Neuroprotective Properties of Afobazol in Vitro

The Effect of Original Russian Neurotropic Drugs on Organic Anion Transporting Polypeptides OATP1B1 and OATP1B3

In experiments on HepG2 cells, we studied the effect of the original domestic neurotropic drugs omberacetam, fabomotizole, and ethylmethylhydroxypyridine succinate (EMHPS) (1-500 μM) on the activity and content of organic anion transporting polypeptides OATP1B1 and OATP1B3. It was shown that omberacetam (500 μM) increased the content of OATP1B1 and OATP1B3, fabomotizole did not affect the level of both transporters, and EMHPS (500 μM) increased the content of OATP1B1 compared to the control and did not affect the level of OATP1B3. The tested substances also reduced the OATP1B1/OATP1B3 ratio, as evidenced by a decrease in the penetration of atorvastatin, a substrate of the transporters, into HepG2 cells in the presence of omberacetam (100-500 μM), fabomotizole (500 μM), and EMHPS (10-500 μM). Evaluation of clinical significance of the obtained results, according to the FDA approach based on the calculation of the Cmax/IC50 ratio, showed that the effect of the tested substances on OATP1B1/OATP1B3 is clinically insignificant.

Angiogenic Effects of Anxiolytic Fabomotizole

In vitro experiments performed on an isolated human endothelial HUVEC cell culture showed that the anxiolytic fabomotizole, which, in addition to the anxiolytic effect, has neuroprotective and cardioprotective activities largely associated with its agonistic action on sigma-1 receptors and shows a pronounced angiogenic activity. Fabomotizole angiogenic activity is realized in the range concentration from 10-5 to 10-8 M and is doze-dependent. In the literature, data on the presence of angiogenic activity in sigma receptor agonists have not been previously reported.

The Antipsychotic D2AAK1 as a Memory Enhancer for Treatment of Mental and Neurodegenerative Diseases

The treatment of memory impairments associated with the central nervous system diseases remains an unmet medical need with social and economic implications. Here we show, that a multi-target ligand of aminergic G protein-coupled receptors with antipsychotic activity in vivo (D2AAK1) stimulates neuron growth and survival and promotes neuron integrity. We focused on the multilevel evaluation of the D2AAK1-related effects on neurons in terms of behavioral, cellular, molecular, and biochemical features in vivo and in vitro, such as memory-related responses, locomotor activity, tissue sections analysis, metabolic activity, proliferation level, neurons morphology, and proteins level involved in intracellular signaling pathways. In silico studies indicate that activation of calcium/calmodulin-dependent protein kinase I (CaMKI) may underline some of the observed activities of the compound. Furthermore, the compound increases hippocampal neuron proliferation via the activation of neurotrophic factors and cooperating signals responsible for cell growth and proliferation. D2AAK1 improves memory and learning processes in mice after both acute and chronic administration. D2AAK1 also causes an increase in the number of hippocampal pyramidal neurons after chronic administration. Because of its neuroprotective properties and pro-cognitive activity in behavioral studies D2AAK1 has the potential for the treatment of memory disturbances in neurodegenerative and mental diseases.

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 mediates the neuroprotective action of afobazole in the 6-OHDA model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease with limited treatment options. Therefore, the identification of therapeutic targets is urgently needed. Previous studies have shown that the ligand activation of the sigma-1 chaperone (Sigma1R) promotes neuroprotection. The multitarget drug afobazole (5-ethoxy-2-[2-(morpholino)-ethylthio]benzimidazole dihydrochloride) was shown to interact with Sigma1Rs and prevent decreases in striatal dopamine in the 6-hydroxydopamine (6-OHDA)-induced parkinsonism model. The aim of the present study was to elucidate the role of Sigma1Rs in afobazole pharmacological activity. Using ICR mice we found that administration of afobazole (2.5 mg/kg, i.p.) or selective agonist of Sigma1R PRE-084 (1.0 mg/kg, i.p.) over 14 days normalizes motor disfunction and prevents decreases in dopamine in the 6-OHDA-lesioned striatum. Afobazole administration also prevents the loss of TH + neurons in the substantia nigra. The pre-administration of selective Sigma1R antagonist BD-1047 (3.0 mg/kg, i.p.) abolishes the activity of either afobazole or PRE-084, as determined using the rotarod test and the analysis of striatal dopamine content. The current study demonstrates the contribution of Sigma1Rs in the neuroprotective effect of afobazole in the 6-OHDA model of Parkinson's disease and defines the therapeutic perspective of Sigma1R agonists in the clinic.

Activation of Sigma Receptors With Afobazole Modulates Microglial, but Not Neuronal, Apoptotic Gene Expression in Response to Long-Term Ischemia Exposure

Stroke continues to be a leading cause of death and serious long-term disability. The lack of therapeutic options for treating stroke at delayed time points (≥6 h post-stroke) remains a challenge. The sigma receptor agonist, afobazole, an anxiolytic used clinically in Russia, has been shown to reduce neuronal and glial cell injury following ischemia and acidosis; both of which have been shown to play important roles following an ischemic stroke. However, the mechanism(s) responsible for this cytoprotection remain unknown. Experiments were carried out on isolated microglia from neonatal rats and cortical neurons from embryonic rats to gain further insight into these mechanisms. Prolonged exposure to in vitro ischemia resulted in microglial cell death, which was associated with increased expression of the pro-apoptotic protein, Bax, the death protease, caspase-3, and reduced expression in the anti-apoptotic protein Bcl-2. Incubation of cells with afobazole during ischemia decreased the number of microglia expressing both Bax and caspase-3, and increased cells expressing Bcl-2, which resulted in a concomitant enhancement in cell survival. In similar experiments, incubation of neurons under in vitro ischemic conditions resulted in higher expression of Bax and caspase-3, while at the same time expression of Bcl-2 was decreased. However, unlike observations made in microglial cells, afobazole was unable to modulate the expression of these apoptotic proteins, but a reduction in neuronal death was still noted. The functional state of surviving neurons was assessed by measuring metabolic activity, resting membrane potential, and responses to membrane depolarizations. Results showed that these neurons maintained membrane potential but had low metabolic activity and were unresponsive to membrane depolarizations. However, while these neurons were not fully functional, there was significant protection by afobazole against long-term ischemia-induced cell death. Thus, the effects of sigma receptor activation on microglial and neuronal responses to ischemia differ significantly.

Synthesis and Investigation of S-Substituted 2-Mercaptobenzoimidazoles as Inhibitors of Hedgehog Signaling

Due to the arising resistance of common drugs targeting the Hedgehog signaling pathway, the identification of new compound classes with inhibitory effect is urgently needed. We were able to identify S-alkylated 2-mercaptobenzoimidazoles as a new compound class that exhibits Hedgehog signaling activity in a low micromolar range. The scope of the 2-mercaptobenzoimidazole motif has been investigated by the syntheses of diverse derivatives, revealing that the elongation of the linker unit and the exchange of particular substitution patterns are tolerable with respect to the activity of the compound class.

Oxidation of diazenyl-protected N-heterocycles – a new entry to functionalized lactams

A strategy for the synthesis ofN-aryldiazenyllactams, offering the direct access to protected lactam derivatives, is based on the oxidation of the corresponding cyclic amines with a ruthenium-based catalyst in CCl₄/CAN/phosphate buffer.

Contribution of Sigma-1 receptor to cytoprotective effect of afobazole

Anxiolytic afobazole (5‐Ethoxy‐2‐[2‐(morpholino)‐ethylthio]benzimidazole dihidrochloride) has pronounced ligand properties toward Sigma‐1 receptor (σ1 receptor,SigmaR1) and MT₃ receptors. Our previous work demonstrated that afobazole possess cytoprotective effect in the in vitro model of menadione genotoxicity (Woods et al. 1997) through interaction with MT₃ receptor (Kadnikov et al. 2014). Present study utilized previously described models to address the contribution of SigmaR1 to cytoprotective action of afobazole. The reduction in afobazole cytoprotective effect observed after preincubation of cell suspension with selective SigmaR1 antagonist BD‐1047 revealed an important contribution of SigmaR1 in afobazole‐mediated effect. We confirmed our observation using selective SigmaR1 agonist PRE‐084. We conclude that pronounced cytoprotective effect of afobazole over PRE‐084 is likely achieved by additive SigmaR1 and MT₃‐mediated effects.

Solid phase syntheses of S,N-substituted 2-mercaptobenzoimidazoles

2-Mercaptobenzoimidazoles are an important class of heterocycles showing biological activity in diverse therapeutic applications.

Cytoprotective Effect of Afobazole and Its Main Metabolite M-11

Cell damage depending on activity of quinone reductase 2 (MT3 receptor) was simulated in experiments on bone marrow cell suspension and assessed by menadione-induced DNA breaks measured by comet assay. We analyzed the protective effect of afobazole interacting with MT1, MT3, σ1 receptors, and monoamine oxidase A and its main metabolite M11 that specifi cally binds to MT3 receptors. Both compounds reduced the level of menadione-induced DNA damage (afobazole was effective in lower concentrations in comparison with M-11). Conclusion was made on the contribution of MT3 receptors to the protective effect of afobazole, but the observed concentration differences indicate possible contribution of other targets of anxiolytic drug to the protective mechanisms.

The pharmacology of actoprotectors: practical application for improvement of mental and physical performance

Actoprotectors are preparations that enhance body stability against physical loads without increasing oxygen consumption or heat production. Or, in short, actoprotectors are synthetic adaptogens with a significant capacity to improve physical performance. This paper explores the history of actoprotectors’development, their pharmacological properties, mechanism of action, and practical application to the improvement of mental and physical performance. A brief summary of the clinico-pharmacological characteristics of the main representatives of this class (bemitil and bromantane) is provided. Some other synthesized compounds, and even natural ones such as ginseng, also are regarded as potential actoprotectors, and these are treated herein as well. Actoprotectors, owing to their wide-ranging pharmacological activities, high efficiency and safety, can be applied under either normal or extreme conditions.

Afobazole activation of σ-1 receptors modulates neuronal responses to amyloid-β25-35

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by a continual decline of cognitive function. No therapy has been identified that can effectively halt or reverse its progression. One hallmark of AD is accumulation of the amyloid-β peptide (Aβ), which alone induces neuronal injury via various mechanisms. Data presented here demonstrate that prolonged exposure (1-24 hours) of rat cortical neurons to Aβ25-35 results in an increase in basal intracellular Ca(2+) concentration ([Ca(2+)]i), and that coincubation with the compound afobazole inhibits these [Ca(2+)]i increases. The effect of afobazole on [Ca(2+)]i is due to activation of σ-1 receptors but could not be mimicked by a second pan-selective σ receptor agonist, 1,3-di-o-tolylguanidine (DTG). Afobazole was also found to lessen nitric oxide (NO) production in response to Aβ25-35 application but did not affect elevations in reactive oxygen species elicited by the Aβ fragment. The reductions in [Ca(2+)]i and NO perturbation produced by afobazole were associated with a decrease in neuronal cell death, whereas DTG failed to enhance cell survival. Examining the molecular mechanisms involved in the increased neuronal survival demonstrates that afobazole incubation results in lower expression of the proapoptotic protein Bax and the death protease caspase-3, while at the same time increasing expression of the antiapoptotic protein, Bcl-2. Given the importance of Aβ neurotoxicity in AD etiology, the findings reported here suggest that afobazole may be an effective AD therapeutic agent. Furthermore, σ-1 receptors may represent a useful target for AD treatment, although not all σ ligands appear to be equally beneficial.

Actoprotective effect of ginseng: improving mental and physical performance

Actoprotectors are preparations that increase the mental performance and enhance body stability against physical loads without increasing oxygen consumption. Actoprotectors are regarded as a subclass of adaptogens that hold a significant capacity to increase physical performance. The focus of this article is studying adaptogen herbs of genus Panax (P. ginseng in particular) and their capabilities as actoprotectors. Some animal experiments and human studies about actoprotective properties of genus Panax attest that P. ginseng (administered as an extract) significantly increased the physical and intellectual work capacities, and the data provided suggests that ginseng is a natural source of actoprotectors. Preparations of ginseng can be regarded as potential actoprotectors which give way to further research of its influence on physical and mental work capacity, endurance and restoration after exhaustive physical loads while compared with reference actoprotectors.

Afobazole modulates neuronal response to ischemia and acidosis via activation of sigma-1 receptors

Afobazole is an anxiolytic medication that has been previously shown to be neuroprotective both in vitro and in vivo. However, the mechanism(s) by which afobazole can enhance neuronal survival remain poorly understood. Experiments were carried out to determine whether afobazole can decrease intracellular calcium overload associated with ischemia and acidosis and whether the effects of afobazole are mediated via interaction of the compound with σ receptors. Fluorometric Ca(2+) imaging was used to resolve how application of afobazole affects intracellular Ca(2+) handling in cortical neurons. Application of afobazole significantly depressed, in a concentration-dependent and reversible manner, the intracellular Ca(2+) overload resulting from in vitro ischemia and acidosis. The IC(50) for afobazole inhibition of ischemia-evoked intracellular Ca(2+) overload was considerably less than that for the inhibition of [Ca(2+)](i) increases induced by acidosis. However, afobazole maximally inhibited only 70% of the ischemia-evoked intracellular Ca(2+) overload but effectively abolished intracellular Ca(2+) increases produced by acidosis. The effects of afobazole on ischemia- and acidosis-induced intracellular Ca(2+) dysregulation were inhibited by preincubating the neurons in the irreversible, pan-selective σ-receptor antagonist, metaphit. Moreover, the effects of afobazole on intracellular Ca(2+) increases triggered by acidosis and ischemia were blocked by the selective σ-1-receptor antagonists, BD 1063 and BD 1047, respectively. Experiments examining the effects of afobazole on neuronal survival in response to ischemia showed that afobazole was neuroprotective. Taken together, these data suggest that afobazole regulates intracellular Ca(2+) overload during ischemia and acidosis via activation of σ-1 receptors. This mechanism is probably responsible for afobazole-mediated neuroprotection.

Afobazole modulates microglial function via activation of both sigma-1 and sigma-2 receptors

Microglial cells play a critical role in the neuroinflammatory response that accompanies various diseases of the central nervous system, such as ischemic stroke, and ATP is a major signaling molecule regulating the response of these cells to these pathophysiological conditions. Experiments were carried out to determine the effects of afobazole on microglial function and to identify the molecular mechanisms by which afobazole affects microglial cells. Afobazole was found to inhibit migration of microglial cells in response to ATP and UTP chemoattraction in a concentration-dependent manner. Inhibition of either σ-1 or σ-2 receptors decreased the effects of afobazole on microglia. In addition to inhibiting microglial cell migration, activation of σ receptors by afobazole decreased intracellular calcium elevation produced by focal application of ATP and UTP in isolated microglial cells. Furthermore, afobazole blocked membrane currents elicited by rapid application of ATP in microglial cells. Taken together, our data indicate that afobazole inhibits microglial response to P2Y and P2X purinergic receptor activation by functioning as a pan-selective σ-receptor agonist. In addition to modulating response to purinergic receptor activation, the effects of afobazole on microglial survival during in vitro ischemia were assessed. Application of afobazole during in vitro ischemia decreased microglial cell death during the ischemic episode and after a 24-h recovery period. Moreover, when afobazole was only applied after the ischemic episode, a significant enhancement in cell survival was still observed. Thus, afobazole acts via σ receptors to decrease microglial response to ATP and provides cytoprotection during and after ischemia.