Investigation Of The Role Of Cdk5 In Neuron Injury Induced By Electromagnetic Exposure

Objectives: With the development of science and technology, a lot of electrical appliances such as mobile phone, microwave oven, etc. step into our daily life rapidly, which lead more and more people exposing to electromagnetic radiation. The nervous syetem is one of the most sensitive targets of electromagnetic exposure. Electromagnetic exposure can cause learning and memory impairment which may result from neuron injury. Though the study on electromagnetic exposure bioeffect has been performed for many years, the bioeffects, pathological mechanisms of neuron injury induced by electromagnetic exposure is not well established yet. Cdk5 is most abundant in the nervous system and it appears to be indispensable for normal neural development and function. Present essentially in post-mitotic neurons, its normal activity is obligatory for neuronal migration and differentiation in developing brain. Studies showed that the deregulation of Cdk5 and its activators might be involved in the process of neuron injury (especially neuron apoptosis). Recently, there is not any study focus on the changes of Cdk5 and its activators p35 and p25 are involved in neuron injury induced by electromagnetic exposure.This study may provide new clues for studying the electromagnetic exposure bioeffect.Methods: (1)The rat primary cortical neurons were cultured for 8 days and then were exposed to 90 W/cm~2 electromagnetic exposure for 10 min. (2) Effects of electromagnetic exposure on cellular viability of neurons were evaluated by CCK-8 Kit. (3) Effects of electromagnetic exposure on the rate of apoptosis of neurons were determined by TUNEL and Hoechst fluorescence staining. (4) Alterations of the mRNA level and the protein level of Cdk5 in neurons at different time points after electromagnetic exposure were studied by RT-PCR and Western-blot respectively. (5) Alterations of the activity of Cdk5 in neurons at different time points after electromagnetic exposure were studied by liquid scintillation counting. (6)Alterations of the protein levels of p35 and p25 in neurons at different time points after electromagnetic exposure were studied by Western-blot. (7) Neurons were pretreated with Cdk5 inhibitor Roscovitine, the cellular viability and the rate of apoptosis were observed after electromagnetic exposure.Results: (1) The cellular viability of neurons significantly decreased at 6h, 12h and 24h after electromagnetic exposure. (2) Electromagnetic exposure led to increasing of the rate of apoptosis, which is the most marked at 12h and 24h after electromagnetic exposure. (3) Electromagnetic exposure did not induce significant change in neither the mRNA level nor the protein level of Cdk5. (4) At 3h and 6h after electromagnetic exposure, the activity of Cdk5 significantly increased by 97% and 51% respectively. (5) Electromagnetic exposure did not induce significant change in the protein level of p35, but the protein level of p25 significantly increased at 0h, 3h and 6h after electromagnetic exposure. (6) Cdk5 inhibitor Roscovitine pretreatment partly reversed the neuron injury induced by electromagnetic exposure.Conclusions: Electromagnetic exposure can decrease the cellular viability and increase the rate of neuron apoptosis as well as disturb the activity of Cdk5 and the protein level of p25 in neurons,and Cdk5 inhibitor Roscovitine pretreatment partly reversed the neuron injury induced by electromagnetic exposure. The results suggest that electromagnetic exposure might lead to neuron injury through Cdk5 and p25 mediated signal pathway.These data provides some new clues to investigate the mechanisms of neuron injury induced by electromagnetic exposure and develop clinical approaches for treatments of neural injury induced by electromagnetic exposure.