Suzuki Yuto, Arakida Yo, Sakai Hiromi, Enoki Yuki, Matsumoto Kazuaki, Taguchi Kazuaki
Division of Pharmacodynamics, Keio University Faculty of Pharmacy, 1-5-30 Shibakoen, Minato-ku, Tokyo 105-8512, Japan.
Department of Chemistry, Nara Medical University, Shijo-cho 840, Kashihara, Nara 634-8521, Japan.
Toxicol Appl Pharmacol. 2023 Dec 15;481:116752. doi: 10.1016/j.taap.2023.116752. Epub 2023 Nov 11.
Methemoglobin (metHb), the oxidized form of hemoglobin, lacks the ability of reversible oxygen binding; however, it has a high binding affinity to toxic substances such as cyanide, hydrosulfide, and azide. This innate property of metHb offers the clinical option to treat patients poisoned with these toxins, by oxidizing the endogenous hemoglobin in the red blood cells (RBCs). The binding properties of naked metHb (isolated from RBC) with these toxins has been studied; however, the binding behaviors of metHb under the intracellular conditions of RBC are unclear because of the difficulty in detecting metHb status changes in RBC. This study aimed to elucidate the binding properties of metHb in RBC under physiological and poisoned conditions using artificial RBC, which was hemoglobin encapsulated in a liposome. The mimic-circumstances of metHb in RBC (metHb-V) was prepared by oxidizing the hemoglobin in artificial RBC. Spectroscopic analysis indicated that the metHb in metHb-V exhibited a binding behavior different from that of naked metHb, depending on the toxic substance: When the pH decreased, (i) the cyanide binding affinity of metHb-V remained unchanged, but that of naked metHb decreased (ii) the hydrosulfide binding affinity was increased in metHb-V but was decreased in naked metHb. (iii) Azide binding was increased in metHb-V, which was similar to that in naked metHb, irrespective of the pH change. Thus, the binding behavior of intracellular metHb in the RBC with cyanide, hydrosulfide, and azide under physiological and pathological conditions were partly elucidated using the oxidized artificial RBC.
高铁血红蛋白（metHb）是血红蛋白的氧化形式，缺乏可逆结合氧的能力；然而，它对氰化物、硫化氢和叠氮化物等有毒物质具有高结合亲和力。高铁血红蛋白的这种固有特性为治疗这些毒素中毒的患者提供了一种临床选择，即通过氧化红细胞（RBC）中的内源性血红蛋白来实现。已经研究了游离高铁血红蛋白（从红细胞中分离）与这些毒素的结合特性；然而，由于难以检测红细胞中高铁血红蛋白状态的变化，红细胞内环境下高铁血红蛋白的结合行为尚不清楚。本研究旨在使用人工红细胞（血红蛋白包裹在脂质体中）阐明生理和中毒条件下红细胞内高铁血红蛋白的结合特性。通过氧化人工红细胞中的血红蛋白制备了红细胞中高铁血红蛋白的模拟环境（metHb-V）。光谱分析表明，metHb-V中的高铁血红蛋白表现出与游离高铁血红蛋白不同的结合行为，这取决于有毒物质：当pH值降低时，（i）metHb-V的氰化物结合亲和力保持不变，而游离高铁血红蛋白的氰化物结合亲和力降低；（ii）metHb-V中硫化氢的结合亲和力增加，而游离高铁血红蛋白中硫化氢的结合亲和力降低；（iii）无论pH值如何变化，metHb-V中叠氮化物的结合增加，这与游离高铁血红蛋白中的情况相似。因此，利用氧化人工红细胞部分阐明了生理和病理条件下红细胞内高铁血红蛋白与氰化物、硫化氢和叠氮化物的结合行为。
