This review aims to cover experimental data on oxidative effects of low-intensity radiofrequency radiation (RFR) in living cells. Analysis of the currently available peer-reviewed scientific literature reveals molecular effects induced by low-intensity RFR in living cells; this includes significant activation of key pathways generating reactive oxygen species (ROS), activation of peroxidation, oxidative damage of DNA and changes in the activity of antioxidant enzymes. It indicates that among 100 currently available peer-reviewed studies dealing with oxidative effects of low-intensity RFR, in general, 93 confirmed that RFR induces oxidative effects in biological systems. A wide pathogenic potential of the induced ROS and their involvement in cell signaling pathways explains a range of biological/health effects of low-intensity RFR, which include both cancer and non-cancer pathologies. In conclusion, our analysis demonstrates that low-intensity RFR is an expressive oxidative agent for living cells with a high pathogenic potential and that the oxidative stress induced by RFR exposure should be recognized as one of the primary mechanisms of the biological activity of this kind of radiation.

The Sir2 histone deacetylase gene family consists of seven mammalian sirtuins (SIRTs) which are NAD-dependent histone/protein deacetylases. Sir2 proteins regulate, for instance, genome stability by chromatin silencing in yeast. In mammals, their function is still largely unknown. Due to the NAD+ dependency, Sir2 might be the link between metabolic activity and histone/protein acetylation. Regulation of gene expression also seems to play an important role in Sir2 functions, since increasing the dosage of Sir2 genes increases genome stability in yeast and Caenorhabditis elegans. We observed that the modification of histone/protein acetylation status by several class I and II histone deacetylase (HDAC) inhibitors induces differential changes in gene expression profiles of seven SIRT mRNAs in cultured neuronal cells. SIRT2, SIRT4 and SIRT7 were upregulated, whereas SIRT1, SIRT5 and SIRT6 were downregulated by trichostatin A (TSA) and n-butyrate. The upregulation of SIRT mRNAs was inhibited by actinomycin D. Interestingly, the regulation of SIRT mRNAs was highly similar both in mouse Neuro-2a neuroblastoma cells and post-mitotic rat primary hippocampal and cerebellar granule neurons. Using a chromatin immunoprecipitation technique, we showed that the upregulation of SIRT2 expression with TSA is related to the hyperacetylation of DNA-bound histone H4 within the first 500 bp upstream of the transcription start site of the SIRT2 gene. Chemically different types of HDAC inhibitors, such as TSA, apicidin, SAHA, M344 and n-butyrate induced remarkably similar responses in SIRT1-7 mRNA expression patterns. Differential responses in SIRT mRNA expression profiles indicate that the expression of the Sir2 family of genes is selectively regulated and dependent on histone/protein acetylation status.

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Recent evidence suggests that energy metabolism contributes to molecular mechanisms controlling stem cell identity. For example, human embryonic stem cells (hESCs) receive their metabolic energy mostly via glycolysis rather than mitochondrial oxidative phosphorylation. This suggests a connection of metabolic homeostasis to stemness. Nicotinamide adenine dinucleotide (NAD) is an important cellular redox carrier and a cofactor for various metabolic pathways, including glycolysis. Therefore, accurate determination of NAD cellular levels and dynamics is of growing importance for understanding the physiology of stem cells. Conventional analytic methods for the determination of metabolite levels rely on linear calibration curves. However, in actual practice many two-enzyme cycling assays, such as the assay systems used in this work, display prominently nonlinear behavior. Here we present a diaphorase/lactate dehydrogenase NAD cycling assay optimized for hESCs, together with a mechanism-based, nonlinear regression models for the determination of NAD(+), NADH, and total NAD. We also present experimental data on metabolic homeostasis of hESC under various physiological conditions. We show that NAD(+)/NADH ratio varies considerably with time in culture after routine change of medium, while the total NAD content undergoes relatively minor changes. In addition, we show that the NAD(+)/NADH ratio, as well as the total NAD levels, vary between stem cells and their differentiated counterparts. Importantly, the NAD(+)/NADH ratio was found to be substantially higher in hESC-derived fibroblasts versus hESCs. Overall, our nonlinear mathematical model is applicable to other enzymatic amplification systems.

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