Bull Caroline, Christensen Helen, Fenech Michael
Nutritional Genomics and DNA Damage Diagnostics Laboratory, CSIRO Animal, Food and Health Sciences, Adelaide, South Australia, Australia; Department of Microbiology & Immunology, School of Molecular & Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia.
Black Dog Institute, Prince of Wales Hospital, Randwick, New South Wales, Australia.
PLoS One. 2015 Mar 6;10(3):e0119367. doi: 10.1371/journal.pone.0119367. eCollection 2015.
Chronic psychological stress and nutritional deficiencies are factors that impact negatively on human health and disease risk. Chronic stress has been associated with accelerated leukocyte telomere shortening in numerous cohorts, however, a mechanistic link has proven elusive. This study tested the hypotheses that chronic exposure to the stress hormone, cortisol, causes telomere shortening and chromosome instability (CIN) in vitro, and that these effects would be further exacerbated by folate (vitamin B9) deficiency. Primary human lymphocytes were maintained in vitro for 12 days in medium containing either 25 nM folic acid (FA(low)) or 100 nM FA (FA(high)), together with either 0, 400, 1000 or 3500 nM cortisol. The interactive effects of cortisol and FA were examined by comparing telomere length (TL), biomarkers of DNA damage, and cytostasis. At day 12 TL was 5-17% longer in lymphocytes cultured in FA(low) conditions (mean ± SD;10.2% ± 1.6), compared with those in FA(high) medium (9.1% ± 1, p = 0.02). Refuting the hypothesis, TL was consistently greater in the presence of cortisol. The effect of FA deficiency on the frequency of DNA damage was significant for nucleoplasmic bridges, circular nuclei, micronuclei and nuclear buds, (p < 0.0001-0.001). The effect of cortisol, however, was negligible, only reaching statistical significance for the frequency of fused nuclei (p = 0.04). Cortisol was significantly associated with reduced cell division and growth and had an apparent protective effect on cell viability in the FA(low) conditions. Conclusions: Both chronic cortisol exposure, and folate deficiency, resulted in telomere elongation, however, the effect of cortisol was marginal relative to that of folate. Cortisol was not associated with increased chromosomal instability, but caused a significant reduction in cell division and growth. Together these results indicate that cortisol is not directly genotoxic and that the telomere shortening associated with increased psychological stress in vivo may not be explained by a direct effect of cortisol.
慢性心理压力和营养缺乏是对人类健康和疾病风险产生负面影响的因素。在众多队列研究中，慢性压力与白细胞端粒加速缩短有关，然而，其作用机制一直难以捉摸。本研究检验了以下假设：长期暴露于应激激素皮质醇会在体外导致端粒缩短和染色体不稳定（CIN），并且叶酸（维生素B9）缺乏会进一步加剧这些影响。原代人淋巴细胞在含有25 nM叶酸（FA（低））或100 nM叶酸（FA（高））以及0、400、1000或3500 nM皮质醇的培养基中体外培养12天。通过比较端粒长度（TL）、DNA损伤生物标志物和细胞生长抑制来研究皮质醇和叶酸的交互作用。在第12天，与在FA（高）培养基中的淋巴细胞相比，在FA（低）条件下培养（平均值±标准差；10.2%±1.6）的淋巴细胞的TL长5 - 17%（9.1%±1，p = 0.02）。与假设相反，在存在皮质醇的情况下，TL始终更长。叶酸缺乏对核质桥、圆形核、微核和核芽的DNA损伤频率有显著影响（p < 0.0001 - 0.001）。然而，皮质醇的影响可忽略不计，仅对融合核频率达到统计学显著水平（p = 0.04）。皮质醇与细胞分裂和生长减少显著相关，并且在FA（低）条件下对细胞活力有明显的保护作用。结论：长期暴露于皮质醇和叶酸缺乏均导致端粒延长，然而，皮质醇的作用相对于叶酸而言较小。皮质醇与染色体不稳定性增加无关，但导致细胞分裂和生长显著减少。这些结果共同表明，皮质醇不是直接的基因毒性物质，体内与心理压力增加相关的端粒缩短可能无法用皮质醇的直接作用来解释。
