Background Human antigen R (HuR) is a ubiquitously expressed member of the ELAV family,and has relatively high cytoplasmic abundance in lung tissue regenerating after injury.In this study,we investigated whether mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MK2) and HuR participate in the tumor necrosis factor (TNF)-induced expression of interleukin-6 (IL-6).Methods Human pulmonary microvascular endothelial cells were treated with TNF following short interfering RNA-mediated knockdown of MK2 or HuR.Cell supatants were collected to detect the mRNA and protein expression of IL-6 at different time points.The expression and half-life of IL-6 mRNA were then determined in cells that had been treated with actinomycin D.Finally,after knockdown of MK2,the cytoplasmic expression of HuR protein was analyzed using West blotting.Results MK2 or HuR knockdown decreased both the mRNA and protein expression of Ik-6 in TNF-stimulated cells.In MK2 knockdown cells,the half-life of IL-6 mRNA was reduced to 36 minutes,compared with 67 minutes in the control group.In HuR knockdown cells,the half-life of IL-6 mRNA decreased from 62 minutes to 24 minutes.Further analysis revealed that knockdown of MK2 resulted in reduced HuR protein expression in the cytoplasm.Conclusions MK2 regulates the TNF-induced expression of IL-6 by influencing the cytoplasmic levels of HuR.