Rats Selected for Different Nervous Excitability: Long-Term Emotional-Painful Stress Affects the Dynamics of DNA Damage in Cells of Several Brain Areas.

The maintenance of genome stability is critical for health, but during individual ontogenesis, different stressors affect DNA integrity, which can lead to functional and/or structural changes in the cells of target organs. In the nervous system, cell genome destabilization is associated with different neurological and psychiatric diseases, but experiments in vivo, where a link between stress and DNA instability has been demonstrated, are relatively rare. Here, we use rat strains selected for the contrast excitability of the tibialis nerve (n. tibialis) and nonselected Wistar rats to investigate the reasons for individual differences in developing post-stress pathologies. Previous research on the behavioral response of these strains to prolonged emotional-painful stress (PEPS) allows us to consider one strain as a model of post-traumatic stress disorder (PTSD) and another strain as a model of compulsive disorder (CD). We study DNA damage in the cells of the prefrontal cortex (PFC), hippocampus, and amygdala, regions involved in stress responses and the formation of post-stress dysfunctions. The evaluation of cell genome integrity via the comet assay shows different responses to PEPS in each brain area analyzed and for all strains used. This could help us to understand the reasons for individual differences in the consequences of stress and the pathophysiology of post-stress disease formation.

Post-stress changes in the gut microbiome composition in rats with different levels of nervous system excitability.

The gut-brain axis is a critical communication system influencing the interactions between the gastrointestinal tract (GI) and the central nervous system (CNS). The gut microbiota plays a significant role in this axis, affecting the development and function of the nervous system. Stress-induced psychopathologies, such as depression and anxiety, have been linked to the gut microbiota, but underlying mechanisms and genetic susceptibility remain unclear. In this study, we examined stress-induced changes in the gut microbiome composition in two rat strains with different levels of nervous system excitability: high threshold (HT strain) and low threshold (LT strain). Rats were exposed to long-term emotional and painful stress using the Hecht protocol, and fecal samples were collected at multiple time points before and after stress exposure. Using 16S rRNA amplicon sequencing, we assessed the qualitative and quantitative changes in the gut microbiota. Our results revealed distinct microbial diversity between the two rat strains, with the HT strain displaying higher diversity compared to the LT strain. Notably, under prolonged stress, the HT strain showed an increase in relative abundance of microorganisms from the genera Faecalibacterium and Prevotella in fecal samples. Additionally, both strains exhibited a decrease in Lactobacillus abundance following stress exposure. Our findings provide valuable insights into the impact of hereditary nervous system excitability on the gut microbiome composition under stress conditions. Understanding the gut-brain interactions in response to stress may open new avenues for comprehending stress-related psychopathologies and developing potential therapeutic interventions targeted at the gut microbiota. However, further research is needed to elucidate the exact mechanisms underlying these changes and their implications for stress-induced disorders. Overall, this study contributes to the growing body of knowledge on the gut-brain axis and its significance in stress-related neurobiology.

Copy-number variation of housekeeping gene rpl13a in rat strains selected for nervous system excitability.

We evaluated copy number variation (CNV) for four genes in rat strains differing in nervous system excitability. rpl13a copy number is significantly reduced in hippocampus and bone marrow in rats with a high excitability threshold and stress. The observed phenomenon may be associated with a role for rpl13a in lipid metabolism.

Acetylation of histones in neocortex and hippocampus of rats exposed to different modes of hypobaric hypoxia: Implications for brain hypoxic injury and tolerance.

Acetylation of nucleosome histones results in relaxation of DNA and its availability for the transcriptional regulators, and is generally associated with the enhancement of gene expression. Although it is well known that activation of a variety of pro-adaptive genes represents a key event in the development of brain hypoxic/ischemic tolerance, the role of epigenetic mechanisms, in particular histone acetylation, in this process is still unexplored. The aim of the present study was to investigate changes in acetylation of histones in vulnerable brain neurons using original well-standardized model of hypobaric hypoxia and preconditioning-induced tolerance of the brain. Using quantitative immunohistochemistry and Western blot, effects of severe injurious hypobaric hypoxia (SH, 180mm Hg, 3h) and neuroprotective preconditioning mode (three episodes of 360mm Hg for 2h spaced at 24h) on the levels of the acetylated proteins and acetylated H3 Lys24 (H3K24ac) in the neocortex and hippocampus of rats were studied. SH caused global repression of the acetylation processes in the neocortex (layers II-III, V) and hippocampus (CA1, CA3) by 3-24h, and this effect was prevented by the preconditioning. Moreover, hypoxic preconditioning remarkably increased the acetylation of H3K24 in response to SH in the brain areas examined. The preconditioning hypoxia without subsequent SH also stimulated acetylation processes in the neocortex and hippocampus. The moderately enhanced expression of the acetylated proteins in the preconditioned rats was maintained for 24h, whereas acetylation of H3K24 was intense but transient, peaked at 3h. The novel data obtained in the present study indicate that large activation of the acetylation processes, in particular acetylation of histones might be essential for the development of brain hypoxic tolerance.