Sirtuins and Sepsis: Cross Talk between Redox and Epigenetic Pathways

Sepsis and septic shock are the leading causes of death among hospitalized patients in the US. The immune response in sepsis transitions from a pro-inflammatory and pro-oxidant hyper-inflammation to an anti-inflammatory and cytoprotective hypo-inflammatory phase. While 1/3rd sepsis-related deaths occur during hyper-, a vast majority of sepsis-mortality occurs during the hypo-inflammation. Hyper-inflammation is cytotoxic for the immune cells and cannot be sustained. As a compensatory mechanism, the immune cells transition from cytotoxic hyper-inflammation to a cytoprotective hypo-inflammation with anti-inflammatory/immunosuppressive phase. However, the hypo-inflammation is associated with an inability to clear invading pathogens, leaving the host susceptible to secondary infections. Thus, the maladaptive immune response leads to a marked departure from homeostasis during sepsis-phases. The transition from hyper- to hypo-inflammation occurs via epigenetic programming. Sirtuins, a highly conserved family of histone deacetylators and guardians of homeostasis, are integral to the epigenetic programming in sepsis. Through their anti-inflammatory and anti-oxidant properties, the sirtuins modulate the immune response in sepsis. We review the role of sirtuins in orchestrating the interplay between the oxidative stress and epigenetic programming during sepsis.

Epigenetic Modifications at the Center of the Barker Hypothesis and Their Transgenerational Implications

Embryo/fetal nutrition and the environment in the reproductive tract influence the subsequent risk of developing adult diseases and disorders, as formulated in the Barker hypothesis. Metabolic syndrome, obesity, heart disease, and hypertension in adulthood have all been linked to unwanted epigenetic programing in embryos and fetuses. Multiple studies support the conclusion that environmental challenges, such as a maternal low-protein diet, can change one-carbon amino acid metabolism and, thus, alter histone and DNA epigenetic modifications. Since histones influence gene expression and the program of embryo development, these epigenetic changes likely contribute to the risk of adult disease onset not just in the directly affected offspring, but for multiple generations to come. In this paper, we hypothesize that the effects of parental nutritional status on fetal epigenetic programming are transgenerational and warrant further investigation. Numerous studies supporting this hypothesis are reviewed, and potential research techniques to study these transgenerational epigenetic effects are offered.

Physiological Performance Curves: When Are They Useful?

This review serves as an introduction to a special issue of Frontiers in Physiology, focused on the importance of physiological performance curves across phylogenetic and functional boundaries. Biologists have used performance curves to describe the effects of changing environmental conditions on animal physiology since the late 1800s (at least). Animal physiologists have studied performance curves extensively over the past decades, and there is a good foundation to understanding how the environment affects physiological functions of individuals. Our goal here was to build upon this research and address outstanding questions regarding the mutability and applicability of performance curves across taxonomic groups and levels of biological organization. Performance curves are not fixed at a taxonomic, population, or individual level – rather they are dynamic and can shift in response to evolutionary pressures (e.g., selection) and epigenetic programming (e.g., plasticity). The mechanisms underlying these shifts are being increasingly used to predict the efficacy with which plasticity and heritability of performance curves can render individuals and populations less vulnerable to climate change. Individual differences in physiological performance curves (and plasticity of performance curves) can also have cascading effects at higher levels of biological organization. For instance, individual physiology likely influences group behaviors in non-additive ways. There is a need therefore to extend the concept of performance curves to social interactions and sociality. Collectively, this special issue emphasizes the power of how within- and between-individual shifts in performance curves might scale up to the population-, species-, and community-level dynamics that inform conservation management strategies.

Excessive fetal growth affects HSC quiescence maintenance through epigenetic programming of EGR1 transcriptional network

Fetal development is a critical period to shape stem cell identity and functions. Detrimental environments during this period are associated with epigenetics alteration of hematopoietic stem and progenitor cells (HSPC) with unknown functional impacts. We implemented a single-cell resolution integrative analysis combining epigenomics, transcriptomics, and functional data to elucidate the epigenetic influence associated with excessive fetal growth on HSPCs. We showed that hematopoietic stem cells (HSC) from large for gestational age neonates present a coordinated DNA hypermethylation and decrease expression for genes of the EGR1 transcriptional network including SOCS3, KLF2, and JUNB known to sustain stem cell quiescence and pluripotency. Furthermore, these changes were associated with a decreased ability for HSCs to stay undifferentiated and a decreased ability to expand in response to stimulation. Taken together, these results show that fetal overgrowth affects hematopoietic stem cells quiescence maintenance program through an epigenetic programming of the EGR1 related transcriptional network.

Revealing the biological basis of mental illness: epigenetic research as a new direction in diagnosis and treatment

Summary. Mental disorders are clinically heterogeneous chronic diseases resulting from complex interactions between genotype variants and environmental factors. Epigenetic processes, such as DNA methylation and post-translational histone modification, determine the interpretation by the body at the cellular and tissue levels of various environmental factors. Given that epigenetic modifications are environmentally sensitive, stable and reversible, epigenetic research in psychiatry may be a promising approach to better understanding and treating mental illness. This review discusses the clinical opportunities and challenges posed by epigenetic research in psychiatry. Using individual examples, the main conclusions are drawn that confirm the role of adverse life events, alone or in combination with genetic risk, in the epigenetic programming of neuropsychiatric systems. Further epigenetic studies show encouraging results in the use of methylation changes as diagnostic markers of disease manifestations and provide predictive tools for assessing progression and response to treatment. The potential for the use of targeted epigenetic pharmacotherapy, combined with psychosocial methods, in the context of the personalized medicine of the future in psychiatry is discussed next. It concludes with a discussion of methodological limitations that can make it difficult to interpret epigenetic data in psychiatry. They mainly arise due to the heterogeneity of individuals, both at the level of the whole organism and at the level of tissues, and require new strategies to better assess the biological significance of epigenetic data and their translational use in psychiatry. Overall, we believe that epigenetics can provide new insights and a more comprehensive understanding of the etiology and pathogenesis of mental illness, and should ultimately improve the nosology, treatment and prevention of mental disorders.

Epigenetic Programming of Cancer-Related Inflammation byncRNA Rheostat: Impact on Tumor Directed Immune Therapies

Accumulating evidences demonstrate that the host genome's epigenetic modificationsare essential for living organisms to adapt extreme conditions.DNA methylation, covalent modifications of histone, andinter-association of non-coding RNAs facilitate the cellular manifestation ofepigenetic changes in the genome. Out of various factors involved in the epigenetic programming of the host, miRNA (microRNA) and LncRNA (Long non-coding RNA) are new generationnon-coding molecules that influence a variety of cellular processes like immunity, cellular differentiation, and tumor development. During tumor development, temporal changes in miRNA/LncRNA rheostat influence sterile inflammatory responses accompanied by the changes in the carcinogenic signalling in the host. At the cellular level, this is manifested by the up-regulation of Inflammasome and inflammatory pathways, which promotes cancer-related inflammation. In view of this, we discuss the potential of lncRNA and miRNA directed interventions in regulating inflammation and tumor development in the host.