Lipid Emulsion Attenuates Acetylcholine-Induced Relaxation in Isolated Rat Aorta

Abstract

We investigated the effect of Lipofundin MCT/LCT and Intralipid on acetylcholine-induced nitric oxide- (NO-) mediated relaxation in rat aorta to determine which lipid emulsion (LE) is more potent in terms of inhibition of NO-induced relaxation. Dose-response curves of responses induced by acetylcholine, the calcium ionophore A23187, and sodium nitroprusside were generated using isolated rat aorta with or without LE. The effect of Lipofundin MCT/LCT on acetylcholine-induced endothelial nitric oxide synthase (eNOS) phosphorylation in human umbilical vein endothelial cells (HUVECs) was investigated using western blotting. Lipofundin MCT/LCT (0.1 and 0.2%) attenuated acetylcholine-induced relaxation in endothelium-intact aorta with or without tiron, whereas 0.2% Intralipid only inhibited relaxation. Lipofundin MCT/LCT inhibited relaxation induced by the calcium ionophore A23187 and sodium nitroprusside in endothelium-intact aorta, but Lipofundin MCT/LCT had no effect on sodium nitroprusside-induced relaxation in the endothelium-denuded aorta. Combined pretreatment with l-arginine plus Lipofundin MCT/LCT increased acetylcholine-induced maximal relaxation in endothelium-intact aorta compared with Lipofundin MCT/LCT alone. l-Arginine attenuated Lipofundin MCT/LCT-mediated inhibition of acetylcholine-induced eNOS phosphorylation in HUVECs. Taken together, Lipofundin MCT/LCT attenuated acetylcholine-induced NO-mediated relaxation via an inhibitory effect on the endothelium including eNOS, which is proximal to activation of guanylyl cyclase.

Lipofundin MCT/LCT Inhibits Levcromakalim-Induced Vasodilation by Inhibiting Endothelial Nitric Oxide Release

“…The medium-chain fatty acids in Lipofundin MCT/LCT are as follows: 28.5% caprylic acid, 20% capric acid, 1% lauric acid, and 0.5% caproic acid [2]. Similar to previous reports indicating that the magnitude of the Lipofundin MCT/LCT-mediated inhibition of vasodilation induced by acetylcholine via NO was higher than that of Intralipid and that Lipofundin MCT/LCT only increased blood pressure, Lipofundin MCT/LCT only inhibited the levcromakalim-induced vasodilation of isolated endothelium-intact rat aortae ( Figure 1B) [11,14]. However, Lipofundin MCT/LCT (2%) had no effect on the levcromakalim-induced vasodilation of isolated endothelium-denuded rat aortae ( Figure 2B) and endothelium-intact rat aortae pretreated with L-NAME ( Figure 3A).…”

“…However, Intralipid, which increases free fatty acids, enhances blood pressure and systemic vascular resistance, reduces flow-mediated vasodilation, which seems to be associated with impaired NO release due to endothelial dysfunction [8][9][10]. Furthermore, lipid emulsion attenuates the NO-mediated relaxation induced by acetylcholine [11]. This pathophysiological state, including hypotension, acidosis and hypoxia induced by local anaesthetic systemic toxicity, causes K ATP channel-induced vasodilation as a protective response through the attenuation of calcium influx and lipid emulsion has been used to alleviate cardiovascular collapse induced by toxic doses of a local anaesthetic mainly through indirect mechanisms [1,3,12,13].…”

Lipid Emulsion for Treating Local Anesthetic Systemic Toxicity

“…However, pretreatment with the nitric oxide synthase inhibitor N W -nitro-L-arginine methyl ester abolished the Intralipid®-mediated increase in left ventricular systolic pressure 67 . Considering previous reports, the lipid emulsion-mediated decreased bioavailability of nitric oxide released by toxic doses of local anesthetics may have partially contributed to the lipid emulsion-mediated reversal of vascular collapse from toxic doses of local anesthetic 31 , 62 - 67 . Intralipid® facilitated recovery from cardiovascular depression induced by bupivacaine in pigs through increased systemic vascular resistance 53 .…”

“…Lipid emulsion attenuated acetylcholine-induced nitric oxide-mediated relaxation in isolated endothelium-intact rat aorta through inhibition of the nitric oxide-producing cellular signaling pathway proximal to guanylyl cyclase activation 62 . Local anesthetics, including levobupivacaine, ropivacaine and mepivacaine, caused vasoconstriction at lower doses and attenuated vasoconstriction (vasodilation) at higher doses in isolated rat aortas 63 - 65 .…”

Lipid emulsion attenuates the vasodilation induced by a toxic dose of a calcium channel blocker through its partitioning into the lipid phase

“…Furthermore, nifedipine and diltiazem enhance nitric oxide production in endothelial cells, whereas verapamil has no effect (Ding and Vaziri 2000). In addition, lipid emulsion inhibits acetylcholine-induced nitric oxide-mediated relaxation (Ok et al 2015). Thus, as these may be confounding factors in the interpretation of the results obtained from the current study, we pretreated endothelium-denuded aortic rings with the nitric oxide synthase inhibitor N W -nitro-L-arginine methyl ester (L-NAME, 10 -4 mol/l) to avoid these confounding factors, with a particular focus on partitioning calcium channel blockers (Ding and Vaziri 2000;Ok et al 2015).…”