Biopterin Research Articles

Urinary neopterin and biopterin indicate that inflammation has a role in autism spectrum disorder.

Inflammation is thought to be involved in the pathogenesis of autism spectrum disorder (ASD). Pteridine metabolites are biomarkers of inflammation that increase on immune system activation. In this study, we investigated the urinary pteridine metabolites in ASD patients as a possible biomarker for immune activation and inflammation. This observational, cross-sectional, prospective study collected urine samples from 212 patients with ASD and 68 age- and sex-matched healthy individuals. Urine neopterin (NE) and biopterin (BIO) levels were measured. Patients who had chronic disorders, active infection at the time of sampling, or high C-reactive protein levels were excluded. The urine NE and BIO concentrations were determined by high-performance liquid chromatography. The ratios of both NE and BIO to creatinine (CRE) were used to standardise the measurements. The NE/CRE and NE/BIO levels were significantly higher in ASD patients than controls. Univariate and multivariate models revealed a significant increase in NE/CRE and NE/BIO in ASD patients. There was a significant relationship between the NE/BIO [average area under the curve (AUC) = 0.717; range: 0.637-0.797] and NE/CRE (average AUC = 0.756; range: 0.684-0.828) ratios, which distinguished individuals with ASD from controls. The elevated NE/CRE and NE/BIO ratios suggest that inflammation and T cell-mediated immunity are involved in the pathophysiology of autism. NE/BIO could serve as a diagnostic inflammatory marker in the pathogenesis of ASD.

Salivary neopterin and related pterins: their comparison to those in plasma and changes in individuals.

Neopterin (NP), biopterin (BP) and monapterin (MP) exist in saliva. The physiological role of salivary NP as well as the pathophysiological role of increased NP in the immune-activated state has been unclear. Saliva is a characteristic specimen different from other body fluids. In this study, we analysed salivary NP and related pterin compounds, BP and MP and revealed some of its feature. High-performance liquid chromatography (HPLC) analysis of saliva and plasma obtained from 26 volunteers revealed that salivary NP existed mostly in its fully oxidized form. The results suggested that salivary NP as well as BP would mostly originate from the oral cavity, perhaps the salivary glands, and that salivary NP levels might not reflect those in the plasma. We also found that a gender difference existed in correlations between concentrations of salivary total concentrations of NP (tNP) and BP (tBP). HPLC analysis of saliva obtained from 5 volunteers revealed that the concentrations of salivary tNP as well as tBP fluctuated in an irregular fashion in various individuals. MP, a diastereomer of NP, might have come from oral cavity NP itself or its precursor. These results indicated that the nature of salivary NP might be different from that of NP in the blood or urine.

Tetrahydrobiopterin Supplementation: Elevation of Tissue Biopterin Levels Accompanied by a Relative Increase in Dihydrobiopterin in the Blood and the Role of Probenecid-Sensitive Uptake in Scavenging Dihydrobiopterin in the Liver and Kidney of Rats.

Tetrahydrobiopterin (BH4) is an essential cofactor of nitric oxide synthase (NOS) and aromatic amino acid hydroxylases. BH4 and 7,8-dihydrobiopterin (BH2) are metabolically interchangeable at the expense of NADPH. Exogenously administered BH4 can be metabolized by the body, similar to vitamins. At present, synthetic BH4 is used as an orphan drug for patients with inherited diseases requiring BH4 supplementation. BH4 supplementation has also drawn attention as a means of treating certain cardiovascular symptoms, however, its application in human patients remains limited. Here, we tracked biopterin (BP) distribution in blood, bile, urine, liver, kidney and brain after BH4 administration (5 mg/kg rat, i.v.) with or without prior treatment with probenecid, a potent inhibitor of uptake transporters particularly including organic anion transporter families such as OTA1 and OAT3. The rapid excretion of BP in urine was driven by elevated blood concentrations and its elimination reached about 90% within 120 min. In the very early period, BP was taken up by the liver and kidney and gradually released back to the blood. BH4 administration caused a considerable decrease in the BH4% in blood BP as an inevitable compensatory process. Probenecid treatment slowed down the decrease in blood BP and simultaneously inhibited its initial rapid excretion in the kidney. At the same time, the BH4% was further lowered, suggesting that the probenecid-sensitive BP uptake played a crucial role in BH2 scavenging in vivo. This suggested that the overproduced BH2 was taken up by organs by means of the probenecid-sensitive process, and was then scavenged by counter-conversion to BH4 via the BH4 salvage pathway. Taken together, BH4 administration was effective at raising BP levels in organs over the course of hours but with extremely low efficiency. Since a high BH2 relative to BH4 causes NOS dysfunction, the lowering of the BH4% must be avoided in practice, otherwise the desired effect of the supplementation in ameliorating NOS dysfunction would be spoiled.

Analysis of neonatal hyperphenylalaninemia screening and therapeutic effect in Xuzhou from 2003 to 2015

Objective To investigate the prevalence, clinical classification, treatment and prognosis of neonatal hyperphenylalaninemia(HPA) in Xuzhou area, China. Methods Infants born between July 1, 2003 and July 1, 2015 in Xuzhou area were investigated. Heel blood samples of neonates were collected at 72 hours after birth, and the concentration of blood phenylalanine(Phe) was determined by fluorescent quantitative method in Xuzhou Maternity and Child Health Care Station Neonatal Disease Screening Center. Differential diagnosis was performed in all 265 cases diagnosed as HPA by urinary pterin analysis and dihydropteridine reductase activity determination. The blood Phe concentration and mental development were followed up regularly in infants with HPA. Mutations of phenylalanine hydroxylase (PAH) gene were analyzed by gene sequencing. The relationship between blood Phe concentration and mental development was analyzed by Bivariate correlation analysis. Results (1) The prevalence of HPA in neonates in Xuzhou was l/4 635. Among the 265 confirmed HPA cases, 260 cases(98.11%) had PAH deficiency, including 90(33.96%) classical phenylketonuria(PKU), 84(31.70%) mild PKU and 86(32.45%) mild HPA. The other five patients(1.89%) diagnosed with tetrahydrobiopterin (BH4) deficiency all had 6-pyruvoyl tetrahydropteirn synthase(PTPS) deficiency. (2) Among the 265 HPA cases, 26 cases refused any treatment, including five cases of PTPS deficiency and 21 cases of PKU. Of the five patients with PTPS deficiency, two died and the other three had normal mental and physical development. Twenty-one PKU patients who refused treatment had mental retardation of various degrees. Among 153 PKU patients who received medical treatment, three died and 12 were lost to follow-up. (3) For 138 PKU patients who received dietary treatment and follow-up, the ages at the last visit were two months to 12 years, 116 of them had normal mental development, the remaining 22 patients had mental retardation, and a negative correlation was observed between mental development and the average Phe concentration. (4) Thirty-five patients with PAH deficiency underwent gene sequencing, and 22 kinds of mutations of PAH gene were detected. Conclusions The prevalence of HPA in Xuzhou area is higher than the average national level. With early diagnosis and standard treatment, most of PKU neonates can have normal mental development. Phe level control is an important factor for mental development. Key words: Phenylketonurias; Phenylalanine hydroxylase; Biopterin; Neonatal screening; Intelligence; Treatment outcome

A simple method to prepare a biopterin sensor chip applicable to crude samples

Biopterin (BP), which is structurally similar to flavin, is potentially associated with a UV-B photoreceptor yet to be identified. The stagnation of research on the BP-associated photoreceptor is because of the lack of a simple method to detect the protein that interacts with BP. We successfully immobilized BP by conducting a coupling reaction between one of the activated hydroxyl groups of BP and pre-introduced primary amino groups on the CM5 surface at a pH higher than usual. This enabled us to detect the protein that interacts with BP using Biacore measurements. The validity of the BP sensor chip was tested by applying the chip to fractions obtained by subjecting a crude extract of the paraflagellar body (PFB), which is the photosensory organelle of Euglena, to an anion exchange column; this test was performed because PFB was spectroscopically shown to contain a pterin binding protein. The BP sensor chip was useful to detect an unknown BP-binding protein in a crude sample.

The significance of neopterin and biopterin concentrations at presentation in haematological malignancies.

Urinary neopterin and biopterin concentrations were measured in 32 healthy controls and 53 patients with newly diagnosed haematological malignancies classified and staged by accepted criteria. The neopterin concentrations were only significantly raised in chronic lymphocytic leukaemia at stages III-IV. Total biopterin concentrations after oxidation with iodine at acid pH were decreased in chronic lymphocytic leukaemia stages O-II, multiple myeloma, and acute myeloid leukaemia but not in chronic lymphocytic leukaemia stages III-IV. Although of research interest, neopterin concentrations proved of little prognostic value at presentation, but taken with the biopterin concentration they may be useful for the assessment of tumour activity.

Quantification of Tetrahydrobiopterin (BH4), Dihydrobiopterin (BH2) and Biopterin (BP) in Mouse Brain and Intestines After Ischemic Injury by Liquid Chromatography-Electrospray Tandem Mass Spectrometry (LC-ESI-MS/MS)

Quantification of Tetrahydrobiopterin (BH4), Dihydrobiopterin (BH2) and Biopterin (BP) in Mouse Brain and Intestines After Ischemic Injury by Liquid Chromatography-Electrospray Tandem Mass Spectrometry (LC-ESI-MS/MS)

Determination of marker pteridins and biopterin reduced forms, tetrahydrobiopterin and dihydrobiopterin, in human urine, using a post-column photoinduced fluorescence liquid chromatographic derivatization method

A liquid chromatographic method for the simultaneous analysis of marker pteridins and biopterin reduced forms, in urine samples is proposed. A Zorbax Eclipse XDB-C18 column was used for the chromatographic separation, using a 98/2 (v/v), citrate buffer (pH 5.5)-acetonitrile mobile phase, in isocratic mode. A post-column photoderivatization was carried out with an on-line photoreactor, located between a diode array detector (DAD) and a fast scanning fluorescence detector (FSFD). Neopterin (NEO), biopterin (BIO), pterin (PT) and dihydrobiopterin (BH2) were determined by measuring native fluorescence, using the photoreactor in OFF-mode, and tetrahydrobiopterin (BH4) was determined by measuring of the induced fluorescence of the generated photoproducts, using the photoreactor in ON-mode. In addition, Creatinine (CREA), as a reference of metabolites excrection in urine, was simultaneously determined using the DAD detector. Detection limits were 0.2, 13.0, 0.3, 0.3 and 3.5 ng mL −1, for NEO, BH2, BIO, PT and BH4, respectively, and 0.4 μg mL −1 for CREA. Ratio values for NEO/CREA, PT/CREA, BH4/CREA, BH2/CREA, NEO/BIO and BIO total/CREA, in urine samples, of healthy children and adults, phenylketonuric children and infected mononucleosis children, are reported. A comparative study, about the mean values obtained for each of the compounds, by the present procedure and by the classical iodine oxidation method (Fukushimás method), has been performed, in urine samples belonging to healthy volunteers. The values obtained were BH4/CREA: 0.41, BH2/CREA: 0.31 and BIO total/CREA: 0.73, by the proposed method, and BH4/CREA: 0.35, BH2/CREA: 0.20 and BIO total/CREA: 0.48, by iodine oxidation method.

The investigation of differential diagnostic development and incidence of tetrahydrobiopterin deficiency

To investigate the development of differential diagnosis of tetrahydrobiopterin (BH4) deficiency among patients with hyperphenylalaninemia (HPA) in provinces or cities of China and to investigate the incidence of BH4 deficiency. Of the thirteen hundreds and ninety-two patients with HPA received, the differential diagnosis for BH4 deficiency during 1993 - 2007 were enrolled in this study. Of which, 591 patients came from outpatient and 801 patients' samples from other provinces or cities were sent to author's laboratory to investigate the case number of differential diagnosis for BH4 deficiency in provinces or cities of China according to the data from both outpatient case histories and laboratory as to investigating the development of differential diagnosis in the whole country. To discuss the diagnostic criteria for BH4 deficiency was according to the results of urinary pterin analysis, determination of dihydropteridine reductase (DHPR) activity and the tetrahydrobiopterin loading test as well as to get the incidence of BH4 deficiency and find some provinces or cities with higher incidence of BH4 deficiency in China. (1) The number of HPA patients, who were performed by urinary pterin analysis and the determination of DHPR activity, were remarkably increased in last three years (2005 - 2007). The patient numbers of both urinary pterin analysis and DHPR activity determination were 217 and 198 respectively in 2005. And in 2007 they increased to 511 and 458, which was about 2.3 times than that in 2005. The patients came from 29 provinces or cities in 2007. (2) The urinary biopterin and biopterin percent were key marks for diagnosis of 6-pyruvoyl tetrahydropterin synthase (PTPS) deficiency. The less than 5% [(1.41 +/- 1.10)%] biopterin percent and very low biopterin level [(0.14 +/- 0.17) mmol/mol Cr] were found in 96.83% (61/63) patients with PTPS deficiency in this study. The blood phenylalanine level was remarkably decreased to normal range at 2 - 6 hours after BH4 loading test. The very low DHPR activity was a final diagnostic mark for DHPR deficiency. The very low DHPR activities of 0.27 nmol/(min x 5 mm disc) (6.11% - 7.00% of normal controls) were found in two patients with DHPR deficiency in this study. (3) The incidences of PTPS deficiency and DHPR deficiency among 1392 patients with hyperphenylalaninemia were 8.41% (117/1392) and 0.18% (2/1108) respectively. About 67.23% (80/119) patients with BH4 deficiency came from the south of Yangtze liver. The 80% (8/10) provinces or cities with higher incidence of BH4 deficiency are located in eastern and southern China. The incidence of PTPS deficiency among patients with HPA and normal newborns was 10.81% (8/74) and 0.007 per thousand (8/1,121,429) respectively in Shanghai, China according to data from neonatal screening. The awareness of differential diagnosis for BH4 deficiency from clinic pediatricians has been increased in most provinces or cities of China in last three years, but it should be more strengthened.

New Results on the Photochemistry of Biopterin and Neopterin in Aqueous Solution

New photochemical studies of the reactivity of biopterin (BPT) and neopterin (NPT) in acidic (pH = 5.5) and alkaline (pH = 10.5) aqueous solutions at 350 nm and room temperature were performed. The photochemical properties of BPT are of particular interest because the photolysis of this compound takes place in the white skin patches of patients affected by vitiligo. The photochemical reactions were followed by UV/VIS spectrophotometry, HPLC, electrochemical measurement of dissolved O(2) and enzymatic methods for hydrogen peroxide (H(2)O(2)) and superoxide anion (O(2)(-)) determinations. When BPT or NPT are exposed to UVA radiation, a red intermediate, very likely 6-formyl-5,8-dihydropterin, is generated in an O(2)-independent process. That product is rapidly oxidized on admission of O(2) to yield 6-formylpterin and H(2)O(2). When the photolysis takes place in aerobic conditions, no additional pathways exist. On the other hand, in the absence of O(2), the intermediate generated is not stable and leads to the formation of many products. O(2)(-) is also generated during photo-oxidation of BPT and NPT. The quantum yields of reactant consumption depends on the O(2) concentration: the higher the O(2) concentration, the lower the quantum yields. This behavior is discussed in connection with the excited state of the pterins.

LC determination of biopterin reduced forms by UV-photogeneration of biopterin and fluorimetric detection

An off-line photoirradiation LC fluorimetric method to determine tetrahydrobiopterin (BH 4), by photogeneration of biopterin (BIO), is described, as an alternative way to the chemical oxidation procedure. To minimize the uncontrolled BH 4 oxidation, due to environmental oxygen, an antioxidant, dithiothreitol (DTT), was used. The acidity of the medium, as well as the presence of hydrogen peroxide, affects the rate of the photoreaction and the nature of the obtained fluorescent photoproducts. The best conditions were achieved by irradiation in hydrochloric acid (0.2 M) medium, in presence of 100 mM hydrogen peroxide, and using an irradiation time of 20 min. The method was tested in the analysis of serum samples containing BH 4, and recoveries between 89 and 105% were found. Also, the proposed method allows the resolution of BH 4 and BIO, in the same sample, by injection of non-irradiated and irradiated sample aliquots in the chromatographic system.

Singlet Oxygen (O2(1Δg)) Quenching by Dihydropterins

Pterins belong to a class of heterocyclic compounds present in a wide range of living systems. They participate in relevant biological functions and are involved in different photobiological processes. Dihydropterins are one of the biologically active forms of pterins. The photoinduced production and quenching of singlet oxygen (1O2) by a series of dihydropterins (7,8-dihydrobiopterin (DHBPT), 7,8-dihydroneopterin (DHNPT), 6-formyl-7,8-dihydropterin (FDHPT), sepiapterin (SPT), 7,8-dihydrofolic acid (DHFA), and 7,8-dihydroxanthopterin (DHXPT)) in aqueous solution at physiological pH ( approximately 7) were investigated, and the quantum yields of 1O2 production (PhiDelta) and rate constants of total quenching (kt) of 1O2 were determined. Studied compounds do not produce 1O2 under UV-A irradiation and are very efficient 1O2 quenchers. The chemical reactions between 1O2 and dihydropterin derivatives were investigated, and the corresponding rate constants (kr) were found to be particularly high. The oxidized pterin derivatives, biopterin (BPT), neopterin (NPT), 6-formylpterin (FPT), and folic acid (FA), were identified and quantified during the reaction of 1O2 with DHBPT, DHNPT, FDHPT, and DHFA, respectively. Besides the oxidation of the dihydropyrazine ring to yield the corresponding oxidized pterins, a second oxidation pathway, leading to fragmentation of the dihydropterin and formation of non-pterinic products, was identified. Mechanisms and biological implications are discussed.

Determination of neopterin and biopterin in pedo-urine by HPLC

目的 建立HPLC法测定小儿高苯丙氨酸血症(HPA)患者尿液中新蝶呤(N)和生物蝶呤(B)含量的方法,以帮助临床对经典型苯丙酮尿症(PKU)和四氢生物蝶呤(BH4)缺乏症的诊断和鉴别诊断.方法 选用Cosmosil 5C18-AR-Ⅱ色谱柱(4.6 I.D.×250 mm),甲醇-水(8∶92)为流动相,用三维荧光检测器检测.结果 新蝶呤线性范围为1.60～40.0 ng/μl,生物蝶呤线性范围为1.73～43.2 ng/μl;最小检测限为0.16 ng/μl和0.1728 ng/μl.样品测定的变异系数(CV)值分别为2.18%和1.70%;原尿样品前处理时氧化的最佳时间为30 min;原尿样品不便于保存,氧化后可于室温或4℃冰箱保存3 d.结论 本方法准确、可靠、简便易行,灵敏度高,方法学实验结果满意,适用于临床HPA患儿的鉴别诊断。

The mechanisms of extracellular-signal regulated protein kinase pathway in biopterin induction in rats with endotoxic shock

To observe the influence of treatment with the inhibitor of extracellular-signal regulated protein kinase (ERK) signal transduction pathway on the expression of biopterin/nitric oxide (NO) as well as the activation of nuclear factor-kappaB (NF-kappaB), and to clarify the potential cross-talk regulation mechanisms between ERK and NF-kappaB pathway in biopterin-mediated NO induction in rats with endotoxic shock. Using an endotoxic shock model, 60 male Wistar rats were randomly divided into normal controls (n = 8), endotoxic shock group (n = 32) and PD98059 treatment group (n = 20). At serial time points animals in each group were sacrificed, and tissue samples from liver, lungs as well as kidneys were harvested to detect NF-kappaB activity, guanosine triphosphate-cyclohydrolase (GTP-CHI) and inducible nitric oxide synthase (iNOS) mRNA expression. Biopterin and NO levels in plasma and tissues were also assayed. It was found that after lipopolysaccharide (LPS) challenge, GTP-CHI mRNA expression and biopterin levels significantly elevated in liver, lungs and kidneys, keeping at high values up to 24 h, so did the values of iNOS mRNA expression and NO levels. NF-kappaB DNA binding activity was enhanced rapidly in various tissues, peaking at 2 h after LPS challenge. Treatment with PD98059, an inhibitor of ERK signal transduction pathway, could significantly inhibit GTP-CHI mRNA expression in kidneys, and GTP-CHI mRNA expression in liver and lungs showed certain down-regulation tendency. At the same time, biopterin level was significantly decreased in plasma, liver and kidneys at 12 h. Similarly, iNOS/NO induction at early stage markedly decreased in various tissues. In addition, treatment with PD98059 reduced NF-kappaB DNA binding activity in liver, lungs, as well as kidneys at 2-6 h, 2 h, 24 h and 24 h after LPS challenge, respectively. Inhibition of ERK pathway could partially inhibit the production of biopterin/NO as well as the activation of NF-kappaB pathway, which indicated that cross-talk regulation seems to be existed between ERK and NF-kappaB pathway, and they might be involved in the regulatory process of biopterin-mediated nitric oxide induction in rats with endotoxic shock.

Serum amino acids, biopterin and neopterin during long-term immunotherapy with interferon-alpha in high-risk melanoma patients

Immunotherapy with interferon-alpha (IFN-α) induces neuropsychiatric side effects, most notably depression. One of the presumed pathophysiological mechanisms is an effect on tryptophan metabolism. As tryptophan is the precursor of serotonin, decreased availability of tryptophan to the central nervous system could result in serotonin deficiency. Tetrahydrobiopterin (BH (4)) is a cofactor for one of the enzymes synthesizing serotonin. We conducted an exploratory study into the serum concentrations of large neutral amino acids (AA), biopterin (BIOP) and neopterin (NEOP), of 67 patients with high-risk melanoma, who were either treated with two different doses of IFN-α or were part of an observation-only control group. We found evidence for IFN-α to decrease concentrations of all AA except phenylalanine. The decrease in tryptophan concentration was most prominent and consistent. These changes persisted throughout a year of maintenance treatment. Concentrations of NEOP rose sharply, whereas, those of BIOP did not change. Except for the increase in NEOP and the increase in the ratio between phenylalanine (PHE) and tyrosine (TYR), no support for derangement in BH (4) metabolism was found. The increase in the ratio between PHE and TYR suggests inhibition of the enzyme phenylalanine hydroxylase. Patients with IFN-α induced anxiety and depression had higher pretreatment concentrations of NEOP. Changes in tryptophan metabolism may play a role in the pathophysiology of the neuropsychiatric side effects of IFN-α, and further research into the predictive potential of NEOP is warranted.

Plasma pteridine concentrations in patients with chronic renal failure.

Pteridine metabolism is impaired in the uraemic state. This may affect cardiovascular function and contribute to malnutrition. We wished to clarify further the impact of impaired pteridine metabolism. Using the HPLC method, the plasma concentrations of endogenous pteridines were determined in 64 patients with chronic renal failure (33 on intermittent haemodialysis (HD) treatment vs 31 not yet on renal replacement therapy), and in 18 healthy controls. The patients were classified into three groups on the basis of creatinine clearance (Ccr): group (a), Ccr >60 ml/min; group (b), Ccr=10-60 ml/min; group (c), all patients receiving HD. Total neopterin (NP) and biopterin (BP) levels and the NP/BP ratio (a biomarker for macrophage activity) were significantly higher, whereas tetrahydrobiopterin (BH(4))/dihydrobiopterin (BH(2)) ratio (a biomarker for nitric oxide synthase and phenylalanine hydroxylase activities) was significantly lower in group (c) (118.9+/-11.7 ng/ml, 18.8+/-1.2 ng/ml, 6.79+/-0.53, and 0.26+/-0.06) than in healthy subjects (5.17+/-0.29 ng/ml, 2.83+/-0.19 ng/ml, 1.92+/-0.13, and 1.15+/-0.11; P<0.01). These significant differences were also observed between control and group (b) (12.4+/-2.20 ng/ml, 4.48+/-0.36 ng/ml, 2.81+/-0.48, and 0.74+/-0.08; P<0.01). In groups (a) and (b), significant negative correlations were found between Ccr and the total NP level (r=-0.663, P<0.01), the total BP level (r=-0.492, P<0.01), the BH(2) level (r=-0.677, P<0.01), and the NP/BP ratio (r=-0.493, P<0.01). Conversely, significant positive correlations were found between Ccr and the BH(4)/BH(2) ratio (r=0.602, P<0.01). The reduction of quinoid-type BH(2) to BH(4) is modified in patients with advanced chronic renal failure, before and after the initiation of regular HD treatment. These metabolic alterations may play a role in the impaired macrophage, endothelial constitutive nitric oxide synthase, or phenylalanine hydroxylase (PH) activities observed in such patients.

Simultaneous Fluorimetric Determination of Pteridin Derivatives: Comparison between Synchronous, Partial Least-Squares, and Hybrid Linear Analysis Methods

Several methods are described for the simultaneous determination of binary mixtures of xanthopterin (XAN) and isoxanthopterin (ISO) and of binary mixtures of xanthopterin and biopterin (BIO). The total luminiscence information from each compound has been used to optimize the most adequate analytical signal. A synchronous spectrofluorometric univariate procedure to analyze XAN and ISO is proposed. The procedure is compared with two multivariate procedures based on partial least-squares (PLS-1) and hybrid linear analysis (HLA/XS), by using synchronous spectral data as analytical signals. For the resolution of binary mixtures of XAN and BIO, a comparison between the predictive ability of the multivariate calibration methods, PLS-1 and HLA/XS, on two spectral data sets, excitation and emission spectra, has been performed. The calculation of the net analyte signal (NAS) by the HLA/XS method allows the determination of selectivity and sensitivity in each case. The proposed procedures are validated in the determination of several mixtures of these compounds, and the error values in a test set are reported.

Analysis of pteridines and creatinine in urine by HPLC with serial fluorimetric and photometric detectors

Although pteridines are excreted in the urine of normal healthy persons, levels of some of these compounds seem to be modified by several diseases. Creatinine is considered to be the best reference for study of the excretion of these markers in urine. A fast, very sensitive, and precise HPLC method with ultraviolet and fluorimetric detection has been established for the simultaneous determination of pterin-6-carboxylic (CAR), neopterin (NEO), xanthopterin (XAN), isoxanthopterin (ISO), biopterin (BIO), and creatinine (CREA) in urine. The influence of conditions such as mobile-phase composition and flow rate, have been studied. 0.015m Tris-HCl-10−3 m NaCl buffer solution, pH 6.8, was selected as mobile phase. These five pteridine derivatives are well resolved in less than six minutes. CREA is determined by photometric detection at 230 nm and pteridines by fluorimetric detection at 444 nm, with excitation at 280 nm. The detection limits are below 25 pg for all pteridines and 0.30 ng for creatinine. The method has been applied to the determination of these compounds in urine. A non-clean-up concentration step is necessary before the separation. The urine sample is oxidized before HPLC injection. Values for the pteridine-to-creatinine ratios found for two groups of healthy persons (younger and older than 30 years) are reported.

Antioxidative activity of 5,6,7,8-tetrahydrobiopterin and its inhibitory effect on paraquat-induced cell toxicity in cultured rat hepatocytes.

The in vitro antioxidative activity of 5,6,7,8-tetrahydrobiopterin (BPH4) was measured and the ability of BPH4 to prevent paraquat-induced cell damage was examined in cultured hepatocytes. The scavenging activity of BPH4 against superoxide anion radicals was assayed in two systems, i.e., xanthine/xanthine oxidase (X/XOD) and rat macrophage/phorbol myristate acetate (M psi/PMA) radical-generating systems. BPH4 showed an extremely strong superoxide anion radical-scavenging activity in both assay systems. Biopterin (BP) itself did not show any activity in the X/XOD system, but was effective in the M psi/PMA system. The antioxidative activities of BPH4 against both superoxide anion and hydroxyl radicals were confirmed by spin trapping-ESR spectrometry. BPH4 also protected rat brain homogenate against auto-oxidation. We further examined the effect of BPH4 on paraquat-induced cell toxicity in cultured rat hepatocytes. The paraquat-induced elevation of the release of lactate dehydrogenase (LDH), a marker enzyme for cytotoxicity from cultured hepatocytes was suppressed by BPH4 in a dose-dependent manner. The elevation of lipid peroxides simultaneously induced by paraquat was also inhibited by BPH4 in the same manner. These results suggest that BPH4 might be useful in the treatment of various diseases whose pathogenesis is active oxygen-related.

Neurotransmitter Levels in Cerebrospinal Fluid in Relation to Severity of Symptoms and Response to Medical Therapy in Parkinson's Disease

Determinations of biopterin (BP), homovanilic acid (HVA), glutamic acid (GTA), and glutamine (GT) levels in cerebrospinal fluid (CSF) obtained through a lumbar tap were performed in 20 parkinsonian patients in different stages of evolution and without medication. In patients with motor symptoms not related to Parkinson's disease (dystonia, dyskinesia and essential tremor) (n = 4). In 7 other neurological patients subjected to spinal tap for diagnostic procedures neurotransmitters were also determined and taken as control groups. In 14 of the patients with Parkinson's disease, the symptoms were evaluated using conventional scales (UPDS, NYPDS, NWPDS, Schwab and England, and Hoehn and Yahr scale). The amplitude and the frequency of tremor were quantitatively evaluated through a single plane accelerometer Grass SP-1, akinesia was measured through reaction time to auditory stimuli, and rigidity through the speed of lineal movement. Evaluations were performed with the patient not on any medication for 1 week and repeated 1 h after the intake of 250 mg of 200/50 L-dopa/carbidopa preparation (Sinemet) and on a different day after the intake of biperiden (Akineton) 6 mg/day. Differences in neurotransmitter or metabolites levels between Parkinson's disease and control groups were determined through an independent Student's t test. Correlation between severity of symptoms in the scales and for each individual symptom measured through the quantitative tests and the levels of neurotransmitters in CSF were evaluated through the Pearson correlation analysis test. Modifications in the motor performance after administration of Sinemet and Akineton, and the levels of neurotransmitters were indirectly determined. RESULTS. (1) There were significant differences between the levels of BP and GT in patients with Parkinson's disease and control groups, (2) lower GTA levels correlated with more severe rigidity and akinesia, and with the best response to the administration of L-dopa and may be an important marker for prognosis, and (3) lower levels of GT correlated with least akinesia, but not with tremor, which may indicate that the akinesia depends on other biochemical abnormalities besides dopamine depletion.