Responses during cell preparation for functional analyses in mouse bone marrow-derived cultured mast cells

Gomisin M2 Inhibits Mast Cell-Mediated Allergic Inflammation via Attenuation of FcεRI-Mediated Lyn and Fyn Activation and Intracellular Calcium Levels

Mast cells are effector cells that induce allergic inflammation by secreting inflammatory mediators. Gomisin M2 (G.M2) is a lignan isolated from Schisandra chinensis (Turcz). Baill. exhibiting anti-cancer activities. We aimed to investigate the anti-allergic effects and the underlying mechanism of G.M2 in mast cell–mediated allergic inflammation. For the in vitro study, we used mouse bone marrow–derived mast cells, RBL-2H3, and rat peritoneal mast cells. G.M2 inhibited mast cell degranulation upon immunoglobulin E (IgE) stimulation by suppressing the intracellular calcium. In addition, G.M2 inhibited the secretion of pro-inflammatory cytokines. These inhibitory effects were dependent on the suppression of FcεRI-mediated activation of signaling molecules. To confirm the anti-allergic effects of G.M2 in vivo, IgE-mediated passive cutaneous anaphylaxis (PCA) and ovalbumin-induced active systemic anaphylaxis (ASA) models were utilized. Oral administration of G.M2 suppressed the PCA reactions in a dose-dependent manner. In addition, G.M2 reduced the ASA reactions, including hypothermia, histamine, interleukin-4, and IgE production. In conclusion, G.M2 exhibits anti-allergic effects through suppression of the Lyn and Fyn pathways in mast cells. According to these findings, we suggest that G.M2 has potential as a therapeutic agent for the treatment of allergic inflammatory diseases via suppression of mast cell activation.

Expression and transcriptional activity of alternative splice variants of Mitf exon 6

Microphthalmia-associated transcription factor (Mitf) is a tissue-specific transcription factor. At least nine distinct mouse isoform mRNAs are encoded by alternative splicing of the first exon of Mitf (Mitf-A, -B, -C, -D, -E, -H, -J, -M, and -mc), while exons 2-9 of all Mitf isoforms examined to date are identical. In addition, alternative splice variants of exon 6a encoding 6 amino acid proximal to the basic region of the protein are known in Mitf-A, -H, and -M. In this study, we identified alternative splice variants of exon 6a in other Mitf isoforms (Mitf-E, -J, and -mc) in melanocytes, mast cells, macrophages, and heart. We also compared the transcriptional activity of Mitf variants containing exon 6a to that of Mitf variants that did not contain exon 6a. PCR-RFLP analysis revealed that expression of Mitf with exon 6a was comparable with that of Mitf without exon 6a, irrespective of the specificity of the first exon, or cell type, although Mitf isoforms with different first exons were expressed in a cell type-dependent manner. Luciferase-based reporter assays revealed that transcription of Tyrosinase, which is known Mitf-regulated gene, was elicited more efficiently by expression of Mitf isoforms containing exon 6a, compared to isoforms that did not contain exon 6a. However, when transcription of Tyrp-1, Mmcp-6, and PAI-1 was examined, no significant differences were detected between Mitf isoforms with exon 6a and those without exon 6a, except for Tyrp-1 transcription by Mitf-D/E isoform. These results reveal a diverse pattern of gene expression and different transcriptional activities of Mitf isoforms, suggesting discrete regulation of gene transcription in specific tissues by Mitf.