Involvement of ion channels in human eosinophil respiratory burst.

Abstract

Human eosinophils possess a variety of ion channels that play a crucial role in the regulation of cellular activity. During eosinophil respiratory burst, efflux of H(+) ions through H(+) channels provides an efficient mechanism of H(+) extrusion and charge compensation. Interestingly, recent studies suggest that other ion channels may also be involved in this process. We sought to investigate the role of ion channels in phorbol 12-myristate 13-acetate-induced superoxide (O(2)(*-)) generation by human eosinophils. O(2)(*-) production was measured by using the superoxide dismutase-inhibitable reduction of cytochrome c. Ion channel expression and function were studied by using RT-PCR and the patch clamp technique, respectively. O(2)(*-) generation was affected by several ion channel blockers, especially 4,4-diisothio-cyanostilbene-2,2'-disulfonic acid. The involvement of Cl(-) channels in this process was confirmed by replacement of Cl(-) with gluconate or other anions. The halide dependence of O(2)(*-) production could be described by the sequence Cl(-)> or =Br(-)>I(-), which is similar to the selectivity sequence of several members of the chloride channel (ClC) family. RT-PCR studies performed with primers for ClC-2, ClC-3, ClC-4, ClC-5, ClC-6, and the cystic fibrosis transmembrane conductance regulator showed only the expression of ClC-3. The presence of phorbol 12-myristate 13-acetate-sensitive Cl(-) channels in human eosinophils with biophysical properties similar to the ClC-3 channel has been studied. Cl(-) channels play an important role in the regulation of O(2)(*-) production by human eosinophils.