The combination of
carbon ion radiotherapy and anti-PD-1 antibody represents a new approach to treating thoracic
tumors. However, the lung damage caused by this combination
therapy may limit its use, and the potential mechanisms for this are worthy of investigation. The objective of this research was to examine the potential involvement of repulsive guidance molecule b (RGMb) in lung damage promoted by the utilization of
carbon ion irradiation combined with an anti-PD-1 antibody. The C57BL/6 mice have been randomly separated into four distinct groups: control, anti-PD-1, whole thorax
carbon ion irradiation, and irradiation in combination with anti-PD-1 treatment groups (combination group). Detection of pathological changes in lung tissue using HE staining. Detection of
pulmonary fibrosis by Masson staining and the
hydroxyproline assay. ELISA to detect TNF-α, TGF-β,
IL-6, and IL-1β expression levels within lung homogenates. The expression of RGMb,
p38 MAPK, and Erk1/2 pathways was detected using a fully automated digital Western blotting system WES (ProteinSimple, USA). Flow cytometry was employed to analyze tissue-resident memory T cells (TRM) within the lung. Subsequently, the
siRNA gene was employed to induce the downregulation of RGMb in mice in order to validate the involvement of RGMb in radiation-immune
lung injury. The present study observed a significant increase in both inflammatory and fibrotic indicators within the mice group's lung tissue that received the combination treatment. The combination group exhibited elevated levels of TGF-β, TNF-α,
IL-6, and IL-1β in lung homogenates. Anti-PD-1 antibody and
carbon ion irradiation, upregulated RGMb, phospho-p38 MAPK and phospho-Erk1/2. The results obtained from the flow cytometry analysis indicated that the combination group was significantly higher in the number of clonal expansion TRMs, which were predominantly characterized by the expression of CD8+CD103+CD69-TRMs. The downregulate of RGMb via
siRNA in mice resulted in a decrease in phospho-p38 MAPK and phospho-Erk1/2. The combination group exhibited a reduction in TNF-α, TGF-β,
IL-6, and IL-1β in their lung tissues, and the number of CD8+CD103+CD69-TRM was significantly reduced. The combination group exhibited a significant improvement in inflammatory and fibrotic indicators within the lung tissues. Anti-PD-1 antibody and
carbon ion irradiation synergistically regulate RGMb, leading to strong clonal expansion of lung TRM through the
p38 MAPK and Erk1/2 pathways. The present study offers valuable insights into the treatment of
lung injury due to the combined administration of
carbon ion radiotherapy and anti-PD-1 antibody
therapy.