KS-C370G對心臟缺血-再灌流之保護與心血管作用評估

Abstract

In cardiac pathology, it is well known that injury from reperfusion could be more serious than ischemia, and generation of reactive oxygen species (ROS) might be the main cause of reperfusion injury. In the reperfusion period, ROS can exacerbate the injury from ischemia directly by breaking DNA and peroxidating lipid or protein, or indirectly by inducing inflammatory responses like complement or neutrophil activation. Therefore, antioxidant therapy is thought to be an effective method to reduce ischemia-reperfusion injury. In these years, the caffeic-acid compounds derived from the propolis of honeybee hives, CAPE (Caffeic acid phenethyl ester), is reported to have remarkable antioxidant effect, and it has been proved that CAPE can protect heart from ischemia-reperfusion injury by various mechanisms. In the series of synthetic CAPE derivatives, KS-C370G has the strongest antioxidant activity in DPPH-radical scavengering assay. Therefore, we chose this compound and evaluated its cardiovascular effects and cardioprotective effects against ischemia-reperusion injury, especially the latter. Furthermore, an analogue of KS-C370G “No.369”, with no radical-scavenging activity, was used to test whether the antioxidant effect was involved in the cardioprotective pathway. In isolated rat RV, contractile force was reduced by KS-C370G, In contrast, contractile force of the left and right atria were reduced by CAPE. Heart rate was not significantly alterd by both compounds. Regional myocardial ischemia-reperfusion model-1 was established by ligating the left main coronary artery of rat hearts forc5 min followed by reperfusion for 30 min in vivo to induce arrhythmia. CAPE and KS-C370G (both 15 mg/kg i.p.) has no effects on reducing VT and VF duration. These results suggested that both compounds had no anti-arrhythmic activity. Model-2 was established by ligating left main coronary artery for 45 min followed by reperfusion for 2 hour in vivo to evaluate the cardioprotective effects. KS-C370G 3 mg/kg and 15 mg/kg i.p. significantly reduced infarct size (IS) dose-dependently, but neither reduced the level of CK-MB and LDH. These results were similar to those of CAPE. Moreover, No.369 15 mg/kg i.p. had no cardioprotective effect in IS. These results suggested that the cardioprotective effects of CAPE and KS-C370G were mainly due to their antioxidant activity. Interestingly, when NOS inhibitor L-NAME (3 mg/kg i.p.) was added 15 min before drug injection, the cardioprotective effects of CAPE and KS-C370G (both 15 mg/kg i.p.) in IS were eliminated. This suggested that NO was an important factor responsible for cardioprotection. However, in the NO content assay, neither CAPE nor KS-C370G significantly increased NO content. In hemodynamic parameters in the time course of ischemia- reperfusion, CAPE, KS-C370G and No.369 (all 15 mg/kg i.p.) had no effects on HR and BP. This suggested that the cardioprotective effects were not due to reduced oxygen comsumption by decreasing heart work. Furthermore, malondialdehyde (MDA) content assay and myoperoxidase (MPO) activity assay were performed to evaluate the effects of compounds on lipid peroxidation and neutrophil acitivation recpectively. CAPE and KS-C370G (both 15 mg/kg i.p.) significantly reduced MDA content, but not No.369 (15 mg/kg i.p.). This indicated that CAPE and KS-C370G treatment reduced the oxidative stress. On the other hand, CAPE and KS-C370G also reduced MPO activity, but not No.369. This suggested that the cardioprotective effects of CAPE and KS-C370G was partly attributed to reducing inflammatory reponse by their antioxidant effects indirectly. In summary, KS-C370G, like CAPE, might exert cardioprotective activity mainly through its antioxidant ability resulting in reduced cardiomyocyte necrosis, lipid peroxidation and neutrophil activation. Nitric oxide might contribute to its protective effects. However, the mechanisms remain to be clarified in further studies.