CDK5 and Alzheimer disease: Additionally, free bilirubin increases the risk of AD, which can aggravate neurotoxicity and induce neuronal damage, tau protein hyperphosphorylation, and deposition of Aβ by activating glycogen synthase kinase-3β (GSK-3β), c-Jun amino terminal kinase (JNK), and cyclin-dependent kinase 5 (CDK5) (Staley et al., 2017); (Kimpara et al., 2000).