Toxic effects of methylmercury on spermatozoa in vitro

Hair mercury (Hg) levels, fish consumption and semen parameters among men attending a fertility center

General population exposure to methylmercury (MeHg), the most common organic mercury compound found in the environment, occurs primarily through the consumption of contaminated fish and shellfish. Due to limited studies and lack of consideration of effect modification by fish consumption, it remains uncertain if exposure to mercury affects semen parameters. Thus, we investigated whether hair Hg levels, a biomarker of mercury exposure, were associated with semen parameters among men attending an academic fertility center, and whether this relationship was modified by intake of fish. This analysis included 129 men contributing 243 semen samples who were enrolled in the Environment and Reproductive Health (EARTH) Study between 2005 and 2013, and had data of hair Hg, intake of fish and semen parameters available. Hair Hg levels were assessed using a direct mercury analyzer. Intake of fish was collected using a validated food frequency questionnaire. Semen parameters were analyzed following WHO 2010 evaluation criteria. Generalized linear mixed models with random intercepts accounting for within-man correlations across semen samples were used to evaluate the association of hair Hg levels and semen parameters adjusting for age, BMI, smoking status, abstinence time and alcohol intake. Effect modification by total fish intake (≤1.68 vs. >1.68 servings/week) was tested. The median hair Hg levels of the men was 0.72ppm and ranged from 0.03 to 8.01ppm; almost 30% of the men had hair Hg levels >1ppm. Hair Hg levels were positively related with sperm concentration, total sperm count, and progressive motility, after adjusting for potential confounders and became attenuated after further adjustment for fish intake. Specifically, men in the highest quartile of hair mercury levels had 50%, 46% and 31% higher sperm concentration, total sperm count and progressive motility, respectively, compared to men in the lowest quartile. These associations were stronger among men whose fish intake was above the study population median. Semen volume and normal morphology were unrelated to hair Hg levels. These results confirmed exposure to MeHg through fish intake and showed the important role of diet when exploring the associations between heavy metals and semen parameters among men of couples seeking fertility care. Further research is needed to clarify the complex relationship between fish intake and Hg, and potential effects on male reproductive health, specifically, semen parameters.

Urinary metal concentrations in relation to semen quality: a cross-sectional study in China

Exposure to metals, including essential and nonessential elements, is widespread and may be associated with altered semen quality. This study aimed to examine the association between urinary metal concentrations and semen quality in a Chinese population. We measured semen quality parameters (sperm concentration, count, motility, normal morphology, and abnormal head) and 13 metals [arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), molybdenum (Mo), mercury (Hg), nickel (Ni), selenium (Se), and zinc (Zn)] in the urine of 394 men from an infertility clinic. Multivariable logistic and linear regressions were used to assess the relationship between the creatinine-adjusted urinary metal concentrations and semen quality parameters. We found a significant trend for decreased odds ratios (ORs) for below-reference sperm count with increasing Se quartiles (p for trend = 0.04) and a significant trend for increased sperm percent abnormal head with increasing Ni quartiles (p for trend = 0.03). These associations persisted, even when considering multiple metals. Our results suggest that Ni exposure may be associated with deteriorated sperm morphology and that Se exposure may be associated with better semen quality. However, our findings warrant further studies in a larger and general population.

Environmental mercury exposure, semen quality and reproductive hormones in Greenlandic Inuit and European men: a cross-sectional study

Several animal studies indicate that mercury is a male reproductive toxicant, but human studies are few and contradictory. We examined semen characteristics and serum levels of reproductive hormones in relation to environmental exposure to mercury. Blood and semen samples were collected from 529 male partners of pregnant women living in Greenland, Poland and Ukraine between May 2002 and February 2004. The median concentration of the total content of mercury in whole blood was 9.2 ng ml(-1) in Greenland (0.2-385.8 ng ml(-1)), 1.0 ng ml(-1) in Poland (0.2-6.4 ng ml(-1)) and 1.0 ng ml(-1) in Ukraine (0.2-4.9 ng ml(-1)). We found a significantly positive association between the blood levels of mercury and serum concentration of inhibin B in men from Greenland (β=0.074, 95% confidence interval (CI)=0.021 to 0.126) and in an analysis including men from all three regions (β=0.067, 95% CI=0.024 to 0.110). The association may be due to beneficial effects of polyunsaturated fatty acids (PUFAs), which are contained in seafood and fish. No significant association (P>0.05) was found between blood concentrations of mercury and any of the other measured semen characteristics (semen volume, total sperm count, sperm concentration, morphology and motility) and reproductive hormones (free androgen index (FAI), follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone and LH × testosterone) in any region. In conclusion, the findings do not provide evidence that environmental mercury exposure in Greenlandic and European men with median whole blood concentration up to 10 ng ml(-1) has adverse effects on biomarkers of male reproductive health.

Mechanism of action of mercury on sperm morphology, adenosine triphosphate content, and motility in Perca fluviatilis (Percidae; Teleostei)

The main objectives of the present study were to investigate the performance of mercury chloride (HgCl2 ) on sperm function and structure, identify sites of action of HgCl2 , and investigate the mechanism of action of HgCl2 on fish (Perca fluviatilis L.) spermatozoa. Direct exposure of nonincubated sperm decreased sperm motility and velocity in a dose-dependent manner and was totally suppressed at 250 µM HgCl2 . Adenosine-5'-triphosphate (ATP) content of sperm after activation in an activation medium (AM) containing more than 25 µM HgCl2 did not differ compared with nonactivated sperm. Motility and velocity of demembranated sperm decreased after activation in an AM containing 62 µM HgCl2 , and was totally suppressed at 250 µM HgCl2 . Incubation of sperm in an immobilizing medium (IM) containing HgCl2 enhanced HgCl2 effects after sperm activation in an AM containing HgCl2 . Sperm motility of incubated sperm in an IM without HgCl2 was totally suppressed at 125 µM HgCl2 after 3 h incubation. In case of incubated sperm in an IM containing HgCl2 , sperm motility was totally suppressed at 31 µM HgCl2 . Adenosine-5'-triphosphate content of sperm was significantly lower in an IM containing HgCl2 greater than 3 µM compared with those of the control (no HgCl2 ) and lower HgCl2 concentrations. Damage to the plasma membrane and axoneme were observed in sperm incubated in an IM containing HgCl2 compared with the control, when HgCl2 concentration and incubation time increased. In conclusion, HgCl2 acts on sperm through disruption of function of the plasma membrane, axoneme, and ATP content.

Relationships between heavy metal concentrations in three different body fluids and male reproductive parameters: a pilot study

BACKGROUND

Animal studies have shown the reproductive toxicity of a number of heavy metals. Very few human observational studies have analyzed the relationship between male reproductive function and heavy metal concentrations in diverse biological fluids.

METHODS

The current study assessed the associations between seminal and hormonal parameters and the concentration of the 3 most frequent heavy metal toxicants (lead, cadmium and mercury) in three different body fluids. Sixty one men attending infertility clinics that participated in a case-control study to explore the role of environmental toxins and lifestyles on male infertility were analyzed. Concentration of lead, cadmium and mercury were measured in blood and seminal plasma and whole blood using anodic stripping voltammetry and atomic absorption spectrophotometry. Serum samples were analyzed for follicle-stimulating hormone, luteinizing hormone and testosterone. Semen analyses were performed according to World Health Organization criteria. Mann-Whitney test and Spearman's rank correlations were used for unadjusted analyses. Multiple linear regression models were performed controlling for age, body mass index and number of cigarettes per day.

RESULTS

There were no significant differences between cases and controls in the concentrations of heavy metals in any of the three body fluids. In multivariate analyses using all subjects no significant associations were found between serum hormone levels and metal concentrations. However there was a significant positive association between the percentage of immotile sperms and seminal plasma levels of lead and cadmium.

CONCLUSIONS

Our results suggest that the presence of lead and cadmium in the reproductive tract of men may be related to a moderate alteration of their seminal parameters.

Protective effect of vitamin E against mercuric chloride reproductive toxicity in male mice

Mercury intoxication has been associated with male reproductive toxicity in experimental animals and mercury may have the potential to produce adverse effects on fertility in men. Vitamin E may protect against toxic effects of mercury in the liver and other tissues. To investigate the protective role of vitamin E against mercuric chloride toxicity for the testis, epididymis, and vas deferens of adult male mice, animals were treated with either mercuric chloride 1.25 mg/kg/day, vitamin E 2 mg/kg/kg, or a combination of the two treatments. Control animals were treated with water. Treatments were administered by daily gavage for 45 days. An additional group of animals treated with mercuric chloride were permitted to recover for 45 days after mercuric chloride treatments. Parameters studied included serum testosterone, epididymal sperm count, motility, and morphology, epididymal and vas deferens adenosine triphosphatase (ATPase), phosphorylase, sialic acid, glycogen and protein, testicular succinate dehydrogenase (SDH), phosphatases, cholesterol, ascorbic acid, and glutathione. Fertility was evaluated by sperm positive vaginal smears after overnight cohabitation with a female. Mercuric chloride produced a reduction in epididymal sperm count, sperm motility, and sperm viability, and there were no sperm-positive smears in this group. Biochemical tests from the male reproductive organs were also altered by mercuric chloride treatment. Coadministration of vitamin E with mercuric chloride prevented the changes in sperm and biochemical parameters and was associated with control rates of sperm positive smears after cohabitation. Animals given vitamin E with mercuric chloride also had lower concentrations of mercury in the testis, epididimyis, and vas deferens. Permitting animals to recover for 45 days after mercuric chloride treatment resulted in partial recovery of sperm and biochemical parameters. Vitamin E cotreatment has a protective role against mercury-induced male reproductive toxicity.

A strategy for assessing the effects of xenobiotics on fish reproduction

Environmental pollutants, such as industrial and agricultural chemicals, heavy metals, drugs and products with hormonal activity may disrupt reproduction of aquatic wildlife such as fish. Such xenobiotics may cause disruption of the reproductive endocrine system, or they may directly affect gamete development and viability as a result either of their cytotoxicity or by altering the hormonal environment during gamete development. The various possible sites of action are reviewed, and it is suggested that tests for toxicity should isolate the specific component of the reproductive system that is most sensitive to such disruption and that this may be at levels well below that which causes mortality or visible signs of stress. Fish are proposed as the most suitable aquatic organism for such tests.

Reversible effects of mercuric chloride on reproductive organs of the male mouse

Effects of oral administration of mercuric chloride (HgCl2, 1.25 mg/kg) daily for 30 d on the mouse testis, vas deferens, epididymis, and cauda epididymal sperm were investigated. Testis, vas deferens, and epididymis functions were evaluated with respect to sperm count, motility, and viability, and biochemical tests, including succinate dehydrogenase (SDH), adenosine triphosphatase, sialic acid, protein, cholesterol, and glycogen levels in these tissue. Sperm morphology and sperm nuclear integrity were evaluated with standard staining methods. Treatment did not affect whole body and tissue weights. Sperm parameters and fertility were reduced by HgCl2 and most of the biochemical parameters declined. Morphologic histologic alterations were also observed in the tissues studied. All parameters partially recovered after withdrawal of HgCl2 for 45 d.

Effect of organic and inorganic mercury on human sperm motility

The effects of mercuric chloride and methyl mercuric chloride on the motility of human spermatozoa in vitro were investigated. Organic as well as inorganic mercury compounds decreased the percentage of motile spermatozoa. After 15 min. incubation with 40 microM mercuric chloride a significant decrease in sperm motility was observed. Less than 5% of spermatozoa were motile after 30 min. of exposure to 20 microM methyl mercuric chloride. These effects could not be attenuated by addition of 5 microM sodium selenite. The ultrastructural localization of mercury was demonstrated by autometallography. Silver-enhanced mercury deposits could be demonstrated only in spermatozoa exposed to inorganic mercury. In these cells mercury grains were most abundant in membranes of midpiece and tail.