Biliary atresia is the most common cause of end-stage cirrhosis in children and the number one indication for pediatric liver transplantation. It results from an inflammatory and fibrosing obstruction of extrahepatic bile ducts that presents as neonatal jaundice. Despite prompt diagnosis and surgical treatment, the disease progresses and causes substantial morbidity and mortality. Although the etiology remains largely undefined, studies pursuing the previous aims of this award have advanced knowledge of pathogenic mechanisms of disease. Specifically, we uncovered a sequential activation of dendritic, NK and CD8+ cells that disrupts the bile duct mucosa and promotes lumenal obstruction. Consistent with a multifactorial basis of disease, we also found that the activation of Th2 signals occurs during biliary injury experimentally and in human tissues. Combined, these studies placed the immune system in a central point of pathogenesis and began to identify potential therapeutic targets. In this competing renewal application, we propose a unifying hypothesis that hepatic inflammatory cells have a dual role as effectors of bile duct injury and as suppliers of survival signals to restore epithelial integrity. This hypothesis will be tested in three closely related bu independent aims.
In Aim 1, we will define the mechanisms used by lymphocyte soluble ligands to induce epithelial injury. This will be done by applying in vitro and powerful animal model systems to examine how TNF? signaling and granzymes serve as molecular executors of cholangiocyte lysis.
In Aim 2, we will determine the roles of macrophages and neutrophils as promoters of biliary injury.
This aim i s built on initial experiments showing that the neonatal livr expresses macrophage and neutrophil chemoattractants. Thus, we will use genetically engineered mice to explore the role of individual cell types in modulating the inflammatory response that produces the disease phenotype. And in Aim 3, we will investigate Th2 cytokines as survival signals to restore epithelial integrity. We generated preliminary evidence that liver-based myeloid cells produce Th2 survival signals with potent mitogenic properties to cholangiocytes. Here, we propose to dissect these signals by investigating the properties of the alarmin IL33 and the IL13-IL4R?-STAT6 axis in cholangiocyte proliferation and restoration of epithelial integrity in experimental biliary atresia. Upon completion, the proposed experiments will advance our understanding of the pathogenic mechanisms of disease and uncover new growth signals that promote repair of the injured tissue. These results will identify an array of targets for new therapies that block progression of disease, restore the biliary epithelium, and foster long-term survival of patients with biliary atresia.
This project studies biliary atresia, the most common cause of chronic liver disease in children and the leading indication for pediatric liver transplantation in the United States. We propose to investigate how the neonatal immune system has a dual role as promoters of bile duct injury and as suppliers of survival signals to restore integrity of the epithelium. These studies will identify novel therapeutic targets to block progression of liver disease and foster improved outcome of children with liver disease.
|Shivakumar, Pranavkumar; Mourya, Reena; Bezerra, Jorge A (2014) Perforin and granzymes work in synergy to mediate cholangiocyte injury in experimental biliary atresia. J Hepatol 60:370-6|
|Bessho, Kazuhiko; Mourya, Reena; Shivakumar, Pranavkumar et al. (2014) Gene expression signature for biliary atresia and a role for interleukin-8 in pathogenesis of experimental disease. Hepatology 60:211-23|
|Li, Jun; Razumilava, Nataliya; Gores, Gregory J et al. (2014) Biliary repair and carcinogenesis are mediated by IL-33-dependent cholangiocyte proliferation. J Clin Invest 124:3241-51|
|Bessho, Kazuhiko; Shanmukhappa, Kumar; Sheridan, Rachel et al. (2013) Integrative genomics identifies candidate microRNAs for pathogenesis of experimental biliary atresia. BMC Syst Biol 7:104|
|Saxena, Vijay; Shivakumar, Pranavkumar; Sabla, Gregg et al. (2011) Dendritic cells regulate natural killer cell activation and epithelial injury in experimental biliary atresia. Sci Transl Med 3:102ra94|
|Bessho, Kazuhiko; Bezerra, Jorge A (2011) Biliary atresia: will blocking inflammation tame the disease? Annu Rev Med 62:171-85|
|Li, Jun; Bessho, Kazuhiko; Shivakumar, Pranavkumar et al. (2011) Th2 signals induce epithelial injury in mice and are compatible with the biliary atresia phenotype. J Clin Invest 121:4244-56|
|Mohanty, Sujit K; Ivantes, Claudia A P; Mourya, Reena et al. (2010) Macrophages are targeted by rotavirus in experimental biliary atresia and induce neutrophil chemotaxis by Mip2/Cxcl2. Pediatr Res 67:345-51|
|Shivakumar, Pranavkumar; Sabla, Gregg E; Whitington, Peter et al. (2009) Neonatal NK cells target the mouse duct epithelium via Nkg2d and drive tissue-specific injury in experimental biliary atresia. J Clin Invest 119:2281-90|
|Erickson, Nissa; Mohanty, Sujit Kumar; Shivakumar, Pranavkumar et al. (2008) Temporal-spatial activation of apoptosis and epithelial injury in murine experimental biliary atresia. Hepatology 47:1567-77|
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