The involvement of oxidative stress has been suggested as a mechanism for toxicity caused by methylmercury (MeHg). One of the major critical sites for oxidative stress is the mitochondria. In this research, to clarify the target site in mitochondria affected by MeHg, the individual activities of the mitochondrial electron transport chain (ETC) (I∼IV) were examined in the liver, cerebrum and cerebellum of MeHg-intoxicated rats. In addition, to elucidate the mechanism underlying MeHg toxicity, cytochrome c release, caspase 3 activity and histological study were examined in the cerebrum and cerebellum. The cerebellum was found to be an exclusive tissue in which significant MeHg-induced alterations were observed. The complex II activity in the cerebellum mitochondria significantly decreased after MeHg exposure. Cytochrome c release from mitochondria increased only in the cerebellum by MeHg exposure. However, no significant alterations in caspase 3 activity or histological structure were found in brain tissues. These results suggest that MeHg acts on the constituents of complex II in the cerebellum, and induces mitochondrial dysfunction, leading to a release of cytochrome c from mitochondria. These events were considered to occur at the early stage of MeHg intoxication.
Cigarette smoke has been known to affect the development of bowel disease. However it has not been fully elucidated how cigarette smoke has effects on the gut. In this context we evaluated not only caecal levels of organic acids but also populations of micro-flora and pH in caecal contents after exposing rats (n = 5) to cigarette smoke for a 4-week in order to investigate whether the gut environment is altered by cigarette smoke or not. After the exposure of cigarette smoke, caecal levels of organic acids such as acetic acid, propionic acid, butyric acid and valeric acid significantly decreased. Additionally the population of Bifidobacterium significantly decreased and the pH significantly elevated. In conclusion cigarette smoke changes caecal levels of certain organic acids, the population of Bifidobacterium and the pH in caecal contents of rats. These results suggest that cigarette smoke may alter the gut environment of rats.
In the present study, in order to reveal novel adverse effects of ultrafine particles (UFP) on the central nervous system, the effects of nanoparticle-rich diesel exhaust particles (NRDEP; count mode diameter, 21.45 nm) on emotional behavior, learning capability and brain neurotransmitter levels were studied in rats by intranasal instillation (iNI). NRDEP (10 and 50 µg/rat) was instilled into 2-week old infant, male rats once a week for 4 weeks. Spontaneous motor activity measured was observed to be inverse to the dose level. In active avoidance tests using a shuttle box, NRDEP-treated animals showed a lower avoidance performance than control animals given air-instillation. The levels of dopamine and its metabolite (DOPAC) in the medial mammillary nucleus of the brain tended to be lower in the NRDEP-treated animals. From these results, although the effects of NRDEP by iNI on the emotionality and the brain neurotransmitter levels were not fully clear, the results obtained by avoidance testing suggested involvement of UFP in learning capability.
Sanguinarine is a benzophenanthridine alkaloid derived from the root of Sanguinaria canadensis. It is known to perform a wide spectrum of biological activities. The aim of this study is to examine the antimicrobial actions of sanguinarine against methicillin-resistant Staphylococcus aureus (MRSA). Sanguinarine antimicrobial activity was assessed by broth dilution method; its mechanism of action was investigated by bacteriolysis, detergent or ATPase inhibitors and transmission electron microscopy were used to monitor the survival characteristics and the changes in bacteria morphology. The activity of sanguinarine against MRSA strains ranged from 3.12 to 6.25 µg/ml, while the minimum inhibitory concentrations of the two reference strains are 3.12 µg/ml and 1.56 µg/ml. The treatment of the cells with sanguinarine induced the release of membrane-bound cell wall autolytic enzymes, which eventually resulted in lysis of the cell. The OD600s of the suspensions treated with the combination of Tris-(hydroxymethyl) aminomethane and Triton X-100 with sanguinarine were reduced to 40% and 8%, respectively. Transmission electron microscopy of MRSA treated with sanguinarineshowed alterations in septa formation. The predisposition of lysis and the altered morphology seen by transmission electron microscopy suggest that sanguinarine compromises the cytoplasmic membrane.
The present study is undertaken to evaluate the protective effect of vitamin E (α-tocopherol) and selenium (Se) against malathion (MTN)-induced oxidative stress and hepatic injuries in experimental rats. Male rats were randomly divided into eight groups comprised of 10 rats each. The 1st group served as a negative control (CN), whereas the 2nd was supplemented with a combination of α-tocopherol (100 mg kg-1 body weight, b.w.)/Se (0.1 mg kg-1 bw). The 3rd, 4th and 5th groups were respectively administered with increasing doses of MTN equivalent to 1/50 LD50 (M1/50), 1/25 LD50 (M1/25) and 1/10 LD50 (M1/10), respectively. The 6th, 7th and 8th groups were administered the same doses of MTN as in the 3rd, 4th and 5th groups with a concomitant supplementation with α-tocopherol/Se. Subchronic exposure of rats to MTN for 45 days resulted in statistical dose-dependent decrease in acetylcholinestrase (AChE) activity, increase in oxidative stress marker lipid peroxidation (LPO) and reduction in reduced glutathione (GSH) level. Moreover, the levels of glutathione persoxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were significantly decline in response to MTN exposure in a dose-dependent fashion. Furthermore, histopathological studies of liver in the rats which received MTN exhibited, moderate to severe degenerative and necrotic changes in the hepatocytes. Notably, the administration of α-tocopherol/Se protected the liver of rats exposed to MTN as evidenced by the appearance of normal histological structures, significant attenuation of the decline in all antioxidant enzymes tested (i.e. GPx, SOD and CAT), significant recovery in the GSH level and statistical reduction in LPO, as compared to the experimental rat. The effect of α-tocopherol/Se supplementation on transcriptional activity of three key stress and apoptosis-related genes (i.e., Tp53, CASP3 and CASP9), in response to MTN exposure in rats, was investigated. Results revealed a significant concentration-dependent up-regulation in the level of expression for the three genes examined, in response to MTN exposure, compared with the control. Interestingly, the supplementation of MTN-treated rats with α-tocopherol/Se modulates the observed significant dose-dependent up-regulation in the level of expression for three selected genes, indicative of an interfering role in the signaling transduction process of MTN-mediated poisoning. Taken together, these data suggest that the administration of α-tocopherol/Se may partially protect against MTN-induced hepatic oxidative stress and injuries.
Chronic toxicity and carcinogenicity of catechin mixture were examined in Wistar Hannover GALAS rats. Administration was in the diet at concentrations of 0, 0.02, 0.3, 1 or 3%. Slight increases in relative liver weight and centrilobular hypertrophy of hepatocytes associated with induction of CYP3A2 were found at the 3% in males of both studies. However, because there were no signs indicative of hepatotoxicity on serum biochemical and histopathological examinations, the changes observed in the liver were regarded as adaptation, and not adverse effects. The slight depressions of body weights at the 3% in females of the chronic toxicity study and in both sexes of the carcinogenicity study were observed. These decreases were because the diet at the highest concentration was frangible and nominal food consumption may not have reflected the actual food consumption resulting in decrease in caloric intake, rather than toxic effects. Thus it was concluded that catechin mixture had no toxicity. In addition, tumor incidences and types were comparable between treated and control groups. Based on the results, the no observed adverse effect levels estimated from the chronic toxicity study were 3% in both sexes equal to 1922.9 in males and 2525.7 mg/kg/day in females. Catechin mixture has no carcinogenic potential in male and female rats.
Contact allergens induce the augmentation of cell surface molecules on and release of cytokines from Langerhans cells (LC) in skin sensitization. THP-1 and U937 cell lines, surrogates of LC, were used as analytical tools of this phenomenon recently. In THP-1 cells, contact allergens are reported to induce the phenotypic alteration including the production of pro-inflammatory cytokines and augmentation of cell surface molecules especially at sub-toxic doses. However, the relationship between phenotypic alteration and cytotoxicity is not clear yet. The purpose of this study is to understand the relationship between the protein expression and cytotoxicity induced by contact allergens. First, we observed that the cytotoxicity induced by contact allergens is caused by both apoptosis and necrosis. Apoptosis was preferentially confirmed in stimulation with contact allergens, but non-allergen sodium lauryl sulfate (SLS) hardly induced apoptosis. Moreover, there was no effect to augmentation of protein expression when apoptosis induction pathways were inhibited. Based on these findings, we proposed that the protein expression and cytotoxicity were controlled independently. Next, oxidative stress was found to be generated by contact allergens at the early phase, and this regulated the protein expression and cytotoxicity at least partially. Finally, the humoral factors from dead cells induced by dinitrochlorobenzene (DNCB) were exposed to fresh THP-1 cells to confirm whether protein expression depended on cytotoxicity. The protein expression was not induced. Altogether, these results suggest that cytotoxicity induced by contact allergens may result in apoptosis and may also be stimulated in parallel with protein expression through an intracellular signal or signals.
Blood alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities are widely used as sensitive markers of liver toxicity. However, these activities are also recognized to be altered by hormonal and nutritional modifications. We investigated the relationships between the activity and gene expression of the hepatic transaminases and the state of hepatic amino acid/glucose/fatty acid metabolism in the ad libitum fed (ALF) and spaced-fed (SF) rats. Acceleration of hepatic gluconeogenesis and fatty acid oxidation was noted in the SF rats. Expression of hepatic clock gene was also altered in the SF rats. Hepatic transaminase activities in the SF rats were higher than those in the ALF rats. These alterations were due to increases in the synthesis of hepatic ALT and AST proteins. In conclusion, the increased transaminase protein synthesis in the liver of the SF rats was considered to be related to the acceleration of hepatic gluconeogenesis under the conditions of spaced feeding.
Four fluoroquinolones (pefloxacin, norfloxacin, ofloxacin and ciprofloxacin) were compared according to their biomechanical and histopathological effects on rat Achilles tendon. Wistar rats were divided into one untreated control and four treatment groups in parallel. Pefloxacin mesylate dihydrate (40 mg/kg), norfloxacin (40 mg/kg), ofloxacin (20 mg/kg) and ciprofloxacin (50 mg/kg) were administered by gavage twice daily for three consecutive weeks. 6 weeks after treatment, the test animals were euthanised and Achilles tendon specimens were collected. A computer monitored tensile testing machine was utilised for biomechanical testing. The mean elastic modulus of the control group was significantly higher than that of the norfloxacin and pefloxacin groups (p < 0.05 and p < 0.01, respectively). The mean yield force (YF) of the control group was significantly higher than those of ciprofloxacin, norfloxacin and pefloxacin groups (p < 0.001, p < 0.05 and p < 0.01, respectively). The mean ultimate tensile force (UTF) of the control group was significantly higher than of the ciprofloxacin, norfloxacin, and pefloxacin groups (p < 0.001, p < 0.05 and p < 0.01, respectively). Hyaline degeneration and fibre disarrangement were observed in the tendons of the ciprofloxacin, pefloxacin, and ofloxacin treated-groups, whereas myxomatous degeneration was observed only in the ciprofloxacin and pefloxacin groups. In conclusion, these findings in our rat model reveal significant deterioration of biomechanical parameters following fluoroquinolone exposure, and indicate significantly higher biomechanical toxicity for ciprofloxacin and pefloxacin.
Acute single administration effects of ethanol on the distribution of total white blood cells (WBCs), neutrophil, basophil, eosinophil, monocyte and lymphocytes were studied in rats. Acute single administration effects of ethanol on the number of red blood cells (RBCs), hemoglobin concentration and hematocrit were also examined. Male 8-week-old Sprague Dawley rats were randomly divided into the ethanol-administered (ETA) group and the control (CON) group. Two parts of an experiment, 1) 1st experiment : (ethanol dose : 1.0 g/kg body weight), and 2) 2nd experiment : (ethanol dose : 2.0 g/kg body weight) were carried out in rats. The rats were starved to 19:00, and deprived of diet for 12 hr and water for 1 hr before the single administration of ethanol. 1.0 or 2.0 g/kg body weight of ethanol (in 20% (w/w) ethanol) was orally administered to ETA group rats via a stainless stomach tube. In the CON group rats, 0.9% NaCl solution was orally given with the solution volume being equal, in the same manner. Single administration of 1.0 or 2.0 g/kg body weight of ethanol did not change the number of RBCs, hemoglobin concentration and hematocrit. Single administration of 1.0 g/kg body weight of ethanol did not also change the number of WBCs. However, administration of 2.0 g/kg body weight of ethanol increased significantly the number of neutrophil, basophil, monocyte and total WBCs without changing the number of eosinophil and lymphocytes. These results suggest that single administration of 2.0 g/kg body weight of ethanol to rats increased markedly the number of the natural immunity cells without changing the number of acquired cells.
Administration of lead ion (Pb) to rats and mice affects hepatic functions such as the induction of hepatic cell proliferation and upregulation of cholesterol biosynthesis. To identify the genes for which expression changes in response to Pb-administration, we analyzed hepatic gene expression patterns in stroke-prone spontaneously hypertensive rat (SHRSP), its normotensive control, Wistar-Kyoto rat (WKY), and Spraque-Dawley (SD) rat strains, 3, 6, and 12 hr later after single i.v. injection of lead nitrate (LN) at a dose of 100 µmol using a DNA microarray technique. The data analysis demonstrated that the expression of a great number of genes was transiently and remarkably downregulated 3 hr after LN-injection, and then recovered to control levels only in LN-injected WKY. These normal hepatic expression levels in WKY and SHRSP were much higher than those in SD rats. Furthermore, most of these genes were ones thought to be expressed specifically in the spermatids and/or testes; i.e. genes encoding protamin 1, transition protein 1, and transition protein 2. These findings suggest that the regulation system common to expression of all of these genes could be a target site of Pb-toxic action, at least, in the liver of WKY, and that this system might be similar to the system essential for spermatogenesis, especially spermiogenesis, in the testis. In addition, it appears that clarifying the cause of the difference between the systems of WKY and SHRSP might aid in identifying the pathologic genes in SHRSP. Finally, it will be an important to clarify how the products of the genes related to spermatogenesis, including spermiogenesis, are functional in the livers of WKY and SHRSP.
Among the naturally occurring three mercury species, metallic mercury (Hg(0)), inorganic mercury (Hg(II)) and methylmercury (MeHg), Hg(II) is well documented to induce metallothionein (MT) in tissues of injected animals. Although Hg(0) and MeHg are considered to be inert in terms of directly inducing MT, MT can be induced by them after in vivo conversion to Hg(II) in an animal body. In the present study we examined accumulations of inorganic mercury and MT inductions in mouse tissues (brain, liver and kidney) up to 72 hr after treatment by one of three mercury compounds of sub-lethal doses. Exposure to mercury compounds caused significant mercury accumulations in mouse tissues examined, except for the Hg(II)-treated mouse brain. Although MeHg caused the highest total mercury accumulation in all tissues among mercury compounds, the rates of inorganic mercury were less than 10% through the experimental period. MT inductions that depended on the inorganic mercury accumulation were observed in kidney and brain. However, MT induction in the liver could not be accounted for by the inorganic mercury accumulation, but by plasma IL6 levels, marked elevation of which was observed in Hg(II) or MeHg-treated mouse. The present study demonstrated that MT was induced in mouse tissues after each of three mercury compounds, Hg(0), Hg(II) and MeHg, but the induction processes were different among tissues. The induction would occur directly through accumulation of inorganic mercury in brain and kidney, whereas the hepatic MT might be induced secondarily through mercury-induced elevation in the plasma cytokines, rather than through mercury accumulation in the tissue.
Hyperproliferative cell growth due to cyclin D1/cdk4, marker of cellular proliferation, is considered to be regulated by the expression of estrogen receptors (ERs). We investigated the immunohistochemical expression of cyclin D1/cdk4 and ERs in N-methyl-N’-nitro-N-nitrosoguanidine (MNNG)-induced rat gastric carcinogenesis. The gastric cancer incidence and expression of cyclin D1/ckd4 in gastric carcinogenesis were significantly higher in males than females. Although the ERα expression index was similar in both sexes, the ERβ expression in preneoplastic hyperplastic lesions as well as gastric cancers was significantly higher in females than in males. The present study revealed a gender difference in MNNG-induced rat gastric carcinogenesis that seemed to involve the sex difference in cyclin D1/cdk4 expression, and ERβ expression became evident at the preneoplastic promotion stage in gastric carcinogenesis.
Carbon nanotubes (CNTs) are attracting significant attention as a novel material for future innovations. Many in vitro studies have assessed the cytotoxicity of CNTs, but the effects of CNTs differ depending on the cell lines and the synthetic method adopted for fabricating CNTs. In the present study, the differential effects of single-walled CNTs (SWCNTs) on the cell viability of A549 cells from human lung carcinomas and FaDu cells from human head and neck carcinomas were investigated. The SWCNTs used in the present study were synthesized with nickel and yttrium (SO-SWCNTs), and iron (FH-P-SWCNTs) as catalysts. Cell viability was evaluated on the basis of cell-membrane biomass, adenosine triphosphate (ATP) content, and intracellular metabolic capacity. After 24-hr exposure of A549 and FaDu cells to 1.0 mg/ml SO-SWCNTs, the cell-membrane biomass of A549 cells decreased to 43% as compared to the control cells, whereas that of FaDu cells remained over 90%. After 24-hr exposure of A549 and FaDu cells to 1.0 mg/ml SO-SWCNT, the intracellular metabolic capacity decreased to 24% and 37%, respectively, and the ATP content decreased to 40% and 54%, respectively. SWCNTs had a greater impact on the viability values of A549 cells than on those of FaDu cells. In addition, cells exposed to FH-P-SWCNTs exhibited a higher viability than those exposed to SO-SWCNTs. Caspase 3/7 activity was not increased at maximum concentration of 1.0 mg/ml SO-SWCNTs. It was surmised that sensitivity to SWCNTs differs among the 2 cell lines; additionally, SWCNT characteristics may produce different effects on these cell lines.
To elucidate the molecular mechanism involved in methylmercury-induced cerebellar disorder, we performed DNA microarray analysis of the cerebellum of methylmercury-treated mice. The expression levels of 21 genes were elevated 2-fold or higher in response to methylmercury, including many genes encoding proteins involved in inflammatory reactions associated with chemokines. The expression levels of 11 genes were reduced by half or more in response to methylmercury.
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