Characterization of azurocidin as a permeability factor in the retina: involvement in VEGF-induced and early diabetic blood-retinal barrier breakdown.
OBJECTIVE
Azurocidin, released by neutrophils during leukocyte-endothelial interaction, is a main cause of neutrophil-evoked vascular leakage. Its role in the retina, however, is unknown.


METHODS
Brown Norway rats received intravitreal injections of azurocidin and vehicle control. Blood-retinal barrier (BRB) breakdown was quantified using the Evans blue (EB) dye technique 1, 3, and 24 hours after intravitreal injection. To block azurocidin, aprotinin was injected intravenously before the intravitreal injections. To investigate whether azurocidin plays a role in vascular endothelial growth factor (VEGF)-induced BRB breakdown, rats were treated intravenously with aprotinin, followed by intravitreal injection of VEGF(164). BRB breakdown was quantified 24 hours later. To investigate whether azurocidin may mediate BRB breakdown in early diabetes, aprotinin or vehicle was injected intravenously each day for 2 weeks to streptozotocin-induced diabetic rats, and BRB breakdown was quantified.


RESULTS
Intravitreal injection of azurocidin (20 microg) induced a 6.8-fold increase in vascular permeability compared with control at 1-3 hours (P < 0.05), a 2.7-fold increase at 3 to 5 hours (P < 0.01), and a 1.7-fold increase at 24 hours (P < 0.05). Aprotinin inhibited azurocidin-induced BRB breakdown by more than 95% (P < 0.05). Furthermore, treatment with aprotinin significantly suppressed VEGF-induced BRB breakdown by 93% (P < 0.05) and BRB breakdown in early experimental diabetes by 40.6% (P < 0.05).


CONCLUSIONS
Azurocidin increases retinal vascular permeability and is effectively blocked by aprotinin. The inhibition of VEGF-induced and early diabetic BRB breakdown with aprotinin indicates that azurocidin may be an important mediator of leukocyte-dependent BRB breakdown secondary to VEGF. Azurocidin may become a new therapeutic target in the treatment of retinal vascular leakage, such as during diabetic retinopathy.
Skondra
Dimitra
D
Angiogenesis Laboratory, Massachusetts Eye & Ear Infirmary, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Noda
Kousuke
K
Almulki
Lama
L
Tayyari
Faryan
F
Frimmel
Sonja
S
Nakazawa
Toru
T
Kim
Ivana K
IK
Zandi
Souska
S
Thomas
Kennard L
KL
Miller
Joan W
JW
Gragoudas
Evangelos S
ES
Hafezi-Moghadam
Ali
A
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007611:Aprotinin / Q000494:pharmacology; D001798:Blood Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D001813:Blood-Retinal Barrier / Q000187:drug effects*; D002199:Capillary Permeability / Q000187:drug effects*; D002352:Carrier Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000150:complications; D003930:Diabetic Retinopathy / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D005070:Evans Blue / Q000378:metabolism; D008297:Male; D018945:Monocyte Chemoattractant Proteins / Q000494:pharmacology; D051381:Rats; D011914:Rats, Inbred BN; D020318:Rats, Long-Evans; D012171:Retinal Vessels / Q000187:drug effects*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology*
C062991:AZU1 protein, human; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D002352:Carrier Proteins; D018945:Monocyte Chemoattractant Proteins; D015842:Serine Proteinase Inhibitors; D042461:Vascular Endothelial Growth Factor A; D005070:Evans Blue; D007611:Aprotinin