Interleukin-1beta regulates the human brain natriuretic peptide promoter via Ca(2+)-dependent protein kinase pathways

We have shown that interleukin-1beta (IL-1beta) activates the human brain natriuretic peptide (hBNP) promoter via a transcriptional mechanism. Others have reported that changes in intracellular calcium (Ca(2+)) mediate the action of IL-1beta. We questioned whether Ca(2+) and Ca(2+)-dependent pathways mediate IL-1beta regulation of the hBNP promoter in cardiac myocytes. The hBNP promoter (-1818 to +100) coupled to a luciferase cDNA reporter gene was transferred into neonatal cardiac myocytes. Cells were then treated with agents that modify Ca(2+) levels or inhibit Ca(2+)-dependent kinases, and luciferase activity was measured as an index of hBNP promoter activity. The Ca(2+) ionophore A23187 increased hBNP promoter activity; however, neither EGTA nor nifedipine reduced IL-1beta-stimulated promoter activity. Long-term treatment with thapsigargin, which depletes intracellular Ca(2+) stores, decreased basal promoter activity and blocked the effect of IL-1beta. Inhibition of protein kinase C completely blocked IL-1beta-stimulated hBNP promoter activity, whereas inhibition of Ca(2+)/calmodulin-dependent kinase II decreased promoter activity by 40%. In contrast, inhibition of the Ca(2+)-regulated phosphatase calcineurin by cyclosporin A had no effect. These data suggest that (1) Ca(2+) activates the hBNP promoter; (2) release of Ca(2+) from intracellular stores is important to IL-1beta regulation of the hBNP promoter, but transport via voltage-sensitive Ca(2+) channels is not; (3) protein kinase C and Ca(2+)/calmodulin-dependent kinase II mediate the action of IL-1beta; and (4) the phosphatase calcineurin is not involved in IL-1beta regulation of the hBNP promoter. Thus, Ca(2+) and Ca(2+)-dependent pathways are critical to IL-1beta regulation of the hBNP promoter.