Abstract 11001: Cyclophilin a Mediates Pulmonary Vascular Remodeling by Rho-Kinase Activation in Patients With Pulmonary Hypertension
Background: Pulmonary arterial hypertension (PAH) is associated with hypoxic exposure, enhanced reactive oxygen species (ROS) and proliferation of vascular smooth muscle cells (VSMC). We have recently demonstrated that ROS stimulate secretion of VSMC-derived cyclophilin A (CyPA) that promotes proliferation and migration of VSMC in vivo and in vitro. In addition, we reported that Rho-kinase is activated in patients with PAH. However, the role of CyPA in the pathogenesis of PAH in humans remains to be examined. In this study, we tested the hypothesis that CyPA contributes to Rho-kinase activation and pulmonary vascular remodeling in PAH patients.
Methods and Results: We used lung tissue and pulmonary VSMC from 8 PAH patients who underwent lung transplantation and 6 controls (normal tissue from lung cancer patients). Immunostaining of the lung revealed that CyPA expression in pulmonary microvasculature (co-localized with αSMA+ cells) was greater in the PAH patients compared with the controls. The numbers of CD45+, CD68+ and CD3+ cells in the lung were all significantly increased in the PAH patients compared with the controls (all P<0.01), suggesting the role of CyPA in inflammatory cell recruitment. In addition, cell proliferation measured by PCNA+ cells significantly correlated with CyPA expression, suggesting that CyPA is involved in VSMC proliferation. In response to hypoxic exposure (1%; O2, 24 hours), CyPA secretion as well as Rho-kinase activity were significantly increased as compared with normoxic condition (21%; O2, 24 hours) in VSMC and the extent of the hypoxia-induced CyPA secretion was markedly enhanced in PAH VSMC compared with control VSMC (P<0.0001). In the organ culture experiment, CyPA secretion from the lung tissue was significantly increased in the PAH patients compared with the controls (P<0.01). Furthermore, treatment with exogenous CyPA (100 nM) significantly increased Rho-kinase activity in PAH VSMC (P<0.01). Finally, pretreatment with the specific Rho-kinase inhibitor, hydroxyfasudil (10 μM), significantly inhibited the hypoxia-induced CyPA secretion from PAH VSMC (P<0.001).
Conclusions: These results provide the direct evidence that the CyPA/Rho-kinase pathway plays an important role in the pathogenesis of PAH in humans.
- © 2010 by American Heart Association, Inc.