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Ординатура / Офтальмология / Английские материалы / Retinal Degenerative Diseases Laboratory and Therapeutic Investigations_Anderson_2008.pdf
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39 Protamine Sulfate Downregulates VEGF Expression and Inhibits VEGF

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Fig. 39.2 Time course of VEGF expression inhibited by protamine sulfate (80 ug/ml) in vascular endothelial cells. VEGF expression level was measured by the semi-quantity method of ICC under normal and hypoxic condition with or without treatment of protamine sulfate

39.3 Discussions

Protamine sulfate is a weak anti-coagulation drug, and it is an antagonist of heparin. Recent studies have suggested that protamine sulfate has a function to inhibit tumor growth through inhibition of new blood vessels of the tumor cells. Since the angiogenic eye diseases such as AMD, diabetic retinopathy and retinal vein occlusion have a similar pathway of new blood vessel development as in tumor cells, so the drugs used for inhibition of new blood vessels of tumors can be tested for potential use for treatment of the angiogenic eye diseases, as well (Barfod and Larsen 1974). It is well known that VEGF is a critical factor of angiogenesis, so we studied the inhibition effect of protamine sulfate on VEGF and investigated the potential use in treatment of angiogenic eye diseases.

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J. Hu et al.

Fig. 39.3 Protamine sulfate inhibits the binding of VEGF and its receptor. RF/6A vascular cells were cultured in different conditions for 96 h with and without protamine sulfate treatment and VEGF was examined by immunocytochemistry assay. a. Normal control group: small, homogenous brown particles in cytoplasm; b. Hypoxia control group:1big, dark particles unevenly distributed in cytoplasm; c. Normal group with protamine sulfate treatment: smaller, homogenous lighter staining particles in cytoplasm compared to those in a. d. Hypoxia with protamine sulfate treatment group; the particles were bigger but lighter compared to those in group b

39.3.1 The Inhibition Effect of Protamine Sulfate on VEGF

In 1998, Gilbert et al. found that VEGF and its receptor were expressed in retinas of normal and diabetic mice using the in situ hybridization method (Heiduschka et al. 2008). They also found that the VEGF and VEGFR2 expression level increased in the retinas of diabetic mice. It was evident that the neovascularization of diabetic retinopathy is because of hypoxia (Eichler et al. 2004). Forooghian et al. (2007) found that the VEGF expression level increased dramatically in ARPE-19 cells after 24 h of hypoxic condition culture, because VEGF expression is regulated by hypoxia-inducible factor (HIF). Our study also confirmed that VEGF expression increased significantly in RF/6A cells after 72 and 96 h of hypoxic condition compared to that of normal condition (p <0.01 and p <0.05, respectively). Protamine sulfate can inhibit VEGF expression of RF/6A cells in both normal and hypoxic condition.

39.3.2 Inhibition of the Binding Between VEGF and Its Receptor

VEGF receptor 2 (VEGFR2) binding with VEGF secreted by the cell itself or other cells activate the downstream signal and cause angiogenesis. VEGF receptor 1 (VEGFR1) has neuron protection function (Wu et al. 2007). We found that