Cadmium Exposure and Testis Susceptibility: a Systematic Review in Murine Models

Cadmium exposure induces Leydig cell injury via necroptosis caused by oxidative stress and TNF-α/TNFR1 signaling

Cadmium, a ubiquitous environmental pollutant, has been linked to testicular damage, primarily through mechanisms such as oxidative stress and various forms of programmed cell death. Despite extensive studies on its toxic effects, the specific role of necroptosis in cadmium-induced reproductive toxicity remains unclear. In this study, we provide critical insights into how cadmium triggers necroptosis in Leydig cells, leading to testicular dysfunction. Using both in vitro and in vivo models, we demonstrated that cadmium exposure induces necroptotic cell death in Leydig cells, with significant involvement of the TNF-α/TNFR1 signaling pathway and reactive oxygen species (ROS) generation. Co-treatment with Nec-1, a specific necroptosis inhibitor, significantly reduced elevated ROS levels and suppressed TNF-α/TNFR1-induced necroptotic cell death, suggesting that ROS and the TNF-α/TNFR1 signaling pathway contribute to necroptosis activation in cadmium-induced Leydig cell injury. In conclusion, we demonstrate that necroptosis is a key driver of cadmium-induced testicular damage, suggesting that targeting necroptosis could offer novel therapeutic strategies for mitigating reproductive toxicity caused by heavy metals.

Comparative Evaluation of Levamisole and Broccoli in Mitigating Testicular Oxidative Stress and Apoptotic Alterations Caused by Cadmium and Lead Exposure in Rats

Considering the significance of heavy metals in infertility and their reduction through natural and synthetic compounds, a comparative study of broccoli and levamisole in cadmium and lead poisoning was conducted. Male Wistar rats (48 in total) were divided into 8 groups. Control, cadmium, lead, levamisole, and broccoli were administered individually to groups 1-5, while groups 6-8 received combinations. Various measurements were taken, including final weight, testicular weight, and the GSI coefficient. Sperm parameters, spermatogenesis cell count, oxidative stress biomarkers, and apoptosis indices were assessed using ELISA kits and methods in testicular tissue. The results indicated that the GSI coefficient was lowest in group 2 and highest in group 4, showing a significant difference (P < 0.001). Sperm concentration peaked in group 1 and broccoli-treated ones, while motility was highest in group 5. Testicular cell counts and Johnson score were highest in groups 1 and 2, and lowest in cadmium-exposed groups. These differences were statistically significant at P < 0.01. Enzyme activities related to oxidative stress varied. Group 2 exhibited the highest catalase (CAT) and superoxide dismutase (SOD) activities, while glutathione peroxidase (GPx) levels peaked in groups 1, 4, and 5. Malondialdehyde (MDA) concentrations were significantly reduced in the group 5 (P < 0.05). Apoptosis indices revealed that broccoli had the highest Bcl-2 levels and lowest Bax/Bcl-2 ratio, indicating its anti-apoptotic effect. Group 4 showed less efficacy compared to broccoli in protecting fertility indices. In conclusion, cadmium and lead significantly impact male fertility, while broccoli extract demonstrates promising efficacy in mitigating damage when compared to levamisole. This underscores its antioxidant and anti-apoptotic properties.

Revisiting cadmium-induced toxicity in the male reproductive system: an update

Heavy metals like cadmium (Cd) are one of the main environmental pollutants, with no biological role in the human body. Cd has been well-documented to have disastrous effects on both plants and animals. It is known to accumulate in kidneys, lungs, liver, and testes and is thought to affect these organs' function over time, which is linked to a very long biological half-life and a very poor rate of elimination. According to recent researches, the testes are extremely vulnerable to cadmium. The disruption of the blood-testis barrier, seminiferous tubules, Sertoli cells, and Leydig cells caused by cadmium leads to the loss of sperm through various mechanisms, such as oxidative stress, spermatogenic cell death, testicular swelling, dysfunction in androgen-producing cells, interference with gene regulation, disruption of ionic homeostasis, and damage to the vascular endothelium. Additionally, through epigenetic control, cadmium disrupts the function of germ cells and somatic cells, resulting in infertile or subfertile males. A full grasp of the mechanisms underlying testicular toxicity caused by Cd is very important to develop suitable strategies to ameliorate male fertility. Therefore, this review article outlines cadmium's impact on growth and functions of the testicles, reviews therapeutic approaches and protective mechanisms, considers recent research findings, and identifies future research directions.

Caffeic acid attenuates memory dysfunction and restores the altered activity of cholinergic, monoaminergic and purinergic in brain of cadmium chloride exposure rats

OBJECTIVES

This study aims to evaluate the neuroprotective effect of caffeic acid (CAF) against cadmium chloride (CdCl2) in rats via its effect on memory index as well as on altered enzymatic activity in the brain of CdCl2-induced neurotoxicity.

METHODS

The experimental rats were divided into seven groups (n=6 rats per group) of healthy rats (group 1), CdCl2 -induced (CD) (3 mg/kg BW) rats (group 2), CD rats + Vitamin C (group 3), CD rats + CAF (10 and 20 mg/kg BW respectively) (group 4 & 5), and healthy rat + CAF (10 and 20 mg/kg BW respectively) (group 6 & 7). Thereafter, CdCl2 and CAF were administered orally to the experimental rats in group 2 to group 5 on daily basis for 14 days. Then, the Y-maze test was performed on the experimental rats to ascertain their memory index.

RESULTS

CdCl2 administration significantly altered cognitive function, the activity of cholinesterase, monoamine oxidase, arginase, purinergic enzymes, nitric oxide (NOx), and antioxidant status of Cd rats (untreated) when compared with healthy rats. Thereafter, CD rats treated with vitamin C and CAF (10 and 20 mg/kg BW) respectively exhibited an improved cognitive function, and the observed altered activity of cholinesterase, monoamine oxidase, arginase, purinergic were restored when compared with untreated CD rats. Also, the level of brain NOx and antioxidant status were significantly (p<0.05) enhanced when compared with untreated CD rats. In the same vein, CAF administration offers neuro-protective effect in healthy rats vis-à-vis improved cognitive function, reduction in the activity of some enzymes linked to the progression of cognitive dysfunction, and improved antioxidant status when compared to healthy rats devoid of CAF.

CONCLUSIONS

This study demonstrated the neuroprotective effect of CAF against CdCl2 exposure and in healthy rats.

Molybdenum and cadmium co-induce apoptosis and ferroptosis through inhibiting Nrf2 signaling pathway in duck (Anas platyrhyncha) testes

Cadmium (Cd) and high molybdenum (Mo) are injurious to the body. Previous research has substantiated that Cd and Mo exposure caused testicular injury of ducks, but concrete mechanism is not fully clarified. To further survey the toxicity of co-exposure to Cd and Mo in testis, 40 healthy 8-day-old Shaoxing ducks (Anas platyrhyncha) were stochasticly distributed to 4 groups and raised with basic diet embracing Cd (4 mg/kg Cd) or Mo (100 mg/kg Mo) or both. At the 16th wk, testis tissues were gathered. The characteristic ultrastructural changes related to apoptosis and ferroptosis were observed in Mo or Cd or both groups. Besides, Mo or Cd or both repressed nuclear factor erythroid 2-related factor 2 (Nrf2) pathway via decreasing Nrf2, Heme oxygenase-1 (HO-1), NAD(P)H quinone oxidoreductase 1 (NQO1), Glutamate-cysteine ligase catalytic subunit (GCLC) and Glutamate-cysteine ligase modifier subunit (GCLM) mRNA expression of and Nrf2 protein expression, then stimulated apoptosis by elevating Bcl-2 antagonist/killer-1 (Bak-1), Bcl-2-associated X-protein (Bax), Cytochrome complex (Cyt-C), caspase-3 mRNA expression, cleaved-caspase-3 protein expression and apoptosis rate, as well as reducing B-cell lymphoma-2 (Bcl-2) mRNA expression and ratio of Bcl-2 to Bax, and triggered ferroptosis by upregulating Acyl-CoA Synthetase Long Chain Family Member 4 (ACSL4), transferrin receptor (TFR1) and Prostaglandin-Endoperoxide Synthase 2 (PTGS2) expression levels, and downregulating ferritin heavy chain 1 (FTH1), ferritin light chain 1 (FTL1), ferroportin 1 (FPN1), solute carrier family 7 member 11 (SCL7A11) and glutathione peroxidase 4 (GPX4) expression levels. The most obvious changes of these indexes were observed in co-treated group. Altogether, the results announced that Mo or Cd or both evoked apoptosis and ferroptosis by inhibiting Nrf2 pathway in the testis of ducks, and co-exposure to Mo and Cd exacerbated these variations.

Building an adverse outcome pathway network for estrogen-, androgen- and steroidogenesis-mediated reproductive toxicity

Introduction: Adverse Outcome Pathways (AOPs) can support both testing and assessment of endocrine disruptors (EDs). There is, however, a need for further development of the AOP framework to improve its applicability in a regulatory context. Here we have inventoried the AOP-wiki to identify all existing AOPs related to mammalian reproductive toxicity arising from disruption to the estrogen, androgen, and steroidogenesis modalities. Core key events (KEs) shared between relevant AOPs were also identified to aid in further AOP network (AOPN) development. Methods: A systematic approach using two different methods was applied to screen and search the entire AOP-wiki library. An AOPN was visualized using Cytoscape. Manual refinement was performed to remove AOPS devoid of any KEs and/or KERs. Results: Fifty-eight AOPs relevant for mammalian reproductive toxicity were originally identified, with 42 AOPs included in the final AOPN. Several of the KEs and KE relationships (KERs) described similar events and were thus merged to optimize AOPN construction. Sixteen sub-networks related to effects on hormone levels or hormone activity, cancer outcomes, male and female reproductive systems, and overall effects on fertility and reproduction were identified within the AOPN. Twenty-six KEs and 11 KERs were identified as core blocks of knowledge in the AOPN, of which 19 core KEs are already included as parameters in current OECD and US EPA test guidelines. Discussion: The AOPN highlights knowledge gaps that can be targeted for further development of a more complete AOPN that can support the identification and assessment of EDs.

Testicular Toxicity in Rats Exposed to AlCl3: a Proteomics Study

Aluminum contamination is a growing environmental and public health concern, and aluminum testicular toxicity has been reported in male rats; however, the underlying mechanisms of this toxicity are unclear. The objective of this study was to investigate the effects of exposure to aluminum chloride (AlCl3) on alterations in the levels of sex hormones (testosterone [T], luteinizing hormone [LH], and follicle-stimulating hormone [FSH]) and testicular damage. Additionally, the mechanisms of toxicity in the testes of AlCl3-exposed rats were analyzed by proteomics. Three different concentrations of AlCl3 were administered to rats. The results demonstrated a decrease in T, LH, and FSH levels with increasing concentrations of AlCl3 exposure. HE staining results revealed that the spermatogenic cells in the AlCl3-exposed rats were widened, disorganized, or absent, with increased severe tissue destruction at higher concentrations of AlCl3 exposure. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment analyses revealed that differentially expressed proteins (DEPs) after AlCl3 exposure were primarily associated with various metabolic processes, sperm fibrous sheath, calcium-dependent protein binding, oxidative phosphorylation, and ribosomes. Subsequently, DEPs from each group were subjected to protein-protein interaction (PPI) analysis followed by the screening of interactional key DEPs. Western blot experiments validated the proteomics data, revealing the downregulation of sperm-related DEPs (AKAP4, ODF1, and OAZ3) and upregulation of regulatory ribosome-associated protein (UBA52) and mitochondrial ribosomal protein (MRPL32). These findings provide a basis for studying the mechanism of testicular toxicity due to AlCl3 exposure.

Exploring the molecular and toxicological mechanism associated with interactions between heavy metals and the reproductive system of Mytilus galloprovincialis

A large number of heavy metals resulted toxic to the reproductive system, but invertebrate infertility has been poorly explored, and above all, there are limited molecular, cellular and toxicological studies. In the present work, we exposed Mytilus galloprovincialis to three individual metal chlorides (CuCl2 15 μM, CdCl2 1.5 μM, NiCl2 15 μM) and their mixture for 24 h, to evaluate the effects on the protamine-like proteins (PLs), sperm DNA and on their interaction in the formation of sperm chromatin. Under all exposure conditions, but particularly after exposure to the metals mix, relevant changes in the electrophoretic pattern, by AU-PAGE and SDS-PAGE, and in fluorescence spectroscopy measurements of PLs were shown. In addition, alterations in DNA binding of these proteins were observed by Electrophoretic Mobility Shift Assay (EMSA) and through their release from sperm nuclei. Moreover, there was evidence of increased accessibility of micrococcal nuclease to sperm chromatin, which was also confirmed by toluidine blue staining. Furthermore, morphological analyses indicated severe gonadal impairments which was also corroborated by increased PARP expression, by Western blotting, and sperm DNA fragmentation, by comet assay. Finally, we investigated the expression of stress genes, gst, hsp70 and mt10, in gonadal tissue. The latter investigations also showed that exposure to this metals mix was more harmful than exposure to the individual metals tested. The present results suggest that these metals and in particular their mixture could have a negative impact on the reproductive fitness of M. galloprovincialis. Based on these evidences, we propose a molecular mechanism.

Toxicology of arsenate, arsenite, cadmium, lead, chromium, and nickel in testes of adult Swiss mice after chronic exposure by intraperitoneal route

BACKGROUND

Some residues such as the heavy metals cadmium (Cd), lead (Pb), chromium (Cr VI), nickel (Ni), and arsenic (As), this last one in its oxidized forms + 5 (arsenate) and + 3 (arsenite), can cause injuries to human health, so they are currently considered environmental health emergencies. In the testis, heavy metals can cause morphological and functional damage due to constant exposure acting chronically in individuals. Thus, we aimed to determine the toxicological mechanism of As+5, As+3, Cd, Cr VI, and Ni that leads to testicular damage and establish for the first time an order of toxicity among these studied heavy metals.

METHODS

Forty-two Swiss mice at reproductive age (140 days) were used, randomly distributed into seven experimental groups (n = 6). Exposure to heavy metals was weekly performed, by intraperitoneal route. Group 1 received 0.7 mL 0.9% saline (control), and the other groups received 1.5 mg/ kg of As+5, As+3, Cd, Pb, Cr VI, or Ni, for six weeks.

RESULTS

These studied heavy metals did not accumulate in the testis tissue. However, exposure to Ni induced moderate pathologies in the seminiferous tubules, plus changes in the tunica propria, blood vessels, lymphatic space, and carbonyl protein levels. Cd exposure caused moderate tubular histopathologies and changes in the blood vessels and lymphatic space. Cr VI induced slight tubular histopathologies, changes in the lymphatic space, blood vessels, and SOD activity. Pb and As+3 exposure triggered moderate tubular pathologies and changes in the SOD activity and carbonyl protein levels, respectively. Finally, As+5 induced only slight tubular pathologies.

CONCLUSION

The testicular histopathologies caused by the studied heavy metals are mainly triggered by changes in testicular oxidative balance. Based on our findings of histomorphological alterations, the toxicity order among the heavy metals is Ni>Cd>Cr(VI)>PbAs+3 >As+5. However, considering oxidative stress results, we propose the following testicular toxicity order for these heavy metals: Ni>As+3 > Cd>Cr(VI)>Pb>As+5. Ni exposure shows the most harmful among the heavy metals to the testis.

Cadmium exposure-induced rat testicular dysfunction and its mechanism of chronic stress

Cadmium is a common environmental pollutant in daily life, the toxic mechanisms of chronic cadmium exposure on the testes have not been fully elucidated. This study aimed to explore the effects of cadmium exposure on male reproductive health and its mechanism. The results showed that cadmium exposure led widened interstitial spaces, abnormal seminiferous tubule morphology, and decreased Leydig cell numbers. Moreover, sperm quality was significantly reduced, along with a decrease in fertility rate. And cadmium exposure could activate the hypothalamic-pituitary-adrenal (HPA) axis, elevate blood glucocorticoid levels, subsequently increase glucocorticoid receptor (GR) expression and activation in testicular Leydig cells. Then GR act on the glucocorticoid receptor element (GRE) in the DNA methyltransferase 3 A (DNMT3A) promoter region and upregulate DNMT3A expression. Consequently, this led to an increase in DNA methylation levels in the angiotensin II receptor 2 (AT2R) promoter region, resulting in reduced AT2R expression and inhibiting testicular steroidogenesis. This study systematically elucidated that cadmium exposure could lead to testicular steroidogenesis suppression and decreased fertility through the GR/DNMT3A/AT2R signaling pathway. This research further provides theoretical and experimental evidence for confirming the threat of cadmium exposure to human reproduction, and contributes to the guidance and protection of male reproductive health.

Physiological response, microbial diversity characterization, and endophytic bacteria isolation of duckweed under cadmium stress

Duckweed is a cadmium (Cd) hyperaccumulator. However, its enrichment characteristics and physiological responses to Cd have not been systematically studied. The physiological responses, enrichment characteristics, diversity of endophytic bacterial communities, and isolation of Cd-resistant endophytes in duckweed (Lemna minor 0014) were studied for different durations and Cd concentrations. The results indicated that peroxidase (POD) and catalase (CAT) activities decreased while superoxide dismutase activity first increased and then decreased with increasing Cd stress duration. POD activities, CAT activities, and O2- increased as Cd concentrations increased. Malondialdehyde content and Cd accumulation in duckweed increased with increasing concentrations and time. This endophytic diversity study identified 488 operational taxonomic units, with the dominant groups being Proteobacteria, Firmicutes, and Actinobacteria. Paenibacillus sp. Y11, a strain tolerant to high concentrations of Cd and capable of significantly promoting duckweed growth, was isolated from the plant. Our study revealed the effects of heavy metals on aquatic plants, providing a theoretical basis for the application of duckweed in water pollution.

Comparative effects of finasteride and minoxidil on the male reproductive organs: A systematic review of in vitro and in vivo evidence

Finasteride and minoxidil are medicaments commonly prescribed for treating benign prostatic hyperplasia (BPA), hypertension, and/or androgenetic alopecia (AGA). The mechanism of action of finasteride is based on the interference in androgenic pathways, which may lead to fertility-related disorders in men. Minoxidil, however, can act in multiple ways, and there is no consensus that its use can adversely affect male fertility. Since finasteride and minoxidil could be risk factors for male fertility, we aimed to compare their impact on the two reproductive organs testis and epididymis of adult murine models, besides testis/epididymis-related cells, and describe the mechanism of action involved. For such, we used the PRISMA guideline. We included 31 original studies from a structured search on PubMed/MEDLINE, Scopus, and Web of Science databases. For in vivo studies, the bias analysis and the quality of the studies were assessed as described by SYRCLE (Systematic Review Centre for Laboratory Animal Experimentation). We concluded that finasteride and minoxidil act as hormone disruptors, causing oxidative stress and morphological changes mainly in the testis. Our results also revealed that finasteride treatment could be more harmful to male reproductive health because it was more associated with reproductive injuries, including damage to the epididymis, erectile dysfunction, decreased libido, and reduced semen volume. Thus, this study contributes to the global understanding of the mechanisms by which medicaments used for alopecia might lead to male reproductive disorders. We hope that our critical analysis expedites clinical research and reduces methodological bias. The registration number on the Prospero platform is CRD42022313347.

Silymarin modulates cadmium-induced oxidative stress in human spermatozoa

Environmental pollutants such as cadmium can negatively affect sperm parameters and decrease male fertility by inducing oxidative stress. Antioxidants are considered a useful strategy for oxidative stress conditions to neutralize free radicals and strengthen the antioxidant defence system. In this study, the effects of the common application of silymarin, as a natural antioxidant, with cadmium were assessed on human sperm. The washed human sperm samples were divided into five groups: (1) spermatozoa at 0- hour; (2) spermatozoa at 3 h; (3) spermatozoa treated with cadmium (20 μM) for 3 h; (4) spermatozoa treated with silymarin (2 μM) + cadmium (20 μM) for 3 h and (5) spermatozoa treated with silymarin (2 μM) for 3 h. Our results displayed that cadmium reduced sperm motility, viability, plasma membrane integrity and acrosome integrity by increasing malondialdehyde levels and decreasing the total antioxidant capacity and antioxidant enzymes activity. While silymarin attenuated oxidative stress biomarkers in human sperm treated with cadmium, and consequently improved the sperm quality. In summary, cadmium-induced oxidative stress impaired human sperm structures and silymarin with its antioxidant properties compensated for the adverse effects of oxidative stress on human spermatozoa.

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.

Aqueous-alcoholic Ferulla extract reduces memory impairments in rats exposed to cadmium chloride

INTRODUCTION

Cadmium (Cd) is the most dangerous heavy metal that is becoming more widespread in nature as a result of industrial activities. One of the toxic effects of Cd on the body is its neurological effect. The mechanism of these effects has been attributed to the induction of oxidative stress. Ferulla plant has antioxidant properties. In the present study, the aim was to reduce the toxic effects of Cd on memory impairment in rats by through the consumption of Ferulla extract.

MATERIALS & METHOD

Rats were randomly divided into five groups of six: (1) control group, (2) 300 μM cadmium exposure group, and three treatment groups with doses of (3) 100, (4) 300, and (5) 600 mg/kg.BW of F. Ferulla extract after Cd exposure. To induce neurotoxicity, Cd was daily injected peritoneally at a concentration of 300 μM in 1 ml of normal saline for a week. Next, for 3 weeks, the Cd group received 1 ml of normal peritoneal saline, and the treatment groups received F. Ferulla extract at concentrations of 100, 300, and 600 mg/kg.BW in 1 ml of normal saline daily for a week. At the end of the treatment period, a water maze was used to assess memory disorders. Malondialdehyde (MDA), glutathione concentration (GSH), and glutathione peroxidase (GPX) activity in nerve tissue were also measured. Morris water maze was also performed after intervention.

RESULTS

Cd-induced neurotoxicity was shown in Cd groups. MDA, GSH, and GPX have a significant difference in comparison between the Cd and 300, 600 treated groups. MDA has a significant increase (p < 0.05), and GSH and GPX have a significant decrease (p < 0.05). The results of the Morris water maze showed that the Cd group spent either 300 or 600 more distances and time to find a place to escape, which was significant (p < 0.05) CONCLUSION: Cd exposure can induce neurotoxicity and disrupt learning and memory. On the other hand, Ferulla extract can improve learning and memory in Cd-induced neurotoxicity model via induced antioxidant defense system.