Xenobiotic metabolism, genetic polymorphisms and male infertility

Aryl hydrocarbon receptor gene transitions (c.-742C>T; c.1661G>A) and idiopathic male infertility: a case-control study with in silico and meta-analysis

Aryl hydrocarbon receptor (AHR) is responsible for crucial events in male reproductive biology. Here, the association of the AHR transitions c.-742C>T and c.1661G>A with idiopathic male infertility was investigated in a case-control study, which is followed by a meta-analysis and a bioinformatic investigation. Blood and semen samples were obtained from a total of 135 idiopathic infertile men and 130 healthy controls. Participants were genotyped for the transitions using a PCR-RFLP method. A meta-analysis of five sets of data evaluated the association of c.1661G>A with male infertility, and using an in silico analysis, the possible molecular effects of the transitions predicted. Genotypes and alleles of AHR-c.-742C>T and c.1661G>A polymorphisms were not associated with the risk of male infertility significantly. However, the frequency of C/A haplotype was significantly associated with the increased risk of male infertility, and T/A haplotype was higher among controls significantly. Also, the frequencies of combined genotypes CT/GG, CT/GA and TT/GG were significantly associated with decreased risk of infertility. And, the meta-analysis showed that the AA versus GA/GG recessive model is associated with decreased risk of male infertility among the Iranian population. In silico analysis predicted that c.-742C>T does not alter the binding sites of the proposed transcription factors, but c.1661G>A poses a tolerable structural disturbance in AHR protein. In conclusion, these results showed that AHR c.-742C>T and c.1661G>A transitions separately could not be nominated as a risk or protective factor for male infertility. However, some combined models could affect infertility risk, especially among Iranian men.

The effect of thiacloprid formulation on DNA/chromosome damage and changes in GST activity in bovine peripheral lymphocytes

The potential genotoxic effect of thiacloprid formulation on bovine peripheral lymphocytes was evaluated using the comet assay and the cytogenetic endpoints: chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and micronuclei (MNi). Whole blood cultures were treated with the insecticide at concentrations of 30, 60, 120, 240 and 480 μg mL(-1) for 24, 48 h and/or 2 h of incubation. A statistically significant increase in the frequency of DNA damage, as well as in unstable chromosome aberrations (% breaks) were found after exposure to the insecticide at concentrations ranging from 120 to 480 μg mL(-1) (P < 0.05, P < 0.01, P < 0.001). For the detection of stable structural chromosome aberrations (e.g., translocations) and numerical aberrations by the FISH method, three whole chromosome painting probes for bovine chromosomes 1, 5 and 7 (BTA1, BTA5 and BTA7) were used in our experiments. We observed numerical aberrations, but without any statistical significance. Regarding the sister chromatid exchanges, no significant elevation in the SCE frequencies was found after 24-h exposure to the insecticide. A dose-related response in the SCE induction was obtained in bovine cultures after the prolonged time of exposure (48 h) to thiacloprid formulation at concentrations ranging from 120 to 480 μg mL(-1) in each donor (P < 0.05, P < 0.01), which was associated with a reduction of the PI (P < 0.05, P < 0.01). The insecticide failed to produce MNi; however, a significant reduction of CBPI was observed. Using real-time PCR, a decrease in the expression of bovine glutathione S-transferase M3 (GSTM3) was detected at the lowest dose. The higher concentrations of thiacloprid formulation caused an increase in the mRNA expression.

Joint effect of glutathione S-transferase genotypes and cigarette smoking on idiopathic male infertility

Inconsistent results of association studies investigated the role of glutathione S-transferase genes in idiopathic male infertility may be explained by ethnical differences in gene-gene and gene-environment interactions. In this study, we investigated a joint contribution of GSTM1, GSTT1 and GSTP1 gene polymorphisms and cigarette smoking to the risk of idiopathic infertility in Russian men. DNA samples from 203 infertile and 227 fertile men were genotyped by a multiplex polymerase chain reaction (GSTM1 and GSTT1 deletions) and PCR-restriction fragment length polymorphism (GSTP1 I105V) methods. The GSTP1 genotype 105IV was associated with increased risk of male infertility (OR = 1.50 95% CI 1.02-2.20 P = 0.04). Genotype combinations GSTP1 105II/GSTT1 del (G1), GSTM1 del/GSTT1 del (G2) and GSTM1 + /GSTT1 del (G3) were associated with decreased risk of male infertility (P ≤ 0.003), whereas a genotype combination GSTP1 105IV/GSTT1 + (G4) was associated with increased disease risk (P = 0.001). The genotype combinations G3 and G4 showed a significant association with infertility in smokers; however, nonsmokers carriers did show the disease risk. In conclusion, GSTM1, GSTT1 and GSTP1 genes are collectively involved in the development of idiopathic male infertility and their phenotypic effects on the disease risk are potentiated by cigarette smoking.

Chronic alcoholism-mediated metabolic disorders in albino rat testes

There is good evidence for impairment of spermatogenesis and reductions in sperm counts and testosterone levels in chronic alcoholics. The mechanisms for these effects have not yet been studied in detail. The consequences of chronic alcohol consumption on the structure and/or metabolism of testis cell macromolecules require to be intensively investigated. The present work reports the effects of chronic alcoholism on contents of free amino acids, levels of cytochrome P450 3A2 (CYP3A2) mRNA expression and DNA fragmentation, as well as on contents of different cholesterol fractions and protein thiol groups in rat testes. Wistar albino male rats were divided into two groups: I - control (intact animals), II - chronic alcoholism (15% ethanol self-administration during 150 days). Following 150 days of alcohol consumption, testicular free amino acid content was found to be significantly changed as compared with control. The most profound changes were registered for contents of lysine (-53%) and methionine (+133%). The intensity of DNA fragmentation in alcohol-treated rat testes was considerably increased, on the contrary CYP3A2 mRNA expression in testis cells was inhibited, testicular contents of total and etherified cholesterol increased by 25% and 45% respectively, and protein SH-groups decreased by 13%. Multidirectional changes of the activities of testicular dehydrogenases were detected. We thus obtained complex assessment of chronic alcoholism effects in male gonads, affecting especially amino acid, protein, ATP and NADPH metabolism. Our results demonstrated profound changes in testes on the level of proteome and genome. We suggest that the revealed metabolic disorders can have negative implication on cellular regulation of spermatogenesis under long-term ethanol exposure.

Correlation between spermatogenesis disorders and rat testes CYP2E1 mRNA contents under experimental alcoholism or type I diabetes

PURPOSE

The aim of the study was to investigate the correlation between spermatogenesis disorders and CYP2E1 mRNA contents in testes of rats with experimental alcoholism or type I diabetes.

MATERIAL/METHODS

Two pathological states characterized by CYP2E1 induction were simulated on Wistar male rats: experimental alcoholism and type I diabetes. As controls for each state, equal number of animals (of the same age and weight) were used. Morphological evaluation of rat testes was carried out. The spermatogenic epithelium state was estimated by four points system. CYP2E1 mRNA expression was rated by method of reverse transcriptase polymerase chain reaction. Pearson correlation coefficients were used for describing relationships between variables.

RESULTS

The presence of alcoholism and diabetes-mediated quantitative and qualitative changes in male rat spermatogenic epithelium in comparison with norm has been demonstrated. The increased levels of testes CYP2E1 have been fixed simultaneously. CYP2E1 mRNA content negatively strongly correlated with spermatogenic index value (r=-0.99; P<0.001) and positively strongly correlated with epithelium desquamation occurrence (r=0.99; P<0.001) in testes of rats with chronic alcoholism. The strong correlation between CYP2E1 mRNA content and number of spermatogonia (r=0.99; P<0.001) and "windows" occurrence (r=0.96; P<0.001) has been fixed in diabetic rats testes.

CONCLUSIONS

Present investigation has demonstrated that the testicular failure following chronic ethanol consumption and diabetes type I in male rats accompanied CYP2E1 mRNA over-expression in testes. The correlation between the levels of CYP2E1 mRNA in testes and spermatogenesis disorders allow supposing the involvement of CYP2E1 into the non-specific pathogenetic mechanisms of male infertility under above-mentioned pathologies.

Synergism between the N-acetyltransferase 2 gene and oxidant exposure increases the risk of idiopathic male infertility

N-acetyltransferase (NAT2) is a phase-II xenobiotic-metabolizing enzyme participating in the detoxification of toxic arylamines, aromatic amines and hydrazines. The present study was designed to investigate whether two common single-nucleotide polymorphisms (SNP) of the NAT2 gene (481C>T, rs1799929; 590G>A, rs1799930) are associated with susceptibility to idiopathic male infertility and to assess if the risk is modified by oxidant and antioxidant exposures. A total 430 DNA samples (203 infertile patients and 227 fertile men) were genotyped for the polymorphisms by PCR and restriction fragment length polymorphism. No association was found between the NAT2 polymorphisms and idiopathic male infertility. However, gene-environment interaction analysis revealed that a low-acetylation genotype, 590GA, was significantly associated with increased disease risk in men who had environmental risk factors such as cigarette smoking (OR 1.71, 95% CI 1.02-2.87, P = 0.042), alcohol abuse (OR 2.14, 95% CI 1.08-4.27, P = 0.029) and low fruit/vegetable intake (OR 1.68, 95% CI 1.01-2.79, P = 0.04). This pilot study found, as far as is known for the first time, that the polymorphism 590G>A of NAT2 is a novel genetic marker for susceptibility to idiopathic male infertility, but the risk is potentiated by exposure to various environmental oxidants.

Association between 3801T>C polymorphism of CYP1A1 and idiopathic male infertility risk: a systematic review and meta-analysis

BACKGROUND

Epidemiological studies have evaluated the association between 3801T>C polymorphism of CYP1A1 gene and the risk for idiopathic male infertility, but the results are inconclusive. We aimed to derive a more precise estimation of the relationship by conducting a meta-analysis of case-control studies.

METHODS

This study conformed to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. PubMed, Embase and CNKI databases were searched through November 2013 to identify relevant studies. Pooled odds ratios with 95% confidence intervals were used to assess the strength of the association between CYP1A1 3801T>C polymorphism and idiopathic male infertility risk. Q-test was performed to evaluate between-study heterogeneity and publication bias was appraised using funnel plots. Sensitivity analyses were conducted to evaluate the robustness of meta-analysis findings.

RESULTS

Six studies involving 1,060 cases and 1,225 controls were included in this meta-analysis. Overall, significant associations between 3801T>C polymorphism and idiopathic male infertility risk were observed in allelic comparison (OR = 1.36, 95% CI: 1.01-1.83), homozygous model (OR = 2.18, 95% CI: 1.15-4.12), and recessive model (OR = 1.86, 95% CI: 1.09-3.20), with robust findings according to sensitivity analyses. However, subgroup analyses did not further identify the susceptibility to idiopathic male infertility in all comparisons. Funnel plot inspections did not reveal evidence of publication bias.

CONCLUSIONS

The current meta-analysis provides evidence of a significant association between CYP1A1 3801T>C polymorphism and idiopathic male infertility risk. Considering the limitation inherited from the eligible studies, further confirmation in large-scale and well-designed studies is needed.

Association of GSTM1 and GSTT1 genes with the susceptibility to male infertility: result from a meta-analysis

The deletion polymorphisms of the glutathione S-transferase M1 (GSTM1) and glutathione S-transferase T1 (GSTT1) genes were considered as candidates for genetic susceptibility factors of male infertility. Previous studies concerning the relationship between the null genotype of the two genes and male infertility have been reported in recent years. However, the results remain elusive. A meta-analysis was performed to estimate the relationship between the deletion polymorphism of the GSTM1 or GSTT1 gene, and male infertility in this study. Sixteen studies concerning the GSTM1 gene, including 2174 cases and 1861 controls, and 13 case-control studies on the GSTT1 gene with a total number of 1992 cases and 1617 controls were processed. The results showed that the null genotype of the GSTM1 gene was associated with male infertility in the overall populations (P=0.003, OR=1.40, 95%CI=1.12-1.75), especially in Caucasian (P=0.012, OR=1.50, 95%CI=1.09-2.07) as well as Chinese (P=0.001, OR=1.55, 95%CI=1.19-2.03). The null genotype of the GSTT1 gene was strongly related to male infertility only in Chinese (P=0.000, OR=1.70, 95%CI=1.34-2.14). These results indicated that the null genotype of the GSTM1 gene might contribute to the susceptibility of male infertility, whereas the null genotype of the GSTT1 gene may be a genetic susceptibility factor of male infertility for the Chinese.

Smoking status modifies the relation between CYP1A1*2C gene polymorphism and idiopathic male infertility: the importance of gene-environment interaction analysis for genetic studies of the disease

The study was designed to investigate the associations of polymorphisms Ile462Val and 3801T>C of the cytochrome P450 1A1 (CYP1A1) gene with idiopathic male infertility (IMI) and to assess the impact of smoking status on the relationship between the polymorphisms and the susceptibility to the disease. DNA samples from 203 patients with IMI and 227 fertile men were genotyped for the polymorphisms by a polymerase chain reaction and restriction fragment length polymorphism methods. We found for the first time that the increased risk of IMI in carriers of genotype 462Ile/Val of the CYP1A1 gene occurred only in smoker men (odds ratio [OR] = 1.91; 95% confidence interval [CI] 1.01-3.59), whereas nonsmoker men did not have the risk of infertility (OR = 1.58; 95% CI 0.66-3.76). The results of our study demonstrate that the analysis of gene-environment interactions is necessary to explain conflicting results of genetic studies of IMI and to improve our understanding of the mechanisms of the disease.

Null genotype of GSTM1 and GSTT1 may contribute to susceptibility to male infertility with impaired spermatogenesis in Chinese population

Glutathione-S-transferases (GSTs) play a protective role during spermatogenesis and GST genes may be involved in impaired spermatogenesis. A case-control study was performed to explore the association of genes GSTM1 and GSTT1, two members of GST gene family, with spermatogenesis impairment. The deletion polymorphism distribution of genes GSTM1 and GSTT1 was investigated in 353 patients with azoospermia or oligospermia and 201 fertile controls in Chinese population using multiplex PCR. As a result, the frequencies of null genotype of genes GSTM1 (67.4% versus 57.7%, p = 0.022, OR = 1.516, 95% CI = 1.001-2.168) and GSTT1 (61.8% versus 46.8%, p = 0.001, OR = 1.838, 95% CI = 1.295-2.610) in patients were significantly higher than those in controls. After stratifying patients, the frequencies of null genotype of gene GSTM1 in oligospermia (68.3% versus 57.7%, p = 0.027, OR = 1.580, 95% CI = 1.051-2.375) and GSTT1 in azoospermia (66.9% versus 46.8%, p < 0.001, OR = 2.299, 95% CI = 1.484-3.562) as well as oligospermia (57.9% versus 46.8%, p = 0.025, OR = 1.567, 95% CI = 1.057-2.322) were still significantly higher compared with controls. The results suggested that null genotypes of GSTM1 and GSTT1 are associated with spermatogenesis impairment and may contribute to susceptibility to spermatogenesis impairment and male infertility in Chinese population.

Effect of mono-(2-ethylhexyl) phthalate on human and mouse fetal testis: In vitro and in vivo approaches

The present study was conducted to determine whether exposure to the mono-(2-ethylhexyl) phthalate (MEHP) represents a genuine threat to male human reproductive function. To this aim, we investigated the effects on human male fetal germ cells of a 10⁻⁵ M exposure. This dose is slightly above the mean concentrations found in human fetal cord blood samples by biomonitoring studies. The in vitro experimental approach was further validated for phthalate toxicity assessment by comparing the effects of in vitro and in vivo exposure in mouse testes. Human fetal testes were recovered during the first trimester (7-12 weeks) of gestation and cultured in the presence or not of 10⁻⁵ M MEHP for three days. Apoptosis was quantified by measuring the percentage of Caspase-3 positive germ cells. The concentration of phthalate reaching the fetal gonads was determined by radioactivity measurements, after incubations with ¹⁴C-MEHP. A 10⁻⁵ M exposure significantly increased the rate of apoptosis in human male fetal germ cells. The intratesticular MEHP concentration measured corresponded to the concentration added in vitro to the culture medium. Furthermore, a comparable effect on germ cell apoptosis in mouse fetal testes was induced both in vitro and in vivo. This study suggests that this 10⁻⁵ M exposure is sufficient to induce changes to the in vivo development of the human fetal male germ cells.

Tissue distribution and gender-divergent expression of 78 cytochrome P450 mRNAs in mice

Cytochrome P450 (Cyp) enzymes from the first four families (Cyp1-4) play a major role in metabolizing xenobiotics, affecting drug pharmacokinetics and chemical-induced toxicity. Due to cloning of the mouse genome, many novel Cyp isoforms have been identified, but their tissue distribution of expression is unknown. This study compared the tissue distribution of all 78 Cyps from the Cyp1-4 families in C57BL/6 mice providing not only an indication of which tissues novel Cyps may have their greatest importance but also a cohesive comparison of the tissue distribution of all Cyp1-4 isoforms. Transcripts of the 78 Cyps were quantified by multiplex suspension arrays and quantitative real-time PCR in 14 tissues. Hierarchical clustering indicated that in male mice, 52% of the Cyp species were expressed highest in liver, 10% in kidney, 10% in duodenum/jejunum, 10% in testes, 5% in lung, and < 4% in colon, brain, heart, and stomach. Female mice had a similar pattern of Cyp messenger RNA expression; however, compared with males, females had 7% more Cyps that were liver predominant, 2% more Cyps that were stomach predominant, but 1% less Cyps that were kidney and lung predominant. Differences in gender expression were observed in 29 of the Cyps, with 24 being higher in females than males. Additionally, the data suggest a correlation between the spatial arrangement of genes within a gene cluster and their organ-predominant expression, indicating a common regulatory mechanism may be present within these clusters. In conclusion, this study provides novel data on the tissue distribution and gender-divergent expression of 78 functional mouse Cyp isoforms.

Constitutive expression of drug metabolizing enzymes and related transcription factors in cattle testis and their modulation by illicit steroids

In veterinary species, little information about extrahepatic drug metabolism is actually available. Therefore, the presence of foremost drug metabolizing enzymes (DMEs) and related transcription factors mRNAs was initially investigated in cattle testis; then, their possible modulation following the in vivo exposure to illicit growth promoters (GPs), which represent a major issue in cattle farming, was explored. All target genes were expressed in cattle testis, albeit to a lower extent compared to liver ones; furthermore, illicit protocols containing dexamethasone and 17β-oestradiol significantly up-regulated cytochrome P450 1A1, 2E1, oestrogen receptor-α and peroxisome proliferator-activated receptor-α mRNA levels. Overall, the constitutive expression of foremost DMEs and related transcription factors was demonstrated for the first time in cattle testis and illicit GPs were shown to affect pre-transcriptionally some of them, with possible consequences upon testicular xenobiotic drug metabolism.

Combined effect of GSTM1 gene deletion, GSTT1 gene deletion and MTHFR C677T mutation in male infertility

The aim of the study was to investigate the association between the GSTM1 and GSTT1 gene deletion and MTHFR C677T mutation and male infertility. The study has encompassed 52 infertile and 56 fertile males. Genotype distributions of GSTM1 and GSTT1 gene deletions and the MTHFR C677T mutation did not differ significantly among the analyzed groups, however, a difference in distribution of certain genotype combinations was observed. The obtained results indicate that carriers of double GSTM1/GSTT1 deletion and the MTHFR 677CC genotype are at higher risk of infertility than carriers of any other combination of genotypes (OR 3.5, 95%CI 0.68-18.30). .

Association of CYP1A1*2A polymorphism with male infertility in Indian population

BACKGROUND

The CYP1A1 gene is a polymorphic gene and encodes for the CYP1A1 enzyme that catalyzes the bioactivation of polycyclic aromatic hydrocarbons (PAHs). PAHs are ubiquitous pollutants in the natural environment, which are capable of forming DNA adducts once being activated to generate DNA reactive metabolites. DNA adducts in sperm cells could be considered as a sign of severe DNA damage, which played an important role in meiotic division during spermatogenesis and could be associated with infertility. Lipophilic compounds undergo metabolic activation by phase I enzymes, which introduce a reactive center into the molecule, followed by phase II conjugation reaction resulting in a water soluble product.

METHODS

We genotyped CYP1A1*2A, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in a hospital based case-control study including 206 infertile men and 230 healthy fertile (control) subjects.

RESULTS

Analysis showed that CYP1A1*2A CC genotype is associated with increased risk of male infertility (OR=6.08, 95% CI=1.91-25.27), while TC genotype showed a non-significantly increased risk of male infertility (OR=1.35 95% CI=0.89-2.05). Further, when the variant genotypes were combined (CYP1A1*2A TC+CC) assuming a co-dominant allele effect, TC plus CC genotypes were also found to be significant with increased risk of male infertility (OR=1.57 95% CI=1.05-2.35 p=0.02). Allele frequencies are calculated for each genotype of CYP1A1*2A and the differences for allele frequencies between the infertile and fertile men are determined using Fisher's exact test. T and C allele frequencies in infertile men are 71% and 29% as against 80% and 20% in fertile men. The differences for allele frequencies are found to be statistically significant (p=0.002). The results showed a drastic decrease in the sperm count and motility and increase in dead sperms in CC genotype when compared to other genotypes in infertile men.

CONCLUSION

Based on Indian study we conclude that CC genotype of CYP1A1 is associated in the pathogenesis of male infertility.

Developmental expression and endocrine regulation of CYP1B1 in rat testis

Mammalian testis expresses xenobiotic-metabolizing enzymes, including cytochrome P450 1B1 (CYP1B1), which catalyzes the bioactivation of procarcinogens and other chemicals. The factors that control testicular expression of CYP1B1 are largely not known. In the present study, we investigated the influence of age and pituitary, gonadal, and thyroid hormones on CYP1B1 expression in rat testis. Immunoblot analysis showed that testicular CYP1B1 protein was expressed at a level of 5.9+/-2.0 (mean+/-S.E.M.) pmol/mg microsomal protein in prepubertal 22-day-old rats, whereas it was 6.6-fold greater in pubertal rats (34 days old) and 9.6-fold greater in adult rats (84-91 days old). Hypophysectomy decreased testicular CYP1B1 protein levels by 69% in adult rats when compared with intact rats of the same age. Intermittent subcutaneous administration of growth hormone to hypophysectomized adult rats further decreased it by 63%. Luteinizing hormone (LH) and follicle-stimulating hormone increased CYP1B1 expression in hypophysectomized rats, but they did not restore protein levels to those in intact adult male rats. Prolactin treatment alone had no effect; however, it potentiated the increase in CYP1B1 mRNA and protein expression by LH. 3,5,3'-Triiodothyronine, but not thyroxine, resulted in a small increase in testicular CYP1B1 protein levels. Likewise, treatment of hypophysectomized rats with testosterone propionate elicited a small increase in CYP1B1 protein expression. In contrast, treatment of intact adult male rats with 17beta-estradiol benzoate decreased it by 91%. Overall, our findings indicate that rat testicular CYP1B1 protein expression is subject to developmental and endocrine control, with multiple hormones playing a role.

Polymorphisms in CYP1A1 gene are associated with male infertility in a Chinese population

Cytochrome P4501A1 (CYP1A1) is a key enzyme in phase I bioactivation of polycyclic aromatic hydrocarbons (PAHs), which have potential reproductive toxicity. The aim of this study was to investigate the association of the CYP1A1 polymorphisms with male infertility in a Han-Chinese population. We genotyped two polymorphisms, CYP1A1*2A and CYP1A1*2C, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in a hospital-based case-control study including 192 infertile patients with non-obstructive azoospermia or severe oligozoospermia and 226 fertile controls. We found that the genotype distribution of CYP1A1*2C was significantly different between the patients and the controls (p = 0.019). Analysis showed that CYP1A1*2C AG genotype was associated with a significantly decreased risk of male infertility [odds ratio (OR) = 0.56, 95% confidence interval (95% CI) = 0.36-0.86, p = 0.005] compared with the AA genotype. A statistically significantly decreased risk of male infertility was found to be associated with the CYP1A1*2C AG genotype plus GG genotype compared with CYP1A1*2C AA genotype (OR = 0.60, 95% CI = 0.40-0.91, p = 0.011). No significant association was detected between CYP1A1*2A polymorphism and male infertility. Haplotypic analysis showed a significantly increased risk of male infertility associated with the C-A haplotype compared with the T-A haplotype (OR = 1.98, 95% CI = 1.27-3.09), indicating a synergic effect of the two polymorphisms. Our results suggest that the CYP1A1 polymorphisms may contribute to the pathogenesis of male infertility in the Han-Chinese population.

Reproductive Deficits in Male Freshwater Turtle Chrysemys picta from Cape Cod, Massachusetts1

Contaminated groundwater plumes have formed on the Massachusetts Military Reservation (MMR), a Superfund site on Cape Cod, Massachusetts, as a result of chemical waste disposal. The plumes are of concern to the local people who rely on groundwater as a drinking water source. We used the freshwater turtle as a sentinel species to monitor the reproductive effects of exposure and, by inference, the potential for impact on human health. Our observations of male Chrysemys picta field-trapped from Moody Pond (an impacted site) and Washburn Pond (a reference site) on Cape Cod extended and supported prior observations of reproductive deficits. Morphometric comparison of precloacal length (PCL), which is a sexually dimorphic trait in the turtle, showed that Moody Pond males had a significantly longer PCL than Washburn Pond males. Moody Pond turtles showed reduced testicular weight, which was associated with significantly smaller seminiferous tubule diameter. Epididymal sperm counts were also markedly reduced in Moody Pond animals compared to Washburn Pond animals. Testicular histology and gonial proliferation, as determined by PCNA, were similar in both male populations, while the Moody Pond males had significantly higher germ cell apoptosis than the animals in Washburn Pond. These results suggest that a low-level mixture of xenobiotic contaminants impairs the reproductive functions of turtles exposed to the impacted site but not to the reference site environment.

Gene-environment interactions: a review of effects on reproduction and development

Polymorphisms in genes can lead to differences in the level of susceptibility of individuals to potentially adverse effects of environmental influences, such as chemical exposure, on prenatal development or male or female reproductive function. We have reviewed the literature in this area, with the caveat that papers involving straight gene knock-outs in experimental animals, without a clear human relevance, were largely excluded. This review represents current knowledge in this rapidly moving field, presenting both human epidemiological and animal data, where available. Among the polymorphic genes and environmental interactions discussed with respect to prenatal development are those for P-glycoprotein (multidrug resistance protein) and the avermectins; methylenetetrahydrofolate reductase (MTHFR), an enzyme in folate metabolism, and dietary folic acid; transforming growth factor alpha (TGFalpha) and cigarette smoke; and alcohol dehydrogenase (ADH) and cytochrome P-450 (CYP) 2E1 in association with alcohol consumption. Effects on male reproduction attributable to gene-environment interaction involve infertility seen as a result of either organophosphorous (OP) pesticide interaction with the polymorphic paraoxonase (PON1) gene or antiandrogenic agent interaction with the androgen receptor (AR). MTHFR, folate metabolism, and dietary folic acid are also considered in conjunction with preeclampsia and early pregnancy loss, and the effect of the interaction of glutathione S-transferase (GST) with exposure to benzene or cigarette smoke on pregnancy maintenance is explored. As a conclusion, we offer a discussion of lessons learned and suggested research needs.

Polymorphisms of glutathione S-transferase M1 and male infertility in Taiwanese patients with varicocele

BACKGROUND

To examine glutathione S-transferase M1 (GST M1) gene polymorphism and male infertility in Taiwanese patients with varicocele, 80 young male patients with varicocele (group 1), 62 young male patients with subclinical varicocele (group 2) and 60 normal young males (group 3) were recruited in this study.

METHODS

GST M1 null homozygous genotype [GST M1-] and the occurrence of a 4977 bp deletion of sperm mitochondrial DNA (mtDNA) were determined by polymerase chain reaction. The 8-hydroxy-2'-deoxyguanosine (8-OHdG) content of sperm DNA was measured by high-performance liquid chromatography.

RESULTS

The frequencies of GST M1- genotype were 43.8, 41.9 and 45% for patients in groups 1, 2 and 3 respectively. In group 1 patients with GST M1- genotype, the frequency of the presence of the 4977 bp deletion in sperm mtDNA (54.3%) was significantly higher than that of the patients without the 4977 bp deletion in sperm mtDNA (45.7%, OR: 2.63, P = 0.04). Patients of groups 1 and 2 with GST M1- genotype had significantly higher 8-OHdG content in sperm DNA and lower protein thiols and ascorbic acid in seminal plasma than those with GST M1+ genotype.

CONCLUSION

GST M1- genotype predisposes to increased oxidative damage to sperm of patients with varicocele.