WNT AGONIST ATTENUATES LIVER INJURY AND IMPROVES SURVIVAL AFTER HEPATIC ISCHEMIA/REPERFUSION

Abstract

The Wnt/β-catenin signaling pathway is well characterized in stem cell biology and plays a critical role in liver development, regeneration, and homeostasis. We hypothesized that pharmacologic activation of Wnt signaling protects against hepatic ischemia/reperfusion (I/R) injury through its known proliferative and antiapoptotic properties. Sprague-Dawley rats underwent 70% hepatic ischemia by microvascular clamping of the hilum of the left and median lobes of the liver for 90 min, followed by reperfusion. Wnt agonist (2-amino-4-[3,4-(methylenedioxy)benzylamino]-6-(3-methoxyphenyl)pyrimidine, 5 mg/kg body weight) or vehicle (20% dimethyl sulfoxide in saline) in 0.5 mL was injected i.p. 1 h before ischemia or infused i.v. over 30 min right after ischemia. Blood and tissue samples from the pretreated groups were collected 24 h after reperfusion, and a survival study was performed. Hepatic expression of β-catenin and its downstream target gene Axin2 were decreased after I/R, whereas Wnt agonist restored their expression to sham levels. Wnt agonist blunted I/R-induced elevations of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase and significantly improved the microarchitecture of the liver. The cell proliferation determined by Ki67 immunostaining significantly increased with Wnt agonist treatment, and inflammatory cascades were dampened in Wnt agonist-treated animals, as demonstrated by attenuations in interleukin 6, myeloperoxidase, inducible nitric oxide synthase, and nitrotyrosine. Wnt agonist also significantly decreased the amount of apoptosis, as evidenced by decreases in both TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining as well as caspase 3 activity levels. Finally, the 10-day survival rate was increased from 27% in the vehicle group to 73% in the pretreated Wnt agonist group and 55% in the Wnt agonist postischemia treatment group. Thus, we propose that direct Wnt/β-catenin stimulation may represent a novel therapeutic approach in the treatment of hepatic I/R.