Background and aim: Dimethyl-Diphenyl-Bicarboxylate (DDB) is a hepatoprotectant used in treatment of chronic viral hepatitis. The mechanism of DDB against liver injury needs further elucidation. Our objective is to explore whether DDB exerts hepatoprotective effect against hepatic ischemia reperfusion injury (I/R) and to identify its potential effect on apoptotic cell death targeting the extrinsic apoptotic pathway. Methods: Rats were divided into four groups: Group I (sham-operated), Group II (I/R group), Group III (DDB Pretreated group): where rats were treated with DDB at 3 dose levels (100 mg/kg, 300 mg/kg, 500 mg/kg) for 10 days, then subjected to I/R and Group IV (DDB treated group): rats were treated with DDB at the same dose levels but without being subjected to I/R. Serum alanine aminotransferase (ALT) & aspartate aminotransferase (AST), tissue levels of GSH, MDA & tumor necrosis factor alpha (TNF-α), activity of signaling Caspases 3, 8, 9 as well as expression of nuclear factor-κB (NF-κB) were measured. End point of apoptosis was detected by DNA fragmentation. Results: DDB administration before I/R, significantly attenuated elevated levels of ALT, AST, MDA and TNF-α and increased GSH content. There were significant decrease in caspases activities, expression of NF-κB as well as DNA fragmentation. DDB administration to normal rats, inhibited lipid peroxidation, enhanced antioxidant activity, decreased TNF-α and downregulated expression of NF-κB. These effects are dose-dependent. Conclusion: DDB exerts potent antioxidant effect in normal and injured livers. It inhibited hepatic I/R induced apoptosis through inhibiting signaling Caspases 3, 8, 9, TNF-α production which regulates the extrinsic apoptotic pathway and down regulates NF-κB expression in liver tissue.
Cilostazol, an antiplatelet drug, exhibits antiatherogenic effects. The purpose of the present study was to determine the effect of cilostazol on the cytotoxicity of cadmium (Cd) and arsenite (iAsIII), which involved in the pathogenesis of vascular disorders such as atherosclerosis, in cultured vascular endothelial cells. Cytotoxicity was evaluated by the lactate dehydrogenase leakage assay and morphological observation. Cd (10 µM) -induced cytotoxicity was prevented by pretreatment with cilostazol (30 and 100 µM) and simultaneous treatment with cilostazol (100 µM). On the other hand, iAsIII-induced cytotoxicity was blocked by pretreatment with cilostazol (30 and 100 µM) but not simultaneous treatment with cilostazol. The mRNA level and the protein level of metallothionein (MT) were significantly increased by cilostazol in the cells. These results suggested, therefore, that pretreatment with cilostazol effectively prevents the cytotoxicity of Cd and iAsIII in cultured vascular endothelial cells, at least in part through the induction of MT synthesis.
Spatial learning and memory (LM) is a property of central importance in the nervous system, yet many of the molecular mechanisms for benzo(a)pyrene[B(a)P]-induced LM deficits remain enshrouded in mystery. In this study, influence of exposure to B(a)P on LM deficits in adult male Sprague-Dawley rats was evaluated by Morris water maze. Then morphological changes in the ultramicrostructure of hippocampal neurons were observed by transmission electron microscopy. Furthermore, to better understand the molecular changes that occur in B(a)P induced LM deficits, antibody-based protein microarrays was used to analyze protein expression changes in rats submitted to sub-chronic oral gavage of B(a)P (2 mg/kg for 90 days). Results suggested that rats in the B(a)P-treated groups have significantly impaired Morris water maze performance when compared to controls. Meanwhile, the B(a)P-induced neuronal damage was also found in the hippocampus under transmission electron microscopy. Our results demonstrate that LM deficits associated protein expression signatures could be identified from tissue proteomes, as well as potential biomarkers such as retinoic acid receptor b (RARb), synaptotagmin iosfomrs 1 (Syt1) and Brain-derived neurotrophic factor (BDNF), previously not found. This study, therefore, identifies, for the first time, multiple novel proteins that are dysregulated by B(a)P, which both enhance our understanding of B(a)Pinduced LM deficits and represent targets of novel therapeutics.
The production of the heavy metal-binding proteins, the metallothioneins (MTs), is induced by heavy metals such as Zn, Cd, and Hg. MTs maintain Zn homeostasis and attenuate heavy metal-induced cytotoxicity by sequestering these metals and lowering their intracellular concentrations. Previously, we had reported that Zn induced the formation of a co-activator complex containing metal response element-binding transcription factor-1 (MTF-1) and the histone acetyltransferase (HAT), p300, which plays an essential role in the activation of MT-1 transcription. In addition, we had shown that Cr(VI) inhibits Zn-induced MT-1 transcription by preventing the Zn-dependent formation of the MTF-1-p300 complex. In the current study, we have shown that the inhibition by Cr(VI) was partially overcome by the overexpression of p300 or MTF-1 in an MT-I promoter-driven luciferase reporter assay system and have used real-time RT-PCR to determine MT-I mRNA levels. It has been reported that Cr(VI) inhibits CYP1A1 transcription by crosslinking histone deacetylase (HDAC) to the promoter. The crosslink inhibits the recruitment of p300 to the MT-1 promoter and blocks HAT-dependent transactivation by p300. However, our results demonstrate that trichostatin A, an HDAC inhibitor, could not block the inhibitory effects of Cr(VI) on MT-1 transcription and that there were no significant differences in the in vitro inhibitory effects of Cr(VI), Cr(III), and Zn on p300 HAT activity. This suggests that the inhibitory effects of Cr(VI) on MT-I transcription may be due to its effects on the HAT-independent transactivation ability rather than the HAT-dependent, HDAC release-related transactivation ability of p300.
An animal model of rheumatoid arthritis can be elicited in male Lewis rats by a single intradermal injection of liquid paraffin containing dead Mycrobacterium tuberculosis (MT adjuvant) into the planar surface of the right hind-foot. In the present study, we used this animal model to examine the changes in expression of hepatic cytochorme P450 (CYP) enzymes during the development of the arthritis. Swellings of the MT adjuvant-injected hind-foot initially occurred at 1-8 days after the injection. Thereafter, the swelling gradually become more severe up to 13 days later and was maintained for up to 25 days. Swellings of the other hind-foot was also observed after 12 days and gradually become more severe up to 15 days with maintenance of the severe swelling for up to 25 days. The gene expression levels and enzyme activities of hepatic CYP 3A and CYP2B subfamily enzymes at 1, 12, and 25 days after the MT adjuvant injection were significantly decreased, compared with the corresponding time-matched controls. The decreases in the gene expression levels and activities of all the enzymes examined were closely correlated with increases in the expression levels of the inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-1α, interleukin-1β and interleukin-6, which were produced in the liver. All of the present findings demonstrate that hepatic CYP3A and CYP2B subfamily enzymes are decreased during the development of MT adjuvant-induced arthritis and further suggest that the decreases are dependent on the production of inflammatory cytokines in the liver.
Cadmium (Cd) causes renal dysfunction with damage to kidney proximal tubule cells; however, the precise mechanisms of the toxicity remain unclear. Previously, we found that the expression of Ube2d4 gene, which is a member of the ubiquitin-conjugating enzyme Ube2d family, is suppressed by Cd in NRK-52E rat renal tubular epithelial cells. To investigate the mechanisms of Cd-induced renal toxicity, we examined the effects of Cd on the ubiquitin-proteasome system, particularly the expression and function of Ube2d family members in the NRK-52E cells and mice. Cd markedly decreased the expression of Ube2d1, Ube2d2, Ube2d3 and Ube2d4 prior to the appearance of cytotoxicity in the NRK-52E cells. Cd also dramatically increased p53 protein levels in the cells, without stimulation of p53 gene expression or inhibition of proteasome activity. In addition, Cd induced phosphorylation of p53 and caused apoptosis in the NRK-52E cells. In vivo, we examined the effect of orally administrated Cd for 12 months on the expression of Ube2d genes and accumulation of p53 in the mouse kidney. Chronic Cd exposure also caused suppression of Ube2d genes expression and accumulation of p53. Cd did not induce severe kidney injury, but caused apoptosis in the renal tubules. These results suggest that the Cd-induced accumulation of p53 may be due to inhibition of p53 degradation through the down-regulation of Ube2d family genes, and that Cd induces p53-dependent apoptosis in renal tubular cells. Moreover, Ube2d family members may be one of the critical targets of renal toxicity caused by Cd.
In previous studies, perfluorooctane sulfonate (PFOS), an environmental organic compound, was reported to cause hepatotoxicity and hypolipidemia in rodents. However, the low dose toxicity of PFOS and the toxic mechanisms involved remain to be determined. To clarify the low dose toxicity and action mechanism in the target organ toxicity, Sprague-Dawley (SD) rats were orally administered with PFOS at the doses of 0, 1.25, 5, 10 mg/kg/day for 28 days. As a result, no death or abnormal symptoms were observed in all groups. The significant loss of mean body weight was observed in female rats treated with 10 mg/kg PFOS and the relative liver weight of 10 mg/kg PFOS-treated group was significantly greater compared to control. Histopathological examination revealed that fatty change was evident in the liver of male rats treated with PFOS (5 and 10 mg/kg) and hypertrophy and cellular swellings in females at the dose of 10 mg/kg, which showed different pattern of pathological lesions. In addition, we demonstrated the expression induction of hepatic caspase-3 and cytochrome P450 4A1 (CYP4A1) related with apoptosis and lipid metabolism, respectively. This study suggested that no-observed-adverse-effect level (NOAEL) of PFOS was 1.25 mg/kg in 28-day repeated toxicity study and, however, the toxic response showed gender differences. The possible toxic mechanism of PFOS was the induction of apoptosis and altering lipid metabolism which resulted in hepatotoxicity.
Plasma alkaline phosphatase (ALP) activity is frequently measured in toxicity studies. In the present study, we assessed the usefulness of a commercially available polyacrylamide-gel (PAG) disk electrophoresis kit used in humans (AlkPhor System, Jokoh Co., Ltd., Tokyo, Japan) for identifying plasma ALP isoenzymes in mice of the Crlj:CD1 strain (ICR mice), which are commonly used in toxicity studies. We also examined age-related changes in plasma ALP isoenzymes in ICR mice. Electrophoresis was performed according to the manufacturer’s instructions. In order to identify the origin of each ALP isoenzyme, in addition to plasma samples, tissue ALP extracts from the liver, bone and small intestine were treated with neuraminidase, anti-small intestinal ALP antibody, ALP inhibitor levamisole and/or wheat germ agglutinin (WGA). The kit revealed that main plasma ALP isoenzyme in intact ICR mice was bone-derived one, and it tended to decrease with age. On the other hand, liver-derived ALP isoenzyme greatly increased in plasma of cholestasis model mice induced by bile duct ligation. This model mouse had also a large molecular ALP detected in the stacking gel. This ALP was thought to be of intestinal origin because its activity remained even after levamisole inhibition. In addition, a minimum sample volume for sufficient resolution of plasma ALP isoenzymes was only 14 µl. The results of this study suggest that the present method is a useful tool for detecting plasma ALP isoenzymes in mice and that pre-treatment of plasma with neuraminidase and concomitant levamisole inhibition with another gel is applicable for the evaluation of organ toxicity.
Our previous studies have demonstrated that maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes a reduction in gonadotropin biosynthesis in the fetal pituitary, resulting in the attenuated expression of steroidogenic proteins in the fetal gonads and the impairment of sexual behaviors in adulthood. However, the mechanism of the attenuation remains unknown. To address this issue, we investigated whether TCDD affects the pituitary production of gonadotropins, using cultured pituitary. In the absence of gonadotropin-releasing hormone (GnRH), a regulator of gonadotropin biosynthesis, TCDD did not affect the expression of gonadotropin mRNAs both in fetal and postnatal pituitaries. On the other hand, in the presence of GnRH, TCDD interfered with the synthesis of gonadotropin β-subunit mRNAs only in the fetal pituitary. A protein kinase C (PKC) activator (phorbol 12-myristate 13-acetate) and a PKA activator (8-bromoadenosine-3’ 5’-cyclic monophosphate) induced the expression of gonadotropin mRNAs in the fetal pituitary. Among the subunits, only the induction of β-subunit was reduced by TCDD treatment. These results suggest that TCDD reduces gonadotropin biosynthesis via damage to GnRH-stimulated PKC and PKA signaling in a β-subunit- and fetal age-specific manner.
Dihydropyrazine (DHP), which is formed by nonenzymatic glycation, generates various radical species that lead to DNA damage and enzyme inhibition. In this study, we examined the reaction between DHP derivatives and glutathione (GSH). DHP exposure caused more intense growth inhibition of a GSH-deficient mutant Escherichia coli strain compared with the wild-type strain. DHP-exposed mouse fibroblasts showed a decrease in the cellular GSH level. The obtained data suggested that the reaction of DHP with GSH possibly potentiates cellular stress via the depletion of cellular GSH levels.
Organophosphorus (OP) are among the most toxic of all substances that cause poisoning in food animals and are the most frequently encountered insecticides, commonly detected in agricultural products, animal-derived foodstuffs, environmental samples, and home use and represent a significant potential health risk. The first-order rate constants obtained for spontaneous reactivation (ks) was found to be higher in sheep compared to cattle, pig, and ranged between 0.133 to 0.323 hr-1 and between 0.021 to 0.088 hr-1 for dichlorvos (DDVP) and diazinon (DZN) respectively. Aging of phosphorylated acetylcholinesterase (AChE) follows the kinetics of a first-order reaction with rate constants of aging (ka) higher in cattle compared to sheep and pig, and ranged between 0.013 to 0.021 hr-1 and between 0.009 to 0.01 hr-1 for DDVP and DZN respectively. Half-time (t1/2) for spontaneous reactivation and aging are higher in DZN compared to DDVP and ranged from 2.3 to 85.3 hr (sheep), 3.2 to 76.3 hr (cattle), and 2.9 to 58.3 hr (pig), respectively.
Paraquat (PQ) is one of the most frequently used pesticides in worldwide. In most countries, PQ is used without restrictions. To investigate the effect of PQ on myogenesis, cultures of C2C12, a useful model to study differentiation of myoblasts into myotubes, were exposed to various concentrations of PQ. Myotube formation did not occur in the presence of 50 µM PQ. Although cell death was not observed at this concentration, growth inhibition was evident in the growth medium. Production of myosin heavy chain, a myogenesis marker protein, decreased dose dependently with the concentration of PQ, which was added to the C2C12 cell culture during differentiation. Inhibition of myogenesis by PQ was not reversed by the addition of ascorbic acid. These results show that PQ is a strong inhibitor of muscle differentiation in vitro.
Benzotriazole ultraviolet stabilizers (BUVSs) enter aquatic environments either directly, via wash-off from skin and clothes during water recreational activities, or indirectly, via discharges of sewage and swimming pool waters. Their potentially toxic effects on biota, particularly aquatic organisms, are of considerable concern. However, not much information on their toxicity to aquatic organisms is available. In the present study, we investigated the acute toxicity of selected BUVSs on a freshwater crustacean (Daphnia pulex) for the first time. The 24 and 48-hr median lethal concentration (LC50) values of UV-571 for D. pulex were estimated to be 6.35 (5.08-8.39) and 2.59 (2.04-3.38) mg/l, respectively. No acute toxicity effects were observed up to 10 mg/l for other BUVSs such as UV-9, -320, -326, -327, -328, -329, and -360. Although acute toxicities of targeted BUVSs were not high, further long-term studies are required to fully assess the effects on growth and reproduction by these compounds on aquatic biota because of their bioaccumulative characteristics.
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