Enalapril alters expression of key growth factors in experimental diabetic retinopathy.
OBJECTIVE
Angiogenic factors such as vascular endothelial growth factor (VEGF), erythropoietin, and angiopoietin play important roles in the development of diabetic retinopathy. However, the suppression of a single factor does not inhibit angiogenesis completely. This study simultaneously evaluated the expression of several angiogenic factors in the retinas of diabetes-induced rats and determined the effects of an angiotensin-converting enzyme inhibitor (enalapril) on the expression of angiogenic factors.


METHODS
Diabetes was chemically induced by injecting 14 of 21 Sprague-Dawley rats with streptozotocin. After induction of diabetes, enalapril (10 mg/kg) was administered orally to seven rats. The rats were divided into normal, diabetes mellitus (DM), and enalapril-treated groups (each group, n = 7). The eyeballs were removed at 8 weeks after the induction of diabetes, and the retinal expression of VEGF, the signal transducer and activator of transcription (STAT)3/5, erythropoietin, and angiopoietin were examined using immunohistochemistry, RT-PCR, and Western blotting.


RESULTS
RT-PCR revealed that the expression of VEGF, VEGF receptors, STAT3, erythropoietin, erythropoietin receptor, STAT5, angiopoietin 2, and Tie2 mRNA increased in the DM group, whereas angiopoietin 1 expression decreased. The enalapril-treated group showed no increase in mRNA expression of angiogenic factors. Immunohistochemical staining and Western blotting showed that the expression of VEGF, STAT3, and erythropoietin receptor proteins increased in the DM group but not in the enalapril-treated group. Erythropoietin and angiopoietin proteins were not detected by immunohistochemical staining or Western blotting. STAT5 protein expression was detected only in the DM group using immunohistochemical staining and Western blotting. The mRNA expression of the angiogenic factors VEGF, erythropoietin, and angiopoietin 2 increased in the DM group but not in the enalapril-treated group. In contrast, angiopoietin 1 mRNA expression decreased in the DM group.


CONCLUSIONS
Enalapril treatment prevented increased angiogenic factor levels in the retinas of experimentally induced diabetic rats.
Kim
Hyun Woong
HW
Department of Ophthalmology, College of Medicine, Inje University, Busan Paik Hospital, Busan, South Korea. maekbak@hanmail.net
Kim
Jung Lim
JL
Lee
Han Kee
HK
Hur
Dae Young
DY
Yun
Il Han
IH
Kim
Sin Dong
SD
D042501:Angiogenic Proteins / Q000378:metabolism*; D042683:Angiopoietin-1 / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000627:therapeutic use*; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D015153:Blotting, Western; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000378:metabolism; D003930:Diabetic Retinopathy / Q000188:drug therapy* / Q000378:metabolism; D004656:Enalapril / Q000627:therapeutic use*; D004921:Erythropoietin / Q000235:genetics / Q000378:metabolism; D007124:Immunoenzyme Techniques; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D050799:STAT5 Transcription Factor / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
D042501:Angiogenic Proteins; D042683:Angiopoietin-1; D000806:Angiotensin-Converting Enzyme Inhibitors; C467629:Angpt1 protein, rat; D001786:Blood Glucose; D012333:RNA, Messenger; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; C494088:Stat3 protein, rat; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D004921:Erythropoietin; D004656:Enalapril