L-buthionine (S,R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, was administered to mice via drinking water for 14 days in order to establish an animal model with continuously depleted levels of GSH. No toxicity was observed at 20 mM BSO, even though a significant decrease in liver weight was observed at 30 mM BSO. GSH levels in the liver, kidney, brain, lung, heart, spleen, pancreas, small intestine, large intestine, skeletal muscle, plasma and blood cells from mice given 20 mM of BSO were all less than those from the control mice continuously throughout a 24-hr period. The ratios of the GSH levels to that of the control were 46.4% and 16.7% in the liver and kidney, respectively, suggesting a decrease in GSH conjugation activity in vivo by GSH depletion. Liver cytochrome P450 content and UDP-glucuronosyltransferase activity to p-nitrophenol were not influenced by the BSO dosing. To confirm the adequacy of this GSH-depletion model, 0.125 or 0.25% of acetaminophen (APAP) was administered via diet to this model for 14 days. Nine out of the ten mice given both 20 mM BSO and 0.25% APAP died on Day 2, and remarkable necrosis was observed in the hepatocytes and renal tubular epithelium. Moreover, focal necrosis of hepatocytes with proliferation of fibroblasts was observed on Day 15 in some mice coadministered 20 mM BSO and 0.125% APAP. However, no toxicity was observed in mice given APAP alone. Based on these results, a mouse given 20 mM of BSO via drinking water for 14 days was concluded to be an animal model with continuously depleted levels of GSH in various organs without toxicity. This model shows high susceptibility to toxicity induced by chemicals which are metabolized to electrophilic and reactive metabolite(s), such as APAP.

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Spleen tyrosine kinase (Syk) is associated with Fcγ receptors (FcγRs) and transmits activation signals through FcγRs in myeloid cells. Thus, application of drugs to inhibit Syk activity can affect the development of immune diseases mediated by autoantibodies, while unexpected systemic effects by the inhibition may be concerned because Syk has multiple physiological functions. We used tamoxifen-inducible systemic conditional Syk knockout (KO) mice to evaluate the role of Syk in the pathogenesis of autoimmune arthritis and to investigate the systemic effects of Syk deletion. In a collagen antibody-induced arthritis model, Syk KO mice were almost completely protected from disease induction and showed significantly attenuated accumulation of neutrophils and macrophages in the joints. Syk-deleted macrophages showed less IL-6 and MCP-1 production upon FcγR ligation and exhibited reduced FcγR-mediated phagocytosis in vitro. Syk-deleted macrophages produce more RANTES upon FcγR ligation, indicating a Syk-independent signaling through the FcγR. We further found that both wild-type and Syk-deleted macrophages induced neutrophil chemotaxis upon FcγR ligation in vitro, and air-pouch model demonstrated that Syk-deleted neutrophils have a potential to infiltrate into local tissues in response to collagen and anti-collagen antibodies. However, Syk-deleted neutrophils exhibited greatly decreased neutrophil extracellular traps formation and FcγR-mediated phagocytosis. Our results indicated that Syk deficiency rendered mice completely unresponsive to immune activation by anti-collagen antibodies with disabling one pathway of FcγR-mediated signaling that was crucial for arthritis induction.

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A novel rat model of hereditary renal cell carcinoma (RC) was found in a rat colony of the SpragueDawley strain in Japan, and named the "Nihon" rat. In this strain, RCs develop from early preneoplastic lesions, which begin to appear at 4 weeks of age, forming adenomas by the age of 16 weeks. The RCs are predominantly of clear cell type. Southern blot, northern blot and SSCP analyses revealed no change in the Tsc1, Tsc2, VHL, and c-Met genes. Thus, the Nihon rat should be a valuable experimental model for understanding renal carcinogenesis, especially clear cell type, which is common among human RCs.Key words: Nihon rats -Tsc2 gene mutant (Eker) rats -Renal carcinogenesis -Hereditary cancer Hereditary cancer was first described in the rat by Eker in 1954.1) The Eker rat model of hereditary renal carcinoma (RC) was the first example of a Mendelian dominantly inherited predisposition to a specific cancer in an experimental animal. In 1994, Hino and colleagues identified a germline mutation in the rat homologous to the human tuberous sclerosis gene (TSC2) as the predisposing Eker gene.2-4) Recently, we found a novel hereditary RC model in the Sprague-Dawley rat in Japan. We have named this novel RC model the Nihon rat. In this report, we described the origin, transmission mode, and phenotypic and molecular features of Nihon rats.All animals were housed individually in stainless steel cages with wood chip bedding in a room controlled at a temperature of 23±2°C, humidity of 55±10%, with a 12 h lighting cycle (from 6 a.m. to 6 p.m.). The rats were fed a standard diet (CR-LPF, Oriental Yeast Co., Ltd., Tokyo) and were allowed tap water ad libitum. Animals were killed by exsanguination under pentobarbital sodium anesthesia. After necropsy, tissues were fixed in 10% neutral buffered formalin, processed to paraffin-embedded blocks, and sectioned at 5 µm using standard procedures. Sections were stained with hematoxylin and eosin for microscopical examination. Midsagittal sections of each kidney were also stained with periodic acid-Schiff (PAS), and with alcian blue for acid mucopolysaccharides. Tail and kidney DNAs from the original (parent) female rat were extracted as reported. [4][5][6][7][8][9] We used Southern blot, northern blot and SSCP analyses to search for mutations of the Tsc1, Tsc2, VHL, and c-Met genes. The gene-specific primers for Tsc1, Tsc2, VHL, and c-Met [Accession No. AB012279 (primer for exon 17), AB012280 (primer for exon 18) and AB012281 (primer for exon 19), kindly provided by Dr. Y. Kikuchi] were described previously. [4][5][6][7][8][9] Bilateral, multicentric renal tubule tumors were found in 15 out of 343 rats during 5 toxicity studies during the safety evaluation of 3 unrelated chemicals in our laboratory, although renal tumors were found in both treated and non-treated rats (Table I). The age of the rats ranged from 7 to 16 weeks at termination of the treatment period in each of the studies (Table I). The rats had all obtained from the same supplier (Clea Japan Inc., Shiga). At necropsy, bilatera...