Сhronically Administered BDNF Dipeptide Mimetic GSB-106 Prevents the Depressive-like Behavior and Memory Impairments after Transient Middle Cerebral Artery Occlusion in Rats.

BACKGROUND: A dipeptide mimetic of the BDNF loop 4, bis (N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide, GSB-106, was designed and synthesized by V.V. Zakusov Research Institute of Pharmacology. The compound activated in vitro TrkB, MAPK/ERK, PI3K/AKT, and PLCγ, like full-length BDNF. In vivo, GSB-106 exhibited antidepressant-like, neuroprotective and neuroregenerative properties. The aim of this work was to study the effects of GSB-106 on depressive-like behavior, cognitive impairments, as well as on hippocampal neuroplasticity in an experimental model of ischemic stroke. METHODS: Male Wistar rats were subjected to 60 minutes of transient middle cerebral artery occlusion (MCAO). Dipeptide GSB-106 was administered intraperitoneally at a dose of 0.1 mg/kg/day for 21 days after surgery. 30-40 days after MCAO, the depressive-like state in the forced swimming test and memory impairment in the novel object recognition test were assessed. Then, the content of CREB, as a neuroplasticity marker, was assessed in the ipsilateral hippocampus. RESULTS: Rats in MCAO group showed depression-like behavior (increase in immobility time in the forced swimming test by 22% compared to sham group), impairments in short-term and long-term memory (decrease in the discrimination index in the novel object recognition test by 70% and 50%, respectively), and a decrease in immunoreactivity to CREB (cAMP response element-binding protein) in the hippocampus by 36% as compared with the sham group. GSB-106 completely prevented the behavior impairments and counteracted the reduction of immunoreactivity to CREB in the hippocampus. CONCLUSION: The BDNF dipeptide mimetic GSB-106 is promising for further development as a drug for the treatment of poststroke neuropsychiatric disorders.

Antidepressant-like Effects of BDNF and NGF Individual Loop Dipeptide Mimetics Depend on the Signal Transmission Patterns Associated with Trk.

Neurotrophins are considered as an attractive target for the development of antidepressants with a novel mechanism of action. Previously, the dimeric dipeptide mimetics of individual loops of nerve growth factor, NGF (GK-6, loop 1; GK-2, loop 4) and brain-derived neurotrophic factor, BDNF (GSB-214, loop 1; GTS-201, loop 2; GSB-106, loop 4) were designed and synthesized. All the mimetics of NGF and BDNF in vitro after a 5-180 min incubation in a HT-22 cell culture were able to phosphorylate the tropomyosin-related kinase A (TrkA) or B (TrkB) receptors, respectively, but had different post-receptor signaling patterns. In the present study, we conduct comparative research of the antidepressant-like activity of these mimetics at acute and subchronic administration in the forced swim test in mice. Only the dipeptide GSB-106 that in vitro activates mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK), phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) and phospholipase C-gamma (PLCγ) post-receptor pathways exhibited antidepressant-like activity (0.1 and 1.0 mg/kg, ip) at acute administration. At the same time, the inhibition of any one of these signaling pathways completely prevented the antidepressant-like effects of GSB-106 in the forced swim test. All the NGF mimetics were inactive after a single injection regardless of post-receptor in vitro signaling patterns. All the investigated dipeptides, except GTS-201, not activating PI3K/AKT in vitro unlike the other compounds, were active at subchronic administration. The data obtained demonstrate that the low-molecular weight BDNF mimetic GSB-106 that activates all three main post-receptor TrkB signaling pathways is the most promising for the development as an antidepressant.

Neuroregenerative Activity of the Dipeptide Mimetic of Brain-derived Neurotrophic Factor GSB-106 Under Experimental Ischemic Stroke.

BACKGROUND: A dimeric dipeptide mimetic of the BDNF loop 4, bis(N-monosuccinyl- L-seryl-L-lysine) hexamethylenediamide (GSB-106) activates TrkB, PI3K/AKT, MAPK/ ERK, and PLC-γ1, and was created at the V.V. Zakusov Research Institute of Pharmacology. GSB-106 showed neuroprotective activity in vitro and in vivo at systemic administration. OBJECTIVE: In this work, we studied the GSB-106 effect on the cerebral infarct volume, as well as on neurogenesis and synaptogenesis under the experimental ischemic stroke induced by intravascular occlusion of the middle cerebral artery in rats. METHODS: GSB-106 was administered i.p. in a dose of 0.1 mg/kg, 24 h after the surgery and then once a day, with the end of administration on day 6 after surgery. On day 7, brain samples were collected for morphometric and biochemical (Western-blot) analysis. RESULTS: It was established that GSB-106 reduced the brain damage volume by 24%, restored impaired neurogenesis and/or gliogenesis (by Ki-67) in the hippocampus and the striatum, and completely restored the reduced immunoreactivity to synaptic markers synaptophysin and PSD-95 in the striatum. CONCLUSION: Thus, the dimer dipeptide BDNF mimetic GSB-106 exhibits neuroregenerative properties at a clinically relevant time window (24 h) in a model of ischemic stroke presumably due to the stimulation of neurogenesis (and/or gliogenesis) and synaptogenesis.

Low-Molecular Weight BDNF Mimetic, Dimeric Dipeptide GSB-106, Reverses Depressive Symptoms in Mouse Chronic Social Defeat Stress.

A mimetic of the BDNF loop 4, bis (N-monosuccinyl-L-seryl-L-lysine) hexamethylenediamide, named GSB-106, was designed and synthesized in our scientific group. The compound activated TrkB, MAPK/ERK, PI3K/AKT, and PLCγ in in vitro experiments. In vivo experiments with rodents revealed its antidepressant-like activity in the forced swim and the tail suspension tests at the dose range of 0.1-5.0 mg/kg (i.p., p.o.). However, GSB-106 was not studied in depression models modulating major depression in humans. In the present study, the GSB-106 antidepressant-like activity was revealed in mice at the depression model induced by 28-day social defeat stress with 21-days oral administration (0.1 mg/kg) after stress. At the same time, GSB-106 restored reduced locomotor activity and completely eliminated the anhedonia manifestations. The compound also restored reduced levels of synaptophysin and CREB in the hippocampus. In addition, the Trk receptor antagonist K252A, and the PLC inhibitor U73122, were found to completely block the antidepressant-like activity of GSB-106 in the forced swimming test in mice. Thus, the present results demonstrate the dipeptide BDNF mimetic GSB-106 reversed depressive-like behavior and restored hippocampal neuroplasticity in a rodent depression model. These effects of GSB-106 are probably regulated by TrkB signaling.

Low-molecular mimetics of nerve growth factor and brain-derived neurotrophic factor: Design and pharmacological properties.

To overcome the limitations of the clinical use of neurotrophins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), scientists have been trying to create their low-molecular-weight mimetics having improved pharmacokinetic properties and lacking side effects of full-sized proteins since the 90s of the last century. The efforts of various research groups have led to the production of peptide and nonpeptide mimetics, being agonists or modulators of the corresponding Trk or p75 receptors that reproduced the therapeutic effects of full-sized proteins. This review discusses different strategies and approaches to the design of such compounds. The relationship between the structure of the mimetics obtained and their action mechanisms and pharmacological properties are analyzed. Special attention is paid to the dipeptide mimetics of individual NGF and BDNF loops having different patterns of activation of Trk receptors signal transduction pathways, phosphoinositide 3-kinase/protein kinase B and mitogen-activated protein kinase/extracellular signal-regulated kinase, which allowed to evaluate the contribution of each pathway to different pharmacological effects. In conclusion, data on therapeutically promising compounds being at different stages of preclinical and clinical studies are summarized.