Fig. 5.

Expression of intracellular IL-1α activates NF-κB in a surface IL-1R-independent manner. MS1 cells were transfected with the empty vector (vector) or with expression vectors encoding pIL-1α, mIL-1α, ppIL-1α, or pIL-18. In each case, cells were cotransfected with a vector containing the NF-κB enhancer upstream of the luciferase gene and pNULL-Renilla. Transfection and culture were performed in the presence of saturating concentrations of IL-1Ra (10 μg/ml) for IL-1 constructs or IL-18BP (1 μg/ml) for the pIL-18 construct. MS-1 WT, cells transfected with the pNFκB-LUC and pNULL-Renilla only (Upper). Mouse embryo fibroblasts from BALB/c and IL-1α-deficient (IL-1α–/–) mice were transfected with pNFκB-LUC and pNULL-Renilla in the presence of IL-1Ra as indicated. On the next day, medium was removed, cells were washed, and fresh medium with or without IL-1Ra was added. Cells were activated with 10 ng/ml TNF-α. Twenty-four hours later, cells were lysed and luciferase was measured (Lower). Data represent the mean ± SEM of three separate experiments performed in triplicate.