To investigate the effect and mechanism of loganin on retinopathy in diabetic retinopathy (DR) rats.

DR rats were established by injection of streptozotocin and high glucose and high fat. They were randomly grouped into model group (0.9% NaCl), experimental -L group, experimental-H group (50, 100 mg·kg^-1 loganin), combined group [100 mg·kg^-1 loganin+10 mg·kg^-1 lysophosphatidic acid (LPA)] and 10 normal rats were taken as control group (0.9% NaCl). After the intervention, retinal histomorphology, the levels of inflammatory factors and oxidative stress, apoptosis of ganglion cells, and the expression of Ras homologous gene family member A (RhoA) and Rho associated coiled coil-forming kinase (ROCK) proteins in retinal tissue were measured in turn.

The number of retinal ganglion cells in experimental -L, -H groups, combined group, model group and control group were 19.75±1.90, 24.32±2.15, 17.80±1.94, 15.44±1.65 and 28.30±2.02; the levels of interleukin-6 were (85.67±8.61), (68.88±6.91), (98.52±9.88), (108.24±10.83) and (62.08±6.22) ng·L^-1; the levels of tumor necrosis factor -α were (150.24±15.11), (110.38±11.06), (186.94±18.77), (200.05±20.08) and (105.34±10.55) ng·L^-1; the levels of malondialdehyde were (7.52±0.78), (4.76±0.48), (9.52±0.96), (10.85±1.09) and (4.58±0.46) μmol·mg^-1; the superoxide dismutase activities were (62.05±6.21), (78.22±7.83), (52.11±5.23), (50.21±5.04) and (79.61±7.98) U·mg^-1; the apoptosis rates of ganglion cells were (12.71±1.06)%, (6.98±0.93)%, (14.69±1.30)%, (19.50±1.42)% and (2.15±0.38)%; the relative expression levels of RhoA protein were 0.81±0.09, 0.42±0.05, 1.08±0.11, 1.16±0.12 and 0.38±0.04; the relative expression levels of ROCK protein were 1.28±0.13, 0.77±0.08, 1.72±0.18, 1.85±0.19 and 0.63±0.07, respectively. Compared with the model group, the above indexes of the control group, experimental -H group and combination group had statistical significance (all P<0.05).

Loganin may improve retinopathy in DR rats by inhibiting the activation of RhoA/ROCK pathway, inhibiting inflammation and oxidative stress response.