2-Benzyloxybenzaldehyde inhibits formyl peptide-stimulated increase in intracellular Ca2+ in neutrophils mainly by blocking Ca2+ entry

2-Benzyloxybenzaldehyde (CCY1a) inhibited the formyl-Met-Leu-Phe (fMLP)-induced elevation of cytosolic Ca²⁺] (Ca²⁺]_i) in rat neutrophils. The late plateau phase, but not the initial Ca²⁺ spike, of the fMLP-induced Ca²⁺]_i change was inhibited by CCY1a. In the absence of external Ca²⁺, CCY1a had no appreciable effect on either the fMLP- or cyclopiazonic acid (CPA)-induced Ca²⁺]_i elevation. CCY1a failed to inhibit Ca²⁺]_i changes induced by N-ethylmaleimide, GEA3162, ionomycin or sphingosine, but slightly inhibited the Ca²⁺ signals elicited by ATP or interleukin-8 (IL-8). In a classical Ca²⁺ readdition protocol, addition of CCY1a after cell activation strongly inhibited the Ca²⁺]_i response to fMLP, whilst that to CPA was only slightly reduced. CCY1a nearly abrogated the fMLP-stimulated Mn²⁺ influx but was less effective on the CPA-induced response. CCY1a attenuated the levels of tyrosine-phosphorylated bands in the 70–85 kDa molecular mass range. CCY1a had no effect on the basal Ca²⁺]_i level, the pharmacologically isolated plasma membrane Ca²⁺-ATPase activity or on the mitochondrial membrane potential. Thus, CCY1a blocks fMLP-induced Ca²⁺ entry into neutrophils probably by blocking the relevant Ca²⁺ channel directly or, alternatively, indirectly through the attenuation of tyrosine phosphorylation of some cellular proteins.