Resveratrol Specifically Kills Cancer Cells by a Devastating Increase in the Ca2+ Coupling Between the Greatly Tethered Endoplasmic Reticulum and Mitochondria

Mitochondria-Endoplasmic Reticulum Contact Sites (MERCS): A New Axis in Neuronal Degeneration and Regeneration

Mitochondria-Endoplasmic Reticulum Contact Sites (MERCS) are dynamic structures whose physiological interaction is vital to direct life and death of the cell. A bevy of tethering proteins, mitofusin-1/2 (Mfn-1/2), glucose-regulated protein-75 (Grp-75), voltage-dependent anion channel-1 (VDAC1), and dynamic-related protein-1 (Drp1), plays an integral role in establishing and regulating this intricate intracellular communication. Dysregulation of this interplay leads to various neurodegenerative disorders, like Alzheimer's disease (AD), Parkinson's disease (PD), stroke, traumatic brain injury (TBI), amyotrophic lateral sclerosis (ALS), and frontotemporal dementia (FTD). Although there is an absence of a well-defined molecular background that dictates the pathway of MERCS, adequate exploration has resulted in preliminary data that suggests its cardinal role in neuroregeneration. The juxtaposition of mitochondria and ER has a critical function in cell senescence, thus regulating regeneration. Axonal regeneration and brain tissue regeneration, using reactive astrocytes, are studied most extensively. Overexpression of Grp-75 promoted axonal regeneration post a nerve injury. Attempts have been made to exploit MERCS as potential therapeutic drug targets for enhancing neuroregeneration and impeding neurodegeneration. Novel strategies have been developed to aid the delivery of mitochondria into the neuronal cell body, which in turn establishes a network with the presiding ER resulting in contact site formation. The fascinating aspect of this mechanism is that despite the lack of inherent regenerative capacity in neurons, it can be induced by modifying MERCS.

Kinase signalling adaptation supports dysfunctional mitochondria in disease

Mitochondria form a critical control nexus which are essential for maintaining correct tissue homeostasis. An increasing number of studies have identified dysregulation of mitochondria as a driver in cancer. However, which pathways support and promote this adapted mitochondrial function? A key hallmark of cancer is perturbation of kinase signalling pathways. These pathways include mitogen activated protein kinases (MAPK), lipid secondary messenger networks, cyclic-AMP-activated (cAMP)/AMP-activated kinases (AMPK), and Ca2+/calmodulin-dependent protein kinase (CaMK) networks. These signalling pathways have multiple substrates which support initiation and persistence of cancer. Many of these are involved in the regulation of mitochondrial morphology, mitochondrial apoptosis, mitochondrial calcium homeostasis, mitochondrial associated membranes (MAMs), and retrograde ROS signalling. This review will aim to both explore how kinase signalling integrates with these critical mitochondrial pathways and highlight how these systems can be usurped to support the development of disease. In addition, we will identify areas which require further investigation to fully understand the complexities of these regulatory interactions. Overall, this review will emphasize how studying the interaction between kinase signalling and mitochondria improves our understanding of mitochondrial homeostasis and can yield novel therapeutic targets to treat disease.

Nano-modulators with the function of disrupting mitochondrial Ca2+ homeostasis and photothermal conversion for synergistic breast cancer therapy

Breast cancer treatment has been a global puzzle, and apoptosis strategies based on mitochondrial Ca2+ overload have attracted extensive attention. However, various limitations of current Ca2+ nanogenerators make it difficult to maintain effective Ca2+ overload concentrations. Here, we constructed a multimodal Ca2+ nano-modulator that, for the first time, combined photothermal therapy (PTT) and mitochondrial Ca2+ overload strategies to inhibit tumor development. By crosslinking sodium alginate (SA) on the surface of calcium carbonate (CaCO3) nanoparticles encapsulating with Cur and ICG, we prepared a synergistic Ca2+ nano-regulator SA/Cur@CaCO3-ICG (SCCI). In vitro studies have shown that SCCI further enhanced photostability while preserving the optical properties of ICG. After uptake by tumor cells, SCCI can reduce mitochondrial membrane potential and down-regulate ATP production by producing large amounts of Ca2+ at low pH. Near-infrared light radiation (NIR) laser irradiation made the tumor cells heat up sharply, which not only accelerated the decomposition of CaCO3, but also produced large amounts of reactive oxygen species (ROS) followed by cell apoptosis. In vivo studies have revealed that the Ca2+ nano-regulators had excellent targeting, biocompatibility, and anti-tumor effects, which can significantly inhibit the proliferation of tumor cells and play a direct killing effect. These findings indicated that therapeutic strategies based on ionic interference and PTT had great therapeutic potential, providing new insights into antitumor therapy.

Anti-Cancer Properties of Resveratrol: A Focus on Its Impact on Mitochondrial Functions

Cancer is one of the most serious public health issues worldwide, demanding ongoing efforts to find novel therapeutic agents and approaches. Amid growing interest in the oncological applications of phytochemicals, particularly polyphenols, resveratrol-a naturally occurring polyphenolic stilbene derivative-has emerged as a candidate of interest. This review analyzes the pleiotropic anti-cancer effects of resveratrol, including its modulation of apoptotic pathways, cell cycle regulation, inflammation, angiogenesis, and metastasis, its interaction with cancer stem cells and the tumor microenvironment. The effects of resveratrol on mitochondrial functions, which are crucial to cancer development, are also discussed. Future research directions are identified, including the elucidation of specific molecular targets, to facilitate the clinical translation of resveratrol in cancer prevention and therapy.

Tumor microenvironment remodeling in oral cancer: Application of plant derived-natural products and nanomaterials

Oral cancers consist of squamous cell carcinoma (SCC) and other malignancies in the mouth with varying degrees of invasion and differentiation. For many years, different modalities such as surgery, radiation therapy, and classical chemotherapy drugs have been used to control the growth of oral tumors. Nowadays, studies have confirmed the remarkable effects of the tumor microenvironment (TME) on the development, invasion, and therapeutic resistance of tumors like oral cancers. Therefore, several studies have been conducted to modulate the TME in various types of tumors in favor of cancer suppression. Natural products are intriguing agents for targeting cancers and TME. Flavonoids, non-flavonoid herbal-derived molecules, and other natural products have shown promising effects on cancers and TME. These agents, such as curcumin, resveratrol, melatonin, quercetin and naringinin have demonstrated potency in suppressing oral cancers. In this paper, we will review and discuss about the potential efficacy of natural adjuvants on oral cancer cells. Furthermore, we will review the possible therapeutic effects of these agents on the TME and oral cancer cells. Moreover, the potential of nanoparticles-loaded natural products for targeting oral cancers and TME will be reviewed. The potentials, gaps, and future perspectives for targeting TME by nanoparticles-loaded natural products will also be discussed.

Sulforaphane modifies mitochondrial-endoplasmic reticulum associations through reductive stress in cardiomyocytes

Mitochondria-endoplasmic reticulum (ER) communication relies on platforms formed at the ER membrane with the mitochondrial outer membrane contact sites (MERCs). MERCs are involved in several processes including the unfolded protein response (UPR) and calcium (Ca2+) signaling. Therefore, as alterations in MERCs greatly impact cellular metabolism, pharmacological interventions to preserve productive mitochondrial-ER communication have been explored to maintain cellular homeostasis. In this regard, extensive information has documented the beneficial and potential effects of sulforaphane (SFN) in different pathological conditions; however, controversy has arisen regarding the effect of this compound on mitochondria-ER interaction. Therefore, in this study, we investigated whether SFN could induce changes in MERCs under normal culture conditions without damaging stimuli. Our results indicate that non-cytotoxic concentration of 2.5 μM SFN increased ER stress in cardiomyocytes in conjunction with a reductive stress environment, that diminishes ER-mitochondria association. Additionally, reductive stress promotes Ca2+ accumulation in the ER of cardiomyocytes. These data show an unexpected effect of SFN on cardiomyocytes grown under standard culture conditions, promoted by the cellular redox unbalance. Therefore, it is necessary to rationalize the use of compounds with antioxidant properties to avoid triggering cellular side effects.

Molecular understanding of ER-MT communication dysfunction during neurodegeneration

Biological researchers are seeing organelles in a new light. These cellular entities have been believed to be singular and distinctive structures that performed specialized purposes for a very long time. But in recentpast years, scientists have learned that organelles become dynamic and make physical contact. Additionally, Biological processes are regulated by organelles interactions and its alteration play an important role in cell malfunctioning and several pathologies, including neurodegenerative diseases. Mitochondrial-ER contact sites (MERCS) have received considerable attention in the domain of cell homeostasis and dysfunction, specifically in the area of neurodegeneration. This is largely due to the significant role of this subcellular compartment in a diverse array of vital cellular functions, including Ca2+ homeostasis, transport, bioenergetics and turnover, mitochondrial dynamics, apoptotic signaling, ER stress, and inflammation. A significant number of disease-associated proteins were found to physically interact with the ER-Mitochondria (ER-MT) interface, causing structural and/or functional alterations in this compartment. In this review, we summarize current knowledge about the structure and functions of the ER-MT contact sites, as well as the possible repercussions of their alteration in notable neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and fronto-temporal dementia. The constraints and complexities in defining the nature and origin of the highlighted defects in ER-MT communication, as well as their concise contribution to the neurodegenerative process, are illustrated in particular. The possibility of using MERCS as a potential drug target to prevent neuronal damage and ultimately neurodegeneration is the topic of our final discussion.

The ER-mitochondria interface, where Ca2+ and cell death meet

Endoplasmic reticulum (ER)-mitochondria contact sites are crucial to allow Ca²⁺ flux between them and a plethora of proteins participate in tethering both organelles together. Inositol 1,4,5-trisphosphate receptors (IP₃Rs) play a pivotal role at such contact sites, participating in both ER-mitochondria tethering and as Ca²⁺-transport system that delivers Ca²⁺ from the ER towards mitochondria. At the ER-mitochondria contact sites, the IP₃Rs function as a multi-protein complex linked to the voltage-dependent anion channel 1 (VDAC1) in the outer mitochondrial membrane, via the chaperone glucose-regulated protein 75 (GRP75). This IP₃R-GRP75-VDAC1 complex supports the efficient transfer of Ca²⁺ from the ER into the mitochondrial intermembrane space, from which the Ca²⁺ ions can reach the mitochondrial matrix through the mitochondrial calcium uniporter. Under physiological conditions, basal Ca²⁺ oscillations deliver Ca²⁺ to the mitochondrial matrix, thereby stimulating mitochondrial oxidative metabolism. However, when mitochondrial Ca²⁺ overload occurs, the increase in [Ca²⁺] will induce the opening of the mitochondrial permeability transition pore, thereby provoking cell death. The IP₃R-GRP75-VDAC1 complex forms a hub for several other proteins that stabilize the complex and/or regulate the complex's ability to channel Ca²⁺ into the mitochondria. These proteins and their mechanisms of action are discussed in the present review with special attention for their role in pathological conditions and potential implication for therapeutic strategies.

Targeting the mitochondrial Ca2+ uniporter complex in cardiovascular disease

Cardiovascular diseases (CVDs), the leading cause of death worldwide, share in common mitochondrial dysfunction, in specific a dysregulation of Ca²⁺ uptake dynamics through the mitochondrial Ca²⁺ uniporter (MCU) complex. In particular, Ca²⁺ uptake regulates the mitochondrial ATP production, mitochondrial dynamics, oxidative stress, and cell death. Therefore, modulating the activity of the MCU complex to regulate Ca²⁺ uptake, has been suggested as a potential therapeutic approach for the treatment of CVDs. Here, the role and implications of the MCU complex in CVDs are presented, followed by a review of the evidence for MCU complex modulation, genetically and pharmacologically. While most approaches have aimed within the MCU complex for the modulation of the Ca²⁺ pore channel, the MCU subunit, its intra- and extra- mitochondrial implications, including Ca²⁺ dynamics, oxidative stress, post-translational modifications, and its repercussions in the cardiac function, highlight that targeting the MCU complex has the translational potential for novel CVDs therapeutics.

Mitochondria-endoplasmic reticulum contacts in sepsis-induced myocardial dysfunction

Mitochondrial and endoplasmic reticulum (ER) are important intracellular organelles. The sites that mitochondrial and ER are closely related in structure and function are called Mitochondria-ER contacts (MERCs). MERCs are involved in a variety of biological processes, including calcium signaling, lipid synthesis and transport, autophagy, mitochondrial dynamics, ER stress, and inflammation. Sepsis-induced myocardial dysfunction (SIMD) is a vital organ damage caused by sepsis, which is closely associated with mitochondrial and ER dysfunction. Growing evidence strongly supports the role of MERCs in the pathogenesis of SIMD. In this review, we summarize the biological functions of MERCs and the roles of MERCs proteins in SIMD.

Phytochemical Targeting of Mitochondria for Breast Cancer Chemoprevention, Therapy, and Sensitization

Breast cancer is a common and deadly disease that causes tremendous physical, emotional, and financial burden on patients and society. Early-stage breast cancer and less aggressive subtypes have promising prognosis for patients, but in aggressive subtypes, and as cancers progress, treatment options and responses diminish, dramatically decreasing survival. Plants are nutritionally rich and biologically diverse organisms containing thousands of metabolites, some of which have chemopreventive, therapeutic, and sensitizing properties, providing a rich source for drug discovery. In this study we review the current landscape of breast cancer with a central focus on the potential role of phytochemicals for treatment, management, and disease prevention. We discuss the relevance of phytochemical targeting of mitochondria for improved anti-breast cancer efficacy. We highlight current applications of phytochemicals and derivative structures that display anti-cancer properties and modulate cancer mitochondria, while describing future applicability and identifying areas of promise.

Resveratrol Carbon Dots Disrupt Mitochondrial Function in Cancer Cells

Resveratrol, a natural polyphenol, exhibits beneficial health properties and has been touted as a potential anti-tumor agent. Here, we demonstrate potent anti-cancer effects of carbon dots (C-dots) synthesized from resveratrol. The mild synthesis conditions retained resveratrol functional moieties upon the carbon dots' (C-dots) surface, an important requisite for achieving specificity toward cancer cells and biological activities. Indeed, the disruptive effects of the resveratrol-C-dot were more pronounced in several cancer cell types compared to normal cells, underscoring targeting capabilities of the C-dots, a pertinent issue for the development of cancer therapeutics. In particular, we observed impairment of mitochondrial functionalities, including intracellular calcium release, inhibition of cytochrome-C oxidase enzyme activity, and mitochondrial membrane perturbation. Furthermore, the resveratrol C-dots were more potent than either resveratrol molecules alone, known anti-cancer polyphenolic agents such as curcumin and triphenylphosphonium, or C-dots prepared from different carbonaceous precursors. This study suggests that resveratrol-synthesized C-dots may have promising therapeutic potential as anti-cancer agents.

Natural Polyphenols as SERCA Activators: Role in the Endoplasmic Reticulum Stress-Related Diseases

Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) is a key protein responsible for transporting Ca²⁺ ions from the cytosol into the lumen of the sarco/endoplasmic reticulum (SR/ER), thus maintaining Ca²⁺ homeostasis within cells. Accumulating evidence suggests that impaired SERCA function is associated with disruption of intracellular Ca²⁺ homeostasis and induction of ER stress, leading to different chronic pathological conditions. Therefore, appropriate strategies to control Ca²⁺ homeostasis via modulation of either SERCA pump activity/expression or relevant signaling pathways may represent a useful approach to combat pathological states associated with ER stress. Natural dietary polyphenolic compounds, such as resveratrol, gingerol, ellagic acid, luteolin, or green tea polyphenols, with a number of health-promoting properties, have been described either to increase SERCA activity/expression directly or to affect Ca²⁺ signaling pathways. In this review, potential Ca²⁺-mediated effects of the most studied polyphenols on SERCA pumps or related Ca²⁺ signaling pathways are summarized, and relevant mechanisms of their action on Ca²⁺ regulation with respect to various ER stress-related states are depicted. All data were collected using scientific search tools (i.e., Science Direct, PubMed, Scopus, and Google Scholar).

Protodioscin Induces Mitochondrial Apoptosis of Human Hepatocellular Carcinoma Cells Through Eliciting ER Stress-Mediated IP3R Targeting Mfn1/Bak Expression

Objective

Protodioscin (PD), a steroidal saponin, has a diverse pharmacological activity including neuroprotection, male fertility improvement, and cytotoxicity against various cancers cell lines of different origins. However, the effect of PD on hepatocellular carcinoma (HCC) is still unclear.

Methods

Cell viability, colony formation and flow cytometry analysis for apoptosis profile, mitochondrial membrane potential endoplasmic reticulum (ER) expansion were employed to determine the effect of PD against HCC cells. Transient transfection of siRNA, immunofluorescent imaging and immunoprecipitation were used to elucidate the anti-cancer mechanism of PD. The in vivo toxicity and efficacy of PD were assessed by a xenograft mouse model.

Results

PD induced apoptosis, loss of mitochondrial membrane potential and ER expansion in HCC cells. Either downregulation of Mfn1 or Bak reversed PD-induced apoptosis and loss of mitochondrial membrane potential. Further analysis revealed that Mfn1 and Bak will form a complex with IP3R to facilitate the transfer of Ca²⁺ from ER to mitochondria and apoptosis. In addition, our tumour xenograft model further verifies the in vivo anti-tumour effect of PD.

Conclusion

Our study sheds light on the understanding of the anti-HCC effects of PD and may open new aspects for the development of novel treatment for human hepatocellular carcinoma.

Visualizing physiological parameters in cells and tissues using genetically encoded indicators for metabolites

The study of metabolism is undergoing a renaissance. Since the year 2002, over 50 genetically-encoded fluorescent indicators (GEFIs) have been introduced, capable of monitoring metabolites with high spatial/temporal resolution using fluorescence microscopy. Indicators are fusion proteins that change their fluorescence upon binding a specific metabolite. There are indicators for sugars, monocarboxylates, Krebs cycle intermediates, amino acids, cofactors, and energy nucleotides. They permit monitoring relative levels, concentrations, and fluxes in living systems. At a minimum they report relative levels and, in some cases, absolute concentrations may be obtained by performing ad hoc calibration protocols. Proper data collection, processing, and interpretation are critical to take full advantage of these new tools. This review offers a survey of the metabolic indicators that have been validated in mammalian systems. Minimally invasive, these indicators have been instrumental for the purposes of confirmation, rebuttal and discovery. We envision that this powerful technology will foster metabolic physiology.

Citrin mediated metabolic rewiring in response to altered basal subcellular Ca2+ homeostasis

In contrast to long-term metabolic reprogramming, metabolic rewiring represents an instant and reversible cellular adaptation to physiological or pathological stress. Ca2+ signals of distinct spatio-temporal patterns control a plethora of signaling processes and can determine basal cellular metabolic setting, however, Ca2+ signals that define metabolic rewiring have not been conclusively identified and characterized. Here, we reveal the existence of a basal Ca2+ flux originating from extracellular space and delivered to mitochondria by Ca2+ leakage from inositol triphosphate receptors in mitochondria-associated membranes. This Ca2+ flux primes mitochondrial metabolism by maintaining glycolysis and keeping mitochondria energized for ATP production. We identified citrin, a well-defined Ca2+-binding component of malate-aspartate shuttle in the mitochondrial intermembrane space, as predominant target of this basal Ca2+ regulation. Our data emphasize that any manipulation of this ubiquitous Ca2+ system has the potency to initiate metabolic rewiring as an instant and reversible cellular adaptation to physiological or pathological stress.

Nanoplatform-mediated calcium overload for cancer therapy

Mitochondria, as the "the plant of power" of cells, have been extensively highlighted with biological functions of offering energy and participating in signaling pathways. In parallel, calcium (Ca2+) plays a...

The multifaceted roles of mitochondria at the crossroads of cell life and death in cancer

Mitochondria are the cytoplasmic organelles mostly known as the "electric engine" of the cells; however, they also play pivotal roles in different biological processes, such as cell growth/apoptosis, Ca²⁺ and redox homeostasis, and cell stemness. In cancer cells, mitochondria undergo peculiar functional and structural dynamics involved in the survival/death fate of the cell. Cancer cells use glycolysis to support macromolecular biosynthesis and energy production ("Warburg effect"); however, mitochondrial OXPHOS has been shown to be still active during carcinogenesis and even exacerbated in drug-resistant and stem cancer cells. This metabolic rewiring is associated with mutations in genes encoding mitochondrial metabolic enzymes ("oncometabolites"), alterations of ROS production and redox biology, and a fine-tuned balance between anti-/proapoptotic proteins. In cancer cells, mitochondria also experience dynamic alterations from the structural point of view undergoing coordinated cycles of biogenesis, fusion/fission and mitophagy, and physically communicating with the endoplasmic reticulum (ER), through the Ca²⁺ flux, at the MAM (mitochondria-associated membranes) levels. This review addresses the peculiar mitochondrial metabolic and structural dynamics occurring in cancer cells and their role in coordinating the balance between cell survival and death. The role of mitochondrial dynamics as effective biomarkers of tumor progression and promising targets for anticancer strategies is also discussed.

Biomolecular Evaluation of Piceatannol's Effects in Counteracting the Senescence of Mesenchymal Stromal Cells: A New Candidate for Senotherapeutics?

Several investigations on senescence and its causative role in aging have underscored the importance of developing senotherapeutics, a field focused on killing senescent cells and/or preventing their accumulation within tissues. Using polyphenols in counteracting senescence may facilitate the development of senotherapeutics given their presence in the human diet, their confirmed tolerability and absence of severe side effects, and their role in preventing senescence and inducing the death of senescent cells. Against that background, we evaluated the effect of piceatannol, a natural polyphenol, on the senescence of mesenchymal stromal cells (MSCs), which play a key role in the body's homeostasis. Among our results, piceatannol reduced the number of senescent cells both after genotoxic stress that induced acute senescence and in senescent replicative cultures. Such senotherapeutics activity, moreover, promoted the recovery of cell proliferation and the stemness properties of MSCs. Altogether, our findings demonstrate piceatannol's effectiveness in counteracting senescence by targeting its associated pathways and detecting and affecting P53-dependent and P53-independent senescence. Our study thus suggests that, given piceatannol's various mechanisms to accomplish its pleiotropic activities, it may be able to counteract any senescent phenotypes.

Lockdown of mitochondrial Ca2+ extrusion and subsequent resveratrol treatment kill HeLa cells by Ca2+ overload

Anticancer effect of resveratrol and the role of sodium/lithium/calcium exchanger in context with calcium ions are studied in human cervical cancer cell line. This therapeutic approach using siNCLX mediated gene silencing and drug therapy with resveratrol indicates the disruption of calcium homeostasis, increase in caspase (-3, 8, 9) mRNA expressions and DNA damage leading to apoptotic cell death. Monitoring the intracellular Ca2+ changes using fluo-4AM indicates highest rise in [Ca2+] level in sodium/lithium/calcium exchanger silenced group with five different stages, that is distinguishable based on the fluorescence intensity. In resveratrol treated and siNCLX + resveratrol treated groups no such cell staging differences were observed, despite uniform Ca2+ rise followed by decrease in the intensity. Integrating RNAi gene silencing of sodium/lithium/calcium exchanger with resveratrol can form the most interesting, efficient and promising therapeutic strategy in the treatment of cancer.

Human astrocytes and astrocytoma respond differently to resveratrol

A fundamental problem in oncology is that anticancer chemotherapeutics kill both cancer and healthy cells in the surrounding tissues. Resveratrol is a natural antioxidant with intriguing and opposing biological properties: it reduces viability of some cancer cells but not of non-transformed ones (in equimolar concentrations). Therefore, we examined resveratrol in human non-transformed primary astrocytes and astrocytoma. Resveratrol reduced reactive oxygen species in astrocytes, but not in astrocytoma. Such cell-type dependent response is particularly evident with analyses at the single cell level showing clear population difference in high and low glutathione levels. Due to resveratrol's poor aqueous solubility that limits its use in clinics, we incorporated it into stimulus-responsive micelles assembled from miktoarm polymers. This could be an attractive chemotherapeutic delivery strategy in nano-oncology. As a proof of principle, we show that these formulations containing resveratrol markedly decrease astrocytoma viability, particularly in combination with temozolomide, a first line chemotherapeutic for astrocytoma.

Clinical significance of P-class pumps in cancer

P-class pumps are specific ion transporters involved in maintaining intracellular/extracellular ion homeostasis, gene transcription, and cell proliferation and migration in all eukaryotic cells. The present review aimed to evaluate the role of P-type pumps [Na⁺/K⁺ ATPase (NKA), H⁺/K⁺ ATPase (HKA) and Ca2⁺-ATPase] in cancer cells across three fronts, namely structure, function and genetic expression. It has been shown that administration of specific P-class pumps inhibitors can have different effects by: i) Altering pump function; ii) inhibiting cell proliferation; iii) inducing apoptosis; iv) modifying metabolic pathways; and v) induce sensitivity to chemotherapy and lead to antitumor effects. For example, the NKA β2 subunit can be downregulated by gemcitabine, resulting in increased apoptosis of cancer cells. The sarcoendoplasmic reticulum calcium ATPase can be inhibited by thapsigargin resulting in decreased prostate tumor volume, whereas the HKA α subunit can be affected by proton pump inhibitors in gastric cancer cell lines, inducing apoptosis. In conclusion, the present review highlighted the central role of P-class pumps and their possible use and role as anticancer cellular targets for novel therapeutic chemical agents.

Protective Effect of Piceatannol Against Cerebral Ischaemia-Reperfusion Injury Via Regulating Nrf2/HO-1 Pathway In Vivo and Vitro

Piceatannol is a natural plant-derived compound with protective effects against cardiovascular diseases. However, its effect on cerebral ischaemia-reperfusion injury (CIRI) induced by oxidative stress remains unclear. This study aimed to investigate piceatannol's antioxidation in CIRI. An in vitro oxygen-glucose deprivation followed by reoxygenation model was used and cell viability was measured. A middle cerebral artery occlusion followed by reperfusion model was used in vivo. Neurological function, encephalisation quotient, oedema, and volume of the cerebral infarction were then evaluated. The effects of piceatannol on histopathological findings, as well as the ultrastructure of the cortex, were analysed. The activity of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and lactate dehydrogenase (LDH) and the malondialdehyde (MDA) content was measured both in vitro and in vivo. Finally, the expression of nuclear factor erythroid-2-related factor 2 (Nrf2), hemeoxygenase-1 (HO-1), and nicotinamide adenine dinucleotide phosphate quinone oxidoreductase 1 (NQO1) in cerebral tissue was detected using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and western blotting. Our results demonstrated that cell viability in the piceatannol groups was increased. The SOD, GSH-Px activities were increased as LDH activity and MDA content decreased in the piceatannol groups both in vitro and in vivo, reflecting a decrease in oxidative stress. The neurological severity score and infarction volume in the piceatannol groups at doses of 10 and 20 mg/kg were lower than those of the model group. Furthermore, the damage seen on histopathological examination was partially attenuated by piceatannol. RT-qPCR and western blot analysis indicated that the expression of Nrf2, HO-1, and NQO1 were significantly increased by piceatannol. The results of the study demonstrate that piceatannol exerts a protective effect against CIRI.

Mitochondrial Ca2+ Signaling in Health, Disease and Therapy

The divalent cation calcium (Ca²⁺) is considered one of the main second messengers inside cells and acts as the most prominent signal in a plethora of biological processes. Its homeostasis is guaranteed by an intricate and complex system of channels, pumps, and exchangers. In this context, by regulating cellular Ca²⁺ levels, mitochondria control both the uptake and release of Ca²⁺. Therefore, at the mitochondrial level, Ca²⁺ plays a dual role, participating in both vital physiological processes (ATP production and regulation of mitochondrial metabolism) and pathophysiological processes (cell death, cancer progression and metastasis). Hence, it is not surprising that alterations in mitochondrial Ca²⁺ (mCa²⁺) pathways or mutations in Ca²⁺ transporters affect the activities and functions of the entire cell. Indeed, it is widely recognized that dysregulation of mCa²⁺ signaling leads to various pathological scenarios, including cancer, neurological defects and cardiovascular diseases (CVDs). This review summarizes the current knowledge on the regulation of mCa²⁺ homeostasis, the related mechanisms and the significance of this regulation in physiology and human diseases. We also highlight strategies aimed at remedying mCa²⁺ dysregulation as promising therapeutical approaches.

Piceatannol-Loaded Bilosome-Stabilized Zein Protein Exhibits Enhanced Cytostatic and Apoptotic Activities in Lung Cancer Cells

Piceatannol (PIC) is a naturally occurring polyphenolic stilbene, and it has pleiotropic pharmacological properties. Moreover, PIC has cytotoxic actions among various cancer cells. In this work, preparations of PIC-loaded bilosome-zein (PIC-BZ) were designed, formulated, and characterized, and the optimized PIC-BZ cytotoxic activities, measured as half maximal inhibitory concentration (IC50), against lung cancer cell line was investigated. Box-Behnken design was utilized in order to examine the effect of preparation factors on drug entrapment and particle size. PIC-BZ showed a spherical shape after optimization, and its particle size was determined as 157.45 ± 1.62 nm. Moreover, the efficiency of drug entrapment was found as 93.14 ± 2.15%. The cytotoxic activity evaluation revealed that the adjusted formulation, which is PIC-BZ formula, showed a substantially smaller IC50 versus A549 cells. Cell cycle analysis showed accumulation of cells in the G2-M phase. Moreover, it showed in the sub-G1 phase, a rise of cell fraction suggestion apoptotic improving activity. Increased early and late phases of apoptosis were demonstrated by staining of cells with annexin V. Furthermore, the cellular caspase-3 protein expression was significantly raised by PIC-BZ. In addition, the wound healing experiment confirmed the results. To conclude, compared to pure PIC, PIC-BZ demonstrated a higher cell death-inducing activity against A549 cells.

LETM1: A Single Entity With Diverse Impact on Mitochondrial Metabolism and Cellular Signaling

Nearly 2 decades since its discovery as one of the genes responsible for the Wolf-Hirschhorn Syndrome (WHS), the primary function of the leucine-zipper EF-hand containing transmembrane 1 (LETM1) protein in the inner mitochondrial membrane (IMM) or the mechanism by which it regulates mitochondrial Ca²⁺ handling is unresolved. Meanwhile, LETM1 has been associated with the regulation of fundamental cellular processes, such as development, cellular respiration and metabolism, and apoptosis. This mini-review summarizes the diversity of cellular functions impacted by LETM1 and highlights the multiple roles of LETM1 in health and disease.

Mind the Gap: Mitochondria and the Endoplasmic Reticulum in Neurodegenerative Diseases

The way organelles are viewed by cell biologists is quickly changing. For many years, these cellular entities were thought to be unique and singular structures that performed specific roles. However, in recent decades, researchers have discovered that organelles are dynamic and form physical contacts. In addition, organelle interactions modulate several vital biological functions, and the dysregulation of these contacts is involved in cell dysfunction and different pathologies, including neurodegenerative diseases. Mitochondria–ER contact sites (MERCS) are among the most extensively studied and understood juxtapositioned interorganelle structures. In this review, we summarise the major biological and ultrastructural dysfunctions of MERCS in neurodegeneration, with a particular focus on Alzheimer’s disease as well as Parkinson’s disease, amyotrophic lateral sclerosis and frontotemporal dementia. We also propose an updated version of the MERCS hypothesis in Alzheimer’s disease based on new findings. Finally, we discuss the possibility of MERCS being used as possible drug targets to halt cell death and neurodegeneration.

Dynamic Control of Mitochondrial Ca2+ Levels as a Survival Strategy of Cancer Cells

Cancer cells have increased energy requirements due to their enhanced proliferation activity. This energy demand is, among others, met by mitochondrial ATP production. Since the second messenger Ca²⁺ maintains the activity of Krebs cycle dehydrogenases that fuel mitochondrial respiration, proper mitochondrial Ca²⁺ uptake is crucial for a cancer cell survival. However, a mitochondrial Ca²⁺ overload induces mitochondrial dysfunction and, ultimately, apoptotic cell death. Because of the vital importance of balancing mitochondrial Ca²⁺ levels, a highly sophisticated machinery of multiple proteins manages mitochondrial Ca²⁺ homeostasis. Notably, mitochondria sequester Ca²⁺ preferentially at the interaction sites between mitochondria and the endoplasmic reticulum (ER), the largest internal Ca²⁺ store, thus, pointing to mitochondrial-associated membranes (MAMs) as crucial hubs between cancer prosperity and cell death. To investigate potential regulatory mechanisms of the mitochondrial Ca²⁺ uptake routes in cancer cells, we modulated mitochondria–ER tethering and the expression of UCP2 and analyzed mitochondrial Ca²⁺ homeostasis under the various conditions. Hence, the expression of contributors to mitochondrial Ca²⁺ regulation machinery was quantified by qRT-PCR. We further used data from The Cancer Genome Atlas (TCGA) to correlate these in vitro findings with expression patterns in human breast invasive cancer and human prostate adenocarcinoma. ER-mitochondrial linkage was found to support a mitochondrial Ca²⁺ uptake route dependent on uncoupling protein 2 (UCP2) in cancer cells. Notably, combined overexpression of Rab32, a protein kinase A-anchoring protein fostering the ER-mitochondrial tethering, and UCP2 caused a significant drop in cancer cells' viability. Artificially enhanced ER-mitochondrial tethering further initiated a sudden decline in the expression of UCP2, probably as an adaptive response to avoid mitochondrial Ca²⁺ overload. Besides, TCGA analysis revealed an inverse expression correlation between proteins stabilizing mitochondrial-ER linkage and UCP2 in tissues of human breast invasive cancer and prostate adenocarcinoma. Based on these results, we assume that cancer cells successfully manage mitochondrial Ca²⁺ uptake to stimulate Ca²⁺-dependent mitochondrial metabolism while avoiding Ca²⁺-triggered cell death by fine-tuning ER-mitochondrial tethering and the expression of UCP2 in an inversed manner. Disruption of this equilibrium yields cancer cell death and may serve as a treatment strategy to specifically kill cancer cells.

The Two-Way Relationship Between Calcium and Metabolism in Cancer

Calcium ion (Ca²⁺) signaling is critical to many physiological processes, and its kinetics and subcellular localization are tightly regulated in all cell types. All Ca²⁺ flux perturbations impact cell function and may contribute to various diseases, including cancer. Several modulators of Ca²⁺ signaling are attractive pharmacological targets due to their accessibility at the plasma membrane. Despite this, the number of specific inhibitors is still limited, and to date there are no anticancer drugs in the clinic that target Ca²⁺ signaling. Ca²⁺ dynamics are impacted, in part, by modifications of cellular metabolic pathways. Conversely, it is well established that Ca²⁺ regulates cellular bioenergetics by allosterically activating key metabolic enzymes and metabolite shuttles or indirectly by modulating signaling cascades. A coordinated interplay between Ca²⁺ and metabolism is essential in maintaining cellular homeostasis. In this review, we provide a snapshot of the reciprocal interaction between Ca²⁺ and metabolism and discuss the potential consequences of this interplay in cancer cells. We highlight the contribution of Ca²⁺ to the metabolic reprogramming observed in cancer. We also describe how the metabolic adaptation of cancer cells influences this crosstalk to regulate protumorigenic signaling pathways. We suggest that the dual targeting of these processes might provide unprecedented opportunities for anticancer strategies. Interestingly, promising evidence for the synergistic effects of antimetabolites and Ca²⁺-modulating agents is emerging.

The contribution of uncoupling protein 2 to mitochondrial Ca2+ homeostasis in health and disease - A short revisit

Considering the versatile functions attributed to uncoupling protein 2 (UCP2) in health and disease, a profound understanding of the protein's molecular actions under physiological and pathophysiological conditions is indispensable. This review aims to revisit and shed light on the fundamental molecular functions of UCP2 in mitochondria, with particular emphasis on its intricate role in regulating mitochondrial calcium (Ca²⁺) uptake. UCP2's modulating effect on various vital processes in mitochondria makes it a crucial regulator of mitochondrial homeostasis in health and disease.

IFI6 depletion inhibits esophageal squamous cell carcinoma progression through reactive oxygen species accumulation via mitochondrial dysfunction and endoplasmic reticulum stress

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of the most lethal forms of adult cancer with poor prognosis. Substantial evidence indicates that reactive oxygen species (ROS) are important modulators of aggressive cancer behavior. However, the mechanism by which ESCC cells integrate redox signals to modulate carcinoma progression remains elusive.

METHODS

The expression of interferon alpha inducible protein 6 (IFI6) in clinical ESCC tissues and cell lines was detected by RT-PCR and Western blotting. The correlation between IFI6 expression levels and aggressive ESCC disease stage was examined by immunohistochemistry. Bioinformatic analysis was conducted to explore the potential function of IFI6 in ESCC. ESCC cell lines stably depleted of IFI6 and ectopically expressing IFI6 were established using lentiviruses expressing shRNAs and an IFI6 expression plasmid, respectively. The effects of IFI6 on ESCC cells were determined by cell-based analyses, including EdU assay, apoptotic assay, cellular and mitochondria-specific ROS detection, seahorse extracellular flux, and mitochondrial calcium flux assays. Blue native-polyacrylamide gel electrophoresis was used to determine mitochondrial supercomplex assembly. Transcriptional activation of NADPH oxidase 4 (NOX4) via ATF3 was confirmed by dual luciferase assay. In vivo tumor growth was determined in mouse xenograft models.

RESULTS

We find that the expression of IFI6, an IFN-stimulated gene localized in the inner mitochondrial membrane, is markedly elevated in ESCC patients and a panel of ESCC cell lines. High IFI6 expression correlates with aggressive disease phenotype and poor prognosis in ESCC patients. IFI6 depletion suppresses proliferation and induces apoptosis by increasing ROS accumulation. Mechanistically, IFI6 ablation induces mitochondrial calcium overload by activating mitochondrial Ca2+ uniporter and subsequently ROS production. Following IFI6 ablation, mitochondrial ROS accumulation is also induced by mitochondrial supercomplex assembly suppression and oxidative phosphorylation dysfunction, while IFI6 overexpression produces the opposite effects. Furthermore, energy starvation induced by IFI6 inhibition drives endoplasmic reticulum stress through disrupting endoplasmic reticulum calcium uptake, which upregulates NOX4-derived ROS production in an ATF3-dependent manner. Finally, the results in xenograft models of ESCC further corroborate the in vitro findings.

CONCLUSION

Our study unveils a novel redox homeostasis signaling pathway that regulates ESCC pathobiology and identifies IFI6 as a potential druggable target in ESCC.

Chemical Modulation of Mitochondria-Endoplasmic Reticulum Contact Sites

Contact sites between mitochondria and endoplasmic reticulum (ER) are points in which the two organelles are in close proximity. Due to their structural and functional complexity, their exploitation as pharmacological targets has never been considered so far. Notwithstanding, the number of compounds described to target proteins residing at these interfaces either directly or indirectly is rising. Here we provide original insight into mitochondria–ER contact sites (MERCs), with a comprehensive overview of the current MERCs pharmacology. Importantly, we discuss the considerable potential of MERCs to become a druggable target for the development of novel therapeutic strategies.

Piceatannol-Loaded Emulsomes Exhibit Enhanced Cytostatic and Apoptotic Activities in Colon Cancer Cells

Piceatannol (PIC), a naturally occurring polyphenolic stilbene, has pleiotropic pharmacological activities. It has reported cytotoxic activities against different cancer cells. In the present study, PIC emulsomes (PIC-E) were formulated and assessed for cytotoxic activity. A Box–Behnken design was employed to investigate the influence of formulation factors on particle size and drug entrapment. After optimization, the formulation had a spherical shape with a particle size of 125.45 ± 1.62 nm and entrapment efficiency of 93.14% ± 2.15%. Assessment of cytotoxic activities indicated that the optimized PIC-E formula exhibited significantly lower IC₅₀ against HCT 116 cells. Analysis of the cell cycle revealed the accumulation of cells in the G2-M phase as well as increased cell fraction in the sub-G1 phase, an indication of apoptotic-enhancing activity. Staining of cells with Annexin V indicated increased early and late apoptosis. Further, the cellular contents of caspase - 3 and Bax/Bcl-2 mRNA expression were significantly elevated by PIC-E. In addition, the mitochondrial membrane potential (MMP) was disturbed and reactive oxygen species (ROS) production was increased. In conclusion, PIC-E exhibited superior cell death-inducing activities against HCT 116 cells as compared to pure PIC. This is mediated, at least partly, by enhanced pro-apoptotic activity, disruption of MMP, and stimulation of ROS generation.

Natural products and phytochemical nanoformulations targeting mitochondria in oncotherapy: an updated review on resveratrol

Mitochondria are intracellular organelles with two distinct membranes, known as an outer mitochondrial membrane and inner cell membrane. Originally, mitochondria have been derived from bacteria. The main function of mitochondria is the production of ATP. However, this important organelle indirectly protects cells by consuming oxygen in the route of energy generation. It has been found that mitochondria are actively involved in the induction of the intrinsic pathways of apoptosis. So, there have been efforts to sustain mitochondrial homeostasis and inhibit its dysfunction. Notably, due to the potential role of mitochondria in the stimulation of apoptosis, this organelle is a promising target in cancer therapy. Resveratrol is a non-flavonoid polyphenol that exhibits significant pharmacological effects such as antioxidant, anti-diabetic, anti-inflammatory and anti-tumor. The anti-tumor activity of resveratrol may be a consequence of its effect on mitochondria. Multiple studies have investigated the relationship between resveratrol and mitochondria, and it has been demonstrated that resveratrol is able to significantly enhance the concentration of reactive oxygen species, leading to the mitochondrial dysfunction and consequently, apoptosis induction. A number of signaling pathways such as sirtuin and NF-κB may contribute to the mitochondrial-mediated apoptosis by resveratrol. Besides, resveratrol shifts cellular metabolism from glycolysis into mitochondrial respiration to induce cellular death in cancer cells. In the present review, we discuss the possible interactions between resveratrol and mitochondria, and its potential application in cancer therapy.

Mitochondrial Dysfunction at the Center of Cancer Therapy

Significance: Mitochondria undergo constant morphological changes through fusion, fission, and mitophagy. As the key organelle in cells, mitochondria are responsible for numerous essential cellular functions such as metabolism, regulation of calcium (Ca²⁺), generation of reactive oxygen species, and initiation of apoptosis. Unsurprisingly, mitochondrial dysfunctions underlie many pathologies including cancer. Recent Advances: Currently, the gold standard for cancer treatment is chemotherapy, radiation, and surgery. However, the efficacy of these treatments varies across different cancer cells. It has been suggested that mitochondria may be at the center of these diverse responses. In the past decade, significant advances have been made in understanding distinct types of mitochondrial dysfunctions in cancer. Through investigations of underlying mechanisms, more effective treatment options are developed. Critical Issues: We summarize various mitochondria dysfunctions in cancer progression that have led to the development of therapeutic options. Current mitochondrial-targeted therapies and challenges are discussed. Future Directions: To address the "root" of cancer, utilization of mitochondrial-targeted therapy to target cancer stem cells may be valuable. Investigation of other areas such as mitochondrial trafficking may offer new insights into cancer therapy. Moreover, common antibiotics could be explored as mitocans, and synthetic lethality screens can be utilized to overcome the plasticity of cancer cells.

Lipid Transfer Proteins and Membrane Contact Sites in Human Cancer

Lipid-transfer proteins (LTPs) were initially discovered as cytosolic factors that facilitate lipid transport between membrane bilayers in vitro. Since then, many LTPs have been isolated from bacteria, plants, yeast, and mammals, and extensively studied in cell-free systems and intact cells. A major advance in the LTP field was associated with the discovery of intracellular membrane contact sites (MCSs), small cytosolic gaps between the endoplasmic reticulum (ER) and other cellular membranes, which accelerate lipid transfer by LTPs. As LTPs modulate the distribution of lipids within cellular membranes, and many lipid species function as second messengers in key signaling pathways that control cell survival, proliferation, and migration, LTPs have been implicated in cancer-associated signal transduction cascades. Increasing evidence suggests that LTPs play an important role in cancer progression and metastasis. This review describes how different LTPs as well as MCSs can contribute to cell transformation and malignant phenotype, and discusses how “aberrant” MCSs are associated with tumorigenesis in human.

Modelling of dysregulated glucagon secretion in type 2 diabetes by considering mitochondrial alterations in pancreatic α-cells

Type 2 diabetes mellitus (T2DM) has been associated with insulin resistance and the failure of β-cells to produce and secrete enough insulin as the disease progresses. However, clinical treatments based solely on insulin secretion and action have had limited success. The focus is therefore shifting towards α-cells, in particular to the dysregulated secretion of glucagon. Our qualitative electron-microscopy-based observations gave an indication that mitochondria in α-cells are altered in Western-diet-induced T2DM. In particular, α-cells extracted from mouse pancreatic tissue showed a lower density of mitochondria, a less expressed matrix and a lower number of cristae. These deformities in mitochondrial ultrastructure imply a decreased efficiency in mitochondrial ATP production, which prompted us to theoretically explore and clarify one of the most challenging problems associated with T2DM, namely the lack of glucagon secretion in hypoglycaemia and its oversecretion at high blood glucose concentrations. To this purpose, we constructed a novel computational model that links α-cell metabolism with their electrical activity and glucagon secretion. Our results show that defective mitochondrial metabolism in α-cells can account for dysregulated glucagon secretion in T2DM, thus improving our understanding of T2DM pathophysiology and indicating possibilities for new clinical treatments.

Modelling of dysregulated glucagon secretion in type 2 diabetes by considering mitochondrial alterations in pancreatic α-cells

Type 2 diabetes mellitus (T2DM) has been associated with insulin resistance and the failure of β-cells to produce and secrete enough insulin as the disease progresses. However, clinical treatments based solely on insulin secretion and action have had limited success. The focus is therefore shifting towards α-cells, in particular to the dysregulated secretion of glucagon. Our qualitative electron-microscopy-based observations gave an indication that mitochondria in α-cells are altered in Western-diet-induced T2DM. In particular, α-cells extracted from mouse pancreatic tissue showed a lower density of mitochondria, a less expressed matrix and a lower number of cristae. These deformities in mitochondrial ultrastructure imply a decreased efficiency in mitochondrial ATP production, which prompted us to theoretically explore and clarify one of the most challenging problems associated with T2DM, namely the lack of glucagon secretion in hypoglycaemia and its oversecretion at high blood glucose concentrations. To this purpose, we constructed a novel computational model that links α-cell metabolism with their electrical activity and glucagon secretion. Our results show that defective mitochondrial metabolism in α-cells can account for dysregulated glucagon secretion in T2DM, thus improving our understanding of T2DM pathophysiology and indicating possibilities for new clinical treatments.

Resveratrol Activates Neuronal Autophagy Through AMPK in the Ischemic Brain

During cerebral ischemia, oxygen and glucose levels decrease, producing many consequences such as the generation of reactive oxygen species, tissue injury, and the general metabolism collapse. Resveratrol triggers signaling dependent on the protein kinase activated by adenosine monophosphate (AMPK), the sensor of cellular energy metabolism that regulates autophagy, eliminates damaged mitochondria, and increases energy sources. In the present study, we investigated the participation of AMPK activation in the protective effect of resveratrol on cerebral ischemia and excitotoxicity. We found that resveratrol increased the levels of phosphorylated AMPK in the cerebral cortex of rats subjected to middle cerebral artery occlusion (MCAO) and in primary cultured neurons exposed to glutamate-induced excitotoxicity. Resveratrol (1.8 mg/Kg; i. v.; administered at the beginning of reperfusion) decreased the infarct area and increased survival of rats subjected to MCAO. In neuronal cultures, resveratrol treatment (40 μM, after excitotoxicity) reduced the production of superoxide anion, prevented the overload of intracellular Ca⁺² associated to mitochondrial failure, reduced the release of the lactate dehydrogenase enzyme, and reduced death. It also promoted mitophagy (increased Beclin 1 level, favored the recruitment of LC3-II, reduced LAMP1, and reduced mitochondrial matrix protein HSP60 levels). In both models, inhibition of AMPK activation with Compound C obstructed the effect of resveratrol, showing that its protective effect depends, partially, on the activation of the AMPK/autophagy pathway.

Polyphenol-rich extract induces apoptosis with immunogenic markers in melanoma cells through the ER stress-associated kinase PERK

Polyphenols elicit antitumor activities, in part, through the induction of anti- or pro-oxidant effects in cancer cells which promote priming of protective anti-tumor immunity. We recently characterized a polyphenol-rich extract from Caesalpinia spinosa (P2Et) that stimulates in vivo antitumor responses against breast and melanoma tumor models via the promotion of immunogenic cancer cell death (ICD). However, the primary mediators whereby P2Et promotes ICD remained unknown. Here, we sought to elucidate the role that severe endoplasmic reticulum (ER) stress plays in mediating P2Et-induced apoptosis and ICD in murine melanoma cells. Our findings demonstrate a substantial selective induction of specific ER-stress mediators in B16-F10 melanoma cells treated with P2Et. While knockout of the ER stress-associated PKR-like ER kinase (PERK) prevented induction of apoptosis and expression of ICD markers in P2Et-treated cells, deletion of X-box binding protein 1 (Xbp1) did not. P2Et-driven activation of PERK in melanoma cells was found to promote ER-calcium release, disrupt mitochondrial membrane potential, and trigger upregulation of ICD drivers, surface calreticulin expression, and extracellular release of ATP and HMGB1. Notably, calcium release inhibition, but not targeting of PERK-driven integrated stress responses, prevented P2Et-induced apoptosis. Collectively, these results underline the central role of PERK-directed calcium release in mediating the antitumor and immunogenic actions of P2Et in melanoma cells.

Impaired Mitochondrial ATP Production Downregulates Wnt Signaling via ER Stress Induction

Wnt signaling affects fundamental development pathways and, if aberrantly activated, promotes the development of cancers. Wnt signaling is modulated by different factors, but whether the mitochondrial energetic state affects Wnt signaling is unknown. Here, we show that sublethal concentrations of different compounds that decrease mitochondrial ATP production specifically downregulate Wnt/β-catenin signaling in vitro in colon cancer cells and in vivo in zebrafish reporter lines. Accordingly, fibroblasts from a GRACILE syndrome patient and a generated zebrafish model lead to reduced Wnt signaling. We identify a mitochondria-Wnt signaling axis whereby a decrease in mitochondrial ATP reduces calcium uptake into the endoplasmic reticulum (ER), leading to endoplasmic reticulum stress and to impaired Wnt signaling. In turn, the recovery of the ATP level or the inhibition of endoplasmic reticulum stress restores Wnt activity. These findings reveal a mechanism that links mitochondrial energetic metabolism to the control of the Wnt pathway that may be beneficial against several pathologies.

MICU1 controls cristae junction and spatially anchors mitochondrial Ca2+ uniporter complex

Recently identified core proteins (MICU1, MCU, EMRE) forming the mitochondrial Ca²⁺ uniporter complex propelled investigations into its physiological workings. Here, we apply structured illumination microscopy to visualize and localize these proteins in living cells. Our data show that MICU1 localizes at the inner boundary membrane (IBM) due to electrostatic interaction of its polybasic domain. Moreover, this exclusive localization of MICU1 is important for the stability of cristae junctions (CJ), cytochrome c release and mitochondrial membrane potential. In contrast to MICU1, MCU and EMRE are homogeneously distributed at the inner mitochondrial membrane under resting conditions. However, upon Ca²⁺ elevation MCU and EMRE dynamically accumulate at the IBM in a MICU1-dependent manner. Eventually, our findings unveil an essential function of MICU1 in CJ stabilization and provide mechanistic insights of how sophistically MICU1 controls the MCU-Complex while maintaining the structural mitochondrial membrane framework.

Mitochondrial-Endoplasmic Reticulum Interplay: A Lifelong On-Off Relationship?

This article comments recent publications that highlight an intriguing importance of specific settings in the interaction between the mitochondria and the endoplasmic reticulum to ensure cell-specific functions like the responsiveness to elevated glucose in pancreatic β-cells. Hence, alterations of the mitochondria–endoplasmic reticulum communications under various pathological conditions like aging or cancer often come with enhanced Ca²⁺ transfer that, in turn, yields stimulation of basal mitochondrial activity to meet the increasing adenosine triphosphate demand of the very cell. Such observations identify mitochondria-associated membranes as potential target for new therapeutic strategies against aging or cancer.

Targeting mitochondria-associated membranes as a potential therapy against endothelial injury induced by hypoxia

Mitochondrial dysfunction plays a principal role in hypoxia-induced endothelial injury, which is involved in hypoxic pulmonary hypertension and ischemic cardiovascular diseases. Recent studies have identified mitochondria-associated membranes (MAMs) that modulate mitochondrial function under a variety of pathophysiological conditions such as high-fat diet-mediated insulin resistance, hypoxia reoxygenation-induced myocardial death, and hypoxia-evoked vascular smooth muscle cell proliferation. However, the role of MAMs in hypoxia-induced endothelial injury remains unclear. To explore this further, human umbilical vein endothelial cells and human pulmonary artery endothelial cells were exposed to hypoxia (1% O₂ ) for 24 hours. An increase in MAM formation was uncovered by immunoblotting and immunofluorescence. Then, we performed small interfering RNA transfection targeted to MAM constitutive proteins and explored the biological effects. Knockdown of MAM constitutive proteins attenuated hypoxia-induced elevation of mitochondrial Ca²⁺ and repressed mitochondrial impairment, leading to an increase in mitochondrial membrane potential and ATP production and a decline in reactive oxygen species. Then, we found that MAM disruption mitigated cell apoptosis and promoted cell survival. Next, other protective effects, such as those pertaining to the repression of inflammatory response and the promotion of NO synthesis, were investigated. With the disruption of MAMs under hypoxia, inflammatory molecule expression was repressed, and the eNOS-NO pathway was enhanced. This study demonstrates that the disruption of MAMs might be of therapeutic value for treating endothelial injury under hypoxia, suggesting a novel strategy for preventing hypoxic pulmonary hypertension and ischemic injuries.

Anti-Cancer Agents in Proliferation and Cell Death: The Calcium Connection

Calcium (Ca2+) signaling and the modulation of intracellular calcium ([Ca2+]i) levels play critical roles in several key processes that regulate cellular survival, growth, differentiation, metabolism, and death in normal cells. On the other hand, aberrant Ca2+-signaling and loss of [Ca2+]i homeostasis contributes to tumor initiation proliferation, angiogenesis, and other key processes that support tumor progression in several different cancers. Currently, chemically and functionally distinct drugs are used as chemotherapeutic agents in the treatment and management of cancer among which certain anti-cancer drugs reportedly suppress pro-survival signals and activate pro-apoptotic signaling through modulation of Ca2+-signaling-dependent mechanisms. Most importantly, the modulation of [Ca2+]i levels via the endoplasmic reticulum-mitochondrial axis and corresponding action of channels and pumps within the plasma membrane play an important role in the survival and death of cancer cells. The endoplasmic reticulum-mitochondrial axis is of prime importance when considering Ca2+-signaling-dependent anti-cancer drug targets. This review discusses how calcium signaling is targeted by anti-cancer drugs and highlights the role of calcium signaling in epigenetic modification and the Warburg effect in tumorigenesis.

Piceatannol markedly upregulates heme oxygenase-1 expression and alleviates oxidative stress in skeletal muscle cells

Piceatannol (PIC), a phytochemical, is abundant in passion fruit (Passiflora edulis) seeds. In this study, we investigated the effects of PIC on the expression levels of antioxidant enzymes in C2C12 skeletal muscle cells and compared its effects with those of PIC analogues and polyphenols. We also evaluated its effects on hydrogen peroxide–induced accumulation of reactive oxygen species in C2C12 myotubes. Treatment with PIC led to dose-dependent upregulation of heme oxygenase-1 (Ho-1) and superoxide dismutase 1 (Sod1) mRNA expression in C2C12 myotubes. PIC was the most potent inducer of Ho-1 among the PIC analogues and major polyphenols tested. In addition, treatment with PIC suppressed the hydrogen peroxide–induced increase in intracellular reactive oxygen species levels. Our results suggest that PIC protects skeletal muscles from oxidative stress by activating antioxidant enzymes such as HO-1 and SOD1 and can therefore help prevent oxidative stress–induced muscle dysfunction such as muscle fatigue and sarcopenia.

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PIC induced antioxidant enzymes in C2C12 skeletal muscle cell line.

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PIC was the most potent inducer of Ho-1 among other polyphenols tested.

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Induction potency of PIC for Sod1 was similar level with those of other polyphenols.

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PIC suppressed the hydrogen peroxide-induced increase in intracellular ROS levels.

PACS2 is required for ox-LDL-induced endothelial cell apoptosis by regulating mitochondria-associated ER membrane formation and mitochondrial Ca2+ elevation

Oxidized low-density lipoprotein (ox-LDL)-induced endothelial cell (EC) apoptosis is the initial step of atherogenesis and associated with Ca²⁺ overload. Mitochondria-associated endoplasmic reticulum (ER) membrane (MAM), regulated by tethering proteins such as phosphofurin acidic cluster sorting protein 2 (PACS2), is essential for mitochondrial Ca²⁺ overload by mediating ER-mitochondria Ca²⁺ transfer. In our study, we aimed to investigate the role of PACS2 in ox-LDL-induced apoptosis in human umbilical vein endothelial cells (HUVECs) and the underlying mechanisms. Ox-LDL dose- and time-dependently increased cell apoptosis concomitant with mitochondrial Ca²⁺ elevation, mitochondrial membrane potential (MMP) loss, reactive oxygen species (ROS) production, and cytochrome c release. Silencing PACS2 significantly inhibited ox-LDL-induced cell apoptosis at 24 h in addition to the effects of ox-LDL on mitochondrial Ca²⁺, MMP, and ROS at 2 h. Besides, ox-LDL promoted PACS2 localization at mitochondria as well as ER-mitochondria contacts at 2 h. Not only that, ox-LDL upregulated PACS2 expression at 24 h. Furthermore, silencing PACS2 inhibited ox-LDL-induced mitochondrial localization of PACS2 and MAM formation at 24 h. Altogether, our findings suggest that PACS2 plays an important role in ox-LDL-induced EC apoptosis by regulating MAM formation and mitochondrial Ca²⁺ elevation, implicating that PACS2 may be a promising therapeutic target for atherosclerosis.

Resveratrol Enhances Apoptotic and Oxidant Effects of Paclitaxel through TRPM2 Channel Activation in DBTRG Glioblastoma Cells

Numerous studies have reported a strong association between increased production of reactive oxygen species (ROS) and the pathobiology of several diseases, and cancer in particular. Therefore, manipulation of cellular oxidative stress levels represents an important therapeutic target. Recently, resveratrol (RESV), a naturally occurring phytochemical, has been shown to sensitize several cell lines to the anticancer effects of other chemotherapeutic agents, including paclitaxel (PAX). However, the molecular mechanisms of action of RESV through oxidative sensitive TRPM2 channel activation remain unclear. The aim of this study was to evaluate the effect of combination therapy of RESV and PAX on activation of TRPM2 in DBTRG glioblastoma cells. DBTRG cells were divided into four treatment groups: control, RESV (50 μM), PAX (50 μM), and PAX + RESV for 24 hours. Our data shows that markers for apoptosis, mitochondrial membrane depolarization and mitochondrial function, intracellular steady-state ROS levels, caspase 3 activity, TRPM2 current density, and Ca²⁺ florescence intensity were significantly increased in DBTRG cells following treatment with PAX and RESV, respectively, although cell viability was also decreased by these treatments. These biochemical markers were further increased to favor the anticancer effects of PAX in DBTRG cells in combination with RESV. The PAX and RESV-mediated increase in current density and Ca²⁺ florescence intensity was decreased with a TRPM2 blocker. This suggests that for this combination therapy to have a substantial effect on apoptosis and cell viability, the TRPM2 channel must be stimulated.