Hamycin inhibits IL-8-induced biologic response by modulating its receptor in human polymorphonuclear neutrophils.

Abstract

IL-8, a neutrophil chemotactic agent, is involved in a large number of neutrophil-driven acute and chronic inflammatory diseases. We have found that hamycin, an antifungal agent, reduces IL-8-induced migration and binding of 125I-labeled IL-8 to neutrophils by 66 and 75%, respectively. Other IL-8-induced biologic functions, such as superoxide generation, intracellular Ca2+ mobilization, and enzyme release were also reduced in hamycin-treated cells by 50 to 75%. Anti-IL-8R Ab (C-X-CR1) and IL-8 itself failed to protect the cells from the effect of hamycin. Scatchard analysis of IL-8 binding data demonstrated that while the normal cells expressed 23,000 +/- 1,704 receptors/cell (Kd = 3.5 nM), the number was reduced to 8,000 +/- 592 receptors/cell (Kd = 3.43 nM) in hamycin-treated cells. Chemical cross-linking of 125I-labeled IL-8 to its receptor followed by 10% SDS-PAGE analysis and autoradiography showed that the signals in hamycin-treated cells were considerably reduced compared with those in controls. In the immunoblot, however, the signals in control and hamycin-treated cells were almost identical. The intensity of the fluorescence emission of diphenyl hexatriene at 430 nm and membrane microviscosity measured by diphenyl hexatriene were considerably reduced in hamycin-treated cells, resulting in a reduced number of functional IL-8R, presumably by conformational change in the receptor. The study suggests that hamycin may be a potent immunomodulator of the IL-8R for alleviation of inflammatory distress.