Design, Synthesis and Anticonvulsant Activity of Cinnamoyl Derivatives of 3,4,6,7,8,9-hexahydrodibenzo[b,d]furan-1-(2H)-one Oxime

BACKGROUND

Epilepsy continues to be a significant global health problem and the search for new drugs for its treatment remains an urgent task. 5-HT2 and GABAA-receptors are among promising biotargets for the search for new anticonvulsants.

METHODS

New potential 5-HT2 and GABAA ligands in the series of substituted cinnamoyl derivatives of 3,4,6,7,8,9-hexahydrodibenzo[b,d]furan-1-(2H)-one oxime were designed using pharmacophore model and molecular docking analysis. The synthesis of new compounds was carried out from 3,4,6,7,8,9-hexahydrodibenzo[b,d]furan-1(2H)-one oxime and substituted cinnamoyl chlorides. The anticonvulsant activity of new substances has been established using the maximal electroshock seizure test.

RESULTS

Several synthesized substituted cinnamoyl derivatives of 3,4,6,7,8,9-hexahydrodibenzo [b,d]furan-1-(2H)-one oxime significantly reduced the severity of convulsive manifestations and completely prevented the death of animals after MES. The structure-activity relationship was investigated. The most effective compound was found to be GIZH-348 (1g) (3,4,6,7,8,9-hexahydrodibenzo[ b,d]furan-1(2Н)-one О-(4-chlorophenyl)acryloyl)oxime) at the doses of 10-20 mg/kg.

CONCLUSION

Molecular and pharmacophore modelling methods allowed us to create a new group of substituted cinnamoyl derivatives of 3,4,6,7,8,9-hexahydrodibenzo[b,d]furan-1-(2H)-one oxime with anticonvulsant activity.

Antidiabetic Effect of a New Original NT-3 Dipeptide Mimetic

It was previously established that the original dipeptide mimetic of the 4th loop of NT-3, hexamethylenediamide bis-(N-monosuccinyl-L-asparaginyl-L-asparagine) (GTS-301), has a pronounced neuroprotective effect in vitro at concentrations of 10-5-10-12 М. In the present study, experiments on the streptozotocin-induced diabetes model in C57Bl/6 mice showed that GTS-301, when administered intraperitoneally for 32 days at doses of 0.1 and 0.5 mg/kg, has antidiabetic activity manifested in a reduction of hyperglycemia and polydipsia and in an increase in animal survival. The results obtained confirm the concept of the similarity of neurochemical mechanisms underlying the regulation of functions of neurons and β-cells.

Pharmacogenetic Analysis of the Interaction of the Low-Molecular-Weight BDNF Mimetic Dipeptide GSB-106 with TRK Receptors

Using TrkA or TrkB receptor gene knockout HT-22 cells, the selectivity of the interaction of the low-molecular-weight dipeptide BDNF mimetic GSB-106 (hexamethylenediamide bis(N-monosuccinyl-L-seryl-L-lysine)) with TrkB receptors was shown.

Experimental Study of Antidepressant Properties of Afobazole

We studied the effects of oral administration of Afobazole in a dose of 10 mg/kg for 5 days on depressive-like behavior of male C57BL/6 mice in the tail suspension test in comparison with amitriptyline (10 mg/kg) or fluoxetine (20 mg/kg) treatment. Afobazole produced an antidepressant effect similar to amitriptyline, but inferior to fluoxetine. The σ1 receptor antagonist BD-1047 in a dose of 5 mg/kg blocked the antidepressant effect of Afobazole, which indicates the involvement of σ1 receptors in the antidepressant effect of the drug.

Specifics of Experimental Modeling 8-OH-DPAT-Induced Perseverative Behavior in Mice

The effect of 5-HT_1A receptor agonist 8-OH-DPAT (intraperitoneal injection in doses of 1, 2, and 4 mg/kg) on spontaneous alternation behavior of mice in Y-maze was studied without and with habituation procedure and food reward. In the first case, 8-OH-DPAT administration led to a decrease in spontaneous alternation and locomotor activity in mice. At the same time, 8-OH-DPAT treatment after habituation and food deprivation increased repeated choices of goal arms without affecting locomotor activity, which was consistent with perseverative behavior. 8-OH-DPAT-induced decrease in spontaneous alternation behavior in Y-maze in mice with habituation and food reward is the most suitable procedure for experimental modeling of the perseverative behavior and studying the anticompulsive activity of new substances.

Pharmacological Analysis of GABAA Receptor and Sigma1R Chaperone Interaction: Research Report I-Investigation of the Anxiolytic, Anticonvulsant and Hypnotic Effects of Allosteric GABAA Receptors' Ligands

Two groups of facts have been established in previous drug development studies of the non-benzodiazepine anxiolytic fabomotizole. First, fabomotizole prevents stress-induced decrease in binding ability of the GABA_A receptor's benzodiazepine site. Second, fabomotizole is a Sigma1R chaperone agonist, and exposure to Sigma1R antagonists blocks its anxiolytic effect. To prove our main hypothesis of Sigma1R involvement in GABA_A receptor-dependent pharmacological effects, we performed a series of experiments on BALB/c and ICR mice using Sigma1R ligands to study anxiolytic effects of benzodiazepine tranquilizers diazepam (1 mg/kg i.p.) and phenazepam (0.1 mg/kg i.p.) in the elevated plus maze test, the anticonvulsant effects of diazepam (1 mg/kg i.p.) in the pentylenetetrazole-induced seizure model, and the hypnotic effects of pentobarbital (50 mg/kg i.p.). Sigma1R antagonists BD-1047 (1, 10, and 20 mg/kg i.p.), NE-100 (1 and 3 mg/kg i.p.), and Sigma1R agonist PRE-084 (1, 5, and 20 mg/kg i.p.) were used in the experiments. Sigma1R antagonists have been found to attenuate while Sigma1R agonists can enhance GABA_ARs-dependent pharmacological effects.

Neuroprotective Effect of the Neuropeptide Cycloprolylglycine Depends on AMPA- and TrkB-Receptor Activation

Previously, we have shown that the endogenous neuropeptide cycloprolylglycine (CPG) is the positive modulator of AMPA receptors and revealed the dependence of its anxiolytic and antihypoxic action on BDNF/Trk signaling. In the present work, we for the first time conducted in vitro experiments using the AMPA receptor blockers DNQX and GYKI 52466 and the Trk receptor blocker K252a. It is shown that the neuroprotective effect of CPG depends on the activation of both AMPA and Trk receptors.

The neuropeptide cycloprolylglycine produces antidepressant-like effect and enhances BDNF gene expression in the mice cortex

BACKGROUND

Cycloprolylglycine (CPG) is an endogenous dipeptide with a wide range of psychotropic activity and putative therapeutic potential for depression. A small but growing body of data suggests that antidepressant-like effect of CPG is associated with neuroplastic changes in the brain or 5-HT system modulation. However, the mechanisms of the dipeptide action remain elusive.

AIMS

Here, we characterize the effects of chronic CPG administration on behavior and genes expression of antidepressants sensitive catalepsy (ASC) mice strain, characterized by depressive-like behavior.

METHODS

ASC mice were injected with saline, fluoxetine (10 mg/kg/day), or CPG (1 and 2 mg/kg/day) during 2 weeks. Behavior was studied using the open field test, novel object test, elevated plus maze test, forced swim test, and tail suspension test (TST). The expressions of genes coding BDNF, CREB, 5-HT_1A and 5-HT_2A receptors, TPH2, and SERT in the brain were measured with quantitative real-time reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Chronic intraperitoneal administration of 1 and 2 mg/kg of CPG revealed the significant antidepressant-like effect by decreasing immobility time in the TST. At the same time, CPG did not negatively affect locomotor activity, cognition, or anxiety. In the real-time quantitative polymerase chain reaction (PCR) assay, chronic CPG treatment (2 mg/kg for 14 days) increased Bdnf mRNA level in the frontal cortex.

CONCLUSIONS

Our findings extend the evidence for the effectiveness of CPG to reduce depressive-like behaviors. The antidepressant-like effect of CPG is mediated, as least in part, by BDNF-dependent mechanism. The exact mechanism remains to be elucidated, and further studies are warranted.

Neuroprotective Properties of Quinone Reductase 2 Inhibitor M-11, a 2-Mercaptobenzimidazole Derivative

The ability of NQO2 to increase the production of free radicals under enhanced generation of quinone derivatives of catecholamines is considered to be a component of neurodegenerative disease pathogenesis. The present study aimed to investigate the neuroprotective mechanisms of original NQO2 inhibitor M-11 (2-[2-(3-oxomorpholin-4-il)-ethylthio]-5-ethoxybenzimidazole hydrochloride) in a cellular damage model using NQO2 endogenous substrate adrenochrome (125 µM) and co-substrate BNAH (100 µM). The effects of M-11 (10-100 µM) on the reactive oxygen species (ROS) generation, apoptosis and lesion of nuclear DNA were evaluated using flow cytometry and single-cell gel electrophoresis assay (comet assay). Results were compared with S29434, the reference inhibitor of NQO2. It was found that treatment of HT-22 cells with M-11 results in a decline of ROS production triggered by incubation of cells with NQO2 substrate and co-substrate. Pre-incubation of HT-22 cells with compounds M-11 or S29434 results in a decrease of DNA damage and late apoptotic cell percentage reduction. The obtained results provide a rationale for further development of the M-11 compound as a potential neuroprotective agent.

Involvement of Chaperone Sigma1R in the Anxiolytic Effect of Fabomotizole

Sigma-1 receptor (chaperone Sigma1R) is an intracellular protein with chaperone functions, which is expressed in various organs, including the brain. Sigma1R participates in the regulation of physiological mechanisms of anxiety (Su, T. P. et al., 2016) and reactions to emotional stress (Hayashi, T., 2015). In 2006, fabomotizole (ethoxy-2-[2-(morpholino)-ethylthio]benzimidazole dihydrochloride) was registered in Russia as an anxiolytic (Seredenin S. and Voronin M., 2009). The molecular targets of fabomotizole are Sigma1R, NRH: quinone reductase 2 (NQO2), and monoamine oxidase A (MAO-A) (Seredenin S. and Voronin M., 2009). The current study aimed to clarify the dependence of fabomotizole anxiolytic action on its interaction with Sigma1R and perform a docking analysis of fabomotizole interaction with Sigma1R. An elevated plus maze (EPM) test revealed that the anxiolytic-like effect of fabomotizole (2.5 mg/kg i.p.) administered to male BALB/c mice 30 min prior EPM exposition was blocked by Sigma1R antagonists BD-1047 (1.0 mg/kg i.p.) and NE-100 (1.0 mg/kg i.p.) pretreatment. Results of initial in silico study showed that fabomotizole locates in the active center of Sigma1R, reproducing the interactions with the site's amino acids common for established Sigma1R ligands, with the ΔGbind value closer to that of agonist (+)-pentazocine in the 6DK1 binding site.

Dimeric mimetic of BDNF loop 4 promotes survival of serum-deprived cell through TrkB-dependent apoptosis suppression

Brain-derived neurotrophic factor (BDNF) is involved in the regulation of neuronal cell growth, differentiation, neuroprotection and synaptic plasticity. Although aberrant BDNF/TrkB signaling is implicated in several neurological, neurodegenerative and psychiatric disorders, neurotrophin-based therapy is challenging and is limited by improper pharmacokinetic properties of BDNF. Dimeric dipeptide compound GSB-106 (bis-(N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide) has earlier been designed to mimic the TrkB-interaction 4 loop of BDNF. It displayed protective effect in various cell-damaging models in vitro. Animal studies uncovered antidepressive and neuroprotective properties upon GSB-106 per os administration. Current study shows that GSB-106 acts similarly to BDNF, promoting survival of serum-deprived neuronal-like SH-SY5Y cells. 100 nmol concentration of GSB-106 provided maximum neurotrophic effect, which corresponds to about 37% of the maximum effect provided by BDNF. Protective properties of GSB-106 arise from its ability to counteract cell apoptosis via activation of TrkB-dependent pro-survival mechanisms, including inactivation of pro-apoptotic BAD protein and suppression of caspases 9 and 3/7. Thus, our study has characterized neurotrophic activity of small dimeric compound GSB-106, which mimics certain biological functions of BDNF and neurotrophin-specific protective mechanisms. GSB-106 also displays similarities to some known low weight peptide and non-peptide TrkB ligands.

Assessment of Susceptibility of Outbred Albino Rats to the Formation of Depression-Like State of Learned Helplessness

Learned helplessness (a model of depression-like state) was developed in rats by exposure to repeated inescapable electric stimulation and evaluated by the absence of attempts to escape when it could be performed. In randomly grouped outbred white rats, 37.5% animals after the above procedure meet the criterion of learned helplessness. On experimental day 14, the latent period and the number of applied electric shocks prior to the first escape to the safe compartment in rats with learned helplessness were significantly higher than in the control, but no significant differences in these parameters were observed on day 21. The Porsolt forced swimming test performed on days 14 and 21 revealed no differences from the control group. After the rats were divided into low- and high-active subgroups according to their open field behavior, 35% rats with learned helplessness were in the low-active subgroup group and 30% rats with learned helplessness were in the high-active subgroup. On day 14, the parameters of learned helplessness significantly surpassed the control levels only in the low-active subgroup. Only in rats with learned helplessness and low activity in the open field, the immobility time in the Porsolt test was longer than in control low-active rats. These findings attest to advisability of preliminary splitting of outbred animals by their open-field behavior into low- and high-active subgroups and the use of only animals for modeling learned helplessness.

Peptide Mimetic of BDNF Loop 4 Blocks Behavioral Signs of Morphine Withdrawal Syndrome and Prevents the Increase in ΔFosB Level in the Striatum of Rats

Activity of compound GSB-106, a low-molecular mimetic of loop 4 of the brain neurotrophic factor (BDNF), was studied in experimental morphine withdrawal syndrome simulated in outbred rats. Single and subchronic (5 intraperitoneal injections) administration of GSB-106 in a dose of 0.1 mg/kg significantly reduced the total index of morphine withdrawal syndrome by 55.2 and 45.6%, respectively. GSB-106 reduced the severity of some behavioral signs (piloerection, gnashing of teeth, wet-dog shaking, and runaway attempts), but had no effect on mechanical allodynia formed in the rats with dependence. Subchronic treatment with GSB-106 prevented the increase in the content of ΔFosB (product of early response gene) in the striatum induced by morphine withdrawal. The results confirmed the concept on the involvement of neurotrophins, specifically BDNF and its analogs, in the mechanisms associated with the formation of opiate dependence.

Cognitive Enhancer Noopept Activates Transcription Factor HIF-1

The effect of noopept (N-phenylacetyl-L-prolyl-glycine ethyl ester) on the DNA-binding activity of HIF-1 in SH-SH5Y cells and the mechanisms of stabilization of this transcription factor were studied in vitro. Noopept was shown to increase both the basal DNA-binding activity of HIF-1 and the activity induced by various hypoxia mimetics. The mechanism of stabilization of the oxygen-sensitive HIF1α subunit by noopept involves the inhibition of HIF-1 prolyl hydroxylase, which is indirectly indicated by the data obtained using the ODD-Luc reporter, and the positive effect on the level of the HIF1α protein. It was revealed that the effect of noopept is accompanied by changes in gene expression, which belong to different metabolic pathways and are controlled by the transcription factor HIF-1.

Dipeptide Mimetics of Different NGF and BDNF Loops Activate PLC-γ1

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.

Deferred Administration of Afobazole Induces Sigma1R-Dependent Restoration of Striatal Dopamine Content in a Mouse Model of Parkinson's Disease

Previously, we demonstrated that the immediate administration of multitarget anxiolytic afobazole slows down the progression of neuronal damage in a 6-hydroxidodamine (6-OHDA) model of Parkinson's disease due to the activation of chaperone Sigma1R. The aim of the present study is to evaluate the therapeutic potential of deferred afobazole administration in this model. Male ICR mice received a unilateral 6-OHDA lesion of the striatum. Fourteen days after the surgery, mice were treated with afobazole, selective Sigma1R agonist PRE-084, selective Sigma1R antagonist BD-1047, and a combination of BD-1047 with afobazole or PRE-084 for another 14 days. The deferred administration of afobazole restored the intrastriatal dopamine content in the 6-OHDA-lesioned striatum and facilitated motor behavior in rotarod tests. The action of afobazole accorded with the effect of Sigma1R selective agonist PRE-084 and was blocked by Sigma1R selective antagonist BD-1047. The present study illustrates the Sigma1R-dependent effects of afobazole in a 6-OHDA model of Parkinson's disease and reveals the therapeutic potential of Sigma1R agonists in treatment of the condition.

Analysis of Cytoprotective Properties of Afobazole in Streptozotocin Model of Diabetes

Previous in vitro and in vivo studies revealed the neuroprotective effect of anxiolytic Afobazole. Based on similarities in the regulation of functions of neurons and β cells, we studied the effect of Afobazole on streptozotocin (STZ) model of type 2 diabetes in Wistar rats. Immunohistochemical analysis showed that the decrease in the number of β cells and a violation of their morphological structure caused by STZ were significantly alleviated by Afobazole administration (10 mg/kg orally for 28 days) to diabetic animals. A correlation between morphometric data and blood glucose level was revealed. A possible role of σ1-receptors in the cytoprotective effects of Afobazole in respect to pancreatic β cells is discussed.

Chaperone Sigma1R and Antidepressant Effect

This review analyzes the current scientific literature on the role of the Sigma1R chaperone in the pathogenesis of depressive disorders and pharmacodynamics of antidepressants. As a result of ligand activation, Sigma1R is capable of intracellular translocation from the endoplasmic reticulum (ER) into the region of nuclear and cellular membranes, where it interacts with resident proteins. This unique property of Sigma1R provides regulation of various receptors, ion channels, enzymes, and transcriptional factors. The current review demonstrates the contribution of the Sigma1R chaperone to the regulation of molecular mechanisms involved in the antidepressant effect.

The Anxiolytic Effect of the Neuropeptide Cycloprolylglycine Is Mediated by AMPA and TrkB Receptors

Previously we have shown that the neuropeptide cycloprolylglycine is an endogenous positive modulator of AMPA receptors and assumed that the pharmacological effects of CPG are associated with the brain neurotrophic factor. In this paper, we have first demonstrated that DNQX, an inhibitor of AMPA receptors, and K252A, an ihibitor of Trk receptors, prevented the anxiolytic effect of CPG, which confirms the formulated hypothesis.

Effect of Neuropeptide Cyclo-L-Prolylglycine on Cell Proliferative Activity

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.

Behavioral Effects of Dimeric Dipeptide BDNF Mimetic GSB-106 in a Rat Model of Depressive-Like State

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.

Low-Molecular-Weight Compound GSB-106 Mimics the Cellular Effects of BDNF after Serum Deprivation

The in vitro model of serum deprivation shows that the survival of SH-SY5Y neuronal cells is ensured by the intrinsic trophic activity of BDNF loop 4 mimetic GSB-106 (10^-7 М), which is comparable to that of endogenous neurotrophin (10^-9 М). The analysis of the cell cycle and S-phase showed that GSB-106, similarly to BDNF, induces the cell-cycle arrest in the G₁ phase, diminishes the number of cells in the S-phase, reduces the number of apoptotic cells, and does not stimulate proliferation.

[Results of a clinical study of a new anxiolytic, a blocker of central cholecystokinin receptors]

AIM

To evaluate anxiolytic action of GB-115, a low-affinity blocker of central cholecystokinin receptors, used in tablets in a dose of 1 mg for the treatment of patients with anxiety disorders in order to determine effective dose, safety, tolerability and efficacy in clinical settings.

MATERIAL AND METHODS

The study included 31 patients (22 women, 9 men) diagnosed with generalized anxiety disorder (GAD, F41.1 according to ICD-10), aged from 22 to 53 years. The duration of treatment was 21 days. The Hamilton Anxiety Rating scale, Psychopathologic symptoms severity evaluation scale (PSSES), Spilberger State-Anxiety Inventory, Multidimensional Fatigue Inventory (MFI), Clinical Global Impression scale (CGI), computerized battery for evaluation of cognitive functions ('NS-Psychotest') were used.

RESULTS AND CONCLUSION

The effective dose of GB-115 was determined at 6 mg per day. Drug action is characterized by fast onset of anxiolytic effect with stimulating properties and beneficial effect on sleep disturbances and autonomic symptoms. GB-115 treatment was associated with favorable changes in attention parameters, reaction time and overall performance. In contrast to first-line drugs for GAD treatment (SSRIs and SNRIs), GB-115 does not induce initial overactivation, anxiety and sleep disturbances. GB-115 is safe and has a good tolerability.

Afobazole Alleviates Cognitive Rigidity in Experimental Model of Autism Spectrum Disorders

Afobazole (10 mg/kg) alleviated cognitive rigidity in BALB/c mice, a phenotypic model of autism spectrum disorders. It improved spatial memory and retraining in T-maze with drinking reinforcement and restored the retrieval of acquired skill during reversal learning in Morris water maze.

Effect of Fabomotizole on Brain Gene Expression in MR Rats in the Open Field Test

Selective anxiolytic fabomotizole (Afobazol®) has affinity for the Sigma-1 chaperone receptor site, quinone reductase 2 (NQO2) and MAO-A regulatory sites, and melatonin receptor type 1 (MT₁ receptor). The analysis of the effect of fabomotizole on the gene expression profile in the brain of MR (Maudsley Reactive) rats was carried out when modeling emotional stress in the open field test. A change in the expression of 14 genes was found, the results of the functional annotation of which showed that the mechanisms of action of fabomotizole may be associated with the regulation of translation of proteins (Rpl5, Rpl15, Ncl, and Ybx1), synaptic functions (Cplx2, Dlg4, Syngap1, Add1, Rab8b, Klc1, and Chn1), and cellular metabolism (Akr1d1, Bcat1, and Pkm).

Examination of Cardioprotective Effects of Fabomotizole Hydrochloride in Translational Rat Model of Chronic Heart Failure

A translational rat model of chronic heart failure was employed to examine the cardioprotective effect of fabomotizole hydrochloride. Fabomotizole therapy for 28 days (15 mg/kg/day intraperitoneally) restored inotropic function of the left ventricle and increased ejection fraction from 54±3 to 65±3% (p=0.001). The inotropic function returned to normal against the background of significantly reduced myocardial expression of angiotensin (p=0.01) and glucocorticoid (p=0.03) receptors and significant increased expression of sigma-1 receptors (p=0.04). Inhibition of abnormal expression of angiotensin and glucocorticoid receptors responsible for activation of the pathological cascades underlying the postinfarction remodeling of the left ventricle as well as activation of the expression of cytoprotective sigma-1 receptors are viewed as the key features of the cardioprotective action of fabomotizole hydrochloride.

[An experimental evaluation of the therapeutic window of the neuroprotective activity of a low-molecular nerve growth factor mimetic GK-2]

AIM

To identify the time interval for the preservation of the effect of GK-2 depending on the start of administration after modeling ischemic stroke by the transient occlusion of the middle cerebral artery in rats.

MATERIAL AND METHODS

The experiments were performed on 33 wild-type male rats and 81 male Wistar rats. Animals were kept in standard conditions. Ischemic stroke was modelled by thread occlusion of the middle cerebral artery.

RESULTS AND CONCLUSION

It was found that GK-2 at a daily dose of 1 mg/kg, intraperitoneally, during 7 days statistically significantly reduces brain infarct volume by 20-60% at the first injection from 4 to 24h, with the highest effect 6-8 hours after surgery. Thus, the 'therapeutic window' of GK-2 detected in the experiment is no less than 24 hours, which exceeds the existing neuroprotective agents.

Drug with Neuroprotective Properties Noopept Does Not Stimulate Cell Proliferation

Effects of Noopept (N-phenylacetyl-L-prolylglycine ethyl ester) on the relative level of proliferation marker Ki-67 and cell cycle parameters were studied in HEK293 and SH-SY5Y cell lines. The previously established multifactorial mechanism of action of the drug includes enhancement of neurotrophin NGF and BDNF expression and increase in HIF-1 activity. The possible mitogenic action of Noopept was estimated by its effect on cell proliferation. Noopept did not affect cell distribution over G1, S, G2 cell cycle phases and the relative level of proliferation marker Ki-67 in the cell lines under study. These data suggest that Noopept does not stimulate cell growth.

On the Mechanism of the Cardioprotective Action of σ1 Receptor Agonist Anxiolytic Fabomotizole Hydrochloride (Afobazole)

Original translational rat model of chronic heart failure provoked by experimental anterior transmural myocardium infarction was employed to examine the preventive action of anxiolytic Afobazole (15 mg/kg/day administered intraperitoneally during the first 15 days after coronary occlusion) on the development of the heart failure assessed in 3 months after infarction. Afobazole prevented the development of pathologic remodeling of the myocardium, maintained its inotropic function, and decreased the plasma level of brain natriuretic peptide known as a biochemical marker of chronic heart failure. In the myocardium, Afobazole down-regulated overexpression of the genes induced in chronic heart failure and assessed by corresponding RNA levels, which code angiotensin (AT1A-R), vasopressin (V1A-R), and glucocorticoid (GR) receptors as well as Epac2 protein. The revealed biochemical changes are consistent with the data on cardioprotective action of Afobazole.

Dipeptide Mimetic of the BDNF GSB-106 with Antidepressant-Like Activity Stimulates Synaptogenesis

Dipeptide mimetic of the brain-derived neurotrophic factor bis(N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide (working name GSB-106), which reproduces the homodimeric structure of BDNF and the beta-turn of its fourth loop, activates TrkB, AKT, and ERK, exhibits neuroprotective and antidepressant activity, and is able to stimulate neurogenesis in the hippocamp of stressed mice. Using Western blot hybridization and synaptophysin (synaptogenesis marker), we showed the ability of chronically administered GSB-106 to stimulate synaptogenesis, increasing the synaptic density in the hippocamp by 50%. Under the same conditions, GSB-106 exhibited antidepressant activity (decreased (by 18%) immobility of animals in Porsolt test), which may be associated with the stimulation of neurogenesis and synaptogenesis in the hippocamp.

Non-Competitive NMDA Receptor Antagonist Hemantane Reduces Ethanol Consumption in Long-Term Alcohol Experienced Rats

Activity of hemantane, an amino adamantane derivative, exhibiting the properties of lowaffinity non-competitive NMDA receptor antagonist, was evaluated in experimental in vivo models of alcoholism. Hemantane had no effects on the formation and manifestation of behavioral sensitization to ethanol in DBA/2 mice. Under conditions of free choice between 10% ethanol and water, hemantane (20 mg/kg/day for 14 days, intraperitoneally) significantly reduced the daily ethanol intake in random-bred male rats with formed alcohol motivation (>4 g/kg of ethanol). During modelling of withdrawal syndrome, hemantane administered intraperitoneally in doses of 5-20 mg/kg dose-dependently attenuated alcohol-deprivation effect after acute withdrawal with no effects on protracted abstinence. It was found that hemantane suppressed alcohol drinking behavior in long-term ethanol experienced rats and attenuated alcohol-seeking behavior after acute withdrawal.

Comparison of the Pharmacological Effects of Dimeric Dipeptide Nerve Growth Factor Mimetic GK-2 and Mexidol on the Model of Ischemic Stroke in Rats

We compared the effects of GK-2 (dimeric dipeptide mimetic of nerve growth factor) and Mexidol (standard preparation for the therapy of stroke) on rat model of transient occlusion of the middle cerebral artery. GK-2 and Mexidol were administered intraperitoneally in the most active doses (1 and 100 mg/kg, respectively) 6 h after surgery and then once a day for 6 days. The preparations reduced the volume of cerebral infarction (by 60 and 30%, respectively). At the same time, GK-2 had a pronounced and statistically more reliable effect in a dose that is lower by two orders of magnitude. In addition, GK-2 significantly reduced the neurological deficit in the limb placement test, while Mexidol was ineffective in this test.

A novel dimeric dipeptide mimetic of the BDNF selectively activates the MAPK-Erk signaling pathway

On the basis of the structure of beta-turn of loop 2 of brain-derived neurotrophic factor (BDNF), its new dimeric dipeptide mimetic bis-(N-hexanoyl-L-seryl-L-lysine) hexamethylenediamide (GTS-201) was created. It activated TrkB and Erk, did not activate Akt, and exhibited neuroprotective activity in vitro at concentrations of 10^-5-10^-8 M. Unlike the mimetics that activate Erk and Akt, GTS-201 did not exhibit antidepressant properties. For the manifestation of the antidepressant activity of BDNF mimetics, the activation of its both major signaling pathways is required.

Activation of σ1 and σ2 receptors by afobazole increases glial cell survival and prevents glial cell activation and nitrosative stress after ischemic stroke

Activation of sigma receptors at delayed time points has been shown to decrease injury following ischemic stroke. The mixed σ1/σ2 receptor agonist, 5-ethoxy-2-[2-(morpholino)-ethylthio]benzimidazole (afobazole), provides superior long-term outcomes compared to other σ ligands in the rat middle cerebral artery occlusion (MCAO) stroke model. Experiments using the MCAO model were carried out to determine the molecular mechanism involved in the beneficial effects of afobazole. Administration of afobazole (3 mg/kg) at delayed time points post-stroke significantly increased the number of microglia and astrocytes detected in the ipsilateral hemisphere at 96 h post-surgery. Morphological analysis of the microglia indicated that a greater number of these cells were found in the ramified resting state in MCAO animals treated with afobazole relative to MCAO vehicle controls. Similarly, fewer reactive astrocytes were detected in the injured hemisphere of afobazole-treated animals. Both the enhanced survival and reduced activation of glial cells were abolished by co-application of either a σ1 (BD-1063) or a σ2 (SM-21) receptor antagonist with afobazole. To gain further insight into the mechanisms by which afobazole lessens stroke injury, we probed the brain sections for markers of neuroinflammation (tumor necrosis factor α) and nitrosative stress (S-nitrosocysteine). Data show that afobazole significantly reduces S-nitrosocysteine levels, but does not alter tumor necrosis factor α expression 96 h after an ischemic stroke. Taken together our data indicate that afobazole acting via both σ1 and σ2 receptors decreases stroke injury by enhancing glial cell survival, blocking ischemia-induced glial cell activation, and decreasing nitrosative stress.

Pharmacological Correction of Alcohol Motivation Depends on the Phenotype of the Response to Emotional Stress

The specific features of alcohol behavior were studied in MR and MNRA rats that exhibit an opposite reaction to emotional stress. We evaluated the effect of a dipeptide anxiolytic GB-115 (N-phenyl-hexanoyl-glycyl-L-tryptophan amide, neuropeptide cholecystokinin-4 analogue with antagonistic activity) on alcohol motivation in rats, which was formed over 12 months. High-emotionality MR rats were more sensitive to the anxiolytic effect of ethanol in the conflict situation test than low-emotionality MNRA rats. MNRA rats consumed a greater amount of ethanol under a free-choice condition with 15% ethanol solution and water (as in comparison with MR rats). However, the behavior of MR rats was transformed due to a significant increase in alcohol motivation from the 5th month of long-term free access to ethanol. An anxiolytic GB-115 (0.025 mg/kg intraperitoneally for 14 days) with selective activity in high-emotionality rats was shown to reduce significantly the average daily consumption and alcohol-deprivation effect in MR rats, but did not modulate ethanol addiction in MNRA rats.

Angiogenic Effects of Dimeric Dipeptide Mimetic of Loop 4 of Nerve Growth Factor

Angiogenic action of compound GK-2, a dimeric dipeptide mimetic of loop 4 of nerve growth factor (NGF), was studied in in vitro and in vivo experiments. Experiments on human endothelial cell culture HUVEC showed that compound GK-2 significantly (p<0.05) stimulated the initial stage of angiogenesis, and its angiogenic activity was not inferior to the reference neurotrophin NGF. In experiments with hindlimb ischemia modeled in rats, GK-2 (1 mg/kg intraperitoneally for 14 days) significantly increased the total length of capillary vessels (p<0.003) and the number of vessels per 1 mm2 ischemic tissue (p<0.001) in comparison with the control. Our findings indicate that under experimental conditions compound GK-2 exhibits not only angiogenic, but also anti-ischemic activity.

Dipeptide Piracetam Analogue Noopept Improves Viability of Hippocampal HT-22 Neurons in the Glutamate Toxicity Model

Effect of noopept (N-phenylacetyl-prolylglycine ethyl ester) on viability of neurons exposed to neurotoxic action of glutamic acid (5 mM) was studied in vitro in immortalized mouse hippocampal HT-22 neurons. Noopept added to the medium before or after glutamic acid improved neuronal survival in a concentration range of 10-11-10-5 M. Comparison of the effective noopept concentrations determined in previous studies on cultured cortical and cerebellar neurons showed that hippocampal neurons are more sensitive to the protective effect of noopept.

[PHARMACOLOGICAL STUDY OF NEW COMPOUNDS ACTING AS REGULATORS OF 18-KDA TRANSLOCATOR PROTEIN LIGANDS]

The interaction of new original 1-arylpyrrolo[1,2-a]pyrazine-3-carboxamide derivatives with mitochondrial translocator protein (MTP) 18 kDa has been studied by radioligand binding assay. Compounds GML-1 (Ki = 5.2 x 10⁻⁸ M) and GML-3 (Ki = 5.3 x 10⁻⁷ M) exhibit high binding affinity for MTP. GML-1 and GML-3 in a dose range of 0.1-1 mg/kg (i.p.) demonstrated anxiolytic-like effects in the elevated plus-maze test in CD-1 mice, which were blocked by the MTP selective antagonist PK11195. The data obtained on the molecular target, anxiolytic-like effects and low toxicity GML-1 and GML-3 suggest that these compounds are promising for further investigation as anxiolytics.

PECULIARITIES OF THE EFFECT OF AMINOADAMANTANE DERIVATIVES ON ETHANOL-INDUCED ATAXIA. SEDATION. AND HYPERLOCOMOTION IN MICE

The influence of two aminoadamantane derivatives representing low-affinity NMDA receptor antagonists, which show antiparkinsonian-like activity both in animal models and in patients with Parkinson's disease, have been studied in vivo on mice with acute ethanol-induced disorders. N-(adamant-2-yl) hexamethyleneimine hydrochloride (himantane) in doses of 5--20 mg/kg, i.p., dose-dependently prevented ethanol-induced ataxia in CD-I mice, sedation in C57BI/6 mice, and hyperlocomotion in DBA/2 mice. At the same time, I -aminoadamantane (amantadine) in doses of 10 - 20 mg/kg, i.p., did not attenuate acute ethanol-induced (2 g/kg, i.p.) effects. Neither himantane nor amantadine influenced the duration of ethanol narcosis (5.5 g/kg, i.p.) in CD-I mice. The obtained data showed a difference of the pharmacodynamic profile of himantane as low-affinity NMDA receptor antagonist in interaction with ethanol at doses inducing behavioral disorders.

[The development of a pharmacologically active low-molecular mimetic of the nerve growth factor]

Authors present an overview of theirs author's works on the design of low-molecular mimetic of the nerve growth factor and studies of mechanisms of action and pharmacological properties of the compound. The original working hypothesis, underlying the design of the compound, posited that different neurotrophin hairpin loops could activate different signaling cascades by interaction with the receptor and so be responsible for different effects. The mimetic bis(N-succinyl-L-glutamyl-L-lysine)hexametylendiamide (GK-2), that was designed on the basis of NGF loop 4 β-turn sequence, activated TrkA and PI3K/Akt, but not MAPK/Erk. GK-2 showed neuroprotective activity in concentrations up to 10-9М against H(2)O(2) or glutamate or MPTP-induced neurotoxicity in РС12, НТ22 cells and primary rat hippocampal neurons. At that, GK-2 has no differentiating activity. In in vivo experiments, GK-2 exhibited significant anti-ischemic, anti-parkinsonic effect, reversed impaired cognitive functions in models of Alzheimer's disease in doses 0.01 - 5 mg/kg intraperitoneally and 5-10 mg/kg orally, but does not induce side effects accompanying the full-length neurotrophin treatment, which are hyperalgesia and weight loss. It was shown that GK-2 was a low-toxicity compound (LD50=700 mg/kg, intraperitoneally, mice) and capable of crossing the blood-brain barrier. The agent GK-2 is promising for development as a neuroprotective agent and is currently in preclinical studies.

[Effect of the nerve growth factor mimetic GK-2 on post-resuscitation expression of neurotrophic factors]

THE OBJECTIVE

to elucidate an influence of nerve growth factor mimetic GK-2 on the expression of neurotrophic factors and the process of neuronal death after ischemia-reperfusion. Materials and methods. Adult white male rats underwent cardiac arrest for 12 minutes, followed by resuscitation. 10 rats were injected GK-2 (Img/kg i/ρ) at 30 minutes and 48 hours after resuscitation. 10 untreated animals received equivalent doses of saline. The control group consisted of sham-operated animals (n = 10). On the 7th postoperative day the total density of hypoxia-sensitive cerebellar Purkinje cells was determined by morphometric analysis. Immunohistochemical study of proteins FGFb, NT4, BDNF was performed by indirect peroxidase-antiperoxidase method using primary polyclonal antibodies. The number of neurons with different expression levels of the neurotrophic factors was determined.

RESULTS

In the post-resuscitation period the neuronal loss was detected in untreated animals. Namely NT4-negative, FGFb-negative and BDNF-negative cells died. GK-2 had no effect on the expression level of FGFb and NT4, however, promoted an increase in the expression level of BDNF. Initiating the expression of BDNF in neurons that were not previously producing this factor, GK-2 prevents the development of post-resuscitation neuronal death. Obtained facts lead to the conclusion that one of the mechanisms of neuroprotective action of nerve growth factor mimetic GK-2 is its ability to activate the expression of BDNF in nerve cells.

Noopept normalizes parameters of the incretin system in rats with experimental diabetes

Experiments on adult Wistar rats with streptozotocin-induced diabetes showed that antihyperglycemic activity of an original nootropic and neuroprotective drug Noopept (N-phenylacetyl-L-prolylglycine ethyl ester) is more pronounced under conditions of oral application than after intraperitoneal injection. These data provided a basis for studying the effect of Noopept on major indexes of the incretin system. Streptozotocin was shown to decrease the concentrations of incretin GLP-1 and insulin in the blood. Noopept had a normalizing effect on these parameters. This influence of Noopept was not related to the inhibition of a major enzyme metabolizing incretins (dipeptidyl peptidase IV). A reference drug sitagliptin also increased the contents of incretins and insulin, which was associated with the inhibition of dipeptidyl peptidase IV. It is known that GLP-1 increases NGF expression in the insular system. Our results suggest that the increase in incretin activity contributes to the antiapoptotic effect of Noopept on pancreatic β cells. The mechanism for an increase in blood GLP-1 level after oral application of Noopept requires further investigations.

Afobazole protects rats exposed to peat smoke in utero

Female outbred albino rats were daily subjected to forced inhalations of peat smoke (4 cores packed with a mixture of peat (70%) and wood pulp (30%); 0.46 g, pH at least 5.5, core burning time 6 min,; total exposure 44 min) per se and in combination with oral afobazole (anxiolytic) in doses of 1 and 10 mg/kg on days 1-20 of pregnancy. Some groups of females received oral afobazole (200 mg/kg) after delivery, due to which their newborn rats received the drug in doses of 1-10 mg/kg with maternal milk on days 1-20 of life. Exposure to peat smoke inhibited body weight gain in the progeny on days 5-60 of life. Afobazole treatment during the pre- and postnatal periods prevented this effect. Open field testing showed that exposure to peat smoke prolonged the motor activity in the progeny and impaired the loss of orientation and exploratory behavior during repeated testing. Oral afobazole (1 and 10 mg/kg) during the prenatal and/or postnatal period (with maternal milk) prevented the effects of peat smoke.

Prenatal effects of peat combustion products and afobazole correction thereof in the rat progeny

Female outbred albino rats were daily subjected to forced inhalations of peat smoke (4 cores packed with a mixture of peat (70%) and wood pulp (30%); 0.46 g, pH ≥ 5.5) per se and in combination with oral afobazole (anxiolytic) on days 1-20 of pregnancy. Exposure to peat smoke inhibited body weight gain in pregnant rats, caused an increase of postimplantation deaths, reduction of fetal weights, and an increase in the number of hematomas and hemorrhages in fetuses. Afobazole in doses of 1 and 10 mg/kg reduced significantly the untoward effects of peat smoke on fetal development.

Antihypoxic activity of cycloprolylglycine analogs

We studied antihypoxic activity of analogs of endogenous cyclic dipeptide cycloprolylglycine in a mouse model of normobaric hypoxia with hypercapnia and found that antixypoxic effect depends on the structure of the substance. It was shown that different pharmacophores are responsible for the antihypoxic, nootropic, and anxiolytic effects of cycloprolylglycine.

[EXPERIMENTAL PHARMACOKINETICS AND PHARMACODYNAMICS OF GB-115 DIPEPTIDE ANXIOLYTIC SUBSTANCES]

Pharmacokinetics and pharmacological activity of GB-115 dipeptide anxiolytic after oral administration in the form of crystalline and micronized substances was studied in albino male rats. In contrast to crystalline, the micronized substance exhibited better pharmacokinetic parameters and higher bioavailability. In the "elevated plus maze" test, GB-115 in micronized form at a dose 0.3 mg/kg demonstrated pronounced anxiolytic properties during prolonged period as compared to crystalline substance at the same dose. The obtained data allow the micronized substance of GB-115 to be recommended for inclusion in pharmaceutical composition of new dipeptide anxiolytic drug formulations.

Impaired prenatal development and glycemic status in the offspring of rats with experimental streptozotocin-induced diabetes and their correction with afobazole

Diabetes mellitus was simulated in rats on gestation day 1 by a single intraperitoneal injection of streptozotocin in doses of 40 and 50 mg/kg. Pregnant females showed increased glucose concentrations n the blood and urine, embryonic developmental disorders, such as tongue protrusion, edema, and skin hyperemia with concomitant vascular damage (hemorrhage, hematoma) as well as pre- and post-implantation embryo loss. Afobazole administered orally in doses of 10 and 50 mg/kg to pregnant rats with streptozotocin-induced diabetes significantly decreased prenatal developmental disorders and pre- and post-implantation embryo loss rate. Afobazole in a dose of 50 mg/kg produced maximum protective effect: in rats receiving 40 mg/kg streptozotocin, post-implantation embryo loss decreased by 14.7 times. Afobazole in doses of 10 and 50 mg/kg significantly reduced blood glucose concentration in pregnant rats and normalized glycemia in 90-day-old male offspring.

Temporal characteristics of stress-induced decrease in benzodiazepine reception in C57BL/6 and BALB/c mice

We studied the duration of the drop of specific (3)H-flunitrazepam binding by synaptosomal membranes from the brain of C57Bl/6 and BALB/c mice after open-field and "contact with predator" tests. It was found that reduced benzodiazepine reception in BALB/c mice after open-field test persisted for 1.5 h, but no changes of this parameter were found in C57Bl/6 mice. After contact with predator, the binding capacity of the benzodiazepine site of GABAA receptor was reduced for 8 h in BALB/c mice and for 24 h in C57Bl/6 mice.

Afobazole modifies the neurotoxic and genotoxic effects in rat prenatal alcoholization model

Prenatal ethanol leads to the formation of a wide spectrum of neurotoxic injuries to the brain in embryos by day 20 of intrauterine development. High levels of DNA aberrations and apoptotic comets were detected in tissues of 13-day embryos and placentas of rats receiving 40% ethanol orally (4 ml/kg) during gestation. The increase in the levels of DNA aberrations and apoptotic comets in the embryonic and placental tissues of alcoholic rats on day 13 of gestation correlated with the emergence of morphological abnormalities of the brain in the embryos on day 20 of intrauterine development. Afobazole (antimutagen) in doses of 1 and 10 mg/kg reduced the genotoxic effects of ethanol in embryonic and placental tissues and the relevant neurotoxic involvement of the brain.