Vagus Nerve Stimulation Accelerates Thrombosis via α7 Nicotinic Acetylcholine Receptors and Improves Clot Formation in Hemophilia A Mice

Abstract

INTRODUCTION: Hemophilia A, factor VIII deficiency, decreases thrombin and fibrin formation, resulting in abnormal bleeding. Vagus nerve stimulation (VNS) increases thrombin generation via α7 nicotinic acetylcholine receptors (α7nAChR). We reasoned that VNS would improve local clot stability in a FeCl3-induced thrombosis model in wild-type (WT) and factor VIII–deficient (F8-KO), but not in α7nAChR-deficient (α7-KO) mice. METHODS: Mice underwent left cervical VNS (1 V, 30 Hz, 2 ms, 5 minute), and then FeCl3 solution was applied to the right carotid artery. For WT and α7-KO experiments, a 5% solution was applied for 1 minute. For F8-KO experiments, a 10% solution was applied for 3 minutes. Time to occlusion (TTO) was defined as absence of arterial waveform for greater than 1 minute. RESULTS: In WT mice, VNS significantly decreases TTO (VNS vs sham: 7.1 ± 1.3 vs 15.8 ± 3.4 minutes, n = 5, p < 0.05), but fails to decrease TTO in α7-KO mice (VNS vs sham: 19.3 ± 3.7 vs 17.9 ± 4.3 minutes, n = 5, p = NS). F8-KO mice have significantly longer TTO vs WT mice (WT vs F8-KO sham: 6.55 ± 0.63 minutes vs 25 ± 0 minutes, n = 6, p <0.0001). VNS significantly decreases TTO in F8-KO mice (F8-KO VNS vs F8-KO sham: 9.26 ± 1.38 minutes vs 25 ± 0 minutes, n = 6, p < 0.0001) (Figure).Figure.: F8-KO, factor VIII–deficient; VNS, vagus nerve stimulation.CONCLUSION: VNS improves local clot stability. VNS requires α7nAChR, but bypasses factor VIII deficiency, suggesting that vagal control of thrombin generation is independent of this critical clotting factor.