Antamanide Prevents Bradykinin-lnduced Filamin Translocation by Inhibiting Extracellular Calcium Influx

Bradykinin-induced paracellular gap formation in cultured endothelial cells (ECs) is preceded by cytoskeletal rearrangement. Actin binding proteins, such as nonmuscle filamin, perform a pivotal role in modulating actin organization. In response to bradykinin treatment, EC filamin translocates from the cell periphery to the cytosol within 1 min and the dynamics of filamin translocation parallel intracellular Ca(2+) increases. Intracellular Ca(2+) increases are essential for bradykinin-induced filamin translocation. In this study, we examine the role of extracellular Ca(2+) influx in mediating bradykinin-induced filamin translocation. Several K(+) channel blockers, including antamanide, tetraethylam-monium chloride (TEA), and charybdotoxin (CTX), are evaluated. All of these agents inhibit extracellular Ca(2+) influx with minimal or partial inhibition of intracellular Ca(2+) release. Bradykinin-induced filamin translocation is prevented by pretreatment with these K(+) channel blockers. Moreover, incubation of ECs in high-K(+) saline inhibits bradykinin-induced extracellular Ca(2+) influx as well as filamin translocation. To examine the efficacy of antamanide as an anti-inflammatory drug that affects filamin translocation, bradykinin-induced paracellular gap formation is quantified and compared in the presence or absence of antamanide pretreatment. Antamanide does not completely block bradykinin-induced gap formation; however, a significant attenuation is observed. This suggests that extracellular Ca(2+) influx is required for bradykinin-induced filamin translocation, which in part regulates microvascular EC barrier function, and that antamanide may be a useful anti-inflammatory agent.