Irisin Contributes to the Hepatoprotection of Dexmedetomidine during Intestinal Ischemia/Reperfusion

Abstract

Intestinal ischemia/reperfusion (I/R), which is associated with high morbidity and mortality, is also accompanied with abnormal energy metabolism and liver injury. Irisin, a novel exercise-induced hormone, can regulate adipose browning and thermogenesis. The following study investigated the potential role of dexmedetomidine in liver injury during intestinal I/R in rats. Adult male Sprague-Dawley rats underwent occlusion of the superior mesenteric artery for 90 min followed by 2 h of reperfusion. Dexmedetomidine or irisin-neutralizing antibody was intravenously administered for 1 h before surgery. The results demonstrated that severe intestine and liver injuries occurred during intestinal I/R as evidenced by pathological scores and an apparent increase in serum diamine oxidase (DAO), aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) levels. In addition, the hepatic irisin, cleaved caspase-3, Bax, and NLRP3 inflammasome components (including NLRP3, ASC, and caspase-1), protein expressions, apoptotic index, reactive oxygen species (ROS), malondialdehyde (MDA), myeloperoxidase (MPO), tumor necrosis factor- (TNF-) α, and interleukin- (IL-) 6 levels increased; however, the serum irisin level and hepatic Bcl-2 protein expression and superoxide dismutase (SOD) activity decreased after intestinal I/R. Interestingly, dexmedetomidine could reduce the above listed changes and increase the irisin levels in plasma and the liver in I/R rats. Dexmedetomidine-mediated protective effects on liver injury and NLRP3 inflammasome activation during intestinal I/R were partially abrogated via irisin-neutralizing antibody treatment. The results suggest that irisin might contribute to the hepatoprotection of dexmedetomidine during intestinal ischemia/reperfusion.

Figure 1

Effect of dexmedetomidine on histologic injuries of the liver and intestine. Dexmedetomidine reduced the histologic injuries of the liver and intestine after intestinal I/R in different groups (hematoxylin and eosin staining, scale bar = 25 or 50 μm; inset, magnified photographs). Black arrows indicate denuded villi and haemorrhage, and black asterisks indicate Gruenhagen's space. The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^$P < 0.05 vs. I/R+Dex1 group).

Figure 2

Dexmedetomidine improved serum DAO and liver dysfunction. Dexmedetomidine treatment decreased (a) DAO, (b) ALT, (c) AST, and (d) LDH levels and improved intestinal I/R-induced liver dysfunction. The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^$P < 0.05 vs. I/R+Dex1 group).

Figure 3

The effect of dexmedetomidine on TNF-α, IL-6, and MPO in liver tissues. Dexmedetomidine treatment decreased the (a) TNF-α, (b) IL-6, and (c) MPO levels after intestinal I/R in different groups. The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^$P < 0.05 vs. I/R+Dex1 group).

Figure 4

Dexmedetomidine attenuated hepatic oxidative stress. Dexmedetomidine treatment decreased the contents of (a) ROS and (b) MDA and increased (c) SOD activity. The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^$P < 0.05 vs. I/R+Dex1 group).

Figure 5

Dexmedetomidine improved hepatic Bax, Bcl-2, and cleaved caspase-3 expressions and reduced liver apoptosis. Dexmedetomidine treatment downregulated cleaved caspase-3 and Bax expressions and upregulated Bcl-2 expression in the liver after intestinal I/R in different groups. Moreover, TUNEL immunofluorescent labelling in the liver. Dexmedetomidine reduced the apoptosis index of the liver (magnification ×400, scale bars = 20 μm; inset, magnified photographs). TUNEL (red) and nuclei (blue) staining were performed after 2 h of reperfusion. The pink in the merged images of red and blue fluorescence indicates TUNEL-positive cells (white arrow).The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^$P < 0.05 vs. I/R+Dex1 group).

Figure 6

Dexmedetomidine improved the serum and hepatic irisin levels. Dexmedetomidine treatment increased the levels of irisin in the (a) serum and (b) liver. The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^$P < 0.05 vs. I/R+Dex1 group).

Figure 7

Correlation analysis. Correlations (N = 32) between the serum irisin levels and the liver injury scores (a), the serum irisin levels and the hepatic TNF-α levels (b), and the serum irisin levels and the hepatic IL-6 levels (c).

Figure 8

Effect of irisin-neutralizing antibody on the levels of serum and hepatic irisin in I/R and I/R with Dex rats. Irisin-neutralizing antibody treatment reduced the levels of serum (a) and hepatic (b) irisin. The results were presented as the mean ± standard deviation (0: irisin-neutralizing antibody 0 μg; 20: irisin-neutralizing antibody 20 μg; 30: irisin-neutralizing antibody 30 μg; 40: irisin-neutralizing antibody 40 μg) (n = 8; ^∗P < 0.05 vs. 0 μg; ^#P < 0.05 vs. 20 μg).

Figure 9

Irisin contributed to the hepatoprotection of dexmedetomidine against intestinal I/R. (a-h) Effect of administration of irisin-neutralizing antibody (irisin NA) on the liver injury (hematoxylin and eosin staining, magnification ×400, scale bars = 25 μm; inset, magnified photographs) (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^&P < 0.05 vs. I/R+Dex group).

Figure 10

Irisin mediated the protection of dexmedetomidine against hepatic inflammation and oxidative stress injury. Effect of administration of irisin NA on (a) TNF-α, (b) IL-6, (c) MPO, (d) ROS, and (e) MDA levels and (f) SOD activity. The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^&P < 0.05 vs. I/R+Dex group).

Figure 11

Dexmedetomidine inhibited NLRP3 inflammasome activation via irisin. Effect of administration of irisin NA on NLRP3, ASC, and caspase-1. The results were presented as the mean ± standard deviation (n = 8; ^∗P < 0.05, ^∗∗P < 0.01 vs. sham group; ^#P < 0.05; ^##P < 0.01 vs. I/R group; ^&P < 0.05 vs. I/R+Dex group).