The Role of LCN2 in Modulating Inflammatory and Regenerative Pathways in APAP-induced Acute Liver Failure

Date of Award

2020

Degree Type

Thesis

Degree Name

Master of Science in Biomedical Sciences

First Advisor

Vishakha Bhave, BS, PhD

Second Advisor

Francis E. Jenney, Jr., PhD

Third Advisor

Shashidharamurthy Taval, PhD

Fourth Advisor

Richard White, PhD

Abstract

Acetyl- para-aminophenol (APAP, Tylenol®) is a commonly used analgesic medication that can be found as the main ingredient in over 600 different OTC and prescription medications. APAP overdose is one of the most common causes of acute liver failure (ALF) in USA. Following bioactivation by CYP3A4 and CYP2E1 enzymes, APAP generates a reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI). Under normal doses, this reactive metabolite gets quenched into a non-toxic metabolite by cellular glutathione. However, following an overdose, the unquenched NAPQI covalently binds to liver macromolecules and causes centrilobular necrosis and sterile inflammation. Lipocalin-2 (LCN2) is an acute phase innate immune protein induced in the liver following injury. Recent data from our lab show that LCN2 KO mice are protected from ALF caused by APAP overdose when compared to WT mice. This protection was not due to differences in bioactivation based events but rather significantly less hepatocellular damage (histopathology and ALT) and higher liver regeneration (PCNA) at later stages (24-48h) post APAP overdose. Furthermore, we also demonstrated that LCN2 KO mice undergo increased autophagy as compared to WT mice. Preliminary studies done in our lab investigated the role of IL-17α and LCN2 in an APAP overdose model using enzyme linked immunosorbent assay (ELISA). This study found that LCN2 KO mice induced more IL-17α at 24 hours which correlated with the time point that showed a decrease in liver injury between WT and LCN2 KO mice. Our research suggests that regenerative pathways involving IL-17α may be inhibited in the presence of LCN2. The objective of this study is to investigate the mechanism of how LCN2 contributes to progression of injury in ALF. We hypothesize that LCN2 modulates the inflammatory and regenerative pathways via cytokines, prostaglandins and lipoxygenase pathways. The inflammation pathway will be investigated by measuring levels of 5-lipoxygenase and IL-1alpha in WT and LCN2 KO mice through ELISA. Prostaglandin E2 and IL-10 levels will be measured as anti-inflammatory markers. Regeneration pathways will be investigated by measuring levels of cyclooxygenase-2 (COX2), IL17α, and KI67 in WT and LCN2 KO mice. Findings from this study will identify a novel pathway in progressive phase of injury involving LCN2 and could potentially recognize targets for slowing down or inhibiting the progressive phase of liver injury that leads to ALF due to APAP overdose.

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