Current Alzheimer Research - Volume 17, Issue 11, 2020

Alzheimer’s disease is the most common form of dementia. Due to the lack of effective interventions, early and accurate diagnosis for new interventions are emphasized. However, significant neuronal loss and neuropathological lesions can damage the brain substantially before diagnosis. With our growing knowledge of the role of neuroinflammation in the pathogenesis of Alzheimer’s disease, inflammatory biomarkers are attracting increasing interest in the context of diagnosis. This review is focused on the use of inflammatory biomarkers detected through neuroimaging, cerebrospinal fluid, and peripheral blood for diagnosing Alzheimer’s disease, and also suggests clinical implications. This review includes the following biomarkers: neuroimaging, various ligands binding to the translocator protein (TSPO); cerebrospinal fluid, soluble triggering receptor expressed on myeloid cells (sTREM2), human cartilage glycoprotein-39 (YKL-40), and monocyte chemoattractant protein 1 (MCP-1), and various biomarkers in peripheral blood. Although accumulating evidence has suggested the potential role of these inflammatory biomarkers in diagnosing AD, there are limitations to their use. However, combining these biomarkers with conventional diagnostic clues such as genotype and amyloid pathology may improve the stratification and selection of patients for targeted early interventions.

Background: Sporadic Alzheimer’s Disease (AD) is assumed to be associated with different biological/genetic vulnerability, as well as with neuroinflammation, mediated by cytokines. The present study evaluated the role of cytokines in AD. Objective: The aim was to determine the possible association of TNF-α (rs1800629), IL1-α (rs1800587) and IL-10 (rs1800896) polymorphisms with AD, and to assess serum TNF-α, IL-1α and IL-10 concentrations in patients with AD and in subjects with mild cognitive impairment (MCI). Methods: The study included 645 Caucasian participants: 395 subjects with AD and 250 subjects with MCI. Genotyping was performed using real-time PCR in all 645 subjects, while serum concentrations of TNF-α, IL-1α and IL-10 and were determined using ELISA in 174 subjects. Results: The frequency of the TNF-α rs1800629, IL1-α rs1800587 or IL-10 rs1800896 genotypes did not differ significantly between patients with AD and MCI. Serum concentration of IL-1α and IL-10 were significantly decreased, while the concentration of TNF-α was significantly higher in patients with AD than in MCI subjects. TNF-α, IL1-α or IL-10 concentrations were similar in subjects with AD or MCI subdivided into carriers of the corresponding TNF-α rs1800629, IL1-α rs1800587 or IL-10 rs1800896 genotypes. Conclusion: Similar distribution of the IL1-α rs1800587, TNF-α rs1800629 or IL-10 rs1800896 genotypes in subjects with AD and MCI failed to confirm that these specific risk genotypes are associated with vulnerability to develop AD. Alteration in IL-1α, IL-10 and TNF-α concentrations in patients with AD partially confirmed the association with the neuroinflammatory response in AD.

Background: Chronic inflammation is a feature of Alzheimer´s disease (AD), resulting in excessive production of inflammatory mediators that can lead to neuroinflammation, contributing to alterations in Aβ production and deposition as Senile Plaques (SPs), and to neurofibrillary tangles (NFTs) formation, due to hyperphosphorylated Tau protein. Objective: This work addressed the impact of the interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), two chemokines, on Tau phosphorylation; and also evaluated the chemokines’ levels in plasma using samples from a regional cohort. Methods: Human neuronal SH-SY5Y cells exposed to IL-8 and MCP-1 chemokines were monitored for their protein and phosphorylated protein levels by western blotting analysis. A serine/threonine protein phosphatase (PPs) activity assay was employed to monitor PPs activity. Subsequently, flow cytometry was used to monitor chemokines levels in plasma samples from individuals with cognitive deficits. Results: Chemokines’ exposure resulted only in minor cytotoxicity effects on SH-SY5Y, and in increased Tau phosphorylation, particularly at the S396 residue. Tau phosphorylation correlated with PPs inhibition and was consistent with GSK3β phosphorylation-mediated inhibition. Subsequent analysis of plasma from individuals with cognitive deficits showed that IL-8 levels were decreased. Conclusion: Data shows that both chemokines tested can exert an effect on GSK3β phosphorylation and modulate PPs activity, potentially resulting in increased Tau phosphorylation and subsequent NFTs formation. One can deduce that increased chemokines stimulation during chronic inflammation can exacerbate this event. The work contributes to a better understanding of the mode of action of these chemokines on AD pathogenesis and opens novel research avenues.

Alzheimer’s disease (AD) is a neurodegenerative disorder characterized by the progressive loss of neurons leading to cognitive and memory decay. The main signs of AD include the irregular extracellular accumulation of amyloid-beta (Aβ) protein in the brain and the hyper-phosphorylation of tau protein inside neurons. Changes in Aβ expression or aggregation are considered key factors in the pathophysiology of sporadic and early-onset AD and correlate with the cognitive decline seen in patients with AD. Despite decades of research, current approaches in the treatment of AD are only symptomatic in nature and are not effective in slowing or reversing the course of the disease. Encouragingly, recent evidence revealed that exposure to electromagnetic fields (EMF) can delay the development of AD and improve memory. This review paper discusses findings from in vitro and in vivo studies that investigate the link between EMF and AD at the cellular and behavioural level, and highlights the potential benefits of EMF as an innovative approach for the treatment of AD.

Purpose of Review: To provide an updated analysis of the possible use of non-steroidal anti-inflammatory drugs (NSAIDs) as treatments for Alzheimer´s disease (AD). Recent Findings: Neuroinflammation in AD is an active field of research, with increasing evidence from basic and clinical studies for an involvement of innate or adaptive immune responses in the pathophysiology of AD. Few clinical trials with anti-inflammatory drugs have been performed in the last decade, with negative results. Summary: Besides the information gathered from basic research, epidemiological studies have provided conflicting findings, with most case-control or prevalence studies suggesting an inverse relationship between NSAIDs use and AD, but divided results in prospective population-based incident cohort studies. Clinical trials with different NSAIDs are almost unanimous in reporting an absence of clear benefit in AD. Conclusion: The modulation of inflammatory responses is a promising therapeutic strategy in AD. After three decades of research, it seems that conventional NSAIDs are not the best pharmacological option, both for their lack of clear effects and for an unfavorable side-effect profile in long-term treatment. The development of other anti-inflammatory drugs as candidate treatments in AD may benefit from the knowledge acquired with NSAIDs.

Background: Despite the effect of education and APOE ε4 allele on amyloid-beta (Aβ) retention and memory, previous studies have not dealt with an interaction between two factors on Aβ deposition and memory function in the course of Alzheimer’s disease (AD). Objective: To evaluate education by APOE ε4 allele interactions for Aβ retention and neuropsychological test scores in cognitively normal older adults without Aβ deposition [CN(Aβ-), n=45] and Alzheimer’s disease patients with Aβ retention [AD(Aβ+), n=33]. Methods: Multiple regression analyses (adjusted for age, gender) were conducted to examine the effects of education, APOE ε4 allele, and the interaction between the two factors on global, regional Aβ load quantified using [¹⁸F]flutemetamol standardized uptake value ratio with the pons as a reference region, and on neuropsychological test scores in each group. Results: The interaction between education and APOE ε4 allele had an effect on amyloid load in parietal lobes (uncorrected p<0.05) and striatum (Bonferroni corrected p<0.05) in each CN(Aβ-) and AD(Aβ+). There was also an interaction effect of education and APOE ε4 allele on the memory performance in each CN(Aβ-) and AD(Aβ+) (uncorrected p<0.05). APOE ε4 carriers of both groups showed opposing slopes with each other in the correlation between the education years and αβ load, memory performance. Conclusion: The current results suggest a possible explanation of the differential effects of education and APOE ε4 allele interactions on AD pathology and memory function at the beginning and end of AD progress. However, further study with a validating cohort is needed for confirming this explanation.

Background: Neurogenesis, the key mechanism to generate new neurons from existing stem cell niches continues throughout the life in the adult mammalian brain, although decelerate with aging or the progression of neurodegenerative disorders like Alzheimer’s disease (AD). In the past few years, impaired adult hippocampal neurogenesis emerged as a contributing hallmark of AD pathophysiology along with amyloid beta (Aβ) and tau hyper phosphorylation-induced neurotoxicity. However, no conclusive evidence exists that indicates the up/down-regulation of adult hippocampal neurogenesis during the course of AD progression. Methods: In this study, we examined alterations in adult hippocampal neurogenesis and cognitive deficits using Aβ(1-42)-induced mouse model of AD. Results: Our results demonstrate that Aβ administration induces an anxiety like behavior and impairs spatial and non-spatial memory and learning in BALB/c mice. Extensive neuronal loss was also evident in the dentate gyrus (DG), CA1, CA2 and CA3 regions of hippocampus in Aβ-treated animals. Furthermore, Aβ-exposure markedly reduced the real-time expression of markers of cell proliferation and migration i.e. Ki67 and DCX, whereas immunohistochemistry analysis revealed a substantial reduction in the expression levels of Ki67 and NeuN. Conclusion: Our findings highlight the association of Aβ-induced neurotoxicity with altered neurogenesis and memory formation; however further insight is warranted to explore the underlying molecular pathway(s). Moreover, the treatment strategies aiming to repair the adult hippocampal neurogenesis hold potential as AD therapeutics.

Background: Parkinson’s disease (PD) is a common neurodegenerative disorder that is characterized by motor symptoms related to the deficiency in dopamine levels, and cognitive symptoms that are similar in nature to those manifested during Alzheimer’s disease. Levosimendan, on the other hand, is a calcium sensitizer and phosphodiesterase inhibitor that was shown to possess neuroprotective, memoryenhancing, and anti-apoptotic properties. Objective: In the current study, the possible protective effect of levosimendan was investigated in two animal models of Parkinson’s disease. Methods: Both intracerebral injection 6-hydroxydopamine (6-OHDA) and the direct injection of lipopolysaccharide (LPS) into the substantia nigra were used as models to induce Parkinson’s-like behavior. Levosimendan (12 μg/kg intraperitoneally once weekly) was started 7 days before or 2 days after lesioning of the animals. At day 14 post-lesioning, animals were subjected to apomorphine challenge, which was correlated with dopamine levels in the striatum and tyrosine hydroxylase (TH)-positive nigral cells. Results: Results showed that levosimendan restored the number of rotations in the apomorphine challenge test, the levels of dopamine in the striatum, and the TH-positive nigral cells when administered 7 days before, but not two days after 6-OHDA lesioning. In the LPS model of PD, the number of rotations in the apomorphine challenge test, the levels of dopamine in the striatum, and the TH-positive nigral cells were restored when levosimendan was administered 7 days before as well as two days after lesioning. Conclusion: Levosimendan seems to provide a promising agent with potential clinical value for PD.