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.

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.

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.

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.

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.