Cadmium induces reactive oxygen species generation and lipid peroxidation in cortical neurons in culture

Effects of Se and Cd Co-treatment on the Morphology, Oxidative Stress, and Ion Concentrations in the Ovaries of Laying Hens

This study aims at revealing the effects of the combined treatment of selenium and cadmium on ovary morphology, oxidative stress, and 28 kinds of ion concentrations in laying hens. In this experiment, 128 healthy 31-week-old chickens were selected and divided into four treatment groups, three of which were separately fed the basic diets supplemented with either Se or Cd or both Se and Cd for 90 days, and the remaining group was fed the basic diet and treated as a control. The chickens were sacrificed for collecting ovarian tissues. Morphological structure and ultrastructure analysis of ovaries in the Cd-treated group revealed ovarian damage, with decreased activities of SOD and GPx, along with increased levels of MDA and H₂O₂. Cd treatment also resulted in disturbances in ion balance. The concentrations of Ca, Ti, Cu, Zn, and Ba were significantly reduced, while the concentrations of Fe, Mo, and Cd were significantly increased when compared with the control group. Interestingly, the damages caused by cadmium were alleviated in the Se+Cd-treated group. These results indicate that selenium can alleviate cadmium-induced ovarian damages.

Cadmium telluride quantum dots induce apoptosis in human breast cancer cell lines

Introduction:

Semiconductor quantum dots (QDs), especially those containing cadmium, have undergone marked improvements and are now widely used nanomaterials in applicable biological fields. However, great concerns exist regarding their toxicity in biomedical applications. Because of the lack of sufficient data regarding the toxicity mechanism of QDs, this study aimed to evaluate the cytotoxicity of three types of QDs: CdTe QDs, high yield CdTe QDs, and CdTe/CdS core/shell QDs on two human breast cancer cell lines MDA-MB468 and MCF-7.

Methods:

The breast cancer cells were treated with different concentrations of QDs, and cell viability was evaluated via MTT assay. Hoechst staining was applied for observation of morphological changes due to apoptosis. Apoptotic DNA fragmentation was visualized by the agarose gel electrophoresis assay. Flow cytometric annexin V/propidium iodide (PI) measurement was used for apoptosis detection.

Results:

A significant decrease in cell viability was observed after QDs treatment ( p < 0.05). Apoptotic bodies and chromatin condensation was observed by Hoechst staining. DNA fragmentation assay demonstrated a DNA ladder profile in the exposed cells and also annexin V/PI flow cytometry confirmed apoptosis in a dose-dependent manner.

Conclusion:

Our results revealed that CdTe, high yield CdTe, and CdTe/CdS core/shell QDs induce apoptosis in breast cancer cell lines in a dose-dependent manner. This study would help realizing the underlying cytotoxicity mechanism, at least partly, of CdTe QDs and may provide information for the development of nanotoxicology and safe use of biological applications of QDs.

Cadmium favors F-actin depolymerization in rat renal mesangial cells by site-specific, disulfide-based dimerization of the CAP1 protein

Cadmium is a toxic metal that produces oxidative stress and has been shown to disrupt the actin cytoskeleton in rat renal mesangial cells (RMC). In a survey of proteins that might undergo Cd2+-dependent disulfide crosslinking, we identified the adenylyl cyclase-associated protein, CAP1, as undergoing a dimerization in response to Cd2+ (5-40 µM) that was sensitive to disulfide reducing agents, was reproduced by the disulfide crosslinking agent diamide, and was shown by site-directed mutagenesis to involve the Cys29 residue of the protein. Reactive oxygen species are not involved in the thiol oxidation, and glutathione modulates background levels of dimer. CAP1 is known to enhance cofilin's F-actin severing activity through binding to F-actin and cofilin. F-actin sedimentation and GST-cofilin pulldown studies of CAP1 demonstrated enrichment of the CAP1 dimer's association with cofilin, and in the cofilin-F-actin pellet, suggesting that Cd2+-induced dimer increases the formation of a CAP1-cofilin-F-actin complex. Both siRNA-based silencing of CAP1 and overexpression of a CAP1 mutant lacking Cys29 (and therefore, incapable of dimerization in response to Cd2+) increased RMC viability and provided some protection of F-actin structures against Cd2+. It is concluded that Cd2+ brings about disruption of the RMC cytoskeleton in part through formation of a CAP1 dimer that increases recruitment of cofilin to F-actin filaments.

Redox metals homeostasis in multiple sclerosis and amyotrophic lateral sclerosis: a review

The effect of redox metals such as iron and copper on multiple sclerosis and amyotrophic lateral sclerosis has been intensively studied. However, the origin of these disorders remains uncertain. This review article critically describes the physiology of redox metals that produce oxidative stress, which in turn leads to cascades of immunomodulatory alteration of neurons in multiple sclerosis and amyotrophic lateral sclerosis. Iron and copper overload has been well established in motor neurons of these diseases’ lesions. On the other hand, the role of other metals like cadmium participating indirectly in the redox cascade of neurobiological mechanism is less studied. In the second part of this review, we focus on this less conspicuous correlation between cadmium as an inactive-redox metal and multiple sclerosis and amyotrophic lateral sclerosis, providing novel treatment modalities and approaches as future prospects.

Metabolomic analysis of the toxic effect of chronic exposure of cadmium on rat urine

This study aimed to assess the toxic effect of chronic exposure to cadmium through a metabolomic approach based on ultra-performance liquid chromatography/mass spectrometry (UPLC-MS). Forty male Sprague-Dawley rats were randomly assigned to the following groups: control, low-dose cadmium chloride (CdCl₂) (0.13 mg/kg body weight (bw)), middle-dose CdCl₂ (0.8/kg bw), and high-dose CdCl₂ (4.9 mg/kg bw). The rats continuously received CdCl₂ via drinking water for 24 weeks. Rat urine samples were then collected at different time points to establish the metabolomic profiles. Multiple statistical analyses with principal component analysis and partial least squares-discriminant analysis were used to investigate the metabolomic profile changes in the urine samples and screen for potential biomarkers. Thirteen metabolites were identified from the metabolomic profiles of rat urine after treatment. Compared with the control group, the treated groups showed significantly increased intensities of phenylacetylglycine, guanidinosuccinic acid, 4-pyridoxic acid, 4-aminohippuric acid, 4-guanidinobutanoic acid, allantoic acid, dopamine, LysoPC(18:2(9Z,12Z)), and L-urobilinogen. By contrast, the intensities of creatinine, L-carnitine, taurine, and pantothenic acid in the treated groups were significantly decreased. These results indicated that Cd disrupts energy and lipid metabolism. Meanwhile, Cd causes liver and kidney damage via induction of oxidative stress; serum biochemical indices (e.g., creatinine and urea nitrogen) also support the aforementioned results.

In vitro toxic effects of reduced graphene oxide nanosheets on lung cancer cells

The intriguing properties of reduced graphene oxide (rGO) have paved the way for a number of potential biomedical applications such as drug delivery, tissue engineering, gene delivery and bio-sensing. Over the last decade, there have been escalating concerns regarding the possible toxic effects, behaviour and fate of rGO in living systems and environments. This paper reports on integrative chemical-biological interactions of rGO with lung cancer cells, i.e. A549 and SKMES-1, to determine its potential toxicological impacts on them, as a function of its concentration. Cell viability, early and late apoptosis and necrosis were measured to determine oxidative stress potential, and induction of apoptosis for the first time by comparing two lung cancer cells. We also showed the general trend between cell death rates and concentrations for different cell types using a Gaussian process regression model. At low concentrations, rGO was shown to significantly produce late apoptosis and necrosis rather than early apoptotic events, suggesting that it was able to disintegrate the cellular membranes in a dose dependent manner. For the toxicity exposures undertaken, late apoptosis and necrosis occurred, which was most likely resultant from limited bioavailability of unmodified rGO in lung cancer cells.

Acute toxicity of cadmium in Anisops sardeus (Heteroptera:Notonectidae): Effects on adult and nymphal survival and swimming behavior

Adult female and male, and final instar nymph of Anisops sardeus (Heteroptera: Notonectidae) were exposed to graded concentrations of cadmium in 96h static-with-renewal acute toxicity tests, which were conducted in dry (March) and wet (May-June) seasons. The 96h LC₅₀ values for instar V nymph, adult female and male were found to be 0.9, 0.59 and 0.51mgL^-1 Cd, respectively, in wet season, while these were 26.7 and 20.2mgL^-1 Cd for adult female and male, respectively, in dry season. Adult males were most sensitive to Cd, followed by females in both seasons, while highest tolerance in wet season was observed in instar V nymph. There was a steep decline in LC₅₀ values from 24 to 96h in wet season. Besides mortality at higher concentrations of Cd, sublethal effects in terms of reduced 'velocity magnitude' (swimming speed) and mostly increased 'rotation angle' (turning angle) could be discerned at concentrations as low as 0.03mgL^-1. The swimming pattern of Cd-exposed nymph and adults were also affected. Based on the bioaccumulation factor (BAF) values, A. sardeus could be designated as a macroconcentrator of Cd (BAF > 2), with highest Cd accumulation in instar V nymph, followed by that in female, and with lowest Cd accumulation in male.

Short-term social memory deficits in adult female mice exposed to tannery effluent and possible mechanism of action

The accumulated organic residues in tannery-plant courtyards are an eating attraction to small rodents; however, the contact of these animals with these residues may change their social behavior. Thus, the aim of the present study is to investigate whether the exposure to tannery effluent (TE) can damage the social recognition memory of female Swiss mice, as well as to assess whether vitamin C supplementation could provide information about how TE constituents can damage these animals' memory. We have observed that resident females exposed to TE (without vitamin supplementation) did not explore the anogenital region, their body or chased intruding females for shorter time or with lower frequency during the retest session of the social recognition test, fact that indicates social recognition memory deficit in these animals. Such finding is reinforced by the confirmation that there was no change in the animals' olfactory function during the buried food test, or locomotor changes in females exposed to the pollutant. Since no behavioral change was observed in the females exposed to TE and treated with vitamin C (before or after the exposure), it is possible saying that these social cognitive impairments seem to be directly related to the imbalance between the cellular production of reactive oxygen species and the counteracting antioxidant mechanisms (oxidative stress) in female mice exposed to the pollutant (without vitamin supplementation). Therefore, the present study evidences that the direct contact with tannery effluent, even for a short period-of-time, may cause short-term social memory deficits in adult female Swiss mice.

Modulation of cadmium-induced phytotoxicity in Cabomba caroliniana by urea involves photosynthetic metabolism and antioxidant status

Urea is a widespread organic pollutant, which can be a nitrogen source, playing different roles in the growth of submerged macrophytes depending on concentrations, while high cadmium (Cd) concentrations are often toxic to macrophytes. In order to evaluate the combined effect of urea and Cd on a submerged macrophyte, Cabomba caroliniana, the morphological and physiological responses of C. caroliniana in the presence of urea and Cd were studied. The results showed that high concentrations of urea (400mgL^-1) and Cd (500µmolL^-1) had negative effects on C. caroliniana. There were strong visible symptoms of toxicity after 4 days of exposure under Cd-alone, 400mgL^-1 urea, and Cd+400mgL^-1 urea treatments. In addition, 400mgL^-1 urea and Cd had adverse effects on C. caroliniana's pigment system. Significant losses in chlorophyll fluorescence and photosynthetic rates, as well as Rubisco activity were also observed under Cd-alone, 400mgL^-1 urea, and Cd+400mgL^-1 urea treatments. 400mgL^-1 urea markedly enhanced Cd toxicity in C. caroliniana, reflected by a sharp decrease in photosynthetic activity and more visible toxicity symptoms. The results of thiobarbituric acid reactive substances (TBARS) pointed to extreme oxidative stress in C. caroliniana induced under Cd or 400mgL^-1 urea exposure. Exogenous ascorbate (AsA) protected C. caroliniana from adverse damage in 400mgL^-1 urea, which further corroborated the oxidative stress claim under 400mgL^-1 urea. However, results also demonstrated that lower urea concentration (10mgL^-1) alleviated Cd-induced phytotoxicity by stimulating chlorophyll synthesis and photosynthetic activity, as well as activating the activity of catalase (CAT) and glutathione-S-transferase (GST), which may explain the alleviating effect of urea on C. caroliniana under Cd stress.

The longitudinal effects of early developmental cadmium exposure on conditioned place preference and cardiovascular physiology in zebrafish

Cadmium (Cd) is a naturally occurring trace metal that is widely considered to be highly toxic to aquatic organisms and a significant health hazard to humans (Amzal et al., 2009; Bernhoft 2013; Burger, 2008; Satarug et al., 2009). The zebrafish (Danio rerio) has been used as a model organism for toxicological studies with Cd (Banni et al., 2011; Blechinger et al., 2007; Chow et al., 2009; Chow et al., 2008; Favorito et al., 2011; Kusch et al., 2007; Matz et al., 2007; Wang and Gallagher, 2013). We asked what the lasting longitudinal effects would be from short early developmental Cd exposure (between 24 and 96h post-fertilization) in a range that larvae might experience living atop typical Cd-containing surface sediments (0, 0.01, 0.1, 1.0 and 10μM CdCl2: 1.124, 11.24, 112.4 and 1124μg Cd/L). The goal of this exposure window was to specifically target secondary neurogenesis, monoaminergic differentiation and cardiovascular development, without affecting earlier patterning processes. Developmental abnormalities in body size and CNS morphology increased with concentration, but were statistically significant only at the highest concentration used (10μM). Heart rate for Cd-treated larvae increased with concentration, and was significant even at the lowest concentration used (0.01μM). Longitudinal survival was significantly lower for fish developmentally exposed to the highest concentration. Except for brain weight, overall morphology was not affected by developmental Cd exposure. However, developmental exposure to lower concentrations of Cd (0.01, 0.1, and 1.0μM) progressively lowered cocaine-induced conditioned place preference (CPP), used to measure function of the reward pathways in the brain. Baseline heart rate was significantly lower in longitudinal fish developmentally exposed to 1.0μM Cd. Cardiovascular response to isoproterenol, a potent ß-adrenergic agonist, in longitudinal adults was also significantly affected by developmental exposure to Cd at low doses (0.01, 0.1 and 1.0μM). Surviving longitudinal adult fish exposed to the highest concentration of Cd showed normal CPP and cardiovascular physiology. The data imply that even lower exposure concentrations can potentially result in fitness-affecting parameters without affecting survival in a laboratory setting.

The impact of modified nano-carbon black on the earthworm Eisenia fetida under turfgrass growing conditions: Assessment of survival, biomass, and antioxidant enzymatic activities

Modified nano-carbon adsorbents have been employed in the immobilization of heavy metals in soil due to their good adsorption capabilities regarding metal ions. However, an assessment of their risks has not been extensively performed with soil organisms. To assess the toxic effects of three types of modified nano-carbon black (CB) on soil organisms, a laboratory test was conducted to expose the earthworm Eisenia fetida to artificial soil supplemented with 5% H₂SO₄-, HNO₃- and KMnO₄-modified nano-CB (SCB, NCB and KCB, respectively) under turfgrass growing conditions. The tested earthworms were systematically investigated for survival, biomass and the activities of antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). SCB and NCB were found to be more toxic and ecologically dangerous to E. fetida because significant decreases in biomass and survival were observed after 35- and 60-d exposures and the survival rate showed a tendency to decrease with exposure duration. The activities of SOD, CAT and POD were inhibited in all treatments with modified nano-CBs at 35- and 60-d, which indicated that oxidative stress was induced by modified nano-CBs. The results suggest that there is potential harm to earthworms in soil with 5% modified nano-CB and that it deserves special attention.

Melatonin confers plant tolerance against cadmium stress via the decrease of cadmium accumulation and reestablishment of microRNA-mediated redox homeostasis

Although melatonin-alleviated cadmium (Cd) toxicity both in animals and plants have been well studied, little is known about its regulatory mechanisms in plants. Here, we discovered that Cd stress stimulated the production of endogenous melatonin in alfalfa seedling root tissues. The pretreatment with exogenous melatonin not only increased melatonin content, but also alleviated Cd-induced seedling growth inhibition. The melatonin-rich transgenic Arabidopsis plants overexpressing alfalfa SNAT (a melatonin synthetic gene) exhibited more tolerance than wild-type plants under Cd conditions. Cd content was also reduced in root tissues. In comparison with Cd stress alone, ABC transporter and PCR2 transcripts in alfalfa seedlings, PDR8 and HMA4 in Arabidopsis, were up-regulated by melatonin. By contrast, Nramp6 transcripts were down-regulated. Changes in above transporters were correlated with the less accumulation of Cd. Additionally Cd-triggered redox imbalance was improved by melatonin. These could be supported by the changes of the Cu/Zn Superoxide Dismutase gene regulated by miR398a and miR398b. Histochemical staining, laser scanning confocal microscope, and H₂O₂ contents analyses showed the similar tendencies. Taking together, we clearly suggested that melatonin enhanced Cd tolerance via decreasing cadmium accumulation and reestablishing the microRNAs-mediated redox homeostasis.

Dyslipdemia induced by chronic low dose co-exposure to lead, cadmium and manganese in rats: the role of oxidative stress

Lead (Pb), cadmium (Cd) and manganese (Mn) have many potential adverse health effects in vitro and in animal models of clinical toxicity. The current study investigated the dyslipidaemic and oxidative stress effects of chronic low-dose oral exposure to Pb, Cd and Mn and the combination (Pb+Cd+Mn) in rats for 15 weeks. Chronic exposure to the metals did not significantly (P>0.05) alter serum lipid profiles. However, the atherogenic index decreased by 32.2% in the Pb+Cd+Mn group, relative to the control. The triglyceride/high-density lipoprotein cholesterol ratio decreased by 39.4% in the Pb+Cd+Mn group, relative to the control, and elevated by 81.8, 94.8 and 20.8%, relative to the Pb, Cd and Mn groups, respectively. While the serum concentrations of malondialdehyde significantly increased in the Mn and Pb+Cd+Mn groups, that of glutathione peroxidase-1 decreased in the Pb+Cd+Mn group, and metallothionein-1 and zinc concentrations markedly decreased in all the metal treatment groups. The results suggest that long-term exposure of rats to Pb+Cd+Mn may result in hypolipidaemia, mediated via oxidative stress and metal interactions. Individuals who are constantly exposed to environmentally relevant levels of the metals may be at risk of hypolipidaemia.

The Protective Effects of Polysaccharides from Agaricus blazei Murill Against Cadmium-Induced Oxidant Stress and Inflammatory Damage in Chicken Livers

This study aimed to assess the protective roles of polysaccharides from Agaricus blazei Murill (ABP) against cadmium (Cd)-induced damage in chicken livers. A total of 80 Hy-Line laying chickens (7 days old) were randomly divided into four groups (n = 20). Group I (control) was fed with a basic diet and 0.2 ml saline per day, group II (Cd-treated group) was fed with a basic diet containing 140 mg/kg cadmium chloride (CdCl₂) and 0.2 ml saline per day, group III (Cd + ABP-treated group) was fed with a basic diet containing 140 mg/kg CdCl₂ and 0.2-ml ABP solution (30 mg/ml) per day via oral gavage, and group IV (ABP-treated group) was fed with 0.2-ml ABP solution (30 mg/ml) per day via oral gavage. The contents of Cd and malondialdehyde (MDA), the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX), the messenger RNA (mRNA) levels of inflammatory cytokines and heat shock proteins (HSPs), the protein levels of HSPs, and the histopathological changes of livers were evaluated on days 20, 40, and 60. The results showed that Cd exposure resulted in Cd accumulating in livers and inhibiting the activities of antioxidant enzymes (SOD and GSH-PX). Cd exposure caused histopathological damage and increased the MDA content, the mRNA levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) and HSPs (HSP27, HSP40, HSP60, HSP70, and HSP90) and the protein levels of HSPs (HSP60, HSP70, and HSP90). ABP supplementation during dietary exposure to Cd reduced the histopathological damage and decreased the contents of Cd and MDA and the expression of inflammatory cytokines and HSPs and improved the activities of antioxidant enzymes. The results indicated that ABP could partly ameliorate the toxic effects of Cd on chicken livers.

Cadmium and α-lipoic acid activate similar de novo synthesis and recycling pathways for glutathione balance

Glutathione (GSH) protects cells against oxidative stress. Redox modifiers induce GSH biosynthesis and recycling to maintain reduced environment inside cells. Cadmium (Cd²⁺) is a heavy metal that activates redox-sensitive transcriptional factors. The antioxidant α-lipoic acid (ALA) has shown to modulate GSH pathways. This study aimed to investigate de novo synthesis and recycling pathways for GSH balance by different Cd²⁺ concentrations and ALA in HepG2 cells. ALA activates Nrf2 pathway leading to GSH increment. Pre-treatment with 1μM Cd²⁺ or ALA produces tolerance to 5μM Cd²⁺ toxic effects. 5μM Cd²⁺ exposure significantly augmented nuclear Nrf2, GSH and GCLC, GCLM, HMOX1, TNFα and IL-6 mRNA expression but not GSR, however these upsurges were significantly abrogated by ALA or 1μM Cd²⁺ pre-treatments. Exposure to low Cd²⁺ concentration generate timely protective responses, similar to that elicited by ALA, maintaining a normal redox balance inside the cell due to GSH replenishment.

Response of antioxidant enzymes to cadmium-induced cytotoxicity in rat cerebellar granule neurons

Cadmium (Cd) accumulates in the brain and can damage neurons via complex processes involving oxidative stress induction. In this study we used a homogenous population of neurons which are cerebellar granule neurons (CGNs) to investigate damage induced by Cd and its effects on antioxidant enzyme activity. The exposure of CGNs to increasing concentrations of Cd (2.5 μM-100 μM) during 24 h, 48 h, or 72 h led to the induction of neuronal death in a dose- and exposure time-dependent manner. The necrotic and/or apoptotic pathway involved in the cell death trigged by Cd seems to depend on the concentration of Cd and the exposure time. In addition to its cell damage, Cd was shown to affect the activity of superoxide dismutase (SOD) and catalase (CAT) depending on the concentration of Cd and the exposure time. We also found that the exposure to Cd induces a bigger change in SOD activity than in CAT activity. Taken together, our findings explain, in part, the mechanism of Cd toxicity in a specific type of neuron which can provide information related to neurological pathologies ascribed to Cd toxicity.

Association of blood heavy metals with developmental delays and health status in children

The aim of this study was to evaluate the association of blood lead, mercury, and cadmium concentrations with developmental delays and to explore the association of these concentrations with the health status of children. This study recruited 89 children with developmental delays and 89 age- and sex-matched children with typical development. Their health status was evaluated using the Pediatric Quality of Life (PedsQL) Inventory for health-related quality of life (HRQOL) and the Pediatric Outcomes Data Collection Instrument for function. Family function was also evaluated. Blood lead, mercury, and cadmium concentrations were measured using inductively coupled mass spectrometry. The children with developmental delays had a considerably poorer HRQOL, lower functional performance and family function, and a higher blood lead concentration than those with typical development. The blood lead concentration had a significantly positive association with developmental delays [odds ratio (OR) = 1.54, p < 0.01] in a dose-response manner, and it negatively correlated with PedsQL scores (regression coefficient: −0. 47 to −0.53, p < 0.05) in all the children studied. The higher blood cadmium concentration showed a significantly positive association with developmental delays (OR = 2.24, for >1.0 μg/L vs. <0.6 μg/L, p < 0.05). The blood mercury concentration was not associated with developmental delays and health status.

Celastrol Attenuates Cadmium-Induced Neuronal Apoptosis via Inhibiting Ca2+ -CaMKII-Dependent Akt/mTOR Pathway

Cadmium (Cd), an environmental and industrial pollutant, affects the nervous system and consequential neurodegenerative disorders. Recently, we have shown that celastrol prevents Cd-induced neuronal cell death partially by suppressing Akt/mTOR pathway. However, the underlying mechanism remains to be elucidated. Here, we show that celastrol attenuated Cd-elevated intracellular-free calcium ([Ca²⁺ ]_i ) level and apoptosis in neuronal cells. Celastrol prevented Cd-induced neuronal apoptosis by inhibiting Akt-mediated mTOR pathway, as inhibition of Akt with Akt inhibitor X or ectopic expression of dominant negative Akt reinforced celastrol's prevention of Cd-induced phosphorylation of S6K1/4E-BP1 and cell apoptosis. Furthermore, chelating intracellular Ca²⁺ with BAPTA/AM or preventing [Ca²⁺ ]_i elevation using EGTA potentiated celastrol's repression of Cd-induced [Ca²⁺ ]_i elevation and consequential activation of Akt/mTOR pathway and cell apoptosis. Moreover, celastrol blocked Cd-elicited phosphorylation of CaMKII, and pretreatment with BAPTA/AM or EGTA enhanced celastrol's suppression of Cd-increased phosphorylation of CaMKII in neuronal cells, implying that celastrol hinders [Ca²⁺ ]_i -mediated CaMKII phosphorylation. Inhibiting CaMKII with KN93 or silencing CaMKII attenuated Cd activation of Akt/mTOR pathway and cell apoptosis, and this was strengthened by celastrol. Taken together, these data demonstrate that celastrol attenuates Cd-induced neuronal apoptosis via inhibiting Ca²⁺ -CaMKII-dependent Akt/mTOR pathway. Our findings underscore that celastrol may act as a neuroprotective agent for the prevention of Cd-induced neurodegenerative disorders. J. Cell. Physiol. 232: 2145-2157, 2017. © 2016 Wiley Periodicals, Inc.

Celastrol ameliorates Cd-induced neuronal apoptosis by targeting NOX2-derived ROS-dependent PP5-JNK signaling pathway

Celastrol, a plant-derived triterpene, has neuroprotective benefit in the models of neurodegenerative disorders that are characterized by overproduction of reactive oxygen species (ROS). Recently, we have reported that cadmium (Cd) activates c-Jun N-terminal kinase (JNK) pathway leading to neuronal cell death by inducing ROS inactivation of protein phosphatase 5 (PP5), and celastrol prevents Cd-activated JNK pathway against neuronal apoptosis. Therefore, we hypothesized that celastrol could hinder Cd induction of ROS-dependent PP5-JNK signaling pathway from apoptosis in neuronal cells. Here, we show that celastrol attenuated Cd-induced expression of NADPH oxidase 2 (NOX2) and its regulatory proteins (p22^phox , p40^phox , p47^phox , p67^phox , and Rac1), as well as the generation of ROS in PC12 cells and primary neurons. Also, N-acetyl-l-cysteine, a ROS scavenger, potentiated celastrol's inhibition of the events in the cells triggered by Cd, implying neuroprotection by celastrol via blocking Cd-evoked NOX2-derived ROS. Further research revealed that celastrol was involved in the regulation of PP5 inactivation and JNK/c-Jun activation induced by Cd, as celastrol prevented Cd from reducing PP5 expression, and over-expression of wild-type PP5 or dominant negative c-Jun strengthened celastrol's inhibition of Cd-induced phosphorylation of JNK and/or c-Jun, as well as apoptosis in neuronal cells. Of importance, inhibiting NOX2 with apocynin or silencing NOX2 by RNA interference enhanced the inhibitory effects of celastrol on Cd-induced inactivation of PP5, activation of JNK/c-Jun, ROS, and apoptosis in the cells. Furthermore, we noticed that expression of wild-type PP5 or dominant negative c-Jun, or pretreatment with JNK inhibitor SP600125 reinforced celastrol's suppression of Cd-induced NOX2 and its regulatory proteins, and consequential ROS in neuronal cells. These findings indicate that celastrol ameliorates Cd-induced neuronal apoptosis via targeting NOX2-derived ROS-dependent PP5-JNK signaling pathway. Our data highlight a beneficial role of celastrol in the prevention of Cd-induced oxidative stress and neurodegenerative diseases.

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.

Hydrogen Peroxide Pretreatment Mitigates Cadmium-Induced Oxidative Stress in Brassica napus L.: An Intrinsic Study on Antioxidant Defense and Glyoxalase Systems

Cadmium (Cd) is considered as one of the most toxic metals for plant growth and development. In the present study, we investigated the role of externally applied hydrogen peroxide (H2O2) in regulating the antioxidant defense and glyoxalase systems in conferring Cd-induced oxidative stress tolerance in rapeseed (Brassica napus L.). Seedlings were pretreated with 50 μM H2O2 for 24 h. These pretreated seedlings as well as non-pretreated seedlings were grown for another 48 h at two concentrations of CdCl2 (0.5 and 1.0 mM). Both the levels of Cd increased MDA and H2O2 levels and lipoxygenase activity while ascorbate (AsA) declined significantly. However, reduced glutathione (GSH) content showed an increase at 0.5 mM CdCl2, but glutathione disulfide (GSSG) increased at any level of Cd with a decrease in GSH/GSSG ratio. The activities of ascorbate peroxidase (APX) and glutathione S-transferase (GST) upregulated due to Cd treatment in dose-dependent manners, while glutathione reductase (GR) and glutathione peroxidase (GPX) increased only at 0.5 mM CdCl2 and decreased at higher dose. The activity of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II) decreased under Cd stress. On the other hand, H2O2 pretreated seedlings, when exposed to Cd, AsA and GSH contents and GSH/GSSG ratio increased noticeably. H2O2 pretreatment increased the activities of APX, MDHAR, DHAR, GR, GST, GPX, and CAT of Cd affected seedlings. Thus enhancement of both the non-enzymatic and enzymatic antioxidants helped to decrease the oxidative damage as indicated by decreased levels of H2O2 and MDA. The seedlings which were pretreated with H2O2 also showed enhanced glyoxalase system. The activities of Gly I, and Gly II and the content of GSH increased significantly due to H2O2 pretreatment in Cd affected seedlings, compared to the Cd-stressed plants without H2O2 pretreatment which were vital for methylglyoxal detoxification. So, the major roles of H2O2 were improvement of antioxidant defense system and glyoxalase system which protected plants from the damage effects of ROS and MG. The mechanism of H2O2 to induce antioxidant defense and glyoxalase system and improving physiology under stress condition is not known clearly which should be elucidated. The signaling roles of H2O2 and its interaction with other signaling molecules, phytohormones or other biomolecules and their roles in stress protection should be explored.

Combined effects of cadmium, temperature and hypoxia-reoxygenation on mitochondrial function in rainbow trout (Oncorhynchus mykiss)

Although aquatic organisms face multiple environmental stressors that may interact to alter adverse outcomes, our knowledge of stressor-stressor interaction on cellular function is limited. We investigated the combined effects of cadmium (Cd), hypoxia-reoxygenation (H-R) and temperature on mitochondrial function. Liver mitochondria from juvenile rainbow trout were exposed to Cd (0-20μM) and H-R (0 and 5min) at 5, 13 and 25°C followed by measurements of mitochondrial Cd load, volume, complex І active (A)↔deactive (D) transition, membrane potential, ROS release and ultrastructural changes. At high temperature Cd exacerbated H-R-imposed reduction of maximal complex I (CI) respiration whereas at low temperature 5 and 10μM stimulated maximal CI respiration post H-R. The basal respiration showed a biphasic response at high temperatures with low Cd concentrations reducing the stimulatory effect of H-R and high concentrations enhancing this effect. At low temperature Cd monotonically enhanced H-R-induced stimulation of basal respiration. Cd and H-R reduced both the P/O ratio and the RCR at all 3 temperatures. Temperature rise alone increased mitochondrial Cd load and toxicity, but combined H-R and temperature exposure reduced mitochondrial Cd load but surprisingly exacerbated the mitochondrial dysfunction. Mitochondrial dysfunction induced by H-R was associated with swelling of the organelle and blocking of conversion of CІ D to A form. However, low amounts of Cd protected against H-R induced swelling and prevented the inhibition of H-R-induced CI D to A transition. Both H-R and Cd dissipated mitochondrial membrane potential Δψ_m and damaged mitochondrial structure. We observed increased reactive oxygen species (H₂O₂) release that together with the protection afforded by EGTA, vitamin E and N-acetylcysteine against the Δψ_m dissipation suggested direct involvement of Cd and oxidative stress. Overall, our findings indicate that mitochondrial sensitivity to Cd toxicity was enhanced by the effects of H-R and temperature, and changes in mitochondrial Cd load did not always explain this effect.

Neurodegeneration Induced by Metals in Caenorhabditis elegans

Metals are a component of a variety of ecosystems and organisms. They can generally be divided into essential and nonessential metals. The essential metals are involved in physiological processes once the deficiency of these metals has been associated with diseases. Although iron, manganese, copper, and zinc are important for life, it has been evidenced that they are also involved in neuronal damage in many neurodegenerative disorders. Nonessential metals, which are metals without physiological functions, are present in trace or higher levels in living organisms. Occupational, environmental, or deliberate exposures to lead, mercury, aluminum, and cadmium are clearly correlated with the increase of toxicity and varied kinds of pathological situations. Actually, the field of neurotoxicology needs to satisfy two opposing demands: the testing of a growing list of chemicals and resource limitations and ethical concerns associated with testing using traditional mammalian species. Toxicological assays using alternative animal models may relieve some of this pressure by allowing testing of more compounds while reducing expenses and using fewer mammals. The nervous system is by far the more complex system in C. elegans. Almost a third of their cells are neurons (302 neurons versus 959 cells in adult hermaphrodite). It initially underwent extensive development as a model organism in order to study the nervous system, and its neuronal lineage and the complete wiring diagram of its nervous system are stereotyped and fully described. The neurotransmission systems are phylogenetically conserved from nematodes to vertebrates, which allows for findings from C. elegans to be extrapolated and further confirmed in vertebrate systems. Different strains of C. elegans offer a new perspective on neurodegenerative processes. Some genes have been found to be related to neurodegeneration induced by metals. Studying these interactions may be an effective tool to slow neuronal loss and deterioration.

Neurotoxicity induced by arsenic in Gallus Gallus: Regulation of oxidative stress and heat shock protein response

Arsenic, a naturally occurring heavy metal pollutant, is one of the functioning risk factors for neurological toxicity in humans. However, little is known about the effects of arsenic on the nervous system of Gallus Gallus. To investigate whether arsenic induce neurotoxicity and influence the oxidative stress and heat shock proteins (Hsps) response in chickens, seventy-two 1-day-old male Hy-line chickens were treated with different doses of arsenic trioxide (As₂O₃). The histological changes, antioxidant enzyme activity, and the expressions of Hsps were detected. Results showed slightly histology changes were obvious in the brain tissues exposure to arsenic. The activities of Glutathione peroxidase (GSH-Px) and catalase (CAT) were decreased compared to the control, whereas the malondialdehyde (MDA) content was increased gradually along with increase in diet-arsenic. The mRNA levels of Hsps and protein expressions of Hsp60 and Hsp70 were up-regulated. These results suggested that sub-chronic exposure to arsenic induced neurotoxicity in chickens. Arsenic exposure disturbed the balance of oxidants and antioxidants. Increased heat shock response tried to protect chicken brain tissues from tissues damage caused by oxidative stress. The mechanisms of neurotoxicity induced by arsenic include oxidative stress and heat shock protein response in chicken brain tissues.

Studies on the removal of Cd ions by gastrointestinal lactobacilli

Accumulation of toxic metal ions in food and water is nowadays a growing health-related problem. One detoxification method involves the use of microorganisms naturally inhabiting the gastrointestinal tract (GIT). The purpose of this study was to prove that lactic acid bacteria derived from the GIT are able to effectively remove Cd²⁺ from water solution. Seven strains of lactobacilli, out of 11 examined, showed tolerance to high concentrations of cadmium ions. The metal-removal efficiencies of these seven lactobacilli ranged from 6 to 138.4 μg/h mg. Among these bacteria, Lactobacillus gallinarum and Lactobacillus crispatus belonged to the highest (85%) Cd-removal efficiency class. An analysis of the zeta potential (ζ) indicated that the bacterial cell surface had a negative charge at the pH ranging from 3 to 10. The presence of carboxyl, amide, and phosphate groups was favorable for Cd²⁺ binding to the cell surface, which found confirmation in FTIR-ATR spectra. Elemental SEM/EDS analysis and TEM imaging not only confirmed the adsorption of Cd²⁺ on the cell envelope but also gave us a reason to suppose that Lb. crispatus accumulates metal ions inside the cell. Our findings open perspectives for further research on the new biological function of GIT lactobacilli as natural biosorbents.

Effects of Divalent Cations on Outward Potassium Currents in Leech Retzius Nerve Cells

The present study examines the effects of divalent metals, cadmium (Cd2+) and manganese (Mn2+), on the outward potassium currents of Retzius cells in the hirudinid leeches Haemopis sanguisuga using conventional two-microelectrode voltageclamp techniques. The outward potassium current is activated by depolarization and plays an important role in determining both the neuronal excitability and action potential duration. A strong inhibition of the fast current and a clear reduction in the late currents of the outward current with 1 mM Cd2+were obtained, which indicated that both components are sensitive to this metal. Complete blockage of the fast and partial reduction of the slow outward currents was observed after adding 1 mM Mn2+to the extracellular fluid. These data show that the outward K+current in leech Retzius nerve cells comprises at least two components: a voltage-dependent K+current and a Ca2+- activated K+current. These observations also indicate that Cd2+is more eff ective than Mn2+in blocking ion fl ow through these channels and that suppressing Ca2+-activated K+outward currents can prolong the action potential in nerve cells.

Heavy metals (Pb, Cd, As and MeHg) as risk factors for cognitive dysfunction: A general review of metal mixture mechanism in brain

Human exposure to toxic heavy metals is a global challenge. Concurrent exposure of heavy metals, such as lead (Pb), cadmium (Cd), arsenic (As) and methylmercury (MeHg) are particularly important due to their long lasting effects on the brain. The exact toxicological mechanisms invoked by exposure to mixtures of the metals Pb, Cd, As and MeHg are still unclear, however they share many common pathways for causing cognitive dysfunction. The combination of metals may produce additive/synergetic effects due to their common binding affinity with NMDA receptor (Pb, As, MeHg), Na⁺ - K⁺ ATP-ase pump (Cd, MeHg), biological Ca⁺² (Pb, Cd, MeHg), Glu neurotransmitter (Pb, MeHg), which can lead to imbalance between the pro-oxidant elements (ROS) and the antioxidants (reducing elements). In this process, ROS dominates the antioxidants factors such as GPx, GS, GSH, MT-III, Catalase, SOD, BDNF, and CERB, and finally leads to cognitive dysfunction. The present review illustrates an account of the current knowledge about the individual metal induced cognitive dysfunction mechanisms and analyse common Mode of Actions (MOAs) of quaternary metal mixture (Pb, Cd, As, MeHg). This review aims to help advancement in mixture toxicology and development of next generation predictive model (such as PBPK/PD) combining both kinetic and dynamic interactions of metals.

Celastrol prevents cadmium-induced neuronal cell death by blocking reactive oxygen species-mediated mammalian target of rapamycin pathway

BACKGROUND AND PURPOSE

Increasing evidence has suggested cadmium (Cd), as an inducer of ROS, is a potential pathogenic factor in human neurodegenerative diseases. Thus, it is important to find effective interventions for Cd-induced oxidative stress in the CNS. Here, we have studied the effects of celastrol, a plant-derived triterpene, on ROS production and cell death in neuronal cells, induced by Cd.

EXPERIMENTAL APPROACH

PC12, SH-SY5Y cells and primary murine neurons were used to study celastrol neuroprotection against Cd-poisoning. Cd-induced changes in cell viability, apoptosis, ROS and AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway in the cells were analysed by Trypan blue exclusion, DAPI and TUNEL staining, ROS imaging, immunofluorescence staining and Western blotting. Pharmacological and genetic approaches were employed to investigate the mechanisms underlying Cd neurotoxicity.

RESULTS

Celastrol attenuated Cd-induced apoptosis by suppressing Cd activation of mTOR, which was attributed to preventing Cd inactivation of AMPK. Inhibition of AMPK with compound C or expression of dominant negative AMPKα prevented celastrol from hindering Cd-induced dephosphorylation of AMPKα, activation of mTOR and apoptosis. Inhibition of mTOR with rapamycin or knockdown of mTOR potentiated prevention by celastrol, of Cd-induced phosphorylation of p70 S6 kinase 1/eukaryotic initiation factor 4E binding protein 1 and apoptosis. Celastrol attenuated Cd-induced cell death by suppressing induction of mitochondrial ROS.

CONCLUSIONS AND IMPLICATIONS

Celastrol prevented the inactivation of AMPK by mitochondrial ROS, thus attenuating Cd-induced mTOR activation and neuronal apoptosis. Celastrol may be a promising agent for prevention of Cd-induced oxidative stress and neurodegenerative diseases.

Cadmium induces oxidative stress and apoptosis in lung epithelial cells

Cadmium (Cd) is one of the well-known highly toxic environmental and industrial pollutants. Cd first accumulates in the nucleus and later interacts with zinc finger proteins of antiapoptotic genes and inhibit the binding of transcriptional factors and transcription. However, the role of Cd in oxidative stress and apoptosis is less understood. Hence, the present study was undertaken to unveil the mechanism of action. A549 cells were treated with or without Cd and cell viability was measured by MTT assay. Treatment of cells with Cd shows reduced viability in a dose-dependent manner with IC₅₀ of 45 μM concentration. Cd significantly induces the reactive oxygen species (ROS), lipid peroxidation followed by membrane damage with the leakage of lactate dehydrogenase (LDH). Cells with continuous exposure of Cd deplete the antioxidant super oxide dismutase (SOD) and glutathione peroxidase (GSH-Px) enzymes. Further, analysis of the expression of genes involved in apoptosis show that both the extrinsic and intrinsic apoptotic pathways were involved. Death receptor marker tumor necrosis factor-α (TNF-α), executor caspase-8 and pro-apoptotic gene (Bax) were induced, while antiapoptotic gene (Bcl-2) was decreased in Cd-treated cells. Fluorescence-activated cell sorting (FACS) analysis further confirms the induction of apoptosis in Cd-treated A549 cells.

Programmed Effects in Neurobehavior and Antioxidative Physiology in Zebrafish Embryonically Exposed to Cadmium: Observations and Hypothesized Adverse Outcome Pathway Framework

Non-communicable diseases (NCDs) are a major cause of premature mortality. Recent studies show that predispositions for NCDs may arise from early-life exposure to low concentrations of environmental contaminants. This developmental origins of health and disease (DOHaD) paradigm suggests that programming of an embryo can be disrupted, changing the homeostatic set point of biological functions. Epigenetic alterations are a possible underlying mechanism. Here, we investigated the DOHaD paradigm by exposing zebrafish to subtoxic concentrations of the ubiquitous contaminant cadmium during embryogenesis, followed by growth under normal conditions. Prolonged behavioral responses to physical stress and altered antioxidative physiology were observed approximately ten weeks after termination of embryonal exposure, at concentrations that were 50–3200-fold below the direct embryotoxic concentration, and interpreted as altered developmental programming. Literature was explored for possible mechanistic pathways that link embryonic subtoxic cadmium to the observed apical phenotypes, more specifically, the probability of molecular mechanisms induced by cadmium exposure leading to altered DNA methylation and subsequently to the observed apical phenotypes. This was done using the adverse outcome pathway model framework, and assessing key event relationship plausibility by tailored Bradford-Hill analysis. Thus, cadmium interaction with thiols appeared to be the major contributor to late-life effects. Cadmium-thiol interactions may lead to depletion of the methyl donor S-adenosyl-methionine, resulting in methylome alterations, and may, additionally, result in oxidative stress, which may lead to DNA oxidation, and subsequently altered DNA methyltransferase activity. In this way, DNA methylation may be affected at a critical developmental stage, causing the observed apical phenotypes.

Neuroprotective efficacy of hesperetin against cadmium induced oxidative stress in the brain of rats

The present study was designed to investigate the neuroprotective effect of hesperetin (Hp) against cadmium (Cd)-induced neurotoxicity in rats. Cadmium (3 mg/kg body weight (b.w.), subcutaneous) administration for 3 weeks demonstrated neurotoxicity in rats by the decreased activity of acetylcholinesterase in the brain. The oxidative stress markers (thiobarbituric acid reactive substances and protein carbonyls) were significantly increased with decreased enzymatic (superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase) and non-enzymatic antioxidants (reduced glutathione, total sulphydryl groups and vitamin C). The proteolytic and membrane-bound enzymes (Na⁺ K⁺-ATPase, Mg²⁺-ATPase and Ca²⁺-ATPase) were also decreased with increased apoptotic markers (Bcl2 Associated X Protein (Bax), cytochrome C, caspase 3 and 9) and decreased anti-apoptotic marker (B-cell lymphoma 2 (Bcl2)) in the brain of Cd-treated rats. Moreover, Cd administration significantly decreased the mitochondrial electron transport chain complexes (I, II, III and IV) in the brain of rats. Preadministration of Hp (40 mg/kg b.w., oral) significantly attenuated the Cd-induced oxidative stress and mitochondrial dysfunction, restored the antioxidant and membrane-bound enzyme activities and decreased apoptosis in the brain of rats.

l-Theanine attenuates cadmium-induced neurotoxicity through the inhibition of oxidative damage and tau hyperphosphorylation

Cadmium (Cd) has long been known to induce neurological degenerative disorders. We studied effects of l-theanine, one of the major amino acid components in green tea, on Cd-induced brain injury in mice. Male ICR mice were intraperitoneally injected with l-theanine (100 or 200mg/kg/day) or saline and after one hour these mice were orally administrated with CdCl₂ (3.75-6mg/kg). The treatment was conducted for 8 weeks. l-Theanine significantly reduced Cd level in the mouse brain and plasma. Cd-induced neuronal cell death in the mouse cortex and hippocampus were apparently inhibited by l-theanine treatment. l-Theanine also decreased the levels of malondialdehyde (MDA) and ROS, and obviously elevated the levels of glutathione (GSH) and activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in the mouse brain. Hyperphosphorylation of tau protein is proposed to be an early event for the evolution of tau pathology, and may play an important role in Cd-induced neurodegeneration. Our results showed that l-theanine significantly suppressed Cd-induced tau protein hyperphosphorylation at Ser199, Ser202, and Ser396. Mechanism study showed that l-theanine inhibited the activation of glycogen synthase kinase-3β (GSK-3β) which contributed to the hyperphosphorylation of tau and Cd-induced cytotoxicity. Furthermore, l-theanine reduced Cd-induced cytotoxicity possibly by interfering with the Akt/mTOR signaling pathway. In conclusion, our study indicated that l-theanine protected mice against Cd-induced neurotoxicity through reducing brain Cd level and relieved oxidative damage and tau hyperphosphorylation. Our foundings provide a novel insight into the potential use of l-theanine as prophylactic and therapeutic agents for Cd-induced neurodegenerative diseases.

Enhancing the Antioxidant Ability of Trametes versicolor Polysaccharopeptides by an Enzymatic Hydrolysis Process

Polysaccharopeptides (PSPs) are among the main bioactive constituents of Trametes versicolor (T. versicolor). The purpose of this research was to investigate the antioxidant activities of enzymatic hydrolysates obtained from T.versicolor polysaccharopeptides by 80 U/mL β-1,3-glucanase (PSPs-EH80). The half-inhibitory concentration (IC₅₀) of PSPs-EH80 in metal chelating assay, ABTS and DPPH radical scavenging test results were 0.83 mg/mL, 0.14 mg/mL and 0.52 mg/mL, respectively, which were lower than that of PSPs-EH 20 U/mL. The molecular weights of the PSPs-EH80 hydrolysates were 300, 190, 140 and 50 kDa, respectively, and the hydrolysis of polysaccharides by β-1,3-glucanase did not change the original functional group. PSPs-EH80 reduced the reactive oxygen species (ROS) content at least twice that of treatment without PSPs-EH80. In addition, an oxidative damage test showed that PSPs-EH80 can improve HaCaT cell survival. According to our results, PSP demonstrates the potential of anti-oxidative damage; besides, enzyme hydrolysis can improve the ability of the PSP.

Mitochondrial DNA depletion causes decreased ROS production and resistance to apoptosis

Mitochondrial DNA (mtDNA) depletion occurs frequently in many diseases including cancer. The present study was designed in order to examine the hypothesis that mtDNA‑depleted cells are resistant to apoptosis and to explore the possible mechanisms responsible for this effect. Parental human osteosarcoma 143B cells and mtDNA‑deficient (Rho˚ or ρ˚) 206 cells (derived from 143B cells) were exposed to different doses of solar-simulated ultraviolet (UV) radiation. The effects of solar irradiation on cell morphology were observed under both light and fluorescence microscopes. Furthermore, apoptosis, mitochondrial membrane potential (MMP) disruption and reactive oxygen species (ROS) production were detected and measured by flow cytometry. In both cell lines, apoptosis and ROS production were clearly increased, whereas MMP was slightly decreased. However, apoptosis and ROS production were reduced in the Rho˚206 cells compared with the 143B cells. We also performed western blot analysis and demonstrated the increased release of cytosolic Cyt c from mitochondria in the 143B cells compared with that in the Rho˚206 cells. Thus, we concluded that Rho˚206 cells exhibit more resistance to solar‑simulated UV radiation‑induced apoptosis at certain doses than 143B cells and this is possibly due to decreased ROS production.

Liver histological changes and lipid peroxidation in the amphibian Ambystoma mexicanum induced by sediment elutriates from the Lake Xochimilco

Lacustrine sediments accumulate pollutants that input from the lake watershed and can be released to the water column by sediment resuspension; thus, pollutants can change their bioavailability and exert adverse effects to aquatic biota. Shallow-urban lakes are particularly susceptible to receive pollutants from urban discharges and sediment resuspension. Lake Xochimilco, in Mexico City, an urban-shallow lake, faces multiple problems: urban sprawl, overexploitation of aquifers, drying of springs, discharge of wastewater from treatment plants, and sediment resuspension. The aquatic biota living in this ecosystem is continuously exposed to the release of pollutants from the sediments. We assessed the risk that pollutants released from sediments from Lake Xochimilco, Touristic (TZ) and Agriculture zone (AZ), can exert on a native amphibian species of the lake (Ambystoma mexicanum) through exposure bioassays to sediment elutriates. We evaluate alterations in the amphibian by three approaches: biochemical (level of lipid peroxidation, LPO), cellular (ultrastructure) and the liver histology of A. mexicanum and we compare them with a batch control. Additionally, we assessed heavy metals (Pb, Cd and Hg) in elutriates. Elutriates from TZ showed the highest concentrations of the metals assessed. Organisms exposed to sediment elutriates from either study sites showed higher LPO values than control organisms (p<0.05). Organisms exposed to elutriates from the TZ showed the most conspicuous damages: hepatic vasodilation of sinusoids, capillaries with erythrocytes, leukocyte infiltration and cytoplasmic vacuolation in hepatocytes. The biological responses assessed reflected the risk that faces A. mexicanum when is exposed for prolonged periods to sediment resuspension in Lake Xochimilco.

Luteolin decreases the UVA‑induced autophagy of human skin fibroblasts by scavenging ROS

Luteolin (LUT) is a flavone, which is universally present as a constituent of traditional Chinese herbs, and certain vegetables and spices, and has been demonstrated to exhibit potent radical scavenging and cytoprotective properties. Although LUT has various beneficial effects on health, the effects of LUT on the protection of skin remain to be fully elucidated. The present study investigated whether LUT can protect human skin fibroblasts (HSFs) from ultraviolet (UV) A irradiation. It was found that, following exposure to different doses of UVA irradiation, the HSFs exhibited autophagy, as observed by fluorescence and transmission electron microscopy, and reactive oxygen species (ROS) bursts, analyzed by flow cytometry, to differing degrees. Following incubation with micromolar concentrations of LUT, ROS production decreased and autophagy gradually declined. In addition, the expression of hypoxia-inducible factor-1α and the classical autophagy-associated proteins, LC3 and Beclin 1 were observed by western blotting. Western blot analysis showed that the expression levels of HIF-1α, LC3-II and Beclin 1 gradually decreased in the UVA-irradiated HSFs following treatment with LUT. These data indicated that UVA-induced autophagy was mediated by ROS, suggesting the possibility of resistance against UV by certain natural antioxidants, including LUT.

Protective Role of Quercetin in Cadmium-Induced Cholinergic Dysfunctions in Rat Brain by Modulating Mitochondrial Integrity and MAP Kinase Signaling

With the increasing evidences of cadmium-induced cognitive deficits associated with brain cholinergic dysfunctions, the present study aimed to decipher molecular mechanisms involved in the neuroprotective efficacy of quercetin in rats. A decrease in the binding of cholinergic-muscarinic receptors and mRNA expression of cholinergic receptor genes (M1, M2, and M4) was observed in the frontal cortex and hippocampus on exposure of rats to cadmium (5.0 mg/kg body weight, p.o.) for 28 days compared to controls. Cadmium exposure resulted to decrease mRNA and protein expressions of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) and enhance reactive oxygen species (ROS) generation associated with mitochondrial dysfunctions, ultrastructural changes, and learning deficits. Enhanced apoptosis, as evidenced by alterations in key proteins involved in the pro- and anti-apoptotic pathway and mitogen-activated protein (MAP) kinase signaling, was evident on cadmium exposure. Simultaneous treatment with quercetin (25 mg/kg body weight, p.o.) resulted to protect cadmium-induced alterations in cholinergic-muscarinic receptors, mRNA expression of genes (M1, M2, and M4), and expression of ChAT and AChE. The protective effect on brain cholinergic targets was attributed to the antioxidant potential of quercetin, which reduced ROS generation and protected mitochondrial integrity by modulating proteins involved in apoptosis and MAP kinase signaling. The results exhibit that quercetin may modulate molecular targets involved in brain cholinergic signaling and attenuate cadmium neurotoxicity.

Effects of biochar amendment on relieving cadmium stress and reducing cadmium accumulation in pepper

Biochar is widely used in agricultural soils or heavy metal-polluted soils to improve the quality of the soils, which would affect the growth of the plant. However, the information of biochars' effect on the plant growth was still lacking, especially for the physiological response of the plant. Pot experiments were used to examine the effect of willow-derived biochars at two temperatures (450 and 600 °C) on cadmium (Cd) accumulation in pepper and to reveal the response of physiological parameters to exogenous Cd stress (1 and 5 mg/kg). The results showed that the accumulation of Cd in pepper roots was higher than that in pepper shoots. For low level of Cd treatments, high additional rates of the biochars could obviously reduce the accumulation of Cd in the pepper roots. Moreover, there was a negative correlation between the C content of the biochar-amended soils and the Cd content of the pepper root, suggesting that the application of biochar to the soil decreased the Cd accumulation in the root. A positive relationship between the H/C ratios of biochar-amended soils and their corresponding Cd concentrations in pepper root indicated that low thermal temperature-derived biochar could play an important role in immobilizing Cd in the soil. Furthermore, on the condition of low Cd level of treatments, the malondialdehyde content decreased in biochar-amended soils, especially at high biochar application rate. The chlorophyll content increased with increasing the rates of the biochar application. The physiological parameters indirectly proved that the application of biochar did not always alleviate the toxic effects of Cd on pepper leaves at high Cd concentration.

Oxidative Stress and Cardiovascular Dysfunction Associated with Cadmium Exposure: Beneficial Effects of Curcumin and Tetrahydrocurcumin

Cadmium (Cd) is a non-essential heavy metal with high toxicity potential. Humans are exposed to Cd present in diet, polluted air, and cigarette smoke. Cd exposure has been associated with increased risk of chronic diseases, including hypertension, atherosclerosis, diabetes, and nephropathy, all of which could be attributable to dysfunctional endothelial and smooth muscle cells. Cd toxicity is correlated with increased reactive oxygen formation and depletion of antioxidants, resulting in an oxidative stress. Chelation of Cd has proved useful in the removal of the Cd burden. However, several chelating agents cause side effects in clinical usage. Recent studies have shown that the antioxidant compounds curcumin and tetrahydrocurcumin can alleviate vascular dysfunction and high blood pressure caused by Cd toxicity. In chronic Cd exposure, these antioxidants protect vascular endothelium by increasing nitric oxide (NO•) bioavailability and improving vascular function. Antioxidant activity against Cd intoxication results directly and/or indirectly through free radical scavenging, metal chelation, enhanced expression of the antioxidant defense system, regulation of inflammatory enzymes, increase in NO• bioavailability, and reduction of gastrointestinal absorption and tissue Cd accumulation. This review summarizes current knowledge of Cd-induced oxidative stress and cardiovascular dysfunction and a possible protective effect conferred by the antioxidants curcumin and tetrahydrocurcumin.

Earthworms, pesticides and sustainable agriculture: a review

The aim of this review is to generate awareness and understand the importance of earthworms in sustainable agriculture and effect of pesticides on their action. The natural resources are finite and highly prone to degradation by the misuse of land and mismanagement of soil. The world is in utter need of a healthy ecosystem that provides with fertile soil, clean water, food and other natural resources. Anthropogenic activities have led to an increased contamination of land. The intensification of industrial and agricultural practices chiefly the utilization of pesticides has in almost every way made our natural resources concave. Earthworms help in a number of tasks that support many ecosystem services that favor agrosystem sustainability but are degraded by exhaustive practices such as the use of pesticides. The present review assesses the response of earthworm toward the pesticides and also evaluates the relationship between earthworm activity and plant growth. We strictly need to refresh and rethink on the policies and norms devised by us on sustainable ecology. In an equivalent way, the natural resources should be utilized and further, essential ways for betterment of present and future livelihood should be sought.

Regucalcin counteracts tert-butyl hydroperoxide and cadmium-induced oxidative stress in rat testis

Regucalcin (RGN) is a calcium (Ca²⁺ )-binding protein with multiple physiological roles and has also been linked to the suppression of oxidative stress. It is widely known that oxidative stress adversely affects spermatogenesis, disrupting the development of germ cells, and interfering with sperm function. The present study aims to analyze the role of RGN modulating testicular oxidative stress. To address this issue, seminiferous tubules (SeT) from transgenic rats overexpressing RGN (Tg-RGN) and wild-type (WT) were cultured ex vivo for 24 h in the presence/absence of pro-oxidant stimuli, tert-butyl hydroperoxide (TBHP, 250 and 500 μM) and cadmium chloride (Cd, 10 and 20 μM). Noteworthy, SeT from Tg-RGN animals displayed a significantly higher antioxidant capacity and diminished levels of thiobarbituric acid reactive substances relatively to their WT counterparts, both in control and experimental conditions. Regarding the antioxidant defense systems, a significant increase in the activity of glutathione-S-transferase was found in the SeT of Tg-RGN whereas no differences were observed in superoxide dismutase activity throughout experimental conditions. The activity of apoptosis executioner caspase-3 was significantly increased in the SeT of WT rats treated with 250 μM of TBHP or 10 μM of Cd, an effect not seen in Tg-RGN animals. These results showed that the SeT of Tg-RGN animals displayed lower levels of oxidative stress and increased antioxidant defenses, exhibiting protection against oxidative damage and apoptosis. Moreover, the present findings support the antioxidant role of RGN in spermatogenesis, which may be an important issue of further research in the context of male infertility. Copyright © 2016 John Wiley & Sons, Ltd.

Neuroglial alterations in the zebrafish brain exposed to cadmium chloride

Cadmium is an extremely toxic heavy metal that widely occurs in industrial workplaces with various hazardous effects on brain functions. The cytotoxic effects of cadmium chloride (CdCl₂ ) on the neuroglial components of the zebrafish brain were analysed by detecting the glial fibrillary acidic protein (GFAP) expression and the mRNA levels of myelin genes mbp, mpz and plp1 in adult specimens exposed to cadmium for 2, 7 and 16 days. A significant decrease in the GFAP protein by Western blotting experiments was observed after 2 days of treatment, reaching 55% after 16 days. No change was observed in the mRNA levels. Using immunohistochemistry, a reduction in GFAP-positive structures was revealed with a progressive trend in all the brains at 2, 7 and 16 days of treatment. In particular, a considerable reduction in GFAP-positive fibres, with a different course, was observed in the ventricle areas and at the pial surface and in blood vessels after 16 days. Our experiments also showed a structural and chemical alteration of myelin and upregulation of mpz mRNA levels, the oligodendrocyte gene that is upregulated in experiments of neuronal injury, but not of plp1 and mbp mRNA levels, other myelin structural genes. These data confirm the toxic action of cadmium on the zebrafish brain. This action is time-dependent and involves the glial cells, key components of the protection and function of nerve cells, hence the basis for many neurological diseases. Copyright © 2016 John Wiley & Sons, Ltd.

Cadmium and arsenic override NF-κB developmental regulation of the intestinal UGT1A1 gene and control of hyperbilirubinemia

Humanized UDP-glucuronosyltransferase (UGT)-1 (hUGT1) mice encode the UGT1 locus including the UGT1A1 gene. During neonatal development, delayed expression of the UGT1A1 gene leads to hyperbilirubinemia as determined by elevated levels of total serum bilirubin (TSB). We show in this report that the redox-sensitive NF-κB pathway is crucial for intestinal expression of the UGT1A1 gene and control of TSB levels. Targeted deletion of IKKβ in intestinal epithelial cells (hUGT1/Ikkβ(ΔIEC) mice) leads to greater neonatal accumulation of TSB than observed in control hUGT1/Ikkβ(F/F) mice. The elevation in TSB levels in hUGT1/Ikkβ(ΔIEC) mice correlates with a reduction in intestinal UGT1A1 expression. As TSB levels accumulate in hUGT1/Ikkβ(ΔIEC) mice during the neonatal period, the increase over that observed in hUGT1/Ikkβ(F/F) mice leads to weight loss, seizures and eventually death. Bilirubin accumulates in brain tissue from hUGT1/Ikkβ(ΔIEC) mice inducing an inflammatory state as shown by elevated TNFα, IL-1β and IL-6, all of which can be prevented by neonatal induction of hepatic or intestinal UGT1A1 and lowering of TSB levels. Altering the redox state of the intestines by oral administration of cadmium or arsenic to neonatal hUGT1/Ikkβ(F/F) and hUGT1/Ikkβ(ΔIEC) mice leads to induction of UGT1A1 and a dramatic reduction in TSB levels. Microarray analysis following arsenic treatment confirms upregulation of oxidation-reduction processes and lipid metabolism, indicative of membrane repair or synthesis. Our findings indicate that the redox state in intestinal epithelial cells during development is important in maintaining UGT1A1 gene expression and control of TSB levels.