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Arterioscler Thromb Vasc Biol. 2009 Sep;29(9):1370-5. doi: 10.1161/ATVBAHA.109.188813. Epub 2009 Jun 18.

Activation of NF-kappaB by palmitate in endothelial cells: a key role for NADPH oxidase-derived superoxide in response to TLR4 activation.

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1
Department of Medicine, University of Washington, Seattle, WA 98109, USA.

Abstract

OBJECTIVE:

We investigated whether NADPH oxidase-dependent production of superoxide contributes to activation of NF-kappaB in endothelial cells by the saturated free fatty acid palmitate.

METHODS AND RESULTS:

After incubation of human endothelial cells with palmitate at a concentration known to induce cellular inflammation (100 mumol/L), we measured superoxide levels by using electron spin resonance spectroscopy and the spin trap 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine (CMH). Palmitate exposure induced a >2-fold increase in superoxide levels, an effect associated with activation of NF-kappaB signaling as measured by phospho-IkappaBalpha, NF-kappaB activity, IL-6, and ICAM expression. Reduction in superoxide levels by each of 3 different interventions-pretreatment with superoxide dismutase (SOD), diphenylene iodinium (DPI), or knockdown of NADPH oxidase 4 (NOX4) by siRNA-attenuated palmitate-mediated NF-kappaB signaling. Inhibition of toll like receptor-4 (TLR4) signaling also suppressed palmitate-mediated superoxide production and associated inflammation, whereas palmitate-mediated superoxide production was not affected by overexpression of a phosphorylation mutant IkappaBalpha (NF-kappaB super repressor) that blocks cellular inflammation downstream of IKKbeta/NF-kappaB. Finally, high-fat feeding increased expression of NOX4 and an upstream activator, bone morphogenic protein (BMP4), in thoracic aortic tissue from C57BL/6 mice, but not in TLR4(-/-) mice, compared to low-fat fed controls.

CONCLUSIONS:

These results suggest that NADPH oxidase-dependent superoxide production links palmitate-stimulated TLR4 activation to NF-kappaB signaling in endothelial cells.

PMID:
19542021
PMCID:
PMC2775080
DOI:
10.1161/ATVBAHA.109.188813
[Indexed for MEDLINE]
Free PMC Article

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