VDAC1 regulates mitophagy in NLRP3 inflammasome activation in retinal capillary endothelial cells under high-glucose conditions

The role and mechanism of VDAC1 in type 2 diabetes: An underestimated target of environmental pollutants

Type 2 diabetes (T2D) is a chronic metabolic disease that accounts for more than 90% of diabetic patients. Its main feature is hyperglycemia due to insulin resistance or insulin deficiency. With changes in diet and lifestyle habits, the incidence of T2D in adolescents has burst in recent decades. The deterioration in the exposure to the environmental pollutants further aggravates the prevalence of T2D, and consequently, it imposes a significant economic burden. Therefore, early prevention and symptomatic treatment are essential to prevent diabetic complications. Mitochondrial number and electron transport chain activity are decreased in the patients with T2D. Voltage-Dependent Anion Channel 1 (VDAC1), as a crucial channel protein on the outer membrane of mitochondria, regulates signal transduction between mitochondria and other cellular components, participating in various biological processes. When VDAC1 exists in oligomeric form, it additionally facilitates the entry and exit of macromolecules into and from mitochondria, modulating insulin secretion. We summarize and highlight the interplay between VDAC1 and T2D, especially in the environmental pollutants-related T2D, shed light on the potential therapeutic implications of targeting VDAC1 monomers and oligomers, providing a new possible target for the treatment of T2D.

Resilience to diabetic retinopathy

Chronic elevation of blood glucose at first causes relatively minor changes to the neural and vascular components of the retina. As the duration of hyperglycemia persists, the nature and extent of damage increases and becomes readily detectable. While this second, overt manifestation of diabetic retinopathy (DR) has been studied extensively, what prevents maximal damage from the very start of hyperglycemia remains largely unexplored. Recent studies indicate that diabetes (DM) engages mitochondria-based defense during the retinopathy-resistant phase, and thereby enables the retina to remain healthy in the face of hyperglycemia. Such resilience is transient, and its deterioration results in progressive accumulation of retinal damage. The concepts that co-emerge with these discoveries set the stage for novel intellectual and therapeutic opportunities within the DR field. Identification of biomarkers and mediators of protection from DM-mediated damage will enable development of resilience-based therapies that will indefinitely delay the onset of DR.

Zishen Tongyang Huoxue decoction (TYHX) alleviates sinoatrial node cell ischemia/reperfusion injury by directing mitochondrial quality control via the VDAC1-β-tubulin signaling axis

ETHNOPHARMACOLOGICAL RELEVANCE

Zishen Tongyang Huoxue decoction (TYHX) has been used clinically for nearly 40 years to treat sick sinus syndrome. Previous reports showed that TYHX can inhibit calcium flux by regulating mitochondrial homeostasis via β-tubulin and increase sinoatrial node cell (SNC) activity. However, the underlying mechanisms remain unclear.

AIM OF THE STUDY

We aimed to verify the protective effect of TYHX against SNC ischemia by regulating mitochondrial quality control (MQC) through β-tubulin and voltage-dependent anion-selective channel 1 (VDAC1) silencing.

MATERIALS AND METHODS

We established an in vitro model of SNC ischemia/reperfusion (I/R) injury and performed rescue experiments by silencing β-tubulin and VDAC1 expression. Cell-Counting Kit 8 assays were performed to detect cell viabilities, and terminal deoxynucleotidyl transferase dUTP nick-end labeling assays (paired with confocal microscopy) were performed to detect fragmentation. Mitochondrial-energy metabolism was detected using the Seahorse assay system. Reverse transcription-quantitative polymerase chain reaction analysis was performed to detect the mRNA-expression levels of MQC-related genes.

RESULTS

TYHX inhibited SNC mitochondrial injury. During I/R simulation, TYHX maintained β-tubulin stability, regulated synergy between mitophagy and the mitochondrial unfolded-protein response (UPRmt), and inhibited mitochondrial oxidative stress and overactive SNC fission. Next-generation sequencing suggested that mitochondrial-membrane injury caused SNC apoptosis. We also found that TYHX regulated β-tubulin expression through VDAC1 and inhibited dynamin-related protein 1 migration to mitochondria from the nucleus. After preventing excessive mitochondrial fission, the mitophagy-UPRmt pathway, mitochondrial-membrane potential, and mitochondrial energy were restored. VDAC1 silencing affected the regulatory mechanism of MQC in a β-tubulin-dependent manner via TYHX.

CONCLUSION

TYHX regulated mitochondrial membrane-permeability through VDAC1, which affected MQC through β-tubulin and inhibited mitochondrial apoptosis. Our findings may help in developing drugs to protect the sinoatrial node.

Role of mitophagy in ocular neurodegeneration

Neurons in the central nervous system are among the most metabolically active cells in the body, characterized by high oxygen consumption utilizing glucose both aerobically and anaerobically. Neurons have an abundance of mitochondria which generate adequate ATP to keep up with the high metabolic demand. One consequence of the oxidative phosphorylation mechanism of ATP synthesis, is the generation of reactive oxygen species which produces cellular injury as well as damage to mitochondria. Mitochondria respond to injury by fusion which serves to ameliorate the damage through genetic complementation. Mitochondria also undergo fission to meet an increased energy demand. Loss of mitochondria is also compensated by increased biogenesis to generate new mitochondria. Damaged mitochondria are removed by mitophagy, an autophagic process, in which damaged mitochondria are surrounded by a membrane to form an autophagosome which ultimately fuses with the lysosome resulting in degradation of faulty mitochondria. Dysregulation of mitophagy has been reported in several central nervous system disorders, including, Alzheimer's disease and Parkinson's disease. Recent studies point to aberrant mitophagy in ocular neurodegenerative disorders which could be an important contributor to the disease etiology/pathology. This review article highlights some of the recent findings that point to dysregulation of mitophagy and it's underlying mechanisms in ocular neurodegenerative diseases, including, glaucoma, age-related macular degeneration and diabetic retinopathy.

Overexpression of the mitochondrial anti-viral signaling protein, MAVS, in cancers is associated with cell survival and inflammation

Mitochondrial anti-viral signaling protein (MAVS) plays an important role in host defense against viral infection via coordinating the activation of NF-κB and interferon regulatory factors. The mitochondrial-bound form of MAVS is essential for its anti-viral innate immunity. Recently, tumor cells were proposed to mimic a viral infection by activating RNA-sensing pattern recognition receptors. Here, we demonstrate that MAVS is overexpressed in a panel of viral non-infected cancer cell lines and patient-derived tumors, including lung, liver, bladder, and cervical cancers, and we studied its role in cancer. Silencing MAVS expression reduced cell proliferation and the expression and nuclear translocation of proteins associated with transcriptional regulation, inflammation, and immunity. MAVS depletion reduced expression of the inflammasome components and inhibited its activation/assembly. Moreover, MAVS directly interacts with the mitochondrial protein VDAC1, decreasing its conductance, and we identified the VDAC1 binding site in MAVS. Our findings suggest that MAVS depletion, by reducing cancer cell proliferation and inflammation, represents a new target for cancer therapy.

Identification of mitochondrial-related genes as potential biomarkers for the subtyping and prediction of Alzheimer's disease

Introduction

Alzheimer's disease (AD) is a progressive and debilitating neurodegenerative disorder prevalent among older adults. Although AD symptoms can be managed through certain treatments, advancing the understanding of underlying disease mechanisms and developing effective therapies is critical.

Methods

In this study, we systematically analyzed transcriptome data from temporal lobes of healthy individuals and patients with AD to investigate the relationship between AD and mitochondrial autophagy. Machine learning algorithms were used to identify six genes-FUNDC1, MAP1LC3A, CSNK2A1, VDAC1, CSNK2B, and ATG5-for the construction of an AD prediction model. Furthermore, AD was categorized into three subtypes through consensus clustering analysis.

Results

The identified genes are closely linked to the onset and progression of AD and can serve as reliable biomarkers. The differences in gene expression, clinical features, immune infiltration, and pathway enrichment were examined among the three AD subtypes. Potential drugs for the treatment of each subtype were also identified.

Discussion

The findings observed in the present study can help to deepen the understanding of the underlying disease mechanisms of AD and enable the development of precision medicine and personalized treatment approaches.

Mitophagy and Traumatic Brain Injury: Regulatory Mechanisms and Therapeutic Potentials

Traumatic brain injury (TBI), a kind of external trauma-induced brain function alteration, has posed a financial burden on the public health system. TBI pathogenesis involves a complicated set of events, including primary and secondary injuries that can cause mitochondrial damage. Mitophagy, a process in which defective mitochondria are specifically degraded, segregates and degrades defective mitochondria allowing a healthier mitochondrial network. Mitophagy ensures that mitochondria remain healthy during TBI, determining whether neurons live or die. Mitophagy acts as a critical regulator in maintaining neuronal survival and healthy. This review will discuss the TBI pathophysiology and the consequences of the damage it causes to mitochondria. This review article will explore the mitophagy process, its key factors, and pathways and reveal the role of mitophagy in TBI. Mitophagy will be further recognized as a therapeutic approach in TBI. This review will offer new insights into mitophagy's role in TBI progression.

Mitochondrial dysfunction in vascular endothelial cells and its role in atherosclerosis

The mitochondria are essential organelles that generate large amounts of ATP via the electron transport chain (ECT). Mitochondrial dysfunction causes reactive oxygen species accumulation, energy stress, and cell death. Endothelial mitochondrial dysfunction is an important factor causing abnormal function of the endothelium, which plays a central role during atherosclerosis development. Atherosclerosis-related risk factors, including high glucose levels, hypertension, ischemia, hypoxia, and diabetes, promote mitochondrial dysfunction in endothelial cells. This review summarizes the physiological and pathophysiological roles of endothelial mitochondria in endothelial function and atherosclerosis.

Research Progress on Mitochondrial Dysfunction in Diabetic Retinopathy

Diabetic Retinopathy (DR) is one of the most important microvascular complications of diabetes mellitus, which can lead to blindness in severe cases. Mitochondria are energy-producing organelles in eukaryotic cells, which participate in metabolism and signal transduction, and regulate cell growth, differentiation, aging, and death. Metabolic changes of retinal cells and epigenetic changes of mitochondria-related genes under high glucose can lead to mitochondrial dysfunction and induce mitochondrial pathway apoptosis. In addition, mitophagy and mitochondrial dynamics also change adaptively. These mechanisms may be related to the occurrence and progression of DR, and also provide valuable clues for the prevention and treatment of DR. This article reviews the mechanism of DR induced by mitochondrial dysfunction, and the prospects for related treatment.

Identification of two patterns of mitochondrial DNA-copy number variation in postcentral gyrus during aging, influenced by body mass index and type 2 diabetes

AIMS

Mitochondrial (mt) DNA replication is strongly associated with oxidative stress, a condition triggered by aging and hyperglycemia, both of which contribute to mitophagy disruption and inflammation. This observational exploratory study evaluated mtDNA-copy number (mtDNA-CN) and expression of genes involved in mitochondriogenesis (PPARGC1A, TFAM, TFB1M, TFB2M), mitophagy (PINK1, PRKN), and inflammatory pathways triggered by hyperglycemia (TXNIP, NLRP3, NFKB1), in the postcentral gyrus of adults and older individuals with and without type 2 diabetes mellitus (T2D).

MAIN METHODS

Quantitative real-time PCR was employed to evaluate mtDNA-CN and gene expression; tissue autofluorescence, a marker of aging and of cells with damaged organelles, was also quantified.

KEY FINDINGS

No correlation was found between age and mtDNA-CN, but a direct correlation was observed for cases with mtDNA-CN >1000 (r = 0.41). The mtDNA-CN >1000 group had greater tissue autofluorescence and higher body mass index compared to the mtDNA-CN <1000 group (BMI; 25.7 vs 22.0 kg/m², respectively). mtDNA-CN correlated with tissue autofluorescence in the overall sample (r = 0.55) and in the T2D group (r = 0.64). PINK and PRKN expressions were inversely correlated with age. Mitochondriogenesis genes and TXNIP expressions were higher in the T2D group, and correlations among the mitochondriogenesis genes were also stronger in this group, relative to the subgroup with mtDNA-CN >1000.

Spotlight on pyroptosis: role in pathogenesis and therapeutic potential of ocular diseases

Pyroptosis is a programmed cell death characterized by swift plasma membrane disruption and subsequent release of cellular contents and pro-inflammatory mediators (cytokines), including IL‐1β and IL‐18. It differs from other types of programmed cell death such as apoptosis, autophagy, necroptosis, ferroptosis, and NETosis in terms of its morphology and mechanism. As a recently discovered form of cell death, pyroptosis has been demonstrated to be involved in the progression of multiple diseases. Recent studies have also suggested that pyroptosis is linked to various ocular diseases. In this review, we systematically summarized and discussed recent scientific discoveries of the involvement of pyroptosis in common ocular diseases, including diabetic retinopathy, age-related macular degeneration, AIDS-related human cytomegalovirus retinitis, glaucoma, dry eye disease, keratitis, uveitis, and cataract. We also organized new and emerging evidence suggesting that pyroptosis signaling pathways may be potential therapeutic targets in ocular diseases, hoping to provide a summary of overall intervention strategies and relevant multi-dimensional evaluations for various ocular diseases, as well as offer valuable ideas for further research and development from the perspective of pyroptosis.

Inhibition of mitochondrial fission alters neo-intimal hyperplasia via PI3K/Akt signaling in arteriovenous fistulas

BACKGROUND/OBJECTIVE

Arteriovenous fistulas (AVFs) are the preferred vascular access for hemodialysis of patients with end-stage renal disease. However, there is a high incidence of AVF failures caused by insufficient outward remodeling or venous neo-intimal hyperplasia formation. Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) play an important role in many cardiovascular diseases. Abnormal VSMC proliferation and migration could be abolished by inhibition of mitochondrial division.

METHOD

We found that abnormal proliferation and migration of VSMCs and increased mitochondrial fission were associated with AVF stenosis in patients. We also investigated the mechanisms, particularly the role of mitochondrial dynamics, underlying these VSMC behaviors. In vitro, we observed that inhibition of mitochondrial fission and Akt phosphorylation can diminish proliferation and migration of VSMCs induced by platelet-derived growth factor-BB (PDGF-BB). In vivo, daily intraperitoneal injections of mitochondrial division inhibitor 1 (Mdivi-1) decreased VSMC proliferation and reduced AVF wall thickness in a rat AVF model.

CONCLUSION AND RESULT

Our results suggest that inhibition of mitochondrial fission improves AVF patency by reducing wall thickening through the PI3K/Akt signaling pathway. Therefore, inhibition of mitochondrial fission has the clinical potential to improve AVF patency.