Protective Effect of Heat Shock Proteins 70.1 and 70.3 on Retinal Photic Injury after Systemic Hyperthermia

PURPOSE: This study aimed to determine the relationship between the heat shock protein 70 from hsps70.1 and 70.3 on retinal photic injury after systemic hyperthermia. METHODS: Eight-week-old female C57BL/6 mice were kept at a constant temperature of 41~42 degrees C for 25~30 minutes. After dark-adaptation for 8 hours, intense light of 11000 lux was maintained for 6 hours. Histology and immunohistochemistry for the inducible heat shock protein 70 (hsp70), the constitutive heat shock protein 70 (hsc70), and western blot analysis, reverse transcriptase-polymerase chain reaction for hsp70.1 and hsp70.3 were performed just before photic injury and after 1, 4, 7, and 14 days. RESULTS: Light-induced retinal degeneration was prevented by thermotolerance. After hyperthermia, hsp70 was densely expressed in the inner segment of the photoreceptor layer on the photic injury. Hsp70 expression increased for 4 days after photic injury and slowly decreased thereafter. mRNA from hsp70.3 was induced earlier than that of hsp70.1. CONCLUSIONS: Retinal photic injury was prevented by hyperthermia-induced hsp70. Hsp70 from hsp70.3 may be a rapid and short-lived responder, and that from hsp70.1 is a slower and more sustained responder. Hsp70 from hsp70.3 may be an initial retinal chaperone while hsp70 from hsp70.1 may be a sustained chaperone.

Effect of the Absence of Heat Shock Protein 70.1 (hsp70.1) on Retinal Photic Injury

This study aimed to evaluate the protective effect of heat shock protein70 (hsp70) on retinal photic injuries, and to determine the relationship between hsp70s from hsp70.1 and 70.3. C57BL/6 wild type (hsp70.1+/+) and knockout type (hsp70.1-/-) mice from the same littermates were placed in light of 11000 lux for 6 hours, and were sacrificed at 1, 4, 7, and 14 days after stress. H & E staining, immunohistochemistry, and western blot analysis were performed. The hsp70.1-/- mice exhibited more disarranged and more diffusely destroyed photoreceptors than the hsp70.1+/+ mice. Hsp70 induction by light in both the hsp70.1 +/+ and hsp70.1 -/- mice peaked at 1 day after light stress. The Hsp70 level in the hsp70.1 +/+ mice reduced slowly and was almost constant for 7 days. However, in the hsp70.1 -/- mice, it decreased rapidly and returned, after 7 days, to a similar level to that prior to light exposure. According to which gene they originate from, hsp70s may play specific roles in protecting the retina against stresses. Hsp70 from the hsp70.1 gene may act as a sustained responder to retinal photic injury.

The Effect of Heat Shock Protein 70.1 gene (hsp70.1) on Retinal Ganglion Cell Damage after Partial Lesion of the Optic Nerve in Mice

PURPOSE: Heat shock protein (HSP) 70 has been known to have neuroprotective effect on the retinal ganglion cells (RGCs) in vitro and in a rat glaucoma model. This study was to evaluate the inducible HSP70 expresseion in the retinal ganglion cell (RGC) after partial crush injury in mice and to determine the effect of hsp70.1 on the RGCs in the normal condition and after partial crush injury of the optic nerve. METHODS: The optic nerve was crushed by clipping optic nerve with aneurysm clip (110G) for 30 seconds. H and E staining and immunohistochemical staining for inducible HSP70 was performed in the hsp70.1 knockout mice and wild type mice. The RGC counts before crush injury were compared and the losses of RGCs after 3 weeks were compared between the two groups. Loss of RGCs was monitored as a percentage of cells decreased relative to the contralateral sham-operated eye. RESULTS: Immunohistochemical staining showed HSP70 induction in the RGC layer after optic nerve crush injury in both hsp70.1 knockout mice and wild type mice. RGC count before crush injury showed no significant difference (n=8, Mann-Whitney test), and the loss of RGCs was 31.0%+/-0.1% (mean+/-SD) in the hsp70.1 knock-out mice and 32.6%+/-0.1% in the wild type mice without any significant difference between the two groups (n=8, Mann-Whitney test). CONCLUSIONS: HSP70 was induced in the mice RGC layer by optic nerve crush injury and the hsp70.1 gene didn't affect the RGC counts in normal condition and RGC survival after optic nerve crush injury in the mouse.