Effect of water-immersion restraint stress on tryptophan catabolism through the kynurenine pathway in rat tissues
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The aim of this study was to clarify the effect of water-immersion restraint stress (WIRS) on tryptophan (Trp) catabolism through the kynurenine (Kyn) pathway in rat tissues. The tissues of rats subjected to 6 h of WIRS (+WIRS) had increased tryptophan 2,3-dioxygenase (TDO) and indoleamine 2,3-dioxygenase (IDO) activities and increased TDO and IDO1 (one of two IDO isozymes in mammals) mRNA expression levels, with decreased Trp and increased Kyn contents in the liver. +WIRS rats had unchanged TDO and IDO activities in the kidney, decreased TDO activity and unchanged IDO activity in the brain, and unchanged IDO activity in the lung and spleen, with increased Kyn content in all of these tissues. Pretreatment of stressed rats with RU486, a glucocorticoid antagonist, attenuated the increased TOD activity, but not the increased IDO activity, with partial recoveries of the decreased Trp and increased Kyn contents in the liver. These results indicate that WIRS enhances hepatic Trp catabolism by inducing both IDO1 and TDO in rats.
KeywordsWater-immersion restraint stress (rats) Liver tryptophan catabolism Tryptophan 2,3-Dioxygenase Indoleamine 2,3-Dioxygenase 1 Glucocorticoid Interferon-γ
This study was partially supported by a grant from the Research Foundation of Fujita Health University, Grants-in-Aids for Scientific Research (24592734, 26860368) from the Japan Society for the Promotion of Science (JSPS), and a Research Grant from the Smoking Research Foundation (SRF).
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Conflict of interest
The authors declare that they have no conflicts of interest concerning this article.
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