Open Access

Anastasia Pyanova, Vjatscheslav U. Kalentchuk, Vladimir N. Serebryakov, Rudolf Schubert

• Vascular smooth muscle BK channels are affected by several signaling pathways, in particular by PKC and calcium release from intracellular stores. However, little is known about how the cross-talk of these pathways is orchestrated. Melatonin is widely recognized for its role in circadian regulation, yet its vascular actions remain incompletely understood. The hypothesis that cross-talk of PLC-mediated stimulation of PKC and calcium release determines the role of the BK channel in melatonin-induced vasocontraction was tested. The patch-clamp technique was used on freshly isolated smooth muscle cells and wire myography on intact rat tail arteries. Melatonin markedly stimulates an outward current. Iberiotoxin, a specific BK channel inhibitor, abolished this effect. The effect of melatonin was not affected by 4P-PDOT, a selective MT2–receptor antagonist, but considerably depressed by luzindole, a MT1- and MT2–receptor antagonist. Mechanistically, the melatonin-induced stimulation of the BKVascular smooth muscle BK channels are affected by several signaling pathways, in particular by PKC and calcium release from intracellular stores. However, little is known about how the cross-talk of these pathways is orchestrated. Melatonin is widely recognized for its role in circadian regulation, yet its vascular actions remain incompletely understood. The hypothesis that cross-talk of PLC-mediated stimulation of PKC and calcium release determines the role of the BK channel in melatonin-induced vasocontraction was tested. The patch-clamp technique was used on freshly isolated smooth muscle cells and wire myography on intact rat tail arteries. Melatonin markedly stimulates an outward current. Iberiotoxin, a specific BK channel inhibitor, abolished this effect. The effect of melatonin was not affected by 4P-PDOT, a selective MT2–receptor antagonist, but considerably depressed by luzindole, a MT1- and MT2–receptor antagonist. Mechanistically, the melatonin-induced stimulation of the BK current was abolished by GDPβS, an inhibitor of G-protein function, U-73122, a PLC-inhibitor, and low molecular weight heparin, an inhibitor of IP3 –induced calcium release. Calphostin C, a specific PKC-inhibitor, further stimulated the BK current in the presence of melatonin, suggesting functional cross-talk between distinct PLC-dependent signaling branches. At the functional level, melatonin reversibly contracted intact vessel preparations. Vessel pre-treatment with TEA or iberiotoxin augmented the effect of melatonin. Together, these findings identify BK channels as a key downstream target of melatonin signaling in vascular smooth muscle and reveal a previously unrecognized PLC-dependent signaling cross-talk that contributes to melatonin-induced vasocontraction.…