which plays a pivotal role in the initiation and development of OPIDN through inducing SARM1-mediated axonal degeneration and activating the necroptotic signaling pathway.

The mystery of methylmercury-perturbed calcium homeostasis: AMPK-DRP1-dependent mitochondrial fission initiates ER-mitochondria contact formation

Methylmercury (MeHg), as a global environmental pollutant, is of concern globally due to its neurodevelopmental toxicity. Mitochondria-associated membranes (MAMs) are highly dynamic sites of endoplasmic reticulum (ER)-haemocyte contact. MAMs are closely associated with the pathophysiology of neurological disorders due to their role in the transfer of calcium ions (Ca2+) between mitochondria and the ER. However, the molecular mechanisms that control these interactions in MeHg-induced neurotoxicity have not yet been characterized. In the current study, MeHg caused increases in the levels of both cytosolic and mitochondrial Ca2+ in PC12 cells and promoted MAMs formation in both in vivo and in vitro experiments. Of note, MeHg perturbed mitochondrial dynamics, promoting a shift toward a fission phenotype, and this was supported by the dysregulation of fission regulators. Interestingly, the MeHg-induced promotion of MAMs formation and increase in Ca2+ levels were effectively attenuated by the inhibition of mitochondrial fission using Mdivi-1, a DRP1 inhibitor. Furthermore, MeHg triggered the AMPK pathway, and most of the aforementioned changes were significantly rescued by Compound C. Mechanistic investigations revealed a reciprocal relationship between AMPK- and Ca2+-mediated mitochondrial fission. The specific inhibitor of Ca2+ uniporter, ruthenium-red (RuR), effectively abolished the feedback regulation of mitochondrial dynamics and MAMs formation mediated by AMPK in response to MeHg-induced Ca2+ overload. This study reveals a novel role of AMPK-DRP1-mediated mitochondrial fragmentation in the coupling of ER-mitochondrial calcium microdomains in MeHg-induced neurotoxicity. The findings provide valuable insights for the development of strategies to regulate mitochondrial imbalances in neurological diseases.

Nicotinamide Mononucleotide and Nicotinamide Riboside Reverse Ovarian Aging in Rats Via Rebalancing Mitochondrial Fission and Fusion Mechanisms

PURPOSE

This study examined the effects of nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) on folliculogenesis and mitochondrial dynamics (fission and fusion mechanisms) in ovaries of middle-aged female rats.

METHODS

Experimental groups were young, middle-aged (control), middle-aged + NMN and middle-aged + NR. NMN was administered at a concentration of 500 mg/kg intraperitoneally but NR at a concentration of 200 mg/kg by gavage. Follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels were analyzed by ELISA. Hematoxylin-eosin staining sections were used for histopathological examination and follicles-counting. Expression levels of mitochondrial fission (Drp1, Mff and Fis1) and fusion (Mfn1, Mfn2, Opa1, Fam73a and Fam73b) genes as well as Sirt1 gene were analyzed by RT-PCR. Expression levels of fission-related proteins (DRP1, MFF, FIS1 and SIRT1) were analyzed by Western Blot.

RESULTS

Higher ovarian index, more corpus luteum and antral follicles were detected in NMN and NR groups compared to the control. NMN or NR could rebalance LH/FSH ratio. The control group was determined to possess higher expression levels of fission genes and lower expression levels of fusion genes when compared the young group. In comparison with the control group, both NMN and NR group were found to exhibit less mitochondrial fission but more mitochondrial fussion. Higher gene and protein levels for Sirt1 were measured in NMN and NR groups compared to the control group.

CONCLUSION

This study reveals that NMN alone or NR alone can rebalance mitochondrial dynamics by decreasing excessive fission in middle-aged rat ovaries, thus alleviating mitochondrial stress and correcting aging-induced folliculogenesis abnormalities.

Senolytic therapeutics: An emerging treatment modality for osteoarthritis

Osteoarthritis (OA), a chronic joint disease affecting millions of people aged over 65 years, is the main musculoskeletal cause of diminished joint mobility in the elderly. It is characterized by lingering pain and increasing deterioration of articular cartilage. Aging and accumulation of senescent cells (SCs) in the joints are frequently associated with OA. Apoptosis resistance; irreversible cell cycle arrest; increased p16INK4a expression, secretion of senescence-associated secretory phenotype factors, senescence-associated β-galactosidase levels, secretion of extracellular vesicles, and levels of reactive oxygen and reactive nitrogen species; and mitochondrial dysregulation are some common changes in cellular senescence in joint tissues. Development of OA correlates with an increase in the density of SCs in joint tissues. Senescence-associated secretory phenotype has been linked to OA and cartilage breakdown. Senolytics and therapeutic pharmaceuticals are being focused upon for OA management. SCs can be selectively eliminated or killed by senolytics to halt the pathogenesis and progression of OA. Comprehensive understanding of how aging affects joint dysfunction will benefit OA patients. Here, we discuss age-related mechanisms associated with OA pathogenesis and senolytics as an emerging modality in the management of age-related SCs and pathogenesis of OA in preclinical and clinical studies.

Ca2+ oscillation in vascular smooth muscle cells control myogenic spontaneous vasomotion and counteract post-ischemic no-reflow

Ischemic stroke produces the highest adult disability. Despite successful recanalization, no-reflow, or the futile restoration of the cerebral perfusion after ischemia, is a major cause of brain lesion expansion. However, the vascular mechanism underlying this hypoperfusion is largely unknown, and no approach is available to actively promote optimal reperfusion to treat no-reflow. Here, by combining two-photon laser scanning microscopy (2PLSM) and a mouse middle cerebral arteriolar occlusion (MCAO) model, we find myogenic vasomotion deficits correlated with post-ischemic cerebral circulation interruptions and no-reflow. Transient occlusion-induced transient loss of mitochondrial membrane potential (ΔΨm) permanently impairs mitochondria-endoplasmic reticulum (ER) contacts and abolish Ca2+ oscillation in smooth muscle cells (SMCs), the driving force of myogenic spontaneous vasomotion. Furthermore, tethering mitochondria and ER by specific overexpression of ME-Linker in SMCs restores cytosolic Ca2+ homeostasis, remotivates myogenic spontaneous vasomotion, achieves optimal reperfusion, and ameliorates neurological injury. Collectively, the maintaining of arteriolar myogenic vasomotion and mitochondria-ER contacts in SMCs, are of critical importance in preventing post-ischemic no-reflow.

TMEM135 maintains the equilibrium of osteogenesis and adipogenesis by regulating mitochondrial dynamics

BACKGROUND

Disturbance in the differentiation process of bone marrow mesenchymal stem cells (BMSCs) leads to osteoporosis. Mitochondrial dynamics plays a pivotal role in the metabolism and differentiation of BMSCs. However, the mechanisms underlying mitochondrial dynamics and their impact on the differentiation equilibrium of BMSCs remain unclear.

METHODS

We investigated the mitochondrial morphology and markers related to mitochondrial dynamics during BMSCs osteogenic and adipogenic differentiation. Bioinformatics was used to screen potential genes regulating BMSCs differentiation through mitochondrial dynamics. Subsequently, we evaluated the impact of Transmembrane protein 135 (TMEM135) deficiency on bone homeostasis by comparing Tmem135 knockout mice with their littermates. The mechanism of TMEM135 in mitochondrial dynamics and BMSCs differentiation was also investigated in vivo and in vitro.

RESULTS

Distinct changes in mitochondrial morphology were observed between osteogenic and adipogenic differentiation of BMSCs, manifesting as fission in the late stage of osteogenesis and fusion in adipogenesis. Additionally, we revealed that TMEM135, a modulator of mitochondrial dynamics, played a functional role in regulating the equilibrium between adipogenesis and osteogenesis. The TMEM135 deficiency impaired mitochondrial fission and disrupted crucial mitochondrial energy metabolism during osteogenesis. Tmem135 knockout mice showed osteoporotic phenotype, characterized by reduced osteogenesis and increased adipogenesis. Mechanistically, TMEM135 maintained intracellular calcium ion homeostasis and facilitated the dephosphorylation of dynamic-related protein 1 at Serine 637 in BMSCs.

CONCLUSIONS

Our findings underscore the significant role of TMEM135 as a modulator in orchestrating the differentiation trajectory of BMSCs and promoting a shift in mitochondrial dynamics toward fission. This ultimately contributes to the osteogenesis process. This work has provided promising biological targets for the treatment of osteoporosis.

Characteristics of Developmental and Epileptic Encephalopathy Associated with PACS2 p.Glu209Lys Pathogenic Variant-Our Experience and Systematic Review of the Literature

BACKGROUND

Developmental and epileptic encephalopathies (DEE) encompass a group of rare diseases with hereditary and genetic causes as well as acquired causes such as brain injuries or metabolic abnormalities. The phosphofurin acidic cluster sorting protein 2 (PACS2) is a multifunctional protein with nuclear gene expression. The first cases of the recurrent c.625G>A pathogenic variant of PACS2 gene were reported in 2018 by Olson et al. Since then, several case reports and case series have been published.

METHODS

We performed a systematic review of the PUBMED and SCOPUS databases using Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Our search parameters included DEE66 with a pathogenic PACS2 gene p.Glu209Lys mutation published cases to which we added our own clinical experience regarding this pathology.

RESULTS

A total of 11 articles and 29 patients were included in this review, to which we added our own experience for a total of 30 patients. There was not a significant difference between sexes regarding the incidence of this pathology (M/F: 16/14). The most common neurological and psychiatric symptoms presented by the patients were: early onset epileptic seizures, delayed global development (including motor and speech delays), behavioral disturbances, limited intellectual capacity, nystagmus, hypotonia, and a wide-based gait. Facial dysmorphism and other organs' involvement were also frequently reported. Brain MRIs evidenced anomalies of the posterior cerebellar fossa, foliar distortion of the cerebellum, vermis hypoplasia, white matter reduction, and lateral ventricles enlargement. Genetic testing is more frequent in children. Only 4 cases have been reported in adults to date.

CONCLUSIONS

It is important to maintain a high suspicion of new pathogenic gene variants in adult patients presenting with a characteristic clinical picture correlated with radiologic changes. The neurologist must gradually recognize the distinct evolving phenotype of DEE66 in adult patients, and genetic testing must become a scenario with which the neurologist attending adult patients should be familiar. Accurate diagnosis is required for adequate treatment, genetic counseling, and an improved long-term prognosis.

Natural products as pharmacological modulators of mitochondrial dysfunctions for the treatment of diabetes and its complications: An update since 2010

Diabetes, characterized as a well-known chronic metabolic syndrome, with its associated complications pose a substantial and escalating health and healthcare challenge on a global scale. Current strategies addressing diabetes are mainly symptomatic and there are fewer available curative pharmaceuticals for diabetic complications. Thus, there is an urgent need to identify novel pharmacological targets and agents. The impaired mitochondria have been associated with the etiology of diabetes and its complications, and the intervention of mitochondrial dysfunction represents an attractive breakthrough point for the treatments of diabetes and its complications. Natural products (NPs), with multicenter characteristics, multi-pharmacological activities and lower toxicity, have been caught attentions as the modulators of mitochondrial functions in the therapeutical filed of diabetes and its complications. This review mainly summarizes the recent progresses on the potential of 39 NPs and 2 plant-extracted mixtures to improve mitochondrial dysfunction against diabetes and its complications. It is expected that this work may be useful to accelerate the development of innovative drugs originated from NPs and improve upcoming therapeutics in diabetes and its complications.

Hydromorphone hydrochloride preconditioning combined with postconditioning attenuates myocardial ischemia/reperfusion injury in rats by improving mitochondrial function and activating the PI3K/Akt signaling pathway

Thrombolytic therapy or percutaneous coronary intervention for myocardial infarction often cause myocardial ischemia/reperfusion injury (MIRI) and poor prognosis of patients. This study aimed to explore the protective effect and potential mechanism of hydromorphone hydrochloride (HH) on MIRI. Fifty Sprague-Dawley male rats were randomly divided into Sham group, I/R group, HH-pre group, HH-post group, and HH-pre + post group. Except Sham group, MIRI models were established by ligating and relaxing the left anterior descending coronary artery, followed by tail vein injection of HH (0.3 μmol/L) 10 min before ligation (HH-pre group), 10 min after reperfusion (HH-post group), and twice at the above two time points (HH-pre + post group). After intervention, the cardiac function of rats was evaluated by echocardiography, and the levels of myocardial injury markers, oxidative stress indicators, and mitochondrial function indicators were detected. Next, the myocardial infarction area was evaluated by 2,3,5-triphenyltetrazolium chloride staining, mitochondrial biogenesis, and phosphoinositide 3 kinase (PI3K)/protein kinase B (Akt) signaling pathway by western blot. Compared with the I/R group, HH intervention improved cardiac function, decreased myocardial infarction area, reduced serum myocardial injury markers, alleviated oxidative stress, improved mitochondrial function, up-regulated mitochondrial biogenesis, and activated PI3K/Akt signaling pathway. Moreover, the HH-pre + post group was superior to the HH-pre and HH-post groups in the above aspects. Collectively, HH had protective effect on MIRI rats, and HH preconditioning combined with postconditioning showed optimal efficacy. Such efficacy may be achieved by promoting mitochondrial biogenesis to improve mitochondrial function and reduce oxidative stress, and activating the PI3K/Akt signaling pathway.

Cristae shaping and dynamics in mitochondrial function

Mitochondria are multifunctional organelles of key importance for cell homeostasis. The outer mitochondrial membrane (OMM) envelops the organelle, and the inner mitochondrial membrane (IMM) is folded into invaginations called cristae. As cristae composition and functions depend on the cell type and stress conditions, they recently started to be considered as a dynamic compartment. A number of proteins are known to play a role in cristae architecture, such as OPA1, MIC60, LETM1, the prohibitin (PHB) complex and the F1FO ATP synthase. Furthermore, phospholipids are involved in the maintenance of cristae ultrastructure and dynamics. The use of new technologies, including super-resolution microscopy to visualize cristae dynamics with superior spatiotemporal resolution, as well as high-content techniques and datasets have not only allowed the identification of new cristae proteins but also helped to explore cristae plasticity. However, a number of open questions remain in the field, such as whether cristae-resident proteins are capable of changing localization within mitochondria, or whether mitochondrial proteins can exit mitochondria through export. In this Review, we present the current view on cristae morphology, stability and composition, and address important outstanding issues that might pave the way to future discoveries.

Tumor-targeting hydroxyapatite nanoparticles for remodeling tumor immune microenvironment (TIME) by activating mitoDNA-pyroptosis pathway in cancer

In recent years, immunotherapy has emerged as a promising strategy for treating solid tumors, although its efficacy remains limited to a subset of patients. Transforming non-responsive "cold" tumor types into immuno-responsive "hot" ones is critical to enhance the efficacy of immune-based cancer treatments. Pyroptosis, a programmed cell death mechanism, not only effectively eliminates tumor cells but also triggers a potent inflammatory response to initiate anti-tumor immune activities. This sheds light on the potential of pyroptosis to sensitize tumors to immune therapy. Hence, it is urgent to explore and develop novel treatments (e.g., nanomedicines) which are capable of inducing pyroptosis. In this study, we constructed tumor-targeting nanoparticles (CS-HAP@ATO NPs) by loading atorvastatin (ATO) onto chondroitin sulfate (CS) modified hydroxyapatite (HAP) nanoparticles (CS-HAP). CS was strategically employed to target tumor cells, while HAP exhibited the capacity to release calcium ions (Ca2+) in response to the tumor microenvironment. Moreover, ATO disrupted the mitochondrial function, leading to intracellular energy depletion and consequential changes in mitochondrial membrane permeability, followed by the influx of Ca2+ into the cytoplasm and mitochondria. CS and HAP synergetically augmented mitochondrial calcium overload, inciting the production of substantial amount of reactive oxygen species (ROS) and the subsequent liberation of oxidized mitochondrial DNA (OX-mitoDNA). This intricate activation process promoted the assembly of inflammasomes, most notably the NLRP3 inflammasome, followed by triggering caspase-1 activation. The activated caspase-1 was able to induce gasderminD (GSDMD) protein cleavage and present the GSDM-N domain, which interacted with phospholipids in the cell membrane. Then, the cell membrane permeability was raised, cellular swelling was observed, and abundant cell contents and inflammatory mediators were released. Ultimately, this orchestrated sequence of events served to enhance the anti-tumor immunoresponse within the organism.

Alveolar macrophage-derived gVPLA2 promotes ventilator-induced lung injury via the cPLA2/PGE2 pathway

BACKGROUND

Ventilator-induced lung injury (VILI) is a clinical complication of mechanical ventilation observed in patients with acute respiratory distress syndrome. It is characterized by inflammation mediated by inflammatory cells and their secreted mediators.

METHODS

To investigate the mechanisms underlying VILI, a C57BL/6J mouse model was induced using high tidal volume (HTV) mechanical ventilation. Mice were pretreated with Clodronate liposomes to deplete alveolar macrophages or administered normal bone marrow-derived macrophages or Group V phospholipase A2 (gVPLA2) intratracheally to inhibit bone marrow-derived macrophages. Lung tissue and bronchoalveolar lavage fluid (BALF) were collected to assess lung injury and measure Ca2 + concentration, gVPLA2, downstream phosphorylated cytoplasmic phospholipase A2 (p-cPLA2), prostaglandin E2 (PGE2), protein expression related to mitochondrial dynamics and mitochondrial damage. Cellular experiments were performed to complement the animal studies.

RESULTS

Depletion of alveolar macrophages attenuated HTV-induced lung injury and reduced gVPLA2 levels in alveolar lavage fluid. Similarly, inhibition of alveolar macrophage-derived gVPLA2 had a similar effect. Activation of the cPLA2/PGE2/Ca2 + pathway in alveolar epithelial cells by gVPLA2 derived from alveolar macrophages led to disturbances in mitochondrial dynamics and mitochondrial dysfunction. The findings from cellular experiments were consistent with those of animal experiments.

CONCLUSIONS

HTV mechanical ventilation induces the secretion of gVPLA2 by alveolar macrophages, which activates the cPLA2/PGE2/Ca2 + pathway, resulting in mitochondrial dysfunction. These findings provide insights into the pathogenesis of VILI and may contribute to the development of therapeutic strategies for preventing or treating VILI.

Connection between oxidative stress and subcellular organelle in subarachnoid hemorrhage: Novel mechanisms and therapeutic implications

Spontaneous subarachnoid hemorrhage (SAH) is one of the most devastating forms of stroke, with limited treatment modalities and poor patient outcomes. Previous studies have proposed multiple prognostic factors; however, relative research on treatment has not yet yielded favorable clinical outcomes. Moreover, recent studies have suggested that early brain injury (EBI) occurring within 72 h after SAH may contribute to its poor clinical outcomes. Oxidative stress is recognized as one of the main mechanisms of EBI, which causes damage to various subcellular organelles, including the mitochondria, nucleus, endoplasmic reticulum (ER), and lysosomes. This could lead to significant impairment of numerous cellular functions, such as energy supply, protein synthesis, and autophagy, which may directly contribute to the development of EBI and poor long-term prognostic outcomes. In this review, the mechanisms underlying the connection between oxidative stress and subcellular organelles after SAH are discussed, and promising therapeutic options based on these mechanisms are summarized.

Modulation of oxidized low-density lipoprotein-affected macrophage efferocytosis by mitochondrial calcium uniporter in a murine model

OBJECTIVE

Efferocytosis dysfunction contributes to the progression and rupture of atherosclerotic plaques. Efferocytosis is crucially modulated by intracytoplasmic Ca2+, and mitochondrial calcium uniporter (MCU) complex proteins serve as key channels for regulating Ca2+ concentration. Therefore, it was speculated that MCU may affect the development of atherosclerosis (AS) by regulating efferocytosis. In the present study, we aimed to investigate whether MCU could affect foam cell formation by regulating efferocytosis.

METHODS

We stimulated primary macrophages (Møs) using oxidized low-density lipoprotein (ox-LDL) to mimic the atherosclerotic microenvironment and treated them with Ru360, an MCU-specific inhibitor, and UNC1062, an inhibitor of efferocytosis. Additionally, we conducted double staining to determine the Mø efferocytosis rate. We measured the expression of MCU complexes and efferocytosis-associated proteins using western blotting (WB) and real-time quantitative polymerase chain reaction (RT-qPCR), respectively. In addition, we separately detected the Ca2+ level in the cytoplasm and mitochondria (MT) using Fluo-4 AM and Rhod-2 methods. We separately determined the reactive oxygen species (ROS) level in cytoplasm and MT using dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescent probing method and Mito-SOXTM superoxide indicator staining. Additionally, we conducted the enzyme-linked immunosorbent assay (ELISA) to detect the production of interleukin-6 (IL-6), interleukin-18 (IL-18), interleukin-1β (IL-1β), and tumor necrosis factor-alpha (TNF-α). Oil Red O staining was performed to measure cytoplasmic lipid levels.

RESULTS

Ru360 attenuated ox-LDL-induced efferocytosis dysfunction, and attenuated the upregulation of MCU and MCUR1 induced by ox-LDL, and meanwhile attenuated the downregulation of MCUb induced by ox-LDL. Ru360 attenuated the decrease of intracytoplasmic Ca2+ concentration induced by ox- LDL, Ru360 also attenuated the ROS production induced by ox- LDL, attenuated the release of IL-6, IL-18, IL-1β, and TNF-α induced by ox- LDL, and attenuated the increase of intracytoplasmic lipid content induced by ox-LDL. UNC1062 attenuated the effects of Ru360 in reducing inflammatory cytokines and intracytoplasmic lipid content.

CONCLUSIONS

In this study, we found that MCU inhibition modulated intracytoplasmic Ca2+ concentration, improved impaired Mø efferocytosis, and reduced ROS generation. Macrophage efferocytosis removed apoptotic cells and prevented the release of inflammatory factor and foam cell formation, and this can be a potential new therapeutic target for alleviating atherosclerosis.

Metformin alleviates cerebral ischemia/reperfusion injury aggravated by hyperglycemia via regulating AMPK/ULK1/PINK1/Parkin pathway-mediated mitophagy and apoptosis

Stroke remains the main leading cause of death and disabilities worldwide, with diabetes mellitus being a significant independent risk factor for it. Metformin, as an efficient hypoglycemic drug in treating type 2 diabetes, has been reported to alleviate the risk of diabetes-related stroke. However, its underlying mechanisms remain unclear. This study aimed to investigate the role of mitophagy and its regulatory pathway in the neuroprotective mechanism of metformin against cerebral ischemia/reperfusion (I/R) injury aggravated by hyperglycemia. A hyperglycemic cerebral I/R animal model and a high glucose cultured oxygen-glucose deprivation/reperfusion (OGD/R) cell model were used in the experiment. The indexes of brain injury, cell activity, mitochondrial morphology and function, mitophagy, mitochondrial pathway apoptosis and the AMPK pathway were observed. In diabetic rats, metformin treatment decreased cerebral infarction volume and neuronal apoptosis, and improved neurological symptoms following I/R injury. Additionally, metformin induced activation of the AMPK/ULK1/PINK1/Parkin mitophagy pathway to have neuroprotective effects. In vitro, high glucose culture and OGD/R treatment impaired mitochondrial morphology and function, mitochondrial membrane potential, and induced apoptosis. However, metformin activated AMPK/ULK1/PINK1/Parkin mitophagy pathway, normalized mitochondrial injury. This protection was reversed by autophagy inhibitor 3-methyladenine (3MA) and AMPK inhibitor compound C. In conclusion, our present study validates the potential mechanism of metformin in alleviating hyperglycemia aggravated cerebral I/R injury by the activation of AMPK/ULK1/PINK1/Parkin mitophagy pathway.

Mitochondria during T cell aging

Mitochondrial dysfunction is a hallmark of aging that contributes to inflammaging. It is characterized by alterations of the mitochondrial DNA, reduced respiratory capacity, decreased mitochondrial membrane potential and increased reactive oxygen species production. These primary alterations disrupt other interconnected and important mitochondrial-related processes such as metabolism, mitochondrial dynamics and biogenesis, mitophagy, calcium homeostasis or apoptosis. In this review, we gather the current knowledge about the different mitochondrial processes which are altered during aging, with special focus on their contribution to age-associated T cell dysfunction and inflammaging.

β-carotene targets IP3R/GRP75/VDAC1-MCU axis to renovate LPS-induced mitochondrial oxidative damage by regulating STIM1

Endoplasmic reticulum (ER) and mitochondria are the main sites for the storage and regulation of Ca2+ homeostasis. An imbalance of Ca2+ homeostasis can cause ER stress and mitochondrial dysfunction, thereby inducing apoptosis. The store-operated calcium entry (SOCE) is the main channel for extracellular calcium influx. Mitochondria-associated endoplasmic reticulum (MAM) is an important agent for Ca2+ transfer from the ER to the mitochondria. Therefore, regulation of SOCE and MAMs has potential therapeutic value for disease prevention and treatment. In this study, bovine mammary epithelial cells (BMECs) and mice were used as models to explore the mechanisms of β-carotene to relieve ER stress and mitochondrial dysfunction. BAPTA-AM, EGTA (Ca2+ inhibitor), and BTP2 (SOCE channel inhibitor) alleviated ER stress and mitochondrial oxidative damage induced by increased intracellular Ca2+ levels after lipopolysaccharide (LPS) stimulation. Furthermore, inhibition of ER stress by 4-PBA (ER stress inhibitor), 2-APB (IP3R inhibitor), and ruthenium red (mitochondrial calcium uniporter (MCU) inhibitor) restored mitochondrial function by reducing mitochondrial ROS. Our data also confirm that β-carotene targeted STIM1 and IP3R channels to repair LPS-induced ER stress and mitochondrial disorders. Consistent with the in vitro study, in vito experiments in mice further showed that β-carotene attenuated LPS-induced ER stress and mitochondrial oxidative damage by inhibiting the expression of STIM1 and ORAI1, and reducing the level of Ca2+ in mouse mammary glands. Therefore, ER stress-mitochondrial oxidative damage mediated by the STIM1-ER-IP3R/GRP75/VDAC1-MCU axis plays an vital role in the development of mastitis. Our results provided novel ideas and therapeutic targets for the prevention and treatment of mastitis.

PE_PGRS45 (Rv2615c) protein of Mycobacterium tuberculosis perturbs mitochondria of macrophages

The PE_PGRS proteins have coevolved with the antigenic ESX-V secretory system and are abundant in pathogenic Mycobacterium. Only a few PE_PGRS proteins have been characterized, and research suggests their role in organelle targeting, cell death pathways, calcium (Ca2+ ) homeostasis and disease pathogenesis. The PE_PGRS45 (Rv2615c) protein was predicted to contain mitochondria targeting sequences by in silico evaluation. Therefore, we investigated the targeting of the Rv2615c protein to host mitochondria and its effect on mitochondrial functions. In vitro experiments showed the Rv2615c protein colocalized with the mitochondria and led to morphological mitochondrial perturbations. Recombinant Rv2615c was observed to cause increased levels of intracellular reactive oxygen species and the adenosine diphosphate-to-adenosine triphosphate ratio. The Rv2615c protein also induced mitochondrial membrane depolarization and the generation of mitochondrial superoxide. We observed the release of cytochrome C into the cytoplasm and increased expression of proapoptotic genes Bax and Bim with no significant change in anti-apoptotic Bcl2 in Rv2615c-stimulated THP1 macrophages. Ca2+ is a key signaling molecule in tuberculosis pathogenesis, modulating host cell responses. As reported for other PE_PGRS proteins, Rv2615c also has Ca2+ -binding motifs and thus can modulate calcium homeostasis in the host. We also observed a high level of Ca2+ influx in THP1 macrophages stimulated with Rv2615c. Based on these findings, we suggest that Rv2615c may be an effector protein that could contribute to disease pathogenesis by targeting host mitochondria.

Mitochondrial dysfunction: roles in skeletal muscle atrophy

Mitochondria play important roles in maintaining cellular homeostasis and skeletal muscle health, and damage to mitochondria can lead to a series of pathophysiological changes. Mitochondrial dysfunction can lead to skeletal muscle atrophy, and its molecular mechanism leading to skeletal muscle atrophy is complex. Understanding the pathogenesis of mitochondrial dysfunction is useful for the prevention and treatment of skeletal muscle atrophy, and finding drugs and methods to target and modulate mitochondrial function are urgent tasks in the prevention and treatment of skeletal muscle atrophy. In this review, we first discussed the roles of normal mitochondria in skeletal muscle. Importantly, we described the effect of mitochondrial dysfunction on skeletal muscle atrophy and the molecular mechanisms involved. Furthermore, the regulatory roles of different signaling pathways (AMPK-SIRT1-PGC-1α, IGF-1-PI3K-Akt-mTOR, FoxOs, JAK-STAT3, TGF-β-Smad2/3 and NF-κB pathways, etc.) and the roles of mitochondrial factors were investigated in mitochondrial dysfunction. Next, we analyzed the manifestations of mitochondrial dysfunction in muscle atrophy caused by different diseases. Finally, we summarized the preventive and therapeutic effects of targeted regulation of mitochondrial function on skeletal muscle atrophy, including drug therapy, exercise and diet, gene therapy, stem cell therapy and physical therapy. This review is of great significance for the holistic understanding of the important role of mitochondria in skeletal muscle, which is helpful for researchers to further understanding the molecular regulatory mechanism of skeletal muscle atrophy, and has an important inspiring role for the development of therapeutic strategies for muscle atrophy targeting mitochondria in the future.