The Different Effects of Pharmacological or Low-Doses of IFN-γ on Endothelial Cells are Mediated by Distinct Intracellular Signalling Pathways

Background: Interferon (IFN)-γ is a proinflammatory cytokine with a crucial role in intercellular communication during innate and acquired immune responses. IFN-γ interacts with various cell types, including endothelial cells. Here, we investigated the effects of pharmacological or low doses of IFN-γ in cultured endothelial cells. Methods: Human endothelial cells were cultured in the presence of pharmacological or low-dose concentrations of IFN-γ. Signal transducer and activator of transcription (STAT) and Extracellular signal-regulated kinase (ERK) phosphorylation were investi- gated by enzyme linked immunosorbent assay (ELISA). Western blot for ERK was also performed. Transient ERK silencing was obtained by short interfering RNA (siRNA). Cell proliferation and migration were analysed by cell counting and wound assay, respectively. Results: At pharmacological concentrations, IFN-γ activates the Janus kinases (JAK)/STAT pathway, leading to the overexpres- sion of the cyclin-dependent kinase inhibitor 1A/p21 (CDKN1A/p21), which inhibits cell growth. In contrast, low-dose activated IFN-γ does not trigger the canonical JAK/STAT pathway and induces the phosphorylation of ERK. ERK activation is responsible for endothelial cell migration induced by low-dose activated IFN-γ. Conclusions: We demonstrate that pharmacological and low-dose activated IFN-γ exert distinct effects on endothelial cells by triggering different signal transduction pathways. These findings shed light on the intricate signalling pathways employed by IFN-γ, and suggest that low-doses of IFN-γ might play a homeostatic role in endothelial cell during innate and acquired immune responses.