Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Aichi, Japan.
Department of Biomedical Sciences, College of Life and Health Sciences, Chubu University, Kasugai, Aichi, Japan.
Biochem Pharmacol. 2019 May;163:178-193. doi: 10.1016/j.bcp.2019.02.015. Epub 2019 Feb 20.
Melanin is a dark naturally occurring pigment produced in nature and in many organisms. Although several reports have demonstrated applications for melanins in various therapeutic treatments, to date, no research has examined the anti-allergic effect of melanin. In this study, we for the first time found that solubilized or synthesized soluble melanin acts as a potent inhibitor of the degranulation of mast cells. We found that squid-ink-derived melanin significantly inhibited antigen-IgE-FcεRI-mediated degranulation of the mucosal mast cell line RBL-2H3. A homogenized melanin nanoparticle prepared by laser ablation also clearly suppressed antigen-induced mast cell degranulation. We also successfully solubilized synthetic melanin in a neutral biochemical buffer and found that it also significantly inhibited IgE-sensitized mast cells. The anti-degranulation activity of synthesized melanin was abolished in the melanin fraction below 50-kD molecular weight. All melanins used in this study did not exert significant cell death. Signal transduction analysis revealed that melanin suppressed antigen-triggered phosphorylation of signaling molecules as well as calcium influx. Transmission electron microscopy revealed that homogenized melanin nanoparticles partially attached to the cell surface and some nanoparticles were internalized to the cell. Flow cytometry revealed that the number of FcεRI-bound IgE molecules was decreased by melanin. Fluorescence recovery after photobleaching analysis indicated that melanin attenuated both plasma membrane and cytoplasmic fluidity, implying that melanin increased their viscosities. In vivo experiments using passive systemic anaphylaxis (PSA) and passive cutaneous anaphylaxis (PCA) mouse models demonstrated that oral administration of melanin accelerated the recovery of decreased body temperature after antigen infection in PSA, and combination sensitization of IgE with melanin attenuated antigen-induced extravasation in PCA. These findings indicated that melanin exhibits preventative effects against IgE-mast cell-mediated anaphylaxis. This study provides the first evidence that homogenized melanin may be a potential therapeutic agent for diseases involving mast cells.
黑色素是一种天然存在的深色色素，存在于自然界和许多生物体中。尽管有几项报告表明黑色素在各种治疗中的应用，但迄今为止，还没有研究检查黑色素的抗过敏作用。在这项研究中，我们首次发现，可溶或合成的可溶性黑色素是肥大细胞脱粒的有效抑制剂。我们发现，鱿鱼墨衍生的黑色素可显著抑制抗原-IgE-FcεRI 介导的黏膜肥大细胞系 RBL-2H3 的脱粒。通过激光烧蚀制备的均质黑色素纳米颗粒也明显抑制了抗原诱导的肥大细胞脱粒。我们还成功地在中性生化缓冲液中溶解了合成的黑色素，并发现它也显著抑制 IgE 致敏的肥大细胞。低于 50kD 分子量的黑色素部分抑制了合成黑色素的脱粒活性。本研究中使用的所有黑色素均未表现出明显的细胞死亡。信号转导分析表明，黑色素抑制了抗原触发的信号分子磷酸化以及钙内流。透射电子显微镜显示，均质黑色素纳米颗粒部分附着在细胞表面，一些纳米颗粒被内化到细胞内。流式细胞术显示，黑色素减少了 FcεRI 结合的 IgE 分子数量。光漂白后荧光恢复分析表明，黑色素减弱了质膜和细胞质的流动性，这意味着黑色素增加了它们的粘度。被动全身性过敏 (PSA) 和被动皮肤过敏 (PCA) 小鼠模型的体内实验表明，黑色素口服给药可加速 PSA 中抗原感染后体温下降的恢复，而 IgE 与黑色素联合敏化可减轻 PCA 中抗原诱导的渗出。这些发现表明黑色素对 IgE-肥大细胞介导的过敏反应具有预防作用。本研究首次提供了均质黑色素可能是一种潜在的治疗涉及肥大细胞的疾病的治疗剂的证据。
