[Epimedii Folium-Ligustri Lucidi Fructus protects airway epithelial barrier from recurrent injury by inhibiting PI3K].

The present study aimed to investigate whether the herb pair Epimedii Folium-Ligustri Lucidi Fructus(YN) protects airway epithelial cells(AECs) from recurrent injury by inhibiting the phosphatidylinositol 3-kinase(PI3K). The experiment was carried out with the following groups: control, model, PI3K inhibitor, YN, PI3K agonist, and PI3K agonist+YN. Except the control group, the other groups were subjected to repeated poly-L-arginine(PLA) stimulation to induce recurrent injury in 16 human bronchial epithelial cells(16HBEC). PI3K inhibitor(LY294002), YN-containing serum, PI3K agonist(740 Y-P), or YN-containing serum+740 Y-P were administered in corresponding groups. After treatment, ultrastructural changes were observed by electron microscopy. Cell status was evaluated in terms of viability, proliferation, autophagy, and apoptosis. Barrier function of the airway epithelium was assessed based on transepithelial electrical resistance(TEER), dextran permeability, and expression of junction proteins including zonula occludens-1(ZO-1), E-cadherin, occludin, β-catenin, and the mesenchymal marker vimentin. Western blot and qPCR were employed to determine the expression levels of molecules in the PI3K/protein kinase B(Akt)/mammalian target of rapamycin(mTOR) pathway at protein and mRNA levels, respectively. The results showed that repeated PLA stimulation led to marked ultrastructural and morphological damage in 16HBEC, along with significantly increased proliferation and decreased apoptosis and autophagy. The barrier function of 16HBEC was severely impaired, as indicated by reduced TEER and elevated dextran permeability. The expression of junction proteins was downregulated, while that of vimentin was upregulated. In addition, the PI3K/Akt/mTOR signaling pathway was markedly activated. Both YN and the PI3K inhibitor suppressed the PI3K/Akt/mTOR pathway, ameliorated ultrastructural damage, reduced abnormal proliferation, promoted autophagy and apoptosis, upregulated junction protein expression, and downregulated vimentin expression. Notably, the protective effects of YN were partially reversed by the PI3K agonist. These findings indicate that YN mitigates recurrent airway epithelial injury and restores barrier function primarily through inhibiting the PI3K pathway.