HMG-CoA reductase inhibitor increases GTP cyclohydrolase I mRNA and tetrahydrobiopterin in vascular endothelial cells.
OBJECTIVE
Endothelial nitric oxide synthase (eNOS) activity is supported by tetrahydrobiopterin (BH4), which appears to be important for generating protective NO but decreases uncoupling formation of superoxide. We investigated the effects of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, or statins, in terms of BH4 metabolism in human umbilical vein endothelial cells (HUVECs).


RESULTS
We measured the mRNA levels of GTP cyclohydrolase I (GTPCH), the rate-limiting enzyme in the first step of de novo BH4 synthesis, by real-time polymerase chain reaction. The mRNA of GTPCH, as well as of eNOS, was upregulated in HUVECs treated with cerivastatin. This increase was time and dose dependent. Fluvastatin was also observed to enhance GTPCH and eNOS mRNA levels. In parallel with this observation, cerivastatin increased intracellular BH4. Incubating HUVECs with tumor necrosis factor (TNF-alpha) was observed to increase GTPCH mRNA while decreasing eNOS mRNA. In the presence of cerivastatin, the TNF-alpha-mediated increase in GTPCH mRNA was enhanced, and the TNF-alpha-mediated decrease in eNOS mRNA was attenuated. Cerivastatin increased the stability of eNOS mRNA. However, it did not alter the stability of GTPCH mRNA but increased GTPCH gene transcription, as shown by nuclear run-on assays. Preteatment of HUVECs with the selective GTPCH inhibitor, 2,4-diamino-6-hydroxypyrimidine, caused a decrease in intracellular BH4 and decreased citrulline formation after stimulation with ionomycin. Furthermore, the potentiating effect of cerivastatin was decreased by limiting the cellular availability of BH4.


CONCLUSIONS
Our data demonstrate that statins elevate GTPCH mRNA, thereby increasing BH4 levels in vascular endothelial cells. In addition to augmenting eNOS expression, statins potentiate GTPCH gene expression and BH4 synthesis, thereby increasing NO production and preventing relative shortages of BH4.
Hattori
Yoshiyuki
Y
Department of Endocrinology and Metabolism, Dokkyo University School of Medicine, Mibu, Tochigi 321-0293, Japan. yhattori@dokkyomed.ac.jp
Nakanishi
Nobuo
N
Akimoto
Kazumi
K
Yoshida
Mika
M
Kasai
Kikuo
K
D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism*; D002460:Cell Line; D003199:Computer Systems; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000201:enzymology*; D004790:Enzyme Induction / Q000187:drug effects; D006136:GTP Cyclohydrolase / Q000378:metabolism*; D006801:Humans; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D016133:Polymerase Chain Reaction / Q000379:methods; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology / Q000187:drug effects / Q000201:enzymology
D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D011725:Pyridines; D012333:RNA, Messenger; D001708:Biopterins; C086276:cerivastatin; C496314:NOS3 protein, human; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D006136:GTP Cyclohydrolase; C003402:sapropterin