ABSTRACT
Background Retinitis pigmentosa (RP)is a common hereditary blinding eye disease in ophthalmology.Current researches documented that RP may have the common pathophysiologic basis to Alzheimer disease and chronic neurodegenerative disease.Understanding this mechanism will offer a new therapeutic target for RP.Objective The purpose of the present study was to investigate the roles of cyclin-dependent kinase 5 (Cdk5)/P25 activation in the apoptosis of retinal neural cells of RCS rats.Methods Eighteen SPF RCS rats and 18 RCS-rdy+ rats were randomized into 17-,25-and 35-day groups respectively and 6 rats for each.The rats were sacrificed at corresponding time points and retinal hemogenete was prepared.Expressions of CdkS,P35,P25 and tau phosphorylation in the retinas were detected by Western blot,and the kinase activity of Cdk5/P25 was analyzed by quantitative colorimetric assay.Results The expressing level of P35 protein(A340) in the retinas of 17-day-old RCS rats was near that of 17-day-old RCS-rdy+ rats(t =0.52,P＞0.05).In 25-and 35-day-old RCS rats,the expressing levels of P35 protein were 2.20±0.48 and 1.23±0.14,which were higher than those of RCS-rdy+ rats(1.43±0.13 and 0.93±0.10),showing significant differences between them(t =3.78,4.28,P＜0.05).The expression of P25 was undetectable at postnatal 17 days in RCS rats and RCS-rdy+ rats,but it showed significantly higher in RCS rats(0.300±0.003 and 0.230±0.004) than that in RCS-rdy+ rats(0.040±0.004 and 0.070±0.004) at postnatal 25 days and 35 days(t=121.81,77.51,P＜0.01).No significant difference was found in the expression of Cdk5 in RCS rats and RCS-rdy+ rats at different ages (t =-0.60,0.19,1.62,P＞ 0.05).The kinase activity of Cdk5/P25 did not show significantly different between RCS and RCS-rdy+ rats at postnatal 17 days(t =0.19,P＞0.05),but significantly higher kinase activity of Cdk5/P25 was seen in RCS rats (0.0058 ±0.0005 and 0.0056±0.0004) than that in RCS-rdy+ rats(0.0038±0.0003 and 0.0032 ±0.0007) at postnatal 25 days and 35 days (t =8.07,5.97,P＜ 0.01).No expression of tau phosphorylation was detected in RCS rats at postnatal 17 days,but significantly higher tau phosphorylation level was seen in RCS rats at postnatal 25 days and 35 days(1.80±0.22 and 1.23±0.17),which were significant different in comparison with RCS-rdy+ rats at postnatal 25 days and 35 days(1.60 ±0.20 and 1.04 ±0.12)(t=4.71,3.17,P＜0.05).Conclusions The Cdk5/P25 kinase activity shows a consistent trend with theexpressions of P25 and tau phosphorylation in the RCS rats,indicating that the upregulation of P25 induces the enhance of enzyme activity of Cdk5,which phosphorylate its substrates to result in more apoptosis of retinal neural cells.
ABSTRACT
Background RCS-rdy--P+ rat occur retinitis pigmentosa (PR) with the aging and development.To find OUt the retinal functional change using electrophysiological technique is useful for the further study of RCS-rdy--P+ rat. Ohjectlve The goal of this experiment was to investigate the dark-adapted electroretinogram (ERG) of RCS rats with aging. Methods The series of seotopic ERG were recorded in postnatal 21-,32-,37-,45-,60-day-old RCS-rdy--P+ rats respectively,and the age-matched RCS-rdy+-P+ rats were simultaneously recorded as control group.The ERG record was performed by a series of flash with RETI-scan system,gold-foil ring form cornea recording electrode and home-made stainless steel needle electrode.The use of animals complied with the Regulations of the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission. Results Increase dark adaptation duration led to an ascended amplitude in ERG b-wave within 12 hours under the same light intensity,frequency and body temperature.Compared with the RCS-rdy+-P+ rats,the amplitudes of scotopic ERG a-wave and b-wave in RCS-rdy--P+ rats with postnatal 21 days age were apparently declined,showing significant difference between them(P<0.01).The implicit time of both RCS-rdy+-P+ rats and RCS-rdy--P+ rats were delayed, especially for the a-wave. The amplitudes of a-wave and b-wave were declined drastically with the growth of RCS-rdy--P+ rats and progression of their retinal degeneration, and the ERG responses were undetectable at the postnatal 60 days. Both the b-wave and a-wave amplitudes were lowered at P21-day RCS-rdy+-P+ rats and after that,significant increase amplitudes were noted till the P32-day rats. Thereafter, the b-wave amplitude and a-wave amplitude were stable from P32 d to P45 d,and much more ascending of b-wave and a-wave amplitudes was at P60 d RCS-rdy+-P+ rats. Conclusion RCS-rdy--P+ rats occur the retrogression of retinal function along with the ages growth. The scotopic ERG changes of RCS-rdy--P+ rats with aging is evidently different and is in accordance to the characteristics of the RP.