Changes of lipid peroxidation and glutathione redox system, and expression of glutathione peroxidase regulatory genes as effect of short-term aflatoxin B1 exposure in common carp

Epigallocatechin Gallate and Glutathione Attenuate Aflatoxin B1-Induced Acute Liver Injury in Ducklings via Mitochondria-Mediated Apoptosis and the Nrf2 Signalling Pathway

Aflatoxin B1 (AFB1) exists widely in feed and food with severe hazards, posing a serious threat to human and animal health. Epigallocatechin gallate (EGCG) and glutathione (GSH) have been reported as having anti-oxidative and other functions. The present study aimed to investigate the detoxification effect of EGCG and GSH alone or in combination on AFB1 exposure in ducklings. Fifty one-day-old male ducklings were randomly assigned into five experimental groups (n = 10): 1. Control (CTR); 2. 0.3 mg/kg BW AFB1 (AFB1); 3. 0.3 mg/kg BW AFB1 + 100 mg/kg BW EGCG (AFB1 + EGCG); 4. 0.3 mg/kg BW AFB1 + 30 mg/kg BW GSH (AFB1 + GSH); 5. 0.3 mg/kg BW AFB1 + 100 mg/kg BW EGCG + 30 mg/kg BW GSH (AFB1 + EGCG + GSH). The experiment lasted for seven days. Compared with the CTR group, AFB1 reduced growth performance, total serum protein and albumin content, increased serum enzyme activity (alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and γ-glutamyl transpeptidase), and caused pathological damage to the ducklings' livers. AFB1 exposure increased malondialdehyde content and decreased superoxide dismutase, total antioxidant capacity, catalase, glutathione peroxidase activities, and glutathione content in the liver. EGCG and GSH alone or in combination mitigated these adverse effects. Meanwhile, EGCG and GSH attenuate apoptosis of hepatocytes, and regulated AFB1-induced changes in the abundance of genes contained in the Keap1/Nrf2 signalling and apoptotic pathways. Collectively, these results suggest that EGCG and GSH alleviate the hepatocyte injury induced by AFB1 by inhibiting oxidative stress and attenuating excessive mitochondria-mediated apoptosis.

Individual and Combined Effects of Aflatoxin B1 and Sterigmatocystin on Lipid Peroxidation and Glutathione Redox System of Common Carp Liver

The purpose of the study was to evaluate the short-term effects of aflatoxin B1 (AFB1 100 µg/kg feed) and sterigmatocystin (STC 1000 μg/kg feed) exposure individually and in combination (100 μg AFB1 + 1000 μg STC/kg feed) on the parameters of lipid peroxidation and glutathione redox system both in biochemical and gene expression levels in one-year-old common carp. Lipid peroxidation parameters were slightly affected, as significant differences were observed only in conjugated diene and triene concentrations. Reduced glutathione content decreased more markedly by STC than AFB1 or AFB1+STC, but glutathione peroxidase activity did not change. Expression of gpx4a, gpx4b, gss, and gsr genes was down-regulated due to STC compared to AFB1 or AFB1+STC, while an induction was found as effect of AFB1+STC in the case of gpx4a, but down-regulation for gpx4b as compared to AFB1. Expression of the glutathione biosynthesis regulatory gene, gss, was higher, but glutathione recycling enzyme encoding gene, gsr, was lower as an effect of AFB1+STC compared to AFB1. These results are supported by the changes in the expression of transcription factors encoding genes, nrf2, and keap1. The results revealed that individual effects of AFB1 and STC on different parameters are synergistic or antagonistic in multi-toxin treatment.

Contamination of Aflatoxins Induces Severe Hepatotoxicity Through Multiple Mechanisms

Aflatoxins (AFs) are commonly contaminating mycotoxins in foods and medicinal materials. Since they were first discovered to cause “turkey X” disease in the United Kingdom in the early 1960s, the extreme toxicity of AFs in the human liver received serious attention. The liver is the major target organ where AFs are metabolized and converted into extremely toxic forms to engender hepatotoxicity. AFs influence mitochondrial respiratory function and destroy normal mitochondrial structure. AFs initiate damage to mitochondria and subsequent oxidative stress. AFs block cellular survival pathways, such as autophagy that eliminates impaired cellular structures and the antioxidant system that copes with oxidative stress, which may underlie their high toxicities. AFs induce cell death via intrinsic and extrinsic apoptosis pathways and influence the cell cycle and growth via microribonucleic acids (miRNAs). Furthermore, AFs induce the hepatic local inflammatory microenvironment to exacerbate hepatotoxicity via upregulation of NF-κB signaling pathway and inflammasome assembly in the presence of Kupffer cells (liver innate immunocytes). This review addresses the mechanisms of AFs-induced hepatotoxicity from various aspects and provides background knowledge to better understand AFs-related hepatoxic diseases.

Impact of milk thistle (Silybum marianum) on the mycotoxin caused redox-homeostasis imbalance of ducks liver

The Fusarium mycotoxins deoxynivalenol (DON) and zearalenone (ZEA) frequently contaminate grain crops, especially maize, the basis of poultry's feed. Mycotoxins enter the food chain and induce pathological changes in edible tissues. Milk thistle (Silybum marianum) has been used for the treatment of liver disease in humans because of its antioxidant and hepatoprotective effects, but its utility in veterinary use is poorly examined. To investigate possible protective properties against mycotoxin caused oxidative stress in poultry, pressed form of milk thistle seed (0.5%) was tested in white, female, Hungarian ducks over a feeding period of 47 days. Ducks were separated into 3 groups. The first group was fed with normal diet. The second group was fed with normal diet contaminated with DON (4.9 mg/kg) and ZEA (0.66 mg/kg). The third group received mycotoxin contaminated feed with milk thistle supplementation. Histological examination, markers of the redox status and metal element concentration measurements were carried out. The results showed alterations in the histological examination and in the redox homeostasis markers as a short-term effect by strengthening the antioxidant system. Acute exposure of mycotoxins caused an oxidative stress, which induced an effective antioxidant defensive response of the organism indicated by the free sulfhydryl group content (from 0.72 ± 0.06 to 0.77 ± 0.11) and the reducing power (0.49 ± 0.06 to 0.52 ± 0.08) elevation. The short-term free radical injury may be compensated by the liver resulting in decreased lipid peroxidation markers (malondialdehyde concentration: from 16.86 ± 0.49 to 0.94 ± 0.15, conjugated diene concentration: from 0.21 ± 0.07 to 0.17 ± 0.03). Silymarin further strengthtened the antioxidant defense by the elevation of sulfhydryl groups concentration and reducing power property resulted in decreased total scavenger capacity. However the concentration of lipid peroxidation markers were further elevated by the used antioxidant treatment (MDA: 5.2 ± 0.35, DC: 0.26 ± 0.08). In conclusion, the mycotoxin-contamination activated effectively the antioxidant system. The milk thistle supplementation has cytoprotective effects according to the histological findings, activated the antioxidant system, however the elevation of lipid peroxidation products need further explanation.

Combined effects of aflatoxin B1 and deoxynivalenol on the expression of glutathione redox system regulatory genes in common carp

The purpose of the present study was to evaluate the short-term effects of aflatoxin B₁ (AFB₁ ) and deoxynivalenol (DON) exposure on the expression of the genes encoding the glutathione redox system glutathione peroxidase 4a (gpx4a), glutathione peroxidase 4b (gpx4b), glutathione synthetase (gss) and glutathione reductase (gsr) and the oxidative stress response-related transcription factors Kelch-like ECH-associated protein 1 (keap1) and nuclear factor-erythroid 2 p45-related factor 2 (nrf2) in liver, kidney and spleen of common carp. During the 24-hr long experiment, three different doses (5 µg AFB₁ and 110 µg DON; 7.5 µg AFB₁ and 165 µg DON or 10 µg AFB₁ and 220 µg DON/kg bw) were used. The results indicated that the co-exposure of AFB₁ and DON initiated free radical formation in liver, kidney and spleen, which was suggested by the increase in Nrf2 dependent genes, namely gpx4a, gpx4b, gss and gsr. Expression of keap1 gene showed upregulation after 8 hr of mycotoxin exposure, and also upregulation of nrf2 gene was found in kidney after 8 hr of exposure, while in the liver, only slight differences were observed. The changes in the expression of the analysed genes suggest that level of reactive oxygen species reached a critical level where other signalling pathway was activated as described by the hierarchical model of oxidative stress.

Sitagliptin protects liver against aflatoxin B1-induced hepatotoxicity through upregulating Nrf2/ARE/HO-1 pathway

Dipeptidyl peptidase-4 inhibitor (DPP-4 inhibitor) such as sitagliptin has been presented as antidiabetic drugs and has numerous restorative advantages over different diseases; however, its defensive role against aflatoxin b1 (AFB1) liver toxicity has not been previously examined. Wistar rats (65 weeks, male) were utilized in the investigation. Animals were divided into five different groups (n = 10): control; AFB1; AFB1 + Sita (50); AFB1 + Sita (100); and Sita (100). Sitagliptin significantly (*p ≤ .05, **p ≤ .01, and ***p ≤ .001) altered the levels of various serum liver enzymes (lactate dehydrogenase, alkaline phosphate, aspartate aminotransferase, and alanine aminotransferase). It decreased the concentration of an oxidative stress marker, that is, malondialdehyde and increased the level of antioxidant enzymes such as reduced glutathione, catalase, superoxide dismutase, and glutathione peroxidase in AFB1-administered rats. It also improved the Nrf2 expression and HO-1 level in AFB1-intoxicated rats. This investigation discusses innovative evidence on the protective role of sitagliptin against AFB1-induced hepatotoxicity in rats.