Effects of ionizing radiation on retinoic acid-inducible gene-I-like receptors.

Retinoic acid-inducible gene-I (RIG-I)-like receptors [RLRs; RIG-I and melanoma differentiation-associated gene 5 (MDA5)] sense virus-derived RNA or a synthetic analog of double-stranded RNA polyinosinic-polycytidylic acid [poly(I:C)] and are responsible for host defense against viruses. However, it remains unclear whether radiation affects RLRs. Therefore, the present study investigated the effects of ionizing radiation on RIG-I and MDA5 expression and the response to poly(I:C) using THP1 (human monocytic cell line)-derived macrophages. Non- and X-irradiated (1-10 Gy) macrophages expressed RIG-I and MDA5 at mRNA and protein levels and there was no significant difference in the expression levels. Non- and X-irradiated macrophages expressed antiviral cytokine interferon (IFN)-β mRNA following poly(I:C)-low molecular weight/LyoVec™ and poly(I:C)-high molecular weight/LyoVec™ stimulation, the agonist of RIG-I and MDA5, respectively. In line with the results of the expression of RIG-I and MDA5, no significant difference in the expression of IFN-β mRNA was observed between non- and X-irradiation. These results indicate that ionizing radiation hardly affects RLR expression and the response to their agonist poly(I:C) in THP1-derived macrophages.