Abstract
The Toll-like receptor-4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway is vital in the pathogenesis of hepatic ischemia/reperfusion (HIR) injury. Dipeptidyl peptidase-4 (DPP4) inhibitors exert protective effects on IR injury of the kidney, heart, and lung; however, their effect on the liver is still unknown. Thus, the purpose of this study was to examine whether pretreatment with vildagliptin (Vilda), a DPP4 inhibitor, produces hepatic protection against IR injury and to investigate its influence on TLR4/NF-κB signaling in a rat model. Thirty male Wistar rats were divided into 3 groups: the sham group: subjected to a sham operation and received normal saline; the HIR group: subjected to HIR and received normal saline; and the Vilda + HIR group: subjected to HIR with pretreatment of 10 mg/kg/day Vilda for 10 days intraperitoneally. Hepatic ischemia lasted for 45 minutes followed by 3-hour reperfusion; then blood and liver samples were collected for biochemical and histopathological examination. The HIR group produced a significant increase in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatic malondialdehyde (MDA), nitric oxide (NO), and tumor necrosis factor alpha (TNF-α) levels and a significant reduction in the hepatic catalase level in comparison to the sham group. Moreover, a significant upregulation of gene and protein expressions of TLR4, NF-κB, and high-mobility group box-1 (HMGB1) along with caspase-3 protein expression was observed in the HIR group when compared with the sham group. Histopathological examination of the liver from the HIR group showed necrosis, sinusoidal congestion, hemorrhage, and hepatocyte degeneration. Administration of Vilda ameliorated the biochemical and histopathological changes caused by HIR. Vildagliptin showed for the first time a hepatoprotective effect in HIR injury through downregulation of TLR4/NF-κB/HMGB1 and caspase-3 hepatic expressions.
Highlights
Hepatic ischemia/reperfusion (HIR) is commonly performed in clinical liver surgeries including liver transplantation [1]
The serum levels of alanine transaminase (ALT) and aspartate transaminase (AST) increased significantly in both HIR and Vilda + HIR groups when compared with the sham group (p < 0 05)
Administration of Vilda caused a significant reduction in hepatic MDA and nitric oxide (NO) contents with a significant increase in hepatic catalase levels in comparison to the HIR group (p < 0 05)
Summary
Hepatic ischemia/reperfusion (HIR) is commonly performed in clinical liver surgeries including liver transplantation [1]. The Toll-like receptors (TLRs) constitute a family of transmembrane receptors that have an important role in the detection of the microbial infection through innate immune system activation [4]. TLR4 signaling was reported to be activated by high-mobility group box-1 (HMGB1), heparan sulfate, and others [7,8,9]. TLR4 has been recognized as a mediator of inflammation and organ injury in different models including hepatic [8, 10], renal [11], and pulmonary [12] I/R injury. The TLR4/NF-κB signaling was found to play a significant role in the pathogenesis of HIR injury [13]
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