Pharmacologic induction of heme oxygenase-1 plays a protective role in diabetic retinopathy in rats.
OBJECTIVE
We investigated the protective effects of HO-1, induced by hemin, in the retinas of streptozotocin (STZ)-induced diabetic rats, and document the possible anti-inflammatory, anti-apoptotic, and anti-proliferative mechanisms underlying the protection.


METHODS
Sprague-Dawley (SD) rats were induced to diabetes by intraperitoneal injection of STZ (60 mg/kg). Later, some of the rats were given intraperitoneal injections of hemin (20 mg/kg) to induce expression of HO-1. The protective effects of hemin were evaluated by examining the hemoglobin concentration (Hb) and the glycosylated hemoglobin (HbA1c) level of blood from the rats, further calculating the numbers of TUNEL positive cells in retinal ganglion cell (RGC) layer and diI-labeled RGCs. We also documented the expressions of HO-1, HIF-1α, SOD-1, VEGF, p53, and bcl-2 by Western blot analysis and real-time quantitative PCR. Expressions of Nrf2, tERK 1/2, and pERK 1/2 were detected only by Western blot analysis. HO-1, Nrf2, pERK, and GFAP proteins were detected by immunofluorescence.


RESULTS
The Hb level was higher in hemin-treated rat blood than nontreated diabetic group, while the HbA1c level was lower. Hemin significantly activated HO-1 expression in the retinas of diabetic rats, combined with accordant changes of Nrf2/pERK protein expression, and upregulated the expression of GFAP in retina. Retinal ganglion cells displayed greater sensitivity to apoptosis when the HO-1 level was lower. Overexpression of HO-1 was associated with an increase in the activation of SOD-1 and bcl-2, and a decrease of the expression of HIF-1α, VEGF, and p53.


CONCLUSIONS
HO-1 is an important positive modulator of the Nrf2/ERK-related signaling. Overexpression of HO-1 by hemin induction protected retinal ganglion cells in diabetic retinopathy through anti-inflammatory, anti-apoptotic, and anti-proliferative effects.
EENT Hospital, Eye Institute, Fudan University, Shanghai, China.
Jiawen
J
Fan
Gezhi
G
Xu
Tingting
T
Jiang
Yaowu
Y
Qin
D000818:Animals; D015153:Blotting, Western; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000201:enzymology / Q000517:prevention & control; D003930:Diabetic Retinopathy / Q000097:blood / Q000201:enzymology / Q000517:prevention & control*; D004790:Enzyme Induction / Q000187:drug effects; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology; D006442:Glycated Hemoglobin / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis* / Q000235:genetics; D006427:Hemin / Q000008:administration & dosage / Q000494:pharmacology*; D006454:Hemoglobins / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D020287:In Situ Nick-End Labeling; D007274:Injections, Intraperitoneal; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D018613:Microscopy, Confocal; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
D006442:Glycated Hemoglobin; D006419:Heme Oxygenase (Decyclizing); D006427:Hemin; D006454:Hemoglobins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D016159:Tumor Suppressor Protein p53; D042461:Vascular Endothelial Growth Factor A; C497444:Hif1a protein, rat; C467498:vascular endothelial growth factor A, rat; C491523:Hmox1 protein, rat; C000606292:Sod1 protein, rat