Role of the nuclear receptor subfamily 4a in mast cells in the development of irritable bowel syndrome

Three-dimensional imaging and computational quantitation as a novel approach to assess nerve fibers, enteric glial cells, mast cells, and the proximity of mast cells to the nerve fibers in human sigmoid mucosal biopsies from healthy subjects

BACKGROUND

The visualization and quantitation of nerve fibers (NFs), enteric glial cells (EGCs), mast cells (MCs), and their spatial configurations in the human colonic mucosa represent considerable challenges due to the meshed network of these components and the arborizing of NFs in a three-dimensional (3D) structure.

NEW METHOD

We developed a novel approach combining tissue clearing, 3D imaging and computerized quantitation of NFs, EGCs and MCs in sigmoid mucosal biopsies of healthy subjects using a modified CLARITY tissue clearing protocol and adapting Imaris Surfaces Rendering Technology.

RESULTS

The cleared colonic biopsies are compatible with immunostaining using 10 marker antibodies and capable of generating 3D images rendering clear spatial views and computational quantitation of NFs, MCs, EGCs, in particular the proximity of MCs to NFs with Imaris 9.7-9.9.

COMPARISON WITH EXISTING METHODS

Our modified tissue clearing protocol shortened the membrane lipid removal time to 1 day from the original 1-2 weeks and total tissue clearing time to 3-4 days from the original 2-4 weeks. The 3D images displayed a clear spatial landscape of NFs, MCs and EGCs in the biopsies which cannot be portrayed with 2D images acquired from sections. Computerized quantitation is faster than measuring manually, allowing us to quantify a larger number of samples with less bias.

CONCLUSION

The novel approach enables faster tissue clearing/immunolabeling, high-quality 3D imaging and precise computational quantitation of NFs, cells and proximity of MCs to NFs in human sigmoid biopsies which may allow new insight to detect alterations in colonic-related diseases.

Zinc treatment prevents IgE-mediated Ca2+ influx and allergic response in RBL-2H3 cells

Zinc (Zn) is an essential metal in the body. It binds to many proteins and regulates their functions. In the immune system, it is known that administration of ZnSO4 suppresses T cell activation, but its effects on allergies are still unknown. In this study, we investigated the effects of ZnSO4 administration on allergic reactions using the rat basophilic leukemia cell line, RBL-2H3. ZnSO4 treatment inhibited cell degranulation induced by antigen and IgE stimulation, as well as by A23187, a Ca2+ ionophore. Antigen and IgE stimulation increased mRNA expression of IL-4, IL-13, and COX-2, and ZnSO4 treatment inhibited this expression. The elevation of intracellular Zn concentration and depletion of Zn did not affect degranulation. Phosphorylation of the proteins spleen tyrosine kinase, p38, ERK1/2, JNK, and Akt was increased by antigen stimulation, but ZnSO4 treatment did not inhibit this phosphorylation. ZnSO4 treatment inhibited the elevation of intracellular Ca2+ concentration induced by antigen and IgE stimulation, as well as by A23187. Additionally, ZnSO4 treatment inhibited thapsigargin, a store-operated Ca2+ entry stimulant, from inducing degranulation and increasing intracellular Ca2+ concentration. These data indicate that exogenous Zn2+ possesses a preventive effect on RBL-2H3 activation via inhibition of Ca2+ influx. The effect of Zn may involve Ca2+ release-activated channels. This study suggests that ZnSO4 treatment is valuable in suppressing allergic responses.

Neural circuits regulating visceral pain

Visceral hypersensitivity, a common clinical manifestation of irritable bowel syndrome, may contribute to the development of chronic visceral pain, which is a major challenge for both patients and health providers. Neural circuits in the brain encode, store, and transfer pain information across brain regions. In this review, we focus on the anterior cingulate cortex and paraventricular nucleus of the hypothalamus to highlight the progress in identifying the neural circuits involved in visceral pain. We also discuss several neural circuit mechanisms and emphasize the importance of cross-species, multiangle approaches and the identification of specific neurons in determining the neural circuits that control visceral pain.

Store-operated calcium entry mediates hyperalgesic responses during neuropathy

Neuropathic pain (NP), resulting from nerve injury, alters neural plasticity in spinal cord and brain via the release of inflammatory mediators. The remodeling of store-operated calcium entry (SOCE) involves the refilling of calcium in the endoplasmic reticulum via STIM1 and Orai1 proteins and is crucial for maintaining neural plasticity and neurotransmitter release. The mechanism underlying SOCE-mediated NP remains largely unknown. In this study, we found SOCE-mediated calcium refilling was significantly higher during neuropathic pain, and the major component Orai1 was specifically co-localized with neuronal markers. Intrathecal injection of SOCE antagonist SKF96365 remarkably alleviated nerve injury- and formalin-induced pain and suppressed c-Fos expression in response to innocuous mechanical stimulation. RNA sequencing revealed that SKF96365 altered the expression of spinal transcription factors, including Fos, Junb, and Socs3, during neuropathic pain. In order to identify the genes critical for SKF96365-induced effects, we performed weighted gene co-expression network analysis (WGCNA) to identify the genes most correlated with paw withdrawal latency phenotypes. Of the 16 modules, MEsalmon module was the most highly correlated with SKF96365 induced effects. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that the enriched genes of MEsalmon module were significantly related to Toll-like receptor signaling, steroid biosynthesis, and chemokine signaling, which may mediate the analgesic effect caused by SKF9636 treatment. Additionally, the SOCE antagonist YM-58483 produced similar analgesic effects in nerve injury- and formalin-induced pain. Our results suggest that manipulation of spinal SOCE signaling might be a promising target for pain relief by regulating neurotransmitter production and spinal transcription factor expression.

A Novel Mast Cell Stabilizer JM25-1 Rehabilitates Impaired Gut Barrier by Targeting the Corticotropin-Releasing Hormone Receptors

Mast cell (MC) plays a central role in intestinal permeability; however, few MC-targeting drugs are currently available for protection of the intestinal barrier in clinical practice. A nonfluorinated Lidocaine analog 2-diethylamino-N-2,5-dimethylphenyl acetamide (JM25-1) displays anti-allergic effect, but its impact on MC remains elusive. In this study, we explored whether JM25-1 has therapeutic potential on intestinal barrier defect through stabilizing MC. JM25-1 alleviated release of β-hexosaminidase and cytokine production of MC. The paracellular permeability was redressed by JM25-1 in intestinal epithelial cell monolayers co-cultured with activated MC. In vivo, JM25-1 diminished intestinal mucosal MC amount and cytokine production, especially downregulating the expression of CRHR1, accompanied by an increase of CRHR2. Protective effects appeared in JM25-1-treated stress rats with a recovery of weight and intestinal barrier integrity. Through network pharmacology analysis, JM25-1 showed a therapeutic possibility for irritable bowel syndrome (IBS) with predictive targeting on PI3K/AKT/mTOR signaling. As expected, JM25-1 reinforced p-PI3K, p-AKT, p-mTOR signaling in MC, while the mTOR inhibitor Rapamycin reversed the action of JM25-1 on the expression of CRHR1 and CRHR2. Moreover, JM25-1 successfully remedied intestinal defect and declined MC and CRHR1 expression in rat colon caused by colonic mucus of IBS patients. Our data implied that JM25-1 possessed therapeutic capacity against intestinal barrier defects by targeting the CRH receptors of MC through PI3K/AKT/mTOR signaling.