Fifth complement cascade protein (C5) cleavage fragments disrupt the SDF-1/CXCR4 axis: further evidence that innate immunity orchestrates the mobilization of hematopoietic stem/progenitor cells.
OBJECTIVE
Having previously demonstrated that the complement system modulates mobilization of hematopoietic stem/progenitor cells (HSPC) in mice, we investigated the involvement of C5 cleavage fragments (C5a/(desArg)C5a) in human HSPC mobilization.


METHODS
C5 cleavage fragments in the plasma were evaluated by enzyme-linked immunosorbent assay using human anti-(desArg)C5a antibody, and expression of the C5a/(desArg)C5a receptor (CD88) in hematopoietic cells by flow cytometry. We also examined the chemotactic responses of hematopoietic cells to C5 cleavage fragments and expression of stromal cell-derived factor-1 (SDF-1)-degrading proteases that perturb retention of HSPC in bone marrow, namely matrix metalloproteinase (MMP)-9, membrane type (MT) 1-MMP, and carboxypeptidase M.


RESULTS
We found that plasma levels of (desArg)C5a are significantly higher in patients who are good mobilizers and correlate with CD34(+) cell and white blood cell counts in mobilized peripheral blood. C5 cleavage fragments did not chemoattract myeloid progenitors (colony-forming unit granulocyte-macrophage), but (desArg)C5a did strongly chemoattract mature nucleated cells. Consistently, CD88 was not detected on CD34(+) cells, but appeared on more mature myeloid precursors, monocytes, and granulocytes. Moreover, granulocyte colony-stimulating factor-mobilized peripheral blood mononuclear cells and polymorphonuclear cells had a significantly higher percentage of cells expressing CD88 than nonmobilized peripheral blood. Furthermore, C5a stimulation of granulocytes and monocytes decreased CXCR4 expression and chemotaxis toward an SDF-1 gradient and increased secretion of MMP-9 and expression of MT1-MMP and carboxypeptidase M.


CONCLUSIONS
C5 cleavage fragments not only induce a highly proteolytic microenvironment in human bone marrow, which perturbs retention through the CXCR4/SDF-1 axis, but also strongly chemoattracts granulocytes, promoting their egress into mobilized peripheral blood, which is crucial for subsequent mobilization of HSPC.
Canadian Blood Services R & D, University of Alberta, Edmonton, Alberta, Canada.
Ali
A
Jalili
Neeta
N
Shirvaikar
Leah
L
Marquez-Curtis
Yuanyuan
Y
Qiu
Chris
C
Korol
HakMo
H
Lee
A Robert
AR
Turner
Mariusz Z
MZ
Ratajczak
Anna
A
Janowska-Wieczorek
D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D054377:Chemokine CXCL12 / Q000276:immunology*; D002633:Chemotaxis / Q000187:drug effects / Q000276:immunology; D003182:Complement C5 / Q000276:immunology*; D015936:Complement C5a / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000187:drug effects; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism; D019650:Hematopoietic Stem Cell Mobilization; D006412:Hematopoietic Stem Cells / Q000276:immunology; D006801:Humans; D007113:Immunity, Innate; D008228:Lymphoma, Non-Hodgkin / Q000276:immunology*; D051379:Mice; D010446:Peptide Fragments / Q000378:metabolism; D044087:Receptor, Anaphylatoxin C5a / Q000378:metabolism; D019718:Receptors, CXCR4 / Q000276:immunology*; D015854:Up-Regulation
D054377:Chemokine CXCL12; D003182:Complement C5; D010446:Peptide Fragments; D044087:Receptor, Anaphylatoxin C5a; D019718:Receptors, CXCR4; D016179:Granulocyte Colony-Stimulating Factor; D015936:Complement C5a; D002392:Catechin; C045651:epigallocatechin gallate