Nuclear GAPDH in cortical microglia mediates cellular stress-induced cognitive inflexibility.

We report a mechanism that underlies stress-induced cognitive inflexibility at the molecular level. In a mouse model under subacute cellular stress in which deficits in rule shifting tasks were elicited, the nuclear glyceraldehyde dehydrogenase (N-GAPDH) cascade was activated specifically in microglia in the prelimbic cortex. The cognitive deficits were normalized with a pharmacological intervention with a compound (the RR compound) that selectively blocked the initiation of N-GAPDH cascade without affecting glycolytic activity. The normalization was also observed with a microglia-specific genetic intervention targeting the N-GAPDH cascade. At the mechanistic levels, the microglial secretion of High-Mobility Group Box (HMGB), which is known to bind with and regulate the NMDA-type glutamate receptors, was elevated. Consequently, the hyperactivation of the prelimbic layer 5 excitatory neurons, a neural substrate for cognitive inflexibility, was also observed. The upregulation of the microglial HMGB signaling and neuronal hyperactivation were normalized by the pharmacological and microglia-specific genetic interventions. Taken together, we show a pivotal role of cortical microglia and microglia-neuron interaction in stress-induced cognitive inflexibility. We underscore the N-GAPDH cascade in microglia, which causally mediates stress-induced cognitive alteration.

Preventative effects of 1-methyl-1,2,3,4-tetrahydroisoquinoline derivatives (N-functional group loading) on MPTP-induced parkinsonism in mice.

1,2,3,4-tetrahydroisoquinoline (TIQ) is endogenously present in the human brain, and some of its derivatives are thought to contribute to the induction of Parkinson's disease (PD)-like signs in rodents and primates. In contrast, the endogenous TIQ derivative 1-methyl-TIQ (1-MeTIQ) is reported to be neuroprotective. In the present study, we compared the effects of artificially modified 1-MeTIQ derivatives (loading an N-propyl, N-propenyl, N-propargyl, or N-butynyl group) on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD-like signs in mice. In a behavioral study, MPTP-induced bradykinesia was significantly decreased by all compounds. However, only 1-Me-N-propargyl-TIQ showed an inhibitory effect by blocking the MPTP-induced reduction in striatal dopamine content and the number of nigral tyrosine hydroxylase-positive cells. Western blot analysis showed that 1-Me-N-propargyl-TIQ and 1-Me-N-butynyl-TIQ potently prevented the MPTP-induced decrease in dopamine transporter expression, whereas 1-MeTIQ and 1-Me-N-propyl-TIQ did not. These results suggest that although loading an N-propargyl group on 1-MeTIQ clearly enhanced neuroprotective effects, other N-functional groups showed distinct pharmacological properties characteristic of their functional groups. Thus, the number of bonds and length of the N-functional group may contribute to the observed differences in effect.

Effect of psilocin on extracellular dopamine and serotonin levels in the mesoaccumbens and mesocortical pathway in awake rats.

Psilocin (3-[2-(dimethylamino)ethyl]-1H-indol-4-ol) is a hallucinogenic component of the Mexican mushroom Psilocybe mexicana and a skeletal serotonin (5-HT) analogue. Psilocin is the active metabolite of psilocybin (3-[2-(dimethylamino)ethyl]-1H-indol-4-yl dihydrogen phosphate). In the present study, we examined the effects of systemically administered psilocin on extracellular dopamine and 5-HT concentrations in the ventral tegmental area (VTA), nucleus accumbens, and medial prefrontal cortex of the dopaminergic pathway in awake rats using in vivo microdialysis. Intraperitoneal administration of psilocin (5, 10 mg/kg) significantly increased extracellular dopamine levels in the nucleus accumbens. Psilocin did not affect the extracellular 5-HT level in the nucleus accumbens. Conversely, systemic administration of psilocin (10 mg/kg) significantly increased extracellular 5-HT levels in the medial prefrontal cortex of rats, but dopamine was decreased in this region. However, neither extracellular dopamine nor 5-HT levels in the VTA were altered by administration of psilocin. Behaviorally, psilocin significantly increased the number of head twitches. Thus, psilocin affects the dopaminergic system in the nucleus accumbens. In the serotonergic system, psilocin contribute to a crucial effect in the medial prefrontal cortex. The present data suggest that psilocin increased both the extracellular dopamine and 5-HT concentrations in the mesoaccumbens and/or mesocortical pathway.

Properties of 3-methyl-TIQ and 3-methyl-N-propargyl-TIQ for preventing MPTP-induced parkinsonism-like symptoms in mice.

BACKGROUND: Selegiline, a therapeutic drug for Parkinson's disease (PD), structurally resembles the endogenous parkinsonism-related compound 1,2,3,4-tetrahydroisoquinoline (TIQ). In the present study, we evaluated the effects of 3-methyl-TIQ (3-MeTIQ) and 3-methyl-N-propargyl-TIQ (3-Me-N-proTIQ), selegiline mimetic TIQ derivatives, for preventing 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism-like symptoms in mice. METHODS: We evaluated the preventative effects of 3-MeTIQ and 3-Me-N-proTIQ on MPTP-induced bradykinesia and depletion of striatal dopamine (DA) and nigral tyrosine hydroxylase (TH)-positive cells. RESULTS: MPTP-induced bradykinesia was not different when mice were pretreated with 3-MeTIQ, except for the high-dose group. However, pretreatment with 3-Me-N-proTIQ significantly prevented the appearance of this akinesic status. MPTP-induced striatal DA and 3,4-dehydroxyphenylacetic acid reduction were significantly prevented by pretreatment with 3-Me-N-proTIQ, but not 3-MeTIQ, in a dose-dependent manner. On the other hand, levels of serotonin and its metabolite, 5-hydroxyindole acetic acid, in the striatum were increased following treatment with 3-MeTIQ. In addition, the MPTP-induced decrease in TH-positive cells in the substantia nigra was significantly reduced by pretreatment with 3-Me-N-proTIQ, but not 3-MeTIQ. CONCLUSIONS: These results suggest that not only does 3-Me-N-proTIQ have potential as a candidate compound for disease-modifying therapy for PD, but also the N-propargyl functional group plays an important role in neuroprotection.

Synthesis of chiral 3-methyl- and 3-methyl-N-propargyl-1,2,3,4-tetrahydroisoquinoline and prevention of MPP+ -induced cytotoxicity.

The chemical structure of selegiline, a commercially available drug for Parkinson's disease (PD), resembles that of 1,2,3,4-tetrahydroisoquinoline (TIQ), an endogenous parkinsonism-inducing compound. In the present study, we evaluated the direct cytotoxicity of (R)- and (S)-3-methyl-TIQ (3-MeTIQ) and (R)- and (S)-3-methyl-N-propargyl-TIQ (3-Me-N-propargyl-TIQ), as selegiline-mimetic TIQ derivatives, and their ability to prevent 1-methyl-4-phenylpyridinium iodide (MPP(+))-induced cell death. Synthesis of optically-pure 3-MeTIQs was achieved via the super acid-induced cyclization of chiral N-benzyl-N-[1-methyl-2-(phenylsulfinyl)ethyl]formamide using a Pummerer-type cyclization reaction as the key step in producing excellent yields. Subsequent N-propargylation of chiral 3-MeTIQs using propynylbromide gave the corresponding 3-Me-N-propargyl-TIQs. In our in vitro experiments, the direct cytotoxicity of chiral 3-MeTIQs and 3-Me-N-propargyl-TIQs was almost identical, with no relationship to optical chirality except for (S)-3-Me-N-propargyl-TIQ, which had significantly weaker direct cytotoxicity than the other 3-MeTIQ derivatives. However, the decreased viability of PC12 cells induced by treatment with MPP(+) was accelerated by the coexistence of 3-MeTIQs and inhibited by 3-Me-N-propargyl-TIQs without any participation of the stereochemistry at the 3-position. These results suggest that the N-propargyl group is necessary for protection of cells against the toxicity of MPP(+). Furthermore, the stereochemistry of the 3-position appears to partially participate in the direct cytotoxicity of 3-Me-N-propargyl-TIQs.

Synthesis and in vitro cytotoxicity of 1,2,3,4-tetrahydroisoquinoline derivatives.

Several 1-alkyl-1,2,3,4-tetrahydroisoquinoline (TIQ) derivatives, which may play a role in Parkinson's disease, have been synthesized via Pummerer-type cyclization of the sulfonium ion formed in situ from N-formyl sulfoxide. Using an in vitro trypan blue exclusion assay, high concentrations of TIQ derivatives possessing bulky alkyl group substituents such as 1-cyclobutyl-, 1-cyclohexyl-, 1-phenyl- or 1-benzyl- at the C-1 position were found to significantly affect the viability of PC12 cells. Moreover, TIQ derivatives that moderately or strongly induced apoptosis (e.g., 1-phenyl-TIQ and 1-cyclohexyl-TIQ, respectively) paralleled the results obtained using the trypan blue exclusion assay. These results suggest that the size and electron-donating properties of functional groups may affect the cytotoxicity of TIQ derivatives.

Synthesis and neurotoxicity of tetrahydroisoquinoline derivatives for studying Parkinson's disease.

Parkinson's disease involves the progressive degeneration of dopaminergic neurons in the substantia nigra. However, the etiology of the disease remains to be elucidated. Endogenous amines, such as 1,2,3,4-tetrahydroisoquinoline (TIQ) derivatives present in the mammalian brain, are known to participate in the pathogenesis of Parkinson's disease. These endogenous neurotoxins have been extensively studied because of their structural resemblance to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), an agent widely used for generating animal models of Parkinson's disease-like symptoms. Investigations of the synthesis and pharmacological properties of TIQ derivatives are expected to contribute to the development of new therapeutic agents for treating Parkinson's disease. In the present study, we describe more efficient synthesis methods for TIQ derivatives via Pummerer-type cyclization of the substrate N-acyl sulfoxide. Furthermore, the modified Pummerer reaction provided a convenient and efficient method for synthesizing various TIQs. TIQ and its derivative, 1-benzyl-TIQ, can induce parkinsonism in primates and rodents. On the other hand, one TIQ derivative, 1-methyl-TIQ, has been shown to prevent MPTP, TIQ, and 1-benzyl-TIQ induced behavioral abnormalities. Therefore, TIQ derivatives are considered to play an important role in both the onset and prevention of Parkinson's disease. In this article, we focus on the synthesis and pharmacological aspects of 1,2,3,4-tetrahydroisoquinoline derivatives in Parkinson's disease.

Ab initio molecular-orbital study of structures and energetics of Si3H3 neutral and anion.

The geometric structures and isomeric stabilities of various stationary points in Si(3)H(3) neutral and its anion are investigated at the coupled-cluster singles, doubles (triples) [CCSD(T)] level of theory. For geometrical surveys, the basis sets used are of the Dunning's correlation consistent basis sets of triple-zeta quality for the neutral. To the anions, the Dunning's correlation consistent basis sets of double-zeta quality with diffuse functions are applied. For the three lower-lying anion isomers, the Dunning's correlation consistent basis sets of triple-zeta quality with diffuse functions (aug-cc-pVTZ) are also used. The final energies for the optimized stationary points are calculated at the CCSD(T) level of theory with the aug-cc-pVTZ basis sets. The basis sets of 6-311++G(3df,2pd) were also used for the lower-lying anion isomers. The Gaussian-2 method was performed only for the lower-lying anion isomers to clarify the relative stabilities. The global minimum neutral 1 (C(1):(2)A) has an unsymmetrical hydrogen-bridged bond; the conformer 2 in C(s) symmetry is a saddle point connecting the two equivalent isomers 1. Two lower-lying isomers (3 and 4) are also predicted within the energy range of 20 kJmol. In the anion, however, the conformer 4 (C(s):(1)A(')) with five formal valence electrons is a global minimum. Two more isomers (2 and 3) lie within 20 kJmol as in the neutral; the conformer 1 converts to the isomer 2. The quartets for the neutrals and diradical triplets for the anions were further studied; lower-lying quartets and triplets, competing with the corresponding doublet and singlet, respectively, were not found in the present systems. The vertical and adiabatic electron affinities of the global minimum neutral 1, producing the second lowest-lying anion isomer 2, amount to 2.18 and 2.35 eV, respectively, at the CCSD(T)/aug-cc-pVTZ level of theory. The electron addition to the third lowest-lying neutral isomer 4 produces the largest vertical electron affinities of 2.48 eV. The D(3h) structure, being the global minimum in the corresponding Si(3)H(3) (+) cation (trisilacyclopropenyl cation), converts to the isomer 8 (C(s)) or 11 (C(2)) due to the Jahn-Teller effect in the Si(3)H(3) neutral.

Theoretical study on isomeric stabilities of C2H2Si and its ionization potentials and electron affinities.

The geometric structures and isomeric stabilities of various stationary points in C(2)H(2)Si neutral and its cation and anion are investigated at the coupled-cluster singles, doubles (triples) [CCSD(T)] level of theory. For the geometrical survey, the basis sets used are of the Dunning's correlation consistent basis sets of triple-zeta quality (cc-pVTZ) for the neutral and cation. For the anions, the cc-pVTZ basis sets with diffuse functions (aug-cc-pVTZ) are used. The final energies are calculated by the use of the CCSD(T) level of theory with the aug-cc-pVTZ basis set at their optimized geometries. To lower lying neutrals and cations, the Dunning's correlation consistent basis sets of quadruple-zeta quality (cc-pVQZ) are also applied. Both the global minima of the C(2)H(2)Si neutral and cation, N-1 (C(2v):(1)A(1)) and C-1 (C(2v):(2)B(2)), respectively, are silacyclopropenylidene conformers, having a CCSi ring with a C[Double Bond]C double bond. No competitive stable isomers exist in the present C(2)H(2)Si neutral. In the cation, however, the second lowest lying isomer C-2 lies 10.8 kJ/mol above the most stable C-1. The vertical and adiabatic ionization potentials from the lowest lying neutral N-1 are 9.83 and 8.97 eV, respectively, at the CCSD(T)/cc-pVQZ level of theory. The electron addition to the N-1 does not result in the anion with positive (real) electron affinities. On the other hand, the electron addition to the N-2 isomer produces the global minimum anion A-1 (C(2v):(2)B(1)) with the positive electron affinities of 1.13 eV. The second lowest lying anion isomer A-2 with silylenylacetylene conformer, produced from an electron addition to the N-3 neutral, very well competes with the A-1 after the zero-point vibrational energy corrections. The energy difference between the two lowest lying isomers of the neutral and its anion, N-1 and A-1, is only 0.39 eV.

A synthesis of heteroaromatic analogues of 1-methyl-1,2,3,4-tetrahydroisoquinoline using the Pummerer-type cyclization reaction: observation of tandem cyclization reaction.

The sulfoxides 7b and 7d carrying thiophene or benzothiophene as heteroaromatic nucleophiles, when treated with trifluoroacetic anhydride at room temperature (Pummerer reaction), underwent an intramolecular alkylation in an exclusive manner to yield 4,5,6,7-tetrahydro-7-methyl-4-phenylsulfanylthieno[2,3-c]pyridine-6-carbaldehyde (10) and the corresponding benzothiophene derivative (12b) in high yields, respectively. Thus, this route provides biologically interesting nitrogen heterocycles (1b) and (2b). On the other hand, the sulfoxide (7c) carrying benzofuran as a nucleophile on reaction with TFAA yielded not only the Pummerer-type cyclization product (12a), but also the diastereoisomeric tandem cyclization products (13) and (14) having a noble 11-aza-2-oxa-7-thiatricyclo[4.3.3.0(1,5)]dodecane ring system (B). The formation of these products can be readily rationalized by the intervention of the oxonium ion intermediate (21).

A synthesis of chiral 1,1,3-trisubstituted 1,2,3,4-tetrahydro-beta-carbolines by the Pictet-Spengler reaction of tryptophan and ketones: conversion of (1R,3S)-diastereomers into their (1S,3S)-counterparts by scission of the C(1)-N(2) bond.

The Pictet-Spengler cyclization of the imines (3) prepared by the condensation of L-tryptophan methyl ester (1) and aryl methyl ketones (2), using titanium(IV) isopropoxide as an iminating reagent, quantitatively proceeded, when treated with trifluoroacetic acid (TFA) or formic acid, to provide two diastereomers, that is (1S,3S)-1-aryl-3-isopropoxycarbonyl-1-methyl-1,2,3,4-tetrahydro-beta-carbolines (4) and their (1R,3S)-diastereomers (5), of which the diastereomer ratios varied from 1 to 5 depending on the reaction conditions. The (1R,3S)-diastereomers (5) are thermodynamically more stable than their (1S,3S)-congeners (4), as shown by equilibration experiments in TFA. The conversion of 4 to 5 (also 5 to 4) should occur under acidic conditions by cleavage of the C(1)-N(2) bond with complete retention of configuration at the C-3 chiral center. The low diastereo-selectivity observed in the Pictet-Spengler reaction of 1 and 2 is concluded to be a stereochemical outcome under conditions of kinetic control (lower temperature, shorter reaction time), while the high diastereo selectivity with preferential formation of the more stable isomer (5) is the result of thermodynamically controlled experiments (higher temperature, longer reaction time).

Super acid-induced Pummerer-type cyclization reaction: improvement in the synthesis of chiral 1,3-dimethyl-1,2,3,4-tetrahydroisoquinolines.

Improved synthesis of four stereoisomeric chiral 1,3-dimethyl-1,2,3,4-tetrahydroisoquinolines (1a, b, ent-1a, b) was achieved via the super acid-induced cyclization of chiral N-[1-methyl-2-(phenylsulfinyl)ethyl]-N-(1-phenylethyl)formamides (4a, b, ent-4a, b) using the Pummerer-type cyclization reaction as a key step. The cyclization leading to the isoquinoline ring proceeded in a quantitative manner when trifluoromethane sulfonic acid (TFSA) was used as the super acid, although Friedel-Crafts-type alkylation of 4-phenylsulfanyl TIQ derivatives (5) with benzene used as the solvent accompanied cyclization to yield the 4-phenyl-TIQs (7). The byproduct (7) was exclusively formed when a large excess amount of TFSA was used.

No reduction of dopamine transporter binding sites in mice following treatment with the TIQ analogue 1-benzyl-1,2,3,4-tetrahydroisoquinoline.

1-Benzyl-1,2,3,4-tetrahydroisoquinoline (1-BnTIQ) and TIQ are endogenous substances inducing bradykinesia, one of the symptoms of parkinsonism, in rodents and primates, and 2-methyl-TIQ is postulated to be an active form of TIQ. We investigated the effect of 1-BnTIQ-, TIQ- or 2-methyl-TIQ-treatment on the binding of 2-beta-carbomethoxy-3-beta-(4-fluorophenyl)-[N-methyl-11C]tropane to striatal dopamine transporters (DATs) in mice. Neither 1-BnTIQ (80 mg/kg, i.p., twice per day for 10 days) nor 2-methyl-TIQ (40 mg/kg, i.p., twice per day for 10 days) affected the radioligand-DAT binding, while TIQ (80 mg/kg, i.p., twice per day for 10 days) induced a 14% decrease. These results indicate that 1-BnTIQ does not affect the density of DATs on dopaminergic neurons, and that it is not clear whether or not 2-methyl-TIQ is an active form of TIQ.

A convenient synthesis of 1,1-disubstituted 1,2,3,4-tetrahydroisoquinolines via Pictet-Spengler reaction using titanium(IV) isopropoxide and acetic-formic anhydride.

A synthesis of 1,1-disubstituted 1,2,3,4-tetrahydroisoquinolines (6) was achieved in a highly efficient manner via Pictet-Spengler reaction of arylethylamines (1) and acyclic and cyclic ketones (2) using titanium (IV) isopropoxide and acetic-formic anhydride. The cyclization of the in situ formed acyliminium ion (4) to N-formyl 1,2,3,4-tetrahydroisoquinoline (5) was greatly facilitated by using trifluoroacetic acid as an additional reagent. The Pictet-Spengler reaction was carried out by one pot procedure, providing a convenient and effective method for preparing various 1,2,3,4-tetrahydroisoquinolines.