Failed Hepatocyte Eviction Drives Zonation Loss via Nrf2-Mediated Ferroptosis Adaptation and Senescence-Associated Wnt Antagonism

Hypothesis: The liver’s attempt to remove inefficient hepatocytes via ferroptosis is subverted by Nrf2‑driven metabolic reprogramming that creates a survival‑competent but senescent population. These ferroptosis‑adapted hepatocytes upregulate cystine/glutamate exchange (SLC7A11) to boost glutathione, thereby resisting lipid‑peroxide‑dependent death【Aging promotes ferroptotic signaling in hepatocytes, creating ferroptosis-adapted cells that survive but remain dysfunctional](https://pmc.ncbi.nlm.nih.gov/articles/PMC12810195/)】. The heightened cystine uptake depletes extracellular cystine, compromising the antioxidant capacity of neighboring Zone 2 hepatocytes and distorting the oxidative gradient that patterns Wnt/β‑catenin signaling. Senescent adapted cells further secrete Wnt antagonists such as DKK1 and sFRPs, flattening the zonation cascade. Consequently, metabolic zonation collapses, lipogenic enzymes invade periportal zones, and fatty acid oxidation fails in pericentral regions, driving steatosis. This mechanism is especially pronounced in Zone 3, where low oxygen predisposes cells to ferroptotic pressure【Zone 3 hepatocytes are preferentially affected by steatosis due to their inherent low-oxygen microenvironment](https://pmc.ncbi.nlm.nih.gov/articles/PMC9790419/)】 and where mitochondrial dysfunction limits fatty acid oxidation【Senescent hepatocytes display mitochondrial dysfunction and reduced capacity for fatty acid metabolism](https://doi.org/10.1038/ncomms15691)】. Eliminating senescent cells with senolytics reduces fat accumulation, showing a causal link【Cellular senescence causally drives age-dependent hepatic steatosis, and eliminating senescent cells reduces fat accumulation](https://doi.org/10.1038/ncomms15691)】, while loss of zonation marks progression to NASH【Progression to NASH is associated with loss of metabolic zonation](https://pmc.ncbi.nlm.nih.gov/articles/PMC9790419/)】.

Predictions: (1) Hepatocyte‑specific Nrf2 knockout in a MASLD mouse model will prevent the formation of ferroptosis‑adapted cells, lower senescent burden (p16^hi^ cells), and preserve zonation markers (CYP2E1^high^ in Zone 3, glutamine synthetase^high^ in Zone 1). (2) Pharmacologic Nrf2 activation will expand the adapted pool, accelerate zonation loss, and worsen steatosis despite unchanged iron load. (3) Combining a senolytic (e.g., navitoclax) with Nrf2 inhibition will clear existing senescent hepatocytes and block the adaptive replenishment pathway, yielding a greater reduction in steatosis than either treatment alone. (4) Hepatic cystine levels will be inversely correlated with zonation integrity and directly correlated with the proportion of SLC7A11^high^ hepatocytes.

Falsifiable outcomes: If Nrf2 loss does not diminish ferroptosis‑adapted hepatocyte frequency or if zonation remains disrupted despite reduced senescence, the hypothesis is refuted. Similarly, if Nrf2 activation fails to increase the adapted population or exacerbate zonation loss, the proposed mechanistic link between Nrf2‑mediated cystine uptake and zonation collapse is invalid.