The Expression Of TNF-α On Retinal Excitotoxicity Injury Induced By NMDA

Objective To evaluate the role of TNF-a on rat's retina excitotoxicity injury induced by NMDA.Methods 42 Wistar rats were randomly divided into three groups, normal control group including 6 rats, PBS group including 6 rats and NMDA group including 30 rats.2μl of NMDA of concentration of 80 nmol/1 was intravtreal injected into the one random eye of every animal of NMDA group and same volume PBS was intravtreal injected into the one random eye of PBS group. The rats of normal control group received no treatment. The rats of NMDA group were sacrificed at 2h,8h,16h,24h, and 48h randomly and respectively after intravtreal injection. The rats'retina were HE stained and observed under light microscope, and the protein level of TNF-a were detected by immunohistochemistry; TNF-a mRNA in rats'retina were detected by Real-Time quantitative reverse transcription polymerase chain reaction(Real-Time RT-PCR).Results 1. HE staining:The structure of retina of normal control group and PBS group was histologically well-defined, uniform in staining, and with regular cell shape. In NMDA group,2h after injection, mild edema appeared in the nerve fiber layer(NFL) and retina ganglion cells(RGCs); 8h, the NFL and RGCs were dropsical the most severely and retina became thick; 16h, the dropsical condition was alleviative, the RGCs were irregular in shape and loosely arranged and the number decreased.24h, the RGCs with striking chromatin condensation were loosely arranged and its number decreased. The retinal nerve fiber layer and ganglion cell layer became thin; 48h, fewer RGCs were found in the retina that became atrophic and thinner.2. Immunohistochemistry (IHC) results:No marked expression of TNF-a was observed in the retinal of normal control group and PBS group. In NMDA group, there was slight expression of TNF-a protein 2h following injection that compared with the normal(p<0.05), peaked at 8h (p<0.05), then it decreased gradually from 16h to 48h that was still stronger than the normal(p<0.05), but there was no significant difference between 24h,48h and 16h(p>0.05). The positive expression of TNF-a was detected in the nerve fiber layer, ganglion cell layer and inner plexiform layer.3. Real-Time RT-PCR results:The TNF-a mRNA expression increased after 2h of injection that was higher than the normal(p<0.05), peaked at 8h(p<0.05) and decreased gradually from 16h to 48h that was still stronger than the normal(p<0.05), but there was no significant difference between 24h,48h and 16h(p>0.05).Conclusion:The expression of TNF-a in the retina excitotoxicity injury induced by NMDA increases and it may play an important role in the pathogenesis of retina excitotoxicity injury.