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Previously, we designed and synthesized dipeptide mimetics of individual loops of the nerve growth factor (NGF) and the brain-derived neurotrophic factor (BDNF). It was shown that these mimetics activate the corresponding tyrosine kinase (Trk) receptors and have different patterns of activation of the PI3K/AKT and MAPK/ERK postreceptor signaling pathways in vitro. In the present study, it was shown on HT-22 cells that all these compounds activate the phospholipase C-γ1 (PLC-γ1) cascade. [ABSTRACT FROM AUTHOR]

The optimal synthetic scheme for the potential nootropic drug GZK-111 (N-phenylacetylglycyl-L-proline ethyl ester) was developed. Three synthetic schemes were tested, each of which included the following steps: 1) esterification of L-proline; 2) preparation of N-phenylacetylglycine; 3) formation of the peptide bond. Esterification of proline per Brenner and preparation of N-phenylacetylglycine via acylation of glycine with phenylacetyl chloride under Schotten—Baumann conditions were used in all synthetic schemes. Three methods for forming the peptide bond between N-phenylacetylglycine and the proline ester were tried (mixed anhydride under Anderson conditions, activated benzotriazole ester, and activated succinimide ester methods) and showed that the mixed anhydride method was optimal, giving a total yield of 42%. [ABSTRACT FROM AUTHOR]

Previously, researchers at Zakusov State Institute of Pharmacology used an original strategy for designing pharmacologically active dipeptides based on non-peptide drug structures to prepare the dipeptide ligands of 18-kDa translocator protein (TSPO) N-carbobenzoxy-L-tryptophanyl-L-isoleucine amide (GD-23) and N-phenylpropionyl-L-tryptophanyl-L-leucine amide (GD-102) that showed anxiolytic activity in standard behavioral tests. The present work reports GD-102 analogs with the reverse amino-acid sequence, i.e., N-phenylpropionyl-L-leucyl-L-tryptophan methylamide (GD-140), N-phenylpropionyl-L-leucyl-L-tryptophan (GD-139), N-phenylacetyl-L-leucyl-L-tryptophan amide (GD-141), N-phenylpropionyl-L-leucyl-L-tryptophan methyl ester (GD-138), and N-phenylpropionyl-L-leucyl-L-tryptophan amide (GD-136). Open-field (OF) tests of mice after i.p. administration showed that the newly synthesized dipeptides were less active than GD-102 (0.01 – 0.1 mg/kg). Dipeptide GD-140 showed anxiolytic activity at doses of 0.1, 0.5, and 1 mg/kg; GD-139, 0.5 and 5.0; GD-141, 1 and 5. Dipeptide GD-138 at a dose of 0.1 mg/kg reduced locomotor activity of animals in the OF test. GD-136 was inactive in the dose range 0.1 – 5 mg/kg. Molecular docking studies demonstrated that the studied compounds could be placed at the TSPO binding site of ligand PK 11195 (PDB ID: 2MGY). Also, π-stacking of the phenyl groups of dipeptides GD-136, GD-139, GD-140, and GD-141 with Trp107 of the receptor was revealed. For dipeptides GD-140 and GD-102, π-stacking with Trp95 was also detected. GD-138 did not exhibit π-stacking with either Trp107 or Trp95. It was concluded that the key interaction affecting the manifestation of anxiolytic activity was π-stacking of the dipeptide ligand with Trp95 of the receptor. The Trp-Leu sequence was preferred over the Leu-Trp sequence for the TSPO dipeptide ligands. [ABSTRACT FROM AUTHOR]

Endogenous neuropeptide cyclo-L-prolylglycine possesses mnemotropic and neuroprotective properties, which can result from its positive effect on the level of brain-derived neurotrophic factor and modulation of activity of insulin-like growth factor-1 and AMPA receptors. For detection of possible mitogenic action of cyclo-L-prolylglycine, we analyzed its effect on proliferative activity of HEK293 and SH-SY5Y cells assessed by expression of Ki-67 proliferation marker, cell cycle examination, and incorporation of modified nucleotide analog EdU into DNA. Cyclo-L-prolylglycine did not affect the level of Ki-67 in examined cell lines and distribution of the cells over G1 and G2 phases of the cell cycle, although it insignificantly reduced the percentage of S phase cells, which attested to the absence of intrinsic mitogenic activity of the peptide. At the same time, cyclo-L-prolylglycine reduced the number of the early apoptotic cells, which can be a mechanisms of its protective action. [ABSTRACT FROM AUTHOR]

Previously, ALM-802 (N1-(2,3,4-trimethoxybenzyl)-N2-{2-[(2,3,4-trimethoxybenzyl)amino]ethyl}-1,2-ethanediamine trihydrochloride) and ALM-803 (N1-(3,4,5-trimethoxybenzyl)-N2-{2-[(3,4,5-trimethoxybenzyl) amino]ethyl}-1,2-ethanediamine trihydrochloride), which combined pharmacophores of the free fatty-acid oxidation inhibitors trimetazidine and ranolazine and the slow Ca2+-channel blocker verapamil, were synthesized by us. These compounds possessed anti-ischemic and antiarrhythmic activities. Herein, the new compound ALM-843 (N1-(3,4-dimethoxybenzyl)-N2-{2-[(3,4-dimethoxybenzyl)amino]ethyl}-1,2-ethanediamine trihydrochloride), which exhibited only antiarrhythmic activity, was prepared. The results led to the hypothesis that the antiarrhythmic activity of the linear alkoxyphenyltriazaalkanes was due to the presence of a 3,4-dimethoxyphenyl pharmacophore, which is also present in verapamil. This hypothesis was confirmed using molecular docking to show that the above alkoxyphenyltriazaalkanes bound similarly to the verapamil binding site of the voltage-gated Ca2+-channel. [ABSTRACT FROM AUTHOR]

The effects of GSB-106, a low-molecular mimetic of BDNF loop 4, that represents a substituted dimeric dipeptide bis (N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide, on cognitive and motor impairments in a model of a depressive-like state in rats caused by unavoidable electric foot-shock were studied using active avoidance and open-field tests. GSB-106 (0.5 mg/kg, per os, 10 days) completely restored the number of avoidance reactions that was reduced in rats exposed to foot-shock and the percentage of trained rats in active avoidance training. In the open-field test, the peptide restored reduced horizontal activity and the number of explored holes. Thus, GSB-106 corrected impaired learning and memory, as well as locomotor activity and exploratory behavior in a model of depression in rats. [ABSTRACT FROM AUTHOR]

A dimeric dipeptide mimetic of nerve growth factor (NGF), bis-(N-monosuccinyl-L-glutamyl-L-lysine) hexamethylenediamide (GK-2), was previously developed at V. V. Zakusov State Institute of Pharmacology, activated specific TrkA receptors, and exhibited neuroprotective activity in vitro (10–5 – 10–9 M) and in vivo (0.1 – 10 mg/kg i.p. and p.o.). GK-2 was designed based on the beta-turn (-Asp94-Glu95-Lys96-Gln97-) of the NGF 4th loop and preserved the central dipeptide fragment (-Glu95-Lys96-). The Asp94 residue was replaced by its monosuccinyl bioisostere. The dimeric structure of NGF was reproduced using a bivalent hexamethylenediamine spacer. The structure—activity (neuroprotective) relationship for GK-2 was studied in the present work using a glycine scan, i.e., successive replacement of the peptide side groups by H. The bis-(N-acetyl-L-glutamyl-L-lysine) (GK-2Ac), bis-(N-monosuccinylglycyl-L-lysine) (GK-2-Gly1), and bis-(N-monosuccinyl-L-glutamylglycine) hexamethylenediamides (GK-2-Gly2) were less active with neuroprotective activity in vitro under oxidative stress for HT22 cells at concentrations 10 – 100 times greater than GK-2. The conclusion was drawn that each side radical of GK-2 was important for manifestation of the full neuroprotective activity of dimeric dipeptide GK-2, a mimetic of the NGF 4th loop. However, removal of any of the side radicals would probably not change the active structure of the beta-turn so that the two remaining side radicals should retain the ability to bind to their TrkA subsites. This could explain the retention of neuroprotective activity in the GK-2 glycine analogs. [ABSTRACT FROM AUTHOR]

Cardioprotective effect of 1-({4 [(4 chlorobenzoyl)amino]phenyl}sulfonyl-L-proline (compound AL-828) was studied in rats with modeled acute myocardial infarction. The test compound was administered intragastrically in a dose of 30 mg/kg/day for 3 days prior to infarction modeling. Metalloproteinase inhibitor antibiotic doxycycline served as the reference drug and was administered in a dose of 40 mg/kg/day by the same schedule. It was shown that AL-828 similar to doxycycline significantly reduced the intensity of myocardial remodeling and maintained the inotropic function of the myocardium in the acute phase of myocardial infarction. By the 20th minute of ischemia, the end-systolic dimension of the left ventricle in control animals increased from 1.98±0.12 to 3.84±0.16 mm, while in animals treated with AL-828, this increase was significantly (p=0.007) less pronounced (from 1.84±0.07 and 2.87±0.21 mm, respectively). The ejection fraction characterizing the inotropic status of the left ventricle in animals treated with AL-828 was significantly higher (p=0.02). By its cardioprotective activity, AL-828 was not inferior to the reference drug doxycycline. It can be assumed that the cardioprotective activity of compound AL-828 is related to suppression of MMP-9 expression and/or inhibition of its activity as was previously demonstrated by us. [ABSTRACT FROM AUTHOR]

Peptide mimetic of nerve growth factor GK-2 in a dose of 1-2 mg/liter improves survival of cultured rat cerebellar granule neurons exposed to the cytotoxic effect of zinc ions, but has no protective effect against copper ion cytotoxicity. Experiments on cultured rat hippocampal slices demonstrated that GK-2 did not affect reactivity of pyramidal neurons and long-term potentiation in the hippocampal field CA1 and the probability of glutamate release from presynaptic terminals in the synapses of the CA3-CA1 fields. The results suggest that GK-2 does not affect the functional properties of synaptic transmission under normal conditions, but protects neurons from the toxic effects of zinc, which creates prerequisites for GK-12 use in the treatment of neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

New dibenzofuranone-oxime derivatives were designed based on active structures of oxime esters. Compounds of the proposed group were synthesized using 3,4,6,7,8,9-hexahydrodibenzo[b,d]furan-1(2H)-one oxime and aromatic acid chlorides. The anticonvulsant activity of the new compounds was studied. The structure— activity relationship was analyzed. Compound 1a [3,4,6,7,8,9-hexahydrodibenzo[b,d]furan-1(2H)-one O-(3,4-dichlorobenzoyl)oxime] was the most active compound after i.p. injection to mice in the maximal electroshock test over a wide dose range of 20 – 100 mg/kg. Compound 1a at doses of 10 and 30 mg/kg exhibited antihypoxic activity in a hypoxia test with hypercapnia in a hermetic chamber and anti-ischemic activity at a dose of 10 mg/kg in a rat ischemic stroke model. [ABSTRACT FROM AUTHOR]

In experiments on BALB/c mice, prediabetes was modeled by administration of streptozotocin in a dose of 130 mg/kg. DNA damage was assessed by the method of DNA comets. Noopept (0.5 mg/kg intraperitoneally) was administered for 14 days before and for 6, 13, or 14 days after streptozotocin administration. Despite moderate hyperglycemia and increased malondialdehyde level, the intensity of DNA damage in cells of the pancreas, liver, and kidneys significantly surpassed the control values. Noopept normalized these parameters due to its pronounced antigenotoxic effect. For both the damaging effect of streptozotocin and the normalizing effect of Noopept, DNA changes manifested mainly in terms of atypical DNA comets. Our findings confirm the role of DNA damage in the pathogenesis of diabetes. They indicate the possibility of pharmacological protection of pancreatic β cells with the neuroprotective drug and provide an important argument in favor of the hypothesis about the similarity of the mechanisms of formation of the resistance of neurons and β cells to the cytotoxic influences. [ABSTRACT FROM AUTHOR]

A group of new 1-(methoxybenzyl)-4-{2-[(methoxybenzyl)amino]ethyl}piperazines (1) were synthesized. The relationship of the structure of the triazaalkane linker and the cardiotropic activity in a series of these compounds was compared with that of previously studied linear and cyclic methoxyphenyltriazaalkanes. The most active compound in the group was 1e (1-(3,4,5-trimethoxybenzyl)-4-{2-[(3,4,5-trimethoxybenzyl)amino] ethyl}piperazine trihydrochloride) with statistically significant antiarrhythmic activity in aconitine and CaCl2 arrhythmia models. [ABSTRACT FROM AUTHOR]

Results from an interspecies scaling study of the elimination half-lives of the anxiolytic GB-115 and the antipsychotic dilept in rats, rabbits, and humans are presented. The elimination half-lives of the studied drugs are calculated in real (chronological) and corrected time (pharmacokinetic). Elimination half-lives in animals and volunteers are compared. Rabbits are found to be a better scaling model for GB-115 although a single preference for dilept was not found. [ABSTRACT FROM AUTHOR]

The novel group of 4-GABA-3-nitrocoumarines, 1-thiocoumarines, quinolone-2-ones, and their derivatives was designed as potential anticonvulsants using GABA pharmacophore and corresponding heterocyclic moieties. A number of compounds of this group were synthesized and studied in the maximum electroshock seizure (MES) test and in the model of primary-generalized convulsions caused by subcutaneous pentylenetetrazole (scPTZ) in mice. The most active compound in the MES test was found to be 1a (N-(3-nitrocoumarin-4-yl)-4-aminobutyric acid) at a dose range of 60–80 mg/kg that increased the number of survived animals up to 60% in comparison with the control group, whose survival rate was 10%. Compounds 1d (N-(3,6-dinitrocoumarin-4-yl)-4-amino-butyric acid methyl ester) at doses of 10–40 mg/kg and 3a (N-(3-nitro-2-oxo-1,2-dihydroquinolin-4-yl)-4-amino-butyric acid methyl ester) at a dose of 12.5 mg/kg had the most pronounced anticonvulsant effect in scPTZ test. [ABSTRACT FROM AUTHOR]

A new group of compounds – 1-(methoxybenzyl)-4-[2-((methoxybenzyl)amino)ethyl]piperazin-2,3-diones was synthesized. As compared with previously studied linear methoxyphenyltriazaalkanes, the structure of the triazaalkane linker was found to influence the cardiotropic actions of the corresponding compounds. The most effective among the new group was 1-(2,4-dimethoxybenzyl)-4{2-[2,4-dimethoxybenzyl)amino]ethyl}piperazin-2,3-dione, which had significant antiarrhythmic activity at a dose of 2 mg/kg in a calcium chloride arrhythmia model, along with activity at the level of a tendency in models of aconitin arrythmia and reperfusion ventricular fibrillation. [ABSTRACT FROM AUTHOR]

We present here results of studies of the antidiabetic activity of compound GK-2 (bis-(N-monosuccinyl-glutamyl-L-lysine) hexamethylenediamide), an NGF mimetic, in a model of streptozotocin-induced type 2 diabetes mellitus in Wistar rats. Two-week prophylactic courses of oral GK-2 did not decrease blood glucose levels in healthy animals but reduces the severity of hyperglycemia and eliminated the insulin resistance effect induced by streptozotocin. Morphological analysis of the pancreas of the animals using monoclonal antibodies to insulin showed that while streptozotocin decreased the number of insulin-producing cells in the pancreas, GK-2 produced a statistically significant reduction in this harmful effect and promoted recovery of pancreatic islet size. A strong correlation was found between the extent of the cytoprotective action as indicated by morphometric measures and the strength of the hypoglycemic effect. [ABSTRACT FROM AUTHOR]

A new group of potential pFOX inhibitors among linear methoxyphenyltriazaalkanes were designed and synthesized. Cardiotropic activity in rodent experiments was found for most of the synthesized compounds. The most active compound N1-(2,3,4-trimethoxybenzyl)-N2-{2-[(2,3,4-trimethoxybenzyl)amino]ethyl}-1,2-ethanediamine trihydrochloride (LM-1) combined anti-ischemic, antiarrhythmic, and antifibrillatory activities (1 mg/kg, i.v.) and low toxicity (LD50 = 119 mg/kg, mice, i.p.) and was selected for development as a potential cardiotropic drug. [ABSTRACT FROM AUTHOR]

Dimeric dipeptide mimetic GK-2 or hexamethylenediamide bis-(N-monosuccinyl-L-glutamyl-L-lysine), which activated TrkA receptors and exhibited neuroprotective activity in vitro (10–5 – 10–9 M) and in vivo (0.05 – 5 mg/kg i.p.), was designed by us earlier based on the beta-turn of the nerve growth factor (NGF) fourth loop. The effect of dimerizing spacer length on the manifestation of neuroprotective activity was studied by synthesizing GK-2 (11 σ-bonds) analogs tetramethylenediamide bis-(N-monosuccinyl-L-glutamyl-Llysine) (GK-2c); pentamethylenediamide bis-(N-monosuccinyl-L-glutamyl-L-lysine) (GK-2b); and trimethylenediamide bis-(N-monosuccinyl-L-glutamyl-L-lysyl-6-aminohexanoic acid) (GK-2a) containing 9, 10, and 22 σ-bonds, respectively, between the lysine Cα-atoms of the dipeptide fragments. Neuroprotective activity was investigated in vitro using HT-22 mouse hippocampal neuronal cell culture under H2O2-induced oxidative stress and showed that the neuroprotective activity as measured by the minimum effective concentration was 104 times less if the distance between the dipeptide fragments increased from 11 to 22 σ-bonds. The neuroprotective activity decreased insignificantly if this distance was decreased from 11 to 10 σ bonds (GK-2b) and disappeared with 9 σ -bonds (GK-2c). Therefore, the hexamethylene spacer was optimal although the distance between the corresponding amino-acid moieties of natural NGF from an x-ray structure analysis was considerably greater at 33 σ-bonds. This contradiction could have arisen because two ionically bound mimetic molecules interacted with TrkA receptors. Another possible explanation was that TrkA molecules could approach closer in the presence of bis-dipeptide GK-2 than NGF. [ABSTRACT FROM AUTHOR]

Experiments on Wistar rats using a model of type 2 diabetes induced by streptozotocin (STZ) at a dose of 40 mg/kg addressed the effects of the proline-containing dipeptide noopept (the ethyl ester of N-phenylacetyl-L-prolylglycine) on nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) contents. Untreated diabetic rats showed 59% and 33% decreases in NGF content in the pancreas and liver, respectively, while BDNF contents decreased by 30% and 40% in the pancreas and liver, respectively, as compared with controls. Noopept given to diabetic rats at a dose of 0.5 mg/kg for 14 days increased the NGF content in the pancreas by 48% compared with untreated diabetic rats and produced a 19% increase in the NGF content in the liver as compared with the control group. Noopept given to diabetic rats normalized BDNF content in the pancreas but had no effect on the decreased level in the liver. The data obtained here identify one of the mechanisms of the antidiabetic action of noopept described in our previous reports. [ABSTRACT FROM AUTHOR]

Anti-ischemic activity of N1-(2,3,4-trimethoxybenzyl)-N2-{2-[(2,3,4-trimethoxybenzyl)amino] ethyl}-1,2-ethanediamine (ALM-802) based on the structure of standard p-FOX inhibitors trimetazidine and ranolazine was studied on the model of endocardial ischemia in intact rats and animals with endothelial dysfunction. Acute endocardial myocardial ischemia was caused by infusion of isoproterenol (20 μg/kg/min intravenously). Endothelial dysfunction in rats was modeled by inducing hyperhomocysteinemia (3 g/kg methionine intragastrically one a day over 7 days). The reference drugs trimetazidine (30 mg/kg, intravenously) and ranolazine 10 mg/kg, intravenously) that were effective only in intact rats. In contrast, ALM-802 (2 mg/kg, intravenously) showed a pronounced anti-ischemic effect in animals with endothelial dysfunction, which suggests that the mechanisms of its cardioprotective action differ from those known for p-FOX inhibitors. [ABSTRACT FROM AUTHOR]

New 4-phenylpyrrolidone derivatives were designed from racetam structures that combine nootropic and anticonvulsant activity. The proposed compounds were synthesized using 4-phenylpyrrolidone and aromatic amines. The anticonvulsant activity of the new compounds was studied. The structure–activity relationship was analyzed. The most active compound was the 2,6-dimethylanilide of (2-oxo-4-phenylpyrrolidin-1-yl)acetic acid at doses of 2.5 – 5.0 mg/kg, which surpassed the reference drug levetiracetam at doses of 2.5 – 600 mg/kg in all tests and possessed distinct nootropic activity that was comparable to that of the reference nootropic drug piracetam at a dose of 400 mg/kg. [ABSTRACT FROM AUTHOR]

Novel pyrrolo[1,2-a]pyrazine ligands of 18-kDa translocator protein (TSPO) were synthesized at Zakusov Research Institute of Pharmacology. Pharmacological studies of drug substance N-benzyl-N-methyl-1-phenylpyrrolo[1,2-a]pyrazine-3-carboxamide (GML-1) were consistent with high affinity for TSPO and significant anxiolytic activity. A finished dosage form of GML-1 drug substance was developed and exhibited pronounced anxiolytic activity after intragastric administration over a wide dose range. [ABSTRACT FROM AUTHOR]

Voltage clamp and concentration-jump methods were employed to examine the effects of endogenous neuropeptide cycloprolylglycine on GABA-activated ionic currents in isolated cerebellar Purkinje cells. In the concentration range of 0.1-10.0 μM, short-term (600 msec) external application of cycloprolylglycine against the background of GABA-evoked current produced no effect on its amplitude. In contrast, application of 1 μM cycloprolylglycine increased current up to 177±15% control level. The development of potentiating effect and return to the control level of ionic current were slow, which was indicative of possible implication of second messenger systems in these processes. Functional augmentation of GABAA receptors under the action of cycloprolylglycine can underlie the established neuroprotective and anxiolytic effects of this endogenous dipeptide. [ABSTRACT FROM AUTHOR]

The synthesis and anticonvulsant activity of new coumarin derivatives are reported. N-(3-Nitrocoumarin-4-yl)-4-aminobutyric acid (1a) at doses of 60 and 80 mg/kg (in the MES test) and methyl N-(3,6-dinitrocoumarin-4-yl)-4-aminobutyrate (1e) at doses of 20 and 40 mg/kg (in the corazole antagonism test) possessed the greatest anticonvulsant activity of the synthesized compounds. The results indicated that the coumarin derivatives were promising for further development as potential anticonvulsant agents. [ABSTRACT FROM AUTHOR]

Voltage clamp and concentration-jump methods were employed to examine the effects of endogenous neuropeptide cycloprolylglycine on GABA-activated ionic currents in isolated cerebellar Purkinje cells. In the concentration range of 0.1-10.0 μM, short-term (600 msec) external application of cycloprolylglycine against the background of GABA-evoked current produced no effect on its amplitude. In contrast, application of 1 μM cycloprolylglycine increased current up to 177±15% control level. The development of potentiating effect and return to the control level of ionic current were slow, which was indicative of possible implication of second messenger systems in these processes. Functional augmentation of GABAA receptors under the action of cycloprolylglycine can underlie the established neuroprotective and anxiolytic effects of this endogenous dipeptide. [ABSTRACT FROM AUTHOR]

On the basis of the first dipeptide ligand of TSPO, N-carbobenzoxy-L-tryptophanyl-L-isoleucine amide (GD-23), which was obtained by us earlier, we synthesized a new dipeptide, N-phenylpropionyl-L-tryptophanyl-L-leucine amide (GD-102). GD-102 exhibited anxiolytic activity in the open field test in BALB/c mice and in the elevated plus maze test in ICR mice. The minimum effective dose of GD-102 was one order of magnitude lower than that of GD-23. Compound PK11195, a selective antagonist of TSPO, completely blocked the anxiolytic activity of GD-102, which testified to the involvement of TSPO in the realization of the anxiolytic effect of GD-102. The results were confirmed by molecular docking data. [ABSTRACT FROM AUTHOR]

A dimeric dipeptide mimetic of brain-derived neurotrophic factor loop 2, bis-(N-hexanoyl-seryl-lysine) hexamethylenediamide or GTS-201, was designed and synthesized. It exhibited neuroprotective activity at concentrations of 10-5 - 10-8 M in HT-22 immortalized hippocampal neuronal cell culture under H2O2-induced oxidative stress. Western-blot analysis showed that it activated TrkB receptors and Erk but not Akt. GTS-201 did not exhibit antidepressant activity in a Porsolt forced swim test on BALB/c mice at i.p. doses of 0.1, 1.0, and 5.0 mg/kg, in contrast with previously synthesized GSB-106, a dimeric dipeptide mimetic of loop 4. The results confirmed the previous original hypothesis about the possible discrimination of neurotrophin functions by low-molecular-mass mimetics of their separate loops. [ABSTRACT FROM AUTHOR]

Previously, a dimeric dipeptide mimetic bis-(N-monosuccinyl-L-glutamyl-L-lysine) hexamethylenediamide (GK-2) based on the β-turn of the fourth loop of nerve growth factor was prepared by us, activated TrkA, and exhibited neuroprotective activity in vitro (10-5 - 10-9 M) and in vivo (0.05 - 5 mg/kg i.p.). The present work reports the synthesis of two of its diastereomers, bis-(N-monosuccinyl-L-glutamyl-D-lysine) (GK-2LD) and bis-(N-monosuccinyl-D-glutamyl-L-lysine) hexamethylenediamides (GK-2DL). Studies of their neuroprotective activities using HT-22 neuronal culture under oxidative stress showed that switching L-lysine to D-lysine led to a significant activity decrease whereas switching L-glutamic acid to the D-stereoisomer caused it to disappear completely. Both dipeptide residues were concluded to be involved in interactions with the TrkA receptor. [ABSTRACT FROM AUTHOR]