Roles of TRPM2 in oxidative stress

Navigating the Controversies: Role of TRPM Channels in Pain States

Chronic pain is a debilitating condition that affects up to 1.5 billion people worldwide and bears a tremendous socioeconomic burden. The success of pain medicine relies on our understanding of the type of pain experienced by patients and the mechanisms that give rise to it. Ion channels are among the key targets for pharmacological intervention in chronic pain conditions. Therefore, it is important to understand how changes in channel properties, trafficking, and molecular interactions contribute to pain sensation. In this review, we discuss studies that have demonstrated the involvement of transient receptor potential M2, M3, and M8 channels in pain generation and transduction, as well as the controversies surrounding these findings.

NOX2-TRPM2 coupling promotes Zn2+ inhibition of complex III to exacerbate ROS production in a cellular model of Parkinson's disease

Reactive oxygen species (ROS) serve vital physiological functions, but aberrant ROS production contributes to numerous diseases. Unfortunately, therapeutic progress targeting pathogenic ROS has been hindered by the limited understanding of whether the mechanisms driving pathogenic ROS differ from those governing physiological ROS generation. To address this knowledge gap, we utilised a cellular model of Parkinson's disease (PD), as an exemplar of ROS-associated diseases. We exposed SH-SY5Y neuroblastoma cells to the PD-toxin, MPP+ (1-methyl-4-phenylpyridinium) and studied ROS upregulation leading to cell death, the primary cause of PD. We demonstrate: (1) MPP+ stimulates ROS production by raising cytoplasmic Ca2+ levels, rather than acting directly on mitochondria. (2) To raise the Ca2+, MPP+ co-stimulates NADPH oxidase-2 (NOX2) and the Transient Receptor Potential Melastatin2 (TRPM2) channel that form a positive feedback loop to support each other's function. (3) Ca2+ exacerbates mitochondrial ROS (mtROS) production not directly, but via Zn2+. (4) Zn2+ promotes electron escape from respiratory complexes, predominantly from complex III, to generate mtROS. These conclusions are drawn from data, wherein inhibition of TRPM2 and NOX2, chelation of Ca2+ and Zn2+, and prevention of electron escape from complexes -all abolished the ability of MPP+ to induce mtROS production and the associated cell death. Furthermore, calcium ionophore mimicked the effects of MPP+, while Zn2+ ionophore replicated the effects of both MPP+ and Ca2+. Thus, we unveil a previously unrecognized signalling circuit involving NOX2, TRPM2, Ca2+, Zn2+, and complex III that drives cytotoxic ROS production. This circuit lies dormant in healthy cells but is triggered by pathogenic insults and could therefore represent a safe therapeutic target for PD and other ROS-linked diseases.

The relationship of redox signaling with the risk for atherosclerosis

Oxidative balance plays a pivotal role in physiological homeostasis, and many diseases, particularly age-related conditions, are closely associated with oxidative imbalance. While the strategic role of oxidative regulation in various diseases is well-established, the specific involvement of oxidative stress in atherosclerosis remains elusive. Atherosclerosis is a chronic inflammatory disorder characterized by plaque formation within the arteries. Alterations in the oxidative status of vascular tissues are linked to the onset, progression, and outcome of atherosclerosis. This review examines the role of redox signaling in atherosclerosis, including its impact on risk factors such as dyslipidemia, hyperglycemia, inflammation, and unhealthy lifestyle, along with dysregulation, vascular homeostasis, immune system interaction, and therapeutic considerations. Understanding redox signal transduction and the regulation of redox signaling will offer valuable insights into the pathogenesis of atherosclerosis and guide the development of novel therapeutic strategies.

Activation of endothelial TRPM2 exacerbates blood-brain barrier degradation in ischemic stroke

AIMS

Damage of the blood-brain barrier (BBB) is a hallmark of brain injury during the early stages of ischemic stroke. The subsequent endothelial hyperpermeability drives the initial pathological changes and aggravates neuronal death. Transient receptor potential melastatin 2 (TRPM2) is a Ca2+-permeable nonselective cation channel activated by oxidative stress. However, whether TRPM2 is involved in BBB degradation during ischemic stroke remains unknown. We aimed to investigate the role of TRPM2 in BBB degradation during ischemic stroke and the underlying molecular mechanisms.

METHODS AND RESULTS

Specific deletion of Trpm2 in endothelial cells using Cdh5 Cre produces a potent protective effect against brain injury in mice subjected to middle cerebral artery occlusion (MCAO), which is characterized by reduced infarction size, mitigated plasma extravasation, suppressed immune cell invasion, and inhibited oxidative stress. In vitro experiments using cultured cerebral endothelial cells (CECs) demonstrated that either Trpm2 deletion or inhibition of TRPM2 activation attenuates oxidative stress, Ca2+ overload, and endothelial hyperpermeability induced by oxygen-glucose deprivation (OGD) and CD36 ligand thrombospondin-1 (TSP1). In transfected HEK293T cells, OGD and TSP1 activate TRPM2 in a CD36-dependent manner. Noticeably, in cultured CECs, deleting Trpm2 or inhibiting TRPM2 activation also suppresses the activation of CD36 and cellular dysfunction induced by OGD or TSP1.

CONCLUSIONS

In conclusion, our data reveal a novel molecular mechanism in which TRPM2 and CD36 promote the activation of each other, which exacerbates endothelial dysfunction during ischemic stroke. Our study suggests that TRPM2 in endothelial cells is a promising target for developing more effective and safer therapies for ischemic stroke.

ROS-Activated TRPM2 Channel: Calcium Homeostasis in Cardiovascular/renal System and Speculation in Cardiorenal Syndrome

The transient receptor potential melastatin 2 (TRPM2) channel is a nonselective calcium channel that is sensitive to oxidative stress (OS), and is widely expressed in multiple organs, such as the heart, kidney, and brain, which is inextricably related to calcium dyshomeostasis and downstream pathological events. Due to the increasing global burden of kidney or cardiovascular diseases (CVDs), safe and efficient drugs specific to novel targets are imperatively needed. Notably, investigation of the possibility to regard the TRPM2 channel as a new therapeutic target in ROS-related CVDs or renal diseases is urgently required because the roles of the TRPM2 channel in heart or kidney diseases have not received enough attention and thus have not been fully elaborated. Therefore, we aimed to review the involvement of the TRPM2 channel in cardiovascular disorders related to kidney or typical renal diseases and attempted to speculate about TRPM2-mediated mechanisms of cardiorenal syndrome (CRS) to provide representative perspectives for future research about novel and effective therapeutic strategies.

Antagonist of transient receptor potential melastatin 2 suppresses mechanical hypersensitivity and activation of microglia induced by infraorbital nerve ligation in male rats

Activation of microglia is known to be involved in neuropathic pain. However, the pathway that regulates the microglial activation is not completely understood. Transient receptor potential (TRP) melastatin 2 (TRPM2), which is part of the TRP superfamily, is reportedly expressed on microglia and is suggested to be involved in neuropathic pain. To explore the effect of a TRPM2 antagonist on orofacial neuropathic pain and the relationship between TRPM2 and the activation of microglia, experiments were conducted using male rats that underwent infraorbital nerve (ION) ligation as orofacial neuropathic pain models. TRPM2 expression was detected on microglia in the trigeminal spinal subnucleus caudalis (Vc). The immunoreactivity of TRPM2 in the Vc increased after ION ligation. Mechanical threshold for head-withdrawal response was measured using von Frey filament, and it decreased after ION ligation. When the TRPM2 antagonist was administered to the ION-ligated rats, the low mechanical threshold for head-withdrawal response increased, and the number of phosphorylated extracellular signal-regulated kinase (pERK)-immunoreactive cells in the Vc decreased. The number of CD68-immunoreactive cells in the Vc also decreased after the administration of the TRPM2 antagonist in the ION-ligated rats. These findings suggest that TRPM2 antagonist administration suppresses hypersensitivity to mechanical stimulation induced by ION ligation and microglial activation, and TRPM2 is also involved in microglial activation in orofacial neuropathic pain.

The Effects of N-acetylcysteine on Transient Receptor Potential Melastatin 2 Channels Activation and Expression in Testicular Tissue of Diabetic Rats

INTRODUCTION

Diabetes mellitus (DM) is a common, chronic metabolic disease that has harmful effects on many diverse tissues, including the testis. One of the ways of tissue damage is the modification of transient receptor potential melastatin 2 (TRPM2) channels by increased reactive oxygen species (ROS). In our study for the first time, it was aimed to investigate TRPM2 channel activation in testicular tissues of diabetic rats induced by streptozotosin (STZ) and to examine the efficacy of N-acetylcysteine (NAC) treatment, which is an antioxidant.

METHODS

In our study, 28 Wistar albino male rats aged 8-10 weeks were used, and animals were divided into four groups: control group, NAC group, DM group, and DM + NAC group. The experimental phase was designed as eight weeks. The malondialdehyde (MDA) level, which is an indicator for lipid peroxidation due to oxidative stress, was measured by the spectrophotometric method. The Tunel assay was used to determine apoptosis on testicular tissue. TRPM2 immunoreactivity was determined by the avidin-biotin-peroxidase complex method, and quantitative polymerase chain reaction (QPCR) was used to determine TRPM2 expression levels.

RESULTS

It was seen that MDA levels were significantly increased in the DM group and decreased after NAC treatment. Similarly, it was observed that apoptosis levels, which increased significantly in diabetic rats, decreased to the levels of the control group after treatment. It was seen that TRPM2 activation and expression levels were significantly decreased in the DM group.

CONCLUSION

 The results of this study show that NAC regulates TRPM2 activation in the testicular tissue of patients with diabetes and has tissue-protective properties.

Ion Channels in Gliomas-From Molecular Basis to Treatment

Ion channels provide the basis for the nervous system's intrinsic electrical activity. Neuronal excitability is a characteristic property of neurons and is critical for all functions of the nervous system. Glia cells fulfill essential supportive roles, but unlike neurons, they also retain the ability to divide. This can lead to uncontrolled growth and the formation of gliomas. Ion channels are involved in the unique biology of gliomas pertaining to peritumoral pathology and seizures, diffuse invasion, and treatment resistance. The emerging picture shows ion channels in the brain at the crossroads of neurophysiology and fundamental pathophysiological processes of specific cancer behaviors as reflected by uncontrolled proliferation, infiltration, resistance to apoptosis, metabolism, and angiogenesis. Ion channels are highly druggable, making them an enticing therapeutic target. Targeting ion channels in difficult-to-treat brain tumors such as gliomas requires an understanding of their extremely heterogenous tumor microenvironment and highly diverse molecular profiles, both representing major causes of recurrence and treatment resistance. In this review, we survey the current knowledge on ion channels with oncogenic behavior within the heterogeneous group of gliomas, review ion channel gene expression as genomic biomarkers for glioma prognosis and provide an update on therapeutic perspectives for repurposed and novel ion channel inhibitors and electrotherapy.

Ginkgolide A downregulates transient receptor potential (melastatin) 2 to protect cisplatin-induced acute kidney injury in rats through the TWEAK/Fn14 pathway: Ginkgolide A improve acute renal injury

PURPOSE

In order to seek effective drugs for treating cisplatin-induced acute renal injury and explore the corresponding potential mechanism.

METHODS

Mouse kidney injury model was established by intraperitoneal injection of 20 mg/kg cisplatin. The temporal expression of TRPM2 and the regulation of Ginkgolide A on its expression were analyzed by western blot. In order to perform the mechanical analysis, we used TRPM2-KO knockout mice. In this study, we evaluated the repair effect of GA on acute kidney injury through renal function factors, inflammatory factors and calcium and potassium content. Pathological injury and cell apoptosis were detected by H&E and TUNEL, respectively.

RESULT

Ginkgolide A inhibited inflammatory reaction and excessive oxidative stress, reduced renal function parameters, and improved pathological injury. Meanwhile, we also found that the repair effect of Ginkgolide A on renal injury is related to TRPM2, and Ginkgolide A downregulated TRPM2 expression and inactivated TWEAK/Fn14 pathway in cisplatin-induced renal injury model. We also found that inhibition of TWEAK/Fn14 pathway was more effective in TRPM2-KO mice than TRPM2-WT mice.

CONCLUSION

Ginkgolide A was the effective therapeutic drug for cisplatin-induced renal injury through acting on TRPM2, and TWEAK/Fn14 pathway was the downstream pathway of Ginkgolide A in acute renal injury, and Ginkgolide A inhibited TWEAK/Fn14 pathway in cisplatin-induced renal injury model.

The effect of high temperature on kinetics of reactive species generation in patients with type 2 diabetes

The excessive amount of reactive species under chronic inflammation, which are accompanied by an increase body temperature, lead to diabetic complications. Phagocyte NADPH oxidase is the key enzyme in these processes. The role of high temperature in its regulation in diabetes is not clear. The aim was to investigate the effect of high temperature on NADPH-oxidase-dependent generation of reactive species in diabetic patients. Chemiluminescent method was applied to assess respiratory burst kinetics initiated by opsonized zymosan in blood or phorbol ester in isolated granulocytes. Analyzing ROC curves, the main predictors and changes in stages of activation of NADPH oxidase were determined. Phosphoisoforms of p47^phox and p67^phox were quantified by immunoblotting. Response to opsonized zymosan was lower in all subjects at 40 °C vs 37 °C, its kinetic parameters (except T_max) were higher in blood of patients vs controls. Response rate was the main significant predictor to distinguish groups of subjects at 40 °C indicating NADPH oxidase upregulation in diabetes. Ca²⁺-dependent generation of reactive species by cells increased in both groups at 40 °C vs 37 °C, kinetic parameters were higher in patients. Initial phospho-p47^phox level was higher in patient cells vs ones in controls. It was increased by ionomycin, phorbol ester, or 40 °C in control cells and unchanged in patient ones. Phospho-p67^phox level was unchangeable in intact cells of healthy donors and patients at both temperatures. Excessive amounts of reactive species in patient cells were the consequence of granulocyte priming due to p47^phox phosphorylation. Thus, high temperature decreased phagocytosis- and enhanced Ca²⁺-dependent generation of reactive species making the differences between controls and patients less pronounced. The effect of temperature on the generation of reactive species in blood granulocytes is associated with activity of NADPH oxidase that can be a prospective therapeutic target for pathologies accompanied by inflammation including type 2 diabetes.

Pathological Mechanisms Induced by TRPM2 Ion Channels Activation in Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion (IR) injury triggers a cascade of signaling reactions involving an increase in Ca^{2 +} charge and reactive oxygen species (ROS) levels resulting in necrosis, inflammation, apoptosis, and subsequently acute kidney injury (AKI).Transient receptor potential (TRP) channels include an essential class of Ca²⁺ permeable cation channels, which are segregated into six main channels: the canonical channel (TRPC), the vanilloid-related channel (TRPV), the melastatin-related channel (TRPM), the ankyrin-related channel (TRPA), the mucolipin-related channel (TRPML) and polycystin-related channel (TRPP) or polycystic kidney disease protein (PKD2). TRP channels are involved in adjusting vascular tone, vascular permeability, cell volume, proliferation, secretion, angiogenesis and apoptosis.TRPM channels include eight isoforms (TRPM1-TRPM8) and TRPM2 is the second member of this subfamily that has been expressed in various tissues and organs such as the brain, heart, kidney and lung. Renal TRPM2 channels have an important role in renal IR damage. So that TRPM2 deficient mice are resistant to renal IR injury. TRPM2 channels are triggered by several chemicals including hydrogen peroxide, Ca²⁺, and cyclic adenosine diphosphate (ADP) ribose (cADPR) that are generated during AKI caused by IR injury, as well as being implicated in cell death caused by oxidative stress, inflammation, and apoptosis.

Floralozone improves cognitive impairment in vascular dementia rats via regulation of TRPM2 and NMDAR signaling pathway

Vascular dementia (VD) is the second largest type of dementia after Alzheimer's disease. At present, the pathogenesis is complex and there is no effective treatment. Floralozone has been shown to reduce atherosclerosis in rats caused by a high-fat diet. However, whether it plays a role in VD remains elusive. In the present study, the protective activities and relevant mechanisms of Floralozone were evaluated in rats with cognitive impairment, which were induced by bilateral occlusion of the common carotid arteries (BCCAO) in rats. Cognitive function, pathological changes and oxidative stress condition in the brains of VD rats were assessed using Neurobehavioral tests, Morris water maze tests, hematoxylin-eosin staining, Neu N staining, TUNEL staining, Golgi staining, Western blot assay and antioxidant assays (MDA, SOD, GSH), respectively. The results indicated that VD model was established successfully and BCCAO caused a decline in spatial learning and memory and hippocampal histopathological abnormalities of rats. Floralozone (50, 100, 150 mg/kg) dose-dependently alleviated the pathological changes, decreased oxidative stress injury, which eventually reduced cognitive impairment in BCCAO rats. The same results were shown in further experiments with neurobehavioral tests. At the molecular biological level, Floralozone decreased the protein level of transient receptor potential melastatin-related 2 (TRPM2) in VD and normal rats, and increased the protein level of NR2B in hippocampus of N-methyl-D-aspartate receptor (NMDAR). Notably, Floralozone could markedly improved learning and memory function of BCCAO rats in Morris water maze (MWM) and improved neuronal cell loss, synaptic structural plasticity. In conclusion, Floralozone has therapeutic potential for VD, increased synaptic structural plasticity and alleviating neuronal cell apoptosis, which may be related to the TRPM2/NMDAR pathway.

TRPM2 Promotes Atherosclerotic Progression in a Mouse Model of Atherosclerosis

Atherosclerosis is a chronic inflammatory arterial disease characterized by build-up of atheromatous plaque, which narrows the lumen of arteries. Hypercholesterolemia and excessive oxidative stress in arterial walls are among the main causative factors of atherosclerosis. Transient receptor potential channel M2 (TRPM2) is a Ca²⁺-permeable cation channel activated by oxidative stress. However, the role of TRPM2 in atherosclerosis in animal models is not well studied. In the present study, with the use of adeno-associated virus (AAV)-PCSK9 and TRPM2 knockout (TRPM2^−/−) mice, we determined the role of TRPM2 in hypercholesterolemia-induced atherosclerosis. Our results demonstrated that TRPM2 knockout reduced atherosclerotic plaque area in analysis of En face Oil Red O staining of both whole aortas and aortic-root thin sections. Furthermore, TRPM2 knockout reduced the expression of CD68, α-SMA, and PCNA in the plaque region, suggesting a role of TRPM2 in promoting macrophage infiltration and smooth-muscle cell migration into the lesion area. Moreover, TRPM2 knockout reduced the expression of ICAM-1, MCP-1, and TNFα and decreased the ROS level in the plaque region, suggesting a role of TRPM2 in enhancing monocyte adhesion and promoting vascular inflammation. In bone-marrow-derived macrophages and primary cultured arterial endothelial cells, TRPM2 knockout reduced the production of inflammatory cytokines/factors and decreased ROS production. In addition, a TRPM2 antagonist N-(p-amylcinnamoyl) anthranilic acid (ACA) was able to inhibit atherosclerotic development in an ApoE^−/− mouse model of atherosclerosis. Taken together, the findings of our study demonstrated that TRPM2 contributes to the progression of hypercholesterolemia-induced atherosclerosis. Mechanistically, TRPM2 channels may provide an essential link that can connect ROS to Ca²⁺ and inflammation, consequently promoting atherosclerotic progression.

TRPM2 deficiency in mice protects against atherosclerosis by inhibiting TRPM2-CD36 inflammatory axis in macrophages

Atherosclerosis is the major cause of ischemic heart disease and stroke, the leading causes of mortality worldwide. The central pathological features of atherosclerosis include macrophage infiltration and foam cell formation. However, the detailed mechanisms regulating these two processes remain unclear. Here we show that oxidative stress-activated Ca2+-permeable transient receptor potential melastatin 2 (TRPM2) plays a critical role in atherogenesis. Both global and macrophage-specific Trpm2 deletion protect Apoe -/- mice against atherosclerosis. Trpm2 deficiency reduces oxidized low-density lipoprotein (oxLDL) uptake by macrophages, thereby minimizing macrophage infiltration, foam cell formation and inflammatory responses. Activation of the oxLDL receptor CD36 induces TRPM2 activity, and vice versa. In cultured macrophages, TRPM2 is activated by CD36 ligands oxLDL and thrombospondin-1 (TSP1), and deleting Trpm2 or inhibiting TRPM2 activity suppresses the activation of CD36 signaling cascade induced by oxLDL and TSP1. Our findings establish the TRPM2-CD36 axis as a molecular mechanism underlying atherogenesis, and suggest TRPM2 as a potential therapeutic target for atherosclerosis.

A Systemic Review of the Integral Role of TRPM2 in Ischemic Stroke: From Upstream Risk Factors to Ultimate Neuronal Death

Ischemic stroke causes a heavy health burden worldwide, with over 10 million new cases every year. Despite the high prevalence and mortality rate of ischemic stroke, the underlying molecular mechanisms for the common etiological factors of ischemic stroke and ischemic stroke itself remain unclear, which results in insufficient preventive strategies and ineffective treatments for this devastating disease. In this review, we demonstrate that transient receptor potential cation channel, subfamily M, member 2 (TRPM2), a non-selective ion channel activated by oxidative stress, is actively involved in all the important steps in the etiology and pathology of ischemic stroke. TRPM2 could be a promising target in screening more effective prophylactic strategies and therapeutic medications for ischemic stroke.

TRPM2 Plays a Minor Role in AKI and Kidney Fibrosis

TRPM2 is a Ca2⁺-permeable cationic channel and serves as an oxidative stress sensor.TRPM2 deletion was harmful in renal ischemia-reperfusion injury, whereas TRPM2 deletion mitigated kidney fibrosis.Our findings suggest the role of TRPM2 in kidney diseases is context dependent.

Inhibition of TRPM2 by AG490 Is Neuroprotective in a Parkinson's Disease Animal Model

Parkinson's disease (PD) is characterized by motor impairment and dopaminergic neuronal loss. There is no cure for the disease, and treatments have several limitations. The transient receptor potential melastatin 2 (TRPM2), a calcium-permeable non-selective cation channel, has been reported to be upregulated in neuronal death. However, there are no in vivo studies evaluating TRPM2's role and neuroprotective effects in PD. Here, we test the hypothesis that TRPM2 is upregulated in the 6-hydroxydopamine (6-OHDA) mouse model of PD and that its inhibition, by the AG490, is neuroprotective. For that, AG490 or vehicle were intraperitoneally administered into C57BL/6 mice. Mice then received 6-OHDA into the right striatum. Motor behavior assessments were evaluated 6, 13, and 20 days after surgery using the cylinder and apomorphine-induced rotational testes, and 7, 14, and 21 days after surgery using rotarod test. Brain samples of substantia nigra (SNc) and striatum (CPu) were collected for immunohistochemistry and immunoblotting on days 7 and 21. We showed that TRPM2 protein expression was upregulated in 6-OHDA-treated animals. In addition, AG490 prevented dopaminergic neuron loss, microglial activation, and astrocyte reactivity in 6-OHDA-treated animals. The compound improved motor behaviors and Akt/GSK-3β/caspase-3 signaling. We conclude that TRPM2 inhibition by AG490 is neuroprotective in the 6-OHDA model and that the TRPM2 channel may represent a potential therapeutic target for PD.

On the effects of temperature and pH on tropical and temperate holothurians

Ocean acidification and increased ocean heat content has direct and indirect effects on marine organisms such as holothurians (sea cucumbers) that are vulnerable to changes in pH and temperature. These environmental factors have the potential to influence organismal performance and fitness at different life stages. Tropical and temperate holothurians are more vulnerable to temperature and pH than those from colder water environments. The high level of environmental variation observed in the oceans could influence organismal responses and even produce a wide spectrum of compensatory physiological mechanisms. It is possible that in these areas, larval survival will decline by up to 50% in response to a reduction of 0.5 pH units. Such reduction in pH may trigger low intrinsic growth rates and affect the sustainability of the resource. Here we describe the individual and combined effects that temperature and pH could produce in these organisms. We also describe how these effects can scale from individuals to the population level by using age-structured spatial models in which depensation can be integrated. The approach shows how physiology can improve the conservation of the resource based on the restriction of growth model parameters and by including a density threshold, below which the fitness of the population, specifically intrinsic growth rate, decreases.

Effects of N-acetyl cysteine on TRPM2 expression in kidney and liver tissues following malathion intoxication

We investigated the effects of N-acetyl cysteine (NAC) on transient receptor potential melastatin 2 (TRPM2) channel expression in rat kidney and liver tissues following experimental malathion intoxication. We used seven groups of six male Wistar albino rats: control group, NAC, pralidoxime + atropine, malathion, malathion + pralidoxime + atropine, malathion + pralidoxime + atropine + NAC, and malathion + NAC. Single doses of 100 mg/kg N-acetyl cysteine, 40 mg/kg pralidoxime, 2 mg/kg atropine and 1/3 the lethal dose of malathion were administered. No difference in malondialdehyde (MDA) levels, apoptosis or TRPM2 immunoreactivity was found in liver tissue among the groups. In kidney tissue, MDA levels, apoptosis and TRPM2 immunoreactivity were increased significantly in the malathion and malathion + NAC groups compared to the control group. We found that organophosphate intoxication did not affect MDA, apoptosis or TRPM2 immunoreactivity in rat liver during the acute period. By contrast, we found that in kidney tissue, MDA, apoptosis, and TRPM2 immunoreactivity were increased significantly following administration of malathion. Also, NAC given in addition to pralidoxime and atropine reduced MDA to control levels.

Helminth derived factors inhibit neutrophil extracellular trap formation and inflammation in bacterial peritonitis

Despite their protective antimicrobial function, neutrophil extracellular traps (NETs) have been implicated in propagation of inflammatory responses in several disease conditions including sepsis. Highly diffusible exogenous ROS produced under such inflammatory conditions, can induce exuberant NETs, thus making inhibition of NETs desirable in inflammatory diseases. Here we report that helminth parasite excretory/secretory factors termed as parasitic ligands (PL) inhibit ROS-induced NETs by blocking the activation of nonselective calcium permeable channel Transient Receptor Potential Melastatin 2 (TRPM2). Therapeutic implication of PL mediated blockage of NET formation was tested in preclinical model of septic peritonitis, where PL treatment regulated neutrophil cell death modalities including NET formation and mitigated neutrophil mediated inflammatory response. This translated into improved survival and reduced systemic and local bacterial load in infected mice. Overall, our results posit PL as an important biological regulator of neutrophil functions with implications to a variety of inflammatory diseases including peritonitis.

Serotonin and chronic hypoxic pulmonary hypertension activate a NADPH oxidase 4 and TRPM2 dependent pathway for pulmonary arterial smooth muscle cell proliferation and migration

5-Hydroxytryptamine (5-HT)-dependent signaling mediated through its transporters and receptors plays important roles in chronic hypoxic pulmonary hypertension (CHPH), which is associated with aberrant reactive oxygen species (ROS) production. NADPH oxidase 4 (NOX4) is one of the major sources of ROS in pulmonary vasculature, and has been implicated in the development of PH. NOX4 generates H2O2, which can activate the transient receptor potential melastatin 2 (TRPM2) channels, providing Ca2+ signals for cell proliferation and migration. However, the connection between 5-HT, NOX4, ROS and TRPM2 in the context of PH has not been established. Here we examined the level of 5-HT and expression of NOX4 and TRPM2, and their roles in pulmonary arterial smooth muscle cells (PASMCs) proliferation and migration. NOX4 and TRPM2 were upregulated in pulmonary arteries of CHPH rats, which were associated with elevated levels of 5-HT and ROS, and enhanced proliferation and migration in PASMCs. The increase in ROS, and the enhanced proliferation and migration of PASMCs from CHPH rats were mimicked by treating normoxic PASMCs with 5-HT. 5-HT; and CH-induced ROS production were reversed by catalase, the NOX1/NOX4 inhibitor GKT137831, and Nox4 siRNA. 5-HT and H2O2 elicited Ca2+ responses were significantly augmented in CHPH PASMCs; and the augmented Ca2+ responses were obliterated by the 2-Aminoethoxydiphenyl borate (2-APB) and Trpm2-specific siRNA. Moreover, 5-HT and CH-induced proliferation and migration were suppressed by Nox4 or Trpm2 siRNA; and simultaneous transfection of both siRNA did not cause further inhibition. These results suggest that the 5-HT and CH-induced PASMC proliferation and migration were mediated, at least in part, by TRPM2 via activation of NOX4-dependent ROS production; and revealed a novel NOX4-ROS-TRPM2 signaling pathway for the pathogenesis of CHPH.

TRPM2 ion channels steer neutrophils towards a source of hydrogen peroxide

Neutrophils must navigate accurately towards pathogens in order to destroy invaders and thus defend our bodies against infection. Here we show that hydrogen peroxide, a potent neutrophil chemoattractant, guides chemotaxis by activating calcium-permeable TRPM2 ion channels and generating an intracellular leading-edge calcium "pulse". The thermal sensitivity of TRPM2 activation means that chemotaxis towards hydrogen peroxide is strongly promoted by small temperature elevations, suggesting that an important function of fever may be to enhance neutrophil chemotaxis by facilitating calcium influx through TRPM2. Chemotaxis towards conventional chemoattractants such as LPS, CXCL2 and C5a does not depend on TRPM2 but is driven in a similar way by leading-edge calcium pulses. Other proposed initiators of neutrophil movement, such as PI3K, Rac and lyn, influence chemotaxis by modulating the amplitude of calcium pulses. We propose that intracellular leading-edge calcium pulses are universal drivers of the motile machinery involved in neutrophil chemotaxis.

TRP Channels in Brain Tumors

Malignant glioma including glioblastoma (GBM) is the most common group of primary brain tumors. Despite standard optimized treatment consisting of extensive resection followed by radiotherapy/concomitant and adjuvant therapy, GBM remains one of the most aggressive human cancers. GBM is a typical example of intra-heterogeneity modeled by different micro-environmental situations, one of the main causes of resistance to conventional treatments. The resistance to treatment is associated with angiogenesis, hypoxic and necrotic tumor areas while heterogeneity would accumulate during glioma cell invasion, supporting recurrence. These complex mechanisms require a focus on potential new molecular actors to consider new treatment options for gliomas. Among emerging and underexplored targets, transient receptor potential (TRP) channels belonging to a superfamily of non-selective cation channels which play critical roles in the responses to a number of external stimuli from the external environment were found to be related to cancer development, including glioma. Here, we discuss the potential as biological markers of diagnosis and prognosis of TRPC6, TRPM8, TRPV4, or TRPV1/V2 being associated with glioma patient overall survival. TRPs-inducing common or distinct mechanisms associated with their Ca²⁺-channel permeability and/or kinase function were detailed as involving miRNA or secondary effector signaling cascades in turn controlling proliferation, cell cycle, apoptotic pathways, DNA repair, resistance to treatment as well as migration/invasion. These recent observations of the key role played by TRPs such as TRPC6 in GBM growth and invasiveness, TRPV2 in proliferation and glioma-stem cell differentiation and TRPM2 as channel carriers of cytotoxic chemotherapy within glioma cells, should offer new directions for innovation in treatment strategies of high-grade glioma as GBM to overcome high resistance and recurrence.

Role of Oxidative Stress and Ca2+ Signaling in Psychiatric Disorders

Psychiatric disorders are caused by complex and diverse factors, and numerous mechanisms have been proposed for the pathogenesis of these disorders. Accumulating evidence suggests that oxidative stress is one of the general factors involved in the pathogenesis/pathophysiology of major psychiatric disorders, including bipolar disorder, depression, anxiety disorder, and schizophrenia. Indeed, some clinical trials have shown improvement of the symptoms of these disorders by antioxidant supplementation. However, the molecular basis for the relationship between oxidative stress and the pathogenesis of psychiatric disorders remains largely unknown. In general, Ca2+ channels play central roles in neuronal functions, including neuronal excitability, neurotransmitter release, synaptic plasticity, and gene regulation, and genes that encode Ca2+ channels have been found to be associated with psychiatric disorders. Notably, a class of Ca2+-permeable transient receptor potential (TRP) cation channels is activated by changes in cellular redox status, whereby these TRP channels can link oxidative stress to Ca2+ signals. Given the unique characteristic of redox-sensitive TRP channels, these channels could be a target for delineating the pathogenesis or pathophysiology of psychiatric disorders. In this review, we summarize the outcomes of clinical trials for antioxidant treatment in patients with psychiatric disorders and the current insights into the physiological/pathological significance of redox-sensitive TRP channels in the light of neural functions, including behavioral phenotypes, and discuss the potential role of TRP channels in the pathogenesis of psychiatric disorders. Investigation of redox-sensitive TRP channels may lead to the development of novel therapeutic strategies for the treatment of psychiatric disorders.

Environmental pharmaceuticals and climate change: The case study of carbamazepine in M. galloprovincialis under ocean acidification scenario

Contaminants of emerging concern and ocean changes are key environmental stressors for marine species with possibly synergistic, but still unexplored, deleterious effects. In the present study the influence of a simulated ocean acidification scenario (pH = 7.6) was investigated on metabolism and sub-lethal effects of carbamazepine, CBZ (1 µg/L), chosen as one of the most widely diffused pharmaceuticals in marine organisms. A multidisciplinary approach was applied on mussels, M. galloprovincialis, integrating measurement of drug bioaccumulation with changes in the whole transcriptome, responsiveness of various biochemical and cellular biomarkers including immunological parameters, lipid and oxidative metabolism, onset of genotoxic effects. Chemical analyses revealed a limited influence of hypercapnia on accumulation and excretion of CBZ, while a complex network of biological responses was observed in gene expression profile and functional changes at cellular level. The modulation of gamma-aminobutyric acid (GABA) pathway suggested similarities with the Mechanism of Action known for vertebrates: immune responses, cellular homeostasis and oxidative system represented the processes targeted by combined stressors. The overall elaboration of results through a quantitative Weight of Evidence model, revealed clearly increased cellular hazard due to interactions of CBZ with acidification compared to single stressors.

Neuroprotective Effect of 2-Aminoethoxydiphenyl Borate (2-APB) in Amyloid β-Induced Memory Dysfunction: A Mechanistic Study

β-Amyloid (Aβ) peptide is a characteristic feature of Alzheimer's disease (AD) and accumulation of Aβ is associated with loss of synaptic plasticity and neuronal cell death. Aggregation of Aβ initiates numerous molecular signalling pathways leading to oxidative stress, mitochondrial dysfunction as well as an imbalance of calcium ion influx homeostasis. Recently, it has been shown that transient receptor potential melastatin 2 (TRPM2), a non-selective calcium-permeable cation channel has been postulated to play a vital role in the neuronal death, indicating the potential of TRPM2 inhibition in CNS disease. In this study, neuroprotective potential of 2-aminoethoxydiphenyl borate (2-APB), a broad-spectrum calcium channels blocker was investigated in Aβ-induced memory deficits in rats. In addition, effect of 2-APB on TRPM2 channels gene and protein expressions and also on calcium and memory related proteins was investigated in the hippocampus. Intracerebroventricular (I.C.V.) administration of Aβ (Aβ_25-35, 10 μg) markedly induced cognitive impairment and upregulation of mRNA and protein expression of TRPM2 in the hippocampus. In addition, AChE activity was also increased in the cortex of the Aβ administered animals. Three-week treatment with 2-APB led to the down-regulation of TRPM2 mRNA and protein expression in the hippocampus and also improved the cognitive functions which was evident from the behavioral parameters. Moreover, 2-APB treatment also increased the calcium and memory associated proteins namely p-CaMKII, p-GSK-3β, p-CREB and PSD-95 in the hippocampus and reduced the mRNA level of calcium buffering proteins and calcineurin A (PPP3CA) in the hippocampus. Furthermore, 2-APB treatment significantly reduced the AChE activity in the cortex. Thus, our findings suggest the neuroprotective effect of 2-APB in Aβ-induced cognitive impairment.

Lacking transient receptor potential melastatin 2 attenuates lipopolysaccharide-induced bladder inflammation and its associated hypersensitivity in mice

OBJECTIVE

To study the role of transient receptor potential melastatin 2 in bladder function and inflammation-associated hypersensitivity.

METHODS

We evaluated physiological function of the bladder and intravesical lipopolysaccharide-induced inflammatory nociceptive responses in female wild-type and transient receptor potential melastatin 2-knockout mice. In vivo frequency/volume and decerebrated unanesthetized cystometry measurements, as well as in vitro detrusor strip functional studies, were carried out to evaluate bladder function. Mice received intravesical lipopolysaccharide (2.0 mg/mL) or saline instillation to evaluate responses to bladder inflammation. Voiding and bladder pain-like behaviors, cystometry measurements and histological evaluation were carried out before and after intravesical lipopolysaccharide instillation.

RESULTS

Few phenotypic differences in in vivo and in vitro physiological function were found between the two genotypes. Comparison of measurements taken before and 24-48 h after intravesical lipopolysaccharide instillation showed that voiding parameters did not change in transient receptor potential melastatin 2-knockout mice, whereas an increased voiding frequency was observed in wild-type mice. At 24 h after intravesical lipopolysaccharide instillation, the numbers of bladder pain-like behaviors and of infiltrated inflammatory cells in the bladder submucosal layer were significantly increased, and the voided volume and the intercontraction interval were significantly decreased on cystometry measurements in wild-type mice compared with those in both transient receptor potential melastatin 2-knockout mice and in wild-type mice treated with saline instillation.

CONCLUSIONS

Although the physiological roles of transient receptor potential melastatin 2 channels in the bladder might be limited, inflammation and associated hypersensitivity of the bladder caused by intravesical lipopolysaccharide instillation are attenuated in transient receptor potential melastatin 2-knockout mice, suggesting pathophysiological roles of transient receptor potential melastatin 2 channels in these processes.

Transient Receptor Potential Melastatin 2 (TRPM2) Inhibition by Antioxidant, N-Acetyl-l-Cysteine, Reduces Global Cerebral Ischemia-Induced Neuronal Death

A variety of pathogenic mechanisms, such as cytoplasmic calcium/zinc influx, reactive oxygen species production, and ionic imbalance, have been suggested to play a role in cerebral ischemia induced neurodegeneration. During the ischemic state that occurs after stroke or heart attack, it is observed that vesicular zinc can be released into the synaptic cleft, and then translocated into the cytoplasm via various cation channels. Transient receptor potential melastatin 2 (TRPM2) is highly distributed in the central nervous system and has high sensitivity to oxidative damage. Several previous studies have shown that TRPM2 channel activation contributes to neuroinflammation and neurodegeneration cascades. Therefore, we examined whether anti-oxidant treatment, such as with N-acetyl-l-cysteine (NAC), provides neuroprotection via regulation of TRPM2, following global cerebral ischemia (GCI). Experimental animals were then immediately injected with NAC (150 mg/kg/day) for 3 and 7 days, before sacrifice. We demonstrated that NAC administration reduced activation of GCI-induced neuronal death cascades, such as lipid peroxidation, microglia and astroglia activation, free zinc accumulation, and TRPM2 over-activation. Therefore, modulation of the TRPM2 channel can be a potential therapeutic target to prevent ischemia-induced neuronal death.

Intracellular Ca2+ Signalling in the Pathogenesis of Acute Pancreatitis: Recent Advances and Translational Perspectives

Intracellular Ca²⁺ signalling is a major signal transductional pathway in non-excitable cells, responsible for the regulation of a variety of physiological functions. In the secretory epithelial cells of the exocrine pancreas, such as acinar and ductal cells, intracellular Ca²⁺ elevation regulates digestive enzyme secretion in acini or fluid and ion secretion in ductal cells. Although Ca²⁺ is a uniquely versatile orchestrator of epithelial physiology, unregulated global elevation of the intracellular Ca²⁺ concentration is an early trigger for the development of acute pancreatitis (AP). Regardless of the aetiology, different forms of AP all exhibit sustained intracellular Ca²⁺ elevation as a common hallmark. The release of endoplasmic reticulum (ER) Ca²⁺ stores by toxins (such as bile acids or fatty acid ethyl esters (FAEEs)) or increased intrapancreatic pressure activates the influx of extracellular Ca²⁺ via the Orai1 Ca²⁺ channel, a process known as store-operated Ca²⁺ entry (SOCE). Intracellular Ca²⁺ overload can lead to premature activation of trypsinogen in pancreatic acinar cells and impaired fluid and HCO₃^- secretion in ductal cells. Increased and unbalanced reactive oxygen species (ROS) production caused by sustained Ca²⁺ elevation further contributes to cell dysfunction, leading to mitochondrial damage and cell death. Translational studies of AP identified several potential target molecules that can be modified to prevent intracellular Ca²⁺ overload. One of the most promising drugs, a selective inhibitor of the Orai1 channel that has been shown to inhibit extracellular Ca²⁺ influx and protect cells from injury, is currently being tested in clinical trials. In this review, we will summarise the recent advances in the field, with a special focus on the translational aspects of the basic findings.

Nanoparticle-Mediated Therapeutic Application for Modulation of Lysosomal Ion Channels and Functions

Applications of nanoparticles in various fields have been addressed. Nanomaterials serve as carriers for transporting conventional drugs or proteins through lysosomes to various cellular targets. The basic function of lysosomes is to trigger degradation of proteins and lipids. Understanding of lysosomal functions is essential for enhancing the efficacy of nanoparticles-mediated therapy and reducing the malfunctions of cellular metabolism. The lysosomal function is modulated by the movement of ions through various ion channels. Thus, in this review, we have focused on the recruited ion channels for lysosomal function, to understand the lysosomal modulation through the nanoparticles and its applications. In the future, lysosomal channels-based targets will expand the therapeutic application of nanoparticles-associated drugs.

The protective effect of EGF-activated ROS in human corneal epithelial cells by inducing mitochondrial autophagy via activation TRPM2

Oxidative stress is a major pathogenesis of some ocular surface diseases. Our previous study demonstrated that epidermal growth factor (EGF)-activated reactive oxygen species (ROS) could protect against human corneal epithelial cell (HCE) injury. In the present study, we aimed to explore the role and mechanisms of oxidative stress and mitochondrial autophagy in HCE cells subjected to scratch injury. CCK-8 assays, EdU assays, Western blot analysis, wound-healing assays, and flow cytometry were conducted to determine cell viability, proliferation, protein expression, cell apoptosis, and intracellular ROS levels, respectively. The results showed that EGF could promote damage repair and inhibit cell apoptosis in scratch injured HCE cells by upregulating ROS (**p < .01, ***p < .001). EGF also induced mitochondrial autophagy and alleviated mitochondrial damage. Interestingly, the combination of the mitochondrial autophagy inhibitor and mitochondrial division inhibitor 1 (MDIVI-1) with EGF could reduce cell proliferation, viability, and the ROS level (*p < .05, **p < .01, ***p < .001). Treatment using the ROS inhibitor N-acetyl- l-cysteine abrogated the increase in mitochondrial membrane potential after EGF treatment. (*p < .05). Taken together, these findings indicated that EGF plays an important role in HCE damage repair and could activate ROS to protect against HCE injury by inducing mitochondrial autophagy via activation of TRPM2.

TRPM2-mediated extracellular Ca2+ entry promotes acinar cell necrosis in biliary acute pancreatitis

KEY POINTS

Acute biliary pancreatitis is a significant clinical challenge as currently no specific pharmaceutical treatment exists. Intracellular Ca²⁺ overload, increased reactive oxygen species (ROS) production, mitochondrial damage and intra-acinar digestive enzyme activation caused by bile acids are hallmarks of acute biliary pancreatitis. Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that has recently emerged as an important contributor to oxidative-stress-induced cellular Ca²⁺ overload across different diseases. We demonstrated that TRPM2 is expressed in the plasma membrane of mouse pancreatic acinar and ductal cells, which can be activated by increased oxidative stress induced by H₂ O₂ treatment and contributed to bile acid-induced extracellular Ca²⁺ influx in acinar cells, which promoted acinar cell necrosis in vitro and in vivo. These results suggest that the inhibition of TRPM2 may be a potential treatment option for biliary pancreatitis.

ABSTRACT

Acute biliary pancreatitis poses a significant clinical challenge as currently no specific pharmaceutical treatment exists. Disturbed intracellular Ca²⁺ signalling caused by bile acids is a hallmark of the disease, which induces increased reactive oxygen species (ROS) production, mitochondrial damage, intra-acinar digestive enzyme activation and cell death. Because of this mechanism of action, prevention of toxic cellular Ca²⁺ overload is a promising therapeutic target. Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that has recently emerged as an important contributor to oxidative-stress-induced cellular Ca²⁺ overload across different diseases. However, the expression and possible functions of TRPM2 in the exocrine pancreas remain unknown. Here we found that TRPM2 is expressed in the plasma membrane of mouse pancreatic acinar and ductal cells, which can be activated by increased oxidative stress induced by H₂ O₂ treatment. TRPM2 activity was found to contribute to bile acid-induced extracellular Ca²⁺ influx in acinar cells, but did not have the same effect in ductal cells. The generation of intracellular ROS in response to bile acids was remarkably higher in pancreatic acinar cells compared to isolated ducts, which can explain the difference between acinar and ductal cells. This activity promoted acinar cell necrosis in vitro independently from mitochondrial damage or mitochondrial fragmentation. In addition, bile-acid-induced experimental pancreatitis was less severe in TRPM2 knockout mice, whereas the lack of TRPM2 had no protective effect in cerulein-induced acute pancreatitis. Our results suggest that the inhibition of TRPM2 may be a potential treatment option for biliary pancreatitis.

The TRPM2 Ion Channel Regulates Inflammatory Functions of Neutrophils During Listeria monocytogenes Infection

During infection, phagocytic cells pursue homeostasis in the host via multiple mechanisms that control microbial invasion. Neutrophils respond to infection by exerting a variety of cellular processes, including chemotaxis, activation, phagocytosis, degranulation and the generation of reactive oxygen species (ROS). Calcium (Ca²⁺) signaling and the activation of specific Ca²⁺ channels are required for most antimicrobial effector functions of neutrophils. The transient receptor potential melastatin-2 (TRPM2) cation channel has been proposed to play important roles in modulating Ca²⁺ mobilization and oxidative stress in neutrophils. In the present study, we use a mouse model of Listeria monocytogenes infection to define the role of TRPM2 in the regulation of neutrophils' functions during infection. We show that the susceptibility of Trpm2^−/− mice to L. monocytogenes infection is characterized by increased migration rates of neutrophils and monocytes to the liver and spleen in the first 24 h. During the acute phase of L. monocytogenes infection, Trpm2^−/− mice developed septic shock, characterized by increased serum levels of TNF-α, IL-6, and IL-10. Furthermore, in vivo depletion of neutrophils demonstrated a critical role of these immune cells in regulating acute inflammation in Trpm2^−/− infected mice. Gene expression and inflammatory cytokine analyses of infected tissues further confirmed the hyperinflammatory profile of Trpm2^−/− neutrophils. Finally, the increased inflammatory properties of Trpm2^−/− neutrophils correlated with the dysregulated cytoplasmic concentration of Ca²⁺ and potentiated membrane depolarization, in response to L. monocytogenes. In conclusion, our findings suggest that the TRPM2 channel plays critical functional roles in regulating the inflammatory properties of neutrophils and preventing tissue damage during Listeria infection.

A Role for H2O2 and TRPM2 in the Induction of Cell Death: Studies in KGN Cells

Recent studies showed that KGN cells, derived from a human granulosa cell tumor (GCT), express NADPH oxidase 4 (NOX4), an important source of H₂O₂. Transient receptor potential melastatin 2 (TRPM2) channel is a Ca²⁺ permeable cation channel that can be activated by H₂O₂ and plays an important role in cellular functions. It is also able to promote susceptibility to cell death. We studied expression and functionality of TRPM2 in KGN cells and examined GCT tissue microarrays (TMAs) to explore in vivo relevance. We employed live cell, calcium and mitochondrial imaging, viability assays, fluorescence activated cell sorting (FACS) analysis, Western blotting and immunohistochemistry. We confirmed that KGN cells produce H₂O₂ and found that they express functional TRPM2. H₂O₂ increased intracellular Ca²⁺ levels and N-(p-Amylcinnamoyl)anthranilic acid (ACA), a TRPM2 inhibitor, blocked this action. H₂O₂ caused mitochondrial fragmentation and apoptotic cell death, which could be attenuated by a scavenger (Trolox). Immunohistochemistry showed parallel expression of NOX4 and TRPM2 in all 73 tumor samples examined. The results suggest that GCTs can be endowed with a system that may convey susceptibility to cell death. If so, induction of oxidative stress may be beneficial in GCT therapy. Our results also imply a therapeutic potential for TRPM2 as a drug target in GCTs.

Trpm2 enhances physiological bioenergetics and protects against pathological oxidative cardiac injury: Role of Pyk2 phosphorylation

The mechanisms by which Trpm2 channels enhance mitochondrial bioenergetics and protect against oxidative stress-induced cardiac injury remain unclear. Here, the role of proline-rich tyrosine kinase 2 (Pyk2) in Trpm2 signaling is explored. Activation of Trpm2 in adult myocytes with H₂ O₂ resulted in 10- to 21-fold increases in Pyk2 phosphorylation in wild-type (WT) myocytes which was significantly lower (~40%) in Trpm2 knockout (KO) myocytes. Pyk2 phosphorylation was inhibited (~54%) by the Trpm2 blocker clotrimazole. Buffering Trpm2-mediated Ca²⁺ increase with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) resulted in significantly reduced pPyk2 in WT but not in KO myocytes, indicating Ca²⁺ influx through activated Trpm2 channels phosphorylated Pyk2. Part of phosphorylated Pyk2 translocated from cytosol to mitochondria which has been previously shown to augment mitochondrial Ca²⁺ uptake and enhance adenosine triphosphate generation. Although Trpm2-mediated Ca²⁺ influx phosphorylated Ca²⁺ -calmodulin kinase II (CaMKII), the CaMKII inhibitor KN93 did not significantly affect Pyk2 phosphorylation in H₂ O₂ -treated WT myocytes. After ischemia/reperfusion (I/R), Pyk2 phosphorylation and its downstream prosurvival signaling molecules (pERK1/2 and pAkt) were significantly lower in KO-I/R when compared with WT-I/R hearts. After hypoxia/reoxygenation, mitochondrial membrane potential was lower and superoxide level was higher in KO myocytes, and were restored to WT values by the mitochondria-targeted superoxide scavenger MitoTempo. Our results suggested that Ca²⁺ influx via tonically activated Trpm2 phosphorylated Pyk2, part of which translocated to mitochondria, resulting in better mitochondrial bioenergetics to maintain cardiac health. After I/R, Pyk2 activated prosurvival signaling molecules and prevented excessive increases in reactive oxygen species, thereby affording protection from I/R injury.

Mechanism of TRPM2 channel gating revealed by cryo-EM

Transient receptor potential melastatin 2 (TRPM2) is a non-selective cation channel that allows Ca²⁺ influx across the plasma membrane and efflux from lysosomes upon opening. TRPM2 is best known as a biosensor of reactive oxygen species (ROS), which mediates some of the body's responses to oxidative stress. As such, TRPM2 is involved in a plethora of biological processes including immune response, insulin secretion, body temperature control and neuronal cell death, and represents an emerging therapeutic target for many human diseases, from diabetes to inflammatory and neurodegenerative diseases. A direct ligand of TRPM2 is ADP-ribose (ADPR), which accumulates in cells at high levels of ROS, and activates TRPM2 synergistically with intracellular calcium (Ca²⁺ ). Here, we describe recent cryo-electron microscopy (cryo-EM) structures of TRPM2 and summarize the insights they provided into the gating mechanism of the channel.

Pharmacology of JNJ-28583113: A novel TRPM2 antagonist

Transient receptor potential melastatin type 2 (TRPM2) is a cation channel activated by free intracellular ADP-ribose and reactive oxygen species. TRPM2 signaling has been linked to the pathophysiology of CNS disorders such as neuropathic pain, bipolar disorder and Alzheimer's disease. In this manuscript, we describe the discovery of JNJ-28583113, a potent brain penetrant TRPM2 antagonist. Ca²⁺ flux assays in cells overexpressing TRPM2 and electrophysiological recordings were used to test the pharmacology of JNJ-28583113. JNJ-28583113 was assayed in vitro on GSK-3 phosphorylation levels, cell death, cytokine release in microglia and unbiased morphological phenotypic analysis. Finally, we dosed animals to evaluate its pharmacokinetic properties. Our results showed that JNJ-28583113 is a potent (126 ± 0.5 nM) TRPM2 antagonist. Blocking TRPM2 caused phosphorylation of GSK3α and β subunits. JNJ-28583113 also protected cells from oxidative stress induced cell death as well as morphological changes induced by non-cytotoxic concentrations of H₂O₂. In addition, inhibiting TRPM2 blunted cytokine release in response to pro-inflammatory stimuli in microglia. Lastly, we showed that JNJ-28583113 was brain penetrant but not suitable for systemic dosing as it was rapidly metabolized in vivo. While the in-vitro pharmacology of JNJ-28583113 is the best in class, its in-vivo properties would need optimization to assist in further probing key roles of TRPM2 in CNS pathophysiology.

TRPM2 ion channel promotes gastric cancer migration, invasion and tumor growth through the AKT signaling pathway

Transient Receptor Potential Melastatin-2 (TRPM2) ion channel is emerging as a great therapeutic target in many types of cancer, including gastric cancer - a major health threat of cancer related-death worldwide. Our previous study demonstrated the critical role of TRPM2 in gastric cancer cells bioenergetics and survival; however, its role in gastric cancer metastasis, the major cause of patient death, remains unknown. Here, using molecular and functional assays, we demonstrate that TRPM2 downregulation significantly inhibits the migration and invasion abilities of gastric cancer cells, with a significant reversion in the expression level of metastatic markers. These effects were concomitant with decreased Akt and increased PTEN activities. Finally, TRPM2 silencing resulted in deregulation of metastatic markers and abolished the tumor growth ability of AGS gastric cancer cells in NOD/SCID mice. Taken together, our results provide compelling evidence on the important function of TRPM2 in the modulation of gastric cancer cell invasion likely through controlling the PTEN/Akt pathway.

TRPM2 Channel in Microglia as a New Player in Neuroinflammation Associated With a Spectrum of Central Nervous System Pathologies

Microglial cells in the central nervous system (CNS) are crucial in maintaining a healthy environment for neurons to function properly. However, aberrant microglial cell activation can lead to excessive generation of neurotoxic proinflammatory mediators and neuroinflammation, which represents a contributing factor in a wide spectrum of CNS pathologies, including ischemic stroke, traumatic brain damage, Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, psychiatric disorders, autism spectrum disorders, and chronic neuropathic pain. Oxidative stress is a salient and common feature of these conditions and has been strongly implicated in microglial cell activation and neuroinflammation. The transient receptor potential melastatin-related 2 (TRPM2) channel, an oxidative stress-sensitive calcium-permeable cationic channel, is highly expressed in microglial cells. In this review, we examine the recent studies that provide evidence to support an important role for the TRPM2 channel, particularly TRPM2-mediated Ca²⁺ signaling, in mediating microglial cell activation, generation of proinflammatory mediators and neuroinflammation, which are of relevance to CNS pathologies. These findings lead to a growing interest in the TRPM2 channel, a new player in neuroinflammation, as a novel therapeutic target for CNS diseases.

The ion channel, TRPM2, contributes to the pathogenesis of radiodermatitis

Radiodermatitis is a painful side effect for cancer patients undergoing radiotherapy. Irradiation of the skin causes inflammation and breakdown of the epidermis and can lead to significant morbidity and mortality in severe cases, as seen in exposure from accidents or weapons such as "dirty bombs" and ultimately leads to tissue fibrosis. However, the pathogenesis of radiodermatitis is not fully understood. Using a mouse model of radiodermatitis, we showed that the Transient Receptor Potential Melastatin 2 (TRPM2) ion channel plays a significant role in the development of dermatitis following exposure to ionizing radiation. Irradiated TRPM2-deficient mice developed less inflammation, fewer severe skin lesions and decreased fibrosis when compared to wild type mice. The TRPM2-deficient mice also showed a faster recovery period as seen by their increased weight gain post irradiation. Finally, TRPM2-deficient mice exhibited lower systemic inflammation with a reduction in inflammatory cytokines present in the serum. These findings suggest that TRPM2 may be a potential therapeutic target for reducing the severity of radiodermatitis.

Carvacrol Attenuates Hippocampal Neuronal Death after Global Cerebral Ischemia via Inhibition of Transient Receptor Potential Melastatin 7

Over the last two decades, evidence supporting the concept of zinc-induced neuronal death has been introduced, and several intervention strategies have been investigated. Vesicular zinc is released into the synaptic cleft, where it then translocates to the cytoplasm, which leads to the production of reactive oxygen species and neurodegeneration. Carvacrol inhibits transient receptor potential melastatin 7 (TRPM7), which regulates the homeostasis of extracellular metal ions, such as calcium and zinc. In the present study, we test whether carvacrol displays any neuroprotective effects after global cerebral ischemia (GCI), via a blockade of zinc influx. To test our hypothesis, we used eight-week-old male Sprague–Dawley rats, and a GCI model was induced by bilateral common carotid artery occlusion (CCAO), accompanied by blood withdrawal from the femoral artery. Ischemic duration was defined as a seven-minute electroencephalographic (EEG) isoelectric period. Carvacrol (50 mg/kg) was injected into the intraperitoneal space once per day for three days after the onset of GCI. The present study found that administration of carvacrol significantly decreased the number of degenerating neurons, microglial activation, oxidative damage, and zinc translocation after GCI, via downregulation of TRPM7 channels. These findings suggest that carvacrol, a TRPM7 inhibitor, may have therapeutic potential after GCI by reducing intracellular zinc translocation.

The TRPM2 channel nexus from oxidative damage to Alzheimer's pathologies: An emerging novel intervention target for age-related dementia

Alzheimer's disease (AD), an age-related neurodegenerative condition, is the most common cause of dementia among the elder people, but currently there is no treatment. A number of putative pathogenic events, particularly amyloid β peptide (Aβ) accumulation, are believed to be early triggers that initiate AD. However, thus far targeting Aβ generation/aggregation as the mainstay strategy of drug development has not led to effective AD-modifying therapeutics. Oxidative damage is a conspicuous feature of AD, but this remains poorly defined phenomenon and mechanistically ill understood. The TRPM2 channel has emerged as a potentially ubiquitous molecular mechanism mediating oxidative damage and thus plays a vital role in the pathogenesis and progression of diverse neurodegenerative diseases. This article will review the emerging evidence from recent studies and propose a novel 'hypothesis' that multiple TRPM2-mediated cellular and molecular mechanisms cascade Aβ and/or oxidative damage to AD pathologies. The 'hypothesis' based on these new findings discusses the prospect of considering the TRPM2 channel as a novel therapeutic target for intervening AD and age-related dementia.

Trpm2 Ablation Accelerates Protein Aggregation by Impaired ADPR and Autophagic Clearance in the Brain

TRPM2 a cation channel is also known to work as an enzyme that hydrolyzes highly reactive, neurotoxic ADP-ribose (ADPR). Although ADPR is hydrolyzed by NUT9 pyrophosphatase in major organs, the enzyme is defective in the brain. The present study questions the role of TRPM2 in the catabolism of ADPR in the brain. Genetic ablation of Trpm2 results in the disruption of ADPR catabolism that leads to the accumulation of ADPR and reduction in AMP. Trpm2^−/− mice elicit the reduction in autophagosome formation in the hippocampus. Trpm2^−/− mice also show aggregations of proteins in the hippocampus, aberrant structural changes and neuronal connections in synapses, and neuronal degeneration. Trpm2^−/− mice exhibit learning and memory impairment, enhanced neuronal intrinsic excitability, and imbalanced synaptic transmission. These results respond to long-unanswered questions regarding the potential role of the enzymatic function of TRPM2 in the brain, whose dysfunction evokes protein aggregation. In addition, the present finding answers to the conflicting reports such as neuroprotective or neurodegenerative phenotypes observed in Trpm2^−/− mice.

Oxidative stress promotes redistribution of TRPM2 channels to the plasma membrane in hepatocytes

Transient Receptor Potential Melastatin (TRPM) 2 is a non-selective Ca²⁺ permeable cation channel and a member of the Transient Receptor Potential (TRP) channel family. TRPM2 has unique gating properties; it is activated by intracellular ADP-ribose (ADPR), whereas Ca²⁺ plays a role of an important co-factor in channel activation, increasing TRPM2 sensitivity to ADPR. TRPM2 is highly expressed in rat and mouse hepatocytes, where it has been shown to contribute to oxidative stress-induced cell death and liver damage due to paracetamol-overdose. The mechanisms regulating the activity of TRPM2 channels in hepatocytes, however, are not well understood. In this paper, we investigate the localisation of TRPM2 protein in hepatocytes. The presented results demonstrate that in rat hepatocytes under normal conditions, most of the TRPM2 protein is localised intracellularly. This was determined by confocal microscopy using TRPM2-and plasma membrane (PM)-specific antibodies and immunofluorescence, and biotinylation studies followed by western blotting. Interestingly, in hepatocytes treated with either H₂O₂ or paracetamol, the amount of TRPM2 co-localised with PM is significantly increased, compared to the untreated cells. It is concluded that trafficking of TRPM2 to the PM could potentially contribute to a positive feedback mechanism mediating Ca²⁺ overload in hepatocytes under conditions of oxidative stress.

TRPM2 in the Brain: Role in Health and Disease

Transient receptor potential (TRP) proteins have been implicated in several cell functions as non-selective cation channels, with about 30 different mammalian TRP channels having been recognized. Among them, TRP-melastatin 2 (TRPM2) is particularly involved in the response to oxidative stress and inflammation, while its activity depends on the presence of intracellular calcium (Ca²⁺). TRPM2 is involved in several physiological and pathological processes in the brain through the modulation of multiple signaling pathways. The aim of the present review is to provide a brief summary of the current insights of TRPM2 role in health and disease to focalize our attention on future potential neuroprotective strategies.

TRP Channel Involvement in Salivary Glands-Some Good, Some Bad

Salivary glands secrete saliva, a mixture of proteins and fluids, which plays an extremely important role in the maintenance of oral health. Loss of salivary secretion causes a dry mouth condition, xerostomia, which has numerous deleterious consequences including opportunistic infections within the oral cavity, difficulties in eating and swallowing food, and problems with speech. Secretion of fluid by salivary glands is stimulated by activation of specific receptors on acinar cell plasma membrane and is mediated by an increase in cytosolic [Ca²⁺] ([Ca²⁺]_i). The increase in [Ca²⁺]_i regulates a number of ion channels and transporters that are required for establishing an osmotic gradient that drives water flow via aquaporin water channels in the apical membrane. The Store-Operated Ca²⁺ Entry (SOCE) mechanism, which is regulated in response to depletion of ER-Ca²⁺, determines the sustained [Ca²⁺]_i increase required for prolonged fluid secretion. Core components of SOCE in salivary gland acinar cells are Orai1 and STIM1. In addition, TRPC1 is a major and non-redundant contributor to SOCE and fluid secretion in salivary gland acinar and ductal cells. Other TRP channels that contribute to salivary flow are TRPC3 and TRPV4, while presence of others, including TRPM8, TRPA1, TRPV1, and TRPV3, have been identified in the gland. Loss of salivary gland function leads to dry mouth conditions, or xerostomia, which is clinically seen in patients who have undergone radiation treatment for head-and-neck cancers, and those with the autoimmune exocrinopathy, Sjögren’s syndrome (pSS). TRPM2 is a unique TRP channel that acts as a sensor for intracellular ROS. We will discuss recent studies reported by us that demonstrate a key role for TRPM2 in radiation-induced salivary gland dysfunction. Further, there is increasing evidence that TRPM2 might be involved in inflammatory processes. These interesting findings point to the possible involvement of TRPM2 in Sjögren’s Syndrome, although further studies will be required to identify the exact role of TRPM2 in this disease.

Oxidant sensor cation channel TRPM2 regulates neutrophil extracellular trap formation and protects against pneumoseptic bacterial infection

Neutrophil extracellular trap (NET) formation constitutes an important extracellular antimicrobial function of neutrophils that plays a protective role in bacterial pneumonia. Formation of reactive oxygen species (ROS) such as highly diffusible hydrogen peroxide (H2O2) is a hallmark of oxidative stress during inflammatory lung conditions including pneumonia. However, the impact of exogenous ROS on NET formation and the signaling pathway involved in the process is not completely understood. Here we demonstrate that the ROS-sensing, nonselective, calcium-permeable channel transient receptor potential melastatin 2 (TRPM2) is required for NET formation in response to exogenous H2O2. This TRPM2-dependent H2O2-mediated NET formation involved components of autophagy and activation of AMPK and p38 MAPK, but not PI3K and AKT. Primary neutrophils from Trpm2-/- mice fail to activate this pathway with a block in NET release and a concomitant decrease in their antimicrobial capacity. Consequently, Trpm2-/- mice were highly susceptible to pneumonic infection with Klebsiella pneumoniae owing to an impaired NET formation and high bacterial burden despite increased neutrophil infiltration in their lungs. These results identify a key role of TRPM2 in regulating NET formation by exogenous ROS via AMPK/p38 activation and autophagy machinery, as well as a protective antimicrobial role of TRPM2 in pneumonic bacterial infection.-Tripathi, J. K., Sharma, A., Sukumaran, P., Sun, Y., Mishra, B. B., Singh, B. B., Sharma, J. Oxidant sensor cation channel TRPM2 regulates neutrophil extracellular trap formation and protects against pneumoseptic bacterial infection.

TRPM2: a candidate therapeutic target for treating neurological diseases

Transient receptor potential melastatin 2 (TRPM2) is a calcium (Ca²⁺)-permeable non-selective cation channel belonging to the TRP ion channel family. Oxidative stress-induced TRPM2 activation provokes aberrant intracellular Ca²⁺ accumulation and cell death in a variety of cell types, including neurons. Aberrant TRPM2 function has been implicated in several neurological disorders including ischemia/stroke, Alzheimer's disease, neuropathic pain, Parkinson's disease and bipolar disorder. In addition to research identifying a role for TRPM2 in disease, progress has been made in the identification of physiological functions of TRPM2 in the brain, including recent evidence that TRPM2 is necessary for the induction of N-methyl-D-aspartate (NMDA) receptor-dependent long-term depression, an important form of synaptic plasticity at glutamate synapses. Here, we summarize recent evidence on the role of TRPM2 in the central nervous system (CNS) in health and disease and discuss the potential therapeutic implications of targeting TRPM2. Collectively, these studies suggest that TRPM2 represents a prospective novel therapeutic target for neurological disorders.

Design, synthesis and biological activities of 2,3-dihydroquinazolin-4(1H)-one derivatives as TRPM2 inhibitors

Transient receptor potential melastatin 2 (TRPM2), a Ca²⁺-permeable cationic channel, plays critical roles in insulin release, cytokine production, body temperature regulation and cell death as a reactive oxygen species (ROS) and temperature sensor. However, few TRPM2 inhibitors have been reported, especially TRP-subtype selective inhibitors, which hampers the investigation and validation of TRPM2 as a drug target. To discover novel TRPM2 inhibitors, 3D similarity-based virtual screening method was employed, by which 2,3-dihydroquinazolin-4(1H)-one derivative H1 was identified as a TRPM2 inhibitor. A series of novel 2,3-dihydroquinazolin-4(1H)-one derivatives were subsequently synthesized and characterized. Their inhibitory activities against the TRPM2 channel were evaluated by calcium imaging and electrophysiology approaches. Some of the compounds exhibited significant inhibitory activity, especially D9 which showed an IC₅₀ of 3.7 μM against TRPM2 and did not affect the TRPM8 channel. The summarized structure-activity relationship (SAR) provides valuable insights for further development of specific TRPM2 targeted inhibitors.

TRPV4 inhibition attenuates stretch-induced inflammatory cellular responses and lung barrier dysfunction during mechanical ventilation

Mechanical ventilation is an important tool for supporting critically ill patients but may also exert pathological forces on lung cells leading to Ventilator-Induced Lung Injury (VILI). We hypothesised that inhibition of the force-sensitive transient receptor potential vanilloid (TRPV4) ion channel may attenuate the negative effects of mechanical ventilation. Mechanical stretch increased intracellular Ca²⁺ influx and induced release of pro-inflammatory cytokines in lung epithelial cells that was partially blocked by about 30% with the selective TRPV4 inhibitor GSK2193874, but nearly completely blocked with the pan-calcium channel blocker ruthenium red, suggesting the involvement of more than one calcium channel in the response to mechanical stress. Mechanical stretch also induced the release of pro-inflammatory cytokines from M1 macrophages, but in contrast this was entirely dependent upon TRPV4. In a murine ventilation model, TRPV4 inhibition attenuated both pulmonary barrier permeability increase and pro-inflammatory cytokines release due to high tidal volume ventilation. Taken together, these data suggest TRPV4 inhibitors may have utility as a prophylactic pharmacological treatment to improve the negative pathological stretch-response of lung cells during ventilation and potentially support patients receiving mechanical ventilation.