Protection Effect And Mechanism Of "Lingqi Huangban Granula" On Light-induced Retinal Damage In Rats

Objective: To observe the morphologic, electrophysiologic, biochemical and apoptosis changes of the retina after light exposure, and study the protective effect and mechanism of"Lingqi Huangban Granula"(LQHB) against photic injury of retina.Metheods:1. Sprague-Dawley (SD) rats were randomly divided into 3 groups: normal control group, light damage with vehicle group and light damage with LQHB group. Retinal light damage was induced by exposure to constant white fluorescent light for 5 hours at an illumination of 2800±150Lux. LQHB were given 10 days before light exposure until the animals were killed in light damage with LQHB group and equal volume distilled water for the rats in light damage with vehicle group. No special treatment was given in the normal control group. Electroretinogrom (ERG) was recorded from all animals 14 days after light exposure and killed for histopathological examination of retina. The phathological changes of the retina were examined with light microscope, and the layer number of outer nuclear layers (ONL) on the superior and inferior retina was counted.2. Three days after light exposure, the electron microscope of the retinas were examined, and the apoptotic cells were detected with TUNEL method.3. The levels of malondialdehyde (MDA), total superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the retinal tissues were determined 24 h after light exposure.4. The level of aspartate (Asp), glutamate (Glu), glycine (Gly) Taurine (Tau) andγ-aminobutyric acid (GABA) were measured by amino acid automatic analytical apparatus in the retina of rats.5. The mRNA and protein expression of c-fos, caspase-3, bcl-xL was observed by RT-PCR and western bolt methods.6. The expression of GFAP was observed by immunohistochemical methods.Results:1. The rat retinal damage model was successfully established. The retina was morphologically integrated 7 d and 14 d after light exposure in light damage with LQHB group, and the ONL was much thicker than that in light damage with vehicle group 14 d after light exposure. The a-, b-wave amplitude and oscillatory potentials amplitudes of ERGs in light damage with LQHB group were much higher than those in light damage with vehicle group.2. Ultrastructure changes 3 d after light damage in rats were shown. RPE cell showed loss of apical microvilli and basal infoldings, and outer segments of photoreceptors arrangement was irregular and partly disappear in light damage with vehicle group, while RPE layer was intact and outer segments of photoreceptors arrangement was regular relatively in light damage with LQHB group. Three days after light exposure, there were major TUNEL-positive nuclei in the outer nuclear layer in light damage with vehicle group, while a few positive nuclei existed in that of light damage with LQHB group.3. One day after exposure, the MDA levels in the light damage with LQHB group were significantly lower than that in light damage with vehicle group; and the activities of T-SOD, GSH-Px, and CAT were significantly higher than those in in light damage with vehicle group.4. The levels of Glu, Asp, Gly, Tau and GABA in the retina were increased 14 days after light exposure. Compared with the light damage with vehicle group, the level of amino acid in light damage with LQHB had reduced significantly. 5. The mRNA and protein expression of c-fos and caspase-3 was upregulated in light damage with vehicle group, which was higher than those in light damage with LQHB group. The mRNA and protein expression of bcl-xL was downregulated regulated in light damage with vehicle group, which was lower than those in light damage with LQHB group.6. The expression of GFAP was increased in light damage with vehicle group after light exposure, which was higher than that in light damage with LQHB group.Conclusions:1. LQHB has a protective effect both on function and morphology of the retina from light induced retinal damage.2. LQHB could relieve oxidative stress induced by light exposure, and regulate the neural transmitter in retina, to improve biological cycle and metabolism of retinal nerve tissue.3. LQHB could inhibit the apoptosis of photoreceptors and gliosis, which were related to the upregulated expression of c-fos, caspase-3, downregulated bcl-xL and inhibited expression of GFAP.