Inhibition of the CDK5/caspase-3 Pathway by p5-TAT Protects Hippocampal Neurogenesis and Alleviates Radiation-induced Cognitive Dysfunction.

Radiation-induced cognitive dysfunction is a common complication associated with cranial radiation therapy. Inhibition of hippocampal neurogenesis and proliferation plays a critical role in this complication. Relieving hippocampal apoptosis may significantly protect hippocampal neurogenesis and proliferation. Previous studies have demonstrated that hyperactivity of cyclin-dependent kinase 5 (Cdk5) is closely related to apoptosis. The exact molecular changes and function of Cdk5 in radiation-induced cognitive dysfunction are still not clear. Whether inhibition of Cdk5 and the relevant caspase-3 could improve hippocampal neurogenesis and ameliorate radiation-induced cognitive dysfunction needs further exploration. We hypothesized that inhibition of the Cdk5/caspase-3 pathway by p5-TAT could protect hippocampal neurogenesis and alleviate radiation-induced cognitive dysfunction. In our study, we reported that radiation induced hyperactivity of Cdk5 accompanied by elevation of the levels of cleaved caspase-3, a marker of neuronal apoptosis. Inhibition of hippocampal neurogenesis and proliferation as well as cognitive dysfunction was also observed. p5-TAT, a specific inhibitor of Cdk5, decreased the overactivation of Cdk5 without affecting the levels of Cdk5 activators. Additionally, this treatment suppressed the expression of cleaved caspase-3. We further demonstrated that p5-TAT treatment reduced hippocampal dysfunction and improved behavioral performance. Therefore, Cdk5 inhibition by the small peptide p5-TAT is a promising therapeutic strategy for radiation-induced cognitive dysfunction.