P2Y12 deficiency in mouse impairs noradrenergic system in brain, and alters anxiety-like neurobehavior and memory

Effectiveness of Psychobiotic Bifidobacterium breve BB05 in Managing Psychosomatic Diarrhea in College Students by Regulating Gut Microbiota: A Randomized, Double-Blind, Placebo-Controlled Trial

Diarrhea of college students (DCS) is a prevalent issue among college students, affecting their daily lives and academic performance. This study aims to explore the potential effect of Bifidobacterium breve BB05 supplements on the DCS. Initially, fifty healthy and fifty diarrheal students were recruited in the observational experiment and allocated into control and diarrhea groups, respectively. Subsequently, one hundred diarrheal students were newly recruited in the intervention experiment and randomly allocated into placebo and probiotic groups, both treated for 2 weeks. Questionnaires (BSS, HAMA-14, and HDRS-17) were performed to assess the students' diarrheal states and mental health at baseline and post-treatment. Fecal samples underwent 16S rRNA sequencing and Enzyme-Linked Immunosorbent Assay to evaluate gut microbiota and fecal metabolite alternations. Results indicated that B. breve BB05 supplementation significantly enriched (p < 0.05) the reduced gut microbial diversity caused by diarrhea. Diarrhea resulted in notable alterations in gut microbiota composition, as exhibited by elevated Collinsella and Streptococcus, alongside substantially decreased Bifidobacterium, Bacteroides, and Prevotella, while B. breve BB05 supplementation partially restored the compromised gut microbiota at both the phylum and genus levels, particularly by increasing Bifidobacterium and Roseburia (p < 0.05). Importantly, questionnaire results suggested that B. breve BB05 administration achieved superior efficacy in relieving diarrhea symptoms and the associated anxiety and depression in college students. An increased fecal concentration of 5-hydroxytryptamine (5-HT) was also observed in the probiotic group, while Acetylcholine (ACH), Epinephrine (EPI), and Noradrenaline/Norepinephrine (NANE) reduced, revealing the potential of B. breve BB05 in alleviating anxiety and depression via modulating the microbiota-gut-brain axis. Furthermore, correlation analysis suggested that the altered microbiota and fecal neurotransmitters were closely associated with the mental symptoms. These results endorse B. breve BB05 intervention as a promising and innovative approach to alleviate both diarrhea and mental health conditions among college students.

Extracellular ATP Is a Homeostatic Messenger That Mediates Cell-Cell Communication in Physiological Processes and Psychiatric Diseases

Neuronal activity is the basis of information encoding and processing in the brain. During neuronal activation, intracellular ATP (adenosine triphosphate) is generated to meet the high-energy demands. Simultaneously, ATP is secreted, increasing the extracellular ATP concentration and acting as a homeostatic messenger that mediates cell-cell communication to prevent aberrant hyperexcitability of the nervous system. In addition to the confined release and fast synaptic signaling of classic neurotransmitters within synaptic clefts, ATP can be released by all brain cells, diffuses widely, and targets different types of purinergic receptors on neurons and glial cells, making it possible to orchestrate brain neuronal activity and participate in various physiological processes, such as sleep and wakefulness, learning and memory, and feeding. Dysregulation of extracellular ATP leads to a destabilizing effect on the neural network, as found in the etiopathology of many psychiatric diseases, including depression, anxiety, schizophrenia, and autism spectrum disorder. In this review, we summarize advances in the understanding of the mechanisms by which extracellular ATP serves as an intercellular signaling molecule to regulate neural activity, with a focus on how it maintains the homeostasis of neural networks. In particular, we also focus on neural activity issues that result from dysregulation of extracellular ATP and propose that aberrant levels of extracellular ATP may play a role in the etiopathology of some psychiatric diseases, highlighting the potential therapeutic targets of ATP signaling in the treatment of these psychiatric diseases. Finally, we suggest potential avenues to further elucidate the role of extracellular ATP in intercellular communication and psychiatric diseases.

Purinergic receptors in cognitive disturbances

Purinergic receptors (Rs) of the ATP/ADP, UTP/UDP (P2X, P2Y) and adenosine (A1, A2A)-sensitive classes broadly interfere with cognitive processes both under quasi normal and disease conditions. During neurodegenerative illnesses, high concentrations of ATP are released from the damaged neuronal and non-neuronal cells of the brain; then, this ATP is enzymatically degraded to adenosine. Thus, the primary injury in neurodegenerative diseases appears to be caused by various protein aggregates on which a superimposed damage mediated by especially P2X7 and A2AR activation develops; this can be efficiently prevented by small molecular antagonists in animal models of the above diseases, or are mitigated in the respective knockout mice. Dementia is a leading symptom in Alzheimer's disease (AD), and accompanies Parkinson's disease (PD) and Huntington's disease (HD), especially in the advanced states of these illnesses. Animal experimentation suggests that P2X7 and A2ARs are also involved in a number of psychiatric diseases, such as major depressive disorder (MDD), obsessive compulsive behavior, and attention deficit hyperactivity disorder. In conclusion, small molecular antagonists of purinergic receptors are expected to supply us in the future with pharmaceuticals which are able to combat in a range of neurological/psychiatric diseases the accompanying cognitive deterioration.

Movers and shakers: Microglial dynamics and modulation of neural networks

Microglia are multifaceted cells that act as immune sentinels, with important roles in pathological events, but also as integral contributors to the normal development and function of neural circuits. In the last decade, our understanding of the contributions these cells make to synaptic health and dysfunction has expanded at a dizzying pace. Here we review the known mechanisms that govern the dynamics of microglia allowing these motile cells to interact with synapses, and recruit microglia to specific sites on neurons. We then review the molecular signals that may underlie the function of microglia in synaptic remodeling. The emerging picture from the literature suggests that microglia are highly sensitive cells, reacting to neuronal signals with dynamic and specific actions tuned to the need of specific synapses and networks.

P2 receptor-mediated signaling in the physiological and pathological brain: From development to aging and disease

The purinergic pathway mediates both pro-inflammatory and anti-inflammatory responses, whereas the breakdown of adenosine triphosphate (ATP) is in a critical equilibrium. Under physiological conditions, extracellular ATP is maintained at a nanomolar concentration. Whether released into the medium following tissue damage, inflammation, or hypoxia, ATP is considered a clear indicator of cell damage and a marker of pathological conditions. In this overview, we provide an update on the participation of P2 receptor-mediated purinergic signaling in normal and pathological brain development, with special emphasis on neurodevelopmental psychiatric disorders. Since purinergic signaling is ubiquitous, it is not surprising that it plays a prominent role in developmental processes and pathological alterations. The main aim of this review is to conceptualize the time-dependent dynamic changes in the participation of different players in the purinome in shaping the normal and aberrant developmental patterns and diseases of the central nervous system over one's lifespan.

N-Methyl D-aspartate receptor subtype 2B/Ca2+/calmodulin-dependent protein kinase II signaling in the lateral habenula regulates orofacial allodynia and anxiety-like behaviors in a mouse model of trigeminal neuralgia

Trigeminal neuralgia (TN) is a peripheral nerve disorder often accompanied by abnormalities in mood. The lateral habenula (LHb) plays important roles in the modulation of pain and emotion. In the present study, we investigated the involvement of the LHb in the mechanisms underlying allodynia and anxiety induced by partial transection of the infraorbital nerve (pT-ION) in mice. Our results indicated that pT-ION induced persistent orofacial allodynia and anxiety-like behaviors, which were correlated with increased phosphorylation of N-Methyl D-aspartate receptor (NMDAR) subtype 2B (p-NR2B) and Ca²⁺/calmodulin-dependent protein kinase II (p-CaMKII) in LHb neurons. Bilateral inhibition of NMDARs and CaMKII in the LHb attenuated the allodynia and anxiety-like behavior induced by pT-ION. Furthermore, bilateral activation of NMDARs in the LHb increased the expression of p-NR2B and p-CaMKII and induced orofacial allodynia and anxiety-like behaviors in naive mice. Adeno-associated virus (AAV)-mediated expression of hM3D(Gq) in CaMKII⁺ neurons of the bilateral LHb, followed by clozapine-N-oxide (CNO) administration, also triggered orofacial allodynia and anxiety-like behaviors in naïve mice with successful virus infection in LHb neurons (verified based on immunofluorescence). In conclusion, these findings suggest that activation of NMDA/CaMKII signaling in the LHb contributes to the occurrence and development of TN and related anxiety-like behaviors. Therefore, suppressing the activity of CaMKII⁺ neurons in the bilateral LHb by targeting NMDA/CaMKII may represent a novel strategy for treating pain and anxiety associated with TN.

Ginsenoside Rg5 allosterically interacts with P2RY12 and ameliorates deep venous thrombosis by counteracting neutrophil NETosis and inflammatory response

Background

Deep venous thrombosis (DVT) highly occurs in patients with severe COVID-19 and probably accounted for their high mortality. DVT formation is a time-dependent inflammatory process in which NETosis plays an important role. However, whether ginsenoside Rg5 from species of Panax genus could alleviate DVT and its underlying mechanism has not been elucidated.

Methods

The interaction between Rg5 and P2RY₁₂ was studied by molecular docking, molecular dynamics, surface plasmon resonance (SPR), and molecular biology assays. The preventive effect of Rg5 on DVT was evaluated in inferior vena cava stasis–induced mice, and immunocytochemistry, Western blot, and calcium flux assay were performed in neutrophils from bone marrow to explore the mechanism of Rg5 in NETosis via P2RY₁₂.

Results

Rg5 allosterically interacted with P2RY₁₂, formed stable complex, and antagonized its activity via residue E188 and R265. Rg5 ameliorated the formation of thrombus in DVT mice; accompanied by decreased release of Interleukin (IL)-6, IL-1β, and tumor necrosis factor-α in plasma; and suppressed neutrophil infiltration and neutrophil extracellular trap (NET) release. In lipopolysaccharide- and platelet-activating factor–induced neutrophils, Rg5 reduced inflammatory responses via inhibiting the activation of ERK/NF-κB signaling pathway while decreasing cellular Ca²⁺ concentration, thus reducing the activity and expression of peptidyl arginine deiminase 4 to prevent NETosis. The inhibitory effect on neutrophil activity was dependent on P2RY₁₂.

Conclusions

Rg5 could attenuate experimental DVT by counteracting NETosis and inflammatory response in neutrophils via P2RY₁₂, which may pave the road for its clinical application in the prevention of DVT-related disorders.

Genetics and Brain Transcriptomics of Completed Suicide

OBJECTIVE

The authors sought to study the transcriptomic and genomic features of completed suicide by parsing the method chosen, to capture molecular correlates of the distinctive frame of mind of individuals who die by suicide, while reducing heterogeneity.

METHODS

The authors analyzed gene expression (RNA sequencing) from postmortem dorsolateral prefrontal cortex of patients who died by suicide with violent compared with nonviolent means, nonsuicide patients with the same psychiatric disorders, and a neurotypical group (total N=329). They then examined genomic risk scores (GRSs) for each psychiatric disorder included, and GRSs for cognition (IQ) and for suicide attempt, testing how they predict diagnosis or traits (total N=888).

RESULTS

Patients who died by suicide by violent means showed a transcriptomic pattern remarkably divergent from each of the other patient groups but less from the neurotypical group; consistently, their genomic profile of risk was relatively low for their diagnosed illness as well as for suicide attempt, and relatively high for IQ: they were more similar to the neurotypical group than to other patients. Differentially expressed genes (DEGs) associated with patients who died by suicide by violent means pointed to purinergic signaling in microglia, showing similarities to a genome-wide association study of Drosophila aggression. Weighted gene coexpression network analysis revealed that these DEGs were coexpressed in a context of mitochondrial metabolic activation unique to suicide by violent means.

CONCLUSIONS

These findings suggest that patients who die by suicide by violent means are in part biologically separable from other patients with the same diagnoses, and their behavioral outcome may be less dependent on genetic risk for conventional psychiatric disorders and be associated with an alteration of purinergic signaling and mitochondrial metabolism.

Biology of Perseverative Negative Thinking: The Role of Timing and Folate Intake

Past-oriented rumination and future-oriented worry are two aspects of perseverative negative thinking related to the neuroticism endophenotype and associated with depression and anxiety. Our present aim was to investigate the genomic background of these two aspects of perseverative negative thinking within separate groups of individuals with suboptimal versus optimal folate intake. We conducted a genome-wide association study in the UK Biobank database (n = 72,621) on the "rumination" and "worry" items of the Eysenck Personality Inventory Neuroticism scale in these separate groups. Optimal folate intake was related to lower worry, but unrelated to rumination. In contrast, genetic associations for worry did not implicate specific biological processes, while past-oriented rumination had a more specific genetic background, emphasizing its endophenotypic nature. Furthermore, biological pathways leading to rumination appeared to differ according to folate intake: purinergic signaling and circadian regulator gene ARNTL emerged in the whole sample, blastocyst development, DNA replication, and C-C chemokines in the suboptimal folate group, and prostaglandin response and K+ channel subunit gene KCNH3 in the optimal folate group. Our results point to possible benefits of folate in anxiety disorders, and to the importance of simultaneously taking into account genetic and environmental factors to determine personalized intervention in polygenic and multifactorial disorders.

P2Y2 deficiency impacts adult neurogenesis and related forebrain functions

Adult neurogenesis occurs particularly in the subgranular zone (SGZ) of the hippocampus and the subventricular zone (SVZ) of the lateral ventricle. This continuous addition of neurons to pre-existing neuronal networks is essential for intact cognitive and olfactory functions, respectively. Purinergic signaling modulates adult neurogenesis, however, the role of individual purinergic receptor subtypes in this dynamic process and related cognitive performance is poorly understood. In this study, we analyzed the role of P2Y₂ receptor in the neurogenic niches and in related forebrain functions such as spatial working memory and olfaction using mice with a targeted deletion of the P2Y₂ receptor (P2Y2^-/- ). Proliferation, migration, differentiation, and survival of neuronal precursor cells (NPCs) were analyzed by BrdU assay and immunohistochemistry; signal transduction pathway components were analyzed by immunoblot. In P2Y2^-/- mice, proliferation of NPCs in the SGZ and the SVZ was reduced. However, migration, neuronal fate decision, and survival were not affected. Moreover, p-Akt expression was decreased in P2Y2^-/- mice. P2Y2^-/- mice showed an impaired performance in the Y-maze and a higher latency in the hidden food test. These data indicate that the P2Y₂ receptor plays an important role in NPC proliferation as well as in hippocampus-dependent working memory and olfactory function.

Brain Neurotransmitter Modulation by Gut Microbiota in Anxiety and Depression

Anxiety and depression are highly prevalent mental illnesses worldwide and have long been thought to be closely associated to neurotransmitter modulation. There is growing evidence indicating that changes in the composition of the gut microbiota are related to mental health including anxiety and depression. In this review, we focus on combining the intestinal microbiota with serotonergic, dopaminergic, and noradrenergic neurotransmission in brain, with special emphasis on the anxiety- and depression-like behaviors in stress-related rodent models. Therefore, we reviewed studies conducted on germ-free rodents, or in animals subjected to microbiota absence using antibiotics, as well as via the usage of probiotics. All the results strongly support that the brain neurotransmitter modulation by gut microbiota is indispensable to the physiopathology of anxiety and depression. However, a lot of work is needed to determine how gut microbiota mediated neurotransmission in human brain has any physiological significance and, if any, how it can be used in therapy. Overall, the gut microbiota provides a novel way to alter neurotransmitter modulation in the brain and treat gut–brain axis diseases, such as anxiety and depression.

Loss of P2Y12 Has Behavioral Effects in the Adult Mouse

While microglia have been established as critical mediators of synaptic plasticity, the molecular signals underlying this process are still being uncovered. Increasing evidence suggests that microglia utilize these signals in a temporally and regionally heterogeneous manner. Subsequently, it is necessary to understand the conditions under which different molecular signals are employed by microglia to mediate the physiological process of synaptic remodeling in development and adulthood. While the microglial purinergic receptor P2Y12 is required for ocular dominance plasticity, an adolescent form of experience-dependent plasticity, it remains unknown whether P2Y12 functions in other forms of plasticity at different developmental time points or in different brain regions. Using a combination of ex vivo characterization and behavioral testing, we examined how the loss of P2Y12 affects developmental processes and behavioral performance in adulthood in mice. We found P2Y12 was not required for an early form of plasticity in the developing visual thalamus and did not affect microglial migration into barrels in the developing somatosensory cortex. In adult mice, however, the loss of P2Y12 resulted in alterations in recognition and social memory, as well as anxiety-like behaviors, suggesting that while P2Y12 is not a universal regulator of synaptic plasticity, the loss of P2Y12 is sufficient to cause functional defects.

A-Type Cinnamon Procyanidin Oligomers Protect Against 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine-Induced Neurotoxicity in Mice Through Inhibiting the P38 Mitogen-Activated Protein Kinase/P53/BCL-2 Associated X Protein Signaling Pathway

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disorder. Cinnamon procyanidin oligomers (CPOs) are flavonoids with many claimed health benefits.

OBJECTIVE

This study aimed to elucidate the neuroprotection of A-type CPOs (CPO-A) and the underlying mechanisms in cultured cell and animal models of PD.

METHODS

Thirty male mice (C57BL/6, 9-wk old) were assigned to 3 groups (n = 10), and were given daily gavage of saline [control and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) groups] or CPO-A (150 mg/kg, CPO-A group) during days 1-15 and daily intraperitoneal injections of saline (control group) or MPTP (20 mg/kg; MPTP and MPTP + CPO-A groups) during days 11-15. After the motor behavior test, all mice were killed on day 16 to collect the substantia nigra (SN) for assaying the neuroprotective effects of CPO-A. SH-SY5Y cells were treated with 12.5 μM CPO-A for 2 h or 3 activators of stress-related kinases (5-25 μM) for 12-48 h followed by 1 mM 1-methyl-4-phenylpyridinium (MPP+) for assays of viability, morphology, and stress status.

RESULTS

Compared with the control, the MPTP treatment decreased (P < 0.05) locomotor activity by 21%, and tyrosine hydroxylase (TH) positive neurons by 55% and Th mRNA concentration by 51% in the SN. The CPO-A treatment attenuated or restored (P < 0.05) these changes and inhibited (P < 0.05) the MPTP-induced activation of P38 mitogen-activated protein kinase (P38MAPK) and P53, along with the downstream expression of BCL-2 associated X protein (BAX) in the SN. In SH-SY5Y cells, the CPO-A treatment blocked (P < 0.01) the MPP+-induced accumulation of intracellular reactive oxygen species and neurotoxicity. However, this protection was abolished (P < 0.05) by activators of the P38MAPK/P53/BAX pathway.

CONCLUSION

CPO-A protected against MPP+-induced cytotoxicity in SH-SY5Y cells and MPTP-induced neurotoxicity in mice by regulating the P38MAPK/P53/BAX signaling. Our findings reveal a novel role and mechanism of a food flavonoid CPO-A in preventing neurodegeneration.

Tacr3 in the lateral habenula differentially regulates orofacial allodynia and anxiety-like behaviors in a mouse model of trigeminal neuralgia

Trigeminal neuralgia (TN) is debilitating and is usually accompanied by mood disorders. The lateral habenula (LHb) is considered to be involved in the modulation of pain and mood disorders, and the present study aimed to determine if and how the LHb participates in the development of pain and anxiety in TN. To address this issue, a mouse model of partial transection of the infraorbital nerve (pT-ION) was established. pT-ION induced stable and long-lasting primary and secondary orofacial allodynia and anxiety-like behaviors that correlated with the increased excitability of LHb neurons. Adeno-associated virus (AAV)-mediated expression of hM4D(Gi) in glutamatergic neurons of the unilateral LHb followed by clozapine-N-oxide application relieved pT-ION-induced anxiety-like behaviors but not allodynia. Immunofluorescence validated the successful infection of AAV in the LHb, and microarray analysis showed changes in gene expression in the LHb of mice showing allodynia and anxiety-like behaviors after pT-ION. Among these differentially expressed genes was Tacr3, the downregulation of which was validated by RT-qPCR. Rescuing the downregulation of Tacr3 by AAV-mediated Tacr3 overexpression in the unilateral LHb significantly reversed pT-ION-induced anxiety-like behaviors but not allodynia. Whole-cell patch clamp recording showed that Tacr3 overexpression suppressed nerve injury-induced hyperexcitation of LHb neurons, and western blotting showed that the pT-ION-induced upregulation of p-CaMKII was reversed by AAV-mediated Tacr3 overexpression or chemicogenetic inhibition of glutamatergic neurons in the LHb. Moreover, not only anxiety-like behaviors, but also allodynia after pT-ION were significantly alleviated by chemicogenetic inhibition of bilateral LHb neurons or by bilateral Tacr3 overexpression in the LHb. In conclusion, Tacr3 in the LHb plays a protective role in treating trigeminal nerve injury-induced allodynia and anxiety-like behaviors by suppressing the hyperexcitability of LHb neurons. These findings provide a rationale for suppressing unilateral or bilateral LHb activity by targeting Tacr3 in treating the anxiety and pain associated with TN.