Purpose: To explore the effect of PD-1 inhibitors combined with irradiation on myocardial injury and the changes of HMGB1-associated inflammatory markers.
Methods: Four groups of five mice were used, each groupformed by randomly dividing 20 mice (group A control; group B PD-1 inhibitors; group C Irradiation; group D PD-1 inhibitors+irradiation; n = 5 for each). The mice were treated with either PD-1 inhibitors or a 15 Gy dose of single heart irradiation, or both. Hematoxylin-eosin staining assessed the morphology and pathology of heart tissue; Masson staining assessed heart fibrosis; Tunel staining evaluated heart apoptosis; flow cytometry detected CD3+, CD4+, and CD8+ T lymphocytes in heart tissues; enzyme linked immunosorbent assay evaluated IL-1β, IL-6, and TNF-ɑ of heart tissue; Western blot and quantitative real-time PCR (qPCR) detected the expression of protein and mRNA of HMGB1, TLR-4, and NF-κB p65 respectively.
Results: The degree of heart injury, collagen volume fraction (CVF) and apoptotic index (AI) in groups B, C, and D were higher than group A, but the differences between the CVF and AI of group A and group B were not statistical significance (P> 0.05). Similarly, the absolute counts and relative percentage of CD3+ and CD8+ T lymphocytes and the concentrations of IL-1β, IL-6, and TNF-α in heart tissue with group D were significantly higher than the other groups (P< 0.05). In addition, compared with group A, the expression of protein and mRNA of HMGB1 and NF-κB p65 in other groups were higher, and the differences between each group were statistically significant while TLR4 was not. In addition, interaction by PD-1 inhibitors and irradiation was found in inflammatory indicators, especially in the expression of the HMGB1 and CD8+ T lymphocytes.
Conclusion: PD-1 inhibitors can increase the expression of HMGB1-associated inflammatory cytokines and aggravate radiation-induced myocardial injury.
Keywords: HMGB1, PD-1 inhibitors, radiotherapy, heart injury