Phenotypic commitment of monocytes towards a protective hemoglobin scavenging phenotype (CD14(pos)CD163(high)HLA-DR(low))following cardiopulmonary bypass.
BACKGROUND
Intravascular hemolysis may cause tissue injury directly or via a systemic inﬂammatory response. Under physiological conditions, extracorpuscular hemoglobin (Hb) is bound by haptoglobin(Hp) and the complex internalized via the hemoglobin scavenger receptor CD163 on monocytes, prior to catabolism via heme-oxygenase-1 (HO-1). Recently, a novel subset of CD68(pos)CD163(high)HLA-DR(low) macrophages with high expression of HO-1 was recognized in hemorrhagic areas of atherosclerotic plaques, distinct from CD68(pos)CD163(low)HLA-DR(high) foam cell macrophages with low- HO-1 content. Considering the hemolytic insult during CPB, we hypothesized that an equivalent compensatory CD163(high)HLA-DR(low) phenotype will evolve in circulating CD14(pos) monocytes post surgery.


METHODS
Twelve patients undergoing elective surgery with CPB were enrolled with informed consent.Whole-blood samples were collected in EDTA at predetermined time-points, pre- intra-, and postoperatively. Whole-blood was evaluated by three-color flow cytometry for expression of CD14, CD163, and HLA-DR; CD14(pos) cells were also permeabilized to detect intracellular HO-1 protein. Plasma [Hp-Hb] concentration was determined by ELISA.


RESULTS
A striking phenotypic switch from CD163(low)HLA-DR(high) preoperatively to CD163(high)HLA-DR(low) postoperatively at 24 h was observed on circulating CD14(pos) monocytes. Intracellular HO-1 protein was also significantly up-regulated at 24 h after declamping. These phenotypic changes were preceded by peak Hb-Hp levels observed at 2 h.


CONCLUSIONS
We have shown for the first time, a phenotypic commitment of monocytes towards a protective CD14(pos)CD163(high)HLA-DR(low) population with increased intracellular HO-1 occurring in the circulation during the recovery phase of CPB. These findings have implications for monitoring of anti-inflammatory interventions and linkage to clinical outcomes.
Edmund Cohen Laboratory for Vascular Research, Chronic Disease Research Centre, Tropical Medicine Research Institute, University of the West Indies, Barbados.
Kim R
KR
Quimby
Andre
A
Greenidge
Anthony
A
Harris
R Clive
RC
Landis
D015703:Antigens, CD / Q000097:blood / Q000276:immunology; D015214:Antigens, Differentiation, Myelomonocytic / Q000097:blood / Q000276:immunology; D002315:Cardiopulmonary Bypass; D005434:Flow Cytometry; D005487:Foam Cells / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D006684:HLA-DR Antigens / Q000097:blood / Q000276:immunology; D006242:Haptoglobins / Q000032:analysis / Q000276:immunology; D051547:Heme Oxygenase-1 / Q000032:analysis; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000097:blood / Q000276:immunology; D009000:Monocytes / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D010641:Phenotype; D011184:Postoperative Period; D011956:Receptors, Cell Surface / Q000097:blood / Q000276:immunology; D015854:Up-Regulation; D000098902:CD163 Antigen
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D006684:HLA-DR Antigens; D006242:Haptoglobins; D006454:Hemoglobins; D018950:Lipopolysaccharide Receptors; D011956:Receptors, Cell Surface; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1