Sorting for secreted molecule production using a biosensor-in-microdroplet approach

Sorting large libraries of cells for improved small molecule secretion is throughput limited. Here, we combine producer/secretor cell libraries with whole-cell biosensors using a microfluidic-based screening workflow. This approach enables a mix-and-match capability using off-the-shelf biosensors through either coencapsulation or pico-injection. We demonstrate the cell type and library agnostic nature of this workflow by utilizing single-guide RNA, transposon, and ethyl-methyl sulfonate mutagenesis libraries across three distinct microbes (Escherichia coli, Saccharomyces cerevisiae, and Yarrowia lipolytica), biosensors from two organisms (E. coli and S. cerevisiae), and three products (triacetic acid lactone, naringenin, and L-DOPA) to identify targets improving production/secretion.

Cost-Effective Production of L-DOPA by Tyrosinase-Immobilized Polyhydroxyalkanoate Nanogranules in Engineered Halomonas bluephagenesis TD01

3,4-dihydroxyphenyl-L-alanine (L-DOPA) is a preferred drug for Parkinson's disease, with an increasing demand worldwide that mainly relies on costly and environmentally problematic chemical synthesis. Yet, biological L-DOPA production is unfeasible at the industrial scale due to its low L-DOPA yield and high production cost. In this study, low-cost Halomonas bluephagenesis TD01 was engineered to produce tyrosinase TyrVs-immobilized polyhydroxyalkanoate (PHA) nanogranules in vivo, with the improved PHA content and increased immobilization efficiency of TyrVs accounting for 6.85% on the surface of PHA. A higher L-DOPA-forming monophenolase activity of 518.87 U/g PHA granules and an L-DOPA concentration of 974.36 mg/L in 3 h catalysis were achieved, compared to those of E. coli. Together with the result of L-DOPA production directly by cell lysates containing PHA-TyrVs nanogranules, our study demonstrated the robust and cost-effective production of L-DOPA by H. bluephagenesis, further contributing to its low-cost industrial production based on next-generation industrial biotechnology (NGIB).

Active tyrosine phenol-lyase aggregates induced by terminally attached functional peptides in Escherichia coli

The formation of inclusion bodies (IBs) without enzyme activity in bacterial research is generally undesirable. Researchers have attempted to recovery the enzyme activities of IBs, which are commonly known as active IBs. Tyrosine phenol-lyase (TPL) is an important enzyme that can convert pyruvate and phenol into 3,4-dihydroxyphenyl-L-alanine (L-DOPA) and IBs of TPL can commonly occur. To induce the correct folding and recover the enzyme activity of the IBs, peptides, such as ELK16, DKL6, L6KD, ELP10, ELP20, L6K2, EAK16, 18A, and GFIL16, were fused to the carboxyl terminus of TPL. The results showed that aggregate particles of TPL-DKL6, TPL-ELP10, TPL-EAK16, TPL-18A, and TPL-GFIL16 improved the enzyme activity by 40.9%, 50.7%, 48.9%, 86.6%, and 97.9%, respectively. The peptides TPL-DKL6, TPL-EAK16, TPL-18A, and TPL-GFIL16 displayed significantly improved thermostability compared with TPL. L-DOPA titer of TPL-ELP10, TPL-EAK16, TPL-18A, and TPL-GFIL16, with cells reaching 37.8 g/L, 53.8 g/L, 37.5 g/L, and 29.1 g/L, had an improvement of 111%, 201%, 109%, and 63%, respectively. A higher activity and L-DOPA titer of the TPL-EAK16 could be valuable for its industrial application to biosynthesize L-DOPA.

Highly efficient biocatalytic synthesis of L-DOPA using in situ immobilized Verrucomicrobium spinosum tyrosinase on polyhydroxyalkanoate nano-granules

L-DOPA (3,4-dihydroxyphenyl-L-alanine) is a preferred drug for Parkinson's disease, and is currently in great demand every year worldwide. Biocatalytic conversion of L-tyrosine by tyrosinases is the most promising method for the low-cost production of L-DOPA in both research and industry. Yet, it has been hampered by low productivity, low conversion rate, and low stability of the biocatalyst, tyrosinase. An alternative tyrosinase TyrVs from Verrucomicrobium spinosum with more efficient expression in heterologous host and better stability than the commercially available Agaricus bisporus tyrosinase was identified in this study. Additionally, it was prepared as a novel nano-biocatalyst based on the distinct one-step in situ immobilization on the surface of polyhydroxyalkanoate (PHA) nano-granules. The resulting PHA-TyrVs nano-granules demonstrated improved L-DOPA-forming monophenolase activity of 9155.88 U/g (Tyr protein), which was 3.19-fold higher than that of free TyrVs. The nano-granules also exhibited remarkable thermo-stability, with an optimal temperature of 50 °C, and maintained more than 70% of the initial activity after incubation at 55 °C for 24 h. And an enhanced affinity of copper ion was observed in the PHA-TyrVs nano-granules, making them even better biocatalysts for L-DOPA production. Therefore, a considerable productivity of L-DOPA, amounting to 148.70 mg/L h, with a conversion rate of L-tyrosine of 90.62% can be achieved by the PHA-TyrVs nano-granules after 3 h of biocatalysis under optimized conditions, without significant loss of enzyme activity or L-DOPA yield after 8 cycles of repeated use. Our study provides an excellent and robust nano-biocatalyst for the cost-effective production of L-DOPA.

Biochemical characterization and spatio-temporal analysis of the putative L-DOPA pathway in Mucuna pruriens

Transcriptome analysis and biochemical characterization of the putative l-3,4-dihydroxyphenylalanine (l-DOPA) pathway in Mucuna pruriens (L.) DC have been performed. Spatio-temporal quantification of the putative l-DOPA biosynthetic pathway genes and its correlation with respective metabolites was established. l-tyrosine, l-DOPA, and dopamine from all plant parts were quantified. The de novo transcriptome analysis was performed using leaves of the selected M. pruriens mutant T-IV-9 during maturity. The putative L-DOPA pathway and its regulatory genes were retrieved from transcriptome data and the L-DOPA pathway was biochemically characterized. The spatial and temporal gene expression for the L-DOPA pathway was identified with respect to the chemical constituents. L-tyrosine, L-DOPA, and dopamine contents were highest in leaves during maturity (about 170-day-old plants). The polyphenol oxidase (PPO) was highly expressed in tender stems (230-fold higher as compared to seeds) as well as a high L-DOPA content. The PPO gene was highly expressed in leaves (3367.93 in FPKM) with a 79-fold increase compared to control plants during maturity. L-DOPA was found in every part with varied levels. The highest L-DOPA content was found in mature dried seed (3.18-5.8%), whereas the lowest amount was recorded in mature and dried leaves. The reproductive parts of the plant had a higher amount of L-DOPA content (0.9-5.8%) compared to the vegetative parts (0.2-0.91%). Various amino acid transporters and permeases were expressed in M. pruriens. The transcripts of dopa decarboxylase (DDC) were found in almost all parts of the plant, but its higher content was limited to the leaf.

Tetrahydrobiopterin biosynthesis as an off-target of sulfa drugs

The introduction of sulfa drugs for the chemotherapy of bacterial infections in 1935 revolutionized medicine. Although their mechanism of action is understood, the molecular bases for most of their side effects remain obscure. Here, we report that sulfamethoxazole and other sulfa drugs interfere with tetrahydrobiopterin biosynthesis through inhibition of sepiapterin reductase. Crystal structures of sepiapterin reductase with bound sulfa drugs reveal how structurally diverse sulfa drugs achieve specific inhibition of the enzyme. The effect of sulfa drugs on tetrahydrobiopterin-dependent neurotransmitter biosynthesis in cell-based assays provides a rationale for some of their central nervous system-related side effects, particularly in high-dose sulfamethoxazole therapy of Pneumocystis pneumonia. Our findings reveal an unexpected aspect of the pharmacology of sulfa drugs and might translate into their improved medical use.

Production of 3,4-dihydroxy L-phenylalanine by a newly isolated Aspergillus niger and parameter significance analysis by Plackett-Burman design

BACKGROUND

The amino acid derivative 3,4-dihydroxy L-phenylalanine (L-dopa) is gaining interest as a drug of choice for Parkinson's disease. Aspergillus oryzae is commonly used for L-dopa production; however, a slower growth rate and relatively lower tyrosinase activity of mycelia have led to an increasing interest in exploiting alternative fungal cultures. In the present investigation, we report on the microbiological transformation of L-tyrosine to L-dopa accomplished by a newly isolated filamentous fungus Aspergillus niger.

RESULTS

The culture A. niger (isolate GCBT-8) was propagated in 500 ml Erlenmeyer flasks and the pre-grown mycelia (48 h old) were used in the reaction mixture as a source of enzyme tyrosinase. Grinded mycelia gave 1.26 fold higher L-dopa production compared to the intact at 6% glucose (pH 5.5). The rate of L-tyrosine consumption was improved from 0.198 to 0.281 mg/ml. Among the various nitrogen sources, 1.5% peptone, 1% yeast extract and 0.2% ammonium chloride were optimized. The maximal L-dopa was produced (0.365 mg/ml) at 0.3% potassium dihydrogen phosphate with L-tyrosine consumption of 0.403 mg/ml.

CONCLUSION

Over ~73% yield was achieved (degree of freedom 3) when the process parameters were identified using 2k-Plackett-Burman experimental design. The results are highly significant (p ≤ 0.05) and mark the commercial utility (LSD 0.016) of the mould culture which is perhaps the first ever report on L-dopa production from A. niger.

[Recombinant adenovirus-mediated expression of tyrosine hydroxylase in 293 cells and activity assay of the expressed protein in vitro by capillary electrophoresis]

OBJECTIVE

To construct a recombinant adenovirus for carry tyrosine hydroxylase (TH) gene and expressing bioactive TH protein in the animal model of Parkinson disease.

METHODS

The TH gene was inserted into the shuttle plasmid, which was transformed into E.coli BJ-5183 for homologous recombination with the adenovirus genome. 293 cells were transfected with the recombinant adenovirus genome to obtain the recombinant virus, and the transcription and expression of TH were determined by RT-PCR and immunofluorescence assay, respectively. The production of L-DOPA in the in vitro reaction system was determined using capillary electrophoresis.

RESULTS

We have successfully constructed the recombinant adenovirus. The TH mRNA and the corresponding protein were detected by RT-PCR and immunofluoresence assay in 293 cells. L-DOPA was also detected in the reaction system.

CONCLUSION

The adenovirus constructed allows efficient expression of bioactive TH protein in vitro, which provides a basis for future study of gene therapy of Parkinson disease in animal models.

[Monoamine synthesis by non-monoaminergic neurons: illusion of reality]

Apart from monoaminergic neurons possessing the whole set of enzymes of monoamine synthesis from the precursor amino acid, the neurons expressing individual enzymes of monoamine synthesis have been discovered in the mid-eighties. Most numerous monoenzymatic neurons express individual enzymes of dopamine (DA), thyrosine hydroxylase (TH) or aromatic L-amino acid decarboxylase (AADC). Functional characteristics and the functional significance of the monoenzymatic neurons have been evaluated in a series of our studies, mainly of the hypothalamic arcuate nucleus (AN), one of the most important DA-ergic centers of the brain. It has been demonstrated that the AN of rats contains numerous monoenzymatic neurons. Their portion among the neurons expressing enzymes of DA synthesis exceeded 99 % whereas it decreased continuously in postnatal period still reaching 50 % in adulthood. It was shown that the monoenzymatic neurons expressing complementary enzymes of DNA synthesis produce this neurotransmitter in cooperation. In this case, L-tyrosine is transformed to L-DOPA in TH containing neurons that is followed by L-DOPA release and uptake to AADC containing neurons with a semi-specific membrane transporter of large neutral amino acids for DA synthesis. Turning on the expression of enzymes of DA synthesis in non-dopaminergic neurons is an adaptive reaction under the functional insufficiency of DA-ergic neurons. So, hyperprolactinemia that is developed under the degeneration of DA-ergic neurons of the AN and the deficiency of DA, the prolactin-inhibiting neurohormone, was compensated in due time to increase in number of monoenzymatic neurons and the strengthening of cooperative synthesis of DA in the nucleus. The same compensatory cooperative synthesis if DA is supposed to be turned on under the degeneration of DA-ergic neurons of the nigrostriatal system that was manifested by appearance of the neurons expressing enzymes of DA synthesis in the deafferentiated striatum in rats. The expression of enzymes of DA synthesis in non-dopaminergic neurons is under the control by intercellular signals. e.g., catecholamines. Thus, numerous non-monoaminergic neurons in the brain expressing individual complementary enzymes of monoamine synthesis produce monoamines in cooperation that is a compensatory reaction to a functional insufficiency of monoaminergic neurons.

Innovative effect of illite on improved microbiological conversion of L-tyrosine to 3,4 dihydroxy phenyl L-alanine (L-DOPA) by Aspergillus oryzae ME2 under acidic reaction conditions

In the present investigation, the previous ultraviolet irradiated mutant strain of Aspergillus oryzae UV-7 was further improved in terms of 3,4 dihydroxy phenyl L-alanine (L-DOPA) activity after chemical mutagenesis through 1-methyl 3-nitro 1-nitroso guanidine (MNNG = 250-1500 microg/ml) treatment (0-30 min). Among several mutant variants, the one that produced a larger amount of L-DOPA from L-tyrosine was designated to as ME2 and it was made 2-deoxy-D-glucose-resistant by growing it at various concentrations of 2 dg (0.01-0.025 %, w/v) in Vogel's agar medium. Relatively better production of L-DOPA (> 0.60 mg/ml) was obtained when 2.0% (w/v) glucose was used as a carbon source in the mycelium production medium and the tyrosinase activity increased constitutively (1.08 mg/ml), which resulted in a greater production of L-DOPA. At optimum pH0 (pH 6.0) and reaction time (60 min), more than 65% sugar was utilized for cell mass formation. The maximum conversion of L-tyrosine to L-DOPA (0.428 mg/ml) was achieved 60 min after the biochemical reaction. Mould mycelium was used for microbiological conversion of L-tyrosine to L-DOPA because tyrosinases, beta-carboxylases, and tyrosine hydroxylases are intracellular enzymes. The effect of illite (1.0 x 10(6)-6.0 x 10(6) M) on biochemical conversion of L-tyrosine to L-DOPA by Aspergillus oryzae ME(2 )was also carried out. Best results of L-DOPA biosynthesis were observed when the concentration of illite was 3.5 x 10(-6) M (1.686 mg/ml L-DOPA produced with 1.525 mg/ml consumption of L-tyrosine). It was noted that the addition of illite not only increased enzyme activity but also enhanced the permeability of cell membrane to facilitate the secretion of enzymes into the reaction broth. The comparison of kinetic parameters showed the ability of mutant to yield L-DOPA (i.e., Yp/x 7.360 +/- 0.04 mg/mg). When the culture grown on various illite concentrations was monitored for Qp, Qs, and qp, there was significant enhancement (p < 0.025) in these variables over the control, which indicate that the study can be commercially applicable on stirred and magnetic rotary drums. Overall, there was up to 3-fold (Qp = 0.290 mg/L-DOPA produced/ml/h) enhancement in the product formation rate, which is highly encouraging (HS, LSD 0.456).

Lateral root bridging as a strategy to enhanceL-DOPA production inStizolobium hassjoo hairy root cultures by using a mesh hindrance mist trickling bioreactor

Stizolobium hassjoo hairy roots exhibited a lateral root bridging behavior, enabling not only root dry weight but enhancement of intracellular L-DOPA content. When a single root tip was exerted a proper hindrance, the primary root growth was inhibited while lateral roots were profusely induced. The hindrance-induced lateral roots from individual primary root could bridge together under appropriate inoculation densities, leading to high density hairy root cultures producing secondary metabolites. In the present paper, a novel bioreactor was proposed based on a strategy of lateral root bridging by utilizing mesh as a hindrance, called "mesh hindrance mist trickling bioreactor (MHMTB)". Significant improvements of dry weight and L-DOPA production by using MHMTB were 1.8 and 2.2-folds, respectively, higher than those in the control run without the mesh hindrance within the root bed.

DJ-1 transcriptionally up-regulates the human tyrosine hydroxylase by inhibiting the sumoylation of pyrimidine tract-binding protein-associated splicing factor

Loss-of-function mutations in DJ-1 cause a subset of familial Parkinson disease (PD). However, the mechanism underlying the selective vulnerability in dopaminergic pathway due to the inactivation of DJ-1 is unclear. Previously, we have reported that DJ-1 is a neuroprotective transcriptional co-activator interacting with the transcriptional co-repressor pyrimidine tract-binding protein-associated splicing factor (PSF). Here we show that DJ-1 and PSF bind and regulate the human tyrosine hydroxylase (TH) promoter. Inactivation of DJ-1 by small interference RNA (siRNA) results in decreased TH expression and l-DOPA production in human dopaminergic cell lines. Consistent with its role as a transcriptional regulator, DJ-1 specifically suppresses the global SUMO-1 modification. High molecular weight sumoylated protein species, including PSF, accumulate in the lymphoblast cells from the patients carrying pathogenic DJ-1 mutations. DJ-1 elevates the TH expression by inhibiting the sumoylation of PSF and preventing its sumoylation-dependent recruitment of histone deacetylase 1. Furthermore, siRNA silencing of DJ-1 decreases the acetylation of TH promoter-bound histones, and histone deacetylase inhibitors restore the DJ-1 siRNA-induced repression of TH. Therefore, our results suggest DJ-1 as a regulator of protein sumoylation and directly link the loss of DJ-1 expression and transcriptional dysfunction to impaired dopamine synthesis.

Double mutant of Aspergillus oryzae for improved production of L-dopa (3,4-dihydroxyphenyl-L-alanine) from L-tyrosine

Aspergillus oryzae mutant strain UV-7 was further improved for the production of L-dopa from L-tyrosine using chemical mutation. Different putative mutant strains of the organism were tested for the production of L-dopa in triplicate shake-flask cultures. Among these putative mutants, the strain designated SI-12 gave a maximal production of L-dopa (444+/-14 mg of L-dopa/g of cells). The regulation of L-dopa from different carbon source solutions [initial substrate concentration (S(0))=30 g/l] by the mutant culture was investigated. At an initial pH (pH(0)) of 5.0 and a temperature (T) of 30 degrees C, 100% of sugars were utilized for product and cell mass formation, corresponding to final L-dopa product yield of 189+/-8 mg/g of substrate utilized and maximum volumetric and specific productivities of 145+/-5 mg/h per litre and 155+/-8 mg/h per g of cells respectively. There was up to 3-fold enhancement in product formation rate. This enhancement is, to our knowledge, the highest reported in the literature. To explain the kinetic mechanism of L-dopa formation and its thermal inactivation, the thermodynamic parameters were determined with the application of the Arrhenius model. Activation enthalpy and entropy for product formation, in the case of the mutant derivative, were 40 kJ/mol and 0.076 kJ.mol(-1).K(-1) for its production and 116 kJ/mol and 0.590 kJ.mol(-1).K(-1) for thermal inactivation respectively. The respective values for product formation and product de-activation were lower than the respective values for the parental culture. Therefore the mutant strain was thermodynamically more resistant to thermal denaturation during the product-formation process.

Effective production of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) with Erwinia herbicola cells carrying a mutant transcriptional regulator TyrR

The enzymatic production of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) using Erwinia herbicola cells involves the action of tyrosine phenol-lyase (Tpl, EC 4.1.99.2). Since Tpl is only synthesized under L-tyrosine-induced conditions, the addition of L-tyrosine to the medium is unavoidable when preparing cells (the enzyme source), but severely impedes the pure preparation of the final product L-DOPA. We circumvented this problem by using recombinant E. herbicola cells carrying a mutant transcriptional regulator TyrR, which is capable of activating the tpl promoter in the absence of L-tyrosine.

Reversal of dyskinesias in an animal model of Parkinson's disease by continuous L-DOPA delivery using rAAV vectors

Dyskinesias are a major complication of long-term l-3,4-dihydroxyphenylalanine (L-DOPA) treatment in Parkinson's disease, and are believed to result from the intermittent and pulsatile supply of L-DOPA. Daily injections of L-DOPA can prime similar abnormal involuntary movements of the limb, orolingual and axial muscles in rats rendered parkinsonian by destruction of the nigrostriatal dopamine (DA) neurons. In this study we used 33 rats with severe nigrostriatal dopamine depletion and showed that in vivo gene transfer of the DA-synthetic enzymes tyrosine hydroxylase (TH) and GTP cyclohydrolase 1 (GCH1) using recombinant adeno-associated virus vectors can provide a constant source of DOPA production locally in the striatum, at a level that is effective in reducing L-DOPA-induced dyskinesias by >85%, and reverse lesion-induced motor impairments. Furthermore, the abnormal expression of DeltaFosB, prodynorphin and preproenkephalin mRNA within the striatal projection neurons normally seen in dyskinetic animals was completely reversed by TH-GCH1 gene transfer. These findings form a strong basis for replacing, or supplementing, conventional systemic L-DOPA therapy by continuous intrastriatal DOPA using in vivo gene transfer in the treatment of patients with advanced Parkinson's disease.

Fate of allelopathic substances in space--allelopathy of velvet bean plant and gravity

Interactions between organisms and species have been long known. It has not been known that the interactive phenomena (allelopathy) may (or may not) differ in space from those on earth. We have studied the gravitational effects on allelopathy by exposing a plant-plant system to pseudo-microgravity, which was generated by a 3D-clinostat. We hypothesized that allelopathy would be modified under altered gravity. L-DOPA (L-3,4-dihydroxyphenylalanine) is known to be the major substance in the allelopathy of velvet bean, released from its root. It has been found that there have been some differences of the allelopathic action of velvet bean plant under pseudo-microgravity. Biosynthesis, release, transport and sensing mechanism associated with allelopathy might be affected by gravity.

Production of L-DOPA by tyrosinase immobilized on modified polystyrene

Mushroom tyrosinase was immobilized on modified polystyrene- polyamino styrene (PSNH) and polymethylchloride styrene (PSCL)-to produce L-DOPA from L-tyrosine. Glutaraldehyde was used as an activating agent for the PSNH to immobilize the tyrosinase, and 10% (w/v) glutaraldehyde was optimal in conferring the highest specific activity (11.96 U/g) to the PSNH. Methylchloride on the PSCL was directly linked with the tyrosinase, and 1.5 mmol of Cl/g was optimal in attaining the specific activity of 17.0 U/g. The temperature and optimal acidity were, respectively, 60 degrees C and pH 5.5 for the PSNH, and 70 degrees C and pH 3.0 for the PSCL. In a 50-mL batch reactor working over 36 h, the L-DOPA production rate at 30 degrees C was 1.44 mg/(L x h) for the PSNH and 2.33 mg/(L x h) for the PSCL. The production rate over 36 h was 3.86 mg/(L x h) for the PSNH at 60 degrees C and 5.54 mg/(L x h) for the PSCL at 70 degrees C. Both of the immobilized enzymes showed a remarkable stability with almost no change in activity after being stored wet. The operational stability study indicated a 22.4% reduction in L-DOPA production for the PSNH and an 8.63% reduction for the PSCL over seven runs (each run was for 144 h at 30 degrees C) when the immobilized enzymes were used under turnover conditions. The immobilized tyrosinase was more stable on the PSCL than on the PSNH.

[Dopamine synthesis by non-dopaminergic neurons of the rat fetus arquate nucleus]

Our hypothesis was tested in respect to dopamine synthesis by non-dopaminergic neurons expressing individual complementary enzymes of the DA synthetic pathway. According to the hypothesis, L-dihydroxyphenylalanine (L-DOPA) synthesised in tyrosine hydroxylase(TH)-expressing neurons for conversion to dopamine. The mediobasal hypothalamus of rats on the 21st embryonic day was used as an experimental model. The fetal substantia nigra containing dopaminergic neurons served as control. Dopamine and L-DOPA were measured by high performance liquid chromatography in cell extracts and incubation medium in presence or absence of L-tyrosine. L-tyrosine administration increased L-DOPA synthesis in the mediobasal hypothalamus and substantia nigra. Moreover, L-tyrosine provoked an increase of dopamine synthesis in substantia nigra and a decrease in the mediobasal hypothalamus. This is, probably, due to an L-tyrosine-induced competitive inhibition of the L-DOPA transport to monoenzymatic AADC neurons after its release from the monoenzymatic TH neurons. This study provides a convincing evidence of dopamine synthesis by non-dopaminergic neurons expressing TH or AADC, in cooperation.

Pleiotrophin mRNA is highly expressed in neural stem (progenitor) cells of mouse ventral mesencephalon and the product promotes production of dopaminergic neurons from embryonic stem cell-derived nestin-positive cells

Neural stem cells are promising candidates for donor cells in neural transplantation. However, the mechanism by which neural stem cells differentiate into neurons is not well understood. In the present study, a serial analysis of gene expression (SAGE) was carried out to generate a gene file of neural stem (progenitor) cells from the mouse ventral mesencephalon. Among the 15,815 tags investigated, the mRNA of the housekeeping genes (elongation factor 1-alpha, ATPase subunit 6, GAPDH, actin), laminin receptor 1, HSP 70, pleiotrophin, and nestin were highly expressed. Because pleiotrophin (PTN) exhibits mitogenic and trophic effects on neural development and exhibits trophic effects on survival of dopaminergic (DAergic) neurons, we investigated the role of PTN in neurogenesis, especially to DAergic neurons. Here, we show that PTN increased the production of tyrosine hydroxylase (TH)-positive neurons from embryonic stem (ES) cell-derived nestin-positive cells. The expression of Nurr1 mRNA was enhanced by PTN. L-dopa in the culture medium was increased by PTN. This effect was as strong as with sonic hedgehog. Data suggest that PTN mRNA is highly expressed in neural stem (progenitor) cells of mouse ventral mesencephalon, and PTN promotes the production of DAergic neurons from ES cell-derived nestin-positive cells.

Dopamine synthesis by non-dopaminergic neurons expressing individual complementary enzymes of the dopamine synthetic pathway in the arcuate nucleus of fetal rats

This study was aimed to test our hypothesis about dopamine (DA) synthesis by non-DAergic neurons expressing individual complementary enzymes of the DA synthetic pathway in cooperation, i.e. L-dihydroxyphenylalanine (L-DOPA) synthesized in tyrosine hydroxylase (TH)-expressing neurons is transported to aromatic L-amino acid decarboxylase (AADC)-expressing neurons for conversion to DA. The mediobasal hypothalamus of rats at the 21st embryonic day was used as an experimental model because it contains mainly monoenzymatic TH neurons and AADC neurons (>99%) whereas the fraction of bienzymatic (DAergic) neurons does not exceed 1%. The fetal substantia nigra containing DAergic neurons served as a control. DA and L-DOPA were measured by high performance liquid chromatography in: (1) cell extracts of the cell suspension prepared ex tempora; (2) cell extracts and incubation medium after the static incubation of the cell suspension with, or without exogenous L-tyrosine; (3) effluents of the incubation medium during perifusion of the cell suspension in the presence, or the absence of L-tyrosine. Total amounts of DA and L-DOPA in the incubation medium and cell extracts after the static incubation were considered as the indexes of the rates of their syntheses. L-Tyrosine administration caused the increased L-DOPA synthesis in the mediobasal hypothalamus and substantia nigra. Moreover, L-tyrosine provoked an increase of DA synthesis in the substantia nigra and its decrease in the mediobasal hypothalamus. This contradiction is most probably explained by the L-tyrosine-induced competitive inhibition of the L-DOPA transport to the monoenzymatic AADC-neurons after its release from the monoenzymatic TH neurons. Thus, this study provides convincing evidence of cooperative DA synthesis by non-DAergic neurons expressing TH or AADC in fetal rats at the end of the intrauterine development.

Melanin Pigment Formation and Increased UV Resistance in Bacillus thuringiensis Following High Temperature induction

The pigment melanin is well known to protect against the damaging effects of UV radiation. In this study, we show that thirty-five of thirty-seven tested Bacillus thuringiensis strains possess the potential to produce melanin in the presence of L-tyrosin at elevated temperature (42 degrees C). These findings offer a method of protecting insecticidal toxins produced by B. thuringiensis from UV degredation and may therefore have important applications in the field of crop protection. Toxicity assays on Heliothis armigera suggested that the insecticidal activity of B. thuringiensis that produced melanin was significantly higher after UV irradiation than when melanin was not produced.

[Expression and assessment of double genes of tyrosine hydroxylase gene and aromatic L-amino acid decarboxylase gene in vitro]

The characteristic pathological changes of Parkinson s disease (PD) include a severe loss of dopamine neurons in the substantia nigra and a severe decrease in dopamine in the striatum. Since the expression of tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) in the biosynthetic pathway for dopamine are low, a promising approach to the gene therapy of PD is to augment the gene expression of the enzymes in the biosynthetic pathway for dopamine. In the present study, human TH and AADC genes were reconstructed into retrovirous vectors pLHCX and pLNCX(2) respectively. Then pLHCX/TH and pLNCX(2)/AADC were transfected into packaging cell line PA317 with liposome. PA317/TH and PA317/AADC were selected by different antibiotics. Gene expression was examined by methods of immunohistochemistry and in situ hybridization. The catalytic activity of two cloned gene enzymes was assessed in vitro by HPLC-EC. Immunocytochemical staining showed that TH and AADC were expressed efficiently in vitro. Both TH and AADC mRNA were transcripted in PA317 cell lines by using in situ hybridazation. HPLC-EC experiments revealed that the transfected cells produced a significantly higher level of dopamine and L-dopa than the untransfected cells. The two genetically modified cells could improve the production of L-dopa and dopamine in response to suitable substrate. The present results suggest that not only recombinant TH and AADC genes are successfully expressed in vitro, but also the enzymes have respective functional activities. These results have set up a way for in vivo gene therapy of PD with TH and AADC genes.

Truffle thio-flavours reversibly inhibit truffle tyrosinase

Tyrosinase is an enzyme having two copper atoms at the reactive site occurring in prokaryotic and eukaryotic organisms. In animals tyrosinase is responsible for pigmentation, in plants for protection of injured tissues or, as in fungi, to harden cell walls. Some of us have previously shown that tyrosinase is involved in truffle development and differentiation. Here we present the purification, the molecular properties and the reversible inhibition of Tuber melanosporum tyrosinase by dimethyl-sulfide and bis[methylthio]methane, the main flavour compounds of black and whitish truffles. The MW(r) is 39000. L-3,4-dihydroxyphenylalanine and L-tyrosine stain corresponding bands as expected for a true tyrosinase. Phenylthiourea, diethyldithiocarbamate and mimosine inhibit L-tyrosine and L-3,4-dihydroxyphenylalanine oxidation.

Inducive effect of cresoquinone on microbiological transformation of L-tyrosine to 3,4 dihydroxy phenyl L-alanine by Aspergillus oryzae NG-11(P1)

The present work describes the inducive effect of cresoquinone on microbiological transformation of L-tyrosine to 3,4 dihydroxy phenyl L-alanine ( L-DOPA) by Aspergillus oryzae NG-11(P1). Mould mycelium was used for biochemical conversion of L-tyrosine to L-DOPA because tyrosinases, beta-carboxylases and tyrosine hydroxylases are intracellular enzymes. The maximum conversion of L-tyrosine to L-DOPA (0.428 mg/ml) was achieved after 60 min of biochemical reaction. To enhance the production of L-DOPA, cresoquinone was added to the reaction mixture. Best L-DOPA biosynthesis results were observed when the concentration of cresoquinone was 3.5 x 10(-6) M (1.686 mg/ml L-DOPA produced with 1.525 mg/ml consumption of L-tyrosine). Cresoquinone not only increased enzyme activity but also enhanced cell membrane permeability to facilitate secretion of enzymes into the reaction broth. Comparison of kinetic parameters revealed the ability of the mutant to yield L-DOPA [Y(p/x) [i.e., mg L-DOPA formed (mg cells formed)(-1)] =7.360+/-0.04]. When the culture grown on various cresoquinone levels was monitored for Q(p), Q(s) and q(p) [ Q(p): mg L-DOPA produced ml(-1) x h(-1); Q(s): mg substrate consumed ml(-1) x h(-1); q(p): mg L-DOPA formed (mg cells)(-1) h(-1)], there was significant enhancement ( P<0.025) of these variables.

Biosynthesis of L-DOPA by Aspergillus oryzae

The present investigation deals with the biosynthesis of L-DOPA by parental (GCB-6) and mutant (UV-7) strains of Aspergillus oryzae. There was a marked difference between the mycelial morphology and pellet type of parental and UV-irradiated mutant culture. The mutant strain of A. oryzae UV-6 exhibited pellet-like mycelial morphology and improved tyrosinase activity. Mould mycelium was used for biochemical conversion of L-tyrosine to L-DOPA because tyrosinase is an intracellular enzyme. The mutant was found to yield 3.72 fold higher production of L-DOPA than the parental strain. The mutant strain is stable and D-glc-resistant. The comparison of kinetic parameters was also done which showed the greater ability of the mutant to yield L-DOPA (i.e., Yp/x 40.00+/-0.01 d mg/mg with parent and 182.86+/-0.02a mg/mg in case of mutant). When cultures grown for various incubation periods, were monitored for Qp, Qs and q(p), there was significant enhancement (p < 0.0025-0.005) in these variables by the mutant strain of A. oryzae UV-7 over GCB-6 on all the rates. L-DOPA (3,4-dihydroxy phenyl L-alanine) is a drug of choice in the treatment of Parkinson's disease and myocardium following neurogenic injury.

Expression of the mel gene from Pseudomonas maltophilia in Bacillus thuringiensis

AIMS

The objective of this work was to express a novel mel gene, responsible for melanin formation, in Bacillus thuringiensis.

METHODS AND RESULTS

A novel mel gene from Pseudomonas maltophilia was sub-cloned into B. thuringiensis using a shuttle vector plasmid and electroporation. Results revealed that the mel gene was expressed under the control of the CryIIIA promoter in B. thuringiensis and conferred u.v. protection on the recipient strain.

CONCLUSIONS

The novel mel gene from Ps. maltophilia expressed in B. thuringiensis conferred u.v. protection on the recipient strain.

SIGNIFICANCE AND IMPACT OF THE STUDY

Products containing B. thuringiensis for pest control are sensitive to u.v. degradation. As melanin has the ability to act as a u.v. absorber, a recombinant B. thuringiensis strain producing melanin provides a new stability for B. thuringiensis preparations.

Modification of tyrosine hydroxylase activity by chloral derived beta-carbolines in vitro

Beta-carbolines have been suggested to be involved in the pathogenesis of Parkinson's disease as a result of their structural similarity to the neurotoxin N -methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The chloral-derived beta-carboline derivative 1-trichloromethyl-1,2,3,4-tetrahydro-beta-carboline (TaClo) causes cell loss in neuronal and glial cell cultures and induces a slowly developing neurodegenerative process in rats. In our experiments, effects of TaClo and its derivatives 2-methyl-TaClo (2-Me-TaClo), and 1-dichloromethylene-1,2,3,4-tetrahydro-beta-carboline (1-CCl(2) -THbetaC) on tyrosine hydroxylase (TH) activity were investigated in TH assays using homogenate preparations of the rat nucleus accumbens and recombinant human TH (hTH1). TH activity was determined in vitro by measuring l-DOPA production with HPLC-ECD. Using homogenate preparations, TaClo, 2-Me-TaClo, and 1-CCl(2) -THbetaC inhibited TH in concentrations of 0.1 mm, while 1-CCl(2) -THbetaC in low concentrations enhanced TH activity. When TH was activated by PACAP-27, TaClo, 2-Me-TaClo, or 1-CCl(2) -THbetaC also inhibited activated enzyme activity in high concentrations. However, in the case of 2-Me-TaClo and 1-CCl(2) -THbetaC a biphasic effect was observed with a marked increase of TH activity in the nanomolar range. In our experiments using recombinant hTH1, TaClo, 2-Me-TaClo, or 1-CCl(2) -THbetaC did not modify enzyme activity. After activation of hTH1 by PKA all the tetrahydro-beta-carbolines investigated in this study decreased l-DOPA formation. We suggest that these beta-carbolines modulate dopamine synthesis by interacting with a protein kinase TH-activating system.

Glycosphingolipids are required for sorting melanosomal proteins in the Golgi complex

Although glycosphingolipids are ubiquitously expressed and essential for multicellular organisms, surprisingly little is known about their intracellular functions. To explore the role of glycosphingolipids in membrane transport, we used the glycosphingolipid-deficient GM95 mouse melanoma cell line. We found that GM95 cells do not make melanin pigment because tyrosinase, the first and rate-limiting enzyme in melanin synthesis, was not targeted to melanosomes but accumulated in the Golgi complex. However, tyrosinase-related protein 1 still reached melanosomal structures via the plasma membrane instead of the direct pathway from the Golgi. Delivery of lysosomal enzymes from the Golgi complex to endosomes was normal, suggesting that this pathway is not affected by the absence of glycosphingolipids. Loss of pigmentation was due to tyrosinase mislocalization, since transfection of tyrosinase with an extended transmembrane domain, which bypassed the transport block, restored pigmentation. Transfection of ceramide glucosyltransferase or addition of glucosylsphingosine restored tyrosinase transport and pigmentation. We conclude that protein transport from Golgi to melanosomes via the direct pathway requires glycosphingolipids.

Rat marrow stromal cells rapidly transduced with a self-inactivating retrovirus synthesize L-DOPA in vitro

Autologous bone marrow stromal cells engineered to produce 3,4,-dihydroxyphenylalanine (L-DOPA) can potentially be used as donor cells for neural transplantation in Parkinson's disease. Here, we examined the possibility of using several different promoters and either a self-inactivating retrovirus (pSIR) or standard retroviruses to introduce into marrow stromal cells (MSCs), the two genes necessary for the cells to synthesize L-DOPA. pSIR vectors were constructed using the mouse phosphoglycerate kinase-1 (PGK) promoter or the cytomegalovirus (CMV) promoter to drive expression of either a GFP reporter gene or a bicistronic sequence containing the genes for human tyrosine hydroxylase type I (TH) and rat GTP cyclohydrolase I (GC) separated by an internal ribosome entry site (IRES). rMSCs were successfully transduced with both standard retroviral vectors and pSIR containing the PGK promoter. Transduced rMSCs expressed GFP (90.4--94.4% of cells) or were able to synthesize and secrete L-DOPA (89.0--283 pmols/10(6) cells/h). After transduced rMSCs were plated at low density (3--6 cells/cm(2)), the cells expanded over 1000-fold in 3--4 weeks, and the rMSCs continued to either express GFP or produce L-DOPA. Furthermore, two high-expressing clones were isolated and expanded at low-density from rMSCs transduced with pSIR driven by the PGK promoter (97.0% GFP+ or 1096.0 pmols L-DOPA/10(6) cells/h).

Medium optimization of transformed root cultures of Stizolobium hassjoo producing L-DOPA with response surface methodology

Medium optimization of B5 medium for hairy root cultures producing secondary metabolites was studied through statistical experimental design. Transformed root cultures of Stizolobium hassjoo producing L-DOPA were used as a model system. The serial dilution experiments facilitated logical choice of the upper and lower bounds on executing 2(11)(-)(6) fractional factorial design. Steepest ascent method as well as central composite design were sequentially employed to optimize the media of shake flask cultures. The modified B5 media of GM, PM, and GPM were obtained, indicating the optimum medium compositions for enhancing hairy root dry weight, L-DOPA content in hairy roots, and L-DOPA production, respectively. When cultivating S. hassjoo hairy roots in GM, PM and GPM for 16 days, the dry wt of hairy roots, L-DOPA content, and L-DOPA production obtained were ca. 530 mg per flask (10.6 g/L), 10.8% dry wt, and 806 mg/L, which were 1.8-, 2-, and 2.8-fold of basal B5 medium control runs, respectively.

Reversing the substrate specificities of phenylalanine and tyrosine hydroxylase: aspartate 425 of tyrosine hydroxylase is essential for L-DOPA formation

The catalytic domains of the pterin-dependent enzymes phenylalanine hydroxylase and tyrosine hydroxylase are homologous, yet differ in their substrate specificities. To probe the structural basis for the differences in specificity, seven residues in the active site of phenylalanine hydroxylase whose side chains are dissimilar in the two enzymes were mutated to the corresponding residues in tyrosine hydroxylase. Analysis of the effects of the mutations on the isolated catalytic domain of phenylalanine hydroxylase identified three residues that contribute to the ability to hydroxylate tyrosine, His264, Tyr277, and Val379. These mutations were incorporated into full-length phenylalanine hydroxylase and the complementary mutations into tyrosine hydroxylase. The steady-state kinetic parameters of the mutated enzymes showed that the identity of the residue in tyrosine hydroxylase at the position corresponding to position 379 of phenylalanine hydroxylase is critical for dihydroxyphenylalanine formation. The relative specificity of tyrosine hydroxylase for phenylalanine versus tyrosine, as measured by the (V/K(phe))/(V/K(tyr)) value, increased by 80000-fold in the D425V enzyme. However, mutation of the corresponding valine 379 of phenylalanine hydroxylase to aspartate was not sufficient to allow phenylalanine hydroxylase to form dihydroxyphenylalanine at rates comparable to that of tyrosine hydroxylase. The double mutant V379D/H264Q PheH was the most active at tyrosine hydroxylation, showing a 3000-fold decrease in the (V/K(phe))/(V/K(tyr)) value.

Multipotential marrow stromal cells transduced to produce L-DOPA: engraftment in a rat model of Parkinson disease

Bone marrow stromal cells can be used as an alternative source of cells for neural transplantation and repair. Here, the efficacy of genetically modified marrow stromal cells was examined in a rat model of Parkinson disease. Rat marrow stromal cells (rMSCs) and human marrow stromal cells (hMSCs) were genetically engineered by transduction with retroviruses encoding tyrosine hydroxylase (TH) and GTP cyclohydrolase I, the enzyme necessary for production of the tetrahydrobiopterin cofactor for TH (BH4). Transduced cells synthesized 3,4-dihydroxyphenylalanine (L-DOPA) in vitro and maintained their multipotentiality after retroviral transduction. To examine the cells in vivo, transduced rMSCs were injected into the striatum of 6-hydroxydopamine-lesioned rats. L-DOPA and metabolites were detected by microdialysis in the denervated striatum of rats that received doubly transduced rMSCs. Also, there was a significant reduction in apomorphine-induced rotation when compared with controls. The cells engrafted and survived for at least 87 days. However, expression of the transgenes ceased at about 9 days, an observation consistent with reports from other laboratories in which similar retroviruses were used to express transgenes in the brain.

Dopamine turnover and metabolism in the striatum of parkinsonian rats grafted with genetically-modified human astrocytes

The potential of a novel therapeutic approach for treating Parkinson's disease, which involves the transplantation of a transfected human astrocyte cell line SVG-TH, that stably expresses the rate-limiting enzyme for dopamine production, tyrosine hydroxylase, was examined. SVG-TH and untransfected parent cells were grafted into the diseased striatum of rats in which Parkinson's disease had been induced by the administration of 6-hydroxydopamine. The in situ production and spillover of 3,4-dihydroxyphenylalanine (the precursor of dopamine), dopamine and their metabolites in the striatal extracellular fluid of the grafted rats was determined in conscious animals using the microdialysis technique and a high pressure liquid chromatography apparatus. Alleviation of symptoms of Parkinson's disease (abnormal movements) was evaluated by rotation tests. Upon transplantation of the SVG-TH cells into the striatum of the parkinsonian rats, the levels of dopamine in extracellular fluid of the striatum reached those of the normal rats, and correlated well with the improvement (74%) in their rotating behaviour (behavioural deficit). The levels of the two main dopamine metabolites, dihydroxyphenylacetic acid and homovanillic acid, were low in the lesioned rats, even after SVG-TH transplantation. An alternative route of metabolism of dopamine may occur in the transplanted striatum, since the dopamine metabolite, 3-O-methoxy-4-hydroxy-phenylethylamine, appeared, which indicates activity of catechol-O-methyl transferase. Upon blockade of L-aromatic-amino acid decarboxylase, 3,4-dihydroxyphenylalanine accumulated in extracellular fluid of the 6-hydroxydopamine-lesioned and SVG-TH-grafted rats, which indicated that these cells produced active tyrosine hydroxylase in vivo. These findings indicate the potential of treating Parkinson's disease by the intrabrain grafting of human astrocyte cells transfected with the rate limiting enzyme for dopamine production.

In vivo L-DOPA production by genetically modified primary rat fibroblast or 9L gliosarcoma cell grafts via coexpression of GTPcyclohydrolase I with tyrosine hydroxylase

To investigate the biochemical requirements for in vivo L-DOPA production by cells genetically modified ex vivo in a rat model of Parkinson's disease (PD), rat syngeneic 9L gliosarcoma and primary Fischer dermal fibroblasts (FDFs) were transduced with retroviral vectors encoding the human tyrosine hydroxylase 2 (hTH2) and human GTP cyclohydrolase I (hGTPCHI) cDNAs. As GTPCHI is a rate-limiting enzyme in the pathway for synthesis of the essential TH cofactor, tetrahydrobiopterin (BH4), only hTH2 and GTPCHI cotransduced cultured cells produced L-DOPA in the absence of added BH4. As striatal BH4 levels in 6-hydroxydopamine (6-OHDA)-lesioned rats are minimal, the effects of cotransduction with hTH2 and hGTPCHI on L-DOPA synthesis by striatal grafts of either 9L cells or FDFs in unilateral 6-OHDA-lesioned rats were tested. Microdialysis experiments showed that those subjects that received cells cotransduced with hTH2 and hGTPCHI produced significantly higher levels of L-DOPA than animals that received either hTH2 or untransduced cells. However, animals that received transduced FDF grafts showed a progressive loss of transgene expression until expression was undetectable 5 weeks after engraftment. In FDF-engrafted animals, no differential effect of hTH2 vs hTH2 + hGTPCHI transgene expression on apomorphine-induced rotation was observed. The differences in L-DOPA production found with cells transduced with hTH2 alone and those cotransduced with hTH2 and hGTPCHI show that BH4 is critical to the restoration of the capacity for L-DOPA production and that GTPCHI expression is an effective means of supplying BH4 in this rat model of PD.

Production of L-DOPA(3,4-dihydroxyphenyl-L-alanine) from benzene by using a hybrid pathway

As an alternative approach to the production of L-DOPA from a cheap raw material, we constructed a hybrid pathway consisting of toluene dioxygenase, toluene cis-glycol dehydrogenase, and tyrosine phenol-lyase. In this pathway, catechol is formed from benzene through the sequential action of toluene dioxygenase and toluene cis-glycol dehydrogenase, and L-DOPA is synthesized from the resulting catechol in the presence of pyruvate and ammonia by tyrosine phenol-lyase cloned from Citrobacter freundii. When the hybrid pathway was expressed in E. coli, production of L-DOPA was as low as 3 mM in 4 h due to the toxic effect of benzene on the cells. In order to reduce lysis of cells, Pseudomonas aeruginosa was employed as an alternative, which resulted in accumulation of about 14 mM L-DOPA in 9 h, showing a stronger resistance to benzene.

Therapeutic Potential of a Polymer-Encapsulated L-Dopa and Dopamine-Producing Cell Line in Rodent and Primate Models of Parkinson's Disease

Encapsulation of cells within polymer membranes prior to transplantation provides a novel means of achieving continuous, site-specific delivery of therapeutic molecules to the CNS. The use of encapsulated dopamine-secreting cells that can be transplanted directly into the striatum has particular appeal for the treatment of Parkinson's disease. This article provides a brief and timely review of the progress that has been made over the past decade using encapsulated PC12 cells as a means of delivering dopamine and l-DOPA to the striatum in rodent and primate models of Parkinson's disease. The polymer membranes are well tolerated and biocompatible. Encapsulated PC12 cells survive in vivo for up to 6 mo, they release dopamine into the surrounding host striatum, and they clearly improve behavioral function in both dopamine-depleted rodents and primates. Although these results are promising, fundamental issues remain concerning the extent of dopamine diffusion from the polymer membranes and the number of devices needed for behavioral improvement, and the duration and consistency of cell viability and device output. Nevertheless, this technology appears to be a promising means of avoiding many of the practical, societal, and ethical issues that have been associated with other transplantation approaches.

L-tyrosine and nicotine induce synthesis of L-Dopa and norepinephrine in human lymphocytes

Catecholamines (CA) were studied in peripheral human lymphocytes in basal conditions as well as after L-tyrosine and/or acetylcholine (ACh) stimulation. Nicotinic and muscarinic receptor activation and blockade were assessed. CA were determined after ultrasonic cell disruption in peripheral lymphocytes after incubation (1 h at 37 degrees C) with the chemicals employed. L-tyrosine significantly increased (P < 0.01) L-Dopa and norepinephrine (NE) content of lymphocytes. ACh in the low microM range did not modify, whereas ACh (60 microM) and (120 microM) significantly increased (P < 0.01), both L-Dopa and NE intracellular levels. L-tyrosine plus ACh (60 microM) or (120 microM) significantly increased (P < 0.01) intracellular L-Dopa and NE versus control, versus L-tyrosine alone and versus ACh alone. The increase was higher than the algebraic sum of the individual increases. Nicotine (250 microM), but not muscarine (50 microM), significantly increased L-Dopa and NE in lymphocytes. Tetraethylammonium (500 microM) (nicotinic blocker), but not atropine (100 microM) (muscarinic blocker), inhibited the ACh-mediated increase of intracellular L-Dopa and NE. These data show that lymphocyte synthesis of CA is under nicotinic control. Since intracellular L-Dopa after L-tyrosine plus ACh increased 6-fold versus basal, 2-fold versus L-tyrosine alone and 3-fold versus ACh alone, it is concluded that ACh might regulate CA synthesis in lymphocytes through an activation of the rate limiting enzyme tyrosine hydroxylase.

L-Dopa and dopamine-producing gene cassettes for gene therapy approaches to Parkinson's disease

As an aid in the development of vector systems for use in gene therapy paradigms of central nervous system disorders such as Parkinson's disease, we have developed L-Dopa or dopamine-producing gene cassettes. Specifically, a human tyrosine hydroxylase cDNA (HTH-2) was rendered constitutively active by truncation of the N-terminal regulatory domain (tHTH). In addition, a bicistronic construct capable of directing the production of dopamine was created by inserting an internal ribosome entry site downstream of tHTH followed by the coding sequences of aromatic amino acid decarboxylase. All three constructs generated immunoreactive peptides of the predicted size, were enzymatically active, and produced L-Dopa (HTH-2, tHTH) or dopamine (bicistronic construct) following transient transfection of COS-7 cells. These constructs, in conjunction with viral or nonviral expression systems, may be efficacious in gene therapy approaches to Parkinson's disease.

[Intracerebral transplantation of genetically modified cells for Parkinson's disease]

The clinical application of brain transplantation for treating Parkinson's disease (PD) is limited because it is difficult to obtain ideal donor cells. In this study, the tyrosine hydroxylase (TH) gene was introduced into NIH-3T3 cell line and the genetically modified cells reacted positively with TH antiserum and released L-dopa. These cells were implanted into the striatum of PD rats. 3,6,9,12 days after implantation, the average rate of the abnormal rotational behavior recovery was 52.6%, 68.4%, 63.2%, 44.7%, respectively. This result is considered to be potential for further clinical application.

Catecholamine content and in vitro catecholamine synthesis in peripheral human lymphocytes

We studied the catecholamine (CA) content in peripheral human lymphocytes and the ability of these cells to synthesize CA in vitro. CA were separated by high performance liquid chromatography (HPLC) and determined in the supernatant by electrochemical detection as well as being determined after ultrasonic cell disruption in mononuclear leukocytes, adherent cells (monocytes/macrophages), total lymphocytes, and B- and T-cell enriched fractions. T lymphocytes contained L-Dopa and norepinephrine (NE), whereas B lymphocytes contained only L-Dopa. Lymphocytes seem to be able to synthesize NE from both L-tyrosine and L-Dopa added to the incubation medium in concentrations similar to the peripheral venous plasma (i.e. 5 x 10(-5) m and 10(-8) m, respectively). The addition of D-Dopa did not increase intracellular NE. alpha-methyl-p-L-tyrosine, benserazide, disulfiram, and fusaric acid (which are inhibitors of the enzymatic pathway) all decreased the synthesis of NE. After the addition of [3H]-L-Dopa (10(-8) m and 10(-7) m) to the incubation medium, [3H]-NE and [3H]-dopamine appeared. By increasing the concentration of L-Dopa in the medium (< 10(-6) m), CA were detected in the supernatant as well. These data show that peripheral human T lymphocytes contain and are able to synthesize CA from normal precursors in physiologic concentrations, i.e. a CA synthetic pathway is shown in nonneural cells. These data seem to support the hypothesis of autocrine and paracrine loops in the regulation of lymphocyte activity in lymphocytes taken from human cerebrospinal fluid (as suggested by other authors).

Regulation of L-DOPA production by genetically modified primary fibroblasts transfected with retrovirus vector system

Although intracerebral grafting has become established as a new strategy for the treatment of Parkinson's disease, there are many problems regarding such grafts. We focused on the grafting of primary skin fibroblasts. Rat primary skin fibroblasts were transfected with a retrovirus vector containing cDNA of human tyrosine hydroxylase (TH) type 1 (LTHSNL) or of cytomegalovirus promoter (CTHSNL) as a foreign promoter. In these genetically modified fibroblasts, L-DOPA production and release were analyzed in vitro by immunocytochemistry and high-performance liquid chromatography with electrochemical detection (HPLC-ECD). Being supplemented with the biopterin (BH4:(6R)-L-erythro-tetrahydrobiopterin) cofactors required for TH activity, these cells produced and released L-DOPA into the culture medium. When CTHSNL and BH4 were combined, L-DOPA production increased with time, regardless of the number of cell passages, or the duration of liquid nitrogen freezing. This suggests that the foreign gene (THcDNA) containing retrovirus vector integrates into the chromosomal DNA of the target cells (fibroblasts). Primary fibroblasts can be easily obtained and cultured. Thus, genetically modified primary skin fibroblasts transfected with a retrovirus vector system containing the TH cDNA may be promising grafts for transplantation and gene therapy in Parkinson's disease.

Regulation of L-DOPA biosynthesis by site-specific phosphorylation of tyrosine hydroxylase in AtT-20 cells expressing wild-type and serine 40-substituted enzyme

De novo L-DOPA biosynthesis was studied in stably transfected AtT-20 cells expressing wild-type- or [Leu40]-recombinant tyrosine hydroxylase (rTH). Basal rates of DOPA accumulation were much higher by cells expressing rTH in which Leu was substituted for Ser4O (S40L-rTH) than by those expressing wild-type rTH (WT-rTH). Treatment of WT-rTH cells with forskolin produced an increase in DOPA accumulation and a concomitant increase in WT-rTH phospho-Ser40 content, whereas DOPA production by cells expressing S40L-rTH was entirely unaffected by forskolin. After forskolin treatment of 32Pi-prelabeled cells, WT-rTH was phosphorylated at Ser8, Ser19, Ser31, and Ser40, whereas 32P incorporation into S40L-rTH was restricted to Ser8, Ser19, and Ser31. Relatively prolonged treatment of AtT-20 cells expressing WT-rTH with either a depolarizing agent (elevated potassium) or a phosphatase inhibitor (okadaic acid) increased DOPA production and increased the phosphorylation state of Ser40; but, unlike forskolin, these treatments also increased DOPA production by cells expressing S40L-rTH. Thus, the present studies demonstrate that Ser40 phosphorylation mediates forskolin-induced increases in DOPA biosynthesis directly but that mechanisms other than Ser40 phosphorylation can mediate the increases in DOPA biosynthesis produced either by depolarization or by protein phosphatase inhibition.

Double transduction with GTP cyclohydrolase I and tyrosine hydroxylase is necessary for spontaneous synthesis of L-DOPA by primary fibroblasts

Gene transfer of tyrosine hydroxylase (TH) in animal models of Parkinson's disease (PD), using either genetically modified cells or recombinant virus vectors, has produced partial restoration of behavioral and biochemical deficits. The limited success of this approach may be related to the availability of the cofactor, tetrahydrobiopterin (BH4), because neither the dopamine-depleted striatum nor the cells used for gene transfer possess a sufficient amount of BH4 to support TH activity. To determine the role of BH4 in gene therapy, fibroblast cells transduced with the gene for TH were additionally modified with the gene for GTP cyclohydrolase l; an enzyme critical for BH4 synthesis. In contrast to cells transduced with only TH, doubly transduced fibroblasts spontaneously produced both BH4 and 3, 4-dihydroxy-L-phenylalanine. To examine further the importance of GTP cyclohydrolase I in gene therapy for PD, in vivo micro-dialysis was used to assess the biochemical changes in the dopamine-denervated striatum containing grafts of genetically modified fibroblasts. Only denervated striata grafted with fibro-blasts possessing both TH and GTP cyclohydrolase I genes displayed biochemical restoration. However, no significant differences from controls were observed in apomorphine-induced rotation. This is partly attributable to a limited duration of gene expression in vivo. These differences between fibroblasts transduced with TH alone and those additionally modified with the GTP cyclohydrolase I gene indicate that BH4 is critical for biochemical restoration in a rat model of PD and that GTP cyclohydrolase I is sufficient for production of BH4.

Parenteral application of NADH in Parkinson's disease: clinical improvement partially due to stimulation of endogenous levodopa biosynthesis

Exogenous application of levodopa is conventionally used to equalize the striatal dopamine deficit in idiopathic Parkinson's disease (PD). The stimulation of endogenous biosynthesis of levodopa via activation of tyrosine hydroxylase (TH) has been proposed as new therapeutic concept in PD. This may be achieved by exogenous supply with the reduced coenzyme nicotinamide adenine dinucleotide (NADH). Aim of this open prospective study was to investigate (1) the efficacy of a new developed, parenteral application form of NADH on Parkinsonian symptoms and (2) the influence of bioavailability of levodopa. 15 patients, suffering from idiopathic PD (11 male, 4 female, age: 61.40[mean] +/- 10.27[SD] range: 44-74 years, Hoehn and Yahr stage: 3.03 +/- 0.69, range 2-4) received intravenous infusions of NADH (10 mg a' 30 min) over a period of 7 days in addition to conventional Parkinsonian pharmacotherapy. Parkinsonian symptoms were scored before (day 1) and after NADH treatment (day 8). Levodopa plasma levels were estimated over a period of four hours on the day before and on the first day of NADH application by HPLC. Parkinsonian patients showed a significant response, evaluated by the Unified Parkinson's Disease Rating Scale Version 3.0 (p = 0.025; Wilcoxon test). Moreover application of NADH significantly increased bioavailability of plasma levodopa (AUC, p = 0.035; Cmax p = 0.025). In conclusion NADH in used galenic form may be a potent stimulator of endogenous levodopa biosynthesis with clinical benefit for Parkinsonian patients.

Tyrosine hydroxylase in the cerebral ganglia of the American cockroach (Periplaneta americana L.): an immunohistochemical study

We have investigated the distribution of tyrosine-hydroxylase-like immunoreactivity in the cerebral ganglia of the American cockroach, Periplaneta americana. Groups of tyrosine-hydroxylase-immunoreactive cell bodies occur in various parts of the three regions of the cerebral ganglia. In the protocerebrum, single large neurons or small groups of neurons are located in the lateral neuropil, adjacent to the calyces, and in the dorsal portion of the pars intercerebralis. Small scattered cell bodies are found in the outer layers of the optic lobe, and clusters of larger cell bodies can be found in the deutocerebrum, medial and lateral to the antennal glomeruli. Thick bundles of tyrosine-hydroxylase-positive nerve fibers traverse the neuropil in the proto- and deutocerebrum and innervate the glomerular and the non-glomerular neuropil with fine varicose terminals. Dense terminal patterns are present in the medulla and lobula of the optic lobe, the pars intercerebralis, the medial tritocerebrum, and the area surrounding the antennal glomeruli, the central body and the mushroom bodies. The pattern of tyrosine-hydroxylase-like immunoreactivity is similar to that previously described for catecholaminergic neurons, but it is distinctly different from the distribution of histaminergic and serotonergic neurons.

[L-DOPA-producing primary fibroblasts genetically modified with a retrovirus vector system]

Although intracerebral grafting has become a new strategy for the treatment of Parkinson's disease, many problems related to the grafts remain. We focused on primary skin fibroblasts as grafts. Rat primary skin fibroblasts were transfected with a retrovirus vector containing the cDNA of human tyrosine hydroxylase (TH) (pLTHSNL) or cytomegalovirus promoter (pCTHSNL) as a foreign promoter, and catecholamine production and release by these genetically modified fibroblasts, were analyzed in vitro immunocytochemically and by high-performance liquid chromatography with electrochemical detection (HPLC-ECD). The cells were supplemented with biopterin (BH4; (6R)-L-erythro-tetrahydrobiopterin), a cofactor required for TH activity, and they produced and released L-DOPA into the culture medium. When exposed to the combination of a foreign promoter and BH4, L-DOPA production increased in a time-dependent manner, and was unaffected by the number of cell-passages or the duration of liquid-nitrogen freezing. This suggests that the foreign gene (THcDNA)-containing retrovirus vector had integrated into the chromosomal DNA of the target cells (fibroblasts). Primary fibroblasts can be easily obtained and cultured. Thus, genetically modified primary skin fibroblasts transfected with THcDNA using this retrovirus vector system appear to be a promising graft for transplantation and gene therapy of Parkinson's disease in the future.

Nicotinamidadenindinucleotide (NADH): the new approach in the therapy of Parkinson's disease

The coenzyme Nicotinamidadenindinucleotide (NADH) has been used as novel medication in 34 Parkinson patients in an open label trial. In all patients, a beneficial clinical effect was observed. Twenty-one patients (61.7 percent) showed a very good (better than 30 percent) improvement of disability and 13 patients (38.3 percent) a moderate (up to 30 percent) improvement. The effect of NADH was dependent on the dosage and the severity of the case. The best therapeutic dose was in the range of 25 to 50 mg per day. The clinical improvement was more pronounced after i.v. and less after i.m. administration. Concomitant with improvement of the disability, the urine level of homovanillinic acid (HVA) increased significantly in all patients (in some patients by more than a 100 percent), indicating a stimulation of the endogenous L-DOPA biosynthesis. The daily "on phases" of the patients could be increased from two up to nine hours in the individual patients by NADH administration.