Inhibition of corneal neovascularization by blocking the angiotensin II type 1 receptor.
OBJECTIVE
To determine the role of angiotensin II type 1 receptor (AT1R) signaling in corneal neovascularization.


METHODS
Corneal neovascularization was induced by suturing 10-0 nylon 1 mm away from limbal vessels in C57 BJ6 mice. Angiotensinogen and its receptor (AT1R) gene expression levels were evaluated by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). The expression of angiotensin II (Ang2) and AT1R was confirmed by Western blotting and immunohistochemistry. To investigate the function of Ang2 in corneal neovascularization, infiltrating macrophages in vascularized corneas and the neovascularized area were investigated after intraperitoneal injection of an AT1R antagonist (telmisartan, 10 mg/kg). Further, corneal mRNA of VEGF, MCP-1, IL-6, ICAM-1, and TNF-alpha was examined in control and telmisartan-treated mice.


RESULTS
Ang2 and AT1R markedly increased in the neovascularized corneas compared with normal corneas. Ang2 and AT1R were expressed in epithelium and stromal cells (vascular endothelium, infiltrating leukocytes, and keratocytes) in neovascularized cornea at protein levels and were weakly detected in normal corneal epithelium. Infiltrating macrophages were reduced in telmisartan-treated mice on day 7 after suturing. Neovascularized area in the cornea of telmisartan-treated mice was 70% smaller than that of control mice on day 7 after suturing. A PPAR-gamma antagonist partially, but significantly, reversed the suppressive effect of telmisartan on induction of corneal neovascularization. The expression of VEGF, MCP-1, IL-6, and ICAM-1 was significantly inhibited in telmisartan-treated mice.


CONCLUSIONS
These findings indicate that Ang2, abundantly expressed in neovascularized corneas, has a significant role in inflammation-related driven corneal neovascularization. AT1R may be a therapeutic target for the suppression of corneal neovascularization.
Usui
Tomohiko
T
Department of Ophthalmology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan. tomohiko-tky@umin.ac.jp
Sugisaki
Kenji
K
Iriyama
Aya
A
Yokoo
Seiichi
S
Yamagami
Satoru
S
Nagai
Norihiro
N
Ishida
Susumu
S
Amano
Shiro
S
D000804:Angiotensin II / Q000235:genetics / Q000378:metabolism*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000627:therapeutic use*; D000818:Animals; D001562:Benzimidazoles / Q000627:therapeutic use*; D001565:Benzoates / Q000627:therapeutic use*; D015153:Blotting, Western; D018932:Chemokine CCL2 / Q000235:genetics; D016510:Corneal Neovascularization / Q000378:metabolism / Q000517:prevention & control*; D003319:Corneal Stroma / Q000378:metabolism; D019573:Epithelium, Corneal / Q000378:metabolism; D015870:Gene Expression; D007150:Immunohistochemistry; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D015850:Interleukin-6 / Q000235:genetics; D008264:Macrophages / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D012333:RNA, Messenger / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*; D012084:Renin-Angiotensin System / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077333:Telmisartan; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics
D047228:Angiotensin II Type 1 Receptor Blockers; D001562:Benzimidazoles; D001565:Benzoates; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D015850:Interleukin-6; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D000804:Angiotensin II; D018799:Intercellular Adhesion Molecule-1; D000077333:Telmisartan