College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China.
Jiangsu Co-innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou 225009, China.
Mediators Inflamm. 2019 Apr 30;2019:1897820. doi: 10.1155/2019/1897820. eCollection 2019.
In our previous study, lipopolysaccharide (LPS) significantly reduced the cell viability of primary bovine mammary epithelial cells (bMEC) leading to cell apoptosis, which were prevented by caffeic acid (CA) through inhibiting NF-B activation and reducing proinflammatory cytokine expression. While the underlying mechanism remains unclear, here, we determined that LPS induced the extensive microstructural damage of bMEC, especially the mitochondria and endoplasmic reticulum. Then, the obvious reduction of mitochondrial membrane potential and expression changes of apoptosis-associated proteins (Bcl-2, Bax, and casepase-3) indicated that apoptosis signaling through the mitochondria should be responsible for the cell viability decrease. Next, the high-throughput cDNA sequencing (RNA-Seq) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were employed to verify that the MAPK and JAK-STAT signaling pathways also were the principal targets of LPS. Following, the critical proteins (ERK, JNK, p38, and c-jun) of the MAPK signaling pathways were activated, and the release of proinflammatory cytokines (TNF-, IL-1, IL-6, and IL-8) regulated by NF-B and MAPKs was significantly increased, which can promote a cascade of inflammation that induces cell injury and apoptosis. Meanwhile, CA significantly inhibited the activation of MAPKs and the release of proinflammatory cytokines in a dose-dependent manner, which were similar to its effects on the NF-B activation that we previously published. So we concluded that CA regulates the proteins located in the upstream of multiple cell signal pathways which can reduce the LPS-induced activation of NF-B and MAPKs, thus weakening the inflammatory response and maintaining cell structure and function, which accordingly inhibit apoptosis.
在我们之前的研究中,脂多糖(LPS)显著降低原代牛乳腺上皮细胞(bMEC)的细胞活力,导致细胞凋亡,而咖啡酸(CA)通过抑制 NF-B 激活和减少促炎细胞因子表达来阻止这种情况。虽然其潜在机制尚不清楚,但在这里,我们确定 LPS 诱导 bMEC 的广泛微观结构损伤,特别是线粒体和内质网。然后,线粒体膜电位明显降低和凋亡相关蛋白(Bcl-2、Bax 和 caspase-3)的表达变化表明,通过线粒体的凋亡信号应该是导致细胞活力下降的原因。接下来,我们采用高通量 cDNA 测序(RNA-Seq)和京都基因与基因组百科全书(KEGG)通路富集分析来验证 MAPK 和 JAK-STAT 信号通路也是 LPS 的主要靶点。随后,MAPK 信号通路的关键蛋白(ERK、JNK、p38 和 c-jun)被激活,并且 NF-B 和 MAPKs 调节的促炎细胞因子(TNF-α、IL-1、IL-6 和 IL-8)的释放显著增加,这可以促进级联炎症,导致细胞损伤和凋亡。同时,CA 以剂量依赖的方式显著抑制 MAPKs 的激活和促炎细胞因子的释放,这与其我们之前发表的对 NF-B 激活的作用相似。因此,我们得出结论,CA 调节位于多个细胞信号通路上游的蛋白,可降低 LPS 诱导的 NF-B 和 MAPK 的激活,从而减弱炎症反应并维持细胞结构和功能,从而抑制凋亡。