RUNX1 promotes denervation-induced muscle atrophy by activating the JUNB/NF-κB pathway and driving M1 macrophage polarization.

Abstract

Peripheral nerve injury-induced muscle atrophy is characterized by chronic inflammation and dysregulated macrophage polarization. RUNX1, a transcription factor upregulated in denervated muscle, has been implicated in linking muscle degeneration to inflammatory processes, but its downstream targets and mechanisms remain unclear. The aim of this study is to delineate the RUNX1-JUNB-NF-κB axis in driving inflammation-mediated muscle atrophy. The GSE183802 single-nucleus RNA sequencing dataset was analyzed to identify RUNX1-associated pathways. A sciatic nerve transection model in mice was established to validate RUNX1 expression dynamics. Chromatin immunoprecipitation, dual-luciferase reporter assays, and siRNA-mediated knockdown were used to confirm RUNX1's transcriptional regulation of JUNB. In vitro models (C2C12 myotubes, RAW 264.7 macrophages) assessed RUNX1-driven inflammatory responses, NF-κB activation, and extracellular matrix remodeling. RUNX1 was significantly upregulated in denervated muscle, particularly in myonuclei and macrophage subclusters, correlating with elevated atrophy markers (MuRF1, Atrogin-1). RUNX1 overexpression directly activated JUNB transcription via promoter binding, leading to NF-κB pathway activation (increased p65 phosphorylation) and M1 macrophage polarization (enhanced IL-1β/TNF-α secretion). JUNB knockdown reversed RUNX1-induced pro-inflammatory cytokine release, NF-κB signaling, and muscle atrophy markers. This study identifies the RUNX1-JUNB-NF-κB axis as a central regulator of inflammation-driven muscle atrophy following denervation. Targeting this pathway may offer therapeutic potential to mitigate neurogenic muscle degeneration and immune-mediated damage in conditions such as peripheral nerve injuries or motor neuron diseases.