Function of the vascular endothelial growth factor receptors Flt-1 and Flk-1/KDR in the alloimmune response in vivo.
BACKGROUND
We have recently reported that vascular endothelial growth factor (VEGF) functions as a proinflammatory cytokine to regulate the trafficking of leukocytes into allografts in the early posttransplant period. VEGF binds two major VEGF receptors: VEGFR-1 (flt-1) and VEGFR-2 (flk-1/KDR). Here, we wished to investigate the expression and function of VEGF receptors in the process of acute allograft rejection in vivo.


METHODS
We performed fully MHC-mismatched C57BL/6 (H-2b) into BALB/c (H-2d) vascularized heterotopic murine cardiac transplants and we examined the expression of VEGF and VEGF receptors by immunohistochemistry during acute allograft rejection. Next, we treated mice with specific neutralizing monoclonal antibodies against murine VEGFR-1 and VEGFR-2 and examined their effect on the development of acute allograft rejection by histology and by analysis of graft survival. The intragraft expression of cytokines and chemokines were also evaluated by quantitative real-time PCR analysis.


RESULTS
The expression of VEGF, VEGFR-1 and VEGFR-2 were significantly up-regulated during allograft rejection as compared to isografts. Administration of either anti-VEGFR-1 or anti-VEGFR-2 alone failed to inhibit allograft rejection. However, coadministration of both antibodies together inhibited leukocyte infiltration of allografts and prolonged allograft survival. Furthermore, the effect of VEGFR blockade was associated with the downregulation of intragraft cytokine and chemokine expression.


CONCLUSIONS
Our data suggest that VEGF-VEGFR interactions function in the alloimmune response in vivo. Targeting VEGFRs may represent a novel therapy to protect allografts following clinical transplantation.
Sho
Masayuki
M
Department of Surgery, Nara Medical University, Nara, Japan. m-sho@naramed-u.ac.jp
Akashi
Satoru
S
Kanehiro
Hiromichi
H
Hamada
Kaoru
K
Kashizuka
Hisanori
H
Ikeda
Naoya
N
Nomi
Takeo
T
Kuzumoto
Yukiyasu
Y
Tsurui
Yoshikazu
Y
Yoshiji
Hitoshi
H
Wu
Yan
Y
Hicklin
Daniel J
DJ
Briscoe
David M
DM
Nakajima
Yoshiyuki
Y
D000208:Acute Disease; D000818:Animals; D018925:Chemokines / Q000235:genetics; D016207:Cytokines / Q000235:genetics; D006084:Graft Rejection / Q000276:immunology*; D007150:Immunohistochemistry; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics; D014184:Transplantation, Homologous; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000276:immunology* / Q000378:metabolism*
D018925:Chemokines; D016207:Cytokines; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D040281:Vascular Endothelial Growth Factor Receptor-1