Modulation of MEK/ERK and PI3K/Akt pathways to the expression of DDR2 and MMP-13 in choroidal neovascularization / 中华实验眼科杂志

ABSTRACT

Background It is estimated that discoidin domain receptor 2 (DDR2) and matrix metalloproteinase-13 (MMP-13) play an important role in the development of tumor angiogenesis.However,their effects on choroidal neovascularizaiton (CNV) have not been clarified yet.Objective This study was to observe the expression pattern of DDR2 and MMP-13 in CNV and to further investigate the regulation role of MEK/ERK and PI3K/Akt pathways to the expression of DDR2 and MMP-13 in CNV.Methods CNV models were established in 78 Brown Norway (BN) rats by retinal photocoagulation with 532 nm laser.Then the animals were randomly divided into the normal control group (n =7),the model control group (n =39),PD98059 (MEK1 inhibitor) group (n =16) and LY294002 (PI3K inhibitor) group (n =16),and 5 mmol/L PD98059 or 5 mmol/L LY294002 3 μl was intravitreally injected 1 day and 7 days after photocoagulation in the PD98059 group or LY294002 group.The expression of DDR2 and MMP-13 mRNA and proteins in the CNV area were detected by using reverse transcription PCR (RT-PCR),and the expression levels of p-ERK/ERK and p-Akt/Akt protein were detected by Western blot assay.CNV thickness was measured by pathological examination 14 days after photocoagulation,and the changes of CNV thickness,the expression levels of DDR2 and MMP-13 in CNV were compared among the model control group,PD98059 group and LY294002 group.Results Three days after photocoagulation,the cells within the lasered lesions proliferated,then CNV formed 7 days after photocoagulation and became stable 14 days after photocoagulation.Immunohistochemistry staining indicated that DDR2 was weakly expressed in the cells of ganglion cell layer,inner nuclear layer and vascular endothelial cells;while MMP-13 was strongly expressed in the cells of the inner limiting membrane layer,photoreceptor layer and sclera layer.Both DDR2 and MMP-13 were strongly expressed in CNV area.Double immunofluorescence staining revealed that MMP-13 and DDR2 co-expression in CNV area.RT-PCR revealed that the relative DDR2 mRNA levels at 1 day,3 days,7 days and 14 days after photocoagulation were 55.22±4.03,47.74±2.23,14.82±4.56 and 5.59±2.47 respectively,while the relative MMP-13 mRNA levels were 25.54±3.83,43.51±4.36,10.90±4.00 and 5.23±3.23 respectively.Compared with the normal control group,the expression of DDR2 and MMP-13 were significantly increased (all at P＜0.05).Immunofluorescence staining showed that the relative fluorescence unit (RFU) values at 1 day,3 days,7 days and 14 days after photocoagulation were 2.73±0.53,5.21±0.31 and 3.22±0.33 for DDR2 and 1.66±0.17,3.57±0.44,2.67±0.21 for MMP-13,respectively.The RFU values in the PD98059 group and LY294002 group 14 days after photocoagulation were 1.14±0.19,1.03±0.14 for DDR2 and 1.37±0.25,1.24±0.20 for MMP-13,respectively.Compared with the model control group,the differences were statistically significant (both at P＜0.05).Western blot results showed that,compared to the normal control group,the expression levels of p-ERK and p-Akt pretein increased at day 7 after photocoagulation (both at P＜0.05),and returned back to the baseline at day 14 after photocoagulation (both at P＞0.05).Both PD98059 and LY294002 treatment were able to attenuate the thickness of CNV to 57.21％ and 50.34％ at day 14 after photocoagulation and further decrease the expression levels of DDR2 and MMP-13 in CNV (all at P＜0.05).Conclusions The expressions of DDR2 and MMP-13 up-regulate in laser-induced CNV.MEK/ERK and PI3K/Akt pathways suppress the development of CNV by regulating the expression of DDR2 and MMP-13.