Pinellia pedatisecta lectin exerts a proinflammatory activity correlated with ROS-MAPKs/NF-κB pathways and the NLRP3 inflammasome in RAW264.7 cells accompanied by cell pyroptosis

Abstract

Pinellia pedatisecta, a widely used herb in Chinese medicine, has proinflammatory toxicity related to its Pinellia pedatisecta lectin (PPL), but the mechanism is still unknown. However, for safer use, it is necessary to clarify its proinflammatory mechanism. Herein, we studied the mechanism in RAW264.7 cells. PPL decreased the mitochondrial membrane potential (MMP) and increased the outflow of calcium, accompanied by the overproduction of reactive oxygen species (ROS), which resulted in the activation of the MAPK and NF-κB pathways and the release of IL-1β. The maturation of IL-1β relied on caspase-1 p20, the active caspase-1, as demonstrated by adding caspase-1 inhibitor. While caspase-1 was associated with the activation of the NLRP3 inflammasome, we further found that the stimulation of PPL also contributed to the activation. In addition, TXNIP was downregulated, whereas NLRP3/caspase-1 p20/ASC was upregulated, and there was binding of TXNIP with NLRP3. There was also binding of NLRP3 with ASC and caspase-1. Further, we found that N-acetylcysteine (NAC), an ROS scavenger, could inhibit the PPL-stimulated activation of these pathways and the release of IL-1β. Moreover, PPL led to cell pyroptosis with pyknotic nuclei and plasma membrane rupture, which could be inhibited by NAC. All of these findings demonstrated an important role of ROS in the inflammation caused by PPL. Taken together, our data provide new mechanistic insights into the possible endogenous signaling pathways involved in the inflammation of RAW264.7 cells, stimulated by PPL.

Keywords: IL-1β; Lectin; MAPK and NF-κB/NLRP3 pathways; Pinellia pedatisecta; Pyroptosis; ROS.