It has been demonstrated that activation of autophagy is involved in the development of
pulmonary arterial hypertension (PAH). Recent studies have shown that cytosolic
forkhead box protein O1 (FoxO1) activates autophagy in
cancer cells.
Paclitaxel has been found to potentially reverse PAH progression. However, the role of FoxO1 and the effects of
paclitaxel on autophagy in the pathogenesis of PAH remain unknown. PAH was generated by
intraperitoneal injection of
monocrotaline (MCT) to rats. The right ventricular systolic pressure (RVSP), the right ventricle
hypertrophy index (RV/LV+S), and the percentage of medial wall thickness (%MT) were used to detect the development of PAH.
Hematoxylin and
eosin staining was performed to measure pulmonary
vascular remodeling. The
protein level, phosphorylation, and nucleus translocation of FoxO1 and the levels of LC3A, LC3B, and
Beclin-1 were examined by immunoblotting. The results showed that in spite of reduced expression of FoxO1, elevated phosphorylation of FoxO1 caused most of FoxO1 accumulating in cytosolic fraction in MCT-PAH rats. Autophagy was also activated in the MCT-PAH group. In cultured rat pulmonary arterial smooth muscle cells (PASMCs), knockdown of FoxO1 markedly blocked autophagy activation, indicating that elevation of cytosolic FoxO1 stimulates autophagy activation. Treatment of PAH rats with
paclitaxel reduced FoxO1 phosphorylation and increased FoxO1 nuclear accumulation, despite increased FoxO1 expression, therefore suppressed autophagy, finally reduced elevated RVSP, RV/LV+S, and %MT in MCT-induced PAH. Taken together,
paclitaxel inhibits pulmonary
vascular remodeling by FoxO1-mediated autophagy suppression, suggesting that
paclitaxel might be a novel therapeutic agent for the prevention and treatment of PAH.