Increased Expression of TRAIL and Its Death Receptors TRAIL-R1/2 Correlates with Progression of Radioactive Skin Injury

Abstract

Background: The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) serves as a key mediator of apoptosis and inflammation. However, the role of TRAIL and its receptors in ionizing radiation (IR)-induced skin injury remains unclear. Soluble death receptor 5-Fc (sDR5-Fc), a synthetic TRAIL blocking agent, is comprised of the small, unstable, and short half-life endogenous human soluble death receptor 5 (sDR5) molecule along with the Fc portion of human immunoglobulin 1 (IgG 1). This compound has demonstrated efficacy in treating various diseases induced by TRAIL. The primary objective of this study was to investigate whether the TRAIL signaling pathway is implicated in the development of radiation-induced skin injury and to assess whether sDR5-Fc could alleviate such damage. Methods: The expression of TRAIL and its receptors in IR-induced human cells and C57 mouse skin was investigated through the application of immunohistochemistry (IHC) and flow cytometry (FCM). FCM and the Cell Counting Kit-8 (CCK-8) assay were employed to assess the apoptotic and proliferative effects of TRAIL on human keratinocyte (HaCat) cells. The potential alleviation of IR-induced skin damage in HaCat and human foreskin fibroblast-1 (HFF-1) cells, as well as in C57 mice, by sDR5-Fc, was examined using Western Blot (WB), flow cytometry (FCM), terminal deoxynucleotidyl transferase-mediated dUTP Nick-End Labeling (TUNEL) assay, and hematoxylin-eosin (H&E) staining. Results: The expression of TRAIL and TRAIL-R2 in the skin tissues of mice was upregulated after exposure to 30 gamma rays (Gy). Following IR, the expression of secreted TRAIL (sTRAIL), as well as TRAIL-R1 and TRAIL-R2 on the surface of HaCat cells, significantly increased. The addition of TRAIL induced apoptosis and dose-dependently inhibited the proliferation of HaCat cells. IR induced apoptosis in HaCat cells in a manner dependent on both time and dose, directly and through the bypass effect. This inhibited cell proliferation and stimulated interleukin-6 (IL-6) secretion from HaCat cells, which could be partially prevented by sDR5-Fc treatment. Furthermore, sDR5-Fc alleviated radiation-induced skin injury in mice, resulting in a significantly lower skin injury score, a thinner epidermis, more hair follicles, and fewer collagen fibers. Conclusions: We have demonstrated that TRAIL signaling plays a role in the pathogenesis of radiation-induced skin injury. This injury is alleviated both in vivo and in vitro through the use of sDR5-Fc, a TRAIL blocker.