Upregulation of GADD45α, TP53 and CASP3 mRNA Expression in the Rat Lens after In vivo Exposure to Sub-threshold Dose of UVR B

Purpose: The objective of the present study was to investigate the evolution of mRNA expression of the stress sensor GADD45α, the apoptosis initiator TP53 and the apoptosis executor CASP3 in the rat lens after in vivo exposure to sub-threshold dose of UVR-B. Methods: Forty six-week-old female albino Sprague-Dawley rats were unilaterally exposed to a sub-threshold dose, 1 kJ/m2 (1.1 W/m2 for 15 min), of UVR (λmax = 300 nm). Anesthetized and dilated eyes were exposed to UVB radiation. The animals were sacrificed at 1, 5, 24 and 120 h post-exposure. mRNA expression of the GADD45α, TP53 and CASP3 genes in the lenses was measured by quantitative RT-PCR, and fold change in mRNA expression between exposed and unexposed lenses was calculated. Results: mRNA expression for GADD45α increased to a 1.2 fold change at 1 h after exposure and then returned to no change at 120 h. mRNA expression for TP53 increased with a regression coefficient of 0.04 h-1 to a maximum of 1.67 fold change. mRNA expression for CASP3 increased with a regression coefficient of 4.5 x 10-3 rel. units/h to a 1.46 fold change at 120 h after exposure. Conclusions: A sub-threshold in vivo exposure to UVR-B causes a transient upregulation of the stress sensor GADD45α at 1 h after exposure, a saturating upregulation of TP53 and a subsequent constant upregulation of CASP3 in the rat lens.