Effect of mercury on porcine ovarian granulosa cells in vitro

Levels of trace metals and their impact on oocyte: A review

Trace metals play a vital role in a variety of biological processes, but excessive amounts can be toxic and are receiving increasing attention. Trace metals in the environment are released from natural sources, such as rock weathering, volcanic eruptions, and other human activities, such as industrial emissions, mineral extraction, and vehicle exhaust. Lifestyle, dietary habits and environmental quality are the main sources of human exposure to trace metals, which play an important role in inducing human reproductive infertility. The purpose of this review is to summarize the distribution of various trace metals in oocyte and to identify the trace metals that may cause oocyte used in the design and execution of toxicological studies.

In vitro assessment of the impact of nickel on the viability and steroidogenesis in the human adrenocortical carcinoma (NCI-H295R) cell line

Nickel is a ubiquitous environmental pollutant, which has various effects on reproductive endocrinology. In this study, human adrenocortical carcinoma (NCI-H295R) cell line was used as an in vitro biological model to study the effect of nickel chloride (NiCl2) on the viability and steroidogenesis. The cells were exposed to different concentrations (3.90; 7.80; 15.60; 31.20; 62.50; 125; 250 and 500 microM) of NiCl2 and compared with control group (culture medium without NiCl2). The cell viability was measured by the metabolic activity assay. Production of sexual steroid hormones was quantified by enzyme linked immunosorbent assay. Following 48 h culture of the cells in the presence of NiCl2 a dose-dependent depletion of progesterone release was observed even at the lower concentrations. In fact, lower levels of progesterone were detected in groups with higher doses (>/=125 microM) of NiCl2 (P<0.01), which also elicited cytotoxic action. A more prominent decrease in testosterone production (P<0.01) was also noted in comparison to that of progesterone. On the other hand, the release of 17beta-estradiol was substantially increased at low concentrations (3.90 to 62.50 microM) of NiCl2. The cell viability remained relatively unaltered up to 125 microM (P>0.05) and slightly decreased from 250 microM of NiCl2 (P<0.05). Our results indicate endocrine disruptive effect of NiCl2 on the release of progesterone and testosterone in the NCI-H295R cell line. Although no detrimental effect of NiCl2 (</=62.50 microM) could be found on 17beta-estradiol production, its toxicity may reflect at other points of the steroidogenic pathway.

Effects of Cadmium, Lead, and Mercury on the Structure and Function of Reproductive Organs

Reproductive organs are essential not only for the life of an individual but also for the survival and development of the species. The response of reproductive organs to toxic substances differs from that of other target organs, and they may serve as an ideal “barometer” for the deleterious effects of environmental pollution on animal and human health. The incidence of infertility, cancers, and associated maladies has increased in the last fifty years or more, while various anthropogenic activities have released into the environment numerous toxic substances, including cadmium, lead, and mercury. Data from epidemiological studies suggested that environmental exposure to cadmium, lead, and mercury may have produced reproductive and developmental toxicity. The present review focused on experimental studies using rats, mice, avian, and rabbits to demonstrate unambiguously effects of cadmium, lead, or mercury on the structure and function of reproductive organs. In addition, relevant human studies are discussed. The experimental studies reviewed have indicated that the testis and ovary are particularly sensitive to cadmium, lead, and mercury because these organs are distinguished by an intense cellular activity, where vital processes of spermatogenesis, oogenesis, and folliculogenesis occur. In ovaries, manifestation of toxicity induced by cadmium, lead, or mercury included decreased follicular growth, occurrence of follicular atresia, degeneration of the corpus luteum, and alterations in cycle. In testes, toxic effects following exposure to cadmium, lead, or mercury included alterations of seminiferous tubules, testicular stroma, and decrease of spermatozoa count, motility and viability, and aberrant spermatozoa morphology.

Effects of subchronic exposure of mercuric chloride on intestinal histology and microbiota in the cecum of chicken

This study aimed to investigate the influences of mercuric chloride (HgCl₂, 250 ppm, drink water) on the growth performance, cecal morphology and microbiota of chickens (n = 60) after 30, 60, and 90 days of exposure. A control group of sixty chickens received water free of HgCl₂. Our results suggested that mercury exposure reduced the body weight and changed the cecal morphology of chickens after the 90-day treatment. Furthermore, sequence analysis of 16 S rRNA gene revealed that the diversity and composition of cecal microbiota in chickens differed between the control and exposure group. At the phylum level, Proteobacteria and Tenericutes phyla both significantly increased in mercury exposure groups on day 30 while only Tenericutes phyla significantly increased on day 60. At the genus level, we observed that the change in microbial populations are most dramatic on day 30. Besides, compared with the control group, the genus Prevotellaceae_UCG-001 significantly increased in exposure group on day 30 but showed no significant difference on day 60, whereas there was a significant decrease on day 90. PICRUSt analysis revealed potential metabolic changes, such as Bacterial invasion of epithelial cells and Metabolism of xenobiotics, associated with mercury exposure in chickens. Taken together, the data show that subchronic exposure to mercury not only affected the growth and development but also caused the dysbiosis of gut microbiota, which may further induced metabolic disorders in chickens.

Molecular mechanism of mercuric chloride inhibiting progesterone secretion in ovarian granulosa cells of laying hens

This study investigated the effect of mercury (Hg) on progesterone secretion in ovarian granulosa cells of laying hens. The gene expressions of steroidogenic acute regulatory protein (StAR), cytochrome P450 cholesterol side-chain cleavage (P450scc) and 3β-hydroxysteroid dehydrogenase (3β-HSD), cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway and intracellular calcium ion (Ca²⁺ ) were further investigated to uncover the molecular mechanism. Results revealed that the cell viability was gradually decreased after Hg exposure from 0 to 24 hr. Besides, progesterone secretion was significantly decreased (p < 0.05) as the concentration of Hg increased from 0 to 4 μM followed by a plateau in 6 μM Hg group at 12-hr time point. Compared with 0 μM Hg group, 4 and 6 μM Hg for 48 hr had significantly decreased progesterone secretion (p < 0.05), while Hg exposure for 6 and 24 hr had no apparent effect on progesterone secretion. In addition, positive correlations occurred among intracellular progesterone, cAMP, PKA, mRNA expressions of StAR, P450scc and 3β-HSD at 12-h and 24-h time points. On the contrary, intracellular Ca²⁺ level was negatively related to cAMP level at 6 time point and was negatively correlated with progesterone and PKA level at 48 time point. It could be concluded that Hg dose- and time-dependently inhibited progesterone secretion by means of attenuating cAMP-PKA signal pathway, gene expressions of StAR, P450scc and 3β-HSD and enhancing intracellular Ca²⁺ in ovarian granulosa cells of laying hens.

Ovarian steroid hormone secretion activity examined after supplementation of green tea extract

This study aimed at examining the secretion activity of steroid hormones progesterone and 17beta-estradiol by porcine ovarian granulosa cells after addition of green tea extract. Granulosa cells were incubated with green tea extract (at doses of 0.01, 0.1, 1, 10 and 100 microg.ml(-1). Another set of cells were incubated with green tea extract at the above doses along with additional supplementation of follicle stimulating hormone (FSH) at 10 microg.ml(-1). Release of hormones by granulosa cells was assessed by EIA after 24 h exposure. Secretion of steroid hormones was not affected either by green tea extract alone or after FSH supplementation with green tea extract. Results indicate that ovarian steroidogenesis is not affected by green tea under conditions used in the experiment.