TIMP-3 ameliorates hepatic ischemia/reperfusion injury through inhibition of tumor necrosis factor-alpha-converting enzyme activity in rats

BACKGROUND. Tumor necrosis factor (TNF)-α and its receptors play a critical role in the inflammatory cascade after hepatic ischemia/reperfusion injury. TNF-α converting enzyme (TACE) or disintegrin and metalloproteinase (ADAM)-17 is a metalloproteinase disintegrin that specifically cleaves precursor TNF-α to its mature form and is involved in the ectodomain shedding of TNF receptors. The regulation of TACE is poorly understood and its role in liver injury and/or regeneration is unknown. METHODS. Male Wistar rats were subjected to 10 or 30 min of partial warm hepatic ischemia followed by 3 to 24 hr of reperfusion. Serum and/or hepatic TACE, TNF-α, TNF receptor 1 (TNFR1), and interleukin (IL)-6 levels were assessed by enzyme-linked immunosorbent assay, real-time reverse-transcriptase polymerase chain reaction, and/or Western blot. RESULTS. Low levels of TACE were detected in normal liver tissue. Both 10 and 30 min warm ischemia resulted in a rise in TACE expression which peaked six hr after reperfusion. TNF-α, TNFR1, and IL-6 levels were up-regulated in a pattern similar to TACE messenger RNA (mRNA) levels. Moreover, selective inhibition of TACE activity by specific inhibitor tissue inhibitor of metalloproteinase (TIMP)-3 at dosages of 100 or 1000 ng/kg body weight showed significant decrease of circulating TNF-α and serum alanine transferase (ALT) levels and histological improvement of hepatic ischemia/reperfusion injuries. CONCLUSIONS. TACE expression and its activity, as measured by increases in TNF-α, TNFR1, and IL-6 levels, are increased following hepatic ischemia/reperfusion injury, implying that TACE plays an important role in hepatic ischemia/reperfusion injury. Amelioration of hepatic ischemia/reperfusion injury after inhibition of TACE activity by TIMP-3 suggests that TACE inhibition may play an important role in preventing liver ischemia/reperfusion injury warranting further experimental and clinical study.