Investigating the inhibitory effects of ginsenoside Rg3 on the NLRP3 inflammasome in J774A.1 murine macrophage cells

Abstract

The nucleotide-binding domain, leucine-rich-repeat-containing family, pyrin domain-containing 3 (NLRP3) inflammasome is a multiprotein complex found in many myeloid cells that plays an important role in regulating the innate immune response. The NLRP3 inflammasome requires two signals to become fully activated; a pathogen-associated molecular pattern (PAMP) to prime the NF-ΚB pathway and a damage-associated molecular pattern (DAMP) to activate inflammasome formation.  The priming of the NF-ΚB pathway results in the production of pro-IL-1β, pro-IL-18, and pro-caspase-1, along with a variety of other cytokines such as TNF-α. The activated NLRP3 inflammasome cleaves the pro-caspase-1 into mature caspase-1 which then cleaves the pro-Il-1β and pro-Il-18 into mature Il-1β and Il-18 respectively.  The mature Il-1β and Il-18 can then leave the cell via secretion or pyroptosis. Panax ginseng is used widely in East Asian traditional medicine for its anti-inflammatory properties. Many of its medicinal properties are thought to come from ginsenoside Rg3 which is thought to play a role in regulating the NLRP3 inflammasome. In this study, we sought to develop a working model for the activation of the NLRP3 inflammasome in J774A.1 murine macrophage cells, and to investigate if Rg3 has inhibitory effects on the priming, activation, or both signals leading to NLRP3 inflammasome assembly. We were able to detect pro-IL-1β following treatment with LPS. Further, we were able to demonstrate the apparent down-regulation of TNF-α production in LPS-treated J774A.1 cells by ginsenoside Rg3.