Suppression of abnormal α-synuclein expression by activation of BDNF transcription ameliorates Parkinson's disease-like pathology

Small molecule modulators of alpha-synuclein aggregation and toxicity: Pioneering an emerging arsenal against Parkinson's disease

Parkinson's disease (PD) is primarily characterized by loss of dopaminergic neurons in the substantia nigra pars compacta region of the brain and accumulation of aggregated forms of alpha-synuclein (α-Syn), an intrinsically disordered protein, in the form of Lewy Bodies and Lewy Neurites. Substantial evidences point to the aggregated/fibrillar forms of α-Syn as a central event in PD pathogenesis, underscoring the modulation of α-Syn aggregation as a promising strategy for PD treatment. Consequently, numerous anti-aggregation agents, spanning from small molecules to polymers, have been scrutinized for their potential to mitigate α-Syn aggregation and its associated toxicity. Among these, small molecule modulators like osmoprotectants, polyphenols, cellular metabolites, metals, and peptides have emerged as promising candidates with significant potential in PD management. This article offers a comprehensive overview of the effects of these small molecule modulators on the aggregation propensity and associated toxicity of α-Syn and its PD-associated mutants. It serves as a valuable resource for identifying and developing potent, non-invasive, non-toxic, and highly specific small molecule-based therapeutic arsenal for combating PD. Additionally, it raises pertinent questions aimed at guiding future research endeavours in the field of α-Syn aggregation remodelling.

Intranasal AdipoRon mitigates motor and cognitive deficits in hemiparkinsonian rats through neuroprotective mechanisms against oxidative stress and synaptic dysfunction

While motor symptoms are the most well-known manifestation of Parkinson's disease (PD), patients may also suffer from non-motor signs like cognitive impairments. The adiponectin receptor agonist AdipoRon (Adipo) has shown neuroprotective effects in preclinical studies. The objective of this study was to determine the potential benefits of chronic intranasal treatment of Adipo on motor function and cognitive performance in a hemiparkinsonian rat model caused by injecting 6-hydroxydopamine (6-OHDA) into the left forebrain bundle. After one week, PD rats were given either a vehicle or one of three dosages of Adipo (0.1, 1, and 10 μg) or levodopa (10 mg/kg orally) daily for 21 days. Recognition and spatial memory were determined using the novel object recognition test (NORT) and the Barnes maze test, respectively. The hippocampal tissues of the animals were harvested to examine oxidative stress status as well as the protein expressions of brain-derived neurotrophic factor (BDNF) and postsynaptic density protein 95 (PSD-95). In hemiparkinsonian rats, motor impairments, recognition memory, and spatial memory were all improved by chronic intranasal Adipo at 1 and 10 μg. Furthermore, we found that unilateral 6-OHDA injection elevated hippocampal oxidative stress (ROS) while concurrently reducing total antioxidant capacity (TAC), BDNF, PSD-95, and antioxidant enzymes (SOD, GPx). However, Adipo 10 μg significantly reduced these biochemical alterations in the hippocampus of 6-OHDA-lesioned rats. Chronic intranasal Adipo ameliorated spatial and recognition memory deterioration in hemiparkinsonian rats, presumably by increasing hippocampal synaptic protein levels, reducing oxidative stress, and increasing BDNF.

Beneficial effects of physical exercise on cognitive-behavioral impairments and brain-derived neurotrophic factor alteration in the limbic system induced by neurodegeneration

Neurodegenerative diseases (NDDs) are a class of neurological disorders marked by the progressive loss of neurons that afflict millions of people worldwide. These illnesses affect brain connection, impairing memory, cognition, behavior, sensory perception, and motor function. Alzheimer's, Parkinson's, and Huntington's diseases are examples of common NDDs, which frequently include the buildup of misfolded proteins. Cognitive-behavioral impairments are early markers of neurodevelopmental disorders, emphasizing the importance of early detection and intervention. Neurotrophins such as brain-derived neurotrophic factor (BDNF) are critical for neuron survival and synaptic plasticity, which is required for learning and memory. NDDs have been associated with decreased BDNF levels. Physical exercise, a non-pharmacological intervention, benefits brain health by increasing BDNF levels, lowering cognitive deficits, and slowing brain degradation. Exercise advantages include increased well-being, reduced depression, improved cognitive skills, and neuroprotection by lowering amyloid accumulation, oxidative stress, and neuroinflammation. This study examines the effects of physical exercise on cognitive-behavioral deficits and BDNF levels in the limbic system impacted by neurodegeneration. The findings highlight the necessity of including exercise into NDD treatment to improve brain structure, function, and total BDNF levels. As research advances, exercise is becoming increasingly acknowledged as an important technique for treating cognitive decline and neurodegenerative disorders.

Apilarnil exerts neuroprotective effects and alleviates motor dysfunction by rebalancing M1/M2 microglia polarization, regulating miR-155 and miR-124 expression in a rotenone-induced Parkinson's disease rat model

Microglial activation contributes to the neuropathology of Parkinson's disease (PD). Inhibiting M1 while simultaneously boosting M2 microglia activation may therefore be a potential treatment for PD. Apilarnil (API) is a bee product produced from drone larvae. Recent research has demonstrated the protective effects of API on multiple body systems. Nevertheless, its impact on PD or the microglial M1/M2 pathway has not yet been investigated. Thus, we intended to evaluate the dose-dependent effects of API in rotenone (ROT)-induced PD rat model and explore the role of M1/M2 in mediating its effect. Seventy-two Wistar rats were equally grouped as; control, API, ROT, and groups in which API (200, 400, and 800 mg/kg, p.o.) was given simultaneously with ROT (2 mg/kg, s.c.) for 28 days. The high dose of API (800 mg/kg) showed enhanced motor function, higher expression of tyrosine hydroxylase and dopamine levels, less dopamine turnover and α-synuclein expression, and a better histopathological picture when compared to the ROT group and the lower two doses. API's high dose exerted its neuroprotective effects through abridging the M1 microglial activity, illustrated in the reduced expression of miR-155, Iba-1, CD36, CXCL10, and other pro-inflammatory markers' levels. Inversely, API high dose enhanced M2 microglial activity, witnessed in the elevated expression of miR-124, CD206, Ym1, Fizz1, arginase-1, and other anti-inflammatory indices, in comparison to the diseased group. To conclude, our study revealed a novel neuroprotective impact for API against experimentally induced PD, where the high dose showed the highest protection via rebalancing M1/M2 polarization.

PDCD4 triggers α-synuclein accumulation and motor deficits via co-suppressing TFE3 and TFEB translation in a model of Parkinson's disease

TFE3 and TFEB, as the master regulators of lysosome biogenesis and autophagy, are well characterized to enhance the synaptic protein α-synuclein degradation in protecting against Parkinson's disease (PD) and their levels are significantly decreased in the brain of PD patients. However, how TFE3 and TFEB are regulated during PD pathogenesis remains largely vague. Herein, we identified that programmed cell death 4 (PDCD4) promoted pathologic α-synuclein accumulation to facilitate PD development via suppressing both TFE3 and TFEB translation. Conversely, PDCD4 deficiency significantly augmented global and nuclear TFE3 and TFEB distributions to alleviate neurodegeneration in a mouse model of PD with overexpressing α-synuclein in the striatum. Mechanistically, like TFEB as we reported before, PDCD4 also suppressed TFE3 translation, rather than influencing its transcription and protein stability, to restrain its nuclear translocation and lysosomal functions, eventually leading to α-synuclein aggregation. We proved that the two MA3 domains of PDCD4 mediated the translational suppression of TFE3 through binding to its 5'-UTR of mRNA in an eIF-4A dependent manner. Based on this, we developed a blood-brain barrier penetrating RVG polypeptide modified small RNA drug against pdcd4 to efficiently prevent α-synuclein neurodegeneration in improving PD symptoms by intraperitoneal injections. Together, we suggest PDCD4 as a PD-risk protein to facilitate α-synuclein neurodegeneration via suppressing TFE3 and TFEB translation and further provide a potential small RNA drug against pdcd4 to treat PD by intraperitoneal injections.

BDNF/TrkB activators in Parkinson's disease: A new therapeutic strategy

Parkinson's disease (PD) is a neurodegenerative disorder of the brain and is manifested by motor and non-motor symptoms because of degenerative changes in dopaminergic neurons of the substantia nigra. PD neuropathology is associated with mitochondrial dysfunction, oxidative damage and apoptosis. Thus, the modulation of mitochondrial dysfunction, oxidative damage and apoptosis by growth factors could be a novel boulevard in the management of PD. Brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin receptor kinase type B (TrkB) are chiefly involved in PD neuropathology. BDNF promotes the survival of dopaminergic neurons in the substantia nigra and enhances the functional activity of striatal neurons. Deficiency of the TrkB receptor triggers degeneration of dopaminergic neurons and accumulation of α-Syn in the substantia nigra. As well, BDNF/TrkB signalling is reduced in the early phase of PD neuropathology. Targeting of BDNF/TrkB signalling by specific activators may attenuate PD neuropathology. Thus, this review aimed to discuss the potential role of BDNF/TrkB activators against PD. In conclusion, BDNF/TrkB signalling is decreased in PD and linked with disease severity and long-term complications. Activation of BDNF/TrkB by specific activators may attenuate PD neuropathology.

Biomimetic nanodecoys deliver cholesterol-modified heteroduplex oligonucleotide to target dopaminergic neurons for the treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder characterized by the accumulation of α-synuclein (α-syn) aggregates called Lewy bodies leading to the gradual loss of dopaminergic (DA) neurons in the substantia nigra. Although α-syn expression can be attenuated by antisense oligonucleotides (ASOs) and heteroduplex oligonucleotide (HDO) by intracerebroventricular (ICV) injection, the challenge to peripheral targeted delivery of oligonucleotide safely and effectively into DA neurons remains unresolved. Here, we designed a new DNA/DNA double-stranded (complementary DNA, coDNA) molecule with cholesterol conjugation (Chol-HDO (coDNA)) based on an α-syn-ASO sequence and evaluated its silence efficiency. Further, Chol-HDO@LMNPs, Chol-HDO-loaded, cerebrovascular endothelial cell membrane with DSPE-PEG2000-levodopa modification (L-DOPA-CECm)-coated nanoparticles (NPs), were developed for the targeted treatment of PD by tail intravenous injection. CECm facilitated the blood-brain barrier (BBB) penetration of NPs, together with cholesterol escaped from reticuloendothelial system uptake, as well as L-DOPA was decarboxylated into dopamine which promoted the NPs toward the PD site for DA neuron regeneration. The behavioral tests demonstrated that the nanodecoys improved the efficacy of HDO on PD mice. These findings provide insights into the development of biomimetic nanodecoys loading HDO for precise therapy of PD. STATEMENT OF SIGNIFICANCE: The accumulation of α-synuclein (α-syn) aggregates is a hallmark of PD. Our previous study designed a specific antisense oligonucleotide (ASO) targeting human SNCA, but the traumatic intracerebroventricular (ICV) is not conducive to clinical application. Here, we further optimize the ASO by creating a DNA/DNA double-stranded molecule with cholesterol-conjugated, named Chol-HDO (coDNA), and develop a DA-targeted biomimetic nanodecoy Chol-HDO@LMNPs by engineering cerebrovascular endothelial cells membranes (CECm) with DSPE-PEG2000 and L-DOPA. The in vivo results demonstrated that tail vein injection of Chol-HDO@LMNPs could target DA neurons in the brain and ameliorate motor deficits in a PD mouse model. This investigation provides a promising peripheral delivery platform of L-DOPA-CECm nanodecoy loaded with a new Chol-HDO (coDNA) targeting DA neurons in PD therapy.

The Possible Role of Brain-derived Neurotrophic Factor in Epilepsy

Epilepsy is a neurological disease characterized by repeated seizures. Despite of that the brain-derived neurotrophic factor (BDNF) is implicated in the pathogenesis of epileptogenesis and epilepsy, BDNF may have a neuroprotective effect against epilepsy. Thus, the goal of the present review was to highlight the protective and detrimental roles of BDNF in epilepsy. In this review, we also try to find the relation of BDNF with other signaling pathways and cellular processes including autophagy, mTOR pathway, progranulin (PGN), and α-Synuclein (α-Syn) which negatively and positively regulate BDNF/tyrosine kinase receptor B (TrkB) signaling pathway. Therefore, the assessment of BDNF levels in epilepsy should be related to other neuronal signaling pathways and types of epilepsy in both preclinical and clinical studies. In conclusion, there is a strong controversy concerning the potential role of BDNF in epilepsy. Therefore, preclinical, molecular, and clinical studies are warranted in this regard.

Activation of cyclic AMP signaling pathway in dopaminergic neurons rescues locomotion defects in a Drosophila larval model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease showing uncontrollable motor symptoms that are primarily caused by the progressive loss of dopaminergic neurons in the brain. Currently no treatment exists to prevent PD progression. Therefore, discovery of new neuroprotective strategies still has great potential to benefit PD patients. A handful of studies show that activation of cAMP pathways is neuroprotective against PD progression. However, the neuroprotective role of this signaling cascade specifically in DA neurons has not been explored. In this study, fruit fly Drosophila melanogaster was used because of its sophisticated and powerful genetic approaches, especially with related to cAMP signaling pathway. We have investigated molecular mechanisms of neuroprotection in a fly larval model of PD by administering an environmental PD toxin rotenone. Increased cAMP signaling in the dunce mutant fly carrying defects in phosphodiesterase (PDE) gene, is neuroprotective against rotenone-induced locomotion deficits. Furthermore, the neuroprotective role of cAMP signaling specifically in DA neurons has been studied as it has not been explored. By using transgenic flies expressing designer receptors exclusively activated by designer drugs (DREADDs), we have shown that an increase of cAMP levels in DA neurons rescues rotenone-induced locomotion deficits. We also showed that this neuroprotection is mediated by activation of Gαs and PKA-C1 subunits. The results provide novel findings that expand our knowledge of neuroprotective mechanisms in DA neurons affecting PD progression, which could contribute to the development of new therapeutic treatments against PD. An important future study will explore downstream targets of cAMP-PKA signaling.

Plausible Role of Mitochondrial DNA Copy Number in Neurodegeneration-a Need for Therapeutic Approach in Parkinson's Disease (PD)

Parkinson's disease (PD) is an advancing age-associated progressive brain disorder which has various diverse factors, among them mitochondrial dysfunction involves in dopaminergic (DA) degeneration. Aging causes a rise in mitochondrial abnormalities which leads to structural and functional modifications in neuronal activity and cell death in PD. This ends in deterioration of mitochondrial function, mitochondrial alterations, mitochondrial DNA copy number (mtDNA CN) and oxidative phosphorylation (OXPHOS) capacity. mtDNA levels or mtDNA CN in PD have reported that mtDNA depletion would be a predisposing factor in PD pathogenesis. To maintain the mtDNA levels, therapeutic approaches have been focused on mitochondrial biogenesis in PD. The depletion of mtDNA levels in PD can be influenced by autophagic dysregulation, apoptosis, neuroinflammation, oxidative stress, sirtuins, and calcium homeostasis. The current review describes the regulation of mtDNA levels and discusses the plausible molecular pathways in mtDNA CN depletion in PD pathogenesis. We conclude by suggesting further research on mtDNA depletion which might show a promising effect in predicting and diagnosing PD.

Bear bile powder alleviates Parkinson's disease-like behavior in mice by inhibiting astrocyte-mediated neuroinflammation

Parkinson's disease (PD) is a common neurodegenerative disease in middle-aged and elderly people. In particular, increasing evidence has showed that astrocyte-mediated neuroinflammation is involved in the pathogenesis of PD. As a precious traditional Chinese medicine, bear bile powder (BBP) has a long history of use in clinical practice. It has numerous activities, such as clearing heat, calming the liver wind and anti-inflammation, and also exhibits good therapeutic effect on convulsive epilepsy. However, whether BBP can prevent the development of PD has not been elucidated. Hence, this study was designed to explore the effect and mechanism of BBP on suppressing astrocyte-mediated neuroinflammation in a mouse model of PD. PD-like behavior was induced in the mice by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) (30 mg·kg-1) for five days, followed by BBP (50, 100, and 200 mg·kg-1) treatment daily for ten days. LPS stimulated rat C6 astrocytic cells were used as a cell model of neuroinflammation. THe results indicated that BBP treatment significantly ameliorated dyskinesia, increased the levels of tyrosine hydroxylase (TH) and inhibited astrocyte hyperactivation in the substantia nigra (SN) of PD mice. Furthermore, BBP decreased the protein levels of glial fibrillary acidic protein (GFAP), cyclooxygenase 2 (COX2) and inducible nitric oxide synthase (iNOS), and up-regulated the protein levels of takeda G protein-coupled receptor 5 (TGR5) in the SN. Moreover, BBP significantly activated TGR5 in a dose-dependent manner, and decreased the protein levels of GFAP, iNOS and COX2, as well as the mRNA levels of GFAP, iNOS, COX2, interleukin (IL) -1β, IL-6 and tumor necrosis factor-α (TNF-α) in LPS-stimulated C6 cells. Notably, BBP suppressed the phosphorylation of protein kinase B (AKT), inhibitor of NF-κB (IκBα) and nuclear factor-κB (NF-κB) proteins in vivo and in vitro. We also observed that TGR5 inhibitor triamterene attenuated the anti-neuroinflammatory effect of BBP on LPS-stimulated C6 cells. Taken together, BBP alleviates the progression of PD mice by suppressing astrocyte-mediated inflammation via TGR5.

18β-glycyrrhetinic acid ameliorates MPTP-induced neurotoxicity in mice through activation of microglial anti-inflammatory phenotype

RATIONALE

18β-glycyrrhetinic acid (18β-GA) has been reported to have anti-inflammatory and neuroprotective effects. However, the therapeutic effect of 18β-GA in Parkinson's disease (PD) has not been defined.

OBJECTIVE

The current study aimed to evaluate the potential therapeutic effects of 18β-GA in treating PD by mitigating 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity.

RESULTS

The study showed that 18β-GA has anti-inflammatory effects by upregulating TREM2 expression in BV2 cells, which correlates with the presence of NF-E2-related factor-2 (Nrf2). 18β-GA reduced inflammation in BV2 cells treated with 1-methyl-4- phenylpyridinium (MPP+) by enhancing TREM2 expression, which promotes an anti-inflammatory microglial phenotype. Repeated administration of 18β-GA in MPTP-treated mice led to therapeutic effects by enhancing TREM2 expression, resulting in the activation of anti-inflammatory microglia. Moreover, 18β-GA attenuated the decrease in brain-derived neurotrophic factor (BDNF) levels in both MPP+-induced BV2 cells and MPTP-intoxicated mice, indicating the involvement of BDNF in the beneficial effects of 18β-GA.

CONCLUSIONS

It is probable that activating microglial anti-inflammatory response through TREM2 expression might serve as a novel therapeutic strategy for PD. Additionally, 18β-GA seems to hold potential as a new therapeutic agent for PD.

Molecular mechanisms of rapid-acting antidepressants: New perspectives for developing antidepressants

Major depressive disorder (MDD) is a chronic relapsing psychiatric disorder. Conventional antidepressants usually require several weeks of continuous administration to exert clinically significant therapeutic effects, while about two-thirds of the patients are prone to relapse of symptoms or are completely ineffective in antidepressant treatment. The recent success of the N-methyl-D-aspartic acid (NMDA) receptor antagonist ketamine as a rapid-acting antidepressant has propelled extensive research on the action mechanism of antidepressants, especially in relation to its role in synaptic targets. Studies have revealed that the mechanism of antidepressant action of ketamine is not limited to antagonism of postsynaptic NMDA receptors or GABA interneurons. Ketamine produces powerful and rapid antidepressant effects by affecting α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid receptors, adenosine A1 receptors, and the L-type calcium channels, among others in the synapse. More interestingly, the 5-HT2A receptor agonist psilocybin has demonstrated potential for rapid antidepressant effects in depressed mouse models and clinical studies. This article focuses on a review of new pharmacological target studies of emerging rapid-acting antidepressant drugs such as ketamine and hallucinogens (e.g., psilocybin) and briefly discusses the possible strategies for new targets of antidepressants, with a view to shed light on the direction of future antidepressant research.

Are Therapies That Target α-Synuclein Effective at Halting Parkinson's Disease Progression? A Systematic Review

There are currently no pharmacological treatments available that completely halt or reverse the progression of Parkinson's Disease (PD). Hence, there is an unmet need for neuroprotective therapies. Lewy bodies are a neuropathological hallmark of PD and contain aggregated α-synuclein (α-syn) which is thought to be neurotoxic and therefore a suitable target for therapeutic interventions. To investigate this further, a systematic review was undertaken to evaluate whether anti-α-syn therapies are effective at preventing PD progression in preclinical in vivo models of PD and via current human clinical trials. An electronic literature search was performed using MEDLINE and EMBASE (Ovid), PubMed, the Web of Science Core Collection, and Cochrane databases to collate clinical evidence that investigated the targeting of α-syn. Novel preclinical anti-α-syn therapeutics provided a significant reduction of α-syn aggregations. Biochemical and immunohistochemical analysis of rodent brain tissue demonstrated that treatments reduced α-syn-associated pathology and rescued dopaminergic neuronal loss. Some of the clinical studies did not provide endpoints since they had not yet been completed or were terminated before completion. Completed clinical trials displayed significant tolerability and efficacy at reducing α-syn in patients with PD with minimal adverse effects. Collectively, this review highlights the capacity of anti-α-syn therapies to reduce the accumulation of α-syn in both preclinical and clinical trials. Hence, there is potential and optimism to target α-syn with further clinical trials to restrict dopaminergic neuronal loss and PD progression and/or provide prophylactic protection to avoid the onset of α-syn-induced PD.

Diabetic Polyneuropathy: New Strategies to Target Sensory Neurons in Dorsal Root Ganglia

Diabetic polyneuropathy (DPN) is the most common type of diabetic neuropathy, rendering a slowly progressive, symmetrical, and length-dependent dying-back axonopathy with preferential sensory involvement. Although the pathogenesis of DPN is complex, this review emphasizes the concept that hyperglycemia and metabolic stressors directly target sensory neurons in the dorsal root ganglia (DRG), leading to distal axonal degeneration. In this context, we discuss the role for DRG-targeting gene delivery, specifically oligonucleotide therapeutics for DPN. Molecules including insulin, GLP-1, PTEN, HSP27, RAGE, CWC22, and DUSP1 that impact neurotrophic signal transduction (for example, phosphatidylinositol-3 kinase/phosphorylated protein kinase B [PI3/pAkt] signaling) and other cellular networks may promote regeneration. Regenerative strategies may be essential in maintaining axon integrity during ongoing degeneration in diabetes mellitus (DM). We discuss specific new findings that relate to sensory neuron function in DM associated with abnormal dynamics of nuclear bodies such as Cajal bodies and nuclear speckles in which mRNA transcription and post-transcriptional processing occur. Manipulating noncoding RNAs such as microRNA and long-noncoding RNA (specifically MALAT1) that regulate gene expression through post-transcriptional modification are interesting avenues to consider in supporting neurons during DM. Finally, we present therapeutic possibilities around the use of a novel DNA/RNA heteroduplex oligonucleotide that provides more efficient gene knockdown in DRG than the single-stranded antisense oligonucleotide.

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.

Pathogenesis of α-Synuclein in Parkinson's Disease: From a Neuron-Glia Crosstalk Perspective

Parkinson's disease (PD) is a progressive neurodegenerative disorder. The classical behavioral defects of PD patients involve motor symptoms such as bradykinesia, tremor, and rigidity, as well as non-motor symptoms such as anosmia, depression, and cognitive impairment. Pathologically, the progressive loss of dopaminergic (DA) neurons in the substantia nigra (SN) and the accumulation of α-synuclein (α-syn)-composed Lewy bodies (LBs) and Lewy neurites (LNs) are key hallmarks. Glia are more than mere bystanders that simply support neurons, they actively contribute to almost every aspect of neuronal development and function; glial dysregulation has been implicated in a series of neurodegenerative diseases including PD. Importantly, amounting evidence has added glial activation and neuroinflammation as new features of PD onset and progression. Thus, gaining a better understanding of glia, especially neuron-glia crosstalk, will not only provide insight into brain physiology events but also advance our knowledge of PD pathologies. This review addresses the current understanding of α-syn pathogenesis in PD, with a focus on neuron-glia crosstalk. Particularly, the transmission of α-syn between neurons and glia, α-syn-induced glial activation, and feedbacks of glial activation on DA neuron degeneration are thoroughly discussed. In addition, α-syn aggregation, iron deposition, and glial activation in regulating DA neuron ferroptosis in PD are covered. Lastly, we summarize the preclinical and clinical therapies, especially targeting glia, in PD treatments.

A key role of miR-132-5p in the prefrontal cortex for persistent prophylactic actions of (R)-ketamine in mice

(R,S)-ketamine is known to elicit persistent prophylactic effects in rodent models of depression. However, the precise molecular mechanisms underlying its action remain elusive. Using RNA-sequencing analysis, we searched for novel molecular target(s) that contribute to the prophylactic effects of (R)-ketamine, a more potent enantiomer of (R,S)-ketamine in chronic restraint stress (CRS) model. Pretreatment with (R)-ketamine (10 mg/kg, 1 day before CRS) significantly ameliorated body weight loss, increased immobility time of forced swimming test, and decreased sucrose preference of sucrose preference test in CRS-exposed mice. RNA-sequencing analysis of prefrontal cortex (PFC) revealed that several miRNAs such as miR-132-5p might contribute to sustained prophylactic effects of (R)-ketamine. Methyl CpG binding protein 2 (MeCP2) is known to regulate brain-derived neurotrophic factor (BDNF) expression. Quantitative RT-PCR confirmed that (R)-ketamine significantly attenuated altered expression of miR-132-5p and its regulated genes (Bdnf, Mecp2, Tgfb1, Tgfbr2) in the PFC of CRS-exposed mice. Furthermore, (R)-ketamine significantly attenuated altered expression of BDNF, MeCP2, TGF-β1 (transforming growth factor β1), and synaptic proteins (PSD-95, and GluA1) in the PFC of CRS-exposed mice. Administration of agomiR-132-5p decreased the expression of Bdnf and Tgfb1 in the PFC, resulting in depression-like behaviors. In contrast, administration of antagomiR-132-5p blocked the increased expression of miR-132-5p and decreased expression of Bdnf in the PFC of CRS-exposed mice, resulting in antidepressant-like effects. In conclusion, our data show a novel role of miR-132-5p in the PFC underlying depression-like phenotypes in CRS model and the sustained prophylactic effects of (R)-ketamine.

Arketamine, a new rapid-acting antidepressant: A historical review and future directions

The N-methyl-d-aspartate receptor (NMDAR) antagonist (R,S)-ketamine causes rapid onset and sustained antidepressant actions in treatment-resistant patients with major depressive disorder (MDD) and other psychiatric disorders, such as bipolar disorder and post-traumatic stress disorder. (R,S)-ketamine is a racemic mixture consisting of (R)-ketamine (or arketamine) and (S)-ketamine (or esketamine), with (S)-enantiomer having greater affinity for the NMDAR. In 2019, an esketamine nasal spray by Johnson & Johnson was approved in the USA and Europe for treatment-resistant depression. In contrast, an increasing number of preclinical studies show that arketamine has greater potency and longer-lasting antidepressant-like effects than esketamine in rodents, despite the lower binding affinity of arketamine for the NMDAR. Importantly, the side effects, i.e., psychotomimetic and dissociative effects and abuse liability, of arketamine are less than those of (R,S)-ketamine and esketamine in animals and humans. An open-label study demonstrated the rapid and sustained antidepressant effects of arketamine in treatment-resistant patients with MDD. A phase 2 clinical trial of arketamine in treatment-resistant patients with MDD is underway. This study was designed to review the brief history of the novel antidepressant arketamine, the molecular mechanisms underlying its antidepressant actions, and future directions.