Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
Cytometry A. 2010 Mar;77(3):220-30. doi: 10.1002/cyto.a.20860.
Pyroglutamyl proline-rich oligopeptides, present in the venom of the pit viper Bothrops jararaca (Bj-PROs), are the first described naturally occurring inhibitors of the angiotensin I-converting enzyme (ACE). The inhibition of ACE by the decapeptide Bj-PRO-10c (<ENWPHPQIPP) and other Bj-PROs was classically used to explain the pharmacological effects of these venom peptides in mammals resulting in a decrease of blood pressure. Recent studies, however, suggest that ACE inhibition alone is not sufficient for explaining the antihypertensive actions exerted by these peptides. In this study, we show that intracerebroventricular injection of Bj-PRO-10c induced a significant reduction of mean arterial pressure (MAP) together with a decrease of heart rate (HR) in spontaneously hypertensive rats, indicating that Bj-PRO-10c may act on the central nervous system. In agreement with its supposed neuronal action, this peptide dose-dependently evoked elevations of intracellular calcium concentration (Ca(2+)) in primary culture from postnatal rat brain. The N-terminal sequence of the peptide was not essential for induction of calcium fluxes, while any changes of C-terminal Pro or Ile residues affected Bj-PRO-10c's activity. Using calcium imaging by confocal microscopy and fluorescence imaging plate reader analysis, we have characterized Bj-PRO-10c-induced Ca(2+) transients in rat brain cells as being independent from bradykinin-mediated effects and ACE inhibition. Bj-PRO-10c induced pertussis toxin-sensitive G(i/o)-protein activity mediated through a yet unknown receptor, influx and liberation ofcalcium from intracellular stores, as well as reduction of intracellular cAMP levels. Bj-PRO-10c promoted glutamate and GABA release that may be responsible for its antihypertensive activity and its effect on HR.
吡咯并脯氨酸丰富的寡肽，存在于矛头蝮蛇（Bothrops jararaca）的毒液中（Bj-PROs），是第一个被描述的天然血管紧张素转化酶（ACE）抑制剂。十肽 Bj-PRO-10c（<ENWPHPQIPP）和其他 Bj-PROs 对 ACE 的抑制作用，经典地用于解释这些毒液肽在哺乳动物中的药理学效应，导致血压降低。然而，最近的研究表明，ACE 抑制作用本身不足以解释这些肽发挥的降压作用。在这项研究中，我们表明，Bj-PRO-10c 脑室内注射可引起自发性高血压大鼠平均动脉压（MAP）的显著降低，同时心率（HR）降低，表明 Bj-PRO-10c 可能作用于中枢神经系统。与假定的神经元作用一致，这种肽剂量依赖性地引起原代培养的新生大鼠脑内细胞内钙浓度 (Ca(2+))的升高。肽的 N 端序列对于诱导钙流不是必需的，而 C 端 Pro 或 Ile 残基的任何变化都会影响 Bj-PRO-10c 的活性。通过共聚焦显微镜和荧光成像板读数分析的钙成像，我们已经确定了 Bj-PRO-10c 诱导的大鼠脑细胞中 Ca(2+)瞬变与缓激肽介导的效应和 ACE 抑制无关。Bj-PRO-10c 诱导百日咳毒素敏感的 G(i/o)-蛋白活性，通过未知的受体介导，从细胞内储存库中流入和释放钙，以及降低细胞内 cAMP 水平。Bj-PRO-10c 促进谷氨酸和 GABA 的释放，这可能是其降压活性及其对 HR 的影响的原因。
