Human β-Defensin 2 Is a Novel Opener of Ca 2+ -Activated Potassium Channels and Induces Vasodilation and Hypotension in Monkeys

Human β-defensin 2 (HBD2) is a cysteine-rich cationic antimicrobial peptide known for its important role in innate immune system. Intensive studies have demonstrated its antimicrobial and chemotactic activities in vitro. In this study, ELISA analysis showed that HBD2 was significantly downregulated in sera of patients with hypertension. It relaxed vessel smooth muscle by acting on the major regulatory pathways, contributing to vessel smooth muscle contraction. Electrophysiology analysis indicated that HBD2 acted as an opener of large-conductance Ca(2+)-activated potassium (BKCa)-mSlo+hβ1 channels and increased BKCa currents. Mutation analysis revealed that HBD2 activated BKCa-mSlo+hβ1 channels via interacting with Leu41 and Gln43 of β1-loop. In vivo experiments suggested that HBD2 at 4 × to 6 × of physiological concentration exerted hypotensive effect in monkeys significantly, whereas the selective blocker of BKCa channels, Paxilline, inhibited the effect. HBD2 is the first peptide opener of BKCa-mSlo+hβ1 channels. It may be a novel regulator of blood pressure and provides a new therapeutic target for the treatment of hypertension. The HBD2 blockade of the BKCa channels may represent a new type of cross-talk between immune and cardiovascular systems.