Relationship Between Cdk5and Apoptosis In The Pathogenesis Of Retinitis Pigmentos In RCS Rats

Objective To observe the expression of cyclin dependent kinase5(Cdk5) andp25in the pathogenesis of retinitis pigmentosa(RP) in Royal College of Surgeon(RCS) rats and its relationships with apoptosis. To explore the mechanism of Cdk5and p25induced photoreceptor apoptosis in the pathogenesis of RP.Methods Retinas of RCS and RCS-rdy+rats were obtained at the ages ofpostnatal day17,25,35,60.The retinal structure and thickness of outer nuclear layerwere measured by optical microscopy.The expression of Cdk5, p25, cleave-caspase3in the retina was evaluated by immunecytochemistry. The protein expression ofcleave-caspase3in the retina was determined by western blot. The apoptosis ofretinal cells was examined by TUNEL assay.The mean absorbance value of apoptoticcells was analysed by SPSS17.0software.Results The retinal thickness of the RCS rats was significantly reduced incomparison to the RCS-rdy+rats as of postnatal days progressed, particularly in thelayer of rods and cones and the outer nuclear layer. The expression level of Cdk5,p25, cleave-caspase3of RCS rats increased from postnatal17days to postnatal35days,while decreased on postnatal60days;but there was no obvious change of aboveindexes in RCS-rdy+rats. The protein expression of cleave-caspase3in the RCS ratswas significantly increased with progression of postnatal days to postnatal35;butthere was no obvious similar change in RCS-rdy+rats.The results of TUNEL showedthat the apoptotic cells significantly increased in the outer nuclear layer of RCS rats from postnatal17days to postnatal35days,while decreased on postnatal60days;butthere was no obvious change of above index in RCS-rdy+rats.This study showed thatthere were significant correlations between the following variables:Cdk5expressionand p25expression, Cdk5expression and cleave-caspase3expression,Cdk5expression and apoptotic cells,p25expression and cleave-caspase3expression, p25expression and apoptotic cells,cleave-caspase3expression and apoptotic cells. Thepartial correlation coefficients were0.949,0.808,0.959,0.887,0.979,0.852,respectively and the P value was0.000.Conclusions The apoptotic cells significantly increases and the expression levelof Cdk5, p25,cleave-caspase3of RCS rats increase from postnatal17days topostnatal35days.The tendency of apoptotic cells photoreceptor cells is related toincreasing expression of Cdk5and p25in RCS rats.Cdk5may be involved in thedevelopment of RP in RCS rats.