*Department of Emergency Medicine, National Taiwan University, College of Medicine and National Taiwan University Hospital, Taipei, Taiwan, R.O.C.
†Cardiology Section, Department of Internal Medicine, National Taiwan University, College of Medicine and National Taiwan University Hospital, Taipei, Taiwan, R.O.C.
Am J Chin Med. 2019;47(5):1043-1056. doi: 10.1142/S0192415X19500538. Epub 2019 Jul 17.
Baicalein is a natural flavonoid with anti-oxidant activities protecting against ischemia/reperfusion (I/R) injury. Previous studies suggest that oxidative burst early after reperfusion accelerates cell death. We therefore investigated the critical therapeutic window of baicalein by examining the timing of baicalein treatment in relation to its oxidant modulating and cytoprotective effects. Using an established chick cardiomyocyte model of I/R, we administered baicalein at various time points after reperfusion and assessed cell viability and the profiles of reactive oxygen species (ROS), nitric oxide (NO), and Akt phosphorylation. Baicalein administered at the onset of reperfusion resulted in a concentration-dependent reduction of cell death (25 M %, 50M %, 100M %, vs. I/R control %, all ). Baicalein (100M) timely and effectively scavenged ROS burst and enhanced NO production in the early reperfusion phase. Cotreatment with NO synthase (NOS) inhibitor l-NAME (200M) partially abrogated the cytoprotective effect. Baicalein (100M) given after reperfusion lost protective effect in a time-dependent manner with cytoprotection completely lost if min. Even with only 15-min delay after reperfusion, the ROS scavenging effect was abolished and the NO enhancing effect markedly reduced. The phosphorylation of Akt, an upstream regulator of eNOS, also diminished as the delay lengthened. In conclusion, baicalein treatment after reperfusion confers cardioprotection in a concentration- and time-dependent manner. The critical therapeutic window lies in the early reperfusion phase, during which ROS scavenging and Akt-eNOS mediated NO signaling are most effective.
黄芩素是一种具有抗氧化活性的天然黄酮类化合物，可防止缺血/再灌注（I/R）损伤。先前的研究表明，再灌注后早期的氧化爆发会加速细胞死亡。因此，我们通过研究黄芩素治疗与氧化剂调节和细胞保护作用的关系，来研究黄芩素的关键治疗窗口。我们使用已建立的鸡心肌细胞 I/R 模型，在再灌注后的不同时间点给予黄芩素，并评估细胞活力以及活性氧（ROS）、一氧化氮（NO）和 Akt 磷酸化的特征。再灌注开始时给予黄芩素会导致细胞死亡呈浓度依赖性降低（25μM%、50μM%、100μM%，与 I/R 对照%相比，均）。黄芩素（100μM）在再灌注早期及时有效地清除 ROS 爆发，并增强 NO 的产生。同时给予一氧化氮合酶（NOS）抑制剂 l-NAME（200μM）部分阻断了细胞保护作用。再灌注后给予黄芩素会随时间依赖性丧失保护作用，如果延迟 min，则完全丧失细胞保护作用。即使再灌注后仅延迟 15 分钟，其清除 ROS 的作用也会被消除，增强 NO 的作用也会明显降低。Akt 的磷酸化（eNOS 的上游调节剂）也随着延迟时间的延长而减弱。总之，再灌注后给予黄芩素治疗以浓度和时间依赖性方式提供心脏保护。关键的治疗窗口在于再灌注的早期阶段，在此期间，清除 ROS 和 Akt-eNOS 介导的 NO 信号传递最为有效。
