Mechanism of the Susceptibility of Remodeled Pulmonary Vessels to Drug-Induced Cell Killing

Background Pulmonary arterial hypertension remains a devastating disease without a cure. The major complication of this disease is the abnormal growth of vascular cells, resulting in pulmonary vascular remodeling. Thus, agents, which affect the remodeled vessels by killing unwanted cells, should improve treatment strategies. The present study reports that antitumor drugs selectively kill vascular cells in remodeled pulmonary vessels in rat models of pulmonary hypertension. Methods and Results After developing pulmonary vascular remodeling in chronic hypoxia or chronic hypoxia/SU-5416 models, rats were injected with antitumor drugs including proteasome inhibitors (bortezomib and MG-132) and daunorubicin. Within 1 to 3 days, these agents reduced the media and intima thickness of remodeled pulmonary vascular walls, but not the thickness of normal pulmonary vessels. These drugs also promoted apoptotic and autophagic death of vascular cells in the remodeled vessels, but not in normal vessels. We provide evidence that the upregulation of annexin A1, leading to GATA4-dependent downregulation of Bcl-xL, is a mechanism for specific apoptotic killing, and for the role of parkin in defining specificity of autophagic killing of remodeled vascular cells. The reversal of pulmonary vascular remodeling increased the capacity of vasodilators to reduce pulmonary arterial pressure. Conclusions These results suggest that antitumor drugs can specifically kill cells in remodeled pulmonary vascular walls and may be useful for improving the efficacy of current therapeutic strategies to treat pulmonary arterial hypertension.