Glycyrrhizic Acid Ameliorates LPS-Induced WI-38 Cell Inflammation, Oxidative Stress, and Ferroptosis via Targeting METTL14 in Infantile Pneumonia

Abstract

Background

Infantile pneumonia is a common and significant health concern in the world, with elevated morbidity and mortality rates among affected children. This research is designed to demonstrate the therapeutic action of glycyrrhizic acid (GA) on infantile pneumonia and unravel the underlying mechanisms involved.

Methods

The models in vitro and in vivo were created to analyse the action of GA in infantile pneumonia. Human embryonic lung WI-38 cells were treated with lipopolysaccharide (LPS), and mice were administered LPS to mimic infantile pneumonia. Cell viability was tested via cell counting kit-8 (CCK8). The lactate dehydrogenase (LDH) content was examined using the LDH Cytotoxicity Assay Kit. Flow cytometry was performed to analyse cell apoptosis. The pro-inflammatory cytokine (tumour necrosis factor-alpha [TNF-a], interleukin [IL]-6 and IL-1β) levels were detected using TNF-a, IL-6 and IL-1β ELISA assay kits. The levels of ferrous ion (Fe²⁺), antioxidant glutathione (GSH), malondialdehyde (MDA) and reactive oxygen species (ROS) were analysed using corresponding assay kits. The potential target genes of GA in infantile pneumonia were predicted using molecular docking. The m6A level of mRNA was tested using the m6A RNA Methylation Assay Kit. Lung tissue pathology was analysed using haematoxylin and eosin staining.

Results

GA abolished LPS-induced inhibition of WI-38 cell viability and promotion of cell apoptosis, while reducing production of LDH, TNF-a, IL-6 and IL-1β. Besides, GA suppressed the levels of Fe²⁺, MDA and ROS and facilitated the GSH, solute carrier family 7 member 11 (SLC7A11), and glutathione peroxidase 4 (GPX4) levels. The molecular docking predicted that the methyltransferase-like 14 (METTL14) was a potential target of GA and had good bonding ability. Interestingly, METTL14 expression was promoted in LPS-stimulated WI-38 cells and the serum of patients with infantile pneumonia. GA repressed cell apoptosis, levels of LDH, TNF-a, IL-6, IL-1β, Fe²⁺, MDA and ROS, and facilitated the GSH, SLC7A11 and GPX4 levels of LPS-induced WI-38 cells by METTL14 silence. GA abrogated lung injury of LPS-induced mice.

Conclusion

GA alleviates LPS-induced WI-38 cell cytotoxicity, inflammation, oxidative stress and ferroptosis by METTL14 knockdown. Our findings suggest that GA may pave the way for the treatment of infantile pneumonia.