Cadmium induced skeletal underdevelopment, liver cell apoptosis and hepatic energy metabolism disorder in Bufo gargarizans larvae by disrupting thyroid hormone signaling

Cadmium bioaccumulation dynamics during amphibian development and metamorphosis

Cadmium pollution poses a significant threat to aquatic ecosystems due to its propensity to bioaccumulate and cause toxicity. This study assessed the complex dynamics of cadmium uptake, accumulation and distribution across anuran development to provide new insights into the fate of cadmium burdens during metamorphosis and compare the susceptibility of different life stages to cadmium accumulation. Tadpoles of various developmental stages were exposed to dissolved 109-cadmium and depurated in clean water in a series of experiments. Temporal changes in whole-body and tissue concentrations were analysed using gamma spectroscopy, and anatomical distributions were visualised using autoradiography. Results showed that animals exposed at the onset of metamorphic climax (forelimb emergence) retained significantly less cadmium than animals exposed through larval stages. After exposure, cadmium partitioned predominantly in the skin, gills and remains of metamorphs, whereas larvae accumulated cadmium predominately through their gut. This shows a shift in the primary route of uptake at the onset of climax, which relates to the structural and functional changes of uptake sites through metamorphosis. During climax, some cadmium was redistributed in tissues developing de novo, such as the forelimbs, and concentrated in the regressing tail. Our findings highlight the need for stage-specific considerations in assessing exposure risks.

Cadmium Exposure was Associated with Sex-Specific Thyroid Dysfunction: Consistent Evidence from Two Independent Cross-Sectional Studies Based on Urinary and Blood Cadmium Measurements

Population-based studies on the association between cadmium (Cd) exposure and thyroid function are limited and have shown conflicting results. Two independent cross-sectional studies using different Cd biomarkers were carried out in six rural areas with different soil Cd levels in China. Thyroid dysfunction was defined based on levels of thyroid stimulating hormone (TSH) and free thyroxine (FT4). Multivariable linear regression, multiple logistic regression, and restrictive cubic splines models were used to estimate the association between Cd and thyroid dysfunction. For both of the two independent studies, higher Cd levels were observed to be associated with lower TSH levels and higher risk of thyroid dysfunction. The negative relationship between urinary Cd and TSH was found in both total participants (β =  - 0.072, p = 0.008) and males (β =  - 0.119, p = 0.020) but not in females; however, the negative relationship between blood Cd and TSH was only found in females (β =  - 0.104, p = 0.024). Higher urinary Cd was associated with higher risk of thyroid dysfunction (OR = 1.77, p = 0.031), while higher blood Cd was associated with higher risk of thyroid dysfunction (OR = 1.95, p = 0.011). Results from the two independent cross-sectional studies consistently suggested that higher Cd levels were associated with sex-specific thyroid dysfunction.

Hepatocellular degeneration in mice co-exposed to in-utero aluminium and cadmium: Implication of a disordered antioxidant and energy homeostatic response in the liver

The current study comprised four groups of pregnant animals viz; Control (CTR) received 10 ml/kg of normal saline, Al:10 mg/kg of AlCl3, Cd: 1.5 mg/Kg of CdCl2 Al+Cd; 10 mg/kg of AlCl3 and 1.5 mg/Kg of CdCl2. Treatment was done from pregnancy days (PNT) 7-20. After delivery, male animals were weaned on PSD 21 and sacrificed on PSD 78. From the study significant increases on serum liver enzymes in the group exposed to Cd and that exposed to Al+Cd were observed. The study further showed altered serum and hepatic antioxidant balance for the Cd, Al and Al+Cd groups compared to control. Similarly, lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activities in the liver were elevated in Cd and Al+Cd groups while an altered liver histological feature in treated groups were also observed. it was concluded that in utero co-exposure to Al and Cd had the ability to alter hepatic functional indices.

Higher cadmium exposure was associated with sex-specific thyroid dysfunction: Consistent evidence from two independent cross-sectional studies based on urinary and blood cadmium measurements

Population-based studies on the association between cadmium (Cd) exposure and thyroid function are limited and have shown conflicting results. Two independent cross-sectional studies using different Cd biomarkers were carried out in six rural areas with different soil Cd levels in China. Thyroid dysfunction was defined based on levels of thyroid stimulating hormone (TSH) and free thyroxine (FT4). Both multivariable linear regression, multiple logistic regression and restrictive cubic splines models were used to estimate the association between Cd and thyroid dysfunction. For both of the two independent studies, higher Cd levels were observed to be associated with lower TSH levels and higher risk of thyroid dysfunction. The negative relationship between urinary Cd and TSH was found in both total participants (β = -0.072, p = 0.008) and males (β = -0.119, p = 0.020) but not in females, however, the negative relationship between blood Cd and TSH was only found in females (β = -0.104, p = 0.024). Higher urinary Cd (> 2.52 μg/g creatinine) was associated with higher risk of thyroid dysfunction, while higher blood Cd was associated with higher risk of hyperthyroidism status. The adjusted Odds Ratio (OR) for the risk of hyperthyroidism status was 3.48 (95%CI:1.36-8.92) and 6.94 (95%CI:1.23-39.31) times higher with every natural log unit higher in blood Cd in total participants and males, respectively. Results from the two independent cross-sectional studies consistently suggested that higher Cd levels were associated with sex-specific thyroid dysfunction.

Cadmium influence on lipid metabolism in Sprague-Dawley rats through linoleic acid and glycerophospholipid metabolism pathways

Cadmium (Cd) is widely distributed in the environment and easy adsorbed by living organisms with adverse effects. Exposure to Cd-contaminated food may disrupt lipid metabolism and increase human health risk. To study the perturbation effect of Cd on lipid metabolism in vivo, 24 male Sprague-Dawley (SD) rats were randomly assigned four groups and treated by Cd chloride solution (0, 1.375 mg/kg, 5.5 mg/kg, 22 mg/kg) for 14 days. The characteristic indexes of serum lipid metabolism were analyzed. Afterwards, untargeted metabolomics analysis was applied to explore the adverse effects of Cd on rats by liquid chromatography coupled with mass spectrometry (LC-MS). The results revealed that Cd exposure obviously decreased the average serum of triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) and caused an imbalance of endogenous compounds in the 22 mg/kg Cd-exposed group. Compared with the control group, 30 metabolites with significant differences were identified in the serum. Our results indicated that Cd caused lipid metabolic disorders in rats by disrupting linoleic acid and glycerophospholipid metabolism pathways. Furthermore, there were three kinds of remarkable differential metabolites-9Z,12Z-octadecadienoic acid, PC(20:4(8Z,11Z,14Z,17Z)/0:0), and PC(15:0/18:2(9Z,12Z)), which enriched the two significant metabolism pathways and could be the potential biomarkers.

Metabolomic responses in livers of female and male zebrafish (Danio rerio) following prolonged exposure to environmental levels of zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnONPs) are widespread pollutants that are present in diverse environmental samples. Here, we determined metabolomic and bioenergetic responses in the liver of female and male zebrafish exposed to a prolonged environmentally relevant concentration of ZnONPs. Metabolome analysis revealed that exposure to 500 μg/L ZnONPs reduced the abundance of metabolites in the tricarboxylic acid (TCA) cycle by modulating the activities of rate-limiting enzymes α-ketoglutarate dehydrogenase and isocitrate dehydrogenase. Moreover, oxidative phosphorylation (OXPHOS) was negatively impacted in the liver based upon decreased activities of mitochondrial Complex I and V in both female and male livers. Our results revealed that bioenergetic responses were not attributed to dissolved Zn²⁺ and were not sex-specific. However, the metabolic responses in liver following exposure to ZnONPs did show sex-specific responses. Females exposed to ZnONPs compensated for the energetic stress via increasing fatty acids and amino acids metabolism, while males compensated to ZnONPs exposure by adjusting amino acids metabolism, based upon transcript profiles. This study demonstrates that zebrafish adjust the transcription of metabolic enzymes in the liver to compensate for metabolic disruption following ZnONPs exposure. Taken together, this study contributes to a comprehensive understanding of risks related to ZnONPs exposure in relation to metabolic activity in the liver. Environmental implication Zinc oxide nanoparticles (ZnONPs) are widely used in industry and are subsequently released into environments. However, biological responses between female and male following ZnONPs exposure has never been compared. Our data revealed for the first time that female and male zebrafish showed comparable bioenergetic responses, but different metabolic responses to ZnONPs at an environmentally relevant dose. Females compensated for the energetic stress via increasing fatty acids and amino acids metabolism, while males compensated to ZnONPs exposure by adjusting amino acids metabolism in livers. This study reveals that sex may be an important variable to consider in risk assessments of nanoparticles released into environments.

Chronic exposure to low-dose cadmium facilitated nonalcoholic steatohepatitis in mice by suppressing fatty acid desaturation

Exposure to cadmium (Cd), a toxic metal, is epidemiologically linked to nonalcoholic steatohepatitis (NASH) in humans. However, the role of Cd in NASH remains to be fully elucidated. This study employed a novel murine NASH model to investigate the effects of chronic low-dose Cd on hepatic pathology and its underlying mechanisms. NASH is characterized by lipid accumulation, extensive cell death, and persistent inflammation in the liver. We found that treatment with Cd in drinking water (10 mg/L) for 6 or 12 weeks significantly boosted hepatic fat deposition, increased hepatocyte destruction, and amplified inflammatory responses in mice, confirming that low-dose Cd can facilitate NASH development in vivo. Mechanistically, chronic Cd exposure reshaped the hepatic transcriptional landscape, with PPAR-mediated fatty acid metabolic pathways being the most significantly altered. In particular, Cd repressed fatty acid desaturation, leading to the accumulation of saturated fatty acids whose lipotoxicity exacerbated cell death and, consequently, inflammatory activation. In summary, we validated the causal effects of chronic low-dose Cd on NASH in vivo and identified the fatty acid desaturation program as a novel target for Cd to instigate hepatopathological alterations.

The role of DRP1- PINK1-Parkin-mediated mitophagy in early cadmium-induced liver damage

Cadmium (Cd) is an important environmental pollutant that causes varying degrees of damage to multiple systems of the body. However, the specific mechanism of Cd-induced liver mitophagy remains unclear. In the present study, 5-week-old BALB/c mice and a mouse liver parenchyma cell line (AML12) were studied using a combination of in vivo and in vitro studies. We found that Cd damaged liver cells, destroy the structure and function of mitochondria, and increased the production of superoxide anions. This study further examined the effect of Cd on mitochondrial dynamics and mitophagy and showed that Cd increased mitochondrial division and induced mitophagy. The PINK1-Parkin pathway is a classical mitophagy pathway. Cd-induced mitophagy was inhibited after significantly knocking down Pink1. Mdivi-1 can effectively inhibit mitochondrial division. In this study, Mdivi-1 inhibited the expression of DRP1 and significantly inhibited the occurrence of mitophagy induced by Cd. We further examined the effect of Cd on mitophagy flux. Cd did not increase lysosomal colocalization with mitochondria. In summary, Cd increase the level of oxidative stress, destroy the structure and function of mitochondria, destroy the homeostasis of mitochondrial division and fusion, induce mitophagy through the PINK1-Parkin pathway. Mitophagy plays a protective role in early cadmium-induced liver damage.

The role of microRNAs in regulating cadmium-induced apoptosis by targeting Bcl-2 in IEC-6 cells

Cadmium (Cd) is one of the most harmful environmental pollutants and has been found to have adverse effects on the gut. However, the toxic effects and potential mechanism of Cd on intestinal epithelial cells (IECs) are poorly understood. This study evaluated the effects of Cd exposure (0, 0.25, 0.5, 1, 2, and 4 μM) on IEC-6 cells in terms of cell viability and apoptosis, as well as apoptosis-associated gene expression. The results indicated that low doses (0.25- 1 μM) of Cd exhibited hormetic effects, while high doses of Cd (2 and 4 μM) reduced cell viability. The apoptotic effect increased in a dose-dependent pattern. Moreover, the mRNA levels of the Bcl-2, Bax and Caspase 3 genes were altered, which was in agreement with their protein expression. Based on sequencing analysis, the expression pattern of the microRNAs (miRNAs) changed significantly in the 2 μM Cd-treated group. QRT-PCR verified that 7 miRNAs, including miR-124-3p and miR-370-3p, were all upregulated with dose-effect relationship. Besides, transfection of miR-124-3p and miR-370-3p mimics /inhibitor and Bcl-2 siRNA into IEC-6 cells verified that these two miRNAs could regulate Cd-induced apoptosis by targeting Bcl-2. Finally, the direct targeting relationship between miR-370-3p and Bcl-2 gene was confirmed by luciferase reporter assay. Overall, the results demonstrated that Cd exposure could induce apoptosis in IEC-6 cells. The potential mechanism may be interference with the regulation of Bcl-2 gene expression by miR-370-3p and miR-124-3p.

Subacute cadmium exposure promotes M1 macrophage polarization through oxidative stress-evoked inflammatory response and induces porcine adrenal fibrosis

Cadmium (Cd) is a widely distributed environmental pollutant with immunotoxicity and endocrine toxicity. M1/M2 macrophages participate in the immune response and exert an essential influence on fibrosis. Nevertheless, whether Cd can induce porcineadrenal fibrosis by affecting the polarization of M1/M2 macrophages and its potential regulatory mechanism have not been explored. We added 20 mg/kg CdCl₂ to the pig diet for 40 days to investigate the fibrogenic effect of subacute Cd exposure on the adrenal gland. The results indicated that the ACTH and CORT in serum were decreased by 15.26 % and 21.99 %, respectively. The contents of adrenal mineral elements Cd, Cr, Mn were increased up to 34, 1.93, 1.42 folds and Co, Zn, Sn were reduced by 21.57 %, 20.52 %, 15.75 %. Concurrently, the pro-oxidative indicators (LPO, MDA and H₂O₂) were increased by 1.85, 2.20, 2.77 folds and 3.60, 11.15, 4.11 folds upregulated mRNA levels of TLR4, NF-κB, NLRP3 were observed. Subsequently, the expression of M1 macrophages polarization markers (IL-6, iNOS, TNF-α, CCL2 and CXCL9) were raised by 2.03, 2.30, 2.35, 1.58, 1.56 folds, while M2 macrophages (IL-4, CCL24, Arg1, IL-10, MRC1) showed a 62.34 %, 31.88 %, 50.26 %, 74.00 %, 69.34 % downregulation. The expression levels of AMPK subunits and genes related to glycolysis, oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO) were also markedly increased. Additionally, the expression level of TGF-β1, Smad2/3 and downstream pro-fibrotic markers was obviously upregulated. Taken together, we conclude that Cd activates the oxidative stress-mediated TLR4/NF-κB/NLRP3 inflammatory signal transduction, leading to porcine adrenal fibrosis by promoting macrophage polarization toward M1.