Partial negative allosteric modulators (NAM) of the mGlu5 receptor are an excellent alternative to full antagonists and NAMs because they retain some therapeutic effects and, at the same time, have a much broader therapeutic window. Here, we investigated whether partial mGlu5 NAM, M-5MPEP induced a fast and sustained antidepressant-like effect, characteristic of rapid-acting antidepressant drugs (RAADs) like ketamine, in C57BL/6J mice. M-5MPEP caused a rapid, dose-dependent antidepressant-like action in the tail suspension test (TST) 60 min after injection. This effect was antagonized by an AMPA receptor antagonist (NBQX) and a TrkB receptor antagonist (ANA-12) but not by 5HT1A and 5HT2A/2C receptor antagonists. Furthermore, M-5MPEP (30 mg/kg) induced sustained antidepressant-like effects 24 h after the last of four administrations. These effects were revealed in the splash test, designed to measure apathy-like state, and in the TST. Western blot and ELISA analyses indicated the involvement of the TrkB/BDNF pathway in the sustained M-5MPEP effects. Additionally, prolonged effects of M-5MPEP were entirely reversed by the TrkB receptor antagonist ANA-12 in both the splash test and the TST, confirming the critical role of TrkB receptor activation in the sustained antidepressant-like effect of M-5MPEP. Importantly, M-5MPEP enhanced the subthreshold dose of (R)-ketamine in the TST, indicating both substances' convergent mechanisms of action and the possibility of their practical use in treating depression.

Neuronal cell fate is predominantly controlled by the effects of growth factors, such as neurotrophins, and the activation of a variety of signaling pathways acting through neurotrophin receptors, namely Trk and p75 (p75NTR). Despite their beneficial effects on brain function, their therapeutic use is compromised, due to their polypeptidic nature and blood–brain-barrier impermeability. To overcome these limitations, our previous studies have proven that DHEA-derived synthetic analogs can act like neurotrophins, lacking endocrine side effects. The present study focuses on the biological characterization of a newly synthesized analog, ENT-A044, and its role on inducing cell specific functions of p75NTR. We show that ENT-A044 can induce cell death and phosphorylation of JNK protein by activating p75NTR. Additionally, ENT-A044 can induce the phosphorylation of TrkB receptor, indicating that our molecule can activate both neurotrophin receptors, leading towards the protection of neuronal populations that express both receptors. Furthermore, the present study demonstrates for the first time the expression of p75NTR in human induced Pluripotent Stem Cells - derived Neural Progenitor Cells (hiPSCs - derived NPCs) and receptor-dependent cell death induced by ENT-A044 treatment. In conclusion, ENT-A044 could be proven a lead molecule for the development of novel pharmacological agents, aiming on new therapeutic approaches and research tools, by controlling p75NTR actions.

Neural precursors (NPs) present in the hippocampus can be modulated by several neurogenic stimuli including environmental enrichment (EE) and antidepressant treatment acting through BDNF-TrkB signaling. We have recently identified NPs in meninges, however menigneal niche response to pro-neurogenic stimuli has never been investigated. To this aim, we analyzed the effects of 4 weeks fluoxetine administration or 1 week EE treatment on NP distribution in mouse brain meninges. Following neurogenic stimuli, although we did not detect modification of meningeal cell number and proliferation, we observed, in meninges, an increased number of β3-Tubulin⁺ immature neuronal cells. Lineage-tracing experiment confirmed that EE-induced β3-Tubulin⁺ immature neuronal cells present in meninges originated from GLAST⁺ radial glia cells. To investigate the molecular mechanism responsible for this response, we studied the BDNF-TrkB interaction. Treatment with ANA-12, a TrkB non-competitive inhibitor, abolished the EE-induced increase of β3-Tubulin⁺ immature neuronal cells in meninges.Overall these data showed, for the first time, that the meningeal niche responded to neurogenic stimuli by increasing the immature neuronal population through TrkB-mediated signaling. A better understanding of the neurogenic stimuli effects on NPs in meninges may be useful to improve the effectiveness of depression and mood disorders treatments.

Knee Osteoarthritis (KOA) is a chronic disease characterized by progressive disability and joint pain. Meniscus chondrocytes apoptosis is the main cause of reduced chondrocyte number and self-repair function. The purpose of this study was to investigate the role of miR-27b-3p in KOA.In this study, we found that the expression of miR-27b-3p was downregulated in cultured IL-1β treated chondrocyte and cartilage tissues in KOA. KOA overexpression evidently reduced IL-1β induced chondrocyte apoptosis and caspase-3 and caspase-9 expression.The upregulated iNOS and COX-2 mRNA and proteins expression was also inhibited by miR-27b-3p mimics. The expression of nitric oxide, PGE2, TNF-α and IL-6 was also inhibited by miR-27b-3p mimics. The target gene of miR-27b-3p was confirmed to be BDNF. TrkB/CREB pathway was proved to be the downstream pathway of miR-27b-3p/BDNF axis.The apoptotic cell percentage and nitric oxide, PGE2, TNF-α and IL-6 expression was induced by BDNF+IL-1β. This induction was inhibited by miR-27b-3p mimics. The cartilage tissues stained with safranin O results showed miR-27b-3p greatly decreased KOA induced cartilage degradation. The expression of BDNF、TrkB and p-CREB was inhibited by len-miR-27b-3p. MiR-27b-3p also reduced the expression of TNF-α、IL-6 and Bax, and increased Bcl-2 expression. These results indicated miR-27b-3p could applied to inhibit the development of KOA and miR-27b-3p/BDNF/TrkB/CREB pathway could serve as novel treatment target to handle KOA.

Curcumin is one of the bioactive metabolites of turmeric (Curcuma longa), known for its pleiotropic pharmacological actions, including antioxidant and anti-inflammation, anticholinesterase, immunomodulation, and neuroprotection. Substantial evidence suggests the therapeutic benefits of curcumin against neurodegenerative disorders, including Alzheimer’s disease (AD), acting on a diverse array of brain targets that make the molecular mechanisms complicated. System biology level-investigation could potentially present a comprehensive molecular mechanism to delineate the neuropharmacological action of curcumin. In this study, we used integrated system pharmacology and molecular simulation analysis to gain insights into the underlying mechanism of curcumin action against AD. Network pharmacology study identified curcumin-targeted potential cellular pathways such as phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) signaling, neurotrophin signaling, toll-like receptor (TLR) signaling, and autophagy, and proteins such as tropomyosin receptor kinase B (TrkB), liver X-receptor-beta (LXR-β), estrogen receptor-β (ER-β), mammalian target of rapamycin (mTOR), TLR-2, N-methyl-D-acetate receptor subunit 2B (GluN2B), β-secretase and glycogen synthase kinase-3β (GSK-3β), which are intimately associated with neuronal growth and survival, immune response, and inflammation. Moreover, the molecular modeling further verified that curcumin showed a significant binding affinity to mTOR, TrkB, LXR-β, TLR-2, ER-β, GluN2B, β-secretase, and GSK-3β, which are the crucial regulators of molecular and cellular processes associated with AD. Together, the present system pharmacology and in silico findings demonstrate that curcumin might play a significant role in modulating AD-pathobiology, supporting its therapeutic application for the prevention and treatment of AD.

Both brain-derived neurotrophic factor (BDNF) and glucocorticoids (GCs) have multiple roles in the various aspects of neurons, including cell survival and synaptic function. BDNF and its receptor TrkB express in the central nervous system (CNS) neurons extensively, and contribution of BDNF/TrkB system in neuronal function is evident, thus, its downregulation has been considered to be involved in the pathogenesis of Alzheimer’s disease (AD). GCs, a stress-related molecule, and glucocorticoid receptor (GR) are also considered to be associated with AD, in addition to mental disorders such as depression. Importantly, a growing body of evidence suggest a close relationship between BDNF/TrkB-mediated signaling and GCs/GR system in the CNS. Here, we introduce current studies on the interaction among neurotrophic system and stress in CNS neurons, and discuss their involvement in the pathophysiology of AD.

An array of diverse processes and factors have been linked to the pathoetiology and pathophysiology of Parkinson’s disease (PD), including systemic CNS factors. This article reviews some of the many processes and factors linked to the emergence and progression of PD that culminates in the loss of substantia nigra pars compacts (SNpc) in PD patients. It is proposed that SNpc astrocytes may be a key hub, with numerous systemic and CNS factors acting to suppress the astrocyte tryptophan-melatonin pathway, leading to a loss of astrocyte melatonin and lactate for SNpc dopamine neurons. Consequently, dopamine neurons show an increase in α-synuclein, oxidative stress and suboptimal mitochondrial function, partly due to the loss of melatonin induced PTEN-associated kinase (PINK)1/parkin and mitophagy. This leads to an increase in the major histocompatibility (MHC)-1 and the chemoattraction of CD8+ T cells that destroy SNpc dopamine neurons in an ‘autoimmune’/’immune-mediated’ manner. The upstream processes driving the end-point ‘chaos’ of SNpc dopamine neuron loss are proposed to be driven by the suppression of night-time pineal melatonin, gut microbiome derived butyrate and possibly bcl2-associated athanogene (BAG)-1, which all act to suppress the glucocorticoid receptor (GR) translocation to the nucleus in all systemic and CNS cells, thereby potentiating the effects of the rising levels of cortisol over the night and accelerated rise in the course of the cortisol awakening response (CAR). The potentiation of cortisol effects at the GR has consequences for the homeostatic regulation of the diverse array of systemic and CNS microenvironments, as well as a distinct regulation of different immune and glia cells. The morning CAR is classically proposed to ‘prepare the body for the coming day’. However, the differential regulation of the GR over the circadian rhythm at night would indicate that such preparation for the coming day may be powerfully determined by night-time factors and processes. The article integrates this systemic, night-time pathoetiology with the ‘immune-mediated’ processes that ultimately drive SNpc dopamine neuron loss. This has a number of novel future research and treatment implications.