[Experimental study on the therapeutic effect and mechanism of erlotinib on non-proliferative diabetic retinopathy].

Objective: To investigate the therapeutic effect and mechanism of erlotinib, an epidermal growth factor receptor (EGFR) inhibitor, on non-proliferative diabetic retinopathy (NPDR). Methods: An experimental research was conducted. Human retinal Müller cells (RMC) were MIO-M1 cells from Moorfields Ophthalmology Hospital and the Institute of Ophthalmology at London University College. MIO-M1 cells were divided into normal, hypertonic, high glucose, high glucose+dimethyl sulfoxide (DMSO), high glucose+erlotinib 0.5 mmol/L, high glucose+erlotinib 1 mmol/L, and high glucose+erlotinib 2 mmol/L groups using a random number table method. Detection of the effect of erlotinib on the proliferation of MIO-M1 cells under high glucose conditions was performed by 5-ethynyl-2'-deoxyuridine (EdU) method. Western blotting (WB) was used to detect the effect of erlotinib on the activation markers of glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS) protein levels in MIO-M1 cells under high glucose conditions. WB was used to detect the effect of erlotinib on the protein levels of nerve growth factor receptor (p75NTR), vimentin, and cell retinol binding protein (CRALBP) in RMC under high glucose conditions. MIO-M1 cells were divided into normal group, high glucose group, high glucose+DMSO group, and high glucose+erlotinib (1 mmol/L) group using random number table method. The effect of erlotinib on EGFR nuclear translocation under high glucose conditions was detected by cell immunofluorescence staining. Immunoprecipitation was used to detect the effect of erlotinib on the interaction between EGFR and transcription intermediate factor 2 (TIF2) in MIO-M1 cells under high glucose conditions. MIO-M1 cells were randomly divided into normal group, high glucose group, high glucose+DMSO group, high glucose+Myc-DDK empty body group, high glucose+erlotinib group, high glucose+erlotinib+human doublet protein group, high glucose+erlotinib+TIF2 plasmid group, and high glucose+erlotinib+human doublet protein+TIF2 plasmid group. Cell immunofluorescence staining was used to detect the effect of erlotinib on the binding of EGFR and TIF2 in MIO-M1 cells under high glucose conditions through the EGFR/TIF2 axis. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect the regulatory effect of EGFR and TIF2 binding on cyclin D1 transcription in MIO-M1 cells under high glucose conditions. The mouse model of diabetes retinopathy (DR) was constructed and divided into normal group, DR group, DR+DMSO group, DR+erlotinib 0.25 mg·kg-1·d-1 group, DR+erlotinib 0.5 mg·kg-1·d-1 group and DR+erlotinib 1 mg·kg-1·d-1 group. 25 mice in total, 5 in each group. Tissue immunofluorescence staining was used to detect the expression of RMC activation marker GFAP. The FITC-dextran injection experiment was used to detect the effect of erlotinib on retinal vascular leakage in a murine DR model. Results: Compared with the normal group (32.4%±3.0%), the proportion of EdU positive cells in RMC in the high glucose group (59.2%±3.8%) increased (P<0.001). Compared with the high glucose group (59.2%±3.8%), the proportion of EdU positive cells in the high glucose+1 mmol/L erlotinib group (37.6%±4.4%) decreased (P<0.001). Compared with the normal group, the expression of GFAP in RMC in the high glucose group increased (1 in the normal group, 2.27±0.11 in the high glucose group, P<0.001), while the expression of GS decreased (1 in the normal group, 0.32±0.03 in the high glucose group, P<0.001). 1 mmol/L erlotinib treatment reduced the expression of GFAP in RMC under high glucose conditions (1.32±0.13 and 2.27±0.11, respectively; P<0.001), and increased the expression of GS (0.71±0.06 and 0.32±0.03, respectively; P<0.001). The colocalization of EGFR and DAPI in RMC of the high glucose+1 mmol/L erlotinib group was lower than that of the high glucose group (52.2%±4.1% and 76.4%±5.7%, respectively; P<0.001). The expression of TIF2 or EGFR both increased while using EGF or TIF2 antibodies to precipitate TIF2 or EGFR under high glucose conditions compared to the normal group (1 in the normal group, 2.27±0.20 in the high glucose group, 2.17±0.21 in the EGFR, all P<0.05). And the expression of TIF2 (1.38±0.10) or EGFR (1.32±0.13) in the high glucose+erlotinib group was lower than that in the high glucose group (2.27±0.20) and the high glucose group (2.17±0.21) (all P<0.05). The colocalization of EGFR and TIF2 (17.2%±3.9%) and the mRNA level of Cyclin D1 (1.32±0.16) in the RMC of the high glucose+erlotinib group were lower than those in the high glucose group (54.6%±3.7% of EGFR and TIF2 colocalization ratio, 2.58±0.19 of Cyclin D1 mRNA level,all P<0.05). The high glucose+erlotinib+AREG (EGFR agonist) group, high glucose+erlotinib+Myc DDK-TIF2 plasmid group and high sugar+erlotinib+AREG+Myc-DDK-TIF2 plasmid group EGFR colocalization with TIF2 (colocalization ratios 24.1%±1.9%, 26.0%±2.3%, 35.3%±2.5%) and TIF2 mRNA levels (1.71±0.16, 1.72±0.18, 2.20±0.18). Compared with the high glucose+erlotinib group, The increases were statistically significant (all P<0.05). Compared to the normal group, the expression of GFAP in mouse retina tissue was increased in the DR group (1 in the normal group, 3.07±0.19 in the DR group, P<0.001), and 0.5 mg·kg-1·d-1 erlotinib (1.73±0.30) significantly reduced the expression of GFAP in the retina of DR group mice (P<0.05). Compared to the normal group (3.97±0.47), the DR group (23.13±2.15) showed an increase in fluorescein leakage, while the DR+erlotinib group (11.66±1.45) showed a significant decrease in leakage compared to the DR group (all P<0.05). Conclusions: Erlotinib inhibits the proliferation and activation of RMC induced by high glucose, inhibits the entry of EGFR into the nucleus, inhibits the binding of EGFR to TIF2 in RMC, and reduces the transcription of Cyclin D1 in RMC by inhibiting the interaction between EGFR and TIF2. At the same time, erlotinib inhibits the proliferation and activation of RMC in the mouse DR model, ameliorating retinal vascular leakage in mice. These results suggest that erlotinib inhibits the activation and proliferation of RMC by downregulating the EGFR/TIF2/Cyclin D1 pathway under high glucose conditions, thereby alleviating the progression of NPDR.