The antibacterial activity of human neutrophils and eosinophils requires proton channels but not BK channels.
Electrophysiological events are of central importance during the phagocyte respiratory burst, because NADPH oxidase is electrogenic and voltage sensitive. We investigated the recent suggestion that large-conductance, calcium-activated K(+) (BK) channels, rather than proton channels, play an essential role in innate immunity (Ahluwalia, J., A. Tinker, L.H. Clapp, M.R. Duchen, A.Y. Abramov, S. Page, M. Nobles, and A.W. Segal. 2004. Nature. 427:853-858). In PMA-stimulated human neutrophils or eosinophils, we did not detect BK currents, and neither of the BK channel inhibitors iberiotoxin or paxilline nor DPI inhibited any component of outward current. BK inhibitors did not inhibit the killing of bacteria, nor did they affect NADPH oxidase-dependent degradation of bacterial phospholipids by extracellular gIIA-PLA(2) or the production of superoxide anion (O(2*)(-)). Moreover, an antibody against the BK channel did not detect immunoreactive protein in human neutrophils. A required role for voltage-gated proton channels is demonstrated by Zn(2+) inhibition of NADPH oxidase activity assessed by H(2)O(2) production, thus validating previous studies showing that Zn(2+) inhibited O(2*)(-) production when assessed by cytochrome c reduction. In conclusion, BK channels were not detected in human neutrophils or eosinophils, and BK inhibitors did not impair antimicrobial activity. In contrast, we present additional evidence that voltage-gated proton channels serve the essential role of charge compensation during the respiratory burst.
Femling
Jon K
JK
Inflammation Program, Roy J. and Luille A. Carver College of Medicine, University of Iowa, Coralville, 52241, USA.
Cherny
Vladimir V
VV
Morgan
Deri
D
Rada
Balázs
B
Davis
A Paige
AP
Czirják
Gabor
G
Enyedi
Peter
P
England
Sarah K
SK
Moreland
Jessica G
JG
Ligeti
Erzsébet
E
Nauseef
William M
WM
DeCoursey
Thomas E
TE
D000818:Animals; D001770:Blood Bactericidal Activity; D019556:COS Cells; D045744:Cell Line, Tumor; D002712:Chlorides / Q000494:pharmacology; D002522:Chlorocebus aethiops; D004305:Dose-Response Relationship, Drug; D004804:Eosinophils / Q000382:microbiology* / Q000502:physiology*; D006801:Humans; D007473:Ion Channels / Q000037:antagonists & inhibitors / Q000502:physiology; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors / Q000502:physiology*; D009504:Neutrophils / Q000382:microbiology* / Q000502:physiology*; D011522:Protons; D013211:Staphylococcus aureus / Q000187:drug effects / Q000502:physiology; D017967:Zinc Compounds / Q000494:pharmacology
D002712:Chlorides; D007473:Ion Channels; D051036:Large-Conductance Calcium-Activated Potassium Channels; D011522:Protons; D017967:Zinc Compounds; C016837:zinc chloride