Proton pump inhibitor lansoprazole is a nuclear liver X receptor agonist

Selection of lansoprazole from an FDA-approved drug library to inhibit the Alzheimer's disease seed-dependent formation of tau aggregates

The efficacy of current treatments is still insufficient for Alzheimer's disease (AD), the most common cause of Dementia. Out of the two pathological hallmarks of AD amyloid-β plaques and neurofibrillary tangles, comprising of tau protein, tau pathology strongly correlates with the symptoms of AD. Previously, screening for inhibitors of tau aggregation that target recombinant tau aggregates have been attempted. Since a recent cryo-EM analysis revealed distinct differences in the folding patterns of heparin-induced recombinant tau filaments and AD tau filaments, this study focused on AD seed-dependent tau aggregation in drug repositioning for AD. We screened 763 compounds from an FDA-approved drug library using an AD seed-induced tau aggregation in SH-SY5Y cell-based assay. In the first screening, 180 compounds were selected, 72 of which were excluded based on the results of lactate dehydrogenase assay. In the third screening with evaluations of soluble and insoluble tau, 38 compounds were selected. In the fourth screening with 3 different AD seeds, 4 compounds, lansoprazole, calcipotriene, desogestrel, and pentamidine isethionate, were selected. After AD seed-induced real-time quaking-induced conversion, lansoprazole was selected as the most suitable drug for repositioning. The intranasal administration of lansoprazole for 4 months to AD seed-injected mice improved locomotor activity and reduced both the amount of insoluble tau and the extent of phosphorylated tau-positive areas. Alanine replacement of the predicted binding site to an AD filament indicated the involvement of Q351, H362, and K369 in lansoprazole and C-shaped tau filaments. These results suggest the potential of lansoprazole as a candidate for drug repositioning to an inhibitor of tau aggregate formation in AD.

Clinical Use of Lansoprazole and the Risk of Osteoporosis: A Nationwide Cohort Study

BACKGROUND

Proton pump inhibitor (PPI) lansoprazole acts as a liver X receptor agonist, which plays a crucial role in the crosstalk of osteoblasts and osteoclasts in vitro and during bone turnover in vivo. However, epidemiological studies on the association between the use of lansoprazole and osteoporosis risk are limited. We aimed to determine the risk of developing osteoporosis in patients with lansoprazole use.

METHODS

A retrospective cohort study was conducted using the National Health Insurance Research Database of Taiwan dated from 2000 to 2013. The study includes 655 patients with lansoprazole use (the exposed cohort) and 2620 patients with other PPI use (the comparison cohort). The main outcome was the primary diagnosis of osteoporosis. The hazard ratios (HRs) and 95% confidence intervals (CIs) were used to assess the association between the use of lansoprazole and risk of osteoporosis.

RESULTS

Patients receiving lansoprazole treatment had a reduced risk of osteoporosis as compared with those undergoing other PPI therapy (adjusted HR, 0.56; 95% CI, 0.46-0.68). Moreover, this inverse association is evident in both sexes and in various age groups.

CONCLUSIONS

This population-based cohort study demonstrated that lansoprazole use was associated with a reduced risk of osteoporosis. The clinical implications of the present study need further investigations.

Chronic omeprazole use in the elderly is associated with decreased risk of dementia and cognitive decline

BACKGROUND

The association between proton pump inhibitor (PPI) use and increased risk of dementia is controversial.

AIM

Investigating this issue in a large population of community-dwelling elders.

METHODS

Our database was retrospectively searched for all community-dwelling patients aged ≥65 years who newly diagnosed with dementia/cognitive decline (DCD) between January 2002 - December 2012. Receiving ≥11 prescriptions of PPIs/year was categorized as PPI users. Clinical data were collected from the medical files. Risk of DCD in PPI users was analyzed by Cox regression models.

RESULTS

Included 48,632 elders of whom 8,848 were diagnosed with DCD (18.2%). PPI use was documented in 10,507, of whom 1,959 were subsequently diagnosed with DCD (18.6%). Among 38,125 non-PPI users, 6,889 (18.1%) were diagnosed with DCD. The hazard ratio for occurrence of DCD in PPI users compared to non-users was 0.85 (95% CI: 0.81-0.89, P <0.001) in an un-adjusted Cox regression model and 0.83 in a Cox regression model adjusted for age and sex (95% CI: 0.79-0.87, P <0.001). Multivariate Cox regression accounting for background diseases, marital status, and socioeconomic state yielded a hazard ratio of 0.77 (95% CI: 0.73-0.81, P <0.001).

CONCLUSION

PPI use wasn't associated with DCD development in chronic PPI users.

The Janus-like Association between Proton Pump Inhibitors and Dementia

Early pharmacoepidemiological studies suggested that Proton Pump Inhibitors (PPIs) might increase the risk of Alzheimer’s Disease (AD) and non-AD related dementias. These findings were supported by preclinical studies, specifically stressing the proamyloidogenic and indirect anticholinergic effects of PPIs. However, further large-scale pharmacoepidemiological studies showed inconsistent results on the association between PPIs and dementia. Pharmacodynamically, these findings might be related to the LXR/RXR-mediated amyloid clearance effect and anti-inflammatory action of PPIs. Further aspects that influence PPI effects on AD are related to patient-specific pharmacokinetic and pharmacogenomic characteristics. In conclusion, a personalized (individualized) medicinal approach is necessary to model and predict the potential harmful or beneficial effects of PPIs in AD and non-AD-related dementias in the future.

Biological processes and key druggable targets involved in age-associated memory loss: A systematic review

Age-associated memory loss is highly prevalent in the elder population. The inception of neurodegenerative diseases acts as a causative factor for the onset of memory loss in aged individuals. The pathophysiological mechanisms of memory loss associated with the onset of neurodegenerative diseases and normal aging processes share certain similarities as well as differences. The normal age-associated memory loss is attributed to the impairment of calcium metabolism, dysregulated cholesterol metabolism, the prevalence of oxidative stress, inappropriate functioning of hormones as well as genetic factors. Vital information regarding the key biological processes and the druggable targets involved in the onset of memory loss in the elder population has been provided in this article. The genomic and proteomic profiles of key druggable targets retrieved from the experimental evidence, co-expression studies and databases are also presented in this article. The genomic and proteomic information of druggable targets will aid in the identification of therapeutic agents which could effectively regulate the key biological processes involved in the age-associated memory loss.

Binding of omeprazole to protein targets identified by monoclonal antibodies

Omeprazole is the most commonly used proton pump inhibitor (PPI), a class of medications whose therapeutic mechanism of action involves formation of a disulfide linkage to cysteine residues in the H+/K+ ATPase pump on gastric secretory cells. Covalent linkage between the sole sulfur group of omeprazole and selected cysteine residues of the pump protein results in inhibition of acid secretion in the stomach, an effect that ameliorates gastroesophageal reflux and peptic ulcer disease. PPIs, though useful for specific conditions when used transiently, are associated with diverse untoward effects when used long term. The mechanisms underlying these potential off-target effects remain unclear. PPIs may, in fact, interact with non-canonical target proteins (non-pump molecules) resulting in unexpected pathophysiological effects, but few studies describe off-target PPI binding. Here, we describe successful cloning of monoclonal antibodies against protein-bound omeprazole. We developed and used monoclonal antibodies to characterize the protein target range of omeprazole, stability of omeprazole-bound proteins, and the involvement of cysteines in binding of omeprazole to targets. We demonstrate that a wide range of diverse proteins are targeted by omeprazole. Protein complexes, detected by Western blotting, are resistant to heat, detergents, and reducing agents. Reaction of omeprazole occurs with cysteine-free proteins, is not fully inhibited by cysteine alkylation, occurs at neutral pH, and induces protein multimerization. At least two other clinically used PPIs, rabeprazole and tenatoprazole, are capable of binding to proteins in a similar fashion. We conclude that omeprazole binds to multiple proteins and is capable of forming highly stable complexes that are not dependent on disulfide linkages between the drug and protein targets. Further studies made possible by these antibodies may shed light on whether PPI-protein complexes underlie off-target untoward effects of chronic PPI use.

Brothers in Arms: ABCA1- and ABCG1-Mediated Cholesterol Efflux as Promising Targets in Cardiovascular Disease Treatment

Atherosclerosis is a leading cause of cardiovascular disease worldwide, and hypercholesterolemia is a major risk factor. Preventive treatments mainly focus on the effective reduction of low-density lipoprotein cholesterol, but their therapeutic value is limited by the inability to completely normalize atherosclerotic risk, probably due to the disease complexity and multifactorial pathogenesis. Consequently, high-density lipoprotein cholesterol gained much interest, as it appeared to be cardioprotective due to its major role in reverse cholesterol transport (RCT). RCT facilitates removal of cholesterol from peripheral tissues, including atherosclerotic plaques, and its subsequent hepatic clearance into bile. Therefore, RCT is expected to limit plaque formation and progression. Cellular cholesterol efflux is initiated and propagated by the ATP-binding cassette (ABC) transporters ABCA1 and ABCG1. Their expression and function are expected to be rate-limiting for cholesterol efflux, which makes them interesting targets to stimulate RCT and lower atherosclerotic risk. This systematic review discusses the molecular mechanisms relevant for RCT and ABCA1 and ABCG1 function, followed by a critical overview of potential pharmacological strategies with small molecules to enhance cellular cholesterol efflux and RCT. These strategies include regulation of ABCA1 and ABCG1 expression, degradation, and mRNA stability. Various small molecules have been demonstrated to increase RCT, but the underlying mechanisms are often not completely understood and are rather unspecific, potentially causing adverse effects. Better understanding of these mechanisms could enable the development of safer drugs to increase RCT and provide more insight into its relation with atherosclerotic risk. SIGNIFICANCE STATEMENT: Hypercholesterolemia is an important risk factor of atherosclerosis, which is a leading pathological mechanism underlying cardiovascular disease. Cholesterol is removed from atherosclerotic plaques and subsequently cleared by the liver into bile. This transport is mediated by high-density lipoprotein particles, to which cholesterol is transferred via ATP-binding cassette transporters ABCA1 and ABCG1. Small-molecule pharmacological strategies stimulating these transporters may provide promising options for cardiovascular disease treatment.

Proton Pump Inhibitors and Dementia: Physiopathological Mechanisms and Clinical Consequences

Alzheimer's disease (AD) is the most common type of dementia, mainly encompassing cognitive decline in subjects aged ≥65 years. Further, AD is characterized by selective synaptic and neuronal degeneration, vascular dysfunction, and two histopathological features: extracellular amyloid plaques composed of amyloid beta peptide (Aβ) and neurofibrillary tangles formed by hyperphosphorylated tau protein. Dementia and AD are chronic neurodegenerative conditions with a complex physiopathology involving both genetic and environmental factors. Recent clinical studies have shown that proton pump inhibitors (PPIs) are associated with risk of dementia, including AD. However, a recent case-control study reported decreased risk of dementia. PPIs are a widely indicated class of drugs for gastric acid-related disorders, although most older adult users are not treated for the correct indication. Although neurological side effects secondary to PPIs are rare, several preclinical reports indicate that PPIs might increase Aβ levels, interact with tau protein, and affect the neuronal microenvironment through several mechanisms. Considering the controversy between PPI use and dementia risk, as well as both cognitive and neuroprotective effects, the aim of this review is to examine the relationship between PPI use and brain effects from a neurobiological and clinical perspective.

Pterosin Sesquiterpenoids from Pteris cretica as Hypolipidemic Agents via Activating Liver X Receptors

Four new pterosin sesquiterpenoids (1-4), a new ent-kaurane diterpenoid (17), and 18 known compounds were isolated from the aerial parts of Pteris cretica L. The structures of the isolates were elucidated based on spectroscopic data analysis, and their absolute configurations were determined by comparison of experimental and calculated electronic circular dichroism spectra. The compounds were evaluated for lipid-lowering effects in 3T3-L1 adipocytes. Compounds 4, 8, 17, and 22 were more potent than the positive control, berberine, in decreasing triglycerides activity, with compound 4 exerting the most potent activity. Compound 4 activated LXRα/β in a HEK 293T cell-based reporter gene assay. Molecular dynamic simulations revealed that compound 4 activates liver X receptors (LXRs) through hydrogen bonding with the residues of LXRα/β, suggesting that compound 4 reduces total triglycerides through the regulation of LXRα/β.

Proton pump inhibitors and statins: a possible interaction that favors low-density lipoprotein cholesterol reduction?

BACKGROUND

Proton pump inhibitors (PPIs) might influence the metabolism of cholesterol and statins in the liver.

AIM

The impact of PPIs on low-density lipoprotein cholesterol (LDL-C) levels in statin-treated patients.

METHODS

Retrospective observational study including consecutive statin-treated individuals followed for ≥3 years in a university hospital lipid clinic. Demographic characteristics as well as clinical and laboratory data were recorded at baseline and the most recent visit. High, moderate and low-intensity statin therapy was defined according to the expected LDL-C reduction (≥50%, 30-50%, and <30%, respectively). We compared the LDL-C reduction in subjects receiving statin + PPI with those on statin alone and assessed the overall effect of PPI administration on LDL-C lowering.

RESULTS

Of 648 statin-treated subjects, 7% were also taking a PPI. There was no difference between PPI vs. non-PPI group regarding baseline characteristics and intensity of lipid-lowering therapy. Stepwise linear regression analysis showed that PPI use was significantly associated with LDL-C reduction (b =0.104, p =0.005) along with baseline LDL-C levels (b =0.482, p <0.001), treatment with ezetimibe (b =0.198, p <0.001), presence of diabetes (b =0.168, p <0.001), compliance with treatment (b =0.205, p <0.001), intensity of statin treatment (b =0.101, p =0.005) and cardiovascular risk (b =0.082, p =0.049). Subjects receiving statin + PPI had a higher LDL-C reduction by 6.4% compared with those taking a statin alone (fully adjusted p =0.005).

CONCLUSIONS

PPIs may modestly boost the statin-mediated LDL-C reduction. This effect should be confirmed by prospective clinical studies. Hippokratia 2015; 19 (4): 332-337.

Identifying farnesoid X receptor agonists by naïve Bayesian and recursive partitioning approaches

For the first time, NB and RP were successfully employed to predict FXR agonists. Two new FXR agonists were identified with the models, and confirmed with cell-based experiments.

Proton pump inhibitors induce changes in colonocyte gene expression that may affect Clostridium difficile infection

BACKGROUND

Proton pump inhibitors seem to promote Clostridium difficile infection (CDI). Although the current literature suggests that this association is mediated through gastric acid suppression, there has been little investigation into whether a direct effect on expression of colonocyte genes may also have a role. The aim of this study was to investigate the effect of omeprazole on genome-wide gene expression in a human colonic cell line.

METHODS

T84 cell monolayers were treated with acid-activated omeprazole at 0, 1, 10, or 100 μmol/L for 48 hours. Cells were lysed and total RNA samples were reverse transcribed and used to generate biotinylated cRNA. Whole-genome transcript expression levels were then quantified using an Illumina HT-12 BeadChip microarray targeting 25,440 genes. Transcripts with a stringent minimum absolute fold change of 1.5 and an adjusted nominal P value <.05 (false discovery) were identified as being differentially expressed.

RESULTS

Significant changes in expression were observed for 322 colonocyte transcripts, including genes with potential implications for susceptibility to CDI. These genes include roles in cell junctions, toxin susceptibility, and bile acid metabolism and transport.

CONCLUSION

Omeprazole treatment decreases the expression of genes that have important functions in colonocyte integrity. Such impairment in colonocyte function may promote CDI.

Action mechanisms of Liver X Receptors

The two Liver X Receptors, LXRα and LXRβ, are nuclear receptors belonging to the superfamily of ligand-activated transcription factors. They share more than 78% homology in amino acid sequence, a common profile of oxysterol ligands and the same heterodimerization partner, Retinoid X Receptor. LXRs play crucial roles in several metabolic pathways: lipid metabolism, in particular in preventing cellular cholesterol accumulation; glucose homeostasis; inflammation; central nervous system functions and water transport. As with all nuclear receptors, the transcriptional activity of LXR is the result of an orchestration of numerous cellular factors including ligand bioavailability, presence of corepressors and coactivators and cellular context i.e., what other pathways are activated in the cell at the time the receptor recognizes its ligand. In this mini-review we summarize the factors regulating the transcriptional activity and the mechanisms of action of these two receptors.

Genome-wide approaches reveal EGR1-controlled regulatory networks associated with neurodegeneration

Early growth response gene 1 (Egr1) is a member of the immediate early gene (IEG) family of transcription factors and plays a role in memory formation. To identify EGR1 target genes in brain of Alzheimer's disease (AD) model mice - APP23, we applied chromatin immunoprecipitation (ChIP) followed by high-throughput DNA sequencing (ChIP-seq). Functional annotation of genes associated with EGR1 binding revealed a set of related networks including synaptic vesicle transport, clathrin-mediated endocytosis (CME), intracellular membrane fusion and transmission of signals elicited by Ca(2+) influx. EGR1 binding is associated with significant enrichment of activating chromatin marks and appears enriched near genes that are up-regulated in the brains of APP23 mice. Among the putative EGR1 targets identified and validated in this study are genes related to synaptic plasticity and transport of proteins, such as Arc, Grin1, Syn2, Vamp2 and Stx6, and genes implicated in AD such as Picalm, Psen2 and App. We also demonstrate a potential regulatory link between EGR1 and its newly identified targets in vivo, since conditions that up-regulate Egr1 levels in brain, such as a spatial memory test, also lead to increased expression of the targets. On the other hand, protein levels of EGR1 and ARC, SYN2, STX6 and PICALM are significantly lower in the brain of adult APP mice than in age-matched wild type animals. The results of this study suggest that EGR1 regulates the expression of genes involved in CME, vesicular transport and synaptic transmission that may be critical for AD pathogenesis.

Defensive effect of lansoprazole in dementia of AD type in mice exposed to streptozotocin and cholesterol enriched diet

The present study investigates the potential of lansoprazole (a proton pump inhibitor and agonist of liver x receptors) in experimental dementia of AD type. Streptozotocin [STZ, 3 mg/kg, injected intracerebroventricular (i.c.v), and high fat diet (HFD, administered for 90 days)] were used to induce dementia in separate groups of Swiss mice. Morris water maze (MWM) test was performed to assess learning and memory of the animals. A battery of biochemical and histopathological studies were also performed. Extent of oxidative stress was measured by estimating the levels of brain reduced glutathione (GSH) and thiobarbituric acid reactive species (TBARS). Brain acetylcholinestrase (AChE) activity and serum cholesterol levels were also estimated. The brain level of myeloperoxidase (MPO) was measured as a marker of inflammation. STZ and HFD produced a marked decline in MWM performance of the animals, reflecting impairment of learning and memory. STZ/HFD treated mice exhibited a marked accentuation of AChE activity, TBARS and MPO levels along with a fall in GSH levels. Further, the stained micrographs of STZ/HFD treated mice indicated pathological changes, severe neutrophilic infiltration and amyloid deposition. Lansoprazole treatment significantly attenuated STZ and HFD -induced memory deficits, biochemical and histopathological alterations. It also prevented HFD-induced rise in the cholesterol level. Therefore, the findings demonstrate potential of lansoprazole in memory dysfunctions which may probably be attributed to its anti-cholinesterase, anti-oxidative and anti-inflammatory effects. Moreover, both cholesterol-dependent as well as cholesterol-independent effects of lansoprazole appear to play a role. In addition study indicates the role of liver x receptors in dementia.

Synthesis and identification of new flavonoids targeting liver X receptor β involved pathway as potential facilitators of Aβ clearance with reduced lipid accumulation

Alzheimer's disease (AD) is associated with impaired Aβ degradation in the brain. Enhancing the process of Aβ clearance is an attractive potential AD therapy. Treatment with LXR agonists may reduce Aβ levels in vivo. However, the clinical potential of many LXR agonists is limited because of their nonselective actions on LXRα/β, which lead to undesired hepatic lipogenesis via LXRα-dependent pathways. In this study, ABCA1 up-regulators were identified from a series of flavonoids and were found to preferentially activate LXRβ and up-regulate expression of ABCA1 and apoE in different cell lines. Further investigations confirmed that these compounds facilitate intracellular Aβ clearance in Aβ-loaded BV2 cells. Administration of compound 19 reduced total brain Aβ and plaque burden in APP/PS1 double transgenic mice, associated with elevated ABCA1 and apoE expression. Compared with the nonselective LXR agonists, the active compounds reported here induced less accumulation of undesired lipids and triglycerides in HepG2 cells.

Liver X receptor α bidirectionally transactivates human CYP1A1 and CYP1A2 through two cis-elements common to both genes

CYP1A1 and CYP1A2 are involved in both detoxification and metabolic activation of xenobiotics. Human CYP1A1 (hCYP1A1) and hCYP1A2 exist in a head-to-head orientation in chromosome 15 with the overlapping 5'-flanking region. We have recently reported that nuclear receptor constitutive androstane receptor (CAR), in addition to aryl hydrocarbon receptor, bidirectionally transactivates these genes through common motifs. In this study, we have investigated a role of liver X receptor α (LXRα), another liver-enriched nuclear receptor, in the expression hCYP1A1 and hCYP1A2. In reporter assays with dual-reporter constructs containing their promoter region between two different reporter genes, LXRα simultaneously transactivated hCYP1A1 and hCYP1A2 through two regions, independent of aryl hydrocarbon receptor. In electrophoretic mobility shift assays, LXRα/retinoid X receptor α heterodimer bound to two ER8-type motifs found at around -520 and -460 of hCYP1A1. The former corresponds to the CAR-binding motif previously identified. Reporter assays using mutated constructs confirmed the critical roles of these motifs in the LXRα-mediated simultaneous transcription of hCYP1A1 and hCYP1A2. hCYP1A1 and hCYP1A2 mRNA levels were increased in human hepatoma HuH-7 cells and human primary hepatocytes, respectively, after treatment with the LXRα ligand GW3965. Our results suggest that LXRα transactivates the expression of hCYP1A1 and hCYP1A2 through common two cis-elements.

Regulation of cerebral cholesterol metabolism in Alzheimer disease

Alzheimer disease (AD) is an age-related neurodegenerative disorder that manifests as a progressive loss of memory and deterioration of higher cognitive functions. Alzheimer disease is characterized by accumulation in the brain of the β-amyloid peptide generated by β- and γ-secretase processing of amyloid precursor protein. Epidemiological studies have linked elevated plasma cholesterol and lipoprotein levels in midlife with AD development. Cholesterol-fed animal models exhibit neuropathologic features of AD including accumulation of β-amyloid peptide. Specific isoforms of the cholesterol transporter apolipoprotein E are associated with susceptibility to AD. Although multiple lines of evidence indicate a role for cholesterol in AD, the exact impact and mechanisms involved remain largely unknown. This review summarizes the current state of our knowledge of the influence of cholesterol and lipid pathways in AD pathogenesis in vitro and in vivo.

Regulation of cerebral cholesterol metabolism in Alzheimer disease

Alzheimer disease (AD) is an age-related neurodegenerative disorder that manifests as a progressive loss of memory and deterioration of higher cognitive functions. Alzheimer disease is characterized by accumulation in the brain of the β-amyloid peptide generated by β- and γ-secretase processing of amyloid precursor protein. Epidemiological studies have linked elevated plasma cholesterol and lipoprotein levels in midlife with AD development. Cholesterol-fed animal models exhibit neuropathologic features of AD including accumulation of β-amyloid peptide. Specific isoforms of the cholesterol transporter apolipoprotein E are associated with susceptibility to AD. Although multiple lines of evidence indicate a role for cholesterol in AD, the exact impact and mechanisms involved remain largely unknown. This review summarizes the current state of our knowledge of the influence of cholesterol and lipid pathways in AD pathogenesis in vitro and in vivo.

ABCA1, apoE and apoA-I as potential therapeutic targets for treating Alzheimer’s disease

SUMMARY The association between apoE genotype and risk and age of onset for Alzheimer’s disease (AD) was first discovered in 1993. Innumerable studies since then have defined Aβ-dependent and Aβ-independent roles for apoE in AD pathogenesis. Although therapeutic approaches that specifically target apoE are not yet developed for AD, apoE may have a more fundamental role in brain physiology than previously appreciated. ApoE is the major apolipoprotein in the CNS, coordinating the uptake and delivery of lipids among various cell types in the brain. ApoE receives lipids from the membrane-bound cholesterol and phospholipid transporter ATP-binding cassette transporter A1 (ABCA1). Genetic and pharmacological methods to enhance ABCA1 activity generate lipid-rich apoE particles and provide cognitive and neuropathological benefits in animal models of AD. Recent studies on apoA-I, which is the major lipid acceptor for ABCA1 in peripheral tissues and is also present in the CNS, suggest that increasing apoA-I function may also have neuroprotective effects. In this article, we will discuss the potential of ABCA1, apoE and apoA-I as therapeutic targets for the treatment of AD.

Proton pump inhibitors reduce interferon-γ-induced neurotoxicity and STAT3 phosphorylation of human astrocytes

Proton pump inhibitors (PPIs) are known to possess anti-inflammatory properties. Inflammatory processes, including astrocytic activation, are implicated in the pathogenesis of different neurodegenerative diseases. Our recent study has indicated that interferon (IFN)-γ-induced astrocytic neurotoxicity is mediated, at least in part, by phosphorylation of signal transducer and activator of transcription (STAT) 3. We therefore studied the effects of PPIs on IFN-γ-induced neurotoxicity and STAT3 activation of human astrocytes. Both lansoprazole (LPZ) and omeprazole (OPZ) significantly attenuated IFN-γ-induced neurotoxicity of human astrocytes and astrocytoma cells. These drugs inhibited IFN-γ-induced phosphorylation of STAT 3, but not STAT1. We found that LPZ significantly reduced secretion of IFN-γ-inducible T cell α chemoattractant from IFN-γ-activated astrocytes. Neither LPZ nor OPZ suppressed expression of intercellular adhesion molecule-1 by IFN-γ-activated astrocytes. These results suggest that PPIs attenuate IFN-γ-induced neurotoxicity of human astrocytes through inhibition of the STAT3 signaling pathway. PPIs that possess antineurotoxic properties may be a useful treatment option for Alzheimer's disease and other neuroinflammatory disorders associated with activated astrocytes.

Liver X receptor agonist treatment ameliorates amyloid pathology and memory deficits caused by high-fat diet in APP23 mice

High-fat diet and certain dietary patterns are associated with higher incidence of sporadic Alzheimer's disease (AD) and cognitive decline. However, no specific therapy has been suggested to ameliorate the negative effects of high fat/high cholesterol levels on cognition and amyloid pathology. Here we show that in 9-month-old APP23 mice, a high-fat/high-cholesterol (HF) diet provided for 4 months exacerbates the AD phenotype evaluated by behavioral, morphological, and biochemical assays. To examine the therapeutic potential of liver X receptor (LXR) ligands, APP23 mice were fed HF diet supplemented with synthetic LXR agonist T0901317 (T0). Our results demonstrate that LXR ligand treatment causes a significant reduction of memory deficits observed during both acquisition and retention phases of the Morris water maze. Moreover, the effects of T0 on cognition correlate with AD-like morphological and biochemical parameters. We found a significant decrease in amyloid plaque load, insoluble Abeta and soluble Abeta oligomers. In vitro experiments with primary glia demonstrate that Abca1 is essential for the proper lipidation of ApoE and mediates the effects of T0 on Abeta degradation by microglia. Microdialysis experiments performed on awake freely moving mice showed that T0 decreased Abeta levels in the interstitial fluid of the hippocampus, supporting the conclusion that this treatment increases Abeta clearance. The data presented conclusively shows that LXR activation in the context of a metabolic challenge has critical effects on AD phenotype progression by attenuating Abeta deposition and facilitating its clearance.

The role of ATP-binding cassette transporter A1 in Alzheimer's disease and neurodegeneration

ATP-binding cassette transporter A1 - ABCA1, is the most extensively studied transporter in human pathology. ABCA1 became a primary subject of research in many academic and pharmaceutical laboratories immediately after the discovery that mutations at the gene locus cause severe familial High Density Lipoprotein (HDL) deficiency and, in the homozygous form - Tangier disease. The protein is the major regulator of intracellular cholesterol efflux which is the initial and essential step in the biogenesis and formation of nascent HDL particles. The transcriptional regulation of ABCA1 by nuclear Liver X Receptors (LXR) provided a starting point for drug discovery and development of synthetic LXR ligands/ABCA1 activators for treatment of arteriosclerosis. A series of reports that revealed the role of ABCA1 in Abeta deposition and clearance, as well as the possibility for association of some ABCA1 genetic variants with risk for Alzheimer's disease (AD) brought a new dimension to ABCA1 research. The LXR-ABCA1-APOE regulatory axis is now considered a promising therapeutic target in AD, which includes the only proven risk factor for AD - APOE, at two distinct levels - transcriptional regulation by LXR, and ABCA1 controlled lipidation which can influence Abeta aggregation and amyloid clearance. This review will summarize the results of research on ABCA1, particularly related to AD and neurodegeneration.