Pennogenin-3--α--Rhamnopyranosyl-(1→2)-[α--Rhamnopyranosyl-(1→3)]-β--Glucopyranoside (Spiroconazol A) Isolated from L. var. Induces Autophagic Cell Death by p38 MAPK Activation in NSCLC Cells.

In our previous study, we reported the isolation of pennogenin-3--α--rhamnopyranosyl-(1→2)-[α--rhamnopyranosyl-(1→3)]-β--glucopyranoside (spiroconazol A), a steroidal saponin, from the flowers of L. var. . In the present study, we aimed to investigate the effects of spiroconazol A on autophagy and its underlying mechanisms in A549 and NCI-H358 human non-small cell lung cancer (NSCLC) cells. Spiroconazol A inhibited the proliferation of NSCLC cells in a concentration- and time-dependent manner. To determine the type of programmed cell death induced by spiroconazol A, we performed a characterization of apoptosis in spiroconazol A-treated A549 cells. Our results showed that spiroconazol A significantly suppressed A549 cell viability but did not influence cell apoptosis because phosphatidylserine and caspase activation were not detected. Furthermore, spiroconazol A treatment upregulated the expression of LC3-II and autophagy-related Beclin-1 protein, suggesting that spiroconazol A induces autophagy in A549 cells. Moreover, spiroconazol A activated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) but did not affect the phosphorylation of Janus kinase or ERK1/2. Notably, SB203580, a p38 MAPK inhibitor, had a significant inhibitory effect on spiroconazol A-induced autophagic cell death in A549 cells. Our results indicated that spiroconazol A-induced autophagy is dependent on p38 MAPK signaling and has potential as a therapeutic target in NSCLC.