The Vitamin E Derivative Garcinoic Acid Suppresses NLRP3 Inflammasome Activation and Pyroptosis in Murine Macrophages

Excessive inflammation in cells are a common cause of inflammation-related diseases such as cardiometabolic diseases. The cellular multiprotein complex nucleotide-binding domain and leucine-rich repeat pyrin domain 3 (NLRP3) inflammasome is a cellular key modulator of inflammatory processes. In addition to classic medications, phytochemicals are known for their anti-inflammatory potential. In African folk medicine the seeds of Garcinia kola are used to support the treatment of inflammatory diseases. Of particular interest is the phytochemical garcinoic acid (GA, trans-13'-carboxy-δ-tocotrienol), which is isolated from the Garcinia kola seeds. This derivative and potential metabolite of the vitamin E congener δ-tocotrienol (T3) shows anti-inflammatory properties in vitro. However, the underlying mechanisms are largely unknown. To get better insights into the molecular mode of action, murine J774A.1 macrophages were stimulated with lipopolysaccharides (LPS) only or in combination with adenosine triphosphate (ATP), which led to canonical activation of the NLRP3 inflammasome and subsequent pyroptosis. A combined treatment with GA resulted in significantly reduced stimulation of the transcription factor nuclear factor 'ĸ-light-chain-enhancer' of activated B-cells (NF-ĸB), decreased expression of inflammasome-related genes and marked downregulation of autoproteolytic cleavage of caspase-1 (Casp-1). Consequently, GA had an inhibitory effect on pyroptosis. The results have been validated using the well-known NLRP3 inflammasome inhibitor MCC950. In conclusion, GA was shown to have relevant effects on the regulation of the NLRP3 inflammasome and pyroptosis in vitro. Our study provides new mechanistic insights into the anti-inflammatory mode of action of GA and highlights its relevance as a potential phytochemical drug for the treatment of inflammation.