Melatonin protects rat cerebellar granule cells against electromagnetic field-induced increases in Na(+) currents through intracellular Ca(2+) release

Melatonin treatment improves ventricular conduction via upregulation of Nav1.5 channel proteins and sodium current in the normal rat heart

Melatonin treatment was reported to reduce the risk of cardiac arrhythmias, and crucial for this antiarrhythmic action was the effect of melatonin on activation spread. The aim of the present study was evaluation of the mechanisms of this activation enhancement. Experiments were performed in a total of 123 control and melatonin-treated (10 mg/kg, daily, for 7 days) male Wistar rats. In epicardial mapping studies (64 leads, interlead distance 0.5 mm) in the anesthetized animals, activation times (ATs) were determined in each lead as dV/dt minimum during QRS complex under sinus rhythm. Epicardial pacing was performed to measure conduction velocity (CV) across the mapped area. Average left ventricular ATs were shorter in the treated animals as compared to the controls, whereas the minimal epicardial ATs indicating the duration of activation propagation via the ventricular conduction system did not differ between the groups. CV was higher in the treated groups indicating that melatonin affected conduction via contractile myocardium The area of Cx43-derived fluorescence, as well as the expression of Cx43 protein, was similar in ventricles in the control and melatonin-treated groups. Expression of Gja1 gene transcripts encoding Cx43, was increased in the last group. An uncoupling agent octanol modified myocardial conduction properties (time of activation, action potential upstroke velocity, passive electrotonic phase duration) similarly in both groups. On the other hand, the expression of both Scn5a gene transcripts encoding Nav1.5 proteins, as well as peak density of transmembrane sodium current were increased in the ventricular myocytes from the melatonin-treated animals. Thus, a week-long melatonin treatment caused the increase of conduction velocity via enhancement of sodium channel proteins expression and increase of sodium current in the ventricular myocytes.

Effects of electromagnetic fields on neuronal ion channels: a systematic review

Many aspects of chemistry and biology are mediated by electromagnetic field (EMF) interactions. The central nervous system (CNS) is particularly sensitive to EMF stimuli. Studies have explored the direct effect of different EMFs on the electrical properties of neurons in the last two decades, particularly focusing on the role of voltage-gated ion channels (VGCs). This work aims to systematically review published evidence in the last two decades detailing the effects of EMFs on neuronal ion channels as per the PRISM guidelines. Following a predetermined exclusion and inclusion criteria, 22 papers were included after searches on three online databases. Changes in calcium homeostasis, attributable to the voltage-gated calcium channels, were found to be the most commonly reported result of EMF exposure. EMF effects on the neuronal landscape appear to be diverse and greatly dependent on parameters, such as the field's frequency, exposure time, and intrinsic properties of the irradiated tissue, such as the expression of VGCs. Here, we systematically clarify how neuronal ion channels are particularly affected and differentially modulated by EMFs at multiple levels, such as gating dynamics, ion conductance, concentration in the membrane, and gene and protein expression. Ion channels represent a major transducer for EMF-related effects on the CNS.

Melatonin MT2 receptor agonist IIK-7 produces antinociception by modulation of ROS and suppression of spinal microglial activation in neuropathic pain rats

Background

In recent years, several melatonin (MLT) receptor agonists have been approved by FDA for the treatment of sleep disorders and depression. Very few studies have shed light on their efficacy against neuropathic pain (NP). IIK-7 is an MT-2 agonist known to promote sleep. Whether IIK-7 suppresses NP has not been reported, and the signaling profile is unknown.

Objective

To investigate the effect of melatonin type 2 receptor agonist IIK-7 on partial sciatic nerve transection-induced NP in rats and elucidate the underlying molecular mechanisms.

Methods

NP was induced by the PSNT in the left leg of adult male Wistar rats. On post-transection day 7, rats were implanted with intrathecal (i.t) catheter connected to an infusion pump and divided in to four groups: sham-operated/vehicle, PSNT/vehicle, PSNT/0.5 μg/hr IIK-7 and PSNT/0.5 μg IIK-7/1 μg 4-p/hr. To test the MT-2 dependence on IIK-7 activity, the animals were implanted with a single i.t catheter and injected MT-2 antagonist 4-Phenyl-2-propionamidotetralin (4-p) 20 mins prior to IIK-7 injection on day 7 after PSNT. The antinociceptive response was measured using a mechanical paw withdrawal threshold. Activation of microglial cells and the expression of NP-associated proteins in the spinal cord dorsal horn was assessed by immunofluorescence assay (IFA) and Western blotting (WB). Reactive oxygen species (ROS) scavenging ability of IIK-7 was evaluated by using bone marrow-derived macrophages (BMDM).

Results

Treatment with the MT-2 agonist IIK-7 significantly alleviated PSNT-induced mechanical allodynia and glial activation along with the inhibition of P44/42 MAPK, HMGB-1, STAT3, iNOS and casp-3 proteins.

Conclusion

IIK-7 attenuates NP through the suppression of glial activation and suppression of proteins involved in inflammation and apoptosis. MT-2 receptor agonists may establish a promising and unique therapeutic approach for the treatment of NP.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Effect of electromagnetic fields and antioxidants on the trace element content of rat teeth

The purpose of this study was to examine the possible effect of extremely low-frequency electromagnetic fields (ELF-EMFs), from a high-voltage source, on rat teeth in terms of changes in trace elements (TEs) and the effect of antioxidants (melatonin [MLT] and Ganoderma lucidum [GL]) in counteracting these effects. We used adult male Wistar albino rats with a mean weight of 250–300 g and divided the rats into eight groups. The groups were subjected to an ELF-EMF that was applied with a high-voltage line for 8 hours/day for 26 days (Groups I, II, and III) or 52 days (Groups V, VI, and VII). Groups IV and VIII were the 26- and 52-day control/sham groups, respectively. Groups II and VI were treated with GL, and Groups III and VII were treated with MLT. MLT and GL were administered daily based on the weight of the animals and appropriate standards. At the end of the study, the rats were euthanized, and their anterior teeth were extracted. The teeth were preserved in pure water before evaluating the major TEs. At the end of the study, TE concentrations (in mg/kg) were assessed in the control and test groups. Compared with Group V, statistically significant differences in the concentrations of zinc (Zn) and strontium (Sr) were found for Group VII (ELF-EMF + MLT) (P<0.05). Therefore, ELF-EMF exposure can change the content of certain TEs in teeth and, after administering MLT and GL, the values of some of the TEs return to normal.

Melatonin modulates the functions of porcine granulosa cells via its membrane receptor MT2 in vitro

Melatonin (N-acetyl-5-methoxytryptamine) is documented as a hormone involved in the circadian regulation of physiological and neuroendocrine function in mammals. Herein, the effects of melatonin on the functions of porcine granulosa cells in vitro were investigated. Porcine granulosa cells were cultivated with variable concentrations of melatonin (0, 0.001, 0.01, 0.1, 1.0, and 10ng/mL) for 48h. Melatonin receptor agonist (IIK7) and antagonist (Luzindole, 4P-PDOT) were used to further examine the action of melatonin. The results showed optimum cell viability and colony-forming efficiency of porcine granulosa cells at 0.01ng/mL melatonin for 48-h incubation period. The percentage of apoptotic granulosa cells was significantly reduced by 0.01 and 0.1ng/mL melatonin within the 48-h incubation period as compared with the rest of the treatments. Estradiol biosynthesis was significantly stimulated by melatonin supplementation and suppressed for the progesterone secretion; the minimum ratio of progesterone to estradiol was 1.82 in 0.01ng/mL melatonin treatment after 48h of cultivation. Moreover, the expression of BCL-2, CYP17A1, CYP19A1, SOD1, and GPX4 were up-regulated by 0.01ng/mL melatonin or combined with IIK7, but decreased for the mRNA levels of BAX, P53, and CASPASE-3, as compared with control or groups treated with Luzindole or 4P-PDOT in the presence of melatonin. In conclusion, the study demonstrated that melatonin mediated proliferation, apoptosis, and steroidogenesis in porcine granulosa cells predominantly through the activation of melatonin receptor MT2 in vitro, which provided evidence of the beneficial role of melatonin as well as its functional mechanism in porcine granulosa cells in vitro.

Small-Conductance Ca2+-Activated Potassium Channels Negatively Regulate Aldosterone Secretion in Human Adrenocortical Cells

Aldosterone, which plays a key role in maintaining water and electrolyte balance, is produced by zona glomerulosa cells of the adrenal cortex. Autonomous overproduction of aldosterone from zona glomerulosa cells causes primary hyperaldosteronism. Recent clinical studies have highlighted the pathological role of the KCNJ5 potassium channel in primary hyperaldosteronism. Our objective was to determine whether small-conductance Ca(2+)-activated potassium (SK) channels may also regulate aldosterone secretion in human adrenocortical cells. We found that apamin, the prototypic inhibitor of SK channels, decreased membrane voltage, raised intracellular Ca(2+) and dose dependently increased aldosterone secretion from human adrenocortical H295R cells. By contrast, 1-Ethyl-2-benzimidazolinone, an agonist of SK channels, antagonized apamin's action and decreased aldosterone secretion. Commensurate with an increase in aldosterone production, apamin increased mRNA expression of steroidogenic acute regulatory protein and aldosterone synthase that control the early and late rate-limiting steps in aldosterone biosynthesis, respectively. In addition, apamin increased angiotensin II-stimulated aldosterone secretion, whereas 1-Ethyl-2-benzimidazolinone suppressed both angiotensin II- and high K(+)-stimulated production of aldosterone in H295R cells. These findings were supported by apamin-modulation of basal and angiotensin II-stimulated aldosterone secretion from acutely prepared slices of human adrenals. We conclude that SK channel activity negatively regulates aldosterone secretion in human adrenocortical cells. Genetic association studies are necessary to determine whether mutations in SK channel subtype 2 genes may also drive aldosterone excess in primary hyperaldosteronism.

Calcium homeostasis and low-frequency magnetic and electric field exposure: A systematic review and meta-analysis of in vitro studies

Low frequency magnetic field (LF MF) exposure is recurrently suggested to have the ability to induce health effects in society. Therefore, in vitro model systems are used to investigate biological effects of exposure. LF MF induced changes of the cellular calcium homeostasis are frequently hypothesised to be the possible target, but this hypothesis is both substantiated and rejected by numerous studies in literature. Despite the large amount of data, no systematic analysis of in vitro studies has been conducted to address the strength of evidence for an association between LF MF exposure and calcium homeostasis. Our systematic review, with inclusion of 42 studies, showed evidence for an association of LF MF with internal calcium concentrations and calcium oscillation patterns. The oscillation frequency increased, while the amplitude and the percentage of oscillating cells remained constant. The intracellular calcium concentration increased (SMD 0.351, 95% CI 0.126, 0.576). Subgroup analysis revealed heterogeneous effects associated with the exposure frequency, magnetic flux density and duration. Moreover, we found support for the presence of MF-sensitive cell types. Nevertheless, some of the included studies may introduce a great risk of bias as a result of uncontrolled or not reported exposure conditions, temperature ranges and ambient fields. In addition, mathematical calculations of the parasitic induced electric fields (IEFs) disclosed their association with increased intracellular calcium. Our results demonstrate that LF MF might influence the calcium homeostasis in cells in vitro, but the risk of bias and high heterogeneity (I(2)>75%) weakens the analyses. Therefore any potential clinical implications await further investigation.

GDF-15 enhances intracellular Ca2+ by increasing Cav1.3 expression in rat cerebellar granule neurons

GDF-15 (growth/differentiation factor 15) is a novel member of the TGF (transforming growth factor)-β superfamily that has critical roles in the central and peripheral nervous systems. We reported previously that GDF-15 increased delayed rectifier outward K⁺ currents and K_v2.1 α subunit expression through TβRII (TGF-β receptor II) to activate Src kinase and Akt/mTOR (mammalian target of rapamycin) signalling in rat CGNs (cerebellar granule neurons). In the present study, we found that treatment of CGNs with GDF-15 for 24 h increased the intracellular Ca²⁺ concentration ([Ca²⁺]_i) in response to membrane depolarization, as determined by Ca²⁺ imaging. Whole-cell current recordings indicated that GDF-15 increased the inward Ca²⁺ current (I_Ca) without altering steady-state activation of Ca²⁺ channels. Treatment with nifedipine, an inhibitor of L-type Ca²⁺ channels, abrogated GDF-15-induced increases in [Ca²⁺]_i and I_Ca. The GDF-15-induced increase in I_Ca was mediated via up-regulation of the Ca_v1.3 α subunit, which was attenuated by inhibiting Akt/mTOR and ERK (extracellular-signal-regulated kinase) pathways and by pharmacological inhibition of Src-mediated TβRII phosphorylation. Given that Ca_v1.3 is not only a channel for Ca²⁺ influx, but also a transcriptional regulator, our data confirm that GDF-15 induces protein expression via TβRII and activation of a non-Smad pathway, and provide novel insight into the mechanism of GDF-15 function in neurons.