Pulmonary
vascular remodeling is a significant pathological feature of
hypoxia-induced pulmonary hypertension (HPH), while pulmonary artery smooth muscle cell (PASMC) proliferation plays a leading role in pulmonary
vascular remodeling. Spermine (Sp), a
polyamine, plays a critical role in periodic cell proliferation and apoptosis. The present study was conducted to observe the association between
hypoxia-induced PASMC proliferation and
polyamine metabolism, and to explore the effects of exogenous Sp on PASMC poliferation and the related mechanisms. In the present study, PASMCs were cultured with
cobalt chloride (CoCl2) to establish a
hypoxia model, and Sp at various final concentrations (0.1, 1, 10 and 100 µM) was added to the medium of PASMCs 40 min prior to the induction of
hypoxia. Cell proliferation was measured by 3-(4,5-dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide (MTT) assay, cell counting kit-8 assay and 5-bromo‑2'‑deoxyuridine (BrdU) incorporation assay. Cell cycle progression was determined by flow cytometry, and the
protein expression levels of
spermidine/
spermine N1-acetyltransferase (SSAT; the key
enzyme in the terminal degradation of
polyamine),
ornithine decarboxylase (ODC; the key
enzyme of
polyamine biosynthesis), cyclin D1 and p27 were measured by western blot analysis. The results revealed that the proliferation of the PASMCs cultured with CoCl2 at 50 µM for 24 h markedly increased. The expression of ODC was decreased and the expression of SSAT was increased in the cells under hypoxic conditions. Exogenous Sp at concentrations of 1 and 10 µM significantly inhibited
hypoxia-induced PASMC proliferation, leading to cell cycle arrest at the G1/G0 phase. In addition, Sp decreased cyclin D1 expression, increased p27 expression, and suppressed the phosphorylation of extracellular signal‑regulated kinase 1/2 (ERK1/2), phosphatidylinositol 3-kinase (PI3K) and
protein kinase B (AKT); however, the above-metioned parameters were not markedly affected by Sp at concentrations of 0.1 or 100 µM. These results suggest that
hypoxia disrupts
polyamine metabolism, and Sp at concentrations of 1 and 10 µM inhibits the increase in human PASMC proliferation caused by chemically-induced
hypoxia via the suppression of the ERK1/2- and PI3K/AKT-associated pathways. This study thus offer new insight into the prevention and treatment of HPH.