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

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), which activates TrkB, PI3K/AKT, MAPK/ERK and PLC-γ1 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 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 surgery and then once a day, with the end of administration on the day 6 after surgery. On the 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%, restores impaired neurogenesis and/or gliogenesis (by Ki-67) in the hippocampus and in the striatum and completely restored the reduced immunoreactivity to synaptic markers synaptophysin and PSD-95 in the striatum.

CONCLUSIONS

Thus, the dimer dipeptide BDNF mimetic GSB-106 exhibits neuroregenerative properties at clinically relevant time window (24 h) in a model of ischemic stroke presumably due to 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.

The Low Molecular Weight Brain-derived Neurotrophic Factor Mimetics with Antidepressant-like Activity

The search for new highly-effective, fast-acting antidepressant drugs is extremely relevant. Brain derived neurotrophic factor (BDNF) and signaling through its tropomyosin-related tyrosine kinase B (TrkB) receptor, represents one of the most promising therapeutic targets for treating depression. BDNF is a key regulator of neuroplasticity in the hippocampus and the prefrontal cortex, the dysfunction of which is considered to be the main pathophysiological hallmark of this disorder. BDNF itself has no favorable drug-like properties due to poor pharmacokinetics and possible adverse effects. The design of small, proteolytically stable BDNF mimetics might provide a useful approach for the development of therapeutic agents. Two small molecule BDNF mimetics with antidepressant-like activity have been reported, 7,8-dihydroxyflavone and the dimeric dipeptide mimetic of BDNF loop 4, GSB-106. The article reflects on the current literature on the role of BDNF as a promising therapeutic target in the treatment of depression and on the current advances in the development of small molecules on the base of this neurotrophin as potential antidepressants.