Targeting cell motility in pulmonary arterial hypertension.

Pulmonary artery smooth muscle cells (PASMC), in pulmonary arterial hypertension (PAH), contribute to obliterative vascular remodelling and are characterised by enhanced proliferation, suppressed apoptosis and, a much less studied, increased migration potential. One of the major proteins that regulate cell migration is focal adhesion kinase (FAK), but its role in PAH is not fully understood. We hypothesised that targeting cell migration by FAK inhibition may be a new therapeutic strategy in PAH. In vivo, inhalation of FAK-siRNA (n=5) or oral delivery of PF-228 (FAK inhibitor PF-573 228; n=5) inhibited rat monocrotaline induced PAH, improving the haemodynamics, vascular remodelling (media thickness), and right ventricular hypertrophy. In vitro, FAK was activated in PAH human lungs (n=8) or PASMC when compared to those form healthy subjects (Western blot, n=5), in a Src-dependent manner, as it was reversed by the specific Src inhibitor PP2. The degree of FAK phosphorylation at Y576 correlated positively with pulmonary vascular resistance in PAH patients. FAK inhibition (siRNA, PF-228 and PP2) in PAH-PASMCs induced a fivefold increase in apoptosis (percentage of terminal deoxynucleotidyl transferase dUTP nick end labelling), a 2.5-fold decrease in proliferation (%Ki67), an 18% decrease in cell migration (colorimetric assay) and a 50% decrease in cell invasion (wound healing). Suppressing PASMC migration by FAK inhibition inhibits PAH progression and may open a new therapeutic window in PAH.

Critical role for the advanced glycation end-products receptor in pulmonary arterial hypertension etiology.

BACKGROUND: Pulmonary arterial hypertension (PAH) is a vasculopathy characterized by enhanced pulmonary artery smooth muscle cell (PASMC) proliferation and suppressed apoptosis. This results in both increase in pulmonary arterial pressure and pulmonary vascular resistance. Recent studies have shown the implication of the signal transducer and activator of transcription 3 (STAT3)/bone morphogenetic protein receptor 2 (BMPR2)/peroxisome proliferator-activated receptor gamma (PPARγ) in PAH. STAT3 activation induces BMPR2 downregulation, decreasing PPARγ, which both contribute to the proproliferative and antiapoptotic phenotype seen in PAH. In chondrocytes, activation of this axis has been attributed to the advanced glycation end-products receptor (RAGE). As RAGE is one of the most upregulated proteins in PAH patients' lungs and a strong STAT3 activator, we hypothesized that by activating STAT3, RAGE induces BMPR2 and PPARγ downregulation, promoting PAH-PASMC proliferation and resistance to apoptosis. METHODS AND RESULTS: In vitro, using PASMCs isolated from PAH and healthy patients, we demonstrated that RAGE is overexpressed in PAH-PASMC (6-fold increase), thus inducing STAT3 activation (from 10% to 40% positive cells) and decrease in BMPR2 and PPARγ levels (>50% decrease). Pharmacological activation of RAGE in control cells by S100A4 recapitulates the PAH phenotype (increasing RAGE by 6-fold, thus activating STAT3 and decreasing BMPR2 and PPARγ). In both conditions, this phenotype is totally reversed on RAGE inhibition. In vivo, RAGE inhibition in monocrotaline- and Sugen-induced PAH demonstrates therapeutic effects characterized by PA pressure and right ventricular hypertrophy decrease (control rats have an mPAP around 15 mm Hg, PAH rats have an mPAP >40 mm Hg, and with RAGE inhibition, mPAP decreases to 20 and 28 mm Hg, respectively, in MCT and Sugen models). This was associated with significant improvement in lung perfusion and vascular remodeling due to decrease in proliferation (>50% decrease) and BMPR2/PPARγ axis restoration (increased by ≥60%). CONCLUSION: We have demonstrated the implications of RAGE in PAH etiology. Thus, RAGE constitutes a new attractive therapeutic target for PAH.