Biomedical subjects

Jun Kanno

Publications and source records attributed to Jun Kanno.

33 records · Page 2Linked to original sources

PubMed2003

Evaluation of nonthreshold leukemogenic response to methyl nitrosourea in p53-deficient C3H/He mice.

The classic controversy of whether genotoxic chemicals induce cancers with or without a certain low-dose limit, i.e., the threshold, is revisited because of a number of current publications available addressing the plausibility of "practical" thresholds even for genotoxic carcinogens, the mechanism of which may be hypothesized to be due, in part, to a repair system composed of ordinarily available various defense mechanisms under the steady-state DNA damage. The question of whether an absolute nonthreshold or a relative nonthreshold, i.e., a "practical" threshold specifically in the low-dose level, is present may not be answered even with the use of a prohibitively large number of wild-type mice. Could the excessive incidence of tumorigenesis in p53-deficient mice contribute to our understanding of the threshold vs nonthreshold issue in genotoxic carcinogenesis? This is considered because an exaggeration of tumorigenesis in p53-deficient mice is hypothesized to reduce or eliminate the range of threshold due to the p53-deficiency-mediated reduction of DNA repair and apoptosis. The present study of chemical leukemogenesis in p53-deficient mice by transplantation assay was designed to answer this question. Briefly, 218 C3H/He mice were lethally irradiated and repopulated with bone marrow cells from wild-type, heterozygous p53-deficient, and homozygous p53-deficient C3H/He mice. This was followed by treatment with a single and graded dose of methyl nitrosourea at 6.6, 14.8, 33.3, 50.0, and 75.0 mg/kg body wt, with the vehicle-treated control groups treated with zero dose for each genotype. Whereas mice repopulated with p53-deficient bone marrow cells showed a marked reduction of the threshold for leukemogenicity, mice repopulated with wild-type bone marrow cells did not exhibit leukemia at a dose of 33.3 mg/kg body wt and showed a curve with a high probability for the linear regression model with a positive dose intercept, predicting a threshold by the likelihood ratio test. Thus, the failure of wild-type mice to show an increase in incidence of leukemogenesis at low doses of genotoxic carcinogens may be due not to a statistical rarity, but to various p53-related pharmacophysiological functions, possibly including DNA repair and apoptosis that may account for a threshold.

Alkylating Agents↗

PubMed2003

Inhibitory effects of Bifidobacterium longum on experimental ulcerative colitis induced in mice by synthetic dextran sulfate sodium.

BACKGROUND/AIMS: The relationship between alterations in intestinal microflora and ulcerative colitis is still not clear. Whether improvement in bacterial populations might be a new strategy for prevention or treatment needs to be tested. METHODS: Ulcerative colitis was induced in mice by oral administration of synthetic dextran sulfate sodium (molecular weight 54,000). Inhibitory effects of concomitant treatment with Bifidobacterium longum were assessed in terms of total colon length and severity of histological changes. In addition, changes of microflora and short-chain fatty acids were tested in fecal samples and compared before and after treatment. RESULTS: Administration of B. longum significantly inhibited both shortening of total colon length and the severity of ulcerative colitis compared to controls. It was confirmed that the administered B. longum resided in the gut and blocked the decrease of lactobacilli in fecal samples in mice with dextran sulfate sodium-induced colitis. CONCLUSIONS: Oral administration of B. longum exerts marked inhibitory effects on ulcerative colitis in mice.

Animals↗

PubMed2003

The OECD program to validate the rat uterotrophic bioassay. Phase 2: dose-response studies.

The Organisation for Economic Co-operation and Development has completed phase 2 of an international validation program for the rodent uterotrophic bioassay. The purpose of the validation program was to demonstrate the performance of two versions of the uterotrophic bioassay, the immature female rat and the adult ovariectomized rat, in four standardized protocols. This article reports the dose-response studies of the validation program; the coded single-dose studies are reported in an accompanying paper. The dose-response study design used five selected weak estrogen agonists, bisphenol A, genistein, methoxychlor, nonylphenol, and o,p -DDT. These weak agonists were administered in a prescribed series of doses to measure the performance and reproducibility of the protocols among the participating laboratories. All protocols successfully detected increases in uterine weights when the weak agonists were administered. Within each protocol, there was good agreement and reproducibility of the dose response among laboratories with each substance. Substance-specific variations were observed in the influence of the route of administration on the uterine response, the potency as related to the dose producing the first statistically significant increase in uterine weights, and the maximum increase in uterine weight. Substantive performance differences were not observed between the uterotrophic bioassay versions or among the standardized protocols, and these were judged to be qualitatively equivalent. It is noteworthy that these results were reproducible under a variety of different experimental conditions (e.g., animal strain, diet, housing, bedding, vehicle, animal age), indicating that the bioassay's performance as a screen is robust. In conclusion, both the intact, immature, and adult OVX versions, and all protocols appear to be reproducible and transferable across laboratories and are able to detect weak estrogen agonists.

Age Factors↗

PubMed2003

The OECD program to validate the rat uterotrophic bioassay. Phase 2: coded single-dose studies.

The Organisation for Economic Co-operation and Development has completed phase 2 of an international validation program for the rodent uterotrophic bioassay. This portion of phase 2 assessed the reproducibility of the assay with a battery of positive and negative test substances. Positive agonists of the estrogen receptor included the potent reference estrogen 17-ethinyl estradiol (EE), and the weak estrogen agonists bisphenol A, genistein, methoxychlor, nonylphenol, and o,p -DDT. The negative test substance or nonagonist was n-dibutylphthalate. The test substances were coded, and prescribed doses of each test substance were administered in 16 laboratories. Two versions of the uterotrophic assay, the intact immature and the adult ovariectomized female rat, were tested and compared using four standardized protocols covering both sc and po administration. Assay reproducibility was compared using a) EE doses identical to those used in phase 1 and in parallel dose-response studies, b) single doses of the weak agonists identical to one of five doses from the dose-response studies, and c) a single dose of the negative test substance. The results were reproducible and in agreement both within individual laboratories and across the participating laboratories for the same test substance and protocol. The few exceptions are examined in detail. The reproducibility was achieved despite a variety of different experimental conditions (e.g., variations in animal strain, diet, housing protocol, bedding, vehicle, animal age). In conclusion, both versions of the uterotrophic bioassay and all protocols appear robust, reproducible, and transferable across laboratories and able to detect weak estrogen agonists. These results will be submitted along with other data for independent peer review to provide support for the validation of the uterotrophic bioassay.

Animal Feed↗

PubMed2003

Mechanisms of benzene-induced hematotoxicity and leukemogenicity: cDNA microarray analyses using mouse bone marrow tissue.

Although the mechanisms underlying benzene-induced toxicity and leukemogenicity are not yet fully understood, they are likely to be complicated by various pathways, including those of metabolism, growth factor regulation, oxidative stress, DNA damage, cell cycle regulation, and programmed cell death. With this as a background, we performed cDNA microarray analyses on mouse bone marrow tissue during and after a 2-week benzene exposure by inhalation. Our goal was to clarify the mechanisms underlying the hematotoxicity and leukemogenicity induced by benzene at the level of altered multigene expression. Because a few researchers have postulated that the cell cycle regulation mediated by p53 is a critical event for benzene-induced hematotoxicity, the present study was carried out using p53-knockout (KO) mice and C57BL/6 mice. On the basis of the results of large-scale gene expression studies, we conclude the following: (a) Benzene induces DNA damage in cells at any phase of the cell cycle through myeloperoxidase and in the redox cycle, resulting in p53 expression through Raf-1 and cyclin D-interacting myb-like protein 1. (b) For G1/S cell cycle arrest, the p53-mediated pathway through p21 is involved, as well as the pRb gene-mediated pathway. (c) Alteration of cyclin G1 and Wee-1 kinase genes may be related to the G2/M arrest induced by benzene exposure. (d) DNA repair genes such as Rad50 and Rad51 are markedly downregulated in p53-KO mice. (e) p53-mediated caspase 11 activation, aside from p53-mediated Bax gene induction, may be an important pathway for cellular apoptosis after benzene exposure. Our results strongly suggest that the dysfunction of the p53 gene, possibly caused by strong and repeated genetic and epigenetic effects of benzene on candidate leukemia cells, may induce fatal problems such as those of cell cycle checkpoint, apoptosis, and the DNA repair system, finally resulting in hemopoietic malignancies. Our cDNA microarray data provide valuable information for future investigations of the mechanisms underlying the toxicity and leukemogenicity of benzene.

Administration, Inhalation↗

PubMed2003

[Twenty-eight day repeated dose oral toxicity test of synergist of a pyrethroid insecticide, 2,3,3,3,2',3',3',3'-Octachlorodipropyl ether (S-421) in rats].

2,3,3,3,2',3',3',3'-Octachlorodipropyl ether (Abbreviation; S-421) is originally developed as synergist of a pyrethroid insecticide. In recent years, S-421 is used widely at home, for a mosquito-repellent incense, electric mosquito-repellent, an insect-killing spray, a vacuum cleaner paper pack, etc. as well. On the other hand, S-421 has been detected in vacuum cleaner dust samples as well as human milk samples in Japan indicating that our living environment is already contaminated by this compound. Long term toxicity studies including a carcinogenesis study have been performed and NOEL of chronic toxicity has been settled. However, it is clear that S-421 is used in close proximity so that acute or subacute exposure at relatively higher dose levels than chronic NOEL values are easily assumed, such as use of a spray in an ill-ventilated room, etc. This study, 28 day repeated oral dose toxicity study of S-421 was performed to monitor the outcome of acute and subacute exposure assuming possible exposure accidents mentioned above. The protocol is as follows; Groups of 10 rats of each sex(5 week-old), were treated with intragastric administration of S-421 with a dose of 0 (olive oil, control), 10, 40, 160 or 640 mg/kg body weight. For recovery test, 14 day after the last treatment, the control and 640 mg/kg groups were examined, respectively. All animals of all groups in both sexes survived. In the 640 mg/kg groups of the both sexes, all animals were set to drowsiness from about 5 hours after administration, however, they recovered by the next morning. In the hematology examination, Hb, MCH, MCHC, WBC values were significantly decreased and MCV value was significant increased in the 640 mg/kg group of both sexes. In the serum biochemistry, items increased in the 640 mg/kg groups of both sexes returned to normal level after 14 days recovery period. Absolute and relative liver weight increase seen in the 160 mg/kg and above also returned to control level after recovery. Histopathologically, slight hepatocellular swelling was observed in the 160 mg/kg groups and severe hepatocellular swelling with vacuolization and slight necrosis was seen in the 640 mg/kg group. In conclusion, the no-observed-effect levels (NOEL) of S-421 under these conditions was judged to be 40 mg/kg/day.

Administration, Oral↗

PubMed2002

Age/sex dependent and non-monotonous dose-response effect of diethylstilbestrol on the immune functions in mice.

High amounts of estrogens are known to suppress immune functions in both human and animal models. Our supportive data is that the immune functions were activated by gonadectomy in young adults mice. However, recent reports indicate that estrogen is required for the normal development of thymus. These findings lead us to an assumption that sex hormone status induces much more complex effects on immune functions depending on the host age/sex and dose ranges. Here, low doses of DES (diet containing 0.4 or 4.0 microg/kg diet) were given for 2 months to young adult and aged C57BL/6 mice, and thymic and splenic parameters including flow-cytometric subpopulation analyses, mitogenic responses and NK activity were monitored. This study revealed that the low dose effects of exogenous estrogen are strongly dependent on the age and sex of the recipients and many parameters show non-monotonous dose response effect. In conclusion, effect of exogenous estrogens on immune functions should be assessed for all age and sex, and in expectation of non-monotonous dose-response relationship.

Age Factors↗

PubMed2002

Phytoestrogen-low diet for endocrine disruptor studies.

Hormonally active chemicals (HACs) that are capable of inducing adverse effects on wildlife as well as human beings are featured as "endocrine disruptors". Various animal studies conducted to clarify the characteristics of HACs, including the uterotrophic assay, are sufficiently sensitive to detect the effect of 17-beta-estradiol in micrograms per kilogram of body weight or lower. In such systems, a trace amount of HACs in the dietary pellets may interfere with the test results and thus can be a serious problem for the low-dose issue, which is now a major topic in the field of endocrine disruptor research. Here, the significance of the hormonal effects of phytoestrogen components in the NIH-07 diet is confirmed and a NIH-07-based open formula "phytoestrogen-low diet" (PLD) is proposed, which effectively reduces uterine weight as well as the uterine luminal epithelial labeling index in ovariectomized rats.

Animals↗

PubMed2002

Significant increase of colonic mutated crypts in ulcerative colitis correlatively with duration of illness.

Mild periodic acid-Schiff (mPAS) staining can discriminate non-O-acetylated(mPAS positive) from O-acetylated (mPAS negative) epithelial sialoglycoproteins in human colonic mucosa, giving three haplotypes of expression of a single polymorphic autosomal gene (oat). Increase in mPAS-positive crypts in heterozygotes is an indication of mutations, and wholly mPAS-positive (stem cell mutated) crypts and clusters of two or more mPAS-positive crypts in heterozygotes of ulcerative colitis (P < 0.0001) were found to be increased significantly, compared with controls. The observed correlation with ulcerative colitis duration (r = 0.892 and 0.853, respectively) supports a chronic inflammation-carcinoma sequence.

Adult↗

PubMed2002

Dysplasia and carcinoma development in a repeated dextran sulfate sodium-induced colitis model.

BACKGROUND: As an important mechanism underlying the increased risk of colorectal carcinoma development in patients with long-standing ulcerative colitis, promotion as a result of the regenerative process has been proposed. In the present study, a dysplasia-carcinoma sequence in a novel repeated colitis model in mice is documented. METHODS: Repeated colitis was induced by nine administration cycles of 3% dextran sulfate sodium (DSS; molecular weight, 54 000): each administration cycle comprised 3% DSS for 7 days followed by distilled water for the subsequent 14 days, to give conditions similar to the clinically observed active and remission phases in humans. RESULTS: Multiple colorectal tumors (nine low- and four high-grade dysplasias and two carcinomas) developed in 25 mice. These neoplastic lesions consisted of tubular structures, presenting as various types of elevated, flat and depressed tumor, similar to those in ulcerative colitis patients. A time-course study with assessment of the severity of colitis and in vivo bromodeoxyuridine uptake during a single 3% DSS administration cycle revealed a high level of regenerative activity in the colitis-affected mucosal epithelia. CONCLUSION: Thus, with the present repeated colitis model, regeneration and neoplastic lesions were apparent, the biological features of which provide evidence of a colorectal dysplasia-invasive carcinoma sequence in ulcerative colitis.

Adenocarcinoma↗

PubMed2002

Aryl hydrocarbon receptor mediates benzene-induced hematotoxicity.

Benzene can induce hematotoxicity and leukemia in humans and mice. Since a review of the literature shows that the CYP2E1 knockout mouse is not known to possess any benzene toxicity, the metabolism of benzene by CYP2E1 in the liver is regarded to be prerequisite for its cytotoxicity and genotoxicity, although the mechanism is not fully understood yet. Because it was found some years ago that benzene was also a substrate for CYP1A1, we investigated the involvement of the aryl hydrocarbon receptor (AhR) in benzene hematotoxicity using AhR wild-type (AhR(+/+)), heterozygous (AhR(+/-)), and homozygous (AhR(-/-)) male mice. Interestingly, following a 2-week inhalation of 300 ppm benzene (a potent dose for leukemogenicity), no hematotoxicity was induced in AhR(-/-) mice. Further, there were no changes in cellularity of peripheral blood and bone marrow (BM), nor in levels of granulocyte-macrophage colony-forming units in BM. This lack of hematotoxicity was associated with the lack of p21 overexpression, which was regularly seen in the wild-type mice following benzene inhalation. Combined treatment with two major benzene metabolites, phenol and hydroquinone, induced hemopoietic toxicity, although it was not known whether this happened due to a surprising lack of expression of CYP2E1 by AhR knockout, or due to a lack of other AhR-mediated CYP enzymes, including 1A1 (i.e., a possible alternative pathway of benzene metabolism). The former possibility, evaluated in the present study, failed to show a significant relationship between AhR and the expression of CYP2E1. Furthermore, a subsequent evaluation of AhR expression after benzene inhalation tended to show higher but less significant expression in the liver, and none in the BM, compared with sham control. Although this study failed to identify the more likely of the above-mentioned two possibilities, the study using AhR knockout mice on benzene inhalation presents the unique possibility that the benzene toxicity may be regulated by AhR signaling.

Administration, Inhalation↗

PubMed2002

Serial transplantation of p53-deficient hemopoietic progenitor cells to assess their infinite growth potential.

Thirty-five years ago, Siminovitch et al. (Siminovitch L, Till JE, McCulloch EA. J Cell Com Physiol 64:23-32, 1964), using serially transplanted mouse spleens at 14-day intervals, observed a markedly progressive decline in the proliferative capacity of bone marrow (BM) cells, with the loss of clonogenicity by the fourth transplant generation. Using the same protocol, we assessed the proliferative capacity of p53-deficient mouse BM cells transplanted serially at the same 14-day intervals into lethally irradiated mice, which was a useful tool for understanding the characteristics of hemopoietic stem cells lacking solely the p53 gene function. BM cells from p53-deficient homozygous (p53(-/-)), p53-heterozygous (p53(+/-)), and wild-type (p53(+/+)) C57BL/6 mice were transplanted into lethally irradiated C57BL/6 recipients. Fourteen days later, the repopulated spleens were harvested, and 10(7)cells were retransplanted into secondary recipients. Serial transplantation was continued at 14-day intervals until hemopoietic repopulation failure. The number of heterozygous and homozygous p53-deficient spleen cells increased logarithmically up to the fourth and fifth passages, respectively, whereas wild-type spleen cells ceased to proliferate by the third passage. The number of macroscopic spleen colonies increased logarithmically until the third passage in recipients of heterozygous and homozygous p53-deficient cells, but ceased to grow by the second passage in recipients of wild-type cells. The numbers of heterozygous and homozygous p53-deficient colony forming units in spleen (CFUs-S) remained stable during the first four transplant generations, whereas that of wild-type CFUs-S decreased progressively from the first transplant generation onward. The clonogenicity of p53-deficient cells was lost when the number of CFUs-S per spleen decreased to below 10. This suggests that one out of 10 CFUs-S might be long-term repopulating cells (LTRCs), and that p53-deficient LTRCs may proliferate more rapidly than wild-type LTRCs. Longer passages that were possible in the p53-deficient groups were considered to be due to the faster cell cycle of the p53-deficient hemopoietic progenitor cells, as determined by bromodeoxyuridine incorporation with purging by UV light exposure, followed by hemopoietic colony assay (BUUV assay).

Animals↗

PubMed2002

Assessment of quantitative dual-parameter flow cytometric analysis for the evaluation of testicular toxicity using cyclophosphamide- and ethinylestradiol-treated rats.

In the drug discovery process, effects to the human spermatogenesis must be fully evaluated before the first human trial. To estimate testicular toxicity, histopathological evaluation has been recommended in addition to the traditional mating procedure. However, it is laborious and time-consuming. Flow cytometric analysis (FCM) has also been applied to estimate testicular toxicity because of its speed, simplicity, and the objectivity of the data. Using cyclophosphamide (CP)- and ethinylestradiol (EE)-treated rat testis, we attempted to validate our dual-parameter, DNA ploidy and cell-size FCM, in a high-throughput toxicity study. Our results showed that CP damaged some spermatogonia and some early meiotic spermatocytes and EE caused severe decrease of spermatogenic cells except for spermatogonia as well as marked decrease of somatic cells, most probably Leydig cells. This is the first report discriminating between the changes of spermatogonia and that of somatic cells with FCM analysis. These results demonstrate that this method is a very useful and powerful tool to assess testicular toxicity, especially in high-throughput toxicological studies.

Animals↗

PubMedDate not supplied

Intrauterine position and postnatal growth in Sprague-Dawley rats and ICR mice.

In rodents, steroid hormones are thought to be transported between adjacent fetuses, and male or female fetuses that develop in utero between female fetuses may have higher serum levels of estradiol, and lower serum levels of testosterone, relative to siblings of the same sex that develop between two male fetuses. The consequence in the variation of postnatal growth, development, and function in the intrauterine position, using various parameters such as anogenital distance, preputial separation and vaginal opening, estrous cycle, locomotor activity, and growth of reproductive organs, were examined in Sprague-Dawley rats. ICR mice were treated with 17beta-estradiol before copulation and during pregnancy to address the interaction with endogenous estradiol during pregnancy. In rats, no evidence of effects of prior intrauterine position was observed for any of the parameters examined. Mouse fetal exposure via the mother to low-dose 17beta-estradiol revealed no changes in the rate of postnatal growth in males and females that developed in any intrauterine position in utero. The results of this study suggested that the intrauterine position of the embryos/fetuses did not affect the postnatal growth of the reproductive organs, sexual maturation, or behavior in rats and mice.

Anal Canal↗

PubMedDate not supplied

Mechanism of benzene-induced hematotoxicity and leukemogenicity: current review with implication of microarray analyses.

Benzene is a potent human leukemogen but the mechanism underlying benzene-induced leukemia remains an enigma due to a number of questions regarding the requirement of extraordinarily long exposure, a relatively low incidence of leukemia for genotoxicity of metabolites and a narrow dose range for leukemogenicity over marrow aplasia (overdoses tend to result in marrow aplasia). Moreover, there were previous controversies as to whether the cell cycle is upregulated or suppressed by the benzene exposure. Subsequently, it was found that the cell cycle is suppressed, but how leukemia develops under such suppression of hemopoiesis remains to be clarified. These questions were fortunately resolved with much effort. Benzene exposure was found to induce the expression of p21, an interlocking counterdevice for cell cycle: due to p53 upregulation, thereby inducing the immediate suppression of the kinetics of hemopoietic progenitors followed by the prominent suppression of hemopoiesis. Intermittent benzene exposure (i.e., cessation of exposure during weekends, for example) allowed an immediate recovery from marrow suppression after terminating exposure, which induced continuous oscillatory changes in marrow hemopoiesis. Benzene-induced leukemia was chiefly due to such an oscillatory change in hemopoiesis, which epigenetically developed leukemia more than 1 year later. The mechanisms of benzene-induced leukemogenicity seem to differ between wild-type mice and mice lacking p53. For p53 knockout mice, DNA damage such as weak mutagenicity or chromosomal damage was retained, and such damage induced consequent activation of proto-oncogenes and related genes, which led cells to undergo further neoplastic changes. In contrast, for wild-type mice carrying the p53 gene, a marked oscillatory change in the cell cycle of the stem cell compartment seems to be important. Compatible and discriminative gene expression profiling between the p53 knockout mice and wild-type mice was observed after benzene exposure by microarray analyses.

Administration, Inhalation↗