Abstract 9454: Arterial Baroreflex Dysfunction Impairs Angiogenesis in Response to Hindlimb Ischemia

Abstract

Objective: We examined whether ischemia-induced angiogenesis was reduced by the arterial baroreflex (ABR) dysfunction, and if so, we further examined whether the reduced angiogenesis was associated with a reduction of endothelium-derived acetylcholine (Ed-ACh) release using a rat model of hindlimb ischemia (HLI). We also determined whether this effect would be restored by the administration of pyridostigmine (Pyr), a cholinesterase inhibitor. Methods and Results: Male Sprague-Dawley rats were randomly assigned to 3 groups that received 1) sham operation (control), 2) sinoaortic denervation (SAD)-induced ABR dysfunction, 3) SAD rat diet with Pyr. 4 weeks after the SAD intervention, HLI was surgically induced in all groups. Infrared spectrum analyses showed that the recovery of the ischemic/normal limb temperature ratio in the SAD rats remained impaired throughout the follow-up period. At postoperative day 14, immunohistochemical analyses in the ischemic limb revealed significantly lower capillary densities in the SAD group than in the control, which were associated with decreased tissue expression of choline acetyltransferase (ChAT) and acetylcholine transporter (AChT). Pyr significantly improved the temperature ratio and capillary densities, accompanied by elevation of ChAT and AChT protein in the ischemic muscles. Interestingly, Pyr not only elevated the levels of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) proteins of ischemic muscles but also improved functional recovery following hindlimb ischemia in α7-nicotinic ACh receptor (α7-nAChR) knockout mice. Furthermore, in vitro, acetylcholine analogue (carbachol) stimulated the expression of VEGF and phosphorylation of VEGF receoptor-2 (VEGFR2) in umbilicus vein endothelial cells, and these changes were diminished by methyllycaconitine, a nicotinic receptor blocker. Conclusions: These findings suggest that the ABR dysfunction likely triggers and impairs angiogenesis in response to ischemia and that the Pyr-mediated augmentation of tissue Ed-ACh activity stimulates VEGF expression and VEGFR2 phosphorylation by the α7-nAChR-dependent/-independent activation of the Pyr, thereby improving vascular angiogenic action.