Forskolin attenuates the NLRP3 inflammasome activation and IL-1 beta secretion in human macrophages

Abstract

BACKGROUND: The treatment of nucleotide-binding domain and leucine-rich repeat containing family, pyrin domain containing 3 (NLRP3) inflammasome-mediated pediatric inflammatory diseases is challenging. Here we studied whether cyclic adenosine monophosphate (cAMP) elevator forskolin could attenuate the nigericin-induced NLRP3-inflammasome activation and interleukin-1 beta (IL-1 beta) secretion in human macrophages. METHODS: The proteins and messenger RNA (mRNA) levels of inflammasome structural proteins and proinflammatory cytokines were measured in forskolin-stimulated nigericin-activated human THP-1 macrophages and primary macrophages. RESULTS: Activation of THP-1 macrophages with nigericin increased the mRNA expression of NLRP3, IL-1 beta, and caspase-1 (P <0.01). Forskolin stimulation had no effect on the mRNA expression of NLRP3, caspase-1, or IL-1 beta in nigericin-activated cells (P> 0.05), while their protein levels were significantly decreased (P <0.05). Forskolin-mediated increase in cytoplasmic cAMP in non-activated cells was attenuated in nigericin-activated macrophages (P <0.05). Basal IL-1 beta secretion increased from 584 to 2696 pg/ml (P <0.01) in nigericin-activated macrophages; forskolin dose-dependently reduced the nigericin-induced secretion of mature IL-1 beta (P <0.01). Forskolin also inhibited the IL-1 beta secretion from activated human primary macrophages. CONCLUSIONS: Forskolin inhibits the NLRP3 inflammasome activation and the secretion of mature IL-1 beta, in human macrophages. Forskolin and other cAMP elevator drugs could represent a novel approach for treatment of diseases associated with excessive inflammasome activation, like pediatric inflammatory diseases.