TITLE:
The Three Main SCFAs Inhibit the Inflammatory Response of A549 Cells Induced by Acinetobacter baumannii
AUTHORS:
Shixiang Fu, Yue Xi, Longkun Ding, Man Yan, Chang Sun, Jun Zhao, Yudong Jiao, Liang Wu
KEYWORDS:
Acinetobacter baumannii, SCFAs, A549 Cells, Inflammatory Injury
JOURNAL NAME:
Journal of Biosciences and Medicines,
Vol.10 No.4,
April
11,
2022
ABSTRACT: Objective: The objective is to explore the mechanism of inhibitory effect of three main SCFAs (acetate, propionate and butyrate) on inflammatory response of A549 cells. Methods: Human lung adenocarcinoma cells (A549 cells) were cultured, and were divided into normal control group (NC group), A. baumannii infection group (A. baumannii group), NF-κB inhibitor group (JSH group), A. baumannii infection + sodium acetate group (NaAc group), A. baumannii infection + sodium propionate group (NaPc group) and A. baumannii infection + sodium butyrate group (NaB group). Real-time quantitative PCR was used to detect the mRNA expression of NLRP3, Caspase-1, IL-1β, IL-6, and TGF-β in A549 cells. Western blotting assay was used to determine the expression of autophagy and “pyroptosis” related proteins of NRLP3, cleaved-Caspase-1 (P20), GSDMD (P30), LC-3 and Beclin-1. At the same time, the expression of NF-κB p65 protein in nucleus and cytoplasm of A549 cells was detected. The level of reactive oxygen species in A549 cells was detected by flow cytometry. Results: Compared with A. baumannii group, the mRNA expression of NLRP3, IL-1β and IL-6 in NaAc group, NaPc group and NaB group decreased significantly, the mRNA expression of Caspase-1 in NaPc group and NaB group decreased significantly, only the mRNA expression of TGF-β in NaB group increased significantly; LC3-II expression increased significantly in NaPc group and NaB group, only Beclin-1 expression increased and GSDMD (p30) expression decreased significantly in NaB group. All three kinds of SCFAs could significantly inhibit the expression of cleaved-Caspase-1 (p20) after A. baumannii infection, but there was no significant change in the protein expression of NLRP3. Compared with NC group, the production of reactive oxygen species in A. baumannii group increased significantly at 3 h after A. baumannii infection. Compared with A. baumannii group, NaB could significantly suppress the production of reactive oxygen species induced by A. baumannii. Compared with A. baumannii group, the expression of NF-κB p65 in nucleus was significantly decreased and the expression of NF-κB p65 in cytoplasm was significantly increased after 24 h pre-incubation with NaB, NaPc and NaAc, respectively. Conclusion: A. baumannii can induce inflammatory injury of pulmonary epithelial cells, and the three major SCFAs can inhibit the activation of NLRP3 inflammasome and the release of pro-inflammatory factors through NF-κB/ROS/NLRP3 pathway, which provides a new way for clinical prevention of severe inflammatory injury caused by A. baumannii infection.