[The effects and mechanism of baicalin in a mouse acute hypertensive glaucoma model]

Objective: To explore the potential neuroprotection effects and associated mechanism of baicalin in a rodent acute hypertensive glaucoma model and oxygen-glucose deprivation/reperfusion (OGD/R) induced retinal ganglion cell (RGC) injury. Methods: Experiment research. A rapid and substantial elevation of intraocular pressure was performed to establish an acute hypertensive glaucoma model, and retinal thickness was assessed at 1, 3, 5, and 7 days. The mice were then randomly divided into three groups: normal control group, hypertension group, and baicalin (50 mg/kg) for hypertension group. The effects of baicalin on the RGCs were evaluated by retrograde transporting of Fluoro-Gold. The mRNA levels of tumor necrosis factor-α, interleukine-1β (IL-1β), and inducible nitric oxide synthase were detected by real-time PCR, and the protein levels were measured by Western blot in the retina tissue of acute hypertensive glaucoma model. Purified primary RGC survival under OGD/R stress was measured by flow cytometry, which was also performed to measure the survival rate of RGCs pretreated by different doses of baicalin (2.5 μmol/L, 5.0 μmol/L, and 10.0 μmol/L). The effects of baicalin on primary RGCs co-cultured with mouse microglia cell line BV2 were evaluated by flow cytometry. The cytokine IL-1β in the culture supernatant was measured by immunochemical analyses. Statistical analysis was performed using analysis of variance. Results: Retinal tissue injuries and RGC loss were observed both in vivo and in vitro. Retinal thickness was decreased to 87.32%±0.94% at 3 days (t=6.73, P<0.01), 74.86%±2.43% at 5 days (t=13.40, P<0.01), and 63.53%±2.15% at 7 days (t=19.46, P<0.01). Treatment of 50 mg/kg baicalin significantly promoted the RGC survival from 61.32%±5.94% to 89.93%±10.08% (t=4.84, P<0.01). Baicalin alleviated the retinal damages by suppressing the expression of inflammatory cytokines as revealed by Western blot and real-time PCR. In vitro the RGC survival under OGD/R stress was increased from 51.53%±1.36% to 69.37%±7.09% and 66.23%±4.25% with 5.0, 10.0 μmol/L baicalin administration (t=5.50, 4.53; both P<0.01). BV2 under OGD/R stress did extra damage to RGCs, and baicalin could reverse the damages and increase the survival from 69.37%±7.09% to 73.00%±5.20% (t=2.82, P=0.048) by reducing the release of IL-1β [(39.97±8.76) pg/ml vs. (61.33±5.78) pg/ml, t=4.19, P=0.010]. Conclusion: Baicalin could alleviate retina tissue injury directly and promote the survival of RGCs by downregulating the expression of inflammatory cytokines and protecting RGCs from ischemia reperfusion injury. (Chin J Ophthalmol, 2020, 56: 376-382).