Andrographolide Inhibits Lipotoxicity-Induced Activation of the NLRP3 Inflammasome in Bone Marrow-Derived Macrophages

Andrographolide is the major bioactive component of the herb Andrographis paniculata and is a potent anti-inflammatory agent. Obesity leads to an excess of free fatty acids, particularly palmitic acid (PA), in the circulation. Obesity also causes the deposition of ectopic fat in nonadipose tissues, which leads to lipotoxicity, a condition closely associated with inflammation. Here, we investigated whether andrographolide could inhibit PA-induced inflammation by activating autophagy, activating the antioxidant defense system, and blocking the activation of the NLRP3 inflammasome. Bone marrow-derived macrophages (BMDMs) were primed with lipopolysaccharide (LPS) and then activated with PA. LPS/PA treatment increased both the mRNA expression of NLRP3 and IL-1 beta and the release of IL-1 beta in BMDMs. Andrographolide inhibited the LPS/PA-induced protein expression of caspase-1 and the release of IL-1 beta. Furthermore, andrographolide attenuated LPS/PA-induced mtROS generation by first promoting autophagic flux and catalase activity, and ultimately inhibiting activation of the NLRP3 inflammasome. Our results suggest that the mechanisms by which andrographolide downregulates LPS/PA-induced IL-1 beta release in BMDMs involve promoting autophagic flux and catalase activity. Andrographolide may thus be a candidate to prevent obesity- and lipotoxicity-driven chronic inflammatory disease.