title: Stimulation of tetrahydrobiopterin synthesis by cyclosporin A in mouse brain microvascular endothelial cells.
abstract: We examined the effect of the immunosuppressant, cyclosporin A (CsA) on the synthesis of tetrahydrobiopterin (BH4), a cofactor for nitric oxide (NO) synthase and a scavenger of reactive oxygen species (ROS), in mouse brain microvascular endothelial cells. Treatment with CsA increased the BH4 content and the expression of mRNA level of GTP cyclohydrolase I, the rate-limiting enzyme of BH4 synthesis. 2,4-Diamino-6-hydroxypyrimidine, an inhibitor of GTP cyclohydrolase I, strongly reduced the CsA-induced increase in BH4 content. Cycloheximide (CHX), a protein synthesis inhibitor, also reduced CsA-induced BH4 synthesis. These findings suggest that CsA stimulates BH4 synthesis via a de novo pathway with the induction of GTP cyclohydrolase I. Moreover, CsA-induced the mRNA level of the inducible type of NO synthase, and stimulated the L-citrulline formation from L-arginine, which is a marker for NO synthesis. The CsA-stimulated L-citrulline formation was attenuated by the co-treatment with GTP cyclohydrolase I inhibitor. The expression of the endothelial type of NO synthase was low under basal condition, and was not affected by the treatment with CsA. These findings suggest that increase in BH4 content induced by CsA is coupled with NO production by inducible type of NO synthase.
authors: Department of Clinical Pharmacy, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
authors: Masakazu
authors: M
authors: Ishii
authors: Shunichi
authors: S
authors: Shimizu
authors: Kazuhiro
authors: K
authors: Shiota
authors: Shinichiro
authors: S
authors: Yamamoto
authors: Yuji
authors: Y
authors: Kiuchi
authors: Toshinori
authors: T
authors: Yamamoto
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001120:Arginine / Q000378:metabolism; D001708:Biopterins / Q000031:analogs & derivatives* / Q000096:biosynthesis*; D002560:Cerebrovascular Circulation / Q000502:physiology; D003513:Cycloheximide / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D006136:GTP Cyclohydrolase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000494:pharmacology; D051379:Mice; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D007166:Immunosuppressive Agents; D011500:Protein Synthesis Inhibitors; D001708:Biopterins; D016572:Cyclosporine; D001120:Arginine; D003513:Cycloheximide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse; D006136:GTP Cyclohydrolase; C003402:sapropterin