Arnold and Marie Schwartz College of Pharmacy and Health Sciences , Long Island University , Brooklyn , New York 11201 , United States.
The Daniel K. Inouye College of Pharmacy , University of Hawaìi at Hilo , Hilo , Hawaii 96720 , United States.
J Nat Prod. 2019 Mar 22;82(3):492-499. doi: 10.1021/acs.jnatprod.8b00861. Epub 2019 Jan 16.
In previous studies, withanolides isolated from Physalis peruviana were found to exhibit anti-inflammatory potential by suppressing nitrite production induced by lipopolysaccharide (LPS) treatment. Currently, we selected two of the most potent compounds, 4β-hydroxywithanolide E (1) and physalactone (2), to examine the underlying mechanism of action. With LPS-stimulated RAW 264.7 cells in culture, the compounds inhibited the mRNA and protein expression of iNOS and COX-2. To determine which upstream signaling proteins were involved in these effects, phosphorylation levels of three mitogen-activated protein kinases (MAPKs) including ERK1/2, JNK1/2, and p38, were examined, but found unaffected. Similarly, the degradation of IκBα was not attenuated by the compounds. However, phosphorylation of Akt at the Ser-473 residue was inhibited, as was the phosphorylation of STAT1. Interestingly, the compounds also reduced the protein level of total STAT1, possibly by ubiquitin-dependent protein degradation. In sum, these results indicate the potential of 1 and 2 to mediate anti-inflammatory effects through the unexpected mechanism of inhibiting the transcription of iNOS and COX-2 via Akt- and STAT1-related signaling pathways.
在先前的研究中，从秘鲁酸浆中分离得到的醉茄内酯通过抑制脂多糖（LPS）处理诱导的亚硝酸盐产生表现出抗炎潜力。目前，我们选择了两种最有效的化合物，4β-羟基醉茄内酯 E（1）和酸浆内酯（2），以研究其作用机制。在 LPS 刺激的 RAW 264.7 细胞培养中，这些化合物抑制了 iNOS 和 COX-2 的 mRNA 和蛋白表达。为了确定这些作用涉及哪些上游信号蛋白，检查了三种丝裂原活化蛋白激酶（MAPKs）包括 ERK1/2、JNK1/2 和 p38 的磷酸化水平，但未发现受影响。同样，化合物也没有减弱 IκBα 的降解。然而，Akt 在 Ser-473 残基的磷酸化被抑制，STAT1 的磷酸化也是如此。有趣的是，这些化合物还降低了总 STAT1 的蛋白水平，可能是通过泛素依赖性蛋白降解。总之，这些结果表明 1 和 2 通过 Akt 和 STAT1 相关信号通路抑制 iNOS 和 COX-2 的转录来介导抗炎作用的潜力。
