The role of poly(ADP-ribose) polymerase and sirtuins in molecular mechanism of cell death. Identification of novel targets for Alzheimer's therapy

The pathology of Alzheimer’s disease (AD) is well characterized, but the pathogenesis and mechanisms underlying brain dysfunction are still unclear and therapy is not successful. A mitochondrial dysfunction and oxidative stress are early events that contribute to synaptic abnormalities and neuronal degeneration in AD. Recent research emphasized the important role of poly(ADP-ribose) polymerase-1 (PARP-1), and sirtuin-1 (SIRT-1) in AD. Mice that produced excessive amounts of the SIRT-1 were less likely to develop AD. SIRT-1 is a member of a family of conserved NAD-dependent proteins with deacetylase and ADP-ribosyl-transferase activity. SIRT-1 regulates expression of genes involved in energy metabolism is able to suppress Aβ production by activating secretase α (ADAM 10). Moreover, SIRT-1 deacetylates tau protein and activates its degradation. It was demonstrated that three other sirtuins (SIRT-3, 4, 5) and probably PARP-1 are located in mitochondria and implicated in energy regulation, but their role in AD is unknown. PARP(s) and SIRT(s) play a key role in DNA repair in regulation of several transcription factors (NFkB, p53, FOXO(s), STAT(s)) and they are most effective NAD consuming enzyme in the brain. They are responsible for cells survival or death. Our previous and recently published results indicate that Aβ-induced neuronal death is mediated by PARP. This enzyme is a requisite factor in Aβ activation of metalloproteinase 9 and microglia. However, the role of PARP in Aβ precursor protein (APP) processing was not investigated. The crosstalk between PARPs and sirtuins very important for genome integrity is not yet studied within the pathogenesis of AD. Furthermore, till now nothing is known about SIRT-3, 4, 5 and PARPs in the metabolic pathway de-regulation, mitochondria function, gene expression in DNA repair and biogenesis alteration occurring in AD. The present project is designed to elucidate the unknown role of PARP(s) and SIRT(s) in mitochondria function and death signaling in cells AD models. Specifically, we will investigate: 1. Analysis of the effect of Aβ peptides on sirtuins (1, 3, 4, 5) and PARPs expression and activity in cellular models of AD (human APP overexpressing cells and in Aβ1-42 toxicity). 2. Identification the role of SIRT-1 and PARP-1 in metabolism of APP, in regulation of expression and activity of secretases (α,β,γ) and metaloproteinases (2,9,10) in APP transfected cells. 3. The role of sirtuins and PARP-1 in regulation of transcription factors (e.g. FOXO, p53, NF-kB, STAT 6) involved in mitochondria functions and cells death. 4. Identification the role of PARP-1 and SIRTs in mitochondria function and biogenesis in AD models. 5. Determination of the role of PARPs and SIRTs in regulation of apoptotic signaling. Conformation of key data obtained in APP cells with the short effect of exogenous Aβ1-42 in neuronal cells, microglia, neuronal/microglia coculture and in mitochondria/synaptosomal fractions from rat brain. Relevance of proposed research to AD: This is the first project aimed at characterizing the mechanistic connection of mitochondrial sirtuins and PARP in AD. Functional aspects between mitochondria and sirtuins and PARPs in AD have never been attempted before. Up till now the role of SIRT-1 and PARP-1 in APP metabolism in regulation of secretases and metaloproteinases in AD model was not investigated. Our proposed study will help to create a new scientific data for drug development strategies in AD using sirtuins and PARP(s) as novel targets.