Radiation combined with PD-1 inhibitor induces time-dependent changes in myocardial injury by regulating HMGB1-associated inflammatory microenvironment

Abstract

Background PD-1 inhibitors may superimpose the toxicity of radiotherapy while increasing the antitumor effect. However, there are fewer studies on immune myocarditis caused by radiotherapy plus anti-PD-1 and the mechanism is still under exploration. Methods 40 C57BL/6 mice were randomly assigned to 4 groups. A: Control, B: PD-1 inhibitor, C: cardiac irradiation and D: thoracic irradiation + PD-1 inhibitor, mice were treated with either anti-PD-1 antibody with or without thoracic radiation (15Gy). Each group contained ten mice, five of which were studied for a duration of 1 month and the remaining five for 3 months. Tunel staining was utilized to observe apoptosis of cardiac tissues; histological analysis was performed to analyze the structural and morphological alterations, fibrosis of the heart tissue. The infiltration of CD3+, CD4+, and CD8 + T-cells into the cardiac was analyzed through flow cytometry; Elisa measured the expression levels of TNF-α, IL-1β, and TLR-4 in the cardiac; and immunoprotein blotting and qPCR were used to observe the protein and mRNA expression levels of HMGB1, TLR-4, and NF-κB p65. Results Group D exhibited a greater degree of cardiac injury, fibrosis, and apoptosis in comparison to groups A, B, and C. Additionally, there was an increase in injury, AI, and CVF values after three months as opposed to one month (P < 0.05).After one month, there was no statistically significant difference in cardiac damage, AI, or CVF values between groups A and B; however, after three months, there was a significant difference (P < 0.05). Group D also had higher levels of IL-1β, IL-6, TNF-α and T-lymphocyte distribution, HMGB1, TLR4, NF-κB P65 protein, and mRNA expression than the other three groups. However, each group's index expression declined over the course of three months as opposed to one month, and this difference was statistically significant (P < 0.05). Conclusion PD-1 inhibitors exacerbated myocardial injury based on radiation by upregulating the expression of inflammatory factors in the HMGB1 signaling pathway. In the early stages of myocardial damage, inflammatory alterations predominated, while in the later stages, fibrosis.