Human diamine oxidase (hDAO) rapidly inactivates histamine by deamination. No pharmacokinetic data are available to better understand its potential as a new therapeutic modality for diseases with excess local and systemic histamine, like anaphylaxis, urticaria or mastocytosis. After intravenous administration of recombinant hDAO to rats and mice, more than 90% of the dose disappeared from the plasma pool within 10 min. Human DAO did not only bind to various endothelial and epithelial cell lines in vitro, but was also unexpectedly internalized and visible in granule-like structures. The uptake of rhDAO into cells was dependent on neither the asialoglycoprotein-receptor (ASGP-R) nor the mannose receptor (MR) recognizing terminal galactose or mannose residues, respectively. Competition experiments with ASGP-R and MR ligands did not block internalization in vitro or rapid clearance in vivo. The lack of involvement of N-glycans was confirmed by testing various glycosylation mutants. High but not low molecular weight heparin strongly reduced the internalization of rhDAO in HepG2 cells and HUVECs. Human DAO was readily internalized by CHO-K1 cells, but not by the glycosaminoglycan- and heparan sulfate-deficient CHO cell lines pgsA-745 and pgsD-677, respectively. A docked heparin hexasaccharide interacted well with the predicted heparin binding site ⁵⁶⁸RFKRKLPK⁵⁷⁵. These results strongly imply that rhDAO clearance in vivo and cellular uptake in vitro is independent of N-glycan interactions with the classical clearance receptors ASGP-R and MR, but is mediated by binding to heparan sulfate proteoglycans followed by internalization via an unknown receptor.

中文翻译：

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体外人二胺氧化酶细胞结合和内化以及体内快速清除不是由 N-聚糖介导的，而是由硫酸乙酰肝素蛋白聚糖相互作用介导的

人二胺氧化酶 (hDAO) 通过脱氨作用快速灭活组胺。没有药代动力学数据可用于更好地了解其作为局部和全身组胺过量疾病（如过敏反应、荨麻疹或肥大细胞增多症）的新治疗方式的潜力。对大鼠和小鼠静脉注射重组 hDAO 后，90% 以上的剂量在 10 分钟内从血浆库中消失。人类 DAO 不仅在体外与各种内皮细胞和上皮细胞系结合，而且还出乎意料地内化并在颗粒状结构中可见。rhDAO 进入细胞的摄取既不依赖于脱唾液酸糖蛋白受体 (ASGP-R) 也不依赖于甘露糖受体 (MR) 识别末端半乳糖或甘露糖残基，分别。ASGP-R 和 MR 配体的竞争实验并未阻止体外内化或体内快速清除。缺乏参与N-聚糖通过测试各种糖基化突变体得到确认。高而不是低分子量肝素强烈降低了 rhDAO 在 HepG2 细胞和 HUVEC 中的内在化。人 DAO 很容易被 CHO-K1 细胞内化，但分别不能被缺乏糖胺聚糖和硫酸乙酰肝素的 CHO 细胞系 pgsA-745 和 pgsD-677 内化。对接的肝素六糖与预测的肝素结合位点⁵⁶⁸ RFKRKLPK ⁵⁷⁵相互作用良好。这些结果强烈暗示 rhDAO 体内清除和体外细胞摄取不依赖于N-聚糖与经典清除受体 ASGP-R 和 MR 的相互作用，而是通过与硫酸乙酰肝素蛋白多糖结合然后通过未知受体内化来介导。