Inhibiting effect of retinal Sigma-1 receptor antagonist on the form deprivation myopia in guinea pigs and its mechanism

Objective

To investigate the role and mechanism of retinal Sigma-1 receptor antagonist N, N-diethyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]ethanaminehydrochloride (NE-100) in the formation of form deprivation myopia (FDM) in guinea pigs.

Methods

Eighty-five 21-day-old guinea pigs were selected, and 36 of them were randomly divided into normal control group, occluded 14-day group and occluded 11-day group, with 12 in each group.The right eyes of guinea pigs in the occluded 14-day group were covered with translucent eye shield for consecutive 14 days, and guinea pigs in the occluded 11-day group were treated in the same way for consecutive 11 days plus 3 days without cover, and guinea pigs in the normal control group were not covered.The other 49 guinea pigs were randomly divided into FDM group (n=10), FDM+ NE-100 6 μg group (n=12), FDM+ NE-100 60 μg group (n=10), FDM+ NE-100 600 μg group (n=9), and FDM+ saline group (n=8). The right eyes in each group received 100 μl peribulbar injection of NE-100 6 μg, 60 μg and 600 μg or saline once a day according to grouping.Ocular refraction and axial dimensions were measured using eccentric infrared photorefractor and A-scan ultrasonography, respectively.Corneal curvature was measured with keratometer.Immunohistochemical staining and Western blot were used to detect the expression levels of Sigma-1 receptor protein, and retinal dopamine content was evaluated by high-performance liquid chromatography with electrochemical detection.This study was approved by an Ethics Committee of the Department of Laboratory Animal Science of Central South University (No.2020sydw0084). The use and care of experimental animals followed the Regulations for the Administration of Affairs Concerning Experimental Animals in China.

Results

There were statistical significant differences in diopter and axial length among the normal control group, occluded 14-day group and occluded 11-day group (F=147.81, 160.10; both at P<0.01). Compared with the normal control group, the relative myopia was the deepest and the axial length was the longest in the occluded 14-day group, then the occluded 11-day group, showing significant differences between them (all at P<0.05). In the normal control group, Sigma-1 protein was mainly expressed in retinal ganglion cells (RGCs), photoreceptor inner segment and the inner nuclear layer.In the occluded 14-day group, Sigma-1 protein staining was enhanced in RGCs and photoreceptor inner segment.Sigma-1 staining positive cells in the inner nuclear layer were increased significantly and were also seen in the inner and outer plexiform layers, especially in Müller cells, in which the expression levels of Sigma-1 receptor protein were significantly increased.Compared with the occluded 14-day group, the Sigma-1 receptor protein expression levels in the retina of the occluded 11-day group was significantly decreased (P<0.01). The diopters of guinea pigs in the FDM+ NE-100 6 μg, 60 μg and 600 μg groups were lower than those in the FDM group, and the diopters of FDM+ NE-100 60 μg and 600 μg guinea pigs were lower than those in the FDM+ NE-100 6 μg group, and the differences were statistically significant (all at P<0.05). The dopamine content in the retina of the FDM+ NE-100 60 μg group was (0.74±0.09) ng/mg, which was significantly higher than (0.57±0.10) ng/mg in the FDM group, with a significant difference between them (t=15.18, P<0.01).

Conclusions

Sigma-1 receptor antagonist inhibits FDM formation, which may be associated with the elevation of dopamine content in retina.

Sigma-1 receptor; Form deprivation; Myopia; Retina; Dopamine; Guinea pig