Biopterin in human brain and urine from controls and parkinsonian patients: application of a new radioimmunoassay

Change of tyrosine hydroxylase in the parkinsonian brain and in the brain of MPTP-treated mice as revealed by homospecific activity

Changes in homospecific activity (unit of enzyme activity per unit of enzyme protein; Rush, Kindler and Udenfriend, 1974. Biochem. Biophys. Res. Commun., 61, 38) of tyrosine hydroxylase (TH) in the striatum of the brain were examined in MPTP-treated mice and parkinsonian patients. After a single injection of MPTP to mice, TH activity was acutely inhibited only in situ without changes in in vitro TH activity (Vmax) and TH protein; TH homospecific activity (TH Vmax/TH protein) did not change. After repeated injection of MPTP to mice for 8 days, in situ TH activity, in vitro TH Vmax, and TH protein were decreased in parallel, and TH homospecific activity did not change. The result indicates that the decreases in in situ TH activity and in TH Vmax are due to the decrease in TH protein by nerve degeneration of dopaminergic neurons in MPTP treated mice. However, when MPP+ was infused in the striatum of rats for 3 hours, in vitro TH activity (Vmax) was decreased without changes in TH protein. Thus, TH homospecific activity was decreased. The results indicate that MPP+ inactivates TH protein in the striatum after continued infusion. In contrast, the homospecific activity of Th in post-mortem parkinsonian striatum was increased 3-fold. The increase in homospecific activity of residual TH in parkinsonian brain suggests such molecular changes in TH molecules as result in a compensatory increase in TH activity.

Immunological evidence for the requirement of sepiapterin reductase for tetrahydrobiopterin biosynthesis in brain

Specific antibodies to sepiapterin reductase were used to investigate its involvement in de novo (6R)-5,6,7,8-tetrahydrobiopterin (BH4) biosynthesis in rat brain. Antisepiapterin reductase (anti-SR) serum totally inhibited NADPH-dependent sepiapterin reductase activity in supernatants from discrete rat brain areas and liver. The anti-SR serum also inhibited the conversion of 7,8-dihydroneopterin triphosphate to BH4 in rat brain extracts. The inhibition was accompanied by a concentration-dependent increase in the formation of 6-lactoyltetrahydropterin (6LPH4), a proposed intermediate in BH4 biosynthesis. In addition, anti-SR serum was used to characterize the distribution and molecular properties of sepiapterin reductase in rat tissues. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by Western blotting indicated that there was a single polypeptide with the same molecular weight (28,000) as that of the subunit of pure sepiapterin reductase present in all tissues examined except for liver, where an immunoreactive protein of higher molecular weight (30,500) also was detected. Two-dimensional gel electrophoresis of rat striatum and liver demonstrated that the isoelectric point of sepiapterin reductase from both tissues was 6.16 and that the higher molecular weight immunoreactive material in liver had an isoelectric point of 7.06. Our studies with specific anti-SR serum confirmed the results of previous studies using chemical inhibitors of sepiapterin reductase, which suggested that sepiapterin reductase activity was essential for BH4 biosynthesis in the CNS and that 6LPH4 could be a precursor of BH4.

The coenzyme nicotinamide adenine dinucleotide (NADH) improves the disability of parkinsonian patients

The coenzyme nicotinamide adenine dinucleotide (NADH) has been used in an open label trial as novel medication in 34 patients with Parkinson's disease, using an intravenous administration technique. In all patients a beneficial clinical effect was observed. 21 patients (61.7%) showed a very good (better than 30%) improvement of disability, 13 patients (38.3%) a moderate (up to 30%) improvement. Concomitant with the improvement of the disability the urine level of homovanillic acid (HVA) increased significantly in all patients (in some patients by more than a 100%). The daily "on phases" of the patients could be increased from 2 up to 9 hours in the individual patients by NADH administration.

Strategy and tactic of modern Parkinson therapy

The aim of modern Parkinson therapy is to overcome the dopamine deficit in the brain of parkinsonian patients which is the cause of their motor disability. This can be achieved in two ways: (a) substitution of the lacking dopamine by l-dopa, or (b) stimulation of the endogenous biosynthesis by activating the enzyme tyrosine hydroxylase. The latter approach is possible by the iron compound oxyferriscorbone or by the coenzyme nicotinamide adenine dinucleotide (NADH). In addition to these two major medications the essential therapeutic additives such as the decarboxylase inhibitor benserazide, the monoamineoxidase B inhibitor deprenyl and the dopamine receptor agonist lisuride should be used for the fine adjustment of the individual patient.

Stimulation of endogenous L-dopa biosynthesis--a new principle for the therapy of Parkinson's disease. The clinical effect of nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotidephosphate (NADPH)

The coenzyme nicotinamide adenine dinucleotide (NADH) has been used as a novel medication in 161 Parkinson patients in an open label trial. In all but 18 patients (11.2%) an improvement in their disability was observed. 115 patients (71.4%) showed a very good (better than 30%) response, and 28 patients (17.4%) a moderate response up to 30%. The best results were obtained with a dose of 25 to 50 mg every second day by i.v. administration. Concomitantly with the improvement in disability, the urine HVA level increased significantly, indicating a stimulation of endogenous L-DOPA biosynthesis. 8 patients have been treated with nicotinamide adenine dinucleotidephosphate (NADPH), 5 of whom exhibited an improvement in their disability from 35 to 55%. The other 3 showed a moderate response of 20 to 25%. In all these patients an increase in the urine level of HVA was detected, reflecting elevated endogenous L-DOPA production.

Possible uses of urinary neopterin and biopterin measurement

The measurement of urinary neopterin and biopterin may be an important non-specific diagnostic tool. Urinary biopterin has been found to be decreased in parkinsonian patients, and in hyperphenylalanemia as a variant of phenylketonuria. Urinary neopterin has been found to be elevated in numerous conditions. It has been shown to be significantly higher in AIDS patients than in ARC patients, and significantly higher in ARC patients than in controls. Urinary neopterin has been shown to be prognostically elevated in a wide range of neoplasias, including multiple myeloma, hematologic and gynecologic neoplasias. Neopterin is thought to be an in-vitro indicator of activation of the immune system.

Tetrahydrobiopterin and Parkinson's disease

Two patients with Parkinson's disease were treated with 1 g tetrahydrobiopterin (BH4) for 5 days. Clinical improvement was not observed. In the cerebrospinal fluid (CSF) a 4-8 fold increase in the concentration of homovanillic acid (HVA), and a 3-fold increase in the concentration of 5-hydroxyindole acetic acid (5-HIAA) was measured. However, the concentration of HVA reached, was only approximately half as high, as that of patients treated with madopar (DOPA + benserazid). In urine, the excretion of HVA increased 13-37 fold, when the patients were treated with madopar, whereas no increase in the HVA excretion was measured after the BH4 administration. Additionally, 2 patients with Parkinson's disease were treated with 1 g BH4 in combination with 15 g tyrosine for 3 days, and 1 parkinsonian patient was treated with 15 g tyrosine daily for 7 weeks. No increase in the CSF concentrations of HVA or 5-HIAA was observed. The results suggest, the BH4 in the dosage used, is not effective in the treatment of Parkinson's disease.

Increased iron (III) and total iron content in post mortem substantia nigra of parkinsonian brain

Significant differences in the content of iron (III) and total iron were found in post mortem substantia nigra of Parkinson's disease. There was an increase of 176% in the levels of total iron and 225% of iron (III) in the substantia nigra of the parkinsonian patients compared to age matched controls. In the cortex (Brodmann area 21), hippocampus, putamen, and globus pallidus there was no significant difference in the levels of iron (III) and total iron. Thus the changes in total iron, iron (III) and the iron (II)/iron (III) ratio in the parkinsonian substantia nigra are likely to be involved in the pathophysiology and treatment of this disorder.

Analysis and clinical significance of pterins

This review briefly describes the biochemistry of pterins, their involvement in pathological processes and the use of pterin measurement in diagnosis and monitoring of disease. Chromatographic and other methods of pterin analysis are detailed with particular emphasis being placed on the need for correct sample collection and handling.

Inactivation of tyrosine hydroxylase in rat striatum by 1-methyl-4-phenylpyridinium ion (MPP+)

We report that 1-methyl-4-phenylpyridinium ion (MPP+), the active metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), inactivated tyrosine hydroxylase (TH) when MPP+ was directly infused into the striatum. We examined both in vitro TH activity and TH content measured by an enzyme immunoassay in the rat striatum after MPP+ was administered by an in vivo brain microdialysis probe. MPP+ caused the inhibition of TH activity but did not influence TH content in the ipsilateral striatum. These results indicate that MPP+ may cause an acute inactivation of TH after continuous exposure at the high concentrations.

Effects of repeated systemic administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on striatal tyrosine hydroxylase activity in vitro and tyrosine hydroxylase content

We examined both in vitro tyrosine hydroxylase (TH) activity and TH content determined by a new enzyme immunoassay in the mouse striatum after repeated systemic injection of MPTP. Repeated systemic administration of MPTP to mice (30 mg/kg per day, subcutaneously for 8 days) caused an approximately 65% decrease of both TH activity and TH content in the striatum. The intensity of immunohistochemical staining of TH protein in the striatum was also reduced in MPTP-treated mice. These results indicate that the reduction of TH activity in vitro after the repeated administration of MPTP is due to reduction of TH protein as a result of nerve degeneration.

Catecholamine levels in the brain of SART (repeated cold)-stressed rats

1 The catecholamine levels in the brains of SART (specific alternation of rhythm in temperature)-stressed (repeated cold-stressed) rats with vagotonic-type dysautonomia, were examined by high performance liquid chromatography with electrochemical detection techniques. 2 The cerebral cortex, hypothalamus and hippocampus of the SART-stressed rats had increased levels of noradrenaline. All brain areas examined showed increased levels of dopamine. 3 These increased catecholamine levels were still maintained by day 10 of SART stress. 4 Among brain areas examined, the hypothalamus showed most rapid change. 5 Cold-stressed rats showed increased noradrenaline levels only in the basal ganglia and dopamine levels in the hippocampus. 6 Rats suffering from restraint and water immersion stress showed decreased noradrenaline levels and increased dopamine levels. 7 These results suggest that SART-stressed animals are in a disease state differing from that of other so-called stressed animals, and changes in the hypothalamus give rise to the various symptoms in SART-stressed animals.

Tyrosine hydroxylase, tryptophan hydroxylase, biopterin, and neopterin in the brains of normal controls and patients with senile dementia of Alzheimer type

The activities of tyrosine hydroxylase and tryptophan hydroxylase, and the concentrations of the biopterin cofactor and the precursor neopterin were measured in 14 regions of postmortem brains from four histologically verified patients of senile dementia of the Alzheimer type (SDAT) and eight histologically normal controls. Neopterin concentrations were measured in the human brain for the first time. The activities of tyrosine hydroxylase and tryptophan hydroxylase in the brains of patients with SDAT were significantly reduced in the substantia nigra and in the lateral segment of the globus pallidus, locus ceruleus, and substantia nigra, respectively. The concentrations of total biopterin in the brains of patients with SDAT were significantly reduced in the putamen and substantia nigra, but the total neopterin concentrations did not change significantly. These results suggest that the reduction in biogenic amines in SDAT might be related to reductions in biosynthetic enzymes associated with biogenic amines, due to destruction of monoaminergic neurons.

Biopterin in Parkinson's disease

Tetrahydrobiopterin is an essential co-factor in the natural synthesis of dopamine. Oral tetrahydrobiopterin was given in small doses to four patients with early Parkinson's disease but had no discernible effect.

Differences in the metabolism of the aromatic amino acid hydroxylase cofactor, tetrahydrobiopterin, in mutant mice with neurological and immunological defects

Tetrahydrobiopterin (BH4) levels and GTP cyclohydrolase activity (GTP-CH) were measured in tissues from mutants and controls of 24 different mouse strains to identify mutants that might be suitable models for diseases which are characterized by a deficiency of the biopterin cofactor, such as parkinsonism and atypical phenylketonuria. BH4 levels and GTP-CH activity were determined in brain, liver, and spleen obtained from 24 mutants with neurological or immunological defects. BH4 levels in brain were slightly but significantly decreased in only two mutants, spastic (spa) and jittery (ji), while GTP-CH activity in brain was not significantly lower than controls in any of the strains examined. GTP-CH levels in liver were significantly decreased in four mutant strains (jittery, ji; leaner, tgla; reeler, rl; and anorexia, anx); however, BH4 levels were significantly lower only in the mutant anorexia (anx). The most significant and widespread changes in both BH4 levels and GTP-CH activity were observed in spleen. In those mutants which were most affected, BH4 levels and GTP-CH activity were decreased 85-90%.

Iron, a new aid in the treatment of Parkinson patients

One of the problems in treating Parkinson patients is the so called "off-effect" which occurs after long term treatment with L-DOPA. Off-effects are characterized by severe rigor and akinesia. Increasing dosages of L-DOPA and decarboxylase- or monoaminooxidase-inhibitors do not improve these symptoms. Intravenously applied iron--in form of a ferri-ferro-complex--exhibited a considerable benefit for all patients treated so far. They regained a remarkable mobility. Their disability score dropped from up to 90% down to 30%. The effect of iron is dosage-dependent and lasts 24 to 48 hours.

Early and late effects of systemically administered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on tyrosine hydroxylase activity in vitro and on tyrosine hydroxylation in tissue slices of mouse striatum

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces a parkinsonian-like state in humans and some animals. To compare the early biochemical abnormalities produced by this neurotoxin with late effects, we examined both in vitro tyrosine hydroxylase activity in striatal homogenates and in situ tyrosine hydroxylation in striatal tissue slices after single and repeated systemic injection of MPTP to mice. The acute administration of MPTP (30 mg/kg, s.c., 1 h prior to sacrifice) in mice resulted in a decrease of tyrosine hydroxylation in situ in tissue slices but not in vitro in homogenates. In contrast, repeated treatment of mice with MPTP (30 mg/kg, s.c. daily for 8 days) caused a decrease of tyrosine hydroxylase activity both in vitro in homogenates and in situ in tissue slices. These results suggest that MPTP inhibits tyrosine hydroxylation in dopaminergic neurons in an early stage and causes reduction of tyrosine hydroxylase itself after repeated administration.

Effect of ischemia on hydroxylase cofactor (tetrahydrobiopterin) and monoamine neurotransmitters in rat brain

Hydroxylase cofactor, monoamine neurotransmitters and their metabolites were measured in ischemic rat brain produced by four-vessel occlusion for 30 and 60 min periods. Slight reduction of hydroxylase cofactor activity was observed in the ischemic cortex after 60 min. Dopamine increased in the brainstem, and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, increased throughout the brain. Decrease in norepinephrine was observed in the whole brain. Decrease in serotonin and increase in 5-hydroxyindoleacetic acid, a metabolite of serotonin, was observed in the ischemic cerebral cortex. The present study has revealed that there appears to be no significant relationship between hydroxylase cofactor activity and monoamine levels in the ischemic brain. Thus, the hydroxylase cofactor does not play a main role in regulating monoamine synthesis in the acute phase of brain ischemia.

A sensitive assay of GTP cyclohydrolase I activity in rat and human tissues using radioimmunoassay of neopterin

A highly sensitive and simple assay for the activity of GTP cyclohydrolase I (EC 3.5.4.16) was established using a newly developed radioimmunoassay. D-erythro-7,8-Dihydroneopterin triphosphate formed from GTP by GTP cyclohydrolase I was oxidized by iodine and dephosphorylated by alkaline phosphatase to D-erythro-neopterin, and quantified by a radioimmunoassay for D-erythro-neopterin. This method was highly sensitive and required only 0.2 mg of rat liver tissues for the measurement of the activity. It was reproducible and can be applied for the simultaneous assay of many samples. The activity of GTP cyclohydrolase I was measured in several rat tissues. For example, the enzyme activity in rat striatum (n = 5) was 13.7 +/- 1.5 pmol/mg protein per hour (mean +/- SE), and agreed well with those obtained by high-performance liquid chromatography with fluorescence detection. The activity in the autopsy human brains (caudate nucleus) was measured by this new method for the first time. The activity in the caudate nucleus from parkinsonian patients (n = 6) was 0.82 +/- 0.56 pmol/mg protein per hour which was significantly lower than the control value, 4.22 +/- 0.43 pmol/mg protein per hour (n = 10).

Neurological aspects of biopterin metabolism

Plasma total biopterin concentration was measured by bioassay in 59 infants with hyperphenylalaninaemia and in 50 children with developmental regression and or movement disorder with normal plasma phenylalanine concentrations. In infants with raised phenylalanine concentrations plasma biopterin concentrations were significantly raised in proportion to the phenylalanine values. Five patients had plasma biopterin concentrations at the extremes of the range, and of these two had defective biopterin metabolism. One with low plasma biopterin concentration apparently had a partial defect of biopterin synthesis but died before investigations were complete. One with high plasma biopterin concentration, even when phenylalanine concentrations had fallen to the normal range, had dihydropteridine reductase deficiency. In this patient concentrations of homovanillic acid and 5-hydroxyindolacetic acid in the cerebrospinal fluid (CSF) were severely reduced. In children without hyperphenylalaninaemia plasma biopterin concentrations were normal. Twenty two patients were subjected to lumbar puncture, of whom six with developmental regression without movement disorder had normal CSF biopterin concentrations, and 11 with movement disorder other than torsion dystonia had significantly lower CSF biopterin concentrations. Five patients with torsion dystonia had normal biopterin concentrations.

Urinary biopterin and neopterin excretion and pituitary-adrenal activity in psychiatric patients

The urinary excretion of biopterin and neopterin, pterin compounds related to tetrahydrobiopterin, the cofactor for the initial steps in monoamine synthesis, was serially measured in a heterogeneous group of psychiatric patients and compared to excretion in control subjects, to state of illness, and to the results of the dexamethasone suppression test. Patients with major depression had increased excretion of biopterin compared to normal subjects. There was no relationship between biopterin or neopterin excretion and postdexamethasone cortisol levels. Pterin excretion did not significantly change with improvement in mood or with conversion from nonsuppressor to suppressor status. The meaning of increased urinary biopterin is presently unclear, although its relation to hormonal state and sympathoadrenal tone deserves further study.

Inhibition of tyrosine hydroxylation in rat striatal tissue slices by 1-methyl-4-phenylpyridinium ion

Pargyline, an inhibitor of monoamine oxidase (MAO), prevented 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced inhibition of dihydroxyphenylalanine (DOPA) production by tyrosine hydroxylase (TH) system in rat striatal tissue slices. The result suggests that the metabolism of MPTP in rat striatal tissue slices by MAO is necessary for the expression of the inhibitory effect. 1-Methyl-4-phenylpyridinium ion (MPP+), the metabolic product of MPTP by MAO, also inhibited DOPA formation in rat striatal tissue slices. The concentration of MPP+ producing significant inhibition was lower than that of MPTP, and the maximal inhibition produced by MPP+ was greater than that caused by MPTP. Since MPP+ at a concentration of 10(-4) M had no effect on the activity of pure TH in vitro, the inhibition of DOPA formation in tissue slices induced by MPP+ may not be due to direct inhibition of TH. Although hydroxylated derivatives of MPTP were reported to inhibit dihydropteridine reductase in vitro at lower concentrations than MPTP, 1-methyl-4-(p-hydroxyphenyl)-1,2,3,6-tetrahydropyridine showed only weak inhibition for tyrosine hydroxylation in striatal tissue slices.

Tryptophan hydroxylase activity in the brains of controls and parkinsonian patients

The activity of tryptophan hydroxylase was measured in nine regions of human brains from controls and patients with Parkinson's disease, striatonigral degeneration, Shy-Drager syndrome and progressive supranuclear palsy by high performance liquid chromatography with fluorescence detection. The regional distribution of the enzyme activity in control brains was similar to that of serotonergic neurons; relatively high activity was found in the raphe nucleus, locus coeruleus and substantia nigra. The activity in the thalamus in Parkinson's disease and that in the locus coeruleus, raphe nucleus and substantia nigra in striato-nigral degeneration were significantly lower than that of controls (p less than 0.05). In most other brain regions in parkinsonian patients the activity was relatively lower than that of controls except the caudate nucleus and nucleus accumbens where the activity was relatively higher than that of controls. Marked decrease in the enzyme activity in various brain regions was observed in striato-nigral degeneration, Shy-Drager syndrome, and progressive supranuclear palsy. These results suggest that the activity of tryptophan hydroxylase in serotonergic neurons is reduced in the brains of parkinsonian patients and of patients with degenerative nervous diseases.

Polarization fluoroimmunoassay of biopterin and neopterin in human urine

A polarization fluoroimmunoassay has been developed for the routine determination of biopterin and neopterin levels in human urine. The method employs fluorescein-labeled biopterin and neopterin. The assay is fast (incubation time: 2 min) and no separation step is required prior to measurement of fluorescence polarization. Linearity, recovery and precision were satisfactory. Estimations of biopterin and neopterin levels in human urine samples closely correlated with those obtained by radioimmunoassay.

Urinary excretion of biopterin and neopterin in psychiatric disorders

Levels of urinary neopterin and biopterin were determined in patients having a diagnosis of schizophrenia, unipolar depression, or bipolar depression. Both neopterin and biopterin levels were significantly higher in the urine of patients with unipolar depression than in the urine of the control group. Subclassification of patients into primary and secondary depression demonstrated a significant elevation of urinary biopterin in both groups, whereas urinary neopterin was elevated only in those patients with primary depression. In patients with bipolar depression, neopterin excretion was elevated, but biopterin excretion did not differ from controls. No significant differences were found in schizophrenic patients.

Effects of tyrosine administration on serum biopterin in normal controls and patients with Parkinson's disease

After administration of tyrosine, total concentration of biopterin, the cofactor for tyrosine hydroxylase, was increased in the striatum, adrenal glands, and serum of rats, and in the serum of humans. Serum biopterin is lower in patients with Parkinson's disease than in normal controls. After oral administration of tyrosine, the increase in serum biopterin concentration was smaller in patients with Parkinson's disease (less than twofold) than in healthy controls (three-to sevenfold). These results suggest that tyrosine may have a regulatory role in biopterin biosynthesis and that patients with Parkinson's disease may have some abnormality in the regulation of biopterin biosynthesis.

Ontogenesis of monoamine-synthesizing enzyme activities and biopterin levels in rat brain or salivary glands, and the effects of thyroxine administration

Neonatal changes in the activities of tyrosine hydroxylase (TH) and tryptophan hydroxylase (TrpH) and in the content of the co-factor, biopterin, were studied in rat midbrain for the first 20 days after birth. Changes in TH activity in the parotid and submandibular glands were also examined. Changes in TH activity per unit weight in the developing rat brain were briefly similar to those in the salivary glands; the activity increased from day 2 or 4 to day 9 after birth, and remained constant or slightly decreased at day 12, then rapidly increased on day 16. TrpH activity in the midbrain increased about twofold up to day 16. The biopterin concentration in the brain increased, reached a maximum level on day 12 after birth, and thereafter decreased. The effect of hyperthyroidism in rats given 0.2 mg/kg i.p. of thyroxine every 2 days postnatally was studied on the activity of TH in rat salivary glands at 12-day-old rats. In parotid or submandibular gland of hyperthyroid rats, TH activity increased at day 12 postnatally. In comparison with the effect on TH activity in the salivary glands, TH activity in the midbrain on day 20 postnatally was not induced by hyperthyroidism. Furthermore, increase of the TrpH activity and biopterin and catecholamine levels in the midbrain of hyperthyroid rats was not found on day 20 after birth in comparison with the corresponding controls. From these data, we suppose that postnatal hyperthyroidism may cause precocious induction of TH in rat salivary gland, but may not increase the activity of TH or TrpH, and the level of their co-factor, biopterin, in rat midbrain.