Effects chronic administration of corticosterone and estrogen on HPA axis activity and telomere length in brain areas of female rats.

Chronic stress is related to the acceleration of telomere shortening. Recent work showed a correlation between chronic psychosocial stress and reduced telomere length in certain cells. The exposure of T lymphocytes to cortisol promoted a significant reduction in telomerase activity. Although stress can promote changes in telomere length, whether increased glucocorticoid concentrations alter telomere length in brain tissue cells is unclear. In addition to modulating the activity of the stress system, estrogen also influences telomere length. The objective of this study was to verify whether chronic exposure to glucocorticoids promotes changes in the telomere length of encephalic areas involved in the control of HPA axis activity and whether estrogen affects these changes. Wistar rats were ovariectomized and treated with estradiol cypionate [(50 or 100 µg/kg, subcutaneously)] or oil and 20 mg/kg corticosterone or vehicle (isotonic saline with 2% Tween 80, subcutaneously) for 28 days. On the day after the end of the hormonal treatment, the animals were euthanized for collection of blood, brain and pituitary gland samples. Estrogen modulated the activity of the HPA axis. CRH, AVP and POMC mRNA levels were reduced by estrogen. At least in doses and treatment time used, there was no correlation between effects of exposure to glucocorticoids and estrogen on telomere length in the brain areas of female rats. However, estrogen treatment reduced the telomere length in the central amygdala and dorsal hippocampus, but not in the PVN, indicating a variation of reaction of telomeres for estrogen in different brain areas.

TERT inhibition leads to reduction of IL-6 expression induced by palmitic acid and interferes with the protective effects of tibolone in an astrocytic cell model.

Although it has been shown that telomerase has neuroprotective effects, mainly as a result of its non-canonical functions in neuronal cells, its role with respect to glial cells remains unknown. There is growing evidence indicating that telomerase plays an important role with respect to inflammation, especially in the regulation of pro-inflammatory cytokine gene expression. The present study aimed to evaluate the role of telomerase in an astrocyte cell model treated with palmitic acid (PA) and tibolone. Cell death, reactive oxygen species production and interleukin-6 expression were evaluated under telomerase inhibition with the BIBR1532 compound in T98G cells treated with tibolone and PA, using fluorometry, flow cytometry, enzyme-linked immunosorbent assays and the quantitative polymerase chain reaction. The results obtained showed that telomerase protein was increased by PA after 36 hours, alone or in combination with tibolone, and that its activity was affected by PA. Telomerase inhibition reduced interleukin-6 expression and it interfered with the protective effects of tibolone on cell death. Moreover, tibolone increased Tyr707 phosphorylation in PA-treated cells. In the present study, we provide novel findings about the regulation of telomerase by PA and tibolone. Telomerase was involved in inflammation by PA and in protective effects of tibolone. Therefore, we conclude that telomerase could play a dual role in these cells.

Anthropogenic Effects on Natural Mammalian Populations: Correlation Between Telomere Length and Coal Exposure.

The Candiota coal mine in Rio Grande do Sul (RS) is one of the largest in Brazil. Coal is a fossil fuel that causes environmental impacts from its extraction to combustion due to the release of different agents, such as polycyclic aromatic hydrocarbons (PAH) and heavy metals. Ctenomys torquatus are herbivorous and subterranean rodents that dig tunnels with their paws and teeth and can be exposed to coal through contaminated food. Exposure to pollutants can cause DNA damage and affect different tissues, inducing alterations in the population structure and genetic diversity. Our study aimed to evaluate the effect of exposure to coal and its derivatives on the C. torquatus population and to examine the relationship of coal exposure with variations in absolute telomere length (aTL), global DNA methylation and genotoxicity. Our study showed an inverse correlation between telomere length and coal exposure in addition to an increase in DNA damage. The results indicate that coal and its byproducts can contribute to the alteration of the C. torquatus population structure, as evidenced by a reduction in the number of adults.

Long-term in vitro treatment with telomerase inhibitor MST-312 induces resistance by selecting long telomeres cells.

Telomerase is a good target for new anticancer drug development because it is present in over 85% of human tumours. However, despite chronic therapy is a condition for anti-telomerase approach, the effects of long-term treatment with telomerase inhibitors remain not well understood. In this work, it was evaluated the effects of long-term treatment of human MDA-MB-231 breast cancer cells with the telomerase inhibitor MST-312. Cells were treated for 72 hours or 140 days, and it was accessed their viability, proliferation rate, morphology, telomeric DNA content, and resistance mechanism. The drug had a clear short-term effect, including chemosensitizing cells for docetaxel and irinotecan, but the chronic exposition led to selection of long telomeres clones, changing characteristics of original cell line. This effect was confirmed in a clonal culture with homogenous karyotype. MRP-1 expression and alternative lengthening of telomeres (ALT) were discarded as additional mechanisms of resistance. This data suggest that, considering the intra-tumour heterogeneity (ITH), what is already a big challenge for treatment of cancer, chronic exposition to telomerase inhibitors can promote tumour adaptations with potential clinical repercussion, drawing attention to ongoing clinical trials and pointing important considerations most times neglected on studies about use of these inhibitors on cancer therapy. SIGNIFICANCE OF THE STUDY: Antitumour action of telomerase inhibitors is well known, but it depends on a long-term exposition because cells will undergo telomere erosion only after many duplication cycles. Recently, the frustrating results of clinical trials with these inhibitors aroused the interest of the scientific community to understand the mechanisms of resistance to anti-telomerase therapy. In this study, we conducted an 18-week experiment to show that telomerase inhibition can lead to cell adaptations and selection of long-telomeres clones, leading to acquisition of resistance. However, we also showed that this inhibitor can sensitize cells to the chemotherapeutic drugs docetaxel and irinotecan.

Exploring telomere length in mother-newborn pairs in relation to exposure to multiple toxic metals and potential modifying effects by nutritional factors.

BACKGROUND: The uterine environment may influence telomere length at birth, which is essential for cellular function, aging, and disease susceptibility over the lifespan. However, little is known about the impact of toxic chemicals on early-life telomeres. Therefore, we assessed the potential impact of multiple toxic metals on relative telomere length (rTL) in the maternal blood, cord blood, and placenta, as well as the potential modifying effects of pro-oxidants. METHOD: In a mother-child cohort in northern Argentina (n = 169), we measured multiple toxic metals in the maternal blood or urine collected during late pregnancy, as well as the placenta and cord blood collected at delivery, using inductively coupled plasma mass spectrometry (ICP-MS). We assessed associations of log2-transformed metal concentrations with rTL, measured in maternal and cord blood leukocytes and the placenta by real-time PCR, using multivariable-adjusted linear regression. Additionally, we tested for modifications by antioxidants (zinc, selenium, folate, and vitamin D3). RESULTS: Exposure to boron and antimony during pregnancy was associated with shorter maternal rTL, and lithium with longer maternal rTL; a doubling of exposure was associated with changes corresponding to 0.2-0.4 standard deviations (SD) of the rTL. Arsenic concentrations in the placenta (n = 98), blood, and urine were positively associated with placental rTL, about 0.2 SD by doubled arsenic. In the cord blood (n = 88), only lead was associated with rTL (inversely), particularly in boys (p for interaction 0.09). Stratifying by newborn sex showed ten times stronger association in boys (about 0.6 SD) than in girls. The studied antioxidants did not modify the associations, except that with antimony. CONCLUSIONS: Elevated exposure to boron, lithium, arsenic, and antimony was associated with maternal or newborn rTL in a tissue-specific, for lead also sex-specific, manner. Nutritional antioxidants did not generally influence the associations.

Chronic Lithium Treatment Increases Telomere Length in Parietal Cortex and Hippocampus of Triple-Transgenic Alzheimer's Disease Mice.

Telomere length (TL) is a biomarker of cell aging, and its shortening has been linked to several age-related diseases. In Alzheimer's disease (AD), telomere shortening has been associated with neuroinflammation and oxidative stress. The majority of studies on TL in AD were based on leucocyte DNA, with little information about its status in the central nervous system. In addition to other neuroprotective effects, lithium has been implicated in the maintenance of TL. The present study aims to determine the effect of chronic lithium treatment on TL in different regions of the mouse brain, using a triple-transgenic mouse model (3xTg-AD). Eighteen transgenic and 22 wild-type (Wt) male mice were treated for eight months with chow containing 1.0 g (Li1) or 2.0 g (Li2) of lithium carbonate/kg, or standard chow (Li0). DNA was extracted from parietal cortex, hippocampus and olfactory epithelium and TL was quantified by real-time PCR. Chronic lithium treatment was associated with longer telomeres in the hippocampus (Li2, p = 0.0159) and in the parietal cortex (Li1, p = 0.0375) of 3xTg-AD compared to Wt. Our findings suggest that chronic lithium treatment does affect telomere maintenance, but the magnitude and nature of this effect depend on the working concentrations of lithium and characteristics of the tissue. This effect was observed when comparing 3xTg-AD with Wt mice, suggesting that the presence of AD pathology was required for the lithium modulation of TL.

Telomere measurement in individuals occupationally exposed to pesticide mixtures in tobacco fields.

Occupational exposure to pesticides in tobacco fields causes genetic damage in farmers. The aim of this study was to analyze tobacco farmers chronically exposed to low doses of pesticides and nicotine (present in the tobacco leaves) in relation to absolute telomere length (aTL), and explore the influence of lifestyle characteristics, oxidative stress, and inorganic element levels. DNA was isolated from peripheral blood samples from agricultural workers and non-exposed individuals, and aTL was measured by quantitative real time polymerase chain reaction (qPCR) analysis. Oxidative stress (thiobarbituric acid reactive substances [TBARS], which measures oxidative damage to lipids; and toxic equivalent antioxidant capacity [TEAC], which measures total equivalent antioxidant capacity) was evaluated in serum, and inorganic element content was analyzed in whole blood through particle-induced X-ray emission technique. It was found that exposure to pesticides and tobacco smoking had significant effects on aTL. Individuals occupationally exposed to complex mixtures of pesticides in tobacco fields and individuals who smoked had decreased aTL compared with the non-exposed group. TBARS and TEAC were significantly elevated in the exposed group. There were no significant differences in inorganic elements. There was no evidence of an influence of age, gender, consumption of alcoholic beverages, or intake of fruits and vegetables on aTL within the groups. In addition, years of work in the tobacco field in the exposed group did not influence any of the variables analyzed. Although further studies were needed, these results suggested differences in telomere maintenance in tobacco farmers compared with the control group, indicating that telomere length may be a good biomarker of occupational exposure.

Increased telomere length and proliferative potential in peripheral blood mononuclear cells of adults of different ages stimulated with concanavalin A.

BACKGROUND: Recently, a direct correlation with telomere length, proliferative potential and telomerase activity has been found in the process of aging in peripheral blood cells. The objective of the study was to evaluate telomere length and proliferative potential in peripheral blood mononuclear cells (PBMCs) after stimulation with Concanavalin A (ConA) of young adults compared with older adults. METHODS: Blood samples were obtained from 20 healthy young males (20-25 years old) (group Y) and 20 males (60-65 years old) (group O). We compared PBMC proliferation before and after stimulation with ConA. DNA was isolated from cells separated before and after culture with ConA for telomeric measurement by real-time polymerase chain reaction. RESULTS: In vitro stimulation of PBMCs from young subjects induced an increase of telomere length as well as a higher replicative capacity of cell proliferation. Samples from older adults showed higher loss of telomeric DNA (p = 0.03) and higher levels of senescent (≤6.2 kb) telomeric DNA (p = 0.02) and displayed a marked decrease of proliferation capacity. Viability cell counts and CFSE tracking in 72-h-old cell cultures indicated that group O PBMCs (CD8+ and CD4+ T cells) underwent fewer mitotic cycles and had shorter telomeres than group Y (p = 0.04). CONCLUSIONS: Our findings confirm that telomere length in older-age adults is shorter than in younger subjects. After stimulation with ConA, cells are not restored to the previous telomere length and undergo replicative senescence. This is in sharp contrast to the response observed in young adults after ConA stimulation where cells increase in telomere length and replicative capacity. The mechanisms involved in this phenomenon are not yet clear and merit further investigation.

A prospective analysis of telomere length and pancreatic cancer in the alpha-tocopherol beta-carotene cancer (ATBC) prevention study.

Smoking and diabetes, consistent risk factors for pancreatic cancer, are also factors that influence telomere length maintenance. To test whether telomere length is associated with pancreatic cancer risk, we conducted a nested case-control study in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study cohort of male smokers, aged 50-69 years at baseline. Between 1992 and 2004, 193 incident cases of pancreatic adenocarcinoma occurred (mean follow-up from blood draw: 6.3 years) among participants with whole blood samples available for telomere length assays. For these cases and 660 controls, we calculated odds ratios (OR) and 95% confidence intervals using unconditional logistic regression, adjusting for age, number of years smoked regularly, and history of diabetes mellitus. Telomere length was categorized into quartiles (shortest to longest) and analyzed as both a categorical and a continuous normal variable (reported per 0.2 unit increase in telomere length). All statistical tests were two-sided. Longer telomere length was significantly associated with increased pancreatic cancer risk (continuous OR = 1.26 95% CI = 1.09-1.46; highest quartile compared to lowest, OR = 1.57, 95% CI = 1.01-2.43, p-trend = 0.007). This association remained for subjects diagnosed within the first five years of blood draw (continuous OR = 1.46, 95% CI = 1.19-1.79 highest quartile OR = 2.92, 95% CI = 1.47-5.77, p-trend = 0.002), but not those diagnosed greater than five years after blood draw (continuous OR = 1.03, 95% CI = 0.85-1.22; highest quartile OR = 1.04, 95% CI = 0.60-1.79). This is the first prospective study to suggest an association between longer blood leukocyte telomere length and increased pancreatic cancer risk.