Abstract
Toll-like receptor 4 (TLR4) is ubiquitously expressed on parenchymal and immune cells of the liver and is the most studied TLR responsible for the activation of proinflammatory signaling cascades in liver ischemia and reperfusion (I/R). Since pharmacological inhibition of TLR4 during the sterile inflammatory response of I/R has not been studied, we sought to determine whether eritoran, a TLR4 antagonist trialed in sepsis, could block hepatic TLR4-mediated inflammation and end organ damage. When C57BL/6 mice were pretreated with eritoran and subjected to warm liver I/R, there was significantly less hepatocellular injury compared to control counterparts. Additionally, we found that eritoran is protective in liver I/R through inhibition of high-mobility group box protein B1 (HMGB1)-mediated inflammatory signaling. When eritoran was administered in conjunction with recombinant HMGB1 during liver I/R, there was significantly less injury, suggesting that eritoran blocks the HMGB1-TLR4 interaction. Not only does eritoran attenuate TLR4-dependent HMGB1 release in vivo, but this TLR4 antagonist also dampened HMGB1's release from hypoxic hepatocytes in vitro and thereby weakened HMGB1's activation of innate immune cells. HMGB1 signaling through TLR4 makes an important contribution to the inflammatory response seen after liver I/R. This study demonstrates that novel blockade of HMGB1 by the TLR4 antagonist eritoran leads to the amelioration of liver injury.
Highlights
Hepatic ischemia and reperfusion (I/R) injury has potentially negative clinical implications for patients undergoing liver resection, transplantation and trauma
Sixty minutes of warm hepatic ischemia followed by 6 h of reperfusion significantly decreased serum alanine transaminase (ALT) levels in eritorantreated mice compared with vehicletreated controls (Figure 1A)
These results demonstrate that the toll-like receptor 4 (TLR4) antagonist eritoran is protective in liver I/R and confirms the role of TLR4 in liver damage in warm I/R
Summary
Hepatic ischemia and reperfusion (I/R) injury has potentially negative clinical implications for patients undergoing liver resection, transplantation and trauma. It is characterized by direct cellular damage as a result of the ischemic insult, as well as delayed dysfunction and damage that results from the activation of inflammatory pathways [1]. The mechanism of this injury response has been extensively studied and is associated with the activation of pattern recognition receptors such as toll-like receptor 4 (TLR4) by endogenous ligands [2,3,4,5]. Activation of TLR4 by endogenous and exogenous ligands leads to hepatocellular apoptosis and necrosis, liver failure and organ injury
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