Role of mitogen-activated protein kinase cascades in mediating lipopolysaccharide-stimulated induction of cyclooxygenase-2 and IL-1 beta in RAW264 macrophages

LPS stimulation of RAW264 macrophages triggered the activation of mitogen- and stress-activated protein kinases-1 and -2 (MSK1, MSK2) and their putati ve substrates, the transcription factors cyclic AMP response element-bindin g protein (CREB) and. activating transcription factor-1 (ATF1), The activat ion of MSK1/MSK2 was prevented by preincubating the cells with a combinatio n of two drugs that suppress activation of the classical mitogen-activated protein kinase cascade and stress-activated protein kinase/p38, respectivel y, but inhibition was only partial in the presence of either inhibitor. The LPS-stimulated activation of CREB and ATF1, the transcription of the cyclo oxygenase-2 (COX-2) and IL-1 beta genes (the promoters of which contain a c yclic AMP response element), and the induction of the COX-2 protein were pr evented by the same drug combination, as well as by Ro 318220 or H89, poten t inhibitors of MSK1/MSK2 Two other transcription factors, C/ERP beta and N F-kappa B have been implicated in the transcription of the COX-2 gene. Howe ver, PD 98059 and/or SE 203580 did not prevent the LPS-induced increase in the level of the transcription factor C/EBP beta, and none of the four inhi bitors used in this study prevented the activation of NF-kappa B, Our resul ts demonstrate that two different mitogen-activated protein kinase cascades are rate limiting for the LPS-induced activation of CREB/ATF1 and the tran scription of the COX-2 and IL-1 beta genes. They also suggest that MSK1 and MSK2 may play a role in these processes and hence are potential targets fo r the development of novel antiinflammatory drugs.