Dopa-responsive dystonia (DRD) is a hereditary dystonia character-ized by a childhood onset of fixed dystonic posture with a dramatic and sustained response to relatively low doses of levodopa. DRD is thought to result from striatal dopamine deficiency due to a reduced synthesis and activity of tyrosine hydroxylase (TH), the synthetic enzyme for dopamine. The mechanisms underlying the genesis of dystonia in DRD present a challenge to models of basal ganglia movement control, given that striatal dopamine deficiency is the hallmark of Parkinson's disease. We report here behavioral and anatomical observations on a transgenic mouse model for DRD in which the gene for 6-pyruvoyl-tetrahydropterin synthase is targeted to render selective dysfunction of TH synthesis in the striatum. Mutant mice exhibited motor deficits phenotypically resembling symptoms of human DRD and manifested a major depletion of TH labeling in the striatum, with a marked posterior-to-anterior gradient resulting in near total loss caudally. Strikingly, within the regions of remaining TH staining in the striatum, there was a greater loss of TH labeling in striosomes than in the surrounding matrix. The predominant loss of TH expression in striosomes occurred during the early postnatal period, when motor symptoms first appeared. We suggest that the differential striosome-matrix pattern of dopamine loss could be a key to identifying the mechanisms underlying the genesis of dystonia in DRD.basal ganglia ͉ movement disorders ͉ Parkinson's disease ͉ striatum

Objective-Diabetes mellitus is associated with increased oxidative stress, which induces oxidation of tetrahydrobiopterin (BH4) in vessel wall. Without enough BH4, eNOS is uncoupled to L-arginine and produces superoxide rather than NO. We examined the role of uncoupled eNOS in vascular remodeling in diabetes. Methods and Results-Diabetes mellitus was produced by streptozotocin in C57BL/6J mice. Under stable hyperglycemia, the common carotid artery was ligated, and neointimal formation was examined 4 weeks later. In diabetic mice, the neointimal area was dramatically augmented. This augmentation was associated with increased aortic superoxide formation, reduced aortic BH4/dihydrobiopterin (BH2) ratio, and decreased plasma nitrite and nitrate (NOx) levels compared with nondiabetic mice. Chronic BH4 treatment (10 mg/kg/d) reduced the neointimal area in association with suppressed superoxide production and inflammatory changes in vessels. BH4/BH2 ratio in vessel wall was preserved, and plasma NOx levels increased. Furthermore, in the presence of diabetes, overexpression of bovine eNOS resulted in augmentation of neointimal area, accompanied by increased superoxide production in the endothelium. Conclusions-In diabetes, increased oxidative stress by uncoupled NOSs, particularly eNOS, causes augmentation of vascular remodeling. These findings indicate restoration of eNOS coupling has an atheroprotective benefit in diabetes. (Arterioscler Thromb Vasc Biol. 2008;28:1068-1076)Key Words: diabetes mellitus Ⅲ eNOS uncoupling Ⅲ tetrahydrobiopterin Ⅲ superoxide Ⅲ vascular remodeling P atients with diabetes mellitus have much greater risk of atherosclerotic vascular disorders than nondiabetics. Several factors have been reported to explain the accelerated atherosclerosis in diabetes, including hyperglycemia itself, production of advanced glycation endproducts (AGEs), hyperlipidemia, insulin resistance, hypertension, and genetic variables. Increased oxidative stress is particularly of great importance as a pathogenic factor of diabetes-associated vascular diseases. 1,2 Nitric oxide (NO) derived from endothelial nitric oxide synthase (eNOS) has a variety of antiatherogenic effects and is shown to affect various cell functions in vitro and in vivo. 3 Diabetes mellitus is accompanied by endothelial dysfunction, and increasing numbers of evidence have demonstrated that the endothelial dysfunction in diabetes mellitus is at least partly caused by uncoupled eNOS. 2,4,5 Under conditions where the balance between eNOS protein levels and vascular tissue levels of tetrahydrobiopterin (BH4), an essential cofactor for eNOS enzymatic activity, is altered, eNOS becomes dysfunctional and produces superoxide rather than NO. Particularly under conditions with increased oxidative stress, reactive oxygen species (ROS) such as peroxynitrite oxidizes BH4 to dihydrobiopterin (BH2) and other biopterin species, which inhibit BH4 binding to eNOS. 6 BH4 facilitates dimerization of NOS, binds L-Arginine to NOS, and donates electrons to the ferrous-diox...

One of the possibly mutated genes in DOPA-responsive dystonia (DRD, Segawa's disease) is the gene encoding GTP cyclohydrolase I, which is the rate-limiting enzyme for tetrahydrobiopterin (BH4) biosynthesis. Based on our findings on 6-pyruvoyltetrahydropterin synthase (PTS) genedisrupted (Pts -/-) mice, we suggested that the amount of tyrosine hydroxylase (TH) protein in dopaminergic nerve terminals is regulated by the intracellular concentration of BH4. In this present work, we rescued Pts -/-mice by transgenic introduction of human PTS cDNA under the control of the dopamine b-hydroxylase promoter to examine regional differences in the sensitivity of dopaminergic neurons to BH4-insufficiency. The DPS-rescued (Pts -/-, DPS) mice showed severe hyperphenylalaninemia. Human PTS was efficiently expressed in noradrenergic regions but only in a small number of dopaminergic neurons. Biopterin and dopamine contents, and TH activity in the striatum were poorly restored compared with those in the midbrain. TH-immunoreactivity in the lateral region of the striatum was far weaker than that in the medial region or in the nucleus accumbens. We concluded that dopaminergic nerve terminals projecting to the lateral region of the striatum are the most sensitive to BH4-insufficiency. Biochemical and pathological changes in DPS-rescued mice were similar to those in human malignant hyperphenylalaninemia and DRD. Keywords: DOPA, dopamine, 6-pyruvoyltetrahydropterin synthase, striatum, tetrahydrobiopterin, tyrosine hydroxylase. L-erythro-5,6,7,8-tetrahydrobiopterin (BH4) is an essential cofactor for tyrosine hydroxylase (TH: EC 1.14.16.3), tryptophan hydroxylase (TPH: EC 1.14.16.4), and phenylalanine hydroxylase (PAH: EC 1.14.16.2, Kaufman 1959), as well as for all types of nitric oxide synthase (Kwon et al. 1989). TH catalyzes the hydroxylation of tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA, Nagatsu et al. 1964); and TPH, and that of tryptophan to 5-hydroxytryptophan (Lovenberg et al. 1967). These two enzymes are rate limiting for the biosynthesis of catecholamines and 5-hydroxytryptamine (serotonin), respectively, which are important neurotransmitters in the central and peripheral nervous system that regulate motor activity, emotion, thinking, sleep, and blood pressure.BH4 is synthesized from guanosine triphosphate (GTP) by three sequential steps catalyzed by GTP cyclohydrolase I (GTPCH: EC 3.5.4.16), 6-pyruvoyltetrahydropterin synthase (PTS: EC 4.6.1.10), and sepiapterin reductase (SR: EC 1.1.1.153). BH4 is oxidized to quinonoid-dihydrobiopterin in a coupling reaction causing aromatic amino acid hydroxylation, and is then reduced to BH4 by the recycling system ( Fig. 1a; Thöny et al. 2000). As the intracellular BH4 Address correspondence and reprint requests to Chiho Sumi-Ichinose, Department of Pharmacology, School of Medicine, Fujita Health University, Toyoake, Aichi 470-1192, Japan. E-mail: csichino@fujita-hu.ac.jpAbbreviations used: AADC, aromatic L-amino acid decarboxylase; BH4, tetrahydrobiopterin; DA, dopamine; D...