alvocidib and Alzheimer-Disease

The ectopic re-activation of cell cycle in neurons is an early event in the pathogenesis of Alzheimer's disease (AD), which could lead to synaptic failure and ensuing cognitive deficits before frank neuronal death. Cytostatic drugs that act as cyclin-dependent kinase (CDK) inhibitors have been poorly investigated in animal models of AD. In the present study, we examined the effects of flavopiridol, an inhibitor of CDKs currently used as antineoplastic drug, against cell cycle reactivation and memory loss induced by intracerebroventricular injection of Aß1-42 oligomers in CD1 mice. Cycling neurons, scored as NeuN-positive cells expressing cyclin A, were found both in the frontal cortex and in the hippocampus of Aβ-injected mice, paralleling memory deficits. Starting from three days after Aβ injection, flavopiridol (0.5, 1 and 3mg/kg) was intraperitoneally injected daily, for eleven days. Here we show that a treatment with flavopiridol (0.5 and 1mg/kg) was able to rescue the loss of memory induced by Aβ1-42, and to prevent the occurrence of ectopic cell-cycle events in the mouse frontal cortex and hippocampus. This is the first evidence that a cytostatic drug can prevent cognitive deficits in a non-transgenic animal model of AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Antineoplastic Agents; Cognition Disorders; Cyclin-Dependent Kinases; Disease Models, Animal; Flavonoids; Frontal Lobe; Hippocampus; Male; Memory; Memory Disorders; Mice; Neurons; Peptide Fragments; Piperidines

The bis-indole indirubin is an active ingredient of Danggui Longhui Wan, a traditional Chinese medicine recipe used in the treatment of chronic diseases such as leukemias. The antitumoral properties of indirubin appear to correlate with their antimitotic effects. Indirubins were recently described as potent (IC(50): 50-100 nm) inhibitors of cyclin-dependent kinases (CDKs). We report here that indirubins are also powerful inhibitors (IC(50): 5-50 nm) of an evolutionarily related kinase, glycogen synthase kinase-3beta (GSK-3 beta). Testing of a series of indoles and bis-indoles against GSK-3 beta, CDK1/cyclin B, and CDK5/p25 shows that only indirubins inhibit these kinases. The structure-activity relationship study also suggests that indirubins bind to GSK-3 beta's ATP binding pocket in a way similar to their binding to CDKs, the details of which were recently revealed by crystallographic analysis. GSK-3 beta, along with CDK5, is responsible for most of the abnormal hyperphosphorylation of the microtubule-binding protein tau observed in Alzheimer's disease. Indirubin-3'-monoxime inhibits tau phosphorylation in vitro and in vivo at Alzheimer's disease-specific sites. Indirubins may thus have important implications in the study and treatment of neurodegenerative disorders. Indirubin-3'-monoxime also inhibits the in vivo phosphorylation of DARPP-32 by CDK5 on Thr-75, thereby mimicking one of the effects of dopamine in the striatum. Finally, we show that many, but not all, reported CDK inhibitors are powerful inhibitors of GSK-3 beta. To which extent these GSK-3 beta effects of CDK inhibitors actually contribute to their antimitotic and antitumoral properties remains to be determined. Indirubins constitute the first family of low nanomolar inhibitors of GSK-3 beta to be described.

Topics: Adenosine Triphosphate; Alkaloids; Alzheimer Disease; Animals; Antibiotics, Antineoplastic; Calcium-Calmodulin-Dependent Protein Kinases; CDC2 Protein Kinase; Cyclin B; Cyclin-Dependent Kinase 5; Cyclin-Dependent Kinases; Dopamine and cAMP-Regulated Phosphoprotein 32; Drugs, Chinese Herbal; Enzyme Inhibitors; Flavonoids; Glycogen Synthase Kinase 3; Glycogen Synthase Kinases; Indoles; Inhibitory Concentration 50; Mice; Molecular Structure; Neostriatum; Nerve Tissue Proteins; Phosphoproteins; Phosphorylation; Phosphothreonine; Piperidines; Staurosporine; tau Proteins

Previous evidence by others has indicated that a variety of cell cycle-related molecules are up-regulated in brains of Alzheimer's disease patients. The significance of this increase, however, is unclear. Accordingly, we examined the obligate nature of cyclin-dependent kinases and select downstream targets of these kinases in death of neurons evoked by B-amyloid (AB) protein. We present pharmacological and molecular biological evidence that cyclin-dependent kinases, in particular Cdk4/6, are required for such neuronal death. In addition, we demonstrate that the substrate of Cdk4/6, pRb/p107, is phosphorylated during AB treatment and that one target of pRb/p107, the E2F x DP complex, is required for AB-evoked neuronal death. These results provide evidence that cell cycle elements play a required role in death of neurons evoked by AB and suggest that these elements play an integral role in Alzheimer's disease-related neuronal death.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Carrier Proteins; Cell Cycle Proteins; Cell Death; Cell Survival; Cyclin-Dependent Kinase 4; Cyclin-Dependent Kinase 6; Cyclin-Dependent Kinases; DNA-Binding Proteins; E2F Transcription Factors; Flavonoids; Growth Inhibitors; Neurons; PC12 Cells; Piperidines; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Rats; Retinoblastoma Protein; Retinoblastoma-Binding Protein 1; Signal Transduction; Transcription Factor DP1; Transcription Factors