Kim Kyun Ha, Han Jin Woo, Jung Sung-Ki, Park Bum-Joon, Han Chang Woo, Joo Myungsoo
School of Korean Medicine, Pusan National University, Yangsan 50612, Republic of Korea.
Division of Allergy, Immune and Respiratory System, Department of Internal Medicine, College of Oriental Medicine, Kyung Hee University, Seoul 130-701, Republic of Korea.
Phytomedicine. 2017 Aug 15;32:8-14. doi: 10.1016/j.phymed.2017.04.008. Epub 2017 Apr 13.
Kaurenoic acid (ent-kaur-16-en-19-oic acid: KA) is a key constituent found in the roots of Aralia continentalis Kitagawa (Araliaceae) that has been used for treating rheumatism in traditional Asian medicine.
Although KA was reported to suppress inflammation by activating Nrf2, the anti-inflammatory function of KA is less characterized. Given the complex nature of the inflammatory response and the critical role of TGF-β in resolving inflammation, we hypothesized that KA suppresses inflammatory response by activating TGF-β signaling.
Murine macrophage RAW 264.7, human lung epithelial cell MRC-5, and a TGFβRII defective cell HCT116 were treated with various amounts of KA. KA was also administered to mouse lung via intratracheal (i.t.) route. Phosphorylated Smad2 and Smad3 were analyzed by western blot. TGFβ-dependent gene expression was determined by immunoblotting of α-SMA and luciferase assay.
KA induced the phosphorylation of Smad2 and Smad3, key activator molecules in TGF-β signaling. EW7197, an inhibitor for activin receptor-like kinase 5/TGF-β receptor I (TGFβR1) suppressed KA-mediated phosphorylation of Smad2. Similarly, KA failed to phosphorylate Smad2 in HCT116, suggesting that KA acts through the prototypic TGFβR. KA treatment increased the transcriptional activity driven by a Smad-binding element in a luciferase reporter assay and induced the α-smooth muscle actin (α-SMA). Similarly, i.t. KA induced the phosphorylation of Smad2 and increased the expression ofα-SMA in mouse lungs.
KA activated TGF-β signaling, suggesting that TGFβ signaling is associated with KA suppressing inflammation.
贝壳杉烯酸（对映-贝壳杉-16-烯-19-酸：KA）是辽东楤木（五加科）根中的一种关键成分，在传统亚洲医学中一直用于治疗风湿病。
尽管据报道KA通过激活Nrf2来抑制炎症，但其抗炎功能的特征尚不明确。鉴于炎症反应的复杂性以及转化生长因子-β（TGF-β）在炎症消退中的关键作用，我们假设KA通过激活TGF-β信号传导来抑制炎症反应。
用不同剂量的KA处理小鼠巨噬细胞RAW 264.7、人肺上皮细胞MRC-5和TGFβRII缺陷细胞HCT116。KA也通过气管内（i.t.）途径给药至小鼠肺部。通过蛋白质免疫印迹分析磷酸化的Smad2和Smad3。通过α-平滑肌肌动蛋白（α-SMA）的免疫印迹和荧光素酶测定来确定TGFβ依赖性基因表达。
KA诱导了TGF-β信号传导中的关键激活分子Smad2和Smad3的磷酸化。激活素受体样激酶5/转化生长因子-β受体I（TGFβR1）的抑制剂EW7197抑制了KA介导的Smad2磷酸化。同样，KA在HCT116中未能使Smad2磷酸化，表明KA通过原型TGFβR起作用。在荧光素酶报告基因测定中，KA处理增加了由Smad结合元件驱动的转录活性，并诱导了α-平滑肌肌动蛋白（α-SMA）。同样，气管内注射KA诱导了Smad2的磷酸化，并增加了小鼠肺中α-SMA的表达。
KA激活了TGF-β信号传导，表明TGFβ信号传导与KA抑制炎症有关。
