Dynamic regulation of cerebral DNA repair genes by psychological stress

Exploring the interplay between stress mediators and skin microbiota in shaping age-related hallmarks: A review

Psychological stress is a major contributing factor to several health problems (e.g., depression, cardiovascular disease). Around 35 % of the world's population suffers from it, including younger generations. Physiologically, stress manifests through neuroendocrine pathways (Hypothalamic-Pituitary-Adrenal (HPA) axis and Sympathetic-Adrenal-Medullary (SAM) system) which culminate in the production of stress mediators like cortisol, epinephrine and norepinephrine. Stress and its mediators have been associated to body aging, through molecular mechanisms such as telomere attrition, mitochondrial dysfunction, cellular senescence, chronic inflammation, and dysbiosis, among others. Regarding its impact in the skin, stress impacts its structural integrity and physiological function. Despite this review focusing on several hallmarks of aging, emphasis was placed on skin microbiota dysbiosis. In this line, several studies, comprising different age groups, demographic contexts and body sites, have reported skin microbiota alterations associated with aging, and some effects of stress mediators on skin microbiota have also been reviewed in this paper. From a different perspective, since it is not a "traditional" stress mediator, oxytocin, a cortisol antagonist, has been related to glucorticoids inhibition and to display positive effects on cellular aging. This hormone dysregulation has been associated to psychological issues such as depression, whereas its upregulation has been linked to positive social interaction.

Stress-induced biological aging: A review and guide for research priorities

Exposure to chronic adverse conditions, and the resultant activation of the neurobiological response cascade, has been associated with an increased risk of early onset of age-related disease and, recently, with an older biological age. This body of research has led to the hypothesis that exposure to stressful life experiences, when occurring repeatedly or over a prolonged period, may accelerate the rate at which the body ages. The mechanisms through which chronic psychosocial stress influences distinct biological aging pathways to alter rates of aging likely involve multiple layers in the physiological-molecular network. In this review, we integrate research using animal, human, and in vitro models to begin to delineate the distinct pathways through which chronic psychosocial stress may impact biological aging, as well as the neuroendocrine mediators (i.e., norepinephrine, epinephrine, and glucocorticoids) that may drive these effects. Findings highlight key connections between stress and aging, namely cellular metabolic activity, DNA damage, telomere length, cellular senescence, and inflammatory response patterns. We conclude with a guiding framework and conceptual model that outlines the most promising biological pathways by which chronic adverse conditions could accelerate aging and point to key missing gaps in knowledge where future research could best answer these pressing questions.

The role of base excision repair in major depressive disorder and bipolar disorder

BACKGROUND

In vivo and in vitro studies suggest that inflammation and oxidative damage may contribute to the pathogenesis of major depressive disorder (MDD) and bipolar disorder (BD). Imbalance between DNA damage and repair is an emerging research area examining pathophysiological mechanisms of these major mood disorders. This systematic review sought to review DNA repair enzymes, with emphasis on the base excision repair (BER), in mood disorders.

METHODS

We conducted a comprehensive literature search of Ovid MEDLINE® Epub Ahead of Print, Ovid MEDLINE® In-Process & Other Non-Indexed Citations, Ovid MEDLINE® Daily, EMBASE (1947), and PsycINFO for studies investigating the alterations in base excision repair in patients with MDD or BD.

RESULTS

A total of 1364 records were identified. 1352 records remained after duplicates were removed. 24 records were selected for full-text screening and a remaining 12 articles were included in the qualitative synthesis. SNPs (single nucleotide polymorphisms) of several BER genes have been shown to be associated with MDD and BD. However, it was difficult to draw conclusions from BER gene expression studies due to conflicting findings and the small number of studies.

LIMITATIONS

All studies were correlational so it was not possible to draw conclusions regarding causality.

CONCLUSION

Future studies comparing DNA repair during the manic or depressive episode to remission will give us a better insight regarding the role of DNA repair in mood disorders. These alterations might be utilized as diagnostic and prognostic biomarkers as well as measuring treatment response.

An evolutionary perspective on stress responses, damage and repair

Variation in stress responses has been investigated in relation to environmental factors, species ecology, life history and fitness. Moreover, mechanistic studies have unravelled molecular mechanisms of how acute and chronic stress responses cause physiological impacts ('damage'), and how this damage can be repaired. However, it is not yet understood how the fitness effects of damage and repair influence stress response evolution. Here we study the evolution of hormone levels as a function of stressor occurrence, damage and the efficiency of repair. We hypothesise that the evolution of stress responses depends on the fitness consequences of damage and the ability to repair that damage. To obtain some general insights, we model a simplified scenario in which an organism repeatedly encounters a stressor with a certain frequency and predictability (temporal autocorrelation). The organism can defend itself by mounting a stress response (elevated hormone level), but this causes damage that takes time to repair. We identify optimal strategies in this scenario and then investigate how those strategies respond to acute and chronic exposures to the stressor. We find that for higher repair rates, baseline and peak hormone levels are higher. This typically means that the organism experiences higher levels of damage, which it can afford because that damage is repaired more quickly, but for very high repair rates the damage does not build up. With increasing predictability of the stressor, stress responses are sustained for longer, because the animal expects the stressor to persist, and thus damage builds up. This can result in very high (and potentially fatal) levels of damage when organisms are exposed to chronic stressors to which they are not evolutionarily adapted. Overall, our results highlight that at least three factors need to be considered jointly to advance our understanding of how stress physiology has evolved: (i) temporal dynamics of stressor occurrence; (ii) relative mortality risk imposed by the stressor itself versus damage caused by the stress response; and (iii) the efficiency of repair mechanisms.

Chronic stress increases transcriptomic indicators of biological aging in mouse bone marrow leukocytes

Research with animals and humans has demonstrated that chronic stress exposure can impact key biological aging pathways such as inflammation and DNA damage, suggesting a mechanism through which stress may increase risk for age-related disease. However, it is less clear whether these effects extend to other hallmarks of the aging process, such as cellular senescence. Male SCID mice were exposed to 14 days of restraint stress, with (n ​= ​6) or without (n ​= ​10) propranolol administration, or a non-stress control condition (n ​= ​10). Normal femoral bone marrow leukocytes were isolated from engrafted leukemia cells that had been injected prior to the stressor, as the mice were also under a cancer challenge. We performed whole genome transcriptional profiling to assess indicators of biological aging: cell stress, DNA damage repair, cellular senescence markers p16^INK4a and p21, and the pro-inflammatory senescence-associated secretory phenotype (SASP). ANCOVAs that adjusted for tumor load and Fisher's pairwise comparisons revealed that stressed mice had enhanced p16^INK4a (p ​= ​.02) and p21 (p ​= ​.004), lower DNA damage repair (p ​< ​.001), and higher SASP (p ​= ​.03) gene expression than control mice. Stressed mice also showed up-regulated beta-adrenergic (CREB) and inflammatory (NF-кB, AP-1) and down-regulated cell stress (Nrf2) transcription factor activity relative to control mice (ps ​< ​.01). Propranolol reversed CREB and Nrf2 activity (ps ​< ​.03). Findings suggest that chronic stress exposure can impact several key biological aging pathways within bone marrow leukocytes and these effects may be partially mediated by sympathetic beta-adrenergic receptor activation.

Dichloromethane increases mutagenic DNA damage and transformation ability in cholangiocytes and enhances metastatic potential in cholangiocarcinoma cell lines

Dichloromethane (DCM), a widely used chlorinated solvent, is classified by IARC (2017) as probably carcinogenic to humans. Exposure to DCM has been associated with increased incidence of cholangiocarcinoma (CCA) in humans. This study aimed to investigate how DCM could contribute to CCA development by investigating the effects of DCM on DNA damage and cell transformation in cholangiocytes (MMNK-1) and on metastatic potential as measured by invasion and cell migration in malignant CCA cell lines (HuCCA-1 and RMCCA-1). MMNK-1 cells treated with the non-cytotoxic concentration of DCM (25 μM, 24 h) significantly increased the levels of mutagenic DNA adducts including 8-hydroxydeoxyguanosine, 8-OHdG, (1.84-fold, p < 0.01) and 8-nitroguanine (1.96-fold, p < 0.01) and enhanced cell transformation by 1.47-fold (p < 0.01). In addition, the expression of various genes involved in carcinogenesis, namely, NFE2L2 (antioxidative response), CXCL8 (inflammation), CDH1 (cell adhesion), MMP9 (tissue remodeling) and MKI67 (cell proliferation) were altered in cholangiocytes treated with DCM. When MMNK-1 cells were transformed by DCM, the expression of all the aforementioned genes was also increased. In malignant cell lines (HuCCA-1 and RMCCA-1), DCM treatment resulted in increased CXCL8 and MMP9 transcription and decreased CDH1 transcription accompanied by increased invasion and migration capabilities of these cells. Taken together, this study demonstrated that DCM exposure could be linked to the development of CCA.

Impaired PARP activity in response to the β-adrenergic receptor agonist isoproterenol

Psychological stress has been associated with DNA damage, thus increasing the risk of numerous diseases including cancer. Here, we investigate the effect of acute and chronic stress on poly(ADP-ribose) polymerase-1 (PARP-1), a sensor of DNA damage and DNA repair initiator. In order to mimic the chronic release of epinephrine, human peripheral blood mononuclear cells (PBMCs) were treated repeatedly with the sympathomimetic drug isoproterenol. We found significant induction of DNA strand breaks that remained unrepaired 24 h after ex vivo incubation. Isoproterenol-induced DNA strand breaks could be partially prevented by pre-treatment with the β-adrenergic receptor antagonist propranolol. Furthermore, the level of PARP-1 protein and PARP activity decreased and the levels of the PARP substrate nicotinamide adenine dinucleotide (NAD⁺) and of adenosine triphosphate (ATP), necessary to replenish NAD⁺ pools, were lowered by isoproterenol treatment. In conclusion our data provide novel insights into the mechanisms of isoproterenol-induced genotoxicity linking β-adrenergic stimulation and PARP-1.

Hippocampal metabolic differences implicate distinctions between physical and psychological stress in four rat models of depression

Major depressive disorder (MDD) is a heterogeneous and multi-factorial disorder, and the underlying molecular mechanisms remain largely unknown. However, many studies have indicated that the molecular mechanisms underlying depression in response to different stress may differ. After screening, 28-30 rats were included in each model of depression (chronic unpredictable mild stress (CUMS); learned helplessness (LH); chronic restraint stress (CRS); or social defeat (SD)). Non-targeted gas chromatography-mass spectrometry was used to profile the metabolic changes in the hippocampus. As a result, all four models exhibited significant depression-like behavior. A total of 30, 24, 19, and 25 differential metabolites were identified in the CUMS, LH, CRS, and SD models, respectively. Interestingly, the hierarchical clustering results revealed two patterns of metabolic changes that are characteristic of the response to cluster 1 (CUMS, LH) and cluster 2 (CRS, SD) stress, which represent physical and psychological stress, respectively. Bioinformatic analysis suggested that physical stress was mainly associated with lipid metabolism and glutamate metabolism, whereas psychological stress was related to cell signaling, cellular proliferation, and neurodevelopment, suggesting the molecular changes induced by physical and psychological stress were different. Nine shared metabolites were opposite in the directions of change between physical and psychological models, and these metabolites were associated with cellular proliferation and neurodevelopment functions, indicating the response to physical and psychological stress was different in the activation and deactivation of the final common pathway to depression. Our results provide a further understanding of the heterogeneity in the molecular mechanisms of MDD that could facilitate the development of personalized medicine for this disorder.

DNA Damage in Major Psychiatric Diseases

Human cells are exposed to exogenous insults and continuous production of different metabolites. These insults and unwanted metabolic products might interfere with the stability of genomic DNA. Recently, many studies have demonstrated that different psychiatric disorders show substantially high levels of oxidative DNA damage in the brain accompanied with morphological and functional alterations. It reveals that damaged genomic DNA may contribute to the pathophysiology of these mental illnesses. In this article, we review the roles of oxidative damage and reduced antioxidant ability in some vastly studied psychiatric disorders and emphasize the inclusion of treatment options involving DNA repair. In addition, while most currently used antidepressants are based on the manipulation of the neurotransmitter regulation in managing different mental abnormalities, they are able to prevent or reverse neurotoxin-induced DNA damage. Therefore, it may be plausible to target on genomic DNA alterations for psychiatric therapies, which is of pivotal importance for future antipsychiatric drug development.