Exosomes derived from mesenchymal stem cells (MSC EXO) have emerged as promising therapeutic candidates for pneumonia. However, the molecular mechanisms underlying MSC EXO-mediated pneumonia protection remain incompletely elucidated. WI-38 fibroblasts were exposed to lipopolysaccharide (LPS) in vitro, while an animal model of pneumonia was generated through intratracheal LPS administration in mice. MSC EXO were isolated and used to treat the pneumonia models. The efficacy of MSC EXO was evaluated by detecting cell viability, proliferation, apoptosis, and pro-inflammatory cytokine secretion. Glutathione S-transferase (GST) pull-down, co-immunoprecipitation (Co-IP), and immunoprecipitation (IP) assays were performed to verify the RNF144A/thyroid-stimulating hormone receptor (TSHR) interaction. TSHR was upregulated in pneumonia serum samples and LPS-stimulated WI-38 fibroblasts. TSHR knockdown attenuated LPS-triggered apoptosis and inflammatory damage in WI-38 fibroblasts. Moreover, ring finger protein 144A (RNF144A) destabilized TSHR through ubiquitination in WI-38 cells. MSC EXO increased RNF144A expression in LPS-stimulated WI-38 fibroblasts. Downregulation of RNF144A diminished the protective effects of MSC EXO against LPS-triggered damage in WI-38 fibroblasts and LPS-induced pneumonia in mice. Additionally, re-expression of TSHR reversed the protective effects of MSC EXO against LPS-triggered injuries in WI-38 fibroblasts. Our findings suggest that MSC EXO protect against LPS-triggered injuries in WI-38 fibroblasts and LPS-evoked pneumonia in mice through RNF144A upregulation-mediated suppression of TSHR expression. This study provides a novel theoretical foundation for the application of MSC EXO in pneumonia treatment.
