Polyamine regulatory pathways as pharmacologic targets in pulmonary arterial hypertension.

Decades of studies in animal models and in humans with pulmonary artery hypertension have left little doubt that the processes culminating in hyper-tensive pulmonary vascular remodeling and sustained increases in pulmonary vascular resistance are complex. Modulations in phenotype, proliferative state, and survival of multiple lung vascular cell populations, changes in the local milieu of growth and differentiation factors, and alterations in the extracellular connective tissue environment all seem to contribute to the pathogenesis of the disorder. From a pharmacologic vantage point, identifying which of these is the most suitable target is challenging.

Putrescine transport in hypoxic rat main PASMCs is required for p38 MAP kinase activation.

Hypoxic pulmonary vascular remodeling in rats is associated with increased polyamine transport in pulmonary artery smooth muscle cells (PASMCs). We therefore defined constitutive and hypoxia-induced polyamine transport properties of rat cultured PASMCs and determined the impact of polyamine transport blockade on hypoxia-induced accumulation of p38 MAP kinase. PASMCs exhibited polyamine transport pathways that were characterized by Michaelis-Menten kinetics.

Regulation of ornithine decarboxylase and polyamine import by hypoxia in pulmonary artery endothelial cells.

In rat lung and cultured lung vascular cells, hypoxia decreases ornithine decarboxylase (ODC) activity and increases polyamine import. In this study, we used rat cultured pulmonary artery endothelial cells to explore the mechanism of hypoxia-induced reduction in ODC activity and determined whether this event was functionally related to the increase in polyamine import. Two strategies known to suppress proteasome-mediated ODC degradation, lactacystin treatment and use of cells expressing a truncated ODC incapable of interacting with the proteasome, prevented the hypoxia-induced decrease in ODC activity.