Effect of Hesperidin on Sciatic Nerve Damage in STZ-Induced Diabetic Neuropathy: Modulation of TRPM2 Channel.

Diabetic neuropathy (DNP) is a severe complication of diabetes mellitus. In this study, we examined the potential of hesperidin (HES) to attenuate DNP and the involvement of the TRPM2 channel in this process. The rats were given a single dose of 45 mg/kg of streptozotocin (STZ) intraperitoneally to induce diabetic neuropathic pain. On the third day, we confirmed the development of diabetes in the DNP and DNP + HES groups. The HES groups were treated with 100 mg/kg and intragastric gavage daily for 14 days. The results showed that treatment with HES in diabetic rats decreased STZ-induced hyperglycemia and thermal hyperalgesia. Furthermore, in the histopathological examination of the sciatic nerve, HES treatment reduced STZ-induced damage. The immunohistochemical analysis also determined that STZ-induced increased TRPM2 channel, type-4 collagen, and fibrinogen immunoactivity decreased with HES treatment. In addition, we investigated the TRPM2 channel activation in the sciatic nerve damage mechanism of DNP model rats created by STZ application using the ELISA method. We determined the regulatory effect of HES on increased ROS, and PARP1 and TRPM2 channel activation in the sciatic nerves of DNP model rats. These findings indicated that hesperidin treatment could attenuate diabetes-induced DNP by reducing TRPM2 channel activation.

NMDA Receptor Activation Stimulates Hypoxia-Induced TRPM2 Channel Activation, Mitochondrial Oxidative Stress, and Apoptosis in Neuronal Cell Line: Modular Role of Memantine.

TRPM2 channel is activated by the increase of hypoxia (HYP)-mediated excessive mitochondrial (mROS) and cytosolic (cROS) free reactive oxygen species generation and intracellular free Ca2+ ([Ca2+]i) influx. The stimulations of the N-methyl-d-aspartate(NMDA) receptor and TRPM2 channel induce mROS and apoptosis in the neurons, although their inhibitions via the treatments of memantine (MEM) and MK-801 decrease mROS and apoptosis. However, the molecular mechanisms underlying MEM treatment and NMDA inhibition' neuroprotection via TRPM2 inhibition in the HYP remain elusive. We investigated the modulator role of MEM and NMDA via the modulation of TRPM2 on oxidative neurodegeneration and apoptosis in SH-SY5Y neuronal cells. Six groups were induced in the SH-SY5Y and HEK293 cells as follows: Control, MEM, NMDA blocker (MK-801), HYP (CoCl2), HYP + MEM, and HYP + MK-801. The HYP caused to the increases of TRPM2 and PARP-1 expressions, and TRPM2 agonist (H2O2 and ADP-ribose)-induced TRPM2 current density and [Ca2+]i concentration via the upregulation of mitochondrial membrane potential, cROS, and mROS generations. The alterations were not observed in the absence of TRPM2 in the HEK293 cells. The increase of cROS, mROS, lipid peroxidation, cell death (propidium iodide/Hoechst) rate, apoptosis, caspase -3, caspase -8, and caspase -9 were restored via upregulation of glutathione and glutathione peroxidase by the treatments of TRPM2 antagonists (ACA or 2-APB), MEM, and MK-801. In conclusion, the inhibition of NMDA receptor via MEM treatment modulated HYP-mediated mROS, apoptosis, and TRPM2-induced excessive [Ca2+]i and may provide an avenue for protecting HYP-mediated neurodegenerative diseases associated with the increase of mROS, [Ca2+]i, and apoptosis.

Effect of curcumin on lipid profile, fibrosis, and apoptosis in liver tissue in abemaciclib-administered rats.

Abemaciclib (ABEM) is an important antitumor agent for breast cancer treatment. However, the side-effects of ABEM are unclear in the liver. This study investigated the protective effect of curcumin (CURC) on liver damage caused by ABEM. The rats were divided into five groups with eight animals in each group; Control, DMSO (150 µL for per rats), CURC, 30 mg/kg/day), ABE (26 mg/kg/day), and ABE + CURC (26 mg/kg/day ABE, 30 mg/kg/day) groups. Injections were administered daily for 28 days. The levels of AST, LDH, HDL, LDL, triglyceride, and total cholesterol in serum, and hepatic tissue fibrosis, caspase-3, Bax, and TNF-α expression were higher in the ABE group compared to the control group (p < 0.05). Also, these parameters in the ABEM + CURC group were lower than in the ABE group (p < 0.05). The results showed that ABE administration could cause liver damage and increase fibrosis in the liver. In addition, it was shown that co-administration of CURC with ABE could suppress the levels of AST, LDH, HDL, LDL, triglyceride, and total cholesterol in serum, and fibrosis, caspase-3, Bax, and TNF-α expressions in the liver. These data are the first in the literature. Therefore, the administration of CURC following ABE may be a therapeutic agent in preventing liver damage.

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 1ß (IL-1ß), 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-1ß, 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.

The protective effect of curcumin on cardiac markers and fibrosis in abemaciclib-induced cardiac damage in rats.

Abemaciclib (ABE) is a cyclin-dependent kinase inhibitor used in combination with an antiestrogen in the treatment of breast cancer. In addition to the important therapeutic properties of this drug, its side effects are not fully known. In this study, we aimed to investigate the protective effect of curcumin (CUR) on cardiac damage caused by ABE administration. Forty rats were equally divided into control, dimethyl sulfoxide (150 µL), CUR (30 mg/kg/day), ABE (26 mg/kg/day), and ABE + CUR (26 mg/kg/day ABE and 30mg/kg/day CUR) groups (n = 8). Injections were administered daily for 28 days. Troponin-I, total cholesterol, and creatine kinase myocardial band (CK-MB) levels and cardiac fibrosis were higher in the ABE group than in the control group (p < 0.05), and were lower in the ABE + CUR group than in the ABE group (p < 0.05). The results showed that ABE administration can cause cardiac damage and increase cardiac fibrosis. However, they showed that coadministration of CUR with ABE could suppress increases in CK-MB, troponin-I, and total cholesterol levels and also cardiac fibrosis associated with cardiac damage. Therefore, we can infer that the subsequent administration of CUR ABE treatment can be used as a therapeutic strategy for preventing cardiac damage.

Valproic Acid Attenuated PTZ-induced Oxidative Stress, Inflammation, and Apoptosis in the SH-SY5Y Cells via Modulating the TRPM2 Channel.

Valproic acid (VPA) is one of the most widely used antiepileptic drugs. The protective role of VPA and the role of the TRPM2 channel in this mechanism in developing neuronal damage due to increased pentylenetetrazol (PTZ)-induced neurotoxicity in SH-SY5Y cells were not clarified. Here, we investigated the role of VPA via modulation of TRPM2 channel on cell death and oxidative neurotoxicity in SH-SY5Y cells. The SH-SY5Y cell toxicity model was constructed by treating SH-SY5Y cells with PTZ. The VPA and TRPM2 channel antagonist N-(p-amylcinnamoyl) anthranilic acid (ACA) were added to prevent neurotoxicity in PTZ-induced SH-SY5Y cells. The role of the VPA and TRPM2 channel was evaluated using an ELISA kit and patch-clamp. Primarily, antioxidant (GSH and GSH-Px) and oxidative stress (MDA and ROS) levels and inflammatory factors (IL-1ß, IL-6, and TNF-α) in cells were determined by ELISA kits. Then, TRPM2 channel activation in cells was detected using both the ELISA kit and patch-clamp methods. In addition, apoptosis and cell viability levels in cells were determined by performing PARP1, caspase-3, caspase-9, and CCK-8 assays by ELISA kits. Our results showed that the TRPM2 channel is vital in damage formation in PTZ-induced cells. Furthermore, we observed that VPA attenuated PTZ-induced neurotoxicity by suppressing cells' oxidative stress and inflammation, and reducing TRPM2 channel activation. In our study, in which the protective effect of VPA and the role of the TRPM2 channel in PTZ-induced SH-SY5Y cells were investigated for the first time, we can conclude that VPA treatment and TRPM2 channel blockade can suppress PTZ-induced neurotoxicity.

The involvement of TRPM2 on the MPP+-induced oxidative neurotoxicity and apoptosis in hippocampal neurons from neonatal mice: protective role of resveratrol.

Parkinson's disease (PD) is an age-related chronic neurodegenerative disease. Although PD is known to be a result of damage to hippocampal neurons, its molecular mechanism has yet to be completely clarified. The neurodegeneration in hippocampal neurons has been suggested to include excessive production of reactive oxygen species (ROS). Mitochondrial dysfunction and disruption of intracellular Ca2+ homeostasis play the most important role in the increase in ROS production for the cells. Remarkably, it is stated in the literature that especially the change of Ca2+ homeostasis triggers neuronal degeneration. TRPM2 is a unique calcium-permeable nonselective cation channel, and densest in the numberless neuronal population. The current study aims to elucidate the effect of antioxidant resveratrol (Resv) on TRPM2-mediated oxidative stress (OS) induced by 1-methyl-4-phenylpyridinium (MPP) exposure in the primary mouse hippocampal neurons. The neurons were divided into four groups as Control, Resv , MPP, and MPP+ Resv. In the current results, the activation of TRPM2 was observed in primary hippocampal neurons with MPP incubation. TRPM2 channel expression levels in the MPP group increased in hippocampal neurons after MPP exposure. In addition, intracellular free Ca2+ concentration and TRPM2 channel currents were highest in MPP groups, although they were decreased by the Resv treatment. In addition, mitochondrial membrane depolarization, ROS, caspase-3, caspase-9, and apoptosis values induced by MPP decreased with resveratrol treatment. In conclusion, in our study, we observed that the dysregulation of OS-induced TRPM2 channel activation in hippocampal neurons exposed to MPP caused apoptotic cell death in neurons, while the use of resveratrol had a protective effect by reducing OS resources in the environment.

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.

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

Microglia as the primary immune cells of brain act protective effects against injuries and infections in the central nervous system. Inflammation via excessive Ca2+ influx and oxygen radical species (ROS) generation is a known factor in many neurodegenerative disorders. Importantly, the Ca2+ permeable TRPM2 channel is activated by oxidative stress. Thus, TRPM2 could provide the excessive Ca2+ influx in the microglia. Although TRPM2 expression level is high in inflammatory cells, the interplay between mouse microglia and TRPM2 channel during inflammation is not fully identified. Thus, it is important to understand the mechanisms and factors involved in order to enhance neuronal regeneration and repair. The data presented here indicate that TRPM2 channels were activated in microglia cells by interferon-gamma (IFNγ). The IFNγ treatment further increased apoptosis (early and late) and cytokine productions (TNF-α, IL-1ß, and IL-6) which were due to increased lipid peroxidation and ROS generations as well as increased activations of caspase -3 (Casp-3) and - 9 (Casp-9). However, selenium treatment diminished activations of TRPM2, cytokine, Casp-3, and Casp-9, and levels of lipid peroxidation and mitochondrial ROS production in the microglia that were treated with IFNγ. Moreover, addition of either PARP1 inhibitors (PJ34 or DPQ) or TRPM2 blockers (2-APB or ACA) potentiated the modulator effects of selenium. These results clearly suggest that IFNγ leads to TRPM2 activation in microglia cells; whereas, selenium prevents IFNγ-mediated TRPM2 activation and cytokine generation. Together the interplay between IFNγ released from microglia cells is importance in brain inflammation and may affect oxidative cytotoxicity in the microglia. Graphical abstract Summary of pathways involved in IFNγ-induced TRPM2 activation and microglia death through excessive reactive oxygen species (ROS): Modulator role of selenium (Se). The IFNγ causes the microglia activation. Nudix box domain of TRPM2 is sensitive to ROS. The ROS induces DNA damage and ADPR-ribose (ADPR) production in the nucleus via PARP1 enzyme activation. ADPR and ROS-induced TRPM2 activation stimulates excessive Ca2+ influx. ROS are produced in the mitochondria through the increase of free cytosolic Ca2+ (via TRPM2 activation) by the IFNγ treatment, although they are diminished by the TRPM2 channel blocker (ACA and 2-APB) and PARP1 inhibitor treatments. The main mechanism in the cell death and inflammatory effects of IFNγ is mediated by stimulation of ROS-mediated caspase (caspase -3 and - 9) activations and cytokine production (TNF-α, IL-1ß, and IL-6) via TRPM2 activation, respectively. The apoptotic, inflammatory, and oxidant actions of IFNγ are modulated through TRPM2 inhibition by the Se treatment.

Melatonin and Selenium Suppress Docetaxel-Induced TRPV1 Activation, Neuropathic Pain and Oxidative Neurotoxicity in Mice.

Docetaxel (DT) has been reported to positive therapeutic actions in the treatment of glioblastoma, breast tumors, and prostate cancers. However, it can also induce peripheral neuropathic pain and neurotoxicity as adverse effects. Expression level of TRPV1 cation channel is high in dorsal root ganglion (DRG), and its activation via capsaicin and reactive oxygen species (ROS) mediates peripheral neuropathic pain in mice. As cancer is known to increase the levels of ROS, the protective roles of melatonin (MT) and selenium (Se) were evaluated on the TRPV1-mediated neurotoxicity and pain in the DT-treated mice. Mice and TRPV1 expressing SH-SY5Y cells were equally divided into control, MT, Se, DT, DT+MT, and DT+Se groups. In the results of pain tests in the mice, we observed a decrease in DT-mediated mechanical and heat neuropathic pain by MT and Se. The results of plate reader assay and laser confocal microscopy image analyses indicated a protective role of MT and Se on the DT-induced increase of mitochondrial ROS, cytosolic ROS, apoptosis, lipid peroxidation, intracellular free Zn2+, Ca2+, and caspase-3 and -9 levels in the DRG and SH-SY5Y cells. MT and Se modulated DT-induced decreases of total antioxidant status, reduced glutathione and glutathione peroxidase in the DRG. However, the effects of DT were not observed in the non-TRPV1 expressing SH-SY5Y cells. Hence, MT and Se mediated protective effects against DT-induced adverse peripheral oxidative neurotoxicity and peripheral pain. These effects may be attributed to potent antioxidant properties of MT and Se.

Resveratrol diminishes bisphenol A-induced oxidative stress through TRPM2 channel in the mouse kidney cortical collecting duct cells.

Bisphenol A (BisPH-A) is a latent danger that threatens our health, which we frequently exposure in our modern life (e.g. the widespread use of drinking water in plastic pet bottles). But the BisPH-A induced transient receptor potential melastatin 2 (TRPM2)-mediated oxidative stress and apoptosis in these cells has not been studied yet. Calcium (Ca2+) plays an important role in a versatile intracellular signal transduction that works over a wide range to regulate oxidative stress processes. TRPM2 is activated by oxidative stress and it has emerged as an important Ca2+ signaling mechanism in a variety of cells, contributing many cellular functions including cell death. Resveratrol (RESV), which belongs to the polyphenol group, acts as an antioxidant, eliminating cellular oxidative stress and increasing the body's resistance to diseases. The current study aimed to elucidate the effect of antioxidant resveratrol on TRPM2-mediated oxidative stress induced by BisPH-A exposure in the mouse kidney cortical collecting duct cells (mpkCCDcl4). The cells were divided into four groups as control, resveratrol (50 µM for 24 h), BisPH-A (100 µM for 24 h) and BisPH-A + RESV. Intracellular free Ca2+ concentrations and TRPM2 channel currents were high in BisPH-A treated cells, but decreased with resveratrol treatment. In addition, BisPH-A induced mitochondrial membrane depolarization, reactive oxygen species (ROS), caspase 3, caspase 9 and apoptosis values were decreased by the resveratrol treatment. In conclusion, resveratrol protected cells from BisPH-A induced oxidative damage. In this study, we showed that TRPM2 channel mediates this protective effect of resveratrol.

Morphine Induces Apoptosis, Inflammation, and Mitochondrial Oxidative Stress via Activation of TRPM2 Channel and Nitric Oxide Signaling Pathways in the Hippocampus.

Morphine as an opioid is an important drug in the treatment of moderate to severe pain. Several stress factors via generation of nitric oxide (NO) and oxidative stress (OS) are responsible for the adverse effects of morphine-induced analgesia, addiction, and antinociceptive tolerance, including altered Ca2+ concentration, inflammation, OS, and release of apoptotic factors. TRPM2 is a Ca2+-permeable cation channel and it is activated by OS and NO. Hence, adverse effect of morphine addiction may occur via the OS and NO-induced TRPM2 activation. Because of the unclear etiology of morphine-induced adverse effects in the hippocampus, investigating the involvement of TRPM2 and NO synthetase (NOS) activations in the treatment of morphine-induced OS, apoptosis, and neuroinflammation is a major challenge. The hippocampal neuron of TRPM2 wild-type (TRPM2-WT) and knockout (TRPM2-KO) mice were divided into control, morphine, NOS inhibitor (L-NAME) + morphine, and TRPM2 channel blockers (ACA and 2-APB) + morphine. The morphine-induced increases of apoptosis, neuron death, OS, lipid peroxidation, caspase-3 and caspase-9, neuroinflammatory cytokines (IL-1ß, TNF-α, IL-6), and Ca2+ levels in the hippocampal neuron of TRPM2-WT mouse were decreased by the L-NAME, ACA, and 2-APB treatments, although cell viability, neuron count, and reduced glutathione and glutathione peroxidase levels were increased by the treatments. However, the effects of morphine were not observed in the hippocampus of TRPM2-KO mice. Taken together, our data show that neurodegeneration adverse effects of morphine were induced by activation of TRPM2, and excessive generations of NO and OS. Thus, inhibition of TRPM2 may modulate morphine-induced neurodegeneration in the hippocampus.

Correction to: Morphine Induces Apoptosis, Inflammation, and Mitochondrial Oxidative Stress via Activation of TRPM2 Channel and Nitric Oxide Signaling Pathways in the Hippocampus.

The original version of this article unfortunately contained some mistake.

Glutathione Depletion and Parkinsonian Neurotoxin MPP+-Induced TRPM2 Channel Activation Play Central Roles in Oxidative Cytotoxicity and Inflammation in Microglia.

Parkinson's disease (PD) is one of most common neurodegenerative diseases. Environmental stressors such as oxidative stress (OS), calcium ion influx, apoptosis, and inflammation mechanisms are linked to activated microglia in patients with PD. The OS-dependent activated transient receptor potential melastatin 2 (TRPM2) channel is modulated in several neurons by glutathione (GSH). However, the cellular and molecular effects of GSH alteration on TRPM2 activation, OS, apoptosis, and inflammation in the microglia remain elusive. The microglia of TRPM2 wild-type (TRPM2-WT) and knockout (TRPM2-KO) mice were divided into control, PD model (MPP), L-buthionine sulfoximine (BSO), MPP + BSO and MPP + BSO + GSH groups. MPP-induced increases in apoptosis, death, OS, lipid peroxidation, PARP1, caspase-3 and caspase-9, inflammatory cytokines (IL-1ß, TNF-α, IL-6), and intracellular free Zn2+ and Ca2+ levels in the microglia of TRPM2-WT mice were further increased by the BSO treatment, although they were diminished by the GSH treatment. Their levels were further reduced by PARP1 inhibitors (PJ34 and DPQ) and TRPM2 blockers (ACA and 2-APB). However, the effects of MPP and BSO were not observed in the microglia of TRPM2-KO mice. Taken together, our data demonstrate that maintaining GSH homeostasis is not only important for quenching OS in the microglia of patients with PD but also equally critical to modulating TRPM2, thus suppressing inflammatory responses elicited by environmental stressors.

Selenium and Neurological Diseases: Focus on Peripheral Pain and TRP Channels.

Pain is a complex physiological process that includes many components. Growing evidence supports the idea that oxidative stress and Ca2+ signaling pathways participate in pain detection by neurons. The main source of endogenous reactive oxygen species (ROS) is mitochondrial dysfunction induced by membrane depolarization, which is in turn caused by Ca2+ influx into the cytosol of neurons. ROS are controlled by antioxidants, including selenium. Selenium plays an important role in the nervous system, including the brain, where it acts as a cofactor for glutathione peroxidase and is incorporated into selenoproteins involved in antioxidant defenses. It has neuroprotective effects through modulation of excessive ROS production, inflammation, and Ca2+ overload in several diseases, including inflammatory pain, hypersensitivity, allodynia, diabetic neuropathic pain, and nociceptive pain. Ca2+ entry across membranes is mediated by different channels, including transient receptor potential (TRP) channels, some of which (e.g., TRPA1, TRPM2, TRPV1, and TRPV4) can be activated by oxidative stress and have a role in the induction of peripheral pain. The results of recent studies indicate the modulator roles of selenium in peripheral pain through inhibition of TRP channels in the dorsal root ganglia of experimental animals. This review summarizes the protective role of selenium in TRP channel regulation, Ca2+ signaling, apoptosis, and mitochondrial oxidative stress in peripheral pain induction.