Interleukin-1 beta regulation of the human brain natriuretic peptide promoter involves Ras-, Rac-, and p38 kinase-dependent pathways in cardiac myocytes

Because both the brain natriuretic peptide (BNP) gene and the cytokine inte rleukin-1 beta (IL-1 beta) are induced in the infarcted myocardium, localiz ed production of IL-1 beta may regulate the BNP gene. We tested whether (1) IL-1 beta regulates the human BNP promoter, (2) cis elements in the proxim al promoter respond to IL-1 beta, and (3) mitogen-activated protein kinase (MAPK) signaling pathways [p42/44, c-jun (JNK) and p38 kinase] are involved . We transferred the hBNP promoter coupled to a luciferase reporter gene or constructs with mutations in the proximal promoter GATA and M-CAT elements into neonatal rat ventricular myocytes and treated the cells with IL-1 bet a for 24 hours. IL-1 beta-stimulated hBNP luciferase activity was eliminate d by pretreatment with the transcription inhibitor actinomycin D, Both the p38 kinase inhibitor SB205380 (SB) and cotransfection of a dominant-negativ e mutant of p38 kinase reduced IL-1 beta stimulation of the hBNP promoter. Dominant-negative mutants of Ras and Rac inhibited IL-1 beta-stimulated hBN P luciferase activity by 64% and 90%, respectively. Constitutively active f orms of Rac and MKK6, the immediate upstream activator of p38, were stimula tory; however, only the effect of MKK6 was inhibited by SE. Neither the p42 /44 nor the JNK pathway was involved in the action of IL-1 beta. Both IL-1 beta and MKK6 activation of the hBNP promoter were partially reduced when t he promoter contained a mutated M-CAT element. In summary, (1) IL-1 beta is a transcriptional activator of the hBNP promoter; (2) IL-1 beta acts throu gh a Ras-dependent pathway not coupled to activation of p42/44 MAPK or JNK; (3) IL-1 beta acts through a Rac-dependent pathway, but the downstream eff ector is not known; and (4) IL-1 beta activation of p38 kinase is partially involved in regulation of the hBNP promoter, targeting the proximal M-CAT element.