Efferocytosis Modulates Inflammatory Responses and M1 Macrophage Phenotype in Ultraviolet B-Induced Corneal Stromal Fibroblast Apoptosis

초록

Purpose : To examine the role of efferocytosis in maintaining corneal homeostasis following ultraviolet B (UVB)-induced human keratocyte apoptosis and its impact on inflammatory responses and the M1 macrophage phenotype in the surrounding microenvironment Methods : Human corneal stromal fibroblasts (HCFs) were exposed to UVB radiation (150 mJ/cm^2) to induce apoptosis and co-cultured with M1 macrophages in a transwell system that allowed macrophage infiltration through insert pores. In this in vitro efferocytosis model, UVB-irradiated HCFs (BHCFs) were assessed for efferocytosis markers, including milk fat globule epidermal growth factor 8 (MFG-E8) and MER proto-oncogene, tyrosine kinase (MERTK), and inflammatory cytokines such as interleukin (IL)-1β and IL-6, using qRT-PCR. Paracrine effects on nearby M1 macrophages were evaluated by assessing changes in inflammatory and anti-inflammatory cytokine profiles and myeloid or macrophage marker expression. Results : UVB exposure increased apoptotic markers in HCFs, indicated by elevated Bax/Bcl-2 and APAF1 expression. Immunofluorescence confirmed efferocytosis between BHCFs and M1 macrophages. Efferocytosis markers MFG-E8 and MERTK were significantly upregulated in BHCFs co-cultured with M1 macrophages, along with a suppression of pro-inflammatory cytokines IL-1β and IL-6. Microenvironmental M1 macrophages showed decreased IL-1β, increased tumor necrosis factor beta 1 expression, and downregulation of myeloid and macrophage markers such as Cd14, Cd68, Cd80, and Cd11c. Conclusions : Efferocytosis plays a critical role in maintaining corneal homeostasis following UVB-induced keratocyte apoptosis by modulating inflammatory responses and altering macrophage phenotype. These findings suggest that an efferocytosis mechanism may exist in the corneal stromal layer under UVB irradiation, supporting immunological homeostasis in cornea.