The importance of the interaction between leukocyte integrin Mac-1 and platelet glycoprotein Ib-a for leukocyte recruitment by platelets and for the inflammatory response to vascular injury.
OBJECTIVE
To assess the importance of the interaction between leukocyte integrin Mac-1 (a Mb 2) and platelet glycoprotein (GP) Ib-a for leukocyte recruitment after vascular injury and the effect of the neutralization of the Mac-1-GPIba interaction on cell proliferation and the neointimal hyperplasia triggered by the vascular injury.


METHODS
A peptide called M2 or anti-M2 antibody was developed to block the Mac-1-GPIba interaction. This peptide was injected and compared to a control-peptide in C57B1/6J mice submitted to vascular injury of the femoral artery with a guide wire. One, five or 28 days after the vascular injury, the femoral arteries were removed for morphometric and immunohistochemical analyses.


RESULTS
The blocking of the Mac-1-GPIba interaction promoted a statistically significant reduction in the number of leukocytes in the neointimal layer on the first day after the vascular injury (control: 7.9+/-5.0% of the cell total versus anti-M2: 2.0+/-1.6%, p=0.021), as well as determined a statistically significant decrease in leukocyte accumulation in the neointimal layer on days 5 and 28 (control: 42.3+/-12.9% versus anti-M2: 24.6+/-10.8%, p=0.047 and control: 7.9+/-3.0% versus anti-M2: 3.3+/-1.3%, p=0.012; respectively). Cell proliferation in the neointimal layer of the vessel five days post-injury was reduced with the blocking of the Mac-1-GPIba interaction (control: 5.0+/-2.9% of the cell total versus anti-M2: 1.8+/-0.5%; p=0.043), along with a significant decrease in cell proliferation in the vessel neointimal layer 28 days post-injury (control: 3.8+/-1.7% versus anti-M2: 2.0+/-1.2%; p=0.047). The blocking of the Mac-1-GPIba interaction also determined a statistically significant decrease of the intimal thickening 28 days post-injury (control: 10,395+/-3,549 microm(2) versus anti-M2: 4,561+/-4,915 microm(2); p=0.012).


CONCLUSIONS
Leukocyte recruitment after a vascular injury depends on the Mac-1-GPIba interaction and the neutralization of this interaction inhibits cell proliferation and neointimal formation.
Zago
Alexandre C
AC
Instituto do Coração, Universidade de São Paulo. zagoac@cardiol.br
Simon
Daniel I
DI
Wang
Yunmei
Y
Sakuma
Masashi
M
Chen
Zhiping
Z
Croce
Kevin
K
Ustinov
Valentin
V
Shi
Can
C
Martinez Filho
Eulógio E
EE
D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage* / Q000276:immunology; D001792:Blood Platelets / Q000378:metabolism; D049109:Cell Proliferation; D005263:Femoral Artery / Q000293:injuries* / Q000378:metabolism; D007074:Immunoglobulin G / Q000008:administration & dosage; D007249:Inflammation / Q000378:metabolism; D007962:Leukocytes / Q000502:physiology*; D016177:Macrophage-1 Antigen / Q000032:analysis / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D010455:Peptides / Q000008:administration & dosage* / Q000276:immunology; D010973:Platelet Adhesiveness / Q000502:physiology; D019038:Platelet Glycoprotein GPIb-IX Complex / Q000187:drug effects* / Q000502:physiology*; D011817:Rabbits; D018709:Statistics, Nonparametric; D017539:Tunica Intima / Q000276:immunology / Q000473:pathology
D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D016177:Macrophage-1 Antigen; D010455:Peptides; D019038:Platelet Glycoprotein GPIb-IX Complex