Neuroprotective Effects of Dipeptide Analogue of Brain-Derived Neurotrophic Factor GSB-106 in In Vitro Experiments

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.

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.