Emerging molecular mechanisms in chemotherapy: Ca2+ signaling at the mitochondria-associated endoplasmic reticulum membranes

Effects of hesperidin on mitochondrial function, mitochondria-associated endoplasmic reticulum membranes and IP3R-MCU calcium axis in the intestine of piglets exposed to deoxynivalenol

Deoxynivalenol (DON) pollution is prevalent in crops, and can induce oxidative stress and intestinal injury. Hesperidin is one of the major flavonoids in citrus fruits that has various biological activities such as antioxidant and anti-inflammatory activities. However, whether hesperidin could alleviate DON-induced intestinal injury and the mechanism remain unclear. Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) have attracted attention for their crucial signaling points to regulate ER-mitochondria calcium transfer. This study aims to evaluate the effects of hesperidin on the intestinal barrier, mitochondrial function, MAMs, and inositol 1,4,5-triphosphate receptor (IP3R)-mitochondrial calcium uniporter (MCU) calcium axis in the intestine of piglets exposed to DON. Twenty-four piglets were randomly divided into four groups in a 2 × 2 factorial arrangement for a 21-d experiment: Control: basal diet; hesperidin group: basal diet + 300 mg kg-1 hesperidin; DON: basal diet + 1.5 mg kg-1 DON; DON + hesperidin group: basal diet + 1.5 mg kg-1 DON + 300 mg kg-1 hesperidin. The data showed that when compared with the DON group, hesperidin improved growth performance and the intestinal barrier, alleviated intestinal oxidative stress and ER stress, and decreased the serum alanine aminotransferase (ALT) level (P < 0.05). Hesperidin also alleviated mitochondrial dysfunction and ferroptosis in the intestine of piglets exposed to DON (P < 0.05). Importantly, hesperidin prevented excessive MAM formation by downregulating the protein levels of Mitofusin 2 (Mfn2) and glucose-regulated protein 75 (GRP75), decreasing the ratio of the mitochondria with MAMs/total mitochondria and the ratio of MAM length/mitochondrial perimeter and lengthening the mitochondria-ER distance in MAMs (P < 0.05). Furthermore, hesperidin regulated the IP3R-glucose-regulated protein 75 (GRP75)-voltage-dependent anion channel 1 (VDAC1)-MCU calcium axis by decreasing the protein levels of GRP75 and MCU and the calcium level of the mitochondria compared with the DON group (P < 0.05). An in vitro experiment was conducted to further explore whether IP3R-mediated ER-mitochondria calcium transfer was involved in the protective effects of hesperidin on the intestinal epithelium barrier and mitochondria. Data showed that hesperidin may exert protective effects on the intestinal epithelium barrier and mitochondria via inhibiting ER-mitochondrial calcium transfer mediated by IP3Rs. These data suggested that hesperidin could alleviate MAM-mediated mitochondrial calcium overload, thereby improving mitochondrial function and alleviating oxidative stress and intestinal injury in DON-challenged piglets.

IP3R2 regulates apoptosis by Ca2+ transfer through mitochondria-ER contacts in hypoxic photoreceptor injury

Mitochondria-associated ER membranes (MAMs) are contact sites that enable bidirectional communication between the ER (endoplasmic reticulum) and mitochondria, including the transfer of Ca2+ signals. MAMs are essential for mitochondrial function and cellular energy metabolism. However, unrestrained Ca2+ transfer to the mitochondria can lead to mitochondria-dependent apoptosis. IP3R2 (Inositol 1,4,5-trisphosphate receptor 2) is an important intracellular Ca2+ channel. This study investigated the contribution of IP3R2-MAMs to hypoxia-induced apoptosis in photoreceptor cells. A photoreceptor hypoxia model was established by subretinal injection of hyaluronic acid (1%) in C57BL/6 mice and 1% O2 treatment in 661W cells. Transmission electron microscopy (TEM), ER-mitochondria colocalization, and the MAM reporter were utilized to evaluate MAM alterations. Cell apoptosis and mitochondrial homeostasis were evaluated using immunofluorescence (IF), flow cytometry, western blotting (WB), and ATP assays. SiRNA transfection was employed to silence IP3R2 in 661W cells. Upon hypoxia induction, MAMs were significantly increased in photoreceptors both in vivo and in vitro. This was accompanied by the activation of mitochondrial apoptosis and disruption of mitochondrial homeostasis. Elevated MAM-enriched IP3R2 protein levels induced by hypoxic injury led to mitochondrial calcium overload and subsequent photoreceptor apoptosis. Notably, IP3R2 knockdown not only improved mitochondrial morphology but also restored mitochondrial function in photoreceptors by limiting MAM formation and thereby attenuating mitochondrial calcium overload under hypoxia. Our results suggest that IP3R2-MAM-mediated mitochondrial calcium overload plays a critical role in mitochondrial dyshomeostasis, ultimately contributing to photoreceptor cell death. Targeting MAM constitutive proteins might provide an option for a therapeutic approach to mitigate photoreceptor death in retinal detachment.

TDCPP and TiO2 NPs aggregates synergistically induce SH-SY5Y cell neurotoxicity by excessive mitochondrial fission and mitophagy inhibition

Tris (1,3-dichloro-2-propyl) phosphate (TDCPP), a halogen-containing phosphorus flame retardant, is widely used and has been shown to possess health risks to humans. The sustained release of artificial nanomaterials into the environment increases the toxicological risks of their coexisting pollutants. Nanomaterials may seriously change the environmental behavior and fate of pollutants. In this study, we investigated this combined toxicity and the potential mechanisms of toxicity of TDCPP and titanium dioxide nanoparticles (TiO2 NPs) aggregates on human neuroblastoma SH-SY5Y cells. TDCPP and TiO2 NPs aggregates were exposed in various concentration combinations, revealing that TDCPP (25 μg/mL) reduced cell viability, while synergistic exposure to TiO2 NPs aggregates exacerbated cytotoxicity. This combined exposure also disrupted mitochondrial function, leading to dysregulation in the expression of mitochondrial fission proteins (DRP1 and FIS1) and fusion proteins (OPA1 and MFN1). Consequently, excessive mitochondrial fission occurred, facilitating the translocation of cytochrome C from mitochondria to activate apoptotic signaling pathways. Furthermore, exposure of the combination of TDCPP and TiO2 NPs aggregates activated upstream mitochondrial autophagy but disrupted downstream Parkin recruitment to damaged mitochondria, preventing autophagosome-lysosome fusion and thereby disrupting mitochondrial autophagy. Altogether, our findings suggest that TDCPP and TiO2 NPs aggregates may stimulate apoptosis in neuronal SH-SY5Y cells by inducing mitochondrial hyperfission and inhibiting mitochondrial autophagy.

Optogenetically engineered calcium oscillations promote autophagy-mediated cell death via AMPK activation

Autophagy is a double-edged sword for cells; it can lead to both cell survival and death. Calcium (Ca2+) signalling plays a crucial role in regulating various cellular behaviours, including cell migration, proliferation and death. In this study, we investigated the effects of modulating cytosolic Ca2+ levels on autophagy using chemical and optogenetic methods. Our findings revealed that ionomycin and thapsigargin induce Ca2+ influx to promote autophagy, whereas the Ca2+ chelator BAPTA-AM induces Ca2+ depletion and inhibits autophagy. Furthermore, the optogenetic platform allows the manipulation of illumination parameters, including density, frequency, duty cycle and duration, to create different patterns of Ca2+ oscillations. We used the optogenetic tool Ca2+-translocating channelrhodopsin, which is activated and opened by 470 nm blue light to induce Ca2+ influx. These results demonstrated that high-frequency Ca2+ oscillations induce autophagy. In addition, autophagy induction may involve Ca2+-activated adenosine monophosphate (AMP)-activated protein kinases. In conclusion, high-frequency optogenetic Ca2+ oscillations led to cell death mediated by AMP-activated protein kinase-induced autophagy.

Targeting GRP75 with a Chlorpromazine Derivative Inhibits Endometrial Cancer Progression Through GRP75-IP3R-Ca2+-AMPK Axis

Tumors often overexpress glucose-regulated proteins, and agents that interfere with the production or activity of these proteins may represent novel cancer treatments. The chlorpromazine derivative JX57 exhibits promising effects against endometrial cancer with minimal extrapyramidal side effects; however, its mechanisms of action are currently unknown. Here, glucose-regulated protein 75 kD (GRP75) is identified as a direct target of JX57 using activity-based protein profiling and loss-of-function experiments. The findings show that GRP75 is necessary for the biological activity of JX57, as JX57 exhibits moderate anticancer properties in GRP75-deficient cancer cells, both in vitro and in vivo. High GRP75 expression is correlated with poor differentiation and poor survival in patients with endometrial cancer, whereas the knockdown of GRP75 can significantly suppress tumor growth. Mechanistically, the direct binding of JX57 to GRP75 impairs the structure of the mitochondria-associated endoplasmic reticulum membrane and disrupts the endoplasmic reticulum-mitochondrial calcium homeostasis, resulting in a mitochondrial energy crisis and AMP-activated protein kinase activation. Taken together, these findings highlight GRP75 as a potential prognostic biomarker and direct therapeutic target in endometrial cancer and suggest that the chlorpromazine derivative JX57 can potentially be a new therapeutic option for endometrial cancer.

Deoxynivalenol induced intestinal barrier injury, mitochondrial dysfunction and calcium overload by inositol 1,4,5-triphosphate receptors (IP3Rs)-mitochondrial calcium uniporter (MCU) calcium axis

Deoxynivalenol (DON) contamination is widespread in crops and could easily cause intestinal injury, which brings hazards to animals. Mitochondria are considered as an important target of DON, nevertheless, the mechanism is still unclear. Mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) have gained arousing interest and are recognized as critical signaling hubs that control calcium signaling transduction between ER and mitochondria. This study aims to investigate the effects of DON on intestinal barrier, mitochondria, MAMs and inositol 1,4,5-triphosphate receptors (IP3Rs)-mitochondrial calcium uniporter (MCU) calcium axis in piglets and porcine intestinal epithelial cells (IPEC-J2). Furthermore, inhibition of IP3Rs or MCU was used to explore whether IP3Rs-MCU axis of MAMs was involved in the mitochondria dysfunction and intestinal epithelium barrier injury induced by DON in IPEC-J2. The data showed that DON induced intestinal barrier injury, mitochondrial dysfunction and ERS in piglets' jejunum and IPEC-J2. Moreover, DON increased MAMs by upregulating the protein level of Mitofusin 2 (Mfn2), increasing the percentage of mitochondria with MAMs/total mitochondria and the ratio of MAMs length/mitochondrial perimeter and shortening the distance between mitochondria and ER of MAMs. Importantly, DON influenced IP3Rs-glucose-regulated protein 75 (GRP75)-voltage-dependent anion channel 1 (VDAC1)-MCU calcium axis by increasing the protein levels of GRP75 and MCU and the interaction of VDAC1-GRP75-IP3Rs complex, which in turn induced mitochondrial calcium overload. Furthermore, inhibition of IP3Rs or MCU alleviated DON-induced intestinal epithelium barrier injury, mitochondrial dysfunction and mitochondrial calcium overload of IPEC-J2. The current investigation proposed that DON induced intestinal injury, mitochondrial dysfunction and calcium overload via IP3Rs-GRP75-VDAC1-MCU calcium axis.

Phenethyl isothiocyanate and irinotecan synergistically induce cell apoptosis in colon cancer HCT 116 cells in vitro

Irinotecan (IRI), an anticancer drug to treat colon cancer patients, causes cytotoxic effects on normal cells. Phenethyl isothiocyanate (PEITC), rich in common cruciferous plants, has anticancer activities (induction of cell apoptosis) in many human cancer cells, including colon cancer cells. However, the anticancer effects of IRI combined with PEITC on human colon cancer cells in vitro were unavailable. Herein, the aim of this study is to focus on the apoptotic effects of the combination of IRI and PEITC on human colon cancer HCT 116 cells in vitro. Propidium iodide (PI) exclusion and Annexin V/PI staining assays showed that IRI combined with PEITC decreased viable cell number and induced higher cell apoptosis than that of IRI or PEITC only in HCT 116 cells. Moreover, combined treatment induced higher levels of reactive oxygen species (ROS) and Ca2+ than that of IRI or PEITC only. Cells pre-treated with N-acetyl-l-cysteine (scavenger of ROS) and then treated with IRI, PEITC, or IRI combined with PEITC showed increased viable cell numbers than that of IRI or PEITC only. IRI combined with PEITC increased higher caspase-3, -8, and -9 activities than that of IRI or PEITC only by flow cytometer assay. IRI combined with PEITC induced higher levels of ER stress-, mitochondria-, and caspase-associated proteins than that of IRI or PEITC treatment only in HCT 116 cells. Based on these observations, PEITC potentiates IRI anticancer activity by promoting cell apoptosis in the human colon HCT 116 cells. Thus, PEITC may be a potential enhancer for IRI in humans as an anticolon cancer drug in the future.

Role of PLC/IP3 /IP3 R axis in excess molybdenum exposure induced apoptosis in duck renal tubular epithelial cells

Excess molybdenum (Mo) is harmful to animals, but its nephrotoxicity has not been comprehensively explained. To appraise the influences of excess Mo on Ca homeostasis and apoptosis via PLC/IP3 /IP3 R axis, primary duck renal tubular epithelial cells were exposed to 480 μM and 960 μM Mo, and joint of 960 μM Mo and 10 μM 2-APB or 0.125 μM U-73122 for 12 h (U-73122 pretreated for 1 h), respectively. The data revealed that the increment of [Ca2+ ]c induced by Mo mainly originated from intracellular Ca storage. Mo exposure reduced [Ca2+ ]ER , elevated [Ca2+ ]mit , [Ca2+ ]c , and the expression of Ca homeostasis-related factors (Calpain, CaN, CRT, GRP94, GRP78 and CaMKII). 2-APB could effectively reverse subcellular Ca2+ redistribution by inhibiting IP3 R, which confirmed that [Ca2+ ]c overload induced by Mo originated from ER. Additionally, PLC inhibitor U-73122 remarkably mitigated the change, and dramatically reduced the number of apoptotic cells, the expression of Bak-1, Bax, cleaved-Caspase-3/Caspase-3, and notably increased the expression of Bcl-xL, Bcl-2, and Bcl-2/Bax ratio. Overall, the results confirmed that the Ca2+ liberation of ER via PLC/IP3 /IP3 R axis was the main cause of [Ca2+ ]c overload, and then stimulated apoptosis in duck renal tubular epithelial cells.

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.

Vitamin E succinate mediated apoptosis by juxtaposing endoplasmic reticulum and mitochondria

Vitamin E succinate (VES) is an esterified form of natural α-tocopherol, has turned out to be novel anticancer agent. However, its anticancer mechanisms have not been illustrated. Previously, we reported VES mediated Ca2+ release from the endoplasmic reticulum (ER) causes mitochondrial Ca2+ overload, leading to mitochondrial depolarization and apoptosis. Here, we elucidated the mechanism of VES-induced Ca2+ transfer from ER to mitochondria by investigating the role of VES in ER-mitochondria contact formation. Transmission electron microscopic observation confirms VES mediated ER-mitochondria contact while fluorescence microscopic analysis revealed that VES increased mitochondria-associated ER membrane (MAM) formation. Pre-treatment with the inositol 1,4,5-triphosphate receptor (IP3R) antagonist 2-aminoethyl diphenylborinate (2-APB) decreased VES-induced MAM formation, suggesting the involvement of VES-induced Ca2+ efflux from ER in MAM formation. The ER IP3R receptor is known to interact with voltage-dependent anion channels (VDAC) via the chaperone glucose-regulated protein 75 kDa (GRP75) to bring ER and mitochondria nearby. Although we revealed that VES treatment does not affect GRP75 protein level, it increases GRP75 localization in the MAM. In addition, the inhibition of Ca2+ release from ER by 2-APB decreases GRP75 localization in the MAM, suggesting the possibility of Ca2+-induced conformational change of GRP75 that promotes formation of the IP3R-GRP75-VDAC complex and thereby encourages MAM formation. This study identifies the mechanism of VES-induced enhanced Ca2+ transfer from ER to mitochondria, which causes mitochondrial Ca2+ overload leading to apoptosis.

Calcium signalling pathways in prostate cancer initiation and progression

Cancer cells proliferate, differentiate and migrate by repurposing physiological signalling mechanisms. In particular, altered calcium signalling is emerging as one of the most widespread adaptations in cancer cells. Remodelling of calcium signalling promotes the development of several malignancies, including prostate cancer. Gene expression data from in vitro, in vivo and bioinformatics studies using patient samples and xenografts have shown considerable changes in the expression of various components of the calcium signalling toolkit during the development of prostate cancer. Moreover, preclinical and clinical evidence suggests that altered calcium signalling is a crucial component of the molecular re-programming that drives prostate cancer progression. Evidence points to calcium signalling re-modelling, commonly involving crosstalk between calcium and other cellular signalling pathways, underpinning the onset and temporal progression of this disease. Discrete alterations in calcium signalling have been implicated in hormone-sensitive, castration-resistant and aggressive variant forms of prostate cancer. Hence, modulation of calcium signals and downstream effector molecules is a plausible therapeutic strategy for both early and late stages of prostate cancer. Based on this premise, clinical trials have been undertaken to establish the feasibility of targeting calcium signalling specifically for prostate cancer.

Broadening horizons: the contribution of mitochondria-associated endoplasmic reticulum membrane (MAM) dysfunction in diabetic kidney disease

Diabetic kidney disease (DKD) is a global health issue that presents a complex pathogenesis and limited treatment options. To provide guidance for precise therapies, it is crucial to accurately identify the pathogenesis of DKD. Several studies have recognized that mitochondrial and endoplasmic reticulum (ER) dysfunction are key drivers of the pathogenesis of DKD. The mitochondria-associated ER membrane (MAM) is a dynamic membrane contact site (MSC) that connects the ER and mitochondria and is essential in maintaining the normal function of the two organelles. MAM is involved in various cellular processes, including lipid synthesis and transport, calcium homeostasis, mitochondrial fusion and fission, and ER stress. Meanwhile, recent studies confirm that MAM plays a significant role in the pathogenesis of DKD by regulating glucose metabolism, lipid metabolism, inflammation, ER stress, mitochondrial fission and fusion, and autophagy. Herein, this review aims to provide a comprehensive summary of the physiological function of MAMs and their impact on the progression of DKD. Subsequently, we discuss the trend of pharmaceutical studies that target MAM resident proteins for treating DKD. Furthermore, we also explore the future development prospects of MAM in DKD research, thereby providing a new perspective for basic studies and clinical treatment of DKD.

Ultrastructural analysis of prostate cancer tissue provides insights into androgen-dependent adaptations to membrane contact site establishment

Membrane trafficking and organelle contact sites are important for regulating cell metabolism and survival; processes often deregulated in cancer. Prostate cancer is the second leading cause of cancer-related death in men in the developed world. While early-stage disease is curable by surgery or radiotherapy there is an unmet need to identify prognostic biomarkers, markers to treatment response and new therapeutic targets in intermediate-late stage disease. This study explored the morphology of organelles and membrane contact sites in tumor tissue from normal, low and intermediate histological grade groups. The morphology of organelles in secretory prostate epithelial cells; including Golgi apparatus, ER, lysosomes; was similar in prostate tissue samples across a range of Gleason scores. Mitochondrial morphology was not dramatically altered, but the number of membrane contacts with the ER notably increased with disease progression. A three-fold increase of tight mitochondria-ER membrane contact sites was observed in the intermediate Gleason score group compared to normal tissue. To investigate whether these changes were concurrent with an increased androgen signaling in the tissue, we investigated whether an anti-androgen used in the clinic to treat advanced prostate cancer (enzalutamide) could reverse the phenotype. Patient-derived explant tissues with an intermediate Gleason score were cultured ex vivo in the presence or absence of enzalutamide and the number of ER-mitochondria contacts were quantified for each matched pair of tissues. Enzalutamide treated tissue showed a significant reduction in the number and length of mitochondria-ER contact sites, suggesting a novel androgen-dependent regulation of these membrane contact sites. This study provides evidence for the first time that prostate epithelial cells undergo adaptations in membrane contact sites between mitochondria and the ER during prostate cancer progression. These adaptations are androgen-dependent and provide evidence for a novel hormone-regulated mechanism that support establishment and extension of MAMs. Future studies will determine whether these changes are required to maintain pro-proliferative signaling and metabolic changes that support prostate cancer cell viability.

Novel tumor therapy strategies targeting endoplasmic reticulum-mitochondria signal pathways

Organelles form tight connections through membrane contact sites, thereby cooperating to regulate homeostasis and cell function. Among them, the contact between endoplasmic reticulum (ER), the main intracellular calcium storage organelles, and mitochondria has been recognized for decades, and its main roles in the ion and lipid transport, ROS signaling, membrane dynamic changes and cellular metabolism are basically determined. At present, many tumor chemotherapeutic drugs rely on ER-mitochondrial calcium signal to function, but the mechanism of targeting resident molecules at the mitochondria-associated endoplasmic reticulum membranes (MAM) to sensitize traditional chemotherapy and the new tumor therapeutic targets identified based on the signal pathways on the MAM have not been thoroughly discussed. In this review, we highlight the key roles of various signaling pathways at the ER-mitochondria contact site in tumorigenesis and focus on novel anticancer therapy strategies targeting potential targets at this contact site.

New frontiers in the design and discovery of therapeutics that target calcium ion signaling: a novel approach in the fight against cancer

INTRODUCTION

The Ca2+ signaling toolkit is currently under investigation as a potential target for addressing the threat of cancer. A growing body of evidence suggests that calcium signaling plays a crucial role in promoting various aspects of cancer, including cell proliferation, progression, drug resistance, and migration-related activities. Consequently, focusing on these altered Ca2+ transporting proteins has emerged as a promising area of research for cancer treatment.

AREAS COVERED

This review highlights the existing research on the role of Ca2+-transporting proteins in cancer progression. It discusses the current studies evaluating Ca2+ channel/transporter/pump blockers, inhibitors, or regulators as potential anticancer drugs. Additionally, the review addresses specific gaps in our understanding of the field that may require further investigation.

EXPERT OPINION

Targeting specific Ca2+ signaling cascades could disrupt normal cellular activities, making cancer therapy complex and elusive. Therefore, there is a need for improvements in current Ca2+ signaling pathway focused medicines. While synthetic molecules and plant compounds show promise, they also come with certain limitations. Hence, exploring the framework of targeted drug delivery, structure-rationale-based designing, and repurposing potential drugs to target Ca2+ transporting proteins could potentially lead to a significant breakthrough in cancer treatment.

SERCA inhibition improves lifespan and healthspan in a chemical model of Parkinson disease in Caenorhabditis elegans

Introduction: The high prevalence of neurodegenerative diseases in our population and the lack of effective treatments encourage the search for new therapeutic targets for these pathologies. We have recently described that submaximal inhibition of the Sarco-Endoplasmic Reticulum Ca²⁺ ATPase (SERCA), the main responsible for ER calcium storage, is able to increase lifespan in Caenorhabditis elegans worms by mechanisms involving mitochondrial metabolism and nutrient-sensitive pathways. Methods: We have studied here the effects of submaximal SERCA inhibition in a chemical model of Parkinson's disease (PD) induced in C. elegans worms by treatment with the mitochondrial complex I inhibitor rotenone. For specific SERCA inhibition, we treated worms with RNAi against sca-1, the sole orthologue of SERCA in C. elegans. Results and Discussion: Our results show that rotenone produces alterations in worms that include decreased lifespan, smaller size, reduced fertility, decreased motility, defecation and pumping rate, increased mitochondrial ROS production, reduced mitochondrial membrane potential and oxygen consumption rate, altered mitochondrial structure, and altered ethanol preference in behavioral studies. Most of these alterations were either fully or partially reversed in worms treated with sca-1 RNAi, suggesting that SERCA inhibition could be a novel pharmacological target in the prevention or treatment of neurodegeneration.

Transient Receptor Potential Ankyrin 1 (TRPA1) Channel as a Sensor of Oxidative Stress in Cancer Cells

Moderate levels of reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂), fuel tumor metastasis and invasion in a variety of cancer types. Conversely, excessive ROS levels can impair tumor growth and metastasis by triggering cancer cell death. In order to cope with the oxidative stress imposed by the tumor microenvironment, malignant cells exploit a sophisticated network of antioxidant defense mechanisms. Targeting the antioxidant capacity of cancer cells or enhancing their sensitivity to ROS-dependent cell death represent a promising strategy for alternative anticancer treatments. Transient Receptor Potential Ankyrin 1 (TRPA1) is a redox-sensitive non-selective cation channel that mediates extracellular Ca²⁺ entry upon an increase in intracellular ROS levels. The ensuing increase in intracellular Ca²⁺ concentration can in turn engage a non-canonical antioxidant defense program or induce mitochondrial Ca²⁺ dysfunction and apoptotic cell death depending on the cancer type. Herein, we sought to describe the opposing effects of ROS-dependent TRPA1 activation on cancer cell fate and propose the pharmacological manipulation of TRPA1 as an alternative therapeutic strategy to enhance cancer cell sensitivity to oxidative stress.

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.

Evaluation of the Anticancer Activity and Mechanism Studies of Glycyrrhetic Acid Derivatives toward HeLa Cells

In this paper, a series of glycyrrhetic acid derivatives 3a–3f were synthesized via the esterification reaction. The cytotoxicity of these compounds against five tumor cells (SGC-7901, BEL-7402, A549, HeLa and B16) and normal LO2 cells was investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. The results showed that compound 3a exhibited high antiproliferative activity against HeLa cells (IC50 = 11.4 ± 0.2 μM). The anticancer activity was studied through apoptosis, cloning, and scratching; the levels of the intracellular ROS, GSH, and Ca2+; and the change in the mitochondrial membrane potential, cell cycle arrest and RNA sequencing. Furthermore, the effects of compound 3a on gene expression levels and metabolic pathways in HeLa cells were investigated via transcriptomics. The experimental results showed that this compound can block the cell cycle in the S phase and inhibit cell migration by downregulating Focal adhesion kinase (FAK) expression. Moreover, the compound can reduce the intracellular glutathione (GSH) content, increase the Ca2+ level and the intracellular ROS content, and induce a decrease in the mitochondrial membrane potential, further leading to cell death. In addition, it was also found that the mechanism of compounds inducing apoptosis was related to the regulation of the expression of mitochondria-related proteins B-cell lymphoma-2 (Bcl-2), Bcl-2-Associated X (Bax), and the activation of the caspase proteins. Taken together, this work provides a help for the development of glycyrrhetinic acid compounds as potential anticancer molecules.

IMMUNEPOTENT CRP increases intracellular calcium through ER-calcium channels, leading to ROS production and cell death in breast cancer and leukemic cell lines

IMMUNEPOTENT CRP (ICRP) is an immunotherapy that induces cell death in cancer cell lines. However, the molecular mechanisms of death are not completely elucidated. Here, we evaluated the implication of intracellular Ca²⁺ augmentation in the cell death induced by ICRP on T-ALL and breast cancer cell lines. Cell death induction and the molecular characteristics of cell death were evaluated in T-ALL and breast cancer cell lines by assessing autophagosome formation, ROS production, loss of mitochondrial membrane potential, ER stress and intracellular Ca²⁺ levels. We assessed the involvement of extracellular Ca²⁺, and the implication of the ER-receptors, IP₃R and RyR, in the cell death induced by ICRP, by using an extracellular calcium chelator and pharmacological inhibitors. Our results show that ICRP increases intracellular Ca²⁺ levels as the first step of the cell death mechanism that provokes ROS production and loss of mitochondrial membrane potential. In addition, blocking the IP₃ and ryanodine receptors inhibited ER-Ca²⁺ release, ROS production and ICRP-induced cell death. Taken together our results demonstrate that ICRP triggers intracellular Ca²⁺-increase leading to different regulated cell death modalities in T-ALL and breast cancer cell lines. See also Figure 1(Fig. 1).

Blocking xCT and PI3K/Akt pathway synergized with DNA damage of Riluzole-Pt(IV) prodrugs for cancer treatment

Cancer treatment requires the participation of multiple targets/pathways, and single approach is hard to effectively curb the proliferation and metastasis of carcinoma cells. In this work, we conjugated FDA-approved riluzole and platinum(II) drugs into a series of unreported riluzole-Pt(IV) compounds, which were designed to simultaneously target DNA, the solute carrier family 7 member 11 (SLC7A11, xCT), and the human ether a go-go related gene 1 (hERG1), to exert synergistic anticancer effect. Among them, c,c,t-[PtCl₂(NH₃)₂(OH)(glutarylriluzole)] (compound 2) displayed excellent antiproliferative activity with IC₅₀ value of 300-times lower than that of cisplatin in HCT-116, and optimal selectivity index between carcinoma and human normal liver cells (LO2). Mechanism studies indicated that compound 2 released riluzole and active Pt(II) species after entering cells to exhibit a prodrug behavior against cancer, which obviously increased DNA-damage and cell apoptosis, as well as suppressed metastasis in HCT-116. Compound 2 persisted in the xCT-target of riluzole and blocked the biosynthesis of glutathione (GSH) to trigger oxidative stress, which could boost the killing to cancer cells and reduce Pt-drug resistance. Meanwhile, compound 2 significantly inhibited invasion and metastasis of HCT-116 cells by targeting hERG1 to interrupt the phosphorylation of phosphatidylinositide 3-kinases/proteinserine-threonine kinase (PI3K/Akt), and reverse epithelial-mesenchymal transformation (EMT). Based on our results, the riluzole-Pt(IV) prodrugs studied in this work could be regarded as a new class of very promising candidates for cancer treatment compared to traditional platinum drugs.

A multifunctional oxidative stress nanoamplifier with ROS amplification and GSH exhaustion for enhanced chemodynamic therapy

Chemodynamic therapy (CDT) eradicates tumors by intratumoral catalytic chemical reaction and subsequently disrupts redox homeostasis, which shows tumor specific reactive oxygen species (ROS)-mediated therapy. However, insufficient ROS generation and high levels of glutathione (GSH) in cancer cells have limited the therapeutic efficacy of CDT. Herein, we constructed a multifunctional oxidative stress nanoamplifier with ROS amplification and GSH exhaustion for enhanced CDT. Such a sandwich-like nanoamplifier comprised layer-by-layer artesunate (AS) and calcium carbonate coatings on the surface of manganese dioxide (MnO2) nanoparticles. The nanoamplifier was disassembled under an acidic environment once accumulated into tumor sites, and subsequently released AS to replenish the intratumoral peroxide pool for ROS amplification. Besides being an AS carrier, MnO2 exhausted GSH to yield Mn2+ ions that catalyzed the overexpression of H2O2 in the tumor, further intensifying the oxidative stress and facilitating cancer cell death. Taken together, our findings not only provide a paradigm for fabricating intratumoral catalytic nanomaterials, but also present a new ROS enhancement strategy to improve anti-tumor efficacy. Our multifunctional oxidative stress nanoamplifier might broaden the future of CDT.

Cancer cells can be killed mechanically or with combinations of cytoskeletal inhibitors

For over two centuries, clinicians have hypothesized that cancer developed preferentially at the sites of repeated damage, indicating that cancer is basically “continued healing.” Tumor cells can develop over time into other more malignant types in different environments. Interestingly, indefinite growth correlates with the depletion of a modular, early rigidity sensor, whereas restoring these sensors in tumor cells blocks tumor growth on soft surfaces and metastases. Importantly, normal and tumor cells from many different tissues exhibit transformed growth without the early rigidity sensor. When sensors are restored in tumor cells by replenishing depleted mechanosensory proteins that are often cytoskeletal, cells revert to normal rigidity-dependent growth. Surprisingly, transformed growth cells are sensitive to mechanical stretching or ultrasound which will cause apoptosis of transformed growth cells (Mechanoptosis). Mechanoptosis is driven by calcium entry through mechanosensitive Piezo1 channels that activate a calcium-induced calpain response commonly found in tumor cells. Since tumor cells from many different tissues are in a transformed growth state that is, characterized by increased growth, an altered cytoskeleton and mechanoptosis, it is possible to inhibit growth of many different tumors by mechanical activity and potentially by cytoskeletal inhibitors.

Modulation of Ca2+ signaling by antiapoptotic Bcl-2 versus Bcl-xL: From molecular mechanisms to relevance for cancer cell survival

Members of the Bcl-2-protein family are key controllers of apoptotic cell death. The family is divided into antiapoptotic (including Bcl-2 itself, Bcl-xL, Mcl-1, etc.) and proapoptotic members (Bax, Bak, Bim, Bim, Puma, Noxa, Bad, etc.). These proteins are well known for their canonical role in the mitochondria, where they control mitochondrial outer membrane permeabilization and subsequent apoptosis. However, several proteins are recognized as modulators of intracellular Ca²⁺ signals that originate from the endoplasmic reticulum (ER), the major intracellular Ca²⁺-storage organelle. More than 25 years ago, Bcl-2, the founding member of the family, was reported to control apoptosis through Ca²⁺ signaling. Further work elucidated that Bcl-2 directly targets and inhibits inositol 1,4,5-trisphosphate receptors (IP₃Rs), thereby suppressing proapoptotic Ca²⁺ signaling. In addition to Bcl-2, Bcl-xL was also shown to impact cell survival by sensitizing IP₃R function, thereby promoting prosurvival oscillatory Ca²⁺ release. However, new work challenges this model and demonstrates that Bcl-2 and Bcl-xL can both function as inhibitors of IP₃Rs. This suggests that, depending on the cell context, Bcl-xL could support very distinct Ca²⁺ patterns. This not only raises several questions but also opens new possibilities for the treatment of Bcl-xL-dependent cancers. In this review, we will discuss the similarities and divergences between Bcl-2 and Bcl-xL regarding Ca²⁺ homeostasis and IP₃R modulation from both a molecular and a functional point of view, with particular emphasis on cancer cell death resistance mechanisms.

Crosstalk between Ca2+ Signaling and Cancer Stemness: The Link to Cisplatin Resistance

In the fight against cancer, therapeutic strategies using cisplatin are severely limited by the appearance of a resistant phenotype. While cisplatin is usually efficient at the beginning of the treatment, several patients endure resistance to this agent and face relapse. One of the reasons for this resistant phenotype is the emergence of a cell subpopulation known as cancer stem cells (CSCs). Due to their quiescent phenotype and self-renewal abilities, these cells have recently been recognized as a crucial field of investigation in cancer and treatment resistance. Changes in intracellular calcium (Ca²⁺) through Ca²⁺ channel activity are essential for many cellular processes such as proliferation, migration, differentiation, and survival in various cell types. It is now proved that altered Ca²⁺ signaling is a hallmark of cancer, and several Ca²⁺ channels have been linked to CSC functions and therapy resistance. Moreover, cisplatin was shown to interfere with Ca²⁺ homeostasis; thus, it is considered likely that cisplatin-induced aberrant Ca²⁺ signaling is linked to CSCs biology and, therefore, therapy failure. The molecular signature defining the resistant phenotype varies between tumors, and the number of resistance mechanisms activated in response to a range of pressures dictates the global degree of cisplatin resistance. However, if we can understand the molecular mechanisms linking Ca²⁺ to cisplatin-induced resistance and CSC behaviors, alternative and novel therapeutic strategies could be considered. In this review, we examine how cisplatin interferes with Ca²⁺ homeostasis in tumor cells. We also summarize how cisplatin induces CSC markers in cancer. Finally, we highlight the role of Ca²⁺ in cancer stemness and focus on how they are involved in cisplatin-induced resistance through the increase of cancer stem cell populations and via specific pathways.

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).

An Emergent Role for Mitochondrial Bioenergetics in the Action of Snake Venom Toxins on Cancer Cells

Beyond the role of mitochondria in apoptosis initiation/execution, some mitochondrial adaptations support the metastasis and chemoresistance of cancer cells. This highlights mitochondria as a promising target for new anticancer strategies. Emergent evidence suggests that some snake venom toxins, both proteins with enzymatic and non-enzymatic activities, act on the mitochondrial metabolism of cancer cells, exhibiting unique and novel mechanisms that are not yet fully understood. Currently, six toxin classes (L-amino acid oxidases, thrombin-like enzymes, secreted phospholipases A2, three-finger toxins, cysteine-rich secreted proteins, and snake C-type lectin) that alter the mitochondrial bioenergetics have been described. These toxins act through Complex IV activity inhibition, OXPHOS uncoupling, ROS-mediated permeabilization of inner mitochondrial membrane (IMM), IMM reorganization by cardiolipin interaction, and mitochondrial fragmentation with selective migrastatic and cytotoxic effects on cancer cells. Notably, selective internalization and direct action of snake venom toxins on tumor mitochondria can be mediated by cell surface proteins overexpressed in cancer cells (e.g. nucleolin and heparan sulfate proteoglycans) or facilitated by the elevated Δψm of cancer cells compared to that non-tumor cells. In this latter case, selective mitochondrial accumulation, in a Δψm-dependent manner, of compounds linked to cationic snake peptides may be explored as a new anti-cancer drug delivery system. This review analyzes the effect of snake venom toxins on mitochondrial bioenergetics of cancer cells, whose mechanisms of action may offer the opportunity to develop new anticancer drugs based on toxin scaffolds.

The mitochondrial associated endoplasmic reticulum membranes: A platform for the pathogenesis of inflammation-mediated metabolic diseases

Mitochondria-associated endoplasmic reticulum membranes (MAM) are specialized subcellular compartments that are shaped by endoplasmic reticulum (ER) subdomains placed side by side to the outer membrane of mitochondria (OMM) being connected by tethering proteins in mammalian cells. Studies showed that MAM has multiple physiological functions. These include regulation of lipid synthesis and transport, Ca2+ transport and signaling, mitochondrial dynamics, apoptosis, autophagy, and formation and activation of an inflammasome. However, alterations of MAM integrity lead to deleterious effects due to an increased generation of mitochondrial reactive oxygen species (ROS) via increased Ca2+ transfer from the ER to mitochondria. This, in turn, causes mitochondrial damage and release of mitochondrial components into the cytosol as damage-associated molecular patterns which rapidly activate MAM-resident Nod-like receptor protein-3 (NLRP3) inflammasome components. This complex induces the release of pro-inflammatory cytokines that initiate low-grade chronic inflammation that subsequently causes the development of metabolic diseases. But, the mechanisms of how MAM is involved in the pathogenesis of these diseases are not exhaustively reviewed. Therefore, this review was aimed to highlight the contribution of MAM to a variety of cellular functions and consider its significance pertaining to the pathogenesis of inflammation-mediated metabolic diseases.

fdrci: FDR confidence interval selection and adjustment for large-scale hypothesis testing

Motivation

Approaches that control error by applying a priori fixed discovery thresholds such as 0.05 limit the ability of investigators to identify and publish weak effects even when evidence suggests that such effects exist. However, current false discovery rate (FDR) estimation methods lack a principled approach for post hoc identification of discovery thresholds other than 0.05.

Results

We describe a flexible approach that hinges on the precision of a permutation-based FDR estimator. A series of discovery thresholds are proposed, and an FDR confidence interval selection and adjustment technique is used to identify intervals that do not cover one, implying that some discoveries are expected to be true. We report an application to a transcriptome-wide association study of the MAVERICC clinical trial involving patients with metastatic colorectal cancer. Several genes are identified whose predicted expression is associated with progression-free or overall survival.

Availability and implementation

Software is provided via the CRAN repository (https://cran.r-project.org/web/packages/fdrci/index.html).

Supplementary information

Supplementary data are available at Bioinformatics Advances online.

Dose Rate Effects on the Selective Radiosensitization of Prostate Cells by GRPR-Targeted Gold Nanoparticles

For a while, gold nanoparticles (AuNPs) have been recognized as potential radiosensitizers in cancer radiation therapy, mainly due to their physical properties, making them appealing for medical applications. Nevertheless, the performance of AuNPs as radiosensitizers still raises important questions that need further investigation. Searching for selective prostate (PCa) radiosensitizing agents, we studied the radiosensitization capability of the target-specific AuNP-BBN in cancer versus non-cancerous prostate cells, including the evaluation of dose rate effects in comparison with non-targeted counterparts (AuNP-TDOTA). PCa cells were found to exhibit increased AuNP uptake when compared to non-tumoral ones, leading to a significant loss of cellular proliferation ability and complex DNA damage, evidenced by the occurrence of multiple micronucleus per binucleated cell, in the case of PC3 cells irradiated with 2 Gy of γ-rays, after incubation with AuNP-BBN. Remarkably, the treatment of the PC3 cells with AuNP-BBN led to a much stronger influence of the dose rate on the cellular survival upon γ-photon irradiation, as well as on their genomic instability. Overall, AuNP-BBN emerged in this study as a very promising nanotool for the efficient and selective radiosensitization of human prostate cancer PC3 cells, therefore deserving further preclinical evaluation in adequate animal models for prostate cancer radiotherapy.

Paclitaxel Promotes Oxidative Stress-Mediated Human Laryngeal Squamous Tumor Cell Death through the Stimulation of Calcium and Zinc Signaling Pathways: No Synergic Action of Melatonin

The paclitaxel (PAX) and melatonin (MLT)-mediated mitochondria reactive free oxygen radical (miROS) generations via the influx of excessive Ca²⁺ and Zn²⁺ induce tumor cell death and apoptosis. However, a presence of resistance was demonstrated against the PAX treatment in the tumor cells. The stimulation of TRPM2 may increase the anticancer action of PAX after the treatment of MLT. We investigated the stimulating role of PAX with/without MLT on the excessive Ca²⁺ influx and miROS generation-mediated human laryngeal squamous cancer (Hep2) cell death through the stimulation of TRPM2. The Hep2 cells were divided into four groups as control, MLT (1 mM for 2 h), PAX (50 μM for 24 h), and PAX + MLT. In some experiments, we induced additional subgroups such as PAX+ACA and PAX+2APB. The stimulation of TRPM2 induced the increase of TRPM2 current densities, lipid peroxidation, cytosolic ROS, miROS, cytosolic Ca²⁺, and Zn²⁺ values in the Hep2 cells after the treatment of PAX, although their values were decreased by the treatment of MLT and TRPM2 antagonists (ACA and 2APB). In addition, the PAX induced apoptosis and cell death via upregulation of caspases and downregulation of antioxidant glutathione peroxidase and glutathione in the cells. The treatment of PAX increased protein band expression values of TRPM2, PARP-1, and caspase 3 and 9 in the Hep2. The increased expression, apoptotic, and cell death values were not affected by the treatment of MLT. In conclusion, PAX induced the increase of Hep2 cell death via upregulations of TRPM2 and Zn²⁺, although its downregulation via the treatment of MLT did not change the antitumor action of PAX.

CD137 Signal Mediates Cardiac Ischemia-Reperfusion Injury by Regulating the Necrosis of Cardiomyocytes

The injury of cardiomyocytes after ischemia-reperfusion is the main reason of cardiac dysfunction. Necrosis is one of the methods of programmed cell death and cardiomyocyte necrosis occurs in the process of reperfusion. The activation of CD137 signal is involved in various diseases. In vivo experiments proved that CD137^-/- mice have less heart damage than wild-type mice after ischemia-reperfusion. In vitro experiments, we found that after inhibiting the CD137 signal, the degree of necrosis of HL-1 cells was reduced and it was caused by reducing the Ca2 + overload in the mitochondria, which caused the reduction of mPTP opening. Ca2 + overload in mitochondria induced by activation of CD137 signal was caused by increased Ca2 + released into mitochondria by activation of IP3R and increased MCU level. These results indicate that CD137 signaling aggravates cardiac ischemia-reperfusion injury by inducing myocardial cell necrosis.

Lon upregulation contributes to cisplatin resistance by triggering NCLX-mediated mitochondrial Ca2+ release in cancer cells

Mitochondria are the major organelles in sensing cellular stress and inducing the response for cell survival. Mitochondrial Lon has been identified as an important stress protein involved in regulating proliferation, metastasis, and apoptosis in cancer cells. However, the mechanism of retrograde signaling by Lon on mitochondrial DNA (mtDNA) damage remains to be elucidated. Here we report the role of Lon in the response to cisplatin-induced mtDNA damage and oxidative stress, which confers cancer cells on cisplatin resistance via modulating calcium levels in mitochondria and cytosol. First, we found that cisplatin treatment on oral cancer cells caused oxidative damage of mtDNA and induced Lon expression. Lon overexpression in cancer cells decreased while Lon knockdown sensitized the cytotoxicity towards cisplatin treatment. We further identified that cisplatin-induced Lon activates the PYK2-SRC-STAT3 pathway to stimulate Bcl-2 and IL-6 expression, leading to the cytotoxicity resistance to cisplatin. Intriguingly, we found that activation of this pathway is through an increase of intracellular calcium (Ca²⁺) via NCLX, a mitochondrial Na⁺/Ca²⁺ exchanger. We then verified that NCLX expression is dependent on Lon levels; Lon interacts with and activates NCLX activity. NCLX inhibition increased the level of mitochondrial calcium and sensitized the cytotoxicity to cisplatin in vitro and in vivo. In summary, mitochondrial Lon-induced cisplatin resistance is mediated by calcium release into cytosol through NCLX, which activates calcium-dependent PYK2-SRC-STAT3-IL-6 pathway. Thus, our work uncovers the novel retrograde signaling by mitochondrial Lon on resistance to cisplatin-induced mtDNA stress, indicating the potential use of Lon and NCLX inhibitors for better clinical outcomes in chemoresistant cancer patients.

Lysophosphatidic Acid Receptor 3 Promotes Mitochondrial Homeostasis against Oxidative Stress: Potential Therapeutic Approaches for Hutchinson–Gilford Progeria Syndrome

Lysophosphatidic acid (LPA) is a growth factor-like lipid mediator that regulates various physiological functions via activation of multiple LPA G protein-coupled receptors. We previously reported that LPA suppresses oxidative stress in premature aging Hutchinson-Gilford progeria syndrome (HGPS) patient fibroblasts via its type 3 receptor (LPA₃). Mitochondria have been suggested to be the primary origin of oxidative stress via the overproduction of reactive oxygen species (ROS). Mitochondria are responsible for producing ATP through oxidative phosphorylation (OXPHOS) and have a calcium buffering capacity for the cell. Defects in mitochondria will lead to declined antioxidant capacity and cell apoptosis. Therefore, we aim to demonstrate the regulatory role of LPA₃ in mitochondrial homeostasis. siRNA-mediated depletion of LPA₃ leads to the depolarization of mitochondrial potential (ΔΨm) and cellular ROS accumulation. In addition, the depletion of LPA₃ enhances cisplatin-induced cytochrome C releasing. This indicates that LPA₃ is essential to suppress the mitochondrial apoptosis pathway. LPA₃ is also shown to improve mitochondrial ADP-ATP exchange by enhancing the protein level of ANT2. On the other hand, LPA₃ regulates calcium uptake from the ER to mitochondria via the IP3R1-VDAC1 channel. Moreover, activation of LPA₃ by selective agonist OMPT rescues mitochondrial homeostasis of H₂O₂-induced oxidative stress cells and HGPS patient fibroblasts by improving mitochondrial ΔΨm and OXPHOS. In summary, our findings imply that LPA₃ acts as the gatekeeper for mitochondrial healthiness to maintain cell youth. Furthermore, LPA₃ can be a promising therapeutic target to prevent mitochondrial oxidative stress in aging and HGPS.

OXER1 mediates testosterone-induced calcium responses in prostate cancer cells

In prostate cancer, calcium homeostasis plays a significant role in the disease's development and progression. Intracellular calcium changes are an important secondary signal, triggered by a variety of extracellular stimuli, that controls many cellular functions. One of the main events affecting calcium is androgen signaling. Indeed, via calcium changes, androgens regulate cell processes like cell growth, differentiation and motility. In the present work we explored the nature of the receptor involved in calcium response induced by membrane-acting testosterone in prostate cancer cells. We report that testosterone, independently of the presence of the classical androgen receptor, can rapidly increase intracellular calcium from calcium stores, through the oxoeicosanoid receptor 1 (OXER1) and a specific signaling cascade that triggers calcium release from the endoplasmic reticulum. These findings reveal for the first time the receptor involved in the rapid calcium changes induced by androgens. Moreover, they further support the notion that androgens, even in the absence of AR, can still exert specific effects that regulate cancer cell fate.

α-Synuclein Interactions in Mitochondria-ER Contacts: A Possible Role in Parkinson's Disease

Endoplasmic reticulum-mitochondria contact sites regulate various biological processes, such as mitochondrial dynamics, calcium homeostasis, autophagy and lipid metabolism. Notably, dysfunctions in these contact sites are closely related to neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis. However, details about the role of endoplasmic reticulum-mitochondria contact sites in neurodegenerative diseases remain unknown. In Parkinson's disease, interactions between α-synuclein in the contact sites and components of tether complexes that connect organelles can lead to various dysfunctions, especially with regards to calcium homeostasis. This review will summarize the main tether complexes present in endoplasmic reticulum-mitochondria contact sites, and their roles in calcium homeostasis and trafficking. We will discuss the impact of α-synuclein accumulation, its interaction with tethering complex components and the implications in Parkinson's disease pathology.

Characterization of a Novel Splicing Variant in Acylglycerol Kinase (AGK) Associated with Fatal Sengers Syndrome

Mitochondrial functional integrity depends on protein and lipid homeostasis in the mitochondrial membranes and disturbances in their accumulation can cause disease. AGK, a mitochondrial acylglycerol kinase, is not only involved in lipid signaling but is also a component of the TIM22 complex in the inner mitochondrial membrane, which mediates the import of a subset of membrane proteins. AGK mutations can alter both phospholipid metabolism and mitochondrial protein biogenesis, contributing to the pathogenesis of Sengers syndrome. We describe the case of an infant carrying a novel homozygous AGK variant, c.518+1G>A, who was born with congenital cataracts, pielic ectasia, critical congenital dilated myocardiopathy, and hyperlactacidemia and died 20 h after birth. Using the patient’s DNA, we performed targeted sequencing of 314 nuclear genes encoding respiratory chain complex subunits and proteins implicated in mitochondrial oxidative phosphorylation (OXPHOS). A decrease of 96-bp in the length of the AGK cDNA sequence was detected. Decreases in the oxygen consumption rate (OCR) and the OCR:ECAR (extracellular acidification rate) ratio in the patient’s fibroblasts indicated reduced electron flow through the respiratory chain, and spectrophotometry revealed decreased activity of OXPHOS complexes I and V. We demonstrate a clear defect in mitochondrial function in the patient’s fibroblasts and describe the possible molecular mechanism underlying the pathogenicity of this novel AGK variant. Experimental validation using in vitro analysis allowed an accurate characterization of the disease-causing variant.

Cellular senescence links mitochondria-ER contacts and aging

Membrane contact sites emerged in the last decade as key players in the integration, regulation and transmission of many signals within cells, with critical impact in multiple pathophysiological contexts. Numerous studies accordingly point to a role for mitochondria-endoplasmic reticulum contacts (MERCs) in modulating aging. Nonetheless, the driving cellular mechanisms behind this role remain unclear. Recent evidence unravelled that MERCs regulate cellular senescence, a state of permanent proliferation arrest associated with a pro-inflammatory secretome, which could mediate MERC impact on aging. Here we discuss this idea in light of recent advances supporting an interplay between MERCs, cellular senescence and aging.

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.

Connexin Hemichannel Activation by S-Nitrosoglutathione Synergizes Strongly with Photodynamic Therapy Potentiating Anti-Tumor Bystander Killing

Simple Summary

Bystander effects depend on direct cell-cell communication and/or paracrine signaling mediated by the release of soluble factors into the extracellular environment and may greatly influence therapy outcome. Although the limited data available suggest a role for intercellular gap junction channels, far less is known about the role of connexin hemichannels. Here, we investigated bystander effects induced by photodynamic therapy in syngeneic murine melanoma models in vivo. We determined that (i) photoactivation of a photosensitizer triggered calcium-dependent cell death pathways in both irradiated and bystander tumor cells; (ii) hemichannel activity and adenosine triphosphate release were key factors for the induction of bystander cell death; and (iii) bystander cell killing and antitumor response elicited by photodynamic therapy were greatly enhanced by combination treatment with S-nitrosoglutathione, which promoted hemichannel opening in these experimental conditions. Therefore, these findings in a preclinical model have important translational potential.

Abstract

In this study, we used B16-F10 cells grown in the dorsal skinfold chamber (DSC) preparation that allowed us to gain optical access to the processes triggered by photodynamic therapy (PDT). Partial irradiation of a photosensitized melanoma triggered cell death in non-irradiated tumor cells. Multiphoton intravital microscopy with genetically encoded fluorescence indicators revealed that bystander cell death was mediated by paracrine signaling due to adenosine triphosphate (ATP) release from connexin (Cx) hemichannels (HCs). Intercellular calcium (Ca²⁺) waves propagated from irradiated to bystander cells promoting intracellular Ca²⁺ transfer from the endoplasmic reticulum (ER) to mitochondria and rapid activation of apoptotic pathways. Combination treatment with S-nitrosoglutathione (GSNO), an endogenous nitric oxide (NO) donor that biases HCs towards the open state, greatly potentiated anti-tumor bystander killing via enhanced Ca²⁺ signaling, leading to a significant reduction of post-irradiation tumor mass. Our results demonstrate that HCs can be exploited to dramatically increase cytotoxic bystander effects and reveal a previously unappreciated role for HCs in tumor eradication promoted by PDT.

Dynamic control of mitochondria-associated membranes by kinases and phosphatases in health and disease

Membrane-contact sites are getting more and more credit for their indispensable role in maintenance of cell function and homeostasis. In the last decades, the ER-mitochondrial contact sites in particular received a lot of attention. While our knowledge of ER-mitochondrial contact sites increases steadily, the focus often lies on a static exploration of their functions. However, it is increasingly clear that these contact sites are very dynamic. In this review, we highlight the dynamic nature of ER-mitochondrial contact sites and the role of kinases and phosphatases therein with a focus on recent findings. Phosphorylation events allow for rapid integration of information on the protein level, impacting protein function, localization and interaction at ER-mitochondrial contact sites. To illustrate the importance of these events and to put them in a broader perspective, we connect them to pathologies like diabetes type II, Parkinson's disease and cancer.

Polydatin Counteracts 5-Fluorouracil Resistance by Enhancing Apoptosis via Calcium Influx in Colon Cancer

Colon cancer is a disease with a high prevalence rate worldwide, and for its treatment, a 5-fluorouracil (5-FU)-based chemotherapeutic strategy is generally used. However, conventional anticancer agents have some limitations, including the development of drug resistance. Therefore, there has recently been a demand for the improvement of antitumor agents using natural products with low side effects and high efficacy. Polydatin is a natural active compound extracted from an annual plant, and widely known for its anticancer effects in diverse types of cancer. However, it is still not clearly understood how polydatin ameliorates several drawbacks of standard anticancer drugs by reinforcing the chemosensitivity against 5-FU, and neither are the intrinsic mechanisms behind this process. In this study, we examined how polydatin produces anticancer effects in two types of colon cancer, called HCT116 and HT-29 cells. Polydatin has the ability to repress the progression of colon cancer, and causes a modification of distribution in the cell cycle by a flow cytometry analysis. It also induces mitochondrial dysfunctions through oxidative stress and the loss of mitochondrial membrane potential. The present study investigated the apoptosis caused by the disturbance of calcium regulation and the expression levels of related proteins through flow cytometry and immunoblotting analysis. It was revealed that polydatin suppresses the signaling pathways of the mitogen-activated protein kinase (MAPK) and PI3K/AKT. In addition, it was shown that polydatin combined with 5-FU counteracts drug resistance in 5-FU-resistant cells. Therefore, this study suggests that polydatin has the potential to be developed as an innovative medicinal drug for the treatment of colon cancer.

Clinical Implications of HBV PreS/S Mutations and the Effects of PreS2 Deletion on Mitochondria, Liver Fibrosis, and Cancer Development

BACKGROUND AND AIMS

PreS mutants of HBV have been reported to be associated with HCC. We conducted a longitudinal study of the role of HBV preS mutations in the development of HCC, particularly in patients with chronic hepatitis B (CHB) having low HBV DNA or alanine aminotransferase (ALT) levels, and investigated the effects of secretion-defective preS2 deletion mutant (preS2ΔMT) on hepatocyte damage in vitro and liver fibrosis in vivo.

APPROACH AND RESULTS

Association of preS mutations with HCC in 343 patients with CHB was evaluated by a retrospective case-control follow-up study. Effects of preS2ΔMT on HBsAg retention, endoplasmic reticulum (ER) stress, calcium accumulation, mitochondrial dysfunction, and liver fibrosis were examined. Multivariate analysis revealed a significant association of preS mutations with HCC (HR, 3.210; 95% CI, 1.072-9.613; P = 0.037) including cases with low HBV DNA or ALT levels (HR, 2.790; 95% CI, 1.133-6.873; P = 0.026). Antiviral therapy reduced HCC risk, including cases with preS mutations. PreS2ΔMT expression promoted HBsAg retention in the ER and unfolded protein response (UPR). Transmission electron microscopic examination, MitoTracker staining, real-time ATP assay, and calcium staining of preS2ΔMT-expressing cells revealed aberrant ER and mitochondrial ultrastructure, reduction of mitochondrial membrane potential and ATP production, and calcium overload. Serum HBV secretion levels were ~100-fold lower in preS2ΔMT-infected humanized Fah-/-/ Rag2-/-/Il2rg-/- triple knockout mice than in wild-type HBV-infected mice. PreS2ΔMT-infected mice displayed up-regulation of UPR and caspase-3 and enhanced liver fibrosis.

CONCLUSIONS

PreS mutations were significantly associated with HCC development in patients with CHB, including those with low HBV DNA or ALT levels. Antiviral therapy reduced HCC occurrence in patients with CHB, including those with preS mutations. Intracellular accumulation of mutated HBsAg induced or promoted ER stress, calcium overload, mitochondrial dysfunction, impaired energy metabolism, liver fibrosis, and HCC.

Overview of Ca2+ signaling in lung cancer progression and metastatic lung cancer with bone metastasis

Intracellular Ca²⁺ ions that are thought to be one of the most important second messengers for cellular signaling, have a substantial diversity of roles in regulating a plethora of fundamental cellular physiology such as gene expression, cell division, cell motility and apoptosis. It has been suggestive of the Ca²⁺ signaling-dependent cellular processes to be tightly regulated by the numerous types of Ca²⁺ channels, pumps, exchangers and sensing receptors. Consequently, dysregulated Ca²⁺ homeostasis leads to a series of events connected to elevated malignant phenotypes including uncontrolled proliferation, migration, invasion and metastasis, all of which are frequently observed in advanced stage lung cancer cells. The incidence of bone metastasis in patients with advanced stage lung cancer is estimated in a range of 30% to 40%, bringing about a significant negative impact on both morbidity and survival. This review dissects and summarizes the important roles of Ca²⁺ signaling transduction in contributing to lung cancer progression, and address the question: if and how Ca²⁺ signaling might have been engaged in metastatic lung cancer with bone metastasis, thereby potentially providing the multifaceted and promising solutions for therapeutic intervention.

Mitochondria: Insights into Crucial Features to Overcome Cancer Chemoresistance

Mitochondria are key regulators of cell survival and are involved in a plethora of mechanisms, such as metabolism, Ca²⁺ signaling, reactive oxygen species (ROS) production, mitophagy and mitochondrial transfer, fusion, and fission (known as mitochondrial dynamics). The tuning of these processes in pathophysiological conditions is fundamental to the balance between cell death and survival. Indeed, ROS overproduction and mitochondrial Ca²⁺ overload are linked to the induction of apoptosis, while the impairment of mitochondrial dynamics and metabolism can have a double-faceted role in the decision between cell survival and death. Tumorigenesis involves an intricate series of cellular impairments not yet completely clarified, and a further level of complexity is added by the onset of apoptosis resistance mechanisms in cancer cells. In the majority of cases, cancer relapse or lack of responsiveness is related to the emergence of chemoresistance, which may be due to the cooperation of several cellular protection mechanisms, often mitochondria-related. With this review, we aim to critically report the current evidence on the relationship between mitochondria and cancer chemoresistance with a particular focus on the involvement of mitochondrial dynamics, mitochondrial Ca²⁺ signaling, oxidative stress, and metabolism to possibly identify new approaches or targets for overcoming cancer resistance.