Activation of integrated stress response and disordered iron homeostasis upon combined exposure to cadmium and PCB77

Linalool may have a therapeutic effect on cadmium-induced nephrotoxicity by regulating NF-κB/TNF and GRP78/CHOP signaling pathways

Cadmium (Cd) is an environmental pollutant heavy metal with nephrotoxic effect. One of the primary constituents of essential oils is Linalool (Lin), a monoterpene having a variety of pharmacological properties including antimicrobial, anti-inflammatory, and antioxidant effects. The purpose of this study was to ascertain how Lin affected endoplasmic reticulum stress (ERS) and pro-inflammatory mediators in Cd-induced nephrotoxicity. In the experiment, 28 male rats were randomly divided into four equal groups as control (no application), Cd (Cd at a dose of 3 mg/kg for the first 7 days), Cd+Lin (Cd at a dose of 3 mg/kg for the first 7 days and 100 mg/kg/day Lin) and Lin (100 mg/kg/day Lin) (n=7). The experiment was completed on the 15th day after all treatments were performed. Blood serum and kidney tissue samples were used for analyses. Cd-induced histopathological changes, inflammation, oxidative stress, and apoptosis were determined to increase in kidney tissue. However, it was observed that Cd-induced adverse effects in kidney tissue were mainly eliminated by Lin treatment. In conclusion, Lin demonstrated anti-inflammatory, anti-oxidant and anti-apoptotic effects in Cd-induced nephrotoxicity. Therefore, we believe that Lin may represent a high potential therapeutic strategy against renal tissue damage.

The attenuating effects of serine against cadmium induced immunotoxicity through regulating M1/M2 and Th1/Th2 balance in spleen of C57BL/6 mice

Cadmium (Cd) has adverse effects on organisms. Serine is an essential nutritional factor and its nutritional value is extremely high for body. To explore the effects of serine on spleen toxicity induced by Cd in mice, cadmium chloride (CdCl2, 50 mg/L) and serine (50 g/L) were individually administered or co-administrated in drinking water of mice for 18 weeks. Results demonstrated that Cd exposure induced splenic toxicity and serine against the toxicity damage caused by Cd in mice. Under Cd stress, trace element homeostasis was disturbed, the mice's body weight and spleen index were increased, and splenic morphology and ultrastructure were altered. Furthermore, Cd exposure led to the cell populations disorder, which in turn triggers cell death. Notably, Cd treatment induced oxidative stress and inflammation, increased M1/M2 (iNOS, CD68) and Th1/Th2 (T-bet, CD4) levels, decreased M1/M2 (Arg1) and Th1/Th2 (GATA3) levels, while disrupted the macrophages and lymphocytes homeostasis, which trigged apoptosis and pyroptosis in spleen. In contrast, serine supplementation changed the levels of Cd and other elements, weakened Cd-induced tissue damage and inflammation, enhanced antioxidant capacity, significantly restored cell homeostasis, and effectively inhibited Cd-induced apoptosis and pyroptosis in the spleen. Shortly, the results verified that serine had an ameliorating toxicity effect and restored the M1/M2 and Th1/Th2 balance, restrained apoptosis and pyroptosis induced by Cd.

Role of iron homeostasis in the mutagenicity of disinfection by-products in mammalian cells

Disinfection by-products (DBPs) generated from water treatment have serious adverse effects on human health and natural ecosystems. However, research on the mutagenicity of DBPs with different chemical structures is still limited. In the present study, we compared the mutagenicity of 8 typical DBPs in human-hamster hybrid (AL) cells and clarified the mechanisms involved. Our data displayed that the rank order for mutagenicity was as follows: iodoacetamide (IAcAm) > iodoacetonitrile (IAN) > iodoacetic acid (IAA) > bromoacetamide (BAcAm) ≈ bromoacetonitrile (BAN) > bromoacetic acid (BAA), which was confirmed by DNA double strand breaks and oxidative DNA damage. In contrast, bromoform (TBM) and iodoform (TIM) had minimal mutagenicity. The mutation spectrum analysis further revealed that IAN, IAcAm, and IAA could induce multilocus deletions in mammalian cells. Interestingly, nitrogenous DBPs (N-DBPs) and IAA were found to cause varying degrees of iron overload and lipid peroxidation, which was mediated by the activation of the Nrf2/HO-1 signaling pathway. Moreover, the presence of deferoxamine (DFO), an iron ion inhibitor, effectively reduced γ-H2AX and 8-OHdG induced by N-DBPs and IAA. These results indicated that the variations in genotoxicity among DBPs with different structures were associated with their ability to disrupt iron homeostasis. This study provided new insights into the mechanisms underlying the structure-dependent toxicity of DBPs and established a foundation for a more comprehensive understanding and intervention of the health risks associated with DBPs.

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

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

Proteomic analysis of the hepatic response to a pollutant mixture in mice. The protective action of selenium

Metals and pharmaceuticals contaminate water and food worldwide, forming mixtures where they can interact to enhance their individual toxicity. Here we use a shotgun proteomic approach to evaluate the toxicity of a pollutant mixture (PM) of metals (As, Cd, Hg) and pharmaceuticals (diclofenac, flumequine) on mice liver proteostasis. These pollutants are abundant in the environment, accumulate in the food chain, and are toxic to humans primarily through oxidative damage. Thus, we also evaluated the putative antagonistic effect of low-dose dietary supplementation with the antioxidant trace element selenium. A total of 275 proteins were affected by PM treatment. Functional analyses revealed an increased abundance of proteins involved in the integrated stress response that promotes translation, the inflammatory response, carbohydrate and lipid metabolism, and the sustained expression of the antioxidative response mediated by NRF2. As a consequence, a reductive stress situation arises in the cell that inhibits the RICTOR pathway, thus activating the early stage of autophagy, impairing xenobiotic metabolism, and potentiating lipid biosynthesis and steatosis. PM exposure-induced hepato-proteostatic alterations were significantly reduced in Se supplemented mice, suggesting that the use of this trace element as a dietary supplement may at least partially ameliorate liver damage caused by exposure to environmental mixtures.

Distinct adverse outcomes and lipid profiles of erythrocytes upon single and combined exposure to cadmium and microplastics

The growing accumulation of environmental microplastics (MPs) has become a global concern. MPs are capable to interact with other environmental contaminants leading to altered toxicity. Red blood cells (RBCs), are the target with highest priority for most of toxic xenobiotics after entering blood stream. Whether co-existence of MPs changes the toxicity of cadmium, a typical hemolysis inducer, in RBCs is unknown. We investigated the adverse effects of CdCl₂ and Polystyrene-MPs (PS-MPs) on RBCs in mice. We found that CdCl₂ induced mild microcytic hypochromic anemia while PS-MPs induced polycythemia vera, indicating distinct outcomes between them. Moreover, co-treatment of PS-MPs with CdCl₂ did not change the phenotype of microcytic hypochromic anemia, indicating an antagonistic relationship between CdCl₂ and PS-MPs. However, the lipid profiles were also distinct between single exposure and combined exposure to CdCl₂ and PS-MPs. The significant changed lipids were mainly involved in altering the physiochemical or biological properties of RBCs, including decreased membrane components, disrupted bilayer thickness and intrinsic lipid curvature. These results indicated impaired membrane functions of RBCs. The altered lipid profiles observed in the current study may represent new and previously unrecognized harmful characteristics of cadmium and MPs on erythrocytes at low dose without apparent induction of anemia.

Distinct responses from triglyceride and cholesterol metabolism in common carp (Cyprinus carpio) upon environmental cadmium exposure

Due to high persistence and bioavailability, Cadmium (Cd) is one of the most prevalent environmental contaminants, posing an elevating threat to the ecosystems. It has been evidenced that high-dose Cd elicits deleterious effects on aquatic organisms, but the potential toxicities of Cd at environmentally relevant concentrations remains underappreciated. In this study, we used common carp to investigate how environmental Cd exposure affects triglyceride (TG) and cholesterol metabolism and underlying mechanisms. The data indicated that Cd resulted in the shift of TG from the liver to blood and the movement of cholesterol in the opposite direction, ultimately giving rise to the storage of crude lipid in liver and muscle, especially hepatic cholesterol retention. Cholesterol, instead of TG, became the principal cause during the progression of hepatic lipid accumulation. Mechanistic investigations at transcriptional and translational levels further substantiated that Cd blocked hepatic biosynthesis of TG and enhanced TG efflux out of the liver and fatty acid β-oxidation, which collectively led to the compromised TG metabolism in the liver and accelerated TG export to the serum. Additionally, strengthened synthesis, retarded export and oxidation of cholesterol detailed the hepatic prominent cholesterol retention. Taken together, our results demonstrated that environmental exposure to Cd perturbed lipid metabolism through triggering distinct responses from hepatic TG and cholesterol homeostasis. These indicated that environmental factors (such as waterborne Cd) could be a potential contributor to the prevalence of non-alcoholic fatty-liver disease in aquaculture and more efforts should be devoted to the ecological risk assessment of pollutants under environmental scenarios.

Cadmium Through Disturbing MTF1-Mediated Metal Response Induced Cerebellar Injury

Cadmium (Cd) is a toxic environmental contaminant, which bio-accumulate in animals through the food chain. Cerebellum is one of the primary target organs for Cd exposure. In this study, we established a chronic Cd exposure model; 60 chickens were treated with Cd (0 mg/kg, 35 mg/kg, 70 mg/kg) for 90 days. Clinical manifestations indicated that the chicken was depressed and has unstable gait under Cd exposure. Histopathological results indicated that Cd induced neuronal shrunken and indistinct nucleoli, and the number of Purkinje cells decreased significantly. Cerebellar metal contents were analyzed by ICP-MS. We found that Cd caused Cd and Cu accumulation and decreased the content of Se, Fe, and Zn, suggesting that Cd disturbed metal homeostasis. Besides, Cd treatment group also showed high levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) content and inhibited selenoprotein transcriptome, suggesting that Cd exposure resulted in oxidative stress. Notably, low-dose Cd exposure activated MTF1 mRNA and protein expression and its target metal-responsive genes, including MT1, MT2, DMT1, ZIP8, ZIP10, TF, and ATP7B which indicate cellular adaptive response against Cd-induced damage. On the other hand, 70 mg/kg Cd downregulated MTF1-mediated metal response, which was involved in Cd-induced cerebellar injury in chicken. In conclusion, our data demonstrated that molecular mechanisms are associated with Cd-induced cerebellar injury due to disturbing MTF1-mediated metal response.

Endoplasmic reticulum stress-mediated autophagy activation is involved in cadmium-induced ferroptosis of renal tubular epithelial cells

Acute cadmium (Cd) exposure is a significant risk factor for renal injury and lacks effective treatment strategies. Ferroptosis is a recently identified iron-dependent form of nonapoptotic cell death mediated by membrane damage resulting from lipid peroxidation, and it is implicated in many diseases. However, whether ferroptosis is involved in Cd-induced renal injury and, if so, how it operates. Here, we show that Cd can induce ferroptosis in kidney and renal tubular epithelial cells, as demonstrated by elevation of intracellular iron levels and lipid peroxidation, as well as impaired antioxidant production. Treatment with a ferroptosis inhibitor alleviated Cd-induced cell death. Intriguingly, we established that Cd-induced ferroptosis depended on endoplasmic reticulum (ER) stress, by demonstrating that Cd activated the PERK-eIF2α-ATF4-CHOP pathway and that inhibition of ER stress reduced ferroptosis caused by Cd. We further found that autophagy was required for Cd-induced ferroptosis because the inhibition of autophagy by chloroquine mitigated Cd-induced ferroptosis. Furthermore, we showed that iron dysregulation by ferritinophagy contributed to Cd-induced ferroptosis, by showing that the iron chelator desferrioxamine alleviated Cd-induced cell death and lipid peroxidation. In addition, ER stress is likely activated by MitoROS which trigger autophagy and ferroptosis. Collectively, our results indicate that ferroptosis is involved in Cd-induced renal toxicity and regulated by the MitoROS-ER stress-ferritinophagy axis.