College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA.
Mass Spectrometry Facility, University of South Carolina, Columbia, SC 29208, USA.
Int J Mol Sci. 2024 Oct 23;25(21):11389. doi: 10.3390/ijms252111389.
CycloAnt is an opioid peptide that produces potent and efficacious antinociception with significantly reduced side effects upon systemic administration in mice. To verify its CNS-mediated antinociception, we determined its binding affinity at the opioid receptors, its proteolytic stability in mouse serum, metabolic stability in mouse liver microsomes, and pharmacokinetics in mice. CycloAnt exhibited stability toward proteolytic degradation in serum and resistance against metabolism mediated by cytochrome P450 enzymes (CYP450s) and UDP-glucuronosyl transferases (UGTs) in mouse liver microsomes. A pharmacokinetic study of CycloAnt in mice confirmed that CycloAnt crossed the blood-brain barrier (BBB) with a brain-to-plasma ratio of 11.5%, a high extent of BBB transport for a peptide. To elucidate the structural basis underlying its BBB penetration, we investigated its conformation in water and DMSO using H NMR spectroscopy. The results show that CycloAnt displays an extended conformation in water with most amide NHs being exposed, while in less polar DMSO, it adopts a compact conformation with all amide NHs locked in intramolecular hydrogen bonds. The chameleonic property helps CycloAnt permeate the BBB.
环抗是一种阿片肽，在小鼠体内系统给药时具有强大而有效的镇痛作用，副作用明显减少。为了验证其中枢神经系统介导的镇痛作用，我们测定了其在阿片受体上的结合亲和力、在小鼠血清中的蛋白水解稳定性、在小鼠肝微粒体中的代谢稳定性以及在小鼠中的药代动力学。环抗在血清中对蛋白水解降解具有稳定性，并且在小鼠肝微粒体中对细胞色素 P450 酶 (CYP450s) 和 UDP-葡萄糖醛酸转移酶 (UGTs) 介导的代谢具有抗性。环抗在小鼠中的药代动力学研究证实，环抗能够穿过血脑屏障 (BBB)，脑血浆比为 11.5%，这是一种肽类物质穿过 BBB 的高程度。为了阐明其穿透 BBB 的结构基础，我们使用 H NMR 光谱法研究了其在水中和 DMSO 中的构象。结果表明，环抗在水中呈现伸展构象，大多数酰胺 NH 暴露在外，而在极性较小的 DMSO 中，它采用紧凑构象，所有酰胺 NH 都被锁定在分子内氢键中。这种变色龙特性有助于环抗穿透 BBB。
