Mimetics of brain-derived neurotrophic factor loops 1 and 4 are active in a model of ischemic stroke in rats

Dipeptide mimetic of BDNF ameliorates motor dysfunction and striatal apoptosis in 6-OHDA-induced Parkinson's rat model: Considering Akt and MAPKs signaling

Parkinson's disease (PD) is a progressive and debilitating neurodegenerative disorder associated with motor and non-motor complaints. Dysregulation of neurotrophic factors and related signaling cascades have been reported to be common events in PD which is accompanied by dopaminergic (DA) neuron demise. However, the restoration of neurotrophic factors has several limitations. Bis-(N-monosuccinyl-L-methionyl-L-serine) heptamethylenediamide (BHME) is a dipeptide mimetic of brain-derived neurotrophic factor (BDNF) with reported anti-oxidant and neuroprotective effects in several experimental models. The current study has investigated the effect of BHME on 6-hydroxydopamine (6-OHDA)-caused motor anomalies in Wistar rats. In this regard, rats were treated daily with BHME (0.1 or 1 mg/kg) 1 h after 6-OHDA-caused damage until the twelfth day. Afterwards, motor behavior and DA neuron survival were evaluated via behavioral tests and immunohistochemistry (IHC) staining, respectively. Moreover, the activity of Akt, mitogen-activated protein kinases (MAPKs) family, and Bax/Bcl-2 ratio were evaluated by Western blotting. Our results indicated that BHME prevents motor dysfunction and DA cell death following 6-OHDA injection, and this improvement was in parallel with an enhancement in Akt activity, decrement of P38 phosphorylation, along with a reduction in Bax/Bcl-2 ratio. In conclusion, our findings indicated that BHME, as a mimetic of BDNF, can be considered for further research and is a promising therapeutic agent for PD therapy.

Growth factors and their peptide mimetics for treatment of traumatic brain injury

Traumatic brain injury (TBI) is a leading cause of disability in adults, caused by a physical insult damaging the brain. Growth factor-based therapies have the potential to reduce the effects of secondary injury and improve outcomes by providing neuroprotection against glutamate excitotoxicity, oxidative damage, hypoxia, and ischemia, as well as promoting neurite outgrowth and the formation of new blood vessels. Despite promising evidence in preclinical studies, few neurotrophic factors have been tested in clinical trials for TBI. Translation to the clinic is not trivial and is limited by the short in vivo half-life of the protein, the inability to cross the blood-brain barrier and human delivery systems. Synthetic peptide mimetics have the potential to be used in place of recombinant growth factors, activating the same downstream signalling pathways, with a decrease in size and more favourable pharmacokinetic properties. In this review, we will discuss growth factors with the potential to modulate damage caused by secondary injury mechanisms following a traumatic brain injury that have been trialled in other indications including spinal cord injury, stroke and neurodegenerative diseases. Peptide mimetics of nerve growth factor (NGF), hepatocyte growth factor (HGF), glial cell line-derived growth factor (GDNF), brain-derived neurotrophic factor (BDNF), platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF) will be highlighted, most of which have not yet been tested in preclinical or clinical models of TBI.

Analysis of the Role of PI3K/Akt Pathway in the Realization of the Normalizing Effect of Low-Molecular-Weight Mimetics of NGF and BDNF on Activity of Prooxidant and Antioxidant Systems in C57BL/6 Mice with Modeled Diabetes

The effect of low-molecular-weight mimetics of NGF and BDNF (GK-2 and GSB-214 in a dose 0.5 mg/kg, respectively) on malondialdehyde content and activity of an antioxidant defense enzyme glutathione peroxidase was studied in experiments on C57BL/6 mice with streptozotocin-induced diabetes. An increase in the malondialdehyde content indicating enhanced formation of peroxidation products and a decrease of glutathione peroxidase activity in the blood plasma of untreated diabetic animals were revealed. Both studied mimetics were shown to attenuate the severity of these disorders. Since the ability of these compounds to activate the PI3K/Akt signaling pathway was previously demonstrated in vitro on HT-22 cell culture, we studied the effect of LY294002, an inhibitor of this pathway, on the above parameters. It was found that LY294002 attenuates the normalizing effect of GK-2 and GSB-214 only in relation to glutathione peroxidase activity, but not malondialdehyde level.

A Low-Molecular-Weight BDNF Mimetic, Dipeptide GSB-214, Prevents Memory Impairment in Rat Models of Alzheimer's Disease

Brain-derived neurotrophic factor (BDNF) is known to be involved in the pathogenesis of Alzheimer's disease (AD). However, the pharmacological use of full-length neurotrophin is limited, because of its macromolecular protein nature. A dimeric dipeptide mimetic of the BDNF loop 1, bis-(N-monosuccinyl-L-methionyl-L-serine) heptamethylene diamide (GSB-214), was designed at the Zakusov Research Institute of Pharmacology. GSB-214 activates TrkB, PI3K/AKT, and PLC-γ1 in vitro. GSB-214 exhibited a neuroprotective activity during middle cerebral artery occlusion in rats when administered intraperitoneally (i.p.) at a dose of 0.1 mg/kg and improved memory in the novel object recognition test (0.1 and 1.0 mg/kg, i.p.). In the present study, we investigated the effects of GSB-214 on memory in the scopolamine- and steptozotocin-induced AD models, with reference to activation of TrkB receptors. AD was modeled in rats using a chronic i.p. scopolamine injection or a single streptozotocin injection into the cerebral ventricles. GSB-214 was administered within 10 days after the exposure to scopolamine at doses of 0.05, 0.1, and 1 mg/kg (i.p.) or within 14 days after the exposure to streptozotocin at a dose of 0.1 mg/kg (i.p.). The effect of the dipeptide was evaluated in the novel object recognition test; K252A, a selective inhibitor of tyrosine kinase receptors, was used to reveal a dependence between the mnemotropic action and Trk receptors. GSB-214 at doses of 0.05 and 0.1 mg/kg statistically significantly prevented scopolamine-induced long-term memory impairment, while not affecting short-term memory. In the streptozotocin-induced model, GSB-214 completely eliminated the impairment of short-term memory. No mnemotropic effect of GSB-214 was registered when Trk receptors were inhibited by K252A.

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 (PLC_γ) 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.

Research advances in the role of endogenous neurogenesis on neonatal hypoxic-ischemic brain damage

Hypoxic-ischemic brain damage (HIBD) is the main cause of perinatal mortality and neurologic complications in neonates, but it remains difficult to cure due to scarce treatments and complex molecular mechanisms remaining incompletely explained. Recent, mounting evidence shows that endogenous neurogenesis can improve neonatal neurological dysfunction post-HIBD. However, the capacity for spontaneous endogenous neurogenesis is limited and insufficient for replacing neurons lost to brain damage. Therefore, it is of great clinical value and social significance to seek therapeutic techniques that promote endogenous neurogenesis, to reduce neonatal neurological dysfunction from HIBD. This review summarizes the known neuroprotective effects of, and treatments targeting, endogenous neurogenesis following neonatal HIBD, to provide available targets and directions and a theoretical basis for the treatment of neonatal neurological dysfunction from HIBD.

Analysis of Antidepressant-like Effects and Action Mechanisms of GSB-106, a Small Molecule, Affecting the TrkB Signaling

Induction of BDNF-TrkB signaling is associated with the action mechanisms of conventional and fast-acting antidepressants. GSB-106, developed as a small dimeric dipeptide mimetic of BDNF, was previously shown to produce antidepressant-like effects in the mouse Porsolt test, tail suspension test, Nomura water wheel test, in the chronic social defeat stress model and in the inflammation-induced model of depression. In the present study, we evaluated the effect of chronic per os administration of GSB-106 to Balb/c mice under unpredictable chronic mild stress (UCMS). It was observed for the first time that long term GSB-106 treatment (1 mg/kg, 26 days) during ongoing UCMS procedure ameliorated the depressive-like behaviors in mice as indicated by the Porsolt test. In addition, chronic per os administration of GSB-106 resulted in an increase in BDNF levels, which were found to be decreased in the prefrontal cortex and hippocampus of mice after UCMS. Furthermore, prolonged GSB-106 treatment was accompanied by an increase in the content of pTrkB^706/707 in the prefrontal cortex and by a pronounced increase in the level of pTrkB⁸¹⁶ in both studied brain structures of mice subjected to UCMS procedure. In summary, the present data show that chronic GSB-106 treatment produces an antidepressant-like effect in the unpredictable chronic mild stress model, which is likely to be associated with the regulation of the BDNF-TrkB signaling.

The involvement of microglial CX3CR1 in heat acclimation-induced amelioration of adult hippocampal neurogenesis impairment in EMF-exposed mice

Microglial CX3C chemokine receptor 1 (CX3CR1) has been implicated in numerous cellular mechanisms, including signalling pathways that regulate brain homoeostasis and adult hippocampal neurogenesis. Specific environmental conditions can impair hippocampal neurogenesis-related cognition, learning and memory. However, the role of CX3CR1 in the neurogenic alterations resulting from the cross-tolerance protection conferred by heat acclimation (HA) against the effects of electromagnetic field (EMF) exposure is less well understood. Here, we investigated the role of microglial CX3CR1 signalling in adult hippocampal neurogenesis induced by HA in EMF-exposed mice. We found that EMF exposure significantly decreased the number of proliferating and differentiating cells in the dentate gyrus (DG) of the hippocampus, resulting in a reduced neurogenesis rate. Moreover, alterations in the phenotypes of activated microglia and decreased expression levels of CX3CR1, but not sirtuin 1 (SIRT1), were observed in the brains of EMF-exposed mice. Remarkably, HA treatment improved microglial phenotypes, restored the expression of CX3CR1, and ameliorated the decrease in the adult hippocampal neurogenesis rate following EMF exposure. Moreover, pharmacological inhibition of CX3CR1 and SIRT1 failed to restore CX3CR1 expression and ameliorate hippocampal neurogenesis impairment following HA plus EMF stimulation. These results indicate that microglial CX3CR1 is involved in the cross-tolerance protective effect of HA on adult hippocampal neurogenesis upon EMF exposure.

Identification of Novel Positive Allosteric Modulators of Neurotrophin Receptors for the Treatment of Cognitive Dysfunction

Alzheimer's disease (AD) is the most common neurodegenerative disorder and results in severe neurodegeneration and progressive cognitive decline. Neurotrophins are growth factors involved in the development and survival of neurons, but also in underlying mechanisms for memory formation such as hippocampal long-term potentiation. Our aim was to identify small molecules with stimulatory effects on the signaling of two neurotrophins, the nerve growth factor (NGF) and the brain derived neurotrophic factor (BDNF). To identify molecules that could potentiate neurotrophin signaling, 25,000 molecules were screened, which led to the identification of the triazinetrione derivatives ACD855 (Ponazuril) and later on ACD856, as positive allosteric modulators of tropomyosin related kinase (Trk) receptors. ACD855 or ACD856 potentiated the cellular signaling of the neurotrophin receptors with EC50 values of 1.9 and 3.2 or 0.38 and 0.30 µM, respectively, for TrkA or TrkB. ACD855 increased acetylcholine levels in the hippocampus by 40% and facilitated long term potentiation in rat brain slices. The compounds acted as cognitive enhancers in a TrkB-dependent manner in several different behavioral models. Finally, the age-induced cognitive dysfunction in 18-month-old mice could be restored to the same level as found in 2-month-old mice after a single treatment of ACD856. We have identified a novel mechanism to modulate the activity of the Trk-receptors. The identification of the positive allosteric modulators of the Trk-receptors might have implications for the treatment of Alzheimer's diseases and other diseases characterized by cognitive impairment.

Peptides Derived from Growth Factors to Treat Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by progressive neuron losses in memory-related brain structures. The classical features of AD are a dysregulation of the cholinergic system, the accumulation of amyloid plaques, and neurofibrillary tangles. Unfortunately, current treatments are unable to cure or even delay the progression of the disease. Therefore, new therapeutic strategies have emerged, such as the exogenous administration of neurotrophic factors (e.g., NGF and BDNF) that are deficient or dysregulated in AD. However, their low capacity to cross the blood-brain barrier and their exorbitant cost currently limit their use. To overcome these limitations, short peptides mimicking the binding receptor sites of these growth factors have been developed. Such peptides can target selective signaling pathways involved in neuron survival, differentiation, and/or maintenance. This review focuses on growth factors and their derived peptides as potential treatment for AD. It describes (1) the physiological functions of growth factors in the brain, their neuronal signaling pathways, and alteration in AD; (2) the strategies to develop peptides derived from growth factor and their capacity to mimic the role of native proteins; and (3) new advancements and potential in using these molecules as therapeutic treatments for AD, as well as their limitations.

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.

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.

Protective Effects of PGC-1α Activators on Ischemic Stroke in a Rat Model of Photochemically Induced Thrombosis

The pharmacological induction and activation of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), a key regulator of ischemic brain tolerance, is a promising direction in neuroprotective therapy. Pharmacological agents with known abilities to modulate cerebral PGC-1α are scarce. This study focused on the potential PGC-1α-modulating activity of Mexidol (2-ethyl-6-methyl-3-hydroxypyridine succinate) and Semax (ACTH(4-7) analog) in a rat model of photochemical-induced thrombosis (PT) in the prefrontal cortex. Mexidol (100 mg/kg) was administered intraperitoneally, and Semax (25 μg/kg) was administered intranasally, for 7 days each. The expression of PGC-1α and PGC-1α-dependent protein markers of mitochondriogenesis, angiogenesis, and synaptogenesis was measured in the penumbra via immunoblotting at Days 1, 3, 7, and 21 after PT. The nuclear content of PGC-1α was measured immunohistochemically. The suppression of PGC-1α expression was observed in the penumbra from 24 h to 21 days following PT and reflected decreases in both the number of neurons and PGC-1α expression in individual neurons. Administration of Mexidol or Semax was associated with preservation of the neuron number and neuronal expression of PGC-1α, stimulation of the nuclear translocation of PGC-1α, and increased contents of protein markers for PGC-1α activation. This study opens new prospects for the pharmacological modulation of PGC-1α in the ischemic brain.

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.

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.

TrkB agonists prevent postischemic emergence of refractory neonatal seizures in mice

Refractory neonatal seizures do not respond to first-line antiseizure medications like phenobarbital (PB), a positive allosteric modulator for GABAA receptors. GABAA receptor-mediated inhibition is dependent upon electroneutral cation-chloride transporter KCC2, which mediates neuronal chloride extrusion and its age-dependent increase and postnatally shifts GABAergic signaling from depolarizing to hyperpolarizing. Brain-derived neurotropic factor-tyrosine receptor kinase B activation (BDNF-TrkB activation) after excitotoxic injury recruits downstream targets like PLCγ1, leading to KCC2 hypofunction. Here, the antiseizure efficacy of TrkB agonists LM22A-4, HIOC, and deoxygedunin (DG) on PB-refractory seizures and postischemic TrkB pathway activation was investigated in a mouse model (CD-1, P7) of refractory neonatal seizures. LM, a BDNF loop II mimetic, rescued PB-refractory seizures in a sexually dimorphic manner. Efficacy was associated with a substantial reduction in the postischemic phosphorylation of TrkB at Y816, a site known to mediate postischemic KCC2 hypofunction via PLCγ1 activation. LM rescued ischemia-induced phospho-KCC2-S940 dephosphorylation, preserving its membrane stability. Full TrkB agonists HIOC and DG similarly rescued PB refractoriness. Chemogenetic inactivation of TrkB substantially reduced postischemic neonatal seizure burdens at P7. Sex differences identified in developmental expression profiles of TrkB and KCC2 may underlie the sexually dimorphic efficacy of LM. These results support a potentially novel role for the TrkB receptor in the emergence of age-dependent refractory neonatal seizures.

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.

Brain-Derived Neurotrophic Factor and Its Potential Therapeutic Role in Stroke Comorbidities

With the rise in the aging global population, stroke comorbidities have become a serious health threat and a tremendous economic burden on human society. Current therapeutic strategies mainly focus on protecting neurons from cytotoxic damage at the acute phase upon stroke onset, which not only is a difficult way to ameliorate stroke symptoms but also presents a challenge for the patients to receive effective treatment in time. The brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the adult brain, which possesses a remarkable capability to repair brain damage. Recent promising preclinical outcomes have made BDNF a popular late-stage target in the development of novel stroke treatments. In this review, we aim to summarize the latest progress in the understanding of the cellular/molecular mechanisms underlying stroke pathogenesis, current strategies and difficulties in drug development, the mechanism of BDNF action in poststroke neurorehabilitation and neuroplasticity, and recent updates in novel therapeutic methods.

Developing Insulin and BDNF Mimetics for Diabetes Therapy

Diabetes is a global public health concern nowadays. The majority of diabetes mellitus (DM) patients belong to type 2 diabetes mellitus (T2DM), which is highly associated with obesity. The general principle of current therapeutic strategies for patients with T2DM mainly focuses on restoring cellular insulin response by potentiating the insulin-induced signaling pathway. In late-stage T2DM, impaired insulin production requires the patients to receive insulin replacement therapy for maintaining their glucose homeostasis. T2DM patients also demonstrate a drop of brain-derived neurotrophic factor (BDNF) in their circulation, which suggests that replenishing BDNF or enhancing its downstream signaling pathway may be beneficial. Because of their protein nature, recombinant insulin or BDNF possess several limitations that hinder their clinical application in T2DM treatment. Thus, developing orally active "insulin pill" or "BDNF pill" is essential to provide a more convenient and effective therapy. This article reviews the current development of non-peptidyl chemicals that mimic insulin or BDNF and their potential as anti-diabetic agents.

Transient Forebrain Ischemia Induces Differential Bdnf Transcript Expression and Histone Acetylation Patterns in the Rat Hippocampus

Forebrain ischemia induces delayed, selective neuronal death in hippocampal CA1. It has been established that BDNF (brain-derived neurotrophic factor) is an important factor in ischemic injury. However, the exact mechanism of BDNF expression in the hippocampus after ischemia is unclear. We found that the decrease of BDNF protein expression in hippocampal CA1 was associated with a decrease of Bdnf transcript IV expression in the same region of the rats after ischemia/reperfusion (I/R). In hippocampal CA3 and DG, the results showed increased expression of BDNF protein and transcripts I, IIc, III, IV, VI, and X1. Furthermore, at the Bdnf promoters, I/R led to decreased H3K27ac, increased H3K9ac, and H3K14ac in CA1; increased H3K9ac, H3K14ac, and H3K27ac in CA3; no significant change of H3K9ac, H3K14ac, and H3K27ac in DG. HDAC inhibitor SAHA increased the expression of Bdnf transcripts IV, VI, and X1 in CA1. These findings suggest a potential of modulation Bdnf transcript expression to resolve ischemic brain injury through histone acetylation patterns at the Bdnf promoters.

Innovative Therapy for Alzheimer's Disease-With Focus on Biodelivery of NGF

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder associated with abnormal protein modification, inflammation and memory impairment. Aggregated amyloid beta (Aβ) and phosphorylated tau proteins are medical diagnostic features. Loss of memory in AD has been associated with central cholinergic dysfunction in basal forebrain, from where the cholinergic circuitry projects to cerebral cortex and hippocampus. Various reports link AD progression with declining activity of cholinergic neurons in basal forebrain. The neurotrophic molecule, nerve growth factor (NGF), plays a major role in the maintenance of cholinergic neurons integrity and function, both during development and adulthood. Numerous studies have also shown that NGF contributes to the survival and regeneration of neurons during aging and in age-related diseases such as AD. Changes in neurotrophic signaling pathways are involved in the aging process and contribute to cholinergic and cognitive decline as observed in AD. Further, gradual dysregulation of neurotrophic factors like NGF and brain derived neurotrophic factor (BDNF) have been reported during AD development thus intensifying further research in targeting these factors as disease modifying therapies against AD. Today, there is no cure available for AD and the effects of the symptomatic treatment like cholinesterase inhibitors (ChEIs) and memantine are transient and moderate. Although many AD treatment studies are being carried out, there has not been any breakthrough and new therapies are thus highly needed. Long-term effective therapy for alleviating cognitive impairment is a major unmet need. Discussion and summarizing the new advancements of using NGF as a potential therapeutic implication in AD are important. In summary, the intent of this review is describing available experimental and clinical data related to AD therapy, priming to gain additional facts associated with the importance of NGF for AD treatment, and encapsulated cell biodelivery (ECB) as an efficient tool for NGF delivery.

The role of neurogenesis in neurorepair after ischemic stroke

Stroke consists of an abrupt reduction of cerebral blood flow resulting in hypoxia that triggers an excitotoxicity, oxidative stress, and neuroinflammation. After the ischemic process, neural precursor cells present in the subventricular zone of the lateral ventricle and subgranular zone of the dentate gyrus proliferate and migrate towards the lesion, contributing to the brain repair. The neurogenesis is induced by signal transduction pathways, growth factors, attractive factors for neuroblasts, transcription factors, pro and anti-inflammatory mediators and specific neurotransmissions. However, this endogenous neurogenesis occurs slowly and does not allow a complete restoration of brain function. Despite that, understanding the mechanisms of neurogenesis could improve the therapeutic strategies for brain repair. This review presents the current knowledge about brain repair process after stroke and the perspectives regarding the development of promising therapies that aim to improve neurogenesis and its potential to form new neural networks.

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.

MicroRNA-150 contributes to ischemic stroke through its effect on cerebral cortical neuron survival and function by inhibiting ERK1/2 axis via Mal

Ischemic stroke, caused by the blockage of blood supply, is a major cause of death worldwide. For identifying potential candidates, we explored the effects microRNA-150 (miR-150) has on ischemic stroke and its underlying mechanism by developing a stable middle cerebral artery occlusion (MCAO) rat model. Gene expression microarray analysis was performed to screen differentially expressed genes associated with MCAO. We evaluated the expression of miR-150 and Mal and the status of ERK1/2 axis in the brain tissues of MCAO rats. Then the cerebral cortical neurons (CCNs) were obtained and introduced with elevated or suppressed miR-150 or silenced Mal to validate regulatory mechanisms for miR-150 governing Mal in vitro. The relationship between miR-150 and Mal was verified by dual luciferase reporter gene assay. Besides, cell growth and apoptosis of CCNs were detected by means of MTT assay and flow cytometry analyses. We identified Mal as a downregulated gene in MCAO, based on the microarray data of GSE16561. MiR-150 was over-expressed and negatively targeted Mal in the brain tissues obtained from MCAO rats and their CCNs. Increasing miR-150 blocked the ERK1/2 axis, resulting in an inhibited cell growth of CNNs but an enhanced apoptosis. Furthermore, MiR-150 inhibition was observed to have effects on CNNs as opposed to those inhibited by miR-150 promotion. The key findings of this study support the notion that miR-150 under-expression-mediated direct promotion of Mal protects CNN functions through the activation of the ERK1/2 axis, and underscore the concept that miR-150 may represent a novel pharmacological target for ischemic stroke intervention.

Antidepressant Effect of an Orally Administered Dipeptide Mimetic of the Brain-Derived Neurotrophic Factor

Involvement of BDNF in the regulation of neuroplasticity and neurogenesis in the hippocampus, impairment of which underlies the pathophysiology of depression, makes this endogenous protein a promising object for the development of new-generation antidepressants with a neurophysiologically based mechanism of action. A low-molecular-weight BDNF mimetic, GSB-106 (a substituted dimeric dipeptide, bis-(N-monosuccinyl- L-seryl-L-lysine) hexamethylenediamide), was designed and synthesized at the Zakusov Institute of Pharmacology. GSB-106 was found to activate BDNF-specific TrkB receptors and their main post-receptor signaling pathways MAPK/ERK and PI3K/AKT. GSB-106 exhibited pronounced antidepressant activity in a rodent test battery at a dose of 0.1 to 1.0 mg/kg administered intraperitoneally. Because oral administration is preferable in the treatment of depression, which is associated with a prolonged duration and outpatient character of pharmacotherapy, we examined the antidepressant properties of GSB-106 administered orally as a pharmaceutical substance (PS) and in tablet dosage form (TDF). In the study, we used the Porsolt forced swim test in rats; a conventional antidepressant, Amitriptyline, was used as a reference drug. The antidepressant activity of GSB-106 was found to retain upon oral administration and to manifest at doses of 0.5-5.0 mg/kg for PS and 0.01-5.0 mg/kg for TDF. The effective dose of TDF was 50-fold lower than that of PS, and the efficacy of tableted GSB-106 exceeded that of Amitriptyline, the "gold standard" in antidepression care. Therefore, GSB-106, both as a substance and as a tablet dosage form, exhibits antidepressant activity when administered orally, which makes it a promising antidepressant agent, the first in the class of BDNF mimetics.

Advances in stroke pharmacology

Stroke occurs when a cerebral blood vessel is blocked or ruptured, and it is the major cause of death and adult disability worldwide. Various pharmacological agents have been developed for the treatment of stroke either through interrupting the molecular pathways leading to neuronal death or enhancing neuronal survival and regeneration. Except for rtPA, few of these agents have succeeded in clinical trials. Recently, with the understanding of the pathophysiological process of stroke, there is a resurrection of research on developing neuroprotective agents for stroke treatment, and novel molecular targets for neuroprotection and neurorestoration have been discovered to predict or offer clinical benefits. Here we review the latest major progress of pharmacological studies in stroke, especially in ischemic stroke; summarize emerging potential therapeutic mechanisms; and highlight recent clinical trials. The aim of this review is to provide a panorama of pharmacological interventions for stroke and bridge basic and translational research to guide the clinical management of stroke therapy.

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.

(-)-Phenserine inhibits neuronal apoptosis following ischemia/reperfusion injury

Stroke commonly leads to adult disability and death worldwide. Its major symptoms are spastic hemiplegia and discordant motion, consequent to neuronal cell death induced by brain vessel occlusion. Acetylcholinesterase (AChE) is upregulated and allied with inflammation and apoptosis after stroke. Recent studies suggest that AChE inhibition ameliorates ischemia-reperfusion injury and has neuroprotective properties. (-)-Phenserine, a reversible AChE inhibitor, has a broad range of actions independent of its AChE properties, including neuroprotective ones. However, its protective effects and detailed mechanism of action in the rat middle cerebral artery occlusion model (MCAO) remain to be elucidated. This study investigated the therapeutic effects of (-)-phenserine for stroke in the rat focal cerebral ischemia model and oxygen-glucose deprivation/reperfusion (OGD/RP) damage model in SH-SY5Y neuronal cultures. (-)-Phenserine mitigated OGD/PR-induced SH-SY5Y cell death, providing an inverted U-shaped dose-response relationship between concentration and survival. In MCAO challenged rats, (-)-phenserine reduced infarction volume, cell death and improved body asymmetry, a behavioral measure of stoke impact. In both cellular and animal studies, (-)-phenserine elevated brain-derived neurotrophic factor (BDNF) and B-cell lymphoma 2 (Bcl-2) levels, and decreased activated-caspase 3, amyloid precursor protein (APP) and glial fibrillary acidic protein (GFAP) expression, potentially mediated through the ERK-1/2 signaling pathway. These actions mitigated neuronal apoptosis in the stroke penumbra, and decreased matrix metallopeptidase-9 (MMP-9) expression. In synopsis, (-)-phenserine significantly reduced neuronal damage induced by ischemia/reperfusion injury in a rat model of MCAO and cellular model of OGD/RP, demonstrating that its anti-apoptotic/neuroprotective/neurotrophic cholinergic and non-cholinergic properties warrant further evaluation in conditions of brain injury.