Toxicological Effects of Cadmium on Mammalian Testis

Fine particulate matter (PM2.5) induces testosterone disruption by triggering ferroptosis through SIRT1/HIF-1α signaling pathway in male mice

Fine particulate matter (PM2.5), a significant component of air pollution particulate matter, is inevitable and closely associated with increasing male reproductive disorder. However, the testicular targets of PM2.5 and its toxicity related molecular mechanisms are still not fully understood. In this study, the conditional knockout (cKO) mice and primary Leydig cells were used to explore the testicular targets of PM2.5 and the related underlying mechanisms. First, apparent the structure impairment of seminiferous tubules, Leydig cells vacuolization, decline of serum testosterone and sperm quality reduction were found in male wild-type (WT) and Sirt1 knockout mice after exposure to PM2.5. Enrichment analyses revealed that differentially expressed genes (DEGs) were enriched in steroid hormone biosynthesis, ferroptosis, and HIF-1 signaling pathway in the mice testes after exposure to PM2.5, which were subsequently verified by the molecular biological analyses. Notably, similar enrichment analyses results were also observed in primary Leydig cells after treatment with PM2.5. In addition, Knockdown of Sirt1 significantly increased PM2.5-induced expression and activation of HIF-1α, which was in parallel to the changes of cellular iron levels, oxidative stress indicators and the ferroptosis markers. In conclusion, this highlights that PM2.5 triggers ferroptosis via SIRT1/HIF-1α signaling pathway to inhibit testosterone synthesis in males. These findings provide a novel research support for the study that PM2.5 causes male reproductive injury.

The Effectiveness of Time in Treatment with Vitamin C and Broccoli Extract on Cadmium Poisoning in Mice: Histological Changes of Testicular Tissue and Cell Apoptotic Index

The growth rate of reproductive system disorders caused by heavy metals is undeniable. The effect of time and interfering compounds are also of paramount importance. The main objective of this study was to compare the effects of broccoli extract and vitamin C in the context of cadmium poisoning on various reproductive parameters in mice, with a specific focus on the influence of time. A total of one hundred and forty-four male mice were randomly assigned to six groups. The control (C) group received only water and a standard diet without any interventions. The Cd group received a single intraperitoneal dose of cadmium chloride at 1.5 mg/kg. The cadmium intervention groups were administered broccoli extract at dosages of 100 mg/kg (Cd + B100), 200 mg/kg (Cd + B200), and 300 mg/kg (Cd + B300), respectively. Additionally, the Cd + VC group was treated with cadmium and vitamin C at 200 mg/kg intraperitoneally for a duration of 28 days. At the end of each week (four stages), five animals were randomly chosen from each group. Epididymal sperm were subjected to analysis for sperm parameters, while testicular tissue sections were examined for histological studies, apoptosis index, and markers of oxidative stress. The influence of time on body and testis weight gain was notably significant in the Cd + B300 and Cd + VC groups (p = 0.001). In all groups, except for Cd + B100, there were marked increases in spermatogenic cell lines and the Johnson coefficient compared to the Cd group (p = 0.001). These changes were particularly pronounced in the Cd + VC and Cd + B300 groups with respect to time (p < 0.001). Furthermore, there was a discernible positive impact of time on sperm count in the high-dose broccoli and vitamin C groups, although this effect did not reach significance in terms of sperm motility and vitality. Over time, the levels of superoxide dismutase (SOD) and catalase (CAT) enzymes increased, while malondialdehyde (MDA) levels decreased in the Cd + VC, Cd + B200, and Cd + B300 groups (p = 0.001). The apoptosis index in testicular tissue reached its highest level in the Cd group and its lowest level in the Cd + B300 and Cd + VC groups during the fourth week (p < 0.05). Linolenic acid, indole, and sulforaphane were identified as the most potent compounds in broccoli during this intervention. Consequently, vitamin C and broccoli extract at a dosage of 300 mg/kg demonstrated significant enhancements in reproductive performance in cases of cadmium poisoning. Overall, the influence of time significantly amplified the process of spermatogenesis and sperm production, with no observable changes in sperm viability and motility.

An in vitro testicular organoid model for the study of testis morphogenesis, somatic cell maturation, endocrine function, and toxicological assessment of endocrine disruptors

Male reproductive capacity has fallen considerably in recent decades; in addition, the incidence of testicular cancer has increased in many developed countries. The cause of this phenomenon is unknown, but environmental toxicants are considered a major contributing factor. To study potential reproductive toxicants, robust in vitro testis models are needed. We have recently established a porcine testis organoid system with a high resemblance to the architectures of innate testis tissue. Here, we further investigated the testis morphogenesis, cell maturation, and endocrine function of the testis organoids. We also challenged this system with abiraterone, a steroidogenic inhibitor, to validate its suitability as an in vitro platform for endocrine toxicology tests. Our results showed that the testis cells in the organoids reorganize into testis cordal structures, and the cordal relative areas increase in the organoids over time of culture. Moreover, the diameters and cell numbers per cross-section of the cordal structures increased over time. Interestingly, Sertoli cells in the organoids gradually underwent maturational changes by showing increased expression of androgen receptors, decreased expression of the anti-müllerian hormone, and formation of the blood-testis barrier. Next, we confirmed that the organoids respond to hormonal stimulation and release multiple sex hormones, including testosterone, estradiol, and progesterone. Finally, we showed that the production of testosterone and estradiol in this system can be inhibited in response to the steroidogenic inhibitor. Taken together, our organoid system provides a promising in vitro platform for male reproductive toxicology studies on testis morphogenesis, somatic cell maturation, and endocrine production.

Exposure to potentially toxic elements (PTEs) and the risk of male infertility- A Systematic review and meta-analysis

BACKGROUND

Infertility has been defined as a failure to conceive for at least 12 months of regular unprotected sexual intercourse. The male factors are responsible for about 50 % of cases. Various factors such as endocrine, immunological, genetic, exposure to toxicants, and idiopathic factors are involved in male infertility. Recently, the role of PTEs in reproductive performance has been explored by various studies.

OBJECTIVES

Current systematic review and meta-analysis have been carried out to compile and statistically analyze the findings of relevant studies and reach some conclusion.

METHODOLOGY

A literature search was done according to the Preferred Reporting Items for Systematic Reviews and Meta Analyses (PRISMA) guidelines in three scientific literature databases; PubMed, Google Scholar, and Science Direct. Meta-analysis was performed using Review Manager 5.4 software. The study's protocol was registered in PROSPERO (CRD42023465776).

RESULTS

Meta-analysis of lead in the blood of infertile cases and healthy controls indicated a significant association with male infertility, observed standard mean difference (SMD) was 0.67 at 95 % confidence interval (CI) (0.07, 1.28), and p = 0.03. In the case of lead analysis in semen, the values are as follows: SMD = 1.19 at 95 % CI (0.42, 1.96) with p = 0.002. Significant association appears for cadmium in semen with SMD 0.92 at 95 % CI (0.54, 1.29) and p < 0.00001. No significant association was observed for arsenic, barium, and mercury in blood.

CONCLUSION

Most of the studies focus on the detection of PTE in semen samples followed by blood as sample type. Lead and cadmium exposure is significantly associated with male infertility. However, non-significant results for arsenic, barium, and mercury are observed.

Melatonin counteracts cadmium-induced rat testicular toxicity via the mechanistic target rapamycin (mTOR) pathway

The protective action of melatonin (MLT) against the harmful effects of cadmium (Cd) on testicular activity in rats has been documented previously; however, the involved molecular mechanisms have yet to be elucidated. Herein, we investigate the involvement of the mammalian target of rapamycin (mTOR) on the ability of MLT to counteract the damage induced by Cd on the rat testicular activity. Our study confirmed that Cd has harmful effects on the testes of rats and the protective action exerted by MLT. We reported, for the first time, that the addition of rapamycin (Rapa), a specific mTOR inhibitor, to animals co-treated with Cd and MLT completely abolished the beneficial effects exerted by MLT, indicating that the mTOR pathway partially modulates its helpful effects on Cd testicular toxicity. Interestingly, Rapa-alone treatment, provoking mTOR inhibition, produced altered morphological parameters, increased autophagy of germ and somatic cells, and reduced serum testosterone concentration. In addition, mTOR inhibition also reduced protein levels of markers of steroidogenesis (3β-Hydroxysteroid dehydrogenase) and blood-testis barrier integrity (occludin and connexin 43). Finally, Rapa altered sperm parameters as well as the ability of mature spermatozoa to perform a proper acrosome reaction. Although further investigation is needed to better clarify the molecular pathway involved in MLT action, we confirm that MLT alleviating Cd effects can be used as a supplement to enhance testicular function and improve male gamete quality.

Reproductive toxicity of cadmium stress in male animals

Cadmium (Cd) is a common heavy metal pollutant in the environment, and the widespread use of products containing Cd compounds in industry has led to excessive levels in the environment, which enter the animal body through the food chain, thus seriously affecting the reproductive development of animals. Related studies have reported that Cd severely affects spermatogonia development and spermatogenesis in animals. In contrast, the reproductive toxicity of Cd in males and its mechanism of action have not been clarified. Therefore, this paper reviewed the toxic effects of Cd on germ cells, spermatogonia somatic cells and hypothalamic-pituitary-gonadal axis (HPG axis) of male animals and its toxic action mechanisms of oxidative stress, apoptosis and autophagy from the perspectives of cytology, genetics and neuroendocrinology. The effects of Cd stress on epigenetic modification of reproductive development in male animals were also analyzed. We hope to provide a reference for the in-depth study of the toxicity of Cd on male animal reproduction.

A metabolomic perspective on the mechanisms by which environmental pollutants and lifestyle lead to male infertility

The incidence of male infertility (MI) is rising annually. According to epidemiological studies, environmental pollution (e.g., organic, inorganic, and air pollutants), occupational exposure (e.g., high temperature, organic solvents, and pesticides), and poor lifestyle (e.g., diet, sleep, smoking, alcohol consumption, and exercise) are important non-genetic causative factors of MI. Due to multiple and complex causative factors, the dose-effect relationship, and the uncertainty of pathogenicity, the pathogenesis of MI is far from fully clarified. Recent data show that the pathogenesis of MI can be monitored by the metabolites in serum, seminal plasma, urine, testicular tissue, sperm, and other biological samples. It is considered that these metabolites are closely related to MI phenotypes and can directly reflect the individual pathological and physiological conditions. Therefore, qualitative and quantitative analysis of the metabolome, the related metabolic pathways, and the identification of biomarkers will help to explore the MI-related metabolic problems and provide valuable insights into its pathogenic mechanisms. Here, we summarized new findings in MI metabolomics biomarkers research and their abnormal metabolic pathways triggered by the presented non-genetic risk factors, providing a metabolic landscape of semen and seminal plasma in general MI patients. Then, we compared the similarities and differences in semen and seminal plasma biomarkers between MI patients exposed to environmental and poor lifestyle factors and MI patients in general, and summarized some common biomarkers. We provide a better understanding of the biological underpinnings of MI pathogenesis, which might offer novel diagnostic, prognostic, and precise treatment approaches to MI.

Cardioprotective Effect of Eugenol Against Cd-Induced Inflammation, Oxidative Stress, and Dyslipidemia in Male Rats: An In Vivo and Molecular Docking Study

Cadmium, a highly toxic heavy metal, can cause severe damage to several vital organs including the kidney, liver, and brain. Many of the natural compounds found in aromatic plants have beneficial pharmacological properties. Eugenol is one such compound reported to have anti-inflammatory and antioxidant properties. The aim of this study is to investigate whether eugenol, a natural compound found in aromatic plants known for its anti-inflammatory and antioxidant properties, can mitigate the detrimental effects of cadmium exposure on cardiac inflammation, oxidative stress, and dyslipidemia. Male albino rats were subjected to randomization into four groups, each comprising six animals, to investigate the potential of eugenol in mitigating cadmium-induced toxicity. All groups received oral gavage treatment for 21 days. Following the treatment regimen, cardiac tissue specimens were collected for analysis. The assessment of cardiac antioxidant status entailed the determination of enzymatic activities including catalase, SOD, GST, and GPx. Additionally, levels of lipid peroxidation, reduced glutathione, protein carbonyl oxidation, and thiol levels were quantified in the cardiac tissue samples. To evaluate cardiac damage, marker enzymes such as LDH and CK-MB were measured. Furthermore, the inflammatory response in the cardiac tissue induced by cadmium exposure was assessed through the quantification of NO, TNF-α, and IL-6 levels. Additionally, molecular docking and dynamics studies were conducted utilizing autodock and GLIDE methodologies. Cadmium administration markedly enhanced the activities of LDH and CK-MB, prominent cardiac markers. Furthermore, cadmium treatment also demonstrated a significant decrease in the reduced glutathione levels and antioxidant enzyme activities. Significant elevation of the inflammatory markers was also observed in the cadmium-treated group. Eugenol treatment effectively ameliorates cadmium-induced biochemical changes. This study underscores the potent anti-inflammatory and antioxidant attributes of eugenol. Co-administration of eugenol alongside cadmium exhibited remarkable protective efficacy against cadmium-induced cardio-toxicity. Eugenol demonstrated the capability to reinstate the cellular redox equilibrium of rats subjected to cadmium treatment to levels akin to those of the normal control group.

Cross-talk between Vimentin and autophagy regulates blood-testis barrier disruption induced by cadmium

The blood-testis barrier (BTB) plays a vital role in mammalian spermatogenesis by separating the seminiferous epithelium into an adluminal and a basal compartment. Cadmium (Cd) is a toxic heavy metal that is widely present in the environment. We observed that Cd can induce BTB disruption, leading to apoptosis of testicular cells. However, the molecular mechanisms contributing to BTB injury induced by Cd have not yet been fully clarified. Vimentin (Vim) is an important desmosome-like junction protein that mediates robust adhesion in the BTB. In this study, we investigated how Vim responds to Cd. We found that Cd treatment led to a significant decrease in Vim expression, accompanied by a marked increase in LC3-II expression and a higer number of autophagosomes. Interestingly, we also observed that Cd-induced autophagy was associated with decreased Vim activity and enhanced apoptosis of testicular cells. To further investigate the role of autophagy in Vim regulation under Cd exposure, we treated cells with an autophagy inhibitor called 3-MA. We found that 3-MA treatment enhanced Vim expression and improved the disruption of the BTB under Cd exposure. Additionally, the inhibition of Vim confirmed the role of autophagy in modulating Vim expression. These results reveal a previously unknown regulatory mechanism of Cd involving the interplay between a heavy metal and a protein.

Prenatal double-hit with aluminium and cadmium mediate testicular atrophy and hypothalamic hypoplasia: the role of oxido-nitrergic stress and endocrine perturbations

There is limited experimental evidence on the biochemical consequences of aluminium (Al) and cadmium (Cd) co-exposures during pregnancy and postnatal life.This study investigated the impacts of perinatal Al chloride (AlCl3) and Cd chloride (CdCl2) co-exposures on neuroendocrine functions in mice offspring during postnatal life. The study comprised of four pregnant experimental groups. Group 1 received AlCl3 (10 mg/kg), group 2 were administered CdCl2 (1.5 mg/kg), while group 3 received both AlCl3 (10 mg/kg) and CdCl2 (1.5 mg/kg) (AlCl3+CdCl2), and group 4 received saline (10 mL/kg) only and served as control group. All experimental animals were chemically exposed once daily from gestation days 7-20. Upon delivery, male pups were regrouped based on maternal chemical exposure on postnatal day 21 (PND 21) and allowed to grow to adulthood until PND 78, after which they were sacrificed for assessment of neuroendocrine markers and histological investigations. There was no statistical significance (p > 0.05) on follicle stimulating hormone, testosterone, estrogen and progesterone, thyroid stimulating hormone, thyroxine (T4) in all treatment groups relative to controls|. However, AlCl3 and AlCl3-CdCl2 significantly (p < 0.05) reduced triiodothyronine (T3) levels, with a profound increase in T3:T4 ratio by AlCl3, and AlCl3+CdCl2 compared to control. Furthermore, pups from pregnant mice treated with CdCl2 and AlCl3+CdCl2 demonstrated increased testicular malondialdehyde concentration with increased catalase activity relative to controls, suggesting oxidative imbalance. In addition, AlCl3, CdCl2, and AlCl3+CdCl2 exposures induced testicular and hypothalamic architectural disruption compared to controls, with marked architectural derangement in the AlCl3+CdCl2 group. Our findings suggest that prenatal co-exposures to Alcl3 and CdCl2 induce testicular and hypothalamic alterations in offspring via a testicular oxidative stress and thyrotoxicosis-dependent mechanisms.

Effects of intratesticular injection of hypertonic mannitol and saline on the quality of donkey sperm, indicators of oxidative stress and testicular tissue pathology

OBJECTIVES

The aim of the present study was to examine donkey sperm quality after intratesticular injection of hypertonic mannitol (HM) and saline (HS).

METHODS

Randomly assigned to five treatment groups were 15 adult male donkeys: (1) Control group (no treatment), (2) Surgery group (surgical castration for testosterone control), (3) NS group (normal saline intratesticular injection), (4) HS group (hypertonic saline), and (5) HM group. We injected 20 mL per testicle. We took 5 mL blood from all donkeys before injection. Castration was performed under general anesthesia 60 days later. Samples included blood and testicular tissue. Total motility (TM), progressive motility (PM), movementy features, DNA damage, morphology, viability, and plasma membrane functionality were evaluated. Hormone analyses, histomorphometric studies and oxidative stress indices including total antioxidant capacity (TAC), glutathione peroxidase (GPx), glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), and NADP+/NADPH were evaluated. Apoptosis, pyroptosis-related Bax, Caspase-1, GSDMD, and Bcl-2 expression were also assessed.

RESULTS

In HS and HM groups, testosterone, epididymal sperm count, motility, viability, and plasma membrane functionality dropped while sperm DNA damage increased. HS and HM groups had significantly lower histomorphometric parameters, TAC, GPx, SOD, GSH, and Bcl-2 gene expression. MDA, NADP+/NADPH, Bax, Caspase-1, and GSDMD gene expression were substantially higher in the HS and HM groups than in the control group.

CONCLUSIONS

Toxic effects of hypertonic saline and mannitol on reproductive parameters were seen following, hence, they might be considered as a good chemical sterilizing treatment in donkeys.

Kaempferol mitigates reproductive dysfunctions induced by Naja nigricollis venom through antioxidant system and anti-inflammatory response in male rats

Naja nigricollis Venom (NnV) contains complex toxins that affects various vital systems functions after envenoming. The venom toxins have been reported to induce male reproductive disorders in envenomed rats. This present study explored the ameliorative potential of kaempferol on NnV-induced male reproductive toxicity. Fifty male wistar rats were sorted randomly into five groups (n = 10) for this study. Group 1 were noted as the control, while rats in groups 2 to 5 were injected with LD50 of NnV (1.0 mg/kg bw; i.p.). Group 2 was left untreated post envenomation while group 3 was treated with 0.2 ml of polyvalent antivenom. Groups 4 and 5 were treated with 4 and 8 mg/kg of kaempferol, respectively. NnV caused substantial reduction in concentrations of follicle stimulating hormone, testosterone and luteinizing hormone, while sperm motility, volume and counts significantly (p < 0.05) decreased in envenomed untreated rats. The venom enhanced malondialdehyde levels and substantially decreased glutathione levels, superoxide dismutase and glutathione peroxidase activities in the testes and epididymis of envenomed untreated rats. Additionally, epididymal and testicular myeloperoxidase activity and nitric oxide levels were elevated which substantiated severe morphological defects noticed in the reproductive organs. However, treatment of envenomed rats with kaempferol normalized the reproductive hormones with significant improvement on sperm functional parameters. Elevated inflammatory and oxidative stress biomarkers in testis and epididymis were suppressed post kaempferol treatment. Severe histopathological lesions in the epididymal and testicular tissues were ameliorated in the envenomed treated groups. Results highlights the significance of kaempferol in mitigating reproductive toxicity induced after snakebite envenoming.

Mechanism of cadmium-induced nephrotoxicity

Heavy metals are found naturally in our environment and have many uses and applications in daily life. However, high concentrations of metals may be a result of pollution due to industrialization. In particular, cadmium (Cd), a white metal abundantly distributed in the terrestrial crust, is found in mines together with zinc, which accumulates after volcanic eruption or is found naturally in the sea and earth. High levels of Cd have been associated with disease. In the human body, Cd accumulates in two ways: via inhalation or consumption, mainly of plants or fish contaminated with high concentrations. Several international organizations have been working to establish the limit values of heavy metals in food, water, and the environment to avoid their toxic effects. Increased Cd levels may induce kidney, liver, or neurological diseases. Cd mainly accumulates in the kidney, causing renal disease in people exposed to moderate to high levels, which leads to the development of end-stage chronic kidney disease or death. The aim of this review is to provide an overview of Cd-induced nephrotoxicity, the mechanisms of Cd damage, and the current treatments used to reduce the toxic effects of Cd exposure.

Salvia officinalis restores semen quality and testicular functionality in cadmium-intoxicated male rats

The present study investigated the potential ability of Salvia officinalis, one of the oldest medicinal plants, to protect male rats against cadmium reproductive toxicity. Twenty-eight healthy male rats were randomly allocated into four groups (n = 7); control, Salvia-extract treated group, cadmium treated group and a group treated with both Cd and Salvia. Administration of cadmium reduced the relative testis to body weight and significantly affected sperm parameters by decreasing motility, viability, count and increasing morphological aberrations. Comet assay was used to detect DNA fragmentation in sperms of the rats exposed to Cd. Serum levels of testosterone T, follicle stimulating hormone FSH, and luteinizing hormone LH were significantly decreased. The biochemical analysis of testicular tissue showed a significant rise in Malondialdehyde MDA level coupled with a decrease in the activity of antioxidant enzymes (superoxide dismutase SOD, glutathione peroxidase GPx and catalase CAT). The histological examination of testis sections after Cd administration revealed severe degeneration of spermatogenic cells. Seminiferous tubules were filled with homogenous eosinophilic fluid associated with atrophy of other seminiferous tubules. Co-treatment with the Salvia officinalis extract restored the oxidative enzymes activities and decreased the formation of lipid peroxidation byproduct, which in turn ameliorated the effect of Cd on sperm parameters, DNA damage and testis histopathology. Taken together, it can be concluded that the synergistic antioxidant and radical savaging activities of Salvia officinalis prevented the effect of Cd on semen quality, sperm DNA damage, along with the oxidative stress and histological abnormalities in the testis tissues.

Rutin ameliorates perfluorooctanoic acid-induced testicular injury in mice by reducing oxidative stress and improving lipid metabolism

This study investigated the protective effect of rutin on reproductive and blood-testis barrier (BTB) damage induced by perfluorooctanoic acid (PFOA) exposure. In this study, male ICR mice were randomly divided into three groups, Ctrl group (ddH2O, 5 mL/kg), PFOA group (PFOA, 20 mg/kg/d, 5 mL/kg), PFOA + rutin group (PFOA, 20 mg/kg/d, 5 mL/kg; rutin, 20 mg/kg/d, 5 mL/kg). Mice were exposed to PFOA for 28 days by gavage once daily in the presence or absence of rutin. Histopathological observations demonstrated that rutin treatment during PFOA exposure can reduce structural damage to testis and epididymis such as atrophy of spermatogenic epithelium and stenosis of epididymal lumen, while increase in the number and layers of spermatogenic cells. Biochemical detection demonstrated that rutin can reduce 8-hydroxy-2'-desoxyguanosine (8-OHdG) concentration in the serum and testis tissues. Rutin can also ameliorate glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) content, and reduce malondialdehyde (MDA) and total cholesterol (TC) content in testis tissues. Biotin tracking immunofluorescence and transmission electron microscopy demonstrated that rutin can ameliorate BTB structural damage during PFOA exposure. Rutin ameliorated the stress expression of tight junction proteins occludin and claudin-11. In conclusion, our findings suggested that rutin has a degree of protection in reproductive and BTB damage, which could put forward a new perspective on the application of rutin to prevent reproductive damage.

A new insight of cadmium-induced cellular evidence of autophagic-associated spermiophagy during spermatogenesis

Autophagy plays a dynamic role in spermatozoa development during spermatogenesis. However, the disruption of autophagic flux induces cell death under metal toxicity and severe oxidative stress. Therefore, we hypothesized that cadmium-induced autophagy might be involved in this mechanism. To verify this hypothesis, we studied cadmium-induced cellular evidence of autophagic-associated spermiophagy within the testis. In the present study, treatment with cadmium caused nuclear depressive disorders and vacuolated mitochondrial damage of Sertoli cells. In addition, spermiophagy through the cellular evidence of spermatozoa phagocytosis, the high lysosomal activity (lysosome engulfment and phagolysosome), and autophagy activity (autolysosome and autophagosome) were observed in the Sertoli cells. The immunohistochemistry of lysosomal membrane protein (LAMP2) to target the phagocytosis of spermatozoa revealed that the immunoreactivity of LAMP2 was overstimulated in the luminal compartment of testis's seminiferous tubules. In addition, the immunohistochemistry and immunofluorescence of autophagy-related protein and microtubule-associated light chain (LC3) results showed the strong immunoreactivity and immunosignaling of LC3 in the Sertoli cells of the testis. Moreover, cadmium caused the overactivation of the expression level of autophagy-related proteins, autophagy-related gene (ATG7), (ATG5), beclin1, LC3, sequestosome 1 (P62), and LAMP2 which were confirmed by western blotting. In summary, this study demonstrated that hazards related to cadmium-induced autophagic-associated spermiophagy with the disruption of autophagic flux, providing new insights into the toxicity of cadmium in mammals and representing a high risk to male fertility.

The Palliative and Antioxidant Effects of Hesperidin against Lead-Acetate-Induced Testicular Injury in Male Wistar Rats

Lead (Pb)-induced reprotoxicity is a detrimental consequence of Pb exposure, which results in abnormal spermatogenesis, testicular degeneration, and pathogenic sperm changes. The association between impaired male reproductive function and Pb-induced oxidative stress (OS) has been demonstrated, with consequent testicular antioxidant deficiency. The current study investigated the protective role of the natural antioxidant hesperidin (HSD) against lead-acetate (PbAc)-induced testicular toxicity. Male Wistar rats (n = 40) were randomly divided into four experimental groups: Group I (negative control) received 2.0 mL/kg BW 0.9% saline; Group II received 100 mg/kg BW PbAc; Group III received 100 mg/kg BW HSD; and Group IV received HSD two hours before PbAc using the abovementioned doses. The treatments were administered daily for 30 consecutive days. The results showed that HSD treatment significantly restored PbAc-induced decrease in body, epididymal, and testicular weights as well as in semen parameters, reproductive hormones, and testicular markers of OS. Reduced MDA levels and improved testicular histopathological findings were also observed. Collectively, this study sheds light on the preventive role of HSD against PbAc-induced testicular injury, which is mediated via the suppression of OS and the modulation of reproductive hormones as well as the plausibility of HSD being used as a supplementary therapeutic option for recovery.

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.

Impact of Cadmium and Lead Exposure on Camel Testicular Function: Environmental Contamination and Reproductive Health

The free grazing habits of camels from various sources may cause heavy metals to bioaccumulate in their tissues and organs, possibly resulting in higher amounts of these toxic substances in their bodies over time. The aim of this study was to assess the exposure impact of lead (Pb) and cadmium (Cd) on bull camels of the Lassi breed, aged 7 to 8 years, at a site near the industrial area and another two non-industrial sites, to analyze the presence of heavy metals. Samples from three sites were collected from thirty camels (n = 10/each), soil and water (n = 30), and five different plants (n = 15/each) for analysis. Testes were collected for atomic absorption spectrometry (AAS), and hematoxylin-eosin (HE) staining. Serum samples were obtained to measure testosterone levels by radioimmunoassay (RIA). Samples were obtained from plants, soil, water, blood, serum and urine for AAS. According to the results, the testes' weight, length, width, and volume significantly decreased at the industrial site compared with the other two sites as a result of exposure to Cd and Pb. Additionally, blood testosterone concentrations were considerably lower at the industrial site, indicating a detrimental impact on testicular steroidogenesis. The histological investigation of the industrial site indicated structural disturbances, including seminiferous tubule degeneration and shedding, cellular debris in seminiferous tubules, lining epithelium depletion, and vacuolation. Elevated amounts of Cd and Pb were found at the industrial site when analyzed using water, soil, plants, testes, serum, and urine. These findings demonstrate the adverse effects of Pb and Cd exposure on camel testicular function, including decreased weight and altered steroidogenesis. These findings are essential for understanding the impact of exposure to Pb and Cd on camel reproductive function and for developing successful prevention and management plans for these exposures in this species.

Zinc and selenium attenuate quaternary heavy metal mixture-induced testicular damage via amplification of the antioxidant system, reduction in metal accumulation, inflammatory and apoptotic biomarkers

Heavy metals (HMs) such as cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) are highly toxic elements. They are often found together in nature as a heavy metal mixture (HMM) and are known to contribute to subfertility/infertility as environmental pollutants. This study aims to evaluate the potential benefits of treating HMM-induced testicular pathophysiology with zinc (Zn) and/or selenium (Se). Six-week-old male Sprague Dawley rats were grouped into 5 (n = 7). The control group received deionized water, while the other groups were treated with PbCl2 (20 mg kg-1), CdCl2 (1.61 mg kg-1), HgCl2 (0.40 mg kg-1), and Na2AsO3 (10 mg kg-1) in deionized water for 60 days. Additionally, groups III to V received Zn, Se, and Zn/Se, respectively, for 60 days. The study evaluated testis weight, metal accumulation, sperm analysis, FSH, LH, testosterone, prolactin, oxidative stress, antioxidants, pro-inflammatory and apoptotic markers, and presented structural changes in the testis as micrographs. HMM caused a significant increase in testis weight, metal accumulation, prolactin, oxidative stress, and pro-inflammatory and apoptotic markers, while significantly decreasing semen analysis, FSH, LH, and testosterone. Histology showed decreased spermatogenesis and spermiogenesis, as evidenced by the structure of the germ cells and spermatids. However, Zn, Se, or both ameliorated and reversed some of the observed damages. This study provides further evidence for the mitigative potential of Zn, Se, or both in reversing the damage inflicted by HMM in the testis, and as a countermeasure towards improving HM-induced decrease in public health fecundity.

Graphical abstract

What do we know about blood-testis barrier? current understanding of its structure and physiology

Blood-testis barrier (BTB) creates a particular compartment in the seminiferous epithelium. Contacting Sertoli cell-Sertoli cell plasma membranes possess specialized junction proteins which present a complex dynamic of formation and dismantling. Thus, these specialized structures facilitate germ cell movement across the BTB. Junctions are constantly rearranged during spermatogenesis while the BTB preserves its barrier function. Imaging methods are essential to studying the dynamic of this sophisticated structure in order to understand its functional morphology. Isolated Sertoli cell cultures cannot represent the multiple interactions of the seminiferous epithelium and in situ studies became a fundamental approach to analyze BTB dynamics. In this review, we discuss the contributions of high-resolution microscopy studies to enlarge the body of morphofunctional data to understand the biology of the BTB as a dynamic structure. The first morphological evidence of the BTB was based on a fine structure of the junctions, which was resolved with Transmission Electron Microscopy. The use of conventional Fluorescent Light Microscopy to examine labelled molecules emerged as a fundamental technique for elucidating the precise protein localization at the BTB. Then laser-scanning confocal microscopy allowed the study of three-dimensional structures and complexes at the seminiferous epithelium. Several junction proteins, like the transmembrane, scaffold and signaling proteins, were identified in the testis using traditional animal models. BTB morphology was analyzed in different physiological conditions as the spermatocyte movement during meiosis, testis development, and seasonal spermatogenesis, but also structural elements, proteins, and BTB permeability were studied. Under pathological, pharmacological, or pollutant/toxic conditions, there are significant studies that provide high-resolution images which help to understand the dynamic of the BTB. Notwithstanding the advances, further research using new technologies is required to gain information on the BTB. Super-resolution light microscopy is needed to provide new research with high-quality images of targeted molecules at a nanometer-scale resolution. Finally, we highlight research areas that warrant future studies, pinpointing new microscopy approaches and helping to improve our ability to understand this barrier complexity.

Evidence of the protective role of D-Aspartate in counteracting/preventing cadmium-induced oxidative stress in the rat testis

Cadmium (Cd), by producing oxidative stress and acting as an endocrine disruptor, is known to cause severe testicular injury, documented by histological and biomolecular alterations, such as decreased serum testosterone (T) level and impairment of spermatogenesis. This is the first report on the potential counteractive/preventive action of D-Aspartate (D-Asp), a well-known stimulator of T biosynthesis and spermatogenesis progression by affecting hypothalamic-pituitary-gonadal axis, in alleviating Cd effects in the rat testis. Our results confirmed that Cd affects testicular activity, as documented by the reduction of serum T concentration and of the protein levels of steroidogenesis (StAR, 3β-HSD, and 17β-HSD) and spermatogenesis (PCNA, p-H3, and SYCP3) markers. Moreover, higher protein levels of cytochrome C and caspase 3, together with the number of cells positive to TUNEL assay, indicated the intensification of the apoptotic process. D-Asp administered either simultaneously to Cd, or for 15 days before the Cd-treatment, reduced the oxidative stress induced by the metal, alleviating the consequent harmful effects. Interestingly, the preventive action of D-Asp was more effective than its counteractive effect. A possible explanation is that giving D-Asp for 15 days induces its significant uptake in the testes, reaching the concentrations necessary for optimum function. In summary, this report highlights, for the first time, the beneficial role played by D-Asp in both counteracting/preventing the adverse Cd effects in the rat testis, strongly encouraging further investigations to consider the potential value of D-Asp also in improving human testicular health and male fertility.

Pharmacological Activity of Flavonoid Quercetin and Its Therapeutic Potential in Testicular Injury

Quercetin is a natural flavonoid widely found in natural fruits and vegetables. Recent studies have shown that quercetin mediates multiple beneficial effects in a variety of organ damage and diseases, and is considered a healthcare supplement with health-promoting potential. Male infertility is a major health concern, and testicular damage from multiple causes is an important etiology. Previous studies have shown that quercetin has a protective effect on reproductive function. This may be related to the antioxidant, anti-inflammatory, and anti-apoptotic biological activities of quercetin. Therefore, this paper reviews the mechanisms by which quercetin exerts its pharmacological activity and its role in testicular damage induced by various etiologies. In addition, this paper compiles the application of quercetin in clinical trials, demonstrating its practical effects in regulating blood pressure and inhibiting cellular senescence in human patients. However, more in-depth experimental studies and clinical trials are needed to confirm the true value of quercetin for the prevention and protection against testicular injury.

Circulating microRNAs as promising testicular translatable safety biomarkers: current state and future perspectives

Drug-induced testicular injury (DITI) is one of the often-observed and challenging safety issues seen during drug development. Semen analysis and circulating hormones currently utilized have significant gaps in their ability to detect testicular damage accurately. In addition, no biomarkers enable a mechanistic understanding of the damage to the different regions of the testis, such as seminiferous tubules, Sertoli, and Leydig cells. MicroRNAs (miRNAs) are a class of non-coding RNAs that modulate gene expression post-transcriptionally and have been indicated to regulate a wide range of biological pathways. Circulating miRNAs can be measured in the body fluids due to tissue-specific cell injury/damage or toxicant exposure. Therefore, these circulating miRNAs have become attractive and promising non-invasive biomarkers for assessing drug-induced testicular injury, with several reports on their use as safety biomarkers for monitoring testicular damage in preclinical species. Leveraging emerging tools such as 'organs-on-chips' that can emulate the human organ's physiological environment and function is starting to enable biomarker discovery, validation, and clinical translation for regulatory qualification and implementation in drug development.

The simultaneous administration of microplastics and cadmium alters rat testicular activity and changes the expression of PTMA, DAAM1 and PREP

This paper confirms the damaging effects produced by MP and Cd on testicular activity in the rat. Oral treatment with both chemicals resulted in testicular damage, documented by biomolecular and histological alterations, particularly by impaired morphometric parameters, increased apoptosis, reduced testosterone synthesis, and downregulation of the steroidogenic enzyme 3β-HSD. We also demonstrated, for the first time, that both MP and Cd can affect the protein level of PTMA, a small peptide that regulates germ cell proliferation and differentiation. Interestingly, the cytoarchitecture of testicular cells was also altered by the treatments, as evidenced by the impaired expression and localization of DAAM1 and PREP, two proteins involved in actin- and microtubule-associated processes, respectively, during germ cells differentiation into spermatozoa, impairing normal spermatogenesis. Finally, we showed that the effect of simultaneous treatment with MP and Cd were more severe than those produced by MP alone and less harmful than those of Cd alone. This could be due to the different ways of exposure of the two substances to rats (in drinking water for Cd and in oral gavage for MP), since being the first contact in the animals’ gastrointestinal tract, MP can adsorb Cd, reducing its bioavailability through the Trojan-horse effect.

Testicular histopathology in rats co-exposed to heat and psychological stressors

Objectives

The present study aimed to investigate the effect of co-exposure to heat and psychological stressors on testicular tissue as one of the major male reproductive organs in rats.

Methods

Forty adult male Wistar rats were divided into four groups of 10 animals each. The first group was exposed to heat stress (Temperature Humidity Index: 57.75 ± 3), the second group was exposed to three psychological stressors including strobe light ultrasonic sound, and tilting cage, and the third group was co-exposed to both heat and psychological stress daily. The order of exposure to various psychological stressors was randomized. Following the last day of the 40 -day exposure, the rats were euthanized and their testicular tissues were fixed in Bouin's solution. Moreover, a tissue processor, a microtome as well as hematoxylin, and eosin staining were used for tissue preparation.

Results

The co-exposure to psychological and heat stress can cause negative testis histopathological changes including spermatid retention, degeneration of round spermatids and spermatocytes, degeneration and depletion of elongated Spermatid, Sertoli cell status, tubular degeneration/atrophy, Leydig cell atrophy, tubular dilatation, re-tubular dilation, and sclerosis status in a number of rats. Moreover, the histopathological changes were higher in the group exposed to heat stress compared with those exposed to psychological stress.

Conclusions

Although exposure to either stressor alone can affect testicular tissue as part of the reproductive system, co-exposure to both stressors may result in an increased risk of adverse effects on testicular tissue.

Does environmental pollution affect male reproductive system in naturally exposed vertebrates? A systematic review

Due to environmental contamination, the environment constantly receives pollutants from various anthropic actions. These pollutants put ecological health at risk due to contamination and accumulation in living organisms, including wild animals and humans. Exposure can cause physiological, morphological, and behavioral changes in living beings. In this context, laboratory studies have frequently investigated how environmental contaminants affect the male reproductive system and gametes. However, few studies have examined how these contaminants affect male reproduction in naturally exposed animals. To better understand this topic, we conducted a systematic review of the effects of exposing male vertebrate animals to polluted environments on their reproductive functions. After an extensive search using the PubMed/MEDLINE, Scopus, and Web of Science databases, 39 studies met our inclusion criteria and were eligible for this review. This study showed that reproductive damages were frequent in fishes, amphibians, reptiles, birds, and mammals exposed to contaminated environments. Wild animals are exposed mainly to endocrine-disrupting compounds (EDCs), toxic metals, and radiation. Exposure to pollutants causes a reduction in androgen levels, impaired spermatogenesis, morphological damage to reproductive organs, and decreased sperm quality, leading to reduced fertility and population decline. Although several species have been studied, the number of studies is limited for some groups of vertebrates. Wildlife has proven valuable to our understanding of the potential effects of environmental contaminants on human and ecosystem health. Thus, some recommendations for future investigations are provided. This review also creates a baseline for the understanding state of the art in reproductive toxicology studies.

Combined Protective Effects of Quercetin, Rutin, and Gallic Acid against Cadmium-Induced Testicular Damages in Young-Adult Rats

Cadmium (Cd) is a toxic metal that damages several tissues of animals and humans including the testis. The ameliorative effects of quercetin (QUE), rutin (RUT), and gallic acid (GAL) at 20 mg kg-1 body weight alone or in combination against testicular injury induced by Cd (24 mg kg-1 body weight) in male Wistar rats were evaluated in this study. Forty-two (42) rats were randomly grouped into six (6) groups: (1) vehicle control group, (2) Cd group, (3) RUT+Cd group, (4) GAL+Cd group, (5) QUE+Cd group, and (6) RUT+GAL+QUE+Cd group. At the end of the oral gavage of the tested chemicals, the rats were sacrificed, blood samples were collected, and testes were harvested and processed for biochemical assays. Cd exposure damaged the testis (smaller epithelium thickness and spermatogenesis index and sloughing of the epithelium); increased lipid peroxidation, glutathione S-transferase activity, and DNA fragmentation; and diminished glutathione reductase activity and serum testosterone level 40 days posttreatment. Treatment with the phenolics separately or in combination attenuated the effect of Cd on serum testosterone, glutathione reductase and glutathione S-transferase activities, lipid peroxidation, and percent fragmented DNA. The increased nitric oxide concentration in the QUE+Cd group was attenuated to control values in the combined (RUT+GAL+QUE+Cd) exposure group. Coadministration of the phenolics appears to have more substantial protective effects than their single effects against Cd-induced testicular DNA damage, glutathione S-transferase activity, and the recovery of testosterone levels and spermatogenesis index. Overall, the tested phenolics can reduce testicular damage more efficiently in their combined form than individual administration.

Coenzyme Q10 enhances testicular functions and sexual behavior through regulating steroidogenic-related gene expression and inflammatory pathways of Japanese quail (Coturnix japonica) aganist cadmium

A progressively essential bird of high economic significance for meat production and commercial egg is the Japanese quail, and so more experiments are necessary to improve the productivity of these birds under stressful encounters. The current work was performed to define the influences of Coenzyme Q10 (CoQ10) on growth, sexual behavior, and testicular characteristics (size of the gonad, traits of spermatic features, levels of plasma testosterone, steroidogenic-related gene expression) of Japanese quail (Coturnix coturnix japonica) aganist cadmium (Cd) administration. Chicks of quail (n = 250), 14 days old of age were distributed into 4 groups: basal ration (Group 1), basal ration and CoQ10 at 100 mg/kg ration (Group 2), basal ration and Cd at 50 mg/kg ration (Group 3), and CoQ10 + Cd (Group 4). Several parameters relating to productive performance, such as weight of the body, weight gain, feed intake, and the conversion ratio of feed, were evaluated. Constant visual scanning of the quails was performed to observe their sexual behaviors. Sperm characteristics, plasma testosterone levels, and testicular inflammatory markers of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were also determined. Oxidative-antioxidant redox status in the testes was evaluated by analyzing MDA level, GPx, and SOD activities. Steroidogenic-related gene expression in the testes (CYP17A1, StAR, 3β-HSD, and Cyp19) was also examined. In addition, testicular apoptosis was assessed by monitoring the alterations in the local expression of stress-induced (HSP70), proteins of anti-apoptotic marker (Bcl-2), and pro-apoptotic markers (caspase-3 and Bax). Cd administration hurts body performance, sexual behavior, and testicular efficiency parameters. Interestingly, CoQ10 supplementation improved reproductive performance. Moreover, it significantly increases the % of birds exhibiting sexual behavior and enhances testicular functions, which were damaged by Cd administration, by enhancing plasma testosterone level, antioxidative enzyme activity, and sperm quality traits while reducing the MDA and pro-inflammatory markers. Furthermore, downregulation of pro-apoptotic factor expression, though it increased the expression of the anti-apoptotic protein, was recorded. Correspondingly, CoQ10 revealed a marked upregulation in the expression of steroidogenic-related genes. Conclusion: It is established that the consumption of CoQ10 in the ration of Japanese quail, following a Cd adminstration, improves productive performance, sexual behavior, and several testicular function parameters as a potent antioxidant.

Expression of RSPH6A in the first wave of rat spermatogenesis and oxidative stress conditions: Attenuation by melatonin

Purpose

Here, we report, for the first time, the temporal expression and localization of axonemal radial spoke head homolog A (RSPH6A) protein during the first wave of rat spermatogenesis and in oxidative stress conditions.

Methods

For the developmental study, testes were collected from rats at different developmental stages (7, 14, 21, 28, 35, 42, and 60 postnatal days); for in vivo treatment, 24 rats were treated with cadmium and/or melatonin. From each sample, western blot (WB) and immunofluorescence (IF) analyses for RSPH6A were performed.

Results

RSPH6A expression starts at 21 PND alongside the appearance of I spermatocytes (SPC) with a significant increase up to 60 PND. Data were confirmed by IF analysis, showing that RPSH6A expression is restricted to I and II SPC, spermatids, and mature sperm. In vivo experiments showed that the expression and localization of RSPH6A in the testis and epididymal spermatozoa of adult rats treated with cadmium were impaired. Interestingly, melatonin (an antioxidant), given together with Cd, can counteract its damaging effects.

Conclusions

All combined data confirm that RSPH6A contributes to the onset of fertility by acting on sperm motility, raising the possibility of using RSPH6A as a marker for normal fertility in the general population.

Apoptosis, inflammation, and oxidative stress in infertility: A mini review

Infertility has been a major issue in our society for many years, and millions of couples all over the world are still experiencing it. There are several reasons for and causes of infertility in both men and women. Recent studies have shown that apoptosis, inflammation, and oxidative stress contribute immensely to infertility. The data regarding this report were obtained through a thorough review of scientific articles published in various databases, including Elsevier, Web of Science, PubMed, Scopus, and Google Scholar. Furthermore, PhD and MSc theses were also reviewed when compiling the data. Apoptosis, also known as "programmed cell death," is a natural and harmless process that occurs in human beings. Although it can become harmful if altered, Inflammation, on the other hand, is the body's reaction to detrimental stimuli caused by toxic substances or compounds, while oxidative stress is a phenomenon that results in an imbalance between the generation and aggregation of reactive oxygen species (ROS) in the cells against antioxidants. These three factors interchangeably bring about several reproductive disorders in the body, resulting in infertility. This review aims at discussing how apoptosis, inflammation, and oxidative stress play a role in human infertility.

Availability of data and material

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Zinc restores functionality in porcine prepubertal Sertoli cells exposed to subtoxic cadmium concentration via regulating the Nrf2 signaling pathway

INTRODUCTION

Among substances released into the environment by anthropogenic activities, the heavy metal cadmium (Cd) is known to induce severe testicular injury causing male subfertility/infertility. Zinc (Zn) is another heavy metal that, unlike Cd, is physiologically present in the testis, being essential for spermatogenesis. We aimed to examine the possibility that 50 µM ZnCl₂ could counteract the toxic effects induced by Cd in an in vitro model of porcine prepubertal Sertoli cells (SCs) exposed to both subtoxic (5 μM) and toxic (10 μM) concentrations of CdCl₂ for 48 h.

MATERIALS AND METHODS

Apoptosis, cell cycle, and cell functionality were assessed. The gene expression of Nrf2 and its downstream antioxidant enzymes, ERK1/2, and AKT kinase signaling pathways were evaluated.

MATERIALS AND RESULTS

We found that Zn, in co-treatment with subtoxic and toxic Cd concentration, increased the number of metabolically active SCs compared to Cd exposure alone but restored SC functionality only in co-treatment with subtoxic Cd concentration with respect to subtoxic Cd alone. Exposure of Cd disrupted cell cycle in SCs, and Zn co-treatment was not able to counteract this effect. Cd alone induced SC death through apoptosis and necrosis in a dose-dependent manner, and co-treatment with Zn increased the pro-apoptotic effect of Cd. Subtoxic and toxic Cd exposures activated the Nrf2 signaling pathway by increasing gene expression of Nrf2 and its downstream genes (SOD, HO-1, and GSHPx). Zn co-treatment with subtoxic Cd attenuated upregulation on the Nrf2 system, while with toxic Cd, the effect was more erratic. Studying ERK1/2 and AKT pathways as a target, we found that the phosphorylation ratio of p-ERK1/2 and p-AKT was upregulated by both subtoxic and toxic Cd exposure alone and in co-treatment with Zn.

DISCUSSION

Our results suggest that Zn could counteract Cd effects by increasing the number of metabolically active SCs, fully or partially restoring their functionality by modulating Nrf2, ERK1/2, and AKT pathways. Our SC model could be useful to study the effects of early Cd exposure on immature testis, evaluating the possible protective effects of Zn.

Cadmium exposure induces pyroptosis in testicular tissue by increasing oxidative stress and activating the AIM2 inflammasome pathway

High doses of cadmium (Cd) cause irreversible injury to the reproductive system, especially testicular tissue. Studies have shown that pyroptosis is involved in Cd-induced tissue damage, but whether pyroptosis is involved in damage to testicular tissue following Cd exposure remains unclear. To investigate the mechanism of pyroptosis in testicular injury induced by Cd exposure, we used 8-week-old male C57BL/6J mice subjected to consecutive 7 days of intraperitoneal injection of cadmium chloride (CdCl₂) at concentrations of 0, 1.0 and 3.0 mg/kg. The results indicated that 3.0 mg/kg CdCl₂ significantly decreased serum testosterone levels, sperm concentration and sperm motility, while increased LDH and IL-1β levels. Testicular HE staining indicated that Cd exposure damaged the interstitial cells and increased the atypical residual bodies. Fluorescence results indicated that 3.0 mg/kg CdCl₂ increased ROS levels, DNA damage, and the number of TUNEL-positive seminiferous tubule cells in testicular tissue. Transcriptome analysis showed that Cd exposure mainly induced inflammatory and chemokine signaling pathways in testicular tissue, with upregulated mRNA levels of Aim2, and reduced mRNA levels of Nlrp3. Further analysis showed that 3.0 mg/kg CdCl₂ increased the expression of testicular HO-1, SOD2, γH2AX and PARP-1, as well as the pyroptosis-related factors GSDMD, GSDME, Caspase-1, ASC and IL-1β. In conclusion, our results provide a possible mechanism by which Cd exposure activates the AIM2 pathway by increasing oxidative stress injury to induce pyroptosis in testicular tissue. This provides a new perspective on testicular damage caused by Cd exposure.

Mechanisms of Cadmium-Induced Testicular Injury: A Risk to Male Fertility

Cadmium is a heavy toxic metal with unknown biological functions in the human body. Over time, cadmium accretion in the different visceral organs (liver, lungs, kidney, and testis) is said to impair the function of these organs, which is associated with a relatively long biological half-life and a very low rate of excretion. Recently studies have revealed that the testes are highly sensitive to cadmium. In this review, we discussed the adverse effect of cadmium on the development and biological functions of the testis. The Sertoli cells (SCs), seminiferous tubules, and Blood Testis Barrier are severely structurally damaged by cadmium, which results in sperm loss. The development and function of Leydig cells are hindered by cadmium, which also induces Leydig cell tumors. The testis's vascular system is severely disturbed by cadmium. Cadmium also perturbs the function of somatic cells and germ cells through epigenetic regulation, giving rise to infertile or sub-fertile males. In addition, we also summarized the other findings related to cadmium-induced oxidative toxicity, apoptotic toxicity, and autophagic toxicity, along with their possible mechanisms in the testicular tissue of different animal species. Consequently, cadmium represents a high-risk factor for male fertility.

Cadmium-induced apoptosis of Leydig cells is mediated by excessive mitochondrial fission and inhibition of mitophagy

Cadmium is one of the environmental and occupational pollutants and its potential adverse effects on human health have given rise to substantial concern. Cadmium causes damage to the male reproductive system via induction of germ-cell apoptosis; however, the underlying mechanism of cadmium-induced reproductive toxicity in Leydig cells remains unclear. In this study, twenty mice were divided randomly into four groups and exposed to CdCl2 at concentrations of 0, 0.5, 1.0 and 2.0 mg/kg/day for four consecutive weeks. Testicular injury, abnormal spermatogenesis and apoptosis of Leydig cells were observed in mice. In order to investigate the mechanism of cadmium-induced apoptosis of Leydig cells, a model of mouse Leydig cell line (i.e. TM3 cells) was subjected to treatment with various concentrations of CdCl2. It was found that mitochondrial function was disrupted by cadmium, which also caused a significant elevation in levels of mitochondrial superoxide and cellular ROS. Furthermore, while cadmium increased the expression of mitochondrial fission proteins (DRP1 and FIS1), it reduced the expression of mitochondrial fusion proteins (OPA1 and MFN1). This led to excessive mitochondrial fission, the release of cytochrome c and apoptosis. Conversely, cadmium-induced accumulation of mitochondrial superoxide was decreased by the inhibition of mitochondrial fission through the use of Mdivi-1 (an inhibitor of DRP1). Mdivi-1 also partially prevented the release of cytochrome c from mitochondria to cytosol and attenuated cell apoptosis. Finally, given the accumulation of LC3II and SQSTM1/p62 and the obstruction of Parkin recruitment into damaged mitochondria in TM3 cells, the autophagosome-lysosome fusion was probably inhibited by cadmium. Overall, these findings suggest that cadmium induces apoptosis of mouse Leydig cells via the induction of excessive mitochondrial fission and inhibition of mitophagy.

Combined Effects of Cadmium- and Cyanide-Contaminated Diet on Oxidative Stress Biomarkers in Different Tissues of Rats

Background. Several toxicants present simultaneously in the environment have combined toxicological effects. In addition, various xenobiotics have distinct effects on oxidative stress biomarkers in animal cells and tissues. The aim of this study was to analyze the effect of cadmium (Cd) and cyanide (CN) through the food chain on some antioxidant indices in the tissues (lungs, testes, heart, and brain) of male Wistar rats. Materials and Methods. The study included sixty African catfish allocated to four groups, each comprising fifteen fish, treated with potassium cyanide (KCN) and cadmium chloride (CdCl2), held at a temperature of 25°C in a 100-litre fish tank aquarium with water contaminated with 0.4 mg of both cyanide and cadmium/100 ml of water. All the fish were later killed, dried, and used to prepare diet for experimental animals. Twenty male rats divided into four groups, each comprising five rats, were used for this study as well, and fed for 28 days as follows: Group A - control diet; Group B - cyanide-contaminated diet; Group C - cadmium-contaminated diet; Group D - diet contaminated with cyanide + cadmium. Subsequently, they were sacrificed. Biochemical analysis of the tissues excised from the rats was done. Results. There was a significant (p < 0.05) increase in lipid peroxidation level and a significant decrease in superoxide dismutase, catalase and reduced glutathione activities in the lungs, testes, heart, and brain of rats fed a catfish diet containing both cyanide and cadmium as compared to controls. In addition, contaminated diet altered acetylcholinesterase activity in the brain, glutathione peroxidase activity, glutathione-S-transferase activity, and glutathione reductase activity in the tissues of experimental rats. Conclusions. Cadmium and cyanide, via the food chain, induce oxidative stress in the lungs, testes, heart, and brain of rats.

Characterization of primary canine Sertoli cells as a model to test male reproductive toxicant

Sertoli cells play critical roles in regulating spermatogenesis and testis development by providing structural and nutritional support. This study aimed to develop a standard protocol for canine Sertoli cell isolation and culture; and characterize its biological features, functionality, and application of compound toxicity testing. Canine testicles were received from the neuter clinic, and three-step of enzymatic digestion was applied to isolate Sertoli cells. We characterized the growth and purity of Sertoli cells with the expression of SOX9, GATA4, and Clusterin. In addition, we selected cadmium as a model toxicant to evaluate the toxic responses in the newly established Sertoli cells using High-content Analysis (HCA). With our optimized protocol, the purity of isolated Sertoli cells was above 95%, as determined with Sertoli cell-specific protein markers of SOX9 and GATA4. More importantly, primary Sertoli cell populations could be expanded rapidly in vitro, passaged (up to seven), and cryopreserved. The HCA-based assay revealed that cadmium at 1 μM induced both disruptions of cytoskeletal and DNA damage responses. Furthermore, we established an HCA assay with the newly isolated and optimized culture of canine Sertoli cells to evaluate the epigenetic markers of histone modification. We found cadmium-induced differential changes in histone modifications H3Me3K9, H3Me3K36, H4Me3K20, and H4acK5. In summary, we have established the standardized protocol to produce canine Sertoli cells with Sertoli cell-specific phenotype. The isolation and expansion of large quantities of canine Sertoli cells will provide broad applications in studying male infertility, reproductive toxicology, testicular cancer, and cell therapy.

Curative Potential of Substances with Bioactive Properties to Alleviate Cd Toxicity: A Review

Rapid urbanization and industrialization have led to alarming cadmium (Cd) pollution. Cd is a toxic heavy metal without any known physiological function in the organism, leading to severe health threat to the population. Cd has a long half-life (10-30 years) and thus it represents serious concern as it to a great extent accumulates in organs or organelles where it often causes irreversible damage. Moreover, Cd contamination might further lead to certain carcinogenic and non-carcinogenic health risks. Therefore, its negative effect on population health has to be minimalized. As Cd is able to enter the body through the air, water, soil, and food chain one possible way to defend and eliminate Cd toxicities is via dietary supplements that aim to eliminate the adverse effects of Cd to the organism. Naturally occurring bioactive compounds in food or medicinal plants with beneficial, mostly antioxidant, anti-inflammatory, anti-aging, or anti-tumorigenesis impact on the organism, have been described to mitigate the negative effect of various contaminants and pollutants, including Cd. This study summarizes the curative effect of recently studied bioactive substances and mineral elements capable to alleviate the negative impact of Cd on various model systems, supposing that not only the Cd-derived health threat can be reduced, but also prevention and control of Cd toxicity and elimination of Cd contamination can be achieved in the future.

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.

Trace elements in Ladoga ringed seal (Pusa hispida ladogensis) hair

Hair samples of two adults, eight molted pups, and four newborn Ladoga ringed seals Pusa hispida ladogensis found stranded ashore on Lake Ladoga, North-West Russia, in 2020-2021, were analyzed for concentrations of trace elements, including toxic heavy metals. Al had the highest median concentration (9.25 μg/g, range 1.26-262 μg/g) among toxic elements, followed by Hg (8.84 μg/g, range 2-12.75 μg/g), and Pb (0.16 μg/g, range 0.04-2 μg/g). The Cd concentration in lanugo compared with adult hair of young-of-the-year was significantly lower, suggesting a barrier effect of the placenta for Cd transport to the fetus. The concentrations of Co, Cr, and Zn were higher before the molt, demonstrating the role of lanugo shedding in the excretion of these metals. The concentrations of Hg, Cd, Pb, and Cu were significantly lower than in the 1990s, and lead and copper continued to decline further after the 2000s. Based on available reference trace element levels in other seal species, we found little evidence of substantially elevated levels or deficiencies in Ladoga seals. Nevertheless, since imbalance of trace elements due to contamination can cause physiological disorders, future trace element monitoring in the Ladoga seal is recommended.

Naja nigricollis venom influenced reproductive and neurological functions via modulation of pro-inflammatory cytokines and oxidative damage in male rats

Reproductive and neurological anomalies are often characterized by malfunctioning of reproductive and nervous organs sometimes attributed to systemic toxins. However, limited information is available on the impact of snake venom toxins on male reproductive and nervous system. This study investigated the toxicological effects of Naja nigricollis venom on male reproductive and neural functions in rat model. Twenty male Wistar rats weighing between 195 and 230 g were divided randomly into two groups of ten rats each. Group 1 served as normal control while rats in group 2 were envenomed with a single intraperitoneal injection of 0.25 mg/kg⁻¹ (LD_12.5) of N. nigricollis venom on first and twenty fifth day within the period of fifty days experiment. The venom significantly decreased sperm counts, motile cells and volume combined with increased sperm abnormalities. The venom induced hormonal imbalances in the envenomed group as levels of testosterone, luteinizing and follicle stimulating hormones depreciated compared to the control. Oxidative stress biomarkers: malondialdehyde significantly increased parallels with depletion of glutathione level and catalase activities in testis, epididymis and brain of envenomed rats. Furthermore, N. nigricollis venom up-regulated tumor necrosis factor-alpha (TNF-α) and interleukin1-beta (IL-1β) production in testis, epididymis and brain of envenomed rats compared to the control. Also, various histological alterations were noticed in tissues of testis, epididymis and brain of envenomed rats. Findings indicated that N. nigricollis venom is capable of inducing reproductive and neurological dysfunction in envenomed victims.

Sub-chronic cadmium and lead compound exposure induces reproductive toxicity and development of testicular germ cell neoplasia in situ in murine model: Attenuative effects of resveratrol

Cadmium and lead are widespread, nonbiodegradable heavy metals of perpetual environmental concerns. The present study aimed to evaluate whether sub-chronic exposure to cadmium chloride (CdCl₂ ) and lead acetate [Pb(CH₃ COO)₂ ] induces reproductive toxicity and development of testicular germ cell neoplasia in situ (GCNIS) in swiss albino mice. The effects of resveratrol to reverse the metal-induced toxicity were also analyzed. The mice were randomly divided into four groups for metal treatments and two groups received two different doses of each metal, CdCl₂ (0.25 and 0.5 mg/kg) and Pb(CH₃ COO)₂ (3 and 6 mg/kg). The fourth group received oral doses of 20 mg/kg resveratrol in combination with 0.5 mg/kg CdCl₂ or 6 mg/kg Pb(CH₃ COO)₂ for 16 weeks. Toxic effects of both metals were estimated qualitatively and quantitatively by the alterations in sperm parameters, oxidative stress markers, testicular histology, and protein expressions of the treated mice. Pronounced perturbation of sperm parameters, cellular redox balance were observed with severe distortion of testicular histo-architecture in metal exposed mice. Significant overexpression of Akt cascade and testicular GCNIS marker proteins were recorded in tissues treated with CdCl₂ . Notable improvements were observed in all the evaluated parameters of resveratrol cotreated mice groups. Taken together, the findings of this study showed that long-term exposure to Cd and Pb compounds, induced acute reproductive toxicity and initiation of GCNIS development in mice. Conversely, resveratrol consumption abrogated metal-induced perturbation of spermatogenesis, testicular morphology, and the upregulation of Akt cascade proteins along with GCNIS markers, which could have induced the development of testicular cancer.

Effect of spermidine on ameliorating spermatogenic disorders in diabetic mice via regulating glycolysis pathway

Diabetes mellitus (DM), a high incidence metabolic disease, is related to the impairment of male spermatogenic function. Spermidine (SPM), one of the biogenic amines, was identified from human seminal plasma and believed to have multiple pharmacological functions. However, there exists little evidence that reported SPM's effects on moderating diabetic male spermatogenic function. Thus, the objective of this study was to investigate the SPM's protective effects on testicular spermatogenic function in streptozotocin (STZ)-induced type 1 diabetic mice. Therefore, 40 mature male C57BL/6 J mice were divided into four main groups: the control group (n = 10), the diabetic group (n = 10), the 2.5 mg/kg SPM-treated diabetic group (n = 10) and the 5 mg/kg SPM-treated diabetic group (n = 10), which was given intraperitoneally for 8 weeks. The type 1 diabetic mice model was established by a single intraperitoneal injection of STZ 120 mg/kg. The results showed that, compare to the control group, the body and testis weight, as well the number of sperm were decreased, while the rate of sperm malformation was significantly increased in STZ-induced diabetic mice. Then the testicular morphology was observed, which showed that seminiferous tubule of testis were arranged in mess, the area and diameter of which was decreased, along with downregulated anti-apoptotic factor (Bcl-2) expression, and upregulated pro-apoptotic factor (Bax) expression in the testes. Furthermore, testicular genetic expression levels of Sertoli cells (SCs) markers (WT1, GATA4 and Vimentin) detected that the pathological changes aggravated observably, such as the severity of tubule degeneration increased. Compared to the saline-treated DM mice, SPM treatment markedly improved testicular function, with an increment in the body and testis weight as well as sperm count. Pro-apoptotic factor (Bax) was down-regulated expression with the up-regulated expression of Bcl-2 and suppression of apoptosis in the testes. What's more, expression of WT1, GATA4, Vimentin and the expressions of glycolytic rate-limiting enzyme genes (HK2, PKM2, LDHA) in diabetic testes were also upregulated by SPM supplement. The evidence derived from this study indicated that the SMP's positive effect on moderating spermatogenic disorder in T1DM mice's testis. This positive effect is delivered via promoting spermatogenic cell proliferation and participating in the glycolytic pathway's activation.

Letrozole protects against cadmium-induced inhibition of spermatogenesis via LHCGR and Hsd3b6 to activate testosterone synthesis in mice

The heavy metal cadmium is proposed to be one of the environmental endocrine disruptors of spermatogenesis. Cadmium-induced inhibition of spermatogenesis is associated with a hormone secretion disorder. Letrozole is an aromatase inhibitor that increases peripheral androgen levels and stimulates spermatogenesis. However, the potential protective effects of letrozole on cadmium-induced reproductive toxicity remain to be elucidated. In this study, male mice were administered CdCl2 (4 mg/kg BW) orally by gavage alone or in combination with letrozole (0.25 mg/kg BW) for 30 days. Cd exposure caused a significant decreases in body weight, sperm count, motility, vitality, and plasma testosterone levels. Histopathological changes revealed extensive vacuolization and decreased spermatozoa in the lumen. However, in the Cd + letrozole group, letrozole treatment compensated for deficits in sperm parameters (count, motility, and vitality) induced by Cd. Letrozole treatment significantly increased serum testosterone levels, which were reduced by Cd. Histopathological studies revealed a systematic array of all germ cells, a preserved basement membrane and relatively less vacuolization. For a mechanistic examination, RNA-seq was used to profile alterations in gene expression in response to letrozole. Compared with that in the Cd-treated group, RNA-Seq analysis showed that 214 genes were differentially expressed in the presence of letrozole. Gene ontology (GO) enrichment analysis and KEGG signaling pathway analysis showed that steroid biosynthetic processes were the processes most affected by letrozole treatment. Furthermore, we found that the expression of the testosterone synthesis-related genes LHCGR (luteinizing hormone/choriogonadotropin receptor) and Hsd3b6 (3 beta- and steroid delta-isomerase 6) was significantly downregulated in Cd-treated testes, but these genes maintained similar expression levels in letrozole-treated testes as those in the control group. However, the transcription levels of inflammatory cytokines, such as IL-1β and IL-6, and oxidative stress-related genes (Nrf2, Nqo1, and Ho-1) showed no changes. The present study suggests that the potential protective effect of letrozole on Cd-induced reproductive toxicity might be mediated by the upregulation of LHCGR and Hsd3b6, which would beneficially increase testosterone synthesis to achieve optimum protection of sperm quality and spermatogenesis.

Effect of heavy metals on epididymal morphology and function: An integrative review

Male fertility has deteriorated over the last decades, and environmental risk factors are among the possible causes of this phenomenon. Pollutants such as heavy metals might accumulate in male reproductive organs to levels that are associated with reproductive disorders. Several studies reported detrimental effects of inorganic arsenic (iAs⁺³/iAs⁺⁵), cadmium (Cd⁺²), lead (Pb⁺²), and mercury (Hg⁺²/CH₃Hg⁺²) on the epididymis, which plays a crucial role in sperm maturation. However, the magnitude of their effects and the consequences on the physiology of the epididymis are still unclear. Therefore, an integrative review with meta-analyses was conducted examining 138 studies to determine how exposure to arsenic, cadmium, lead, and mercury affects epididymal morphology and functions, using primarily murine data from experimental studies as a source. This study showed that exposure to metal(loids) reduced epididymal weight, sperm motility, and sperm number. Inorganic arsenic, cadmium, and lead damaged sperm structures within the epididymal duct. While sodium arsenite, sodium arsenate, and lead acetate generate oxidative stress by an imbalance between ROS production and scavenging, cadmium chloride causes an increase in the pH level of the luminal fluid (from 6.5 to 7.37) that diminishes sperm viability. Inorganic arsenic induced a delay in the sperm transit time by modulating noradrenaline and dopamine secretion. Subacute exposure to heavy metals at concentrations < 0.1 mg L^-1 initiates a dyshomeostasis of calcium, copper, iron, and zinc that disturbs sperm parameters and reduces epididymal weight. These alterations worsen with prolonged exposure time and higher doses. Most studies evaluated the effects of concentrations > 1.1 mg L^-1 of heavy metals on the epididymis rather than doses with relevant importance for human health risk. This meta-analytical study faced limitations regarding a deeper analysis of epididymis physiology. Hence, several recommendations for future investigations are provided. This review creates a baseline for the comprehension of epididymal toxicology.

Effects of Cadmium Exposure on Leydig Cells and Blood Vessels in Mouse Testis

Environmental exposure to cadmium (Cd) contributes to a decline in the quality of human semen. Although the testis is sensitive to Cd exposure, the mechanism underlying how cadmium affects the testis remains to be defined. In this study, male mice were treated with intraperitoneal injections of 0, 0.5, 1.5 and 2.5 mg CdCl₂/kg/day for 10 days, respectively. Both the testicular weight and the 3β-HSD activity of Leydig cells were significantly reduced with the administration of 2.5 mg CdCl₂/kg/day. The height of endothelial cells in the interstitial blood vessels significantly increased with the use of 2.5 mg CdCl₂/kg/day compared with the control. Western blot data showed that the protein levels of CD31, αSMA, caveolin and Ng2 increased with cadmium exposure, and this increase was particularly significant with the administration of 2.5 mg CdCl₂/kg/day. CD31, αSMA, caveolin and Ng2 are related to angiogenesis. Based on our data, cadmium exposure may stimulate the proliferation of the mural cells and endothelial cells of blood vessels, which may lead to abnormal function of the testis.