Neuroprotective effects of heat stress on axonal injury

To investigate the expressions of heat shock protein 70 (HSP70) in neurons and oligodendrocytes after the stretch injury and the effects of heat stress on HSP70 expression and explore neuroprotective effect of HSP70 on axonal injury.Methods Fifty-seven male Wistar rats were randomly divided into four groups:control group (Group A with three rats),stretch-only group (Group B with 18 rats),heat stress-only group (Group C with 18 rats) and heat stress pretreatment plus stretch group (Group D with 18 animals).Stretch injury was induced in the right optic nerves of rats in Group B.Heat stress was applied to animals of Group C.Animals in Group D were subjected to the same stretch injury as Group B posterior to the heat stress similar to Group C.Three animals respectively from each group of Group B,Group C and Group D were killed at 4,8 and 16 hours,1,3 and 5 days,respectively.Morphological changes of optic nerves,retinal ganglion cells(RGCs) and oligodendrocytes (OLs) in optic nerves after stretch injury were examined under light microscope;and expressions of OLs HSP70 in RGCs and OLs after heat stress and/or stretch injury were observed using immunohistochemistry.Results Pathological changes of axons,RGCs and OLs after stretch injury to the optic nerves were identified morphologically or quantitatively,and signficantly ameliorated by pre-treatment with heat stress before stretch injury.An increase expression of OLs HSP70 and RGCs occurred in Groups B and C.A much more enhanced expression of HSP70 was found in Group D with an earlier peak and longer maitenance period.Conclusion Both neurons and glial cells are involved in pathological process after axonal injury.Heat stress can mmore effectively exert the neuroprotective role through enhancing,bringing forward and prolonging expression of HSP70.A new approach to management of DAI may be developed through the enhancement of intrinsic neuroprotective functions.17 refs,6 figs,2 tabs.