Mitochondrial Dynamics, Mitophagy, and Mitochondria–Endoplasmic Reticulum Contact Sites Crosstalk Under Hypoxia

Bibliometric analysis of endoplasmic reticulum stress in hepatocellular carcinoma: trends and future directions

BACKGROUND

Over the past three decades, endoplasmic reticulum (ER) stress has gained considerable attention in the field of hepatocellular carcinoma (HCC) with an increasing number of publications. It is crucial to reveal the global status, research hotspots and future research trends of ER stress in HCC. The aim of this study is to analyze the publications related to ER stress in HCC through bibliometric analysis in order to better understand the current status of ER stress research in HCC and to identify potential new research directions.

METHODS

In this study, articles and reviews on ER stress in HCC up to December 31, 2023 were searched and downloaded from the Science Citation Index-Expanded (SCIE) of the Web of Science Core Collection (WoSCC), Pubmed, Scopus and Embase databases. Using CiteSpace 6.2.R6, VOSviewer 1.6.19, Scimago Graphica and Microsoft Office Excel 2019, the knowledge networks of a variety of countries, regions, authors, references, keywords and journals were analyzed.

RESULTS

A total of 1239 publications were retrieved, including 843 articles and 396 review articles. The number of global publications is increasing every year, with the majority of publications coming from China and the USA. Ih-Jen Su, Wenya Huang and Wei Wei are the top 3 prolific authors. "Progression", "inflammation", "cell cycle arrest", "metabolism", "snsignaling pathways", "pathogenesis" and "non-alcoholic fatty liver disease" have emerged as research hotspots in recent years. The journal with the greatest co-citation is Hepatology.

CONCLUSIONS

Based on current global trends, the total number of publications on ER stress in HCC research will continue to increase, but there is a need for more cooperation between authors and countries/regions. ER stress in HCC will continue to be a research priority.

CONCLUSIONS

Based on current global trends, the total number of publications on ER stress in HCC research will continue to increase, but there is a need for more cooperation between authors and countries/regions. ER stress in HCC will continue to be a research priority.

mtPCDI: a machine learning-based prognostic model for prostate cancer recurrence

Background

This research seeks to formulate a prognostic model for forecasting prostate cancer recurrence by examining the interaction between mitochondrial function and programmed cell death (PCD).

Methods

The research involved analyzing four gene expression datasets from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) using univariate Cox regression. These analyses identified genes linked with mitochondrial function and PCD that correlate with recurrence prognosis. Various machine learning algorithms were then employed to construct an optimal predictive model.

Results

A key outcome was the creation of a mitochondrial-related programmed cell death index (mtPCDI), which effectively predicts the prognosis of prostate cancer patients. It was observed that individuals with lower mtPCDI exhibited higher immune activity, correlating with better recurrence outcomes.

Conclusion

The study demonstrates that mtPCDI can be used for personalized risk assessment and therapeutic decision-making, highlighting its clinical significance and providing insights into the biological processes affecting prostate cancer recurrence.

Polystyrene nanoplastic exposure actives ferroptosis by oxidative stress-induced lipid peroxidation in porcine oocytes during maturation

BACKGROUND

Polystyrene nanoplastics (PS-NPs) are becoming increasingly prevalent in the environment with great advancements in plastic products, and their potential health hazard to animals has received much attention. Several studies have reported the toxicity of PS-NPs to various tissues and cells; however, there is a paucity of information about whether PS-NPs exposure can have toxic effects on mammalian oocytes, especially livestock. Herein, porcine oocytes were used as the model to investigate the potential effects of PS-NPs on mammalian oocytes.

RESULTS

The findings showed that different concentrations of PS-NPs (0, 25, 50 and 100 μg/mL) entering into porcine oocytes could induce mitochondrial stress, including a significant decrease in mitochondrial membrane potential (MMP), and the destruction of the balance of mitochondrial dynamic and micromorphology. Furthermore, there was a marked increase in reactive oxygen species (ROS), which led to oocyte lipid peroxidation (LPO). PS-NPs exposure induced abnormal intracellular iron overload, and subsequently increased the expression of transferrin receptor (TfRC), solute carrier family 7 member 11 (SLC7a11), and acyl-CoA synthetase long-chain family member 4 (ACSL4), which resulted in ferroptosis in oocytes. PS-NPs also induced oocyte maturation failure, cytoskeletal dysfunction and DNA damage. Cotreatment with 5 μmol/L ferrostatin-1 (Fer-1, an inhibitor of ferroptosis) alleviated the cellular toxicity associated with PS-NPs exposure during porcine oocyte maturation.

CONCLUSIONS

In conclusion, PS-NPs caused ferroptosis in porcine oocytes by increasing oxidative stress and altering lipid metabolism, leading to the failure of oocyte maturation.

Pharmacological induction of the hypoxia response pathway in Huh7 hepatoma cells limits proliferation but increases resilience under metabolic stress

The hypoxia response pathway enables adaptation to oxygen deprivation. It is mediated by hypoxia-inducible factors (HIF), which promote metabolic reprogramming, erythropoiesis, angiogenesis and tissue remodeling. This led to the successful development of HIF-inducing drugs for treating anemia and some of these molecules are now in clinic. However, elevated levels of HIFs are frequently associated with tumor growth, poor prognosis, and drug resistance in various cancers, including hepatocellular carcinoma (HCC). Consequently, there are concerns regarding the recommendation of HIF-inducing drugs in certain clinical situations. Here, we analyzed the effects of two HIF-inducing drugs, Molidustat and Roxadustat, in the well-characterized HCC cell line Huh7. These drugs increased HIF-1α and HIF-2α protein levels which both participate in inducing hypoxia response genes such as BNIP3, SERPINE1, LDHA or EPO. Combined transcriptomics, proteomics and metabolomics showed that Molidustat increased the expression of glycolytic enzymes, while the mitochondrial network was fragmented and cellular respiration decreased. This metabolic remodeling was associated with a reduced proliferation and a lower demand for pyrimidine supply, but an increased ability of cells to convert pyruvate to lactate. This was accompanied by a higher resistance to the inhibition of mitochondrial respiration by antimycin A, a phenotype confirmed in Roxadustat-treated Huh7 cells and Molidustat-treated hepatoblastoma cells (Huh6 and HepG2). Overall, this study shows that HIF-inducing drugs increase the metabolic resilience of liver cancer cells to metabolic stressors, arguing for careful monitoring of patients treated with HIF-inducing drugs, especially when they are at risk of liver cancer.

Anticancer Activity of Delta-Tocotrienol in Human Hepatocarcinoma: Involvement of Autophagy Induction

(1) Hepatocellular carcinoma (HCC) is the predominant form of primary liver cancer. Surgical resection, tumor ablation, and liver transplantation are curative treatments indicated for early-stage HCC. The management of intermediate and advanced stages of pathology is based on the use of systemic therapies which often show important side effects. Vitamin E-derivative tocotrienols (TTs) play antitumoral properties in different tumors. Here, we analyzed the activity of delta-TT (δ-TT) on HCC human cell lines. (2) We analyzed the ability of δ-TT to trigger apoptosis, to induce oxidative stress, autophagy, and mitophagy in HepG2 cell line. We evaluated the correlation between the activation of autophagy with the ability of δ-TT to induce cell death. (3) The data obtained demonstrate that δ-TT exerts an antiproliferative and proapoptotic effect in HCC cells. Furthermore, δ-TT induces the release of mitochondrial ROS and causes a structural and functional alteration of the mitochondria compatible with a fission process. Finally, δ-TT triggers selective autophagy process removing dysfunctional mitochondria. Inhibition of autophagy reversed the cytotoxic action of δ-TT. (4) Our results demonstrate that δ-TT through the activation of autophagy could represent a potential new approach in the treatment of advanced HCC.

Altered Mitochondrial Function in MASLD: Key Features and Promising Therapeutic Approaches

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as nonalcoholic fatty liver disease (NAFLD), encompasses a range of liver conditions from steatosis to nonalcoholic steatohepatitis (NASH). Its prevalence, especially among patients with metabolic syndrome, highlights its growing global impact. The pathogenesis of MASLD involves metabolic dysregulation, inflammation, oxidative stress, genetic factors and, notably, mitochondrial dysfunction. Recent studies underscore the critical role of mitochondrial dysfunction in MASLD's progression. Therapeutically, enhancing mitochondrial function has gained interest, along with lifestyle changes and pharmacological interventions targeting mitochondrial processes. The FDA's approval of resmetirom for metabolic-associated steatohepatitis (MASH) with fibrosis marks a significant step. While resmetirom represents progress, further research is essential to understand MASLD-related mitochondrial dysfunction fully. Innovative strategies like gene editing and small-molecule modulators, alongside lifestyle interventions, can potentially improve MASLD treatment. Drug repurposing and new targets will advance MASLD therapy, addressing its increasing global burden. Therefore, this review aims to provide a better understanding of the role of mitochondrial dysfunction in MASLD and identify more effective preventive and treatment strategies.

Metabolic and mitochondria alterations induced by SARS-CoV-2 accessory proteins ORF3a, ORF9b, ORF9c and ORF10

Antiviral signaling, immune response and cell metabolism are dysregulated by SARS-CoV-2, the causative agent of COVID-19. Here, we show that SARS-CoV-2 accessory proteins ORF3a, ORF9b, ORF9c and ORF10 induce a significant mitochondrial and metabolic reprogramming in A549 lung epithelial cells. While ORF9b, ORF9c and ORF10 induced largely overlapping transcriptomes, ORF3a induced a distinct transcriptome, including the downregulation of numerous genes with critical roles in mitochondrial function and morphology. On the other hand, all four ORFs altered mitochondrial dynamics and function, but only ORF3a and ORF9c induced a marked alteration in mitochondrial cristae structure. Genome-Scale Metabolic Models identified both metabolic flux reprogramming features both shared across all accessory proteins and specific for each accessory protein. Notably, a downregulated amino acid metabolism was observed in ORF9b, ORF9c and ORF10, while an upregulated lipid metabolism was distinctly induced by ORF3a. These findings reveal metabolic dependencies and vulnerabilities prompted by SARS-CoV-2 accessory proteins that may be exploited to identify new targets for intervention.

New Molecules in Type 2 Diabetes: Advancements, Challenges and Future Directions

Although good glycemic control in patients with type 2 diabetes (T2D) can prevent cardiovascular complications, many diabetic patients still have poor optimal control. A new class of antidiabetic drugs (e.g., glucagon-like peptide-1-GLP-1 receptor agonists, sodium-glucose co-transporters-SGLT2 inhibitors), in addition to the low hypoglycemic effect, exert multiple beneficial effects at a metabolic and cardiovascular level, through mechanisms other than antihyperglycemic agents. This review aims to discuss the effects of these new antidiabetic drugs, highlighting cardiovascular and metabolic benefits, through the description of their action mechanisms as well as available data by preclinical and clinical studies. Moreover, new innovative tools in the T2D field will be described which may help to advance towards a better targeted T2D personalized care in future.

Mitophagy and its regulatory mechanisms in the biological effects of nanomaterials

Mitophagy is a selective cellular process critical for the removal of damaged mitochondria. It is essential in regulating mitochondrial number, ensuring mitochondrial functionality, and maintaining cellular equilibrium, ultimately influencing cell destiny. Numerous pathologies, such as neurodegenerative diseases, cardiovascular disorders, cancers, and various other conditions, are associated with mitochondrial dysfunctions. Thus, a detailed exploration of the regulatory mechanisms of mitophagy is pivotal for enhancing our understanding and for the discovery of novel preventive and therapeutic options for these diseases. Nanomaterials have become integral in biomedicine and various other sectors, offering advanced solutions for medical uses including biological imaging, drug delivery, and disease diagnostics and therapy. Mitophagy is vital in managing the cellular effects elicited by nanomaterials. This review provides a comprehensive analysis of the molecular mechanisms underpinning mitophagy, underscoring its significant influence on the biological responses of cells to nanomaterials. Nanoparticles can initiate mitophagy via various pathways, among which the PINK1-Parkin pathway is critical for cellular defense against nanomaterial-induced damage by promoting mitophagy. The role of mitophagy in biological effects was induced by nanomaterials, which are associated with alterations in Ca2+ levels, the production of reactive oxygen species, endoplasmic reticulum stress, and lysosomal damage.

Early heart and skeletal muscle mitochondrial response to a moderate hypobaric hypoxia environment

In eukaryotic cells, aerobic energy is produced by mitochondria through oxygen uptake. However, little is known about the early mitochondrial responses to moderate hypobaric hypoxia (MHH) in highly metabolic active tissues. Here, we describe the mitochondrial responses to acute MHH in the heart and skeletal muscle. Rats were randomly allocated into a normoxia control group (n = 10) and a hypoxia group (n = 30), divided into three groups (0, 6, and 24 h post-MHH). The normoxia situation was recapitulated at the University of Granada, at 662 m above sea level. The MHH situation was performed at the High-Performance Altitude Training Centre of Sierra Nevada located in Granada at 2320 m above sea level. We found a significant increase in mitochondrial supercomplex assembly in the heart as soon as the animals reached 2320 m above sea level and their levels are maintained 24 h post-exposure, but not in skeletal muscle. Furthermore, in skeletal muscle, at 0 and 6 h, there was increased dynamin-related protein 1 (Drp1) expression and a significant reduction in Mitofusin 2. In conclusion, mitochondria from the muscle and heart respond differently to MHH: mitochondrial supercomplexes increase in the heart, whereas, in skeletal muscle, the mitochondrial pro-fission response is trigged. Considering that skeletal muscle was not actively involved in the ascent when the heart was beating faster to compensate for the hypobaric, hypoxic conditions, we speculate that the different responses to MHH are a result of the different energetic requirements of the tissues upon MHH. KEY POINTS: The heart and the skeletal muscle showed different mitochondrial responses to moderate hypobaric hypoxia. Moderate hypobaric hypoxia increases the assembly of the electron transport chain complexes into supercomplexes in the heart. Skeletal muscle shows an early mitochondrial pro-fission response following exposure to moderate hypobaric hypoxia.

Functional, structural, and molecular remodelling of the goldfish (Carassius auratus) heart under moderate hypoxia

The goldfish (Carassius auratus) is known for its physiologic ability to survive even long periods of oxygen limitation (hypoxia), adapting the cardiac performance to the requirements of peripheral tissue perfusion. We here investigated the effects of short-term moderate hypoxia on the heart, focusing on ventricular adaptation, in terms of hemodynamics and structural traits. Functional evaluations revealed that animals exposed to 4 days of environmental hypoxia increased the hemodynamic performance evaluated on ex vivo cardiac preparations. This was associated with a thicker and more vascularized ventricular compact layer and a reduced luminal lacunary space. Compared to normoxic animals, ventricular cardiomyocytes of goldfish exposed to hypoxia showed an extended mitochondrial compartment and a modulation of proteins involved in mitochondria dynamics. The enhanced expression of the pro-fission markers DRP1 and OMA1, and the modulation of the short and long forms of OPA1, suggested a hypoxia-related mitochondria fission. Our data propose that under hypoxia, the goldfish heart undergoes a structural remodelling associated with a potentiated cardiac activity. The energy demand for the highly performant myocardium is supported by an increased number of mitochondria, likely occurring through fission events.

AMPK Signaling Pathway as a Potential Therapeutic Target for Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease caused by the loss of dopaminergic neurons. Genetic factors, inflammatory responses, oxidative stress, metabolic disorders, cytotoxic factors, and mitochondrial dysfunction are all involved in neuronal death in neurodegenerative diseases. The risk of PD can be higher in aging individuals due to decreased mitochondrial function, energy metabolism, and AMP-activated protein kinase (AMPK) function. The potential of AMPK to regulate neurodegenerative disorders lies in its ability to enhance antioxidant capacity, reduce oxidative stress, improve mitochondrial function, decrease mitophagy and macroautophagy, and inhibit inflammation. In addition, it has been shown that modulating the catalytic activity of AMPK can protect the nervous system. This article reviews the mechanisms by which AMPK activation can modulate PD.

MTFR2-dependent mitochondrial fission promotes HCC progression

BACKGROUND

The role of mitochondrial dynamics, encompassing fission, fusion, and mitophagy, in cancer progression has been extensively studied. However, the specific impact of mitochondrial dynamics on hepatocellular carcinoma (HCC) is still under investigation.

METHODS

In this study, mitochondrial dynamic genes were obtained from the MitoCarta 3.0 database, and gene expression data were collected from The Cancer Genome Atlas (TCGA) database. Based on the expression of these dynamic genes and differentially expressed genes (DEGs), patients were stratified into two clusters. Subsequently, a prognostic model was constructed using univariate COX regression and the least absolute shrinkage and selection operator (LASSO) regression, and the prognostic signature was evaluated. We analyzed the interaction between these model genes and dynamic genes to identify hub genes and reveal mitochondrial status. Furthermore, we assessed immune infiltration, tumor mutational burden (TMB), tumor stemness indices (TSI), and the response to immune checkpoint block (ICB) therapy using the TIDE algorithm and risk scores. Additionally, transmission electron microscopy (TEM), hematoxylin-eosin (H&E) staining, immunohistochemistry (IHC), western blotting (WB), and immunofluorescence (IF) were conducted to afford detailed visualization of the morphology of the mitochondria and the expression patterns of fission-associated proteins.

RESULTS

Patients in Cluster 2 exhibited heightened mitochondrial fission and had a worse prognosis. The up-regulated dynamic genes in Cluster 2 were identified as fission genes. GO/KEGG analyses reconfirmed the connection of Cluster 2 to augmented mitochondrial fission activities. Subsequently, a ten-gene prognostic signature based on the differentially expressed genes between the two clusters was generated, with all ten genes being up-regulated in the high-risk group. Moreover, the potential links between these ten signature genes and mitochondrial dynamics were explored, suggesting their involvement in mediating mitochondrial fission through interaction with MTFR2. Further investigation revealed that the high-risk group had an unfavorable prognosis, with a higher mutation frequency of TP53, increased immune checkpoint expression, a higher TIS score, and a lower TIDE score. The mitochondrial imbalance characterized by increased fission and upregulated MTFR2 and DNM1L expression was substantiated in both HCC specimens and cell lines.

CONCLUSIONS

In conclusion, we developed a novel MTFR2-related prognostic signature comprising ten mitochondrial dynamics genes. These genes play crucial roles in mitochondrial fission and have the potential to serve as important predictors and therapeutic targets for HCC.

The mitochondrial-endoplasmic reticulum co-transfer in dental pulp stromal cell promotes pulp injury repair

Dental pulp injury remains a clinical challenge with limited therapeutic approaches. In the present study, we sought to prove that dental pulp stromal cells (DPSCs) mitochondrial transfer could promote dental pulp injury repair and endoplasmic reticulum (ER)-mitochondrial contacts have a significant regulatory effect on mitochondrial transfer. Healthy DPSCs were co-cultured directly or indirectly with injured DPSCs in the first molar of 1-2 month SD rats or in vitro. Mitochondrial transfer was observed after 24 h of co-culture using fluorescence microscopy and live cell workstation. After co-culture for 1W, 8-OhdG immunofluorescence, mitochondrial membrane potential and total oxidant status/total antioxidant status were used to detect the mitochondrial function of injured DPSCs before and after mitochondrial transfer. Subsequently, mitochondria-ER co-transfer was regulated by modulating mitochondria-ER binding in healthy DPSCs, and the results of GRP78 and CHOP in DPSCs, and PDI immunofluorescence and haematoxylin and eosin staining of pulp tissue were analysed to clarify the effects of modulating mitochondria-ER co-transfer on endoplasmic reticulum stress (ERS), and on pulp injury repair. Fluorescence microscopy and live cell workstation results showed significant mitochondrial transfer between DPSCs. Meanwhile, mitochondrial transfer significantly restored mitochondrial function in injured DPSCs. By modulating mitochondrial-ER binding, the efficiency of mitochondrial transfer between DPSCs was significantly affected and had an impact on ERS in injured cells. Mitochondrial transfer of DPSCs significantly promotes pulpal injury repair and functional recovery of damaged DPSCs, and mitochondrial transfer of DPSCs is regulated by mitochondria-ER binding.

In vitro anticancer effect of azithromycin targeting hypoxic lung cancer cells via the inhibition of mitophagy

Solid tumors are predisposed to hypoxia, which induces tumor progression, and causes resistance to treatment. Hypoxic tumor cells exploit auto- and mitophagy to facilitate metabolism and mitochondrial renewal. Azithromycin (AZM), a widely used macrolide, inhibits autophagy in cancer cells. The aim of the present study was to determine whether AZM targeted hypoxic cancer cells by inhibiting mitophagy. Lung cancer cell lines (A549, H1299 and NCI-H441) were cultured for up to 72 h under normoxic (20% O2) or hypoxic (0.3% O2) conditions in the presence or absence of AZM (≤25 µM), and the cell survival, autophagy flux and mitophagy flux were evaluated. AZM treatment reduced cell survival under hypoxic conditions, caused mitolysosome dysfunction with raised lysosomal pH and impaired the efficient removal of hypoxia-damaged mitochondria, eventually inducing apoptosis in the cancer cells. The cytotoxic effect of AZM under hypoxic conditions was abolished in mitochondria-deficient A549 cells (ρ° cells). The present study demonstrated that AZM reduced lung cancer cell survival under hypoxic conditions by interfering with the efficient removal of damaged mitochondria through mitophagy inhibition. Thus, AZM may be considered as a promising anticancer drug that targets the mitochondrial vulnerability of hypoxic lung cancer cells.

Endometrial organoids: a reservoir of functional mitochondria for uterine repair

Background: Asherman's syndrome (AS) is a dreadful gynecological disorder of the uterus characterized by intrauterine adhesion with severe fibrotic lesions, resulting in a damaged basalis layer with infertility. Despite extensive research on overcoming AS, evidence-based effective and reproducible treatments to improve the structural and functional morphology of the AS endometrium have not been established. Methods: Endometrial organoids generated from human or mouse endometrial tissues were transplanted into the uterine cavity of a murine model of AS to evaluate their transplantable feasibility to improve the AS uterine environment. The successful engraftment of organoid was confirmed by detection of human mitochondria and cytosol (for human endometrial organoid) or enhanced green fluorescent protein signals (for mouse endometrial organoid) in the recipient endometrium. The therapeutic effects mediated by organoid transplantation were examined by the measurements of fibrotic lesions, endometrial receptivity and angiogenesis, and fertility assessment by recording the number of implantation sites and weighing the fetuses and placenta. To explore the cellular and molecular mechanisms underlying the recovery of AS endometrium, we evaluated the status of mitochondrial movement and biogenetics in organoid transplanted endometrium. Results: Successfully engrafted endometrial organoids with similar morphological and molecular features to the parental tissues dramatically repaired the AS-induced damaged endometrium, significantly reducing fibrotic lesions and increasing fertility outcomes in mice. Moreover, dysfunctional mitochondria in damaged tissues, which we propose might be a key cellular feature of the AS endometrium, was fully recovered by functional mitochondria transferred from engrafted endometrial organoids. Endometrial organoid-originating mitochondria restored excessive collagen accumulation in fibrotic lesions and shifted uterine metabolic environment to levels observed in the normal endometrium. Conclusions: Our findings suggest that endometrial organoid-originating mitochondria might be key players to mediate uterine repair resulting in fertility enhancement by recovering abrogated metabolic circumstance of the endometrium with AS. Further studies addressing the clinical applicability of endometrial organoids may aid in identifying new therapeutic strategies for infertility in patients with AS.

Investigating the Mitoprotective Effects of S1P Receptor Modulators Ex Vivo Using a Novel Semi-Automated Live Imaging Set-Up

In multiple sclerosis (MS), mitochondrial alterations appear to contribute to disease progression. The sphingosine-1-phosphate receptor modulator siponimod is approved for treating secondary progressive MS. Its preceding compound fingolimod was shown to prevent oxidative stress-induced alterations in mitochondrial morphology. Here, we assessed the effects of siponimod, compared to fingolimod, on neuronal mitochondria in oxidatively stressed hippocampal slices. We have also advanced the model of chronic organotypic hippocampal slices for live imaging, enabling semi-automated monitoring of mitochondrial alterations. The slices were prepared from B6.Cg-Tg(Thy1-CFP/COX8A)S2Lich/J mice that display fluorescent neuronal mitochondria. They were treated with hydrogen peroxide (oxidative stress paradigm) ± 1 nM siponimod or fingolimod for 24 h. Afterwards, mitochondrial dynamics were investigated. Under oxidative stress, the fraction of motile mitochondria decreased and mitochondria were shorter, smaller, and covered smaller distances. Siponimod partly prevented oxidatively induced alterations in mitochondrial morphology; for fingolimod, a similar trend was observed. Siponimod reduced the decrease in mitochondrial track displacement, while both compounds significantly increased track speed and preserved motility. The novel established imaging and analysis tools are suitable for assessing the dynamics of neuronal mitochondria ex vivo. Using these approaches, we showed that siponimod at 1 nM partially prevented oxidatively induced mitochondrial alterations in chronic brain slices.

Mitochondrial Dysfunction in Arrhythmia and Cardiac Hypertrophy

Arrhythmia and cardiac hypertrophy are two very common cardiovascular diseases that can lead to heart failure and even sudden death, thus presenting a serious threat to human life and health. According to global statistics, nearly one million people per year die from arrhythmia, cardiac hypertrophy and other associated cardiovascular diseases. Hence, there is an urgent need to find new treatment targets and to develop new intervention measures. Recently, mitochondrial dysfunction has been examined in relation to heart disease with a view to lowering the incidence of arrhythmia and cardiac hypertrophy. The heart is the body's largest energy consuming organ, turning over about 20 kg of adenosine triphosphate (ATP) per day in the mitochondria. Mitochondrial oxidative phosphorylation (OXPHOS) produces up to 90% of the ATP needed by cardiac muscle cells for contraction and relaxation. Dysfunction of heart mitochondria can therefore induce arrhythmia, cardiac hypertrophy and other cardiovascular diseases. Mitochondrial DNA (mtDNA) mutations cause disorders in OXPHOS and defects in the synthesis of muscle contraction proteins. These lead to insufficient production of secondary ATP, increased metabolic requirements for ATP by the myocardium, and the accumulation of reactive oxygen species (ROS). The resulting damage to myocardial cells eventually induces arrhythmia and cardiac hypertrophy. Mitochondrial damage decreases the efficiency of energy production, which further increases the production of ROS. The accumulation of ROS causes mitochondrial damage and eventually leads to a vicious cycle of mitochondrial damage and low efficiency of mitochondrial energy production. In this review, the mechanism underlying the development of arrhythmia and cardiac hypertrophy is described in relation to mitochondrial energy supply, oxidative stress, mtDNA mutation and Mitochondrial dynamics. Targeted therapy for arrhythmia and cardiac hypertrophy induced by mitochondrial dysfunction is also discussed in terms of its potential clinical value. These strategies should improve our understanding of mitochondrial biology and the pathogenesis of arrhythmia and cardiac hypertrophy. They may also identify novel strategies for targeting mitochondria in the treatment of these diseases.

Mitochondrial dysfunction at the crossroad of cardiovascular diseases and cancer

A large body of evidence indicates the existence of a complex pathophysiological relationship between cardiovascular diseases and cancer. Mitochondria are crucial organelles whose optimal activity is determined by quality control systems, which regulate critical cellular events, ranging from intermediary metabolism and calcium signaling to mitochondrial dynamics, cell death and mitophagy. Emerging data indicate that impaired mitochondrial quality control drives myocardial dysfunction occurring in several heart diseases, including cardiac hypertrophy, myocardial infarction, ischaemia/reperfusion damage and metabolic cardiomyopathies. On the other hand, diverse human cancers also dysregulate mitochondrial quality control to promote their initiation and progression, suggesting that modulating mitochondrial homeostasis may represent a promising therapeutic strategy both in cardiology and oncology. In this review, first we briefly introduce the physiological mechanisms underlying the mitochondrial quality control system, and then summarize the current understanding about the impact of dysregulated mitochondrial functions in cardiovascular diseases and cancer. We also discuss key mitochondrial mechanisms underlying the increased risk of cardiovascular complications secondary to the main current anticancer strategies, highlighting the potential of strategies aimed at alleviating mitochondrial impairment-related cardiac dysfunction and tumorigenesis. It is hoped that this summary can provide novel insights into precision medicine approaches to reduce cardiovascular and cancer morbidities and mortalities.

Integrated machine learning survival framework develops a prognostic model based on inter-crosstalk definition of mitochondrial function and cell death patterns in a large multicenter cohort for lower-grade glioma

BACKGROUND

Lower-grade glioma (LGG) is a highly heterogeneous disease that presents challenges in accurately predicting patient prognosis. Mitochondria play a central role in the energy metabolism of eukaryotic cells and can influence cell death mechanisms, which are critical in tumorigenesis and progression. However, the prognostic significance of the interplay between mitochondrial function and cell death in LGG requires further investigation.

METHODS

We employed a robust computational framework to investigate the relationship between mitochondrial function and 18 cell death patterns in a cohort of 1467 LGG patients from six multicenter cohorts worldwide. A total of 10 commonly used machine learning algorithms were collected and subsequently combined into 101 unique combinations. Ultimately, we devised the mitochondria-associated programmed cell death index (mtPCDI) using machine learning models that exhibited optimal performance.

RESULTS

The mtPCDI, generated by combining 18 highly influential genes, demonstrated strong predictive performance for prognosis in LGG patients. Biologically, mtPCDI exhibited a significant correlation with immune and metabolic signatures. The high mtPCDI group exhibited enriched metabolic pathways and a heightened immune activity profile. Of particular importance, our mtPCDI maintains its status as the most potent prognostic indicator even following adjustment for potential confounding factors, surpassing established clinical models in predictive strength.

CONCLUSION

Our utilization of a robust machine learning framework highlights the significant potential of mtPCDI in providing personalized risk assessment and tailored recommendations for metabolic and immunotherapy interventions for individuals diagnosed with LGG. Of particular significance, the signature features highly influential genes that present further prospects for future investigations into the role of PCD within mitochondrial function.

The hypoxia-inducible factor 1 pathway plays a critical role in the development of breast muscle myopathies in broiler chickens: a comprehensive review

In light of the increased worldwide demand for poultry meat, genetic selection efforts have intensified to produce broiler strains that grow at a higher rate, have greater breast meat yield (BMY), and convert feed to meat more efficiently. The increased selection pressure for these traits, BMY in particular, has produced multiple breast meat quality defects collectively known as breast muscle myopathies (BMM). Hypoxia has been proposed as one of the major mechanisms triggering the onset and occurrence of these myopathies. In this review, the relevant literature on the causes and consequences of hypoxia in broiler breast muscles is reviewed and discussed, with a special focus on the hypoxia-inducible factor 1 (HIF-1) pathway. Muscle fiber hypertrophy induced by selective breeding for greater BMY reduces the space available in the perimysium and endomysium for blood vessels and capillaries. The hypoxic state that results from the lack of circulation in muscle tissue activates the HIF-1 pathway. This pathway alters energy metabolism by promoting anaerobic glycolysis, suppressing the tricarboxylic acid cycle and damaging mitochondrial function. These changes lead to oxidative stress that further exacerbate the progression of BMM. In addition, activating the HIF-1 pathway promotes fatty acid synthesis, lipogenesis, and lipid accumulation in myopathic muscle tissue, and interacts with profibrotic growth factors leading to increased deposition of matrix proteins in muscle tissue. By promoting lipidosis and fibrosis, the HIF-1 pathway contributes to the development of the distinctive phenotypes of BMM, including white striations in white striping-affected muscles and the increased hardness of wooden breast-affected muscles.

Cancer stem cell fate determination: mito-nuclear communication

Cancer stem cells (CSCs) are considered to be responsible for tumor recurrence and metastasis. Therefore, clarification of the mechanisms involved in CSC stemness maintenance and cell fate determination would provide a new strategy for cancer therapy. Unregulated cellular energetics has been accepted as one of the hallmarks of cancer cells, but recent studies have revealed that mitochondrial metabolism can also actively determine CSC fate by affecting nuclear stemness gene expression. Herein, from the perspective of mito-nuclear communication, we review recent progress on the influence of mitochondria on CSC potential from four aspects: metabolism, dynamics, mitochondrial homeostasis, and reactive oxygen species (ROS). Video Abstract.

Unraveling the Peculiar Features of Mitochondrial Metabolism and Dynamics in Prostate Cancer

Prostate cancer (PCa) is the second leading cause of cancer deaths among men in Western countries. Mitochondria, the "powerhouse" of cells, undergo distinctive metabolic and structural dynamics in different types of cancer. PCa cells experience peculiar metabolic changes during their progression from normal epithelial cells to early-stage and, progressively, to late-stage cancer cells. Specifically, healthy cells display a truncated tricarboxylic acid (TCA) cycle and inefficient oxidative phosphorylation (OXPHOS) due to the high accumulation of zinc that impairs the activity of m-aconitase, the enzyme of the TCA cycle responsible for the oxidation of citrate. During the early phase of cancer development, intracellular zinc levels decrease leading to the reactivation of m-aconitase, TCA cycle and OXPHOS. PCa cells change their metabolic features again when progressing to the late stage of cancer. In particular, the Warburg effect was consistently shown to be the main metabolic feature of late-stage PCa cells. However, accumulating evidence sustains that both the TCA cycle and the OXPHOS pathway are still present and active in these cells. The androgen receptor axis as well as mutations in mitochondrial genes involved in metabolic rewiring were shown to play a key role in PCa cell metabolic reprogramming. Mitochondrial structural dynamics, such as biogenesis, fusion/fission and mitophagy, were also observed in PCa cells. In this review, we focus on the mitochondrial metabolic and structural dynamics occurring in PCa during tumor development and progression; their role as effective molecular targets for novel therapeutic strategies in PCa patients is also discussed.

Alamandine/MrgD axis prevents TGF-β1-mediated fibroblast activation via regulation of aerobic glycolysis and mitophagy

BACKGROUND

Idiopathic pulmonary fibrosis is a chronic progressive, lethal disease in which ectopic lung fibroblast (LF) activation plays a vital part. We have previously shown that alamandine (ALA) exerts anti-fibrosis effects via the MAS-related G-protein coupled receptor D (MrgD). Here, we further investigate how it moderates transforming growth factor β1 (TGF-β1)-induced LF activation by regulating glucose metabolism and mitochondria autophagy (mitophagy).

METHODS

In vitro, we examined glycolysis-related protein hexokinase 2 (HK2), 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3), and lactic acid in cells treated with TGF-β1. The oxygen consumption rate and the extracellular acidification rate were detected using Seahorse assays. Then, mitophagy was evaluated using transmission electron microscopy, mt-Keima, and the co-localization of Parkin and COX IV with LC3 and LAMP1, respectively. The autophagic degradation of HK2 and PFKFB3 was detected by 3MA and bafilomycin A1 and assessed by their co-localization with LC3 and LAMP1, respectively. The effects of ALA on LF activation markers collagen I and α-SMA were detected. The effects of ALA on glucose metabolism, mitophagy, and the activation of LF were also investigated in vivo.

RESULTS

We found that the ALA/MrgD axis improved TGF-β1-mediated LF activation by repressing glycolysis by downregulating HK2 and PFKFB3 expression. Lactic acid sustained positive feedback between glycolysis and LF activation by maintaining the expression of HK2 and PFKFB3. We also showed that glycolysis enhancement resulted from blocking the autophagic degradation of HK2 and PFKFB3 while upregulated mRNA levels by TGF-β1, while all of those improved by ALA adding. Importantly, we determined that moderation of Parkin/LC3-mediated mitophagy by TGF-β1 also promotes glycolysis but is reversed by ALA. Furthermore, we proved that ALA counteracts the effects of bleomycin on HK2, PFKFB3, LC3, Parkin, and LF activation in vivo.

CONCLUSION

In this study, we show that the ALA/MrgD axis prevents TGF-β1-mediated fibroblast activation via regulation of aerobic glycolysis and mitophagy.

Mitochondrial Control in Inflammatory Gastrointestinal Diseases

Mitochondria play a central role in the pathophysiology of inflammatory bowel disease (IBD) and colorectal cancer (CRC). The maintenance of mitochondrial function is necessary for a stable immune system. Mitochondrial dysfunction in the gastrointestinal system leads to the excessive activation of multiple inflammatory signaling pathways, leading to IBD and increased severity of CRC. In this review, we focus on the mitochondria and inflammatory signaling pathways and its related gastrointestinal diseases.

Construction of a mitochondrial dysfunction related signature of diagnosed model to obstructive sleep apnea

Background: The molecular mechanisms underlying obstructive sleep apnea (OSA) and its comorbidities may involve mitochondrial dysfunction. However, very little is known about the relationships between mitochondrial dysfunction-related genes and OSA. Methods: Mitochondrial dysfunction-related differentially expressed genes (DEGs) between OSA and control adipose tissue samples were identified using data from the Gene Expression Omnibus database and information on mitochondrial dysfunction-related genes from the GeneCards database. A mitochondrial dysfunction-related signature of diagnostic model was established using least absolute shrinkage and selection operator Cox regression and then verified. Additionally, consensus clustering algorithms were used to conduct an unsupervised cluster analysis. A protein-protein interaction network of the DEGs between the mitochondrial dysfunction-related clusters was constructed using STRING database and the hub genes were identified. Functional analyses, including Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, gene set enrichment analysis (GSEA), and gene set variation analysis (GSVA), were conducted to explore the mechanisms involved in mitochondrial dysfunction in OSA. Immune cell infiltration analyses were conducted using CIBERSORT and single-sample GSEA (ssGSEA). Results: we established mitochondrial dysfunction related four-gene signature of diagnostic model consisted of NPR3, PDIA3, SLPI, ERAP2, and which could easily distinguish between OSA patients and controls. In addition, based on mitochondrial dysfunction-related gene expression, we identified two clusters among all the samples and three clusters among the OSA samples. A total of 10 hub genes were selected from the PPI network of DEGs between the two mitochondrial dysfunction-related clusters. There were correlations between the 10 hub genes and the 4 diagnostic genes. Enrichment analyses suggested that autophagy, inflammation pathways, and immune pathways are crucial in mitochondrial dysfunction in OSA. Plasma cells and M0 and M1 macrophages were significantly different between the OSA and control samples, while several immune cell types, especially T cells (γ/δ T cells, natural killer T cells, regulatory T cells, and type 17 T helper cells), were significantly different among mitochondrial dysfunction-related clusters of OSA samples. Conclusion: A novel mitochondrial dysfunction-related four-gen signature of diagnostic model was built. The genes are potential biomarkers for OSA and may play important roles in the development of OSA complications.

Role of mitochondria-associated endoplasmic reticulum membranes in insulin sensitivity, energy metabolism, and contraction of skeletal muscle

Skeletal muscle has a critical role in the regulation of the energy balance of the organism, particularly as the principal tissue responsible for insulin-stimulated glucose disposal and as the major site of peripheral insulin resistance (IR), which has been related to accumulation of lipid intermediates, reduced oxidative capacity of mitochondria and endoplasmic reticulum (ER) stress. These organelles form contact sites, known as mitochondria-associated ER membranes (MAMs). This interconnection seems to be involved in various cellular processes, including Ca²⁺ transport and energy metabolism; therefore, MAMs could play an important role in maintaining cellular homeostasis. Evidence suggests that alterations in MAMs may contribute to IR. However, the evidence does not refer to a specific subcellular location, which is of interest due to the fact that skeletal muscle is constituted by oxidative and glycolytic fibers as well as different mitochondrial populations that appear to respond differently to stimuli and pathological conditions. In this review, we show the available evidence of possible differential responses in the formation of MAMs in skeletal muscle as well as its role in insulin signaling and the beneficial effect it could have in the regulation of energetic metabolism and muscular contraction.