Suppression of IL-12 production by TTP through blocking NF-kappaB nuclear translocation (P3008)

Abstract

Abstract Tristetraprolin (TTP) plays a significant role in regulating the expression of AREs containing mRNAs. TTP-/- Mice develop a systemic autoimmune inflammatory syndrome characterized by cachexia, conjunctivitis and dermatitis. IL-12 plays a crucial role in immune defense against infectious and malignant diseases. In the present study, we found increased production of IL-12 during endotoxic shock and enhanced Th1 cells in TTP knockout mice. The levels of IL-12 p70 and p40 protein as well as p40 and p35 mRNA were also increased in activated macrophages deficient of TTP. In line with these findings, overexpression of TTP suppressed IL-12 p35 and p40 expression at the mRNA and promoter level, while surprisingly had no effects on their mRNA stability. Our data showed that the inhibitory effects of TTP on p35 gene transcription were completely rescued by overexpression of NF-kappaB p65 and c-Rel but not the p50 in activated macrophages. Our data further indicated that TTP acquired its inhibition on IL-12 expression through blocking nuclear translocation of NF-kappaB p65 and c-Rel while enhancing p50 upon stimulation. In summary, our study reveals a novel pathway through which TTP suppresses IL-12 production in macrophages, resulting in suppression of Th1 cell differentiation. This study may provide us with therapeutic targets for treatment of inflammatory and autoimmune disorders