Extracellular Hemoglobin Polarizes the Macrophage Proteome toward Hb-Clearance, Enhanced Antioxidant Capacity and Suppressed HLA Class 2 Expression

Peripheral blood monocytes and macrophages are the only cell population with a proven hemoglobin (Hb) clearance capacity through the CD163 scavenger receptor pathway. Hb detoxification and related adaptive cellular responses are assumed to be essential processes to maintaining tissue homeostasis and promoting wound healing in injured tissues. Using a dual platform mass spectrometry analysis with MALDI-TOF/TOF and LTQ-Orbitrap instruments combined with isobaric tag for relative and absolute quantitation (iTRAQ), we analyzed how Hb exposure could modulate the macrophage phenotype on a proteome level. We identified and relatively quantified 3691 macrophage proteins, representing the largest human macrophage proteome published to date. The Hb polarized macrophage phenotype was characterized by an induced Hb:Hp-CD163-HO1-ferritin pathway and enhanced antioxidant enzymes while suppression of HLA class 2 was the most prominent effect. Enhanced Hb clearance and antioxidant capacity together with reduced antigen presentation might therefore be essential qualities of Hb polarized macrophages in wounded tissues and hemorrhage or atherosclerotic plaques.

外周血单核细胞与巨噬细胞是目前经证实可通过CD163清道夫受体通路行使血红蛋白（hemoglobin，Hb）清除功能的唯一细胞群。血红蛋白解毒及相关适应性细胞应答，被认为是维持组织稳态、促进损伤组织伤口愈合的核心生理过程。本研究采用搭载MALDI-TOF/TOF与LTQ-Orbitrap双平台的质谱分析技术，并结合同位素相对与绝对定量标签（isobaric tag for relative and absolute quantitation，iTRAQ），从蛋白质组层面解析血红蛋白暴露如何调控巨噬细胞表型。本研究共鉴定并相对定量了3691个巨噬细胞蛋白，构建了目前已发表的规模最大的人巨噬细胞蛋白质组数据集。血红蛋白极化的巨噬细胞表型以激活血红蛋白-结合珠蛋白（haptoglobin，Hp）-CD163-血红素氧合酶1（heme oxygenase 1，HO1）-铁蛋白通路、增强抗氧化酶表达为特征，而人类白细胞抗原II类（HLA class 2）表达下调则是其最显著的效应。因此，在伤口组织、出血部位或动脉粥样硬化斑块中，增强的血红蛋白清除能力、抗氧化活性与减弱的抗原呈递能力，或许是血红蛋白极化巨噬细胞的核心功能特质。