Abstract
INTRODUCTION: Pregabalin, a first-line treatment for neuropathic pain, binds to the voltage-gated calcium channel auxiliary subunit alpha2delta-1, reducing neurotransmitter release. Transdermal pregabalin has also shown analgesic effects in neuropathic mouse models. However, its effects on epidermal cells remain unclear. OBJECTIVES: We aimed to investigate the action of pregabalin on the human Merkel cell line (MC). METHODS: We used the cultured human Merkel cell line MCC 14/2 to measure intracellular free calcium concentration ([Ca(2+)](i)) levels using fura-2 and to perform immunofluorescence analysis. RESULTS: To examine effect of pregabalin on a chronic pain condition, we applied Lys-(Des-Arg(9)) bradykinin (BK) for 48 hours (BK group), BK for 48 hours with pregabalin for 24 hours (BK + pregabalin group), or none (as control group) before measuring the direct mechanical stimulation-induced [Ca(2+)](i) response in the MCs. The area under the curve (AUC) of the transient increase in [Ca(2+)](i) was significantly increased in the BK group than that in the control group. Area under the curve did not show any significant differences between control group and BK + pregabalin group. When the Na(+)-Ca(2+) exchanger (NCX) inhibitor KB-R7943 and SEA0400 were applied just before mechanical stimulation in the BK + pregabalin group, AUC was significantly increased compared to that in the absence of KB-R7943 and SEA0400. We could not observe any significant differences in the peak values of mechanical stimulation-induced [Ca(2+)](i) increases among the groups. Merkel cells predominantly expressed the NCX1 isoform. CONCLUSION: These results suggested that the site of action of pregabalin to MCs is Ca(2+) extrusion mechanism via NCX1.