Macrophages and myofibroblasts play important roles in progressive renal fibrosis. Using cisplatin-induced rat renal fibrosis models, the author has investigated patho-biological characteristics of these cells. Macrophages seen in the fibrotic areas involve exudate macrophages, resident macrophages and antigen-presenting cells (activated dendritic cells and macrophages). In the early stages of renal fibrosis, exudate and resident macrophages are key cells for induction of myofibroblasts via producing fibrogenic factors such as transforming growth factor (TGF)-β1 and platelet-derived growth factor (PDGF)-BB. In addition, these macrophages have capacity to phagocytize apoptotic bodies for clearance. The antigen-presenting cells are responsible for immune-mediated T-cell induction and subsequent B cell proliferation in the advanced stages. Myofibroblasts show various cytoskeletons (vimentin, α-smooth muscle actin (SMA), and desmin) during the development. In severely-developed fibrotic lesions, both renal epithelia and interstitial cells give immuno-positive reactions to α-SMA and vimentin, supporting epithelial-mesenchymal transition (EMT) in which renal epithelial cells acquire myofibroblastic nature. Desmin is expressed in interstitial cells, but not in renal epithelia. In vitro exposure of TGF-β1 to porcine renal epithelial cells (LLC-PK1), rat renal interstitial fibroblastic cells (NRK-49F), and rat pluripotential mesenchymal cells (MT-9; pericytes) increase the α-SMA-positive myofibroblastic cell number. PDGF-BB has an additive effect on TGF-β1-induced α-SMA expression in these cell lines. Collectively, different macrophage populations participate in progressive renal fibrosis, and precursors of myofibroblasts are heterogeneous (renal epithelial cells undergoing EMA, interstitial fibroblasts and immature mesenchymal cells). The regulation of macrophages and myofibroblast development would provide therapeutic strategies in clinical trials of progressive renal fibrosis.

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Since it has been revealed that PPAR (Peroxisome Proliferator-Activated Receptor) agonists induce various types of tumors in various organs and tissues in rodents, the US FDA has been requesting performance of 2-year carcinogenicity studies prior to initiation of clinical studies longer than 6 months, and does not accept data from alternative carcinogenicity studies such as those in transgenic mouse models, which are recommended in the ICH S1B guideline. In general, although PPAR agonists do not possess genotoxic potential, the tissue distribution of PPAR does correspond to the target organs and tissues of tumor induction, and carcinogenic potential is closely correlated with potency of PPAR agonistic effect. It is thus not possible to rule out the possibility that the mode of action (MOA) of tumorigenesis by PPAR agonists is receptor- mediated. The ILSI-HESI PPAR Agonist Project was organized and is currently conducting collaborative research to elucidate the MOA of PPAR agonist-induced carcinogenicity (for urinary bladder tumor, hemangioma/hemangiosarcoma, and fibrosarcoma/liposarcoma) and to evaluate the human relevance of the results of rodent bioassays of PPAR agonists. In this paper, carcinogenicity data on PPAR agonists disclosed by the CDER of the US FDA and current activities of the ILSI-HESI PPAR Agonist Project are explained, and the possible usefulness of transgenic mouse models, especially rasH2 mice, for assessing carcinogenic potential and the MOA of PPAR agonists are addressed.

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Tooth lesions may be either spontaneous or induced in nature. Such lesions may be acquired by trauma or iatrogenic mechanically induced. Examples are mechanically induced lesions at a high incidence in mice of an oncogenicity study and induced tooth lesions in dogs out of pulp-dentin test studies. In contrast, chemically induced lesions may be also recorded. There are examples discussed in rats of an oncogenicity study induced by a compound acting on the vasotonus, as well as in mice of a subacute toxicity study induced by a fluorinated compound. Also neoplasia may be recorded, that may be induced by chemical products, or intrinsic as genetical background lesion, or even in some rare cases spontaneous in nature. The incidence and types of spontaneous odontogenic neoplasia is discussed for rats, mice including transgenic mice (Tg.AC), and dogs.

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Dietary habit is instrumental in about 50% of human colorectal cancers. Consumption of fruits and vegetables is associated with decreased risk of several types of cancer, including colorectal malignancy. These foods contain many non-nutritive as well as nutritive compounds, such as carotenoids, dithiolthiones, flavonoids, glucosinolates, indoles, isothiocyanates, monoterpenes, phenols, sterols, sulfhydryls and vitamins (including C, E and folate). There may be other unknown non-nutritive constituents in foods that can reduce cancer development. Studies using experimental chemical carcinogenesis models have indicated that several non-nutritive components, belonging to different chemical groups, in foods protect against certain types of cancer, including colorectal neoplasm. Many of these chemicals are known as potential "cancer chemopreventive agents" and are antioxidants that suppress carcinogenesis by (i) inhibiting phase I enzymes or blocking carcinogen formation, (ii) induction of phase II (detoxification) enzymes, (iii) scavenging DNA reactive agents, (iv) modulation of hormone homeostasis, (v) suppression of hyper-cell proliferation induced by carcinogen, (vi) induction of apoptosis, (vii) depression of tumor angiogenesis, and/or (viii) inhibition of certain phenotypic expressions of preneoplastic and neoplastic cells. Given the definite increase in the increase of colorectal cancer, we should determine the most effective mean of prevention and understand the mechanism(s) underlying successful prevention. There are critical interrelationships between diet, environmental factors and genetics that can affect cancer risk. However, non-nutritive compounds in fruits, vegetables and other dietary constituents (teas, spices and herbs) consumed as part of the diet have the ability to reduce cancer occurrence in pre-clinical animal carcinogenesis models. Although epidemiologic studies show similar associations, there have been very few intervention studies to date. This article describes our recent studies to determine whether several naturally occurring non-nutritive products from edible plants have any effective chemopreventive effects on colorectal carcinogenesis in rodents.

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This study was performed to develop mouse anaphylaxis model using ovalbumin (OA) as an antigen, with no adjuvant, and an intravenous route of administration. OA at dose levels from 0.5 to 500 mg/kg was injected 3 times into the tail vein of female CD-1 (ICR) mice at 4-day intervals. Clinical signs and extravasation of Evans blue dye (vascular permeability) were observed, serum histamine levels and airway resistance were measured, and histopathological examinations were performed. Furthermore, to detect serum IgE and IgG, heterologous and homologous passive cutaneous anaphylaxis tests were performed. Additionally, strain differences in susceptibility to OA anaphylaxis was examined with 3 mouse strains: ICR, BALB/c and C57BL/6 mice. Shortly after the 3^rd injection, most of the animals exhibited systemic anaphylactic signs including death, and this was accompanied by increases in vascular permeability, plasma histamine levels, and airway resistance. Four days after the 2^nd injection, anti-OA IgE and IgG were detected in sera of mice injected with 0.5 and 5.0 mg/kg or higher doses of OA, respectively. Histological findings included: congestion in many tissues; detachment of mucosal epithelial cells in the gastrointestinal tract; enhanced death, decreased numbers of lymphocytes, and increased numbers of macrophages in the lymphoid tissues. ICR mice were shown to be most susceptible to the OA anaphylaxis of the 3 mouse strains examined. In conclusion, the results demonstrate that 3 intermittent intravenous injections of OA without adjuvant at 4-day intervals can induce anaphylactic shock in mice, in particular, most effectively in ICR mice, and that the anaphylaxis is characterized by specific IgE and IgG production.

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The effects of n-3 α-linolenic acid-rich perilla oil (P-oil) or n-6 linoleic acid-rich corn oil (C-oil) and indomethacin (IM), either alone or in combination, were examined in a rat medium-term multiorgan carcinogenesis model. Male F344 rats were given N-diethylnitrosamine (DEN), N-methyl-nitrosourea (MNU), N-butyl- N-(4-hydroxybutyl) nitrosamine (BBN), N-nitrosobis (2-hydroxypropyl) amine (DHPN) and 1,2- dimethylhydrazine (DMH) during the initial 4 weeks as initiators. This was followed by additional of 10% each of P-oil or C-oil to each their diet, alone or with IM 40 ppm in their drinking water for, 32 weeks. The animals were sacrificed at week 36, and proliferative lesions in major organs, such as the liver, kidney, lung and colon, were examined histopathologically. IM significantly lowered the multiplicity of colon tumors. P-oil tended to lower the incidences and multiplicities of colon tumors while C-oil tended to increase them. Additional treatment with IM caused further decreases in animals receiving P-oil, but the effect was less than additive. In the C-oil group, additional treatment with IM nullified its enhancing effect. In the lung, C-oil weakly increased the incidence and multiplicity of lung tumors. However, this was again suppressed by additional treatment with IM. While perilla oil and IM alone did not influence lung and renal carcinogenesis, their combination again enhanced carcinogenesis in the lung and kidney. In the liver, P-oil or C-oil alone significantly decreased the number and/or area of GST-P positive foci, while additional treatment with IM tended to nullify the decrease. These results suggest that IM exerts different modifying effects in the presence of different fats in the diet.

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Spontaneous occurrence of renal tubule carcinoma in mice is known to be rare. The following features of this tumor are recognized as areas of hemorrhage and massive necrosis and many show atypical cells and numerous mitotic figures. The present renal tubule carcinoma developed in an untreated B6C3F₁ male mouse at the age of 109 weeks. The tumor mass occupied nearly the entire renal cortex and invasion of normal renal tissue was observed. The tumor had solid cell nests, a gland-like structure, definite neovascularization and capsular invasion. The tumor cells had clear eosinophilic cytoplasm, a brush border structure and high proliferative activity. Although tumors derived from the proximal tubule reportedly show basophilic cytoplasm, the tumor cells in this mouse had clear eosinophilic cytoplasm. Consequently, the animal was diagnosed as having an unusual renal tubule carcinoma (classification: solid type).

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Reddish skin covering the entire body (erythroderma) was observed in a preliminary one-week oral toxicity study of a type of proton pump inhibitor in Beagle dogs. Histologically, full-thickness epidermal necrosis accompanied by apoptosis, evidenced by an immunohistochemical positive reaction to cleaved caspase-3, and detachment of the epidermis were observed in the skin. In the epidermis and upper dermis, a slight infiltration of mononuclear cells was seen, which was predominantly positive for MAC387 (macrophages) and partly positive for CD3 (T lymphocytes). These findings have some similarities to drug-induced severe skin reactions such as Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) and may represent incipient changes of such lesions. The skin lesions observed in these dogs are being considered as a potential animal model of cutaneous drug reactions.

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Mutations in the mitochondrial DNA (mtDNA) displacement loop (D-loop) region were investigated to clarify the possible molecular mechanisms underlying the development of hamster pancreatic tumors. Female Syrian golden hamsters received 30 mg/kg N-nitrosobis(2-oxopropyl)amine (BOP), followed by repeated exposure to an augmentation pressure regimen consisting of a choline-deficient diet combined with ethionine, then methionine injections and a further administration of 20 mg/kg BOP. A total of 11 pancreatic duct adenocarcinomas (PDAs) were obtained 10 weeks after beginning the experiment, and three cell lines established from subcutaneously transplantable PDAs in syngeneic hamsters were examined for mutations using polymerase chain reaction (PCR) - single strand conformation polymorphism (SSCP) analysis. No mutations were detected in the 11 PDAs and 3 cell lines. These results suggest that alterations of the mtDNA D-loop might not be involved in BOP-induced pancreatic duct carcinogenesis in hamsters.

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