Nagano C, Azuma A, Ishiyama H, Sekiguchi K, Imagawa K, Kikuchi M
Third Institute of New Drug Research, Otsuka Pharmaceutical Co., Ltd., 463-10, Kagasuno, Kawauchi-cho, Tokushima 771-0192, Japan.
J Pharmacol Exp Ther. 2001 Apr;297(1):388-94.
The purpose of the present work was to investigate the mechanism underlying the inhibitory action of rebamipide on superoxide anion (O2) production induced by the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (fMLP) in human neutrophils. Phosphatidylinositol 3,4,5-trisphosphate (PIP(3)), a product of phosphoinositide 3-OH-kinase (PI 3-kinase) accumulated in response to fMLP and this accumulation was well correlated with O2 production in human neutrophils. Rebamipide inhibited PIP(3) production in parallel with the inhibition of fMLP-induced O2 production. PI 3-kinase activity in anti-PI 3-kinase p85 immunoprecipitates was not affected by the presence of rebamipide, therefore rebamipide did not have a direct inhibitory action on PI 3-kinase activity. Since rebamipide had no inhibitory effect on O2 production induced by NaF, a direct activator of G protein, the target of the inhibitory action of rebamipide appears to be a component of the signal transduction pathway upstream of G protein. Scatchard analysis of [3H]fMLP binding to human neutrophil membrane revealed that rebamipide increased the K(D) value of [3H]fMLP without altering the number of [3H]fMLP binding sites, suggesting that rebamipide has a competitive antagonistic action against the fMLP-receptor. The competitive antagonistic action was further confirmed by the finding that rebamipide caused a parallel shift to the right in the dose-response curve of O2 production induced by fMLP. These results provide evidence that the competitive inhibitory action of rebamipide on the fMLP-receptor plays a main role in its inhibitory action on fMLP-induced O2 production.
本研究的目的是探讨瑞巴派特对人中性粒细胞中趋化肽甲酰甲硫氨酰亮氨酰苯丙氨酸（fMLP）诱导的超氧阴离子（O₂）产生的抑制作用机制。磷脂酰肌醇3,4,5-三磷酸（PIP(3)）是磷酸肌醇3-OH激酶（PI 3-激酶）的产物，其在人中性粒细胞中响应fMLP而积累，且这种积累与O₂产生密切相关。瑞巴派特抑制PIP(3)产生的同时也抑制fMLP诱导的O₂产生。抗PI 3-激酶p85免疫沉淀物中的PI 3-激酶活性不受瑞巴派特存在的影响，因此瑞巴派特对PI 3-激酶活性没有直接抑制作用。由于瑞巴派特对G蛋白直接激活剂氟化钠诱导的O₂产生没有抑制作用，瑞巴派特抑制作用的靶点似乎是G蛋白上游信号转导通路的一个成分。对[³H]fMLP与人中性粒细胞膜结合的Scatchard分析表明，瑞巴派特增加了[³H]fMLP的解离常数（K(D)）值，而不改变[³H]fMLP结合位点的数量，这表明瑞巴派特对fMLP受体具有竞争性拮抗作用。fMLP诱导的O₂产生剂量反应曲线向右平行移动这一发现进一步证实了这种竞争性拮抗作用。这些结果提供了证据，表明瑞巴派特对fMLP受体的竞争性抑制作用在其对fMLP诱导的O₂产生的抑制作用中起主要作用。
