Patel Hemal H, Zhang Shen, Murray Fiona, Suda Ryan Y S, Head Brian P, Yokoyama Utako, Swaney James S, Niesman Ingrid R, Schermuly Ralph T, Pullamsetti Soni Savai, Thistlethwaite Patricia A, Miyanohara Atsushi, Farquhar Marilyn G, Yuan Jason X-J, Insel Paul A
University of California, San Diego, Department of Pharmacology, 9500 Gilman Dr., La Jolla, CA 92093-0636, USA.
FASEB J. 2007 Sep;21(11):2970-9. doi: 10.1096/fj.07-8424com. Epub 2007 Apr 30.
Vasoconstriction and vascular medial hypertrophy, resulting from increased intracellular [Ca2+] in pulmonary artery smooth muscle cells (PASMC), contribute to elevated vascular resistance in patients with idiopathic pulmonary arterial hypertension (IPAH). Caveolae, microdomains within the plasma membrane, contain the protein caveolin, which binds certain signaling molecules. We tested the hypothesis that PASMC from IPAH patients express more caveolin-1 (Cav-1) and caveolae, which contribute to increased capacitative Ca2+ entry (CCE) and DNA synthesis. Immunohistochemistry showed increased expression of Cav-1 in smooth muscle cells but not endothelial cells of pulmonary arteries from patients with IPAH. Subcellular fractionation and electron microscopy confirmed the increase in Cav-1 and caveolae expression in IPAH-PASMC. Treatment of IPAH-PASMC with agents that deplete membrane cholesterol (methyl-beta-cyclodextrin or lovastatin) disrupted caveolae, attenuated CCE, and inhibited DNA synthesis of IPAH-PASMC. Increasing Cav-1 expression of normal PASMC with a Cav-1-encoding adenovirus increased caveolae formation, CCE, and DNA synthesis; treatment of IPAH-PASMC with siRNA targeted to Cav-1 produced the opposite effects. Treatments that down-regulate caveolin/caveolae expression, including cholesterol-lowering drugs, reversed the increased CCE and DNA synthesis in IPAH-PASMC. Increased caveolin and caveolae expression thus contribute to IPAH-PASMC pathophysiology. The close relationship between caveolin/caveolae expression and altered cell physiology in IPAH contrast with previous results obtained in various animal models, including caveolin-knockout mice, thus emphasizing unique features of the human disease. The results imply that disruption of caveolae in PASMC may provide a novel therapeutic approach to attenuate disease manifestations of IPAH.
肺动脉平滑肌细胞（PASMC）内细胞内[Ca2+]升高导致的血管收缩和血管中层肥厚，是特发性肺动脉高压（IPAH）患者血管阻力升高的原因。小窝是质膜内的微区，含有窖蛋白，窖蛋白可结合某些信号分子。我们检验了这样一个假设，即IPAH患者的PASMC表达更多的窖蛋白-1（Cav-1）和小窝，这会导致钙池调控性钙内流（CCE）增加和DNA合成增加。免疫组织化学显示，IPAH患者肺动脉的平滑肌细胞而非内皮细胞中Cav-1表达增加。亚细胞分级分离和电子显微镜证实，IPAH-PASMC中Cav-1和小窝表达增加。用消耗膜胆固醇的试剂（甲基-β-环糊精或洛伐他汀）处理IPAH-PASMC会破坏小窝，减弱CCE，并抑制IPAH-PASMC的DNA合成。用编码Cav-1的腺病毒增加正常PASMC的Cav-1表达会增加小窝形成、CCE和DNA合成；用靶向Cav-1的siRNA处理IPAH-PASMC则产生相反的效果。包括降胆固醇药物在内的下调窖蛋白/小窝表达的处理，逆转了IPAH-PASMC中增加的CCE和DNA合成。因此，窖蛋白和小窝表达增加促成了IPAH-PASMC的病理生理学。IPAH中窖蛋白/小窝表达与细胞生理学改变之间的密切关系与之前在各种动物模型（包括窖蛋白基因敲除小鼠）中获得的结果形成对比，从而强调了人类疾病的独特特征。结果表明，破坏PASMC中的小窝可能为减轻IPAH的疾病表现提供一种新的治疗方法。
