Authors: Yu Hongfei, Dong Zhijun, Zhang Tiemin, Yang Fan
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Diabetic retinopathy (DR) is a chronic inflammatory disease, with pathological changes of retinal microvessels.Studies demonstrated that sericin has anti-inflammation and anti-oxidation effects, inferring that sericin might play a protective effect on diabetic microangiopathy.
This study was to investigate the effects of sericin on intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and Cx43 expressions in retina and explore the protection of sericin to retinal microangiopathy in diabetic rats.
Forty-eight specific pathogen free male SD rats were randomly divided into normal control group, diabetic model group, sericin-treated group and calcium dobesilate-treated group, with 12 rats for each group.The diabetic models were established by intraperitoneal injection of streptozotocin (STZ) for 3 consecutive days and feeding up with high lipid foods.Normal saline solution, 2.4 g/(kg·d) sericin solution and 0.2 g/(kg·d) calcium dobesilate were used by gavage administration in the rats of the diabetic model group, sericin-treated group and calcium dobesilate-treated for 3 months group, respectively.The rats were sacrificed and retinal sections were prepared, and the retinal morphology was examined by hematoxylin-eosin staining.The expressions of ICAM-1, VCAM-1 and Cx43 proteins and mRNA in retinas were detected by Western blot assay and reverse transcription PCR.The use and care of the rats complied with Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission and ARVO statement.
The retinal structure was normal in the normal control group.The swell and rupture of inter limiting membrane (ILM), scatter vascular endothelial cell nuclei breakthrough ILM and decrease of retinal ganglion cells (RGCs) were displayed in the diabetic model group; while in the sericin-treated group and calcium dobesilate-treated group, the mild thickening of ILM and disorder of retinal cells were obtained.The relative expression levels of ICAM-1 and VCAM-1 were significantly raised and those of Cx43 were reduced in the diabetic model group, sericin-treated group and calcium dobesilate-treated group when compared with the normal control group (all at P<0.05). Compared with the diabetic model group, the expressions of ICAM-1 and VCAM-1 proteins and mRNA in the sericin-treated group were significantly reduced (ICAM-1 protein: 0.834 3±0.032 1 vs. 0.918 9±0.042 4; VCAM-1 protein: 0.726 4±0.011 2 vs. 1.235 0±0.078 9; ICAM-1 mRNA: 0.716 3±0.008 6 vs. 0.956 8±0.012 5; VCAM-1 mRNA: 0.393 7±0.035 0 vs.0.477 9±0.020 6) and those of Cx43 protein and mRNA were evidently elevated (Cx43 protein: 0.133 1±0.015 3 vs.0.039 2±0.002 0; Cx43 mRNA: 0.676 8±0.064 8 vs.0.430 8±0.111 3) (all at P<0.05).
Sericin can relieve retinal microangiopathy and protect retina against the pathogenesis and development of DR by down-regulating the expressions of ICAM-1, VCAM-1 and up-regulating the expression of Cx43 in retinas of diabetic rats.