Melatonin modulates wireless (2.45 GHz)-induced oxidative injury through TRPM2 and voltage gated Ca(2+) channels in brain and dorsal root ganglion in rat

Modulation of oxidative stress and Ca(2+) mobilization through TRPM2 channels in rat dorsal root ganglion neuron by Hypericum perforatum

A main component of St. John's Wort (Hypericum perforatum, HP) is hyperforin which has antioxidant properties in dorsal root ganglion (DRG) neurons, due to its ability to modulate NADPH oxidase and protein kinase C. Recent reports indicate that oxidative stress through NADPH oxidase activates TRPM2 channels. HP may be a useful treatment for Ca(2+) entry and oxidative stress through modulation of TRPM2 channels in the DRG. We aimed to investigate the protective role of HP on Ca(2+) entry and oxidative stress through TRPM2 channels in DRG neurons of rats. The native rat DRG neurons were used in whole-cell patch-clamp, Fura-2 and antioxidant experiments. Appropriate, nontoxic concentrations and incubation times for HP were determined in the DRG neurons by assessing cell viability. The H2O2-induced TRPM2 currents were inhibited by 2-aminoethyl diphenylborinate (2-APB) and N-(p-amylcinnamoyl)anthranilic acid (ACA). TRPM2 current densities and cytosolic free Ca(2+) concentration in the neurons were also reduced by HP (2 and 24h). In Fura-2 experiments, cytosolic Ca(2+) mobilization was reduced by voltage-gated calcium channel blockers (verapamil+diltiazem, V+D) and HP. Glutathione peroxidase activity and GSH values in the DRG were high in HP, 2-APB and V+D groups although lipid peroxidation level was low in the groups. In conclusion, we observed a protective role for HP on Ca(2+) entry through a TRPM2 channel in the DRG neurons. Since over-production of oxidative stress and Ca(2+) entry are implicated in the pathophysiology of neuropathic pain and neuronal inflammation, our findings may be relevant to the etiology and treatment of neuropathology in DRG neurons.

Effects of aluminum and extremely low frequency electromagnetic radiation on oxidative stress and memory in brain of mice

This study was aimed to investigate the effect of aluminum and extremely low-frequency magnetic fields (ELF-MF) on oxidative stress and memory of SPF Kunming mice. Sixty male SPF Kunming mice were divided randomly into four groups: control group, ELF-MF group (2 mT, 4 h/day), load aluminum group (200 mg aluminum/kg, 0.1 ml/10 g), and ELF-MF + aluminum group (2 mT, 4 h/day, 200 mg aluminum/kg). After 8 weeks of treatment, the mice of three experiment groups (ELF-MF group, load aluminum group, and ELF-MF + aluminum group) exhibited firstly the learning memory impairment, appearing that the escaping latency to the platform was prolonged and percentage in the platform quadrant was reduced in the Morris water maze (MWM) task. Secondly are the pathologic abnormalities including neuronal cell loss and overexpression of phosphorylated tau protein in the hippocampus and cerebral cortex. On the other hand, the markers of oxidative stress were determined in mice brain and serum. The results showed a statistically significant decrease in superoxide dismutase activity and increase in the levels of malondialdehyde in the ELF-MF group (P < 0.05 or P < 0.01), load aluminum group (P < 0.01), and ELF-MF + aluminum group (P < 0.01). However, the treatment with ELF-MF + aluminum induced no more damage than ELF-MF and aluminum did, respectively. In conclusion, both aluminum and ELF-MF could impact on learning memory and pro-oxidative function in Kunming mice. However, there was no evidence of any association between ELF-MF exposure with aluminum loading.

Wi-Fi (2.45 GHz)- and mobile phone (900 and 1800 MHz)-induced risks on oxidative stress and elements in kidney and testis of rats during pregnancy and the development of offspring

The present study was designed to determine the effects of both Wi-Fi (2.45 GHz)- and mobile phone (900 and 1800 MHz)-induced electromagnetic radiation (EMR) on oxidative stress and trace element levels in the kidney and testis of growing rats from pregnancy to 6 weeks of age. Thirty-two rats and their 96 newborn offspring were equally divided into four different groups, namely, control, 2.45 GHz, 900 MHz, and 1800 MHz groups. The 2.45 GHz, 900 MHz, and 1,800 MHz groups were exposed to EMR for 60 min/day during pregnancy and growth. During the fourth, fifth, and sixth weeks of the experiment, kidney and testis samples were taken from decapitated rats. Results from the fourth week showed that the level of lipid peroxidation in the kidney and testis and the copper, zinc, reduced glutathione (GSH), glutathione peroxidase (GSH-Px), and total antioxidant status (TAS) values in the kidney decreased in the EMR groups, while iron concentrations in the kidney as well as vitamin A and vitamin E concentrations in the testis increased in the EMR groups. Results for fifth-week samples showed that iron, vitamin A, and β-carotene concentrations in the kidney increased in the EMR groups, while the GSH and TAS levels decreased. The sixth week results showed that iron concentrations in the kidney and the extent of lipid peroxidation in the kidney and testis increased in the EMR groups, while copper, TAS, and GSH concentrations decreased. There were no statistically significant differences in kidney chromium, magnesium, and manganese concentrations among the four groups. In conclusion, Wi-Fi- and mobile phone-induced EMR caused oxidative damage by increasing the extent of lipid peroxidation and the iron level, while decreasing total antioxidant status, copper, and GSH values. Wi-Fi- and mobile phone-induced EMR may cause precocious puberty and oxidative kidney and testis injury in growing rats.

Electromagnetic fields (UHF) increase voltage sensitivity of membrane ion channels; possible indication of cell phone effect on living cells

The effects of ultra high frequency (UHF) nonionizing electromagnetic fields (EMF) on the channel activities of nanopore forming protein, OmpF porin, were investigated. The voltage clamp technique was used to study the single channel activity of the pore in an artificial bilayer in the presence and absence of the electromagnetic fields at 910 to 990 MHz in real time. Channel activity patterns were used to address the effect of EMF on the dynamic, arrangement and dielectric properties of water molecules, as well as on the hydration state and arrangements of side chains lining the channel barrel. Based on the varied voltage sensitivity of the channel at different temperatures in the presence and absence of EMF, the amount of energy transferred to nano-environments of accessible groups was estimated to address the possible thermal effects of EMF. Our results show that the effects of EMF on channel activities are frequency dependent, with a maximum effect at 930 MHz. The frequency of channel gating and the voltage sensitivity is increased when the channel is exposed to EMF, while its conductance remains unchanged at all frequencies applied. We have not identified any changes in the capacitance and permeability of membrane in the presence of EMF. The effect of the EMF irradiated by cell phones is measured by Specific Absorption Rate (SAR) in artificial model of human head, Phantom. Thus, current approach applied to biological molecules and electrolytes might be considered as complement to evaluate safety of irradiating sources on biological matter at molecular level.

Suppression of voltage-gated Na(+) channels and neuronal excitability by imperatorin

Imperatorin is a naturally occurring furocoumarin compound isolated from plants such as Angelica archangelica and Cnidium monnieri. It has multiple pharmacological effects including anticonvulsant effects. Here we determined the effects of imperatorin on voltage-gated Na(+) channels (VGSC) using whole-cell patch clamp techniques in differentiated neuronal NG108-15 cells. We showed that imperatorin inhibited VGSC; such inhibition did not show state-dependence. Imperatorin caused a left shift in the steady-state inactivation curve without affecting activation gating. The inhibition of VGSC by imperatorin displayed a mild frequency-dependence. Imperatorin was also shown to inhibit VGSC and action potential amplitude without affecting voltage-gated K(+) channels in rat hippocampal CA1 neurons. In conclusion, our results suggest that imperatorin dampens neuronal excitability by inhibiting VGSC.

Vitamin E modulates oxidative stress and protein kinase C activator (PMA)-induced TRPM2 channel gate in dorsal root ganglion of rats

It is well known that Ca(2+) influx through cation channels induces peripheral pain in dorsal root ganglion (DRG) neurons. Melastatin-like transient receptor potential 2 (TRPM2) channel is a oxidative redox sensitive Ca(2+)-permeable cation channel. There is scarce report on block of the channels. Since the mechanisms that lead to TRPM2 inhibition in response to oxidative stress and protein kinase C (PKC) activation are not understood, we investigated effects of the antioxidants on the inhibition of TRPM2 channel currents in the DRG neurons of rats. The DRG peripheral neurons were freshly isolated from rats and the neurons were incubated by phorbol 12-myristate 13-acetate (PMA) which leads to activation of PKC and cause oxidative stress. In whole-cell patch clamp experiments, TRPM2 currents in the DRG incubated with PMA were stimulated by H2O2. In addition, the PMA-induced activation of TRPM2 channels were blocked by nonspecific TRPM2 channels inhibitors [2-aminoethyl diphenylborinate (2-APB) and N-(p-amylcinnamoyl)anthranilic acid (ACA)]. The currents in the neurons are also totally blocked by vitamin E incubation. However, administration of catalase and vitamin C with/without the vitamin E incubation did not block the currents. In conclusion, we indicated that vitamin E modulated oxidative stress-induced TRPM2 channel activation in the DRG neurons. The results may be useful modulation of oxidative stress-induced peripheral pain in sensory neurons.

Role of melatonin on electromagnetic radiation-induced oxidative stress and Ca2+ signaling molecular pathways in breast cancer

AIMS

Exposure to electromagnetic radiation (EMR) may increase breast cancer risk by inducing oxidative stress and suppressing the production of melatonin. Aim of the present review is to discuss the mechanisms and risk factors of EMR and oxidative stress-induced breast cancer, to summarize the controlled studies evaluating measures for prevention, and to conclude with evidence-based strategies for prevention.

MATERIALS

Review of the relevant literature and results from our recent basic studies, as well as critical analyses of published systematic reviews were obtained from the Pubmed and the Science Citation Index.

RESULTS

It has been proposed that chronic exposure to EMR may increase the risk of breast cancer by suppressing the production of melatonin; this suppression may affect the development of breast cancer either by increasing levels of circulation of estrogen or through over production of free oxygen radicals. Most epidemiological studies have also indicated overall effect of EMR exposure in premenopausal women, particularly for estrogen receptor positive breast tumors. Enhanced voltage-dependent Ca(2+) current and impaired inhibitory G-protein function, and derangement of intracellular organelles with a Ca(2+) buffering effect, such as endoplasmic reticulum and mitochondria have been also shown to contribute to disturbed Ca(2+) signaling in breast cancer.

CONCLUSION

Melatonin may modulate breast cancer through modulation of enhanced oxidative stress and Ca(2+) influx in cell lines. However, there is not enough evidence on increased risk of breast cancer related to EMR exposure.

Selenium and topiramate attenuates blood oxidative toxicity in patients with epilepsy: a clinical pilot study

It is well known that oxidative stress plays an important role in the etiology of epilepsy. We investigated effects of selenium (Se) and topiramate (TPM) combination supplementation on antioxidant and oxidant values in control and patients with epilepsy and refractory epilepsy. For the aim, we used control (n = 19), epilepsy + TPM (n = 19), epilepsy + TPM + Se (n = 15) groups. We also used control (n = 15), refractory epilepsy (n = 15), and refractory epilepsy + Se (n = 8) groups. TPM (0.2 mg/daily) and Se, as sodium selenite (twice daily with 0.1 mg doses), were orally supplemented to the patients for 45 days. Erythrocyte lipid peroxidation levels were higher in refractory epilepsy groups than in control although its level and seizure numbers were decreased in TPM and TPM + Se supplemented groups of the patients. The erythrocyte reduced glutathione (GSH), glutathione peroxidase (GSH-Px), plasma total antioxidant status (TAS), and vitamin E concentration in refractory epilepsy group were lower than in control. However, the erythrocyte and plasma TAS, erythrocyte GSH and GSH-Px, and plasma vitamins A and C values were increased either by Se or Se + TPM in epilepsy and refractory epilepsy groups. There were no effects of TPM and Se on plasma β-carotene values in the groups. In conclusion, TPM and selenium caused protective effects on the epilepsy and refractory epilepsy-induced oxidative injury by inhibiting free radical production and supporting antioxidant redox system.

Pineal melatonin level disruption in humans due to electromagnetic fields and ICNIRP limits

The International Agency for Research on Cancer (IARC) classifies electromagnetic fields (EMFs) as 'possibly carcinogenic' to humans that might transform normal cells into cancer cells. Owing to high utilisation of electricity in day-to-day life, exposure to power-frequency (50 or 60 Hz) EMFs is unavoidable. Melatonin is a natural hormone produced by pineal gland activity in the brain that regulates the body's sleep-wake cycle. How man-made EMFs may influence the pineal gland is still unsolved. The pineal gland is likely to sense EMFs as light but, as a consequence, may decrease the melatonin production. In this study, more than one hundred experimental data of human and animal studies of changes in melatonin levels due to power-frequency electric and magnetic fields exposure were analysed. Then, the results of this study were compared with the International Committee of Non-Ionizing Radiation Protection (ICNIRP) limit and also with the existing experimental results in the literature for the biological effect of magnetic fields, in order to quantify the effects. The results show that this comparison does not seem to be consistent despite the fact that it offers an advantage of drawing attention to the importance of the exposure limits to weak EMFs. In addition to those inconsistent results, the following were also observedfrom this work: (i) the ICNIRP recommendations are meant for the well-known acute effects, because effects of the exposure duration cannot be considered and (ii) the significance of not replicating the existing experimental studies is another limitation in the power-frequency EMFs. Regardless of these issues, the above observation agrees with our earlier study in which it was confirmed that it is not a reliable method to characterise biological effects by observing only the ratio of AC magnetic field strength to frequency. This is because exposure duration does not include the ICNIRP limit. Furthermore, the results show the significance of disruption of melatonin due to exposure to weak EMFs, which may possibly lead to long-term health effects in humans.

Oxidative stress-modulated TRPM ion channels in cell dysfunction and pathological conditions in humans

The transient receptor potential melastatin (TRPM) protein family is an extensive group of ion channels expressed in several types of mammalian cells. Many studies have shown that these channels are crucial for performing several physiological functions. Additionally, a large body of evidence indicates that these channels are also involved in numerous human diseases, known as channelopathies. A characteristic event frequently observed during pathological states is the raising in intracellular oxidative agents over reducing molecules, shifting the redox balance and inducing oxidative stress. In particular, three members of the TRPM subfamily, TRPM2, TRPM4 and TRPM7, share the remarkable feature that their activities are modulated by oxidative stress. Because of the increase in oxidative stress, these TRPM channels function aberrantly, promoting the onset and development of diseases. Increases, absences, or modifications in the function of these redox-modulated TRPM channels are associated with cell dysfunction and human pathologies. Therefore, the effect of oxidative stress on ion channels becomes an essential part of the pathogenic mechanism. Thus, oxidative stress-modulated ion channels are more susceptible to generating pathological states than oxidant-independent channels. This review examines the most relevant findings regarding the participation of the oxidative stress-modulated TRPM ion channels, TRPM2, TRPM4, and TRPM7, in human diseases. In addition, the potential roles of these channels as therapeutic tools and targets for drug design are discussed.

Enhancement of docetaxel-treated MCF-7 cell death by 900-MHz radiation

The aim of the study was to investigate the effect of high-frequency electromagnetic field of 900 MHz at 8 W input power on metabolic activity of human breast adenocarcinoma MCF-7 cells. With the aid of the colorimetric MTT assay, it was shown that there is significant change in cell culture survival exposed to docetaxel in field-free conditions in comparison with cells treated with docetaxel simultaneously exposed to high-frequency electromagnetic field.

Neuroprotection induced by N-acetylcysteine against cytosolic glutathione depletion-induced Ca2+ influx in dorsal root ganglion neurons of mice: role of TRPV1 channels

Glutathione (GSH) and N-acetylcysteine (NAC) are thiol-containing antioxidants, and also act through a direct reaction with free radicals. Transient receptor potential vanilloid 1 (TRPV1) is the principal transduction channel serving as a polymodal detector. Despite the importance of oxidative stress in pain sensitivity, its role in TRPV1 modulation is poorly understood. NAC may also have a regulator role on TRPV1 channel activity in the dorsal root ganglion (DRG) neuron. Therefore, we tested the effects of GSH and NAC on TRPV1 channel current, Ca(2+) influx, oxidative stress and caspase activity in the DRG of mice. DRG neurons were freshly isolated from mice and the neurons were incubated for 6 and 24h with buthionine sulfoximine (BSO). Pretreatment of cultured DRG neurons with NAC, results in a protection against oxidative damages. This neuroprotection is associated with the attenuation of a Ca(2+) influx triggered by oxidative agents such as H2O2, 5,5'-dithiobis-(2-nitrobenzoic acid) and GSH depletion via BSO. Here, we demonstrate the contribution of cytosolic factors (related to thiol group depletion) on the activation of TRPV1 channels in this mechanism. TRPV1 channels are activated by various agents including capsaicin (CAP), the pungent component of hot chili peppers, and are blocked by capsazepine. An oxidative environment also increased CAP-evoked TRPV1 currents in the neurons. When NAC and GSH were included in the patch pipette as well as extracellularly in the chamber, TRPV1 channels were not activated by CAP and H2O2. TRPV1 inhibitors, 2-aminoethyl diphenylborinate and N-(p-amylcinnamoyl)anthranilic acid strongly reduced BSO-induced oxidative toxicity and Ca(2+) influx, in a manner similar to pretreatment with NAC and GSH. Caspase-3 and -9 activities of all groups were not changed by the agonists or antagonists. In conclusion, in our experimental model, TRPV1 channels are involved in the oxidative stress-induced neuronal death, and negative modulation of this channel activity by GSH and NAC pretreatment may account for their neuroprotective activity against oxidative stress.

Modulation of wireless (2.45 GHz)-induced oxidative toxicity in laryngotracheal mucosa of rat by melatonin

It is well known that oxidative stress induces larynx cancer, although antioxidants induce modulator role on etiology of the cancer. It is well known that electromagnetic radiation (EMR) induces oxidative stress in different cell systems. The aim of this study was to investigate the possible protective role of melatonin on oxidative stress induced by Wi-Fi (2.45 GHz) EMR in laryngotracheal mucosa of rat. For this purpose, 32 male rats were equally categorized into four groups, namely controls, sham controls, EMR-exposed rats, EMR-exposed rats treated with melatonin at a dose of 10 mg/kg/day. Except for the controls and sham controls, the animals were exposed to 2.45 GHz radiation during 60 min/day for 28 days. The lipid peroxidation levels were significantly (p < 0.05) higher in the radiation-exposed groups than in the control and sham control groups. The lipid peroxidation level in the irradiated animals treated with melatonin was significantly (p < 0.01) lower than in those that were only exposed to Wi-Fi radiation. The activity of glutathione peroxidase was lower in the irradiated-only group relative to control and sham control groups but its activity was significantly (p < 0.05) increased in the groups treated with melatonin. The reduced glutathione levels in the mucosa of rat did not change in the four groups. There is an apparent protective effect of melatonin on the Wi-Fi-induced oxidative stress in the laryngotracheal mucosa of rats by inhibition of free radical formation and support of the glutathione peroxidase antioxidant system.

Role of TRPM2 and TRPV1 cation channels in cellular responses to radiation-induced DNA damage

BACKGROUND

Radiation exposure causes DNA damage, and DNA repair systems are essential to rescue damaged cells. Although DNA damage or oxidative stress activates transient receptor potential melastatin 2 (TRPM2) and vanilloid 1 (TRPV1) cation channels, it has not been established whether these TRP channels are involved in cellular responses to radiation-induced DNA damage. Here, we investigated the contribution of TRPM2 and TRPV1 channels to γ-irradiation- and UVB-induced DNA damage responses in human lung cancer A549 cells.

METHODS

A549 cells were irradiated with γ-rays (2.0Gy) or UVB (5-10mJ/cm(2)). γH2AX foci, ATM activation, 53BP1 accumulation and EGFR expression were evaluated by immunofluorescence staining. Extracellular ATP concentration was measured by luciferin-luciferase assay. Knockdown of TRPM2 and TRPV1 expression was done by siRNA transfection.

RESULTS

γ-Irradiation-induced γH2AX focus formation, ATM activation, 53BP1 accumulation and EGFR nuclear translocation, which are all associated with DNA repair, were suppressed by knockdown of TRPM2 and TRPV1 channels in A549 cells. Release of ATP, which mediates DNA damage response-associated activation of P2Y receptors, was suppressed by pre-treatment with catalase or knockdown of TRPM2 channel, but not TRPV1 channel. Similarly, UVB-induced γH2AX focus formation was suppressed in TRPM2- and TRPV1-knockdown cells, while UVB-induced ATP release was blocked in TRPM2- but not TRPV1-knockdown cells.

CONCLUSION

Our results suggest that the activation of TRPM2 channel, which mediates ATP release, and TRPV1 channel plays significant roles in the cellular responses to DNA damage induced by γ-irradiation and UVB irradiation.

GENERAL SIGNIFICANCE

Our results provide a new insight into the function of TRP channels from the viewpoint of radiation biology.

Extremely low-frequency magnetic field induces manganese accumulation in brain, kidney and liver of rats

The aim of the present study was to determine the effects of extremely low-frequency magnetic field (ELF-MF) on accumulation of manganese (Mn) in the kidney, liver and brain of rats. A total of 40 rats were randomly divided into eight groups. Four control groups received 0, 3.75, 15 and 60 mg Mn per kg body weight orally every 2 days for 45 days, respectively. The remaining four groups received same concentrations of Mn and were also exposed to ELF-MF (1.5 mT; 50 Hz) for 4 h for 5 days a week during 45 days. Following the last exposure, kidney, liver and brain were taken from all rats and they were analyzed for Mn accumulation levels using an inductively coupled plasma-optical emission spectrometer. In result of the current study, we observed that Mn levels in brain, kidney and liver were higher in Mn groups than in control groups. Mn levels in brain, kidney and liver were also higher in Mn plus ELF-MF groups than in Mn groups. In conclusion, result of the current study showed that the ELF-MF induced manganese accumulation in kidney, liver and brain of rats.

Protective effects of melatonin against oxidative injury in rat testis induced by wireless (2.45 GHz) devices

Wireless devices have become part of everyday life and mostly located near reproductive organs while they are in use. The present study was designed to determine the possible protective effects of melatonin on oxidative stress-dependent testis injury induced by 2.45-GHz electromagnetic radiation (EMR). Thirty-two rats were equally divided into four different groups, namely cage control (A1), sham control (A2), 2.45-GHz EMR (B) and 2.45-GHz EMR+melatonin (C). Group B and C were exposed to 2.45-GHz EMR during 60 min day(-1) for 30 days. Lipid peroxidation levels were higher in Group B than in Group A1 and A2. Melatonin treatment prevented the increase in the lipid peroxidation induced by EMR. Also reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) levels in Group D were higher than that of exposure group. Vitamin A and E concentrations decreased in exposure group, and melatonin prevented the decrease in vitamin E levels. In conclusion, wireless (2.45 GHz) EMR caused oxidative damage in testis by increasing the levels of lipid peroxidation and decreasing in vitamin A and E levels. Melatonin supplementation prevented oxidative damage induced by EMR and also supported the antioxidant redox system in the testis.

Melatonin modulates apoptosis and TRPM2 channels in transfected cells activated by oxidative stress

Transient receptor potential melastatin-like 2 (TRPM2) is a non-selective Ca(2+) permeable cation channel and is known to be activated by H(2)O(2), one of the most important indicators of intracellular oxidative stress. A neurohormone melatonin may have a modulator role on TRPM2 channels activated by oxidative stress because it is a strong antioxidant. In this study we investigated the effects of melatonin on apoptosis, whole cell currents and Ca(2+) influx arising from TRPM2 channels activated by H(2)O(2). In whole-cell patch clamp experiments, TRPM2 channels in transfected Chinese hamster ovary (CHO) cells were activated by H(2)O(2). However, the currents were inhibited either by intracellular or by extracellular melatonin. When intracellular melatonin was introduced by pipette, TRPM2 channel currents were not activated by H(2)O(2) although H(2)O(2)-induced Ca(2+) gating and release were not blocked 2-aminoethyldiphenyl borate (2-APB). Cytosolic Ca(2+) release was measured by Fura-2 and was higher in H(2)O(2) groups than in control. Melatonin also inhibited apoptosis in the transfected cells. In conclusion, we observed modulator roles of intracellular and extracellular melatonin on Ca(2+) influx and apoptosis through a TRPM2 channel in transfected CHO cells.