VDAC regulation by the Bcl-2 family of proteins

Permeabilization of the outer mitochondrial membrane: Mechanisms and consequences

Permeabilization of the outer mitochondrial membrane is а physiological process that can allow certain molecules to pass through it, such as low molecular weight solutes required for cellular respiration. This process is also important for the development of various modes of cell death. Depending on the severity of this process, cells can die by autophagy, apoptosis, or necrosis/necroptosis. Distinct types of pores can be opened at the outer mitochondrial membrane depending on physiological or pathological stimuli, and different mechanisms can be activated in order to open these pores. In this comprehensive review, all these types of permeabilization, the mechanisms of their activation, and their role in various diseases are discussed.

BCL2L13 at endoplasmic reticulum-mitochondria contact sites regulates calcium homeostasis to maintain skeletal muscle function

The physical connection between mitochondria and endoplasmic reticulum (ER) is an essential signaling hub to ensure organelle and cellular functions. In skeletal muscle, ER-mitochondria calcium (Ca2+) signaling is crucial to maintain cellular homeostasis during physical activity. High expression of BCL2L13, a member of the BCL-2 family, was suggested as an adaptive response in endurance-trained human subjects. In adult zebrafish, we found that the loss of Bcl2l13 impairs skeletal muscle structure and function. Ca2+ signaling is altered in Bcl2l13 knockout animals and mitochondrial complexes activity is decreased. Organelle fractioning in mammalian cells shows BCL2L13 at mitochondria, ER, and mitochondria-associated membranes. ER-mitochondria contact sites number is not modified by BCL2L13 modulation, but knockdown of BCL2L13 in C2C12 cells changes cytosolic Ca2+ release and mitochondrial Ca2+ uptake. This suggests that BCL2L13 interaction with mitochondria and ER, and its role in Ca2+ signaling, contributes to proper skeletal muscle function.

Ferroptosis in the adjuvant treatment of lung cancer-the potential of selected botanical drugs and isolated metabolites

Ferroptosis represents a distinct form of cell death that is not associated with necrosis, autophagy, apoptosis, or pyroptosis. It is characterised by intracellular iron-dependent lipid peroxidation. The current literature indicates that a number of botanical drugs and isolated metabolites can modulate ferroptosis, thereby exerting inhibitory effects on lung cancer cells or animal models. The aim of this review is to elucidate the mechanisms through which botanical drugs and isolated metabolites regulate ferroptosis in the context of lung cancer, thereby providing potential insights into lung cancer treatment. It is crucial to highlight that these preclinical findings should not be interpreted as evidence that these treatments can be immediately translated into clinical applications. In the future, we will continue to study the pharmacology, pharmacokinetics and toxicology of these drugs, as well as evaluating their efficacy and safety in clinical trials, with the aim of providing new approaches to the development of new agents for the treatment of lung cancer.

The correlation between mitochondria-associated endoplasmic reticulum membranes (MAMs) and Ca2+ transport in the pathogenesis of diseases

Mitochondria and the endoplasmic reticulum (ER) are vital organelles that influence various cellular physiological and pathological processes. Recent evidence shows that about 5%-20% of the mitochondrial outer membrane is capable of forming a highly dynamic physical connection with the ER, maintained at a distance of 10-30 nm. These interconnections, known as MAMs, represent a relatively conserved structure in eukaryotic cells, acting as a critical platform for material exchange between mitochondria and the ER to maintain various aspects of cellular homeostasis. Particularly, ER-mediated Ca2+ release and recycling are intricately associated with the structure and functionality of MAMs. Thus, MAMs are integral in intracellular Ca2+ transport and the maintenance of Ca2+ homeostasis, playing an essential role in various cellular activities including metabolic regulation, signal transduction, autophagy, and apoptosis. The disruption of MAMs observed in certain pathologies such as cardiovascular and neurodegenerative diseases as well as cancers leads to a disturbance in Ca2+ homeostasis. This imbalance potentially aggravates pathological alterations and disease progression. Consequently, a thorough understanding of the link between MAM-mediated Ca2+ transport and these diseases could unveil new perspectives and therapeutic strategies. This review focuses on the changes in MAMs function during disease progression and their implications in relation to MAM-associated Ca2+ transport.

VDAC1-interacting molecules promote cell death in cancer organoids through mitochondrial-dependent metabolic interference

The voltage-dependent anion-selective channel isoform 1 (VDAC1) is a pivotal component in cellular metabolism and apoptosis with a prominent role in many cancer types, offering a unique therapeutic intervention point. Through an in-silico-to-in-vitro approach we identified a set of VA molecules (VDAC Antagonists) that selectively bind to VDAC1 and display specificity toward cancer cells. Biochemical characterization showed that VA molecules can directly interact with VDAC1 with micromolar affinity by competing with the endogenous ligand NADH for a partially shared binding site. NADH displacement results in mitochondrial distress and reduced cell proliferation, especially when compared to non-cancerous cells. Experiments performed on organoids derived from intrahepatic cholangiocarcinoma patients demonstrated a dose-dependent reduction in cell viability upon treatment with VA molecules with lower impact on healthy cells than conventional treatments like gemcitabine. VA molecules are chemical entities representing promising candidates for further optimization and development as cancer therapy strategies through precise metabolic interventions.

Particulate Matter-Induced Neurotoxicity: Unveiling the Role of NOX4-Mediated ROS Production and Mitochondrial Dysfunction in Neuronal Apoptosis

Urban air pollution, a significant environmental hazard, is linked to adverse health outcomes and increased mortality across various diseases. This study investigates the neurotoxic effects of particulate matter (PM), specifically PM2.5 and PM10, by examining their role in inducing oxidative stress and subsequent neuronal cell death. We highlight the novel finding that PM increases mitochondrial ROS production via stimulating NOX4 activity, not through its expression level in Neuro-2A cells. Additionally, PMs provoke ROS production via increasing the expression and activity of NOX2 in SH-SY5Y human neuroblastoma cells, implying differential regulation of NOX proteins. This increase in mitochondrial ROS triggers the opening of the mitochondrial permeability transition pore (mPTP), leading to apoptosis through key mediators, including caspase3, BAX, and Bcl2. Notably, the voltage-dependent anion-selective channel 1 (VDAC1) increases at 1 µg/mL of PM2.5, while PM10 triggers an increase from 10 µg/mL. At the same concentration (100 µg/mL), PM2.5 causes 1.4 times higher ROS production and 2.4 times higher NOX4 activity than PM10. The cytotoxic effects induced by PMs were alleviated by NOX inhibitors GKT137831 and Apocynin. In SH-SY5Y cells, both PM types increase ROS and NOX2 levels, leading to cell death, which Apocynin rescues. Variability in NADPH oxidase sources underscores the complexity of PM-induced neurotoxicity. Our findings highlight NOX4-driven ROS and mitochondrial dysfunction, suggesting a potential therapeutic approach for mitigating PM-induced neurotoxicity.

Multi-omics analysis identifies sex-specific hepatic protein-metabolite networks in yellow catfish (Pelteobagrus fulvidraco) exposed to chronic hypoxia

Hypoxia disrupts the endocrine system of teleosts. The liver plays important roles in the endocrine system, energy storage, and metabolic processes. The aim of this study was to investigate the sex-specific hepatic response of yellow catfish under chronic hypoxia at the multi-omics level. Common hepatic responses in both sexes included the HIF-1 signaling pathway, glycolysis/gluconeogenesis, and steroid biosynthesis. Hypoxia dysregulated primary bile acid biosynthesis, lipid metabolism, and vitellogenin levels in female fish. Endoplasmic reticulum function in females also tended to be disrupted by hypoxia, as evidenced by significantly enriched pathways, including ribosome, protein processing in the endoplasmic reticulum, and RNA degradation. Other pathways, including the TCA cycle, oxidative phosphorylation, and Parkinson's and Huntington's disease, were highly enriched by hypoxia in male fish, suggesting that mitochondrial function was dysregulated. In both sexes of yellow catfish, the cell cycle was arrested and apoptosis was inhibited under chronic hypoxia. Multi-omics suggested that SLC2A5, CD209, LGMN, and NEDD8 served as sex-specific markers in these fish under chronic hypoxia. Our results provide insights into hepatic adaptation to chronic hypoxia and facilitate our understanding of sex-specific responses in fish.

Endurance training increases mitochondrial myoglobin and enhances its interaction with complex IV in rat plantaris muscle

AIM

Endurance exercise training is known to increase mitochondrial respiration in skeletal muscle. However, the molecular mechanisms behind this are not fully understood. Myoglobin (Mb) is a member of the globin family, which is highly expressed in skeletal and cardiac muscles. We recently found that Mb localizes inside mitochondria in skeletal muscle and interacts with cytochrome c oxidase subunit IV (COXIV), a subunit of mitochondrial complex IV, which regulates respiration by augmenting complex IV activity. In the present study, we investigated the effect of endurance training on Mb-COXIV interaction within mitochondria in rat skeletal muscle.

METHODS

Eight-week-old male Wistar rats were subjected to 6-week treadmill running training. Forty-eight hours after the last training session, the plantaris muscle was removed under anesthesia and used for biochemical analysis.

RESULTS

The endurance training increased mitochondrial content in the skeletal muscle. It also augmented complex IV-dependent oxygen consumption and complex IV activity in isolated mitochondria from skeletal muscle. Furthermore, endurance training increased Mb expression at the whole muscle level. Importantly, mitochondrial Mb content and Mb-COXIV binding were increased by endurance training.

CONCLUSION

These findings suggest that an increase in mitochondrial Mb and the concomitant enhancement of Mb interaction with COXIV may contribute to the endurance training-induced upregulation of mitochondrial respiration by augmenting complex IV activity.

The Role of Protein S-Nitrosylation in Mitochondrial Quality Control in Central Nervous System Diseases

S-Nitrosylation is a reversible covalent post-translational modification. Under physiological conditions, S-nitrosylation plays a dynamic role in a wide range of biological processes by regulating the function of substrate proteins. Like other post-translational modifications, S-nitrosylation can affect protein conformation, activity, localization, aggregation, and protein interactions. Aberrant S-nitrosylation can lead to protein misfolding, mitochondrial fragmentation, synaptic damage, and autophagy. Mitochondria are essential organelles in energy production, metabolite biosynthesis, cell death, and immune responses, among other processes. Mitochondrial dysfunction can result in cell death and has been implicated in the development of many human diseases. Recent evidence suggests that S-nitrosylation and mitochondrial dysfunction are important modulators of the progression of several diseases. In this review, we highlight recent findings regarding the aberrant S- nitrosylation of mitochondrial proteins that regulate mitochondrial biosynthesis, fission and fusion, and autophagy. Specifically, we discuss the mechanisms by which S-nitrosylated mitochondrial proteins exercise mitochondrial quality control under pathological conditions, thereby influencing disease. A better understanding of these pathological events may provide novel therapeutic targets to mitigate the development of neurological diseases.

Augmented mitochondrial apoptotic signaling impairs C2C12 myoblast differentiation following cellular aging through sequential passaging

Aging is associated with the steady decline of several cellular processes. The loss of skeletal muscle mass, termed sarcopenia, is one of the major hallmarks of aging. Aged skeletal muscle exhibits a robust reduction in its regenerative capacity due to dysfunction (i.e., senescence, lack of self-renewal, and impaired differentiation) of resident muscle stem cells, called satellite cells. To replicate aging in vitro, immortalized skeletal muscle cells (myoblasts) can be treated with various agents to mimic age-related dysfunction; however, these come with their own set of limitations. In the present study, we used sequential passaging of mouse myoblasts to mimic impaired differentiation that is observed in aged skeletal muscle. Further, we investigated mitochondrial apoptotic mechanisms to better understand the impaired differentiation in these "aged" cells. Our data shows that sequential passaging (>20 passages) of myoblasts is accompanied with significant reductions in differentiation and elevated cell death. Furthermore, high-passage (HP) myoblasts exhibit greater mitochondrial-mediated apoptotic signaling through mitochondrial BAX translocation, CYCS and AIFM1 release, and caspase-9 activation. Finally, we show that inhibition of mitochondrial outer membrane permeability partly recovered differentiation in HP myoblasts. Together, our findings suggests that mitochondrial apoptotic signaling is a contributing factor to the diminished differentiation that is observed in aged myoblasts.

Selective vulnerability of hippocampal CA1 and CA3 pyramidal cells: What are possible pathomechanisms and should more attention be paid to the CA3 region in future studies?

Transient ischemia and reperfusion selectively damage neurons in brain, with hippocampal pyramidal cells being particularly vulnerable. Even within hippocampus, heterogeneous susceptibility is evident, with higher vulnerability of CA1 versus CA3 neurons described for several decades. Therefore, numerous studies have focused exclusively on CA1. Pediatric cardiac surgery is increasingly focusing on studies of hippocampal structures, and a negative impact of cardiopulmonary bypass on the hippocampus cannot be denied. Recent studies show a shift in selective vulnerability from neurons of CA1 to CA3. This review shows that cell damage is increased in CA3, sometimes stronger than in CA1, depending on several factors (method, species, age, observation period). Despite a highly variable pattern, several markers illustrate greater damage to CA3 neurons than previously assumed. Nevertheless, the underlying cellular mechanisms have not been fully deciphered to date. The complexity is reflected in possible pathomechanisms discussed here, with numerous factors (NMDA, kainate and AMPA receptors, intrinsic oxidative stress potential and various radicals, AKT isoforms, differences in vascular architecture, ratio of pro- and anti-apoptotic Bcl-2 factors, vulnerability of interneurons, mitochondrial dysregulation) contributing to either enhanced CA1 or CA3 vulnerability. Furthermore, differences in expressed genome, proteome, metabolome, and transcriptome in CA1 and CA3 appear to influence differential behavior after damaging stimuli, thus metabolomics-, transcriptomics-, and proteomics-based analyses represent a viable option to identify pathways of selective vulnerability in hippocampal neurons. These results emphasize that future studies should focus on the CA3 field in addition to CA1, especially with regard to improving therapeutic strategies after ischemic/hypoxic brain injury.

Mitochondria: one of the vital hubs for molecular hydrogen's biological functions

As a novel antioxidant, a growing body of studies has documented the diverse biological effects of molecular hydrogen (H2) in a wide range of organisms, spanning animals, plants, and microorganisms. Although several possible mechanisms have been proposed, they cannot fully explain the extensive biological effects of H2. Mitochondria, known for ATP production, also play crucial roles in diverse cellular functions, including Ca2+ signaling, regulation of reactive oxygen species (ROS) generation, apoptosis, proliferation, and lipid transport, while their dysfunction is implicated in a broad spectrum of diseases, including cardiovascular disorders, neurodegenerative conditions, metabolic disorders, and cancer. This review aims to 1) summarize the experimental evidence on the impact of H2 on mitochondrial function; 2) provide an overview of the mitochondrial pathways underlying the biological effects of H2, and 3) discuss H2 metabolism in eukaryotic organisms and its relationship with mitochondria. Moreover, based on previous findings, this review proposes that H2 may regulate mitochondrial quality control through diverse pathways in response to varying degrees of mitochondrial damage. By combining the existing research evidence with an evolutionary perspective, this review emphasizes the potential hydrogenase activity in mitochondria of higher plants and animals. Finally, this review also addresses potential issues in the current mechanistic study and offers insights into future research directions, aiming to provide a reference for future studies on the mechanisms underlying the action of H2.

ATP functions as a primary alarmin in allergen-induced type 2 immunity

Environmental allergens that interact with the airway epithelium can activate cellular stress pathways that lead to the release of danger signals known as alarmins. The mechanisms of alarmin release are distinct from damage-associated molecular patterns (DAMPs), which typically escape from cells after loss of plasma membrane integrity. Oxidative stress represents a form of allergen-induced cellular stress that stimulates oxidant-sensing mechanisms coupled to pathways, which facilitate alarmin mobilization and efflux across the plasma membrane. In this review, we highlight examples of alarmin release and discuss their roles in the initiation of type 2 immunity and allergic airway inflammation. In addition, we discuss the concept of alarmin amplification, where "primary" alarmins, which are directly released in response to a specific cellular stress, stimulate additional signaling pathways that lead to secretion of "secondary" alarmins that include proinflammatory cytokines, such as IL-33, as well as genomic and mitochondrial DNA that coordinate or amplify type 2 immunity. Accordingly, allergen-evoked cellular stress can elicit a hierarchy of alarmin signaling responses from the airway epithelium that trigger local innate immune reactions, impact adaptive immunity, and exacerbate diseases including asthma and other chronic inflammatory conditions that affect airway function.

Involvement of protein L-isoaspartyl methyltransferase in the physiopathology of neurodegenerative diseases: Possible substrates associated with synaptic function

Synaptic dysfunction is a typical pathophysiologic change in neurodegenerative diseases (NDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Hintington's disease (HD) and amyotrophic lateral sclerosis (ALS), which involves protein post-translational modifications (PTMs) including L-isoaspartate (L-isoAsp) formed by isomerization of aspartate or deamidation of asparagine. The formation of L-isoAsp could be repaired by protein L-isoaspartyl methyltransferase (PIMT). Some synaptic proteins have been identified as PIMT potential substrates and play an essential role in ensuring synaptic function. In this review, we discuss the role of certain synaptic proteins as PIMT substrates in neurodegenerative disease, thus providing therapeutic synapse-centered targets for the treatment of NDs.

Synergism of small molecules targeting VDAC with sorafenib, regorafenib or lenvatinib on hepatocarcinoma cell proliferation and survival

Voltage dependent anion channels (VDAC) in the outer mitochondrial membrane regulate the influx of metabolites that sustain mitochondrial metabolism and the efflux of ATP to the cytosol. Free tubulin and NADH close VDAC. The VDAC-binding small molecules X1 and SC18 modulate mitochondrial metabolism. X1 antagonizes the inhibitory effect of tubulin on VDAC. SC18 occupies an NADH-binding pocket in the inner wall of all VDAC isoforms. Here, we hypothesized that X1 and SC18 have a synergistic effect with sorafenib, regorafenib or lenvatinib to arrest proliferation and induce death in hepatocarcinoma cells. We used colony formation assays to determine cell proliferation, and a combination of calcein/propidium iodide, and trypan blue exclusion to assess cell death in the well differentiated Huh7 and the poorly differentiated SNU-449 cells. Synergism was assessed using the Chou-Talalay method. The inhibitory effect of X1, SC18, sorafenib, regorafenib and lenvatinib was concentration and time dependent. IC50s calculated from the inhibition of clonogenic capacity were lower than those determined from cell survival. At IC50s that inhibited cell proliferation, SC18 arrested cells in G0/G1. SC18 at 0.25-2 IC50s had a synergistic effect with sorafenib on clonogenic inhibition in Huh7 and SNU-449 cells, and with regorafenib or lenvatinib in SNU-449 cells. X1 or SC18 also had synergistic effects with sorafenib on promoting cell death at 0.5-2 IC50s for SC18 in Huh7 and SNU-449 cells. These results suggest that small molecules targeting VDAC represent a potential new class of drugs to treat liver cancer.

Novel Strategies in the Early Detection and Treatment of Endothelial Cell-Specific Mitochondrial Dysfunction in Coronary Artery Disease

Although elevated cholesterol and other recognised cardiovascular risk factors are important in the development of coronary artery disease (CAD) and heart attack, the susceptibility of humans to this fatal process is distinct from other animals. Mitochondrial dysfunction of cells in the arterial wall, particularly the endothelium, has been strongly implicated in the pathogenesis of CAD. In this manuscript, we review the established evidence and mechanisms in detail and explore the potential opportunities arising from analysing mitochondrial function in patient-derived cells such as endothelial colony-forming cells easily cultured from venous blood. We discuss how emerging technology and knowledge may allow us to measure mitochondrial dysfunction as a potential biomarker for diagnosis and risk management. We also discuss the "pros and cons" of animal models of atherosclerosis, and how patient-derived cell models may provide opportunities to develop novel therapies relevant for humans. Finally, we review several targets that potentially alleviate mitochondrial dysfunction working both via direct and indirect mechanisms and evaluate the effect of several classes of compounds in the cardiovascular context.

Hexokinase dissociation from mitochondria promotes oligomerization of VDAC that facilitates NLRP3 inflammasome assembly and activation

NLRP3 inflammasome activation is a highly regulated process for controlling secretion of the potent inflammatory cytokines IL-1β and IL-18 that are essential during bacterial infection, sterile inflammation, and disease, including colitis, diabetes, Alzheimer's disease, and atherosclerosis. Diverse stimuli activate the NLRP3 inflammasome, and unifying upstream signals has been challenging to identify. Here, we report that a common upstream step in NLRP3 inflammasome activation is the dissociation of the glycolytic enzyme hexokinase 2 from the voltage-dependent anion channel (VDAC) in the outer membrane of mitochondria. Hexokinase 2 dissociation from VDAC triggers activation of inositol triphosphate receptors, leading to release of calcium from the ER, which is taken up by mitochondria. This influx of calcium into mitochondria leads to oligomerization of VDAC, which is known to form a macromolecule-sized pore in the outer membranes of mitochondria that allows proteins and mitochondrial DNA (mtDNA), often associated with apoptosis and inflammation, respectively, to exit the mitochondria. We observe that VDAC oligomers aggregate with NLRP3 during initial assembly of the multiprotein oligomeric NLRP3 inflammasome complex. We also find that mtDNA is necessary for NLRP3 association with VDAC oligomers. These data, together with other recent work, help to paint a more complete picture of the pathway leading to NLRP3 inflammasome activation.

Cytoprotective Properties of a New Nanocomplex of Selenium with Taxifolin in the Cells of the Cerebral Cortex Exposed to Ischemia/Reoxygenation

The neuroprotective effect of the natural antioxidant taxifolin (TAX) is well known for ischemic pathologies. However, the limitations of taxifolin application are described-poor solubility, low ability to penetrate the blood-brain barrier, and side effects from high doses for stroke therapy. We proposed the problem of targeted delivery of taxifolin and achievement effective concentrations could be solved by developing a nanocomplex of selenium nanoparticles (SeNPs) with taxifolin (Se-TAX). In this study, we developed a selenium-taxifolin nanocomplex based on selenium nanoparticles with a 100 nm size. It was shown that TAX, SeNPs, and Se-TAX were all able to suppress the production of ROS in neurons and astrocytes under exposure to exogenous H₂O₂ and ischemia-like conditions. However, the Se-TAX nanocomplex appeared to be the most effective, displaying a lower working concentration range and negligible pro-oxidant effect compared with pure SeNPs. The mechanism of Se-TAX beneficial effects involved the activation of some antioxidant enzymes and the suppression of ROS-generating systems during OGD/reoxygenation, while TAX and "naked" SeNPs were less effective in regulating the cellular redox status. Naked SeNPs inhibited a global increase in Ca²⁺ ions in cytosol, but not OGD-induced hyperexcitation of the neuroglial network, while Se-TAX suppressed both [Ca²⁺]i rise and hyperexcitation. The effect of TAX at similar doses appeared exclusively in inhibiting OGD-induced hyperexcitation. Analysis of necrosis and apoptosis after OGD/reoxygenation revealed the highest efficiency of the Se-TAX nanocomplex as well. Se-TAX suppressed the expression of proinflammatory and proapoptotic proteins with simultaneous activation of protective genes. We conclude that the Se-TAX nanocomplex combines the antioxidative features taxifolin and the antiapoptotic effect of nanoselenium, involving the regulation of Ca²⁺ dynamics.

Balancing life and death: BCL-2 family members at diverse ER-mitochondrial contact sites

The outer mitochondrial membrane is a busy place. One essential activity for cellular survival is the regulation of membrane integrity by the BCL-2 family of proteins. Another critical facet of the outer mitochondrial membrane is its close approximation with the endoplasmic reticulum. These mitochondrial-associated membranes (MAMs) occupy a significant fraction of the mitochondrial surface and serve as key signaling hubs for multiple cellular processes. Each of these pathways may be considered as forming their own specialized MAM subtype. Interestingly, like membrane permeabilization, most of these pathways play critical roles in regulating cellular survival and death. Recently, the pro-apoptotic BCL-2 family member BOK has been found within MAMs where it plays important roles in their structure and function. This has led to a greater appreciation that multiple BCL-2 family proteins, which are known to participate in numerous functions throughout the cell, also have roles within MAMs. In this review, we evaluate several MAM subsets, their role in cellular homeostasis, and the contribution of BCL-2 family members to their functions.

Hedyotis diffusa injection induces ferroptosis via the Bax/Bcl2/VDAC2/3 axis in lung adenocarcinoma

BACKGROUND

Lung cancer has the highest mortality rate among all cancer types. In combination with multiple chemotherapeutic options, traditional Chinese medicine has proven indispensable for the comprehensive treatment of lung cancer.

PURPOSE

To investigate the effects of Hedyotis diffusa on lung adenocarcinoma cell lines and a BALB/c nude mouse xenograft model, and determine whether HDI could induce ferroptosis in lung adenocarcinoma cells along with the underlying mechanism.

METHODS

The anti-tumor activity of HDI was determined in vitro by cell counting kit-8, clonogenic, and transwell assays. Subsequently, electron microscopy, a lipid reactive oxygen species assay, ferrous ion staining, and a malondialdehyde assay were performed to determine the effect on ferroptosis in lung adenocarcinoma cells. The mechanism was then further investigated using small molecule inhibitors, siRNA, and plasmid overexpression in vitro. Finally, the effects of HDI were assessed in tumor-bearing BALB/c nude mice, and HE staining was performed to observe tissue damage after HDI treatment.

RESULTS

In vitro experiments showed that HDI could inhibit the viability of lung adenocarcinoma cells and induce lung adenocarcinoma cells ferroptosis via mechanisms independent of GPX4 and PUFA-PLS pathways but closely associated with VDAC2/3. HDI regulated VDAC2/3 activity by promoting Bax via inhibiting Bcl2, thereby inducing ferroptosis in lung adenocarcinoma cells. Furthermore, in vivo experiments showed that HDI significantly inhibited the growth of subcutaneous tumors in BALB/c nude mice with less organ damage and toxicity, and significantly increased the expression of the ferroptosis-related indicators 4HNE, TFR, and HMOX1 in tumor tissue.

CONCLUSION

HDI can significantly reduce the survival of lung adenocarcinoma cells in vitro, inhibit the growth of subcutaneously transplanted tumors in BALB/c nude mice in vivo, and induce ferroptosis in lung adenocarcinoma cells via Bcl2 inhibition to promote Bax regulation of VDAC2/3.

Mitochondria-Mediated Moderation of Apoptosis by EGCG in Cytotoxic Neuronal Cells Induced by Lead (Pb) and Amyloid Peptides

The developmental, epigenetic, and epidemiological studies on lead (Pb) toxicity have reported a strong connection between lead exposure and the progression of Alzheimer's disease (AD). The amyloid peptides were the main triggering elements, in the generation of extracellular plaques through which multiple cellular signaling events such as apoptosis and primarily oxidant-antioxidant balancing system will be affected, which leads to neuronal cell death. Our previous studies indicated that epigallocatechin gallate (EGCG), abundantly present in green tea, was found to be effective in alleviating the metal-induced neurotoxicity at the cellular level in terms of cell viability and apoptosis The aim of this study was to explore the protective mechanism of EGCG on the markers of oxidant-antioxidant system and mitochondria, which are involved in metal-induced neuronal cell death. Initially, the IC₅₀ values for lead(Pb-5 µM), amyloid peptides (AP(1-40)-60 µM; AP(1-40)-8 µM), and EC₅₀ value for EGCG(50 µM) were determined by both time- (12 h, 24 h, 48 h) and concentration-dependent manner and analyzed by MTT assay. The experimental groups were designed initially by treating with Pb and APs individually and in different combinations along with the presence of EGCG and are compared to the Pb and AP treated group without EGCG exposure. The cell lysates were used for analyzing oxidative stress markers by standardized laboratory protocol and the expression of mitochondrial markers such as VDAC and cytochrome C which were analyzed by both western blot and real-time PCR. Our results indicate that the EGCG-treated group has shown a significant increase in antioxidant marker expression levels (GSH, SOD, catalase, vitamin C) and a decrease in oxidative stress marker (NOS, MDA) levels when compared to the group without EGCG treatment (p < 0.05). Similarly, a significant decrease in expression levels of VDAC and cytochrome c were observed in the EGCG-treated group when compared to the group without EGCG treatment (p < 0.05). Our approach revealed that EGCG protects SH-SY5Y cells from Pb- and AP-induced cytotoxicity by regulating voltage-dependent anion channel (VDAC) expression and oxidant-antioxidant system and inhibits neuronal cell death.

Cross-Species Analysis Reveals Co-Expressed Genes Regulating Antler Development in Cervidae

Antlers constitute an interesting model for basic research in regenerative biology. Despite decades of being studied, much is still unknown about the genes related to antler development. Here, we utilized both the genome and antlerogenic periosteum (AP) transcriptome data of four deer species to reveal antler-related genes through cross-species comparative analysis. The results showed that the global gene expression pattern matches the status of antler phenotypes, supporting the fact that the genes expressed in the AP may be related to antler phenotypes. The upregulated genes of the AP in three-antlered deer showed evidence of co-expression, and their protein sequences were highly conserved. These genes were growth related and likely participated in antler development. In contrast, the upregulated genes in antler-less deer (Chinese water deer) were involved mainly in organismal death and growth failure, possibly related to the loss of antlers during evolution. Overall, this study demonstrates that the co-expressed genes in antlered deer may regulate antler development.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Structure and Gating Behavior of the Human Integral Membrane Protein VDAC1 in a Lipid Bilayer

The voltage-dependent anion channel (VDAC), the most abundant protein in the outer mitochondrial membrane, is responsible for the transport of all ions and metabolites into and out of mitochondria. Larger than any of the β-barrel structures determined to date by magic-angle spinning (MAS) NMR, but smaller than the size limit of cryo-electron microscopy (cryo-EM), VDAC1’s 31 kDa size has long been a bottleneck in determining its structure in a near-native lipid bilayer environment. Using a single two-dimensional (2D) crystalline sample of human VDAC1 in lipids, we applied proton-detected fast magic-angle spinning NMR spectroscopy to determine the arrangement of β strands. Combining these data with long-range restraints from a spin-labeled sample, chemical shift-based secondary structure prediction, and previous MAS NMR and atomic force microscopy (AFM) data, we determined the channel’s structure at a 2.2 Å root-mean-square deviation (RMSD). The structure, a 19-stranded β-barrel, with an N-terminal α-helix in the pore is in agreement with previous data in detergent, which was questioned due to the potential for the detergent to perturb the protein’s functional structure. Using a quintuple mutant implementing the channel’s closed state, we found that dynamics are a key element in the protein’s gating behavior, as channel closure leads to the destabilization of not only the C-terminal barrel residues but also the α2 helix. We showed that cholesterol, previously shown to reduce the frequency of channel closure, stabilizes the barrel relative to the N-terminal helix. Furthermore, we observed channel closure through steric blockage by a drug shown to selectively bind to the channel, the Bcl2-antisense oligonucleotide G3139.

Therapeutic Peptides to Treat Myocardial Ischemia-Reperfusion Injury

Cardiovascular diseases (CVD) including acute myocardial infarction (AMI) rank first in worldwide mortality and according to the World Health Organization (WHO), they will stay at this rank until 2030. Prompt revascularization of the occluded artery to reperfuse the myocardium is the only recommended treatment (by angioplasty or thrombolysis) to decrease infarct size (IS). However, despite beneficial effects on ischemic lesions, reperfusion leads to ischemia-reperfusion (IR) injury related mainly to apoptosis. Improvement of revascularization techniques and patient care has decreased myocardial infarction (MI) mortality however heart failure (HF) morbidity is increasing, contributing to the cost-intense worldwide HF epidemic. Currently, there is no treatment for reperfusion injury despite promising results in animal models. There is now an obvious need to develop new cardioprotective strategies to decrease morbidity/mortality of CVD, which is increasing due to the aging of the population and the rising prevalence rates of diabetes and obesity. In this review, we will summarize the different therapeutic peptides developed or used focused on the treatment of myocardial IR injury (MIRI). Therapeutic peptides will be presented depending on their interacting mechanisms (apoptosis, necroptosis, and inflammation) reported as playing an important role in reperfusion injury following myocardial ischemia. The search and development of therapeutic peptides have become very active, with increasing numbers of candidates entering clinical trials. Their optimization and their potential application in the treatment of patients with AMI will be discussed.

Inhibition of the Anti-Apoptotic Bcl-2 Family by BH3 Mimetics Sensitize the Mitochondrial Permeability Transition Pore Through Bax and Bak

Mitochondrial permeability transition pore (MPTP)-dependent necrosis contributes to numerous pathologies in the heart, brain, and skeletal muscle. The MPTP is a non-selective pore in the inner mitochondrial membrane that is triggered by high levels of matrix Ca²⁺, and sustained opening leads to mitochondrial dysfunction. Although the MPTP is defined by an increase in inner mitochondrial membrane permeability, the expression of pro-apoptotic Bcl-2 family members, Bax and Bak localization to the outer mitochondrial membrane is required for MPTP-dependent mitochondrial dysfunction and subsequent necrotic cell death. Contrary to the role of Bax and Bak in apoptosis, which is dependent on their oligomerization, MPTP-dependent necrosis does not require oligomerization as monomeric/inactive forms of Bax and Bak can facilitate mitochondrial dysfunction. However, the relationship between Bax and Bak activation/oligomerization and MPTP sensitization remains to be explored. Here, we use a combination of in vitro and ex vivo approaches to determine the role of the anti-apoptotic Bcl-2 family members, which regulate Bax/Bak activity, in necrotic cell death and MPTP sensitivity. To study the role of each predominantly expressed anti-apoptotic Bcl-2 family member (i.e., Mcl-1, Bcl-2, and Bcl-xL) in MPTP regulation, we utilize various BH3 mimetics that specifically bind to and inhibit each. We determined that the inhibition of each anti-apoptotic Bcl-2 family member lowers mitochondrial calcium retention capacity and sensitizes MPTP opening. Furthermore, the inhibition of each Bcl-2 family member exacerbates both apoptotic and necrotic cell death in vitro in a Bax/Bak-dependent manner. Our findings suggests that mitochondrial Ca²⁺ retention capacity and MPTP sensitivity is influenced by Bax/Bak activation/oligomerization on the outer mitochondrial membrane, providing further evidence of the crosstalk between the apoptotic and necrotic cell death pathways.

VDAC2 and the BCL-2 family of proteins

The BCL-2 protein family govern whether a cell dies or survives by controlling mitochondrial apoptosis. As dysregulation of mitochondrial apoptosis is a common feature of cancer cells, targeting protein–protein interactions within the BCL-2 protein family is a key strategy to seize control of apoptosis and provide favourable outcomes for cancer patients. Non-BCL-2 family proteins are emerging as novel regulators of apoptosis and are potential drug targets. Voltage dependent anion channel 2 (VDAC2) can regulate apoptosis. However, it is unclear how this occurs at the molecular level, with conflicting evidence in the literature for its role in regulating the BCL-2 effector proteins, BAK and BAX. Notably, VDAC2 is required for efficient BAX-mediated apoptosis, but conversely inhibits BAK-mediated apoptosis. This review focuses on the role of VDAC2 in apoptosis, discussing the current knowledge of the interaction between VDAC2 and BCL-2 family proteins and the recent development of an apoptosis inhibitor that targets the VDAC2–BAK interaction.

Insight of the role of mitochondrial calcium homeostasis in hepatic insulin resistance

Due to the rapid rise in the prevalence of chronic metabolic disease, more and more clinicians and basic medical researchers focus their eyesight on insulin resistance (IR), an early and central event of metabolic diseases. The occurrence and development of IR are primarily caused by excessive energy intake and reduced energy consumption. Liver is the central organ that controls glucose homeostasis, playing a considerable role in systemic IR. Decreased capacity of oxidative metabolism and mitochondrial dysfunction are being blamed as the direct reason for the development of IR. Mitochondrial Ca²⁺ plays a fundamental role in maintaining proper mitochondrial function and redox stability. The maintaining of mitochondrial Ca²⁺ homeostasis requires the cooperation of ion channels in the inner and outer membrane of mitochondria, such as mitochondrial calcium uniporter complex (MCUC) and voltage-dependent anion channels (VDACs). In addition, the crosstalk between the endoplasmic reticulum (ER), lysosome and plasma membrane with mitochondria is also significant for mitochondrial calcium homeostasis, which is responsible for an efficient network of cellular Ca²⁺ signaling. Here, we review the recent progression in the research about the regulation factors for mitochondrial Ca²⁺ and how the dysregulation of mitochondrial Ca²⁺ homeostasis is involved in the pathogenesis of hepatic IR, providing a new perspective for further exploring the role of ion in the onset and development of IR.

Deconstructing the molecular genetics behind the PINK1/Parkin axis in Parkinson’s disease using Drosophila melanogaster as a model organism

Background

Parkinson’s disease (PD) is a multifactorial neurodegenerative disorder marked by the death of nigrostriatal dopaminergic neurons in response to the compounding effects of oxidative stress, mitochondrial dysfunction and protein aggregation. Transgenic Drosophila models have been used extensively to decipher the underlying genetic interactions that exacerbate neural health in PD. Autosomal recessive forms of the disease have been linked to mutations in the serine/threonine kinase PINK1(PTEN-Induced Putative Kinase 1) and E3 ligase Parkin, which function in an axis that is conserved in flies. This review aims to probe the current understanding of PD pathogenesis via the PINK1/Parkin axis while underscoring the importance of several molecular and pharmacologic rescues brought to light through studies in Drosophila.

Main body

Mutations in PINK1 and Parkin have been shown to affect the axonal transport of mitochondria within dopaminergic neurons and perturb the balance between mitochondrial fusion/fission resulting in abnormal mitochondrial morphology. As per studies in flies, ectopic expression of Fwd kinase and Atg-1 to promote fission and mitophagy while suppressing fusion via MUL1 E3 ligase may aid to halt mitochondrial aggregation and prolong the survival of dopaminergic neurons. Furthermore, upregulation of Hsp70/Hsp90 chaperone systems (Trap1, CHIP) to target misfolded mitochondrial respiratory complexes may help to preserve their bioenergetic capacity. Accumulation of reactive oxygen species as a consequence of respiratory complex dysfunction or antioxidant enzyme deficiency further escalates neural death by inducing apoptosis, lipid peroxidation and DNA damage. Fly studies have reported the induction of canonical Wnt signalling to enhance the activity of transcriptional co-activators (PGC1α, FOXO) which induce the expression of antioxidant enzymes. Enhancing the clearance of free radicals via uncoupling proteins (UCP4) has also been reported to ameliorate oxidative stress-induced cell death in PINK1/Parkin mutants.

Conclusion

While these novel mechanisms require validation through mammalian studies, they offer several explanations for the factors propagating dopaminergic death as well as promising insights into the therapeutic importance of transgenic fly models in PD.

Metabolic imbalance of T cells in COVID-19 is hallmarked by basigin and mitigated by dexamethasone

Metabolic pathways regulate immune responses and disrupted metabolism leads to immune dysfunction and disease. Coronavirus disease 2019 (COVID-19) is driven by imbalanced immune responses, yet the role of immunometabolism in COVID-19 pathogenesis remains unclear. By investigating 87 patients with confirmed SARS-CoV-2 infection, 6 critically ill non-COVID-19 patients, and 47 uninfected controls, we found an immunometabolic dysregulation in patients with progressed COVID-19. Specifically, T cells, monocytes, and granulocytes exhibited increased mitochondrial mass, yet only T cells accumulated intracellular reactive oxygen species (ROS), were metabolically quiescent, and showed a disrupted mitochondrial architecture. During recovery, T cell ROS decreased to match the uninfected controls. Transcriptionally, T cells from severe/critical COVID-19 patients showed an induction of ROS-responsive genes as well as genes related to mitochondrial function and the basigin network. Basigin (CD147) ligands cyclophilin A and the SARS-CoV-2 spike protein triggered ROS production in T cells in vitro. In line with this, only PCR-positive patients showed increased ROS levels. Dexamethasone treatment resulted in a downregulation of ROS in vitro and T cells from dexamethasone-treated patients exhibited low ROS and basigin levels. This was reflected by changes in the transcriptional landscape. Our findings provide evidence of an immunometabolic dysregulation in COVID-19 that can be mitigated by dexamethasone treatment.

VDAC Modulation of Cancer Metabolism: Advances and Therapeutic Challenges

Most anionic metabolites including respiratory substrates, glycolytic adenosine triphosphate (ATP), and small cations that enter mitochondria, and mitochondrial ATP moving to the cytosol, cross the outer mitochondrial membrane (OMM) through voltage dependent anion channels (VDAC). The closed states of VDAC block the passage of anionic metabolites, and increase the flux of small cations, including calcium. Consequently, physiological or pharmacological regulation of VDAC opening, by conditioning the magnitude of both anion and cation fluxes, is a major contributor to mitochondrial metabolism. Tumor cells display a pro-proliferative Warburg phenotype characterized by enhanced aerobic glycolysis in the presence of partial suppression of mitochondrial metabolism. The heterogeneous and flexible metabolic traits of most human tumors render cells able to adapt to the constantly changing energetic and biosynthetic demands by switching between predominantly glycolytic or oxidative phenotypes. Here, we describe the biological consequences of changes in the conformational state of VDAC for cancer metabolism, the mechanisms by which VDAC-openers promote cancer cell death, and the advantages of VDAC opening as a valuable pharmacological target. Particular emphasis is given to the endogenous regulation of VDAC by free tubulin and the effects of VDAC-tubulin antagonists in cancer cells. Because of its function and location, VDAC operates as a switch to turn-off mitochondrial metabolism (closed state) and increase aerobic glycolysis (pro-Warburg), or to turn-on mitochondrial metabolism (open state) and decrease glycolysis (anti-Warburg). A better understanding of the role of VDAC regulation in tumor progression is relevant both for cancer biology and for developing novel cancer chemotherapies.

Cellular Interactome of Mitochondrial Voltage-Dependent Anion Channels: Oligomerization and Channel (Mis)Regulation

Voltage-dependent anion channels (VDACs) of the outer mitochondrial membrane are known conventionally as metabolite flux proteins. However, research findings in the past decade have revealed the multifaceted regulatory roles of VDACs, from governing cellular physiology and mitochondria-mediated apoptosis to directly regulating debilitating cancers and neurodegenerative diseases. VDACs achieve these diverse functions by establishing isoform-dependent stereospecific interactomes in the cell with the cytosolic constituents and endoplasmic reticulum complexes, and the machinery of the mitochondrial compartments. VDACs are now increasingly recognized as regulatory hubs of the cell. Not surprisingly, even the transient misregulation of VDACs results directly in mitochondrial dysfunction. Additionally, human VDACs are now implicated in interaction with aggregation-prone cytosolic proteins, including Aβ, tau, and α-synuclein, contributing directly to the onset of Alzheimer's and Parkinson's diseases. Deducing the interaction dynamics and mechanisms can lead to VDAC-targeted peptide-based therapeutics that can alleviate neurodegenerative states. This review succinctly presents the latest findings of the VDAC interactome, and the mode(s) of VDAC-dependent regulation of biochemical physiology. We also discuss the relevance of VDACs in pathophysiological states and aggregation-associated diseases and address how VDACs will facilitate the development of next-generation precision medicines.

Lipids modulate the BH3-independent membrane targeting and activation of BAX and Bcl-xL

Regulation of apoptosis is tightly linked with the targeting of numerous Bcl-2 proteins to the mitochondrial outer membrane (MOM), where their activation or inhibition dictates cell death or survival. According to the traditional view of apoptotic regulation, BH3-effector proteins are indispensable for the cytosol-to-MOM targeting and activation of proapoptotic and antiapoptotic members of the Bcl-2 protein family. This view is challenged by recent studies showing that these processes can occur in cells lacking BH3 effectors by as yet to be determined mechanism(s). Here, we exploit a model membrane system that recapitulates key features of MOM to demonstrate that the proapoptotic Bcl-2 protein BAX and antiapoptotic Bcl-xL have an inherent ability to interact with membranes in the absence of BH3 effectors, but only in the presence of cellular concentrations of Mg²⁺/Ca²⁺ Under these conditions, BAX and Bcl-xL are selectively targeted to membranes, refolded, and activated in the presence of anionic lipids especially the mitochondrial-specific lipid cardiolipin. These results provide a mechanistic explanation for the mitochondrial targeting and activation of Bcl-2 proteins in cells lacking BH3 effectors. At cytosolic Mg²⁺ levels, the BH3-independent activation of BAX could provide localized amplification of apoptotic signaling at regions enriched in cardiolipin (e.g., contact sites between MOM and mitochondrial inner membrane). Increases in MOM cardiolipin, as well as cytosolic [Ca²⁺] during apoptosis could further contribute to its MOM targeting and activity. Meanwhile, the BH3-independent targeting and activation of Bcl-xL to the MOM is expected to counter the action of proapoptotic BAX, thereby preventing premature commitment to apoptosis.

Small Hexokinase 1 Peptide against Toxic SOD1 G93A Mitochondrial Accumulation in ALS Rescues the ATP-Related Respiration

Mutations in Cu/Zn Superoxide Dismutase (SOD1) gene represent one of the most common causes of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder that specifically affects motor neurons (MNs). The dismutase-active SOD1 G93A mutant is responsible for the formation of toxic aggregates onto the mitochondrial surface, using the Voltage-Dependent Anion Channel 1 (VDAC1) as an anchor point to the organelle. VDAC1 is the master regulator of cellular bioenergetics and by binding to hexokinases (HKs) it controls apoptosis. In ALS, however, SOD1 G93A impairs VDAC1 activity and displaces HK1 from mitochondria, promoting organelle dysfunction, and cell death. Using an ALS cell model, we demonstrate that a small synthetic peptide derived from the HK1 sequence (NHK1) recovers the cell viability in a dose-response manner and the defective mitochondrial respiration profile relative to the ADP phosphorylation. This correlates with an unexpected increase of VDAC1 expression and a reduction of SOD1 mutant accumulation at the mitochondrial level. Overall, our findings provide important new insights into the development of therapeutic molecules to fight ALS and help to better define the link between altered mitochondrial metabolism and MNs death in the disease.

Pleiotropic nature of curcumin in targeting multiple apoptotic-mediated factors and related strategies to treat gastric cancer: A review

Gastric cancer (GC) is one of the major reasons for cancer-associated death and exhibits the second-highest mortality rate worldwide. Several advanced approaches have been designed to treat GC; however, these strategies possess many innate complications. In view of this, the upcoming research relying on natural products could result in designing potential anticancer agents with fewer side effects. Curcumin, isolated from the rhizomes of Curcuma longa L. has several medicinal properties like antiinflammatory, antioxidant, antiapoptotic, antitumor, and antimetastatic. Such pleiotropic nature of curcumin impedes the invasion and proliferation of GC by targeting several oncogenic factors like p23, human epidermal factor receptor2 including Helicobacter pylori. The side effect of chemotherapy, that is, chemotherapeutic resistance and radiotherapy could be reduced combination therapy of curcumin. Moreover, the photodynamic therapy of curcumin destroys the cancer cells without affecting normal cells. However, further more potential studies are required to establish the potent efficacy of curcumin in the treatment of GC. The current review details the anticancer activities of curcumin and related strategies which could be employed to treat GC with additional focus on its inhibitory properties against viability, proliferation, and migration of GC cells through cell cycle arrest and stimulation by apoptosis-mediated factors.

Nonalcoholic Fatty Liver Disease (NAFLD). Mitochondria as Players and Targets of Therapies?

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and represents the hepatic expression of several metabolic abnormalities of high epidemiologic relevance. Fat accumulation in the hepatocytes results in cellular fragility and risk of progression toward necroinflammation, i.e., nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually hepatocellular carcinoma. Several pathways contribute to fat accumulation and damage in the liver and can also involve the mitochondria, whose functional integrity is essential to maintain liver bioenergetics. In NAFLD/NASH, both structural and functional mitochondrial abnormalities occur and can involve mitochondrial electron transport chain, decreased mitochondrial β-oxidation of free fatty acids, excessive generation of reactive oxygen species, and lipid peroxidation. NASH is a major target of therapy, but there is no established single or combined treatment so far. Notably, translational and clinical studies point to mitochondria as future therapeutic targets in NAFLD since the prevention of mitochondrial damage could improve liver bioenergetics.

Structure, gating and interactions of the voltage-dependent anion channel

The voltage-dependent anion channel (VDAC) is one of the most highly abundant proteins found in the outer mitochondrial membrane, and was one of the earliest discovered. Here we review progress in understanding VDAC function with a focus on its structure, discussing various models proposed for voltage gating as well as potential drug targets to modulate the channel's function. In addition, we explore the sensitivity of VDAC structure to variations in the membrane environment, comparing DMPC-only, DMPC with cholesterol, and near-native lipid compositions, and use magic-angle spinning NMR spectroscopy to locate cholesterol on the outside of the β-barrel. We find that the VDAC protein structure remains unchanged in different membrane compositions, including conditions with cholesterol.

Oxygenated phosphatidylethanolamine navigates phagocytosis of ferroptotic cells by interacting with TLR2

During cancer therapy, phagocytic clearance of dead cells plays a vital role in immune homeostasis. The nonapoptotic form of cell death, ferroptosis, exhibits extraordinary potential in tumor treatment. However, the phagocytosis mechanism that regulates the engulfment of ferroptotic cells remains unclear. Here, we establish a novel pathway for phagocytic clearance of ferroptotic cells that is different from canonical mechanisms by using diverse ferroptosis models evoked by GPX4 dysfunction/deficiency. We identified the oxidized phospholipid, 1-steaoryl-2-15-HpETE-sn-glycero-3-phosphatidylethanolamine (SAPE-OOH), as a key eat-me signal on the ferroptotic cell surface. Enriching the plasma membrane with SAPE-OOH increased the efficiency of phagocytosis of ferroptotic cells by macrophage, a process that was suppressed by lipoprotein-associated phospholipase A₂. Ligand fishing, lipid blotting, and cellular thermal shift assay screened and identified TLR2 as a membrane receptor that directly recognized SAPE-OOH, which was further confirmed by TLR2 inhibitors and gene silencing studies. A mouse mammary tumor model of ferroptosis verified SAPE-OOH and TLR2 as critical players in the clearance of ferroptotic cells in vivo. Taken together, this work demonstrates that SAPE-OOH on ferroptotic cell surface acts as an eat-me signal and navigates phagocytosis by targeting TLR2 on macrophages.

Mitochondria Associated Membranes (MAMs): Architecture and physiopathological role

In the last decades, the communication between the Endoplasmic reticulum (ER) and mitochondria has obtained great attention: mitochondria-associated membranes (MAMs), which represent the contact sites between the two organelles, have indeed emerged as central hub involved in different fundamental cell processes, such as calcium signalling, apoptosis, autophagy and lipid biosynthesis. Consistently, dysregulation of ER-mitochondria crosstalk has been associated with different pathological conditions, ranging from diabetes to cancer and neurodegenerative diseases. In this review, we will try to summarize the current knowledge on MAMs' structure and functions in health and their relevance for human diseases.

Mitochondrial Dysfunction is a Key Pathway that Links Saturated Fat Intake to the Development and Progression of NAFLD

Non-Alcoholic fatty liver disease (NAFLD) is the most common form of liver disease and is characterized by fat accumulation in the liver. Hypercaloric diets generally increase hepatic fat accumulation, whereas hypocaloric diets decrease liver fat content. In addition, there is evidence to suggest that moderate amounts of unsaturated fatty acids seems to be protective for the development of a fatty liver, while consumption of saturated fatty acids (SFA) appears to predispose toward hepatic steatosis. Recent studies highlight a key role for mitochondrial dysfunction in the development and progression of NAFLD. It is proposed that changes in mitochondrial structure and function are key mechanisms by which SFA lead to the development and progression of NAFLD. In this review, it is described how SFA intake is associated with liver steatosis and decreases the efficiency of the respiratory transport chain. This results in the production of reactive oxygen species and damage to nearby structures, eventually leading to inflammation, apoptosis, and scarring of the liver. Furthermore, studies demonstrating that SFA intake affects the composition of mitochondrial membranes are presented, and this process accelerates the progression of NAFLD. It is likely that events are intertwined and reinforce each other, leading to a constant deterioration in health.

Sphingolipids as a Culprit of Mitochondrial Dysfunction in Insulin Resistance and Type 2 Diabetes

Insulin resistance is defined as a complex pathological condition of abnormal cellular and metabolic response to insulin. Obesity and consumption of high-fat diet lead to ectopic accumulation of bioactive lipids in insulin-sensitive tissues. Intracellular lipid accumulation is regarded as one of the major factors in the induction of insulin resistance and type 2 diabetes (T2D). A significant number of studies have described the involvement of ceramides and other sphingolipids in the inhibition of insulin-signaling pathway in both skeletal muscles and the liver. Adverse effects of sphingolipid accumulation have recently been linked to the activation of protein kinase Cζ (PKCζ) and protein phosphatase 2A (PP2A), which, in turn, negatively affect phosphorylation of serine/threonine kinase Akt [also known as protein kinase B (PKB)], leading to decreased glucose uptake in skeletal muscles as well as increased gluconeogenesis and glycogenolysis in the liver. Sphingolipids, in addition to their direct impact on the insulin signaling pathway, may be responsible for other negative aspects of diabetes, namely mitochondrial dysfunction and deficiency. Mitochondrial health, which is characterized by appropriate mitochondrial quantity, oxidative capacity, controlled oxidative stress, undisturbed respiratory chain function, adenosine triphosphate (ATP) production and mitochondrial proliferation through fission and fusion, is impaired in the skeletal muscles and liver of T2D subjects. Recent findings suggest that impaired mitochondrial function may play a key role in the development of insulin resistance. Mitochondria stay in contact with the endoplasmic reticulum (ER), Golgi membranes and mitochondria-associated membranes (MAM) that are the main places of sphingolipid synthesis. Moreover, mitochondria are capable of synthesizing ceramide though ceramide synthase (CerS) activity. Recently, ceramides have been demonstrated to negatively affect mitochondrial respiratory chain function and fission/fusion activity, which is also a hallmark of T2D. Despite a significant correlation between sphingolipids, mitochondrial dysfunction, insulin resistance and T2D, this subject has not received much attention compared to the direct effect of sphingolipids on the insulin signaling pathway. In this review, we focus on the current state of scientific knowledge regarding the involvement of sphingolipids in the induction of insulin resistance by inhibiting mitochondrial function.

Voltage-Dependent Anion Channels Influence Cytotoxicity of ME-344, a Therapeutic Isoflavone

ME-344 is a second-generation cytotoxic isoflavone with anticancer activity promulgated through interference with mitochondrial functions. Using a click chemistry version of the drug together with affinity-enriched mass spectrometry, voltage-dependent anion channels (VDACs) 1 and 2 were identified as drug targets. To determine the importance of VDAC1 or 2 to cytotoxicity, we used lung cancer cells that were either sensitive (H460) or intrinsically resistant (H596) to the drug. In H460 cells, depletion of VDAC1 and VDAC2 by small interfering RNA impacted ME-344 effects by diminishing generation of reactive oxygen species (ROS), preventing mitochondrial membrane potential dissipation, and moderating ME-344-induced cytotoxicity and mitochondrial-mediated apoptosis. Mechanistically, VDAC1 and VDAC2 knockdown prevented ME-344-induced apoptosis by inhibiting Bax mitochondrial translocation and cytochrome c release as well as apoptosis in these H460 cells. We conclude that VDAC1 and 2, as mediators of the response to oxidative stress, have roles in modulating ROS generation, Bax translocation, and cytochrome c release during mitochondrial-mediated apoptosis caused by ME-344. SIGNIFICANCE STATEMENT: Dissecting preclinical drug mechanisms are of significance in development of a drug toward eventual Food and Drug Administration approval.

The apoptosis inhibitor Bcl-xL controls breast cancer cell migration through mitochondria-dependent reactive oxygen species production

The Bcl-xL apoptosis inhibitor plays a major role in vertebrate development. In addition to its effect on apoptosis, Bcl-xL is also involved in cell migration and mitochondrial metabolism. These effects may favour the onset and dissemination of metastasis. However, the underlying molecular mechanisms remain to be fully understood. Here we focus on the control of cell migration by Bcl-xL in the context of breast cancer cells. We show that Bcl-xL silencing led to migration defects in Hs578T and MDA-MB231 cells. These defects were rescued by re-expressing mitochondria-addressed, but not endoplasmic reticulum-addressed, Bcl-xL. The use of BH3 mimetics, such as ABT-737 and WEHI-539 confirmed that the effect of Bcl-xL on migration did not depend on interactions with BH3-containing death accelerators such as Bax or BH3-only proteins. In contrast, the use of a BH4 peptide that disrupts the Bcl-xL/VDAC1 complex supports that Bcl-xL by acting on VDAC1 permeability contributes to cell migration through the promotion of reactive oxygen species production by the electron transport chain. Collectively our data highlight the key role of Bcl-xL at the interface between cell metabolism, cell death, and cell migration, thus exposing the VDAC1/Bcl-xL interaction as a promising target for anti-tumour therapy in the context of metastatic breast cancer.

Cancer-Related Increases and Decreases in Calcium Signaling at the Endoplasmic Reticulum-Mitochondria Interface (MAMs)

Endoplasmic reticulum (ER)-mitochondria regions are specialized subdomains called also mitochondria-associated membranes (MAMs). MAMs allow regulation of lipid synthesis and represent hubs for ion and metabolite signaling. As these two organelles can module both the amplitude and the spatiotemporal patterns of calcium (Ca²⁺) signals, this particular interaction controls several Ca²⁺-dependent pathways well known for their contribution to tumorigenesis, such as metabolism, survival, sensitivity to cell death, and metastasis. Mitochondria-mediated apoptosis arises from mitochondrial Ca²⁺ overload, permeabilization of the mitochondrial outer membrane, and the release of mitochondrial apoptotic factors into the cytosol. Decreases in Ca²⁺ signaling at the ER-mitochondria interface are being studied in depth as failure of apoptotic-dependent cell death is one of the predominant characteristics of cancer cells. However, some recent papers that linked MAMs Ca²⁺ crosstalk-related upregulation to tumor onset and progression have aroused the interest of the scientific community.In this review, we will describe how different MAMs-localized proteins modulate the effectiveness of Ca²⁺-dependent apoptotic stimuli by causing both increases and decreases in the ER-mitochondria interplay and, specifically, by modulating Ca²⁺ signaling.

Mechanisms of action of amyloid-beta and its precursor protein in neuronal cell death

Extracellular senile plaques and intracellular neurofibrillary tangles are the neuropathological findings of the Alzheimer's disease (AD). Based on the amyloid cascade hypothesis, the main component of senile plaques, the amyloid-beta (Aβ) peptide, and its derivative called amyloid precursor protein (APP) both have been found to place their central roles in AD development for years. However, the recent therapeutics have yet to reverse or halt this disease. Previous evidence demonstrates that the accumulation of Aβ peptides and APP can exert neurotoxicity and ultimately neuronal cell death. Hence, we discuss the mechanisms of excessive production of Aβ peptides and APP serving as pathophysiologic stimuli for the initiation of various cell signalling pathways including apoptosis, necrosis, necroptosis and autophagy which lead to neuronal cell death. Conversely, the activation of such pathways could also result in the abnormal generation of APP and Aβ peptides. An elucidation of actions of APP and its metabolite, Aβ, could be vital in suggesting novel therapeutic opportunities.

The role of mitochondria-associated membranes in cellular homeostasis and diseases

Mitochondria and endoplasmic reticulum (ER) are fundamental in the control of cell physiology regulating several signal transduction pathways. They continuously communicate exchanging messages in their contact sites called MAMs (mitochondria-associated membranes). MAMs are specific microdomains acting as a platform for the sorting of vital and dangerous signals. In recent years increasing evidence reported that multiple scaffold proteins and regulatory factors localize to this subcellular fraction suggesting MAMs as hotspot signaling domains. In this review we describe the current knowledge about MAMs' dynamics and processes, which provided new correlations between MAMs' dysfunctions and human diseases. In fact, MAMs machinery is strictly connected with several pathologies, like neurodegeneration, diabetes and mainly cancer. These pathological events are characterized by alterations in the normal communication between ER and mitochondria, leading to deep metabolic defects that contribute to the progression of the diseases.

Effects of MiR-107 on The Chemo-drug Sensitivity of Breast Cancer Cells

Background

A growing body of evidence indicates that aberrant expression of miR-107 plays a core role in cancers. This study aims to demonstrate the function of miR-107 and its roles in chemo-drug resistance in breast cancer cells.

Methodology

CCK-8 assays were carried out to test the effect of miR-107 mimics on the proliferation of MCF-7 cells. The apoptosis level of each group was detected by flow cytometry. miR-107 level, mRNA levels of Bcl-2/Bax and TRIAP1 were detected by quantitative real-time Polymerase Chain Reaction (qRT-PCR) analysis. Protein levels of Bcl-2/Bax, p-Akt/Akt in MCF-7 cells were detected by using Western Blot. Lastly, the dual luciferase reporter gene assay system was used to confirm interaction between miR-107 and its target gene TRIAP1.

Results

CCK-8 assays indicated that miR-107 mimics augmented Taxol-induced cell viability inhibition. Flow cytometry showed that miR-107 mimics augmented Taxol-induced elevation of cell apoptosis. qRT-PCR analysis revealed that miR-107 mimics inhibited the mRNA expression of Bcl-2 and induced the mRNA level of Bax. Western Blotting indicated that miR-107 mimics inhibited the expression of proteins Bcl-2 and p-Akt, and induced the expression of Bax, while showing no significant effects on Akt. The relative luciferase activity revealed that oncogene TRIAP1 is a potential target gene of miR-107.

Conclusions

miR-107 plays a role in regulating chemo-drug sensitivity in mammary cancer cell by targeting TRIAP1.

Interorganellar calcium signaling in the regulation of cell metabolism: A cancer perspective

Organelles were originally considered to be individual cellular compartments with a defined organization and function. However, recent studies revealed that organelles deeply communicate within each other via Ca²⁺ exchange. This communication, mediated by specialized membrane regions in close apposition between two organelles, regulate cellular functions, including metabolism and cell fate decisions. Advances in microscopy techniques, molecular biology and biochemistry have increased our understanding of these interorganelle platforms. Research findings suggest that interorganellar Ca²⁺ signaling, which is altered in cancer, influences tumorigenesis and tumor progression by controlling cell death programs and metabolism. Here, we summarize the available data on the existence and composition of interorganelle platforms connecting the endoplasmic reticulum with mitochondria, the plasma membrane, or endolysosomes. Finally, we provide a timely overview of the potential function of interorganellar Ca²⁺ signaling in maintaining cellular homeostasis.

Goat and buffalo milk fat globule membranes exhibit better effects at inducing apoptosis and reduction the viability of HT-29 cells

Bovine milk fat globule membrane (MFGM) has shown many health benefits, however, there has not been much study on non-cattle MFGMs. The purpose of this study was to compare the anti-proliferation effects and investigate the mechanisms of MFGMs from bovine, goat, buffalo, yak and camel milk in HT-29 cells. Results showed that protein content in MFGM of yak milk is the highest among five MFGM. All MFGMs reduced cellular viability which was in agreement with cell morphology and apoptosis. However, the number of cells in S-phase from 24 h to 72 h was increased significantly by treatment with goat, buffalo and bovine MFGMs (100 μg/mL), but not yak and camel. All MFGMs treatment significantly reduced the mitochondrial membrane potential (with an order of goat > buffalo > bovine > camel > yak) and Bcl-2 expression, but increased the expression of both Bax and Caspase-3. Taken together, the results indicate that all MFGMs, especially goat and buffalo MFGMs, showed better effects at inducing apoptosis and reduction the viability of HT-29 cells. The mechanism might be arresting the cell cycle at S phase, depolarization of mitochondrial membrane potential, down-regulation of Bcl-2 expression and increase of Bax and Caspase-3 expression.