The Study On The Relationship Between HSP70 And TNF-a On Retinal Excitotoxicity Injury In Rats

Objective To discuss the correlative change between HSP70 and TNF-a on retinal excitotoxicity injury in rats.Methods 50 Wistar rats were randomly divided into three groups, normal control group including 6 rats, the positive control group including 20 rats with intravitreal injection with NMDA and the experimental group including 25 rats with intraperitoneal injection with zinc sulfate and intravitreal injection with NMDA. The rats in experimental group were injected with zinc sulfate (24.6mg/Kg),5 rats were randomly sacrificed at 10h.The rats in positive control group and experimental group were injected with intravitreal injection with NMDA (2μl 80mmol/l) on one eye, and marked them.5 rats were randomly and respectively sacrificed at 2h,8h,16h and 24h after intravitreal injection both in positive control group and experimental group. The rats in normal control group received no treatment, were sacrificed at any time. The rats’retina were HE stained and observed under light microscope, and TNF-a mRNA and HSP70mRNA 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 was histologically well-defined, uniform in staining, and with regular cell shape. In positive control group, 2h after injection, mild edema appeared in the retina ganglion cells (RGCs); 8h, the RGCs were dropsical the most severely and vacuolated mitochondria could be found, retina became thick; 16h, the dropsical condition was alleviative, the RGCs were irregular in shape and loosely arranged and chromatin condensation could be seen in some of them, the number of RGCs 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. The damage of experimental group was slighter than the positive control group.2. Real-Time RT-PCR results:There was no expression of TNF-a mRNA and mild HSP70mRNA in the normal control group. In positive control group,2h after NMDA injection, the TNF-a mRNA expression increased and that was higher than the normal (p<0.05), The TNF-a mRNA expression got to the peak at 8h (P<0.05), decreased gradually from 16h to 24h that was still stronger than the normal (p<0.05), but there was no significant difference between 24h and 16h (p>0.05).2h after NMDA injection, the HSP70 mRNA expression increased and that was higher than the normal (p<0.05), the HSP70 mRNA expression increased rapidly (p<0.05), and got to the peak at 16h (P<0.05), decreased at 24h and that was still stronger than the normal (p<0.05). In the experimental group, after 10h of zinc sulfate injection, there was no expression of TNF-a mRNA.2h after NMDA injection, the TNF-a mRNA expression increased and that was higher than the normal (p<0.05), and lower than positive control group (p<0.05), the TNF-a mRNA expression got to the peak at 8h (P<0.05), and lower than positive control group (p<0.05), decreased gradually from 16h to 24h that was still stronger than the normal (p<0.05) and lower than positive control group (p<0.05), but there was no significant difference between 24h and 16h (p>0.05). After 10h of zinc sulfate injection, the HSP70 mRNA expression increased and that was higher than the normal (p<0.05), and higher than positive control group (p<0.05),2h after NMDA injection, the HSP70 mRNA expression increased rapidly and that was higher than the normal (p<0.05), and higher than positive control group (p<0.05), the HSP70 mRNA expression got to the peak at 8h (P<0.05), and higher than positive control group (p<0.05), decreased mildly at 16h that was still stronger than the normal (p<0.05) and higher than positive control group (p<0.05), but there was no significant difference between 2h、8h and 16h (p>0.05), decreased at 24h and that was still stronger than the normal (p<0.05), and lower than the 16h (p<0.05), but higher than positive control group (p<0.05).Conclusion:On the retinal excitotoxicity injury, the expression of HSP70 induced by zinc sulfate increase, and reduce the expression of TNF-a.With the increase of expression of HSP70, the expression of TNF-a is reduced. And indicate that HSP70 have the inhibitory action on TNF-a.