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The Phase 2 Enzyme Inducers Ethacrynic Acid, DL-sulforaphane, and Oltipraz Inhibit Lipopolysaccharide-Induced High-Mobility Group Box 1 Secretion by RAW 264.7 Cells

The Phase 2 Enzyme Inducers Ethacrynic Acid, DL-sulforaphane, and Oltipraz Inhibit Lipopolysaccharide-Induced High-Mobility Group Box 1 Secretion by RAW 264.7 Cells

Meaghan E Killeen, Joshua A Englert, Donna Beer Stolz, Mingchen Song, Yusheng Han, Russell L Delude, John A Kellum, Mitchell P Fink

J Pharmacol Exp Ther. 2006 Mar;316(3):1070-9.

PMID: 16382025

Abstract:

The diuretic ethacrynic acid (EA) has been shown to inhibit signaling by the proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB). Accordingly, we sought to determine whether this compound is capable of inhibiting the release of cytokines [interleukin (IL)-6 and IL-10] and NO from RAW 264.7 murine macrophage-like cells stimulated with lipopolysaccharide (LPS). Additionally, we sought to determine whether EA can inhibit secretion of high-mobility group box 1 (HMGB1), a nuclear protein that is secreted by immunostimulated macrophages and functions in the extracellular milieu as a proinflammatory mediator. In a concentration-dependent manner, EA inhibited secretion of IL-6, IL-10, nitric oxide, and HMGB1. As expected, EA inhibited NF-kappaB DNA binding in LPS-stimulated RAW 264.7 cells. Treating these cells with pyrrolidine dithiocarbamate, SN50 (amino acid sequence AAVALLPAVLLALLAPVQRKRQKLMP) or 5-(thien-3-yl)-3-aminothiophene-2-carboxamide (SC-514) also inhibited LPS-induced NF-kappaB DNA binding, but these compounds failed to inhibit LPS-induced HMGB1 secretion. These findings suggested that inhibition of HMGB1 secretion by EA might occur via a mechanism unrelated to the NF-kappaB signaling pathway. Because EA is an electrophilic compound that is known to be capable of inducing expression of so-called phase 2 proteins, we sought to determine whether two other phase 2 enzyme inducers, oltipraz and DL-sulforaphane, also are capable of inhibiting HMGB1 release from immunostimulated macrophages. Incubating RAW 264.7 cells with either oltipraz or DL-sulforaphane inhibited LPS-induced HMGB1 secretion. Moreover, both EA and DL-sulforaphane inhibited relocalization of nuclear HMGB1 into the cytoplasm of LPS-stimulated RAW 264.7 cells. These data suggest that phase 2 inducers may exert anti-inflammatory effects by inhibiting secretion of the cytokine-like nuclear protein HMGB1.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP4478937	DL-Sulforaphane		4478-93-7	Price

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