Histamine activates phospholipase C in human airway epithelial cells via a phorbol ester-sensitive pathway.

Abstract

In human airway epithelial cell lines 9HTEo- and CFNPE9o, histamine causes a transient elevation of intracellular free calcium concentration ([Ca2+]i) detected by fura 2 fluorescence, which is due to both release from intracellular stores and extracellular Ca2+ entry. The effect of histamine is abolished by the Ca(2+)-ATPase inhibitor thapsigargin. Histamine also stimulates inositol phosphate accumulation. Changes in [Ca2+]i and inositol phosphate production exhibit a similar dose-response relationship for histamine (maximal effect at 10(-4) M), with both phenomena being blocked by the H1 antagonist mepyramine and being insensitive to pertussis toxin treatment. The effects of histamine on phosphoinositide metabolism and [Ca2+]i are abolished by a short-term preincubation with phorbol ester, and this effect is reversed by staurosporine and calphostin C, suggesting a feedback regulation by protein kinase C. The results indicate that human airway epithelial cells contain H1 receptors coupled to phospholipase C through a pertussis toxin-insensitive G protein.