Endotoxemia Induces IκBβ/NF-κB–Dependent Endothelin-1 Expression in Hepatic Macrophages

Abstract

Elevated serum concentrations of the vasoactive protein 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 NFκB inhibitory protein IκB expression, we demonstrate that LPS-induced ET-1 expression occurs via an NFκB dependent pathway. Finally, the specific role of the cRel/p65 inhibitory protein IκBβ was evaluated. Although cytoplasmic IκBβ inhibits activity of cRel containing NFκB dimers, nuclear IκBβ stabilizes NFκB/DNA binding and enhances gene expression. Using targeted pharmacologic therapies to specifically prevent IκBβ/NFκB signaling, as well as mice genetically modified to overexpress IκBβ, we show that nuclear IκBβ is both necessary and sufficient to drive LPS-induced ET-1 expression. Together, these results mechanistically link the innate immune response mediated by IκBβ/NFκB to ET-1 expression and potentially reveals therapeutic targets for patients with gram-negative septic shock.

Lipopolysaccharide promotes the development of murine endometriosis‐like lesions via the nuclear factor‐kappa B pathway

“…To our knowledge, this is the first study in which the chronic inflammatory peritoneal environment of endometriosis was reproduced using the mouse model established by repeated LPS. The animal models, in which a single shot of LPS was given for acute inflammation, such as a septic model, have been reported . Although we tested various amounts of LPS for 4 weeks in the juvenile mice, higher amounts (5‐10 mg/kg, every day or twice injections per week) were sometimes fatal.…”

Perinatal Endotoxemia Induces Sustained Hepatic COX-2 Expression through an NFκB-Dependent Mechanism

“…We have previously demonstrated that in adult mice, lethal endotoxemia acutely (by 2 hours) induces NFκB activation as measured by IκBα and IκBβ degradation. [21] However, the kinetics of IκB degradation following exposure to sublethal endotoxemia have not been reported in adult mice, nor have the kinetics of IκB degradation following exposure to lethal or sublethal endotoxemia been reported in neonatal mice. Thus, to determine if LPS-induced hepatic NFκB activation was temporally related to COX-2 expression, we evaluated hepatic IκBα and IκBβ expression in the liver of adult mice exposed to sublethal endotoxemia, and in neonatal mice exposed to either lethal or sublethal endotoxemia.…”

“…To corroborate these findings, we determined COX-2 mRNA expression in purified intrahepatic mononuclear cells (ihMNCs) isolated from livers of endotoxemic neonatal mice. Isolation of ihMNCs was chosen as this population of cells is inclusive of macrophage populations [21]. We found that when compared to hepatocytes, hepatic macrophages demonstrated significantly higher COX-2 expression (Fig.…”

“…Hepatocytes and macrophages were collected from neonatal livers by gradient centrifugation as previously described [21]. Following collection, cells were lysed in Buffer RLT and RNA was collected using the RNeasy Mini Kit (Qiagen) according to the manufacturer’s instructions.…”

“…Bone Marrow-Derived Macrophages (BMDM) were collected from 6–10 week old male ICR mice and were cultured as previously described. [21] Cells were exposed to LPS (1 μg/ml; catalog number L5418, Sigma) and RNA was collected using the RNeasy Mini Kit (Qiagen).…”