Mychica R. Jones

Curcumin Structure-Function, Bioavailability, and Efficacy in Models of Neuroinflammation and Alzheimer's Disease

Curcumin can reduce inflammation and neurodegeneration, but its chemical instability and metabolism raise concerns, including whether the more stable metabolite tetrahydrocurcumin (TC) may mediate efficacy. We examined the antioxidant, anti-inflammatory, or anti-amyloidogenic effects of dietary curcumin and TC, either administered chronically to aged Tg2576 APPsw mice or acutely to lipopolysaccharide (LPS)-injected wild-type mice. Despite dramatically higher drug plasma levels after TC compared with curcumin gavage, resulting brain levels of parent compounds were similar, correlating with reduction in LPS-stimulated inducible nitric-oxide synthase, nitrotyrosine, F2 isoprostanes, and carbonyls. In both the acute (LPS) and chronic inflammation (Tg2576), TC and curcumin similarly reduced interleukin-1β. Despite these similarities, only curcumin was effective in reducing amyloid plaque burden, insoluble β-amyloid peptide (Aβ), and carbonyls. TC had no impact on plaques or insoluble Aβ, but both reduced Tris-buffered saline-soluble Aβ and phospho-c-Jun NH2-terminal kinase (JNK). Curcumin but not TC prevented Aβ aggregation. The TC metabolite was detected in brain and plasma from mice chronically fed the parent compound. These data indicate that the dienone bridge present in curcumin, but not in TC, is necessary to reduce plaque deposition and protein oxidation in an Alzheimers model. Nevertheless, TC did reduce neuroinflammation and soluble Aβ, effects that may be attributable to limiting JNK-mediated transcription. Because of its favorable safety profile and the involvement of misfolded proteins, oxidative damage, and inflammation in multiple chronic degenerative diseases, these data relating curcumin dosing to the blood and tissue levels required for efficacy should help translation efforts from multiple successful preclinical models.

GSK3 inhibitors show benefits in an Alzheimer's disease (AD) model of neurodegeneration but adverse effects in control animals

The dysregulation of glycogen synthase kinase-3 (GSK3) has been implicated in Alzheimer disease (AD) pathogenesis and in Abeta-induced neurotoxicity, leading us to investigate it as a therapeutic target in an intracerebroventricular Abeta infusion model. Infusion of a specific GSK3 inhibitor SB216763 (SB) reduced a downstream target, phospho-glycogen synthase 39%, and increased glycogen levels 44%, suggesting effective inhibition of enzyme activity. Compared to vehicle, Abeta increased GSK3 activity, and was associated with elevations in levels of ptau, caspase-3, the tau kinase phospho-c-jun N-terminal kinase (pJNK), neuronal DNA fragmentation, and gliosis. Co-infusion of SB corrected all responses to Abeta infusion except the induction of gliosis and behavioral deficits in the Morris water maze. Nevertheless, SB alone was associated with induction of neurodegenerative markers and behavioral deficits. These data support a role for GSK3 hyperactivation in AD pathogenesis, but emphasize the importance of developing inhibitors that do not suppress constitutive activity.

Clinical development of curcumin in neurodegenerative disease

Curcumin, a polyphenolic antioxidant derived from the turmeric root has undergone extensive preclinical development, showing remarkable efficacy in wound repair, cancer and inflammatory disorders. This review addresses the rationale for its use in neurodegenerative disease, particularly Alzheimer’s disease. Curcumin is a pleiotropic molecule, which not only directly binds to and limits aggregation of the β-sheet conformations of amyloid characteristic of many neurodegenerative diseases but also restores homeostasis of the inflammatory system, boosts the heat shock system to enhance clearance of toxic aggregates, scavenges free radicals, chelates iron and induces anti-oxidant response elements. Although curcumin corrects dysregulation of multiple pathways, it may exert many effects via a few molecular targets. Pharmaceutical development of natural compounds like curcumin and synthetic derivatives have strong scientific rationale, but will require overcoming various hurdles including; high cost of trials, concern about profitability and misconceptions about drug specificity, stability, and bioavailability.

[F-18]FDDNP microPET imaging correlates with brain Aβ burden in a transgenic rat model of Alzheimer disease: Effects of aging, in vivo blockade, and anti-Aβ antibody treatment

In vivo detection of Alzheimers disease (AD) neuropathology in living patients using positron emission tomography (PET) in conjunction with high affinity molecular imaging probes for β-amyloid (Aβ) and tau has the potential to assist with early diagnosis, evaluation of disease progression, and assessment of therapeutic interventions. Animal models of AD are valuable for exploring the in vivo binding of these probes, particularly their selectivity for specific neuropathologies, but prior PET experiments in transgenic mice have yielded conflicting results. In this work, we utilized microPET imaging in a transgenic rat model of brain Aβ deposition to assess [F-18]FDDNP binding profiles in relation to age-associated accumulation of neuropathology. Cross-sectional and longitudinal imaging demonstrated that [F-18]FDDNP binding in the hippocampus and frontal cortex progressively increases from 9 to 18months of age and parallels age-associated Aβ accumulation. Specificity of in vivo [F-18]FDDNP binding was assessed by naproxen pretreatment, which reversibly blocked [F-18]FDDNP binding to Aβ aggregrates. Both [F-18]FDDNP microPET imaging and neuropathological analyses revealed decreased Aβ burden after intracranial anti-Aβ antibody administration. The combination of this non-invasive imaging method and robust animal model of brain Aβ accumulation allows for future longitudinal in vivo assessments of potential therapeutics for AD that target Aβ production, aggregation, and/or clearance. These results corroborate previous analyses of [F-18]FDDNP PET imaging in clinical populations.

Use of Copper and Insulin-Resistance to Accelerate Cognitive Deficits and Synaptic Protein Loss in a Rat Aβ-Infusion Alzheimer’s Disease Model

The rat amyloid-beta (Abeta) intracerebroventricular infusion can model aspects of Alzheimers disease (AD) and has predicted efficacy of therapies such as ibuprofen and curcumin in transgenic mouse models. High density lipoprotein (HDL), a normal plasma carrier of Abeta, is used to attenuate Abeta aggregation within the pump, causing Abeta-dependent toxicity and cognitive deficits within 3 months. Our goal was to identify factors that might accelerate onset of Abeta-dependent deficits to improve efficiency and cost-effectiveness of model. We focused on: 1) optimizing HDL-Abeta preparation for maximal toxicity; 2) evaluating the role of copper, a factor typically in water that can impact oligomer stability; and 3) determining impact of insulin resistance (type II diabetes), a risk factor for AD. In vitro studies were performed to determine doses of copper and methods of Abeta-HDL preparation that maximized toxicity. These preparations when infused resulted in earlier onset of cognitive deficits within 6 weeks post-infusion. Induction of insulin resistance did not exacerbate Abeta-dependent cognitive deficits, but did exacerbate synaptic protein loss. In summary, the newly described in vivo infusion model may be useful cost-effective method for screening for new therapeutic drugs for AD.

Neuronal pentraxin 1: A synaptic-derived plasma biomarker in Alzheimer's disease

Synaptic neurodegeneration is thought to be an early event initiated by soluble β-amyloid (Aβ) aggregates that closely correlates with cognitive decline in Alzheimer disease (AD). Apolipoprotein ε4 (APOE4) is the most common genetic risk factor for both familial AD (FAD) and sporadic AD; it accelerates Aβ aggregation and selectively impairs glutamate receptor function and synaptic plasticity. However, its molecular mechanisms remain elusive and these synaptic deficits are difficult to monitor. AD- and APOE4-dependent plasma biomarkers have been proposed, but synapse-related plasma biomarkers are lacking. We evaluated neuronal pentraxin 1 (NP1), a potential CNS-derived plasma biomarker of excitatory synaptic pathology. NP1 is preferentially expressed in brain and involved in glutamate receptor internalization. NP1 is secreted presynaptically induced by Aβ oligomers, and implicated in excitatory synaptic and mitochondrial deficits. Levels of NP1 and its fragments were increased in a correlated fashion in both brain and plasma of 7-8 month-old E4FAD mice relative to E3FAD mice. NP1 was also found in exosome preparations and reduced by dietary DHA supplementation. Plasma NP1 was higher in E4FAD+ (APOE4+/+/FAD+/-) relative to E4FAD- (non-carrier; APOE4+/+/FAD-/-) mice, suggesting NP1 is modulated by Aβ expression. Finally, relative to normal elderly, plasma NP1 was also elevated in patients with mild cognitive impairment (MCI) and elevated further in the subset who progressed to early-stage AD. In those patients, there was a trend towards increased NP1 levels in APOE4 carriers relative to non-carriers. These findings indicate that NP1 may represent a potential synapse-derived plasma biomarker relevant to early alterations in excitatory synapses in MCI and early-stage AD.

DIETARY LINOLEIC ACID DIFFERENTIALLY INFLUENCES BRAIN FADS ACTIVITIES INCREASING AN N-6 METABOLITE THAT INHIBITS INFLAMMATION AND PROMOTES AMYLOID-β CLEARANCE

Background: Alzheimer’s disease (AD) is a neurodegenerative disease associated with the deposition of extracellular (Aß) plaques within the brain and neuroinflammation. The NLRP3 inflammasome, in particular, is activated in AD. This results in the downstream production of the proinflammatory cytokines IL1ß and IL18, a reduced generation of the anti-inflammatory IL33 cytokine, and the impairment of Ab-phagocytosis. Herein we analyzed possible correlations between inflammasome activation and Ab-phagocytosis in an in vitro system. Methods: Existing flow cytometry methods that lack image-based analysis capabilities fail to fully discriminate between adherent or cells-internalized Aß; the AMNIS technology can perform simultaneous detection of Aß-phagocytosis in different in vitro conditions. THP-1 cells differentiated into macrophages by PMA were stimulated with LPS (1ug/ml for 24 hours)+ Aß (1ug/ml for 1 hour), or with LPS+ Aß+ the NLRP3 activators Nigericin (5uM for 1 hour) or only with Aß (1ug/ml for 1 hour) in the presence/absence of IL33 (10ng/ml for 18 hours). Phagocitosis was measured as the ratio between intra and extra cellular FITC-conjugated Aß; cytokine production was measured by ELISA. Results: A significant increase in IL1ß production (p1⁄40.001) and a drastic reduction of Ab-phagocytosis (p1⁄40.0001) were seen when cells stimulated by LPS+ Ab+Nigericin were compare to those stimulated by LPS+Aß or Aß alone. Notably, IL1ß production was drastically reduced and Aßphagocytosis was significantly increased (both p1⁄40.001) in LPS+ Aß+Nigericin-stimulated cells in the presence of IL33. Conclusions: IL33 reduces inflammasome-associated inflammation and improves macrophage-mediated Aß-phagocytosis. These results allow the speculation that this cytokine could be beneficial in the therapy of AD.

APOE4-DEPENDENT SYNAPTIC-DERIVED PLASMA BIOMARKERS IN ALZHEIMER'S DISEASE

with positive beta-amyloid deposition on PiB PET, defined using a standardized uptake value ratio (SUVR) of 1.5, were included. All voxels in the PiB-PET images were divided by median uptake in cerebellum and transformed into template space. Partial volume correction (PVC) was performed. Voxel-level comparisons were performed across groups both with and without PVC using SPM5.Results were assessed after correction for multiple comparisons using family-wise error at p<0.05. Subjects also completed memory, language, and visuospatial tests that may have been used to augment DATand PCA diagnosis, but was not used in diagnosis of LPA. Results:Cognitively, DAT subjects had poorer memory than lvPPA and PCA subjects, lvPPA subjects had poorer language scores than DAT and PCA subjects, and PCA had poorer visuospatial scores that lvPPA and DAT subjects. The groups did not differ on global SUVR. Regional distribution of PiB-PET was similarly widespread in each of the three groups, although PCA showed greater uptake in bilateral occipital lobe compared to DAT, and greater uptake in right occipital lobe compared to lvPPA. These findings were observed both with and without PVC. No other regional PiB-PET differences were observed across groups. Conclusions:These findings suggest that while beta-amyloid deposition is typically diffuse in Alzheimer’s disease variants, regional differences exist as compared to DAT, although this DAT group may represent those with an earlier onset. The occipital lobe is particularly vulnerable to beta-amyloid deposition, as well as neurodegeneration, in PCA.

Novel, small molecule inhibitors of protein aggregation for treatment of amyloid-related diseases

Ab plaque burden. Catalytically incompetent 2E6 treated with a protease inhibitor and a non-proteolytic control IgVL2 did not express these activities. The major 2E6-cleavage site in Ab was the His14-Gln15 peptide bond. Epitope mapping indicated competitive inhibition of 2E6-catalyzed I-Ab degradation by the remote Ab29-40 peptide, identifying this region as the noncovalent recognition epitope. 2E6-Ab immune complexes were undetectable by ELISA, consistent with rapid progress of the reaction to the catalysis step. 2E6 did not cleave His-Gln containing proteins, indicating that specificity for Ab derives from the noncovalent binding step. Conclusions: The Ab fragment targets monomer and aggregate forms of Ab and clears brain Ab plaques by initial noncovalent recognition of the amyloidogenic C terminal region followed by cleavage at remote peptide bonds. Catalysis is rapid and no immune complexes are detectable. This catalytic antibody fragment can be developed for more effective and safe AD immunotherapy.