The theory of Darwinian Medicine linked to an extension of Darwin’s evolutionary theory is based on the approach from the aspect of “why we become ill?”. This theory enables us to understand the relationship between humans and diseases by thinking from evolutional perspective, shows an important help for preventive medicine, and is meaningful to consider the future human healthcare. Toxicology has been defined as a research of adverse effect of xenobiotic substances backed up by diverse-sciences. Toxic effects are basically responses to xenobiotic substances, and expressed as triggering or additional accelerating adverse effects toward abnormal condition. Toxic effects, biological adverse responses, are interpreted as protective responses of living body, and the adverse effects caused by drugs are also considered to be protective responses. This logic can be translated as “Darwinian Toxicology” corresponding to “Darwinian Medicine”, replying to “why we get into toxic condition by xenobiotics exposure”. This paper refers to the meaning of toxic effects based on mechanisms underlying and comprehensive drug safety evaluation from Darwinian Medicine perspectives.

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Since there is a possibility of inhaling the fibers of multi-wall carbon nanotube (MWCNT) without any agglomeration, it is important that the pulmonary toxicity is evaluated by intratracheal instillation without agglomeration. MWCNT suspended in an artificial lung surfactant (ALS) with or without grinding in an agate mortar was instilled once intratracheally to rats to determine whether differences of the effects to pulmonary toxicity by different amounts of agglomerated MWCNT particle. The MWCNT suspension preparation method with grinding was effective at reducing agglomerates and in increasing uniform dispersion of the fibers. The ground MWCNT induced higher LDH levels and neutrophil ratios in the bronchoalveolar lavage fluid (BALF). There were no remarkable responses in rats in the non-ground MWCNT group, with the exception of inflammatory responses in the early phase. Some histopathological findings varied between rats given the ground MWCNT and non-ground MWCNT. A major difference was an MWCNT-laden macrophage infiltration site in the lung, which were in the alveolus in the ground MWCNT group, and in the interstitium in non-ground MWCNT group. Accordingly, the preparation method with grinding is considered to be effective at reducing agglomerates and ensuring uniform dispersion of the fibers. These findings lead us to conclude that the amount of agglomerates in the suspension is an important factor affecting the pulmonary toxicity of MWCNT.

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ARTCEREB_® irrigation and perfusion solution (Artcereb), an ethical pharmaceutical, is typically applied inside the skull and spinal cavity as artificial fluid. Artcereb is composed of glucose and electrolytes (Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^-, HCO₃^- and P) and has a pH of 7.3. An in vitro assessment of the effects of Artcereb on cell culture of rat fetal astrocytes or rat fetal brain cells was performed in comparison with normal saline and lactated Ringer’s solutions. Furthermore, the effects of Artcereb on cell culture of rat fetal brain cells were also assessed in comparison with Krebs bicarbonate solution. Cell function after exposure to Artcereb was assessed based on ³H-thymidine incorporation activity. Cell function after exposure to Artcereb and lactated Ringer’s solution in primary cultures of rat fetal astrocytes remained unaffected when compared to that after exposure to normal saline. Cell function after exposure to Artcereb in a primary culture of rat brain cells remained unaffected as compared to that after exposure to normal saline and lactated Ringer’s solution. However, function decreased after exposure to a modified Artcereb formulation lacking bicarbonate, thus confirming that the presence of bicarbonate is essential for the Artcereb formulation.

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We have evaluated pharmacokinetics of a fixed dose combination (FDC) of ceftriaxone and sulbactam (2:1) or sulbactomax in eight healthy volunteers. A 1.5 g dose of sulbactomax, 1 g dose of ceftriaxone and 0.5 g sulbactam were given intravenously in a balanced two-ways cross-over study. Serially collected plasma sample was analyzed for ceftriaxone and sulbactam by high performance liquid chromatography (HPLC). The mean peaks of ceftriaxone and sulbactam concentrations in plasma were 152.06 ± 6.65 μg/ml and 21.32 ± 1.80 μg/ml, respectively and plasma half-lives for ceftriaxone and sulbactam were 5.2 ± 0.35 hr and 0.94 ± 0.038 hr, respectively. The AUC0-24 for ceftriaxone and sulbactam was 760.16 ± 27.68 μg.hr/ml and 20.74 ± 2.34 μg.hr/ml, respectively, with elimination rate constant of 0.133 ± 0.009 hr ^-1 and 0.732 ± 0.029 hr ^-1, respectively. The kinetics of ceftriaxone and sulbactum did not change in combination as compared to the alone treatment. Also, concentration of the ceftriaxone after 24 hr is higher than the minimum inhibitory concentration (MIC) of the most of the gram positive and gram negative bacteria indicating that one dose in a day is sufficient to treat the disease caused by these organisms.

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Cadmium (Cd) is a toxic heavy metal with no uniform mechanism of toxicity. In this the present study, the toxic effect of 5, 10 and 50 μM of Cd chloride was compared in three human cell lines; a human hepatoma cell line HepG2, a human astrocytoma cell line 1321N1, and a human embryonic kidney cell HEK 293. The results indicate a decrease in the viability of all three cell lines following exposure to Cd with HepG2 cells (IC₅₀ = 13.96 μM) showing the most sensitivity when measured using the MTT assay. There was significant increase in lactate dehydrogenase leakage, DNA damage, malondialdeyde and antioxidant enzymes activities in all three cell lines especially at 50 μM Cd. Significant decreases in ATP production were also observed at all Cd concentrations in HepG2 and HEK 293 cell lines. ROS levels significantly increase and GSH/GSSG ratio significantly decrease in all the three cell lines after Cd exposure, but these effects were attenuated by the presence of N-acetylcysteine (NAC). The present study therefore shows that ROS production and glutathione (GSH) depletion may play a role in Cd-induced toxicity in all the three cell lines. The endogenous levels of protective enzymes as well as their responsiveness are likely to determine a cell’s susceptibility to Cd.

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Etimicin sulfate, an ethylization derivative of gentamicin, is a new soluble wide-spectrum synthetic aminoglycoside drug. It has wide antibacterial spectrum with high effect and less cross resistance as compared to other aminoglycosides. In order to further explore its safety and tolerance, we have conducted a subactute toxicity study on swiss albino mice. Results from the present study have elucidated that treatment of etimicin sulfate exerts no significant signs of toxicity at any dose level used in the study. Physiological as well as hematological parameters were unaltered throughout the study. Biochemical examination and histopathology of all organs confirmed no significant alteration at any dose levels. The result of this study has suggested there was no obvious toxicity observed with the treatment of etimicin sulphate. It was found to be a safe alternative for various severe infections.

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To attempt a risk assessment of the excess intake of trivalent chromium (Cr), tissue Cr accumulation and urinary Cr excretion were examined in weanling rats fed experimental diets containing graded levels of Cr chloride (CrCl₃) or Cr picolinate (CrPic). Thirty-six male weanling 4-weeks-old Wistar rats were divided into six groups and fed a casein-based semi-purified diet (Cr content: < 0.02 µg/g) supplemented with 1, 10, or 100 µg Cr/g as CrCl₃ or CrPic for 28 days. Among the experimental groups, no significant difference was observed in body weight; however, supplementation of 100 µg Cr/g to the diets caused a significant low liver weight irrespective of the chemical species of Cr. Activities of serum aspartate aminotransferase and alanine aminotransferase were significantly elevated in rats given CrPic at 100 µg Cr/g. In the liver, kidney and femur, Cr accumulation increased with elevation of the dietary Cr level. No influence of the difference in the chemical species of supplemented Cr was observed in the liver and kidney, but CrCl₃ caused significantly higher Cr accumulation than CrPic in the femur of rats given 100 µg Cr/g. Daily urinary Cr excretion elevated with the increase of the dietary Cr level. Rats given CrPic showed significantly higher daily urinary Cr excretion than those given CrCl₃, particularly at a dietary Cr level of 100 µg/g. The rate of urinary Cr excretion in rats given CrPic was constant, irrespective of the dietary Cr level, but that of rats given CrCl₃ fell with the increase of the dietary Cr level. These results indicate that the lowest adverse effect level of dietary Cr is less than 100 µg/g, irrespective of the chemical species of Cr.

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This study was designed to evaluate and characterize any subchronic toxicity of rhamsan gum, a polysaccharide produced from Sphingomonas strain ATCC 31961, when administered to both sexes of Crl:CD(SD)IGS rats at dietary levels of 0 (control), 0.5, 1.5, and 5.0% (10 rats/sex/group). During the study, the treatment had no adverse effects on clinical signs, survival, body weights and food and water consumption, or on findings of urinalysis, ophthalmology, hematology, or blood biochemistry.  Examination of gross pathology and histopathology exhibited no differences of toxicological significance between control and treated rats. Increased relative cecum (filled) and cecum (empty) weights, evident in males of 1.5% group and both sexes of the 5.0% group, were considered to be a physiological adaptation. Thus, the results indicated the toxic level of rhamsan gum to be more than 5.0%, and the no-observedadverse- effect level (NOAEL) was concluded to be 5.0% (3,362 mg/kg body weights/day for males, and 4,304 mg/kg body weights/day for males) from the present study.

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Interstitial lung disease has been reported in cancer patients treated with epidermal growth factor receptor tyrosine kinase inhibitors, erlotinib and gefitinib. Preclinical safety studies with erlotinib did not show any evidence for an induction of injury on intact lungs in rats and dogs. In the present study, we investigated the effects of erlotinib on lung injury induced by intratracheal administration of bleomycin (BLM) in rats. In Experiment 1, we examined the effects of short-term (7- and 21-day) administration of erlotinib (10 mg/kg/day, p.o.; subtoxic dose) on the BLM (0.1 or 0.6 mg/rat)-induced lung injury of slight and moderate severity. In Experiment 2, we examined the effects of long term (up to 63-day) administration of higher-dose (up to 20 mg/kg/day; toxic dose; accompanied with decreased body weight gain and severe skin lesions) erlotinib on the BLM-induced lung injury. In rats receiving erlotinib alone, no lung lesions were noted. In rats receiving BLM alone, diffuse alveolar damage (DAD) and, subsequently, pulmonary fibrosis of slight or moderate severity was observed. The administration of erlotinib to BLM-treated rats showed no exacerbation of lung injuries in indices such as macroscopic findings, lung weights, histopathological scores (lung lesion density and lung fibrosis score), and pulmonary hydroxyproline (HyP) level. These results suggest that erlotinib does not have any exacerbating effects on lung injuries induced by BLM in rats.

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The expression of the CAR gene is lost in most cultured cell lines, and exogenously expressed CAR accumulates spontaneously in the nuclear compartment, where CAR is constitutively active. Therefore, the assessment of CAR-dependent transcriptional activation has to be evaluated using either animal models or primary cultured hepatocytes. Furthermore, due to the species-specific response of CAR to individual compounds, the results obtained with animal models are not directly applicable to human cases. We established a novel screening system for hCAR ligands (including agonists and inverse agonists) by expressing GAL4/DBD-fused hCAR/LBD, in which three consecutive alanine residues were inserted between helix 11 and helix 12 of LBD, and a commercially obtained plasmid consisting of the firefly luciferase gene downstream of the GAL4 responsive element in a cultured cell line. Androstenol (Andro) and clotrimazole (CLT), which are both inverse agonists of hCAR, were classified as an antagonist and weak agonist, respectively, in our novel assay system.  Among DDT and its metabolites DDE and DDD, only DDT worked as an agonist of the hCAR mutant, although all of them were enrolled as agonists of SXR.  Using this system, the screening for hCAR ligands can be conducted without sacrificing animals.

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Perfluorooctanoic acid (PFOA) has similar characteristics to perfluorooctane sulfonate (PFOS) in reproduction toxicity featured by neonatal death. We found that PFOS exposure to mice during pregnancy led to intracranial blood vessel dilatation of fetuses accompanied by severe lung collapse which caused neonatal mortality. Thus, we adopted the corresponding experimental design to PFOS in order to characterize the neonatal death by PFOA. Pregnant ICR mice were given 1, 5 and 10 mg/kg PFOA daily by gavage from gestational day (GD) 0 to 17 and 18 for prenatal and postnatal evaluations, respectively. Five to nine dams per group were sacrificed on GD 18 for prenatal evaluation; other 10 dams were left to give birth. No maternal death was observed. The liver weight increased dose-dependently, with hepatocellular hypertrophy, necrosis, increased mitosis and mild calcification at 10 mg/kg. PFOA at 10 mg/kg increased serum enzyme activities (GGT, ALT, AST and ALP) with hypoproteinemia and hypolipidemia. PFOA treatment reduced the fetal body weight at 5 and 10 mg/kg. Teratological evaluation showed delayed ossification of the sternum and phalanges and delayed eruption of incisors at 10 mg/kg, but did not show intracranial blood vessel dilatation. Postnatal evaluation revealed that PFOA reduced the neonatal survival rate at 5 and 10 mg/kg. At 5 mg/kg pups were born alive and active and 16% died within 4 days observation, while all died within 6 hr after birth at 10 mg/kg without showing intracranial blood vessel dilatation. The cause of neonatal death by PFOA may be different from PFOS.

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Our goal in the present study was to evaluate whether decabromodiphenyl ether (BDE-209), which is the most abundant polybrominated diphenyl ether (PBDE) found in human samples, affects against target organs. Sprague-Dawley male rats were exposed to vehicle or BDE-209 (100, 300, or 600 mg/kg body weight, daily) from postnatal day (PND) 10 to PND 42. There was no significant difference in body and male reproductive organ weight changes compared with controls. However, liver, thyroid and adrenal gland weights were significantly increased in the high-dose of BDE-209 group. BDE-209 significantly induced the expression of cytochrome P450 (CYP1A2, CYP3A1, and CYP2B1) enzymes in the liver. Furthermore, constitutive androstane receptor (CAR) and pregnane xenobiotic receptor (PXR) expression levels were also increased in a dose-dependent manner. Total serum triiodothyronine (T3) concentration was significantly reduced in a dose-dependent manner, whereas the level of thyroid-stimulating hormone was significantly increased with BDE-209 treatment. In the histological findings, multiple areas of degenerated follicular epithelium and slight attenuation of the follicular epithelium were observed in the thyroid glands by high doses (300 and 600 mg/kg) of BDE-209 treatment. The presence of hepatocytic fatty degeneration and inflammatory foci were also observed in the 300 and 600 mg/kg of BDE-209 group. These findings demonstrate that BDE-209 induces hyperthyroidism and hepatotoxicity. In the future, further research is needed to determine the relationship between target organ toxicity and blood concentrations of BDE-209.

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Azo dyes, amaranth, allura red and new coccine, which are currently used as food color additives in Japan, have been reported to cause colon specific DNA damage in mice. To examine species difference in the DNA damage between rats and mice, each of dyes was administered to male mice (1 and 10 mg/kg) and male rats (10, 100 and 1,000 mg/kg) by gavage. Brain, lung, liver, kidney, glandular stomach, colon, urinary bladder and bone marrow were sampled 3 hr (for mice) and 3, 6, 12 and 24 hr (for rats) after the treatment. The alkaline comet assay showed DNA damage in the mouse colon 3 hr after the administration of all of the dyes at 10 mg/kg. In rats, however, none of the dyes damaged DNA. Azo dyes should undergo metabolic reduction in the colon to be adducted to DNA. To determine transit time of the dyes to the colon after their administration, gastric emptying and intestinal transport in mice and rats were examined using brilliant blue FCF (BB) as an indicator. The half times of gastric emptying were 70 and 80 min for mice and rats, respectively; and about 60% of the BB was removed from the stomach 1 hr after the gastric intubation in both mice and rats. BB reached the mouse and rat colon 1 and 3 hr after the administration, respectively. Considering the wide dose range and sampling times well covering the transit time to the colon, rats may be insensitive to these azo dye-induced DNA damage.

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We investigated the genotoxicities or mutagenicities of 2 chemicals (octane and tetrasodium pyrophosphate) with limited toxicological data in spite of their common usage based on Ames reverse mutation test. In this test, treatment of 2 chemicals at each five dose did not induce mutagenicity in Salmonella typhimurium TA98, TA100, TA1535, TA1537, and in Escherichia coli WP2uvrA with and without metabolic activation. These results indicate that 2 chemicals do not have mutagenic potentials under the conditions examined in each study. Despite these results, it can affect by inducing inhalation, skin or eye contact, ingestion, and have affected central nervous system as a target organ. It is thus necessary to prepare the local exhaust system and personal protective equipments. Based on this study, we suggest that future studies should be directed toward chronic inhalation, carcinogenic test and so on.

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Some forms of reproductive and developmental toxicity by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) occur via initial damage to the pituitary synthesis of gonadotropins followed by the reduced expression of gonadal steroidogenic proteins. Defects in gonadotropin synthesis are highly specific to the periods from late fetal to early newborn stages. The reason for this specificity remains unknown. To address this issue, we compared the tissue distribution of ¹⁴C-TCDD between fetal and adult rats. In adult male rats, the major portion of TCDD given orally (approximately 33-42% dose) accumulated in the liver during day 1 and 5 after treatment. Very little TCDD (approximately 0.01% of the dose) distributed into the brain. A similar picture was also observed in TCDD-treated pregnant rats. The amount of TCDD transferred from a dam to the fetuses was extremely low (around 0.02% of the maternal dose/fetus) after 1 day of treatment. Male and female fetuses showed the same pattern in the brain distribution of TCDD. The rate of TCDD distribution to fetal brain, which was calculated on the basis of body burden to a fetus, was 100 times or more than that in adults. However, the brain content of TCDD (ng/g tissue) was comparable in fetuses and their dams, and adult males exposed to TCDD. These results suggest that although TCDD easily translocates to fetal brain, this is not a major mechanism for a fetal age-specific reduction in gonadotropin synthesis.

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The nuclear receptor superfamily consists of ligand-dependent transcription factors. Among them, constitutive androstane receptor (CAR) plays a key role in the detoxification of xenobiotics, inducing various drug-metabolizing enzymes including human CYP2B6 and its homologues of other species. AMP-activated protein kinase (AMPK) acts as an important energy sensor, being activated by an increased AMP/ATP ratio. CAR is activated by phenobarbital (PB) treatment. It has been recently reported that AMPK is involved in PB-mediated CYP2B induction both in vitro and in vivo. We investigated the relationship between the functions of AMPK and CAR in rat primary hepatocyte. The AMPK-activator 5-aminoimidazole-4-Carboxamide-1-β-Ribofuranoside (AICAR) unexpectedly repressed PB-induced CYP2B mRNA expression as well as AMPK-inhibitor compound C. In contrast, both the AMPK-activator metformin and the constitutive active form of AMPK enhanced PB-induced PB-responsive enhancer module-driven reporter gene expression. We demonstrated that AICAR prevented nuclear translocation of CAR in an AMPK-independent manner in rat primary hepatocytes. AICAR might be a convenient probe for studying the mechanisms of PB-induced activation, especially nuclear translocation, of CAR in rat primary hepatocytes.

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Technical imidacloprid was evaluated for its effect on oxidative stress and Lipid peroxidation (LPO) in female rats for No Observed Effect Level (NOEL). Activities of Superoxide dismutase  (SOD), Catalase (CAT), Glutathione peroxidase (GPx), and level of Glutathione (GSH) and LPO were estimated in liver, kidney and brain of rats after oral administration of imidacloprid (5, 10, 20 mg/kg/day) for 90 days. Imidacloprid at 5 and 10 mg/kg/day has not produced changes in SOD, CAT, GPx and level of GSH and LPO in liver, brain and kidney. However 20 mg/kg/day has produced significant changes in SOD, CAT, GPx, GSH, LPO in liver; SOD, CAT and GPx in brain and LPO in kidney. Therefore, it is concluded that imidacloprid has not generated oxidative stress at 5 and 10mg/kg/day but induced changes at 20 mg/kg/day. Hence 10 mg/kg/day may be considered as NOEL through antioxidant enzymes and LPO in female rats.

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The main pungent component of wasabi (Eutrema japonica) is known to be isothiocyanate and its derivatives, volatile substances.  Allyl isothiocyanate (AITC) accounts for more than half of isothiocyanate derivatives.  However, there is a little information on the effects of AITC on the immune system by analyzing the number of white blood cells (WBCs) over the course of days of AITC administration.  In the present study, we studied the effects of AITC (dose=20 mg/kg body weight/day for 10 days, subcutaneous: s.c.) on the number of WBCs (total WBCs, lymphocytes, monocyte, neutrophil, basophil and eosinophil) and plasma corticosterone concentrations in adult male rats.  Administration of AITC decreased significantly the number of total WBCs on days 1-4 post s.c. injection by 25-27%.  Administration of AITC also decreased the number of lymphocytes on days 1-10 by 21-36% and monocyte on days 1-8 by 28-78%.  However, administration of AITC increased the number of neutrophil on days 8-10 by 61-112%.  AITC did not change the number of eosinophil and basophil.  Plasma corticosterone concentrations during the experimental period were 4.7-8.4 times significantly higher in the AITC group than in the control group, indicating that AITC induced stress-responses.  The relative weights of thymus and adrenals per body weight were significantly lower and clearly higher in the AITC group than in the control group, respectively.  These results suggest that AITC-mediated stress-responses are at least in part attributable to changes in the number of circulating WBCs.

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The biological toxic potentials of aqueous extracts from the dinophycean flagellates Gymnodinium impudicum and Alexandrium affine and the raphidophycean flagellate Chattonella ovata were examined in both in vitro and in vivo systems. Interestingly, the extract from A. affine was the only one that showed potent cytotoxicities towards HeLa, Vero, and Neuro-2a cells in a concentration-dependent manner. Mice given intraperitoneal injections of the extracts revealed that none of the extracts exhibited serious toxicities in mice. However, temporal body weight loss was observed in the mice injected with the extract from A. affine during the early stage, and the dramatic enlargement of spleens was also observed in the mice on the 7th day after injection. Since A. affine extract showed potent hemolytic activity in vitro towards mouse erythrocytes, hemolytic anemia may be a possible mechanism responsible for the splenomegaly in the mice injected with A. affine extract. Similar marginal effects were observed in the mice injected with the extract from C. ovata; however, no significant toxic or detrimental effects were detected in the mice injected with the extract from G. impudicum. These results suggest that the extract from G. impudicum may not be contaminated with detectable levels of biologically hazardous compounds and may be relatively safe compared with the other two extracts.

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The environmental pollutant methylmercury is a potent neurotoxin. The mechanisms of toxicity and biological defense remain largely unknown. We found that inhibiting the expression of PRKAA1 (AMPKα1), an activated subunit of AMP-activated protein kinase (AMPK), increased susceptibility of HEK293 cells to methylmercury toxicity. Treatment of the cells with AICAR (5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside), an AMPK activator, reduced the methylmercury toxicity. Here, we suggest for the first time that the activation (phosphorylation) of AMPK may play an important role in reducing the toxicity of methylmercury.

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The persistent pesticide 1,1,1-trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane (o,p’-DDT) has been implicated as an endocrine-disrupting chemical. In this study, we performed DNA microarray analysis to assess hepatic gene expression in male Japanese medaka (Oryzias latipes) exposed to 1 ppb and 100 ppb o,p’-DDT for 48 hr. Results showed that 1 ppb o,p’-DDT induced the expression of choriogenins (chgH, chgL, and chgH minor), and 100 ppb induced the expression of vitellogenins (vtgI and vtgII) and estrogen receptor alpha. These genes showed considerably high up-regulation among the genes assayed and showed good dose-dependency. Thus, in this study the female hormone-like endocrine-disrupting effect of o,p’-DDT at gene expression level was clearly observed in Japanese medaka.

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J. Toxicol. Sci., 35, 295-298 (2010).

    Error : Fig. 1 was not printed [Page 297, left side, line 17-18].
-> Correction : Fig. 1 was printed.

The editorial board apologizes for the error.

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