Abstract

We provided a comprehensive line of evidence indicating Lanthanide-based nanoparticles elicited NLRP3 dependent inflammasome activation in vitro and inflammatory response in vivo. A short synthetic peptide identified by our group, RE-1(ACTARSPWICG), could form a stable coating layer on the surface of Lanthanide-based nanoparticles (LNs) through specifically binding and effectively block their autophagy-inducing activity and liver toxicity. Recently, RE-1 coating were also demonstrated to significantly abrogate LN-elicited inflammasome activation without influencing cell uptake of nanocrystals in macrophage cells, and inflammatory response in peritoneal cavity. Furthermore, the mechanism of the inflammasome-inhibiting effect of RE-1 coating was investigated. RE-1 coating did not effectively reduce LN-elicited potassium efflux, while the potassium channel inhibitor glibenclamide did, indicating that potassium efflux was necessary but insufficient for LN-induced inflammasome activation. RE-1 did reduce lysosomal damage induced by LNs, However, the inhibitor of cathepsin B could not alter LN-elicited caspase-1 activation and IL-1β release, indicating that lysosomal damage was not critically important for LN-induced inflammasome activation. In contrast, RE-1 could dramatically inhibit LN-induced up-regulation of intracellular reactive oxygen species (ROS), greatly important for inflammasome activation. And, the reduction on NADPH oxidase-generated ROS was more critical for RE-1's inflammasome-inhibiting effect than the reduction on mitochondria-generated ROS. ROS generation further triggered Transient Receptor Potential M2 (TRPM2) regulated Ca²⁺ influx to induce inflammasome activation, which could be completely canceled by RE-1 coating. In conclusion, RE-1 primarily inhibited NADPH oxidase regulated ROS generation and subsequently curbed TRPM2-mediated Ca²⁺ influx to abrogate LN-induced inflammasome activation. Our study gives a new direction to modulate the inflammatory response of nanocrystals to realize immune escape via surface peptide coating, great value for in vivo applications of engineered nanomaterials.

Keywords: Lanthanide-based nanoparticles (LNs); NLRP3 inflammasome; RE-1 peptide; NADPH oxidase; ROS generation; Ca²⁺ influx; TRPM2