Elevated serum concentrations of the vasoactive protein endothelin-1 (ET-1) occur in the setting of systemic inflammatory response syndrome and contribute to distal organ hypoperfusion and pulmonary hypertension. Thus, understanding the cellular source and transcriptional regulation of systemic inflammatory stress-induced ET-1 expression may reveal therapeutic targets. Using a murine model of LPS-induced septic shock, we demonstrate that the hepatic macrophage is the primary source of elevated circulating ET-1, rather than the endothelium as previously proposed. Using pharmacologic inhibitors, ET-1 promoter luciferase assays, and by silencing and overexpressing NF-êB inhibitory protein IêB expression, we demonstrate that LPS-induced ET-1 expression occurs via an NF-êB-dependent pathway. Finally, the specific role of the cRel/p65 inhibitory protein IêBâ was evaluated. Although cytoplasmic IêBâ inhibits activity of cRel-containing NF-êB dimers, nuclear IêBâ stabilizes NF-êB/DNA binding and enhances gene expression. Using targeted pharmacologic therapies to specifically prevent IêBâ/NF-êB signaling, as well as mice genetically modified to overexpress IêBâ, we show that nuclear IêBâ is both necessary and sufficient to drive LPS-induced ET-1 expression. Together, these results mechanistically link the innate immune response mediated by IêBâ/NF-êB to ET-1 expression and potentially reveal therapeutic targets for patients with Gram-negative septic shock.
Animals Cell Line