OPN regulates hypoxia-induced autophagy and proliferation in pulmonary artery smooth muscle cells through PI3K/AKT/mTOR signaling pathway

  Background  Osteopontin (OPN) can participate in the vascular remodeling induced by hypoxia and increase the pulmonary artery pressure. However, the mechanism of OPN regulating autophagy of hypoxic induced pulmonary artery smooth muscle cells (PASMCs) in the formation of hypoxic pulmonary hypertension (HPH) remains unclear.

  Objective  To study the role of OPN in PASMCs proliferation and autophagy through PI3K/AKT/mTOR signaling pathway at the hypoxia condition.

  Methods  PASMCs were isolated and smooth muscle cells were identified by immunocytochemistry. The cells were divided into Normoxia control group (Normoxia), Hypoxia control group (Hypoxia), Hypoxia + OPN interference empty virus group (H + OPN EV), Hypoxia + OPN interference lentivirus group (H + OPN shRNA), Hypoxia + PI3K inhibitor LY294002 group (H + LY). EdU positive labeling rate was used to detect cell proliferation. The expression levels of OPN, PI3K, AKT, mTOR and autophagy-related proteins Beclin1 and LC3B in PASMCs were detected by Western blot. The autophagy of PASMCs in each group was observed by transmission electron microscopy and immunofluorescence.

  Results  Compared with the Normoxia group, the expression levels of OPN, PI3K, AKT, mTOR, Beclin1 and LC3B significantly increased in the Hypoxia group (P<0.05), the proliferation of PASMCs was enhanced (P<0.05), the number of autophagosomes increased, and the red fluorescence intensity of LC3B, Beclin1 was also enhanced (P<0.05). Compared with the Hypoxia group, all indicators in H + OPN EV group had no statistically significant difference (P>0.05), while the expression levels of OPN, PI3K, AKT and mTOR in the H + OPN shRNA group and H + LY group decreased (P<0.05), the expression levels of Beclin1 and LC3B increased (P<0.05), the proliferation of PASMCs decreased (P<0.05), the number of autophagosomes increased, and the red fluorescence intensity of LC3B, Beclin1 was enhanced (P<0.05).

  Conclusion  Under hypoxia condition, OPN can promote the proliferation of PASMCs and inhibit autophagy in PASMCs through PI3K/AKT/mTOR signaling pathway.