Quercetin alleviates pulmonary angiogenesis in a rat model of hepatopulmonary syndrome

Quercetin shows protective effects against hepatopulmonary syndrome (HPS), as demonstrated in a rat model. However, whether these effects involve pulmonary vascular angiogenesis in HPS remains unclear. Therefore, this study aimed to assess the effect of quercetin on pulmonary vascular angiogenesis and explore the underlying mechanisms. Male Sprague-Dawley rats weighing 200-250 g underwent sham operation or common bile duct ligation (CBDL). Two weeks after surgery, HIF-1α and NFκB levels were assessed in rat lung tissue by immunohistochemistry and western blot. Then, CBDL and sham-operated rats were further divided into 2 subgroups each to receive intraperitoneal administration of quercetin (50 mg/kg daily) or 0.2% Tween for two weeks: Sham (Sham+Tween; n=8), CBDL (CBDL+Tween; n=8), Q (Sham+quercetin; n=8), and CBDL+Q (CBDL+quercetin; n=8). After treatment, lung tissue specimens were assessed for protein (immunohistochemistry and western blot) and/or gene expression (quantitative real-time PCR) levels of relevant disease markers, including VEGFA, VEGFR2, Akt/p-Akt, HIF-1α, vWf, and IκB/p-IκB. Finally, arterial blood was analyzed for alveolar arterial oxygen pressure gradient (AaPO2). Two weeks after CBDL, HIF-1α expression in the lung decreased, but was gradually restored at four weeks. Treatment with quercetin did not significantly alter HIF-1α levels, but did reduce AaPO2 as well as lung tissue NF-κB activity, VEGFA gene and protein levels, Akt activity, and angiogenesis. Although hypoxia is an important feature in HPS, our findings suggest that HIF-1α was not the main cause for the VEGFA increase. Interestingly, quercetin inhibited pulmonary vascular angiogenesis in rats with HPS, with involvement of Akt/NF-κB and VEGFA/VEGFR-2 pathways.

已有大鼠模型研究证实，槲皮素（quercetin）对肝肺综合征（hepatopulmonary syndrome, HPS）具有保护作用，但其保护作用是否通过调控肝肺综合征中的肺血管生成途径实现，目前仍不明确。为此，本研究旨在评估槲皮素对肺血管生成的影响，并探究其潜在分子机制。
本研究选取体重200~250 g的雄性斯普拉格-道利（Sprague-Dawley, SD）大鼠，分别接受假手术或胆总管结扎术（common bile duct ligation, CBDL）。术后2周，采用免疫组化与蛋白质免疫印迹（western blot）检测大鼠肺组织中缺氧诱导因子-1α（HIF-1α）及核因子κB（NFκB）的表达水平。
随后，将假手术组与胆总管结扎术组大鼠各分为2个亚组，连续2周分别腹腔注射槲皮素（每日50 mg/kg）或0.2%吐温（Tween）溶液，具体分组为：假手术+吐温组（"Sham+Tween", n=8）、胆总管结扎+吐温组（"CBDL+Tween", n=8）、假手术+槲皮素组（"Sham+quercetin", n=8）以及胆总管结扎+槲皮素组（"CBDL+quercetin", n=8）。
给药结束后，采集肺组织标本，通过免疫组化、蛋白质免疫印迹及实时定量聚合酶链反应（quantitative real-time PCR）检测相关疾病标志物的蛋白及基因表达水平，涵盖血管内皮生长因子A（VEGFA）、血管内皮生长因子受体2（VEGFR2）、Akt/磷酸化Akt（p-Akt）、HIF-1α、血管性血友病因子（vWf）以及IκB/磷酸化IκB（p-IκB）。同时采集动脉血样，检测肺泡动脉氧分压差（alveolar arterial oxygen pressure gradient, AaPO2）。
胆总管结扎术后2周，大鼠肺组织中HIF-1α的表达水平降低，但于术后4周逐渐恢复至基础水平。槲皮素干预未显著改变HIF-1α的表达水平，但可有效降低肺泡动脉氧分压差，同时抑制肺组织NF-κB活性、VEGFA的基因与蛋白表达、Akt活性及肺血管生成。尽管缺氧是肝肺综合征的重要病理特征，但本研究结果显示，HIF-1α并非导致VEGFA表达升高的主要诱因。值得注意的是，槲皮素可通过调控Akt/NF-κB及VEGFA/VEGFR-2信号通路，抑制肝肺综合征模型大鼠的肺血管生成。