Cadmium generates reactive oxygen- and carbon-centered radical species in rats: insights from in vivo spin-trapping studies

Cadmium transport by mammalian ATP-binding cassette transporters

Cellular responses to toxic metals depend on metal accessibility to intracellular targets, reaching interaction sites, and the intracellular metal concentration, which is mainly determined by uptake pathways, binding/sequestration and efflux pathways. ATP-binding cassette (ABC) transporters are ubiquitous in the human body-usually in epithelia-and are responsible for the transfer of indispensable physiological substrates (e.g. lipids and heme), protection against potentially toxic substances, maintenance of fluid composition, and excretion of metabolic waste products. Derailed regulation and gene variants of ABC transporters culminate in a wide array of pathophysiological disease states, such as oncogenic multidrug resistance or cystic fibrosis. Cadmium (Cd) has no known physiological role in mammalians and poses a health risk due to its release into the environment as a result of industrial activities, and eventually passes into the food chain. Epithelial cells, especially within the liver, lungs, gastrointestinal tract and kidneys, are particularly susceptible to the multifaceted effects of Cd because of the plethora of uptake pathways available. Pertinent to their broad substrate spectra, ABC transporters represent a major cellular efflux pathway for Cd and Cd complexes. In this review, we summarize current knowledge concerning transport of Cd and its complexes (mainly Cd bound to glutathione) by the ABC transporters ABCB1 (P-glycoprotein, MDR1), ABCB6, ABCC1 (multidrug resistance related protein 1, MRP1), ABCC7 (cystic fibrosis transmembrane regulator, CFTR), and ABCG2 (breast cancer related protein, BCRP). Potential detoxification strategies underlying ABC transporter-mediated efflux of Cd and Cd complexes are discussed.

The dynamic face of cadmium-induced Carcinogenesis: Mechanisms, emerging trends, and future directions

Cadmium (Cd) is a malleable element with odorless, tasteless characteristics that occurs naturally in the earth's crust, underground water, and soil. The most common reasons for the anthropological release of Cd to the environment include industrial metal mining, smelting, battery manufacturing, fertilizer production, and cigarette smoking. Cadmium-containing products may enter the environment as soluble salts, vapor, or particle forms that accumulate in food, soil, water, and air. Several epidemiological studies have highlighted the association between Cd exposure and adverse health outcomes, especially renal toxicity, and the impact of Cd exposure on the development and progression of carcinogenesis. Also highlighted is the evidence for early-life and even maternal exposure to Cd leading to devastating health outcomes, especially the risk of cancer development in adulthood. Several mechanisms have been proposed to explain how Cd mediates carcinogenic transformation, including epigenetic alteration, DNA methylation, histone posttranslational modification, dysregulated non-coding RNA, DNA damage in the form of DNA mutation, strand breaks, and chromosomal abnormalities with double-strand break representing the most common DNA form of damage. Cd induces an indirect genotoxic effect by reducing p53's DNA binding activity, eventually impairing DNA repair, inducing downregulation in the expression of DNA repair genes, which might result in carcinogenic transformation, enhancing lipid peroxidation or evasion of antioxidant interference such as catalase, superoxide dismutase, and glutathione. Moreover, Cd mediates apoptosis evasion, autophagy activation, and survival mechanisms. In this review, we decipher the role of Cd mediating carcinogenic transformation in different models and highlight the interaction between various mechanisms. We also discuss diagnostic markers, therapeutic interventions, and future perspectives.

Nrf2 protects against renal fibrosis induced by chronic cadmium exposure in mice

Environmental cadmium (Cd) exposure is a serious public health concern, as the kidney is the primary target for Cd exposure. The present study aimed to investigate the role and underlying mechanisms of nuclear factor erythroid-derived 2-like 2 (Nrf2) in renal fibrosis induced by chronic Cd exposure. Nrf2 knockout (Nrf2-KO) mice and their wild-type littermates (Nrf2-WT) were exposed to 100 or 200 ppm Cd in drinking water for up to 16 or 24 weeks. Following the Cd exposures, Nrf2-KO mice showed elevated urinary neutrophil gelatinase-associated lipocalin (NGAL) and BUN levels compared to Nrf2-WT mice. Masson's trichrome staining and expression of fibrosis-associated proteins revealed that more severe renal fibrosis occurred in Nrf2-KO than that in Nrf2-WT mice. Renal Cd content in the Nrf2-KO mice exposed to 200 ppm Cd was lower than that in Nrf2-WT mice, which might be a consequence of the severe renal fibrosis in the Nrf2-KO mice. Mechanistic studies showed that Nrf2-KO mice exhibited higher levels of oxidative damage, lower antioxidant levels, and more regulated cell death, apoptosis in particular, than those in Nrf2-WT mice caused by Cd exposure. In conclusion, Nrf2-KO mice were more prone to develop renal fibrosis induced by chronic Cd exposure, partially due to a weakened antioxidant, detoxification capacity and increased oxidative damage.

Systemic impact of heavy metals and their role in cancer development: a review

Heavy metals are well-recognised as environmental hazards due to their toxicity, environmental persistence, and bioaccumulation in living organisms. Human health is a crucial concern related to terrestrial and aquatic ecosystems poisoned by harmful heavy metals. Most heavy metals pollute the air, water, and soil, which can be fatal to humans. Humans and other species can be exposed to heavy metals through the food chain if the metals oxidise or combine with other environmental elements (such as water, soil, or air). Their entry into the food chain assures interactions with biological macromolecules in living systems, including humans, resulting in undesirable outcomes. Human poisonings have typically been caused by mercury, lead, chromium, cadmium, and arsenic. The build-up of these metals in living organisms causes various harmful consequences on different organs and tissues. The gravitas of heavy metal toxicity regarding molecular impact and carcinogenesis needs in-depth understanding despite the plethora of available data. Hence, additionally, we attempt to elaborate on the multi-level impact of five heavy metals and emphasise their role in cancer development. The rationale of this essay is thus to understand the role of five heavy metals, viz., lead (Pb), cadmium (Cd), chromium (Cr), arsenic (As), and mercury (Hg), in carcinogenesis. Heavy metals interfere with various biological functions, including proliferation, differentiation, repair of damage, and apoptosis. By comparing their modes of action, we see that these metals share common mechanisms for inducing toxicity, such as reactive oxygen species (ROS) production, antioxidant defence weakening, enzyme inactivation, and oxidative stress.

The immune status of the organism of bulls under cadmium load and the effects of correcting factors

Man-made pollution of the environment through food chains has a significant impact on animal productivity and product quality. The studied environmental pollutant, cadmium, is classified as an extremely dangerous heavy metal. That is why the study of the effect of this toxicant on the immune system of the body of young cattle and the development of its correction is relevant. Research in this direction is relevant and has significant prospects. The experiments were carried out on six-month-old bulls, a Ukrainian black-and-white dairy breed. The bulls were subjected to a cadmium load by feeding cadmium chloride with feed at a dose of 0.04 mg/kg of animal body weight. It has been established that the cadmium load in bulls had an immunosuppressive effect on the activity of the immune system, which indicates a decrease in the indicators of humoral and nonspecific parts of the immune defense. To prevent the development of chronic cadmium toxicosis, experimental animals were given the feed additive Metisevit at a dose of 0.36 g/kg of feed and the liposomal preparation Butaintervit at a dose of 5 ml per animal. These preparations contributed to an increase in nonspecific resistance, in particular, an increase in the bactericidal and lysozyme activity of blood serum, phagocytic activity and phagocytic index with a simultaneous decrease in the level of circulating immune complexes in their blood. Under the experimental cadmium load, the best effect on the immune defense of the organism of bulls was exerted by the combined use of the feed additive Metisevit and the liposomal preparation Butaintervit. These changes in the body of young cattle are associated with the complex action of both the components of the feed additive and the liposomal preparation. The liposomal form of Butaintervit has a more pronounced and lasting effect. Metisevit and the liposomal preparation Butaintervit complement the prescribed therapy and, when used together with a cadmium load, show high therapeutic efficacy

Antagonism of cadmium-induced liver injury in ducks by α-bisabolol

Cadmium (Cd) is an ecological pollutant which causes hazardous effects in animals and humans. The aim of this study was to investigate the role of α-bisabolol (BISA) in antagonizing the Cd-induced hepatotoxicity in ducks. Two-week old ducks were allocated into 8 groups (10 ducks/group): Group I received basal diet and was gavaged with sunflower oil (BISA vehicle, 1.1 mL/kg/day); group II was administered BISA orally (50 mg/kg/day; diluted with sunflower oil); groups III, IV, and V were fed the basal diet mixed with CdCl2 at 37.5, 75, and 150 mg/kg diet, respectively, and were gavaged with sunflower oil; group VI, VII, and VIII were given basal diet containing CdCl2 at the aforementioned consecutive doses plus BISA. All treatments were provided daily for 4 weeks. Exposure to CdCl2 induced mortality in ducks, increased hepatic Cd content and serum levels of hepatopathic biomarkers, and caused oxidative stress and morphological alterations in ducks' liver. Furthermore, exposure to Cd caused upregulation of the mRNA of proinflammatory cytokine tumor necrosis factor-α and apoptotic gene Bax, and that of cyclooxygenase-2 protein in the liver. All effects of Cd were dose-dependent. BISA antagonized all of the aforementioned CdCl2-induced changes. These findings suggested that BISA exert the hepatoprotective effect against Cd toxicity through reducing the hepatic content of Cd as well as antagonizing oxidative insults, inflammation, and apoptosis. Thus, BISA has a great potential to be used as an antidote in the control of Cd poisoning.

Impacts of cadmium on male fertility: Lessons learnt so far

Cadmium (Cd) is one of the most dangerous heavy metals in the world. Globally, toxicities associated with cadmium and its attendant negative impact on humans and animals cannot be under-estimated. Cd is a heavy metal, and people are exposed to it through contaminated foods and smoking. Cd exerts its deleterious impacts on the testes (male reproductive system) by inducing oxidative stress, spermatogenic cells apoptosis, testicular inflammation, decreasing androgenic and sperm cell functions, disrupting ionic homeostasis, pathways and epigenetic gene regulation, damaging vascular endothelium and blood testes barrier. In association with other industrial by-products, Cd has been incriminated for the recent decline of male fertility rate seen in both man and animals. Understanding the processes involved in Cd-induced testicular toxicity is vital for the innovation of techniques that will help ameliorate infertility in males. In this review, we summed up recent studies on the processes of testicular toxicity and male infertility due to Cd exposure. Also, the usage of different compounds including phytochemicals, and plant extracts to manage Cd reprotoxicity will be reviewed.

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.

Activated Nrf-2 Pathway by Vitamin E to Attenuate Testicular Injuries of Rats with Sub-chronic Cadmium Exposure

Cadmium (Cd), a heavy metal element, cumulates in the testis and can cause male reproductive toxicity. Although vitamin E (VE) as one of potential antioxidants protects the testis against toxicity of Cd, the underlying mechanism remained uncompleted clear. The aim of this study was to investigate whether the Nrf-2 pathway is involved with the protective effect of VE on testicular damages caused by sub-chronic Cd exposure. Thirty-two SD rats were divided into four groups and orally administrated with VE and/or Cd for 28 consecutive days: control group, VE group (100 mg VE/kg), Cd group (5 mg CdCl₂/kg), and VE + Cd group (100 mg VE/kg + 5 mg CdCl₂/kg). The results showed that 28-day exposure of Cd caused accumulation of Cd, histopathological lesions, and alternations of sperm parameters (elevated rate of abnormal sperm, decreased count of sperm, declined motility, and viability of sperm). Moreover, the rats exposed to Cd showed significant oxidative stress (increased contents of MDA and decreased levels or activities of T-AOC, GSH, CAT, SOD and GSH-Px) and inhibition of Nrf-2 signaling pathway (downregulation of Nrf-2, HO-1, NQO-1, GCLC, GCLM and GST) of the testes. In contrast, VE treatment significantly reduced the Cd accumulation, alleviated histopathological lesions and dysfunctions, activated Nrf-2 pathway, and attenuated the oxidative stress caused by Cd in the testes of rats. In conclusion, VE, through upregulating Nrf-2 pathway, could protect testis against oxidative damages induced by sub-chronic Cd exposure.

Arctigenin alleviates cadmium-induced nephrotoxicity: Targeting endoplasmic reticulum stress, Nrf2 signaling, and the associated inflammatory response

AIM

Nephrotoxicity is a critical consequence of cadmium toxicity. Cadmium induces nephrotoxicity through disruption of cellular redox balance and induction of endoplasmic reticulum stress (ERS) and inflammatory responses. The present study investigated the renoprotective effects of the naturally occurring arctigenin against the cadmium-induced nephrotoxicity.

MAIN METHODS

Male Wistar rats were randomized into normal control, arctigenin control, cadmium, and cadmium/arctigenin groups. Cadmium and arctigenin were administered daily over a seven-day period. On the eighth day, blood and kidney tissue specimens were collected and subjected to spectrophotometric, ELISA, and immunoblotting analysis.

KEY FINDINGS

Arctigenin significantly improved renal functions and reduced renal tubular injury in the cadmium-intoxicated rats as reflected by increased GFR and reduced levels of serum creatinine, BUN, urinary albumin-to-creatinine ratio, and protein expression of KIM-1. Arctigenin alleviated the cadmium-induced oxidative DNA damage and lipid peroxidation while boosted reduced glutathione level and antioxidant enzymes activity. Mechanistically, arctigenin enhanced nuclear translocation of the antioxidant transcription factor Nrf2 and up-regulated its downstream redox-regulating enzymes HO-1 and NQO1. Importantly, arctigenin ameliorated the cadmium-evoked ERS as demonstrated by reduced protein expression of the key molecules Bip, PERK, IRE1α, CHOP, phspho-eIF2α, and caspase-12 and diminished activity of caspase-12. Additionally, arctigenin down-regulated the cadmium-induced NF-κB nuclear translocation and decreased its downstream pro-inflammatory cytokines TNF-α and IL-1β.

SIGNIFICANCE

The current work underlines the alleviating activity of arctigenin against cadmium-evoked nephrotoxicity potentially through mitigating ERS and targeting Nrf2 and NF-κB signaling. The current findings support possible therapeutic application of arctigenin in controlling cadmium-induced nephrotoxicity although clinical investigations are necessary.

Role of Fucoxanthin towards Cadmium-induced renal impairment with the antioxidant and anti-lipid peroxide activities

Kidney damages caused by cadmium are considered to be one of the most dangerous consequences for the human body. This study aimed to investigate the protective effects of fucoxanthin supplementation on mice models subjected to cadmium-induced kidney damage. The mice treated with cadmium chloride (CdCl₂) were observed to have significantly reduced the cross-section area of glomeruli. Cadmium exposure has also caused the damage of the structural integrity of mitochondria and increased blood urea nitrogen (BUN), kidney injury molecule 1 (KIM1), and neutrophil gelatinase associated lipocalin (NGAL) levels. Peroxidase (POD), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) levels in cadmium-exposed mice were markedly declined. Caspase3, caspase8, and caspase9 gene expressions in association with apoptosis were dramatically elevated in renal tissues. The CdCl₂ treated mice were orally administered with 50 mg/kg Shenfukang, 10 mg/kg, 25 mg/kg, and 50 mg/kg fucoxanthin for 14 days. The results revealed that high doses of fucoxanthin administration significantly decreased BUN, KIM1, NGAL levels, increasing POD, SOD, CAT, and ascorbate APX levels. Fucoxanthin administration also promoted recovery of the renal functions, micro-structural organization, and ultra-structural organization in the renal cells. In summary, the ameliorative effects of fucoxanthin supplementation against cadmium-induced kidney damage were mediated via inhibiting oxidative stress and apoptosis, promoting the recovery of structural integrity of mitochondria.

Construction of Mode of Action for Cadmium-Induced Renal Tubular Dysfunction Based on a Toxicity Pathway-Oriented Approach

Although it is recognized that cadmium (Cd) causes renal tubular dysfunction, the mechanism of Cd-induced nephrotoxicity is not yet fully understood. Mode of action (MOA) is a developing tool for chemical risk assessment. To establish the mechanistic MOA of Cd-induced renal tubular dysfunction, the Comparative Toxicogenomics Database (CTD) was used to obtain genomics data of Cd-induced nephrotoxicity, and Ingenuity^® Pathway Analysis (IPA) software was applied for bioinformatics analysis. Based on the perturbed toxicity pathways during the process of Cd-induced nephrotoxicity, we established the MOA of Cd-induced renal tubular dysfunction and assessed its confidence with the tailored Bradford Hill criteria. Bioinformatics analysis showed that oxidative stress, DNA damage, cell cycle arrest, and cell death were the probable key events (KEs). Assessment of the overall MOA of Cd-induced renal tubular dysfunction indicated a moderate confidence, and there are still some evidence gaps to be filled by rational experimental designs.

Combining Patulin with Cadmium Induces Enhanced Hepatotoxicity and Nephrotoxicity In Vitro and In Vivo

Food can be contaminated by various types of contaminants such as mycotoxins and toxic heavy metals. Therefore, it is very likely that simultaneous intake of more than one type of food contaminant by consumers may take place, which provides a strong rationale for investigating the combined toxicities of these food contaminants. Patulin is one of the most common food-borne mycotoxins, whereas cadmium is a representative of toxic heavy metals found in food. The liver and kidneys are the main target organ sites for both patulin and cadmium. We hypothesized that simultaneous exposure to patulin and cadmium could produce synergistic hepatotoxicity and nephrotoxicity. Alpha mouse liver 12 (AML12) and Human embryonic kidney (HEK) 293 (HEK293) cell lines together with a mouse model were used to explore the combination effect and mechanism. The results demonstrated, for the first time, that the co-exposure of liver or renal cells to patulin and cadmium caused synergistic cytotoxicity in vitro and enhanced liver toxicity in vivo. The synergistic toxicity caused by the co-administration of patulin and cadmium was attributed to the boosted reactive oxygen species (ROS) generation. c-Jun N-terminal kinase 1 (JNK1) and p53 as downstream mediators of oxidative stress contributed to the synergistic toxicity by co-exposure of patulin and cadmium, while p53/JNK1 activation promoted the second-round ROS production through a positive feedback loop. The findings of the present study extend the toxicological knowledge about patulin and cadmium, which could be beneficial to more precisely perform risk assessments on these food contaminants.

Multi-Biomarker Responses of Asian Clam Corbicula fluminea (Bivalvia, Corbiculidea) to Cadmium and Microplastics Pollutants

One of the most widespread aquatic organisms in the rivers and estuarine ecosystems, in the world, is Asian clam Corbiculafluminea. This clam, that can adapt to environmental changes, is an invasive species in several areas and it was adopted as a model for toxicity tests. This study evaluated the effects of the exposure to cadmium (Cd), to microplastics (MPs) and their mixtures on C. fluminea. The oxidative stress responses, lipid peroxidation (LPO), changes in the activity of energy-related enzymes and neurotoxicity were assessed on the gill, digestive gland and gonad. The results show that Cd, MPs and their mixtures cause oxidative stress, damage and neurotoxicity. The enzymes superoxide dismutase (SOD), glutathione S-transferase (GST), acetylcholinesterase (AChE) and the LPO levels could be chosen as biomarkers of Cd pollution. Exposure to MPs induced an increase in reduced/oxidized glutathione (GSH/GSSG) ratio and increased AChE activity. The combined exposure to Cd and MPs caused a synergetic effect in gill and gonad, while an antagonism response was recorded in the digestive gland. The results provide new insights for unveiling the biologic effects of heavy metal, microplastics and their mixtures on C. fluminea. Besides, we demonstrated that the Asian clam is a good bioindicator of microplastic pollution that can occur in aquatic environments.

Oxidative stress and apoptotic effects of copper and cadmium in the zebrafish liver cell line ZFL

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Oxidative stress and apoptosis created by Cu²⁺ and Cd²⁺ insults were studied in ZFL.

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Cu²⁺ and Cd²⁺ both created lipid peroxidation, causing oxidative stress in cytoplasm.

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Mitochondrial superoxide was induced by Cd²⁺ but supressed by Cu²⁺.

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Cu²⁺ suppressed Casp3 activity, resulting in suppressed the apoptosis.

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Pre-treatments of low concentration of Cu²⁺ protected the cell from Cd²⁺ insults.

Copper (Cu) and cadmium (Cd) are widely used in industrial activities, resulting in Cu and Cd contamination in aquatic systems worldwide. Although Cu plays an essential role in many biological functions, an excessive amount of the metal causes cytotoxicity. In contrast, Cd is a non-essential metal that usually co-exists with Cu. Together, they cause oxidative stress in cells, leading to cell damage. These metal ions are also believed to cause cell apoptosis. In this study, we used a zebrafish liver cell line, ZFL, to study combined Cu and Cd cytotoxicity. Although Cd is more toxic than Cu, both were found to regulate the expression of oxidative stress related genes, and neither significantly altered the activity of oxidative stress related enzymes. Co-exposure tests with the antioxidant N-acetyl-l-cysteine and the Cu chelator bathocuproinedisulfonic acid disodium salt demonstrated that Cd toxicity was due to the oxidative stress caused by Cu, and that Cu at a low concentration could in fact exert an antioxidant effect against the oxidative stress in ZFL. Excessive Cu concentration triggered the expression of initiator caspases (caspase 8 and caspase 9) but suppressed that of an executioner caspase (caspase 3), halting apoptosis. Cd could only trigger the expression of initiator caspases; it could not halt apoptosis. However, a low concentration of Cu reduced the mitochondrial superoxide level, suppressing the Cd-induced apoptotic effects in ZFL.

Pathophysiology and treatment options of varicocele: An overview

Varicocele is the most common correctable cause for male infertility, but not all men with varicocele are affected equally by this condition. The pathophysiology of varicocele-induced fertility remains ill-defined. While evidence suggests that oxidative stress remains a central factor, other mechanisms likely include scrotal hyperthermia, reflux of metabolites, hypoxia and cadmium accumulation. Microsurgical varicocelectomy remains the gold standard treatment option for infertile men with a clinically palpable varicocele and abnormal semen parameters. Newer evidence suggests a potential role for antioxidant supplementation and a meaningful role of varicocelectomy for patients destined for ART to improve pregnancy outcomes.

Rosmarinic Acid Attenuates Cadmium-Induced Nephrotoxicity via Inhibition of Oxidative Stress, Apoptosis, Inflammation and Fibrosis

The present investigation was executed to reveal the protective mechanism of rosmarinic acid (RA) against cadmium (Cd)-induced nephrotoxicity. RA exhibited a concentration-dependent anti-apoptotic effect against CdCl2 in isolated mouse proximal tubular epithelial cells. Cd treatment significantly (p < 0.01) imparted oxidative stress to the renal cells via excessive ROS production, triggering NO level, NADPH oxidase activation, and impairment of cellular redox defense system. Cd-mediated oxidative stress significantly (p < 0.01) endorsed apoptosis to the murine kidney cells by triggering NF-κB/PKC-δ/TNFR2 activation. In addition, CdCl2 induced renal fibrosis by triggering TGF-β1/SMAD3/α-SMA/collagen signaling within renal cells. On the other hand, RA significantly (p < 0.05-0.01) attenuated Cd-provoked oxidative stress and associated pathological signal transduction in murine renal cells. RA treatment also could significantly (p < 0.05-0.01) reciprocate Cd-mediated pathological changes in blood and urine parameters in mice. In addition, histological data supported the pharmacological findings. In silico chemometric analyses predicted the possible interactions between RA and different signal proteins and anticipated drug-likeness characteristics of RA. Hence, RA can potentially be applied as a therapeutic agent to treat Cd-mediated nephrotoxicity in future.

Toxicokinetic and toxicodynamic (TK-TD) modeling to study oxidative stress-dependent toxicity of heavy metals in zebrafish

Adverse outcome pathways (AOP) have been proposed as a new method to improve the ecological risk assessment of pollutants, but it requires quantitation linkage between exposure, biomarker response and toxicity of pollutants. A toxicokinetic and toxicodynamic (TK-TD) model was used to quantify AOP of the toxicity of Cd and Pb to zebrafish, including the quantitative relationship between Cd and Pb accumulation in gill and oxidative damage level based on ROS or MDA, and LC₅₀ values at different times. Significant relationships were found between the oxidative damage level characterized by ROS and MDA content and Cd or Pb accumulation in gill (R² > 0.60), and the TK model could better simulate the Pb accumulation in the gills (R² > 0.60) than Cd. The increasing of Cd or Pb concentrations induced the generation of ROS and the formation of ROS initiated the fluctuation of MDA level in the cells as compared to controls (p < 0.05). For the individual level effect, the Damage Assessment Model (DAM) could successfully explain the change of LC_50-ROS and LC_50-MDA values at different times (R² > 0.99). Our findings suggested that the TK-TD model based on ROS and MDA could be used as a quantitative AOP to predict toxicity of metals to zebrafish.

Real-Time Imaging of Free Radicals for Mitochondria-Targeting Hypoxic Tumor Therapy

Free radicals have emerged as new-type and promising candidates for hypoxic tumor treatment, and further study of their therapeutic mechanism by real-time imaging is of great importance to explore their biomedical applications. Herein, we present a smart free-radical generator AuNC-V057-TPP for hypoxic tumor therapy; the AuNC-V057-TPP not only exhibits good therapeutic effect under both hypoxic and normoxic conditions but also can monitor the release of free radicals in real-time both in vitro and in vivo. What is more, with the mitochondria-targeting ability, the AuNC-V057-TPP is demonstrated with improved antitumor efficacy through enhanced free radical level in mitochondria, which leads to mitochondrial membrane damage and ATP production reduction and finally induces cancer cell apoptosis.

Review of polyphenol-rich products as potential protective and therapeutic factors against cadmium hepatotoxicity

Recently, the growing attention of the scientific community has been focused on the threat to health created by environmental pollutants, including toxic metals such as cadmium (Cd), and on the need of finding effective ways to prevent and treat the unfavorable health effects of exposure to them. Particularly promising for Cd, and thus arousing the greatest interest, is the possibility of using various ingredients present in plants, including mainly polyphenolic compounds. As the liver is one of the target organs for this toxic metal and disturbances in the proper functioning of this organ have serious consequences for health, the aim of the present review was to discuss the possibility of using polyphenol-rich food products (e.g., chokeberry, black and green tea, blueberry, olive oil, rosemary and ginger) as the strategy in protection from this xenobiotic hepatotoxicity and treatment of this heavy metal-induced liver damage. Owing to the ability of polyphenols to bind ions of Cd and the strong antioxidative potential of these compounds, as well as their abundance in dietary products, it seems to be of high importance to consider the possibility of using polyphenols as potential preventive and therapeutic agents against Cd hepatotoxicity, determined by its strong pro-oxidative properties. Although most of the data on the effectiveness of polyphenols comes from studies in animals, the fact that some of them are derived from experimental models that reflect human exposure to this metal allows us to assume that some polyphenol-rich food products may be promising protective agents against Cd hepatotoxicity in humans.

The effect of astaxanthin and cadmium on rat erythrocyte G6PD, 6PGD, GR, and TrxR enzymes activities in vivo and on rat erythrocyte 6PGD enzyme activity in vitro

In this study, the effects of astaxanthin (AST) that belongs to carotenoid family and cadmium (Cd), which is an important heavy metal, on rat erythrocyte G6PD, 6PGD, GR, and TrxR enzyme activities in vivo and on rat erythrocyte 6PGD enzyme activity in vitro were studied. In in vitro studies, 6PGD enzyme was purified from rat erythrocytes with 2',5'-ADP Sepharose4B affinity chromatography. Results showed inhibition of enzyme by Cd at IC₅₀ ; 346.5 μM value and increase of 6PGD enzyme activity by AST. In vivo studies showed an increase in G6PD, 6PGD, and GR enzyme activities (P ˃ 0.05) and no chance in TrxR enzyme activity by AST. Cd ion inhibited G6PD, 6PGD, and GR enzyme activities (P ˂ 0.05) and also decreased TrxR enzyme activity (P ˃ 0.05). AST + Cd group G6PD enzyme activity was statistically low compared with control group (P ˂ 0.05). 6PGD and TrxR enzyme activities decreased without statistical significance (P ˃ 0.05); however, GR enzyme activity increased statistically significantly (P ˂ 0.05).

Cadmium specific proteomic responses of a highly resistantPseudomonas aeruginosasan ai

Pseudomonas aeruginosa san ai is a promising candidate for bioremediation of cadmium pollution, as it resists a high concentration of up to 7.2 mM of cadmium. Leaving biomass of P. aeruginosa san ai exposed to cadmium has a large biosorption potential, implying its capacity to extract heavy metal from contaminated medium. In the present study, we investigated tolerance and accumulation of cadmium on protein level by shotgun proteomics approach based on liquid chromatography and tandem mass spectrometry coupled with bioinformatics to identify proteins. Size exclusion chromatography was used for protein prefractionation to preserve native forms of metalloproteins and protein complexes. Using this approach a total of 60 proteins were observed as up-regulated in cadmium-amended culture. Almost a third of the total numbers of up-regulated were metalloproteins. Particularly interesting are denitrification proteins which are over expressed but not active, suggesting their protective role in conditions of heavy metal exposure. P. aeruginosa san ai developed a complex mechanism to adapt to cadmium, based on: extracellular biosorption, bioaccumulation, the formation of biofilm, controlled siderophore production, enhanced respiration and modified protein profile. An increased abundance of proteins involved in: cell energy metabolism, including denitrification proteins; amino acid metabolism; cell motility and posttranslational modifications, primarily based on thiol-disulfide exchange, were observed. Enhanced oxygen consumption of biomass in cadmium-amended culture versus control was found. Our results signify that P. aeruginosa san ai is naturally well equipped to overcome and survive high doses of cadmium and, as such, has a great potential for application in bioremediation of cadmium polluted sites.

When exposed to cadmium a highly resistant strain P. aeruginosa san ai responds by an increased metalloprotein expression (particularly denitrification proteins), an enhanced respiration, and a pronounced thiol-disulfide protein modifications.

Urine cadmium levels and albuminuria in a general population from Spain: A gene-environment interaction analysis

BACKGROUND

The interaction of cadmium with genes involved in oxidative stress, cadmium metabolism and transport pathways on albuminuria can provide biological insight on the relationship between cadmium and albuminuria at low exposure levels.

OBJECTIVES

We tested the hypothesis that specific genotypes in candidate genes may confer increased susceptibility to cadmium exposure.

METHODS

Cadmium exposure was estimated by inductively coupled plasma mass spectrometry (ICPMS) in urine from 1397 men and women aged 18-85years participating in the Hortega Study, a representative sample of a general population from Spain. Urine albumin was measured by automated nephelometric immunochemistry. Abnormal albuminuria was defined as urine albumin greater than or equal to 30mg/g.

RESULTS

The weighted prevalence of abnormal albuminuria was 6.3%. The median level of urine cadmium was 0.39 (IQR, 0.23-0.65) μg/g creatinine. Multivariable-adjusted geometric mean ratios of albuminuria comparing the two highest to the lowest tertile of urine cadmium were 1.62 (95% CI, 1.43-1.84) and 2.94 (95% CI, 2.58-3.35), respectively. The corresponding odds ratios of abnormal albuminuria were 1.58 (0.83, 3.02) and 4.54 (2.58, 8.00). The association between urine cadmium and albuminuria was observed across all participant subgroups evaluated including participants without hypertension, diabetes or chronic kidney disease. We observed Bonferroni-corrected statistically significant interactions between urine cadmium levels and polymorphisms in gene SLC30A7 and RAC1.

CONCLUSIONS

Increasing urine cadmium concentrations were cross-sectionally associated with increased albuminuria in a representative sample of a general population from Spain. Genetic variation in oxidative stress and cadmium metabolism and transport genes may confer differential susceptibility to potential cadmium effects.

Biological activities of ginger against cadmium-induced renal toxicity

Our aim was to evaluate the protective and antioxidant effects of ginger extract against cadmium-induced renal toxicity in animal models and to support the use of ginger as anti-renal failure natural remedy. Seventy rats were examined in a 4-week experiment to evaluate the effect of Ginger (Zingiber officinale) at doses of 100 and 200 mg/kg body weight on molecular DNA content, antioxidant status, and renal function in rats intoxicated with cadmium at dose of (5 mg/kg) using biochemical and histological analysis. Renal dysfunction, kidney tissue damage, and oxidative effect were evident in cadmium intoxicated rats as estimated by significant increase in (creatinine, urea), decrease in (creatinine clearance and reabsorption rate of urine albumin), increase in MDA, decrease in total antioxidant status (TAC), reduction in DNA content, and histopathological changes of kidneys' tissues compared to control rats. Treatment with ginger resulted in significant restoring of renal function biomarkers, TAC, molecular DNA, and histological improvements which occurs via free radical scavenging and regenerative mechanisms. The activity of ginger was supported by estimation of bioactive phenolic and falvinods constituents. Twenty-eight polyphenolic compounds were estimated in ginger extract; [6]-gingerol, [6]-shogaol, citral and pyrogallol were the highest amounts in ginger, and supposed to be responsible for its major antioxidant and free radical scavenging activity as shown by In vitro DPPH/β-carotene-linolic acid assay tests. Consequently, ginger extracts could have a potent protective effects against nephrotoxicity induced by various toxicants.

Disulfiram moderately restores impaired hepatic redox status of rats subchronically exposed to cadmium

Examination of cadmium (Cd) toxicity and disulfiram (DSF) effect on liver was focused on oxidative stress (OS), bioelements status, morphological and functional changes. Male Wistar rats were intraperitoneally treated with 1 mg CdCl₂/kg BW/day; orally with 178.5 mg DSF/kg BW/day for 1, 3, 10 and 21 days; and co-exposed from 22nd to 42nd day. The co-exposure nearly restored previously suppressed total superoxide dismutase (SOD), catalase (CAT) and increased glutathione peroxidase (GPx) activities; increased previously reduced glutathione reductase (GR) and total glutathione-S-transferase (GST) activities; reduced previously increased superoxide anion radical (O₂^·−) and malondialdehyde (MDA) levels; increased zinc (Zn) and iron (Fe), and decreased copper (Cu) (yet above control value), while magnesium (Mg) was not affected; and decreased serum alanine aminotransferases (ALT) levels. Histopathological examination showed signs of inflammation process as previously demonstrated by exposure to Cd. Overall, we ascertained partial liver redox status improvement, compared with the formerly Cd-induced impact.

Environmentally Realistic Doses of Cadmium as a Possible Etiologic Agent for Idiopathic Pathologies

Cadmium is a heavy metal of increasing environmental concern that has long been associated to several human pathological processes. Recent population surveys have correlated cadmium non-occupational exposure to widespread idiopathic pathologies. Food and tobacco are reported to be the main exposure sources of cadmium to the general population, as phosphate fertilizers are rich in such a metal, thus contaminating the crops. Although its mechanisms of toxicity are not a consensus in the literature, it is well established that reactive oxygen species play a key role in this process, leading to the oxidation of several biological molecules. We have therefore assessed whether three environmentally realistic doses of cadmium alter the oxidative status of Wistar rat testis and eventually result in histological damages. Our results show that even the lowest environmental dose of cadmium was able to disturb the endogenous antioxidant system in Wistar testis, although an increase in lipid peroxidation was observed only within the group exposed to the highest environmental dose. Despite that no remarkable morphological changes were observed in any group, significant alterations in blood vessel lumen were reported for some cadmium-exposed animals, suggesting that endothelium is one of the primary targets involved in cadmium toxicity.

Temporal changes in rat liver gene expression after acute cadmium and chromium exposure

U.S. Service Members and civilians are at risk of exposure to a variety of environmental health hazards throughout their normal duty activities and in industrial occupations. Metals are widely used in large quantities in a number of industrial processes and are a common environmental toxicant, which increases the possibility of being exposed at toxic levels. While metal toxicity has been widely studied, the exact mechanisms of toxicity remain unclear. In order to further elucidate these mechanisms and identify candidate biomarkers, rats were exposed via a single intraperitoneal injection to three concentrations of CdCl₂ and Na₂Cr₂O₇, with livers harvested at 1, 3, or 7 days after exposure. Cd and Cr accumulated in the liver at 1 day post exposure. Cd levels remained elevated over the length of the experiment, while Cr levels declined. Metal exposures induced ROS, including hydroxyl radical (•OH), resulting in DNA strand breaks and lipid peroxidation. Interestingly, ROS and cellular damage appeared to increase with time post-exposure in both metals, despite declines in Cr levels. Differentially expressed genes were identified via microarray analysis. Both metals perturbed gene expression in pathways related to oxidative stress, metabolism, DNA damage, cell cycle, and inflammatory response. This work provides insight into the temporal effects and mechanistic pathways involved in acute metal intoxication, leading to the identification of candidate biomarkers.

Protective effect of Irvingia gabonensis stem bark extract on cadmium-induced nephrotoxicity in rats

Cadmium has been considered a risk factor for humans as it accumulates in body tissues, such as the liver, lungs, kidneys, bones, and reproductive organs. The aim of the present study was to evaluate the effect of Irvingia gabonensis (IG) against cadmium (Cd)-induced nephrotoxicity. The study was performed on twenty (20) male rats divided into four groups: control group, cadmium group (4 mg/kg/day, intraperitoneally), cadmium + extract (200 mg/kg body weight by oral gavage) and cadmium + extract (400 mg/kg body weight by oral gavage). Changes in the kidney biochemical markers, namely glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), aminotransferase (ALT), aspartate aminotransferase (AST) activities and levels of malondialdehyde (MDA), urea, and creatinine were determined in serum. Histological examinations were monitored. Exposure to Cd lowered the activities of kidney antioxidants, while it increased LPO levels. Levels of all disrupted parameters were alleviated by co-administration of IG extract. The malondialdehyde concentration of the rats treated with 200 and 400 mg/kg body weight of the extract significantly decreased (p<0.05) compared with the untreated cadmium rats. Yet the creatinine concentration decreased significantly (p<0.05) when the cadmium animals treated with 200 and 400 mg/kg body weight of the extract were compared with the cadmium control. Furthermore, histological alterations in the kidney were observed in cadmium untreated rats and these were ameliorated in cadmium treated rats by co-administration of IG extract. IG showed apparent protective and curative effect on Cd-induced nephrotoxicity.

Manganese pre-treatment attenuates cadmium induced hepatotoxicity in Swiss albino mice

Cadmium (Cd) is a soft, malleable bluish-white metal with low melting point, a ubiquitous heavy metal and an environmental pollutant, found in soil, water and air. The presence of Cd in the components of the environment such as air, soil and groundwater is to a large part due to human activity, and the general population is exposed mainly by contaminated drinking water or food. Manganese (Mn) is a component in many enzymes, which play an important role in counteracting oxidative stress. In vitro experiments have revealed the ability of Mn to scavenge oxygen free radicals generated in differently mediated lipid peroxidation (LPO) conditions. The aim of the present study was to investigate the in vivo preventive effect of Mn(2+) pre-treatment on acute Cd-intoxication with regard to oxidative stress biomarker and antioxidant defense system in liver of Swiss albino mice. On exposure to Cd a significant increase in LPO levels, decrease in thiol content and induction in glutathione metabolizing enzyme were observed. Mn pre-treatment attenuated the modulation caused in the above-mentioned parameters due to acute Cd exposure in mice. In conclusion, the results from this study demonstrate that the protective effect of Mn in Cd-induced systemic toxicity in mice. Further investigations are required on the relation between Mn accumulation and resistance to oxidative stress and on the factors influencing Mn/Cd transport in rodents are needed to elucidate the molecular basis of this protective effect.

Prophylactic Effects of Ethanolic Extract of Irvingia gabonensis Stem Bark against Cadmium-Induced Toxicity in Albino Rats

The prophylactic effect of ethanolic extract of Irvingia gabonensis stem bark on cadmium-induced oxidative damage in male albino rats’ liver was investigated. Male Wistar rats were divided into control, cadmium, and treatment groups. In the prophylactic experiment, Irvingia gabonensis (200 and 400 mg/kg body weight) was administered by oral gavage for 21 days before exposure to cadmium. Antioxidant marker enzymes such as reduced glutathione (GSH) levels, catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), and lipid peroxidation (LPO) were determined in the liver and heart alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities were monitored and histological examination was carried out. Results indicate that cadmium-induced rats had significantly increased relative weight of liver and heart when compared to controls. Treatment with Irvingia gabonensis at 200 and 400 mg/kg caused a significant decrease in relative weight of the organs. In cadmium-induced rats, serum ALT and AST activities and levels of LPO were increased whereas hepatic and cardiac marker enzymes significantly decreased. Furthermore, histological alteration in liver and aorta was observed in cadmium untreated rats and was ameliorated in cadmium rats treated with Irvingia gabonensis. In conclusion, the extract indicates antioxidant and hepatoprotective properties that eliminate the deleterious effects of toxic metabolites of cadmium.

Cadmium exposure induces vascular injury due to endothelial oxidative stress: the role of local angiotensin II and COX-2

Cadmium is an environmental pollutant that is closely linked with cardiovascular diseases, such as atherosclerosis and hypertension. Moreover, cadmium can induce an increase in oxidative stress. One of the main sites affected by oxidative stress is the aorta, which consequently develops atherosclerosis. However, there are few reports demonstrating aortic effects induced by small concentrations of cadmium that are similar to those found in the blood resulting from occupational exposure. Furthermore, several studies have reported on chronic cadmium exposure, and the results of these studies may have been influenced by the secondary effects induced by this metal, such as hypertension. Therefore, we investigated the effects of acute cadmium exposure on the vascular reactivity to phenylephrine of aortic rings isolated from male Wistar rats. Cadmium increased phenylephrine reactivity without changing the vasorelaxation induced by acetylcholine and sodium nitroprusside. Endothelial damage or incubation with L-NAME shifted the phenylephrine concentration-response curves leftward in arteries incubated with or without cadmium, but the curves were shifted to a lesser degree after cadmium incubation. Enalapril, losartan, the nonselective COX inhibitor indomethacin, the TXA(2) synthase inhibitor furegrelate, the selective COX-2 inhibitor NS 398, the TP receptor antagonist SQ 29.548, the EP1 receptor antagonist SC 19.220, superoxide dismutase, and the NADPH oxidase inhibitor apocynin partially reverted the cadmium-induced effects on the reactivity to phenylephrine. Cadmium exposure increased vasoconstrictor activity by reducing NO bioavailability owing to the increased production of ROS by NADPH oxidase. The results of the tested cadmium concentration, which is below the reference values, suggest that acute cadmium exposure may induce vascular injury through endothelial oxidative stress. These data contribute to the evidence indicating that cadmium is a high risk to public health.

Cadmium induced hepatotoxicity in chickens (Gallus domesticus) and ameliorative effect by selenium

Cadmium (Cd) is one of the most toxic metal compounds released into the environment. It was well known that Cd induced hepatotoxicity in animal models. However, little is known about the negative effects of Cd toxicity in the liver of birds. To investigate the Cd hepatotoxicity in birds and the protective effects of selenium (Se) against subchronic exposure to dietary Cd, 100-day-old cocks received either Se (as 10mg Na2SeO3 per kg of diet), Cd (as 150mg CdCl2 per kg of diet) or Cd+Se in their diets for 60 days. Histological and ultrastructural changes in the liver, the concentrations of Cd and Se, the lipid peroxidation (LPO) and nitric oxide (NO) production, the activities of the antioxidants superoxide dismutase (SOD) and glutathione peroxidase (GPx), nitric oxide synthase (NOS) activities and apoptosis were determined. Exposure to Cd significantly reduced SOD and GPx activity, Se content in the liver tissue. It increased the LPO and NO production, the numbers of apoptotic cells and Cd concentration and caused obvious histopathological changes in the liver. Concurrent treatment with Se reduced the Cd-induced liver histopathological changes, oxidative stress, overexpression of NO and apoptosis, suggesting that the toxic effects of Cd on the liver is partly ameliorated by inorganic Se. Se supplementation also modified the distribution of Cd in the liver.

Effect of cadmium-polluted water on plasma levels of tumor necrosis factor-α, interleukin-6 and oxidative status biomarkers in rats: protective effect of curcumin

The present study was designed to investigate the effect of CdCl₂-polluted drinking water (40 mg CdCl₂/L) on the level of TNF-α and IL-6, as well as oxidative status biomarkers in plasma of rats. The possible protective effect of oral administration of curcumin (50 mg/kg body weight/day) was assessed. Results illustrated that Cd exposure significantly elevated the plasma levels of TNF-α and IL-6 (p<0.001) as compared to normal rats. Also, Cd administration resulted in a significant elevation in the lipid peroxidation and markedly reduction in the activities of SOD and catalase as well as the level of glutathione and total antioxidant capacity in plasma. The co-treatment of Cd with curcumin significantly reduced the levels of TNF-α and IL-6 and ameliorated the alteration in oxidative status biomarkers induced by Cd. Negative correlation between IL-6 or TNF-α was and the plasma activities of catalase, SOD and the level of total antioxidant capacity were found in rats exposed to Cd.

CONCLUSION

Cadmium toxicity induced the release of TNF-α and IL-6 which is associated with systemic oxidative stress. This may be involved in the mechanism of the Cd toxicity. On the other hand, the findings suggest the curative action of curcumin against Cd toxicity.

Cadmium-Induced Pathologies: Where Is the Oxidative Balance Lost (or Not)?

Over the years, anthropogenic factors have led to cadmium (Cd) accumulation in the environment causing various health problems in humans. Although Cd is not a Fenton-like metal, it induces oxidative stress in various animal models via indirect mechanisms. The degree of Cd-induced oxidative stress depends on the dose, duration and frequency of Cd exposure. Also the presence or absence of serum in experimental conditions, type of cells and their antioxidant capacity, as well as the speciation of Cd are important determinants. At the cellular level, the Cd-induced oxidative stress either leads to oxidative damage or activates signal transduction pathways to initiate defence responses. This balance is important on how different organ systems respond to Cd stress and ultimately define the pathological outcome. In this review, we highlight the Cd-induced oxidant/antioxidant status as well as the damage versus signalling scenario in relation to Cd toxicity. Emphasis is addressed to Cd-induced pathologies of major target organs, including a section on cell proliferation and carcinogenesis. Furthermore, attention is paid to Cd-induced oxidative stress in undifferentiated stem cells, which can provide information for future therapies in preventing Cd-induced pathologies.

Characterization and expression of superoxide dismutase genes in Chironomus riparius (Diptera, Chironomidae) larvae as a potential biomarker of ecotoxicity

Superoxide dismutase (SOD, EC 1.15.1.1) is an enzyme involved in the scavenging of reactive oxygen species (ROS) into molecular oxygen and hydrogen peroxide. In this study, a copper-zinc superoxide dismutase (Cu-ZnSOD) gene and a manganese superoxide dismutase (MnSOD) gene in aquatic midge, Chironomus riparius (CrSODs) was identified using an Expressed Sequence Tag (EST) database generated by 454 pyrosequencing. A multiple sequence alignment of C. riparius sequences revealed high homology with other insect sequences in terms of the amino acid level. Phylogenetic analysis of the CrSODs revealed that they were grouped with SODs of other organisms, such as Polypedilum vanderplanki, Drosophila melanogaster, Aedes aegypti, Anopheles gambiae, Culex quinquefasciatus and Bombyx mori. Expression of the corresponding CrSODs was analyzed during different developmental stages and following exposure to various environmental contaminants with different mode of actions i.e., paraquat, cadmium, benzo[a]pyrene, and chloropyrifos. CrSOD gene expression was significantly up or down regulated in response to exposure to the chemicals tested. The overall results suggested that SOD gene expression provided a platform for the understanding of oxidative stress responses caused by exposure to various environmental contaminants, and the SOD genes could be used as biomarkers for environmental disturbances such as oxidative stress initiated by xenobiotics.

Ovarian toxicity induced by dietary cadmium in hen

To investigate the toxicity of cadmium (Cd) on female reproduction in birds, this study was conducted to determine the changes in biochemical parameters of serum and ovary tissue caused by dietary cadmium in hens. Ninety 50-day-old hyline white hens were randomly divided into three groups (30 hens per group): a control group was fed with basal diet, a low dose group was fed with basal diet containing 140 mg/kg CdCl(2) and a high dose group was fed with basal diet containing 210 mg/kg CdCl2. After being treated with Cd for 20, 40 and 60 days, ovary and serum samples were collected and examined for Cd content, histological evaluations, malondialdehyde (MDA) content, glutathione peroxidase (GPx) content, activities of superoxide dismutase (SOD), nitric oxide (NO) content, nitric oxide synthase (NOS) activity, and serum estradiol and progestogen levels. The results showed that the content of Cd, MDA, NO and the activity of NOS in ovary and serum were increased (P < 0.05), while the level of GPx and the activity of SOD were decreased (P < 0.05) in low dose and high dose groups. A time- and dose-dependent correlation was observed between serum and ovary tissue cadmium levels. The number of apoptotic cells in the ovary was increased in the Cd treatment group (P < 0.05). Extensive damage was observed in the ovary. The level of estradiol and progestogen in the serum of low dose and high dose groups was decreased significantly (P < 0.05). It indicated that Cd exposure resulted in oxidative damage of hens' ovary tissue by altering antioxidant defense enzyme systems, lipid peroxidation, apoptosis and endocrine disturbance which may be possible underlying reproductive toxicity mechanisms induced by Cd.

Gadolinium chloride pretreatment ameliorates acute cadmium-induced hepatotoxicity

Cadmium is a known industrial and environmental pollutant. It causes hepatotoxicity upon acute administration. Features of cadmium-induced acute hepatoxicity encompass necrosis, apoptosis, peliosis and inflammatory infiltration. Gadolinium chloride (GdCl3) may prevent cadmium-induced hepatotoxicity by suppressing Kupffer cells. The effect of GdCl3 pretreatment on a model of acute cadmium-induced liver injury was investigated. Male Wistar rats 4–5 months old were injected intraperitoneally with normal saline followed by cadmium chloride (CdCl2; 6.5 mg/kg) or GdCl3 (10 mg/kg) followed by CdCl2 (6.5 mg/kg; groups I and II, respectively). Rats of both the groups were killed at 9, 12, 16, 24, 48 and 60 h after cadmium intoxication. Liver sections were analyzed for necrosis, apoptosis, peliosis and mitoses. Liver regeneration was also evaluated by tritiated thymidine incorporation into hepatic DNA. Serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were also determined. Hepatic necrosis, hepatocyte and nonparenchymal cell apoptosis and macroscopic and microscopic types of peliosis hepatis were minimized by gadolinium pretreatment. Serum levels of AST and ALT were also greatly diminished in rats of group II. Tritiated thymidine incorporation into hepatic DNA was increased in gadolinium pretreatment rats. Kupffer cell activation was minimal in both the groups of rats. Gadolinium pretreatment attenuates acute cadmium-induced liver injury in young Wistar rats, with mechanisms other than Kupffer cell elimination.

Expression of catalase and glutathione S-transferase genes in Chironomus riparius on exposure to cadmium and nonylphenol

Antioxidant enzymes play important roles in the protection against oxidative damage caused by environmental pollutants by scavenging high levels of reactive oxygen species and have been quantified as oxidative stress markers. However, combining mRNA expressions of genes coding for detoxification enzymes along with enzyme activities will be more useful biomarkers of stress. Therefore, in this study the cDNA of the catalase gene from the aquatic midge, Chironomus riparius (CrCAT) was sequenced using 454 pyrosequencing. The 2139 bp CrCAT cDNA included an open reading frame of 1503 bp encoding a putative protein of 500 amino acids with a predicted molecular mass of 56.72 kDa. There was an 18 bp 5' and a long 618 bp 3' untranslated region with a polyadenylation signal site (AATAAA). The deduced amino acid sequence of CrCAT contained several highly conserved motifs including the proximal heme-ligand signature sequence RLFSYNDTX and the proximal active site signature FXRERIPERVVHAKGXGA. A comparative analysis showed the presence of conserved amino acid residues and all of the catalytic amino acids (His(70), Asn(143), and Tyr(353)) were conserved in all species. The CrCAT contained three potential glycosylation sites and a peroxisome targeting signal of 'AKM'. The mRNA was detected using RT-PCR at all developmental stages. The time-course expression of CrCAT was measured using quantitative real-time PCR after exposure to different concentration and durations of Paraquat (PQ), cadmium chloride (Cd) and nonylphenol (NP). The expression of CrCAT was significantly up regulated on exposure to 50 and 100mg/L PQ for 12 and 24h. Among the different concentrations and durations of Cd tested, significantly highest level of expression for CrCAT mRNA and catalase enzyme activity was observed on exposure to 10mg/L for 24h. In the case of NP, the highest level of CrCAT expression was observed after exposure to 100 μg/L for 24h. The expression profiles of three selected C. riparius glutathione S-transferase genes (CrGSTs) viz. CrGSTdelta3, CrGSTsigma4 and CrGSTepsilon1 was also studied on exposure to NP and were up or down regulated at different time points and concentrations. Significantly highest level of expression for CrGSTdelta3 was observed after 48 h and for CrGSTsigma4 and CrGSTepsilon1 after 24h exposure to 100 μg/L of NP. The results show that CrGSTs and CrCAT could be used as potential biomarkers in C. riparius for aquatic ecotoxicological studies.

Characterization and transcriptional regulation of thioredoxin reductase 1 on exposure to oxidative stress inducing environmental pollutants in Chironomus riparius

We characterized thioredoxin reductase 1 (TrxR1) from Chironomus riparius (CrTrxR1) and studied its expression under oxidative stress. The full-length cDNA is 1820bp long and contains an open reading frame (ORF) of 1488bp. The deduced CrTrxR1 protein has 495 amino acids and a calculated molecular mass of 54.41kDa and an isoelectric point of 6.15. There was a 71bp 5' and a 261bp 3' untranslated region with a polyadenylation signal site (AATAAA). Homologous alignments showed the presence of conserved catalytic domain Cys-Val-Asn-Val-Gly-Cys (CVNVGC), the C-terminal amino acids 'CCS' and conserved amino acids required in catalysis. The expression of CrTrxR1 is measured using quantitative real-time PCR after exposure to 50 and 100mg/L of paraquat (PQ) and 2, 10 and 20mg/L of cadmium chloride (Cd). CrTrxR1 mRNA was upregulated after PQ exposure at all conditions tested. The highest level of CrTrxR1 expression was observed after exposure to 10mg/L of Cd for 24h followed by 20mg/L for 48h. Significant downregulation of CrTrxR1 was observed after exposure to 10 and 20mg/L of Cd for 72h. This study shows that the CrTrxR1 could be potentially used as a biomarker of oxidative stress inducing environmental contaminants.

Interrelationships between cadmium, zinc and antioxidants in the liver of the rat exposed orally to relatively high doses of cadmium and zinc

Zinc (Zn) reduces cadmium (Cd)-induced toxicity in the liver although it increases Cd tissue burden in some conditions; hence, the present study is designed to study the relationships between Cd, Zn and antioxidants in the liver of rats exposed to Cd. Livers of male rats which received orally relatively high doses of Cd (200 mg Cd/L as Cd chloride or Cd (200 mg/L)+Zn (500 mg Zn as Zn chloride) during five weeks, were investigated. Cd induced an accumulation of Cd and Zn in parallel to depletion in important variables (GSH, GSH/GSSG, CuZn-SOD and GPx activities) and to elevation in others (Cd/Zn and GSSG). Cd, did not affect CuZn SOD/GPx, nor Mn-SOD in the liver. Cd accumulation, Cd/Zn, CuZn SOD activity and CuZn SOD/GPx, was increased remarkably under Zn action. Zn supply ameliorated GSH level and partially reversed the decrease in GSH/GSSG, but it did not ameliorate GPx activity. Analysis showed high correlations between Cd and the majority of the variables, while Zn was positively correlated with only GSSG. We suggest from our results that Zn has indirect ameliorative effects on Cd-induced toxicity in the liver and that the increase in Cd retention is probably the key mechanism modulating, in the case of relatively high doses of Cd, the antioxidant response during exposure to Cd and Zn.

Antioxidant responses, hepatic intermediary metabolism, histology and ultrastructure in Synechogobius hasta exposed to waterborne cadmium

The present study was conducted to determine antioxidant responses, hepatic intermediary metabolism, histology and ultrastructure in Synechogobius hasta after a 15-days of waterborne cadmium (Cd) exposure at the concentrations of 0 (control), 0.10, 0.17 and 0.29 mg Cd/l (corresponding to 0, 12.6%, 21.5% and 36.7% of 96 h LC₅₀), respectively. Growth performance and survival declined, but hepatosomatic index (HSI) increased with increasing waterborne Cd levels (P < 0.05). Waterborne Cd exposure also significantly increased lipid contents in whole body and liver (P < 0.05), and Cd accumulation in whole body, muscle and vertebrae. Waterborne Cd exposure changed hepatic enzymatic activities involved in intermediary metabolism, induced antioxidant responses and increased lipid peroxidation level in the gill, liver and spleen. Waterborne Cd exposure also caused considerable histological alterations of gill, liver and spleen, led ultrastructures damage of liver and spleen of fish, and induced fatty liver for this fish species.

Identification, characterization and expression profiles of Chironomus riparius glutathione S-transferase (GST) genes in response to cadmium and silver nanoparticles exposure

In this study, we report the identification and characterization of 13 cytosolic GST genes in Chironomus riparius from Expressed Sequence Tags (ESTs) database generated using pyrosequencing. Comparative and phylogenetic analyses were undertaken with Drosophila melanogaster and Anopheles gambiae GSTs and 3 Delta, 4 Sigma, 1 each in Omega, Epsilon, Theta, Zeta and 2 unclassified classes of GSTs were identified and characterized. The relative mRNA expression levels of all of the C. riparius GSTs (CrGSTs) genes under different developmental stages were varied with low expression in the larval stage. The antioxidant role of CrGSTs was studied by exposing fourth instar larvae to a known oxidative stress inducer Paraquat and the relative mRNA expression to different concentrations of cadmium (Cd) and silver nanoparticles (AgNPs) for various time intervals were also studied. All the CrGSTs showed up- or down regulation to varying levels based upon the concentration, and duration of exposure. The highest mRNA expression was noticed in Delta3, Sigma4 and Epsilon1 GST class in all treatments. These results show the role of CrGST genes in defense against oxidative stress and its potential as a biomarker to Cd and AgNPs exposure.

Metallothionein gene expression in liver of rats exposed to cadmium and supplemented with zinc and selenium

Cadmium (Cd), one of the most widely distributed heavy metals, is highly toxic to humans and animals. It is well known that zinc (Zn) and selenium (Se) administration reduce the Cd-induced toxicity and that metallothioneins can have a protective effect to mitigate Cd toxicity in biological systems. In this study we report the expression analysis of the two metallothioneines gene classes MT-1 and MT-2 as well as the total metalloprotein content in the liver of rats exposed to Cd (200 ppm), Cd + Zn (200 ppm + 500 ppm), Cd + Se (200 ppm + 0.1 ppm) or Cd + Zn + Se (200 ppm + 500 ppm + 0.1 ppm) in their drinking water for 35 days. Metals accumulation was quantified in rat liver. Cd decreased significantly the hepatic concentrations of Se and increased those of Zn. The treatment of Cd-exposed rats with Se alone or combined with Zn reversed the Cd-induced depletion of Se concentrations in the liver. However, Zn or Zn + Se administration significantly increased the liver Cd uptake and had no effect on the Cd-induced increase in hepatic concentrations of Zn. The molecular assay showed a decreasing trend of MT-1 relative gene expression levels in animals supplemented with Zn (6.87-fold), Se (3.58-fold), and their combination (1.69-fold) when compared to Cd-treated animals (16.22-fold). Upregulation of the MT-2 expression were recorded in all conditions, although fold induction levels were less pronounced than MT-1 expressions. Our data suggest that the well-established protective effect of Zn and Se against Cd-induced toxicity passes through non-MT gene expression mechanisms, being more dependent on the oxidative stress status of the cell.