Interaction of suplatast tosilate (IPD) with chloride channels in human blood eosinophils: a potential mechanism underlying its anti-allergic and anti-asthmatic effects.
BACKGROUND
Alterations in chloride ion channels have been implicated in the induction of changes in cell shape and volume. Because blood and tissue eosinophilia are hallmarks of bronchial asthma, in this study we examined the role of chloride channels in the underlying effects of suplatast tosilate (IPD), an anti-allergic drug, in human blood eosinophils.


METHODS
Eosinophils were isolated and purified from the blood of allergic asthmatic donors. Chloride ion currents were recorded using the whole-cell patch-clamp technique in freshly isolated eosinophils. The current-voltage relationship of whole-cell currents in human blood eosinophils was calculated and recorded. The effect of chloride channel blockers was examined on superoxide release, eosinophil chemotaxis as measured by the Boyden chamber, and eosinophil adhesion to endothelial cells. Radioligand binding studies with [3H]IPD and competition curves with chloride channel blockers were performed.


RESULTS
IPD increased both inward and outward chloride currents in human blood eosinophils. IPD in 1 ng/mL did not have significant effect on chloride current. However, at 5 ng/mL IPD activated both outward and inward currents in human blood eosinophils. Chloride channel blockers inhibited IPD-induced respiratory burst in eosinophils, eosinophil chemotaxis, and eosinophil adhesion to endothelial cells. All these effects of IPD on chloride current and the resultant functional responses in human blood eosinophils were not due to its basic salt, p-toluenesulphonic acid monohydrate. Human blood eosinophils contained specific binding sites for [3H]IPD with K(D) and B(max) values of 187.7+/-105.8 nm and 58.7+/-18.7 fmol/10(6) cells, respectively. Both NPPB and DIDS competed, in a dose-dependent manner, for the specific binding of [3H]IPD in human blood eosinophils.


CONCLUSIONS
These data suggest that the anti-allergic and anti-asthmatic effects of IPD could be due to its interaction with chloride channels in human blood eosinophils.
Agrawal
D K
DK
Creighton University School of Medicine, Omaha, NE 68178, USA. dkagr@creighton.edu
Cheng
G
G
Kim
M-J
MJ
Kiniwa
M
M
D000328:Adult; D000368:Aged; D018926:Anti-Allergic Agents / Q000494:pharmacology*; D018927:Anti-Asthmatic Agents / Q000494:pharmacology*; D001190:Arylsulfonates / Q000494:pharmacology*; D001249:Asthma / Q000276:immunology; D001665:Binding Sites; D002448:Cell Adhesion; D002633:Chemotaxis; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000187:drug effects*; D002712:Chlorides / Q000378:metabolism; D042783:Endothelial Cells / Q000276:immunology; D004804:Eosinophils / Q000187:drug effects* / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016897:Respiratory Burst; D012130:Respiratory Hypersensitivity / Q000276:immunology; D013452:Sulfonium Compounds / Q000494:pharmacology*
D018926:Anti-Allergic Agents; D018927:Anti-Asthmatic Agents; D001190:Arylsulfonates; D018118:Chloride Channels; D002712:Chlorides; D013452:Sulfonium Compounds; C073028:suplatast tosilate