The role of ferroptosis in chronic and acute liver diseases

• Die Rolle der Ferroptose in chronischen und akuten Lebererkrankungen

Grube, Julia; Zimmer-Bensch, Geraldine Marion (Thesis advisor); Trautwein, Christian (Thesis advisor); Pradel, Gabriele (Thesis advisor)

Aachen (2022)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2022

Abstract

Ferroptosis is a new form of programmed cell death that differs from apoptosis in that it involves iron-dependent peroxidation of membrane phospholipids. In recent years, ferroptosis has been hypothesised to play a role in several human diseases, including cancer and acute liver injury. While ferroptosis may act as an endogenous tumour suppressor in several cancers, its role in the development and progression of liver cancer, particularlyhepatocellular carcinoma (HCC), is still unknown. According to in vitro studies, ACSL4 (Acyl-CoA synthetase long chain family member 4) plays a major role in ferroptosis. HCC patients showed an association between increased ACSL4 expression and complete or partial response to sorafenib treatment.In drug-induced liver injury (DILI) drugs can cause aberrant transaminases, including life-threatening acute liver failure. Previous studies have shown an impact of ferroptosis in acetaminophen (APAP)-induced hepatotoxicity. However, the role in other DILIs is not fully elucidated. In APAP-induced cell death, inhibition of ferroptosis mediator GPX4 (glutathione peroxidase 4) activity was shown to occur. Therefore, the present work aimed to investigate the relevance of ferroptosis for disease progression using hepatocyte-specific ACSL4 deletion in models of chronic liver disease, as well as hepatocyte-specific GPX4 deletion in models of acute liver injury. Because HCC occurs most frequently in chronically injured livers, we used two established mouse models of chronic injury-dependent HCC formation: Streptozotocin (STZ) treatment and high-fat diet as a model for metabolic injury, and diethylnitrosamine (DEN) and carbon tetrachloride (CCl4) treatment as a model for toxic injury. A shorttreatment with the hepatotoxin (CCl4) was performed to induce liver failure. Interestingly, preventing ferroptotic cell death in hepatocytes by deleting ACSL4 does not lead to increased HCC formation. Moreover, ACSL4-deficient livers show less fibrosis and proliferation, especially in the HCC model with toxic damage. Furthermore, in this model, the absence of ACSL4-dependent ferroptosis significantly slows HCC growth. On the other hand, GPX4-deficient livers exhibited increased liver injury and cell death after short-term treatment with (CCl4). Remarkably, this effect was completely reversed by the additional deletion of KEAP1.These results suggest that ferroptotic cell death during HCC formation in a chronically damaged liver is not an endogenous tumour suppressive mechanism. Instead, we find that ACSL4-dependent ferroptosis has an unexpected cancer-promoting effect during HCC formation, most likely due to exacerbated liver injury as evidenced by increased liver fibrosis. Previous studies have shown that ferroptosis is beneficial for patients following HCC therapy with sorafenib or chemotherapy. Consequently, ferroptosis appears to have both cancer-promoting and cancer-inhibiting effects during HCC progression and therapy.In addition, ferroptosis plays an important role in DILI. Our results have shown that GPX4-dependent ferroptosis exacerbates liver damage occurring in DILI. Further studies should be conducted to understand the specific mechanisms of ferroptosis in the development of acute liver injury to develop novel therapeutic approaches.