Low-dose acetylsalicylic acid inhibits the secretion of interleukin-6 from white adipose tissue

Abstract

Background: Chronically elevated interleukin-6 (IL-6) is implicated in obesity-associated pathologies, where a proportion of this cytokine is derived from adipose tissue. Proinflammatory prostaglandins, which regulate this cytokine elsewhere, are also produced by this tissue. Objective: To investigate whether constitutively active cyclooxygenase (COX)/prostaglandin (PG) pathway in white adipose tissue (WAT) is responsible for basal IL-6 production. Design: The effect of acetylsalicylic acid (ASA), an inhibitor of COX, on IL-6 was assessed in human subjects and mice. COX, downstream PG synthase (PGS) activity and PG receptor signalling were determined in subcutaneous (SC), gonadal (GN) WAT and adipocytes. Methods and Results: In obese humans, low-dose ASA (150 mg day-1 for 10 days) inhibited systemic IL-6 and reduced IL-6 release from SC WAT ex vivo (0.2 mM). Similarly, in mice, ASA (0.2 and 2.0 mg kg -1) suppressed SC WAT 6-keto-PGF1α (a stable metabolite of prostacyclin) and IL-6 release. Although both COX isoforms are comparably expressed, prostacyclin synthase expression is higher in GN WAT, with levels of activity correlating directly with IL-6. Both ASA (5 mM) and NS-398 (COX-2 selective inhibitor μ1 μM), but not SC-560 (COX-1 selective inhibitor μ1 μM), attenuated IL-6 release from murine WAT in vitro and abolished its depot differences. Prostacyclin receptor (IP) and, to a lesser extent, PGE2 (EP2 and EP4) receptor agonists elevated the release of IL-6 from adipocytes. Conclusions: In adipose tissue, constitutive COX-2-coupled prostacyclin triggers the release of basal IL-6, which in obese subjects is significantly dampened by ASA ingestion, thus offering a novel, modifiable pathway to regulate the potentially pathological component of this cytokine. © 2008 Macmillan Publishers Limited All rights reserved.