Objective 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.
Methods 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.
Results 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.
Conclusions 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.