Nanotube topography inhibits NLRP3 inflammasome activation by reducing microtubule glutamylation

The topography of the implant surface is critical in modulating the inflammatory immune environment and serves as a crucial determinant for the success of osseointegration. Immune cells, particularly macrophages, are capable of detecting mechanical alterations in the implant surface topography through their cytoskeletal network, with microtubules being integral components in the mechanosensing process. Nevertheless, the mechanisms by which macrophages regulate microtubule dynamics in response to surface morphology and subsequently remodel the local immune environment remain elusive. This study employs titanium dioxide nanotubes (TNTs) to investigate the macrophage responses to implant morphology. The results demonstrate that the distinctive topography of TNTs disrupts microtubule stability and organization, diminishes microtubule polyglutamylation levels and consequently inhibits NLRP3 inflammasome assembly and activation. Upregulation of microtubule glutamylation levels reverses TNT-mediated inhibition of NLRP3 inflammasome activation. Additionally, TNTs suppress the expression of microtubule-associated kinase 4 (MARK4), which is closely related to microtubule function. Further investigation reveals that TNT-induced MARK4 downregulation reduces microtubule glutamylation, thereby preventing excessive activation of the NLRP3 inflammasome. Consistent with the in vitro findings, in a rat model of oral peri-implantitis, implants with nanotube topologies showed reduced NLRP3 inflammasome activation, as well as decreased MARK4 expression and microtubule glutamylation at the implant surface. This study is the first to demonstrate that microtubule glutamylation is involved in the assembly and activation of the NLRP3 inflammasome, offering valuable insights for the design of implants with enhanced osteoimmunomodulatory properties.

MARK4; Microtubule posttranslational modification; NLRP3 inflammasome; Nanotopology.