Arsenic induced progesterone production in a caspase-3-dependent manner and changed redox status in preovulatory granulosa cells

Mechanism of arsenic-induced liver injury in rats revealed by metabolomics and ionomics based approach

Arsenic (As) is an environmental toxicant and human carcinogen, long-term exposure to As can lead to varying degrees of liver injury. In this study, the liver injury model of As poisoned Sprague-Dawley (SD) rats was established, and the potential mechanism was investigated by metabonomics and ionomics. A total of 164 differential expressed metabolites (DEMs) were identified between the As poisoned group and the control group, which mainly involved in nicotinate and nicotinamide metabolism, steroid hormone biosynthesis, taurine and hypotaurine metabolism, and porphyrin metabolism. The levels of 10 ions were significantly increased in As poisoned group, including As, bismuth (Bi), cadmium (Cd), mercury (Hg), manganese (Mn), rubidium (Rb), antimony (Sb), strontium (Sr), uranium(U), and zinc (Zn), in contrast, the levels of lead (Pb) and thallium (TI) were significantly decreased. Spearman correlation analysis showed that As, Cd, Hg and Pb were negatively correlated with androstenedione, protoporphyrinogen IX and estriol, whereas As and Mn was positively correlated with progesterone (PROG), Cd was positively correlated with NAD+ and 3-Sulfino-L-alanine. There are sex differences in changes in metabolites and ions levels. Male and female rats shared 60 DEMs and 2 pathways (steroid hormone biosynthesis and porphyrin metabolism pathway). The levels of As, Cd, Hg, and Sr were significantly changed in both male and female rats. In both female and male rats, As was positively correlated with PROG, and Cd was positively correlated with coproporphyrin III. The results of this study provide new insights to elucidate the mechanism of As-induced liver injury in rats.

The associations of the concentrations of toxic metals (including metalloid) in blood and follicular fluid with the risk of diminished ovarian reserve

BACKGROUND

Diminished ovarian reserve (DOR), a triggering factor for female infertility, affects 10% ∼ 35% of women of reproductive age. It is still unclear whether exposure to toxic metals (including metalloid) is associated with DOR risk, especially with respect to their relationships with the clinical phenotypes of DOR.

METHODS

A case-control study including 439 patients was conducted, and Ba, Ni, As, Tl, Cd, Pb, Hg, Al and Cr levels in BL and FF were measured. Subsequent analyses were focused on Ba, Ni, As and Tl, which had the highest weights in the associations of the nine toxic metals (including metalloid) with DOR risk, by integrating weighted quantile sum (WQS) regression and bayesian kernel machine regression (BKMR) models. Conditional logistic regression models and BKMR models were used to assess the individual and combined effects of Ba, Ni, As and Tl exposures on DOR risk. Multiple linear regression models were used to investigate the relationships between toxic metal (including metalloid) levels in BL and FF and the clinical characteristics of DOR.

RESULTS

The levels of Ba [second vs. lowest tertile: adjusted odds ratio (aOR) and 95 % confidence interval (CI) = 1.97 (1.13, 3.44); highest vs. lowest tertile: aOR (95 % CI) = 2.38 (1.32, 4.26)], Ni [highest vs. lowest tertile: aOR (95 % CI) = 2.59 (1.45, 4.65)] and As [highest vs. lowest tertile: aOR (95 % CI) = 1.96 (1.18, 3.25)] in BL, and Ba [highest vs. lowest tertile: aOR (95 % CI) = 4.60 (1.68, 12.61)] in FF were significantly associated with a higher risk of DOR, respectively. The significantly positive combined effect of the four toxic metals (including metalloid) on DOR risk was exhibited when their BL levels exceeded the 25th percentile compared with their median levels. Among these, As (0.9822) and Ba (0.9704) were the primary contributors to this relationship. Similarly, this finding was confirmed by the statistical results from FF samples, with a linear positive correlation between combined exposure and DOR risk, where Ba (0.9440) was the primary contributor. Finally, elevated levels of Ba, Ni, and As in BL and Ba in FF were significantly linked to the higher follicle-stimulating hormone (FSH) levels. The levels of Ba in BL and FF, as well as As in BL, were significantly associated with the lower luteinizing hormone (LH)/FSH ratio values.

CONCLUSION

Overall, the results of this study indicate that elevated levels of Ba, Ni, As and Tl are associated with a higher risk of DOR, whether individually or in combination, and that Ba levels in BL and FF are stable contributors. In addition, exposure to Ba, Ni, As and Tl is linked to various clinical phenotype parameters of DOR. Further research is needed to confirm these associations and to identify potential mechanisms involved.

Pentachloronitrobenzene alters progesterone production and primordial follicle recruitment in cultured granulosa cells and rat ovary†

Pentachloronitrobenzene (PCNB) is an organochlorine fungicide widely used for crop production and has become an environmental concern. Little is known about the effect of PCNB on ovarian steroidogenesis and follicular development. We found that PCNB stimulated Star expression and progesterone production in cultured rat granulosa cells in a dose-dependent manner. PCNB activated mitogen-activated protein kinase (MAPK3/1) extracellulat regulated kinase (ERK1/2), thus inhibition of either protein kinase A (PKA) or MAPK3/1 signaling pathway significantly attenuated progesterone biosynthesis caused by PCNB, suggesting that PCNB induced progesterone production by activating the cyclic adenosine monophosphate (cAMP/PKA) and MAPK3/1 signaling pathways. Further investigation demonstrated that PCNB induced Star expression and altered MAPK3/1 signaling in ovary tissues of immature SD rats treated with PCNB at the dose of 100, 200, or 300 mg/kg by daily gavage for 7 days, while serum progesterone level was dose-dependently decreased. We demonstrated that PCNB exposure accelerated the recruitment of primordial follicles into the growing follicle pool in ovary tissues, accompanied by increased levels of anti-Mullerian hormone (AMH) in both ovary tissues and serum. Taken together, our data demonstrate for the first time that PCNB stimulated Star expression, altered MAPK3/1 signaling and progesterone production in vivo and in vitro, and accelerated follicular development with a concomitant increase in AMH in ovary tissues and serum. Our findings provide novel insight into the toxicity of PCNB to animal ovary function.

Mechanisms of arsenic disruption on gonadal, adrenal and thyroid endocrine systems in humans: A review

Due to its toxicity as a carcinogen and wide distribution in the environment, arsenic (As) exposure in humans is of public concern globally. Many studies have manifested that As exposure induces cancers besides pathological effects in humans. Animal studies showed that chronic As exposure induces serious neurological effects. Based on recent studies, researchers proposed that As, including arsenate (AsV) and arsenite (AsIII), is also an endocrine disruptor. This review discusses the mechanisms of As toxicity on three endocrine systems including gonadal, adrenal and thyroid endocrine systems. Arsenic methylation and oxidative stress are responsible for As-induced disorders of endocrine systems, however, strong binding of AsIII to thiols also play an important role. Some studies showed AsV toxicity on endocrine systems, but mechanistic investigation is lacking. Research is needed to look into their toxicity mechanisms to help cure the illnesses caused by As-induced endocrine system disorders.

Knockdown of glutamate cysteine ligase catalytic subunit by siRNA causes the gold nanoparticles-induced cytotoxicity in lung cancer cells

Gold nanoparticles (GNPs) have shown promising medical applications in cancer treatment involved in the regulation of intracellular redox balance. Previously, we have reported that GNPs can trigger apoptosis and necrosis in human lung cancer cells (A549) when L-buthionine-sulfoximine (BSO) was used to decrease the expression of intracellular glutathione (GSH). Herein, we investigated the cytotoxicity of GNPs toward lung cancer cells under the glutamate cysteine ligase catalytic subunit (GCLC) was silenced by siRNA. Our results showed that GNPs cause apoptosis and necrosis in cells transfected with GCLC siRNA by elevating intracellular reactive oxygen species (ROS). These findings demonstrated that the regulation of glutathione synthesis by GCLC siRNA in A549 cells can initiate the gold nanoparticles-induced cytotoxicity.

Dexamethasone altered steroidogenesis and changed redox status of granulosa cells

Glucocorticoids have been widely used in clinical application for anti-inflammatory and immunosuppressive function. Previous study reported that glucocorticoids adversely affect the reproductive system and can directly act on ovary. Here, we found that progesterone production induced by dexamethasone requiring activation of caspase-3 which may mediate differentiation and apoptosis of granulosa cells. Further study displayed that cellular glutathione level was increased and reactive oxygen species was decreased accompanied with unchanged mitochondrial membrane potential which may contribute to the maintenance of steroidogenesis in granulosa cells treated with dexamethasone. Dexamethasone also augmented the level of anti-Müllerian hormone secreted by preovulatory granulosa cells which indicated that dexamethasone may promote preantral follicles development.

Progesterone production requires activation of caspase-3 in preovulatory granulosa cells in a serum starvation model

Granulosa cells proliferate, differentiate, and undergo apoptosis throughout follicular development. Previous studies have demonstrated that stimulation of progesterone production is accompanied by caspase-3 activation. Moreover, we previously reported that arsenic enhanced caspase-3 activity coupled with progesterone production. Inhibition of caspase-3 activity can significantly inhibit progesterone production induced by arsenic or follicle-stimulating hormone (FSH). Here, we report that serum starvation induces caspase-3 activation coupled with augmentation of progesterone production. Serum starvation also increased the levels of cytochrome P450 cholesterol side chain cleavage enzyme (P450scc) and steroidogenic acute regulatory (StAR) protein, both of which may contribute to progesterone synthesis in preovulatory granulosa cells. Inhibition of caspase-3 activity resulted in a decrease in progesterone production. Deactivation of caspase-3 activity by caspase-3 specific inhibitor also resulted in decreases in P450scc and StAR expression, which may partly contribute to the observed decrease in progesterone production. Our study demonstrates for the first time that progesterone production in preovulatory granulosa cells is required for caspase-3 activation in a serum starvation model. Inhibition of caspase-3 activity can result in decreased expression of the steroidogenic proteins P450scc and StAR. Our work provides further details on the relationship between caspase-3 activation and steroidogenesis and indicates that caspase-3 plays a critical role in progesterone production by granulosa cells.

Isoliquiritigenin treatment induces apoptosis by increasing intracellular ROS levels in HeLa cells

This study focuses on the relationship between the apoptosis induced by isoliquiritigenin (ISL) and the production of reactive oxygen species (ROS). Cell viability was evaluated using sulforhodamine B assay. The apoptotic rate was determined via flow cytometry. Intracellular ROS level was assessed using the 2,7-dichlorofluorescein probe assay. Poly-ADP-ribose polymerase (PARP) protein expression was examined using Western blot analysis. The results showed that ISL treatment inhibited cell proliferation by inducing apoptosis. The increased apoptotic rate and ROS production induced by ISL were inhibited by the co-treatment of ISL and free radical scavenger N-acetyl-cysteine (NAC), catalase (CAT), and 4,5-dihydroxyl-1,3-benzededisulfonic acid (Tiron). On the contrary, the increased apoptotic rate and the ROS production were compensated by the co-treatment of ISL and l-buthionine-(S,R)-sulfoximine (BSO). ISL treatment increased the degradation of PARP, which was counteracted by antioxidants (NAC or CAT), whereas the combination treatment of ISL and pro-oxidant (BSO) enhanced the PARP degradation induced by ISL. Our findings suggested that ISL treatment induced apoptosis by increasing intracellular ROS levels in HeLa cells.

Tributyltin impairs the reproductive cycle in female rats

Triorganotins are environmental contaminants, commonly used in antifouling agents for boats, that bioaccumulate and thus are found in mammals and humans due to ingestion of contaminated seafood diets. The importance of triorganotins as environmental endocrine disruptors and consequent reproductive toxicity in different animal models is well known; however, the adverse effects on reproductive cycle are less well understood. The potential reproductive toxicity of tributyltin (TBT) on regular reproductive cycling of female rats was examined. Wistar female rats (12 wk old, weighing approximately 230 g) were divided into two groups: control (vehicle, ethanol 0.4%) and tributyltin (100 ng/kg/d, 7 d/wk, for 16 d by gavage). Tributyltin significantly decreased the cycle regularity (%), duration of the reproductive cycle, the proestrus and diestrus phases, and number of epithelial cell in proestrus phase. TBT also increased the duration of metestrus and the number of cornified cells in this phase. Ovary weight and serum 17β-estradiol levels decreased markedly, accompanied by a significant increase in progesterone levels. Histological analysis showed apoptotic cells in corpus luteum and granulosa cells layer, with cystic follicles after TBT exposure. Tributyltin also elevated number of atretic follicles and corpoa lutea. The micronucleus (MN) test, using Chinese hamster ovary cells, demonstrated a concentration-dependent mutagenic effect of TBT, and at 2.0 × 10(-2)ng/ml most of the cells were nonviable. The toxic potential of TBT over the reproductive cycle may be attributed to changes found in the ovarian weight, unbalanced levels of sexual female hormones, and number of ovarian follicles and corpora lutea.