Combined Incubation of Cadmium, Docosahexaenoic and Eicosapentaenoic Acid Affecting the Oxidative Stress and Antioxidant Response in Human Hepatocytes In Vitro

The function of omega-3 polyunsaturated fatty acids in response to cadmium exposure

Throughout history, pollution has become a part of our daily life with the improvement of life quality and the advancement of industry and heavy industry. In recent years, the adverse effects of heavy metals, such as cadmium (Cd), on human health have been widely discussed, particularly on the immune system. Here, this review summarizes the available evidence on how Cd exposure may affect health. By analyzing the general manifestations of inflammation caused by Cd exposure, we find that the role of omega-3 (n-3) polyunsaturated fatty acids (PUFAs) in vivo can counteract Cd-induced harm. Additionally, we elucidate the effects of n-3 PUFAs on the immune system, and analyze their prophylactic and therapeutic effects on Cd exposure. Overall, this review highlights the role of n-3 PUFAs in the pathological changes induced by Cd exposure. Although n-3 PUFAs remain to be verified whether they can be used as therapeutic agents, as rehabilitation therapy, supplementation with n-3 PUFAs is reliable and effective.

Interplay between dietary lipids and cadmium exposure in rainbow trout liver: Influence on fatty acid metabolism, metal accumulation and stress response

The present study aimed at investigating interactive effects between dietary lipids and both short- and long-term exposures to a low, environmentally realistic, cadmium (Cd) concentration. Juvenile rainbow trout were fed four isolipidic diets (31.7 g/kg) enriched in either linoleic acid (LA, 18:2n-6), alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3) or docosahexaenoic acid (DHA, 22:6n-3). From the 4th week of this 10-week experiment, the lipid level of the diet was increased (120.0 g/kg) and half of the fish fed each diet were aqueously exposed to Cd (0.3 μg/L) while the other half were not exposed to Cd (control). Fish were sampled and their liver was harvested for fatty acid profile, hepatic Cd and calcium concentrations, total glutathione level and gene expression assessment, either (i) after 4 weeks of feeding and 24 h of Cd contamination (day 29) (short-term Cd exposure) or (ii) after 10 weeks of feeding and 6 weeks of Cd contamination (day 70) (long-term Cd exposure). We found that both dietary lipids and Cd exposure influenced fatty acid homeostasis and metabolism. The hepatic fatty acid profile mostly reflected that of the diet (e.g. n-3/n-6 ratio) with some differences, including selective retention of specific long chain polyunsaturated fatty acids (LC-PUFAs) like DHA and active biotransformation of dietary LA and ALA into LC-PUFAs. Cd effects on hepatic fatty acid profiles were influenced by the duration of the exposure and the nutritional status of the fish. The effects of diet and Cd exposure on the fatty acid profiles were only sparsely explained by variation of the expression pattern of genes involved in fatty acid metabolism. The biological responses to Cd were also influenced by dietary lipids. Fish fed the ALA-enriched diet seemed to be the least affected by the Cd exposure, as they showed a higher detoxifying ability against Cd with an early upregulation of protective metallothionein a (MTa) and apoptosis regulator BCL2-Like1 (BCLx) genes, an increased long-term phospholipid synthesis and turnover and fatty acid bioconversion efficiency, as well as a lower long-term accumulation of Cd in their liver. In contrast, fish fed the EPA-enriched diet seemed to be the most sensitive to a long-term Cd exposure, with an impaired growth performance and a decreased antioxidant capacity (lower glutathione level). Our results highlight that low, environmentally realistic aqueous concentrations of Cd can affect biological response in fish and that these effects are influenced by the dietary fatty acid composition.

Study on the Pharmacological Character of an Insulin-Mimetic Small Molecular Compound of Vanadyl Trehalose

To investigate the effect of vanadyl trehalose (VT) on oxidative stress and reduced glutathione/glutathione-S-transferase (GSH/GSTs) pathway gene expression in mouse gastrointestinal tract, as well as the protective effects of vitamin C (VC) and reduced glutathione (GSH). Thirty male Kunming mice were randomly divided into five groups: control group (group A), VT group (group B), VC + VT group (group C), GSH + VT group (group D) and VC + GSH + VT group (group E). The content of reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) activity and the expressions of glutamate-cysteine ligase catalytic subunit (GCLC), glutathione synthetase (GSS), regulated through glutathione reductase (GSR) and glutathione-S-transferase pi (GSTpi) in stomach and duodenum in vanadyl trehalose treated group were lower than those in group A (P<0.05). The C, D, E group can significantly improve the above indicators, but those only in the stomach in E group reached the level of the control group. Vanadyl trehalose (VT) was able to cause oxidative stress damage to the gastrointestinal tract of mice, which affects GSH content and GSH-Px activity and interferes with the normal expression of GSH/GSTs pathway. Exogenous vitamin C, reduced glutathione and the combination of the two could play a specific role in antioxidant protection and reduce the toxicity of vanadyl trehalose.

Estimation of cadmium content in Egyptian foodstuffs: health risk assessment, biological responses of human HepG2 cells to food-relevant concentrations of cadmium, and protection trials using rosmarinic and ascorbic acids

Cadmium (Cd) is an environmental pollutant that can get entry into human body via ingestion of contaminated foods causing multiple organ damage. This study aimed at monitoring Cd residues in 20 foodstuffs of animal origin that are commonly consumed in Egypt. Health risk assessment was conducted via calculation of Cd dietary intakes and non-carcinogenic target hazard quotient. An in vitro approach was performed to investigate the constitutive effects of Cd on human hepatoma (HepG2) cells under food-relevant concentrations. Trials to reduce Cd-induced adverse effects on HepG2 cells were done using rosmarinic (RMA) and ascorbic acids (ASA). The achieved results indicated contamination of the tested foodstuffs with Cd at high levels with potential human health hazards. Cd at food-relevant concentrations caused significant cytotoxicity to HepG2 cells. This may be attributed to induction of oxidative stress and inflammation, as indicated by the overexpression of stress and inflammatory markers. At the same time, Cd downregulated xenobiotic transporters and upregulated the proliferation factors. Co-exposure of HepG2 cells to Cd and micronutrients such as RMA and ASA led to recovery of cells from the oxidative damage, and subsequently cell viability was strongly improved. RMA and ASA ameliorated the biological responses of HepG2 cells to Cd exposure.

Transient increase in cellular dehydrogenase activity after cadmium treatment precedes enhanced production of reactive oxygen species in human proximal tubular kidney cells

Cadmium is a heavy metal causing toxicity especially in kidney cells. The toxicity is linked also with enhanced oxidative stress leading to cell death. On the other hand, our recent experiments have shown that an increase of total intracellular dehydrogenases activity can also occur in kidney cells before declining until cell death. The aim of the present study, therefore, was to evaluate this transient enhancement in cell viability after cadmium treatment. The human kidney HK-2 cell line was treated with CdCl(2) at concentrations 0-200 microM for 2-24 h and intracellular dehydrogenase activity was tested. In addition, we measured reactive oxygen species (ROS) production, glutathione levels, mitochondrial membrane potential, and C-Jun-N-terminal kinase (JNK) activation. We found that significantly increased dehydrogenase activity could occur in cells treated with 25, 100, and 200 microM CdCl(2). Moreover, the results showed an increase in ROS production linked with JNK activation following the enhancement of dehydrogenase activity. Other tests detected no relationship with the increased in intracellular dehydrogenase activity. Hence, the transient increase in dehydrogenase activity in HK-2 cells preceded the enhancement of ROS production and our finding provides new evidence in cadmium kidney toxicity.

Exploring the interactions between polyunsaturated fatty acids and cadmium in rainbow trout liver cells: a genetic and proteomic study

Polyunsaturated fatty acids (PUFAs) have key biological roles in fish cells. We recently showed that the phospholipid composition of rainbow trout liver cells (RTL-W1 cell line) modulates their tolerance to an acute cadmium (Cd) challenge. Here, we investigated (i) the extent to which PUFAs and Cd impact fatty acid homeostasis and metabolism in these cells and (ii) possible mechanisms by which specific PUFAs may confer cytoprotection against Cd. First, RTL-W1 cells were cultivated for one week in growth media spiked with 50 μmol L^-1 of either alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3), linoleic acid (LA, 18:2n-6) or arachidonic acid (AA, 20:4n-6) in order to modulate their fatty acid profile. Then, the cells were challenged with Cd (0, 50 or 100 μmol L^-1) for 24 h prior to assaying viability, fatty acid profile, intracellular Cd content, proteomic landscape and expression levels of genes involved in fatty acid metabolism, synthesis of PUFA-derived signalling molecules and stress response. We observed that the fatty acid supply and, to a lesser extent, the exposure to Cd influenced cellular fatty acid homeostasis and metabolism. The cellular fatty acid composition of fish liver cells modulated their tolerance to an acute Cd challenge. Enrichments in ALA, EPA, and, to a lesser extent, AA conferred cytoprotection while enrichment in LA had no impact on cell viability. The present study ruled out the possibility that cytoprotection reflects a decreased Cd burden. Our results rather suggest that the PUFA-derived cytoprotection against Cd occurs through a reduction of the oxidative stress induced by Cd and a differential induction of the eicosanoid cascade, with a possible role of peroxiredoxin and glutaredoxin (antioxidant enzymes) as well as cytosolic phospholipase A2 (enzyme initiating the eicosanoid cascade).

Ligustrazine modulates renal cysteine biosynthesis in rats exposed to cadmium

The objective of this study was to determine the effect of ligustrazine (TMP) on cadmium (Cd)-induced nephrotoxicity and its relevant mechanism. TMP (50mg/kg) was injected intraperitoneally (i.p.) into rats 1h prior to CdCl₂ exposure (at a Cd dose of 0.6mg/kg). TMP reversed Cd-induced nephrotoxicity, evidenced by the relatively normal architecture of the renal cortex. Additionally, TMP alleviated renal oxidative stress of rats that were exposed to Cd, evidenced by the decreased levels of malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), elevated levels of glutathione (GSH) and GSH/GSSG (glutathione disulfide) ratios. Furthermore, TMP also raised the decreased levels of S-adenosylmethionine (SAM) and cystathionine involved in cysteine biosynthesis in rats exposed to Cd. Further analysis revealed that TMP treatment upregulated expression of several proteins involved in cysteine biosynthesis including methionine adenosyltransferases (MATs) and cystathionine-beta-synthase (CBS). Taken together, these results suggest that TMP remodeled metabolomics of cysteine biosynthesis in rat kidneys and attenuated Cd-induced nephrotoxicity.

Effect of cadmium on uptake of iron, zinc and copper and mRNA expression of metallothioneins in HepG2 cells in vitro

The intake of cadmium contaminated fish was mimicked by incubating human hepatoblastoma cells (Cell line HepG2) with a combination of different levels of cadmium (0-5μM) plus the n-3 fatty acids docosahexaenoic acid and eicosapentaenoic acid, which are typical for fish. Uptake of cadmium, iron, copper and zinc was measured by ICP-MS. In addition mRNA expression of two metallothioneins (mt1 g and mt1 m) was evaluated by real-time PCR. The obtained data shows that the presence of cadmium increases the uptake of iron and zinc into the HepG2 cells while the uptake of copper remains unaffected. The presence of the chosen fatty acids did not affect the uptake of either cadmium or iron, zinc and copper. The presence of already 1μM cadmium increased the mRNA expression of mt1 g and mt1 m significantly, while the fatty acids did not interfere with the effect of cadmium.