Fatty Acid-Driven Metabolic Reprogramming Impairs Macrophage Efferocytosis in AKI

Background: Timely clearance of apoptotic cells by macrophages (efferocytosis) is essential for resolution of inflammation and restoration of tissue homeostasis after acute kidney injury (AKI). However, how the injury-associated microenvironment modulates macrophage efferocytic function remains unclear. Methods: We used a murine model of ischemia/reperfusion (I/R)-induced AKI to investigate how local metabolic signals regulate macrophage efferocytosis. Single-cell RNA sequencing (scRNA-seq), lipidomic profiling, and biochemical assays were employed to identify transcriptional and signaling changes in kidney macrophages. Functional studies included genetic deletion and peptide inhibition of Regulator of G-protein signaling 1 (RGS1) to evaluate efferocytic capacity and renal repair outcomes. Results: Following I/R injury, extracellular fatty acids accumulated in the injury-associated microenvironment and suppressed macrophage efferocytosis. scRNA-seq identified a distinct subset of efferocytosis-exhausted macrophages with upregulated Rgs1, induced by fatty acid-activated PPARα signaling. Mechanistically, fatty acids also promoted palmitoylation of RGS1, enhancing its interaction with and inhibition of Rac1, a GTPase essential for actin cytoskeletal remodeling during efferocytosis. Loss of RGS1 restored Rac1 activity and efferocytosis, accelerating resolution of inflammation and recovery of kidney function. A novel peptide that blocks RGS1 palmitoylation similarly enhanced apoptotic cell clearance, suppressed proinflammatory cytokine release, and improved functional recovery in vivo. Conclusion: These findings reveal a dual mechanism by which fatty acids in the injury-associated microenvironment transcriptionally and post-translationally reprogram macrophages to impair efferocytosis. RGS1 emerges as a critical metabolic checkpoint in AKI, offering a potential therapeutic target to enhance inflammation resolution and tissue repair.