Beijing Key Laboratory of Traditional Chinese Veterinary Medicine, Beijing University of Agriculture, No.7 of Beinong road, Huilongguan town, Changping district, Beijing, 102206, People's Republic of China.
Inflammation. 2019 Feb;42(1):365-374. doi: 10.1007/s10753-018-0900-x.
Luteolin inhibits the adhesion of neutrophils to microvascular endothelial cells and plays an important anti-inflammatory role, owing to its mechanism of suppressing the expression of lymphocyte function-associated antigen-1 (LFA-1) in the neutrophils. Our study deals with the different signaling pathways participating in LFA-1 expression in neutrophils along with the regulation of luteolin in order to elucidate new anti-inflammatory targets of luteolin, thus providing a basis for clinical applications. In our study, neutrophils were separated using density gradient centrifugation and the cAMP levels were determined using ELISA. Additionally, phosphorylation levels of p38 mitogen-activated protein kinase (MAPK), extracellular regulated protein kinase (ERK), phosphatidylinositol-3-kinase (PI3K), and Janus kinase (JAK) were also detected by Western blotting. LFA-1 expression was estimated using flow cytometry. The results showed that inhibiting agents used against p38 MAPK, ERK, PI3K, and JAK could significantly inhibit LFA-1 expression on neutrophils (p < 0.05, p < 0.01). Luteolin also induced a noteworthy elevation of cAMP in neutrophil supernatants (p < 0.01). It could also significantly inhibit ERK phosphorylation (p < 0.05, p < 0.01), and had no obvious effect on p38 MAPK phosphorylation in neutrophils (p > 0.05). However, phosphorylation of PI3K and JAK was not detected in neutrophils. To conclude, the p38 MAPK, ERK, PI3K, and JAK pathways are involved in the regulation of LFA-1 expression in neutrophils, and luteolin partially inhibits LFA-1 expression by increasing cAMP levels and suppressing ERK phosphorylation.
木樨草素通过抑制中性粒细胞淋巴细胞功能相关抗原-1（LFA-1）的表达发挥重要的抗炎作用，其机制在于抑制中性粒细胞中 LFA-1 的表达。本研究探讨了不同信号通路参与中性粒细胞 LFA-1 表达的调控以及木樨草素的调节作用，旨在阐明木樨草素的新的抗炎靶点，为临床应用提供依据。本研究采用密度梯度离心法分离中性粒细胞，ELISA 法检测 cAMP 水平，Western blot 法检测 p38 丝裂原活化蛋白激酶（MAPK）、细胞外调节蛋白激酶（ERK）、磷酸肌醇-3-激酶（PI3K）和 Janus 激酶（JAK）的磷酸化水平，流式细胞术检测 LFA-1 的表达。结果显示，p38 MAPK、ERK、PI3K 和 JAK 的抑制剂均可显著抑制中性粒细胞 LFA-1 的表达（p<0.05，p<0.01）。木樨草素也可显著增加中性粒细胞上清液中 cAMP 的含量（p<0.01）。它还可显著抑制 ERK 的磷酸化（p<0.05，p<0.01），但对中性粒细胞 p38 MAPK 的磷酸化无明显影响（p>0.05）。然而，中性粒细胞中未检测到 PI3K 和 JAK 的磷酸化。综上所述，p38 MAPK、ERK、PI3K 和 JAK 通路参与中性粒细胞 LFA-1 表达的调控，木樨草素通过增加 cAMP 水平和抑制 ERK 磷酸化部分抑制 LFA-1 的表达。
