Regulation of BDNF-TrkB Signaling and Potential Therapeutic Strategies for Parkinson's Disease

Treatment of Parkinson's disease model with human umbilical cord mesenchymal stem cell-derived exosomes loaded with BDNF

AIMS

Parkinson's disease (PD) is a common neurodegenerative disease that has received widespread attention; however, current clinical treatments can only relieve its symptoms, and do not effectively protect dopaminergic neurons. The purpose of the present study was to investigate the therapeutic effects of human umbilical cord mesenchymal stem cell-derived exosomes loaded with brain-derived neurotrophic factor (BDNF-EXO) on PD models and to explore the underlying mechanisms of these effects.

MAIN METHODS

6-Hydroxydopamine was used to establish in vivo and in vitro PD models. Western blotting, flow cytometry, and immunofluorescence were used to detect the effects of BDNF-EXO on apoptosis and ferroptosis in SH-SY5Y cells. The in vivo biological distribution of BDNF-EXO was detected using a small animal imaging system, and dopaminergic neuron improvements in brain tissue were detected using western blotting, immunofluorescence, immunohistochemistry, and Nissl and Prussian blue staining.

KEY FINDINGS

BDNF-EXO effectively suppressed 6-hydroxydopamine-induced apoptosis and ferroptosis in SH-SY5Y cells. Following intravenous administration, BDNF-EXO crossed the blood-brain barrier to reach afflicted brain regions in mice, leading to a notable enhancement in neuronal survival. Furthermore, BDNF-EXO modulated microtubule-associated protein 2 and phosphorylated tau expression, thereby promoting neuronal cytoskeletal stability. Additionally, BDNF-EXO bolstered cellular antioxidant defense mechanisms through the activation of the nuclear factor erythroid 2-related factor 2 signaling pathway, thereby conferring neuroprotection against damage.

SIGNIFICANCE

The novel drug delivery system, BDNF-EXO, had substantial therapeutic effects in both in vivo and in vitro PD models, and may represent a new treatment strategy for PD.

BDNF-TrkB Signaling Pathway in Spinal Cord Injury: Insights and Implications

Spinal cord injury (SCI) is a neurodegenerative disorder that has critical impact on patient's life expectance and life span, and this disorder also leads to negative socioeconomic features. SCI is defined as a firm collision to the spinal cord which leads to the fracture and the dislocation of vertebrae. The current available treatment is surgery. However, it cannot fully treat SCI, and many consequences remain after the surgery. Accordingly, finding new therapeutics is critical. BDNF-TrkB signaling is a vital signaling in neuronal differentiation, survival, overgrowth, synaptic plasticity, etc. Hence, many studies evaluate its impact on various neurodegenerative disorders. There are several studies evaluating this signaling in SCI, and they show promising outcomes. It was shown that various exercises, chemical interventions, etc. had significant positive impact on SCI by affecting BDNF-TrkB signaling pathway. This study aims to accumulate and evaluate these data and inspect whether this signaling is effective or not.

BDNF-TrkB Signaling in Mitochondria: Implications for Neurodegenerative Diseases

Brain-derived neurotrophic factor (BDNF) plays a pivotal role in neuronal development, synaptic plasticity, and overall neuronal health by binding to its receptor, tyrosine receptor kinase B (TrkB). This review delves into the intricate mechanisms through which BDNF-TrkB signaling influences mitochondrial function and potentially influences pathology in neurodegenerative diseases. This review highlights the BDNF-TrkB signaling pathway which regulates mitochondrial bioenergetics, biogenesis, and dynamics, mitochondrial processes vital for synaptic transmission and plasticity. Furthermore, we explore how the BDNF-TrkB-PKA signaling in the cytosol and in mitochondria affects mitochondrial transport and distribution and mitochondrial content, which is crucial for supporting the energy demands of synapses. The dysregulation of this signaling pathway is linked to various neurodegenerative diseases, including Alzheimer's and Parkinson's disease, which are characterized by mitochondrial dysfunction and reduced BDNF expression. By examining seminal studies that have characterized this signaling pathway in health and disease, the present review underscores the potential of enhancing BDNF-TrkB signaling to mitigate mitochondrial dysfunction in neurodegenerative diseases, offering insights into therapeutic strategies to enhance neuronal resilience and function.

Sex as a Determinant of Age-Related Changes in the Brain

The notion of notable anatomical, biochemical, and behavioral distinctions within male and female brains has been a contentious topic of interest within the scientific community over several decades. Advancements in neuroimaging and molecular biological techniques have increasingly elucidated common mechanisms characterizing brain aging while also revealing disparities between sexes in these processes. Variations in cognitive functions; susceptibility to and progression of neurodegenerative conditions, notably Alzheimer's and Parkinson's diseases; and notable disparities in life expectancy between sexes, underscore the significance of evaluating aging within the framework of gender differences. This comprehensive review surveys contemporary literature on the restructuring of brain structures and fundamental processes unfolding in the aging brain at cellular and molecular levels, with a focus on gender distinctions. Additionally, the review delves into age-related cognitive alterations, exploring factors influencing the acceleration or deceleration of aging, with particular attention to estrogen's hormonal support of the central nervous system.

FOXA1 Suppresses Endoplasmic Reticulum Stress, Oxidative Stress, and Neuronal Apoptosis in Parkinson's Disease by Activating PON2 Transcription

Endoplasmic reticulum (ER) stress and oxidative stress (OS) are often related states in pathological conditions including Parkinson's disease (PD). This study investigates the role of anti-oxidant protein paraoxonase 2 (PON2) in ER stress and OS in PD, along with its regulatory molecule. PD was induced in C57BL/6 mice using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP) treatment and in SH-SY5Y cells using 1-methyl-4-phenylpyridinium. PON2 was found to be poorly expressed in the substantia nigra pars compacta (SNc) of PD mice, and its overexpression improved motor coordination of mice. Through the evaluation of tyrosine hydroxylase, dopamine transporter, reactive oxygen species (ROS), and C/EBP homologous protein (CHOP) levels and neuronal loss in mice, as well as the examination of CHOP, glucose-regulated protein 94 (GRP94), GRP78, caspase-12, sarco/endoplasmic reticulum calcium ATPase 2, malondialdehyde, and superoxide dismutase levels in SH-SY5Y cells, we observed that PON2 overexpression mitigated ER stress, OS, and neuronal apoptosis both in vivo and in vitro. Forkhead box A1 (FOXA1) was identified as a transcription factor binding to the PON2 promoter to activate its transcription. Upregulation of FOXA1 similarly protected against neuronal loss by alleviating ER stress and OS, while the protective roles were abrogated by additional PON2 silencing. In conclusion, this study demonstrates that FOXA1-mediated transcription of PON2 alleviates ER stress and OS, ultimately reducing neuronal apoptosis in PD.

Multisensory Fusion Training and 7, 8-Dihydroxyflavone Improve Amyloid-β-Induced Cognitive Impairment, Anxiety, and Depression-Like Behavior in Mice Through Multiple Mechanisms

Background

There is growing interest in the role of physical activity in patients with of Alzheimer's disease (AD), particularly regarding its impact of cognitive function, gut microbiota, metabolites, and neurotrophic factors.

Objective

To investigate the impact of multisensory fusion training (MSFT) combined with 7, 8-dihydroxyflavone (DHF) on the behavioral characteristics, protein expression, microbiome, and serum metabolome using the AD model in mice induced with amyloid-β (Aβ).

Methods

We assessed cognitive ability, anxiety-like and depression-like behaviors in Aβ mice using behavioral measures. Western blotting was employed to detect the expression of relevant proteins. The 16S rRNA gene sequencing and metabolomics were used to analyze changes in the intestinal microbial composition and serum metabolic profile, respectively, of Aβ mice.

Results

The behavioral outcomes indicated that a 4-week intervention combining DHF and MSFT yielded remarkable improvements in cognitive function and reduced anxiety and depression-like behaviors in Aβ mice. In the hippocampus of Aβ mice, the combined intervention increased the levels of BDNF, VGF, PSD-95, Nrf2, p-GSK3β and p-CREB proteins. Analyses of sequence and metabolomic data revealed that Bacteroides and Ruminococcaceae were remarkably more abundant following the combined intervention, influencing the expression of specific metabolites directly linked to the maintenance of neuronal and neurobehavioral functions. These metabolites play a crucial role in vital processes, such as amino acid metabolism, lipid metabolism, and neurotransmitter metabolism in mice.

Conclusion

Our study highlighted that MSFT combined with DHF improves cognitive impairment, anxiety, and depression-like behavior in Aβ mice through multiple mechanisms, and further validated the correlation between the gut microbiome and serum metabolome. These findings open up a promising avenue for future investigations into potential treatment strategies for AD.

Mechanisms Underlying Memory Impairment Induced by Fructose

Fructose consumption has increased over the years, especially in adolescents living in urban areas. Growing evidence indicates that daily fructose consumption leads to some pathological conditions, including memory impairment. This review summarizes relevant data describing cognitive deficits after fructose intake and analyzes the underlying neurobiological mechanisms. Preclinical experiments show sex-related deficits in spatial memory; that is, while males exhibit significant imbalances in spatial processing, females seem unaffected by dietary supplementation with fructose. Recognition memory has also been evaluated; however, only female rodents show a significant decline in the novel object recognition test performance. According to mechanistic evidence, fructose intake induces neuroinflammation, mitochondrial dysfunction, and oxidative stress in the short term. Subsequently, these mechanisms can trigger other long-term effects, such as inhibition of neurogenesis, downregulation of trophic factors and receptors, weakening of synaptic plasticity, and long-term potentiation decay. Integrating all these neurobiological mechanisms will help us understand the cellular and molecular processes that trigger the memory impairment induced by fructose.

Oncogenic Roles of Laminin Subunit Gamma-2 in Intrahepatic Cholangiocarcinoma via Promoting EGFR Translation

Intrahepatic cholangiocarcinoma (iCCA) is a highly lethal biliary epithelial cancer in the liver. Here, Laminin subunit gamma-2 (LAMC2) with important oncogenic roles in iCCA is discovered. In a total of 231 cholangiocarcinoma patients (82% of iCCA patients) across four independent cohorts, LAMC2 is significantly more abundant in iCCA tumor tissue compared to normal bile duct and non-tumor liver. Among 26.3% of iCCA patients, LAMC2 gene is amplified, contributing to its over-expression. Functionally, silencing LAMC2 significantly blocks tumor formation in orthotopic iCCA mouse models. Mechanistically, it promotes EGFR protein translation via interacting with nascent unglycosylated EGFR in the endoplasmic reticulum (ER), resulting in activated EGFR signaling. LAMC2-mediated EGFR translation also depends on its interaction with the ER chaperone BiP via their C-terminus. Together LAMC2 and BiP generate a binding "pocket" of nascent EGFR and facilitate EGFR translation. Consistently, LAMC2-high iCCA patients have poor prognosis in two iCCA cohorts. LAMC2-high iCCA cells are highly sensitive to EGFR tyrosine kinase inhibitors (TKIs) treatment both in vitro and in vivo. Together, these data demonstrate LAMC2 as an oncogenic player in iCCA by promoting EGFR translation and an indicator to identify iCCA patients who may benefit from available EGFR-targeted TKIs therapies.

Targeting cathepsin S promotes activation of OLF1-BDNF/TrkB axis to enhance cognitive function

BACKGROUND

Cathepsin S (CTSS) is a cysteine protease that played diverse roles in immunity, tumor metastasis, aging and other pathological alterations. At the cellular level, increased CTSS levels have been associated with the secretion of pro-inflammatory cytokines and disrupted the homeostasis of Ca2+ flux. Once CTSS was suppressed, elevated levels of anti-inflammatory cytokines and changes of Ca2+ influx were observed. These findings have inspired us to explore the potential role of CTSS on cognitive functions.

METHODS

We conducted classic Y-maze and Barnes Maze tests to assess the spatial and working memory of Ctss-/- mice, Ctss+/+ mice and Ctss+/+ mice injected with the CTSS inhibitor (RJW-58). Ex vivo analyses including long-term potentiation (LTP), Golgi staining, immunofluorescence staining of sectioned whole brain tissues obtained from experimental animals were conducted. Furthermore, molecular studies were carried out using cultured HT-22 cell line and primary cortical neurons that treated with RJW-58 to comprehensively assess the gene and protein expressions.

RESULTS

Our findings reported that targeting cathepsin S (CTSS) yields improvements in cognitive function, enhancing both working and spatial memory in behavior models. Ex vivo studies showed elevated levels of long-term potentiation levels and increased synaptic complexity. Microarray analysis demonstrated that brain-derived neurotrophic factor (BDNF) was upregulated when CTSS was knocked down by using siRNA. Moreover, the pharmacological blockade of the CTSS enzymatic activity promoted BDNF expression in a dose- and time-dependent manner. Notably, the inhibition of CTSS was associated with increased neurogenesis in the murine dentate gyrus. These results suggested a promising role of CTSS modulation in cognitive enhancement and neurogenesis.

CONCLUSION

Our findings suggest a critical role of CTSS in the regulation of cognitive function by modulating the Ca2+ influx, leading to enhanced activation of the BDNF/TrkB axis. Our study may provide a novel strategy for improving cognitive function by targeting CTSS.

Functional modification of recombinant brain-derived neurotrophic factor and its protective effect against neurotoxicity

Brain-derived neurotrophic factor (BDNF) is a neurotrophic protein that promotes neuronal survival, increases neurotransmitter synthesis, and has potential therapeutic effects in neurodegenerative and psychiatric diseases, but its drug development has been limited by the fact that recombinant proteins of BDNF are unstable and do not penetrate the blood-brain barrier (BBB). In this study, we fused a TAT membrane-penetrating peptide with BDNF to express a recombinant protein (TBDNF), which was then PEG-modified to P-TBDNF. Protein characterization showed that P-TBDNF significantly improved the stability of the recombinant protein and possessed the ability to penetrate the BBB, and in cellular experiments, P-TBDNF prevented MPTP-induced nerve cell oxidative stress damage, apoptosis and inflammatory response, and its mechanism of action was closely related to the activation of tyrosine kinase B (TrkB) receptor and inhibition of microglia activation. In animal experiments, P-TBDNF improved motor and cognitive deficits in MPTP mice and inhibited pathological changes in Parkinson's disease (PD). In conclusion, this paper is expected to reveal the mechanism of action of P-TBDNF in inhibiting neurotoxicity, provide a new way for treating PD, and lay the foundation for the future development of recombinant P-TBDNF.

Multi-frequency electromagnetic radiation induces anxiety in mice via inflammation in the cerebral cortex

Modern life is filled with radiofrequency electromagnetic radiation (RF-EMR) in various frequency bands, while the health risks are not clear. In this study, mice were whole-body exposed to 0.9/1.5/2.65 GHz radiofrequency radiation at 4 W/kg for 2 h per day for 4 weeks to investigate the emotional effects. It was found that the mice showed anxiety but no severe depression. The ELISA results showed a significant decrease in amino acid neurotransmitters (GABA, DA, 5-HT), although acetylcholine (ACH) levels were not significantly altered. Furthermore, Western blot results showed that BDNF, TrkB, and CREB levels were increased in the cerebral cortex, while NF-κB levels were decreased. In addition, pro-inflammatory factors (IL-6, IL-1β, TNF-α) were significantly elevated, and anti-inflammatory factors (IL-4, IL-10) tended to decrease. In conclusion, multi-frequency electromagnetic radiation induces an inflammatory response through the CREB-BDNF-TrkB and NF-κB pathways in the cerebral cortex and causes a decrease in excitatory neurotransmitters, which ultimately causes anxiety in mice.

Comparative Neuroprotective Effects of Moringa oleifera Seed Oil and Aqueous Extract on Cognitive Functions on a High-Fat, High-Fructose Diet Mice: Focus on Senescence Markers

Several studies have demonstrated that Moringa oleifera (MO) has different pharmacological properties, including neuroprotective effects. However, the role of MO in preventing brain impairment in high-fat, high-fructose diet (HFFD) remains unknown. This study aimed to investigate the neuroprotective effects of MO leaves aqueous extract (MOE) and moringa seed oil (MOO) against brain impairment in mice with HFFD. Twenty-eight male mice were randomly divided into four groups: normal diet, HFFD, HFFD + MOE 500 mg/kgBW, and HFFD + MOO 2 mL/kgBW. Cognitive function was assessed using the Y-maze and novel object recognition (NOR) tests. The p16, p21, and BDNF expressions were analyzed using the RT-PCR method. Senescence-associated beta-galactosidase (SA-β-gal) staining in the brain was also performed. The results showed that administration of MOE or MOO could increase the percentage of alternation and recognition of new objects, prevent the increase of p16 and p21 expression, and ameliorate SA-β-Gal activity in the brain. MOO, but not MOE, increased BDNF expression in senescence brains isolated from HFFD mice. The findings indicate that MOO and MOE possess neuroprotective properties, with MOO demonstrating a greater ability to inhibit the brain senescence process compared to MOE.

PI3K/AKT signaling activation by roflumilast ameliorates rotenone-induced Parkinson's disease in rats

Parkinson's disease (PD) is the second most common progressive age-related neurodegenerative disorder. Paramount evidence shed light on the role of PI3K/AKT signaling activation in the treatment of neurodegenerative disorders. PI3K/AKT signaling can be activated via cAMP-dependent pathways achieved by phosphodiesterase 4 (PDE4) inhibition. Roflumilast is a well-known PDE4 inhibitor that is currently used in the treatment of chronic obstructive pulmonary disease. Furthermore, roflumilast has been proposed as a favorable candidate for the treatment of neurological disorders. The current study aimed to unravel the neuroprotective role of roflumilast in the rotenone model of PD in rats. Ninety male rats were allocated into six groups as follows: control, rotenone (1.5 mg/kg/48 h, s.c.), L-dopa (22.5 mg/kg, p.o), and roflumilast (0.2, 0.4 or 0.8 mg/kg, p.o). All treatments were administrated for 21 days 1 h after rotenone injection. Rats treated with roflumilast showed an improvement in motor activity and coordination as well as preservation of dopaminergic neurons in the striatum. Moreover, roflumilast increased cAMP level and activated the PI3K/AKT axis via stimulation of CREB/BDNF/TrkB and SIRT1/PTP1B/IGF1 signaling cascades. Roflumilast also caused an upsurge in mTOR and Nrf2, halted GSK-3β and NF-ĸB, and suppressed FoxO1 and caspase-3. Our study revealed that roflumilast exerted neuroprotective effects in rotenone-induced neurotoxicity in rats. These neuroprotective effects were mediated via the crosstalk between CREB/BDNF/TrkB and SIRT1/PTP1B/IGF1 signaling pathways which activates PI3K/AKT trajectory. Therefore, PDE4 inhibition is likely to offer a reliable persuasive avenue in curing PD via PI3K/AKT signaling activation.

Therapeutic gene delivery by mesenchymal stem cell for brain ischemia damage: Focus on molecular mechanisms in ischemic stroke

Cerebral ischemic damage is prevalent and the second highest cause of death globally across patient populations; it is as a substantial reason of morbidity and mortality. Mesenchymal stromal cells (MSCs) have garnered significant interest as a potential treatment for cerebral ischemic damage, as shown in ischemic stroke, because of their potent intrinsic features, which include self-regeneration, immunomodulation, and multi-potency. Additionally, MSCs are easily obtained, isolated, and cultured. Despite this, there are a number of obstacles that hinder the effectiveness of MSC-based treatment, such as adverse microenvironmental conditions both in vivo and in vitro. To overcome these obstacles, the naïve MSC has undergone a number of modification processes to enhance its innate therapeutic qualities. Genetic modification and preconditioning modification (with medications, growth factors, and other substances) are the two main categories into which these modification techniques can be separated. This field has advanced significantly and is still attracting attention and innovation. We examine these cutting-edge methods for preserving and even improving the natural biological functions and therapeutic potential of MSCs in relation to adhesion, migration, homing to the target site, survival, and delayed premature senescence. We address the use of genetically altered MSC in stroke-induced damage. Future strategies for improving the therapeutic result and addressing the difficulties associated with MSC modification are also discussed.

Lactobacillus brevis-Fermented Gamma-Aminobutyric Acid Ameliorates Depression- and Anxiety-Like Behaviors by Activating the Brain-Derived Neurotrophic Factor-Tropomyosin Receptor Kinase B Signaling Pathway in BALB/C Mice

This study investigated the effects of Lactobacillus brevis-fermented gamma-aminobutyric acid (LB-GABA) on depressive and anxiety-like behaviors with the underlying molecular mechanism in a chronic stress model of BALB/c mice. LB-GABA attenuates both neuronal cell death and the increase of monoamine oxidase activity induced by hydrogen peroxide. Behavioral tests revealed that GABA significantly increased sucrose preference and reduced immobility time in both tail suspension and forced swimming tests. LB-GABA increased exploration of the open arms in the elevated plus maze and restored activity in the open field. Moreover, LB-GABA lowered stress hormone and inflammatory mediator levels. Mechanistically, LB-GABA increased protein levels of BDNF and TrkB, activating downstream targets (AKT, ERK, and CREB), crucial for neuronal survival and plasticity. Furthermore, LB-GABA protected hippocampal neurons from stress-induced cell death and increased serotonin and dopamine levels. Overall, LB-GABA has the potential to alleviate stress-induced depression and anxiety-like symptoms and neuroinflammation by activating the BDNF-TrkB signaling pathway.

Hypoxia Sensing and Responses in Parkinson's Disease

Parkinson's disease (PD) is associated with various deficits in sensing and responding to reductions in oxygen availability (hypoxia). Here we summarize the evidence pointing to a central role of hypoxia in PD, discuss the relation of hypoxia and oxygen dependence with pathological hallmarks of PD, including mitochondrial dysfunction, dopaminergic vulnerability, and alpha-synuclein-related pathology, and highlight the link with cellular and systemic oxygen sensing. We describe cases suggesting that hypoxia may trigger Parkinsonian symptoms but also emphasize that the endogenous systems that protect from hypoxia can be harnessed to protect from PD. Finally, we provide examples of preclinical and clinical research substantiating this potential.

Effect of Calorie Restriction and Intermittent Fasting Regimens on Brain-Derived Neurotrophic Factor Levels and Cognitive Function in Humans: A Systematic Review

Background: The potential positive interaction between intermittent fasting (IF) and brain-derived neurotrophic factor (BDNF) on cognitive function has been widely discussed. This systematic review tried to assess the efficacy of interventions with different IF regimens on BDNF levels and their association with cognitive functions in humans. Interventions with different forms of IF such as caloric restriction (CR), alternate-day fasting (ADF), time-restricted eating (TRE), and the Ramadan model of intermittent fasting (RIF) were targeted. Methods: A systematic review was conducted for experimental and observational studies on healthy people and patients with diseases published in EMBASE, Scopus, PubMed, and Google Scholar databases from January 2000 to December 2023. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis statements (PRISMA) for writing this review. Results: Sixteen research works conducted on healthy people and patients with metabolic disorders met the inclusion criteria for this systematic review. Five studies showed a significant increase in BDNF after the intervention, while five studies reported a significant decrease in BDNF levels, and the other six studies showed no significant changes in BDNF levels due to IF regimens. Moreover, five studies examined the RIF protocol, of which, three studies showed a significant reduction, while two showed a significant increase in BDNF levels, along with an improvement in cognitive function after RIF. Conclusions: The current findings suggest that IF has varying effects on BDNF levels and cognitive functions in healthy, overweight/obese individuals and patients with metabolic conditions. However, few human studies have shown that IF increases BDNF levels, with controversial results. In humans, IF has yet to be fully investigated in terms of its long-term effect on BDNF and cognitive functions. Large-scale, well-controlled studies with high-quality data are warranted to elucidate the impact of the IF regimens on BDNF levels and cognitive functions.

Characterization of exosomal microRNAs in preterm infants fed with breast milk and infant formula

Breastfeeding not only reduces infection-related morbidity, but also increases growth of preterm infants. Advantages of breast milk (BM) for preterm infants are significant. They continue to be studied. However, because not all preterm infants can receive breastfeeding, bovine-based infant formula (IF) is used as an alternative, which may increase the risk of several preterm complications. Exosomes isolated from biofluids are emerging as biomarkers in research of various diseases. Here, we characterized miRNA contents of exosomes in urine and serum samples of preterm infants who were BM and IF fed and performed transcriptomic analysis of small RNA libraries. We identified significantly up-regulated 6 miRNAs and 10 miRNAs, respectively. Gene Ontology (GO) analysis revealed that target genes of these miRNAs might participate in neuronal development, immunity modulation, detoxification of reactive oxygen species, and transmembrane exchange. Our data suggest that exosome-based systemic screening for preterm infants with breastfeeding might be a screening tool for identifying target molecules involved in therapy for preterm infants in neonatal intensive care unit (NICU) and for future application as nutraceutical formulations or pharmaceuticals.

Molecular mechanism of cognitive impairment associated with Parkinson's disease: A stroke perspective

Parkinson's disease (PD) is a common neurological illness that causes several motor and non-motor symptoms, most characteristically limb tremors and bradykinesia. PD is a slowly worsening disease that arises due to progressive neurodegeneration of specific areas of the brain, especially the substantia nigra of the midbrain. Even though PD has continuously been linked to a higher mortality risk in numerous epidemiologic studies, there have been significant discoveries regarding the connection between PD and stroke. The incidence of strokes such as cerebral infarction and hemorrhage is substantially associated with the development of PD. Moreover, cognitive impairments, primarily dementia, have been associated with stroke and PD. However, the underlying molecular mechanism of this phenomenon is still obscure. This concise review focuses on the relationship between stroke and PD, emphasizing the molecular mechanism of cognition deficit and memory loss evident in PD and stroke. Furthermore, we are also highlighting some potential drug molecules that can target both PD and stroke.

Menopause-Associated Depression: Impact of Oxidative Stress and Neuroinflammation on the Central Nervous System-A Review

Perimenopausal depression, occurring shortly before or after menopause, is characterized by symptoms such as emotional depression, anxiety, and stress, often accompanied by endocrine dysfunction, particularly hypogonadism and senescence. Current treatments for perimenopausal depression primarily provide symptomatic relief but often come with undesirable side effects. The development of agents targeting the specific pathologies of perimenopausal depression has been relatively slow. The erratic fluctuations in estrogen and progesterone levels during the perimenopausal stage expose women to the risk of developing perimenopausal-associated depression. These hormonal changes trigger the production of proinflammatory mediators and induce oxidative stress, leading to progressive neuronal damage. This review serves as a comprehensive overview of the underlying mechanisms contributing to perimenopausal depression. It aims to shed light on the complex relationship between perimenopausal hormones, neurotransmitters, brain-derived neurotrophic factors, chronic inflammation, oxidative stress, and perimenopausal depression. By summarizing the intricate interplay between hormonal fluctuations, neurotransmitter activity, brain-derived neurotrophic factors, chronic inflammation, oxidative stress, and perimenopausal depression, this review aims to stimulate further research in this field. The hope is that an increased understanding of these mechanisms will pave the way for the development of more effective therapeutic targets, ultimately reducing the risk of depression during the menopausal stage for the betterment of psychological wellbeing.

Brain-Derived Neurotrophic Factor - The Protective Agent Against Neurological Disorders

The burden of neurological illnesses on global health is significant. Our perception of the molecular and biological mechanisms underlying intellectual processing and behavior has significantly advanced over the last few decades, laying the groundwork for potential therapies for various neurodegenerative diseases. A growing body of literature reveals that most neurodegenerative diseases could be due to the gradual failure of neurons in the brain's neocortex, hippocampus, and various subcortical areas. Research on various experimental models has uncovered several gene components to understand the pathogenesis of neurodegenerative disorders. One among them is the brain-derived neurotrophic factor (BDNF), which performs several vital functions, enhancing synaptic plasticity and assisting in the emergence of long-term thoughts. The pathophysiology of some neurodegenerative diseases, including Alzheimer's, Parkinson's, Schizophrenia, and Huntington's, has been linked to BDNF. According to numerous research, high levels of BDNF are connected to a lower risk of developing a neurodegenerative disease. As a result, we want to concentrate on BDNF in this article and outline its protective role against neurological disorders.

Brain-derived neurotrophic factor/tropomyosin receptor kinase B signaling in spinal muscular atrophy and amyotrophic lateral sclerosis

Tropomyosin receptor kinase B (TrkB) and its primary ligand brain-derived neurotrophic factor (BDNF) are expressed in the neuromuscular system, where they affect neuronal survival, differentiation, and functions. Changes in BDNF levels and full-length TrkB (TrkB-FL) signaling have been revealed in spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS), two common forms of motor neuron diseases that are characterized by defective neuromuscular junctions in early disease stages and subsequently progressive muscle weakness. This review summarizes the current understanding of BDNF/TrkB-FL-related research in SMA and ALS, with an emphasis on their alterations in the neuromuscular system and possible BDNF/TrkB-FL-targeting therapeutic strategies. The limitations of current studies and future directions are also discussed, giving the hope of discovering novel and effective treatments.

α-Pyrrolidinononanophenone derivatives induce differentiated SH-SY5Y neuroblastoma cell apoptosis via reduction of antioxidant capacity: Involvement of NO depletion and inactivation of Nrf2/HO1 signaling pathway

α-Pyrrolidinononanophenone (α-PNP) derivatives are known to be one of the hazardous new psychoactive substances due to the most extended hydrocarbon chains of any pyrrolidinophenones on the illicit drug market. Our previous report showed that 4'-iodo-α-PNP (I-α-PNP) is the most potent cytotoxic compound among α-PNP derivatives and induces apoptosis due to mitochondrial dysfunction and suppression of nitric oxide (NO) production in differentiated human neuronal SH-SY5Y cells. In this study, to clarify the detailed action mechanisms by I-α-PNP, we investigated the mechanism of reactive oxygen species (ROS) -dependent apoptosis by I-α-PNP in differentiated SH-SY5Y with a focus on the antioxidant activities. Treatment with I-α-PNP elicits overproduction of ROS such as H2O2, hydroxyl radical, and 4-hydroxy-2-nonenal, and pretreatment with antioxidant N-acetyl-L-cysteine is attenuated the SH-SY5Y cells apoptosis by I-α-PNP. These results suggested that the overproduction of ROS is related to SH-SY5Y cell apoptosis by I-α-PNP. In addition, I-α-PNP markedly decreased antioxidant capacity in differentiated cells than in undifferentiated cells and inhibited the upregulation of hemeoxygenase 1 (HO1) and glutathione peroxidase 4 (GPX4) expression caused by induction of differentiation. Furthermore, the treatment with I-α-PNP increased the nuclear expression level of BTB Domain And CNC Homolog 1 (Bach1), a transcriptional repressor of Nrf2, only in differentiated cells, suggesting that the marked decrease in antioxidant capacity in differentiated cells was due to suppression of Nrf2/HO1 signaling by Bach1. Additionally, pretreatment with an NO donor suppresses the I-α-PNP-evoked ROS overproduction, HO1 down-regulation, increased nuclear Bach1 expression and reduced antioxidant activity in the differentiated cells. These findings suggest that the ROS-dependent apoptosis by I-α-PNP in differentiated cells is attributed to the inactivation of the Nrf2/HO1 signaling pathway triggered by NO depletion.

CRISPR/sgRNA-directed synergistic activation mediator (SAM) as a therapeutic tool for Parkinson´s disease

Parkinson`s disease (PD) is the second most prevalent neurodegenerative disease, and different gene therapy strategies have been used as experimental treatments. As a proof-of-concept for the treatment of PD, we used SAM, a CRISPR gene activation system, to activate the endogenous tyrosine hydroxylase gene (th) of astrocytes to produce dopamine (DA) in the striatum of 6-OHDA-lesioned rats. Potential sgRNAs within the rat th promoter region were tested, and the expression of the Th protein was determined in the C6 glial cell line. Employing pseudo-lentivirus, the SAM complex and the selected sgRNA were transferred into cultures of rat astrocytes, and gene expression and Th protein synthesis were ascertained; furthermore, DA release into the culture medium was determined by HPLC. The DA-producing astrocytes were implanted into the striatum of 6-OHDA hemiparkinsonian rats. We observed motor behavior improvement in the lesioned rats that received DA-astrocytes compared to lesioned rats receiving astrocytes that did not produce DA. Our data indicate that the SAM-induced expression of the astrocyte´s endogenous th gene can generate DA-producing astrocytes that effectively reduce the motor asymmetry induced by the lesion.

Bovine Meissner-like corpuscle and evolutionary ecology of mammalian somatosensory acuity

The mammalian snout has Meissner's corpuscles (MCs), which transmit epicritic sensations as the animal explores its surroundings. To comprehend the somatosensory acuity in mammals, we examined the structural organization and density of bovine Meissner-like corpuscles (BMLCs) at various ages and compared the changes with other mammalian MCs. The skin from the snout of cows or oxen (2-11 years old) was obtained and processed through routine histological technique. Five-μm thick sections were prepared, silver stained according to the Bielschowsky technique as modified by Winkelman and Schmidt (Mayo Clinic Proceedings, 1957, 217), and observed under a compound light microscope quantitatively and qualitatively. The glabrous skin of the cow snout consisted of two types of BMLCs: One was a cylindrical or elongated structure found in the dermal papillae. The other type was spherical and developed in the superficial layers of the epidermis. BMLCs consisted of both coarse and fine nerve fibres. In the young, the corpuscle comprised thin nerve fibres with indistinct cell outlines. In adults, nerve fibres in the corpuscles were closely packed, and networks, varicosities and end bulbs were well developed. With advancing age, the MCs attenuated into a disorganized mass of nerve fibres. The bovine snout is a highly evolved somatosensory organ due to its rich nerve supply and functionally resembles the anthropoid fingertip. Somatosensory acuity will be lower in the glabrous bovine skin than in primate glabrous skin of the fingertip, as the nerve terminals within the BMLCs are less elaborate in content and structural complexity.

Dietary Astaxanthin: A Promising Antioxidant and Anti-Inflammatory Agent for Brain Aging and Adult Neurogenesis

Decreased adult neurogenesis, or the gradual depletion of neural stem cells in adult neurogenic niches, is considered a hallmark of brain aging. This review provides a comprehensive overview of the intricate relationship between aging, adult neurogenesis, and the potential neuroregenerative properties of astaxanthin, a carotenoid principally extracted from the microalga Haematococcus pluvialis. The unique chemical structure of astaxanthin enables it to cross the blood-brain barrier and easily reach the brain, where it may positively influence adult neurogenesis. Astaxanthin can affect molecular pathways involved in the homeostasis, through the activation of FOXO3-related genetic pathways, growth, and regeneration of adult brain neurons, enhancing cell proliferation and the potency of stem cells in neural progenitor cells. Furthermore, astaxanthin appears to modulate neuroinflammation by suppressing the NF-κB pathway, reducing the production of pro-inflammatory cytokines, and limiting neuroinflammation associated with aging and chronic microglial activation. By modulating these pathways, along with its potent antioxidant properties, astaxanthin may contribute to the restoration of a healthy neurogenic microenvironment, thereby preserving the activity of neurogenic niches during both normal and pathological aging.

Comparison of the effects of BDNF/TRKB signalling on metabolic biomarkers in the liver of sedentary and trained rats with normal and knockout BDNF genotypes

Introduction: The effect of brain-derived neurotrophic factor (BDNF) on the modulation of metabolic processes in the liver is poorly understood. Therefore, the aim of this study was to investigate whether hepatic concentrations or activities of metabolic biomarkers depend on altered BDNF/TrkB content in the liver, resulting from different BDNF genotypes of rats. In addition, it was assessed whether 5-week moderate endurance training modifies the levels of BDNF/Trk-B signaling and studied hepatic markers. Methods: Experiments were performed on wild-type and heterozygous BDNF knockout (HET, SD-Bdnf) rats, which were divided into four groups: control with normal genotype (Bdnf+/+), control with BDNF knockout genotype (Bdnf+/-), trained with normal genotype (Bdnf+/+T) and trained with BDNF knockout genotype (Bdnf +/-T). BDNF/TrkB concentrations as well as selected metabolic biomarkers including lipids-total cholesterol (CHOL), low-density lipoprotein (LDL), triglycerides (TG); enzymes-alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), gamma-glutamyl transferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP); hormones-insulin (INS) and leptin (LEPT) as well as interleukin-6 (IL-6) as regeneration indicator were measured directly in liver homogenates. Results and Discussion: The study showed that Bdnf+/- rats exhibited reduced BDNF/TrkB signaling (BDNF, p < 0.0001; Trk-B, p = 0.0005), altered lipid levels (CHOL, p < 0.0001; LDL, p < 0.0001; TG, p = 0.0006) and reduced hepatic ALAT (p = 0.0004) and GGT (p < 0.0001) activity, which may contribute to hepatic steatosis and obesity, as well as indicate impairment of specific metabolic pathways in the liver. Interestingly, endurance training did not alter hepatic BDNF and TrkB content, but improved ALAT (p = 0.0366) and ASAT (p = 0.0191) activities and increased hepatic IL-6 (p = 0.0422) levels in Bdnf +/- rats, suggesting enhanced liver regeneration in animals with BDNF allele loss.

The mechanisms of perineuronal net abnormalities in contributing aging and neurological diseases

The perineuronal net (PNN) is a highly latticed extracellular matrix in the central nervous system, which is composed of hyaluronic acid, proteoglycan, hyaluronan and proteoglycan link protein (Hapln), and tenascin. PNN is predominantly distributed in GABAergic interneurons expressing Parvalbumin (PV) and plays a critical role in synaptic function, learning and memory, oxidative stress, and inflammation. In addition, PNN's structure and function are also modulated by a variety of factors, including protein tyrosine phosphatase σ (PTPσ), orthodenticle homeo-box 2 (Otx2), and erb-b2 receptor tyrosine kinase 4 (ErbB4). Glycosaminoglycan (GAG), a component of proteoglycan, also influences PNN through its sulfate mode. PNN undergoes abnormal changes during aging and in various neurological diseases, such as Alzheimer's disease, Parkinson's disease, schizophrenia, autism spectrum disorder, and multiple sclerosis. Nevertheless, there is limited report on the relationship between PNN and aging or age-related neurological diseases. This review elaborates on the mechanisms governing PNN regulation and summarizes how PNN abnormalities contribute to aging and neurological diseases, offering insights for potential treatments.

The activation of spliced X-box binding protein 1 by isorhynchophylline therapy improves diabetic encephalopathy

The primary symptom of diabetic encephalopathy (DE), a kind of central diabetic neuropathy caused by diabetes mellitus (DM), is cognitive impairment. In addition, the tetracyclic oxindole alkaloid isorhynchophylline (IRN) helps lessen cognitive impairment. However, it is still unclear how IRN affects DM and DE and what mechanisms are involved. The effectiveness of IRN on brain insulin resistance was carefully examined in this work, both in vitro and in vivo. We found that IRN accelerates spliced form of X-box binding protein 1 (sXBP1) translocation into the nucleus under high glucose conditions in vitro. IRN also facilitates the nuclear association of pCREB with sXBP1 and the binding of regulatory subunits of phosphatidylinositol 3-kinase (PI3K) p85α or p85β with XBP1 to restore high glucose impairment. Also, IRN treatment improves high glucose-mediated impairment of insulin signaling, endoplasmic reticulum stress, and pyroptosis/apoptosis by depending on sXBP1 in vitro. In vivo studies suggested that IRN attenuates cognitive impairment, ameliorating peripheral insulin resistance, activating insulin signaling, inactivating activating transcription factor 6 (ATF6) and C/EBP homology protein (CHOP), and mitigating pyroptosis/apoptosis by stimulation of sXBP1 nuclear translocation in the brain. In summary, these data indicate that IRN contributes to maintaining insulin homeostasis by activating sXBP1 in the brain. Thus, IRN is a potent antidiabetic agent as well as an sXBP1 activator that has promising potential for the prevention or treatment of DE.

AMPA receptor modulation through sequential treatment with perampanel and aniracetam mitigates post-stroke damage in experimental model of ischemic stroke

The present study evaluates the effect of modulating α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor (AMPAR) by inhibiting them in the acute phase and activating them in the sub-acute phase on post-stroke recovery in middle cerebral artery occlusion (MCAo) model of stroke in rats. After 90 min of MCAo, perampanel (an AMPAR antagonist, 1.5 mg/kg i.p) and aniracetam (an AMPA agonist, 50 mg/kg i.p.) were administered for different durations after MCAo. Later, after obtaining the best time point for the antagonist and the agonist treatment protocols, sequential treatment with perampanel and aniracetam were given, and the effect on neurological damage and post stroke recovery were assessed. Perampanel and aniracetam significantly protected MCAo-induced neurological damage and diminished the infarct percentage. Furthermore, treatment with these study drugs improved the motor coordination and grip strength. Sequential treatment with perampanel and aniracetam reduced the infarct percentage as assessed by MRI. Moreover, these compounds diminished the inflammation via reducing the levels of pro-inflammatory cytokines (TNF-α, IL-1β) and increasing the levels of anti-inflammatory cytokine (IL-10) along with reductions in GFAP expression. Moreover, the neuroprotective markers (BDNF and TrkB) were found to be significantly increased. Levels of apoptotic markers (Bax, cleaved-caspase-3; Bcl2 and TUNEL positive cells) and neuronal damage (MAP-2) were normalized with the AMPA antagonist and agonist treatment. Expressions of GluR1 and GluR2 subunits of AMPAR were significantly enhanced with sequential treatment. The present study thus showed that modulation of AMPAR improves neurobehavioral deficits and reduces the infarct percentage through anti-inflammatory, neuroprotective and anti-apoptotic effects.

Unveiling the LncRNA-miRNA-mRNA Regulatory Network in Arsenic-Induced Nerve Injury in Rats through High-Throughput Sequencing

Arsenic is a natural toxin which is widely distributed in the environment, incurring diverse toxicities and health problems. Previous studies have shown that long non-coding RNAs (LncRNAs) are also reported to contribute to As-induced adverse effects. LncRNAs are involved in the development of nerve injury, generally acting as sponges for microRNAs (miRNAs). This study aimed to investigate the competitive endogenous RNA (ceRNA) regulatory networks associated with arsenic-induced nerve damage. A total of 40 male Wistar rats were exposed to different doses of arsenic for 12 weeks, and samples were collected for pathological observation and high-throughput sequencing. The ceRNA network was constructed using Cytoscape, and key genes were identified through the PPI network and CytoHubba methods. A real-time quantitative PCR assay was performed to validate gene expression levels. The results showed that subchronic exposure to arsenic in drinking water resulted in pathological and ultrastructural damage to the hippocampal tissue, including changes in neuron morphology, mitochondria, and synapses. Exposure to arsenic results in the dysregulation of LncRNA and mRNA expression in the hippocampal tissues of rats. These molecules participated in multiple ceRNA axes and formed a network of ceRNAs associated with nerve injury. This study also verified key molecules within the ceRNA network and provided preliminary evidence implicating the ENRNOT-00000022622-miR-206-3p-Bdnf axis in the mechanism of neural damage induced by arsenic in rats. These findings provide novel insights into the underlying mechanism of nervous system damage induced by arsenic exposure.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

Brain-derived neurotrophic factor - a key player in the gastrointestinal system

Brain-derived neurotrophic factor (BDNF) is highly expressed throughout the gastrointestinal (GI) tract and plays a critical role in the regulation of intestinal motility, secretion, sensation, immunity, and mucosal integrity. Dysregulation of BDNF signalling has been implicated in the pathophysiology of various GI disorders including inflammatory bowel disease, irritable bowel syndrome, functional dyspepsia, and diabetic gastroenteropathy. This review provides a comprehensive overview of BDNF localization, synthesis, receptors, and signalling mechanisms in the gut. In addition, current evidence on the diverse physiologic and pathophysiologic roles of BDNF in the control of intestinal peristalsis, mucosal transport processes, visceral sensation, neuroimmune interactions, gastrointestinal mucosal healing, and enteric nervous system homeostasis are discussed. Finally, the therapeutic potential of targeting BDNF for the treatment of functional GI diseases is explored. Advancing knowledge of BDNF biology and mechanisms of action may lead to new therapies based on harnessing the gut trophic effects of this neurotrophin.

Sericin alleviates motor dysfunction by modulating inflammation and TrkB/BDNF signaling pathway in the rotenone-induced Parkinson's disease model

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the degeneration of nigrostriatal dopaminergic neurons and movement impairment. Based on theories, neuroinflammatory processes may be vital in the etiology of PD and other neurodegenerative diseases. Reports show that rotenone has neurotoxic, inflammatory, and motor impairment effects in PD. Sericin is a natural polymer with effective properties, such as neuroprotective and anti-inflammatory. Therefore, this study aimed to examine the effects of sericin administration on motor dysfunction by modulating inflammation and tyrosine kinase B/brain-derived neurotrophic factor (TrkB/BDNF) pathway in the rotenone-induced PD model.

METHODS

Wistar male rats (3-months-old) were treated with rotenone (2 mg/kg every 48 h for 30 days) to induce a rotenone-induced PD model. Also, sericin was administered orally at dose of 200 mg/kg every 48 h for 30 days. Rotarod and bar tests were performed for motor dysfunction. The protein levels of BDNF, c-fos, TrkB, tumor necrosis factor- α (TNF-α), interleukin-6 (IL-6) and catalase activity were evaluated in the striatum area.

RESULTS

Results showed that sericin increased latent time in the rotarod test and decreased the time staying on the pole in the bar test compared to the PD group (P < 0.001 for both tests). Moreover, sericin treatments decreased TNF-α (P < 0.001) and IL-6 (P < 0.001) concentration levels and enhanced the levels of BDNF (P < 0.001), c-fos (P < 0.001), TrkB (P < 0.001) proteins and catalase activity (P < 0.05) in the striatum area compared to the PD group.

CONCLUSION

These results support a protective benefit of sericin therapy in a rotenone-induced PD paradigm by reducing motor impairment, inflammatory response, and disruption of the TrkB/BDNF signaling pathway.

Silibinin effects on cognitive disorders: Hope or treatment?

Objective

Almost all diseases of the nervous system are related to neuroinflammation, oxidative stress, neuronal death, glia activation, and increased pro-inflammatory cytokines. Cognitive disorders are one of the common complications of nervous system diseases. The role of some plant compounds in reducing or preventing cognitive disorders has been determined. Silibinin is a plant bioflavonoid and exhibits various effects on cognitive functions. This article discusses the different mechanisms of the effect of silibinin on cognitive disorders in experimental studies.

Materials and Methods

Databases, including ISI, , Google Scholar, Scopus, Medline and PubMed, were investigated from 2000 to 2021, using related keywords to find required articles.

Results

Silibinin can improve cognitive disorders by different pathways such as reducing neuroinflammation and oxidative stress, activation of reactive oxygen species- Brain-derived neurotrophic factor- Tropomyosin receptor kinase B (ROS-BDNF-TrkB) pathway in the hippocampus, an increase of dendritic spines in the brain, inhibition of hyperphosphorylation of tau protein and increasing the expression of insulin receptor (IR) and insulin-like growth factor receptor 1 (IGF-1R), inhibiting inflammatory responses and oxidative stress in the hippocampus and amygdala, and decrease of Homovanillic acid/Dopamine (HVA/DA) ratio and 3,4-Dihydroxyphenylacetic acid + Homovanillic acid/Dopamine (DOPAC+ HVA/DA) ratio in the prefrontal cortex and 5-hydroxyindoleacetic acid/5-hydroxytryptamine (5-HIAA/5-HT) ratio in the hippocampus.

Conclusion

These results suggest that silibinin can be considered a therapeutic agent for the symptom reduction of cognitive disorders, and it acts by affecting various mechanisms such as inflammation, programmed cell death, and oxidative stress.

Dopaminergic Input Regulates the Sensitivity of Indirect Pathway Striatal Spiny Neurons to Brain-Derived Neurotrophic Factor

Motor dysfunction in Parkinson's disease (PD) is closely linked to the dopaminergic depletion of striatal neurons and altered synaptic plasticity at corticostriatal synapses. Dopamine receptor D1 (DRD1) stimulation is a crucial step in the formation of long-term potentiation (LTP), whereas dopamine receptor D2 (DRD2) stimulation is needed for the formation of long-term depression (LTD) in striatal spiny projection neurons (SPNs). Tropomyosin receptor kinase B (TrkB) and its ligand brain-derived neurotrophic factor (BDNF) are centrally involved in plasticity regulation at the corticostriatal synapses. DRD1 activation enhances TrkB's sensitivity for BDNF in direct pathway spiny projection neurons (dSPNs). In this study, we showed that the activation of DRD2 in cultured striatal indirect pathway spiny projection neurons (iSPNs) and cholinergic interneurons causes the retraction of TrkB from the plasma membrane. This provides an explanation for the opposing synaptic plasticity changes observed upon DRD1 or DRD2 stimulation. In addition, TrkB was found within intracellular structures in dSPNs and iSPNs from Pitx3-/- mice, a genetic model of PD with early onset dopaminergic depletion in the dorsolateral striatum (DLS). This dysregulated BDNF/TrkB signaling might contribute to the pathophysiology of direct and indirect pathway striatal projection neurons in PD.

Expression and role of cocaine-amphetamine regulated transcript (CART) in the proliferation of biliary epithelium

Cholangiocytes, the epithelial cells that line the biliary tree, can proliferate under the stimulation of several factors through both autocrine and paracrine pathways. The cocaine-amphetamine-regulated-transcript (CART) peptide has several physiological functions, and it is widely expressed in several organs. CART increases the survival of hippocampal neurons by upregulating brain-derived neurotrophic factor (BDNF), whose expression has been correlated to the proliferation rate of cholangiocytes. In the present study, we aimed to evaluate the expression of CART and its role in modulating cholangiocyte proliferation in healthy and bile duct ligated (BDL) rats in vivo, as well as in cultured normal rat cholangiocytes (NRC) in vitro. Liver samples from both healthy and BDL (1 week) rats, were analyzed by immunohistochemistry and immunofluorescence for CART, CK19, TrkB and p75NTR BDNF receptors. PCNA staining was used to evaluate the proliferation of the cholangiocytes, whereas TUNEL assay was used to evaluate biliary apoptosis. NRC treated or not with CART were used to confirm the role of CART on cholangiocytes proliferation and the secretion of BDNF. Cholangiocytes proliferation, apoptosis, CART and TrkB expression were increased in BDL rats, compared to control rats. We found a higher expression of TrkB and p75NTR, which could be correlated with the proliferation rate of biliary tree during BDL. The in vitro study demonstrated increased BDNF secretion by NRC after treatment with CART compared with control cells. As previously reported, proliferating cholangiocytes acquire a neuroendocrine phenotype, modulated by several factors, including neurotrophins. Accordingly, CART may play a key role in the remodeling of biliary epithelium during cholestasis by modulating the secretion of BDNF.

Roles of microglia in adult hippocampal neurogenesis in depression and their therapeutics

Adult hippocampal neurogenesis generates functional neurons from neural progenitor cells in the hippocampal dentate gyrus (DG) to complement and repair neurons and neural circuits, thus benefiting the treatment of depression. Increasing evidence has shown that aberrant microglial activity can disrupt the appropriate formation and development of functional properties of neurogenesis, which will play a crucial role in the occurrence and development of depression. However, the mechanisms of the crosstalk between microglia and adult hippocampal neurogenesis in depression are not yet fully understood. Therefore, in this review, we first introduce recent discoveries regarding the roles of microglia and adult hippocampal neurogenesis in the etiology of depression. Then, we systematically discuss the possible mechanisms of how microglia regulate adult hippocampal neurogenesis in depression according to recent studies, which involve toll-like receptors, microglial polarization, fractalkine-C-X3-C motif chemokine receptor 1, hypothalamic-pituitary-adrenal axis, cytokines, brain-derived neurotrophic factor, and the microbiota-gut-brain axis, etc. In addition, we summarize the promising drugs that could improve the adult hippocampal neurogenesis by regulating the microglia. These findings will help us understand the complicated pathological mechanisms of depression and shed light on the development of new treatment strategies for this disease.

TrkB inhibition of DJ-1 degradation promotes the growth and maintenance of cancer stem cell characteristics in hepatocellular carcinoma

Although TrkB may be associated with the pathogenesis of various cancer by upregulation, how upregulation of TrkB led to tumor progression in hepatocellular carcinoma (HCC) and the signaling mechanisms by which TrkB induces motility, invasion, metastasis, drug resistance, and acquisition of self-renewal traits has remained unclear. Here, we demonstrated that TrkB was significantly upregulated in highly metastatic HCC cells and HCC patients. Also, the increased TrkB levels were significantly correlated with tumor stages and poor survival of HCC patients. Furthermore, the upregulated TrkB expression enhances the metastatic ability of HCC cells through reduced anoikis sensitivity, induced migration, and colony formation. Most strikingly, TrkB markedly enhances the activation of STAT3 by preventing DJ-1 degradation through the formation of the TrkB/DJ-1 complex. This signaling mechanism is responsible for triggering cellular traits of highly aggressive HCC. The activation of the EMT program of HCC via increasing DJ-1 stability by TrkB induces the gain of cancer stem cell states and chemoresistance via the upregulation of stem cells cell markers and ABC transporters. Also, TrkB-mediated inhibition of DJ-1 degradation promotes tumor formation and metastasizes to other organs in vivo. Our observations illustrate that TrkB is a prognostic and therapeutic targeting in promoting aggressiveness and metastasis of HCC.

BDNF alleviates Parkinson's disease by promoting STAT3 phosphorylation and regulating neuronal autophagy

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the gradual death of dopaminergic neurons. Brain-derived neurotrophic factor (BDNF) and its receptors are widely distributed throughout the central nervous system, which can promote the survival and growth of neurons and protect neurons. This study revealed that BDNF promotes STAT3 phosphorylation and regulates autophagy in neurons. The PD mouse model was established by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Moreover, SH-SY5Y cells were treated with 1-methyl-4-phenyl-pyridinium (MPP+) to establish a PD cell model. The level of BDNF was low in PD model mice and SH-SY5Y cells treated with MPP+. BDNF enhanced the levels of p-TrkB, P-STAT3, PINK1, and DJ-1. BDNF promoted autophagy, inhibited the level of p-α-syn (Ser129) and enhanced cell proliferation. The autophagy inhibitor 3-Methyladenine (3-methyladenine, 3-MA) reversed the protective effects of BDNF on neurons. BiFC assay results showed that there was a direct physical interaction between BDNF and STAT3, and coimmunoprecipitation experiments indicated an interaction between STAT3 and PI3K. The PI3K agonist Recilisib activated the PI3K/AKT/mTOR pathway, promoted autophagy, and alleviated neuronal cell damage. BDNF alleviates PD pathology by promoting STAT3 phosphorylation and regulating neuronal autophagy in SH-SY5Y cells and cultured primary neurons. Finally, BDNF has neuroprotective effects on PD model mice.

Polyphenols' Impact on Selected Biomarkers of Brain Aging in Healthy Middle-Aged and Elderly Subjects: A Review of Clinical Trials

With a constantly growing elderly population, incidences of neurodegenerative diseases are also rising and are expected to further increase over the next years, while costing health systems across the world trillions of dollars. Therefore, biomarkers to detect manifestations of brain aging early and interventions to slow down its pace are of great interest. In the last years, the importance of the neurotrophins brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in the context of cognitive function and the aging brain has increased, besides the already well-established amyloid-beta (Aβ) and tau plaques. Due to their wide range of beneficial health effects as well as their antioxidant and anti-inflammatory properties, a class of secondary plant-metabolites, the so-called polyphenols, gained increasing attention. In this review, we discuss the roles of BDNF, Aβ, NGF, and tau proteins as biomarkers of brain aging and the effect of dietary polyphenol interventions on these biomarkers, assessed via blood analysis, magnetic resonance imaging (MRI), and positron emission tomography (PET).

Brain-derived neurotrophic factor (BDNF) has direct anti-inflammatory effects on microglia

Microglia are the primary immunocompetent cells that protect the brain from environmental stressors, but can also be driven to release pro-inflammatory cytokines and induce a cytotoxic environment. Brain-derived neurotrophic factor (BDNF) is important for the regulation of plasticity, synapse formation, and general neuronal health. Yet, little is known about how BDNF impacts microglial activity. We hypothesized that BDNF would have a direct modulatory effect on primary cortical (Postnatal Day 1-3: P1-3) microglia and (Embryonic Day 16: E16) neuronal cultures in the context of a bacterial endotoxin. To this end, we found that a BDNF treatment following LPS-induced inflammation had a marked anti-inflammatory effect, reversing the release of both IL-6 and TNF-α in cortical primary microglia. This modulatory effect was transferrable to cortical primary neurons, such that LPS-activated microglial media was able produce an inflammatory effect when added to a separate neuronal culture, and again, BDNF priming attenuated this effect. BDNF also reversed the overall cytotoxic impact of LPS exposure in microglia. We speculate that BDNF can directly play a role in regulating microglia state and hence, influence microglia-neuron interactions.

Bispecific antibody shuttles targeting CD98hc mediate efficient and long-lived brain delivery of IgGs

The inability of antibodies and other biologics to penetrate the blood-brain barrier (BBB) is a key limitation to their use in diagnostic, imaging, and therapeutic applications. One promising strategy is to deliver IgGs using a bispecific BBB shuttle, which involves fusing an IgG with a second affinity ligand that engages a cerebrovascular endothelial target and facilitates transport across the BBB. Nearly all prior efforts have focused on the transferrin receptor (TfR-1) as the prototypical endothelial target despite inherent delivery and safety challenges. Here we report bispecific antibody shuttles that engage CD98hc (also known as 4F2 and SLC3A2), the heavy chain of the large neutral amino acid transporter (LAT1), and efficiently transport IgGs into the brain parenchyma. Notably, CD98hc shuttles lead to much longer-lived brain retention of IgGs than TfR-1 shuttles while enabling more specific brain targeting due to limited CD98hc engagement in the brain parenchyma. We demonstrate the broad utility of the CD98hc shuttles by reformatting three existing IgGs as CD98hc bispecific shuttles and delivering them to the mouse brain parenchyma that either agonize a neuronal receptor (TrkB) or target other endogenous antigens on specific types of brain cells (neurons and astrocytes).

Differential expression of RET and GDNF family receptor, GFR-α1, between striatum and substantia nigra following nigrostriatal lesion: a case for diminished GDNF-signaling

Although glial cell line-derived neurotrophic factor (GDNF) showed efficacy in preclinical and early clinical studies to alleviate parkinsonian signs in Parkinson's disease (PD), later trials did not meet primary endpoints, giving pause to consider further investigation. While GDNF dose and delivery methods may have contributed to diminished efficacy, one crucial aspect of these clinical studies is that GDNF treatment across all studies began ∼8 years after PD diagnosis; a time point representing several years after near 100% depletion of nigrostriatal dopamine markers in striatum and at least 50% in substantia nigra (SN), and is later than the timing of GDNF treatment in preclinical studies. With nigrostriatal terminal loss exceeding 70% at PD diagnosis, we utilized hemi-parkinsonian rats to determine if expression of GDNF family receptor, GFR-α1, and receptor tyrosine kinase, RET, differed between striatum and SN at 1 and 4 weeks following a 6-hydroxydopamine (6-OHDA) lesion. Whereas GDNF expression changed minimally, GFR-α1 expression decreased progressively in striatum and in tyrosine hydroxylase positive (TH+) cells in SN, correlating with reduced TH cell number. However, in nigral astrocytes, GFR-α1 expression increased. RET expression decreased maximally in striatum by 1 week, whereas in the SN, a transient bilateral increase occurred that returned to control levels by 4 weeks. Expression of brain-derived neurotrophic factor (BDNF) or its receptor, TrkB, were unchanged throughout lesion progression. Together, these results reveal that differential GFR-α1 and RET expression between the striatum and SN, and cell-specific differences in GFR-α1 expression in SN, occur during nigrostriatal neuron loss. Targeting loss of GDNF receptors appears critical to enhance GDNF therapeutic efficacy against nigrostriatal neuron loss.

Significance Statement

Although preclinical evidence supports that GDNF provides neuroprotection and improves locomotor function in preclinical studies, clinical data supporting its efficacy to alleviate motor impairment in Parkinson's disease patients remains uncertain. Using the established 6-OHDA hemi-parkinsonian rat model, we determined whether expression of its cognate receptors, GFR-α1 and RET, were differentially affected between striatum and substantia nigra in a timeline study. In striatum, there was early and significant loss of RET, but a gradual, progressive loss of GFR-α1. In contrast, RET transiently increased in lesioned substantia nigra, but GFR-α1 progressively decreased only in nigrostriatal neurons and correlated with TH cell loss. Our results indicate that direct availability of GFR-α1 may be a critical element that determines GDNF efficacy following striatal delivery.

Highlights

GDNF expression was minimally affected by nigrostriatal lesionGDNF family receptor, GFR-α1, progressively decreased in striatum and in TH neurons in SN.GFR-α1 expression decreased along with TH neurons as lesion progressedGFR-α1 increased bilaterally in GFAP+ cells suggesting an inherent response to offset TH neuron lossRET expression was severely reduced in striatum, whereas it increased in SN early after lesion induction.

Oleuropein confers neuroprotection against rotenone-induced model of Parkinson's disease via BDNF/CREB/Akt pathway

Major pathological features of Parkinson's disease (PD) include increase in oxidative stress leading to the aggregation of α-synuclein, mitochondrial dysfunction and apoptosis of dopaminergic neurons. In addition, downregulation of the expression of neurotrophic factors like-Brain Derived Neurotrophic Factor (BDNF) is also involved in PD progression. There has been a lot of interest in trophic factor-based neuroprotective medicines over the past few decades to treat PD symptoms. Rotenone, an insecticide, inhibits the mitochondrial complex I causing overproduction of ROS, oxidative stress, and aggregation of α-synuclein. It has been shown that BDNF and Tropomyosin receptor kinase B (TrkB) interaction initiates the regulation of neuronal cell development and differentiation by the serine/threonine protein kinases like Akt and GSK-3β. Additionally, Transcription factor CREB (cAMP Response Element-binding protein) also determines the gene expression of BDNF. The homeostasis of these signalling cascades is compromised with the progression of PD. Therefore, maintaining the equilibrium of these signalling cascades will delay the onset of PD. Oleuropein (OLE), a polyphenolic compound present in olive leaves has been documented to cross blood brain barrier and shows potent antioxidative property. In the present study, the dose of 8, 16 and 32 mg/kg body weight (bwt) OLE was taken for dose standardisation. The optimised doses of 16 and 32 mg/kg bwt was found to be neuroprotective in Rotenone induced PD mouse model. OLE improves motor impairment and upregulate CREB regulation along with phosphorylation of Akt and GSK-3β in PD mouse. In addition, OLE also reduces the mitochondrial dysfunction by activation of enzyme complexes and downregulates the proapoptotic markers in Rotenone intoxicated mouse model. Overall, our study suggests that OLE may be used as a therapeutic agent for treatment of PD by regulating BDNF/CREB/Akt signalling pathway.

Increasing Effect of Citrus natsudaidai on Brain-Derived Neurotrophic Factor

The increase in brain-derived neurotrophic factor (BDNF) in the brain is beneficial for the treatment of depression, Alzheimer's disease (AD), and Parkinson's disease (PD); BDNF can cross the blood-brain barrier. Therefore, foods that elevate BDNF concentration in peripheral tissues may increase BDNF in the brain and thereby induce preventive and therapeutic effects against depression, AD, and PD. In this study, we aimed to determine whether Citrus natsudaidai extracts can increase BDNF concentration using the human kidney adenocarcinoma cell line ACHN, which has BDNF-producing and -secreting abilities. As test samples, methanol extracts of C. natsudaidai peel and pulp, and their n-hexane, ethyl acetate, n-butanol, and water fractions were prepared. The BDNF concentrations in culture medium of ACHN cells were assayed after 24 h cultivation in the presence of test samples. Compared with that of control (non-treated) cells, the BDNF concentration increased in the culture medium of ACHN cells treated with the methanol extract of C. natsudaidai peel and its hexane, butanol, and water fractions, as well as the butanol and water fractions of the pulp extract. Quantitative reverse transcription-polymerase chain reaction analysis revealed that ACHN cells treated with the butanol fractions of the peel and pulp extracts showed elevated levels of BDNF mRNA compared with those of non-treated cells. C. natsudaidai may increase BDNF concentration by acting on peripheral tissues and could be a medication for the prevention and treatment of depression, AD, and PD.

Neuroprotective effects of exogenous brain-derived neurotrophic factor on amyloid-beta 1–40-induced retinal degeneration

Amyloid-beta (Aβ)-related alterations, similar to those found in the brains of patients with Alzheimer’s disease, have been observed in the retina of patients with glaucoma. Decreased levels of brain-derived neurotrophic factor (BDNF) are believed to be associated with the neurotoxic effects of Aβ peptide. To investigate the mechanism underlying the neuroprotective effects of BDNF on Aβ_1–40-induced retinal injury in Sprague-Dawley rats, we treated rats by intravitreal administration of phosphate-buffered saline (control), Aβ_1–40 (5 nM), or Aβ_1–40 (5 nM) combined with BDNF (1 µg/mL). We found that intravitreal administration of Aβ_1–40 induced retinal ganglion cell apoptosis. Fluoro-Gold staining showed a significantly lower number of retinal ganglion cells in the Aβ_1–40 group than in the control and BDNF groups. In the Aβ_1–40 group, low number of RGCs was associated with increased caspase-3 expression and reduced TrkB and ERK1/2 expression. BDNF abolished Aβ_1–40-induced increase in the expression of caspase-3 at the gene and protein levels in the retina and upregulated TrkB and ERK1/2 expression. These findings suggest that treatment with BDNF prevents RGC apoptosis induced by Aβ_1–40 by activating the BDNF-TrkB signaling pathway in rats.

Nanowired Delivery of Curcumin Attenuates Methamphetamine Neurotoxicity and Elevates Levels of Dopamine and Brain-Derived Neurotrophic Factor

Curcumin is a well-known antioxidant used as traditional medicine in China and India since ages to treat variety of inflammatory ailments as a food supplement. Curcumin has antitumor properties with neuroprotective effects in Alzheimer's disease. Curcumin elevates brain-derived neurotrophic factor (BDNF) and dopamine (DA) levels in the brain indicating its role in substance abuse. Methamphetamine (METH) is one of the most abused substances in the world that induces profound neurotoxicity by inducing breakdown of the blood-brain barrier (BBB), vasogenic edema and cellular injuries. However, influence of curcumin on METH-induced neurotoxicity is still not well investigated. In this investigation, METH neurotoxicity and neuroprotective effects of curcumin nanodelivery were examined in a rat model. METH (20 mg/kg, i.p.) neurotoxicity is evident 4 h after its administration exhibiting breakdown of BBB to Evans blue albumin in the cerebral cortex, hippocampus, cerebellum, thalamus and hypothalamus associated with vasogenic brain edema as seen measured using water content in all these regions. Nissl attaining exhibited profound neuronal injuries in the regions of BBB damage. Normal curcumin (50 mg/kg, i.v.) 30 min after METH administration was able to reduce BBB breakdown and brain edema partially in some of the above brain regions. However, TiO₂ nanowired delivery of curcumin (25 mg/kg, i.v.) significantly attenuated brain edema, neuronal injuries and the BBB leakage in all the brain areas. BDNF level showed a significant higher level in METH-treated rats as compared to saline-treated METH group. Significantly enhanced DA levels in METH-treated rats were also observed with nanowired delivery of curcumin. Normal curcumin was able to slightly elevate DA and BDNF levels in the selected brain regions. Taken together, our observations are the first to show that nanodelivery of curcumin induces superior neuroprotection in METH neurotoxicity probable by enhancing BDNF and DA levels in the brain, not reported earlier.

Tropomyosin receptor kinase B (TrkB) signalling: targeted therapy in neurogenic tumours

Tropomyosin receptor kinase B (TrkB), a transmembrane receptor protein, has been found to play a pivotal role in neural development. This protein is encoded by the neurotrophic receptor tyrosine kinase 2 (NTRK2) gene, and its abnormal activation caused by NTRK2 overexpression or fusion can contribute to tumour initiation, progression, and resistance to therapeutics in multiple types of neurogenic tumours. Targeted therapies for this mechanism have been designed and developed in preclinical and clinical studies, including selective TrkB inhibitors and pan-TRK inhibitors. This review describes the gene structure, biological function, abnormal TrkB activation mechanism, and current-related targeted therapies in neurogenic tumours.

BDNF-modified human umbilical cord mesenchymal stem cells-derived dopaminergic-like neurons improve rotation behavior of Parkinson's disease rats through neuroprotection and anti-neuroinflammation

Parkinson's disease (PD) is a neurodegenerative disease still without any cure. Brain-derived neurotrophic factor (BDNF) has shown therapeutic potential in PD, which is limited by its short half-life and inability to penetrate the blood-brain barrier. Stem cells not only present migration, differentiation and neurotrophy characteristics, but also can be used as delivery vectors for BDNF. This study aimed to investigate the therapeutic effects and possible mechanisms of BDNF-modified human umbilical cord mesenchymal stem cells (hUC-MSCs)-derived dopaminergic (DAergic)-like neurons in the PD rats. Results showed that transplantation of BDNF-modified hUC-MSCs-derived DAergic-like neurons improved the apomorphine induced rotation behavior of PD rats, increased the dopamine concentration and the expression of glial fibrillary acidic protein (GFAP) and ionized calcium-binding adaptor molecule-1 (Iba-1) in the striatum, promoted the expression of tyrosine hydroxylase (TH), nuclear receptor-related factor 1 (Nurr1), pituitary homeobox 3 (Pitx3), BDNF, tyrosine kinase B (TrkB), phosphatidylinositol-3-hydroxykinase (PI3K), phosphorylated protein kinase B (p-Akt), heat shock protein 60 (Hsp60), toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) and inhibited the neural apoptosis in the substantia nigra (SN) and striatum. Results suggest that BDNF-modified hUC-MSCs-derived DAergic-like neurons improve the rotation of PD rats might through neuroprotection and anti-neuroinflammation by regulating the BDNF-TrkB-PI3K/Akt and Hsp60-TLR4/MyD88 signaling pathways, respectively.