Project description:Background: Anti-type 2 cytokine therapies represent promising interventions for chronic itch; however, their precise mechanisms in restoring nerve architecture and mitigating inflammation and pruritus remain incompletely understood. This study aimed to elucidate the mechanistic roles of IL-4, IL-13, and IL-31 in the pathophysiology of itch associated with type 2 inflammatory skin diseases. Methods: The effect of IL-4, IL-13, and/or IL-31 on neurite outgrowth and/or transcriptomic changes were analyzed in human and mouse dorsal root ganglion (DRG) neuronal cultures. Mouse ear pinnae were processed for histologic, transcriptomic, and proteomic analyses 4 days after intradermal injection of IL-4, IL-13, and/or IL-31. To evaluate functional correlations with neuronal responses, mice were subcutaneously challenged with IL-4, IL-13, and/or IL-31, and scratching behavior was monitored. Association between IL-4/IL-13–IL-4Rα axis and severity of atopic dermatitis (AD) was evaluated through correlative analyses of human DRG transcriptomic changes and AD transcriptomic datasets (GSE130588 and BioMap consortium). Results: IL-4 and IL-13 promote mouse and human DRG sensory neuron growth, with effects similar to or greater than IL-31. In mice, intradermal IL-4, IL-13, and IL-31 increased epidermal nerve growth; however, only IL-4 and IL-13 induced hyperplasia and immune cell recruitment. Multi-omic analyses revealed that IL-4 and IL-13 have a broader impact on neuroimmune interactions than IL-31. In a murine DRG neuron-eosinophil co-culture, IL-4Rα blockade reduced neurite growth. IL-13 and IL-31 elicited acute scratching, demonstrating their roles as direct pruritogens; IL-4 synergistically enhanced IL-13-induced itch, resulting in greater pruritic responses than IL-31. Additionally, a set of itch-associated genes upregulated by IL-4 and IL-13 and downregulated by dupilumab-mediated IL-4Rα blockade in human DRG neuronal cultures showed positive correlation with AD severity. Conclusions: These findings establish the IL-4/IL-13–IL-4Rα axis as a key regulator of inflammatory skin nerve innervation, neuroimmune interactions, barrier integrity, and itch response, highlighting its mechanistic role in modulating sensory neuronal function and shaping the inflammatory microenvironment that drives itch pathophysiology.

Project description:Background: The pathogenesis of neuropathic pain and the reasons for the prolonged unhealing are still unknown. Increasing evidence suggests that oestrogen sex differences play a role in pain sensitivity, but few studies focused on the role of oestrogen receptor which maybe an important molecular component contributing to peripheral pain transduction. We aimed to investigate the impact of ooestrogen receptors in nociceptive neuronal response in the dorsal root ganglion (DRG) and spinal dorsal horn using a spared nerve injury (SNI) rat model of chronic pain. Methods: We used a class of oestrogen receptors antagonists and agonists intrathecal (i.t.) administrated to male rats with SNI or normal rats to identify the main receptor. Moreover, we applied genes identified through genomic metabolic analysis to determine the key metabolism point and elucidate potential mechanisms mediating continuous neuronal sensitisation and neuroinflammation responses in neuropathic pain. The excitability of DRG neurons was detected using the patch clamp technique. Primary culture was used to extract microglia and DRG neurons, and siRNA transfection was used to silence receptor protein expression. Immunofluorescence, Western blotting, qPCR and behavioral testing were used to assess the expressions, cellular distributions, and actions of main receptor and its related signaling molecules. Results: Increasing the expression and function of G protein-coupled oestrogen receptor (GPER), but not oestrogen receptor-α (ERα) and oestrogen receptor-β (ERβ), in the DRG neuron and microglia, but not the dorsal spinal cord, contributed to SNI-induced neuronal sensitisation. Inhibiting GPER expression in the DRG alleviated SNI-induced pain behaviours and neuroinflammation by downregulating iNOS, IL-1β and IL-6 expression as well as restoring GABAα2 expression simultaneously. Additionally, the positive interaction between GPER and β-alanine, β-alanine accumulation enhances pain sensation and promotes chronic pain development. Conclusion: GPER activation in the DRG causes a positive interaction of β-alanine with iNOS, IL-1β and IL-6 expression and represses GABAα2 involved in post-SNI neuropathic pain development. Blocking GPER and eliminating β-alanine in the DRG neuron and microglia may prevent neuropathic pain development.

Project description:Vagal afferent neurons are thought to convey primarily physiological information, whereas spinal afferents transmit noxious signals from the viscera to the central nervous system. In order to elucidate molecular identities for these different properties, we compared gene expression profiles of neurons located in nodose ganglia (NG) and dorsal root ganglia (DRG) in mice. Intraperitoneal administration of Alexa Fluor-488 conjugated Cholera toxin B allowed identification of neurons projecting to the viscera. Fluorescent neurons in DRG (from T10 to T13) and NG were isolated using laser capture microdissection. Gene expression profiles of visceral afferent neurons, obtained by microarray hybridization, were analysed using multivariate spectral map analysis, SAM algorithm (Significance Analysis of Microarray data) and fold-difference filtering. A total of 1996 genes were found to be differentially expressed in DRG versus NG, including 41 G-protein coupled receptors and 60 ion channels. Expression profiles obtained on laser-captured neurons were contrasted to those obtained on whole ganglia demonstrating striking differences and the need for microdissection when studying visceral sensory neurons because of dilution of the signal by somatic sensory neurons. Furthermore, a detailed catalogue of all adrenergic and cholinergic, GABA, glutamate, serotonin and dopamine receptors, voltage-gated potassium, sodium and calcium channels and transient receptor potential cation channels present in visceral afferents is provided. Our genome-wide expression profiling data provide novel insight into molecular signatures that underlie both functional differences and similarities between NG and DRG visceral sensory neurons. Moreover, these findings will offer novel insight into mode of action of pharmacologic agents modulating visceral sensation. Experiment Overall Design: Three separate experiments were performed. First, 5 whole dorsal root ganglia were compared to 7 whole nodose ganglia. Second, Laser captured visceral neurons derived from 5 dorsal root ganglia and 5 nodose ganglia were compared on MG-U74Av2. Third, Laser captured visceral neurons derived from 9 dorsal root ganglia and 11 nodose ganglia were compared on Mouse430_2.

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Tmem45b Modulates itch via Endoplasmic Reticulum Calcium Regulation

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