ACSL4 and its tumor protective role in chronic liver disease

Question The prevalence of non-alcoholic fatty liver disease, ranging from steatosis to non-alcoholic steatohepatitis (NASH), is increasing in developed countries. In some patients, progression towards cirrhosis and hepatocellular carcinoma (HCC) occurs. At present, the underlying mechanisms for disease progression remain incompletely understood. In NASH oxidative stress and lipid peroxidation constitute prominent features and may hence play a key role. Interestingly, accumulation of lipid peroxides can trigger ferroptosis, an iron-dependent mode of cell death. According to in vitro studies, acyl-CoA synthetase long-chain family member 4 (ACSL4) is an essential contributor to ferroptosis. In our study, we aimed to investigate the relevance of ferroptosis for disease progression using hepatocyte-specific ACSL4 inhibition in experimental models of chronic liver disease.

Methods Primary hepatocytes from either wild-type (WT) mice or animals with hepatocyte-specific deletion of ACSL4 (ACSL4Δhepa) were treated with specific inducers (e.g., RSL3) and inhibitors (e.g., Liproxstatin-1) of ferroptosis. In addition, we compared disease development between WT and ACSL4Δhepa mice to investigate the role of ferroptosis. We used STZ (Streptozocin) with high-fat diet as a NASH-HCC model.

Results Treatment of primary hepatocytes with RSL3 leads to increased cell death, which could be rescued by adding Liproxstatin-1 or by using ACSL4-deficient hepatocytes. In our NASH-HCC model, inhibition of ferroptosis in hepatocytes reduces the severity of chronic liver disease as evidenced by decreased serum transaminase levels in ACSL4Δhepa mice. Importantly, while the overall tumor burden was not affected in ACSL4Δhepa mice, the number of smaller tumors was significantly increased. Interestingly, infiltration of immune cells, especially macrophages and granulocytes, was significantly decreased in ACSL4Δhepa mice. Moreover, earlier evaluation of tumorigenesis showed more tumors as well as higher tumor burden in ACSL4Δhepa mice.

Conclusion Our results demonstrate that primary mouse hepatocytes are susceptible to induction of ferroptosis and that this mode of cell death depends on functional ACSL4. Interestingly, ferroptosis has a protective mechanism during tumor initiation, by regulating lipid accumulation and cell death in hepatocytes. Therefore, activation of ferroptosis or inhibiting key molecules regulating cell death, can be a possible therapeutic treatment for human diseases.

Publication History

Article published online:
04 January 2021