Abstract
Purpose :
To elucidate the association between time evolution of light scattering and morphological events and apoptotic markers after in vivo exposure to ultraviolet radiation (UVR).
Methods :
Six week old Albino Sprague-Dawley rats were exposed in vivo to around threshold dose of UVR, 300 nm FWHM 10 nm. The animals were sacrificed in groups at incrementing time intervals after exposure to UVR. Light scattering, light- and transmission electron microscopy (TEM), DNA fragmentation detected with Tunnel labelling, mRNA response for GADD-45-alpha, TP53 and CASP3 measured with qPCR, and protein response for active caspase-3 detected as proportion of lens epithelial cell labelling detected with immunofluorescence, was recorded in independent experiments. The time window studied was 1-120 hrs. after exposure to UVR.
Results :
Light scattering increased exponentially declining against an asymptote after 8 kJ m^-2. TEM revealed apoptotic morphological characteristics already 1 hr. after exposure to UVR in scattered lens epithelial cells. mRNA signal for GADD-45-alpha was increased at 1 hr. after exposure to 1 kJ m^-2 and then declined exponentially with a time constant (1/k) of 4 hrs. After the same UVR exposure, mRNA signal for TP53 was 3 hrs. delayed and then increased exponentially declining towards an asymptote with a time constant of 25 hrs. mRNA signal for CASP3 decreased up to 5 hrs. after exposure and then increased linearly in the time window observed. Expression of active caspase-3 demonstrated a 5 hrs. delay of onset after exposure to 1 kJ m^-2 and then increased to a maximum around 16 hrs. after exposure followed by a decrease. TUNEL labelling, was associated with 5 hrs. delay to onset after 5 kJ m^-2 and then increased to a maximum around 24 hrs. after exposure, followed by a decrease.
Conclusions :
Time evolution of light scattering in the lens after in vivo exposure to UVR is associated with morphological expression of damage to lens epithelial cells and a fast onset of mRNA message for GADD-45-alpha that quickly turns off and a concomitant consumption of mRNA message for CASP3 followed by an increase. Expression of mRNA message for TP53 is turned on with a slightly delay. Active caspase-3 protein expression is further delayed peaking at around 16 hrs. after exposure followed by a similar but slightly more transient onset of TUNEL labelling.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.