Thermal Injury Induces Small Heat Shock Protein in the Optic Nerve Head In Vivo

PURPOSE: To investigate the induction pattern of various heat shock protein (HSP) in the optic nerve head after thermal stress using transpupillary thermotherapy and to determine the dose-response relationship of thermal stress on the induction of various HSP. METHODS: The 810-nm diode laser with 50-μm spot size was aimed to the center of optic nerve head of right eye of Norway brown rats. First, the various exposure powers (100, 120, 140 mW) were used with the same exposure duration, 60 seconds, to investigate power dosing effect. Second, the various exposure durations (1, 2, 3, and 5 minutes) were applied under constant 100 mW laser power to investigate time dosing effect. Left eyes were served as controls. To quantify HSP expression, enucleation was performed at 24 hours after transpupillary thermotherapy. HSP 27 and αB-crystallin inductions in optic nerve head were examined with Western blot. RESULTS: All type of HSP was observed in normal state. After thermal injury, the expression of HSP 27 were increased, and the αB-crystallin were decreased. CONCLUSIONS: Induction pattern of each HSP in the optic nerve head were different after thermal injury. Some HSPs were induced or exhausted. Further research is needed on the characteristic functions and induction conditions of each HSP.