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Neuropathic pain is a debilitating chronic condition that lacks effective treatment. The role of cytokine- and chemokine-mediated neuroinflammation in its pathogenesis has been well documented. Follistatin (FST) is a secreted protein known to antagonize the biological activity of cytokines in the transforming growth factor–β (TGF-β) superfamily. The involvement of FST in neuropathic pain and the underlying mechanism remain largely unknown. Here, we report that FST was up-regulated in A-fiber sensory neurons after spinal nerve ligation (SNL) in mice. Inhibition or deletion of FST alleviated neuropathic pain and reduced the nociceptive neuron hyperexcitability induced by SNL. Conversely, intrathecal or intraplantar injection of recombinant FST, or overexpression of FST in the dorsal root ganglion (DRG) neurons, induced pain hypersensitivity. Furthermore, exogenous FST increased neuronal excitability in nociceptive neurons. The biolayer interferometry (BLI) assay and coimmunoprecipitation (co-IP) demonstrated direct binding of FST to the insulin-like growth factor–1 receptor (IGF1R), and IGF1R inhibition reduced FST-induced activation of extracellular signal–regulated kinase (ERK) and protein kinase B (AKT), as well as neuronal hyperexcitability. Further co-IP analysis revealed that the N-terminal domain of FST exhibits the highest affinity for IGF1R, and blocking this interaction with a peptide derived from FST attenuated Nav1.7-mediated neuronal hyperexcitability and neuropathic pain after SNL. In addition, FST enhanced neuronal excitability in human DRG neurons through IGF1R. Collectively, our findings suggest that FST, released from A-fiber neurons, enhances Nav1.7-mediated hyperexcitability of nociceptive neurons by binding to IGF1R, making it a potential target for neuropathic pain treatment. Editor's summary: Neuroinflammation contributes to the pathogenesis of neuropathic pain. The characterization of signaling pathways involved could help to identify new therapeutic targets. Here, Jiang et al. used a mouse model to show that the glycoprotein follistatin (FST) was up-regulated in sensory neurons in the dorsal root ganglia (DRG) after spinal nerve ligation. FST injections were sufficient to drive mechanical hypersensitivity and excitability of DRG neurons. FST interacted with insulin-like growth factor–1 receptor, and a peptide that blocked these interactions could alleviate neuropathic pain–related behaviors and FST-mediated voltage-gated sodium channel currents, highlighting a potential therapeutic strategy that warrants further examination. —Daniela Neuhofer [ABSTRACT FROM AUTHOR]

Honey bees are vital pollinators in agriculture and important model insects. To understand the genetic and molecular aspects in their development, a reverse transcription quantitative polymerase chain (RT-qPCR) is used to investigate the target genes. However, it is essential to use the appropriate reference genes as endogenous controls for accurate normalization of target genes. To identify stable reference genes in two honey bee species, [Apis mellifera (Am) and Apis cerana (Ac)], we evaluated eight candidate reference genes including, actin, atub, ef1α, gapdh, rpl13a, rpl32, rps18 and tif. Worker bees belonging to the two species were collected at each developmental day during the embryonic and postembryonic developmental stages. The tyrosine hydroxylase (th) gene was used as the target gene to validate the selected reference genes. Our results revealed that rpl13a was the most stable reference gene at all developmental stages of Am and Ac. In addition, gene combinations, including Amrpl13a & Amrps18 & Amactin, Amrpl13a & Amrpl32, Acrpl13a & Acrpl32, Acrpl13a & Acrpl32 & Acef1α followed by other combinations effectively normalized the expression of the target genes during the embryonic and postembryonic developmental stages of Am and Ac, respectively. Our findings provide a foundation for standardized RT-qPCR analysis to improve the accuracy of genes normalization during the different developmental stages of honey bees. [ABSTRACT FROM AUTHOR]

A11 dopaminergic neurons regulate somatosensory transduction by projecting from the diencephalon to the spinal cord, but the function of this descending projection in itch remained elusive. Here, we report that dopaminergic projection neurons from the A11 nucleus to the spinal dorsal horn (dopaminergicA11‐SDH) are activated by pruritogens. Inhibition of these neurons alleviates itch‐induced scratching behaviors. Furthermore, chemogenetic inhibition of spinal dopamine receptor D1‐expressing (DRD1+) neurons decreases acute or chronic itch‐induced scratching. Mechanistically, spinal DRD1+ neurons are excitatory and mostly co‐localize with gastrin‐releasing peptide (GRP), an endogenous neuropeptide for itch. In addition, DRD1+ neurons form synapses with GRP receptor‐expressing (GRPR+) neurons and activate these neurons via AMPA receptor (AMPAR). Finally, spontaneous itch and enhanced acute itch induced by activating spinal DRD1+ neurons are relieved by antagonists against AMPAR and GRPR. Thus, the descending dopaminergic pathway facilitates spinal itch transmission via activating DRD1+ neurons and releasing glutamate and GRP, which directly augments GRPR signaling. Interruption of this descending pathway may be used to treat chronic itch. Synopsis: Dopaminergic neurons projecting from the A11 nucleus to the spinal dorsal horn (SDH) activate spinal DRD1+ neurons to facilitate spinal itch processing. DRD1+ neurons release glutamate and GRP to activate GRPR+ neurons. A11 dopaminergic neurons facilitate spinal itch processing.DopaminergicA11‐SDH projection acts on DRD1+ neurons to enhance itch transmission.DRD1+ neurons form monosynaptic connections with GRPR+ neurons in the SDH. [ABSTRACT FROM AUTHOR]

The Western honey bee (Apis mellifera) is a social insect characterized by caste differentiation in which the queen bee and worker bees display marked differences in morphology, behavior, reproduction, and longevity despite their identical genomes. The main causative factor in caste differentiation is the food fed to queen larvae, termed royal jelly (RJ). Alternative splicing (AS) is an important RNA-mediated post-transcriptional process in eukaryotes. Here we report AS changes in A. mellifera after being fed either A. mellifera RJ or A. cerana RJ. The results demonstrated that the RJ type affected 4 types of AS in adult A. mellifera: exon skipping, intron retention, alternative 5’ splice sites, and alternative 3’splice sites. After feeding with A. cerana RJ, AS occurred in many genes in adult A. mellifera that encode proteins involved in development, growth, the tricarboxylic acid cycle, and substance metabolism. This study provides the first evidence that heterospecific RJ can influence the AS of many genes related to honey bee development and growth.

Introduction Chemokines are a family of small secreted proteins that are well-known regulators of peripheral immune cell trafficking (1). It has become evident that chemokines are also expressed in the [...], Recent studies have implicated chemokines in microglial activation and pathogenesis of neuropathic pain. C-X-C motif chemokine 13 (CXCL13) is a B lymphocyte chemoattractant that activates CXCR5. Using the spinal nerve ligation (SNL) model of neuropathic pain, we found that CXCL13 was persistently upregulated in spinal cord neurons after SNL, resulting in spinal astrocyte activation via CXCR5 in mice. shRNA-mediated inhibition of CXCL13 in the spinal cord persistently attenuated SNL-induced neuropathic pain. Interestingly, CXCL13 expression was suppressed by miR-186-5p, a microRNA that colocalized with CXCL13 and was downregulated after SNL. Spinal overexpression of miR-186-5p decreased CXCL13 expression, alleviating neuropathic pain. Furthermore, SNL induced CXCR5 expression in spinal astrocytes, and neuropathic pain was abrogated in [Cxcr5.sup.-/-] mice. CXCR5 expression induced by SNL was required for the SNL-induced activation of spinal astrocytes and microglia. Intrathecal injection of CXCL13 was sufficient to induce pain hypersensitivity and astrocyte activation via CXCR5 and ERK. Finally, intrathecal injection of CXCL13-activated astrocytes induced mechanical allodynia in naive mice. Collectively, our findings reveal a neuronal/astrocytic interaction in the spinal cord by which neuronally produced CXCL13 activates astrocytes via CXCR5 to facilitate neuropathic pain. Thus, miR-186-5p and CXCL13/CXCR5-mediated astrocyte signaling may be suitable therapeutic targets for neuropathic pain.