Single-cell transcriptome analysis of low-dose radiotherapy-mediated alleviation of LPS-induced acute lung injury

Acute lung injury (ALI), a condition with a high incidence and mortality rate worldwide, is a type of acute respiratory failure characterized by infiltrative lesions in the lungs. Low-dose radiation therapy (LDRT), which uses less than 1 Gy X-ray per session, has been tested for its clinical feasibility in suppressing lung inflammation in conditions that cause ALI. However, a mechanistic understanding of how LDRT alleviates inflammation in the lungs and restores balance in the immune environment is still lacking. In this study, we assessed the immunomodulatory effects of LDRT using single-cell RNA sequencing (scRNA-seq) and flow cytometry in a lipopolysaccharide (LPS)-induced ALI mouse model. LDRT with 1 Gy X-rays reduced the lung inflammation, immunostimulatory cells such as M1 macrophages, and pro-inflammatory cytokines such as interleukin 6 in the bronchoalveolar lavage fluid, while increasing the levels of immunosuppressive cells such as M2 macrophages and the anti-inflammatory cytokine TGF-ß. Furthermore, scRNA-seq analysis of whole lung tissues confirmed that LDRT reduced the number of macrophages and neutrophils and downregulated the genes involved in inflammatory response pathways. Flow cytometry showed that LDRT effectively eliminated pro-inflammatory immune cells via apoptosis. Our findings underscore the potential utility of LDRT in ALI treatment by rebalancing immune homeostasis. Overall design: RNA-seq profiling of mouse lung tissue after injection of PBS or LPS for 48 hours, and low-dose radiation for 24 hours.