Targeting Biomolecular Condensation and Protein Aggregation against Cancer

Biomolecular condensates, membrane-less entities arising from liquid-liquid phase separation, hold dichotomous roles in health and disease. Alongside their physiological functions, these condensates can transition to a solid phase, producing amyloid-like structures implicated in degenerative diseases and cancer. This review thoroughly examines the dual nature of biomolecular condensates, spotlighting their role in cancer, particularly concerning the p53 tumor suppressor. Given that over half of the malignant tumors possess mutations in the TP53 gene, this topic carries profound implications for future cancer treatment strategies. Notably, p53 not only misfolds but also forms biomolecular condensates and aggregates analogous to other protein-based amyloids, thus significantly influencing cancer progression through loss-of-function, negative dominance, and gain-of-function pathways. The exact molecular mechanisms underpinning the gain-of-function in mutant p53 remain elusive. However, cofactors like nucleic acids and glycosaminoglycans are known to be critical players in this intersection between diseases. Importantly, we reveal that molecules capable of inhibiting mutant p53 aggregation can curtail tumor proliferation and migration. Hence, targeting phase transitions to solid-like amorphous and amyloid-like states of mutant p53 offers a promising direction for innovative cancer diagnostics and therapeutics.

Sting and p53 DNA repair pathways are compromised in Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia. A common finding in AD is DNA damage. Double-strand DNA breaks (DSBs) are particularly hazardous to neurons because their post-mitotic state forces neurons to rely on error-prone and potentially mutagenic mechanisms to repair DNA breaks. However, it remains unclear whether DNA damage results from increased DNA damage or failure of DNA repair. Oligomerization of the tumor suppressor protein p53 is an essential part of DSB repair, and p53 phosphorylated on S15 is an indicator of DNA damage. We report that the monomer:dimer ratio of phosphorylated (S15) p53 is increased by 2.86-fold in temporal lobes of AD patients compared to age-matched controls, indicating that p53 oligomerization is compromised in AD. In vitro oxidation of p53 with 100 nM H2O2 produced a similar shift in the monomer:dimer ratio. A COMET test showed a higher level of DNA degradation in AD consistent with double-strand DNA damage or inhibition of repair. Protein carbonylation was also elevated (190% of control), indicating elevated oxidative stress in AD patients. Levels of the DNA repair support protein 14-3-3σ, γ-H2AX, a phosphorylated histone marking double strand DNA breaks, and phosphorylated ataxia telangiectasia mutated (ATM) protein were all increased. cGAS-STING-interferon signaling was impaired in AD and was accompanied by a depletion of STING protein from Golgi and a failure to elevate interferon despite the presence of DSBs. The results suggest that oxidation of p53 by ROS could inhibit the DDR and decrease its ability to orchestrate DSB repair by altering the oligomerization state of p53. The failure of immune-stimulated DNA repair may contribute to cell loss in AD and suggests new therapeutic targets for AD.

The function of p53 and its role in Alzheimer's and Parkinson's disease compared to age-related macular degeneration

The protein p53 is the main human tumor suppressor. Since its discovery, extensive research has been conducted, which led to the general assumption that the purview of p53 is also essential for additional functions, apart from the prevention of carcinogenesis. In response to cellular stress and DNA damages, p53 constitutes the key point for the induction of various regulatory processes, determining whether the cell induces cell cycle arrest and DNA repair mechanisms or otherwise cell death. As an implication, aberrations from its normal functioning can lead to pathogeneses. To this day, neurodegenerative diseases are considered difficult to treat, which arises from the fact that in general the underlying pathological mechanisms are not well understood. Current research on brain and retina-related neurodegenerative disorders suggests that p53 plays an essential role in the progression of these conditions as well. In this review, we therefore compare the role and similarities of the tumor suppressor protein p53 in the pathogenesis of Alzheimer's (AD) and Parkinson's disease (PD), two of the most prevalent neurological diseases, to the age-related macular degeneration (AMD) which is among the most common forms of retinal degeneration.

Identification of risk genes for Alzheimer's disease by gene embedding

Most disease-gene association methods do not account for gene-gene interactions, even though these play a crucial role in complex, polygenic diseases like Alzheimer's disease (AD). To discover new genes whose interactions may contribute to pathology, we introduce GeneEMBED. This approach compares the functional perturbations induced in gene interaction network neighborhoods by coding variants from disease versus healthy subjects. In two independent AD cohorts of 5,169 exomes and 969 genomes, GeneEMBED identified novel candidates. These genes were differentially expressed in post mortem AD brains and modulated neurological phenotypes in mice. Four that were differentially overexpressed and modified neurodegeneration in vivo are PLEC, UTRN, TP53, and POLD1. Notably, TP53 and POLD1 are involved in DNA break repair and inhibited by approved drugs. While these data show proof of concept in AD, GeneEMBED is a general approach that should be broadly applicable to identify genes relevant to risk mechanisms and therapy of other complex diseases.

Post-translational Modifications of the p53 Protein and the Impact in Alzheimer's Disease: A Review of the Literature

Our understanding of Alzheimer's disease (AD) pathogenesis has developed with several hypotheses over the last 40 years, including the Amyloid and Tau hypotheses. More recently, the p53 protein, well-known as a genome guardian, has gained attention for its potential role in the early evolution of AD. This is due to the central involvement of p53's in the control of oxidative stress and potential involvement in the Amyloid and Tau pathways. p53 is commonly regulated by post-translational modifications (PTMs), which affect its conformation, increasing its capacity to adopt multiple structural and functional states, including those that can affect brain processes, thus contributing to AD development. The following review will explore the impact of p53 PTMs on its function and consequential involvement in AD pathogenesis. The greater understanding of the role of p53 in the pathogenesis of AD could result in more targeted therapies benefiting the many patients of this debilitating disease.

Genetic Editing and Pharmacogenetics in Current And Future Therapy Of Neurocognitive Disorders

Dementia is an important issue in western societies, and in the following years, this problem will also rise in the developing regions, such as Africa and Asia. The most common types of dementia in adults are Alzheimer's Disease (AD), Dementia with Lewy Bodies (DLB), Frontotemporal Dementia (FTD) and Vascular Dementia (VaD), of which, AD accounts for more than half of the cases. The most prominent symptom of AD is cognitive impairment, currently treated with four drugs: Donepezil, rivastigmine, and galantamine, enhancing cholinergic transmission; as well as memantine, protecting neurons against glutamate excitotoxicity. Despite ongoing efforts, no new drugs in the treatment of AD have been registered for the last ten years, thus multiple studies have been conducted on genetic factors affecting the efficacy of antidementia pharmacotherapy. The researchers investigate the effects of variants in multiple genes, such as ABCB1, ACE, CHAT, CHRNA7, CYP2C9, CYP2C19, CYP2D6, CYP3A4, CYP3A5, CYP3A7, NR1I2, NR1I3, POR, PPAR, RXR, SLC22A1/2/5, SLC47A1, UGT1A6, UGT1A9 and UGT2B7, associated with numerous pathways: the development of pathological proteins, formation and metabolism of acetylcholine, transport, metabolism and excretion of antidementia drugs and transcription factors regulating the expression of genes responsible for metabolism and transport of drugs. The most promising results have been demonstrated for APOE E4, dementia risk variant, BCHE-K, reduced butyrylcholinesterase activity variant, and CYP2D6 UM, ultrarapid hepatic metabolism. Further studies investigate the possibilities of the development of emerging drugs or genetic editing by CRISPR/Cas9 for causative treatment. In conclusion, the pharmacogenetic studies on dementia diseases may improve the efficacy of pharmacotherapy in some patients with beneficial genetic variants, at the same time, identifying the carriers of unfavorable alleles, the potential group of novel approaches to the treatment and prevention of dementia.

Peripheral BDNF/TrkB protein expression is decreased in Parkinson's disease but not in Essential tremor

BDNF-to-TrkB signaling pathways plays an important role in the long-term maintenance of the nigrostriatal system and that its deficiency may contribute to the onset and progression of Parkinson's disease (PD). To our knowledge this is the first study to investigate the expression of the brain-derived neurotrophic factor (BDNF) and phosphorylation status of TrkB in peripheral blood lymphocytes of 28 PD and 28 Essential tremor (ET) patients and 28 healthy controls using western blot analysis. Compared with controls, no significant difference of BDNF and total and phosphorylated TrkB levels were observed in ET, whereas BDNF and phosphorylated TrkB levels were significantly decreased in the PD groups (p < 0.001). Interestingly, BDNF and phosphorylated TrkB levels were positively correlated with disease duration, UPDRS score, Hoehn-Yahr staging, as well as L-DOPA medication in PD patients. These results suggest that the decreased peripheral alteration of BDNF/TrkB levels found in patients with PD is directly related to the dopaminergic neurons neurodegeneration and that decreased expression of BDNF/TrkB may lead to the development of innovative biomarkers of PD, whereas the increased level of BDNF and phosphorylated TrkB at advanced stages may due to L-DOPA medication.

PARP-1 and p53 Regulate the Increased Susceptibility to Oxidative Death of Lymphocytes from MCI and AD Patients

Mild cognitive impairment (MCI) is a clinically detectable initial stage of cognitive deterioration with a high conversion rate to dementia. There is increasing evidence that some of the cerebral alterations present in Alzheimer type dementia can be found in peripheral tissues. We have previously shown that lymphocytes from Alzheimer’s disease (AD) patients have increased susceptibility to hydrogen peroxide (H₂O₂)-induced death that depends on dementia severity. We here investigated whether lymphocytes from MCI patients show increased vulnerability to death, and explored the involvement of Poly [ADP-ribose] polymerase (PARP-1) and p53 in the regulation of this process. Lymphocytes from 16 MCI and 10 AD patients, and 15 healthy controls (HCs) were submitted to increasing concentrations of H₂O₂ for 20 h. Cell death was determined by flow cytometry, in the presence or absence of PARP-1 inhibitors (3-aminobenzamide (3-ABA) or Nicotinamide (NAM)), or the p53 inhibitor (nutlin-3) or stabilizer (pifithrin-α). PARP-1 and p53 mRNA levels were determined by quantitative PCR (qPCR). Lymphocytes from MCI patients showed increased susceptibility to death, attaining intermediate values between AD and controls. PARP inhibitors -3-ABA and NAM- markedly protected from H₂O₂-induced death, making the difference between MCI and controls disappear, but not the difference between AD and controls. PARP-1 mRNA expression was increased in MCI lymphocytes. Modulation of p53 with Nutlin-3 or pifithrin-α did not modify the H₂O₂-induced death of lymphocytes from MCI or AD patients, but augmented the death in control lymphocytes attaining levels similar to MCI and AD. Accordingly, p53 mRNA expression was increased in AD and MCI lymphocytes compared to controls. In all, these results show that increased oxidative death is present in lymphocytes at the MCI stage. PARP-1 has a preponderant role, with complete death protection achieved with PARP inhibition in MCI lymphocytes, but not in AD, suggesting that PARP-1 might have a protective role. In addition, deregulations of the p53 pathway seem to contribute to the H₂O₂-induced death in MCI and AD lymphocytes, which show increased p53 expression. The results showing a prominent protective role of PARP inhibitors opens the door to study the use of these agents to prevent oxidative death in MCI patients.

Plasma microRNA biomarker detection for mild cognitive impairment using differential correlation analysis

BACKGROUND

Mild cognitive impairment (MCI) is an intermediate state between normal aging and dementia including Alzheimer's disease. Early detection of dementia, and MCI, is a crucial issue in terms of secondary prevention. Blood biomarker detection is a possible way for early detection of MCI. Although disease biomarkers are detected by, in general, using single molecular analysis such as t-test, another possible approach is based on interaction between molecules.

RESULTS

Differential correlation analysis, which detects difference on correlation of two variables in case/control study, was carried out to plasma microRNA (miRNA) expression profiles of 30 age- and race-matched controls and 23 Japanese MCI patients. The 20 pairs of miRNAs, which consist of 20 miRNAs, were selected as MCI markers. Two pairs of miRNAs (hsa-miR-191 and hsa-miR-101, and hsa-miR-103 and hsa-miR-222) out of 20 attained the highest area under the curve (AUC) value of 0.962 for MCI detection. Other two miRNA pairs that include hsa-miR-191 and hsa-miR-125b also attained high AUC value of ≥ 0.95. Pathway analysis was performed to the MCI markers for further understanding of biological implications. As a result, collapsed correlation on hsa-miR-191 and emerged correlation on hsa-miR-125b might have key role in MCI and dementia progression.

CONCLUSION

Differential correlation analysis, a bioinformatics tool to elucidate complicated and interdependent biological systems behind diseases, detects effective MCI markers that cannot be found by single molecule analysis such as t-test.

Aberrant protein phosphorylation in Alzheimer disease brain disturbs pro-survival and cell death pathways

Protein phosphorylation of serine, threonine, and tyrosine residues is one of the most prevalent post-translational modifications fundamental in mediating diverse cellular functions in living cells. Aberrant protein phosphorylation is currently recognized as a critical step in the pathogenesis and progression of Alzheimer disease (AD). Changes in the pattern of protein phosphorylation of different brain regions are suggested to promote AD transition from a presymptomatic to a symptomatic state in response to accumulating amyloid β-peptide (Aβ). Several experimental approaches have been utilized to profile alteration of protein phosphorylation in the brain, including proteomics. Among central pathways regulated by kinases/phosphatases those involved in the activation/inhibition of both pro survival and cell death pathways play a central role in AD pathology. We discuss in detail how aberrant phosphorylation could contribute to dysregulate p53 activity and insulin-mediated signaling. Taken together these results highlight that targeted therapeutic intervention, which can restore phosphorylation homeostasis, either acting on kinases and phosphatases, conceivably may prove to be beneficial to prevent or slow the development and progression of AD.

The amyloid precursor protein (APP) intracellular domain regulates translation of p44, a short isoform of p53, through an IRES-dependent mechanism

p44 is a short isoform of the tumor suppressor protein p53 that is regulated in an age-dependent manner. When overexpressed in the mouse, it causes a progeroid phenotype that includes premature cognitive decline, synaptic defects, and hyperphosphorylation of tau. The hyperphosphorylation of tau has recently been linked to the ability of p44 to regulate transcription of relevant tau kinases. Here, we report that the amyloid precursor protein (APP) intracellular domain (AICD), which results from the processing of the APP, regulates translation of p44 through a cap-independent mechanism that requires direct binding to the second internal ribosome entry site (IRES) of the p53 mRNA. We also report that AICD associates with nucleolin, an already known IRES-specific trans-acting factor that binds with p53 IRES elements and regulates translation of p53 isoforms. The potential biological impact of our findings was assessed in a mouse model of Alzheimer's disease. In conclusion, our study reveals a novel aspect of AICD and p53/p44 biology and provides a possible molecular link between APP, p44, and tau.

p53 in neurodegenerative diseases and brain cancers

More than thirty years elapsed since a protein, not yet called p53 at the time, was detected to bind SV40 during viral infection. Thousands of papers later, p53 evolved as the main tumor suppressor involved in growth arrest and apoptosis. A lot has been done but the protein has not yet revealed all its secrets. Particularly important is the observation that in totally distinct pathologies where apoptosis is either exacerbated or impaired, p53 appears to play a central role. This is exemplified for Alzheimer's and Parkinson's diseases that represent the two main causes of age-related neurodegenerative affections, where cell death enhancement appears as one of the main etiological paradigms. Conversely, in cancers, about half of the cases are linked to mutations in p53 leading to the impairment of p53-dependent apoptosis. The involvement of p53 in these pathologies has driven a huge amount of studies aimed at designing chemical tools or biological approaches to rescue p53 defects or over-activity. Here, we describe the data linking p53 to neurodegenerative diseases and brain cancers, and we document the various strategies to interfere with p53 dysfunctions in these disorders.

Peripheral expression of MAPK pathways in Alzheimer's and Parkinson's diseases

Alteration of mitogen-activated protein kinase pathways may cause aberrant protein phosphorylation and enhanced apoptosis in Alzheimer's disease (AD) and Parkinson's disease (PD). Increased susceptibility of lymphocytes to apoptosis has been reported in AD. To our knowledge this is the first study to investigate the expression and phosphorylation status of p38 mitogen-activated protein kinase (p38MAPK) and c-Jun N-terminal kinase (JNK) in peripheral blood lymphocytes of 20 AD and 20 PD patients and 20 healthy controls using western blot analysis. Compared with controls, no significant difference of total p38MAPK or JNK levels were observed in AD and PD patients, whereas phosphorylated p38MAPK and phosphorylated JNK levels were significantly increased in the AD and PD groups (p<0.001). However, the increased levels of the two phosphorylated kinases in AD versus PD patients presented no significant difference. Interestingly, phosphorylated p38MAPK and phosphorylated JNK levels were positively correlated with disease duration (r=0.602, p=0.005 and r=0.561, p=0.010, respectively) and negatively correlated with the Mini Mental State Examination score (r=-0.664, p=0.001 and r=-0.578, p=0.008, respectively) in AD patients. No correlations between protein levels and clinical variables were found in PD patients. Investigation of peripheral changes in the expression of p38MAPK and JNK may lead to the development of innovative biomarkers of neurodegenerative diseases, particularly for AD.

Cell cycle checkpoint abnormalities during dementia: A plausible association with the loss of protection against oxidative stress in Alzheimer's disease [corrected]

Background

Increasing evidence suggests an association between neuronal cell cycle (CCL) events and the processes that underlie neurodegeneration in Alzheimer’s disease (AD). Elevated levels of oxidative stress markers and mitochondrial dysfunction are also among early events in AD. Recent studies have reported the role of CCL checkpoint proteins and tumor suppressors, such as ATM and p53 in the control of glycolysis and oxidative metabolism in cancer, but their involvement in AD remains uncertain.

Methods and Findings

In this postmortem study, we measured gene expression levels of eight CCL checkpoint proteins in the superior temporal cortex (STC) of persons with varying severities of AD dementia and compare them to those of cognitively normal controls. To assess whether the CCL changes associated with cognitive impairment in AD are specific to dementia, gene expression of the same proteins was also measured in STC of persons with schizophrenia (SZ), which is also characterized by mitochondrial dysfunction. The expression of CCL-checkpoint and DNA damage response genes: MDM4, ATM and ATR was strongly upregulated and associated with progression of dementia (cognitive dementia rating, CDR), appearing as early as questionable or mild dementia (CDRs 0.5–1). In addition to gene expression changes, the downstream target of ATM-p53 signaling - TIGAR, a p53-inducible protein, the activation of which can regulate energy metabolism and protect against oxidative stress was progressively decreased as severity of dementia evolved, but it was unaffected in subjects with SZ. In contrast to AD, different CCL checkpoint proteins, which include p53, CHEK1 and BRCA1 were significantly downregulated in SZ.

Conclusions

These results support the activation of an ATM signaling and DNA damage response network during the progression of AD dementia, while the progressive decrease in the levels of TIGAR suggests loss of protection initiated by ATM-p53 signaling against intensifying oxidative stress in AD.

Lymphocytes of patients with Alzheimer's disease display different DNA damage repair kinetics and expression profiles of DNA repair and stress response genes

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder, characterized by loss of memory and cognitive capacity. Given the limitations to analyze brain cells, it is important to study whether peripheral lymphocytes can provide biological markers for AD, an interesting approach, once they represent the overall condition of the organism. To that extent, we sought to find whether lymphocytes of AD patients present DNA damage and repair kinetics different from those found in elderly matched controls (EC group) under in vitro treatment with hydrogen peroxide. We found that AD patient cells indeed showed an altered DNA repair kinetics (comet assay). Real-time quantitative analysis of genes associated with DNA stress response also showed that FANCG and CDKN1A are upregulated in AD, while MTH1 is downregulated, compared with the control group. In contrast, the expression of ATM, ATR and FEN1 genes does not seem to differ between these groups. Interestingly, TP53 protein expression was increased in AD patients. Therefore, we found that kinetics of the stress response in the DNA were significantly different in AD patients, supporting the hypothesis that repair pathways may be compromised in AD and that peripheral lymphocytes can reveal this condition.

Nonfibrillar Abeta 1-42 inhibits glutamate uptake and phosphorylates p38 in human fibroblasts

Alzheimer disease (AD) is the most prevalent neurodegenerative disease, characterized by an increased deposition of β-amyloid (Abeta) within the central nervous system, leading to neuronal death. The availability of effective models, in which confirming novel pathogenic hypotheses and developing therapeutic targets, represents a very important goal for the field of AD. Fibroblasts from these patients may be relevant models in which addressing these issues, as they display biochemical alterations mirroring SNC ones. In this work, fibroblasts obtained from controls were studied after exposure to nonfibrillar Abeta 1-42, showing decreased glutamate uptake, similar to that observed in AD cells, in absence of transporters modifications. Nonfibrillar Abeta 1-42 was able to induce in control cells mitochondrial alterations and p38-phosphorylation, mirroring similar alterations found in AD fibroblasts. Under our experimental conditions, this treatment induced neither apoptosis nor necrosis. To investigate a putative role of p38-modulation in mediating nonfibrillar Abeta 1-42 toxicity, fibroblasts from controls were pretreated with retinoic-acid, and SB203580, a p38-inhibitor. These pretreatments prevented both p38-phosphorylation and glutamate uptake inhibition. Our results suggest that nonfibrillar Abeta 1-42 downregulates glutamate transporters activity interfering with p38-activation and mitochondrial stress. Thus, modulating complex kinase signaling pathway might represent a future therapeutic target in AD.

An integrated genetics approach for identifying protein signal pathways of Alzheimer's disease

Alzheimer's disease (AD) is considered one of the most common age-associated neurodegenerative disorders, affecting millions of senior people worldwide. Combination of protein-protein interaction (PPI) network analysis and gene expression studies provides a better insight into AD. A computational approach was developed in our work to identify protein signal pathways between amyloid precursor proteins and tau proteins, which are well known as important proteins for AD. First, a modified LA-SEN method, called the network-constrained regularisation analysis, was applied to microarray data from a transgenic mouse model and AD patients. Then protein pathways were constructed based on an integer linear programming model to integrate microarray data and the PPI database. Important pathways of AD, including some cancer-related pathways, were identified finally.

Peripheral expression of key regulatory kinases in Alzheimer's disease and Parkinson's disease

Alteration of key regulatory kinases may cause aberrant protein phosphorylation and aggregation in Alzheimer's disease (AD) and Parkinson's disease (PD). In this study, we investigated expression and phosphorylation status of glycogen synthase kinase 3 (GSK-3), protein kinase B (Akt) and tau protein in peripheral blood lymphocytes of 20 AD, 25 PD patients and 20 healthy controls. GSK-3 was increased in AD and PD patients. In these latter, GSK-3 levels were positively correlated with daily L-Dopa intake. Phosphorylated Akt expression was augmented in both groups; total Akt levels were increased only in AD patients and were positively correlated with disease duration and severity. Total and phosphorylated tau were increased only in AD, with phospho-tau levels being positively correlated with levels of total tau, Akt, and disease duration. No correlations between protein levels and clinical variables were found in PD patients. Investigation of peripheral changes in the expression of specific kinases may, therefore, lead to the development of innovative biomarkers of neurodegeneration, particularly for AD.

High sensitivity to carcinogens in the brain of a mouse model of Alzheimer's disease

Cancer and Alzheimer's disease (AD) are commonly found among elderly patients. Chronic inflammation is the characteristic of both diseases. Amyloid-beta peptide is the main inducer of inflammation in AD. Moreover, chronic inflammation promotes cancer, suggesting that AD patients may be more prone to develop cancer than non-demented people. To test this hypothesis, we injected the carcinogen 20-methylcholanthrene in the brain of transgenic mice overexpressing the mutant forms of amyloid precursor protein (APP) and presenilin 1 (PS1), as a model of AD, and their wild-type (WT) littermates. Mutant mice developed tumors faster and with higher incidence than their WT counterparts. Expression of the inflammatory markers interleukin (IL)-1alpha, IL-1beta, IL-6, IP-10 and tumor necrosis factor-alpha (TNF-alpha) was measured in AD and WT mice of 3 and 12 months of age that had not been exposed to the carcinogen. These cytokines were elevated in older AD mice, indicating the existence of a highly inflammatory milieu in these animals. We also found elevated expression of a mutated form of p53 in older AD mice, suggesting an alternative mechanism for the predisposition of AD brains to develop brain tumors. Clinical studies reporting comorbidity of AD and brain cancer are needed to understand whether our observations hold true for humans.

Interaction of double-stranded RNA-dependent protein kinase (PKR) with the death receptor signaling pathway in amyloid beta (Abeta)-treated cells and in APPSLPS1 knock-in mice

For 10 years, research has focused on signaling pathways controlling translation to explain neuronal death in Alzheimer Disease (AD). Previous studies demonstrated in different cellular and animal models and AD patients that translation is down-regulated by the activation of double-stranded RNA-dependent protein kinase (PKR). Among downstream factors of PKR, the Fas-associated protein with a death domain (FADD) and subsequent activated caspase-8 are responsible for PKR-induced apoptosis in recombinant virus-infected cells. However, no studies have reported the role of PKR in death receptor signaling in AD. The aim of this project is to determine physical and functional interactions of PKR with FADD in amyloid-beta peptide (Abeta) neurotoxicity and in APP(SL)PS1 KI transgenic mice. In SH-SY5Y cells, results showed that Abeta42 induced a large increase in phosphorylated PKR and FADD levels and a physical interaction between PKR and FADD in the nucleus, also observed in the cortex of APP(SL)PS1 KI mice. However, PKR gene silencing or treatment with a specific PKR inhibitor significantly prevented the increase in pT(451)-PKR and pS(194)-FADD levels in SH-SY5Y nuclei and completely inhibited activities of caspase-3 and -8. The contribution of PKR in neurodegeneration through the death receptor signaling pathway may support the development of therapeutics targeting PKR to limit neuronal death in AD.

A common biological mechanism in cancer and Alzheimer's disease?

Cancer and Alzheimer's disease (AD) are two common disorders for which the final pathophysiological mechanism is not yet clearly defined. In a prospective longitudinal study we have previously shown an inverse association between AD and cancer, such that the rate of developing cancer in general with time was significantly slower in participants with AD, while participants with a history of cancer had a slower rate of developing AD. In cancer, cell regulation mechanisms are disrupted with augmentation of cell survival and/or proliferation, whereas conversely, AD is associated with increased neuronal death, either caused by, or concomitant with, beta amyloid (Abeta) and tau deposition. The possibility that perturbations of mechanisms involved in cell survival/death regulation could be involved in both disorders is discussed. Genetic polymorphisms, DNA methylation or other mechanisms that induce changes in activity of molecules with key roles in determining the decision to "repair and live"- or "die" could be involved in the pathogenesis of the two disorders. As examples, the role of p53, Pin1 and the Wnt signaling pathway are discussed as potential candidates that, speculatively, may explain inverse associations between AD and cancer.

Alzheimer's disease: new diagnostic and therapeutic tools

On March 19, 2008 a Symposium on Pathophysiology of Ageing and Age-Related diseases was held in Palermo, Italy. Here, the lectures of M. Racchi on History and future perspectives of Alzheimer Biomarkers and of G. Scapagnini on Cellular Stress Response and Brain Ageing are summarized. Alzheimer's disease (AD) is a heterogeneous and progressive neurodegenerative disease, which in Western society mainly accounts for clinica dementia. AD prevention is an important goal of ongoing research. Two objectives must be accomplished to make prevention feasible: i) individuals at high risk of AD need to be identified before the earliest symptoms become evident, by which time extensive neurodegeneration has already occurred and intervention to prevent the disease is likely to be less successful and ii) safe and effective interventions need to be developed that lead to a decrease in expression of this pathology. On the whole, data here reviewed strongly suggest that the measurement of conformationally altered p53 in blood cells has a high ability to discriminate AD cases from normal ageing, Parkinson's disease and other dementias. On the other hand, available data on the involvement of curcumin in restoring cellular homeostasis and rebalancing redox equilibrium, suggest that curcumin might be a useful adjunct in the treatment of neurodegenerative illnesses characterized by inflammation, such as AD.