The ion channel TRPV5 regulates B-cell signaling and activation.

Introduction: B-cell activation triggers the release of endoplasmic reticulum calcium stores through the store-operated calcium entry (SOCE) pathway resulting in calcium influx by calcium release-activated calcium (CRAC) channels on the plasma membrane. B-cell-specific murine knockouts of SOCE do not impact humoral immunity suggesting that alternative channels may be important. Methods: We identified a member of the calcium-permeable transient receptor potential (TRP) ion channel family, TRPV5, as a candidate channel expressed in B cells by a quantitative polymerase chain reaction (qPCR) screen. To further investigate the role of TRPV5 in B-cell responses, we generated a murine TRPV5 knockout (KO) by CRISPR-Cas9. Results: We found TRPV5 polarized to B-cell receptor (BCR) clusters upon stimulation in a PI3K-RhoA-dependent manner. TRPV5 KO mice have normal B-cell development and mature B-cell numbers. Surprisingly, calcium influx upon BCR stimulation in primary TRPV5 KO B cells was not impaired; however, differential expression of other calcium-regulating proteins, such as ORAI1, may contribute to a compensatory mechanism for calcium signaling in these cells. We demonstrate that TRPV5 KO B cells have impaired spreading and contraction in response to membrane-bound antigen. Consistent with this, TRPV5 KO B cells have reduced BCR signaling measured through phospho-tyrosine residues. Lastly, we also found that TRPV5 is important for early T-dependent antigen specific responses post-immunization. Discussion: Thus, our findings identify a role for TRPV5 in BCR signaling and B-cell activation.

Advanced Dynamic Weight Bearing as an Observer-independent Measure of Hyperacute Hypersensitivity in Mice.

Background: Standard methods assessing pain in rodents are often observer dependent, potentially resulting in biased outcomes. Advanced dynamic weight bearing (ADWB) offers an observer-independent approach that can provide objective, reliable data in preclinical pain research. Aims: The aim of this study was to characterize the use of ADWB in assessing murine responses to allyl isothiocyanate (AITC)-induced hyperacute hypersensitivity and identify best practices for use of the device. Methods: Male C57BL/6J mice received intraplantar injections of saline or 0.1% AITC solution and were assessed using the ADWB system; simultaneous observer-dependent durations of paw licking and biting were measured. ADWB data were analyzed using the proprietary software from Bioseb and correlated to observer-dependent results, with parameters assessed to optimize data collected. Results: ADWB detected pain-directed changes in weight and surface area distribution in AITC-treated mice, with paw weight and surface area placement correlating to paw licking and biting. Optimization of adjustable threshold parameters allowed for reduced coefficients of variability and increased duration of validated data. Conclusions: The ADWB assay provides an efficient and unbiased measure of chemical-induced hyperacute hypersensitivity in mice. ADWB detection parameters influence amount of validated data and variability, a consideration for data analysis in future studies.

Contexte: Les méthodes standard d'évaluation de la douleur chez les rongeurs dépendent souvent de l'observateur, ce qui peut fausser les résultats. La mise en charge dynamique avancée offre une approche indépendante de l'observateur qui peut fournir des données objectives et fiables dans la recherche préclinique sur la douleur.Objectifs: L'objectif de cette étude était de caractériser l'utilisation de la mise en charge dynamique avancée dans l'évaluation des réponses murines à l'hypersensibilité hyperaiguë induite par l'isothiocyanate d'allyle et de répertorier les meilleures pratiques d'utilisation de l'appareil.Méthodes: Des souris C57BL/6J mâles ont reçu des injections intraplantaires de solution saline ou de solution d'isothiocyanate d'allyle à 0,1 % et ont été évaluées à l'aide du système de mise en charge dynamique avancée; les durées simultanées de léchage et de morsure des pattes, dépendantes de l'observateur, ont été mesurées. Les données obtenues par la mise en charge dynamique avancée ont été analysées à l'aide du logiciel propriétaire de Bioseb et corrélées aux résultats dépendants de l'observateur, avec des paramètres évalués pour optimiser les données collectées.Résultats: L'essai réalisé à l'aide de la mise en charge dynamique avancée a détecté des changements de poids et de distribution de surface liés à la douleur chez les souris traitées à l'isothiocyanate d'allyle, le poids des pattes et le placement de la surface étant corrélés au léchage et à la morsure des pattes. L'optimisation des paramètres de seuil ajustables a permis de réduire les coefficients de variabilité et d'augmenter la durée des données validées.Conclusion: L'essai réalisé à l'aide de la mise en charge dynamique avancée fournit une mesure efficace et impartiale de l'hypersensibilité hyperaiguë induite par les produits chimiques chez la souris. Les paramètres de détection du système de mise en charge dynamique avancée influencent la quantité de données validées et la variabilité, ce qui doit être pris en compte pour l'analyse des données dans les études futures.

Circadian rhythms and glial cells of the central nervous system.

Glial cells are the most abundant cells in the central nervous system and play crucial roles in neural development, homeostasis, immunity, and conductivity. Over the past few decades, glial cell activity in mammals has been linked to circadian rhythms, the 24-h chronobiological clocks that regulate many physiological processes. Indeed, glial cells rhythmically express clock genes that cell-autonomously regulate glial function. In addition, recent findings in rodents have revealed that disruption of the glial molecular clock could impact the entire organism. In this review, we discuss the impact of circadian rhythms on the function of the three major glial cell types - astrocytes, microglia, and oligodendrocytes - across different locations within the central nervous system. We also review recent evidence uncovering the impact of glial cells on the body's circadian rhythm. Together, this sheds new light on the involvement of glial clock machinery in various diseases.

Vigilance and behavioral state-dependent modulation of cortical neuronal activity throughout the sleep/wake cycle.

GABAergic inhibitory neurons, through their molecular, anatomic and physiological diversity, provide a substrate for the modulation of ongoing cortical circuit activity throughout the sleep-wake cycle. Here, we investigated neuronal activity dynamics of parvalbumin (PV), vasoactive intestinal polypeptide (VIP) and somatostatin (SST) neurons in naturally-sleeping head-restrained mice at the level of layer 2/3 of the primary somatosensory barrel cortex of mice. Through calcium-imaging and targeted single-unit loose-patch or whole-cell recordings, we found that PV action potential (AP) firing activity was largest during both NREM (non-rapid eye movement) and REM sleep stages, that VIP neurons were most active during REM sleep and that the overall activity of SST neurons remained stable throughout the sleep/wake cycle. Analysis of neuronal activity dynamics uncovered rapid decreases in PV cell firing at wake onset followed by a progressive recovery during wake. Simultaneous local field potential (LFP) recordings further revealed that, except for SST neurons, a large proportion of neurons were modulated by ongoing delta and theta oscillations. During NREM sleep spindles, PV and SST activity increased and decreased, respectively. Finally, we uncovered the presence of whisking behavior in mice during REM sleep and show that the activity of VIP and SST is differentially modulated during awake and sleeping whisking bouts, which may provide a neuronal substrate for internal brain representations occurring during sleep.SIGNIFICANCE STATEMENTIn the sensory cortex, the balance between excitation and inhibition is believed to be highly dynamic throughout the sleep/wake cycle, shaping the response of cortical circuits to external stimuli, while allowing the formation of newly encoded memory. Using in vivo two-photon calcium imaging or targeted single-unit recordings combined with local field potential recordings, we describe the vigilance state and whisking-behavior -dependent activity of excitatory pyramidal and inhibitory GABAergic neurons in the supragranular layers of mouse somatosensory cortex. Interneuronal activity was found to be differentially modulated by ongoing delta and theta waves, sleep spindles and a novel type of whisking observed during Rapid Eye Movement (REM sleep), potentially providing a neuronal substrate for internal brain representations occurring during sleep.