Suppression of diabetes-induced retinal inflammation by blocking the angiotensin II type 1 receptor or its downstream nuclear factor-kappaB pathway.
OBJECTIVE
To investigate the involvement of the renin-angiotensin system (RAS) and the nuclear factor (NF)-kappaB pathway with diabetes-induced retinal inflammation.


METHODS
Six weeks after induction of diabetes, C57BL/6 mice were treated with the angiotensin II type 1 receptor (AT1-R) blocker (ARB) telmisartan or valsartan, the AT2-R blocker PD123319, or the NF-kappaB inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) daily for 1 week. Retinal mRNA and protein levels of the RAS components were examined by RT-PCR and Western blot, respectively. Leukocyte adhesion to the retinal vasculature was evaluated with a concanavalin A lectin perfusion-labeling technique. Retinal expression levels of intercellular adhesion molecule (ICAM)-1 and vascular endothelial growth factor (VEGF) were examined by RT-PCR and ELISA. ARB or DHMEQ was applied to murine capillary endothelial (b-End3) cells stimulated with a high concentration of glucose to analyze nuclear translocation of NF-kappaB via immunohistochemistry for p65 and mRNA and protein levels of ICAM-1 and monocyte chemotactic protein (MCP)-1.


RESULTS
Induction of diabetes led to a significant increase in retinal expression and production of the RAS components including angiotensin II, AT1-R, and AT2-R. Retinal adherent leukocytes were significantly suppressed by AT1-R, but not by AT2-R, blockade. Administration of the ARB, but not of PD123319, inhibited diabetes-induced retinal expression of ICAM-1 and VEGF. DHMEQ also suppressed these cellular and molecular inflammatory parameters in the diabetic retina to the levels obtained with ARB treatment. In vitro, glucose-induced nuclear translocation of NF-kappaB p65 and upregulation of ICAM-1 and MCP-1 were significantly suppressed by application of the ARB. The in vivo treatment with the ARB, as well as DHMEQ, attenuated the diabetes-induced retinal expression of angiotensin II and AT1-R, per se.


CONCLUSIONS
The present data revealed significant a contribution of the AT1-R/NF-kappaB pathway to diabetes-induced retinal inflammation, providing a mechanistic reason for targeting AT1-R or NF-kappaB in the treatment of diabetic retinopathy.
Nagai
Norihiro
N
Laboratory of Retinal Cell Biology, Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.
Izumi-Nagai
Kanako
K
Oike
Yuichi
Y
Koto
Takashi
T
Satofuka
Shingo
S
Ozawa
Yoko
Y
Yamashiro
Kenji
K
Inoue
Makoto
M
Tsubota
Kazuo
K
Umezawa
Kazuo
K
Ishida
Susumu
S
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D057912:Angiotensin II Type 2 Receptor Blockers; D000818:Animals; D001549:Benzamides / Q000494:pharmacology*; D015153:Blotting, Western; D002448:Cell Adhesion; D018932:Chemokine CCL2 / Q000378:metabolism; D003512:Cyclohexanones / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000150:complications; D003930:Diabetic Retinopathy / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D004797:Enzyme-Linked Immunosorbent Assay; D007093:Imidazoles / Q000494:pharmacology; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007962:Leukocytes / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000502:physiology*; D012084:Renin-Angiotensin System / Q000502:physiology; D012173:Retinitis / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013777:Tetrazoles / Q000494:pharmacology; D053778:Thiazolidines / Q000494:pharmacology; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D000068756:Valsartan; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
D047228:Angiotensin II Type 1 Receptor Blockers; D057912:Angiotensin II Type 2 Receptor Blockers; D001549:Benzamides; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D003512:Cyclohexanones; C090509:Icam1 protein, mouse; D007093:Imidazoles; D016328:NF-kappa B; D011725:Pyridines; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D053778:Thiazolidines; D042461:Vascular Endothelial Growth Factor A; C464444:dehydroxymethylepoxyquinomicin; C467480:vascular endothelial growth factor A, mouse; C091508:telmesteine; D018799:Intercellular Adhesion Molecule-1; C073402:PD 123319; D000068756:Valsartan; D014633:Valine