[Novel concepts in the pathobiology of pulmonary arterial hypertension]

Pulmonary arterial hypertension (PAH) is a devastating disease that is characterized by a high mortality. The pathogenesis of PAH is multifactorial. In addition to hereditary factors (e. g., BMPR2 mutations), numerous environmental factors may trigger the onset and progression of the disease. An imbalance between vasoconstrictive and vasodilative factors leads to vasoconstriction in the pulmonary circuit, resulting in an increase of pulmonary vascular resistance and pulmonary artery pressure. Alterations of several signaling pathways (i. e.; endothelin, nitric oxide and prostacyclin pathways) contribute to an increase of pulmonary vascular tone, and these pathways represent the targets of the current therapeutic interventions. However, PAH is increasingly recognized as a chronic proliferative disease particularly of the small pulmonary arteries, that is primarily characterized by morphological changes of the vascular wall ("vascular remodeling"). These changes are particularly induced by peptide growth factors such as platelet-derived growth factor (PDGF) that elicit their signals via activation of membrane-bound receptor tyrosine kinases (RTK). Accordingly, there is both experimental and clinical evidence for a therapeutic efficacy of tyrosine kinase inhibitors (TKI), which provide the basis for "reverse remodeling" strategies and indeed represent a promising novel approach for the treatment of PAH. Epidermal growth factor (EGF), soluble guanylate cyclase (sGC), and phosphodiesterase type 1 (PDE1) may represent additional future target molecules. PAH leads to progressive right heart failure which determines the outcome of PAH patients. The pathomechanisms of right heart failure should therefore also be considered for the development of novel therapeutic concepts.