Epigenetics in the Central Nervous System

Can Environmental Enrichment Modulate Epigenetic Processes in the Central Nervous System Under Adverse Environmental Conditions? A Systematic Review

The aim of this paper is to summarize the available evidence in the literature regarding the effects generated by exposure to an enriched environment (EE) on the modulation of epigenetic processes in the central nervous system under adverse environmental conditions. Searches were conducted in three databases: PubMed/Medline (1053 articles), Scopus (121 articles), and Embase (52 articles), which were subjected to eligibility criteria. Of the 1226 articles found, 173 duplicates were removed. After evaluating titles/abstracts, 904 studies were excluded, resulting in 49 articles, of which 14 were included in this systematic review. EE was performed using different inanimate objects. Adverse environmental conditions included CUMS, sepsis, nicotine exposure, PCP exposure, early stress, WAS, high fructose intake, TBI, and sevoflurane exposure. Regarding microRNA expression, after exposure to EE, an increase in the expression of miR-221 and miR-483 was observed in the prefrontal cortex, and a reduction in the expression of miR-92a-3p and miR-134 in the hippocampus. Regarding histone modifications, in the hippocampus, there was a reduction of HAT, HDAC/HDAC4, H3 (acetyl K14), H4 (acetyl K15), H3K4me3, K3k27me3, and HDAC2/3/5. In the cortex, there was a reduction of HDAC2, and in the prefrontal cortex, there was an increase in acetylated H3. Regarding DNA modifications, there was a reduction of DNMT in the hippocampus. This systematic review concludes that the benefits of EE on the brain and behavior of animals are directly related to different epigenetic mechanisms, reflecting in cell growth and neuroplasticity. EE may be a non-pharmacological and easy-to-apply alternative to prevent symptoms in disorders affecting brain tissue.

The Significance of Modified Histone H3 in Epithelial Dysplasia and Oral Cancer

BACKGROUND

Oral carcinogenesis is complex and influenced by both genetic and epigenetic changes. Altered histone modification is the epigenetic event that plays a role in cancer development and progression. Distinct modification patterns of histones have been shown to affect patient prognosis in selected cancers. This study aimed to evaluate the profiles of histone H3 modification in oral epithelial dysplasia (OED) and oral squamous cell carcinoma (OSCC) in association with the clinical-pathologic characteristics.

METHODS

One hundred patients were divided into 4 groups: low-grade OED, high-grade OED, OSCC, and normal oral mucosa (NOM). The levels of 3 types of histone modification-the H3K18ac, H3K9me3, and H3K9ac-were analysed immunohistochemically. Their expression profiles were compared and correlated with prognostically relevant clinical and pathologic features.

RESULTS

The H3K18ac and H3K9me3 were upregulated in OSCC, compared with OED and NOM. In contrast, the H3K9ac was downregulated in low-grade OED but increased in high-grade OED and OSCC. The hyperacetylations of H3K18 and H3K9 significantly correlated with advanced cancer depth of invasion and high T stage, respectively.

CONCLUSIONS

Histone H3 acetylation and methylation at lysine residues are differentially involved in the multistep oral carcinogenesis and impact aggressive cancer phenotypes. The effect of H3K9ac appears early in OED development, whilst the increased H3K18ac and H3K9me3 may be vital in the emergence of OSCC.