G proteins as biological targets for anti-allergic drugs?

The inhibiting effect of the H1 antihistamine cetirizine on the release of mediators (LTB4, arachidonic acid and phospholipase A2) was measured in different cells in vitro (human PMN, deltaF508 cells, chinese hamster ovary cells and rabbit chondrocytes) using different agonists (fMLP, NaF, calcium ionophore A 23187, bradykinin, adrenaline and IL-1). It was shown that physiological concentrations of the drug inhibited the release when activation of receptor-coupled G proteins was involved. By contrast, there was no inhibiting effect of cetirizine when the release was induced by a calcium ionophore which bypasses the G proteins coupled to cell membrane receptors.