title: Phagolysosome acidification is required for silica and engineered nanoparticle-induced lysosome membrane permeabilization and resultant NLRP3 inflammasome activity.
abstract: NLRP3 inflammasome activation occurs in response to hazardous particle exposures and is critical for the development of particle-induced lung disease. Mechanisms of Lysosome Membrane Permeabilization (LMP), a central pathway for activation of the NLRP3 inflammasome by inhaled particles, are not fully understood. We demonstrate that the lysosomal vATPases inhibitor Bafilomycin A1 blocked LMP in vitro and ex vivo in primary murine macrophages following exposure to silica, multi-walled carbon nanotubes, and titanium nanobelts. Bafilomycin A1 treatment of particle-exposed macrophages also resulted in decreased active cathepsin L in the cytosol, a surrogate measure for leaked cathepsin B, which was associated with less NLRP3 inflammasome activity. Silica-induced LMP was partially dependent upon lysosomal cathepsins B and L, whereas nanoparticle-induced LMP occurred independent of cathepsin activity. Furthermore, inhibition of lysosomal cathepsin activity with CA-074-Me decreased the release of High Mobility Group Box 1. Together, these data support the notion that lysosome acidification is a prerequisite for particle-induced LMP, and the resultant leak of lysosome cathepsins is a primary regulator of ongoing NLRP3 inflammasome activity and release of HMGB1.
authors.affiliation: Center for Environmental Health Sciences, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, United States.
authors.forename: Forrest
authors.initials: F
authors.lastname: Jessop
authors.affiliation: Center for Environmental Health Sciences, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, United States.
authors.forename: Raymond F
authors.initials: RF
authors.lastname: Hamilton
authors.affiliation: Center for Environmental Health Sciences, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, United States.
authors.forename: Joseph F
authors.initials: JF
authors.lastname: Rhoderick
authors.affiliation: Center for Environmental Health Sciences, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, United States.
authors.forename: Paige
authors.initials: P
authors.lastname: Fletcher
authors.affiliation: Center for Environmental Health Sciences, Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, MT, United States. Electronic address: andrij.holian@umontana.edu.
authors.forename: Andrij
authors.initials: A
authors.lastname: Holian
mesh_terms: D000818:Animals; D002463:Cell Membrane Permeability / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002616:Chemical Engineering / Q000379:methods*; D005260:Female; D058847:Inflammasomes / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008247:Lysosomes / Q000737:chemistry / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000378:metabolism*; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism*; D010588:Phagosomes / Q000737:chemistry / Q000378:metabolism*; D012822:Silicon Dioxide / Q000737:chemistry / Q000378:metabolism*
chemical_list: D058847:Inflammasomes; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D012822:Silicon Dioxide
keywords: Lysosome membrane permeabilization; MWCNT; NLRP3 Inflammasome; Silica; TNB