AIM:To investigate the mechanism of curcumin inhibiting the choroidal neovascularization(CNV)of brown Norway(BN)rats.

METHODS: CNV model of 36 BN rats was established through laser photocoagulation induction, and they were divided into 6 groups with 6 rats in each group. Normal group was fed normally with no intervention, while 532nm laser photocoagulation was used to establish a experimental CNV model in BN rats. Rats after modeling were respectively intervened for 14d and divided into model group, ranibizumab group, curcumin low \〖100mg/(kg·d)\〗, medium \〖200mg/(kg·d)\〗, and high \〖400mg/(kg·d)\〗 dose group. The model group was given intragastric administration of saline for 14d, ranibizumab(10mg/mL, 0.2mL/dose)was injected at 2d after photocoagulation with 5μL once for rats in ranibizumab group, and different concentrations of curcumin were intragastrically administrated to the rats in low, medium and high groups for 14d. Fundus photography, fundus fluorescein angiography(FFA)and indocyanine green angiography(ICGA)examination were performed at 14d after photocoagulation. Ocular histopathological specimens of rats with CNV were made, and the central thickness of CNV were observed by HE staining. Ocular histopathological specimens were made, and the expressions of AKT/p-AKT/HIF-1α/VEGF signaling pathway-related proteins were observed by immunohistochemistry. The mRNA relative expressions of AKT/HIF-1α/VEGF factor in CNV tissues were detected by RT-qPCR, and the protein expressions of AKT/p-AKT/HIF-1α/VEGF factor in CNV tissues were detected by Western-blot.

RESULTS: CNV generation rates in the model group, the ranibizumab group, and the low, medium and high-dose curcumin groups were 78.18%, 73.21%, 77.19%, 75.86%, 74.55%, respectively, which were higher than 70%. The average absorbance were 182.12±6.59, 119.22±8.03, 166.45±8.33, 164.34±5.69, 149.22±6.45, respectively; the ranibizumab group was significantly lower than the model group(P<0.05); the low-dose, medium-dose and high-dose groups were significantly higher than the ranibizumab group(P<0.05), and the curcumin high-dose group was significantly lower than the model group(P<0.05). HE staining showed that the retinal tissue structure of BN rats in normal group was clear and neatly arranged. The central thickness of CNV in the ranibizumab group was significantly reduced at 14d after photocoagulation compared with the model group(P<0.05); While the curcumin high-dose group was significantly reduced compared with the model group(P<0.05), but increased when compared with ranibizumab group(P<0.05). Immunohistochemistry results showed that AKT, p-AKT, HIF-1α, and VEGF factors were negatively expressed in the retinal tissue structure of BN rats in the normal group, and no brown-yellow reactants were found. The expression of AKT, p-AKT, HIF-1α, and VEGF factors in the model group were higher than that in the normal group at 14d after photocoagulation(P<0.05); the ranibizumab group was lower than the model group(P<0.05). While the expression of the curcumin high-dose group was significantly decreased compared with the model group(P<0.05), but significantly increased when compared with ranibizumab group(P<0.05). The mRNA results showed that the relative expression levels of AKT, HIF-1α and VEGF mRNA in the model group at 14d after photocoagulation were higher than those of the normal group(P<0.05); the ranibizumab group was lower than the model group(P<0.05). While curcumin high-dose group was significantly decreased compared with the model group(P<0.05), but significantly increased when compared with ranibizumab group(P<0.05). Western-blot results showed that there was no significant difference in the relative expression of AKT protein among each experimental groups at 14d after photocoagulation. The relative expression of p-AKT protein in the model group was significantly higher than that in the normal group(P<0.05); the ranibizumab group was significantly lower than the model group(P<0.05); the curcumin high-dose group was significantly lower than the model group(P<0.05). The relative expression levels of HIF-1α protein were significantly higher in the model group than in the normal group(P<0.05), and the ranibizumab group was lower than in the model group(P<0.05). The relative expression levels of HIF-1α protein was lower in the curcumin high-dose group than in the model group(P<0.05)but higher than ranibizumab group(P<0.05). The relative expression level of VEGF protein was significantly lower in the curcumin medium/high-dose group than in the model group(P<0.05).

CONCLUSION: Curcumin at 400mg/(kg·d)has an inhibitory effect on CNV in BN rats. The mechanism may be closely related to inhibiting the activation of AKT/p-AKT/HIF-1α/VEGF signaling pathways.