Activation of the lipopolysaccharide signaling pathway in hepatic transplantation preservation injury

Endotoxin or lipopolysaccharide (LPS) initiates a cascade of complications of septic shock and multiple organ failure seen in Gram-negative bacterial infections. The first step of this pathway, which leads to activated nuclear factor (NF)-kappaB, activating protein (AP)-1, and other transcription factors, is the formation of the LPS receptor complex by LPS, LPS-binding protein (LBP), CD14, and toll-like receptor (TLR) 2 or 4. We examined whether the LPS signaling pathway is activated by hepatic ischemia/reperfusion injury in the transplant setting. Orthotopic syngeneic rat liver transplantation was performed with 0 to 18 hr of cold preservation in University of Wisconsin solution. Animals were killed 1 to 48 hr after reperfusion. Northern blot analysis for CD14, LBP, and TLR2 mRNA, immunohistochemistry for LBP, liver enzyme analysis, and gel shift assay for NF-kappaB and AP-1 were performed. LPS levels were elevated early after reperfusion. Aspartate aminotransferase and alanine aminotransferase maximally increased 12 hr after transplantation. LBP mRNA and protein and CD14 mRNA were significantly up-regulated peaking at 6 to 12 hr after reperfusion. TLR2 mRNA was also increased. NF-kappaB activity showed a biphasic peak at 1 to 3 hr and 12 hr after reperfusion, whereas AP-1 activity showed a peak at 3 to 6 hr. The induction of CD14 mRNA correlated with the length of cold ischemia time. These data indicate that multiple components of the LPS signaling pathway are activated during ischemia/reperfusion injury after liver transplantation.