Mechanistic studies of amino acid deprivation-induced hepatic fibrosis - PROJECT SUMMARY This application aims to describe a mechanism of hepatic fibrosis caused by asparagine depletion during PEGylated asparaginase (PEG-ASNase) therapy. Hepatic fibrosis is a serious form of liver injury caused by the activation of hepatic stellate cells (HSCs). During this activation process, HSCs upregulate fibrotic gene expression and release retinol from their lipid droplets. PEG-ASNase is a prominent therapy for ALL, effectively disrupting leukemia cell survival by depleting asparagine and inducing cell death. However, the use of PEG- ASNase in adults is limited due to the high risk of dose-limiting liver injury. The mechanism of PEG-ASNase- induced liver injury is not clear. Nonetheless, clinical cases of fatal PEG-ASNase-induced liver injury coincide with the development of hepatic fibrosis. Our previous studies demonstrate that asparagine depletion by PEG- ASNase induces the expression of adipose triglyceride lipase (ATGL) in adipocytes, which is the enzyme responsible for catalyzing the first step in free fatty acid mobilization from stored triglycerides. Previous studies have shown that the peroxisome proliferator-activated receptor gamma (PPAR-γ) transcription factor regulates the expression of ATGL in adipocytes. Based on our preliminary data, we hypothesize that PEG-ASNase treatment activates HSCs through the PPAR-γ-dependent induction of ATGL. Our study has two specific aims: Aim 1: To investigate the role of ATGL in PEG-ASNase-induced-HSC activation. We predict that the ablation or inhibition of ATGL will attenuate HSC activation. Aim 2: To elucidate the role of PPAR-γ in PEG- ASNase-mediated ATGL induction and hepatic fibrosis. We predict that inhibition of PPAR-γ will reduce PEG-ASNase-induced HSC activation. Nevertheless, the roles of ATGL and PPAR-γ in hepatic fibrosis are context-dependent, supporting that various mechanisms can lead to HSC activation and fibrosis. Collectively, these studies will identify a mechanism of PEG-ASNase-induced HSC activation and hepatic fibrosis. This will help develop clinical strategies for preventing PEG-ASNase-induced hepatic fibrosis, increasing survival rates for adult ALL patients. The proposed training plan is sponsored by Dr. Fernandez and Dr. Xie. The overall goal of the training plan is to help Ms. Yin Zhu establish skills to be an independent researcher focusing on elucidating the underlying mechanisms of drug-induced liver injury. Including 1) mice generation and colony management, 2) gain- and loss-of-function in mice model, 3) develop skills in high-performance liquid chromatography-mass spectrometry (HPLC-MS), 4) hepatology knowledge, 5) bioinformatics and statistic skills, 6) mentoring skills, 7) teaching skills, 8) grant writing skills, 9) research independence and leadership skills, and 10) proficient in scientific communication. The overarching objective is to foster Ms. Yin Zhu to be a researcher in the realm of drug- induced liver injury.
