Critical role of interleukin-1beta for transcriptional regulation of endothelial 6-pyruvoyltetrahydropterin synthase.
OBJECTIVE
Synthesis of tetrahydrobiopterin (BH4), an essential cofactor for nitric oxide synthases, is strongly induced on immunostimulation in vascular endothelial cells (VECs). Expression of GTP cyclohydrolase I (GTPCH), the first enzyme in BH4 biosynthesis, is regulated by cytokines and considered rate-limiting. Herein we investigated the molecular mechanism and relevance of cytokine-dependent regulation of 6-pyruvoyltetrahydropterin synthase (PTPS), the second enzyme in BH4 synthesis, in human coronary artery endothelial cells (HCAECs).


RESULTS
Real-time polymerase chain reaction revealed a 4-fold induction of PTPS and a 300-fold induction of GTPCH expression by interleukin (IL)-1beta/tumor necrosis factor-alpha/interferon-gamma, mainly through de novo transcription. On immunostimulation, PTPS became rate-limiting. Importantly, IL-1beta induced PTPS rather than GTPCH. As a result, IL-1beta contributed significantly to the amount of BH4 produced (+40%) but concomitantly reduced the accumulation of the GTPCH intermediate, 7,8-dihydroneopterin triphosphate (-50%).


CONCLUSIONS
Our data show that PTPS induction is necessary for optimized BH4 synthesis in cytokine-stimulated HCAECs and point to IL-1beta as a leading cytokine in this process.
Franscini
Nicola
N
Medical Clinic B Research Unit, Department of Medicine, University Hospital, Zürich, Switzerland.
Blau
Nenad
N
Walter
Roland B
RB
Schaffner
Andreas
A
Schoedon
Gabriele
G
D001708:Biopterins / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology; D004730:Endothelium, Vascular / Q000378:metabolism*; D006136:GTP Cyclohydrolase / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D007375:Interleukin-1 / Q000378:metabolism*; D019798:Neopterin / Q000378:metabolism; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000378:metabolism*; D014158:Transcription, Genetic / Q000502:physiology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D007375:Interleukin-1; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D001708:Biopterins; D019798:Neopterin; D007371:Interferon-gamma; D006136:GTP Cyclohydrolase; D019761:Phosphorus-Oxygen Lyases; C043497:6-pyruvoyltetrahydropterin synthase; C003402:sapropterin