The Role of Vagus Nerve on Dexmedetomidine Induced Survival and Lung Protection in a Sepsis Model in Rats.

Abstract BackgroundSepsis often results in acute lung injury (ALI). Sedative dexmedetomidine (Dex) was reported to protect cells and organs due to its direct cellular effects. This study aims to investigate the role of vagus nerves on Dex induced lung protection in a model of lipopolysaccharide (LPS)-induced ALI in rats. MethodsThe bilateral cervical vagus nerve of male Sprague-Dawley rats was sectioned or just exposed without section as sham surgery. The ALI was induced by intraperitoneal injection of LPS (1 or 10 mg/kg). After LPS administration, Dex antagonist yohimbine (YOH) (1 mg/kg) and/or Dex (25 μg/kg) was injected intraperitoneally at 0, 4, 8 and 12 hours to rats with or without vagotomy. The severity of ALI was determined with survival curve analysis and lung pathological scores of haematoxylin and eosin (H-E) staining sections. The plasma concentrations of interleukin 1beta (IL-1β), tumour necrosis factor-alpha (TNF-α), catecholamine (CA) and acetylcholine (Ach) were measured with enzyme-linked immunosorbent assay (ELISA). ResultsThe median survival time of LPS-induced ALI rats was significantly prolonged by Dex (22 hours, 50% CI, [31.25, 90.63]) compared that in the LPS group (14 hours, 50% CI, [18.75, 81.25], P < 0.05), and the acute lung injury score was significantly reduced by Dex (6.5, 50% CI, [5.75, 7.5] vs 11.5, 50% CI, [10.75, 12.50] in the LPS group, P < 0.01). However, these protective effects of Dex were significantly reduced by either YOH administration or vagotomy. Dex significantly decreased LPS-induced plasma IL-1β (pg/ml) (20.75 ± 0.78 vs. 30.22 ± 2.62, P < 0.01), TNF-α (pg/ml) (205.30 ± 9.39 vs. 273.40 ± 14.50, P < 0.01), and CA (pg/ml) (825.70 ± 43.46 vs. 1188.00 ± 64.40, P < 0.01) but increased the secretion of Ach (pg/ml) (507.20 ± 49.52 vs. 296.50 ± 62.44, P < 0.01); these effects of Dex was partially abolished by vagotomy. ConclusionsOur data suggested that Dex increased vagal nerve tone which partially contributed to its anti-inflammatory and lung protective effects. The indirect anti-inflammation and direct cytoprotection of Dex are likely through high vagal nerve tone and α 2 -adrenoceptor activation, respectively.