Contribution of Borneolum syntheticum to the Intervention Effect of Liuwei Dihuang Pill () on Experimental Retinal Degeneration

To observe the contribution of Borneolum syntheticum to the intervention effect of Liuwei Dihuang Pill (, LDP) on experimental retinal degeneration, and initially investigate the mechanism of Borneolum syntheticum as meridian-lead-in drug. A total of 180 sodium iodateinduced retinital degeneration rats were randomly divided into three groups, including distilled water group, LDP group, and LDP+Borneolum syntheticum (LDP+BS) group. Twenty normal rats were fed regularly without any treatment as normal control. On day 7 and 14 after treatment, histopathological study and transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) test were performed to evaluate the retinopathy. Claudin-5 expression at blood-retina barrier (BRB) was detected by Western blot at different time points from 0.5 to 8 h after gavage. On day 7 and 14 after treatment, the retinal lesion grades were significantly different among the three groups (P < 0.05). The grade in the LDP+BS group was significantly less than the LDP and distilled water groups (both P < 0.05), no significant difference was observed between the LDP and distilled water groups (P > 0.05). The apoptosis rates in the LDP+BS group was significantly less than the distilled water and LDP groups (both P < 0.05), while there was no significant difference between LDP and distilled water groups (P > 0.05). Expression of claudin-5 in LDP+BS group was significantly less than the other two groups at 0.5, 1 and 2 h after gavage (P < 0.05). There was no apparent difference among the three groups at 4 and 8 h after gavage (P > 0.05). Borneolum syntheticum could strengthen the effect of LDP on experimental retinal degeneration, indicated that Borneolum syntheticum might play the role of meridian-lead-in drug in the formula. The mechanism may be due to Borneolum syntheticum could promote the physiologically openness of bloodretina barrier through transiently affecting the expression of claudin-5.