Male reproductive toxicity of CrVI: In-utero exposure to CrVI at the critical window of testis differentiation represses the expression of Sertoli cell tight junction proteins and hormone receptors in adult F1 progeny rats

Unraveling Hypothalamus-Pituitary dysregulation: Hypergonadotropism in F1 progeny due to prenatal exposure to hexavalent chromium

The endocrine disruptor hexavalent chromium [Cr(VI)] is a proven reproductive toxicant. We recently demonstrated that prenatal Cr(VI) exposure causes testicular resistance to gonadotropins, resulting in hypergonadotropic hypoandrogenism in F1 rats. However, the mechanism driving hypergonadotropism in F1 rats exposed to Cr(VI) prenatally remains an enigma. Therefore, we hypothesized that 'Prenatal Cr(VI) exposure may disrupt steroid hormones-mediated negative feedback regulation of the hypothalamic GnRH, and its receptor in the pituitary of F1 rats, leading to hypergonadotropism.' We administered potassium dichromate (50, 100, or 200 mg/L) to pregnant rats through drinking water between days 9 and 14, and their male F1 offspring were euthanized at 60 days of age. Prenatal Cr(VI) exposure in F1 rats resulted in the accumulation of Cr in the hypothalamus and pituitary. Western blot detected decreased hypothalamic GnRH, Kisspeptin1, and its receptor GPR54, along with diminished ERα, AR, aromatase, and 5α reductase, and GnRH regulatory transcription factors Pit-1 and GATA-4 proteins. Immunohistochemical studies revealed increased immunopositivity of GnRH receptor, AR, 5α reductase, ERα, ERβ, and aromatase proteins in the pituitary, whereas decreased Kisspeptin1, GPR54, and inhibin β. Our findings imply that Cr(VI) exposure during the prenatal period disrupts the hypothalamic Kisspeptin-GPR54-Pit-1/GATA4-GnRH network, boosting the pituitary GnRH receptor. We conclude that prenatal exposure to Cr(VI) alters GnRH expression in the hypothalamus and its receptor in the pituitary of F1 progeny through interfering with the negative feedback effect of androgens and estrogens.

Multiple-Pathway Synergy Alters Steroidogenesis and Spermatogenesis in Response to an Immunocastration Vaccine in Goat

BACKGROUND

Animal reproduction performance is crucial in husbandry. Immunocastrated animals serve as an ideal animal model for studying testicular function. During androgen suppression, the testis undergoes dramatic developmental and structural changes, including the inhibition of hormone secretion and spermatogenesis.

METHODS

To characterize this process, we investigated the effects of castration using a recombinant B2L and KISS1 DNA vaccine, and then identified functional genes in the testes of Yiling goats using RNA-seq and WGS. The experimental animals were divided into three groups: the PVAX-asd group (control), PBK-asd-immunized group, and surgically castrated group.

RESULTS

The results demonstrated that the administration of the recombinant PBK-asd vaccine in goats elicited a significant antibody response, and reduced serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH), resulting in smaller scrotal circumferences and decreased sexual desire compared to the control group. In addition, RNA transcriptome sequencing (RNA-seq) analysis of the testes revealed that the biological processes after immunocastration mainly focused on the regulation of cell matrix adhesion, histone acetylation, negative regulation of developmental processes, apoptosis, and activation of the complement system and the thrombin cascade reaction system. Then, we integrated the whole-genome sequencing and testis transcriptome, and identified several candidate genes (FGF9, FST, KIT, TH, TCP1, PLEKHA1, TMEM119, ESR1, TIPARP, LEP) that influence steroidogenesis secretion and spermatogenesis.

CONCLUSIONS

Multiple pathways and polygenic co-expression participate in the response to castration vaccines, altering hormone secretion and spermatogenesis. Taken together, our atlas of the immunocastration goat testis provides multiple insights into the developmental changes and key factors accompanying androgen suppression, and thus may contribute to understanding the genetic mechanism of testis function. Joint analysis of whole genome sequencing and RNA-seq enables reliable screening of candidate genes, benefiting future genome-assisted breeding of goats.

Appraisal of the Pre-Emptive Effect of Lactoferrin Against Chromium-Induced Testicular Toxicity in Male Rats

Lactoferrin (LCF), a potent naturally occurring antioxidant, is a crucial component in preventing potassium dichromate (PDC) toxicity. The goal of the current work was to study the potential efficacy of LCF in preventing PDC(CrVI)-induced testicular toxicity and oxidative injury in rats. Six groups of male rats of Wistar stain were randomly categorized into: group 1, which served as the control; group 2 and 3 received LCF (200 and 300 mg/kg orally, respectively); group 4 received PDC (2 mg/kg i.p.); group 5 and 6 pretreated with LCF, followed by PDC as in group 4 with 90 min apart for 28 days. PDC-intoxicated rats showed a significantly altered spermogram with abnormal sperm morphology. PDC significantly upregulated serum FSH and downregulated testosterone levels. Additionally, PDC decreased the levels of testicular key antioxidant biomarkers (catalase (CAT), superoxide dismutase (SOD), and glutathione (GSH)) with elevated lipid peroxidation marker (TBARS) and testicular chromium content. Moreover, it upregulated testicular proinflammatory cytokines, IL-1, IL-6, IL-10, and TNF-α, induced histopathological changes in testes with significant immunohistochemical expression of FasL and moderate expression of Nrf2. Pretreatment with LCF significantly mitigated PDC-induced testicular toxicity by enhancing spermogram, improving hormonal levels, restoring testicular oxidant/antioxidant balance, and decreasing testicular IL-1, IL6, IL-10, and TNFα levels, and amending both FasL and Nrf2 immunohistochemical-expression. Additionally, LCF improved testicular histopathological picture and spermatogenesis. Our results highlight the importance of LCF as a superior protective modulator of PDC-induced testicular injury.

Putative adverse outcome pathways of the male reproductive toxicity derived from toxicological studies of perfluoroalkyl acids

Adverse outcome pathway (AOP) as a conceptual framework is a powerful tool in the field of toxicology to connect seemingly discrete events at different levels of biological organizations into an organized pathway from molecular interactions to whole organism toxicity. Based on numerous toxicological studies, eight AOPs for reproductive toxicity have been endorsed by the Organization for Economic Co-operation and Development (OECD) Task Force on Hazard Assessment. We have conducted a literature survey on the mechanistic studies on male reproductive toxicity of perfluoroalkyl acids (PFAAs), a class of global environmental contaminants with high persistence, bioaccumulation and toxicity. Using the AOP development strategy, five new AOPs for male reproductive toxicity were proposed here, namely (1) changes in membrane permeability leading to reduced sperm motility, (2) disruption of mitochondrial function leading to sperm apoptosis, (3) decreased gonadotropin-releasing hormone (GnRH) expression in hypothalamus leading to reduced testosterone production in male rats, (4) activation of the p38 signaling pathway leading to disruption of BTB in mice, (5) inhibition of p-FAK-Tyr407 activity leading to the destruction of BTB. The molecular initiating events in the proposed AOPs are different from those in the endorsed AOPs, which are either receptor activation or enzyme inhibition. Although some of the AOPs are still incomplete, they can serve as a building block upon which full AOPs can be developed and applied to not only PFAAs but also other chemical toxicants with male reproductive toxicity.

YTHDF2 controls hexavalent chromium-induced mitophagy through modulating Hif1α and Bnip3 decay via the m6A/mRNA pathway in spermatogonial stem cells/progenitors

Spermatogonial stem cells (SSCs) are the basis of spermatogenesis, and SSC homeostasis is essential for lifelong male fertility. Currently, environmental pollution remains one of the factors affecting human reproductive health. Chromium is a prevalent metal element, and excessive exposure to hexavalent chromium (Cr (VI)) can cause male reproductive disorders. Nevertheless, the toxic effects of Cr (VI) on SSCs and the underlying mechanisms remain incompletely understood. Here, we showed that Cr (VI) exposure triggered mitophagy in mouse SSCs/progenitors in a time-dependent manner. Concurrently, Cr (VI) treatment caused reactive oxygen species (ROS) accumulation and activated the HIF1α-mediated BNIP3 expression to trigger mitophagy. In addition, Cr (VI) exposure significantly decreased the level of m⁶A modification. Further, we identified that YTHDF2 regulated the stability of Bnip3 and Hif1α mRNAs in an m⁶A-dependent manner, which was involved in Cr (VI)-induced mitophagy. Collectively, our study not only expands the mechanisms for Cr (VI)-caused male reproductive toxicity, but also provides pharmacological targets for prevention and treatment of Cr (VI)-induced male fertility impairment.

Intestinal epithelial stem cell transplants as a novel therapy for cerebrovascular stroke

Almost 2/3rds of stroke survivors exhibit vascular cognitive impairment and a third of stroke patients will develop dementia 1-3 years after stroke. These dire consequences underscore the need for effective stroke therapies. In addition to its damaging effects on the brain, stroke rapidly dysregulates the intestinal epithelium, resulting in elevated blood levels of inflammatory cytokines and toxic gut metabolites due to a 'leaky' gut. We tested whether repairing the gut via intestinal epithelial stem cell (IESC) transplants would also improve stroke recovery. Organoids containing IESCs derived from young rats transplanted into older rats after stroke were incorporated into the gut, restored stroke-induced gut dysmorphology and decreased gut permeability, and reduced circulating levels of endotoxin LPS and the inflammatory cytokine IL-17A. Remarkably, IESC transplants also improved stroke-induced acute (4d) sensory-motor disability and chronic (30d) cognitive-affective function. Moreover, IESCs from older animals displayed senescent features and were not therapeutic for stroke. These data underscore the gut as a critical therapeutic target for stroke and demonstrate the effectiveness of gut stem cell therapy.

A comprehensive review on human health effects of chromium: insights on induced toxicity

The growing use of heavy metals in most industrial activities has led to it being considered as the most important environmental pollutant that may cause harm and toxicity to animals and humans. Chromium has been found in the environment in different oxidation states such as Cr⁰, Cr(III), and Cr(VI) and is released from a variety of anthropogenic and natural activities. At among, trivalent and hexavalent chromium are the most stable forms. Considerably, Cr(VI) is frequently more toxic than Cr(III) because of its particular solubility and high mobility. Chronic exposure and bioaccumulation of chromium, as a heavy metal, can cause toxicity and numerous pathophysiological defects, including allergic reactions, anemia, burns, and sores especially in the stomach and small intestine, damage to sperm along with the male reproductive system, and affect various biological systems. Chromium pollution can have severe consequences for water and the soil environment. This article reviews the toxicological effects of Cr(VI) and Cr(III) and their mechanisms of toxicity and carcinogenicity.

Heavy metal and metalloid - induced reproductive toxicity

Heavy metals and metalloid exposure are among the most common factors responsible for reproductive toxicity in human beings. Several studies have indicated that numerous metals and metalloids can display severe adverse properties on the human reproductive system. Metals like lead, silver, cadmium, uranium, vanadium, and mercury and metalloids like arsenic have been known to induce reproductive toxicity. Moderate to minute quantities of lead may affect several reproductive parameters and even affect semen quality. The ecological and industrial exposures to the various heavy metals and metalloids have disastrous effects on the reproductive system ensuing in infertility. This work emphasizes the mechanism and pathophysiology of the aforementioned heavy metals and metalloids in reproductive toxicity. Additionally, this work aims to cover the classical protective mechanisms of zinc, melatonin, chelation therapy, and other trending methods to prevent heavy metal-induced reproductive toxicity.

Prenatal exposure to hexavalent chromium disrupts testicular steroidogenic pathway in peripubertal F1 rats

We have reported sub-fertility in F1 progeny rats with gestational exposure to hexavalent chromium [Cr(VI)], which had disrupted Sertoli cell (SC) structure and function, and decreased testosterone (T). However, the underlying mechanism for reduced T remains to be understood. We tested the hypothesis "transient prenatal exposure to Cr(VI) affects testicular steroidogenesis by altering hormone receptors and steroidogenic enzyme proteins in Leydig cells (LCs)." Pregnant Wistar rats were given drinking water containing 50, 100, and 200 mg/L potassium dichromate during gestational days 9-14, encompassing fetal differentiation window of the testis from the bipotential gonad. F1 male rats were euthanized on postnatal day 60 (peripubertal rats with adult-type LCs alone). Results showed that prenatal exposure to Cr(VI): (i) increased accumulation of Cr(III) in the testis of F1 rats; (ii) increased serum levels of luteinizing and follicle stimulating hormones (LH and FSH), and 17β estradiol, and decreased prolactin and T; (iii) decreased steroidogenic acute regulatory protein, cytochrome P450 11A1, cytochrome P450 17A1, 3β- and 17β-hydroxysteroid dehydrogenases, cytochrome P450 aromatase and 5α reductase proteins, (iv) decreased specific activities of 3β and 17β hydroxysteroid dehydrogenases; (v) decreased receptors of LH, androgen and estrogen in LCs; (vi) decreased 5α reductase and receptor proteins of FSH, androgen, and estrogen in SCs. The current study concludes that prenatal exposure to Cr(VI) disrupts testicular steroidogenesis in F1 progeny by repressing hormone receptors and key proteins of the steroidogenic pathway in LCs and SCs.

Sex differences in stroke outcome correspond to rapid and severe changes in gut permeability in adult Sprague-Dawley rats

BACKGROUND

Sex differences in experimental stroke outcomes are well documented, such that adult males have a greater infarct volume, increased stroke-induced mortality, and more severe sensory-motor impairment. Based on recent evidence that the gut is an early responder to stroke, the present study tested the hypothesis that sex differences in stroke severity will be accompanied by rapid and greater permeability of the gut-blood barrier and gut dysbiosis in males as compared to females.

METHOD

Male and female Sprague-Dawley rats (5-7 months of age) were subject to endothelin (ET)-1-induced middle cerebral artery occlusion (MCAo). Sensory-motor tests were conducted pre- and 2 days after MCAo. Gut permeability was assessed in serum samples using biomarkers of gut permeability as well as functional assays using size-graded dextrans. Histological analysis of the gut was performed with H&E staining, periodic acid-Schiff for mucus, and immunohistochemistry for the tight junction protein, ZO-1. Fecal samples obtained pre- and post-stroke were analyzed for bacterial taxa and short-chain fatty acids (SCFAs).

RESULTS

After stroke, males displayed greater mortality, worse sensory-motor deficit, and higher serum levels of proinflammatory cytokines IL-17A, MCP-1, and IL-5 as compared to females. MCAo-induced gut permeability was rapid and severe in males as indicated by dextran extravasation from the gut to the blood in the hyperacute (< 2 h) and early acute (2 days) phase of stroke. This was accompanied by dysmorphology of the gut villi and dysregulation of the tight junction protein ZO-1 in the acute phase. Fecal 16s sequencing showed no differences in bacterial diversity in the acute phase of stroke. Predictive modeling indicated that markers of gut permeability were associated with acute sensory-motor impairment and infarct volume.

CONCLUSIONS

These data show that extensive leakiness of the gut barrier is associated with severe post-stroke disability and suggest that reinforcing this barrier may improve stroke outcomes.

Associations of prenatal exposure to multiple metals with testicular volume and anogenital distance in infant boys: A longitudinal cohort study

BACKGROUND

Human are widely exposed to multiple metals, some of which have suspected reproductive toxicity, but no human studies have investigated the developmental effects of prenatal metal exposure.

OBJECTIVES

We aimed to evaluate the associations between prenatal multiple metal exposure and reproductive development in boys at 2-3 years using multi-pollutant approach.

METHODS

This prospective study used data of 564 mother-child pairs recruited from the Guangxi Birth Cohort Study. Twenty serum metal concentrations were measured. Least absolute shrinkage and selection operator (LASSO) penalized regression was used to identify independent associations between prenatal multiple metal exposure and testicular volume (TV), and anogenital distance (AGD). Adjusted estimates were then obtained using multiple linear regression analysis, and the regression tree method was used to explore the interactions.

RESULTS

Boys in the highest quartile of prenatal lead exposure had a 0.064 mL (95% CI: -0.124, -0.004) smaller ln-transformed TV, 0.060 cm (95% CI: -0.110, -0.011) shorter ln-transformed anopenile distance (AGDap), and 0.115 cm (95% CI: -0.190, -0.039) shorter ln-transformed anoscrotal distance (AGDas) than boys in the lowest quartile (all Ptrend < 0.05). Chromium was inversely with ln-transformed AGDap (β = -0.078, 95% CI: -0.127, -0.030) and ln-transformed AGDas (β = -0.113, 95% CI: -0.188, -0.038), while stibium was positivity associated with ln-transformed AGDap (β = 0.091, 95% CI: 0.046, 0.136) and strontium was positivity associated with ln-transformed AGDas (β = 0.120, 95% CI: 0.051, 0.189) (all Ptrend < 0.05). And the critical window of vulnerability may be the late pregnancy (the second and third trimester). Moreover, we detected interaction effects between lead, chromium and stibium on AGDap; lead, chromium and strontium on AGDas.

CONCLUSIONS

The results suggest that prenatal exposure to lead, chromium, stibium and strontium may affect TV and/or AGD in infant boys. Potential mechanisms for the complex metal interactive effects during vulnerable periods are worthy of further investigation.

Prenatal exposure to excess chromium attenuates transcription factors regulating expression of androgen and follicle stimulating hormone receptors in Sertoli cells of prepuberal rats

We have reported that gestational exposure to hexavalent chromium (CrVI) represses androgen receptor (Ar) and follicle stimulating hormone receptor (Fshr) in Sertoli cells (SCs) of adult rats, while the mechanism underlying remains obscure. We tested the hypothesis "transient gestational exposure to CrVI during the critical embryonic windows of testicular differentiation and growth may have adverse impact on transcription factors controlling the expression of Ar and Fshr in SCs of the F₁ progeny". CrVI (K₂Cr₂O₇) was given through drinking water (50 ppm, 100 ppm and 200 ppm), to pregnant rats from gestational day 9-14 (testicular differentiation) and 15 to 21 (prenatal differentiation and proliferation of SC); male progenies were sacrificed on postnatal day 30 (Completion of postnatal SC maturation). A significant increase in free radicals and decrease in enzymatic and non-enzymatic antioxidants were observed in SCs of experimental rats. Real time PCR and western blot data showed decreased expression of Ar, Fshr, Inhibin B, Transferrin, Androgen binding protein, Claudin 11 and Occludin in SCs of experimental rats; concentrations of lactate, pyruvate and retinoic acid also decreased. Serum FSH, luteinizing hormone and estradiol increased, whereas testosterone and prolactin decreased in experimental rats. Western blot detection revealed decreased levels of transcription factors regulating Fshr viz., USF-1, USF-2, SF-1, c-fos, c-jun and GATA 1, and those of Ar viz., Sp-1, ARA54, SRC-1 and CBP in experimental rats, whereas the levels of cyclinD1 and p53, repressors of Ar increased. ChIP assay detected decreased USF-1 and USF-2 binding to Fshr promoter, and binding of Sp-1 to Ar promoter. We conclude that gestational exposure to CrVI affects SC structure and function in F₁ progeny by inducing oxidative stress and diminishing the expression of Ar and Fshr through attenuation of their specific transcriptional regulators and their interaction with the respective promoter.

Correlation between urinary chromium level and semen quality in men attending an andrology laboratory

Chromium is an essential element that is required for the normal physiology but can be toxic to humans above a certain level. In spite of growing interest in research on chromium exposure to human health consensus about its effect on human, semen quality has not been achieved. The aim of the present study is to evaluate the impact of chromium exposure on semen parameters. A total of 760 males attending andrology laboratory of Tongji Hospital, Wuhan, for routine semen analysis were enrolled and requested to provide semen and urine samples. The urine level of chromium was evaluated using inductively coupled plasma mass spectrometry (ICP-MS), and computer-assisted semen analysis (CASA) was applied to examine semen parameters. Associations between semen parameters and urinary chromium were analyzed by means of multivariate linear regression analysis. Multivariate analysis showed a negative association between the urinary concentrations of chromium and progressive motility (β = - 0.014, p = 0.040) and total motility (β = - 1.077, p = 0.048), while other semen parameters did not show any statistically significant changes. Urinary chromium could influence semen quality parameters and impair male fecundity.

Inhibition of intestinal villus cell Na/K-ATPase mediates altered glucose and NaCl absorption in obesity-associated diabetes and hypertension

During obesity, diabetes and hypertension inevitably coexist and cause innumerable health disparities. In the obesity, diabetes, and hypertension triad (ODHT), deregulation of glucose and NaCl homeostasis, respectively, causes diabetes and hypertension. In the mammalian intestine, glucose is primarily absorbed by Na-glucose cotransport 1 (SGLT1) and coupled NaCl by the dual operation of Na-H exchange 3 (NHE3) and Cl-HCO3 [down-regulated in adenoma (DRA) or putative anion transporter 1 (PAT1)] exchange in the brush border membrane (BBM) of villus cells. The basolateral membrane (BLM) Na/K-ATPase provides the favorable transcellular Na gradient for BBM SGLT1 and NHE3. How these multiple, distinct transport processes may be affected in ODHT is unclear. Here, we show the novel and broad regulation by Na/K-ATPase of glucose and NaCl absorption in ODHT in multiple species (mice, rats, and humans). In vivo, during obesity inhibition of villus-cell BLM, Na/K-ATPase led to compensatory stimulation of BBM SGLT1 and DRA or PAT1, whereas NHE3 was unaffected. Supporting this new cellular adaptive mechanism, direct silencing of BLM Na/K-ATPase in intestinal epithelial cells resulted in selective stimulation of BBM SGLT1 and DRA or PAT1 but not NHE3. These changes will lead to an increase in glucose absorption, maintenance of traditional coupled NaCl absorption, and a de novo increase in NaCl absorption from the novel coupling of stimulated SGLT1 with DRA or PAT1. Thus, these novel observations provide the pathophysiologic basis for the deregulation of glucose and NaCl homeostasis of diabetes and hypertension, respectively, during obesity. These observations may lead to more efficacious treatment for obesity-associated diabetes and hypertension.-Palaniappan, B., Arthur, S., Sundaram, V. L., Butts, M., Sundaram, S., Mani, K., Singh, S., Nepal, N., Sundaram, U. Inhibition of intestinal villus cell Na/K-ATPase mediates altered glucose and NaCl absorption in obesity-associated diabetes and hypertension.

Beneficial Effects of N-Acetyl-L-cysteine or Taurine Pre- or Post-treatments in the Heart, Spleen, Lung, and Testis of Hexavalent Chromium-Exposed Mice

Hexavalent chromium[Cr(VI)] compounds may induce toxic effects, possibly via reactive intermediates and radicals formed during Cr(VI) reduction. In this study, we probed the possible effects of N-acetyl-L-cysteine (NAC) and taurine pre- or post-treatments on Cr(VI)-induced changes in lipid peroxidation and nonprotein thiols (NPSH) in mice heart, lung, spleen, and testis tissues. The mice were randomly assigned to six groups, consisting of control, Cr(VI)-exposed (20 mg Cr/kg, intraperitoneal ,ip), NAC (200 mg/kg, ip) as pre-treatment and post-treatment, and taurine (1 g/kg, ip) pre-treatment and post-treatment groups. Lipid peroxidation and NPSH levels were determined and the results were compared with regard to tissue- and antioxidant-specific basis. Exposure to Cr(VI) significantly increased lipid peroxidation in all tissues as compared to the control (p < 0.05); and consistent with this data, NPSH levels were significantly decreased (p < 0.05). Notably, administration of NAC and taurine, either before or after Cr(VI) exposure, was able to ameliorate the lipid peroxidation (p < 0.05) in all tissues. In the case of NPSH content, while the decline could be alleviated by both NAC and taurine pre- and post-treatments in the spleen, diverging results were obtained in other tissues. The effects of Cr(VI) on the lung thiols were abolished by pre-treatment with NAC and taurine; however, post-treatments could not exert significant effect. While thiol depletion in the heart was totally replenished by NAC and taurine administrations, NAC pre-treatment was partially more effective than post-treatment. In contrast with lipid peroxidation data, NAC treatment could not provide a statistically significant beneficial effect on NPSH content of the testis, whereas the effect in this tissue by taurine was profound. Thus, these data highlight the importance of tissue-specific factors and the critical role of administration time. Overall, our data suggest that NAC and taurine may have potential in prevention of Cr(VI)-induced toxicity in the heart, lung, spleen, and testis tissues.

Sexually Dimorphic Impact of Chromium Accumulation on Human Placental Oxidative Stress and Apoptosis

Environmental contamination with hexavalent chromium (CrVI) is a growing problem both in the United States and developing countries. Hexavalent chromium is widely used in numerous industries. Environmental exposure to CrVI adversely affects pregnancy outcomes and subsequent health of 2 generations, resulting in higher pregnancy loss, spontaneous abortion and low birth rate. Pregnant women exposed to CrVI through occupational settings experience increased risk of spontaneous abortion, stillbirth, preterm birth, and neonatal death. Children of the CrVI exposed women experience respiratory problems, perinatal jaundice, and increased birth defects. Because placental dysfunction may have a role in such adverse pregnancy outcome, we tested the hypothesis that environmental Cr exposure in pregnant women results in Cr accumulation in the human placenta, which could increase placental oxidative stress by disrupting antioxidant machinery and inducing apoptosis. Studies using frozen, deidentified human term placenta samples indicated that: (1) Cr accumulates in human term placenta tissues and (2) increase in Cr accumulation is positively correlated with oxidative stress and apoptotic markers, and altered antioxidants levels. Interestingly, there was a sexual dimorphism in the correlation between Cr accumulation and oxidative stress, and expression of apoptotic and antioxidant markers. Mechanistic in vitro studies using human trophoblast cells BeWo confirmed the detrimental effects of Cr in altering antioxidant genes. For the first time, this study provides evidence in support of a positive correlation between Cr accumulation in the human placenta and accelerated oxidative stress, with a gender bias toward the male sex.

In utero exposure to hexavalent chromium disrupts rat fetal testis development

Hexavalent chromium (Cr⁶⁺) acts as an endocrine disruptor. Herein, we investigated effects of Cr⁶⁺ on the development of rat fetal Leydig and Sertoli cells, which support differentiation of the male reproductive tract in late gestation. Female pregnant Sprague Dawley rats were gavaged with potassium dichromate (0, 3, 6, and 12 mg/kg) from gestational days (GD) 12 to GD 21. Leydig and Sertoli cell function was evaluated by investigating serum testosterone levels, cell number and distribution, and the expression levels of Leydig and Sertoli cell genes and proteins. Cr⁶⁺ increased serum testosterone level at dose of 3 mg/kg (1.170 ± 0.121 ng/ml vs. 0.720 ± 0.082 ng/ml in the control), while lowered it at dose of 12 mg/kg (0.400 ± 0.098 ng/ml). In addition, it showed that Cr⁶⁺ dose-dependently reduced Leydig cell size and cytoplasmic size and decreased the percentage of medium fetal Leydig cell cluster at dose of 12 mg/kg. Further study demonstrated that the expression of Leydig cell (Lhcgr, Scarb1, and Hsd3b1) and Sertoli cell (Fshr, Pdgfa, and Lif) genes in the testis was upregulated at dose of 3 mg/kg while the expression of Lhcgr, Hsd17b3 and Igf1 was downregulated by Cr⁶⁺ at dose of 12 mg/kg. In conclusion, Cr⁶⁺ had biphasic effects on fetal Leydig cell development with low dose to stimulate testosterone production and high dose to inhibit it, possibly via biphasically regulating growth factor gene expression in fetal Sertoli cells.