AMP-activated protein kinase (AMPK) is metabolic biosensor with anti-inflammatory activities. Gout is commonly associated with excesses in soluble urate and in nutrition, both of which suppress tissue AMPK activity. Gout is driven by macrophage-mediated inflammation transduced partly by NLRP3 inflammasome activation and interleukin (IL)-1β release. Hence, we tested the hypothesis that AMPK activation limits monosodium urate (MSU) crystal-induced inflammation.
We studied bone marrow-derived macrophages (BMDMs) from AMPKα1 knockout and wild-type mice, and assessed the selective AMPK pharmacological activator A-769662 and a low concentration (10 nM) of colchicine. We examined phosphorylation (activation) of AMPKα Thr172, NLRP3 mRNA expression, and caspase-1 cleavage and IL-1β maturation using western blot and quantitative RT-PCR approaches. We also assessed subcutaneous murine air pouch inflammatory responses to MSU crystals in vivo.
MSU crystals suppressed phosphorylation of AMPKα in BMDMs. Knockout of AMPKα1 enhanced, and, conversely, A-769662-inhibited MSU crystal-induced inflammatory responses including IL-1β and CXCL1 release in vitro and in vivo. A-769662 promoted AMPK-dependent macrophage anti-inflammatory M2 polarisation and inhibited NLRP3 gene expression, activation of caspase-1 and IL-1β. Colchicine, at low concentration (10 nM) achieved in gout flare prophylaxis dosing, promoted phosphorylation of AMPKα and macrophage M2 polarisation, and reduced activation of caspase-1 and release of IL-1β and CXCL1 by MSU crystals in BMDMs in vitro.
AMPK activity limits MSU crystal inflammation in vitro and in vivo, and transduces multiple anti-inflammatory effects of colchicine in macrophages. Targeting increased and sustained AMPK activation in inflammatory cells merits further investigation for enhancing efficacy of prophylaxis and treatment of gouty inflammation.