Oxidative Stress Mechanisms in Liver Fibrosis

Liver fibrosis arises from a sustained imbalance between the generation of reactive oxygen species (ROS) and the capacity of antioxidant systems to neutralise them. Under physiological conditions, mitochondria, cytochrome P450 enzymes and NADPH oxidases (NOX) generate ROS as by-products of metabolism and detoxification. In chronic liver injury, excessive ROS production provokes lipid peroxidation, protein oxidation and DNA damage, driving inflammation and activation of hepatic stellate cells (HSCs). Activated HSCs transdifferentiate into myofibroblasts that deposit extracellular matrix proteins, notably type I collagen, culminating in fibrotic scarring. Central to this process is the interplay between ROS and cytokine signalling: ROS enhance transforming growth factor-β (TGF-β) pathways, while TGF-β further stimulates ROS production via NOX isoforms. At the same time, nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates an antioxidant response that can delay fibrosis but is often overwhelmed in progressive disease. Crosstalk with immune cells, including Kupffer cells and infiltrating macrophages, exacerbates oxidative injury through additional NOX-dependent ROS bursts. Understanding these mechanistic networks has informed global efforts to target redox balance, from small-molecule NOX inhibitors to dietary antioxidants, with the aim of interrupting fibrogenic feedback loops and preserving liver architecture.

Research from Nature Portfolio

Recent studies have shown that infiltrating hepatic macrophages generate ROS through dynamin-mediated endocytosis of a monomeric Toll-like receptor 4–MD2 complex, activating NOX2 independently of canonical adaptor proteins. This mechanism links lipid stimuli to innate immune ROS production, promoting pro-inflammatory cytokine expression and fibrogenic signalling. In parallel, investigations into NADPH oxidase 4 (Nox4) in hepatocytes have revealed that Nox4 expression is upregulated by lipopolysaccharide stimulation via TLR4 signalling. Nox4 amplifies NF-κB and AP-1 pathway activation, augmenting tumour necrosis factor-α release and proliferative responses. In Nox4-deficient models, attenuated cytokine induction and reduced cell proliferation highlight Nox4 as a modulator of inflammation-driven fibrosis.

Oxidative Stress Mechanisms in Liver Fibrosis publication trend

The graph below shows the total number of articles in oxidative stress mechanisms in liver fibrosis across all publications each year (not limited to Nature Index journals).

Technical terms

Reactive oxygen species (ROS): chemically reactive molecules containing oxygen that can cause cellular damage.

Hepatic stellate cell (HSC): pericyte-like cells in the liver that, on activation, secrete extracellular matrix proteins.

NADPH oxidase (NOX): enzyme complex that produces ROS by transferring electrons from NADPH to oxygen.

Nuclear factor erythroid 2-related factor 2 (Nrf2): transcription factor regulating antioxidant gene expression.

NLRP3 inflammasome: multiprotein complex that activates inflammatory cytokines in response to stress signals.

References

1. Mitochondrial- and NOX4-dependent antioxidant defence mitigates progression to non-alcoholic steatohepatitis in obesity. Journal of Clinical Investigation (2023).
2. Oxidative Stress in Liver Pathophysiology and Disease. Antioxidants (2023).
3. Pro-inflammatory hepatic macrophages generate ROS through NADPH oxidase 2 via endocytosis of monomeric TLR4–MD2 complex. Nature Communications (2017).
4. NADPH oxidase 4 modulates hepatic responses to lipopolysaccharide mediated by Toll-like receptor-4. Scientific Reports (2017).
5. Ursolic acid reverses liver fibrosis by inhibiting NOX4/NLRP3 inflammasome pathways and bacterial dysbiosis. Gut Microbes (2021).