Chemoprotective Effect of Taurine on Potassium Bromate-Induced DNA Damage,DNA-Protein Cross-Linking and Oxidative Stress in Rat Intestine

Potassium bromate (KBrO₃) is widely used as a food additive and is a major water disinfection by-product. It induces multiple organ toxicity in humans and experimental animals and is a probable human carcinogen. The present study reports the protective effect of dietary antioxidant taurine on KBrO₃-induced damage to the rat intestine. Animals were randomly divided into four groups: control, KBrO₃ alone, taurine alone and taurine+ KBrO₃. Administration of KBrO₃ alone led to decrease in the activities of intestinal brush border membrane enzymes while those of antioxidant defence and carbohydrate metabolism were also severely altered. There was increase in DNA damage and DNA-protein cross-linking. Treatment with taurine, prior to administration of KBrO₃, resulted in significant attenuation in all these parameters but the administration of taurine alone had no effect. Histological studies supported these biochemical results showing extensive intestinal damage in KBrO₃-treated animals and greatly reduced tissue injury in the taurine+ KBrO₃ group. These results show that taurine ameliorates bromate induced tissue toxicity and oxidative damage by improving the antioxidant defence, tissue integrity and energy metabolism. Taurine can, therefore, be potentially used as a therapeutic/protective agent against toxicity of KBrO₃ and related compounds.     

Taurine ameliorates potassium bromate-induced kidney damage in rats

Potassium bromate (KBrO₃) is widely used as a food additive and is a major water disinfection by-product. Several studies have shown that it causes nephrotoxicity in humans and experimental animals. We have investigated the potential role of the sulfonic amino acid taurine in protecting the kidney from KBrO₃-induced damage in rats. Animals were randomly divided into four groups: control, KBrO₃ alone, taurine alone and taurine + KBrO₃. Administration of single oral dose of KBrO₃ alone caused nephrotoxicity as evident by elevated serum creatinine and urea levels. Renal lipid peroxidation and protein carbonyls were increased while total sulfhydryl groups and reduced glutathione levels were decreased suggesting the induction of oxidative stress. The enzymes of renal brush border membrane were inhibited and those of carbohydrate metabolism were altered. There was an increase in DNA damage and DNA–protein cross-linking. Treatment with taurine, prior to administration of KBrO₃, resulted in significant attenuation in all these parameters but the administration of taurine alone had no effect. Histological studies supported these biochemical results showing extensive renal damage in KBrO₃-treated animals and greatly reduced tissue injury in the taurine + KBrO₃ group. These results show that taurine is an effective chemoprotectant against bromate-induced renal damage and this amino acid could prove to be useful in attenuating the toxicity of this compound.     

Mismatch Repair Deficient Mice Show Susceptibility to Oxidative Stress-Induced Intestinal Carcinogenesis

We have previously established an experimental system for oxidative DNA damage-induced tumorigenesis in the small intestine of mice. To elucidate the roles of mismatch repair genes in the tumor suppression, we performed oxidative DNA damage-induced tumorigenesis experiments using Msh2-deficient mice. Oral administration of 0.2% Potassium Bromate, KBrO₃, effectively induced epithelial tumors in the small intestines of Msh2-deficient mice. We observed a 22.5-fold increase in tumor formation in the small intestines of Msh2-deficient mice compared with the wild type mice. These results indicate that mismatch repair is involved in the suppression of oxidative stress-induced intestinal tumorigenesis in mice. A mutation analysis of the Ctnnb1 gene of the tumors revealed predominant occurrences of G:C to A:T transitions. The TUNEL analysis showed a decreased number of TUNEL-positive cells in the crypts of small intestines from the Msh2-deficient mice compared with the wild type mice after treatment of KBrO₃. These results suggest that the mismatch repair system may simultaneously function in both avoiding mutagenesis and inducing cell death to suppress the tumorigenesis induced by oxidative stress in the small intestine of mice.     

Paraquat pre-treatment increases activities of antioxidant enzymes and reduces lipid peroxidation in salt-stressed cucumber leaves

To investigate whether paraquat (PQ) is involved in regulation of antioxidant enzymes and lipid peroxidation under short-term salt stress, and to elucidate the physiological mechanism of salt stress mitigated by PQ, a cucumber cultivar (cv. Chunguang no. 2) was exposed to 100 mM NaCl for 48 h after pre-treatment with 10 μM PQ for 1 h. When compared to the control, salt stress increased the levels of malonaldehyde (MDA), superoxide radical (O₂^·−) and hydrogen peroxide (H₂O₂) and the activities of antioxidant enzymes, such as superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.6.4.2) in the cucumber leaves. Under salt conditions, PQ pre-treatment prevented oxidative stress as observed by the decreases in MDA, H₂O₂ and O₂^·− that correlated with the increase in antioxidant defenses. We propose that, at low concentrations, the PQ pre-treatment can reduce the salt-induced oxidative damage by increasing the antioxidative mechanisms in cucumber plants.     

Effect of chilling on photosynthesis and antioxidant enzymes in Hevea brasiliensis Muell. Arg.

The aim of the present study was to assess the tolerance of Hevea brasiliensis to chilling temperatures since rubber production has been extended to sub-optimal environments. PB260 clone was used to analyze the responses of leaves chilled at 10°C during 96 h, as well as their recovery at 28°C. Some key parameters were used to evaluate photosynthetic apparatus functioning, membrane damage (electrolyte leakage) and oxidative stress. A short-term response versus a long-term one have been recorded, the time point of 24 h, when stomata closure was effective, being the border between the two responses. P _n decreased dramatically at 1 h, and Fv/Fm was slightly affected. NPQ reached its maximal level between 4 and 7 h. Lipid peroxidation and membrane lysis were observed between 48 and 96 h. Activities of antioxidant enzymes increased, along with the induction of antioxidant gene expression. Finally, the plants were capable to recover (net photosynthetic rate, photochemical efficiency, antioxidant enzymes activities) when placed back to 28°C showing that PB260 can withstand long-term chilling.     

Oxidative Stress and Hepatocellular Injury Induced by Oral Administration of Cr3+ in Chicken

This study aims to investigate the oxidative stress and hepatocellular injury induced by Cr³⁺ in chicken. Different doses of CrCl₃ solutions (50% LD₅₀, 25% LD₅₀, and 12.5% LD₅₀) and equivalent water were orally administered to chicken. Chicken liver samples were measured for the activities of antioxidant enzymes, the contents of glutathione, total antioxidant capacity (T‐AOC), malondialdehyde (MDA), and hydrogen peroxide to indirectly evaluate the oxidative stress in chicken liver. Results indicated that the oral administration of Cr³⁺ at high dose significantly increased (P < 0.05) the MDA levels after 28 days of exposure, with decreased T‐AOC, glutathione, and antioxidant enzymes activities. Low and medium doses groups show that T‐AOC, glutathione, and antioxidant enzymes activities increased after 14 days, then decreased gradually, but low and medium groups higher than control group, only high group lower than control group finally. These statistics and histopathological analysis suggest that high dose and long‐term exposure of Cr³⁺ induce oxidative stress and hepatocellular injury.     

Ethylene evolution and antioxidant defence mechanism in Cicer arietinum roots in the presence of nitrate and aminoethoxyvinylglycine

The plants of chickpea (Cicer arietinum L.) cv. HC-1 were raised in earthen pots filled with 5 kg washed river sand under natural conditions of the screen house. Forty to forty-five days after sowing, the roots were exposed to 10, 20 and 40 mM NO₃^– through rooting medium with the aim for studying NO₃^– induced changes in ethylene production and root functioning. Aminoethoxyvinylglycine (AVG, 5 μM), an ethylene biosynthesis inhibitor, was added after 24 h of NO₃^– treatments. Three days after the treatments, NO₃^– applied at 10 mM induced a significant increase in 1-amino cyclopropane-1-carboxylic acid (ACC) content (49 %) and in vivo ACC oxidase activity (100 %) which were associated with an increase in ethylene production (25 %) and with an important increase in both H₂O₂ (60 %) and malondialdehyde (MDA, 1 270 %). In contrast, supply of NO₃^– at 40 mM resulted in an important increase in ethylene production (400 %) by inducing significant enhancement of ACC content (123 %), ACC oxidase activity (128 %) and with simultaneous increase of H₂O₂ (160 %) and MDA (1 900 %). The reversible membrane alteration showed a linear correlation with ethylene production. This was confirmed by a sharp decline in NO₃^– induced ethylene evolution by AVG. An oxidative damage by NO₃^– to the defence mechanism was evident from the increase in H₂O₂ content which is apparent from the decrease in activities of superoxide dismutase (EC 1.15.1.1), catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11) and glutathione reductase (EC 1.11.1.9) to 23–67, 39–43, 33–55 and 26–45 %, respectively. The AVG treatment showed partial recovery in the activities of these enzymes and decrease in H₂O₂ content (17–32 %). It is inferred that ethylene evolution due to NO₃^– is the key marker interfering with the functioning of roots along with the weakening of antioxidant defence mechanism.     

The effects of gradual or abrupt changes in salinity on digestive enzymes activity of Caspian kutum,Rutilus kutum (Kamensky, 1901) larvae

This study investigates the effects of gradual or abrupt changes in rearing salinity on food transit time and digestive enzymes activity of Caspian kutum (Rutilus kutum) larvae. The larvae (532 ± 0.05 mg) were supplied and randomly allocated into 12 tanks at a density of 45 fish per tank. Experimental treatments were fresh water (salinity 0) [FW] as control, exposure to salinity 5 [T₁], and gradual transfer to salinity 10 in two steps of first to 5 h, then and after 12 h to a salinity of 10 [T₂], and abrupt change (direct transfer to a salinity of 10 [T₃]). Results showed at 8 h after start of feeding that the larvae intestine was filled with food pellets except in treatment T₁. Enzyme activity responded to salinity change as follows: the highest trypsin, amylase, and chymotrypsin activities were observed in T₁; however, these were not significantly different to treatment T₃ (P > 0.05). Trypsin activity peaks in the FW and T₂ groups occurred 8 h after feeding, and in T₃ and T₁ groups 5 h after feeding. Peak chymotrypsin and alkaline phosphatase activity was observed 5 and 8 h after feeding in all experiments, respectively. The highest α amylase activity in FW and T₂ groups occurred 5 h after feeding, while in T₃ and T₁ these peaks were observed 8 h after feeding. These results indicate that salinity had some noticeable effects on the activities of digestive enzymes after feeding.     

Deleterious effects of potassium bromate administration on renal and hepatic tissues of Swiss mice

Potassium bromate (KBrO₃) is widely used as a food additive and is a major water disinfection by-product. The present study reports the side effects of KBrO₃ administration in Swiss mice. Animals were randomly divided into three groups: control, low dose KBrO₃ (100 mg/kg/day) and high dose KBrO₃ (200 mg/kg/day) groups. Administration of KBrO₃ led to decreased white blood corpuscles (WBCs), red blood corpuscles (RBCs) and platelets count in the animals of both the high and the low dose groups. Altered lipid profile represented as low density lipoprotein (LDL), high density lipoprotein (HDL) and cholesterol levels were observed in plasma samples of both KBrO₃ treated groups of mice. Also, an increased plasma level of LDH was detected in both KBrO₃ treated groups. Histological investigations showed impaired renal and hepatic histology that was concomitant with increased plasma Creatinine level in both of KBrO₃-treated groups. Nevertheless, decreased glutathione (GSH) level in both renal and hepatic tissue of mice after KBrO₃ intake was detected. These results show that KBrO₃ has serious damaging effects and therefore, its use should be avoided.     

Zearalenone induces ROS‐mediated mitochondrial damage in porcine IPEC‐J2 cells

In this study, the mitochondrial damage effect and mechanism of zearalenone (ZEA) in swine small intestine IPEC‐J2 cells in vitro were comprehensively characterized. The analyses revealed that ZEA at high doses (8 and 7 μg/mL) can significantly increase P < 0.05 the malondialdehyde levels and decrease antioxidant enzymes activities after 48 h of exposure. Meanwhile, the reactive oxygen species (ROS) accumulation increased in high dose ZEA‐treated groups after 2 h treatment, but decreased due to the ROS‐induced mitochondrial damage and the caused cell apoptosis after 48 h of high does ZEA treatment. Moreover, the decreasing of mitochondrial membrane potential (MMP; ΔΨ) in high dose ZEA exposure was observed in line with the increasing ROS production in mitochondria. Results suggest that ZEA exposure can induce mitochondrial damage by reducing antioxidant enzyme activities, accumulation of ROS, and decreasing MMP. The mitochondrial damage had a dramatic concentration–effects relationship with ZEA.     

Enhancement of <Emphasis Type="Italic">Candida albicans</Emphasis> Virulence After Exposition to Cigarette Mainstream Smoke

The habit of cigarette smoking is associated with higher oral candidal carriage and possible predisposition to oral candidosis. The effects of exposure to smoke on the virulence properties of oral yeasts remain obscure. Hence, we showed in vitro the effect of cigarette smoke condensate (CSC) on ten clinical isolates of Candida albicans obtained from nonsmoking volunteers, as well the type-strain CBS562. CSC was generated by complete burn of five commercial cigarettes in an in-house smoking machine and used to prepare the culture broth in which the strains were grown. In 24-h intervals (T₂₄, T₄₈, and T₇₂), the cells were harvested, washed, subcultured, and the resultant growth were evaluated for possible variations for secreted aspartyl protease, phospholipase, chondroitinase, and hemolysins, adhesion to acrylic and cell surface hydrophobicity (CSH). The results indicated a temporal increase in the secretion rates of enzymes, particularly when yeast cells were exposed to CSC for 48–72 h (P < 0.05). Similarly, adhesion to acrylic and CSH increased with exposure period (P < 0.05). Based on foregoing, we concluded that CSC may promote significant enhance in the secretion of candidal histolytic enzymes and adherence to denture surfaces, thereby promoting oral yeast carriage and possible infection.     

Alleviation of free radical mediated oxidative and genotoxic effects of cadmium by farnesol in Swiss albino mice

Abstract

Farnesol is an isoprenoid found in essential oils of ambrette seeds, citronella and in various aromatic plants. Exposure to cadmium from various sources affects the renal system adversely and Cd is an established genotoxic agent. In the present study, we evaluated the antigenotoxic and antioxidant efficacy of farnesol against cadmium chloride (CdCl₂)-induced renal oxidative stress and genotoxicity in Swiss albino mice. Single, intraperitoneal doses of CdCl₂(5 mg/kg body weight) for 24 h resulted in a significant (P < 0.001) increase in chromosomal aberration and micronuclei formation. The oral administration of farnesol at two doses (1% and 2% per kg body weight) for seven consecutive days showed significant (P < 0.05) suppression of the genotoxic effects of CdCl₂ in the modulator groups. To study the mechanism by which farnesol exerts its antigenotoxic potential, enzymes involved in metabolism and detoxification were estimated. CdCl₂ intoxication adversely affected the renal antioxidant armory and increased TBARS formation and xanthine oxidase levels significantly (P < 0.001). Farnesol showed a significant (P < 0.001) recovery in antioxidant status viz, GSH content (and its dependent enzymes) and catalase activity. Farnesol pretreatment in CdCl₂-intoxicated mice showed marked (P < 0.001) suppression of TBARS' formation and XO activity. Our results support the conclusion that the anticlastogenic effect of farnesol could be due to restoration of antioxidants and inhibition of oxidative damage.     

Metrifonate and dichlorvos: Effects of a single oral administration on cholinesterase activity in rat brain and blood

Cholinesterase activities in rat forebrain, erythrocytes, and plasma were assessed after a single oral administration of metrifonate or dichlorvos. In 3-month-old rats, the dichlorvos (10 mg/kg p.o.)-induced inhibition of cholinesterase reached its peak in brain after 15–45 min and after 10–30 min in erythrocytes and plasma. Cholinesterase activity recovered rapidly after the peak of inhibition, but did not reach control values in brain and erythrocytes within 24 h after drug administration. The recovery of plasma cholinesterase activity, in contrast, was already complete 12 h after dichlorvos treatment. Metrifonate (100 mg/kg p.o.) had qualitatively similar inhibition kinetics as dichlorvos, albeit with a slightly delayed onset. Peak values were attained 45–60 min (brain) and 20–45 min (blood), after drug administration. Apparently complete recovery of cholinesterase activity was noted in both tissues 24 h after treatment. The dose-dependence of drug-induced inhibition of cholinesterase in rat blood and brain was determined at the time of maximal inhibition, i.e., 30 min after dichlorvos treatment and 45 min after metrifonate treatment. The oral ED₅₀ values obtained for dichlorvos were 8 mg/kg for brain and 6 mg/kg for both erythrocyte and plasma cholinesterase. The corresponding oral ED₅₀ values for metrifonate were 10 to 15 times higher, i.e., 90 mg/kg in brain and 80 mg/kg in erythrocytes and plasma. In rats deprived of food for 18 h before drug treatment, the corresponding ED₅₀ values for metrifonate were 60 and 45 mg/kg, respectively, indicating an about two-fold higher sensitivity of fasted rats to metrifonate-induced cholinesterase inhibition compared to non-fasted rats. Compared to 3-month-old rats, 19-month-old rats showed a higher sensitivity towards metrifonate and dichlorvos. At the time of maximal inhibition, there was a strong correlation between the degree of cholinesterase inhibition in brain and blood. These results demonstrate that single oral administration of metrifonate and dichlorvos induces an inhibition of blood and brain cholinesterase in the conscious rat in a dose-dependent and apparently fully reversible manner. While the efficiency of a given dose of inhibitor may vary with the satiety status or age of the animal, the extent of brain ChE inhibition can be estimated from the level of blood ChE activity.     

Changes in antioxidants and cell damage in heterotrophic maize seedlings differing in drought sensitivity after exposure to short-term osmotic stress

Seedlings of two cultivars of maize (Zea mays L.) differing in their drought sensitivity were exposed to osmotic stress (0.3 M sorbitol, −1.4 MPa) for 4, 8, 12, 24 and 48 h during their heterotrophic stage of development. Alterations in their antioxidant pools combined with the activities of enzymes involved in defence against oxidative stress were investigated. Significant activation of antioxidative defence mechanisms correlated with drought-induced oxidative stress tolerance, and this phenomenon was shown to be characteristic of the drought-tolerant cv. Nova. Activities of some ROS-scavenging enzymes, superoxide dismutase (SOD), guaiacol peroxidase (POX), catalase (CAT) and ascorbate peroxidase (APX) were already enhanced significantly 4 h after the start of drought exposure in the drought-tolerant cv. Nova. Furthermore, a significant increase in the ascorbate pool was observed in this cultivar. On the other hand, in the drought-sensitive cv. Ankora only SOD and POD activities and the thiol pool were increased. No changes in APX activity or the level of ascorbate were recorded in cv. Ankora. Studies of root cell viability indicated that marked oxidative damage appeared only in cv. Ankora. These results, together with our previous observations, confirmed the higher ability of cv. Nova to tolerate drought stress and cope effectively with oxidative damage.     

Oxidative DNA damage is a preliminary step during rat tongue carcinogenesis induced by 4-nitroquinoline 1-oxide

The aim of this study was to investigate oxidative DNA damage during 4-nitroquinoline 1-oxide (4NQO)-induced rat tongue carcinogenesis. For this purpose, male Wistar rats were distributed into three groups of 10 animals each and treated with 50 ppm 4NQO solution through their drinking water for 4, 12, and 20 weeks. Ten animals were used as negative control. The alkaline Comet assay modified with lesion-specific enzymes was used to detect single and double strand breaks, labile sites (SBs), and oxidised purines and pyrimidines. Although no histopathological abnormalities were induced in the epithelium after 4 weeks of carcinogen exposure, oxidative DNA damage was detected in the ‘normal’ oral epithelium. In pre-neoplastic lesions and squamous cell carcinomas induced after 12 and 20 weeks following carcinogen exposure, respectively, oxidative DNA damage was also increased (P < 0.05) when compared to negative control. In conclusion, our results suggest that oxidative DNA damage is an early event during multistep carcinogenesis assay induced by 4NQO. This kind of approach should be considered to persons with high risk of oral cancer, such as in smokers or alcohol consumers.     

Toxicokinetics and toxicological effects of single oral dose of fumonisin B1 containing Fusarium verticillioides culture material in weaned piglets

Toxicokinetics and the toxicological effects of culture material containing fumonisin B₁ (FB₁) were studied in male weaned piglets by clinical, pathological, biochemical and sphingolipid analyses. The animals received a single oral dose of 5 mg FB₁/kg of body weight, obtained from Fusarium verticillioides culture material. FB₁ was detected by HPLC in plasma collected at 1-h intervals up to 6 h and at 12-h intervals up to 96 h. FB₁ eliminated in feces and urine was quantified over a 96-h period and in liver samples collected 96 h post-intoxication. Blood samples were obtained at the beginning and end of the experiment to determine serum enzyme activity, total bilirubin, cholesterol, sphinganine (Sa), sphingosine (So) and the Sa/So ratio. FB₁ was detected in plasma between 30 min and 36 h after administration. The highest concentration of FB₁ was observed after 2 h, with a mean concentration of 282 μg/ml. Only 0.93% of the total FB₁ was detected in urine between 75 min and 41 h after administration, the highest mean concentration (561 μg/ml) was observed during the interval after 8 at 24 h. Approximately 76.5% of FB₁ was detected in feces eliminated between 8 and 84 h after administration, with the highest levels observed between 8 and 24 h. Considering the biochemical parameters, a significant increase only occurred in cholesterol, alkaline phosphatase and aspartate aminotransferase activities. In plasma and urine, the highest Sa and Sa/So ratios were obtained at 12 and 48 h, respectively.     

Bisphenol A induced toxicity in blood cells of freshwater fish Channa punctatus after acute exposure

The widespread use of bisphenol A (BPA) has led to its ubiquity in the natural environment. It is extensively incorporated into different industrial products and is associated with deleterious health effects on both public and wildlife. The current trial was conducted to determine the toxic potential of bisphenol A using various parameters viz haematological, biochemical, and cytological in freshwater fish Channa punctatus. For this purpose, fish were exposed to 1.81 mg/l (1/4 of LC₅₀) and 3.81 mg/l (1/2 of LC₅₀) of BPA along with positive (acetone) and negative controls (water) for 96 h. The blood samples were collected at 24, 48, 72, and 96 h post-exposure. Compared to the control group, fish after acute exposure to BPA showed a significant decrease in HB content, number of red blood cells, PCV values whereas a significant increase in WBCs count was recorded with an increase in the exposure period. Besides, oxidative stress (determined as malondialdehyde content) increased as BPA concentration increased. Further, the activity of different antioxidant enzymes like catalase, and superoxide dismutase decreased significantly after treatment. Results also showed significantly increased frequency of morphological alterations, nuclear changes, and increased DNA damage potential of BPA in red blood cells. Further structural analysis of erythrocytes in maximally damaged group using Scanning Electron Microscopy was performed. The study concludes that BPA exhibits genotoxic activity and oxidative stress could be one of the mechanisms leading to genetic toxicity.