Influence of environmental cadmium on testicular proliferation in roe deer

Cadmium exposure is associated with testosterone levels in men: A cross-sectional study from the China National Human Biomonitoring

BACKGROUND

Sex hormone disorders can cause adverse health consequences. While experimental data suggests that cadmium (Cd) disrupts the endocrine system, little is known about the link between Cd exposure and sex hormones in men.

METHODS

We measured blood cadmium (B-Cd), urine cadmium (U-Cd), serum testosterone and serum estradiol in men aged ≥18 years old participating in the China National Human Biomonitoring program, from 2017 to 2018. Urine cadmium adjusted for creatinine (Ucr-Cd) and the serum testosterone to serum estradiol ratio (T/E₂) were calculated. The association of Cd exposure to serum testosterone and T/E₂ in men was analyzed with multiple linear regression models.

RESULTS

Among Chinese men ≥18 years old, the weighted geometric mean (95% CI) of B-Cd and Ucr-Cd levels were 1.23 (1.12-1.35) μg/L and 0.53 (0.47-0.59) μg/g, respectively. The geometric means (95% CI) of serum testosterone and T/E₂ were 18.56 (17.92-19.22) nmol/L and 143.86 (137.24-150.80). After adjusting for all covariates, each doubling of B-Cd level was associated with a 5.04% increase in serum testosterone levels (β = 0.071; 95%CI: 0.057-0.086) and a 4.03% increase in T/E₂ (β = 0.057; 95%CI: 0.040-0.075); similar findings were found in Ucr-Cd.

CONCLUSIONS

In Chinese men, Cd may be an endocrine disruptor, which is positively associated with serum testosterone and T/E₂.

Response of male reproductive function to environmental heavy metal pollution in a free-living passerine bird, Passer montanus

Heavy metals affect male reproductive function by impairing reproductive organs, disturbing reproductive hormone levels or directly affecting sperm quality. However, little attention has been given to the effect of environmental heavy metals on reproductive function in wild male birds. The present study investigated the alterations of reproductive function in male tree sparrows (Passer montanus) exposed to environments contaminated by heavy metals in terms of testis parameters, reproductive hormone levels and sperm movement characteristics. Two plots, Baiyin (BY, mainly polluted by copper, zinc, lead and cadmium) and Liujiaxia (LJX, a relatively unpolluted area) were selected as sampling sites. The results showed that tree sparrows from BY (1) accumulated higher levels of cadmium in the testes, (2) showed lower superoxide dismutase (SOD) activity and malondialdehyde level, with higher total antioxidant capacity and apoptosis level in the testes, (3) showed higher plasma levels of estrogen, follicle stimulating hormone and luteinizing hormone (LH), and (4) had better sperm movement performance. Additionally, we found that testis size, SOD activity in testes and LH levels were decisive factors in sperm movement performance in tree sparrows. Heavy metal concentrations in testes negatively correlated with testis size, SOD activity in testes, and estrogen levels in tree sparrows. The present study indicates that heavy metals accumulating in testes of tree sparrows adversely affected some key indicators of male reproductive function. However, testicular function, reproductive hormone levels and sperm quality showed adaptive responses that tended to partially compensate for the negative effects in the heavy metal polluted area. This study further indicated that the regulation of testicular function and reproductive hormone levels was the main factor for better sperm quality in tree sparrows exposed to environments contaminated by heavy metals.

Roe deer as a bioindicator: preliminary data on the impact of the geothermal power plants on the mineral profile in internal and bone tissues in Tuscany (Italy)

The European roe deer (Capreolus capreolus) is one of the most abundant ungulate species in Europe. Many studies have investigated its distribution, behavior, and ecology, but few have focused on its role as bioindicators for pollutants, particularly regarding antlers, which has been shown to indicate also deer physiology. The presence of geothermal power plants can induce accumulation of potentially polluting elements (such as Tl, S, and Pb). Thus, we collected roe deer samples from areas of Tuscany (Italy) where power plants are present. They were divided according to whether their home range included areas close or far from geothermal power plants. We analyzed the body measurements and the profile of the minerals in the liver and antlers tissues using the ICP-OES technique. Results showed that livers from roe deer close to power plant accumulated higher quantity of Bi, Co, Ni, Tl, and S compared to controls. Males culled close to geothermal power plants had significantly lower values for weight and chest circumference, and also, the antlers showed higher values for Li and Sr in the first sampling position. Thus, despite the small sample size in this preliminary study, antlers and livers of roe deer seem to be a bioindicator of industrial impact on the environment.

Transfer of heavy metals through terrestrial food webs: a review

Heavy metals are released into the environment by both anthropogenic and natural sources. Highly reactive and often toxic at low concentrations, they may enter soils and groundwater, bioaccumulate in food webs, and adversely affect biota. Heavy metals also may remain in the environment for years, posing long-term risks to life well after point sources of heavy metal pollution have been removed. In this review, we compile studies of the community-level effects of heavy metal pollution, including heavy metal transfer from soils to plants, microbes, invertebrates, and to both small and large mammals (including humans). Many factors contribute to heavy metal accumulation in animals including behavior, physiology, and diet. Biotic effects of heavy metals are often quite different for essential and non-essential heavy metals, and vary depending on the specific metal involved. They also differ for adapted organisms, including metallophyte plants and heavy metal-tolerant insects, which occur in naturally high-metal habitats (such as serpentine soils) and have adaptations that allow them to tolerate exposure to relatively high concentrations of some heavy metals. Some metallophyte plants are hyperaccumulators of certain heavy metals and new technologies using them to clean metal-contaminated soil (phytoextraction) may offer economically attractive solutions to some metal pollution challenges. These new technologies provide incentive to catalog and protect the unique biodiversity of habitats that have naturally high levels of heavy metals.

Cadmium impairment of reproduction in the female wall lizard Podarcis sicula

The exposure to environmental toxicants such cadmium (Cd) is an important research area in wildlife protection. In this study, the effect of Cd oral administration on the ovarian structure and function and on reproductive performance of the Italian wall lizard Podarcis sicula was studied. In vivo, adult female lizards were randomly assigned to three groups. Cd was given with food in single dose and in multiple doses 3 days/week for 4 weeks at dose of 1.0 μg/g body weight. Following euthanasia, the ovaries were removed and analyzed for morpho-functional changes. Results demonstrated that Cd increases prefollicular germ cells number; the evaluation of the number of follicles detects significantly higher number of atretic growing follicles, whereas primary follicles remain unchanged with respect to controls. After Cd treatments, follicles are deformed by the presence of large protrusions and a general dysregulation in the follicle organization is observed. The zona pellucida is also affected. Cd causes alteration in sugar metabolism and in metallothionein gene expression. Finally, Cd administration significantly reduces clutch size and dramatically increases embryo mortality. In conclusion, data here described show that Cd induces morpho-functional alterations in lizard follicles and indicates that these are responsible for a significant impairment of oogenesis. The effects of the dose are time independent, persisting essentially unchanged regardless of single or multiple administration, so it can be concluded that even occasional, sublethal Cd contamination may significantly impair reproductive performance in these animals.

Cadmium induced cell apoptosis, DNA damage, decreased DNA repair capacity, and genomic instability during malignant transformation of human bronchial epithelial cells

Cadmium and its compounds are well-known human carcinogens, but the mechanisms underlying the carcinogenesis are not entirely understood. Our study was designed to elucidate the mechanisms of DNA damage in cadmium-induced malignant transformation of human bronchial epithelial cells. We analyzed cell cycle, apoptosis, DNA damage, gene expression, genomic instability, and the sequence of exons in DNA repair genes in several kinds of cells. These cells consisted of untreated control cells, cells in the fifth, 15th, and 35th passage of cadmium-treated cells, and tumorigenic cells from nude mice using flow cytometry, Hoechst 33258 staining, comet assay, quantitative real-time polymerase chain reaction (PCR), Western blot analysis, random amplified polymorphic DNA (RAPD)-PCR, and sequence analysis. We observed a progressive increase in cell population of the G0/G1 phase of the cell cycle and the rate of apoptosis, DNA damage, and cadmium-induced apoptotic morphological changes in cerebral cortical neurons during malignant transformation. Gene expression analysis revealed increased expression of cell proliferation (PCNA), cell cycle (CyclinD1), pro-apoptotic activity (Bax), and DNA damage of the checkpoint genes ATM, ATR, Chk1, Chk2, Cdc25A. Decreased expression of the anti-apoptotic gene Bcl-2 and the DNA repair genes hMSH2, hMLH1, ERCC1, ERCC2, and hOGG1 was observed. RAPD-PCR revealed genomic instability in cadmium-exposed cells, and sequence analysis showed mutation of exons in hMSH2, ERCC1, XRCC1, and hOGG1 in tumorigenic cells. This study suggests that Cadmium can increase cell apoptosis and DNA damage, decrease DNA repair capacity, and cause mutations, and genomic instability leading to malignant transformation. This process could be a viable mechanism for cadmium-induced cancers.

Cadmium-induced oxidative stress and apoptotic changes in the testis of freshwater crab, Sinopotamon henanense

Cadmium (Cd), one of the most toxic environmental and industrial pollutants, is known to exert gonadotoxic and spermiotoxic effects. In the present study, we examined the toxic effect of Cd on the testis of freshwater crab, Sinopotamon henanense. Crabs were exposed to different Cd concentrations (from 0 to 116.00 mg·L(-1)) for 7 d. Oxidative stress and apoptotic changes in the testes were detected. The activities of SOD, GPx and CAT initially increased and subsequently decreased with increasing Cd concentrations, which was accompanied with the increase in malondialdehyde (MDA) and H(2)O(2) content in a concentration-dependent manner. Typical morphological characteristic and physiological changes of apoptosis were observed using a variety of methods (HE staining, AO/EB double fluorescent staining, Transmission Electron Microscope observation and DNA fragmentation analysis), and the activities of caspase-3 and caspase-9 were increased in a concentration-dependent manner after Cd exposure. These results led to the conclusion that Cd could induced oxidative damage as well as apoptosis in the testis, and the apoptotic processes may be mediated via mitochondria-dependent apoptosis pathway by regulating the activities of caspase-3 and caspase-9.

Testicular histomorphometry and ultrastructure of rats treated with cadmium and Ginkgo biloba

The aim of this study is to investigate the association of a single low dose of Cd and daily doses of Ginkgo biloba extract (GbE) on the testis and accessory glands of rats. The animals were treated with a single dose of 3 µmol/kg body weight of cadmium chloride (CdCl₂) and/or 100 mg/kg body weight of GbE. The plasma testosterone levels; corporal, testicular, and accessory glands weight; gonadosomatic index, volumetric proportion; and absolute volume of testicular components did not change after the treatments. CdCl₂ caused significant reduction in Leydig cells volume and altered Leydig cell morphology, as well as vacuolated Sertoli cells cytoplasm, irregular chromatin condensation of late spermatids, and modified acrosome formation. However, animals that received GbE did not show these alterations. The reversal of Cd-induced alterations by the extract is a strong indication that G. biloba is helpful in diminishing the effect of Cd toxicity.

Sex- and age-dependent accumulation of heavy metals (Cd, Pb and Zn) in liver, kidney and muscle of roe deer (Capreolus capreolus) from NW Spain

In the present study, bioaccumulation of lead, cadmium and zinc in liver, kidney and muscle of roe deer (Capreolus capreolus) from Galicia (NW Spain) was quantified. Metal analysis was performed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In general the quantified concentrations were associated with background environmental levels, except for Pb, where some markedly elevated concentrations were obtained, but with no toxicological relevance. The effect of sex on Cd, Pb and Zn levels was considered, females showing a general trend to accumulate higher concentrations of these metals, with the exception of the hepatic content of Cd (which was significantly higher in males, P < 0.05) and Pb levels, which did not differ according to sex. The effect of age was analysed only in male animals and was clearly observed for Pb levels, with concentrations significantly higher in adult animals (liver: P < 0.01, kidney: P < 0.05 and muscle: P < 0.001) and for Cd levels in kidney samples (P < 0.001). This study provides the first data on heavy metal content in roe deer from the area of study and suggests that this species could be a good bioindicator of metal pollution, even though both factors, sex and age, could represent an important source of variation in the bioaccumulation of these metals in wild populations.

Reduced sperm quality in relation to oxidative stress in red deer from a lead mining area

We studied the effects of elevated heavy metal uptake on the sperm quality and the antioxidant mechanisms of sperm and testis of red deer from a Pb mining area in Spain. Testis, liver and bone of red deer from mining (n = 21) and control (n = 20) areas were obtained from hunters and analyzed for Pb, Zn, Cu, Cd, As and Se. Testes were weighed and measured. Motility, acrosome integrity and viability and functionality of membrane were evaluated in epididymal spermatozoa. Lipid peroxidation, total glutathione, glutathione peroxidase (GPX) and superoxide dismutase (SOD) were studied in testis and spermatozoa. Deer from mined areas showed less Cu in testis, a higher testis mass and size and reduced spermatozoa membrane viability and acrosome integrity. Effects on sperm quality were associated to decreased Cu and increased Se in testis, and to decreases in the activity of SOD and GPX in testis and spermatozoa.

Toxic and essential metal concentrations in four tissues of red deer (Cervus elaphus) from Baranja, Croatia

Kidney (n = 297), liver (n = 52), jawbone (n = 80) and muscle (n = 48) samples collected from red deer (Cervus elaphus) from north-eastern Croatia in the 2002--05 hunting season were analysed for cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), lead (Pb), selenium (Se) and zinc (Zn) using atomic absorption spectrometry. Statistical evaluation of results showed age-related accumulations of renal cortex Cd and Zn, bone Pb, and muscle Zn. Renal cortex Cd and Zn were significantly associated. In addition, concentrations of Cd and Pb in muscle tissue were significantly correlated with Fe content. Found levels of toxic metals were not likely to affect the health status of animals. A total of 49% of the muscle, 60% of the kidney and 6% of the liver samples were unsuitable for human consumption according to Croatian regulations for Cd in food. However, the calculated intake of Cd through deer meat consumption is small and represents no health risk when consumption is moderate.

Fertility and content of cadmium in pheasant (Phasianus colchicus) following cadmium intake in drinking water

In this study, the effects of cadmium applied per os on fertility, live weight of newly hatched chicks, and cadmium concentrations in some organs of young and adult pheasants were investigated. The metal was applied at the concentration of 1.5 mg Cd(2+)/L during 3 months. After the egg laying, the numbers of eggs laid, cracked, and unfertilized were determined and the live weights of newly hatched chicks were measured. The cadmium concentrations in liver, kidney, and muscle (m. pectoralis) of young and adult pheasants were analyzed. We found that cadmium exposure of the adults did not affect the number of eggs laid but resulted in more eggs being damaged. Hatchlings were significantly heavier in the cadmium-treated group (21.36 +/- 2.28 g) compared to the control group (20.91 +/- 1.97 g) 4 weeks after the cadmium intake. Higher cadmium concentrations were observed in the muscle and kidney tissue of newly hatched pheasants after 4 weeks compared to the cadmium-exposed groups after 8 and 12 weeks. The cadmium concentrations in kidneys and liver increased significantly in adult pheasants. The metal had accumulated especially in kidneys of the adult pheasants and reached levels up to 9.64 mg/kg wet weight 3 months after the daily cadmium intake in drinking water. The concentration in liver of the adults was 3.53 mg/kg wet weight.

Effects on rat testes of the thiosemicarbazone derivative Schiff base (4-(1-phenylmethylcyclobutane-3-yl)-2-(2-hydroxybenzylidenehydrazino)thiazole) and its cadmium(II) complex

The aim of this study was to investigate structural and biochemical changes in testes of rats treated with the thiosemicarbazone derivative thiazole ring Schiff base, (4-(1-phenyl-methylcyclobutane-3-yl)-2-(2-hydroxybenzylidene-hydrazino) thiazole (L), and its Cd(II) complex (CdL(2)). The animals were divided into three groups. Group I was designated as control. The rats in groups II and III were injected subcutaneously with L or CdL(2) respectively at 150-mg kg(-1) doses at 3-day intervals for 15 days. At the end of the study, blood samples were collected for biochemical analysis, and testes were removed for histological examinations. Serum levels of vitamin A, E and MDA of the L-injected group were similar to the control group. While CdL(2) treatment decreased serum vitamin A and E levels, it increased the MDA level compared to other groups. Histologically, the testes structures of L-treated animals were similar to the control. Spermatogenic cells in seminiferous tubules of CdL(2)-treated animals displayed necrosis. Nuclei of spermatogonia and primary spermatocytes were pyknotic and heterochromatic. Homogenous pink particles were present in place of the spermatids. The interstitial areas were oedematous and intertubular vessels were plugged. In conclusion, the present results indicate that L does not cause biochemical and morphological alterations, but its Cd(II) complex has degenerative effects in normal rat testes.

Fungi ingestion as an important factor influencing heavy metal intake in roe deer: evidence from faeces

In nature, animals have to cope with the fluctuating bioavailable metal pool in their habitat, which results in a seasonal variability of heavy metal levels in the animal body. Indeed, a pronounced summer-autumnal peak of heavy metals in roe deer (Capreolus capreolus L.) kidney was recently found in Slovenia. Considering the well-known hyperaccumulative ability of fungi, their ingestion was hypothesised to be one of the main reasons for the peak. Although fungi as a group are known to be a seasonally important food source for roe deer, data on their composition in the nutrition of the species have been lacking. To ascertain the importance of fungi ingestion on heavy metal intake in roe deer, we simultaneously studied fungal spores (by microscopic determination) and heavy metal levels (by inductively coupled plasma mass spectrometry and atomic absorption spectrometry) in roe deer faeces, collected in the period July-November 2001 at Veliki Vrh, the Salek Valley, Slovenia. Irrespective of species, fungal spores were present in 89% of faeces; the following genera were found to be consumed by roe deer: Lycoperdon, Calvatia, Hypholoma, Coprinus, Russula, Elaphomyces, Xerocomus, Enteloma, Amanita, Cortinarius, Agaricus, Inocybe, Boletus, Macrolepiota, Suillus and Pluteus. While the importance of fungi ingestion on the seasonal variability of other metals is less clear, it doubtless influences Hg intake in roe deer, which is confirmed by: (a) the high frequency of fungi in roe deer nutrition; (b) their hyperaccumulative ability; (c) the temporal distribution of Hg in roe deer faeces; (d) differences among three classes of faeces established on the basis of the frequency of spores present; (e) the correlation between the number of fungal genera present and Hg levels in faeces. Therefore, the influence of fungi ingestion has to be taken into consideration in assessing the hazard due to the accumulation of mercury along the food-chain.

Concentration of selected metals in liver, kidney, and muscle of the red deer (Cervus elaphus)

Concentration of cadmium, lead, chromium, zinc, copper, and manganese in liver, kidney, and muscle of red deer was investigated. For analysis of the content of these trace elements an AAS method was used. The concentration of cadmium was significantly (p < 0.05) higher in kidney in comparison with liver and muscle. The level of lead was the highest in muscle (p < 0.05). Lower values were detected in liver and in kidney. The concentration of chromium was very similar in all studied tissues. A higher concentration of zinc was found in muscle, followed by kidney and liver. The level of copper was significantly higher in liver (p < 0.05), and lower in kidneys and muscle. In evaluation of the concentration of manganese in red deer, the highest concentration of this element in liver was detected.

Concentration of copper, iron, zinc, cadmium, lead, and nickel in boar semen and relation to the spermatozoa quality

The concentration of copper, iron, zinc, cadmium, lead, and nickel as well as its relation to spermatozoa quality was investigated. The semen samples were analyzed by atomic absorption spectrophotometry (AAS). The concentration of copper in boar semen was 1.64 +/- 0.28 mg kg(-1) and of iron 16.14 +/- 10.35 mg kg(-1). The concentration of zinc in boar semen reached an average value of 171.74 +/- 64.72 mg kg(-1) and the level of cadmium reached 0.01-0.16 mg kg(-1) with the average value of 0.05 mg kg(-1). The analysis of lead showed that the concentration of this element in boar semen was 0.02 +/- 0.03 mg kg(-1) and the average level of nickel was 0.06 +/- 0.08 mg kg(-1). The total percentage of pathological spermatozoa was 9.82 +/- 1.47%. Detail analysis determined 3.18% of separated flagellum, 2.26% knob twisted flagellum, 0.88% flagellum torso, 0.85% flagellum ball, 0.42% broken flagellum, 0.23% retention of the cytoplasmic drop, 0.14% small heads, 0.03% large heads, and 1.83% forms other of pathological changes. Correlation analysis showed significant (p < 0.05) positive correlation between copper and lead (r = 0.52). High correlation between small head and knob twisted tail (r = 0.67), small head and broken flagellum (r = 0.88) as well as between small head and total number of pathological spermatozoa (r = 0.73) was determined.

Seasonal variability of mercury and heavy metals in roe deer (Capreolus capreolus) kidney

The seasonal variability of Hg, Pb, Cd and Zn was determined in the kidney of 164 roe deer, shot in three areas of Slovenia in 1998. We found a strong seasonal influence on Hg and Pb levels, which were significantly higher in late summer and early autumn. Cd and Zn levels showed a similar seasonal pattern, although not so pronounced; for these elements differences among periods were probably not a consequence of season per se. Seasonal variability in metal levels in roe deer kidney originated in both quantitative and qualitative differences in nutrition of the species. Since the seasonal peaks for the majority of metals appeared in a very narrow summer autumnal period (August-September), it seems that some plant taxons, such as fungi, might represent an important pathway for heavy metal intake into the mammalian organism. The season of sample collection has to be considered whenever using wildlife as an accumulative bioindicator of environmental pollution. Moreover, the influence of the season should be born in mind whenever a hazard due to accumulation of heavy metals along the food chain is assessed.