Laboratory of Electrophysiology and Cardiovascular Pharmacology, Faculty of Health Sciences, Universidade Federal da Grande Dourados, Dourados, MS, Brazil.
Laboratory of Preclinical Research of Natural Products, Paranaense University, Umuarama, PR, Brazil.
Chem Biol Interact. 2020 Aug 25;327:109182. doi: 10.1016/j.cbi.2020.109182. Epub 2020 Jun 15.
Nothofagin is a natural 3'-C-β-D-glucoside of the polyphenol phloretin that is mainly found in Aspalathus linearis, Nothofagus fusca, and Leandra dasytricha. In recent years, nothofagin has been described as a potential therapeutic agent for renal disorders, but the mechanisms that are involved in its renoprotective effects remain unclear. In the present study, perfused rat kidneys were used to test the hypothesis that nothofagin causes the direct relaxation of renal arteries. The molecular mechanisms that underlie these vascular effects were also investigated. The left kidney from Wistar rats was coupled in a perfusion system and continuously perfused with physiological saline solution (PSS). Initially, preparations with and without the endothelium were contracted with phenylephrine and received injections of 1-300 nmol nothofagin. The preparations were then perfused with PSS that contained phenylephrine plus KCl, indomethacin, l-NAME, tetraethylammonium, glibenclamide, 4-aminopyridine, iberiotoxin, charybdotoxin, and apamin. After 15 min under perfusion, nothofagin was injected again. In preparations with an intact endothelium, nothofagin dose-dependently reduced perfusion pressure. Endothelium removal or the inhibition of nitric oxide synthase by l-NAME prevented the vasodilatory effect of nothofagin at all doses tested. Perfusion with PSS that contained KCl or tetraethylammonium chloride also abolished the vasodilatory effect of nothofagin. Treatment with glibenclamide, 4-aminopyridine, and apamin did not affect the vasodilatory effect of nothofagin. Iberiotoxin (selective Ca-activated high-conductance K channel [KCa1.1] blocker) and charybdotoxin (selective KCa1.1 and Ca-activated intermediate-conductance K channel [KCa3.1] blocker) application blocked the vasodilatory effect of nothofagin at all doses tested, pointing to a predominant role for KCa1.1 in the action of nothofagin. However, these data cannot exclude a potential contribution of endothelial KCa3.1 channel in the nothofagin-induced vasodilation. Overall, our findings indicate that nothofagin induces vasodilation in renal arteries, an effect that is mediated by Ca -activated high-conductance K channels opening and endothelial nitric oxide production.
山柰酚 3'-C-β-D-葡萄糖苷（即山柰酚-3'-O-β-D-葡萄糖苷）是一种天然化合物，主要存在于银荆（Aspalathus linearis）、山毛榉（Nothofagus fusca）和 Leandra dasytricha 中。近年来，山柰酚被描述为治疗肾脏疾病的一种有潜力的治疗药物，但它的肾脏保护作用的机制尚不清楚。在本研究中，我们使用灌注大鼠肾脏来检验山柰酚引起肾脏动脉直接松弛的假设。我们还研究了这些血管作用的潜在分子机制。从 Wistar 大鼠的左肾连接到灌注系统中，并持续用生理盐水（PSS）灌注。最初，用苯肾上腺素收缩有和没有内皮的制剂，并注射 1-300nmol 山柰酚。然后，用含有苯肾上腺素加 KCl、吲哚美辛、l-NAME、四乙铵、格列本脲、4-氨基吡啶、iberiotoxin、charybdotoxin 和 apamin 的 PSS 冲洗制剂。灌注 15 分钟后，再次注射山柰酚。在内皮完整的制剂中，山柰酚剂量依赖性地降低灌注压。用 l-NAME 去除内皮或抑制一氧化氮合酶完全阻止了所有测试剂量的山柰酚的血管舒张作用。用含有 KCl 或四乙铵的 PSS 灌注也消除了山柰酚的血管舒张作用。用格列本脲、4-氨基吡啶和 apamin 处理不影响山柰酚的血管舒张作用。iberiotoxin（选择性 Ca 激活的高电导 K 通道[KCa1.1]阻断剂）和 charybdotoxin（选择性 KCa1.1 和 Ca 激活的中间电导 K 通道[KCa3.1]阻断剂）的应用阻断了所有测试剂量的山柰酚的血管舒张作用，表明 KCa1.1 在山柰酚的作用中起主要作用。然而，这些数据不能排除内皮 KCa3.1 通道在山柰酚诱导的血管舒张中的潜在作用。总的来说，我们的研究结果表明，山柰酚诱导肾脏动脉舒张，这种作用是通过 Ca 激活的高电导 K 通道开放和内皮一氧化氮产生介导的。
