The role of CDK5 in inflammatory reaction in experimental model of Alzheimer's disease

The aim of the project.

Alzheimer’s disease (AD) is the most common neurode generative disorder leading to irreversible cognitive impairment in the elderly. Because the risk of AD increases with age, demographic prognosis indicates a significant rise of population affected by AD. It is predicted that in 2050 the population of patients suffering cognitive impairment will reach 170 mln in the world, and 75% of this number will be AD patients. So far, there is no efficient method of prevention nor effective treatment affecting disease progression. Exploring new avenues to find effective treatment is absolutely vital not only to improve human well-being but also to reduce impact of these diseases on the economy which is very significant. This includes early disability and prolonged inability to work. Decreased work performance in patients affected develops many years before evident symptoms.

AD has a complex pathogenesis, and neurodegenerative processes start many years before the clinical symptoms are observed. The hallmarks of AD are extracellular deposits of amyloid Β (Aβ)and intracellular neurofibrillary tangles (NFTs) built of hyperphosphorylated protein tau. Amyloid beta and protein tau remain in the centre of Alzheimer’s disease (AD) research as factors responsible for the activation of the cascade leading to the progression of neurodegeneration. Among the many other processes observed in AD pathophysiology, disturbances of calcium homeostasis, the hyperphosphorylation of MAP tau, oxidative stress and a chronic inflammatory process may be important components of this pathogenic cascade. Cyclin-dependent kinase 5 functionally links all these processes. Amyloid beta evokes disturbances of calcium homeostasis what leads to overactivation of Cdk5 and in consequence to hyperphosphorylation of tau protein.

Deregulation of Cdk5 activity was observed in experimental models of AD in vitro and in vivo, and also in post-mortem analysis of brain tissue of AD patients, however, the consequences of Cdk5 deregulation are not fully understood.

Inflammatory reaction is an important component of pathomechanism of AD, not only late phase when massive neurodegeneration and cognitive impairment occur, but also in early phase of the disease, when no symptoms are present. Some published data suggest that inflammation may be even initiating factor of the cascade leading to overproduction of Aβ and to eurodegeneration. It is necessary to understand the role of inflammatory processes in pathomechanism of AD. The results of in vitro experiments published during last two years demonstrated that Cdk5 plays an important role also in regulation of peripheral inflammatory processes. However, the role of Cdk5 in regulation of inflammatory processes in AD brain has been never studied. One can suppose that inhibition of Cdk5 may be beneficial for Aβ-related inflammation and neurodegeneratiom in the brain.

The aim of the current project is to analyze, using mice experimental model of AD, interactions between Cdk5, inflammatory reaction and Aβ toxicity. The results of the project will provide the novel knowledge about pathomechanism of AD and potentially may suggest new targets for therapeutical intervention.

Scientific hypothesis.

1. Cyclin dependent kinase Cdk5 is involved in regulation of mechanisms of inflammatory reaction activated in the brain by Aβ.
2. Inhibition of Cdk5, by roscovitine will modulate Aβ-evoked neuroinflammation in the brain.
3. Inhibition of Cdk5, by modulation of Aβ-evoked neuroinflammation, will reduce detrimental biochemical  alterations and cognitive impairment.

Research project methodology

The studies will be caried out on mice experimental model. The neurotoxicity of Aβ will be evoked by single intracerebroventricular injection of oligomers of synthetic Aβ. The inhibitor of Cdk5, roscovitine, will be administered together with Aβ.

By using methods of molecular biology (QPCR, Western blotting, microarray), immunochemistry (immunocytochemistry, -istochemistry, ELISA), biochemical methods and behavioral tests, we will analyze the following partial projects (work packages):

WP 1: Expression, phosphorylation and activity of Cdk5 in the brain after administration of Aβ.

WP 2: Effect of roscovitine on Aβ evoked inflammatory processes in the brain.

WP 3: Effect of roscovitine on Aβ evoked alterations of gene expression in the brain.

WP 4: Effect of roscovitine on Aβ evoked alterations of protein expression and phosphorylation pattern in the brain.

WP 5: Effect of roscovitine on Aβ evoked activation of apoptotic and autophagic sign

aling in the brain.

WP 6: Effect of roscovitine on Aβ evoked behavioral alterations.

The effects of the project.

The results of the project will explain:

• whether intracerebroventricular administration of Aβ evokes alterations of expression, phosphorylation and activity of Cdk5 in the brain, and what are consequences of this phenomenon;
• what is the role of Cdk5 in regulation of neuroinflammation evoked in the brain by Aβ peptides;
• what inflammation-related signaling cascades are regulated by Cdk, and what are the key Cdk5 substrates;
• what is the role of Cdk5 in regulation of gene expression profile and protein phosphorylation profile in the brain after administration of Aβ and what is theirs importance for neuroinflammation;
• what is contribution of Cdk5 in neurodegeneration evoked in the brain by Aβ administration and what is its importance for neuroinflammation;
• whether Cdk5 is responsible for Aβ-evoked cognitive impairment;
• whether inhibitor of Cdk5, roscovitine, may affect Aβ-evoked neuroinflammation;
• whether inhibitor of Cdk5, roscovitine, may affect Aβ-evoked biochemical alterations and cognitive impairment. The outcome of the project will increase our knowledge of pathomechanism of age-related neurodegenerative diseases. The role of Cdk5 in Alzheimer’s disease-related inflammatory processes will be explained. Successful discoveries may give the back ground for the future identification of novel targe ts for pharmacological intervention or novel diagnostic methods.