Heat shock protein hyperexpression on chorioretinal layers after transpupillary thermotherapy.
OBJECTIVE
To assess a biological effect induced by temperature elevation during transpupillary thermotherapy (TTT).


METHODS
Six pigmented rabbits were anesthetized, and TTT was performed on the right eye using an 810-nm diode laser installed on a slit lamp (spot size, 1.3 mm; duration, 60 seconds; power, 92-150 mW). A series of laser pulses were aimed at the posterior pole of the retina. The left eyes were used as the control. Twenty-four hours after laser irradiation, a histologic study was performed on the chorioretinal layers. Tissue samples were fixed in formalin and embedded in paraffin. A monoclonal antibody was used to detect heat shock protein (Hsp)70 immunoreactivity, followed by a biotinylated goat anti-mouse antibody, revealed by the avidin-biotin complex and the 3-amino-9-ethyl-carbazole (AEC) chromogen. Retinal structures were further identified by hematoxylin erythrosin saffron (HES) coloration.


RESULTS
The photocoagulation threshold was found to be at the 150-mW laser power. Under this threshold, Hsp70 immunostaining was the strongest at the 127-mW power, with staining of some choroidal cells, including capillary endothelial cells. No Hsp70 immunoreactivity was observed on the retina. At the 107-mW power, Hsp70 reactivity was observed only in occasional choroidal cells. At the 98-mW power, only mild, diffuse Hsp70 immunoreactivity was observed in the choroid. At the 92-mW power, as in nonirradiated eyes, no Hsp70 immunoreactivity was detected.


CONCLUSIONS
Subthreshold transpupillary 810-nm laser irradiation induces choroidal Hsp hyperexpression. This confirms that choroidal Hsp hyperexpression can be induced during TTT, as has been recently hypothesized by several investigators.
Desmettre
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Unité Propre de Recherche de l'Enseignement Superieur (UPRES) EA2689, Institut National de la Santé et de la Recherche Médicale (INSERM), Centre Hospitalier Universitaire (CHU), Lille, France. desmettre@lille.inserm.fr
Maurage
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Mordon
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D000818:Animals; D015415:Biomarkers / Q000032:analysis; D002829:Choroid / Q000378:metabolism* / Q000528:radiation effects; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D006979:Hyperthermia, Induced; D007124:Immunoenzyme Techniques; D028022:Low-Level Light Therapy; D008297:Male; D011680:Pupil; D011817:Rabbits; D012160:Retina / Q000378:metabolism* / Q000528:radiation effects
D015415:Biomarkers; D018840:HSP70 Heat-Shock Proteins