Zhou Hongling, Yang Tangjia, Lu Zibin, He Xuemei, Quan Jingyu, Liu Shanhong, Chen Yuyao, Wu Kangtai, Cao Huihui, Liu Junshan, Yu Linzhong
Third Level Research Laboratory of State Administration of Traditional Chinese Medicine, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, 510515, People's Republic of China.
Guangdong Provincial Key Laboratory of Chinese Medicine Pharmaceutics, School of Traditional Chinese Medicine, Southern Medical University, Guangzhou, 510515, People's Republic of China.
Chin Med. 2023 Apr 3;18(1):35. doi: 10.1186/s13020-023-00739-3.
Licorice (Glycyrrhiza uralensis Fisch.), a well-known traditional medicine, is traditionally used for the treatment of respiratory disorders, such as cough, sore throat, asthma and bronchitis. We aim to investigate the effects of liquiritin (LQ), the main bioactive compound in licorice against acute lung injury (ALI) and explore the potential mechanism.
Lipopolysaccharide (LPS) was used to induce inflammation in RAW264.7 cells and zebrafish. Intratracheal instillation of 3 mg/kg of LPS was used for induction an ALI mice model. The concentrations of IL-6 and TNF-α were tested using the enzyme linked immunosorbent assay. Western blot analysis was used to detect the expression of JNK/Nur77/c-Jun related proteins. Protein levels in bronchoalveolar lavage fluid (BALF) was measured by BCA protein assay. The effect of JNK on Nur77 transcriptional activity was determined by luciferase reporter assay, while electrophoretic mobility shift assay was used to examine the c-Jun DNA binding activity.
LQ has significant anti-inflammatory effects in zebrafish and RAW264.7 cells. LQ inhibited the expression levels of p-JNK (Thr183/Tyr185), p-Nur77 (Ser351) and p-c-Jun (Ser63), while elevated the Nur77 expression level. Inhibition of JNK by a specific inhibitor or small interfering RNA enhanced the regulatory effect of LQ on Nur77/c-Jun, while JNK agonist abrogated LQ-mediated effects. Moreover, Nur77-luciferase reporter activity was suppressed after JNK overexpression. The effects of LQ on the expression level of c-Jun and the binding activity of c-Jun with DNA were attenuated after Nur77 siRNA treatment. LQ significantly ameliorated LPS-induced ALI with the reduction of lung water content and BALF protein content, the downregulation of TNF-α and IL-6 levels in lung BALF and the suppression of JNK/Nur77/c-Jun signaling, which can be reversed by a specific JNK agonist.
Our results indicated that LQ exerts significant protective effects against LPS-induced inflammation both in vivo and in vitro via suppressing the activation of JNK, and consequently inhibiting the Nur77/c-Jun signaling pathway. Our study suggests that LQ may be a potential therapeutic candidate for ALI and inflammatory disorders.
甘草（Glycyrrhiza uralensis Fisch.）是一种著名的传统药物，传统上用于治疗呼吸系统疾病，如咳嗽、喉咙痛、哮喘和支气管炎。我们旨在研究甘草中的主要生物活性化合物甘草苷（LQ）对急性肺损伤（ALI）的影响，并探索其潜在机制。
使用脂多糖（LPS）诱导RAW264.7细胞和斑马鱼发生炎症。通过气管内注入3mg/kg的LPS来诱导建立ALI小鼠模型。使用酶联免疫吸附测定法检测白细胞介素-6（IL-6）和肿瘤坏死因子-α（TNF-α）的浓度。采用蛋白质免疫印迹分析检测JNK/Nur77/c-Jun相关蛋白的表达。通过BCA蛋白质测定法测量支气管肺泡灌洗液（BALF）中的蛋白质水平。通过荧光素酶报告基因测定法确定JNK对Nur77转录活性的影响，同时采用电泳迁移率变动分析检测c-Jun与DNA的结合活性。
LQ在斑马鱼和RAW264.7细胞中具有显著的抗炎作用。LQ抑制了p-JNK（Thr183/Tyr185）、p-Nur77（Ser351）和p-c-Jun（Ser63）的表达水平，同时提高了Nur77的表达水平。使用特异性抑制剂或小干扰RNA抑制JNK可增强LQ对Nur77/c-Jun的调节作用，而JNK激动剂则消除了LQ介导的作用。此外，JNK过表达后，Nur77-荧光素酶报告基因活性受到抑制。Nur77小干扰RNA处理后，LQ对c-Jun表达水平及其与DNA结合活性的影响减弱。LQ显著改善了LPS诱导的ALI，降低了肺含水量和BALF蛋白含量，下调了肺BALF中TNF-α和IL-6水平，并抑制了JNK/Nur77/c-Jun信号通路，而特异性JNK激动剂可逆转这些作用。
我们的结果表明，LQ通过抑制JNK的激活，进而抑制Nur77/c-Jun信号通路，在体内和体外对LPS诱导的炎症均发挥显著的保护作用。我们的研究表明，LQ可能是ALI和炎症性疾病的潜在治疗候选药物。
