Objective: To investigate the potential molecular mechanism of fine particulate matter (PM2.5) on activation of NLRP3 inflammasome and apoptosis in rat alveolar macrophages. Methods: Rat alveolar macrophages were treated with PM2.5suspension collected by medium flow atmospheric sampler. After action of the suspension on rat alveolar macrophages (NR8383)

MTT assay was used to detect the cell survival rate. Western blot was performed to detect the expression of NLRP3

Cathepsin-B and apoptosis-related proteins (Bax

Bcl-2

Caspase-3). The level of Caspase-1

interleukin-18 (IL-18) and interleukin-1β (IL-1β) in the cell supernatant induced by PM2.5were measured by ELISA method. Results: With the increase of PM2.5concentration and the extension of stimulation time

the survival rate of NR8383 decreased (24 h: F=17.253

P=0.000; 48 h: F=18.678

P=0.000; 72 h: F=256.104

P=0.000); PM2.5accelerated the expression of NLRP3 (F=437.166

P=0.000) and Cathepsin-B (F=42.062

P=0.000) in NR8383; PM2.5 up-regulated the expression of pro-apoptotic protein Bax (F=72.827

P=0.000)

down-regulated the expression of anti-apoptotic protein Bcl-2 (F=390.322

P=0.000)

and down-regulated the expression of Caspase-3 (F=169.833

P=0.000); PM2.5increased the level of Caspase-1 (F=629.866

P=0.000)

IL-18 (F=587.165

P=0.000) and IL-1β (F=68.472

P=0.000) in cell culture medium. Conclusion: PM2.5can activate NLRP3 inflammasome in alveolar macrophages through the lysosomal model

promote the secretion of IL-18 and IL-1β

and cause apoptosis of alveolar macrophages.