Interleukin 1 increases stability and transcription of mRNA encoding nerve growth factor in cultured rat fibroblasts

The lymphokine interleukin 1 (IL-1) rapidly increases the levels of mRNA encoding nerve growth factor (NGF) in primary cultures of fibroblasts isolated from adult rat sciatic nerves. The effect of IL-1 on NGF-mRNA was not inhibited by cycloheximide, which itself increased the NGF-mRNA. From the blocking ability of actinomycin D, it was deduced that the IL-1 action depends on continuous RNA synthesis and that the half-life of NGF-mRNA is about 90 min. Nuclear run-on studies showed that, although IL-1 enhances the low basic NGF-mRNA transcription, the main effect of IL-1 results from stabilization of the NGF-mRNA. In addition, indirect evidence is presented indicating that the IL-1 effect of NGF-mRNA levels involves activation of phospholipase A2.