Interleukin-33 Induces a Potent Cholangiocyte Proliferation via a Novel Paracrine Circuit
Jun Li, Pranavkumar Shivakumar, Stephanie Walters, Tatsuki Mizuochi, Reena Mourya, Kazuhiko Bessho, Jorge A. Bezerra
Division of Gastroenterology, Hepatology and Nutrition and the Pediatric Liver Core Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
Background and Aims: Cholangiocyte proliferation is critical for tissue repair and carcinogenesis. We reported previously that the hepatic expression of ST2, the receptor for interleukin-33 (IL33, a Th2 cytokine) increases in patients with biliary atresia, the most common obstructive cholangiopathy in children. Here, we aimed to investigate the role of the IL33/ST2 axis in bile duct repair using complementary human and murine experiments. Methods and Results: We quantified serum IL33 in 81 children with biliary atresia and found it to be higher (93.7±52.6 pg/mL) than the undetectable levels of agematched controls. In a mouse model of biliary atresia, IL33 expression correlated with increased numbers of cholangiocytes in livers and extrahepatic bile ducts (EHBDs), and both IL33 and ST2 were expressed in cholangiocytes of EHBDs of neonatal and adult mice. To determine if IL33 induces mitosis of cholangiocytes, we injected 0.1 μg IL33 daily to adult mice. IL33 induced marked proliferation, with a peak of 76-fold increase in EHBD at day 1(BrdU+ cholangiocytes: 37.9±3.4% vs 0.5±1% in controls, P<0.0001) and ongoing proliferation at days 4 (13.1 ±2.5%) and 7 (5.7±1.2%), evidenced histologically as epithelial hyperplasia. IL33 induced an expansion of the hepatic population of lineage-negative mononuclear cells that expressed ST2 with surface staining for Sca1 +CkitlowICoS+CD127+CD25+CD44+ (known as nuocytes), which overexpressed IL4, IL5, and IL13 upon treatment with PMA-ionomycin in culture. To determine the relevance of nuocytes and IL13 in the proliferative response, we injected IL33 into Rag2-/Il2rgc-/- and Roro% mice, which lack nuocytes, and found decreased proliferation compared to wild-type (WT) in both mouse lines (2.6±0.6% vs WT=26.3±4.3%, P=0.005; 6.3±0.8% vs WT=22.5±3.9%, P=0.02, respectively), but remained above baseline (P<0.01). Adoptive transfer of nuocytes restored the IL33-induced cholangiocyte proliferation. Similarly, proliferation was suppressed in Il1-/- mice (1.3±0.3%), while injections of IL13 induced cholangiocyte proliferation in a dose-dependent manner. By RNAseq, IL33 resulted in the activation of the E2f1, Hif1a, Prrx2, and Myb pathways. Last, injection of IL33 to neonatal mice with atresia suppressed epithelial injury, promoted cholangiocyte hyperplasia, and decreased duct obstruction. Conclusions: IL33 induces proliferation of cholangiocytes directly and by the release of IL13 from nuocytes in a paracrine fashion. The activation of inflammation and cell proliferation pathways and epithelial hyperplasia in a disease model point to a potential role IL33 in tissue repair and oncogenesis.
Jorge A. Bezerra - Grant/Research Support: Molecular Genetics Laboratory,
The following people have nothing to disclose: Jun Li, Pranavkumar Shivakumar, Stephanie Walters, īatsuki Mizuochi, Reena Mourya, Kazuhiko Bessho