Premium
Differential effects of cAMP‐elevating drugs on stimulus‐induced cytosolic calcium changes in human basophils
Author(s) -
Botana Luis M.,
MacGlashan Donald W.
Publication year - 1994
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1002/jlb.55.6.798
Subject(s) - biology , stimulus (psychology) , cytosol , calcium , microbiology and biotechnology , differential effects , neuroscience , pharmacology , endocrinology , biochemistry , medicine , enzyme , cognitive psychology , psychology
Drugs that elevate cAMP levels in human basophils are known to inhibit immunoglobulin E (IgE)‐mediated histamine release. We have examined whether cAMP‐active agents inhibit the cytosolic Ca 2+ , [Ca 2+ ]i, response that normally accompanies activation of basophils. As previously described, this [Ca 2+ ] i response is biphasic, one phase dependent on internal sources of calcium and a second later phase dependent on extracellular calcium, as observed in many cell types. Forskolin and rolipram or their combination had no effect on the initial elevation of cytosolic calcium that follows stimulation with anti‐IgE antibody. In contrast, the second phase of the IgE‐mediated calcium response was inhibited by these agents. For IgE‐mediated responses, the relative efficacy of various cAMP active agents (rolipram forskolin < dibutyryl cAMP < forskolin + rolipram) for the inhibition of histamine release and the second‐phase calcium response was similar and roughly paralleled the measured increase in basophil cAMP. In contrast, neither the first nor the second phase of the f‐Met‐Leu‐Phe (fMLP)‐induced calcium response was inhibited by any of the cAMP‐active agents tested. Indeed, at low concentrations of fMLP, a combination of forskolin and rolipram caused slight enhancement of the calcium response. This result was consistent with the observations that these agents had no effect or caused slight enhancement of histamine or leukotriene released induced by fMLP. Similarly, cAMP‐active agents caused no inhibition of C5a or phorbol ester (phorbol myristate acetate)‐induced histamine release. These observations suggest that inhibition of the phase of the calcium response that is dependent on extracellular calcium could account for the inhibition of histamine release by these agents. However, these studies also suggested that (1) this is effect is not exerted at the level of the inositol trisphosphate (InsP 3 ) receptor or InsP 3 metabolism and (2) the mechanisms that maintain the second‐phase calcium response are possibly distinct for IgE‐ and fMLP‐mediated reactions because cAMP‐active agents inhibited the second‐phase response of only one stimulus. J. Leukoc. Biol. 55: 798–804; 1994.