demonstrating a reversal of pulmonary remod eling processes in hypoxia induced PAH by the platelet derived growth factor receptor antagonist imat inib mesylate. In a case report of selleck kinase inhibitor a patient in a desper ate situation of progressing pulmonary hypertension, Seegers group further substantiates this new concept. PDGF represents a potent mitogen for pulmonary smooth muscle Inhibitors,Modulators,Libraries cells acting via PI3K/Akt/mTOR, a central sig naling pathway for cell cycle entry and progression. This pathway is activated by other growth factors involved in PAH as well suggesting that it may represent a final common pathway towards proliferation. We had, there fore, successfully aimed to inhibit this pathway through usage of rapamycin which potently inhibits mTOR to not only prevent but also reverse vascular remodeling processes and right ventricular signs of pulmonary hyper tension in mice held under hypoxic conditions.
Hypoxia is the main stimulus for the induction of pulmo nary hypertension accompanying chronic ventilatory dis orders such as chronic obstructive pulmonary disease and interstitial lung disease. While acute hypoxia causes selec tive pulmonary arteriolar vasoconstriction, chronic Inhibitors,Modulators,Libraries expo sure to hypoxia results in morphological and functional changes in the pulmonary vascular bed. Indeed, Inhibitors,Modulators,Libraries mTOR signaling seems to play a key role in hypoxia trig gered smooth muscle and endothelial cell proliferation in vitro. The requirement of PI3K, Akt, and mTOR for hypoxia induced proliferation has also been demon strated for pulmonary artery adventitial fibroblasts.
Although it is generally accepted that proliferation Inhibitors,Modulators,Libraries is an important contributor to hypoxia induced vascular remodeling, only few data regarding the kinetics of the proliferative activity are available. Quinlan et al. reported that the number of Inhibitors,Modulators,Libraries 5 bromo 2 deoxyuridine positive cells/vessel is about 50% higher in mice exposed to hypoxia for 4 or 6 days. After three weeks no differences in the proliferative index in the pulmonary vasculature of animals housed at normoxia or hypoxia were detectable. Our data confirm the finding of an only transient increase of proliferative activity within the pulmonary vasculature during hypoxia reaching a maximum within the first week. In our study this increase was sensitive to selleck chem rapamy cin treatment suggesting that inhibition of the early hypoxia triggered cell cycle activity results in reduced chronic vascular remodeling. This way the drug may pre vent further hypoxia triggered proliferation and disease progression. However, prevention of early proliferation does not explain rapamycins effectiveness when given therapeuti cally after 3 weeks of hypoxia when proliferative activity within the pulmonary vasculature was determined even below that of normoxic mice.