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J Biol Chem. 2018 Aug 24;293(34):13257-13269. doi: 10.1074/jbc.RA118.002428. Epub 2018 Jul 5.

High-density lipoprotein inhibits serum amyloid A-mediated reactive oxygen species generation and NLRP3 inflammasome activation.

Shridas P1,2, De Beer MC2,3,4, Webb NR2,4,5.

Author information

1
From the Departments of Internal Medicine, pshri2@uky.edu.
2
Barnstable Brown Diabetes Center, University of Kentucky, Lexington, Kentucky 40536.
3
Physiology, and.
4
Pharmacology and Nutritional Sciences.
5
Saha Cardiovascular Research Center, and.

Abstract

Serum amyloid A (SAA) is a high-density apolipoprotein whose plasma levels can increase more than 1000-fold during a severe acute-phase inflammatory response and are more modestly elevated in chronic inflammation. SAA is thought to play important roles in innate immunity, but its biological activities have not been completely delineated. We previously reported that SAA deficiency protects mice from developing abdominal aortic aneurysms (AAAs) induced by chronic angiotensin II (AngII) infusion. Here, we report that SAA is required for AngII-induced increases in interleukin-1β (IL-1β), a potent proinflammatory cytokine that is tightly controlled by the Nod-like receptor protein 3 (NLRP3) inflammasome and caspase-1 and has been implicated in both human and mouse AAAs. We determined that purified SAA stimulates IL-1β secretion in murine J774 and bone marrow-derived macrophages through a mechanism that depends on NLRP3 expression and caspase-1 activity, but is independent of P2X7 nucleotide receptor (P2X7R) activation. Inhibiting reactive oxygen species (ROS) by N-acetyl-l-cysteine or mito-TEMPO and inhibiting activation of cathepsin B by CA-074 blocked SAA-mediated inflammasome activation and IL-1β secretion. Moreover, inhibiting cellular potassium efflux with glyburide or increasing extracellular potassium also significantly reduced SAA-mediated IL-1β secretion. Of note, incorporating SAA into high-density lipoprotein (HDL) prior to its use in cell treatments completely abolished its ability to stimulate ROS generation and inflammasome activation. These results provide detailed insights into SAA-mediated IL-1β production and highlight HDL's role in regulating SAA's proinflammatory effects.

KEYWORDS:

NLRP3; Serum Amyloid A; high-density lipoprotein (HDL); inflammasome; interleukin 1 (IL-1); reactive oxygen species (ROS)

PMID:
29976759
PMCID:
PMC6109913
[Available on 2019-08-24]
DOI:
10.1074/jbc.RA118.002428
[Indexed for MEDLINE]

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