Metallothionein (MT) is known to reduce chemical carcinogenesis. Carcinogenesis induced by benzo[a]pyrene (B[a]P) which is an environmental chemical carcinogen is related to DNA adduct formation and oxidative damage through metabolic activation. Ten-week-old male MT-I/II null mice and wild-type mice were given a single injection of B[a]P (250 mg/kg, p.o.), and B[a]P-induced DNA damage was evaluated at 6-48 hr later. The frequencies of micronucleated reticulocytes (MNRET) in MT-I/II null mice were significantly increased compared with that of wild-type mice at 48 hr after B[a]P administration. At 48 hr after B[a]P administration, comet scores were significantly increased in MT-I/II null mice but not in wild-type mice. 8-Hydroxy-2’-deoxyguanosine (8-OHdG), a biomarker of oxidative DNA damage, was significantly increased in liver of MT-I/II null mice at 6 and 12 hr after B[a]P administration, although that of wild-type mice was only slightly changed. Because cytochrome P450 (CYP) plays a major role in the process of B[a]P metabolic activation, we attempted to reveal the effect of MT on metabolic activation of B[a]P. Although CYP1A activities were elevated in the livers of MT-I/II null mice and wild-type mice treated with B[a]P, it was not different between both strains of mice. In addition, MT levels in the livers of wild-type mice were significantly increased by the B[a]P treatment, whereas MT was not detected in livers of MT-I/II null mice with or without B[a]P treatment. These results demonstrate that MT acts as an endogenous defensive factor against B[a]P-induced DNA damage.
It is well known that heavy oil such as pollutant caused serious influences on the marine ecosystem. We may suffer from various disorders in our body via intake of marine foods polluted with heavy oil. However the influences of heavy oil on our immune system have not yet been clarified. Here we show the effects of heavy oil extracts, water-soluble fraction (WSF), methanol-soluble fraction (MSF) and ethanol-soluble fraction (ESF), on immunoglobulin production of mouse splenocytes. All extracts increased IgA productivity of splenocytes. In oral administration, shrinkage of the immune organs such as spleen or thymus was observed in only WSF-administrated mice at least during 7 days. The amount of IgG production level in splenocytes cultured medium and sera were reduced by each extract administration. A flowcytometry method, to monitor splenocytes of WSF-administrated mice, has been set up using double staining with B and T cell-specific surface antibody. The results from cell population analysis indicated that B cells, including plasma cells producing antibody were reduced. The decrease in IgG level in sera was caused by reduction of plasma cells in spleen. Hence, it is suggested that reduction of Ig production was affected by the chemical compounds contained in WSF possibly such as polycyclic aromatic hydrocarbons (PAHs) through the estrogen receptor expressed in lymphocytes.
To verify the relationship between oxidative stress and DNA methylation in the young brain, dichlorodiphenyltrichloroethane (DDT) was administered by gavage to male young rats at doses of 0, 0.006, 0.06, 0.6, 6, and 60 mg/kg/day for a period of 4 weeks. The most conspicuous decrease in the lipid peroxidation level was observed in the 0.06 mg/kg/day group compared with controls. Microarray analysis of brain samples from the control and 0.06 mg/kg/day groups revealed that the expression of 40 genes was changed in the hypothalamus, whereas mRNA expression was unaltered in the hippocampus. This result suggests that the hypothalamus is more susceptible to low-level oxidative stress at the young period. We further examined this possibility by selecting 10 genes from the hypothalamic microarray data. RT-PCR analysis revealed that expression of 7 of these 10 genes was significantly changed in the 0.06 mg/kg/day group, compared with controls. Furthermore, RT-PCR analysis showed that mRNA expressions of Dnmt1, Hsp90 and Hsp70 in the hypothalamus were significantly lower in the 0.06 mg/kg/day group than in controls. Methylated DNA-PCR analysis in the hypothalamus revealed that 6 CpG islands were significantly hypomethylated compared with controls. Thus, we speculate that the DNA methylation machinery malfunctions under low levels of oxidative stress, thereby leading to incomplete methylation of specific gene regions. Our data indicate that a low level of oxidative stress appears to correlate positively with transcriptional down-regulation and hypomethylation, but the precise mechanisms underlying these processes are unclear.
Diesel exhaust particles (DEP), a well-known air pollutant, exacerbate type I hypersensitivity conditions, such as asthma and pollen allergy. In this study, we examined the effect of diesel exhaust (DE) exposure on delayed-type hypersensitivity (DTH), a type IV hypersensitivity, induced with methyl-bovine serum albumin (mBSA) in C57BL/6 mice. Mice were exposed to DE containing DEP at a dose of 1.78 mg/m3 in an inhalation chamber for 14 days. On Day 7, DTH mice and DE-exposed DTH mice were injected s.c. with 200 µl of 1.25 mg/ml mBSA emulsified with CFA in the dorsal region as initial sensitization. On Day 14, mice were injected s.c. into one footpad with 20 µl of 10 mg/ml mBSA dissolved in PBS as challenge. On Day15, footpad thickness and spleen weight were measured. Significant footpad swelling (%) was observed in DTH mice compared with normal control mice, and this swelling was significantly augmented by DE exposure. The levels of pro-inflammatory cytokines, including IFN-γ, TNF-α, and IL-6, in DTH mice were significantly higher than in normal mice, and were also further enhanced by DE exposure. DE exposure increased production of IL-17, which enhances local tissue inflammation through up-regulation of pro-inflammatory cytokines, while production of IL-10, which inhibits local tissue inflammation through suppression of immune cell proliferation, was unchanged. No change was observed in the percentage of CD4+CD25+Foxp3+ T regulatory (Treg) cells in splenic lymphocytes following DE exposure. IL-6 production was increased by DE, and this would facilitate the differentiation of naïve T cells to IL-17-producing Th17 cells, while concomitantly suppressing the competing differentiation pathway to IL-10-producing Treg cells. Our results indicate that DE inhalation may, in part, exacerbate the pathological symptoms of DTH and induction of pro-inflammatory cytokines such as IFN-γ, TNF-α, IL-6 and IL-17.
Non-clinical animal studies to assess the safety of compounds under development have to comply with Good Laboratory Practice (GLP). The Organization for Economic Co-operation and Development (OECD) has established the Mutual Acceptance of Data (MAD) system in OECD member countries for the mutual acceptance of non-clinical safety study data. Since 1997 non-OECD-member countries have also been able to participate in the MAD system, if the country meets the level of standardized compliance with OECD GLP. Thus, several Asian non-OECD countries are trying to develop their GLP standards in order to become official members of the MAD system. Pharmaceutical companies face significant expense in the drug-development process, including the cost of non-clinical safety studies; in response, companies in Asian countries are seeking to establish GLP facilities to provide cost-effective services for drug development. To assess the quality and cost of GLP performance in Asian countries, in this study we approached GLP facilities in a number of Asian countries to obtain price and quality information on a ‘virtual compound’ to be assessed in non-clinical safety studies. Also, the development status of GLP in Asian countries in terms of policy and infrastructure was analyzed. We found that, among Asian countries.
Fucoxanthin (FX), a xanthophyll derivative, is an orange-colored pigment present in edible brown algae. As a part of safety evaluation, single and repeated oral dose toxicity study of FX was conducted. In a single dose study, FX purified from seaweed was orally administered to male and female ICR mice at doses of 1,000 and 2,000 mg/kg. In a repeated doses study, FX at doses of 500 and 1,000 mg/kg was orally administered for 30 days. In both studies, no mortality and no abnormalities in gross appearance were observed. In the repeated doses study, histological observation revealed no abnormal changes in liver, kidney, spleen and gonadal tissues of any of the FX-treated groups. However, significantly increased total cholesterol concentrations were shown by plasma biochemical analyses in all FX-treated groups. Although total bilirubin concentrations were increased by FX, it was established that presence of fucoxanthinol, a major metabolite of FX, interfered with bilirubin determination in plasma. To further ascertain the safety of FX, the mechanism by which FX induces hypercholesterolemia in mice and species differences in the induction of hypercholesterolemia should be elucidated.
ARTCEREB®, an irrigation and perfusion solution (Artcereb), is a preparation intended for the irrigation and perfusion of the cerebral ventricles, and it is therefore important to evaluate its effects on cerebrospinal fluid (CSF) and on the surrounding cerebrospinal parenchyma. To confirm the kinetics of the perfusion fluid component, we performed whole body autoradiography and examined glucose balance during ventriculocisternal perfusion with 14C-glucose labeled Artcereb in the rat model, which simulates ventricular irrigation or ventriculocisternal perfusion in clinical neurosurgery. We also performed ventriculocisternal perfusion with Artcereb, lactated Ringer’s solution, or normal saline, and observed the effect of these solutions on animal condition and on brain tissue morphology. In the kinetic study, diffusion of 14C-glucose from the perfused Artcereb to the cerebrospinal tissue was seen on whole body autoradiography, and almost 90% of the glucose in the perfusion fluid was distributed to the cerebrospinal tissue and the systemic circulation. These data indicated that the perfusion fluid interacted actively with the CSF, surrounding parenchyma and the systemic circulation, and suggested that the formation of perfusion fluid affected CSF composition and cerebrospinal tissue functions. Animals perfused with normal saline were associated with serious symptoms including tonic convulsions and death, and exhibited neuronal death in the cerebrum. However, these severe changes were not observed in animals perfused with Artcereb or lactated Ringer’s solution. We therefore propose that during neurosurgery, it is extremely important to use a physiological solution like Artcereb which closely resembles normal human CSF, in order to maintain cerebrospinal function and to alleviate postoperative adverse events.
Functions of the kidney of mammals are immature during the neonatal period, and the neonatal kidney could be susceptible to chemicals, including drugs and environmental toxicants. Among these chemicals, cyclooxygenase (COX)-inducing chemicals should be given attentions as the potential kidney toxicants during the period, and we hypothesized that lithium chloride (LiCl) has such toxicity. Neonatal mice of C57BL/J strain were intraperitoneally injected with LiCl (2 mmol/kg body weight) daily until 21 days of age, and examined on 7 days and 21 days of age. Neonatal treatment of LiCl caused a significant increase in COX-2 mRNA and a decrease in mRNAs of aquaporins on day 7 of age. Osmolarity of urine from LiCl-treated neonates was significantly lower than that of control neonate. Most of the LiCl-treated neonates died during the second week of age. Histological examination revealed renal cysts on day 7 and hydronephrosis on day 21. in the surviving neonates. The present results showed that the kidney of mouse neonates is vulnerable to lithium, and suggested the possibility that COX-2 upregulation is responsible for the severe renal toxicity including hydronephrosis.
A 4-week repeated dose oral toxicity study of phenobarbital (PB) sodium was conducted in F344 rats of both sexes at PB doses of 0.8, 8, and 80 mg/kg/day to fully elucidate its general toxicity including hematological changes. Both sexes in the 80 mg/kg/day group showed staggering gait, lacrimation, and/or sedation, which were more evident in the early stage of treatment. The body weight gain and food consumption were greater in these animals than in controls. Hematology revealed a significant reduction in the hematocrit (Ht), hemoglobin concentration (Hb), and erythrocyte count (RBC) in both sexes at 80 mg/kg/day, which was accompanied by a decrease in the cell mean Hb (CHCM) in mature erythrocytes with an increase in unsaturated iron binding capacity. Female rats also showed reduction in the CHCM in reticulocytes, content of hemoglobin per reticulocyte, and transferrin saturation. PB prolonged the activated partial thromboplastin time and inversely increased the platelet count with no evidence of platelet activation. Well-known toxic effects of PB on the liver and thyroid were observed in a dose-dependent manner, along with altered lipid, glucose, and electrolyte metabolism. The serum levels of PB increased dose-dependently, when examined in females received 8 and 80 mg/kg/day on day 1 and 28; there were no difference in Cmax and AUC0-24 values between day 1 and day 28. These results indicated that PB has the potential to elicit multiple organ toxicity including an effect on the hematopoietic system. The hematological analysis provided evidence for hypochromic anemia, plausibly caused by the impairment of iron utility.
Tributyltin chloride (TBT), an environmental pollutant, is toxic to a variety of eukaryotic and prokaryotic organisms. Although it has been reported that TBT induces apoptotic cell death in mammalian, the action of TBT on eukaryotic microorganisms has not yet been fully investigated. In this study we examined the mechanism involved in cell death caused by TBT exposure in Saccharomyces cerevisiae. The median lethal concentration of TBT was 10 µM for the parent strain BY4741 and 3 µM for the pdr5∆ mutant defective in a major multidrug transporter, respectively. Fluorescence microscopic observations revealed nuclear condensation and chromatin fragmentation in cells treated with TBT indicating that cells underwent an apoptosis-like cell dearth. TBT-induced cell death was suppressed by deletion of the yca1 gene encoding a homologue of the mammalian caspase. In parallel, reactive oxygen species (ROS) were produced by TBT. These results suggest that TBT induces apoptosis-like cell death in yeast via an Yca1p-dependent pathway possibly downstream of the ROS production. This is the first report on TBT-induced apoptotic cell death in yeast.
When the mouse lymphoma Tk assay(MLA) provides a positive result, its cause can be roughly estimated by examining colony sizes. An increase in the number of large colonies means that the compound tested has point mutational potential, while an increase in small colonies indicates the potential for chromosome aberration. However, it was found to be difficult to clearly judge this in the case of caffeine known as a clastogen lacking the potential of point mutation. In our study, caffeine significantly increased the thymidine kinase (Tk) mutation frequencies derived from large colonies as well as those from small colonies in the standard protocol, although the frequencies derived from a small colony were higher than those from large colonies at higher doses. Therefore, we prolonged the expression period from 2 days, a standard period, to 6 days after treatment and then examined the Tk and Hprt mutations simultaneously. The result showed that caffeine gave a completely negative result on a mutation test for both Tk and Hprt. On the other hand, ethyl methanesulfonate (EMS), a genotoxic carcinogen, showed a positive result for both. Moreover, caffeine and EMS significantly increased the frequencies of micronucleated cells. In conclusion, when MLA gives a positive result and the cause is ambiguous, in order to identify the exact cause of the positive response, it is helpful to perform a confirmatory test investigating the potential of Tk and Hprt gene mutation simultaneously after 6-day expression and to perform an in vitro micronucleus assay during the expression period.
The safety of highly purified fullerenes (HPFs) for utilization as antioxidants in the cosmetic industry was evaluated by studying the toxicity and effects on laboratory animals, human epidermal keratinocytes, and human fibroblasts. The HPFs did not induce primary or cumulative skin irritation, skin sensitization, skin photosensitization or contact phototoxicity. No skin reaction was observed in the patch test on human skin. In the primary eye-irritation test on rabbits, conjunctival redness and corneal epithelial defects were observed in all animals of the eye-unwashed group at 1 and 24 hr after application, but disappeared by 48 hr after application. The irritation may have been caused by administration of insoluble fullerene powder. Therefore, the HPFs were assessed as “minimally irritating” in the eye-irritation test. By comparing these results with previously published data, we concluded that HPFs can be safely used in cosmetic ingredients for human skin application. This is the first study performing all the toxicity tests on the same fullerene material for approval as an additive in quasi-drugs.
The direct effects of famotidine, a selective histamine H2 receptor antagonist, on the cardiac repolarization process were assessed using two in vitro test systems. Neither famotidine (0.1 and 1 µM), nor its solvent, dimethylsulfoxide (0.1%), affected any of the action potential parameters of guinea-pig papillary muscles, whereas the positive control, dl-sotalol (30 µM), significantly prolonged the action potential duration. Moreover, neither famotidine (0.1, 1 and 10 µM) nor dimethylsulfoxide affected the human ether-a-go-go-related gene (hERG) K+ current expressed in Chinese hamster ovary-K1 cells, whereas the positive control, E-4031 (0.1 µM), significantly decreased the current. These results indicate famotidine does not directly affect the cardiac repolarization process.
Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are widely used in industrial fields and consumer products, and are ubiquitously found in the environment and animal tissues. In the present study, their neurotoxicity was examined using rats and mice by means of neurobehavioral observation, histopathological inspection and chemical assays. PFOS and PFOA alone did not cause any neurotoxic symptoms up to their sublethal doses (PFOS: 500 mg/kg, PFOA: 1,000 mg/kg). However, tonic convulsions were caused in the PFOS-treated rats (≥ 250 mg/kg) and mice (≥ 125 mg/kg) when ultrasonic stimulus was applied to the animals. The same ultrasonic stimulus never induced convulsions in the control animals and in the animals treated with PFOA. Concentration of PFOS in the brain was considerably lower than in other tissue, but it seemed to increase gradually with time after exposure. No morphological changes were detected by histopathological examination of the brain. There were also no changes in concentrations of norepinephrine, dopamine, serotonin, glycine, 4-aminobutylic acid and glutamic acid in the brain. The present study revealed neurotoxic effects of PFOS in animals. Convulsive effect of PFOS may not be attributed to the quantitative alterations of neurotransmitters or lesions of nerve cells in the brain, although the mechanism of its neurotoxicity has not been cleared.
Tributyltin chloride (TBT), an environmental pollutant, is toxic to a variety of eukaryotic and prokaryotic organisms. Some members of F-ATP synthase (F-ATPase)/vacuolar type ATPase (V-ATPase) superfamily have been identified as the molecular target of this compound. TBT inhibited the activities of H+-transporting or Na+-transporting F-ATPase as well as H+-transporting V-ATPase originated from various organisms. However, the sensitivity to TBT of Na+-transporting V-ATPase has not been investigated. We examined the effect of TBT on Na+-transporting V-ATPase from an eubacterium Enterococus hirae. The ATP hydrolytic activity of E. hirae V-ATPase in purified form as well as in membrane-bound form was little inhibited by less than 10 µM TBT; IC50 for TBT inhibition of purified enzyme was estimated to be about 35 µM. Active sodium transport by E. hirae cells, indicating the in vivo activity of this V-ATPase, was not inhibited by 20 µM TBT. By contrast, IC50 of H+-transporting V-ATPase of the vacuolar membrane vesicles from Saccharomyces cerevisiae was about 0.2 µM. E. hirae V-ATPase is thus extremely less sensitive to TBT.
Morinda citrifolia (noni) fruit juice has been approved as a safe food in many nations. A few cases of hepatitis in people who had been drinking noni juice have been reported, even though no causal link could be established between the liver injury and ingestion of the juice. To more fully evaluate the hepatotoxic potential of noni fruit juice, in vitro hepatotoxicity tests were conducted in human liver cells, HepG2 cell line. A subchronic oral toxicity test of noni fruit was also performed in Sprague-Dawley (SD) rats to provide benchmark data for understanding the safety of noni juice, without the potential confounding variables associated with many commercial noni juice products. Freeze-dried filtered noni fruit puree did not decrease HepG2 cell viability or induce neutral lipid accumulation and phospholipidosis. There were no histopathological changes or evidence of dose-responses in hematological and clinical chemistry measurements, including liver function tests. The no-observed-adverse-effect level (NOAEL) for freeze-dried noni fruit puree is greater than 6.86 g/kg body weight, equivalent to approximately 90 ml of noni fruit juice/kg. These findings corroborate previous conclusions that consumption of noni fruit juice is unlikely to induce adverse liver effects.