Involvement of selenoprotein P and GPx4 gene expression in cadmium-induced testicular pathophysiology in rat

Cadmium exposure induced neuronal ferroptosis and cognitive deficits via the mtROS-ferritinophagy pathway

Exposure to environmental cadmium (Cd) is known to cause neuronal death and cognitive decline in humans. Ferroptosis, a novel iron-dependent type of regulated cell death, is involved in various neurological disorders. In the present study, Cd exposure triggered ferroptosis in the mouse hippocampus and in the HT22 murine hippocampal neuronal cell line, as indicated by significant increases in ferroptotic marker expression, intracellular iron levels, and lipid peroxidation. Interestingly, ferroptosis of hippocampal neurons in response to Cd exposure relied on the induction of autophagy since the suppression of autophagy by 3-methyladenine (3-MA) and chloroquine (CQ) substantially ameliorated Cd-induced ferroptosis. Furthermore, nuclear receptor coactivator 4 (NCOA4)-mediated degradation of ferritin was required for the Cd-induced ferroptosis of hippocampal neurons, demonstrating that NCOA4 knockdown decreased intracellular iron levels and lipid peroxidation and increased cell survival, following Cd exposure. Moreover, Cd-induced mitochondrial reactive oxygen species (mtROS) generation was essential for the ferritinophagy-mediated ferroptosis of hippocampal neurons. Importantly, pretreatment with the ferroptosis inhibitor ferrostatin-1 (Fer-1) effectively attenuated Cd-induced hippocampal neuronal death and cognitive impairment in mice. Taken together, these findings indicate that ferroptosis is a novel mechanism underlying Cd-induced neurotoxicity and cognitive impairment and that the mtROS-ferritinophagy axis modulates Cd-induced neuronal ferroptosis.

Protective effects and mechanism of chemical- and plant-based selenocystine against cadmium-induced liver damage

Although selenium (Se) and cadmium (Cd) often coexist naturally in the soil of China, the health risks to local residents consuming Se-Cd co-enriched foods are unknown. In the present study, we investigated the effects of chemical-based selenocystine (SeCys2) on cadmium chloride-induced human hepatocarcinoma (HepG2) cell injury and plant (Cardamine hupingshanensis)-derived SeCys2 against Cd-induced liver injury in mice. We found that chemical- and plant-based SeCys2 showed protective effects against Cd-induced HepG2 cell injury and liver damage in mice, respectively. Compared with Cd intervention group, co-treatment with chemical- or plant-based SeCys2 both alleviated liver toxicity and ferroptosis by decreasing ferrous iron, acyl-CoA synthetase long-chain (ACSL) family member 4, lysophosphatidylcholine acyltransferase 3, reactive oxygen species and lipid peroxide levels, and increasing ACSL3, peroxisome proliferator-activated receptor α, solute carrier family 7 member 11 (SLC7A11) and glutathione and glutathione peroxidase 4 (GPX4) levels. In conclusion, chemical- and plant-based SeCys2 alleviated Cd-induced hepatotoxicity and ferroptosis by regulating SLC7A11/GPX4 signaling and lipid peroxidation. Our findings indicate that potential Cd toxicity from consuming foods grown in Se- and Cd-rich soils should be re-evaluated. This study offers a new perspective for the development of SeCys2-enriched agricultural products.

Selenomethionine alleviates decabromodiphenyl ether-induced oxidative stress and ferroptosis via the NRF2/GPX4 pathway in the chicken brain

Decabromodiphenyl ether (BDE209) is a toxic environmental pollutant that can cause neurotoxicity, behavioral abnormalities, and cognitive impairment in animals. However, the specific mechanisms of BDE209-induced neurological injury and effective preventative and therapeutic interventions are lacking. Even though selenomethionine (Se-Met) has a significant detoxification effect and protects the nervous system, it remains unclear whether Se-Met can counteract the toxic effects of BDE209. For the in vivo test, we randomly divided 60 1-week-old hy-line white variety chicks into the Con, BDE209, Se-Met, and BDE209 +Se-Met groups. In vitro experiments were performed, exposing chick embryo brain neurons to BDE209, Se-Met, N-Acetylcysteine (NAC, a ROS inhibitor), and RSL3 (a GPX4 inhibitor). We demonstrated that BDE209 induced oxidative stress and ferroptosis in the chicken brain, which mainly manifested as mitochondrial atrophy, cristae breakage, increased Fe2+ and MDA content, decreased antioxidant enzyme activity, and the inhibition of the NRF2/GPX4 signaling pathway in the brain neurons. However, Se-Met supplementation reversed these changes by activating the NRF2/GPX4 pathway, reducing mitochondrial damage, enhancing antioxidant enzyme activity, and alleviating ferroptosis. This study provides insight into the mechanism of BDE209-related neurotoxicity and suggests Se-Met as an effective preventative and control measure against BDE209 poisoning.

Molecular mechanism of selenium against lead-induced apoptosis in chicken brainstem relating to heat shock protein, selenoproteins, and inflammatory cytokines

Extensive application of lead (Pb) brought about environmental pollution and toxic reactions of organisms. Selenium (Se) has the effect of antagonizing Pb poisoning in humans and animals. However, it is still unclear how Pb causes brainstem toxicity. In the present study, we wanted to investigate whether Se can alleviate Pb toxicity in chicken brainstems by reducing apoptosis. One hundred and eighty chickens were randomly divided into four groups, namely the control group, the Se group, the Pb group, and the Se/Pb group. Morphological examination, ultrastructural observation, relative mRNA expressions of genes on heat shock proteins (HSPs); selenoproteins; inflammatory cytokines; and apoptosis-related factors were investigated. The results showed that Pb exposure led to tissue damage and apoptosis in chicken brainstems. Furthermore, an atypical expression of HSPs (HSP27, HSP40, HSP60, HSP70, and HSP90); selenoprotein family glutathione peroxidase (GPx) 1, GPx2, GPx3, and GPx4), thioredoxin reductases (Txnrd) (Txnrd1, Txnrd2, and Txnrd3), dio selenoprotein famliy (diodothyronine deiodinases (Dio)1, Dio2, and Dio3), as well as other selenoproteins (selenoprotein (Sel)T, SelK, SelS, SelH, SelM, SelU, SelI, SelO, Selpb, selenoprotein n1 (Sepn1), Sepp1, Sepx1, Sepw1, 15-kDa selenoprotein (Sep15), and selenophosphate synthetases 2 (SPS2)); inflammatory cytokines (Interleukin 2 (IL-2), IL-4, IL-6, IL-12β, IL-17, and Interferon-γ (IFN-γ)); and apoptosis-related genes (B-cell lymphoma-2 (Bcl-2), tumor protein 53 (p53), Bcl-2 Associated X (Bax), Cytochrome c (Cyt c), and Caspase-3) were identified. An inflammatory reaction and apoptosis were induced in chicken brainstems after exposure to Pb. Se alleviated the abnormal expression of HSPs, selenoproteins, inflammatory cytokines, and apoptosis in brainstem tissues of chickens treated with Pb. The results indicated that HSPs, selenoproteins, inflammatory, and apoptosis were involved in Se-resisted Pb poisoning. Overall, Se had resistance effect against Pb poisoning, and can be act as an antidote for Pb poisoning in animals.

Exploring the association between two groups of metals with potentially opposing renal effects and renal function in middle-aged and older adults: Evidence from an explainable machine learning method

BACKGROUND

Machine learning models have promising applications in capturing the complex relationship between mixtures of exposures and outcomes.

OBJECTIVE

Our study aimed at introducing an explainable machine learning (EML) model to assess the association between metal mixtures with potentially opposing renal effects and renal function in middle-aged and older adults.

METHODS

This study extracted data from two cycle years of the National Health and Nutrition Examination Survey (NHANES). Participants aged 45 years or older with complete data on six metals (lead, cadmium, manganese, mercury, and selenium) and related covariates were enrolled. The EML model was developed by the optimized machine learning model together with Shapley Additive exPlanations (SHAP) to assess the chronic kidney disease (CKD) risk with metal mixtures. The results from EML were further compared in detail with multiple logistic regression (MLR) and Bayesian kernel machine regression (BKMR).

RESULTS

After adjusting for included covariates, MLR pointed out the lead and arsenic were generally positively associated with CKD, but manganese had a negative association. In the BKMR analysis, each metal was found to have a non-linear association with the risk of CKD, and interactions can exist between metals, especially for arsenic and lead. The EML ranked the feature importance: lead, manganese, arsenic and selenium were close behind in importance after gender, age or BMI for participants with CKD. Strong interactions between mercury and lead, manganese and cadmium and arsenic and manganese were identified by partial dependence plot (PDP) of SHAP and bivariate exposure-response effect plots of BKMR. The EML model determined the "trigger point" at which the risk of CKD abruptly changed.

CONCLUSION

Co-exposure to metals with different nephrotoxicity could have different joint association with renal function, and EML can be a powerful method for studying complex exposure mixtures.

GPX4 utilization by selenium is required to alleviate cadmium-induced ferroptosis and pyroptosis in sheep kidney

Cadmium (Cd), a persistent and harmful heavy metal in the environment, can accumulate in the kidneys and cause nephrotoxicity. Selenium (Se) is a beneficial natural element that alleviates the toxicity of Cd. To ascertain the relationship between the protective mechanism of Se against Cd nephrotoxicity and ferroptosis and pyroptosis, we randomly divided 48 sheep into four groups and treated them with Cd chloride and/or sodium selenite for 50 days. The data confirmed that Cd apparently resulted in impaired kidney histology and function, depletion of GSH and nicotinamide adenine dinucleotide phosphate contents and CAT and SOD activities, elevation of MDA level, as well as the reduction in selenoprotein mRNA (GPX1, GPX4, TXNRD1, SELP) levels and GPX4 protein level and immunofluorescence intensity. Meanwhile, Cd induced ferroptosis by causing iron overload, up-regulating PTGS2, NCOA4, TFR1, and LC3B mRNA levels and PTGS2 and LC3B-II/LC3B-I protein levels, reducing SLC7A11 and FTH1 mRNA and protein levels, and enhancing the immunofluorescence co-localization of FTH1/LC3B. Moreover, it was also found that Cd triggered pyroptosis, which was evidenced by the increase of NLRP3 immunohistochemical positive signal, GSDMD-N immunofluorescence intensity, IL-1β and IL-18 release and the levels of pyroptosis-related mRNA (NLRP3, ASC, Caspase-1, GSDMD, IL-1β and IL-18) and proteins (NLRP3, Caspase-1p20, GSDMD-N, IL-1β and IL-18). Notably, Se increased the expression level of GPX4 and the transcription factors TFAP2c and SP1, and ameliorated Cd-induced changes in aforementioned factors. In conclusion, GPX4 utilization by Se might be required to alleviate Cd-induced ferroptosis and pyroptosis in sheep kidney.

Ferroptosis as a mechanism of non-ferrous metal toxicity

Ferroptosis is a recently discovered form of regulated cell death, implicated in multiple pathologies. Given that the toxicity elicited by some metals is linked to alterations in iron metabolism and induction of oxidative stress and lipid peroxidation, ferroptosis might be involved in such toxicity. Although direct evidence is insufficient, certain pioneering studies have demonstrated a crosstalk between metal toxicity and ferroptosis. Specifically, the mechanisms underlying metal-induced ferroptosis include induction of ferritinophagy, increased DMT-1 and TfR cellular iron uptake, mitochondrial dysfunction and mitochondrial reactive oxygen species (mitoROS) generation, inhibition of Xc-system and glutathione peroxidase 4 (GPX4) activity, altogether resulting in oxidative stress and lipid peroxidation. In addition, there is direct evidence of the role of ferroptosis in the toxicity of arsenic, cadmium, zinc, manganese, copper, and aluminum exposure. In contrast, findings on the impact of cobalt and nickel on ferroptosis are scant and nearly lacking altogether for mercury and especially lead. Other gaps in the field include limited studies on the role of metal speciation in ferroptosis and the critical cellular targets. Although further detailed studies are required, it seems reasonable to propose even at this early stage that ferroptosis may play a significant role in metal toxicity, and its modulation may be considered as a potential therapeutic tool for the amelioration of metal toxicity.

Phytomedicinal therapeutics for male infertility: critical insights and scientific updates

Infertility is a significant cause of anxiety, depression, and social stigma among couples and families. In such cases, male reproductive factors contribute widely to the extent of 20-70%. Male infertility is a multifactorial disease with several complications contributing to its diagnosis. Although its management encompasses both modern and traditional medicine arenas, the first line of treatment, adopted by most males, focuses on the reasonably successful medicinal plant-based conventional therapies. Phyto-therapeutics, which relies on active ingredients from traditionally known herbs, influences sexual behavior and male fertility factors. The potency of these phyto-actives depends on their preparation methods and forms of consumption, including decoctions, extracts, semi-purified compounds, etc., as inferred from in vitro and in vivo (laboratory animal models and human) studies. The mechanisms of action therein involve the testosterone pathway for stimulation of spermatogenesis, reduction of oxidative stress, inhibition of inflammation, activation of signaling pathways in the testes [extracellular-regulated kinase (ERK)/protein kinase B(PKB)/transformation of growth factor-beta 1(TGF-β1)/nuclear factor kappa-light-chain-enhancer of activated B cells NF-kB signaling pathways] and mediation of sexual behavior. This review critically focuses on the medicinal plants and their potent actives, along with the biochemical and molecular mechanisms that modulate vital pathways associated with the successful management of male infertility. Such intrinsic knowledge will significantly further studies on medicinal plants that improve male reproductive health.

Antagonistic Interaction of Selenium and Cadmium in Human Hepatic Cells Through Selenoproteins

Cadmium (Cd) is a highly toxic heavy metal for humans and animals, which is associated with acute hepatotoxicity. Selenium (Se) confers protection against Cd-induced toxicity in cells, diminishing the levels of ROS and increasing the activity of antioxidant selenoproteins such as glutathione peroxidase (GPx). The aim of this study was to evaluate the antagonistic effect of selenomethionine (SeMet) against Cd toxicity in HepG2 cells, through the modulation of selenoproteins. To this end, the cells were cultured in the presence of 100 µM SeMet and 5 μM, 15 µM, and 25 µM CdCl₂ and a combination of both species for 24 h. At the end of the experiment, cell viability was determined by MTT assay. The total metal content of Cd and Se was analyzed by triple-quadrupole inductively coupled plasma–mass spectrometry (ICP-QqQ-MS). To quantify the concentration of three selenoproteins [GPx, selenoprotein P (SELENOP), and selenoalbumin (SeAlb)] and selenometabolites, an analytical methodology based on column switching and a species-unspecific isotopic dilution approach using two-dimensional size exclusion and affinity chromatography coupled to ICP-QqQ-MS was applied. The co-exposure of SeMet and Cd in HepG2 cells enhanced the cell viability and diminished the Cd accumulation in cells. Se supplementation increased the levels of selenometabolites, GPx, SELENOP, and SeAlb; however, the presence of Cd resulted in a significant diminution of selenometabolites and SELENOP. These results suggested that SeMet may affect the accumulation of Cd in cells, as well as the suppression of selenoprotein synthesis induced by Cd.

Selenium supplementation influences mice testicular selenoproteins driven by gut microbiota

Selenium is a well-known essential element with important roles in human reproductive health mainly due to its antioxidant character. This study aimed to investigate the potential role of selenoproteins on gut microbiota and male reproductive health. A new assay for the absolute quantification of selenoproteins in testicular tissue based on two dimensional chromatography with inductively coupled plasma mass spectrometry was performed for the first time. The gut microbiota profile was obtained by 16S rRNA gene sequencing. Numerous associations were found between testicular selenoproteins and gut microbiota (e.g. Mucispirillum, related with sperm activity and testosterone, was associated with glutathione peroxidase (GPx) and selenoalbumin (SeAlb), while Escherichia/Shigella, related to sex hormones, correlated with GPx, selenoprotein P (SelP) and SeAlb). The effects of Se-supplementation on testicular selenoproteins only occur in conventional mice, suggesting a potential selenoproteins-microbiota interplay that underlies testicular function. The selenoproteins GPx and SelP have been quantified for the first time in the testicles, and the novel identification of SeAlb, a protein with nonspecifically incorporated Se, is also reported. These findings demonstrate the significant impact of Se-supplementation on gut microbiota and male reproductive health. In addition, the analytical methodology applied here in selenoprotein quantification in testicular tissue opens new possibilities to evaluate their role in gut microbiota and reproductive health axis.

Cadmium induced cerebral toxicity via modulating MTF1-MTs regulatory axis

Metal-responsive transcription factor 1 (MTF1) participates in redox homeostasis and heavy metals detoxification via regulating the expression of metal responsive genes. However, the exact role of MTF1 in Cd-induced cerebral toxicity remains unclear. Herein, we explored the mechanism of Cd-elicited cerebral toxicity through modulating MTF1/MTs pathway in chicken cerebrum exposed to different concentrations of Cd (35 mg, 70 mg, and 140 mg/kg CdCl₂) via diet. Notably, cerebral tissues showed varying degrees of microstructural changes under Cd exposure. Cd exposure significantly up-regulated the expression of metal transporters (DMT1, ZIP8, and ZIP10) with concomitant elevated Cd level, as determined by ICP-MS. Cd significantly altered other cerebral biometals concentrations (particularly, Zn, Fe, Se, Cr, Mo, and Pb) and redox balance, resulting in increased cerebral oxidative stress. More importantly, Cd exposure suppressed MTF1 mRNA and nuclear protein levels and its target metal-responsive genes, notably metallothioneins (MT1 and MT2), and Fe and Cu transporter genes (FPN1, ATOX1, and XIAP). Moreover, Cd disrupted the regulation of expression of selenoproteome (particularly, GPxs and SelW), and cerebral Se level. Overall, our data revealed that molecular mechanisms associated with Cd-induced cerebral damage might include over-expression of DMT1, ZIP8 and ZIP10, and suppression of MTF1 and its main target metal-responsive genes as well as several selenoproteins.

Comprehensive Review of Cadmium Toxicity Mechanisms in Male Reproduction and Therapeutic Strategies

Cadmium (Cd) has been widely studied as an environmental pollutant for many years. Numerous studies have reported that Cd exposure causes damage to the heart, liver, kidneys, and thyroid in vivo. The emerging evidence suggests that Cd exposure induces damage on male reproductive system, which is related to oxidative stress, inflammation, steroidogenesis disruption, and epigenetics. Current preclinical animal studies have confirmed a large number of proteins and intracellular signaling pathways involved in the pathological process of Cd-induced male reproductive damage and potential measures for prophylaxis and treatment, which primarily include antioxidants, anti-inflammatory agents, and essential ion supplement. However, explicit pathogenesis and effective treatments remain uncertain. This review collects data from the literatures, discusses the underlying mechanisms of Cd-induced toxicity on male reproductive function, and summarizes evidence that may provide guidance for the treatment and prevention of Cd-induced male reproductive toxicity.

Selenium sources differ in their potential to alleviate the cadmium-induced testicular dysfunction

Cadmium (Cd), a major environmental contaminant, is closely associated with male reproductive health. Selenium (Se) has been recognized as an effective chemo-protectant against Cd toxicity, but the underlying mechanisms remain unclear. The objective of present study was to illustrate the toxic effect of Cd on testis, and then compare the antagonistic effect among different Se sources on growth performance, testicular damage, ion homeostasis, antioxidative potential, and the expression of selenotranscriptome and biosynthetic related factors in Cd-treated chicken. Male chickens were fed with (Ⅰ) Control group: basal diet; (Ⅱ) Cd group: basal diet with 140 mg/kg CdCl₂; (Ⅲ) YSe + Cd group: basal diet with 140 mg/kg CdCl₂ and 3 mg/kg Yeast-Se; (Ⅳ) NSe + Cd group: basal diet with 140 mg/kg CdCl₂ and 1 mg/kg Nano-Se; (Ⅴ) SSe + Cd group: basal diet with 140 mg/kg CdCl₂ and 3 mg/kg Na₂SeO₃. It was observed that different Se treatments dramatically alleviated Cd-induced testicular developmental disorder, ion homeostasis disorder, hormone secretion disorder and oxidative stress. Simultaneously, Se mitigated Cd-induced testicular toxicity by regulating selenoprotein biosynthetic related factors to promote selenoprotein transcription. Finally, this study indicated that dietary supplementation of Yeast-Se produced an acceptable Se form to protect testis from Cd exposure.

Novel TrxR1 Inhibitors Show Potential for Glioma Treatment by Suppressing the Invasion and Sensitizing Glioma Cells to Chemotherapy

Currently, available glioblastoma (GBM) treatment remains ineffective, with relapse after initial response and low survival rate of GBM patients. The reasons behind limited capacities for GBM treatment are high tumor heterogeneity, invasiveness, and occurrence of drug resistance. Therefore, developing novel therapeutic strategies is of utmost importance. Thioredoxin reductase (TrxR) is a novel, promising target due to its overexpression in many cancer types and important role in cancer progression. Previous research on Ugi-type Michael acceptors–inhibitors of TrxR showed desirable anticancer properties, with significant selectivity toward cancer cells. Herein, two TrxR inhibitors, 5 and 6, underwent in-depth study on multidrug-resistant (MDR) glioma cell lines. Besides the antioxidative effects, 5 and 6 induced cell death, decreased cell proliferation, and suppressed invasion and migration of glioma cells. Both compounds showed a synergistic effect in combination with temozolomide (TMZ), a first-line chemotherapeutic for GBM treatment. Moreover, 5 and 6 affected activity of P-glycoprotein extrusion pump that could be found in cancer cells and in the blood–brain barrier (BBB), thus showing potential for suppressing MDR phenotype in cancer cells and evading BBB. In conclusion, investigated TrxR inhibitors are effective anticancer compounds, acting through inhibition of the thioredoxin system and perturbation of antioxidative defense systems of glioma cells. They are suitable for combining with other chemotherapeutics, able to surpass the BBB and overcome MDR. Thus, our findings suggest further exploration of Ugi-type Michael acceptors–TrxR inhibitors’ potential as an adjuvant therapy for GBM treatment.

Comparative effects of nano-selenium and sodium selenite supplementations on fertility in aged broiler breeder males

It is well documented that aging has negative effects on fertility. With increasing age, the activity of antioxidant enzymes are reduced and because of roosters sperm composition, a high proportion of polyunsaturated fatty acids (PUFAs), the probability of sperm damage increases. The objective of the present study was to compare the effects of nano-selenium and sodium selenite on fertility in aged male broiler breeder chickens. Thirty-five male broiler breeders (Cobb 500)® at 50 weeks of age were randomly divided into five equal groups: The control group was fed on a commercial diet, group T1 was fed on a commercial diet supplemented with sodium selenite (0.30 mg kg-1 feed), group T2, T3 and T4 were fed on a commercial diet supplemented with nano-selenium (0.15, 0.30 and 0.60 mg kg-1 feed, respectively). Sperm characteristics (sperm count, motility, viability, and maturity) as well as testicular histomorphometric features [tubule differentiation (TDI), spermiation (SPI), Sertoli cell (SCI) and meiotic (MI) indices] were assessed. The results showed that sperm characteristics were gradually decreased with age in the control group, however, it increased in group T3. Also, TDI, SPI, SCI, and MI in group T3 were higher than those of other groups. Our findings revealed that dietary supplementations with nano-selenium boosted fertility in aged male broiler breeders and the best results were obtained when the roosters received 0.30 mg kg-1 nano-selenium. Supplementation of nano-selenium in aged broiler breeder males might be effective to maintain flock fertility and/or increase the flock fertility.

Selenium prevent cadmium-induced hepatotoxicity through modulation of endoplasmic reticulum-resident selenoproteins and attenuation of endoplasmic reticulum stress

Cadmium (Cd), a heavy metal contaminant, exists in humans and animals throughout life and closely associate with severe hepatotoxicity. Selenium (Se) has been recognized as an effective chemo-protectant of Cd, but the underlying mechanisms remain unclear. The objective of the present study is to illustrate the antagonistic effect of Se against Cd-induced hepatotoxicity. Primary hepatocytes were cultured in the presence of 5 μM Cd, 1 μM Se and the mixture of 1 μM Se and 5 μM Cd for 24 h. Cell viability and morphology, antioxidant status, endoplasmic reticulum (ER) stress response and selenotranscriptome were assessed. It was observed that Se treatment dramatically alleviated Cd-induced hepatocytes death and morphological change. Simultaneously, Se mitigated Cd-induced oxidative stress by reducing ROS production, increasing reduced glutathione (GSH) level and increasing selenoenzyme (glutathione peroxidase, GPX) activity. Cd induced hepatotoxicity via disordering ER-resident selenoproteins transcription and triggering ER stress and unfolded protein response. Supplementary Se evidently relieved hepatocytes injury via modulating ER-resident selenoproteins transcription to inhibit ER stress. Collectively, our findings showed a potential protection of Se against Cd-induced hepatotoxicity via suppressing ER stress response.

Cadmium and Lead Hazardous Impact Assessment of Pond Fish Species

The current study aims to assess the concentration of cadmium (Cd) and lead (Pb) in five tissues of Cirrhinus mrigala, Labeo rohita, and Catla catla collected from fishponds of Jamshoro and Larkana, Sindh, Pakistan. Meanwhile, the levels of Cd and Pb in feeding materials, water, and sediments of fishponds of both areas were also studied. The daily intake and hazardous impact assessment of Cd and Pb by muscles of three fish species of fishponds of both areas were estimated. The concentration of Cd in tissues of C. mrigala and C. catla of Larkana were higher than that in tissues of same fish species of Jamshoro whilst Pb contents in tissues of fishes of Jamshoro were high (p > 0.05). The feeding materials of fishponds of Larkana were enriched with Cd whilst Pb was high in feeding material of fishponds of Jamshoro. The estimated bioaccumulation factor, average daily intake, and hazardous quotient of Pb were high as compared to Cd in all studied fish species of fishponds of Larkana and Jamshoro. The hazardous quotient of Pb indicated that the local population of both areas might have a potential toxic risk. Graphical abstract ᅟ.

Selenoprotein-U (SelU) knockdown triggers autophagy through PI3K-Akt-mTOR pathway inhibition in rooster Sertoli cells

Selenium (Se) is a major component of male reproduction which exerts its effects via selenoproteins. Selenoprotein U (SelU), a newly identified protein, is expressed highly in eukaryotes and possesses a conserved motif similar to that existing in other thiol-dependent redox regulating selenoproteins; however its function is unknown. To investigate the role of SelU in testis autophagic and/or apoptosis cell death mechanisms, we established a Sertoli cell (SC) model isolated from 45 day old layer roosters. Small interfering RNA (siRNA) technology was used to develop SelU-knockdown (SelU-KD) and normal (N) SC models. Consequent to transfection, electron microscopy, qPCR, and western blot were performed. The results show that the mRNA and proteins of autophagy and anti-apoptosis genes increased while that of anti-autophagic mammalian target of rapamycin (mTOR) and pro-apoptosis genes decreased significantly in SelU-KD in contrast to N cells. Simultaneously, in contrast to N cells the expression of phosphoinositide-3-kinase (PI3K) and protein kinase B (PKB/Akt) both at the mRNA and protein levels decreased significantly in SelU-KD cells. In-addition, SelU depletion altered the expression of regulatory factors and increased the mRNA of TSC (tuberous sclerosis complex) genes as compared to N cells. Extensive autophagosome formation and lysosome degradation with an intact cytoskeleton were observed in SelU-KD cells. Our data indicate that SelU deprivation elicits autophagy and reduces the expression of important growth factors in SCs by disrupting the PI3K-Akt-mTOR signaling pathway. However SelU attenuation did not induce apoptosis in rooster SCs. Taken together, we conclude that SelU is essential for the survival and normal functioning of SCs.

The association between plasma selenium and chronic kidney disease related to lead, cadmium and arsenic exposure in a Taiwanese population

This study aimed to determine the interaction of red blood cell cadmium and lead, total urinary arsenic, and plasma selenium in chronic kidney disease (CKD). We recruited 220 CKD patients as well as 438 gender- and age-matched controls, and we defined CKD as <60 mL/min/1.73 m² estimated glomerular filtration rate (eGFR) for three or more consecutive months. Plasma selenium and red blood cell cadmium and lead concentrations were measured by ICP-MS. Urinary arsenic species were determined via HPLC-HG-AAS and were summed to determine the total urinary arsenic concentration. Plasma selenium was positively correlated to eGFR, and subjects with high plasma selenium levels (>243.90 μg/L) had a significantly lower odds ratio (OR) and 95% confidence interval (CI) (0.23, 0.13-0.42) for CKD compared to those with low plasma selenium levels (≤ 196.70 μg/L). High plasma selenium and low red blood cell cadmium or lead concentrations interacted to decrease the OR and 95% CI for CKD (0.12, 0.06-0.26; 0.09, 0.04-0.19). High plasma selenium and low red blood cell lead levels also interacted to increase the eGFR (20.70, 15.56-26.01 mL/min/1.73 m²). This study is the first to suggest that selenium modifies the eGFR and OR in CKD induced by environmental toxicants.

Avian Stress-Related Transcriptome and Selenotranscriptome: Role during Exposure to Heavy Metals and Heat Stress

Selenium, through incorporation into selenoproteins, is one of the key elements of the antioxidant system. Over the past few years there has been increased interest in exploring those molecular mechanisms in chicken, responsible for the development of this protection system. In more detail, Cd/Pb poisoning and heat stress increase oxidation, mRNA levels of inflammatory proteins, and apoptotic proteins. Selenium seems to enhance the antioxidant status and alleviates these effects via upregulation of antioxidant proteins and other molecular effects. In this review, we analyze avian transcriptome key elements with particular emphasis on interactions with heavy metals and on relation to heat stress.

Effects of Selenium and Cadmium on Breast Muscle Fatty-Acid Composition and Gene Expression of Liver Antioxidant Proteins in Broilers

The present work was part of a project intended to evaluate whether organic selenium (Se) has the potential to protect against toxic effects exerted by cadmium (Cd). For this reason, 300 as-hatched, one-day-old broiler chickens were randomly allocated in four dietary treatments with five replicate pens per treatment. Chickens in T1 treatment, were offered a diet supplemented with 0.3 ppm Se (as Se-yeast), without added Cd; in T2 treatment, they were offered a diet with 0.3 ppm Se and 10 ppm Cd; in T3 treatment, they were offered a diet with 0.3 ppm Se and 100 ppm Cd; in T4 treatment, chickens were offered a diet supplemented with 3 ppm Se and 100 ppm Cd. Cadmium was added to the diets in T2, T3, and T4 as CdCl₂. On the fourth and sixth weeks, liver and breast samples were obtained from two broilers per replicate pen. Relative gene expression levels of catalase (CAT), superoxide dismutase 1 (SOD1) and 2 (SOD2), methionine sulfoxide reductase A (MSRA) and B3 (MSRB3), iodothyronine deiodinase 1 (DIO1), 2 (DIO2), and 3 (DIO3), glutathione peroxidase 1 (GPX1) and 4 (GPX4), thioredoxin reductase 1 (TXNRD1) and 3 (TXNRD3), and metallothionein 3 (MT3) were analyzed by real-time quantitative PCR in liver, whereas the fatty-acid (FA) profile of breast muscle was determined by gas chromatography. Broilers supplemented with 0.3 ppm Se could tolerate low levels of Cd present in the diets, as there were no significant changes in the breast muscle FA profile, whereas excess Cd led to decreased polyunsaturated fatty acids (PUFAs), and in particular n-6 PUFA. Furthermore, treatments mainly affected the messenger RNA (mRNA) expression of SOD2, TXNRD3, and MT3, while age affected CAT, MSRB3, DIO2, DIO3, GPX4, TXNRD1, and MT3. In conclusion, dietary Se may help against the negative effects of Cd, but cannot be effective when Cd is present at excessive amounts in the diet.

Selenium, selenoprotein P, and Alzheimer's disease: is there a link?

The essential trace element, selenium (Se), is crucial to the brain but it may be potentially neurotoxic, depending on dosage and speciation; Se has been discussed for decades in relation to Alzheimer's disease (AD). Selenoprotein P (SELENOP) is a secreted heparin-binding glycoprotein which serves as the main Se transport protein in mammals. In vivo studies showed that this protein might have additional functions such as a contribution to redox regulation. The current review focuses on recent research on the possible role of SELENOP in AD pathology, based on model and human studies. The review also briefly summarizes results of epidemiological studies on Se supplementation in relation to brain diseases, including PREADViSE, EVA, and AIBL. Although mainly positive effects of Se are assessed in this review, possible detrimental effects of Se supplementation or exposure, including potential neurotoxicity, are also mentioned. In relation to AD, various roles of SELENOP are discussed, i.e. as the means of Se delivery to neurons, as an antioxidant, in cytoskeleton assembly, in interaction with redox-active metals (copper, iron, and mercury) and with misfolded proteins (amyloid-beta and hyperphosphorylated tau-protein).

Interactive effects of chronic dietary selenomethionine and cadmium exposure in rainbow trout (Oncorhynchus mykiss): A preliminary study

The present study investigated the interactive effects of dietary cadmium (Cd) and selenium (Se) on the tissue-specific (liver, kidney, and muscle) accumulation of these two elements, hepatic oxidative stress response, and morphometrics in rainbow trout (Oncorhynchus mykiss) during chronic exposure. Fish were exposed to elevated dietary Cd (45 μg g^-1 dry wt.), and medium (10 μg g^-1 dry wt.) or high (45 μg g^-1 dry wt.) dietary selenium (added as selenomethionine), both alone and in combination, for 30 days. Exposure to dietary Cd alone caused oxidative stress in fish as reflected by reduced thiol redox (GSH:GSSG), increased lipid peroxidation, and induction of anti-oxidative enzymes (catalase, superoxide dismutase, and glutathione peroxidase) in the liver. Also, an increase in tissue-specific Cd burden and impaired morphometrics (hepato-somatic index and condition factor) were also recorded in fish following exposure to dietary Cd. In contrast, the dietary co-exposure to Cd and Se (at both medium and high doses) resulted in a decrease in Cd burden in the liver and kidney of fish. However, co-exposure to medium, but not high, dose of dietary Se completely alleviated Cd-induced oxidative stress and impaired morphometrics in fish, indicating that the reduced Cd tissue burden might not have been the primary factor behind the amelioration of Cd toxicity by Se. Overall, our study demonstrated that the protective effect of Se against the chronic Cd toxicity in fish is mainly mediated by the anti-oxidative properties of Se, but this protective effect is dose-specific and occurs only at a moderate exposure dose.

The Antagonistic Effect of Selenium on Cadmium-Induced Damage and mRNA Levels of Selenoprotein Genes and Inflammatory Factors in Chicken Kidney Tissue

Selenium (Se) is a necessary trace mineral in the diet of humans and animals. Cadmium (Cd) is a toxic heavy metal that can damage animal organs, especially the kidneys. Antagonistic interactions between Se and Cd have been reported in previous studies. However, little is known about the effects of Se against Cd toxicity and on the mRNA levels of 25 selenoprotein genes and inflammatory factors in chicken kidneys. In the current study, we fed chickens with a Se-treated, Cd-treated, or Se/Cd treated diet for 90 days. We then analyzed the mRNA expression of inflammatory factors (including prostaglandin E synthase (PTGES), nuclear factor-kappa B (NF-κB), tumor necrosis factor-α (TNF-α), and cyclooxygenase-2 (COX-2)) and 25 selenoprotein genes (Gpx1, Gpx2, Gpx3, Gpx4, Txnrd1, Txnrd2, Txnrd3, Dio1, Dio2, Dio3, SPS2, Sepp1, SelPb, Sep15, Selh, Seli, Selm, Selo, Sels, Sepx1, Selu, Selk, Selw, Seln, Selt). The results demonstrated that Cd exposure increased the Cd content in the chicken kidneys, renal tubular epithelial cells underwent denaturation and necrosis, and the tubules became narrow or disappeared. However, Se supplementation reduced the Cd content in chicken kidneys and induced normal development of renal tubular epithelial cells. In addition, we also observed that Se alleviated the Cd-induced increase in the mRNA levels of inflammatory factors and ameliorated the Cd-induced downtrend in the mRNA levels of 25 selenoprotein genes in chicken kidneys.

Selenium against lead-induced apoptosis in chicken nervous tissues via mitochondrial pathway

To investigate alleviative effect of selenium (Se) on lead (Pb)-induced apoptosis in chicken nervous tissues, 7-day-old chickens were randomly divided into four groups. The control group was fed a standard diet and drinking water. In the Pb and Se/Pb groups, (CH₃OO)₂Pb was dissolved in drinking water. In the Se and Se/Pb groups, Na₂SeO₃ was put into the standard diet. Embryonic neurocytes were divided into the control, Se (containing Na₂SeO₃), Pb (containing (CH₃COO)₂Pb), and Se/Pb (containing Na₂SeO₃ and (CH₃COO)₂Pb) groups. The following contents were performed: Morphologic observation for 90 days in brain tissues and for 12, 24, 36, and 48 hours in embryonic neurocytes; and antioxidant indexes, messenger RNA (mRNA) expression of twenty-five selenoproteins, and mRNA and protein expression of five apoptosis-related genes for 30, 60, and 90 days in brain tissues and for 12, 24, 36, and 48 hours in embryonic neurocytes. The results indicated that Se alleviated Pb-caused morphological changes; the decrease of superoxide dismutase, glutathione peroxidase (GPx), GPx1, GPx2, GPx3, GPx4, thioredoxin reductases (Txnrd)1, Txnrd2, Txnrd3, iodothyronine deiodinases (Dio)1, Dio2, Dio3, selenoprotein (Sel)T, SelK, SelS, SelH, SelM, SelU, SelI, SelO, Selpb, selenoprotein (Sep)n1, Sepp1, Sepx1, Sepw1, 15-kDa selenoprotein, and selenophosphate synthetases 2, and B-cell lymphoma-2 (Bcl-2); the increase of malondialdehyde, p53, Bcl-2 associated X protein, cytochrome c, and Caspase-3. Pb had time-dependent effects on GPx4, SelM, and malondialdehyde in the brain tissues; and on SelU in the embryonic neurocytes. Our data demonstrated that Se alleviated Pb-induced apoptosis in the chicken nervous tissues via mitochondrial pathway.

Effect of selenium on testicular damage induced by varicocele in adult male Wistar rats

PROJECT

Varicocele is an abnormal tortuosity and distension of the veins of the pampiniform plexus in the spermatic cord. It is the most common surgically correctable cause of male infertility. Several studies have revealed the effects of increased oxidative stress on serum, semen, and testicular tissues in patients with varicocele or in animal models. The aim of this study was to investigate the effects of sodium selenite on testicular damage induced by experimental left varicocele in male Wistar rats.

PROCEDURE

In the present study, the effects of oral administration of sodium selenite (at doses of 0.05, 0.1, 0.2, and 0.4mg/kg bw) were assessed in normal and varicocelized rats.

RESULTS

The varicocelized control rats showed decrease in sperm quality parameters, decreased activity of testes CAT, GPX and SOD, increased levels of MDA, and damage in testicular architecture. Administration of sodium selenite significantly reduced these changes to nearly normal levels, but did not change these parameters in normal rats. Histopathological studies further confirmed the protective effects of sodium selenite on varicocele-induced testicular damage in rats. Administrations of sodium selenite did not change these parameters in normal rats.

CONCLUSIONS

Taken together, the results of this study suggest that sodium selenite treatment may have beneficial effect on the testes of varicocelized rats.

The environment and male reproduction: The effect of cadmium exposure on reproductive function and its implication in fertility

Cadmium is an environmental pollutant known as endocrine disruptor. Testis is particularly susceptible to cadmium, and testis injury occurs at high but even low levels of exposure. Cadmium reproductive toxicity is mediated by multiple mechanisms, including structural damage to testis vasculature and blood-testis barrier, inflammation, cytotoxicity on Sertoli and Leydig cells, oxidative stress mainly by means of mimicry and interference with essential ions, apoptosis, interference with selected signaling pathways and epigenetic regulation of genes involved in the regulation of reproductive function, and disturbance of the hypothalamus-pituitary-gonadal axis. The current review outlines epidemiological observational findings from environmental and occupational exposure in humans, and reports experimental studies in humans and animals. Lastly, a focus on the pathogenetic mechanisms of cadmium toxicity and on the specific mechanisms of cadmium sensitivity and resistance, particularly assessed in animal models, is included. Despite convincing experimental findings in animals and supporting evidences in humans identifying cadmium as reproductive toxicant, observational findings are controversial, suffering from heterogeneity of study design and pattern of exposure, and from co-exposure to multiple pollutants.

An in vitro examination of selenium–cadmium antagonism using primary cultures of rainbow trout (Oncorhynchus mykiss) hepatocytes

Se has antagonistic effects on Cd-induced cytotoxicityviaboth enzymatic and non-enzymatic antioxidative mechanisms and the effects are strictly dose dependent. Confocal fluorescent images of isolated rainbow trout hepatocytes exposed to 100 µM Cd, alone or in combination with low (25 µM) or high (250 µM) concentration of Se, show reduced ROS generation with low concentration of Se.

Effects of dietary selenium on apoptosis of germ cells in the testis during spermatogenesis in roosters

The aim of this study was to determine the effects of dietary selenium (Se) supplementation on apoptosis of germ cells in the testis during spermatogenesis in roosters. Eighty 12-week-old Hy-Line Variety white roosters with an averaged body weight of 1.38 ± 0.2 kg were selected and randomly divided into four experimental groups. They were fed the basal diet (0.044 mg/kg Se dry matter) supplemented with 0 (control), 0.5, 1.0, or 2.0 mg/kg of Se dry matter (from sodium selenite). After the 45-day feeding experiment, testis samples were collected from the roosters of each treatment group to detect the population of apoptotic germ cells using the terminal deoxynucleotidy1 transferase dUTP nick end labeling assay. The protein expression of cell cycle-related genes and the messenger RNA (mRNA) expression of apoptosis and cell cycle-related genes had also been detected. The results show that the population of apoptotic germ cells in the control and 2.0 mg/kg groups was increased (P < 0.05) compared with that in the 0.5 mg/kg and 1.0 mg/kg groups. Expressions of CDC2 and CCNB1 protein in the control and 2.0 mg/kg groups were lower (P < 0.05) than those in the 0.5 mg/kg and 1.0 mg/kg groups. The mRNA level of CDC2 in the 0.5 mg/kg group was higher (P < 0.05) than that in other groups. The lowest (P < 0.05) mRNA expressions of apoptosis-related genes (BCL-2, CASPASE 3, CASPASE 8) were also obtained in the 0.5 mg/kg group. These results show that dietary Se of roosters can affect apoptosis of germ cells by regulating the mRNA expressions of apoptosis- and cell cycle-related genes in the testis during spermatogenesis.

Molecular cloning and sequence analysis of selenoprotein W gene and its mRNA expression patterns in response to metabolic status and cadmium exposure in goldfish, Carassius auratus

Selenoprotein W (SelW) is a low molecular weight and selenocysteine containing protein with redox activity involved in the antioxidant response. In the present study, the full-length cDNA of goldfish (Carassius auratus) selenoprotein W (gfSelW) was successfully cloned from the liver tissue by rapid amplification of cDNA ends technique. The obtained gfSelW cDNA was 730 bp long with a 79 bp 5'-untranslated region (UTR), a 390 bp 3'-UTR containing the consensus polyadenylation signal AATAAA and a 261 bp open reading frame coding a protein of 86 amino acid residues. gfSelW mRNA was observed in all regions of brain and peripheral tissues by semi-quantitative RT-PCR, and the most abundant was detected in testis. After fasting for 1 week, gfSelW mRNA expression levels were significantly decreased compared to the fed group in hypothalamus and liver. After refeeding for 7 days, gfSelW mRNA expression levels were increased back. Furthermore, the mRNA expressions of gfSelW in hypothalamus and liver were varied in periprandial changes and significantly up-regulated after meal 2 h and 4 h, respectively. With cadmium exposure for 24 h, gfSelW mRNA expression levels in gill and leucocytes were significantly decreased at different cadmium concentrations changing from 0.5 ppm to 10 ppm. However, the gfSelW mRNA expression level was sharply increased in liver, relatively to the control about 4.98-fold at 0.5 ppm. The results in this study provide molecular characterization of SelW in goldfish and imply that SelW mRNA expression may be associated with metabolic status and oxidative stress and regulated by metabolic factors and cadmium in fish.

Four endoplasmic reticulum resident selenoproteins may be related to the protection of selenium against cadmium toxicity in chicken lymphocytes

Cadmium could induce the damage of endoplasmic reticulum. In the present study, we investigated the effect of Cadmium on messenger RNA expressions of endoplasmic reticulum resident selenoproteins, selenoprotein K, selenoprotein N, selenoprotein S, and selenoprotein T, in cultured chicken lymphocytes and the antagonistic effect of Selenium. Chicken splenic lymphocytes were treated with 10(-7) mol/L Selenium, 10(-6) mol/L Cadmium, and the mixture of 10(-6) mol/L Selenium and 10(-7) mol/L Cadmium in the culture medium for 12, 24, 36, and 48 h, respectively. Then, we detected the messenger RNA expressions of selenoprotein K, selenoprotein N, selenoprotein S, and selenoprotein T by using real-time polymerase chain reaction method. The results indicated that Selenium significantly increased the expressions of selenoprotein K, selenoprotein N, selenoprotein S, and selenoprotein T, which were reduced by Cadmium in chicken splenic lymphocytes. It indicated that endoplasmic reticulum was one target of Cadmium toxication, and Cadmium toxicity might be related to the reduced expressions of selenoprotein K, selenoprotein N, selenoprotein S, and selenoprotein T in chicken lymphocytes. Selenium reserved the protective role by increasing the expressions of selenoprotein K, selenoprotein N, selenoprotein S, and selenoprotein T. The present study provided a useful clue to investigate the possible pathogenesis of Cadmium toxicity.

Selenium deficiency mainly influences the gene expressions of antioxidative selenoproteins in chicken muscles

Dietary selenium (Se) deficiency induces muscular dystrophy in chicken, but the molecular mechanism remains unclear. The aim of the present study was to investigate the effect of dietary Se deficiency on the expressions of 25 selenoproteins. One-day-old broiler chickens were fed either an Se deficiency diet (0.033 mg Se/kg; produced in the Se-deficient area of Heilongjiang, China) or a diet supplemented with Se (as sodium selenite) at 0.2 mg/kg for 55 days. Then, the mRNA levels of 25 selenoproteins in chicken muscles were examined, and the principal component was further analyzed. The results showed that antioxidative selenoproteins especially Gpxs and Sepw1 were highly and extensively expressed than other types of selenoproteins in chicken muscles. In 25 selenoproteins, Gpxs, Txnrd2, Txnrd 3, Dio1, Dio 3, Selk, Sels, Sepw1, Selh, Sep15, Selu, Selpb, Sepp1, Selo, Sepx1, and SPS2 were downregulated (P < 0.05), and other selenoproteins were not influenced (P > 0.05). Se deficiency decreased the expressions of 19 selenoproteins (P < 0.05), 11 of which were antioxidative selenoproteins. And, principal component analysis (PCA) further indicated that antioxidative selenoproteins, especially Gpx3, Gpx4, and Sepw1, may play crucial roles in chicken muscles. However, compared with these antioxidative selenoproteins, some other lower expressed selenoproteins (Dio1, Selu, Selpb, Sepp1) were excessively decreased (more than 60 %, P < 0.05) by Se deficiency. Thus, it may save the limited Se levels and be beneficial to remain the level of some crucial selenoproteins. These results suggested that Se deficiency mainly influenced the expressions of antioxidative selenoproteins in chicken muscles. And, antioxidative selenoproteins especially Gpxs and Sepw1 may play a crucial role in chicken muscles. Thus, it helps us focus on some specific selenoproteins when studying the role of Se in chicken muscles.

Monosodium glutamate induced testicular toxicity and the possible ameliorative role of vitamin E or selenium in male rats

•

Monosodium glutamate induced testicular damage due to oxidative stress.

•

Using of selenium and/or vitamin E to alleviate the toxicity of monosodium glutamate especially on testis.

•

Increasing of MDA levels in MSG treated group while reduction in SOD, CAT and GPx activities.

Monosodium glutamate (MSG) has been recognized as flavor enhancer that adversely affects male reproductive systems. The present study was carried out to evaluate the potential protective role of vitamin E (vit E) or selenium against MSG induced oxidative stress and histopathological changes in testis tissues of rats. Mature male Wistar rats weighing 150–200 g BW were allocated to evenly twelve groups each group of ten animals, the first group was maintained as control group, the 2nd, 3rd and 4th groups were administered MSG in three different dose levels (low, medium and high) (6, 17.5 and 60 mg/kg BW), the 5th and 6th groups were given vit E in two doses (low and high) (150 and 200 mg/kg), the 7th and 8th groups were administered selenium in two doses (low and high) (0.25 and 1 mg/kg) daily via gavage for a period of 30 days. Meanwhile the 9th and 10th groups were given combinations of MSG (high dose) and vit E while, the 11th and 12th groups were given MSG (high dose) plus selenium in two recommended doses for each one. Monosodium glutamate caused an elevation in lipid peroxidation level parallel with significant decline in SOD, CAT as well as GPx activities in testis tissues. Administration of vit E or selenium to MSG-treated groups declined lipid peroxidation, increased SOD, CAT, GPx activities. Selenium or vit E significantly reduced MSG induced histopathological changes by the entire restoration of the histological structures and the testicular antioxidant status to great extent in treated rats. In conclusion, supplementation of selenium or vit E could ameliorate the MSG induced testicular toxicity to great extent and reduce the oxidative stress on testis tissues.

Effects of dietary selenium deficiency on mRNA levels of twenty-one selenoprotein genes in the liver of layer chicken

Selenium (Se) is an essential trace element in many life forms due to its occurrence as selenocysteine (Sec) residue in selenoproteins. However, little is known about the expression pattern of selenoproteins in the liver of layer chicken. To investigate the effects of Se deficiency on the mRNA expressions of selenoproteins in the liver tissue of layer chickens, 1-day-old layer chickens were randomly allocated into two groups (n=120/group). The Se-deficient group (-Se) was fed a Se-deficient corn-soy basal diet; the Se-adequate group as control (+Se) was fed the same basal diet supplemented with Se at 0.15 mg/kg (sodium selenite). The liver tissue was collected and examined for mRNA levels of 21 selenoprotein genes at 15, 25, 35, 45, 55, and 65 days old. The data indicated that the mRNA expressions of Gpx1, Gpx2, Gpx3, Gpx4, Sepn1, Sepp1, Selo, Sepx1, Selu, Txnrd1, Txnrd2, Txnrd3, Dio1, Dio2, SPS2, Selm, SelPb, Sep15, and Sels were decreased (p<0.05), but not the levels of Dio3 and Seli (p>0.05). The results showed that the mRNA levels of 19 selenoprotein (except Seli and Dio3) genes in the layer chicken liver were regulated by diet Se level. The present study provided some compensated data about the roles of Se in the regulation of selenoproteins.

Selenoprotein P regulates 1-(4-Chlorophenyl)-benzo-2,5-quinone-induced oxidative stress and toxicity in human keratinocytes

Polychlorinated biphenyls and their metabolites are environmental pollutants that are believed to have adverse health effects presumably by inducing oxidative stress. To determine if 1-(4-Chlorophenyl)-benzo-2,5-quinone (4-ClBQ; metabolite of 4-monochlorobiphenyl, PCB3)-induced oxidative stress is associated with changes in the expression of specific antioxidant genes, mRNA levels of 92 oxidative stress-response genes were analyzed using TaqMan Array Human Antioxidant Mechanisms (Life Technologies), and results were verified by performing quantitative RT-PCR assays. The expression of selenoprotein P (sepp1) was significantly downregulated (8- to 10-fold) in 4-ClBQ-treated HaCaT human skin keratinocytes, which correlated with a significant increase in MitoSOX oxidation. Overexpression of Mn-superoxide dismutase or catalase or treatment with N-acetyl-l-cysteine suppressed 4-ClBQ-induced toxicity. Sodium selenite supplementation also suppressed 4-ClBQ-induced decrease in sepp1 expression, which was associated with a significant inhibition in cell death. Furthermore, HaCaT cells overexpressing sepp1 were resistant to 4-ClBQ-induced oxidative stress and toxicity. These results demonstrate that SEPP1 represents a previously unrecognized regulator of PCB-induced biological effects. These results support the speculation that selenoproteins can be an attractive countermeasure for PCB-induced adverse biological effects.

Protection of cisplatin-induced spermatotoxicity, DNA damage and chromatin abnormality by selenium nano-particles

Cisplatin (CIS), an anticancer alkylating agent, induces DNA adducts and effectively cross links the DNA strands and so affects spermatozoa as a male reproductive toxicant. The present study investigated the cellular/biochemical mechanisms underlying possible protective effect of selenium nano-particles (Nano-Se) as an established strong antioxidant with more bioavailability and less toxicity, on reproductive toxicity of CIS by assessment of sperm characteristics, sperm DNA integrity, chromatin quality and spermatogenic disorders. To determine the role of oxidative stress (OS) in the pathogenesis of CIS gonadotoxicity, the level of lipid peroxidation (LPO), antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) and peroxynitrite (ONOO) as a marker of nitrosative stress (NS) and testosterone (T) concentration as a biomarker of testicular function were measured in the blood and testes. Thirty-two male Wistar rats were equally divided into four groups. A single IP dose of CIS (7 mg/kg) and protective dose of Nano-Se (2 mg/kg/day) were administered alone or in combination. The CIS-exposed rats showed a significant increase in testicular and serum LPO and ONOO level, along with a significant decrease in enzymatic antioxidants levels, diminished serum T concentration and abnormal histologic findings with impaired sperm quality associated with increased DNA damage and decreased chromatin quality. Coadministration of Nano-Se significantly improved the serum T, sperm quality, and spermatogenesis and reduced CIS-induced free radical toxic stress and spermatic DNA damage. In conclusion, the current study demonstrated that Nano-Se may be useful to prevent CIS-induced gonadotoxicity through its antioxidant potential.

The protection of selenium on cadmium-induced inhibition of spermatogenesis via activating testosterone synthesis in mice

Selenium (Se) is an essential trance element in testis. However, the potential protective effects of Se against cadmium (Cd)-induced reproductive toxicity remained to be elucidated. Male ICR mice were orally administered by gavage with Na2SeO3 (0.1, 0.2, 0.4 mg/kg BW) for 1h prior to CdCl2 (5 mg/kg BW) alone or in combination for 15, 25 or 35 days. Cd exposure caused a significant decrease in body weight, sperm concentration and motility as well as plasma testosterone level which was accompanied by decreased antioxidant enzymatic activity of SOD and GSH-Px and by increased lipid peroxidation (as malondialdehyde, MDA). Se pretreatment compensated deficits in the sperm parameters (concentration, motility and morphology) induced by Cd. Se (0.4 mg/kg BW) treatment significantly increased serum testosterone level that was reduced by Cd (on 15th, 25th and 35th day) (P<0.01). Se treatment ameliorated Cd-induced reduction in testicular steroidogenic acute regulatory (StAR) and 17β-hydroxysteroid dehydrogenase (17β-HSD) activities. The present study suggest that the protective potential of Se against Cd-induced reprotoxicity might be due to up-regulation StAR and testosterone synthetic enzyme activity, which could be useful for increasing testosterone synthesis for achieving optimum protection in sperm quality and spermatogenesis.

Linking protein oxidation to environmental pollutants: redox proteomic approaches

Environmental pollutants, such as compounds used in agriculture or deriving from vehicles, industries and human activities, can represent major concern for human health since they are considered to contribute significantly to many diseased states with major public health significance. Besides considerable epidemiological evidence linking environmental pollutants with adverse health effects, little information is provided on the effects of these compounds at the cellular and molecular level. Though oxidative stress is generally acknowledged as one of the most important mechanisms of action for pollutant-induced toxicity, redox proteomics, the elective tool to identify post-translationally oxidized proteins, is still in its very infancy in this field of investigation. This review will provide the readers with an outline of the use of redox proteomics in evaluating pollutant-induced oxidative damage to proteins in various biological systems. Future potential applications of redox proteomic approaches from an environmental point of view will be discussed as well.

Cadmium-induced ovarian pathophysiology is mediated by change in gene expression pattern of zinc transporters in zebrafish (Danio rerio)

This study explored the potential for expression pattern of genes encoding zinc (Zn) transporters to be involved in the cadmium (Cd)-induced reproductive toxicity in female of zebrafish. For this purpose, oocytes maturity and ovarian histology as well as Cd, Zn and metallothioneins (MTs) accumulation and expression of genes encoding Zrt-,Irt-related protein 10 (ZIP10), Zn transporter 1 (ZnT1) and zebrafish metallothionein (zMT) were examined in ovaries of adult zebrafish exposed to 0.4 mg/L Cd in water and supplemented with Zn (5 mgkg(-1)) in their diet for 21 days. Cd-exposure decreased the expression of ZnT1 and caused up-regulation of ZIP10 and zMT gene expression. These changes were accompanied by increased Cd and MTs accumulation, decreased Zn contents as well as by histopathological damages in ovarian tissues. The co-exposure of fish to Cd and Zn abolished ZnT1 down-regulation and rendered a persistently increased ZIP10 mRNA level. This treatment also decreased Cd and MTs accumulation, reversed Cd-induced Zn depletion and partially restored Cd-induced histological changes in ovarian tissues. These results imply that the downregulation of ZnT1 as well as the overexpression of ZIP10, in responses to the ovarian Zn depletion induced by Cd, play a major role in Cd accumulation and consequently in its toxicity. The protective effect of dietary Zn supplementation against Cd-induced toxicity is mediated, at least in part, by the increase of Zn availability and subsequently the induction of ZnT1 gene expression.