Fine particulate matter exposure aggravates ischemic injury via NLRP3 inflammasome activation and pyroptosis

Abstract

Aims Accumulating evidence has suggested that airborne fine particulate matter (PM2.5) exposure is associated with an increased risk of ischemic stroke. However, the underlying mechanisms have not been fully elucidated. In this study, we aim to investigate the role and mechanisms of NLRP3 inflammasome and pyroptosis in ischemic stroke after PM2.5 exposure. Methods The BV‐2 and HMC‐3 microglial cell lines were established and subjected to oxygen–glucose deprivation and reoxygenation (OGD/R) with or without PM2.5 exposure. We used the CCK‐8 assay to explore the effects of PM2.5 on cell viability of BV‐2 and HMC‐3 cells. Then, the effects of PM2.5 exposure on NLRP3 inflammasome and pyroptosis following OGD/R were detected by western blotting, ELISA, and the confocal immunofluorescence staining. Afterwards, NLRP3 was knocked down to further validate the effects of PM2.5 on cell viability, NLRP3 inflammasome activation, and pyroptosis after OGD/R in HMC‐3 cells. Finally, the intracellular reactive oxygen species (ROS) was measured and the ROS inhibitor N‐acetyl‐L‐cysteine (NAC) was used to investigate whether ROS was required for PM2.5‐induced NLRP3 inflammasome activation and pyroptosis under ischemic conditions. Results We found that PM2.5 exposure decreased the viability of BV‐2 and HMC‐3 cells in a dose‐ and time‐dependent manner under ischemic conditions. Furthermore, PM2.5 exposure aggravated NLRP3 inflammasome activation and pyroptosis after OGD/R, as indicated by an increased expression of NLRP3, ASC, pro‐caspase‐1, Caspase‐1, GSDMD, and GSDMD‐N; increased production of IL‐1β and IL‐18; and enhanced Caspase‐1 activity and SYTOX green uptake. However, shRNA NLRP3 treatment attenuated the effects of PM2.5 on cell viability, NLRP3 inflammasome activation, and pyroptosis. Moreover, we observed that PM2.5 exposure increased the production of intracellular ROS following OGD/R, while inhibiting ROS production with NAC partially attenuated PM2.5‐induced NLRP3 inflammasome activation and pyroptosis under ischemic conditions. Conclusion These results suggested that PM2.5 exposure triggered the activation of NLRP3 inflammasome and pyroptosis under ischemic conditions, which may be mediated by increased ROS production after ischemic stroke. These findings may provide a more enhanced understanding of the interplay between PM2.5 and neuroinflammation and cell death, and reveal a novel mechanism of PM2.5‐mediated toxic effects after ischemic stroke.

Cell Death Pathways: The Variable Mechanisms Underlying Fine Particulate Matter-Induced Cytotoxicity

“…Compared to the previous studies showing that ROS generated by ZnO nanoparticles would activate NF-κB-mediated NLRP3 inflammasomes in A549 cells, the pyroptosis induced by FPM appeared to be attributed to the metal ion release. In addition, the activation of NLRP3 and the consequent cellular pyroptosis following FPM exposure have been observed both in vitro (such as BV-2 and HMC-3 microglial cell lines) and in vivo . − …”

“…In addition, the activation of NLRP3 and the consequent cellular pyroptosis following FPM exposure have been observed both in vitro (such as BV-2 and HMC-3 microglial cell lines) and in vivo . 71 − 73 …”

A review of respirable fine particulate matter (PM2.5)-induced brain damage

“…These inflammatory mediators become the external stimulus transduction signals required for the activation of the nuclear factor-κB pathway, which further activates the nuclear factor-κB signaling pathway, induces an inflammatory cascade, and aggravates neuroinflammation (Zhang Y. et al, 2018 ). PM 2.5 exposure can also activates the NLRP3 inflammasome, induces increased production of IL-1β and IL-18, causes systemic and neuroinflammation, and leads to endothelial and target organ damage (Gao et al, 2022 ).…”

Combined exposure to high-cholesterol diet and PM 2.5 : Brain injury and regulatory mechanism of HIF-1α in female mice

“…The population survey data have shown that short-term and long-term exposure to PM 2.5 augments the risks of stroke incidence and mortality (Shah et al, 2015;Qiu et al, 2017). Experimental data have documented that in ammation and arteriosclerosis are the vital regulatory mechanisms that PM 2.5 exposure triggers stroke (Gao et al, 2022).…”