Comparative effect of ochratoxin A on inflammation and oxidative stress parameters in gut and kidney of piglets

Ochratoxin A (OTA) is a secondary metabolite produced by fungi of Aspergillus and Penicillium genra. OTA is mainly nephrotoxic but can also cause hepatotoxicity, mutagenicity, teratogenicity, neurotoxicity and immunotoxicity. As recent studies have highlighted the close relationship between gastrointestinal tract and kidney, as principal organs involved in absorption and respective excretion of xenobiotics, the aim of the present study was to analyze the effect of a subchronic exposure (30 days) to 0.05 mg/kg OTA on immune response and oxidative stress parameters at the level of intestine and kidney of young swine. The experiment was realised on twelve crossbred weaned piglets randomly allotted to both control group or toxin group fed 0.050 mg OTA/kg feed. Our results have shown that a subchronic intoxication with a low dose of OTA for 30 days affected the immune response and the anti-oxidant self-defense at gut and kidney level. The gene expression of both markers of signaling pathways involved in inflammation and inflammatory cytokines were affected in a much higher extent in the gut than in the kidney Of OTA intoxicated piglets.     

Disturbed Hsp70 and Hsp27 expression and thiol redox status in porcine kidney PK15 cells provoked by individual and combined ochratoxin A and citrinin treatments

The aim of this study was to explore the oxidative properties of ochratoxin A (OTA) and citrinin (CTN) as a possible underlying mechanism of their individual and/or combined cytotoxicity. Metabolic activity of PK15 porcine kidney cells was significantly reduced with OTA and CTN co-exposures, with synergistic cytotoxic interactions. Single CTN increased both reduced (GSH) and oxidized (GSSG) glutathione after 24 h. However, GSH was significantly lowered with all OTA and CTN combined applications in synergistic manner after 12 and 24 h. GSH/GSSG ratio was reduced in most single and dual treatments, which suggested the presence of oxidative stress. In addition, OTA and CTN exposures significantly decreased concentrations of total thiols, with mycotoxins interactions being synergistic or antagonistic. The expression levels of Hsps were differentially affected by single and dual mycotoxin(s) applications. Single OTA provoked significant down-regulation of Hsp70 and Hsp27 expressions, while CTN stimulated Hsps expressions. Hsps were also up-regulated by dual treatments, and this induction was much stronger then with single CTN. In conclusion, significant alterations in cellular redox status (glutathione, thiols) and protective mechanisms (Hsps) suggest that those disturbances might be involved in OTA and CTN individual and combined mechanisms of cytotoxicity.     

Phenolic acid protects of renal damage induced by ochratoxin A in a 28-days-oral treatment in rats

The present study aimed to characterize the chlorogenic acid (ChlA) capacity to reverse the toxic effects induced by ochratoxin A (OTA) in a subacute toxicity test in rats. Male Wistar rats were fed orally by gavage for 28 days with OTA (0.4 mg/kg bw/day), ChlA (5 mg/kg bw/day) or the combination OTA (0.4 mg/kg bw/day) + ChlA (5 mg/kg bw/day). No deaths, no decrease in feed intake or body weight in any experimental group were recorded. The negative control group and the animals treated with ChlA alone showed no changes in any parameters evaluated. In OTA-treated group significant changes such as decrease in urine volume, proteinuria, occult blood, increase in serum creatinine values; decrease in absolute and relative kidney weight and characteristics histopathological lesions that indicated kidney damage were observed. However, limited effect on oxidative stress parameters were detected in kidneys of OTA-treated group. Animals treated with the combination OTA + ChlA were showed as negative control group in the evaluation of several parameters of toxicity. In conclusion, ChlA, at given concentration, improved biochemical parameters altered in urine and serum and pathological damages in kidneys induced by OTA exposure, showing a good protective activity, but not by an apparent antioxidant mechanism.     

Regional selectivity to ochratoxin A, distribution and cytotoxicity in rat brain

Ochratoxin A (OTA) a chlorodihydro-isocoumarin linked through an amide bond to phenylalanine, is a mycotoxin found as a contaminant in foodstuffs and shown to be nephrotoxic, teratogenic, immunosuppressive, genotoxic, mutagenic and carcinogenic in rodents. Ochratoxin A is known to induce teratogenic effects in neonates (rats and mice) exposed in utero, characterised by microcephaly and modification of the brain levels of free amino acids. Since OTA has been found to accumulate in the brain according to the duration of exposure to doses in the range of natural contamination of feedstuffs, experiments were designed to determine more precisely the structural target of OTA in the brain. After intracerebral injection, OTA (403 ng/10 μl) was not found in the following parts of the brain : the frontal cortex (FC), striatum (ST), ventral mesencephalon (VM) and the cerebellum (CB) in contrast to the rest of the brain, probably due to the detection limit of 0.1 ng/g of tissue. However lactate dehydrogenase (LDH) was increased in extracellular space in the VM to a greater extent than in the rest of the brain, indicating that this structure could be one of the targets of OTA in the brain. Contents of free amino acids were morever similarly modified in the VM and in the rest of the brain. Male rats were given OTA (289 μg/kg per 24 h) by gastric intubation for 8 days and the main brain structures analysed for OTA content and cytotoxicity. OTA was found in the following structures in decreasing order: rest of the brain (50.3%), cerebellum (34.4%), VM (5.1%), striatum (3.3%) and hippocampus (2.9%) of the total OTA amount found in the brain, which represents 0.022% to 0.028% of the given dose. Interestingly cytotoxicity as measured by lactate dehydrogenase (LDH) release in the extracellular space was much more pronounced in the VM, hippocampus, and striatum than in the cerebellum, whereas no cytotoxicity was observed in the rest of the brain. Similarly deoxyribonuclease (DNase) activity in relation to possible necrotic cells was increased in the VM and cerebellum. Altogether these results designated the ventral mesencephalon, hippocampus, striatum and cerebellum as the main OTA-targets in the brain of adult rats and excluded the rest of the brain. Received: 2 April 1998 / Accepted: 28 April 1998     

芍药苷通过调控硫氧还蛋白结合蛋白表达对脂多糖诱导的肾小球系膜细胞氧化应激及凋亡的影响

目的 探讨芍药苷对脂多糖(LPS)诱导的肾小球系膜细胞氧化应激及凋亡的影响及其作用机制.方法 研究起止时间为2018年1月至2019年7月,体外培养人肾小球系膜细胞(HMCL),用不同浓度的(5、10、20μmol/L)芍药苷处理LPS诱导的HMCL细胞.采用流式细胞仪检测细胞凋亡率;应用试剂盒检测细胞中丙二醛(MDA)量及超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)活性;实时荧光定量聚合酶链反应(qRT-PCR)与蛋白质迹法(Western blotting)分别检测硫氧还蛋白结合蛋白(Thioredoxin-interacting protein,TXNIP)表达;观察干扰TXNIP的表达对LPS诱导的HMCL细胞氧化应激与凋亡的影响.结果 与对照组(Con)比较,LPS组细胞凋亡率升高[(6.58±0.66)％比(28.41±2.83)％](P<0.05),MDA含量增加[(1.26±0.13)nmol/L比(5.06±0.49)nmol/L](P<0.05),SOD[(26.41±2.31)U/mL比(12.46±1.21)U/mL]、GSH-Px[(45.61±4.13)U/mL比(8.12±0.83)U/mL]活性下降(P<0.05),TXNIP信使RNA(mRNA)及蛋白表达升高[(1.02±0.09)vs(2.54±0.25);(0.42±0.04)比(0.87±0.05)](P<0.05);与LPS组比较,芍药苷不同剂量组细胞凋亡率降低[(28.41±2.83)％比(22.16±2.17)/(16.48±1.03)/(11.25±1.12)％](P<0.05),MDA含量下降[(5.06±0.49)nmol/L比(4.12±0.41)/(2.94±0.29)/(1.68±0.17)nmol/L](P<0.05),SOD[(12.46±1.21)U/mL比(15.46±1.52)/(18.24±1.63)/(22.54±2.03)U/mL]、GSH-Px[(8.12±0.83)U/mL比(17.62±1.74)/(26.14±2.63)/(39.44±3.25)U/mL]活性升高(P<0.05),TXNIP mRNA及蛋白表达降低[(2.54±0.25)比(2.13±0.21)/(1.84±0.17)/(1.46±0.15);(0.87±0.05)比(0.72±0.05)/(0.61±0.04)/(0.49±0.03)](P<0.05);干扰TXNIP的表达可减轻LPS诱导的HMCL细胞氧化应激损伤,降低细胞凋亡率;TXNIP过表达可逆转芍药苷对LPS诱导的HMCL细胞氧化应激及凋亡的作用.结论 芍药苷可通过抑制TXNIP的表达对LPS诱导的HMCL细胞氧化应激发挥保护作用,抑制细胞凋亡.     

Effects of ochratoxin A on ER stress,MAPK signaling pathway and autophagy of kidney and spleen in pigs

Ochratoxin A (OTA), a worldwide mycotoxin found in food and feeds, is a potent nephrotoxin and immunotoxin in animals and humans. This research was conducted to evaluate whether endoplasmic reticulum (ER) stress, MAPK signaling pathway and autophagy were induced by OTA in kidney and spleen of pigs. Twenty‐seven crossbred pigs randomly allocated to 3 groups were fed for 42 days ad libitum a basal diet without (Con group, 0.00 μg OTA/kg) and with supplementation of OTA at 400 (OTA‐L group) and 800 μg/kg (OTA‐H group). From each group, 6 pigs were randomly selected for blood collection on days 0, 21, and 42 and 3 pigs were randomly selected for tissue collection on day 42. The results showed that OTA at 400 and 800 μg/kg diets significantly increased OTA concentrations in serum and kidney and spleen induced the histopathological lesions of kidney and spleen, decreased TCR‐stimulated T lymphocyte viabilities and IL‐2 concentration, increased TNF‐α concentration, and decreased T‐AOC levels. OTA increased glucose regulated protein 78, p38, and ERK1/2 phosphorylation, and LC3 II and Atg5 protein expression in kidney and spleen of pigs. These results provide new insights into the relationship between OTA and ER stress, p38 and ERK1/2 MAPK signaling pathway and autophagy in pigs.     

Oxidative stress and apoptotic changes in primary cultures of rat proximal tubular cells exposed to lead

Lead is a known nephrotoxic element. In this study, primary cultures of rat proximal tubular (rPT) cells were treated with different concentrations of lead acetate (0.25, 0.5 and 1 μM) to investigate its cytotoxic mechanism. A progressive loss in cell viability together with a significant increase in the number of apoptotic and necrotic cells and lactate dehydrogenase release were seen in the experiment. Simultaneously, elevation of reactive oxygen species levels and intracellular [Ca²⁺]i, depletion of mitochondrial membrane potential and intracellular glutathione were revealed during the lead exposure. In addition, apoptotic morphological changes induced by lead exposure in rPT cells were demonstrated by Hoechst 33258 staining. The apoptosis was markedly prevented by N-acetyl-l-cysteine, while the necrosis was not affected. Moreover, catalase and superoxide dismutase activities in the living cells rose significantly. In conclusion, exposure of rPT cells to low-concentration lead led to cell death, mediated by an apoptotic and a necrotic mechanism. The apoptotic death induced by oxidative stress was the chief mechanism. Meanwhile, a group of cells survived lead action, mediated by their ability to activate antioxidant defense systems.     

Urinary ochratoxin A and ochratoxin alpha in pregnant women

This study determined exposure of pregnant women to ochratoxin A (OTA). Forty samples of first-void urine samples from Croatian women in the third trimester of pregnancy were analyzed for OTA and its major metabolite ochratoxin alpha (OTα). The subjects filled a short food frequency questionnaire (FFQ). Analysis was performed by HPLC-FLD following liquid–liquid extraction. All samples were subjected in parallel to enzymatic treatment (β-glucuronidase/aryl sulfatase) to release OTA and OTα from the conjugates. The median urinary levels of OTA and OTα before treatment were 0.02 (range: nd–1.07) ng/mL and 0.16 (nd–1.86) ng/mL; the concentrations after enzyme hydrolysis were 0.02 (nd–1.11) ng/mL and 1.18 (0.11–7.57) ng/mL. While OTα levels increased significantly following enzymatic treatment, evidence for OTA conjugation was weak. The ratio of urinary OTα medians after and before hydrolysis was 1.5 times higher than previously reported for nonpregnant female subjects, possibly indicating upregulated metabolism and/or elimination of the mycotoxin and metabolites in pregnancy. The mean daily dietary OTA intake calculated from FFQs (1.08 ± 0.57 ng/kg body weight) was well below the provisional tolerable daily intake and the greatest contributors to intake were cereal products, fruit juices, chocolate and coffee.     

Study of ochratoxin A (OTA)-induced oxidative stress markers in broiler chicks

The current study was designed to investigate the effects of ochratoxin A (OTA) on the oxidative stress in day-old broiler chicks. A total of 60-day-old broiler chicks were divided into four equal groups A–D. Group A was control, groups B–D were administered with different levels of OTA (1.6, 3.2 and 6.4?mg/kg of feed), respectively, for 10?days from day one of their age. Superoxide dismutase (SOD), glutathione peroxidase (GPx) and total antioxidant status of blood plasma, RBCs hemolysate and supernatant of tissue homogenates (liver, kidney and muscles) were estimated in all groups on days 11 and 31 in order to determine the oxidative stress in chicks. The results revealed a significant dose-dependent decrease in the SOD, GPx and TAS levels in all OTA-fed groups. It was found persistent even after 21?days of withdrawal of toxin-contaminated feed in all tissues except RBCs hemolysate. Present study described the OTA-induced oxidative stress as indicated by the low levels of SOD, GPx and TAS in different biological samples of broiler chicks.     

Intraperitoneal glycerol induces oxidative stress in rat kidney

1. Glycerol has been used for the treatment of intracranial hypertension, cerebral oedema and glaucoma. Experimentally, intramuscular administration of hypertonic glycerol solution is used to produce acute renal failure. In this model, glycerol causes rhabdomyolysis and myoglobinuria, resulting in the development of renal injury. The pathogenesis is thought to involve vascular congestion, the formation of casts and oxidative stress. However, the effect of glycerol itself independent of rhabdomyolysis has not been investigated. Therefore, the aim of the present study was to investigate the effects of i.p. glycerol on some biochemical and oxidative stress parameters in the kidney of young rats. 2. Rats received 10 mL/kg, i.p., hypertonic glycerol solution (50% v/v) or saline (NaCl 0.85 g%) followed by 24 h water deprivation. Twenty-four hours after the administration of glycerol, rats were killed. Creatinine levels and the activity of creatine kinase (CK) and lactate dehydrogenase (LDH) were determined in the plasma. In addition, CK, pyruvate kinase and LDH activity and oxidative stress parameters (free radical formation, lipid peroxidation and protein carbonylation) were measured in renal tissue. 3. Glycerol did not alter plasma CK activity and increased plasma creatinine levels, suggesting renal insufficiency and the absence of rhabdomyolysis. Renal CK and pyruvate kinase activity was decreased, suggesting diminution of energy homeostasis in the kidney. Plasma and renal LDH activity was decreased, whereas the formation of free radicals, lipid peroxidation and protein carbonylation were increased, suggesting oxidative stress. 4. These results are similar to those described after the intramuscular administration of glycerol. Therefore, it is possible that glycerol may provoke renal lesions by mechanisms other than those induced by rhabdomyolysis.     

Studies on the effect of sodium arsenate on the enzymes of carbohydrate metabolism,brush border membrane,and oxidative stress in the rat kidney

Arsenic is an environmental pollutant and its contamination in drinking water poses serious world wide environmental health threats. It produces multiple adverse effects in various tissues, including the kidney. However, biochemical mechanism and renal response to its toxic insult are not completely elucidated. We hypothesized that sodium arsenate (ARS) induces oxidative stress and alters the structure and metabolic functions of kidney. Male Wistar rats were administered ARS (10 mg/kg body weight/day), intraperitoneally daily for 10 days. ARS administration increased blood urea nitrogen, serum creatinine, cholesterol, glucose, and phospholipids but decreased inorganic phosphate, indicating kidney toxicity. The activity of brush border membrane (BBM) enzymes significantly lowered in both cortex and medulla. Activity of hexokinase, lactate dehydrogenase, glucose-6-phosphate dehydrogenases, and NADP-malic enzyme significantly increased whereas malate dehydrogenase, glucose-6-phosphatase, and fructose 1,6 bis phosphatase decreased by ARS exposure. The activity of superoxide dismutase, GSH-peroxidase, and catalase were selectively altered in renal tissues along with an increase in lipid peroxidation. The present results indicated that ARS induced oxidative stress caused severe renal damage that resulted in altered levels of carbohydrate metabolism and BBM enzymes.     

Protective effect of N-acetylcysteine against DNA damage and S-phase arrest induced by ochratoxin A in human embryonic kidney cells (HEK-293)

N-acetylcysteine (NAC) has recently gained particular interest as a beneficial antioxidant. This study investigated the protective effects of NAC against ochratoxin A (OTA)-induced DNA damage and S-phase arrest in human embryonic kidney cells (HEK-293). OTA exposure results in nephrotoxicity, hepatotoxicity as well as immunotoxicity; and, in the present study, the toxicity of OTA toward HEK-293 cells was explored by analyzing the involvement of the oxidative pathway. It was found that OTA treatment led to oxidative damage; meanwhile, OTA treatment induced significant DNA damage and S-phase arrest by down-regulating cyclin A2, cyclin E1, and CDK2 expression. However, NAC pretreatment alleviated OTA-induced ROS overproduction, the loss of mitochondrial membrane potential (ΔΨ_m), and the decrease in superoxide dismutase (SOD) activity. NAC pretreatment was also discovered to attenuate OTA-induced DNA damage using the comet assay and by determining the expression of γ-H2AX. In addition, NAC pretreatment partly ameliorated OTA-induced S-phase arrest by preventing the down-regulation of cyclin A2, cyclin E1 and CDK2 expression in HEK-293 cells. All of these results demonstrated that oxidative damage was involved in OTA-induced DNA damage and cell cycle arrest in HEK-293 cells. Therefore, NAC has the potential to reverse the DNA damage and S-phase arrest induced by OTA.     

In vitro gene expression data supporting a DNA non-reactive genotoxic mechanism for ochratoxin A

Ochratoxin A (OTA) is a mycotoxin often found in cereals and agricultural products. There is unequivocal evidence of renal carcinogenicity of OTA in male rats, although the mechanism of action is unknown. At present, available data support an epigenetic mechanism (DNA non-reactive) resulting from oxidative stress and cytotoxicity, because a direct OTA interaction with DNA has not been demonstrated. Genotoxic mechanism (DNA-reactive vs. DNA non-reactive) may have implications on human risk assessment. Therefore, the aim of the present work was to identify biological pathways modulated by OTA in vitro in a human renal cell line (HK-2) to contribute to the elucidation of the mechanism of OTA toxicity. For that purpose, cells were exposed to 50 microM OTA during 6 and 24 h, and gene expression profiles were analyzed using Affymetrix Human Genome U133 A 2.0 Gene Chips. Under the same experimental conditions, genotoxicity was evaluated by the modified comet assay using FPG and Endo III to detect oxidative DNA damage, and intracellular ROS level by the H(2)DCF assay. After 6 h, with slight cytotoxicity (83% survival), genes involved in mitochondrial electron transport chain were up-regulated; and after 24 h, with a more pronounced cytotoxicity (51% survival), genes implicated in oxidative stress response were also up-regulated. Increase in intracellular ROS level and oxidative DNA damage was evident at both exposure times being more pronounced with high cytotoxicity. On the contrary, up-regulation of genes implicated in DNA damage response, as cell cycle control or apoptosis, was not detected at any exposure time. In conclusion, these results support a DNA non-reactive mechanism of OTA genotoxicity.     

Propofol ameliorates doxorubicin-induced oxidative stress and cellular apoptosis in rat cardiomyocytes

Background

Propofol is an anesthetic with pluripotent cytoprotective properties against various extrinsic insults. This study was designed to examine whether this agent could also ameliorate the infamous toxicity of doxorubicin, a widely-used chemotherapeutic agent against a variety of cancer diseases, on myocardial cells.

Methods

Cultured neonatal rat cardiomyocytes were administrated with vehicle, doxorubicin (1 μM), propofol (1 μM), or propofol plus doxorubicin (given 1 h post propofol). After 24 h, cells were harvested and specific analyses regarding oxidative/nitrative stress and cellular apoptosis were conducted.

Results

Trypan blue exclusion and MTT assays disclosed that viability of cardiomyocytes was significantly reduced by doxorubicin. Contents of reactive oxygen and nitrogen species were increased and antioxidant enzymes SOD1, SOD2, and GPx were decreased in these doxorubicin-treated cells. Mitochondrial dehydrogenase activity and membrane potential were also depressed, along with activation of key effectors downstream of mitochondrion-dependent apoptotic signaling. Besides, abundance of p53 was elevated and cleavage of PKC-δ was induced in these myocardial cells. In contrast, all of the above oxidative, nitrative and pro-apoptotic events could be suppressed by propofol pretreatment.

Conclusions

Propofol could extensively counteract oxidative/nitrative and multiple apoptotic effects of doxorubicin in the heart; hence, this anesthetic may serve as an adjuvant agent to assuage the untoward cardiac effects of doxorubicin in clinical application.     

Taurine reverses endosulfan-induced oxidative stress and apoptosis in adult rat testis

The present study was aimed to investigate the mechanistic aspect of endosulfan toxicity and its protection by taurine in rat testes. Pre-treatment with taurine (100 mg/kg/day) significantly reversed the decrease in testes weight, and the reduction in sperm count, motility, viability and daily sperm production in endosulfan (5 mg/kg/day)-treated rats. Sperm chromatin integrity and epididymal L-carnitine were markedly decreased by endosulfan treatment. Endosulfan significantly decreased the level of serum testosterone and testicular 3β-HSD, 17β-HSD, G6PDH and LDH-X. Sperm Δψm and mitochondrial cytochrome c content were significantly decreased after endosulfan. Testicular caspases-3, -8 and -9 activities were significantly increased but taurine showed significant protection from endosulfan-induced apoptosis. Oxidative stress was induced by endosulfan treatment as evidenced by increased H₂O₂ level and LPO and decreased the antioxidant enzymes SOD, CAT and GPx activities and GSH content. These alterations were effectively prevented by taurine pre-treatment.In conclusion, endosulfan decreases rat testes weight, and inhibits spermatogenesis and steroidogenesis. It induces oxidative stress and apoptosis by possible mechanisms of both mitochondria and non-mitochondria pathways. These data provide insight into the mode of action of endosulfan-induced toxicity and the beneficial role provided by taurine to counteract endosulfan-induced oxidative stress and apoptosis in rat testis.     

Gene expression changes induced by ochratoxin A in renal and hepatic tissues of male F344 rat after oral repeated administration

Ochratoxin A (OTA), a naturally occurring mycotoxin, is nephrotoxic in all animal species tested and is considered a potent renal carcinogen, particularly in male rats. Its mechanism of toxicity is still unknown, although oxidative stress appears to be a plausible mechanism. Therefore, the objective of this study was to identify the biological pathways that are modulated in vivo by OTA in male F344 rats in order to gain further insight into its mechanism of renal toxicity. Rats were gavaged daily with OTA (500 microg/kg bw) and gene expression profiles in target and non-target organs were analyzed after 7 and 21 days administration. As was expected, a time-dependent increase of OTA concentrations was found in plasma, kidney and liver, with the concentrations found in both tissues being quite similar. However, histopathological examinations only revealed changes in kidney; signs of nephrotoxicity involving single cell necrosis and karyomegalic nuclei were observed in the treated rats. The number of differentially expressed genes in kidney was much higher than in liver (541 versus 11 at both time points). Several similarities were observed with other in vivo gene expression data. However, great differences were found with previous in vitro gene expression data, with the exception of DNA damage response which was not observed at mRNA level in any of our study conditions. Down-regulation was the predominant effect. Oxidative stress response pathway and genes involved in metabolism and transport were inhibited at both time points. RGN (regucalcin) - a gene implicated in calcium homeostasis - was strongly inhibited at both time points and genes implicated in cell survival and proliferation were up-regulated at day 21. Moreover, translation factors and annexin genes were up-regulated at both time points. Apart from oxidative stress, alterations of the calcium homeostasis and cytoskeleton structure may be present at the first events of OTA toxicity.     

Protective role of melatonin against the mercury induced oxidative stress in the rat thyroid

Present study investigated the protective role of melatonin (MLT, 5 mg/kg body wt., ip) against the long term effects of mercuric chloride (MC; 2 and 4 mg/kg body wt., po) in the thyroid gland of the rats through certain antioxidative indices like superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione (GSH), catalase (CAT) and lipid peroxidation (LPO), other biochemical parameters such as succinate dehydrogenase (SDH), adenosine triphosphatase (ATPase), acid phosphatase (ACPase) and alkaline phosphatase (ALPase) were also measured. Antioxidative enzymes and other parameters showed a significant reduction while LPO and mercury levels increased significantly in a dose dependent manner in MC treated animals as compared to control groups. Co-treatment with MLT revealed no significant effect on antioxidative and metabolic indices in the thyroid gland of rats. The results of present study thus strongly suggest that mercury affected antioxidant defense system and other metabolic enzymes of thyroid. Co-administration of melatonin exerted a protective effect against mercury induced endocrine toxicity.     

PM2.5-induced oxidative stress triggers autophagy in human lung epithelial A549 cells

Exposure to higher levels of air pollution particulate matter (PM) with an aerodynamic diameter of less than 2.5 μm (PM_2.5) links with an increased risk of cardiovascular and respiratory deaths and hospital admission as well as lung cancer. Although the mechanism underlying the correlation between PM_2.5 exposure and adverse effects has not fully elucidated, PM_2.5-induced oxidative stress has been considered as an important molecular mechanism of PM_2.5-mediated toxicity. In this work, human lung epithelial A549 cells were used to further investigate the biological effects of PM_2.5 on autophagy. The cell viability showed both time- and concentration-dependent decrease when exposure to PM_2.5, which can be attributed to increase of the levels of extracellular lactate dehydrogenase (LDH) release and intracellular reactive oxygen species (ROS) generation in A549 cells. Moreover, PM_2.5-induced oxidative damage in A549 cells was observed through the alteration of superoxide dismutase (SOD) and catalase (CAT) activities compared to the unexposed control cells. PM_2.5-induced autophagy was indicated by an increase in microtubule-associated protein light chain-3 (LC3) puncta, and accumulation of LC3 in both time- and concentration-dependent manner. PM_2.5-induced mRNA expression of autophagy-related protein Atg5 and Beclin1 was also observed compared with those of the unexposed control cells. These results suggest the possibility that PM_2.5-induced oxidative stress probably plays a key role in autophagy in A549 cells, which may contribute to PM_2.5-induced impairment of pulmonary function.