Department of Pharmaceutical Sciences, Beijing Institute of Radiation Medicine, China.
FEBS Open Bio. 2021 Sep;11(9):2468-2489. doi: 10.1002/2211-5463.13240. Epub 2021 Aug 12.
Unfractionated heparin (UFH) is an anionic glycosaminoglycan that is widely used to prevent blood clotting. However, in certain cases, unwanted side effects can require it to be neutralized. Protamine sulfate (PS), a basic peptide rich in arginine, is the only approved antagonist for UFH neutralization. Many adverse reactions occur with the clinical application of PS, including systemic hypotension, pulmonary hypertension, and anaphylaxis. We previously described R15, a linear peptide composed of 15 arginine molecules, as a potential UFH antagonist. In this study, the in-depth safety of R15 was explored to reveal its merits and associated risks in comparison with PS. In vitro safety studies investigated the interactions of R15 with erythrocytes, fibrin, complement, and rat plasma. In vivo safety studies explored potential toxicity and immunogenicity of R15 and the UFH-R15 complex. Results showed that both PS and R15 can induce erythrocyte aggregation, thicken fibrin fibers, activate complement, and cause anticoagulation in a concentration-dependent manner. However, those influences weakened in whole blood or in live animals and were avoided when R15 was in a complex with UFH. We found dramatically enhanced complement activation when there was excess UFH in analyses involving UFH-PS complexes, and a slight increase in those involving UFH-R15 complexes. Within 2 h, R15 was degraded in rat plasma in vitro, whereas PS was not. Enhanced creatinine was found after a single intravenous injection of PS or R15 (900 U·kg , body weight), suggesting possible abnormal renal function. The UFH-PS complex, but not the UFH-R15 complex, exhibited obvious immunogenicity. In conclusion, R15 is nonimmunogenic and potentially safe at a therapeutic dose to reverse the effects of UFH.
未分级肝素（UFH）是一种广泛用于预防血液凝固的阴离子糖胺聚糖。然而，在某些情况下，需要中和它以防止其产生不良反应。硫酸鱼精蛋白（PS）是一种富含精氨酸的碱性多肽，是唯一批准用于中和 UFH 的拮抗剂。PS 在临床应用中会发生许多不良反应，包括全身低血压、肺动脉高压和过敏反应。我们之前描述了由 15 个精氨酸分子组成的线性肽 R15，作为一种潜在的 UFH 拮抗剂。在这项研究中，深入探讨了 R15 的安全性，以揭示其与 PS 相比的优点和相关风险。体外安全性研究调查了 R15 与红细胞、纤维蛋白、补体和大鼠血浆的相互作用。体内安全性研究探讨了 R15 和 UFH-R15 复合物的潜在毒性和免疫原性。结果表明，PS 和 R15 都可以在浓度依赖性的方式诱导红细胞聚集、纤维蛋白纤维变厚、激活补体并导致抗凝。然而，这些影响在全血或活体内减弱，并且当 R15 与 UFH 形成复合物时会被避免。我们发现，在涉及 UFH-PS 复合物的分析中，当存在过量的 UFH 时，补体激活明显增强，而在涉及 UFH-R15 复合物的分析中，补体激活略有增加。在体外，R15 在大鼠血浆中 2 小时内降解，而 PS 则没有。在单次静脉注射 PS 或 R15（900 U·kg，体重）后，发现肌酐增强，这表明可能存在肾功能异常。UFH-PS 复合物，但不是 UFH-R15 复合物，表现出明显的免疫原性。总之，R15 在治疗剂量下是非免疫原性的，并且具有潜在的安全性，可以逆转 UFH 的作用。
