Pyrrolidine dithiocarbamate inhibits immunostimulant-induced tetrahydrobiopterin synthesis in rat vascular smooth muscle.
GTP cyclohydrolase I is the first and rate-limiting enzyme in the synthesis of tetrahydrobiopterin, a cofactor of nitric oxide (NO) synthase. Immunostimulants increase NO and tetrahydrobiopterin synthesis in vascular smooth muscle cells by coinducing NO synthase and GTP cyclohydrolase I gene expression. Given that nuclear factor kappa(B) mediates the induction of NO synthase gene expression by lipopolysaccharide (LPS), the role of nuclear factor kappa(B) in the induction of GTP cyclohydrolase I in LPS-stimulated rat vascular smooth muscle cells was assessed by examining the effects of pyrrolidine dithiocarbamate, an inhibitor of the activation of nuclear factor kappa(B), on the abundance of GTP cyclohydrolase I mRNA and biopterin synthesis. Pyrrolidine dithiocarbamate inhibited both NO and biopterin synthesis induced by LPS in a dose-dependent manner with similar half-maximal inhibitory concentrations, 12 mu M for NO and 17 mu M for biopterin, respectively. At a concentration of 25 mu M, which inhibited NO and biopterin synthesis but caused no cytotoxicity, pyrrolidine dithiocarbamate substantially reduced the LPS-induced increase in the abundance of NO synthase and GTP cyclohydrolase I mRNAs. These results suggest that pyrrolidine dithiocarbamate inhibits LPS-induced NO and biopterin synthesis by inhibiting the expression of NO synthase and GTP cyclohydrolase I genes. Thus, the induction of both genes necessary for cellular NO synthesis in vascular smooth muscle appears to be regulated, at least in part, by a common mechanism: nuclear factor kappa(B) activation.
Hattori
Y
Y
Department of Endocrinology, Dokkyo University School of Medicine, Mibu, Japan.
Nakanishi
N
N
Kasai
K
K
Shimoda
S I
SI
Gross
S S
SS
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001013:Aorta, Thoracic / Q000378:metabolism*; D001483:Base Sequence; D001708:Biopterins / Q000031:analogs & derivatives* / Q000096:biosynthesis; D019069:Cell Respiration; D004790:Enzyme Induction / Q000187:drug effects; D006136:GTP Cyclohydrolase / Q000096:biosynthesis / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D008297:Male; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D011759:Pyrrolidines / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013859:Thiocarbamates / Q000494:pharmacology*
D000975:Antioxidants; D016328:NF-kappa B; D011759:Pyrrolidines; D013859:Thiocarbamates; D001708:Biopterins; C020972:pyrrolidine dithiocarbamic acid; D009569:Nitric Oxide; D006136:GTP Cyclohydrolase; C003402:sapropterin