Cytoprotective effects of low-frequency pulsed electromagnetic field against oxidative stress in glioblastoma cells.

The low-frequency pulsed electromagnetic field (PEMF) may have possible cytoprotective effects against the destructive effects of oxidative stress. The goal was to investigate if shortterm low-frequency PEMF has cytoprotective effects in glioblastoma cell line following high-dose hydrogen peroxide (H2O2) treatment. U87-MG cells were divided into four groups: Sham-control group; PEMF group (cells exposed to PEMF); H2O2 group (cells treated with H2O2 at time intervals 30 min and 48 h, respectively); H2O2+PEMF group (cells exposed to PEMF after H2O2 treatment at time intervals 30 min and 48 h, respectively). The cell viability, levels of reactive oxygen species, glutathione peroxidase activity, and the amount of glutathione were measured. The cytoprotective effect of PEMF against deleterious effects of oxidative stress triggered by different time interval of H2O2 treatment might be mediated by the increase in the cell viability, the elevation in the antioxidant enzyme activity/amount, and the decrease in the reactive oxygen species level. In addition, the cytoprotective effect of PEMF varies depending on different time intervals of H2O2 treatment. In the light of these findings, further in vivo and/or in vitro studies on neurophysiological effects of PEMFs and their underlying molecular mechanisms are needed to elucidate neurotoxic or neuroprotective role against antioxidant defense mechanisms.

The Role of Acetylcholine on the Effects of Different Doses of Sulfite in Learning and Memory.

In this study, the effects of different doses of sulfite on learning, memory, and long term potentiation as well as the relationship of these effects with acetylcholine pathways, Arc and synapsin 1 levels were investigated. Sixty male Wistar albino rats were randomly divided into three groups as control, S100, and S260. Sodiummetabisulfite (S100;100 mg/kg/day, S260;260 mg/kg/day) was given by oral administration. Behavioral changes were evaluated. After long term potentiation recordings from the perforant pathway-dentate gyrus synapses, animals were sacrificed. Acetylcholinesterase activity, choline acetyltransferase activity, acetylcholine level as well as Arc and Synapsin 1 expressions were analyzed on the hippocampi. The total distance and average velocity values in the open field and Morris water maze tests increased in the sulfite groups, while the discrimination index in the novel object recognition test decreased compared to controls. Acetylcholine levels and choline acetyltransferase activity were also increased in the sulfite groups, while acetylcholinesterase activity was decreased compared to controls. Sulfite intake attenuated long term potentiation in the hippocampus. It has been observed that the excitatory postsynaptic potential slope and population spike amplitude of the field potentials obtained in sulfite groups decreased. This impairment was accompanied by a decrease in Arc and synapsin 1 expressions. In conclusion, it has been shown that sulfite intake in adults impairs learning and memory, possibly mediated by the cholinergic pathway. It is considered that the decrement in Arc and synapsin expressions may play a role in the mechanism underlying the impairment in long term potentiation caused by toxicity.

Upregulation of p53 by tannic acid treatment suppresses the proliferation of human colorectal carcinoma.

The present study's objective is to clarify the molecular mechanisms of tannic acid effects on the viability of human colorectal carcinoma (CRC). Tannic acid is stable for up to 48 h and is localized in both cytoplasm and nucleus. It dose-dependently inhibited the viability of CRC cell lines; SW-620 and HT-29 with IC 50 values of 7.2 ± 0.8 and 37.6 ± 1.4 µmol L-1. Besides, metastatic, invasive, and colony formation properties of CRC cells were significantly inhibited following the tannic acid treatment (p < 0.001). Tannic acid has been found to modulate enzyme, protein, and gene expressions of NQO1 in different levels and the upregulation of protein/gene expressions of p53 (p < 0.001), which leads the cells to trigger apoptosis. In conclusion, the present in vitro study may supply a significant background for in vivo studies in which the molecular mechanisms of antioxidant and chemopreventive activities of tannic acid will completely clarify.

Possible effects of different doses of 2.1 GHz electromagnetic radiation on learning, and hippocampal levels of cholinergic biomarkers in Wistar rats.

The present study evaluated whether short-term exposure to different doses of 2.1 GHz radiofrequency electromagnetic radiation (RF-EMR) has different effects on rats' behaviour and hippocampal levels of central cholinergic biomarkers. Animals were divided into three equal groups namely; group 1 was sham-exposed group, group 2-3 were exposed to 45 V/m and 65 V/m doses of 2.1 GHz frequency for 1 week respectively. Numerical dosimetry simulations were carried out. Object location and Y-maze were used as behavioural tasks. The protein and mRNA expression levels of AChE, ChAT, and VAChT, in the hippocampus were tested using Western Blotting and Real-Time PCR. The impairment performance of rats subjected to 65 V/m dose of 2.1 GHz RF-EMR in both object location and Y-maze tasks was observed. The hippocampal levels of AChE, ChAT, and VAChT, were significantly lower in rats exposed to 65 V/m dose of 2.1 GHz RF-EMR than others. The stronger effect of "65 V/m" dose on both rat's hippocampal-dependent behavioural performances and hippocampal levels of cholinergic biomarkers may be due to the stronger effect of "65 V/m" dose where rats' snouts were located at the nearest distance from the monopole antenna. Furthermore, the simulated SAR values were high for 65 V/m electric-field strengths. For the first time, we report the potential dose-dependent effects of short-term exposure to 2.1 GHz radiation on rat's behavioural performances as well as hippocampal levels of cholinergic biomarkers. Further studies are needed to understand the mechanisms by which RF-EMR influences the function of the central cholinergic system in the brain.

Relationship between the hippocampal expression of selected cytochrome P450 isoforms and the animal performance in the hippocampus-dependent learning task.

Despite very extensive studies on the molecular mechanisms of memory formation, relatively little is known about the molecular correlates of individual variation in the learning skills within a random population of young normal subjects. The role of cytochrome P450 (CYP) enzymes in the brain also remains poorly understood. On the other hand, these enzymes are known to be related to the metabolism of substances important for neural functions including steroids, fatty acids, and retinoic acid. In the present study, we examined the potential correlation between the animals' performance in a place learning task and the levels of selected CYP isoforms (CYP2E1, CYP2D1 and CYP7A1) in the rat hippocampus. According to their performance, rats were classified as "good" learners (percent error/number of trials to criterion ≤ group mean - 3SEM) or "poor" learners (percent error/number of trials to criterion ≥ group mean + 3SEM). The CYP enzyme levels were determined by Western Blot at the early, intermediary and advanced stages of the task acquisition (day 4, day 8 and after reaching a performance criterion of 83% correct responses). In this study, as expected, CYP2E1 and CYP2D1 isoforms have been found in the rat hippocampus. However, a putative CYP7A1 isoform was also visualized. Hippocampal expression of these enzymes was shown to be dependent on the stage of learning and animals' cognitive status. In "good" learners compared to "poor" learners, significantly higher levels of CYP2E1 were found at the early stage of training, significantly higher levels of CYP2D1 were found at the intermediate stage of training, and significantly higher levels of CYP7A1-like protein were found after reaching the acquisition criterion. These findings suggest that the differential expression of some CYP isoforms in the hippocampus may have impact on individual learning skills and that different CYP isoforms may play different roles during the learning process.

α-Actinin Anchors PSD-95 at Postsynaptic Sites.

Despite the central role PSD-95 plays in anchoring postsynaptic AMPARs, how PSD-95 itself is tethered to postsynaptic sites is not well understood. Here we show that the F-actin binding protein α-actinin binds to the very N terminus of PSD-95. Knockdown (KD) of α-actinin phenocopies KD of PSD-95. Mutating lysine at position 10 or lysine at position 11 of PSD-95 to glutamate, or glutamate at position 53 or glutamate and aspartate at positions 213 and 217 of α-actinin, respectively, to lysine impairs, in parallel, PSD-95 binding to α-actinin and postsynaptic localization of PSD-95 and AMPARs. These experiments identify α-actinin as a critical PSD-95 anchor tethering the AMPAR-PSD-95 complex to postsynaptic sites.

Effects of acute and chronic exposure to both 900 MHz and 2100 MHz electromagnetic radiation on glutamate receptor signaling pathway.

PURPOSE: To demonstrate the molecular effects of acute and chronic exposure to both 900 and 2100 MHz radiofrequency electromagnetic radiation (RF-EMR) on the hippocampal level/activity of some of the enzymes - including PKA, CaMKIIα, CREB, and p44/42 MAPK - from N-methyl-D-aspartate receptor (NMDAR)-related signaling pathways. MATERIALS AND METHODS: Rats were divided into the following groups: sham rats, and rats exposed to 900 and 2100 MHz RF-EMR for 2 h/day for acute (1 week) or chronic (10 weeks), respectively. Western blotting and activity measurement assays were used to assess the level/activity of the selected enzymes. RESULTS: The obtained results revealed that the hippocampal level/activity of selected enzymes was significantly higher in the chronic groups as compared to the acute groups at both 900 and 2100 MHz RF-EMR exposure. In addition, hippocampal level/activity of selected enzymes was significantly higher at 2100 MHz RF-EMR than 900 MHz RF-EMR in both acute and chronic groups. CONCLUSIONS: The present study provides experimental evidence that both exposure duration (1 week versus 10 weeks) and different carrier frequencies (900 vs. 2100 MHz) had different effects on the protein expression of hippocampus in Wistar rats, which might encourage further research on protection against RF-EMR exposure.

Comparison of spatial learning in the partially baited radial-arm maze task between commonly used rat strains: Wistar, Spargue-Dawley, Long-Evans, and outcrossed Wistar/Sprague-Dawley.

Strain-related differences in animals' cognitive ability affect the outcomes of experiments and may be responsible for discrepant results obtained by different research groups. Therefore, behavioral phenotyping of laboratory animals belonging to different strains is important. The aim of the present study was to compare the variation in allothetic visuospatial learning in most commonly used laboratory rat strains: inbred Wistar (W) and Sprague-Dawley (SD), outcrossed Wistar/Sprague-Dawley (W/SD), and outbred Long Evans (LE) rats. All rats were trained to the arbitrary performance criterion of 83 % correct responses in the partially baited 12-arm radial maze allowing for simultaneous evaluation of both working and reference memory. In the present study, testing albino versus pigmented and inbred versus outcrossed rats revealed significant strain-dependent differences with the inbred SD rats manifesting lower performance on all learning measures compared to other strains. On the other hand, the outcrossed W/SD rats showed a lower frequency of reference memory errors and faster rate of task acquisition compared to both LE and W rats, with W rats showing a lower frequency of working memory errors compared to other strains. In conclusion, albinism apparently did not reduce the animals' performance in the allothetic visuospatial learning task, while outcrossing improved the spatial learning. A differential effect of strain on the contribution of each error type to the animals' overall performance was observed. The strain-dependent differences were more pronounced between subpopulations of learning-deficient individuals ("poor" learners), and generally the reference memory errors contributed more to the final behavioral output than did the working memory errors.

Hippocampal levels of ChAT, PKA, phospho-PKA and phospho-CaMKIIα but not CaMKIIα positively correlate with spatial learning skills in rats.

Despite very extensive investigations on molecular processes underlying memory formation, there are very few studies examining potential differences in the brain biochemistry between "good" and "poor" learners belonging to a random population of young animals. In the present study, an attempt was made to correlate individual variation in spatial learning in young-adult Long-Evans rats with hippocampal levels of protein kinase A (PKA), calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα), and choline acetyltransferase (ChAT). Additionally, in order to indirectly estimate the activity of CaMKIIα and PKA, hippocampal levels of their phosphorylated forms (pCaMKIIα and pPKA) were assessed using Western blot technique. Rats were classified as "good" and "poor" learners on the basis of their performance in a partially baited 12-arm radial maze. The biochemical assays did not reveal a significant difference in the basal hippocampal levels of the CaMKIIα, however, the level of pCaMKIIα, was significantly higher in "good" learners. Also, hippocampal levels of both PKA and pPKA, as well as that of ChAT, were significantly higher in "good" as compared to "poor" learners. Our results suggest that the differences in the expression level of PKA and ChAT (but not of CaMKIIα), as well as the differences in the activation of both PKA and CaMKIIα, may contribute to the individual variation in learning skills and episodic-like memory in a random population of young-adult subjects.

Correlation between hippocampal levels of neural, epithelial and inducible NOS and spatial learning skills in rats.

In the present study, to better understand the role of different nitric oxide synthase (NOS) isoforms in hippocampus-dependent forms of learning, we examined the expression of neural, endothelial, and inducible NOS in the hippocampus of young-adult rats classified as "poor" and "good" learners on the basis of their performance in the partially baited 12-arm radial maze. Taking into consideration strain-dependent differences in learning skills and NOS expression, experiments were performed on two different lines of laboratory rats: the inbred Wistar (W) and the outcrossed Wistar/Spraque-Dawley (W/S) line. The hippocampal levels of NOS proteins were assessed by Western Blotting. In the present study, genetically more homogenous W rats showed a slower rate of learning compared to the genetically less homogenous outcrossed W/S rats. The deficient performance in the W rat group compared to outcrossed W/S rats, and in "poor" learners of both groups compared to "good" learners was due to a higher percentage of reference memory errors. The overall NOS levels were significantly higher in W group compared to outcrossed W/S rats. In both rat lines, the rate of learning positively correlated with hippocampal levels of nNOS and negatively correlated with iNOS levels. Hippocampal eNOS levels correlated negatively with animals' performance but only in the W rats. These results suggest that all 3 NOS isoforms are implemented but play different roles in neural signaling.