Blood chromium exposure, immune inflammation and genetic damage: Exploring associations and mediation effects in chromate exposed population

Relationships between blood chromium exposure and liver injury: Exploring the mediating role of systemic inflammation in a chromate-exposed population

Hexavalent chromium and its compounds are prevalent pollutants, especially in the work environment, pose a significant risk for multisystem toxicity and cancers. While it is known that chromium accumulation in the liver can cause damage, the dose-response relationship between blood chromium (Cr) and liver injury, as well as the possible potential toxic mechanisms involved, remains poorly understood. To address this, we conducted a follow-up study of 590 visits from 305 participants to investigate the associations of blood Cr with biomarkers for liver injury, including serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), and direct bilirubin (DBIL), and to evaluate the mediating effects of systemic inflammation. Platelet (PLT) and the platelet-to-lymphocyte ratio (PLR) were utilized as biomarkers of systemic inflammation. In the linear mixed-effects analyses, each 1-unit increase in blood Cr level was associated with estimated effect percentage increases of 0.82% (0.11%, 1.53%) in TBIL, 1.67% (0.06%, 3.28%) in DBIL, 0.73% (0.04%, 1.43%) in ALT and 2.08% (0.29%, 3.87%) in AST, respectively. Furthermore, PLT mediated 10.04%, 11.35%, and 10.77% increases in TBIL, DBIL, and ALT levels induced by chromate, respectively. In addition, PLR mediated 8.26% and 15.58% of the association between blood Cr and TBIL or ALT. These findings shed light on the mechanisms underlying blood Cr-induced liver injury, which is partly due to worsening systemic inflammation.

Cr (VI)-induced ribosomal DNA copy number variation is associated with semen quality impairment: Evidence from human to animal study

OBJECTIVES

This study aimed to analyze the possible role of rDNA copy number variation in the association between hexavalent chromium [Cr (VI)] exposure and semen quality in semen donors and further confirm this association in mice.

METHODS

In this cross-sectional study, whole blood and semen samples were collected from 155 semen donors in the Zhejiang Human Sperm Bank from January 1st to April 31st, 2021. Adult C57BL/6 J male mice were treated with different doses of Cr (VI) (0, 10, or 15 mg/kg b.w./day). Semen quality, including semen volume, total spermatozoa count, sperm concentration, progressive motility, and total motility, were analyzed according to the WHO laboratory manual. Cr concentration was detected using inductively coupled plasma mass spectrometry. The rDNA copy number was measured using qPCR.

RESULTS

In semen donors, whole blood Cr concentration was negatively associated with semen concentration and total sperm counts. Semen 5 S and 45 S rDNA copy numbers were negatively associated with whole blood Cr concentration and whole blood 5.8 S rDNA copy number was negatively associated with semen Cr concentration. In mice, Cr (VI) damaged testicular tissue, decreased semen quality, and caused rDNA copy number variation. Semen quality was related to the rDNA copy number in whole blood, testicular tissue, and semen samples in mice.

CONCLUSION

Cr (VI) was associated with decreased semen quality in semen donors and mice. Our findings suggest an in-depth analysis of the role of the rDNA copy number variation in the Cr (VI)-induced impairment of semen quality.

Efficient removal of Cr (VI) by Bifunction zinc porphyrin COF: Coupling adsorption with Photocatalysis, performance Evaluation, and mechanism analysis

HYPOTHESIS

Hexavalent chromium, recognized as one of the most toxic heavy metals, demands the development of advanced materials capable of both adsorption and photocatalysis for effective Cr (VI) removal.

EXPERIMENTS

This study successfully synthesized a two-dimensional zinc porphyrin covalent organic framework (ZnPor-COF) via a solvent-based method. Performance evaluations have demonstrated that the ZnPor-COF possesses outstanding capabilities for the adsorptive and/or photocatalytic elimination of Cr (VI). Particularly noteworthy is the observation that when adsorption and photocatalysis are coupled, the ZnPor-COF attains an exceptional 99.7 % removal rate for a Cr (VI) concentration of 30 mg/L within just 60 min, with minimal susceptibility to coexisting ions. After five consecutive cycles, the material sustains a removal efficiency of 90 %, indicative of its robust cyclability.

FINDINGS

Theoretical calculations, as well as experimental validations, have indicated that the integration of Zn ions into the porphyrin COF not only results in an expanded specific surface area and an increased count of adsorption sites but also significantly improves the COF's photosensitivity and the capability for charge carrier separation. Furthermore, the core of the synergistic effect between adsorption and photocatalysis lies in the ability of photocatalysis to substantially augment the adsorption process.

Cellular senescence mediates hexavalent chromium-associated lung function decline: Insights from a structural equation Model

There is sufficient evidence suggesting that exposure to hexavalent chromium [Cr(VI)] can cause a decline in lung function and the onset of lung diseases. However, no studies have yet explored the underlying mechanisms of these effects from various perspectives such as systemic inflammation, oxidative stress, and cellular senescence, simultaneously. This cross-sectional study was conducted among 304 workers engaged in chromate production and processing in China. Urine was used for detection of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-iso-prostaglandin F2α (8-iso-PGF2α), while RNA and DNA extraction from peripheral blood cells was used for detection of mRNA, telomere length, and ribosomal DNA copy numbers (rDNA CNs). A 2.7-fold elevation in blood chromate (Cr) corresponded to a 7.86% (95% CI: 2.57%, 13.42%) rise in urinary 8-OHdG and a 4.14% (0.02%, 8.42%) increase in urinary 8-iso-PGF2α, indicating that exposure to chromates can cause oxidative stress. Furthermore, strong correlations emerged between blood Cr concentration and mRNA levels of P16, P21, TP53, and P15 in the cellular senescence pathway. Simultaneously, a 2.7-fold elevation in blood Cr associated with a -5.47% (-8.72%, -2.1%) change in telomere length, while rDNA CNs (5S, 5.8S, 18S, and 28S) changed by -3.91% (-7.99%, 0.34%), -9.4% (-15.73%, -2.6%), -8.06% (-14.01%, -1.69%), and -5.86% (-10.67%, -0.78%), respectively. Structural equation model highlighted that cellular senescence exerted significant indirect effects on Cr(VI)-associated lung function decline, with a mediation proportion of 23.3%. This study provided data supporting for 8-iso-PGF2α, telomere length, and rDNA CNs as novel biomarkers of chromate exposure, emphasizing the significant role of cellular senescence in the mechanism underlying chromate-induced lung function decline.

A comparative study on chromium-induced micronuclei assessment in the peripheral blood of Hsd:ICR mice

This study investigated the genotoxic effects of chromium (Cr) in Hsd:ICR mice, considering factors such as oxidative state, apoptosis, exposure pathway, duration, pregnancy, and transplacental exposure. Genotoxicity was assessed using the erythrocytes' micronucleus (MN) assay, while apoptosis was evaluated in nucleated blood cells. The results showed that Cr(III) (CrK(SO4 )2 and CrCl3 ) did not induce any marked genotoxic damage. However, Cr(VI) (CrO3 , K2 Cr2 O7 , Na2 Cr2 O7 , and K2 CrO4 ) produced varying degrees of genotoxicity, with CrO3 being the most potent. MN frequencies increased following 24-h exposure, with a greater effect in male mice. Administering 20 mg/kg of CrO3 via gavage did not lead to significant effects compared to intraperitoneal administration. Short-term oral treatment with a daily dose of 8.5 mg/kg for 49 days elevated MN levels only on day 14 after treatment. Pregnant female mice exposed to CrO3 on day 15 of pregnancy exhibited reduced genotoxic effects compared to nonpregnant animals. However, significant increases in MN levels were found in their fetuses starting 48 h after exposure. In summary, data indicate the potential genotoxic effects of Cr, with Cr(VI) forms inducing higher genotoxicity than Cr(III). These findings indicate that gender, exposure route, and pregnancy status might influence genotoxic responses to Cr.

Cross-sectional and Longitudinal Associations Between Metal Mixtures and Serum C3, C4: Result from the Manganese‑exposed Workers Healthy Cohort

Exposure to metal mixtures compromises the immune system, with the complement system connecting innate and adaptive immunity. Herein, we sought to explore the relationships between blood cell metal mixtures and the third and fourth components of serum complement (C3, C4). A total of 538 participants were recruited in November 2017, and 289 participants were followed up in November 2021. We conducted a cross-sectional analysis at baseline and a longitudinal analysis over 4 years. Least Absolute Shrinkage and Selection Operator (LASSO) was employed to identify the primary metals related to serum C3, C4; generalized linear model (GLM) was further used to evaluate the cross-sectional associations of the selected metals and serum C3, C4. Furthermore, participants were categorized into three groups according to the percentage change in metal concentrations over 4 years. GLM was performed to assess the associations between changes in metal concentrations and changes in serum C3, C4 levels. At baseline, each 1-unit increase in log10-transformed in magnesium, manganese, copper, rubidium, and lead was significantly associated with a change in serum C3 of 0.226 (95% CI: 0.146, 0.307), 0.055 (95% CI: 0.022, 0.088), 0.113 (95% CI: 0.019, 0.206), - 0.173 (95% CI: - 0.262, - 0.083), and - 0.020 (95% CI: - 0.039, - 0.001), respectively. Longitudinally, decreased copper concentrations were negatively associated with an increment in serum C3 levels, while decreased lead concentrations were positively associated with an increment in serum C3 levels. However, no metal was found to be primarily associated with serum C4 in LASSO, so we did not further explore the relationship between them. Our research indicates that copper and lead may affect complement system homeostasis by influencing serum C3 levels. Further investigation is necessary to elucidate the underlying mechanisms.

Hexavalent chromium [Cr(VI)]-induced ribosomal DNA copy number variation and DNA damage responses and their associations with nucleolar protein HRAS in humans and cells

The carcinogenicity of hexavalent chromium [Cr(VI)] and its compounds has been widely recognized, yet the mechanism of genetic damage is still not fully understood. The ribosomal DNA (rDNA) copy number is recently considered a potential marker of cancer-associated stress. To investigate the roles of rDNA copy number variation (CNV) in DNA damage responses (DDRs) induced by Cr(VI) and the potential mechanism from nucleolar protein HRAS, a cross-sectional study in Cr(Ⅵ)-exposed workers and an in vitro experiment using HeLa cells were conducted. Our results showed increased levels of rDNA CNV, DDRs, and HRAS expression in Cr(VI)-exposed workers. Generalized linear regression analyses showed that Cr(VI) exposure was significantly positively associated with increased levels of rDNA CNV, DDRs, and HRAS expression in Cr(VI)-exposed workers. Moreover, there were pairwise associations between rDNA CNV, DDRs, and HRAS levels. Mediation analyses found that rDNA CNV significantly mediated the association between Cr(VI) exposure and DDRs. The in vitro experiments further confirmed that Cr(VI) treatment induced increased levels of rDNA CNV, DDRs, and HRAS expression in HeLa cells. Cr(VI)-induced rDNA CNV, ATM activation, and apoptosis damage were then strongly enhanced by HRAS depletion with siRNA in vitro, suggesting the important role of HRAS in CNV and DDRs caused by Cr(VI). The combined results of the human and cell line studies indicated that Cr(VI) exposure might enhance rDNA CNV by regulation of HRAS expression, which leads to Cr(VI)-induced genetic damage.

Exploration of Whole Blood Chromium as Biomarker of Hexavalent Chromium Exposure: Based on Literature Review and Monte Carlo Simulation

Hexavalent chromium (Cr(VI)) is a sort of common industrial poison and environmental pollutant posing great health threat to the population. Appropriate biomarkers are indispensable indicative tools in the biological monitoring and health risk assessment of Cr(VI). In this study, we explored the rationality and feasibility of whole blood Cr serving as the biomarker of internal exposure with corroboration drawn from literature review and Monte Carlo simulation. It was indicated that the whole blood Cr had practical operability in the large-scale population researches and robust biological significance with broad association with various Cr(VI)-related effect indices. The simulated distribution of whole blood Cr concentration in exposed populations was about three times higher than that of the control (13.52 ± 24.99 vs. 4.25 ± 11.37 μg/L, P < 0.05; 6.73 ± 10.92 μg/L vs. 1.96 ± 2.05 μg/L in China, P < 0.05), which suggested a great discriminatory ability that might be supported as evidence for its reasonable application.

Associations between pyrethroid exposure and serum sex steroid hormones in adults: Findings from a nationally representative sample

BACKGROUND

Pyrethroids have been considered as potential endocrine-disrupting chemicals and have been shown to be associated with endocrine-related health outcomes. However, limited studies directly explored the link between pyrethroid exposure and sex hormones in the general population.

OBJECTIVES

To explore the associations between exposure to pyrethroids and serum sex steroid hormones in adults.

METHODS

We evaluated the cross-sectional associations in 1235 adults aged ≥20 years who had been assigned to the National Health and Nutrition Examination Survey (NHANES) 2013-2014. The urinary concentration of 3-phenoxybenzoic acid (3-PBA) was applied as a biomarker of human pyrethroid exposure levels. Information on sex steroid hormones, including total testosterone (TT), estradiol (E2), and sex hormone-binding globulin (SHBG) in serum were measured. Free androgen index (FAI) and the ratio of TT to E2 (TT/E2) were also calculated. The percent changes with 95% confidence intervals (CIs) for a doubling of 3-PBA concentrations in the serum sex hormone levels were estimated using generalized linear regression models.

RESULTS

The overall median concentrations of creatinine-adjusted 3-PBA were 0.58 μg/g creatinine, and 90.0% of adults had a detectable level of 3-PBA. In females, every two-fold increase in 3-PBA was associated with 4.34% (95% CI: 1.58%, 7.18%) higher levels of TT and 4.05% (95% CI: 7.03%, 1.16%) higher levels of SHBG, respectively. In males, a doubling in 3-PBA was associated with 3.02% (95% CI: 1.21%, 4.86%) increase in SHBG but 1.85% (-3.59%, -0.07%) decrease in FAI, respectively. In addition, significant non-linear associations of 3-PBA with SHBG in both males and females and TT in females were observed.

CONCLUSIONS

Environmental pyrethroid exposure was associated with altered sex hormones in adults. This study provides important epidemiological evidence for the association of pyrethroids with endocrine disruption.