Selenium prevents interferon-gamma induced activation of TRPM2 channel and inhibits inflammation, mitochondrial oxidative stress, and apoptosis in microglia

The Neurodegenerative Hypothesis of Depression and the Influence of Antidepressant Medications

Depression is a complex neurological disease that holds many theories on its aetiology and pathophysiology. The monoamine strategy of treating depression with medications to increase levels of monoamines in the (extra)synapse, primarily through the inhibition of monoamine transporters, does not always work, as seen in patients that lack a response to multiple anti-depressant exposures, as well as a lack of depressive symptoms in healthy volunteers exposed to monoamine reduction. Depression is increasingly being understood not as a single condition, but as a complex interplay of adaptations in various systems, including inflammatory responses and neurotransmission pathways in the brain. This understanding has led to the development of the neurodegenerative hypothesis of depression. This hypothesis, which is gaining widespread acceptance posits that both oxidative stress and inflammation play significant roles in the pathophysiology of depression. This article is a review of the literature focused on neuroinflammation in depression, as well as summarised studies of anti-inflammatory and antioxidant effects of antidepressants.

TRP Ion Channels in Immune Cells and Their Implications for Inflammation

The transient receptor potential (TRP) ion channels act as cellular sensors and mediate a plethora of physiological processes, including somatosensation, proliferation, apoptosis, and metabolism. Under specific conditions, certain TRP channels are involved in inflammation and immune responses. Thus, focusing on the role of TRPs in immune system cells may contribute to resolving inflammation. In this review, we discuss the distribution of five subfamilies of mammalian TRP ion channels in immune system cells and how these ion channels function in inflammatory mechanisms. This review provides an overview of the current understanding of TRP ion channels in mediating inflammation and may offer potential avenues for therapeutic intervention.

TRPM2 knockdown attenuates myocardial apoptosis and promotes autophagy in HFD/STZ-induced diabetic mice via regulating the MEK/ERK and mTORC1 signaling pathway

Diabetic cardiomyopathy (DCM) is a major complication of diabetes. Transient receptor potential melastatin 2 (TRPM2) activity increases in diabetic oxidative stress state, and it is involved in myocardial damage and repair. We explore the protective effect of TRPM2 knockdown on the progression of DCM. A type 2 diabetes animal model was established in C57BL/6N mice by long-term high-fat diet (HFD) feeding combined with a single injection of 100-mg/kg streptozotocin (STZ). Genetic knockdown of TRPM2 in heart was accomplished by the intravenous injection via the tail vein of adeno-associated virus type 9 carrying TRPM2 shRNA. Neonatal rat ventricular myocytes was exposed to 45 mM of high-glucose (HG) stimulation for 72 h in vitro to mimic the in vivo conditions. Western blot, real-time quantitative PCR (RT-qPCR), immunohistochemistry and fluorescence, electron, CCK-8, and flow cytometry were used to evaluate the phenotype of cardiac inflammation, fibrosis, apoptosis, and autophagy. Mice with HFD/STZ-induced diabetes exhibited systolic and diastolic dysfunction, as demonstrated by increased myocardial apoptosis and autophagy inhibition in the heart. Compared to control group, the protein expression of TRPM2, bax, cleaved caspase-3, and P62 was significantly elevated, and the protein expression of bcl-2 and LC3-II was significantly decreased in the myocardial tissues of the HFD/STZ-induced diabetes group. Knockdown of TRPM2 significantly reversed the HFD/STZ-induced myocardial apoptosis and autophagy inhibition. TRPM2 silencing attenuated HG-induced apoptosis and autophagy inhibition in primary cardiomyocytes via regulating the MEK/ERK mTORC1 signaling pathway. TRPM2 knockdown attenuates hyperglycemia-induced myocardial apoptosis and promotes autophagy in HFD/STZ-induced diabetic mice or HG-stimulated cardiomyocytes via regulating the MEK/ERK and mTORC1 signaling pathway.

Blood-cerebrospinal fluid barrier permeability of metals/metalloids and its determinants in pediatric patients

Concerns regarding adverse effects of metal/metalloids exposure on brain development and neurological disorders among children are increasing. However, the transport patterns of metals/metalloids across the blood-cerebrospinal fluid barrier (BCSFB) need to be clarified in children. A total of 99 Chinese pediatric patients were enrolled from February 2020 to August 2021, with a median age of 6.76 months. We detected 16 metal/metalloid levels in matched serum and cerebrospinal fluid (CSF) samples using inductively coupled plasma mass spectrometry. The BCSFB permeability of metals/metalloids were estimated and the potential effects of biomedical parameters were explored. Most metals/metalloids were detectable among > 80.0% of CSF samples. Significant correlations were observed between strontium (Sr, r = 0.46), molybdenum (Mo, r = 0.50), and cadmium (Cd, r = 0.24) concentrations in serum and CSF (P < 0.05). Ratios of metal/metalloid levels in CSF to serum (Rmetal) ranged from 0.02 to 0.74, and hazardous metals/metalloids including arsenic (As), Cd, lead (Pb), thallium (Tl), and manganese (Mn) showed high transfer efficiencies across the BCSFB (Rmetals > 0.5). With the adjustment of age and sex, albumin, β2-microglobulin, and total protein levels in CSF were positively associated with copper (Cu) permeability (FDR-adjusted P < 0.05), while glucose in CSF was negatively correlated with calcium (Ca), Cu, Sr, and Mo BCSFB permeability (FDR-adjusted P < 0.05). Q-Alb promoted Cu permeability across the BCSFB (FDR-adjusted P < 0.001), while C-reactive protein levels in serum were positively associated with selenium (Se) permeability (FDR-adjusted P = 0.046). For the first time, our findings provided data for the BCSFB permeability of 16 metals/metalloids in children, and indicated that some biomedical parameters could influence the transformation of metals/metalloids from serum to CSF. Metals/metalloids with strong BCSFB permeability warrant attention for their potential neurotoxicity.

Modulating mitochondrial calcium channels (TRPM2/MCU/NCX) as a therapeutic strategy for neurodegenerative disorders

Efficient cellular communication is essential for the brain to regulate diverse functions like muscle contractions, memory formation and recall, decision-making, and task execution. This communication is facilitated by rapid signaling through electrical and chemical messengers, including voltage-gated ion channels and neurotransmitters. These messengers elicit broad responses by propagating action potentials and mediating synaptic transmission. Calcium influx and efflux are essential for releasing neurotransmitters and regulating synaptic transmission. Mitochondria, which are involved in oxidative phosphorylation, and the energy generation process, also interact with the endoplasmic reticulum to store and regulate cytoplasmic calcium levels. The number, morphology, and distribution of mitochondria in different cell types vary based on energy demands. Mitochondrial damage can cause excess reactive oxygen species (ROS) generation. Mitophagy is a selective process that targets and degrades damaged mitochondria via autophagosome-lysosome fusion. Defects in mitophagy can lead to a buildup of ROS and cell death. Numerous studies have attempted to characterize the relationship between mitochondrial dysfunction and calcium dysregulation in neurodegenerative diseases such as Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Amyotrophic lateral sclerosis, spinocerebellar ataxia, and aging. Interventional strategies to reduce mitochondrial damage and accumulation could serve as a therapeutic target, but further research is needed to unravel this potential. This review offers an overview of calcium signaling related to mitochondria in various neuronal cells. It critically examines recent findings, exploring the potential roles that mitochondrial dysfunction might play in multiple neurodegenerative diseases and aging. Furthermore, the review identifies existing gaps in knowledge to guide the direction of future research.

Cell death induction and protection by activation of ubiquitously expressed anion/cation channels. Part 3: the roles and properties of TRPM2 and TRPM7

Cell volume regulation (CVR) is a prerequisite for animal cells to survive and fulfill their functions. CVR dysfunction is essentially involved in the induction of cell death. In fact, sustained normotonic cell swelling and shrinkage are associated with necrosis and apoptosis, and thus called the necrotic volume increase (NVI) and the apoptotic volume decrease (AVD), respectively. Since a number of ubiquitously expressed ion channels are involved in the CVR processes, these volume-regulatory ion channels are also implicated in the NVI and AVD events. In Part 1 and Part 2 of this series of review articles, we described the roles of swelling-activated anion channels called VSOR or VRAC and acid-activated anion channels called ASOR or PAC in CVR and cell death processes. Here, Part 3 focuses on therein roles of Ca2+-permeable non-selective TRPM2 and TRPM7 cation channels activated by stress. First, we summarize their phenotypic properties and molecular structure. Second, we describe their roles in CVR. Since cell death induction is tightly coupled to dysfunction of CVR, third, we focus on their participation in the induction of or protection against cell death under oxidative, acidotoxic, excitotoxic, and ischemic conditions. In this regard, we pay attention to the sensitivity of TRPM2 and TRPM7 to a variety of stress as well as to their capability to physicall and functionally interact with other volume-related channels and membrane enzymes. Also, we summarize a large number of reports hitherto published in which TRPM2 and TRPM7 channels are shown to be involved in cell death associated with a variety of diseases or disorders, in some cases as double-edged swords. Lastly, we attempt to describe how TRPM2 and TRPM7 are organized in the ionic mechanisms leading to cell death induction and protection.

Unveiling the Link: Exploring Mitochondrial Dysfunction as a Probable Mechanism of Hepatic Damage in Post-Traumatic Stress Syndrome

PTSD is associated with disturbed hepatic morphology and metabolism. Neuronal mitochondrial dysfunction is considered a subcellular determinant of PTSD, but a link between hepatic mitochondrial dysfunction and hepatic damage in PTSD has not been demonstrated. Thus, the effects of experimental PTSD on the livers of high anxiety (HA) and low anxiety (LA) rats were compared, and mitochondrial determinants underlying the difference in their hepatic damage were investigated. Rats were exposed to predator stress for 10 days. Then, 14 days post-stress, the rats were evaluated with an elevated plus maze and assigned to HA and LA groups according to their anxiety index. Experimental PTSD caused dystrophic changes in hepatocytes of HA rats and hepatocellular damage evident by increased plasma ALT and AST activities. Mitochondrial dysfunction was evident as a predominance of small-size mitochondria in HA rats, which was positively correlated with anxiety index, activities of plasma transaminases, hepatic lipids, and negatively correlated with hepatic glycogen. In contrast, LA rats had a predominance of medium-sized mitochondria. Thus, we show links between mitochondrial dysfunction, hepatic damage, and heightened anxiety in PTSD rats. These results will provide a foundation for future research on the role of hepatic dysfunction in PTSD pathogenesis.

TRPM2-mediated Ca2+ signaling as a potential therapeutic target in cancer treatment: an updated review of its role in survival and proliferation of cancer cells

The transient receptor potential melastatin subfamily member 2 (TRPM2), a thermo and reactive oxygen species (ROS) sensitive Ca²⁺-permeable cation channel has a vital role in surviving the cell as well as defending the adaptability of various cell groups during and after oxidative stress. It shows higher expression in several cancers involving breast, pancreatic, prostate, melanoma, leukemia, and neuroblastoma, indicating it raises the survivability of cancerous cells. In various cancers including gastric cancers, and neuroblastoma, TRPM2 is known to conserve viability, and several underlying mechanisms of action have been proposed. Transcription factors are thought to activate TRPM2 channels, which is essential for cell proliferation and survival. In normal physiological conditions with an optimal expression of TRPM2, mitochondrial ROS is produced in optimal amounts while regulation of antioxidant expression is carried on. Depletion of TRPM2 overexpression or activity has been shown to improve ischemia-reperfusion injury in organ levels, reduce tumor growth and/or viability of various malignant cancers like breast, gastric, pancreatic, prostate, head and neck cancers, melanoma, neuroblastoma, T-cell and acute myelogenous leukemia. This updated and comprehensive review also analyzes the mechanisms by which TRPM2-mediated Ca²⁺ signaling can regulate the growth and survival of different types of cancer cells. Based on the discussion of the available data, it can be concluded that TRPM2 may be a unique therapeutic target in the treatment of several types of cancer. Video Abstract.

Neuroprotection of isookanin against MPTP-induced cell death of SH-SY5Y cells via BCL2/BAX and PI3K/AKT pathways

BACKGROUND AND PURPOSE

Isookanin, an important antioxidant component in Coreopsis tinctoria Nutt., has shown remarkable hypolipidemic, hypoglycemic, and hypotensive effects. However, the neuroprotective effect of isookanin has not been reported yet. Here, the neuroprotective effects and relevant molecular mechanisms of isookanin are explored for the first time.

METHODS

The SH-SY5Y cells were exposed to neurotoxic H₂O₂, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and Aβ_25-35, respectively. Cell viability and apoptosis were evaluated by MTT, lactate dehydrogenase (LDH), and TUNEL assays. Intercellular ROS and mitochondrial membrane potential were assessed by DCFH-DA and JC-1 assay. Western blot and qRT-PCR were used to explore the perturbed signaling at the gene and protein levels. Molecular docking analysis and in vitro assay were further applied to confirm potential target.

RESULTS

Among the three in vitro models, isookanin showed the best neuroprotection against MPTP-induced damage. Isookanin attenuated the levels of LDH, intracellular ROS, and mitochondrial membrane potential. Isookanin upregulated phosphorylation of AKT and PI3K, and increased BCL2/BAX ratio. Isookanin possessed a powerful affinity toward AKT. Besides, the protective effects of isookanin disappeared when cells were co-treated with an AKT inhibitor (AZD5363).

CONCLUSION

Isookanin regulated BCL2/BAX and PI3K/AKT pathways to reduce mitochondrial damage and cellular apoptosis. Isookanin may be a new protector for neurodegenerative diseases.

Involvement of TRPM2 Channel on Doxorubicin-Induced Experimental Cardiotoxicity Model: Protective Role of Selenium

Doxorubicin (DOXR) is an important chemotherapeutic drug used in cancer treatment for many years. Several studies reported that the use of DOXR increased toxicity by causing an increase in oxidative stress (OS), especially in the heart. In this study, we investigated the protective effect of selenium (Se) and the role of transient receptor potential melastatin-2 (TRPM2) channel activation by using N-(p-amylcinnamoyl) anthranilic acid (ACA) in a model of DOXR-induced cardiotoxicity. Sixty female rats were equally divided into the control, dimethyl sulfoxide (DMSO), DOXR, DOXR + Se, DOXR + ACA, and DOXR + Se + ACA groups. Glutathione (GSH), glutathione peroxidase (GSH-Px), caspases (Cas) 3 and 9, interleukin 1β (IL-1β), tumor necrosis factor-α (TNF-α), reactive oxygen species (ROS), poly [ADP-ribose] polymerase 1 (PARP-1), and TRPM2 channel levels were measured by ELISA. In addition, histopathological examination was performed in cardiac tissues and TNF-α, caspase 3, and TRPM2 channel expression levels were determined immunohistochemically. The levels of GSH, GSH-Px, caspases 3 and 9, IL-1β, TNF-α, ROS, PARP-1, and TRPM2 channel in serum, and cardiac tissue in the DOXR group were higher than in the control and DMSO groups (p < 0.05). However, these parameters in Se and/or ACA treatment groups were lower than in the DOXR group (p < 0.05). Also, we determined that Se and/or ACA treatment together with DOXR application decreased the TNF-α, Cas-3, and TRPM2 channel expression levels in the cardiac tissue. The data showed that administration of Se and/or ACA treatment together with DOXR may be used as a therapeutic agent in preventing DOXR-induced cardiotoxicity.

Xanthotoxol alleviates secondary brain injury after intracerebral hemorrhage by inhibiting microglia-mediated neuroinflammation and oxidative stress

BACKGROUND

Oxidative damage and inflammation are two critical mechanisms underlying secondary brain injury (SBI) following intracerebral hemorrhage (ICH). Xanthotoxol is reported to alleviate brain edema and inhibit inflammatory responses. Herein, we investigated the effects of xanthotoxol and its related mechanisms in SBI post-ICH.

METHODS

To explore the clinical effects of xanthotoxol an animal model of ICH was established. Neurological scores, survival rates and brain water content were measured. Inflammatory responses and oxidative damage in the peri-hemorrhagic areas were determined by measuring pro-inflammatory cytokines and oxidative related factors. The activation of the M1/M2 phenotype was detected by western blotting and immunofluorescence.

RESULTS

Xanthotoxol improved the neurological functions and reduced cerebral edema in ICH mice. Additionally, xanthotoxol inhibited microglia activation and promotes microglial phagocytosis. Simultaneously, xanthotoxol promoted the transformation of BV2 cells from M1 phenotype to M2 phenotype, and protected BV2 cells against hemin-induced inflammation and oxidative stress. Mechanistically, xanthotoxol inactivated the NF-κB p65 signaling pathway in the hemin-challenged BV2 cells.

CONCLUSION

Xanthotoxol ameliorates SBI post-ICH by suppressing microglia-mediated neuroinflammation and oxidative stress and enhancing microglial phagocytosis through inhibition of NF-κB signaling.

Mendelian randomization investigation highlights different roles of selenium status in mental disorders

Observational studies have suggested a relationship between selenium status and mental disorders (MDs). However, it remains unclear whether selenium status was causally associated with MDs. Thus, we performed a two-sample Mendelian randomization analysis using genome-wide association studies (GWAS) summary statistics to investigate the causal effects of selenium levels on seven MDs, including schizophrenia, major depressive disorder (MDD), autism spectrum disorder (ASD), bipolar disorder (BD), anorexia nervosa (AN), attention-deficit/hyperactivity disorder (ADHD), and panic disorder (PD). Strong genetic instruments of blood selenium (n = 9) and blood-toenail selenium (n = 12) were applied to the above seven MDs GWAS datasets from Psychiatric Genomics Consortium, which were further replicated in the FinnGen Biobank. The inverse-variance weighted method was employed to calculate the causal effects. The results showed that genetically predicted blood selenium levels were associated with a decreased risk of schizophrenia (odds ratio [OR] = 0.90, 95% CI: 0.87-0.95) and AN (OR = 0.87, 95% CI: 0.77-0.97). However, both blood and blood-toenail selenium levels were linked to an increased risk of MDD (blood: OR = 1.08, 95% CI: 1.05-1.12; blood-toenail: OR = 1.08, 95% CI: 1.04-1.13) and ASD (blood: OR = 1.11, 95% CI: 1.05-1.17; blood-toenail: OR = 1.13, 95% CI: 1.05-1.21), respectively. No obvious associations were found between selenium levels and BD as well as ADHD. Our findings highlighted a protective role of selenium in SZ and AN, while a risk effect in MDD and ASD. Further studies are required to verify the underlying mechanism mediating the unequal effects of Se on different MDs, which will pave a new path for the intervention of MDs.

Suppression of the NLRP3 Inflammasome through Activation of the Transient Receptor Potential Channel Melastatin 2 Promotes Osteogenesis in Tooth Extraction Sockets of Periodontitis

This study explored the role of transient receptor potential channel melastatin 2 (TRPM2)-mediated activation of NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) inflammasome in osteogenesis during healing of tooth extraction sockets. Tooth extraction socket tissue samples were collected from patients with or without periodontitis. In a TRPM2 knockout mouse model of socket healing, mice with or without periodontitis and their wild-type littermates were used for comparing the socket healing phenotypes. Micro-computed tomography imaging, three-dimensional reconstruction of the sockets, and hematoxylin and eosin staining for histopathologic analysis were performed. Immunofluorescence, immunohistochemistry, and Western blot analysis were used for evaluation of protein expression; the mRNA levels were evaluated by quantitative RT-PCR. Osteogenic, chondrogenic, and adipogenic differentiation potential of human bone marrow mesenchymal stem cells (BMMSCs) was evaluated. Calcium deposition was evaluated using Alizarin Red S staining. NLRP3 and CASP1 were up-regulated in tooth sockets of periodontitis patients. NLRP3 knockdown promoted the osteogenic differentiation of maxillary BMMSCs under inflammatory conditions. TRPM2 was up-regulated in the tooth extraction socket tissue of periodontitis. Inhibiting TRPM2 expression mitigated the NLRP3 inflammasome and its deleterious effect on osteogenesis. Activation of the TRPM2 ion channel regulated osteogenesis of BMMSCs under inflammatory conditions via Ca²⁺ influx, the mitochondrial dynamics, and pyroptosis. Targeting the TRPM2/Ca²⁺/NLRP3 axis could be beneficial in the healing process of the tooth extraction sockets of patients with periodontitis.

TRPM2 regulates autophagy to participate in hepatitis B virus replication

Hepatitis B virus (HBV) affects over 300 million people across the world and is further associated with the self-digesting process of autophagy. Accordingly, the current study set out to explore the role of transient receptor potential cation channel subfamily M member 2 (TRPM2) in HBV replication. Firstly, Huh-7 cells were transfected with the pHBV1.3 plasmid to detect the expression patterns of TRPM2 and neutrophil cytosolic factor 1 (p47 phox), followed by evaluating the role of TRPM2 in autophagy and HBV replication and exploring the interaction between TRPM2 and p47 phox. Collaborative experiments were further designed to explore the role of p47 phox and autophagy in TRPM2 regulation of HBV replication, in addition to animal experimentation to validate the role of TRPM2/p47 phox axis in vivo. It was found that TRPM2 up-regulation was associated with HBV replication. On the other hand, silencing of TRPM2 inhibited HBV replication and autophagy in vitro and in vivo, as evidenced by reduced HBV DNA load, HBV mRNA, HBeAg and HBsAg, and diminished autophagic spot number, LC3 II/I ratio, Beclin-1 expressions and increased p62 expressions. Mechanistic experimentation illustrated that TRPM2 interacted with p47 phox and positively regulated p47 phox, such that p47 phox up-regulation or use of Rapamycin (autophagy activator) weakened the inhibitory role of silencing TRPM2. Collectively, our findings indicated that HBV infection promotes TRPM2 expression, and TRPM2 interacts with p47 phox to induce autophagy and facilitate HVB replication.

Use of Generalized Weighted Quantile Sum Regressions of Tumor Necrosis Factor Alpha and Kidney Function to Explore Joint Effects of Multiple Metals in Blood

Exposure to heavy metals could lead to adverse health effects by oxidative reactions or inflammation. Some essential elements are known as reactors of anti-inflammatory enzymes or coenzymes. The relationship between tumor necrosis factor alpha (TNF-α) and heavy metal exposures was reported. However, the interaction between toxic metals and essential elements in the inflammatory response remains unclear. This study aimed to explore the association between arsenic (As), cadmium (Cd), lead (Pb), cobalt (Co), copper (Cu), selenium (Se), and zinc (Zn) in blood and TNF-α as well as kidney function. We enrolled 421 workers and measured the levels of these seven metals/metalloids and TNF-α in blood; kidney function was calculated by CKD-EPI equation. We applied weighted quantile sum (WQS) regression and group WQS regression to assess the effects of metal/metalloid mixtures to TNF-α and kidney function. We also approached the relationship between metals/metalloids and TNF-α by generalized additive models (GAM). The relationship of the exposure−response curve between Pb level and TNF-α in serum was found significantly non-linear after adjusting covariates (p < 0.001). Within the multiple-metal model, Pb, As, and Zn were associated with increased TNF-α levels with effects dedicated to the mixture of 50%, 31%, and 15%, respectively. Grouped WQS revealed that the essential metal group showed a significantly negative association with TNF-α and kidney function. The toxic metal group found significantly positive associations with TNF-α, serum creatinine, and WBC but not for eGFR. These results suggested Pb, As, Zn, Se, and mixtures may act on TNF-α even through interactive mechanisms. Our findings offer insights into what primary components of metal mixtures affect inflammation and kidney function during co-exposure to metals; however, the mechanisms still need further research.

Selenium and Resveratrol Attenuated Diabetes Mellitus-Mediated Oxidative Retinopathy and Apoptosis via the Modulation of TRPM2 Activity in Mice

Diabetes mellitus induces optic nerve injury via the excessive generation of mitochondria reactive free oxygen radical (mitROS). TRPM2 channel is activated by mitROS, although it is inhibited by selenium (Se) and resveratrol (RSV). The activation of TRPM2 induces apoptosis and oxidative injury in the optic nerve. The inhibition of TRPM2 may decrease the optic nerve injury action of diabetes mellitus after the treatments of Se and RSV. Present study aimed to investigate the protective actions of Se and RSV on the excessive Ca²⁺ influx and mitROS generation-mediated optic nerve oxidative injury via the modulation of TRPM2. Fifty-six C57BL/6j male mice were divided into seven groups as control, Se, RSV, streptozotocin (STZ), STZ + Se, STZ + RSV, and STZ + Se + RSV. The STZ-mediated stimulation of TRPM2 increased the cytosolic Ca²⁺, lipid peroxidation, mitROS, cytosolic ROS, apoptosis, caspase-3, caspase-8, and caspase-9 concentrations in the mice, although their concentrations were decreased in the optic nerve by the treatments of Se and RSV. The STZ-induced decrease of optic nerve viability, glutathione, glutathione peroxidase, vitamin A, and vitamin E concentrations was also upregulated by the treatments of Se and RSV. The STZ-induced increase of TRPM2, PARP-1, caspase-3, and caspase-9 protein band expressions was diminished by the treatments of Se and RSV. In conclusion, STZ induced the optic nerve oxidative injury and apoptosis via the upregulation of TRPM2 stimulation, although the treatments of Se and RSV decreased the injury and apoptosis via the downregulation of TRPM2 activity.

Research on the Mechanism of Kaempferol for Treating Senile Osteoporosis by Network Pharmacology and Molecular Docking

Kaempferol (KP), as a natural anti-inflammatory compound, has been reported to have curative effects on alleviating senile osteoporosis (SOP), which is an inflammation-related musculoskeletal disease, but the molecular mechanisms remain unclear due to scanty relevant studies. We predicted the targets of KP and SOP, and the common targets of them were subsequently used to carry out PPI analysis. Moreover, we adopted GO and KEGG enrichment analysis and molecular docking to explore potential mechanisms of KP against SOP. There were totally 152 KP-related targets and 978 SOP-related targets, and their overlapped targets comprised 68 intersection targets. GO enrichment analysis showed 1529 biological processes (p < 0.05), which involved regulation of inflammatory response, oxidative stress, regulation of bone resorption and remodeling, osteoblast and osteoclast differentiation, etc. Moreover, KEGG analysis revealed 146 items including 44 signaling pathways (p < 0.05), which were closely linked to TNF, IL-17, NF-kappa B, PI3K-Akt, MAPK, estrogen, p53, prolactin, VEGF, and HIF-1 signaling pathways. By means of molecular docking, we found that kaempferol is bound with the key targets' active pockets through some connections such as hydrogen bond, pi-alkyl, pi-sigma, pi-pi Stacked, pi-pi T-shaped, and van der Waals, illustrating that kaempferol has close combination with the key targets. Collectively, various targets and pathways involve in the process of kaempferol treatment against SOP through regulating inflammatory response, oxidative stress, bone homeostasis, etc. Moreover, our study first reported that kaempferol may regulate core targets' expression with involvement of inflammatory response, oxidative stress, and bone homeostasis, thus treating SOP.

TRPM2 in ischemic stroke: Structure, molecular mechanisms, and drug intervention

Ischemic stroke has a high lethality rate worldwide, and novel treatments are limited. Calcium overload is considered to be one of the mechanisms of cerebral ischemia. Transient receptor potential melastatin 2 (TRPM2) is a reactive oxygen species (ROS)-sensitive calcium channel. Cerebral ischemia-induced TRPM2 activation triggers abnormal intracellular Ca2+ accumulation and cell death, which in turn causes irreversible brain damage. Thus, TRPM2 has emerged as a new therapeutic target for ischemic stroke. This review provides data on the expression, structure, and function of TRPM2 and illustrates its cellular and molecular mechanisms in ischemic stroke. Natural and synthetic TRPM2 inhibitors (both specific and nonspecific) are also summarized. The three-dimensional protein structure of TRPM2 has been identified, and we speculate that molecular simulation techniques will be essential for developing new drugs that block TRPM2 channels. These insights about TRPM2 may be the key to find potent therapeutic approaches for the treatment of ischemic stroke.

Protective role of selenium on MPP+ and homocysteine-induced TRPM2 channel activation in SH-SY5Y cells

Homocysteine is an intermediate product of biochemical reactions occurring in living organisms. It is known that drugs that increase dopamine synthesis used in Parkinson's disease (PD) cause an increase in the plasma homocysteine level. As the plasma homocysteine level increases, the amount of intracellular free calcium ion ([Ca²⁺]_i) and oxidative stress increase. As a result, it contributes to the excitotoxic effect by causing neurodegeneration. TRPM2 cation channel is activated by high [Ca²⁺]_i and oxidative stress. The role of TRPM2 in the development of neuronal damage due to the increase in homocysteine in PD has not yet been elucidated. In current study, we aimed to investigate the role of the TRPM2 and selenium (Se) in SH-SY5Y neuronal cells treated with homocysteine (HCT) and MPP . SH-SY5Y cells were divided into four groups: control, MPP, MPP + HCT, and MPP + HCT + Se. The results of plate reader assay, confocal microscope imaging, and western blot analyses indicated upregulation of apoptosis, [Ca²⁺]_i, mitochondrial membrane depolarization, caspase activation, and intracellular ROS values in the cells. The MPP + HCT group had considerably higher values than the other groups. The MPP + HCT + Se group had significantly lower values than all the other groups except the control group. In addition, incubation of MPP + HCT and MPP + HCT + Se groups with TRPM2 antagonist 2-APB increased cell viability and reduced intracellular calcium influx and apoptosis levels. It is concluded that the activation of TRPM2 was propagated in HCT and MPP-induced SH-SY5Y cells by the increase of oxidative stress. The antioxidant property of Se regulated the TRPM2 channel activation and neurodegeneration by providing intracellular oxidant/antioxidant balance.

Therapeutic Potential of Selenium in Glioblastoma

Little progress has been made in the long-term management of malignant brain tumors, leaving patients with glioblastoma, unfortunately, with a fatal prognosis. Glioblastoma remains the most aggressive primary brain cancer in adults. Similar to other cancers, glioblastoma undergoes a cellular metabolic reprogramming to form an oxidative tumor microenvironment, thereby fostering proliferation, angiogenesis and tumor cell survival. Latest investigations revealed that micronutrients, such as selenium, may have positive effects in glioblastoma treatment, providing promising chances regarding the current limitations in surgical treatment and radiochemotherapy outcomes. Selenium is an essential micronutrient with anti-oxidative and anti-cancer properties. There is additional evidence of Se deficiency in patients suffering from brain malignancies, which increases its importance as a therapeutic option for glioblastoma therapy. It is well known that selenium, through selenoproteins, modulates metabolic pathways and regulates redox homeostasis. Therefore, selenium impacts on the interaction in the tumor microenvironment between tumor cells, tumor-associated cells and immune cells. In this review we take a closer look at the current knowledge about the potential of selenium on glioblastoma, by focusing on brain edema, glioma-related angiogenesis, and cells in tumor microenvironment such as glioma-associated microglia/macrophages.

Interferon Gamma-Mediated Oxidative Stress Induces Apoptosis, Neuroinflammation, Zinc Ion Influx, and TRPM2 Channel Activation in Neuronal Cell Line: Modulator Role of Curcumin

Host defenses in the brain are modulated by the activation of several factors such as oxygen free radical species (ROS), Ca²⁺ influx, and TRPM2 activation, and they are well-known adverse factors in neurotoxicity and neurodegenerative diseases. Importantly, recent data indicated a protective action of curcumin (CRC) via inhibition of TRPM2 on the inflammation factors, ROS, and apoptosis in hypoxia-induced SH-SY5Y neuronal cells. However, the relationship between interferon gamma (IFNg) exposure and TRPM2 activation in the SH-SY5Y cells are not fully identified. The SH-SY5Y cells as a neuronal cell line model were used in several neuroinflammation studies. Hence, we used the SH-SY5Y cells in the current study, and they were divided into four main groups as control, CRC, IFNg, and IFNg+CRC. The data presented here indicate that IFNg induced excessive Ca²⁺ influx via activation of TRPM2. The IFNg treatment further increased cell death, cell debris amount, apoptosis, and cytokine generations (IL-1β, IL-6, and TNF-α) which were due to increased cytosolic and mitochondrial ROS generations as well as increased activations of caspase-3 and caspase-9. The expression levels of TRPM2, PARP-1, Bax, caspase-3, and caspase-9 were increased in the cells by the IFNg treatment. However, CRC treatment reduced the increase of expression levels, cytokine generations, caspase activations, ROS release, Ca²⁺ influx, cell death, and apoptosis levels via inhibition of TRPM2 in the SH-SY5Y cells that were treated with IFNg. Moreover, the treatment of TRPM2 blockers (ACA and 2-APB) potentiated the modulator effects of CRC. In conclusion, these results suggest that neuroinflammation via IFNg lead to the TRPM2 activation in the SH-SY5Y cells, whereas CRC prevents IFNg-mediated TRPM2 activation, cell death, and cytokine generations.

Involvement of TRPM2 Channel on Hypoxia-Induced Oxidative Injury, Inflammation, and Cell Death in Retinal Pigment Epithelial Cells: Modulator Action of Selenium Nanoparticles

Hypoxia (HYPX) in several eye diseases such as glaucoma and diabetic retinopathy causes oxidative cell death and inflammation. TRPM2 cation channel is activated by HYPX-induced ADP-ribose (ADPR) and oxidative stress. The protective role of selenium via inhibition of TRPM2 on the HYPX-induced oxidative cytotoxicity and inflammation values in the human kidney cell line was recently reported. However, the protective role of selenium nanoparticles (SeNP) on the values in the retinal pigment epithelial (ARPE-19) cells has not been clarified yet. In the current study, we investigated two subjects. First, we investigated the involvement of TRPM2 channel on the HYPX-induced oxidative injury, inflammation, and apoptosis in the ARPE-19 cells. Second, we investigated the protective role of SeNP via inhibition of TRPM2 channel on the HYPX-induced oxidative injury and apoptosis in the ARPE-19 cells. For the aims, the ARPE-19 cells were divided into four main groups as follows: Control (Ctr), SeNP (2.5 μg/ml for 24 h), HYPX (200 μM CoCl₂ for 24 h), and HYPX+SeNP. The TRPM2 current density and Ca²⁺ fluorescence intensity with an increase of mitochondrial membrane depolarization and oxygen free radical (OFR) generations were increased in the ARPE-19 cells by the treatment of HYPX. There was no increase of Ca²⁺ fluorescence intensity in the pre-treated cells with PARP-1 inhibitors (DPQ and PJ34) or in the presence of Ca²⁺-free extracellular buffer. When HYPX-induced TRPM2 activity was treated by SeNP and TRPM2 (2-APB and ACA) blockers, the increases of OFR generation, cytokine (TNF-α and IL-1β) levels, TRPM2, and PARP-1 expressions were restored. In conclusion, the exposure of HYPX caused mitochondrial oxidative cell cytotoxicity and cell death via TRPM2-mediated Ca²⁺ signaling and may provide an avenue for treating HYPX-induced retinal diseases associated with the excessive OFR and Ca²⁺ influx.