Dexmedetomidine Pretreatment Protects Against Myocardial Ischemia/Reperfusion Injury by Activating STAT3 Signaling.

BACKGROUND: Myocardial infarction is a common perioperative complication, and blood flow restoration causes ischemia/reperfusion injury (IRI). Dexmedetomidine (DEX) pretreatment can protect against cardiac IRI, but the mechanism is still insufficiently understood. METHODS: In vivo, myocardial ischemia/reperfusion (30 minutes/120 minutes) was induced via ligation and then reperfusion of the left anterior descending coronary artery (LAD) in mice. Intravenous infusion of 10 µg/kg DEX was performed 20 minutes before ligation. Moreover, the α2-adrenoreceptor antagonist Yohimbine and STAT3 inhibitor Stattic were applied 30 minutes ahead of DEX infusion. In vitro, hypoxia/reoxygenation (H/R) with DEX pretreatment for 1 hour was performed in isolated neonatal rat cardiomyocytes. In addition, Stattic was applied before DEX pretreatment. RESULTS: In the mouse cardiac ischemia/reperfusion model, DEX pretreatment lowered the serum creatine kinase-MB isoenzyme (CK-MB) levels (2.47 ± 0.165 vs 1.55 ± 0.183; P < .0001), downregulated the inflammatory response ( P ≤ .0303), decreased 4-hydroxynonenal (4-HNE) production and cell apoptosis ( P = .0074), and promoted the phosphorylation of STAT3 (4.94 ± 0.690 vs 6.68 ± 0.710, P = .0001), which could be blunted by Yohimbine and Stattic. The bioinformatic analysis of differentially expressed mRNAs further confirmed that STAT3 signaling might be involved in the cardioprotection of DEX. Upon H/R treatment in isolated neonatal rat cardiomyocytes, 5 µM DEX pretreatment improved cell viability ( P = .0005), inhibited reactive oxygen species (ROS) production and calcium overload (both P ≤ .0040), decreased cell apoptosis ( P = .0470), and promoted STAT3 phosphorylation at Tyr705 (0.102 ± 0.0224 vs 0.297 ± 0.0937; P < .0001) and Ser727 (0.586 ± 0.177 vs 0.886 ± 0.0546; P = .0157), which could be abolished by Stattic. CONCLUSIONS: DEX pretreatment protects against myocardial IRI, presumably by promoting STAT3 phosphorylation via the α2-adrenoreceptor in vivo and in vitro.

Anti-TMV Effects of Amaryllidaceae Alkaloids Isolated from the Bulbs of Lycoris radiata and Lycoricidine Derivatives.

Fifteen known amaryllidaceae alkaloids were isolated from the bulbs of Lycoris radiata. Some of the compounds and lycoricidine derivatives had been screened for the activities against tobacco mosaic virus (TMV) by the conventional half-leaf method. Lycoricidine derivatives were also carried out the assay of effect on systemic infection of TMV by western-blot and RT-PCR analysis. The tested compounds showed moderate inactivation effect, whereas the lycoricidine derivatives showed good protective effect. The protective inhibitory activity of compounds L1 (N-methyl-2,3,4-trimethoxylycoricidine) (60.8%) and L3 (N-methyl-2-methoxy-3,4-acetonidelycoricidine) (62.0%) was almost similar to the positive control, Ningnanmycin (66.4%). RT-PCR and Western-blot analysis displayed that compounds L1, L3, L5 (N-allyl-2,3,4-triallyloxylycoricidine) exhibited antiviral activity, which was evidenced by reducing TMV-CP gene replication and TMV-CP protein expression. Additionally, defensive enzyme activities confirmed that compound L1 could increase the activity of PAL, POD, SOD to improve disease resistance of tobacco.