Effects of Curcumin on Epidermal Growth Factor in Proliferative Vitreoretinopathy

Abstract

Background/aims: Proliferative vitreoretinopathy (PVR) is a common refractory eye disease that causes blindness and occurs after retinal detachment or retinal reattachment. Epidermal growth factor (EGF) has been shown to play an important role in the migration and proliferation of retinal pigment epithelium (RPE) cells, which promote PVR. Curcumin inhibits RPE cell proliferation, but it is not known whether it participates in the formation of PVR. Curcumin regulates the biological functions of EGF, which plays important roles in the development of PVR. This study aimed to evaluate the effect of curcumin on the regulation of EGF in PVR.

Methods: Rabbit RPE cells were cultured, and EGF expression was detected by immunocytochemistry. MTT assay was conducted to determine cell proliferation induced by different concentrations of EGF. Immunocytochemical staining was used to detect EGF expression after treatment with curcumin at varying concentrations. Real-time PCR (RT-PCR) and western blot analysis were used to detect the concentrations of EGF mRNA and protein after treatment with curcumin. After RPE cells and curcumin were injected into experimental rabbit eyes, the cornea, aqueous humor, lens, and vitreous opacity were observed and recorded simultaneously by indirect ophthalmoscopy, fundus color photography, and B-ultrasonography. The vitreous body was extracted, and the EGF content in the vitreous humor was measured by enzyme-linked immunosorbent assay (ELISA).

Results: At each time point (24, 48, and 72 h), cell proliferation gradually increased with increasing EGF concentrations (0, 3, 6, and 9 ng/mL) in a dose-dependent manner. Cell proliferation between EGF concentrations of 9 and 12 ng/mL were no different, which suggested that 9 ng/mL EGF was the best concentration to use to stimulate RPE cell proliferation in vitro. Under all EGF concentrations (0, 3, 6, 9, and 12 ng/mL), RPE cell proliferation increased with time (from 24 to 72 h), suggesting a time-effect relationship. Curcumin downregulated EGF expression in RPE cells, which also indicated time-effect and dose-effect relationships. The best curcumin concentration for the inhibition of EGF expression was 15 µg/mL. RT-PCR and western blot analyses indicated that the EGF mRNA and expression of the protein in RPE cells treated with curcumin significantly decreased with time. Ocular examinations revealed that the vitreous opacity was lower and the proliferative membrane was thinner in the curcumin group compared with the control group. The PVR grade and the incidence of retinal detachment were significantly lower in the experimental group than in the control group. ELISA results showed that the EGF content in vitreous humor was higher in the control group than in the curcumin group. The curcumin and control groups were significantly different at each time point.

Conclusion: Curcumin inhibited RPE cell proliferation by downregulating EGF and thus effectively inhibited the initiation and development of PVR.

Keywords: Curcumin; EGF; PVR; RPE cell.