Astragaloside IV Attenuates Lipopolysaccharides-Induced Pulmonary Epithelial Cell Injury through Inhibiting Autophagy

Background: Astragaloside IV has shown its promising effect on acute respiratory distress syndrome (ARDS).

Objectives: We aim to explore whether astragaloside IV is effective for ARDS treatment in a lipopolysaccharides (LPS)-induced cell model and whether autophagy is involved in the therapeutic function of astragaloside IV.

Methods: MLE-12 cells were induced by LPS to construct an ARDS model in vitro. Cell viability was estimated by cell counting kit-8 and cell apoptosis by flow cytometry. Lactate dehydrogenase (LDH), malondialdehyde (MDA) and superoxide dismutase (SOD) levels were measured by enzyme-linked immunosorbent assay kit. The expression of tumour necrosis factor (TNF)-α, interleukin (IL)-6, zonula occludens (ZO)-1, Beclin-1 and autophagy-related (atg) 5 mRNA was evaluated by quantitative PCR, and the expression of ZO-1, microtubule-associated proteins 1A/1B light chain 3B (LC3B) I and, LC3B II protein by Western blot.

Results: LPS effectively inhibited cell viability and LC3B I expression and enhanced LC3B II, Beclin-1 and atg5 expressions in MLE-12 cells. In LPS-induced ARDS cell model, astragaloside IV up-regulated cell viability, SOD activity and ZO-1 and LC3B I expressions but down-regulated cell apoptosis, TNF-α, IL-6, LC3B II, Beclin-1 and atg5 expressions and LDH and MDA levels. 3-methyladenine promoted cell viability and ZO-1 expression, down-regulated Beclin-1 and atg5 expression, while Rapamycin (Rap) had an opposite effect. Astragaloside IV suppressed cell viability and ZO-1 expression after the Rap treatment.

Conclusions: Astragaloside IV might suppress autophagy initiation directly or indirectly through suppressing the oxidative stress and inflammatory response, which further enhances the cell viability and tight junction and reduces apoptosis in LPS-stimulated pulmonary endothelial ARDS cell model, thus exerting its therapeutic function in ARDS.