Objective: To investigate protamine sulfate inhibition of expression of the vascular endothelial growth factor (VEGF) and VEGF-VEGFR binding in vitro and to find a new drug that inhibits neovascularization, which can potentially be used to treat angiogenic eye diseases such as diabetic retinopathy and age-related macular degeneration (AMD).
Methods: Monkey retinal vascular endothelial cells (RF/6A) were cultured in vitro and different concentrations of protamine sulfate were added to the vascular endothelial cells after three passages. VEGF expression level was examined by ELISA and immunohistochemistry after the cells were treated with protamine sulfate.
Results: VEGF expression decreased in a dose-dependent pattern in 10-80 mug/ml of protamine sulfate. We also found that protamine sulfate could inhibit VEGF to bind to its receptor, VEGFR.
Conclusion: Protamine sulfate could inhibit VEGF expression and VEGF-VEGFR binding in vitro. Protamine sulfate may be used for inhibiting neovascularization in angiogenic eye diseases. Angiogenic eye diseases such as diabetic retinopathy (DR), age-related macular degeneration (AMD) and retinal vein occlusion are the main blindness-causing diseases. Previous studies indicated that VEGF and its receptor were involved in the pathogenesis, development and prognosis of these diseases. VEGF inhibition drugs have been used successfully in clinical treatment, but the cost is prohibitive.Protamine sulfate is a common, inexpensive anti-coagulation drug widely used for anti-coagulation in cases when heparin has been overused in the clinic. Recent studies suggest that protamine sulfate can inhibit tumor growth, probably through inhibiting vascular growth of the tumor. In this study we showed that protamine sulfate could inhibit VEGF and the binding of VEGF and its receptor, implying that protamine sulfate may inhibit blood vessel growth through inhibition of the VEGF pathway. This study further suggested that protamine sulfate may be potentially used to treat angiogenic eye diseases.