2-Bromopropane induces DNA damage, impairs functional antioxidant cellular defenses, and enhances the lipid peroxidation process in primary cultures of rat Leydig cells

A Review on the Impact of Oxidative Stress and Medicinal Plants on Leydig Cells

Leydig cells are essential for steroidogenesis and spermatogenesis. An imbalance in the production of reactive oxygen species (ROS) and the cellular antioxidant level brings about oxidative stress. Oxidative stress (OS) results in the dysfunction of Leydig cells, thereby impairing steroidogenesis, spermatogenesis, and ultimately, male infertility. To prevent Leydig cells from oxidative insults, there needs to be a balance between the ROS production and the cellular protective capacity of antioxidants. Evidence indicates that medicinal plants could improve Leydig cell function at specific concentrations under basal or OS conditions. The increased usage of medicinal plants has been considered a possible alternative treatment for male infertility. This review aims to provide an overview of the impact of oxidative stress on Leydig cells as well as the effects of various medicinal plant extracts on TM3 Leydig cells. The medicinal plants of interest include Aspalathus linearis, Camellia sinensis, Moringa oleifera, Morinda officinale, Taraxacum officinale, Trichilia emetica, Terminalia sambesiaca, Peltophorum africanum, Ximenia caffra, Serenoa repens, Zingiber officinale, Eugenia jambolana, and a combination of dandelion and fermented rooibos (CRS-10). According to the findings obtained from studies conducted on the evaluated medicinal plants, it can, therefore, be concluded that the medicinal plants maintain the antioxidant profile of Leydig cells under basal conditions and have protective or restorative effects following exposure to oxidative stress. The available data suggest that the protective role exhibited by the evaluated plants may be attributed to their antioxidant content. Additionally, the use of the optimal dosage or concentration of the extracts in the management of oxidative stress is of the utmost importance, and the measurement of their oxidation reduction potential is recommended.

Multi-organ carcinogenicity by inhalation exposure to 2-Bromopropane in rats

OBJECTIVE

The purpose of this study was to investigate the carcinogenicity of 2-bromopropane (2-BP) in rats.

METHODS

Male and female F344 rats were exposed by whole body inhalation to 2-BP vapor at concentrations of 0, 67, 200, and 600 ppm for 6 h/day, 5 days/week for 2 years.

RESULTS

All rats of both sexes exposed to 600 ppm died or became moribund within 85 weeks. Death/moribundity was caused by 2-BP induced tumors. In males, significantly increased tumors were malignant Zymbal's gland tumors; sebaceous adenoma and basal cell carcinoma of the skin/appendage; adenocarcinoma of the small/large intestine; follicular cell adenoma of the thyroid; fibroma of the subcutis, and malignant lymphoma of the lymph node. In addition, an increased trend in tumor incidence was found in the preputial gland, lung, forestomach, pancreas islet, brain, and spleen. In females, significantly increased tumors were adenocarcinoma and fibroadenoma of the mammary gland, squamous cell papilloma of the vagina, and large granular lymphocytic leukemia of the spleen. In addition, an increased trend in tumor incidence was found in Zymbal's gland, the clitoral gland, skin, large intestine, pancreas islet, uterus, and subcutis. Particularly, malignant Zymbal's gland tumors were induced even in males exposed to the lowest concentration, 67 ppm.

CONCLUSION

Two-year inhalation exposure to 2-BP resulted in multi-organ carcinogenicity in rats. Based on sufficient evidence of carcinogenicity in this study, 2-BP has the potential to be a human carcinogen.

Overview of biological effects of melatonin on testis: A review

Infertility is a major global health issue and male factors account for half of all infertility cases. One of the causes of male infertility is the loss of spermatogonial stem cells, which may occur because of chemotherapy, radiotherapy or genetic defects. In numerous animal species, the evidence suggests the pineal gland and melatonin secretion in their reproductive activities are involved. Recently, considerable attention has pointed to the usage of melatonin in the treatment of diseases. Melatonin is associated with the regulation of circadian and seasonal rhythmic functions, immune system functions, retinal physiology, spermatogenesis and inhibition of tumour growth in different species. Several studies demonstrated that melatonin acts as an anti-apoptotic, anti-inflammatory, anticancer and antioxidant agent. Melatonin can also protect testicles and spermatogonia against oxidative damage, chemotherapy drugs, environmental radiation, toxic substances, hyperthermia, ischemia/reperfusion, diabetes-induced testicular damage, metal-induced testicular toxicity, improve sperm quality and it affects the testosterone secretion pathway by affecting Leydig cells. Therefore, the objective of this study is to investigate the biological effects of melatonin as a natural antioxidant on testicles and their disorders.

Ascorbic acid specifically reduces the misclassification of nonirritating reactive chemicals in the OptiSafe™ macromolecular eye irritation test

Recently, we showed that the addition of physiological concentrations of ascorbic acid, a tear antioxidant, to the OptiSafe™ macromolecular eye irritation test reduced the optical density (OD) of false-positive (FP) chemicals that had reactive chemistries, leading to the formation of reactive oxygen species (ROS) and molecular crosslinking. The purpose of the current study was to 1) increase the number of chemicals tested to comprehensibly determine whether the antioxidant-associated reduction in OD is specific to FP chemicals associated with ROS chemistries and 2) determine whether the addition of antioxidants interferes with the detection of true positive (TP) and true negative (TN) ocular irritants. We report that when ascorbic acid is added to the test reagents, retesting of FP chemicals with reactive chemistries show significantly reduced OD values (P < 0.05). Importantly, ascorbic acid had no significant effect on the OD values of TP or TN chemicals regardless of chemical reactivity. These findings suggest that supplementation of ascorbic acid in alternative ocular irritation test may help improve the detection of TN for those commonly misclassified reactive chemicals.

Antioxidant and antigenotoxic potential of Morinda tinctoria Roxb. leaf extract succeeding cadmium exposure in Asian catfish, Pangasius sutchi

The present study investigated the protective effect of methanolic leaf extract of Morinda tinctoria. Roxb (MEMT) (200 mg/kg) via feed in supplementation with standard compound silymarin (400 mg/kg). M. tinctoria (Roxb.) belonging to Rubiaceae, is an evergreen shrub indigenous to unfarmed lands of tropical countries. It is considered as an essential traditional medicine attributing for the potential antioxidant and anti-inflammatory properties. The enhancements of antioxidant and antigenotoxic status in different tissues of cadmium (Cd) intoxicated Pangasius sutchi were evaluated by using various antioxidant assays (superoxide dismutase (SOD) and catalase (CAT) and lipid peroxidation) in addition to micronuclei (MN), binuclei (BN) and comet assay. The cadmium toxicated fish showed a significant (p < 0.001) increase in lipid peroxidation (LPO) activities in liver, gills, muscle and kidney whereas significant (p < 0.001) decline were observed in superoxide dismutase (SOD) and catalase (CAT) contents in all fish tissues. The results also revealed that, Cd exposure induced the formation of genotoxic endpoints like MN, BN, notched nuclei, kidney shaped nuclei and DNA damage in the fish erythrocytes. Maximum of 26.8% MN frequencies and maximum of 66.74% tail DNA damage were observed on the 7th day of Cd exposure. A time-dependent significant increase (p < 0.001) in the frequencies of MN, BN and tail DNA damage were observed in all treated groups against the control which started to decline from 14th day onwards. There was a decline in the LPO content, frequencies of MN, BN and percentage of tail DNA in contrast to significant elevation in SOD and CAT content in all tissues due to the combined treatment of M. tinctoria feed and water borne Cd exposure. It can be concluded from our observations that, supplementation of M. tinctoria leaf extract through feed alone produced enhanced antioxidant and antigenotoxic status in cadmium treated fish by diminishing oxidative stress and genotoxicity effects in a time dependent manner.

Improvement of Qilin pills on male reproductive function in tripterygium glycoside-induced oligoasthenospermia in rats

This study established an oligoasthenospermic rat model using tripterygium glycosides (TGs) and investigated the mechanism by which Qilin pills (QLPs) ameliorate reproductive hypofunction. Thirty-two male Sprague Dawley rats were allocated to four equal-sized groups: (1) the control group received continuous physiological levels of saline; (2) the oligoasthenospermia model group was induced with TGs by daily intragastric administration for 28 days; (3 and 4) oligoasthenospermic rats were treated intragastrically with low dose (1.62 g kg^-1  d^-1 ) and high dose (3.24 g kg^-1  d^-1 ) of QLPs once daily for 60 days. The QLP-treated rats showed a marked increase (p < .05) in testicular mass, testicular index and semen parameters compared with the untreated rats. Histopathologically, the QLP-treated groups exhibited restored seminiferous tubules in contrast to the model group. Reactive oxygen species and malondialdehyde levels were dramatically decreased (p < .05) in the testes of the QLP-treated rats. QLP treatment partly reverted (p < .05) the circulatory levels of reproductive hormones (FSH, LH, testosterone, prolactin and SHBG) and hepatic and renal function (AST, Cr and urea). Our results showed that oral QLP treatment had a curative effect on the testicular mass, sperm quality, testicular pathomorphology, antioxidants, plasmatic hormones, and liver and renal function of rats.

Neuroprotective effect of grape seed extract against cadmium toxicity in male albino rats

Cadmium toxicity can disturb brain chemistry leading to depression, anxiety, and weakened immunity. Cadmium disturbs the neurotransmitter dopamine, resulting in low energy, lack of motivation, and depression, which are predisposing factors for violence. The purpose of this study was to evaluate the ameliorative effect of grape seed extract (GSE) on the brain of 40 male albino rats after exposure to cadmium chloride (Cd) toxicity. The rats were separated into either the control group, the Cd group, the GSE group, or the GSE and Cd mixture (treated) group. The cerebrum showed evidence of degeneration of some nerve fibers and cells. Fibrosis, vacuolations, and congestion in the blood vessels were demonstrated. Satelletosis was located in the capsular cells. Immunohistochemical expression of Bax was strongly positive in the Cd group and decreased in the treated group. These histopathological changes were decreased in the brain tissue of the treated group, but a few blood vessels still had evidence of congestion. Cadmium administration increased the level of MDA and decreased MAO-A, acetylcholinesterase, and glutathione reductase (GR), while the treatment with GSE affected the alterations in these parameters. In addition, cadmium downregulated the mRNA expression levels of GST and GPx, while GSE treatment normalized the transcript levels. The expression of both dopamine and 5-hydroxytryptamine transporter was downregulated in the rats administered cadmium and the addition of GSE normalized the expression of these aggression associated genes.

Quercetin ameliorates polychlorinated biphenyls-induced testicular DNA damage in rats

Polychlorinated biphenyls (PCBs) are a group of environmental contaminants widely reported to cause gonadal toxicity in both humans and animals. This study investigated the amelioratory role of quercetin in PCBs-induced DNA damage in male Wistar rats. Polychlorinated biphenyls were administered intraperitoneally at a dose of 2 mg kg(-1) alone or in combination with quercetin (orally) at 50 mg kg(-1) for 25 days. Quercetin modulation of PCBs-induced gonadal toxicity was evaluated using selected oxidative stress indices, comet assay, measurement of DNA concentration and histology of the testes. Administration of PCBs alone caused a significant (P < 0.05) depletion in the total thiol level in testes of treated rats. Conversely, the levels of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) production were markedly elevated in testes of PCBs-treated rats compared with control. Further, PCBs exposure produced statistically significant increases in DNA tail migration, degraded double-stranded DNA (dsDNA) concentration and histological alterations of testes of the treated rats compared to control. Quercetin cotreatment significantly improved the testicular antioxidant status, decreased DNA fragmentation and restored the testicular histology, thus demonstrating the protective effect of quercetin in PCBs-treated rats.

Histopathology and cytotoxicity as biomarkers in treated rats with cadmium and some therapeutic agents

The present study aimed to investigate the protective role of ascorbic acid (vitamin C) and zinc (Zn) against cadmium (Cd) induced histopathological changes in tissues of liver, kidney, lung and testis of rats as well as chromosomal aberrations. For this purpose, 60 male albino rats were divided into six groups; each group contained 10 animals. The first group served as control and was given only distilled water. The second and third groups received distilled water supplemented with 2 g ascorbic acid/l and 500 mg Zn/l, respectively. The fourth group received a daily oral dose containing 3 mg Cd/kg b.w. (1/30 LD50). The fifth group received Cd + ascorbic acid (3 mg Cd/kg b.w. + 2 g ascorbic acid/l), while the sixth group received Cd + Zn (3 mg Cd/kg b.w. +500 mg Zn/l). The treatment in all groups lasted for 90 consecutive days. Rats exposed to cadmium showed severe histopathological changes in the liver, kidney, lung and testicular tissues as well as chromosomal aberrations such as: break, ring, centromeric separation and polyploidy. Co-treatment with zinc partially improved the histopathological changes and chromosomal aberrations while co-treatment with vitamin C exhibited a more protective role and markedly reduced tissues damage induced by Cd.

The apoptotic function analysis of p53, Apaf1, Caspase3 and Caspase7 during the spermatogenesis of the Chinese fire-bellied newt Cynops orientalis

BACKGROUND

Spontaneous and stress-induced germ cell apoptosis during spermatogenesis of multicellular organisms have been investigated broadly in mammals. Spermatogenetic process in urodele amphibians was essentially like that in mammals in spite of morphological differences; however, the mechanism of germ cell apoptosis in urodele amphibians remains unknown. The Chinese fire-belly newt, Cynops orientalis, was an excellent organism for studying germ cell apoptosis due to its sensitiveness to temperature, strong endurance of starvation, and sensitive skin to heavy metal exposure.

METHODOLOGY/PRINCIPAL FINDINGS

TUNEL result showed that spontaneous germ cell apoptosis took place in normal newt, and severe stress-induced apoptosis occurred to spermatids and sperm in response to heat shock (40°C 2 h), cold exposure (4°C 12 h), cadmium exposure (Cd 36 h), and starvation stress. Quantitative reverse transcription polymerase chain reactions (qRT-PCR) showed that gene expression of Caspase3 or Caspase7 was obviously elevated after stress treatment. Apaf1 was not altered at its gene expression level, and p53 was significantly decreased after various stress treatment. Caspase assay demonstrated that Caspase-3, -8, -9 enzyme activities in newt testis were significantly elevated after heat shock (40°C 2 h), cold exposure (4°C 12 h), and cadmium exposure (Cd 36 h), while Caspase3 and Caspase8 activities were increased with Caspase9 significantly decreased after starvation treatment.

CONCLUSIONS/SIGNIFICANCE

Severe germ cell apoptosis triggered by heat shock, cold exposure, and cadmium exposure was Caspase3 dependent, which probably involved both extrinsic and intrinsic pathways. Apaf1 may be involved in this process without elevating its gene expression. But starvation-induced germ cell apoptosis was likely mainly through extrinsic pathway. p53 was probably not responsible for stress-induced germ cell apoptosis in newt testis. The intriguing high occurrence of spermatid and sperm apoptosis probably resulted from the sperm morphology and unique reproduction policy of Chinese fire-belly newt, Cynops orientalis.

Resveratrol protects against 2-bromopropane-induced apoptosis and disruption of embryonic development in blastocysts

2-Bromopropane (2-BP) is used as an alternative to ozone-depleting cleaning solvents. Previously, we reported that 2-BP has cytotoxic effects on mouse blastocysts and is associated with defects in subsequent development. In the present work, we show that 2-BP induces apoptosis in the inner cell mass of mouse blastocysts, and inhibits cell proliferation. Both effects are suppressed by resveratrol, a grape-derived phytoalexin with known antioxidant and anti-inflammatory properties. 2-BP-treated blastocysts displayed lower levels of implantation (compared to controls) when plated on culture dishes in vitro, and a reduced ability to proceed to later stages of embryonic development. Pretreatment with resveratrol prevented 2-BP-induced disruption of embryonic development, both in vitro and in vivo. Further investigation of these processes revealed that 2-BP directly promotes ROS generation, loss of mitochondrial membrane potential (MMP), and activation of caspase-3, whereas resveratrol effectively blocks 2-BP-induced ROS production and the accompanying apoptotic biochemical changes. Our results collectively imply that 2-BP triggers the mitochondrion-dependent apoptotic pathway via ROS generation, and the antioxidant activity of resveratrol prevents 2-BP-induced toxicity.

Hazardous apoptotic effects of 2-bromopropane on maturation of mouse oocytes, fertilization, and fetal development

2-Bromopropane (2-BP) is used as an alternative to ozone-depleting cleaning solvents. Previously, we reported that 2-BP has cytotoxic effects on mouse blastocysts and is associated with defects in subsequent development. Here, we further investigate the effects of 2-BP on oocyte maturation and subsequent pre- and post-implantation development, both in vitro and in vivo. Notably, 2-BP induced a significant reduction in the rates of oocyte maturation, fertilization, and in vitro embryonic development. Treatment of oocytes with 2-BP during in vitro maturation (IVM) resulted in increased resorption of postimplantation embryos and decreased fetal weights. Experiments with a mouse model disclosed that consumption of drinking water containing 20 μM 2-BP led to decreased oocyte maturation in vivo and fertilization in vitro, as well as impairment of early embryonic development. Interestingly, pretreatment with a caspase-3-specific inhibitor effectively prevented 2-BP-triggered hazardous effects, suggesting that embryonic impairment by 2-BP occurs via a caspase-dependent apoptotic process. A study using embryonic stem cells as the assay model conclusively demonstrated that 2-BP induces cell death processes through apoptosis and not necrosis, and inhibits early embryo development in mouse embryonic stem cells. These results collectively confirm the hazardous effects of 2-BP on embryos derived from pretreated oocytes.

DNA damage and estrogenic activity induced by the environmental pollutant 2-nitrotoluene and its metabolite

OBJECTIVES

The environmental pollutant 2-nitrotoluene (2-NO(2)-T) is carcinogenic and reproductively toxic in animals. In this study, we elucidated the mechanisms of its carcinogenicity and reproductive toxicity.

METHODS

We examined DNA damage induced by 2-NO(2)-T and its metabolite, 2-nitrosotoluene (2-NO-T), using (32)P-5'-end-labeled DNA. We measured 8-oxo-7, 8-dihydro-2'-deoxyguanosine (8-oxodG), an indicator of oxidative DNA damage, in calf thymus DNA and cellular DNA in cultured human leukemia (HL-60) cells treated with 2-NO(2)-T and 2-NO-T. 8-Oxoguanine DNA glycosylase (OGG1) gene expression in HL-60 cells was measured by real-time polymerase chain reaction (PCR). We examined estrogenic activity using an E-screen assay and a surface plasmon resonance (SPR) sensor.

RESULTS

In experiments with isolated DNA fragments, 2-NO-T induced oxidative DNA damage in the presence of Cu (II) and β-nicotinamide adenine dinucleotide disodium salt (reduced form) (NADH), while 2-NO(2)-T did not. 2-NO-T significantly increased levels of 8-oxodG in HL-60 cells. Real-time polymerase chain reaction (PCR) analysis revealed upregulation of OGG1 gene expression induced by 2-NO-T. An E-screen assay using the human breast cancer cell line MCF-7 revealed that 2-NO(2)-T induced estrogen-dependent cell proliferation. In contrast, 2-NO-T decreased the cell number and suppressed 17β-estradiol-induced cell proliferation. The data obtained with the SPR sensor using estrogen receptor α and the estrogen response element supported the results of the E-screen assay.

CONCLUSIONS

Oxidative DNA damage caused by 2-NO-T and estrogen-disrupting effects caused by 2-NO(2)-T and 2-NO-T may play a role in the reproductive toxicity and carcinogenicity of these entities.

Cytotoxic effects of 2-bromopropane on embryonic development in mouse blastocysts

2-Bromopropane (2-BP), an alternative to ozone-depleting solvents, is used as a cleaning solvent. Here, we examined the cytotoxic effects of 2-bromopropane (2-BP) on mouse embryos at the blastocyst stage, subsequent embryonic attachment and outgrowth in vitro, and in vivo implantation via embryo transfer. Mouse blastocysts were incubated in medium with or without 2-BP (2.5, 5 or 10 μM) for 24 h. Cell proliferation and growth were investigated with dual differential staining, apoptosis was analyzed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) analysis, and implantation and post-implantation development of embryos were assessed using in vitro development analysis and in vivo embryo transfer, respectively. Blastocysts treated with 5 or 10 μM 2-BP displayed significantly increased apoptosis, and decreased inner cell mass (ICM) and trophectoderm (TE) cell number. Additionally, the implantation success rates of 2-BP-pretreated blastocysts were lower than those of untreated controls. In vitro treatment with 5 or 10 μM 2-BP was associated with increased resorption of postimplantation embryos, and decreased placental and fetal weights. Our results collectively indicate that in vitro exposure to 2-BP induces apoptosis, suppresses implantation rates after transfer to host mice, and retards early postimplantation development.

Effects of Exposure Period on the Developmental Toxicity of 2-Bromopropane in Sprague-Dawley Rats

Recently we reported that 2-bromopropane (2-BP) has maternal toxicity, embryotoxicity, and teratogenicity in Sprague-Dawley rats. The aims of this study are to examine the potential effects of 2-BP administration on pregnant dams and embryo-fetal development, and to investigate the effects of metabolic activation induced by phenobarbital (PB) on developmental toxicities of 2-BP. Pregnant rats received 1000 mg/kg/day subcutaneous 2-BP injections on gestational days (GD) 6 through 10 (Group II and Group IIII) or 11 through 15 (Group IV). Pregnant rats in Group III received an intraperitoneal PB injection once daily at 80 mg/kg/day on GD 3 through 5 for induction of the liver metabolic enzyme system. Control rats received vehicle injections only on GD 6 through 15. All dams underwent caesarean sections on GD 20 and their fetuses were examined for external, visceral, and skeletal abnormalities. Significant adverse effects on pregnant dams and embryo-fetal development were observed in all the treatment groups, and the maternal and embryo-fetal effects of 2-BP observed in Group II were higher than those seen in Group IV. Conversely, maternal and embryo-fetal developmental toxicities observed in Group III were comparable to those seen in Group II. These results suggest that the potential effects of 2-BP on pregnant dams and embryo-fetal development are more likely in the first half of organogenesis (days 6~10 of pregnancy) than in the second half and that the metabolic activation induced by PB pre-treatment did not modify the developmental toxic effects of 2-BP in rats.

Bacterial lipopolysaccharide-induced oxidative stress in the impairment of steroidogenesis and spermatogenesis in rats

Microbial infections, localized as well as systemic, are known to cause transitive or permanent male infertility. However, the mechanisms of infection-induced infertility are largely unknown. Earlier reports showed that steroidogenesis and spermatogenesis are affected during bacterial lipopolysaccharide (LPS)-induced acute inflammation. The present study used an LPS rat model to investigate the role of oxidative stress in spermatogenesis. Intraperitoneal administration of bacterial LPS (5mg/kg body weight) to adult male albino rats elevated testicular malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), and decreased the activities of testicular antioxidant enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. The GSH/GSSG ratio also decreased significantly. Time series analysis revealed transitory oxidative stress and expression of inflammatory mediators such as interleukin-1beta (IL-1beta), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) from 3h to 12h after LPS. Testicular expression of steroidogenic acute regulatory (StAR) protein decreased to 24h, in correlation with damage to spermatogenesis. These data are consistent with oxidative stress as a major causal factor in altered steroidogenesis, spermatogenesis, and perhaps male infertility during endotoxin-induced acute inflammation.

Lipoic acid modulates adriamycin-induced testicular toxicity

Adriamycin (ADR), an anthracycline antibiotic, which is widely used as an antineoplastic drug in the treatment of various solid tumors, has been shown to induce reproductive abnormalities in males. In the present study, the effect of lipoic acid (LA) a universal antioxidant was investigated on ADR-induced testicular toxicity in rats. Adult male albino rats of Wistar strain were administered ADR (1mg/kg body weight, i.v.), once a week for 10 weeks. ADR-injected rats showed increased levels of 8-hydroxy-2-deoxyguanosine with high protein carbonyl contents in testicular tissue. These changes were associated with significant increase in DNA damage in the sperm as evidenced by increased single strand breaks in a fluorimetric analysis of DNA unwinding (FADU). The activities of steroidogenic enzymes such as 3beta-hydroxy steroid dehydrogenase and 17beta-hydroxy steroid dehydrogenase, serum testosterone levels were decreased significantly in ADR-treated rats. Flow cytometric evaluation of testicular tissue in ADR-administered rats revealed impaired spermatogenesis and testicular function. Treatment with lipoic acid (35 mg/kg body weight, i.p.) one day prior to ADR administration, maintained near normal steroidogenesis and spermatogenesis, thereby proving it to be an effective cytoprotectant.

DNA damage in leukocytes of workers occupationally exposed to 1-bromopropane

1-bromopropane (1-BP; n-propyl bromide) (CAS No. 106-94-5) is an alternative to ozone-depleting chlorofluorocarbons that has a variety of potential applications as a degreasing agent for metals and electronics, and as a solvent vehicle for spray adhesives. Its isomer, 2-brompropane (2-BP; isopropyl bromide) (CAS No. 75-26-3) impairs antioxidant cellular defenses, enhances lipid peroxidation, and causes DNA damage in vitro. The present study had two aims. The first was to assess DNA damage in human leukocytes exposed in vitro to 1- or 2-BP. DNA damage was also assessed in peripheral leukocytes from workers with occupational exposure to 1-BP. In the latter assessment, start-of- and end-of-work week blood and urine samples were collected from 41 and 22 workers at two facilities where 1-BP was used as a solvent for spray adhesives in foam cushion fabrication. Exposure to 1-BP was assessed from personal-breathing zone samples collected for 1-3 days up to 8h per day for calculation of 8h time weighted average (TWA) 1-BP concentrations. Bromide (Br) was measured in blood and urine as a biomarker of exposure. Overall, 1-BP TWA concentrations ranged from 0.2 to 271 parts per million (ppm) at facility A, and from 4 to 27 ppm at facility B. The highest exposures were to workers classified as sprayers. 1-BP TWA concentrations were statistically significantly correlated with blood and urine Br concentrations. The comet assay was used to estimate DNA damage. In vitro, 1- or 2-BP induced a statistically significant increase in DNA damage at 1mM. In 1-BP exposed workers, start-of- and end-of-workweek comet endpoints were stratified based on job classification. There were no significant differences in DNA damage in leukocytes between workers classified as sprayers (high 1-BP exposure) and those classified as non-sprayers (low 1-BP exposure). At the facility with the high exposures, comparison of end-of-week values with start-of-week values using paired analysis revealed non-sprayers had significantly increased comet tail moments, and sprayers had significantly increased comet tail moment dispersion coefficients. A multivariate analysis included combining the data sets from both facilities, log transformation of 1-BP exposure indices, and the use of multiple linear regression models for each combination of DNA damage and exposure indices including exposure quartiles. The covariates were gender, age, smoking status, facility, and glutathione S-transferase M1 and T1 (GSTM1, GSTT1) polymorphisms. In the regression models, start-of-week comet tail moment in leukocytes was significantly associated with serum Br quartiles. End-of-week comet tail moment was significantly associated with 1-BP TWA quartiles, and serum Br quartiles. Gender, facility, and GSTM1 had a significant effect in one or more models. Additional associations were not identified from assessment of dispersion coefficients. In vitro and in vivo results provide limited evidence that 1-BP exposure may pose a small risk for increasing DNA damage.

Effect of environmental contaminants on male reproduction

A substantial body of evidence has accumulated in recent years that consistently indicate various adverse effects of environmental contaminants on human health. Decreasing trend of male fertility in terms of sperm counts and sperm quality, along with other changes in male reproductive health, including congenital malformations and testicular cancer in humans, and similar problems in wildlife has been correlated to the exposure to environmental contaminants. Many environmental chemicals have been reported to cause these reproductive abnormalities by eliciting changes in endocrine control of reproduction; however the specific underlying mechanisms are poorly understood. The present review summarizes recent studies on environmental contaminants and associated possible mechanism leading to adverse effects on male reproduction. Numerous studies demonstrate the interaction of environmental toxicants with steroid receptors and thereby causing interference with developmental and functional aspects of testis, epididymis and accessory sex organs. Induction of reactive oxygen species (ROS) by environmental contaminants and associated oxidative stress also have role in defective sperm function and male infertility.

The inhibitory effects of polychlorinated biphenyl Aroclor 1254 on Leydig cell LH receptors, steroidogenic enzymes and antioxidant enzymes in adult rats

Polychlorinated biphenyls (PCBs) are global pollutants of major concern to human and animal reproductive health. The present study has examined the impact of Aroclor 1254 exposure on oxidative stress and testicular Leydig cell function. Adult albino male rats of the Wistar strain were dosed for 30 days with daily intraperitoneal injections of 2 mg/kg Aroclor 1254 or vehicle (corn oil). One day after the last treatment, animals were euthanized and blood collected for the assay of serum testosterone and estradiol. Testes were removed and Leydig cells were isolated for the assay of luteinizing hormone (LH) receptors, steroidogenic enzymes cytochrome P450 side chain cleavage enzyme (P450 scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase (17beta-HSD). Cellular antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione reductase (GR), and glutathione-S-transferase (GST) were also assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were quantified. Results showed that Aroclor 1254 exposure lowered serum testosterone and estradiol levels. Leydig cell LH receptor density, activities of the steroidogenic enzymes P450 scc, 3beta-HSD, 17beta-HSD, antioxidant enzymes SOD, CAT, GPX, GR, and GST were significantly diminished whereas, LPO and ROS significantly elevated. Taken together, these results suggest that inefficient LH receptors, steroidogenic enzymes and antioxidant enzymes are possible mechanisms by which Aroclor 1254 treatment disrupts Leydig cell steroidogenesis.

Neuro-reproductive toxicities of 1-bromopropane and 2-bromopropane

2-Bromopropane was used as an alternative to chlorofluorocarbons in a Korean electronics factory and caused reproductive and hematopoietic disorders in male and female workers. This causality was revealed by animal studies, and target cells were identified in subsequent studies. After identification of 2-bromopropane toxicity, 1-bromopropane was introduced to the workplace as a new alternative to ozone-depleting solvents. 1-Bromopropane was considered less mutagenic than 2-bromopropane, but, in contrast, animal experiments revealed that 1-bromopropane is a potent neurotoxic compound compared with 2-bromopropane. It was also revealed that 1-bromopropane has reproductive toxicity, but the target cells are different from those of 2-bromopropane. Exposure to 1-bromopropane inhibits spermiation in male rats and disrupts the development of follicles in female rats, in contrast to 2-bromopropane, which targets spermatogonia and oocytes in primordial follicles. After the first animal study describing the neurotoxicity of 1-bromopropane, human cases were reported. Those cases showed decreased sensation of vibration and perception, paresthesia in the lower extremities, decreased sensation in the ventral aspects of the thighs and gluteal regions, stumbling and headache, as well as mucosal irritation, as the initial symptoms. The dose-response of bromopropanes in humans and mechanism(s) underlying the differences in the toxic effects of the two bromopropanes remain to be determined.

Effect of ascorbic acid supplementation on testicular steroidogenesis and germ cell death in cadmium-treated male rats

Cadmium (Cd) is one of the environmental pollutants affecting various tissues and organs including testis. Harmful effect of Cd in testis is known to be germ cell degeneration and impairment of testicular steroidogenesis. Animals treated with high doses of Cd (0.2 and 0.3 mg/100g BW) showed a significant decrease in serum testosterone (T) level, but a significant induction of testicular lipid peroxidation levels. TUNEL assay showed that low doses of Cd (0.13 and 0.15 mg/100g BW) exhibited typical characteristics of apoptosis while high doses of Cd caused more necrosis than apoptosis. In contrast, supplementation with ascorbic acid reduced testicular lipid peroxidation levels. Ascorbic acid supplementation restored testicular 3beta-hydroxysteroiddehydrogenase (HSD) and 17beta-HSD enzyme activities, 3beta-HSD and cytochrome P450 side chain cleavage (P450(scc)) mRNA levels and serum T concentration to normal in Cd-administered rats. Moreover, administration of ascorbic acid prevented germ cell apoptosis as demonstrated by the reduced number of TUNEL-positive cells in germinal epithelium and inhibited Cd-induced necrosis. These results indicate that ascorbic acid have protective roles in vivo on the Cd-induced overall testicular damage including impaired steroidogenesis and germ cell death possibly through scavenging the reactive oxygen species generated by Cd administration.

Effects of prenatal exposure to the environmental pollutant 2-bromopropane on embryo-fetal development in rats

2-Bromopropane (2-BP), a halogenated propane analogue, is a substitute for chlorofluorocarbones. The present study was carried out to investigate the potential adverse effects of 2-BP on pregnant dams and embryo-fetal development after maternal exposure on gestational days (GD) 6 through 19 in Sprague-Dawley rats. The test chemical was administered subcutaneously to pregnant rats at dose levels of 0, 250, 500, and 1000 mg/kg per day. All dams were subjected to caesarean section on GD 20 and their fetuses were examined for external, visceral and skeletal abnormalities. In the 1000 mg/kg group, maternal toxicity included an increase in the incidence of abnormal clinical signs, a suppression in the body weight and body weight gain, and a decrease in the food intake. Developmental toxicity included an increase in the fetal deaths, a decrease in the litter size, and a reduction in the fetal body weight. In addition, an increase in the incidence of fetal external, visceral, and skeletal abnormalities was seen. In the 500 mg/kg group, minimal developmental toxicity including decreased fetal body weight and increased fetal ossification delay was observed. There were no adverse effects on either pregnant dams or embryo-fetal development in the 250 mg/kg group. These findings suggest that a 14-day subcutaneous dose of 2-BP is embryotoxic and teratogenic at a maternally toxic dose (i.e., 1000 mg/kg per day) and is minimally embryotoxic at a nonmaternally toxic dose (i.e., 500 mg/kg per day) in Sprague-Dawley rats. In the present experimental conditions, the no-observed-adverse-effect level (NOAEL) of 2-BP is considered to be 500 mg/kg per day for dams and 250 mg/kg per day for embryo-fetal development.

Effects of 2-bromopropane on pregnant dams and embryo-fetal development in the ICR mouse

2-Bromopropane (2-BP), a halogenated propane analogue, is a substitute for chlorofluorocarbones (CFCs) which have a great potential to destroy the ozone layer and to warm the earth's environment. The present study was carried out to investigate the potential adverse effects of 2-BP on pregnant dams and embryo-fetal development after maternal exposure during the gestational days (GD) 6-17 in ICR mice. The test chemical was administered subcutaneously to pregnant mice at dose levels of 0, 500, 1000, and 1500mg/kg per day. All dams were subjected to caesarean section on GD 18 and their fetuses were examined for external, visceral and skeletal abnormalities. Throughout the study period, no treatment-related deaths were found in the groups treated with 2-BP. Pregnant mice of the 1000 and 1500mg/kg groups showed treatment-related clinical signs such as rough fur and swelling, induration, crust formation, and ulceration in the injection sites which were dose dependent in incidence and severity. A decrease in fetal weight, an increase in fetal malformation, and an increase in fetal ossification delay were found at a dose level of 1500mg/kg per day in a dose-dependent manner. On the contrary, there were no adverse effects on body weight, body weight gain, gravid uterine weight, food consumption, gross finding at any dose tested. In addition, no treatment-related effects on the number of corpora lutea, implantations, resorptions, dead fetuses, live fetuses, and sex ratio of live fetuses were observed. These findings suggest that 2-BP was embryotoxic and teratogenic at a minimally maternally toxic dose (i.e., 1500mg/kg per day) in ICR mice. In the present experimental conditions, the no-observed-adverse-effect level of 2-BP is considered to be 500mg/kg per day for dams and 1000mg/kg per day for fetuses, respectively.