Personal exposure to NO2 and benzene in the Cape Town region of South Africa is associated with shorter leukocyte telomere length in women

Alterations in leukocyte telomere length and mitochondrial DNA copy number in benzene poisoning patients

OBJECTIVE

The aim of this study is to examine and evaluate the impact of benzene poisoning on the relative content of the mitochondrial MT-ND1 gene and telomere length in individuals with occupational chronic benzene poisoning (CBP) compared to a control group. The study will analyze and gather data on the mitochondrial gene content and telomere length in cases of benzene poisoning, and investigate the relationship with blood routine parameters in order to contribute scientific experimental data for the prevention and treatment of CBP.

METHOD

The case group comprised 30 individuals diagnosed with occupational chronic benzene poisoning, whereas the control group consisted of 60 healthy individuals who underwent physical examinations at our hospital concurrently. Blood routine indicators were detected and analyzed, and the PCR method was employed to measure changes in mitochondrial MT-ND1 content and telomere length. Subsequently, a comparison and analysis of the aforementioned indicators was conducted.

RESULT

The case group exhibited a higher mitochondrial gene content (median 366.2, IQR 90.0 rate) compared to the control group (median 101.5, IQR 12.0 rate), with a statistically significant difference between the two groups (P < 0.05). Additionally, the case group demonstrated lower white blood cell levels (3.78 ± 1.387 × 109/L) compared to the control group (5.74 ± 1.41 × 109/L), with a significant difference between the two groups (P < 0.05). Furthermore, the case group displayed lower red blood cell levels (3.86 ± 0.65 × 1012/L) compared to the control group (4.89 ± 0.65 × 1012/L), with a significant difference between the two groups (P < 0.05). The hemoglobin level in the case group (113.33 ± 16.34 g/L) was lower than that in the control group (138.22 ± 13.22 g/L). There was a significant difference between the two groups (P < 0.05). Platelet levels in the case group (153.80 ± 58.31 × 109/L) is smaller than the control group (244.92 ± 51.99 × 109/L), there was a significant difference between the two groups (P < 0.05). The average telomere length of the normal control group was 1.451 ± 0.475 (rate); The mean telomere length of individuals in the case group diagnosed with benzene poisoning was determined to be 1.237 ± 0.457 (rate). No significant correlation was observed between telomere length and three blood routine parameters, namely white blood cells (WBC), hemoglobin (HB), and platelets (PLT). However, a significant correlation was found between telomere length and red blood cell count (RBC). Additionally, a negative correlation was observed between mitochondrial gene content and white blood cell count (r = - 0.314, P = 0.026), as well as between mitochondrial gene content and red blood cell count (r = - 0.226, P = 0.032). Furthermore, a negative correlation was identified between mitochondrial gene content and hemoglobin (r = - 0.314, P = 0.028), and platelets (r = - 0.445, P = 0.001).

CONCLUSION

Individuals diagnosed with occupational chronic benzene poisoning exhibit a reduction in telomere length and an elevation in the relative content of the mitochondrial MT-ND1 gene. Moreover, a negative correlation is observed between the content of the mitochondrial MT-ND1 gene and four blood routine parameters, namely white blood cells (WBC), red blood cells (RBC), hemoglobin (HB), and platelets (PLT). Consequently, benzene exposure may potentially contribute to the onset of premature aging.

Oxidative stress-affected ACSL1 hydroxymethylation triggered benzene hematopoietic toxicity by inflammation and senescence

Long-term benzene exposure is harmful and causes hematopoietic dysfunction. However, the mechanism of benzene hematopoietic toxicity is still unclear. Acyl-CoA Synthetase Long-Chain Family Member 1 (ACSL1) has been found to participate in the progress of a variety of benign and malignant diseases, but there is no research about its effect on benzene-induced hematopoietic toxicity. Herein, We exposed C57BL/6J mice to benzene to construct an in vivo model. Human peripheral blood mononuclear cells (THP-1 cells) were treated with benzene metabolite 1, 4-BQ to construct an in vitro model. We observed that the ACSL1 expression was upregulated both in vivo and in vitro. Moreover, inhibition of ACSL1 relieved inflammation and senescence development in vitro, suggesting that ACSL1 mediates inflammation and senescence. As for the regulation mechanism of ACSL1 expression, it is closely related to hydroxymethylation modification. This was proved by hydroxymethylated DNA immunoprecipitation (hMeDIP) experiments. Furthermore, oxidative stress influenced the hydroxymethylation process. These results showed that benzene hematopoietic toxicity occurs through the induction of oxidative stress and thus the regulation of ACSL1 hydroxymethylation, which in turn mediates inflammation and senescence. Thus, this study might be of great significance in identifying and preventing benzene exposure in the early stage.

Polystyrene nanoplastics induce haematotoxicity with cell oxeiptosis and senescence involved in C57BL/6J mice

Nanoplastics (NPs) has become a worrying serious environmental problem. However, the toxicological effects and mechanisms of NPs on hematopoiesis are still unknown. To this end, male C57BL/6J mice were directly exposed to the serial concentration gradient of polystyrene NPs (PSNPs, 0, 30, 60, and 120 μg d), respectively, for 42 days by intragastric administration. Results show that PSNPs were clearly visible in bone tissues, meanwhile, induced the count of major blood indicators (WBC, RBC, and LYM) decreased. H&E staining displayed that exposed to PSNPs can cause hematopoietic damage of BM and extramedullary hematopoiesis in spleen. Flow cytometry result show that the proportion of LSK represented a dose-dependent significantly decreased after PSNPs exposure. Further research found that PSNPs can cause the systemic oxidative stress occurs manifested as MDA accumulated. In addition, as the dose of PSNPs increased, the fluorescence intensity of Keap1 and p53 in femur sections gradually increased, meanwhile, the expression of cell oxeiptosis signal pathway Keap1/PGAM5/AIFM1 and the cell senescence signal pathway p53/p21 was all increased, markedly. Overall, our study demonstrated that PSNPs exposure caused oxidative stress, potentially resulting in cell oxeiptosis and senescence to develop haematotoxicity in C57BL/6J mice.

Ambient air pollution, genetic risk and telomere length in UK biobank

BACKGROUND

Telomere length (TL) is a biomarker of genomic aging. The evidence on the association between TL and air pollution was inconsistent. Besides, the modification effect of genetic susceptibility on the air pollution-TL association remains unknown.

OBJECTIVE

We aimed to evaluate the association of ambient air pollution with TL and further assess the modification effect of genetic susceptibility.

METHODS

433,535 participants with complete data of TL and air pollutants in UK Biobank were included. Annual average exposure of NO2, NOx, PM10 and PM2.5 was estimated by applying land use regression models. Genetic risk score (GRS) was constructed using reported telomere-related SNPs. Leukocyte TL was measured by quantitative polymerase chain reaction (qPCR). Multivariable linear regression models were employed to conduct associational analyses.

RESULTS

Categorical exposure models and RCS models both indicated U-shaped (for NO2 and NOx) and L-shaped (for PM10 and PM2.5) correlations between air pollution and TL. In comparison to the lowest quartile, the 2nd and 3rd quartile of NO2 (q2: -1.3% [-2.1%, -0.4%]; q3: -1.2% [-2.0%, -0.3%], NOx (q2: -1.3% [-2.1%, -0.5%]; q3: -1.4% [-2.2%, -0.5%]), PM2.5 (q2: -0.8% [-1.7%, 0.0%]; q3: -1.3% [-2.2%, -0.5%]), and the third quartile of PM10 (q3: -1.1% [-1.9%, -0.2%]) were inversely associated with TL. The highest quartile of NO2 was positively correlated with TL (q4: 1.0% [0.0%, 2.0%]), whereas the negative correlation between the highest quartile of other pollutants and TL was also attenuated and no longer significant. In the genetic analyses, synergistic interactions were observed between the 4th quartile of three air pollutants (NO2, NOx, and PM2.5) and genetic risk.

IMPACT STATEMENT

Our study for the first time revealed a non-linear trend for the association between air pollution and telomere length. The genetic analyses suggested synergistic interactions between air pollution and genetic risk on the air pollution-TL association. These findings may shed new light on air pollution's health effects, offer suggestions for identifying at-risk individuals, and provide hints regarding further investigation into gene-environment interactions.

Hypertension and cellular senescence

Essential or primary hypertension is a wordwide health problem. Elevated blood pressure (BP) is closely associated not only with increased chronological aging but also with biological aging. There are various common pathways that play a role in cellular aging and BP regulation. These include but not limited to inflammation, oxidative stress, mitochondrial dysfunction, air pollution, decreased klotho activity increased renin angiotensin system activation, gut dysbiosis etc. It has already been shown that some anti-hypertensive drugs have anti-senescent actions and some senolytic drugs have BP lowering effects. In this review, we have summarized the common mechanisms underlying cellular senescence and HT and their relationships. We further reviewed the effect of various antihypertensive medications on cellular senescence and suggest further issues to be studied.

Aging of mesenchymal stem cell: machinery, markers, and strategies of fighting

Human mesenchymal stem cells (MSCs) are primary multipotent cells capable of differentiating into osteocytes, chondrocytes, and adipocytes when stimulated under appropriate conditions. The role of MSCs in tissue homeostasis, aging-related diseases, and cellular therapy is clinically suggested. As aging is a universal problem that has large socioeconomic effects, an improved understanding of the concepts of aging can direct public policies that reduce its adverse impacts on the healthcare system and humanity. Several studies of aging have been carried out over several years to understand the phenomenon and different factors affecting human aging. A reduced ability of adult stem cell populations to reproduce and regenerate is one of the main  contributors to the human aging process. In this context, MSCs senescence is a major challenge in front of cellular therapy advancement. Many factors, ranging from genetic and metabolic pathways to extrinsic factors through various cellular signaling pathways, are involved in regulating the mechanism of MSC senescence. To better understand and reverse cellular senescence, this review highlights the underlying mechanisms and signs of MSC cellular senescence, and discusses the strategies to combat aging and cellular senescence.

Effects of air pollution on telomere length: Evidence from in vitro to clinical studies

Air pollution remains the major environmental problem globally. There is extensive evidence showing that the variety of air pollutants from environmental and occupational exposures cause adverse effects to our health. The clinical symptoms of those effects may present at a late stage, so surveillance is difficult to manage. Several biomarkers have been used for the early detection of health issues following exposure to air pollution, including the use of telomere length which indicates cellular senescence in response to oxidative stress. Oxidative stress is one of the most plausible mechanisms associated with exposure to air pollutants. Some specific contexts including age groups, gender, ethnicity, occupations, and health conditions, showed significant alterations in telomere length after exposure to air pollutants. Several reports demonstrated both negative and positive associations between telomere length and air pollution, the studies using different concentrations and exposure times to air pollution on the study of telomere lengths. Surprisingly, some studies reported that low levels of exposure to air pollutants (lower than regulated levels) caused the alterations in telomere length. Those findings suggest that telomere length could be one of most practical biomarkers in air pollution surveillance. Therefore, this review aimed to summarize and discuss the relationship between telomere length and exposure to air pollution. The knowledge from this review will be beneficial for the planning of public health to reduce health problems in the general population, particularly in vulnerable people, who still live in areas with high air pollution.

Personal exposure to benzene, toluene, ethylbenzene, and xylenes (BTEXs) mixture and telomere length: a cross-sectional study of the general US adult population

BACKGROUND

Benzene, Toluene, Ethylbenzene, and Xylenes (BTEXs) are a group of aromatic air pollutants from fossil fuels. There is no research on associations of the BTEXs mixture with telomere length (TL), a marker of cellular aging, in the general population.

METHODS

We analyzed a subsample of 549 US adults aged 20-59 years from the National Health and Nutrition Examination Survey 1999-2000. BTEXs samples were collected by passive exposure badges worn by participants for 48-72 h. Levels of BTEXs were measured with gas chromatography/mass spectrometry. Leukocyte TL was measured with qPCR. We used Bayesian Kernel Machine Regression (BKMR) to examine the effect of the BTEXs mixture on TL adjusting for potential confounders. Analyses were stratified by tobacco smoking status (serum cotinine≥10 ng/mL vs. <10 ng/mL).

RESULTS

Levels of personal exposure to BTEXs were detectable in most participants and were relatively higher in the 150 smokers than in the 399 nonsmokers. The BTEXs were moderately or strongly intercorrelated (0.5 < r ≤ 0.9, P < 0.05). All chemicals had weak, inverse correlations with TL (-0.1<r < 0, P > 0.05). In BKMR models among the nonsmokers, the BTEXs mixture was significantly inversely associated with TL at a low range of the BTEXs (20th-65th percentile) but was not associated with TL at a higher range (>65th percentile). Also, we found a U-shape association of benzene and a positive association of ethylbenzene with TL independent of other BTEXs. Among smokers, neither the BTEXs mixture nor any individual BTEXs were significantly associated with TL.

CONCLUSION

Within a low-to-middle range, exposure to the BTEXs mixture may be associated with shorter telomere length in the general nonsmoking population.

Physical activity attenuated the association of air pollutants with telomere length in rural Chinese adults

BACKGROUND

Exposure to air pollutants (nitrogen dioxide (NO₂) and particulate matters (PMs)) or physical inactivity is linked to telomere length (TL) shortening. However, there is a lack of research on combined effects of either NO₂ or PMs and physical activity (PA) on TL. This study aimed to explore the joint associations of air pollutants (NO₂ or PMs) and PA with relative TL in rural Chinese adults.

METHODS

This study was conducted among 2704 participants aged 18-79 years in rural China. Concentrations of NO₂ and PMs (PM with an aerodynamics diameter ≤ 1.0 μm (PM₁), ≤2.5 μm (PM_2.5) or ≤10 μm (PM₁₀)) were estimated using random forest models incorporated with satellites data, meteorological data, and land use information. Relative TL of each participant was measured by a quantitative real-time polymerase chain reaction. Linear regression models were applied to examine the independent associations between PA, NO₂ or PMs and relative TL. Interaction plots were used to depict the altered associations between NO₂, PM₁, PM_2.5, or PM₁₀ and relative TL along with increasing PA levels.

RESULTS

Each 1 μg/m³ increment in NO₂, PM₁, PM_2.5, or PM₁₀ was associated with a 0.038 (95% confidence intervals (CI): -0.044, -0.033), 0.036 (95% CI: -0.041, -0.031), 0.052 (95% CI: -0.059, -0.045), or 0.022 (95% CI: -0.025, -0.019) decrease in relative TL among all participants; similar findings were observed among normal glucose tolerance or impaired fasting glucose (IFG) participants as well as type 2 diabetes mellitus (T2DM) patients. PA at certain levels counteracted the association of air pollutants (NO₂, PM₁, PM_2.5, and PM₁₀) with relative TL among IFG participants or T2DM patients.

CONCLUSIONS

Long-term exposure to NO₂ and PMs was associated with relative TL shortening and these effects may be counteracted by PA at certain levels in IFG participants or T2DM patients.

Cardiovascular effects of air pollution: current evidence from animal and human studies

Air pollution is a global health concern. Particulate matter (PM)_2.5, a component of ambient air pollution, has been identified by the World Health Organization as one of the pollutants that poses the greatest threat to public health. Cardiovascular health effects have been extensively documented, and these effects are still being researched to provide an overview of recent literature regarding air pollution-associated cardiovascular morbidity and mortality in humans. Additionally, potential mechanisms through which air pollutants affect the cardiovascular system are discussed based on human and additional animal studies. We used the strategy of a narrative review to summarize the scientific literature of studies that were published in the past 7 yr. Searches were carried out on PubMed and Web of Science using predefined search queries. We obtained an initial set of 800 publications that were filtered to 78 publications that were relevant to include in this review. Analysis of the literature showed significant associations between air pollution, especially PM_2.5, and the risk of elevated blood pressure (BP), acute coronary syndrome, myocardial infarction (MI), cardiac arrhythmia, and heart failure (HF). Prominent mechanisms that underlie the adverse effects of air pollution include oxidative stress, systemic inflammation, endothelial dysfunction, autonomic imbalance, and thrombogenicity. The current review underscores the relevance of air pollution as a global health concern that affects cardiovascular health. More rigorous standards are needed to reduce the cardiovascular disease burden imposed by air pollution. Continued research on the health impact of air pollution is needed to provide further insight.

The Chemical Exposome of Human Aging

Aging is an inevitable biological phenomenon displayed by single cells and organs to entire organismal systems. Aging as a biological process is characterized as a progressive decline in intrinsic biological function. Understanding the causative mechanisms of aging has always captured the imagination of researchers since time immemorial. Although both biological and chronological aging are well defined and studied in terms of genetic, epigenetic, and lifestyle predispositions, the hallmarks of aging in terms of small molecules (i.e., endogenous metabolites to chemical exposures) are limited to obscure. On top of the endogenous metabolites leading to the onset and progression of healthy aging, human beings are constantly exposed to a natural and anthropogenic "chemical" environment round the clock, from conception till death, affecting one's physiology, health and well-being, and disease predisposition. The research community has started gaining sizeable insights into deciphering the aging factors such as immunosenescence, nutrition, frailty, inflamm-aging, and diseases till date, without much input from their interaction with exogenous chemical exposures. The "exposome" around us, mostly, accelerates the process of aging by affecting the internal biological pathways and signaling mechanisms that result in the deterioration of human health. However, the entirety of exposome on human aging is far from established. This review intends to catalog the known and established associations of the exposome from past studies focusing on aging in humans and other model organisms. Further discussed are the current technologies and informatics tools that enable the study of aging exposotypes, and thus, provide a window of opportunities and challenges to study the "aging exposome" in granular details.

Interaction effects of environmental response gene polymorphisms and benzene exposure on telomere length in shoe-making workers

Benzene is a globally occurring environmental and occupational pollutant that causes leukemia. To better understand telomere length (TL) as a function of benzene toxicity, we recruited 294 shoe-making workers and 102 controls from Wenzhou, China in 2011. Biomarkers of TL, cytokinesis-block micronucleus (MN) frequency, and white blood cells (WBC) were measured. In total, 18 polymorphic sites in environmental response genes, including metabolic and DNA repair genes, were analyzed. Results indicate that benzene exposure led to a longer TL at a threshold of 32 mg/m³-year of cumulative exposure dose (CED). Furthermore, the TL was longer in members of the damaged group, when evaluated for MN frequency (P < 0.001) and reduced WBC (P < 0.001), than in those of the normal group. Workers carrying genotype TT (β = 0.32, P = 0.042) in rs3212986 of ERCC1 and genotype TC (β = 0.24, P = 0.082) in rs1051740 of mEH exon3 were associated with a longer TL as compared to the wild-type group. TA (β = -0.53, P < 0.001) in rs6413432 of CYP2E1 was associated with a shorter TL. Benzene exposure interacted with the TA type in rs6413432 (β = 0.003, 95% CI: 0, 0.006, P = 0.042) and the CC type in rs1051740 (β = 0.007, 95% CI: 0.001, 0.013, P = 0.015) after adjusting for confounding factors. Our results indicate that benzene induces an increase in TL at a threshold of CED ≥32mg/m³-year. Rs1051740, rs3212986, and rs6413432 were found to be involved in benzene-induced telomere growth; in particular, rs1051740 and rs6413432 interacted with the benzene exposure, resulting in an extended TL.