Targeting Kupffer Cell CD44-Mediated Ammonia Death via the ELAVL1-GLS Metabolic Circuit in Radiation-Induced Liver Disease.

Radiation-induced liver disease (RILD) remains a major dose-limiting toxicity in liver cancer radiotherapy. However, the underlying mechanisms, particularly the immunometabolic reprogramming that sustains inflammatory amplification following irradiation, are still poorly understood. Here, we report that Kupffer cell (KC) depletion significantly attenuated radiation-induced liver inflammation and injury. Irradiation markedly upregulated CD44 expression in KCs, and single-cell RNA sequencing revealed a CD44⁺ macrophage subset associated with injury, inflammatory activation, and metabolic stress signatures. Consistently, genetic deletion or pharmacological inhibition of CD44 protected against RILD by suppressing KC M1 polarization, oxidative stress accumulation, and inflammatory cytokine output. Furthermore, radiation exposure profoundly disrupted nitrogen homeostasis and increased intracellular ammonia levels, effects that were abrogated by CD44 deficiency. Mechanistically, CD44 stabilized the RNA-binding protein ELAVL1 by inhibiting its proteasomal degradation, which subsequently increased the abundance and activity of glutaminase (GLS), elevated the intracellular ammonia burden, and triggered macrophage death. Pharmacological inhibition of GLS with CB-839 rescued the injurious phenotype, while exogenous NH4Cl supplementation confirmed the ammonia dependence of the downstream phenotypes. Our findings reveal a CD44-ELAVL1-GLS immunometabolic circuit that links radiation stress to ammonia dysregulation in KCs and subsequent liver injury, suggesting a potential therapeutic target for RILD.