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Plant cell culture monitoring using an in situ multiwavelength fluorescence probe.

A multiwavelength fluorescence probe is proposed for in situ monitoring of Eschscholtzia californica and Catharanthus roseus plant cell cultures. The potential of the probe as a tool for real-time estimation of biomass and production in secondary metabolites has been studied. The probe excitation range is 270-550 nm and the emission range is 310-590 nm, with a step of 20 nm for both excitation and emission filters. Many endogenous fluorophores such as NAD(P)H, riboflavins (riboflavin and derivatives such as FMN, FAD), tryptamine and tryptophan, and fluorescent secondary metabolites were analyzed simultaneously. NAD(P)H fluorescence signal (350/450 nm) showed to be an adequate signal for estimating cells activity. Riboflavins fluorescence signal (450/530 nm) followed C. roseus cell concentration both for the growth phase and after elicitation with jasmonic acid. Fluorescence from the alkaloids interfered with NAD(P)H signal during the production phase. For C. roseus, tryptophan, tryptamine, ajmalicine and serpentine were monitored by the probe. For E. californica, fluorescence from alkaloids overlapped with riboflavins preventing from using the probe to follow cell growth but global alkaloids production could be followed using the probe.

Bioreactors↗

Benzodiazepine receptor affinity and interaction of some N-(indol-3-ylglyoxylyl)amine derivatives.

Several derivatives, in which tryptamine, tyramine, and dopamine moieties are linked to the indole nucleus by an oxalyl bridge, were tested for their ability to displace the specific binding of [3H]flunitrazepam from bovine brain membranes. GABA ratio and in vivo tests for the most potent compounds showed they behave as inverse agonists at the benzodiazepine receptor (BzR). To better define the structure-activity relationship (SAR) of this kind of ligand, several phenylethylamine derivatives were synthesized to evaluate their affinity to BzR. Some of these derivatives (17, 21, 24, 26, and 30) were found to exhibit high affinity (Ki = 0.51-0.085 microM) for BzR and possessed a partial agonist activity, although their chemical structure is closely related to tryptamine 2-6, tyramine 7-11, and dopamine 12-16 derivatives. A different interaction of these ligands to the receptor site is hypothesized. Moreover, all the prepared 1-methyl derivatives exhibited very low binding affinity to BzR.

Animals↗

Oxidation of serotonin by superoxide radical: implications to neurodegenerative brain disorders.

Many new lines of evidence implicate both superoxide anion radical (O2*-) and biogenic amine neurotransmitters in the pathological mechanisms that underlie neuronal damage caused by methamphetamine (MA), glutamate-mediated oxidative toxicity, ischemia-reperfusion, and other neurodegenerative brain disorders. In this investigation the oxidation of 5-hydroxytryptamine (5-HT, serotonin) by an O2*--generating system (xanthine/xanthine oxidase) in buffered aqueous solution at pH 7.4 has been studied. The major product of the O2*--mediated oxidation of 5-HT is tryptamine-4,5-dione (T-4, 5-D). However, O2*- and H2O2, cogenerated by the xanthine oxidase-mediated oxidation of xanthine to uric acid, together react with trace levels of iron that contaminate buffer constituents to give a chemically ill-defined oxo-iron species. This species mediates the oxidation of 5-HT to a C(4)-centered carbocation intermediate that reacts with 5-HT to give 5,5'-dihydroxy-4, 4'-bitryptamine (4,4'-D) and with uric acid to give 9-[3-(2-aminoethyl)-5-hydroxy-1H-indol-4-yl]-2,6,8-triketo-1H,3H, 7H-purine (7) as the major products. These products differ from those formed in the HO*-mediated oxidation of 5-HT under similar conditions. When the reaction is carried out in the presence of the intraneuronal nucleophile glutathione (GSH), T-4,5-D is scavenged to give 7-(S-glutathionyl)tryptamine-4,5-dione, whereas the putative carbocation intermediate is scavenged to give 4-(S-glutathionyl)-5-hydroxytryptamine. T-4,5-D also reacts with the sulfhydryl residues of a model protein, alcohol dehydrogenase, and inhibits its activity. Previous investigators have proposed that T-4, 5-D is a serotonergic neurotoxin. This raises the possibility that T-4,5-D and perhaps other putative intraneuronal metabolites formed by the O2*-/H2O2/oxo-iron-mediated oxidations of 5-HT might be endotoxins that contribute to neurodegeneration in brain regions innervated by serotonergic neurons caused by MA, ischemia-reperfusion, and other neurodegenerative brain disorders.

Antioxidants↗

(-)1-(Benzofuran-2-yl)-2-propylaminopentane, [(-)BPAP], a selective enhancer of the impulse propagation mediated release of catecholamines and serotonin in the brain.

1. The brain constituents beta-phenylethylamine (PEA) and tryptamine enhance the impulse propagation mediated transmitter release (exocytosis) from the catecholaminergic and serotoninergic neurons in the brain ('catecholaminergic/serotoninergic activity enhancer, CAE/SAE, effect'). (-)Deprenyl (Selegiline) and (-)1-phenyl-2-propylaminopentane [(-)PPAP] are amphetamine derived CAE substances devoid of the catecholamine releasing property. 2. By changing the aromatic ring in PPAP we developed highly potent and selective CAE/SAE substances, structurally unrelated to the amphetamines. Out of 65 newly synthetized compounds, a tryptamine derived structure, (-)1-(benzofuran-2-yl)-2-propylaminopentane [(-)BPAP] was selected as a potential follower of (-)deprenyl in the clinic and as a reference compound for further analysis of the CAE/SAE mechanism in the mammalian brain. 3. (-)BPAP significantly enhanced in 0.18 micromol 1(-1) concentration the impulse propagation mediated release of [(3)H]-noradrenaline and [(3)H]-dopamine and in 36 nmol 1(-1) concentration the release of [(3)H]-serotonin from the isolated brain stem of rats. The amount of catecholamines and serotonin released from isolated discrete rat brain regions (dopamine from the striatum, substantia nigra and tuberculum olfactorium, noradrenaline from the locus coeruleus and serotonin from the raphe) enhanced significantly in the presence of 10(-12) - 10(-14) M (-)BPAP. BPAP protected cultured hippocampal neurons from the neurotoxic effect of beta-amyloid in 10(-14) M concentration. In rats (-)BPAP significantly enhanced the activity of the catecholaminergic and serotoninergic neurons in the brain 30 min after acute injection of 0.1 microg kg(-1) s.c. In the shuttle box, (-)BPAP in rats was about 130 times more potent than (-)deprenyl in antagonizing tetrabenazine induced inhibition of performance.

Animals↗

Site-specific and bulk-phase generation of hydroxyl radicals in the presence of cupric ions and thiol compounds.

Addition of a thiol compound to a solution containing Cu2+ and H2O2 resulted in the generation of hydroxyl radicals (OH.). These radicals were able to oxidize salicylic acid and tryptamine in a reaction that was strongly inhibited by the OH.-scavenger mannitol. Covalent coupling of the thiol compound to tryptamine did not significantly influence the degradation of the indole moiety subsequent to addition of H2O2 and Cu2+. The inhibiting effect of mannitol, however, was strongly reduced, indicating that the scavenger could not interfere with site-specific reactions of OH..

Copper↗

Characterization of the serotoninergic system in the C57BL/6 mouse skin.

We showed expression of the tryptophan hydroxylase gene and of tryptophan hydroxylase protein immunoreactivity in mouse skin and skin cells. Extracts from skin and melanocyte samples acetylated serotonin to N-acetylserotonin and tryptamine to N-acetyltryptamine. A different enzyme from arylalkylamine N-acetyltransferase mediated this reaction, as this gene was defective in the C57BL6 mouse, coding predominantly for a protein without enzymatic activity. Serotonin (but not tryptamine) acetylation varied according to hair cycle phase and anatomic location. Serotonin was also metabolized to 5-hydroxytryptophol and 5-hydroxyindole acetic acid, probably through stepwise transformation catalyzed by monoamine oxidase, aldehyde dehydrogenase and aldehyde reductase. Activity of the melatonin-forming enzyme hydroxyindole-O-methyltransferase was notably below detectable levels in all samples of mouse corporal skin, although it was detectable at low levels in the ears and in Cloudman melanoma (derived from the DBA/2 J mouse strain). In conclusion, mouse skin has the molecular and biochemical apparatus necessary to produce and metabolize serotonin and N-acetylserotonin, and its activity is determined by topography, physiological status of the skin, cell type and mouse strain.

Animals↗

Enantioselective organocatalytic construction of pyrroloindolines by a cascade addition-cyclization strategy: synthesis of (-)-flustramine B.

Pyrroloindoline and bispyrroloindoline are a subclass of alkaloid structural motifs that commonly exhibit biological activity. An enantioselective organocatalytic approach to the synthesis of pyrroloindoline architecture is described. The addition-cyclization of tryptamines with alpha,beta-unsaturated aldehydes in the presence of imidazolidinone catalysts 1 and 8 provides pyrroloindoline adducts in high yield and excellent enantioselectivities. This transformation is successful for a wide range of tryptamine and alpha,beta-unsaturated aldehyde substrates. This amine-catalyzed sequence has been extended to the enantioselective construction of furanoindoline frameworks. Application of this pyrroloindoline-forming reaction to natural product synthesis has been accomplished in the context of the enantioselective synthesis of (-)-flustramine B.

Aldehydes↗

Redirection of tryptophan leads to production of low indole glucosinolate canola.

Cruciferous plants are known to produce over a hundred different mustard oil glycosides, which are derived from methionine, phenylalanine, or tryptophan. In oil-producing crops like Brassica napus (canola), the presence of indole glucosinolates in seed protein meals has decreased meal palatability and has limited their value as animal feed. We have transformed canola plants with a gene that encodes tryptophan decarboxylase (TDC) in an attempt to redirect tryptophan into tryptamine rather than into indole glucosinolates. Transgenic plants that expressed this decarboxylase activity accumulated tryptamine while correspondingly lower levels of tryptophan-derived indole glucosinolates were produced in all plant parts compared with nontransformed controls. Of particular significance, the indole glucosinolate content of mature seeds from transgenic plants was only 3% of that found in nontransformed seeds. These results demonstrate how the creation of artificial metabolic sinks could divert metabolite flow and be used to remove these undesirable indole glucosinolates, thereby increasing the value of the oilseed meals, which are produced after extraction of oil from the seed.

Aromatic-L-Amino-Acid Decarboxylases↗

Individual residues contribute to multiple differences in ligand recognition between vesicular monoamine transporters 1 and 2.

Molecular cloning has identified two vesicular monoamine transporters (VMATs), one expressed in non-neural cells of the periphery (VMAT1) and the other by multiple monoamine cell populations in the brain (VMAT2). Functional analysis has previously shown that VMAT2 has a higher affinity than VMAT1 for monoamine neurotransmitters as well as the inhibitor tetrabenazine. The analysis of chimeric transporters has also identified two major regions required for the high affinity interactions of VMAT2 with these ligands. We have now used site-directed mutagenesis to identify the individual residues responsible for these differences. Focusing on the region that spans transmembrane domains 9 through 12, we have replaced VMAT2 residues with the corresponding residues from VMAT1. Many residues in this region had no effect on the recognition of these ligands, but substitution of Tyr-434 with Phe and Asp-461 with Asn reduced the affinity for tetrabenazine, histamine, and serotonin. Although the ability to affect recognition of multiple ligands suggests a general structural role for these residues, the mutations did not affect dopamine recognition, indicating a more specific role, possibly in recognition of the ring nitrogen that occurs in tetrabenazine, histamine, and serotonin but not dopamine. The mutation K446Q reduced the affinity of VMAT2 for tetrabenazine and serotonin but not histamine, whereas F464Y reduced serotonin affinity and perhaps histamine recognition but not tetrabenazine sensitivity, providing more evidence for specificity. Interestingly, the Vmax of both VMATs for dopamine exceeded that for serotonin by 3-5-fold, indicating a difference in the speed of packaging of these two neurotransmitters. We also found that VMAT1 has a higher affinity for tryptamine than VMAT2. This mutually exclusive interaction with serotonin and tryptamine also suggests a physiological rationale for the existence of two VMATs. Surprisingly, the residue responsible for this difference, Tyr-434, also accounts for the higher affinity interaction of VMAT2 with tetrabenazine, histamine, and serotonin. Interestingly, replacement of Tyr-434 with alanine increases the affinity of VMAT2 for both serotonin and dopamine and reduces the rate of dopamine transport.

Amino Acid Sequence↗

Indoleamine analogs as probes of the substrate selectivity and catalytic mechanism of serotonin N-acetyltransferase.

Serotonin N-acetyltransferase (arylalkylamine N-ace-tyltransferase (AANAT)) catalyzes the reaction of serotonin (or tryptamine) with acetyl-CoA to form N-acetylserotonin (or N-acetyltryptamine) and is responsible for the melatonin circadian rhythm in vertebrates. This study evaluates a series of indoleamine analogs as alternate substrates of AANAT. 3-Indolepropylamine and 3-indolebutylamine were chemically synthesized and found to be processed by AANAT, although 20- and 60-fold less efficiently compared with the natural substrate serotonin, respectively. Racemic alpha-methyltryptamine and Nomega-methyltryptamine were also shown to be substrates for AANAT, again with reduced kcat and kcat/Km compared with serotonin. The enzyme did exhibit approximately 9:1 stereoselectivity for the R-enantiomer of alpha-methyltryptamine versus the S-enantiomer. By measuring the enzymatic rates versus increasing buffer microviscosity, it was demonstrated that diffusional release of product is most likely the principal rate-determining step for the enzymatic transformation of tryptamine (which has similar kcat and kcat/Km compared with serotonin). Analysis of kcat and kcat/Km versus pH for the poor substrate Nomega-methyltryptamine showed that an ionizable group on the enzyme with pKa approximately 7, required to be in its deprotonated form, may be important in catalysis. The alpha-methyltryptamine analog alpha-trifluoromethyltryptamine was not processed by the enzyme, but served as a modest competitive inhibitor. Taken together with the pH-rate analysis, these results favor a model in which the serotonin substrate binds to the enzyme as the positively charged ammonium salt, and nucleophilicity of the amine is important in enzyme-catalyzed acetyl transfer.

Acetyl Coenzyme A↗

Multiple residues contribute independently to differences in ligand recognition between vesicular monoamine transporters 1 and 2.

The two closely related vesicular monoamine transporters (VMATs) 1 and 2 differ substantially in ligand recognition. The neuronal VMAT2 exhibits a higher affinity for monoamine substrates and in particular for histamine as well as a greater sensitivity to the inhibitor tetrabenazine than the nonneuronal VMAT1. The analysis of chimeric transport proteins has previously shown that two major domains, one spanning transmembrane domains (TMDs) 5-8 (TMD5-8) and the other, TMDs 9-12 (TMD9-12), are required for the high affinity interactions characteristic of VMAT2. Using site-directed mutagenesis to replace residues in TMD5-8 of VMAT2 with the equivalent residues from VMAT1, we now show that the sensitivity of VMAT2 to tetrabenazine requires Ala-315, and this interaction occurs independently of the interaction with residues in TMD9-12. The ability to recognize histamine as a substrate depends on Pro-237, and the contribution of TMD9-12 to histamine recognition appears to involve a common mechanism. In contrast, the replacement of many residues in TMD5-8 of VMAT2 with equivalent residues from VMAT1 improves the recognition of both serotonin and tryptamine, and these mutations show a dominant effect on the recognition of both tryptamine and serotonin over mutations in TMD9-12. The results indicate that different ligands interact through distinct mechanisms with the VMATs and that the recognition of each ligand involves multiple, independent interactions with the transport protein.

Amino Acid Sequence↗

Importance of barrier shape in enzyme-catalyzed reactions. Vibrationally assisted hydrogen tunneling in tryptophan tryptophylquinone-dependent amine dehydrogenases.

C-H bond breakage by tryptophan tryptophylquinone (TTQ)-dependent methylamine dehydrogenase (MADH) occurs by vibrationally assisted tunneling (Basran, J., Sutcliffe, M. J., and Scrutton, N. S. (1999) Biochemistry 38, 3218--3222). We show here a similar mechanism in TTQ-dependent aromatic amine dehydrogenase (AADH). The rate of TTQ reduction by dopamine in AADH has a large, temperature independent kinetic isotope effect (KIE = 12.9 +/- 0.2), which is highly suggestive of vibrationally assisted tunneling. H-transfer is compromised with benzylamine as substrate and the KIE is deflated (4.8 +/- 0.2). The KIE is temperature-independent, but reaction rates are strongly dependent on temperature. With tryptamine as substrate reaction rates can be determined only at low temperature as C-H bond cleavage is rapid, and an exceptionally large KIE (54.7 +/- 1.0) is observed. Studies with deuterated tryptamine suggest vibrationally assisted tunneling is the mechanism of deuterium and, by inference, hydrogen transfer. Bond cleavage by MADH using a slow substrate (ethanolamine) occurs with an inflated KIE (14.7 +/- 0.2 at 25 degrees C). The KIE is temperature-dependent, consistent with differential tunneling of protium and deuterium. Our observations illustrate the different modes of H-transfer in MADH and AADH with fast and slow substrates and highlight the importance of barrier shape in determining reaction rate.

Benzylamines↗

Platelet and plasma amine oxidase inhibition and urinary amine excretion changes during phenelzine treatment.

The treatment of depressed patients with the monoamine oxidase (MAO)-inhibiting antidepressant, phenelzine, was found to be accompanied by an 82 per cent reduction in platelet MAO activity and a 91 per cent reduction in plasma amine oxidase activity. Maximum reductions in enzyme activity occurred after 7 to 14 days of treatment; recovery of enzyme activity posttreatment required an average of 14 days for the platelet MAO and greater than 6 weeks for the plasma enzyme. Marked elevations in urinary tryptamine excretion occurred in conjunction with MAO inhibition during phenelzine treatment, but the magnitidue of urinary tryptamine change in individual patients was not closely correlated with the magnitude of enzyme activity reduction. Changes in platelet serotonin content serotonin content and in urinary catecholamine metabolites also occurred in response to phenelzine treatment.

Blood Platelets↗

The production of inflammatory compounds by Propionibacterium acnes and other skin organisms.

Culture supernatants from four species of skin microorganisms (P. acnes, P. avidum, P. granulosum and S. epidermidis) were assayed for smooth muscle contracting substances which are indicative of inflammatory activity. At least three types of smooth muscle contracting substances were detected. These were: first, a substance active on a rat fundic strip preparation and antagonized by N,N-DMT. Activity was enhanced when cultures were grown in the presence of tryptophan. This substance was probably tryptamine. Second, a substance active on a guinea-pig ileum preparation and antagonized by mepyramine. Activity was enhanced when cultures were grown in the presence of histidine. This substance was probably histamine. Third, a substance active on a rat fundic strip preparation but not antagonized by N,N-DMT, mepyramine, atropine or indomethacin. Activity was enhanced when cultures were grown in the presence of glucose. This activity was probably due to acetate, propionate or other short-chain fatty-acid salts. Chromatographic analysis confirmed the presence of histamine, tryptamine and short-chain fatty acids in the culture supernatants. These substances if produced in vivo may cause or contribute to inflammation and pain directly without the prior mediation of the immune system. Cell extracts of Propionibacterium species were analysed by bioassay for the presence of prostaglandin-like compounds. These could not be detected in any of the eight strains of organisms tested.

Acne Vulgaris↗

Platelet monoamine oxidase in a pedigree with schizophrenia: an interlaboratory project.

Conflicting reports on the association between platelet MAO activity and schizophrenia prompted a critical review and determinations on identical samples at one laboratory in Sweden and one in the U.S.A. Samples originated from eight schizophrenics and 27 relatives belonging to a large pedigree, thus ensuring biological homogeneity. In the USA laboratory, a significantly lower MAO activity was found in the schizophrenics when benzylamine or beta-phenylethylamine was used as substrate (but not with tryptamine), while a similar result was obtained in the Swedish laboratory when tryptamine was used (but not with benzylamine or beta-phenylethylamine). Comparisons between materials examined in different laboratories do not seem meaningful until differences in methodologies have been clarified. At present there is neither proof nor disproof of MAO being a "genetic marker" for vulnerability to the schizophrenic disorder.

Benzyl Compounds↗

Purification and properties of strictosidine synthase, the key enzyme in indole alkaloid formation.

A new enzyme, strictosidine synthase, which catalyzes the synthesis of 3-alpha(S)-strictosidine from tryptamine and secologanin was isolated from the soluble protein extract of Catharanthus roseus cell suspension cultures and was purified approximately 50-fold by ammonium sulfate fractionation, column chromatography on DEAE-cellulose. Ultrogel AcA34 and isoelectric focusing. The apparent molecular weight of the enzyme was 34000. The pH optimum was 6.8, apparent Km values for tryptamine and secologanin were 2.3 mM and 3.4 mM respectively for the enzyme to synthesize strictosidine. Strictosidine synthase shows high substrate specificity. No apparent cofactor requirement could be demonstrated. Of several enzyme inhibitors tested, only p-chloromercuribenzoate inhibited the enzyme. The enzyme was relatively stable and could be stored at -20 degrees C for periods of up to 1 year without appreciable loss of catalytic activity. The enzyme was demonstrated to occur in suspension cultures of 15 different species belonging to 9 different genera of the indole-alkaloid-producing subfamily Plumerioideae of the Apocynaceae family. This enzyme is responsible for the synthesis of strictosidine the key intermediate in the formation of the majority of monoterpenoid indole alkaloids occurring in the plant kingdom.

Cells, Cultured↗

Measurement of platelet monoamine oxidase using three different substrates in patients with alcoholism and schizophrenia.

The platelet monoamine oxidase (MAO) activities in alcoholism and schizophrenia were investigated by means of simultaneous determination, using beta-phenyl-ethylamine, tryptamine and serotonin as substrates. No significant difference was found between the MAO levels in the alcoholic and schizophrenic groups, when tryptamine was used as a substrate, but both groups showed lower values than the controls. On the other hand, beta-phenylethylamine, a specific substrate for MAO B used as a substrate, showed no significant difference between the alcoholic and control groups in the activities. These two groups showed higher values in MAO activity than the schizophrenic group, whereas when MAO activity was estimated using serotonin, platelet enzyme was found to be inhibited significantly in alcoholism, and the level of activities in the schizophrenics was similar to that of the controls. Moreover, the beta-phenylethylamine inhibition curve obtained serotonin as the substrate in the pooled platelets of 50 normal human subjects, and the MAO activity could not be inhibited by higher concentrations than the Km value of serotonin. These findings suggested that there might be two interacting catabolic sites having different substrate affinities in blood platelet MAO. Thus, it could be speculated that serotonergic catabolic sites of MAO in the platelets are disturbed in the alcoholics, while beta-phenylethylaminergic catabolic sites of platelet MAO are inherently vulnerable in schizophrenia.

Adult↗

Effect of L-tryptophan on mouse brain 5-hydroxytryptamine: comparison of values obtained using a fluorimetric assay and a liquid Chromatographic assay with electrochemical detection.

5-Hydroxytryptamine (5-HT) in mouse brain and spinal cord was assayed in the same samples using a fluorimetric assay and a high pressure liquid chromatographic (HPLC) assay with electrochemical detection. The HPLC assay was able to detect levels of 5-hydroxytryptamine as low as 0.2-0.5 pmol. With the column (Vydac cation exchange), solvent system (acetate/citrate buffer, 0.1 or 0.2 M, pH 4.8-5.2) extraction procedure and electrode potential (+0.55 V) used, the HPLC assay was specific for 5-HT. When the electrode potential was increased to +0.9 V tryptamine could also be detected, with a longer retention time than 5-hydroxytryptamine. The percent-age increase in mouse brain 5-hydroxytryptamine after pargyline (75 mg/kg) and pargyline L-tryptophan (100 mg/kg) was very similar whether measured by fluorimetry or HPLC, although the fluorimetric assay gave consistently higher absolute values (24-32%) in both control and drug-treated animals. L-Tryptophan (25, 50 and 100 mg/kg) also increased brain 5-hydroxytryptamine with similar percentage increases with either assay method. There was a significant correlation (P less than 0.001) between the values obtained with the two assay methods. The results confirm the use of HPLC with electrochemical detection as a sensitive and specific assay method for 5-hydroxytryptamine and indicate its potential use for the assay of tryptamine, and the importance of determining the electroactivity and retention characteristics of any drugs used.

Animals↗