Targeting the SIRT1-TLR4 axis attenuates oxidative inflammation in a cellular model of bronchopulmonary dysplasia.

Abstract

Bronchopulmonary dysplasia (BPD) features arrested alveolarization with persistent, oxidative inflammation. How the SIRT1-TLR4 axis regulates this program remains unclear. RAW264.7 macrophages and MLE-12 epithelial cells were exposed to 95% O₂ (24 h) or 60% O₂ (48 h); LPS served as a TLR4-pathway comparator. SIRT1 and TLR4 were overexpressed; resveratrol activated SIRT1. Outcomes were quantified by qPCR/immunoblot/ELISA, viability/apoptosis/EdU and MitoSOX microplate readouts. Conditioned medium (CM) tested paracrine effects. ChIP-qPCR assessed p65 occupancy at two κB sites in the murine Tlr4 promoter. Human relevance was examined by GEO2R (GSE32472). Hyperoxia (and LPS) suppressed SIRT1, upregulated TLR4, and activated NF-κB, increasing IL-1β/IL-6/TNF-α and mitochondrial ROS. SIRT1 overexpression or resveratrol reduced cytokines, apoptosis, and MitoSOX, improved macrophage viability, and preserved epithelial junctions/proliferation. Conditioned medium (CM) from SIRT1-modified macrophages protected MLE-12 from hyperoxic injury, whereas TLR4 overexpression abrogated these benefits. Mechanistically, hyperoxia increased p65 binding at two Tlr4 κB sites, which SIRT1 reduced. GEO2R showed lower SIRT1 and higher TLR4 in severe BPD versus controls. SIRT1 constrains hyperoxia-driven TLR4/NF-κB activation and mitigates macrophage-to-epithelial injury. Together with human-correlative data, these in-vitro findings support a candidate SIRT1-TLR4 axis that warrants in-vivo validation. This study suggests a candidate SIRT1-TLR4 axis that restrains oxidative inflammation in BPD-relevant cell models, providing mechanistic hypotheses for future in vivo and human validation. This is the first study to demonstrate the dual role of SIRT1 in modulating macrophage-driven inflammation and epithelial barrier preservation in a BPD-relevant cellular model. Pharmacological or genetic modulation of SIRT1 may represent a promising strategy for early intervention in neonatal lung injury by targeting TLR4-dependent signaling pathways.