APOE genotype and an ApoE-mimetic peptide modify the systemic and central nervous system inflammatory response

The relationship between inflammatory markers and voxel-based gray matter volumes in nondemented older adults

Ageing is characterized by chronically elevated inflammatory markers (IMs). Peripheral IM levels have been found in negative correlations with brain structural measures including global and lobar volumes and the hippocampus. This study investigated the relationship between 10 peripheral IMs and voxel-based gray matter (GM) volumes in nondemented older adults (n = 463). Two proinflammatory cytokines (tumor necrosis factor-α [TNF-α] and interleukin-1β) and 2 vascular IMs (vascular cellular adhesion molecule-1 and plasminogen activator inhibitor-1) were negatively correlated with regional GM volumes. TNF-α and interleukin-1β were both significantly correlated with GM volumes in the left occipitotemporal area, left superior occipital gyrus, and left inferior parietal lobule; TNF-α was also significantly correlated with the bilateral medial prefrontal cortices and approached significance for the correlations with the bilateral hippocampi. Significant GM correlations with vascular cellular adhesion molecule-1 were located in the bilateral anterior cingulate cortices, and with plasminogen activator inhibitor-1 in the cerebellum and right hippocampus. The neuroanatomical correlation patterns of 2 proinflammatory cytokines and 2 vascular IMs might be reflective of the effects of neurodegenerative and vascular pathological processes in the ageing brain.

Genetics ignite focus on microglial inflammation in Alzheimer's disease

In the past five years, a series of large-scale genetic studies have revealed novel risk factors for Alzheimer’s disease (AD). Analyses of these risk factors have focused attention upon the role of immune processes in AD, specifically microglial function. In this review, we discuss interpretation of genetic studies.  We then focus upon six genes implicated by AD genetics that impact microglial function: TREM2, CD33, CR1, ABCA7, SHIP1, and APOE. We review the literature regarding the biological functions of these six proteins and their putative role in AD pathogenesis. We then present a model for how these factors may interact to modulate microglial function in AD.

Role of Genetic Polymorphisms in Predicting Delayed Cerebral Ischemia and Radiographic Vasospasm After Aneurysmal Subarachnoid Hemorrhage: A Meta-Analysis

OBJECTIVE

The pathophysiology on cerebral vasospasm and delayed cerebral ischemia (DCI) remains poorly understood. Much research has been dedicated to finding genetic loci associated with vasospasm and ischemia. We present a systematic review and meta-analysis to identify genetic polymorphisms associated with delayed ischemic neurologic deficit (DIND), radiographic infarction attributed to ischemia, and radiographic vasospasm.

METHODS

PubMed, the Cochrane Library, and Excerpta Medica dataBASE (EMBASE) databases were used to identify relevant studies published up to March 2015 containing the subject terms cerebral or intracranial vasospasm and DCI in combination with genetics, gene, polymorphism or marker. Meta-analyses were performed using a random-effects model to calculate summary odds ratio (ORs) and 95% confidence intervals for each respective gene.

RESULTS

Of 269 articles initially identified, 20 studies with 1670 patients were included in our comprehensive review, including 27 polymorphisms in 11 genes. The following 6 polymorphisms in 3 genes were selected for subsequent meta-analyses: apolipoprotein E (ApoE2, E4); endothelial nitric oxide (eNOS T786C, VNTR intron 4 a/b, G894T); and haptoglobin (Hp) 1/2 phenotypes. The eNOS VNTR a allele was associated with DIND (a vs. b allele: OR 1.92 [1.31-2.81], padj = 0.008). The Hp 2-2 allele was associated with radiographic vasospasm (2-2 vs. 2-1 and 1-1: OR 3.86 [1.86-8.03], padj = 0.003) but did not reach significance for DIND.

CONCLUSIONS

This is the first systemic review and meta-analysis to study and evaluate the associations between genetic polymorphism with DCI and radiographic vasospasm independently. In our study, eNOS VNTR and Hp polymorphisms appear to have the strongest associations with DIND and radiographic vasospasm, respectively.

Neuroprotective peptides fused to arginine-rich cell penetrating peptides: Neuroprotective mechanism likely mediated by peptide endocytic properties

Several recent studies have demonstrated that TAT and other arginine-rich cell penetrating peptides (CPPs) have intrinsic neuroprotective properties in their own right. Examples, we have demonstrated that in addition to TAT, poly-arginine peptides (R8 to R18; containing 8-18 arginine residues) as well as some other arginine-rich peptides are neuroprotective in vitro (in neurons exposed to glutamic acid excitotoxicity and oxygen glucose deprivation) and in the case of R9 in vivo (after permanent middle cerebral artery occlusion in the rat). Based on several lines of evidence, we propose that this neuroprotection is related to the peptide's endocytosis-inducing properties, with peptide charge and arginine residues being critical factors. Specifically, we propose that during peptide endocytosis neuronal cell surface structures such as ion channels and transporters are internalised, thereby reducing calcium influx associated with excitotoxicity and other receptor-mediated neurodamaging signalling pathways. We also hypothesise that a peptide cargo can act synergistically with TAT and other arginine-rich CPPs due to potentiation of the CPPs endocytic traits rather than by the cargo-peptide acting directly on its supposedly intended intracellular target. In this review, we systematically consider a number of studies that have used CPPs to deliver neuroprotective peptides to the central nervous system (CNS) following stroke and other neurological disorders. Consequently, we critically review evidence that supports our hypothesis that neuroprotection is mediated by carrier peptide endocytosis. In conclusion, we believe that there are strong grounds to regard arginine-rich peptides as a new class of neuroprotective molecules for the treatment of a range of neurological disorders.

Genetic association of apolipoprotein E polymorphisms with inflammatory bowel disease

AIM: To study the association of apolipoprotein E (APOE) polymorphisms with the susceptibility of inflammatory bowel disease (IBD) in Saudi patients.

METHODS: APOE genotyping was performed to evaluate the allele and genotype frequencies in 378 Saudi subjects including IBD patients with ulcerative colitis (n = 84) or Crohn’s disease (n = 94) and matched controls (n = 200) using polymerase chain reaction and reverse-hybridization techniques.

RESULTS: The frequencies of the APOE ε2 allele and ε2/ε3 and ε2/ε4 genotypes were significantly higher in IBD patients than in controls (P < 0.05), suggesting that the ε2 allele and its heterozygous genotypes may increase the susceptibility to IBD. On the contrary, the frequencies of the ε3 allele and ε3/ε3 genotype were lower in IBD patients as compared to controls, suggesting a protective effect of APOE ε3 for IBD. The prevalence of the ε4 allele was also higher in the patient group compared to controls, suggesting that the ε4 allele may also increase the risk of IBD. Our results also indicated that the APOE ε4 allele was associated with an early age of IBD onset. No effect of gender or type of IBD (familial or sporadic) on the frequency distribution of APOE alleles and genotypes was noticed in this study.

CONCLUSION: APOE polymorphism is associated with risk of developing IBD and early age of onset in Saudi patients, though further studies with a large-size population are warranted.

Different mechanisms of apolipoprotein E isoform-dependent modulation of prostaglandin E2 production and triggering receptor expressed on myeloid cells 2 (TREM2) expression after innate immune activation of microglia

Several lines of evidence support immune response in brain as a mechanism of injury in Alzheimer disease (AD). Moreover, immune activation is heightened in apolipoprotein E (APOE) ε4 carriers; inhibitors of prostaglandin (PG) synthesis show a partially protective effect on AD risk from APOE ε4; and genetic variants in triggering receptor expressed on myeloid cells 2 (TREM2) are a rare but potent risk for AD. We tested the hypothesis that APOE ε4 inheritance modulates both the PGE2 pathway and TREM2 expression using primary murine microglia from targeted replacement (TR) APOE3/3 and APOE4/4 mice. Microglial cyclooxygenase-2, microsomal PGE synthase, and PGE2 expression were increased 2- to 25-fold in both genotypes by TLR activators; however, this induction was significantly (P < 0.01) greater in TR APOE4/4 microglia with TLR3 and TLR4 activators. Microglial TREM2 expression was reduced approximately 85% by all TLR activators; this reduction was approximately one-third greater in microglia from TR APOE4/4 mice. Importantly, both receptor-associated protein and a nuclear factor κ-light-chain-enhancer inhibitor blocked TR APOE4/4-dependent effects on the PGE2 pathway but not on TREM2 expression. These data demonstrate complementary, but mechanistically distinct, regulation of pro- and anti-inflammatory mediators in TR APOE4/4 murine microglia that yields a more proinflammatory state than with TR APOE3/3.

Quantum dot induced cellular perturbations involving varying toxicity pathways

Quantum dots (QD) with varying surface chemistry can have an impact on cellular uptake and a range of indicators for cell perturbation.

Apolipoprotein E mimetic peptide protects against diffuse brain injury

Apolipoprotein E plays a crucial role in inhibiting chronic neurodegenerative processes. However, its impact on neurological function following diffuse brain injury is still unclear. This study was designed to evaluate the therapeutic effects and mechanisms of action of apolipoprotein E mimetic peptide on diffuse brain injury. Apolipoprotein E mimetic peptide was administered into the caudal vein of rats with diffuse brain injury before and after injury. We found that apolipoprotein E mimetic peptide significantly decreased the number of apoptotic neurons, reduced extracellular signal-regulated kinase1/2 phosphorylation, down-regulated Bax and cytochrome c expression, decreased malondialdehyde content, and increased superoxide dismutase activity in a dose-dependent manner. These experimental findings demonstrate that apolipoprotein E mimetic peptide improves learning and memory function and protects against diffuse brain injury-induced apoptosis by inhibiting the extracellular signal-regulated kinase1/2-Bax mitochondrial apoptotic pathway.

Nasal NSAIDs for Alzheimer's Disease

Alzheimer's disease may result from low-grade inflammation of the brain, and the characteristic amyloid β may be a protective response. Epidemiological observation indicates that long-term oral administration of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen to patients having rheumatoid arthritis results in reduced risk and delayed onset of Alzheimer's disease. However, oral ibuprofen, flurbiprofen, and other NSAIDs are not an effective treatment. The NSAIDs may work as an Alzheimer's preventive but not a treatment because the oral dose to the brain is too small, 1% to 2% of the total plasma concentration. The NSAID brain dose could be significantly increased by delivering the drug intranasally. Flurbiprofen would be preferable to ibuprofen because flurbiprofen has 12½ times the potency of ibuprofen. The smaller nasal dose of flurbiprofen than ibuprofen could significantly increase patient compliance. Alzheimer's disease starts in the entorhinal cortex, which is closely connected to the olfactory nerves, and spreads anatomically in a defined pattern. Therefore, a nasal NSAID would readily reach the region of the brain where it is most likely to be therapeutic.

Human APOE4 increases microglia reactivity at Aβ plaques in a mouse model of Aβ deposition

BACKGROUND

Having the apolipoprotein E4 (APOE-ϵ4) allele is the strongest genetic risk factor for the development of Alzheimer's disease (AD). Accumulation of amyloid beta (Aβ) in the brain is influenced by APOE genotype. Transgenic mice co-expressing five familial AD mutations (5xFAD) in the presence of human APOE alleles (ϵ2, ϵ3 or ϵ4) exhibit APOE genotype-specific differences in early Aβ accumulation, suggesting an interaction between APOE and AD pathology. Whether APOE genotype affects Aβ-plaque-associated neuroinflammation remains unclear. In the current study, we address the role of APOE genotype on Aβ-associated microglial reactivity in the EFAD transgenic mouse model.

METHODS

We analyzed Aβ-induced glial activation in the brains of 6-month-old EFAD transgenic mice (E2FAD, E3FAD and E4FAD). Region-specific morphological profiles of Aβ plaques in EFAD brain sections were compared using immunofluorescence staining. We then determined the degree of glial activation in sites of Aβ deposition while comparing levels of the inflammatory cytokine Interleukin-1β (IL-1β) by ELISA. Finally, we quantified parameters of Aβ-associated microglial reactivity using double-stained EFAD brain sections.

RESULTS

Characterization of Aβ plaques revealed there were larger and more intensely stained plaques in E4FAD mice relative to E2FAD and E3FAD mice. E4FAD mice also had a greater percentage of compact plaques in the subiculum than E3FAD mice. Reactive microglia and dystrophic astrocytes were prominent in EFAD brains, and primarily localized to two sites of significant Aβ deposition: the subiculum and deep layers of the cortex. Cortical levels of IL-1β were nearly twofold greater in E4FAD mice relative to E3FAD mice. To control for differences in levels of Aβ in the different EFAD mice, we analyzed the microglia within domains of specific Aβ deposits. Morphometric analyses revealed increased measures of microglial reactivity in E4FAD mice, including greater dystrophy, increased fluorescence intensity and a higher density of reactive cells surrounding cortical plaques, than in E3FAD mice.

CONCLUSIONS

In addition to altering morphological profiles of Aβ deposition, APOE genotype influences Aβ-induced glial activation in the adult EFAD cortex. These data support a role for APOE in modulating Aβ-induced neuroinflammatory responses in AD progression, and support the use of EFAD mice as a suitable model for mechanistic studies of Aβ-associated neuroinflammation.

Apolipoprotein E, amyloid-beta, and neuroinflammation in Alzheimer's disease

Alzheimer's disease (AD) is characterized by the accumulation and deposition of amyloid-beta (Aβ) peptides in the brain. Neuroinflammation occurs in the AD brain and plays a critical role in the neurodegenerative pathology. Particularly, Aβ evokes an inflammatory response that leads to synaptic dysfunction, neuronal death, and neurodegeneration. Apolipoprotein E (ApoE) proteins are involved in cholesterol transport, Aβ binding and clearance, and synaptic functions in the brain. The ApoE4 isoform is a key risk factor for AD, while the ApoE2 isoform has a neuroprotective effect. However, studies have reached different conclusions about the roles of the isoforms; some show that both ApoE3 and ApoE4 have anti-inflammatory effects, while others show that ApoE4 causes a predisposition to inflammation or promotes an inflammatory response following lipopolysaccharide treatment. These discrepancies may result from the differences in models, cell types, experimental conditions, and inflammatory stimuli used. Further, little was known about the role of ApoE isoforms in the Aβ-induced inflammatory response and in the neuroinflammation of AD. Our recent work showed that ApoE isoforms differentially regulate and modify the Aβ-induced inflammatory response in neural cells, with ApoE2 suppressing and ApoE4 promoting the response. In this article, we review the roles, mechanisms, and interrelations among Aβ, ApoE, and neuroinflammation in AD.

Genetics of primary progressive multiple sclerosis

Multiple sclerosis (MS) patients are classified as either having relapsing onset or progressive onset disease, also known as primary progressive MS (PPMS). Relative to relapsing onset patients, PPMS patients are older at disease onset, are equally likely to be men or women, and have more rapid accumulation of disability that does not respond well to treatments used in relapsing onset MS. Although estimates vary, 5-15% of all MS patients have a PPMS disease course. Genetic variance is a proposed determinant of MS disease course. If distinct genes associated with PPMS were identified study of these genes might lead to an understanding of the biology underlying disease progression and neural degeneration that are the hallmarks of PPMS. These genes and their biological pathways might also represent therapeutic targets. This chapter systematically reviews the PPMS genetic literature. Despite the intuitively appealing notion that differences between PPMS and relapsing onset MS are due to genetics, definite differences associated with these phenotypes at the major histocompatibility complex or elsewhere in the genome have not been found. Recent large-scale genome wide screens identified multiple genes associated with MS susceptibility outside the MHC. The genetic variants identified thus far make only weak individual contributions to MS susceptibility. If the genetic effects that contribute to the differences between PPMS and relapsing MS are similar in magnitude to those that distinguish MS from healthy controls then, given the relative scarcity of the PPMS phenotype, very large datasets will be needed to identify PPMS associated genes. International collaborative efforts could provide the means to identify such genes. Alternately, it is possible that factors other than genetics underlie the differences between these clinical phenotypes.

APOE polymorphism and carotid atherosclerosis in Korean population: the Dong-gu Study and the Namwon Study

OBJECTIVE

We evaluated the association between APOE polymorphism and carotid atherosclerosis in two large independent cohorts from South Korea.

METHODS

The datasets were from the Dong-gu Study (N = 9056) and the Namwon Study (N = 10,158). Carotid ultrasonography was performed to measure carotid intima-media thickness (IMT) and the presence of carotid plaques. The APOE polymorphism was determined by PCR-RFLP. We performed combined and separate analyses for the two datasets.

RESULTS

In the combined analysis, individuals with E2E2 or E2E3 genotype had a lower common carotid IMT compared with individuals with E3E3 genotype (0.684 mm vs. 0.736 mm, p = 0.007; 0.718 mm vs. 0.736 mm, p < 0.001, respectively). This association was very slightly attenuated but remained statistically significant after adjustment for blood lipids (0.690 mm vs. 0.736 mm, p = 0.033; 0.725 mm vs. 0.736 mm, p = 0.005, respectively). Compared with individuals with E3E3 genotype, individuals with E2E3 genotype had lower risk for carotid plaque (odds ratio (OR) = 0.83, 95% confidence interval (CI) = 0.75-0.93), while individuals with E3E4 genotype had a higher risk for carotid plaque (OR = 1.09, 95% CI = 1.00-1.20). After adjustment for blood lipids, ORs of E2E3 genotype for carotid plaque was slightly attenuated but remained significant (OR = 0.87 95% CI = 0.78-0.97), while OR of E3E4 genotype were slightly attenuated and not significant (OR = 1.08, 95% CI, 0.99-1.18).

CONCLUSIONS

We found that APOE polymorphism is associated with carotid atherosclerosis and this association was partly mediated through blood lipid. Our results suggest that APOE polymorphism may influence atherosclerosis through non-lipid pathways.

The role of inflammation in sporadic and familial Parkinson's disease

The etiology of Parkinson's disease (PD) is complex and most likely involves numerous environmental and heritable risk factors. Interestingly, many genetic variants, which have been linked to familial forms of PD or identified as strong risk factors, also play a critical role in modulating inflammatory responses. There has been considerable debate in the field as to whether inflammation is a driving force in neurodegeneration or simply represents a response to neuronal death. One emerging hypothesis is that inflammation plays a critical role in the early phases of neurodegeneration. In this review, we will discuss emerging aspects of both innate and adaptive immunity in the context of the pathogenesis of PD. We will highlight recent data from genetic and functional studies that strongly support the theory that genetic susceptibility plays an important role in modulating immune pathways and inflammatory reactions, which may precede and initiate neuronal dysfunction and subsequent neurodegeneration. A detailed understanding of such cellular and molecular inflammatory pathways is crucial to uncover pathogenic mechanisms linking sporadic and hereditary PD and devise tailored neuroprotective interventions.

Age and apolipoprotein E ε4 effects on neural correlates of odor memory

Alzheimer's disease (AD) affects 5.4 million Americans. Evidence suggests that individuals who are positive for the apolipoprotein E (ApoE) ε4 allele are at higher risk for developing the disease. Studies have also shown that the ε4 allele is linked to olfactory decline. Olfactory functioning may be investigated using olfactory event-related potentials (OERPs). The high temporal resolution of OERPs enables an understanding of the neural correlates of olfactory processing and functioning. This study investigated the effects of age, ApoE ε4 status, response type, and electrode site on OERP latency and amplitude during encoding and retrieval in an odor recognition memory task. The 60 participants were equally divided into 3 age groups matched on ε4 status: younger, middle, and older. Odors were presented using a computer-controlled olfactometer. Participants were notified during encoding that this was a task of odor memory. Results indicated differences in OERP activity as a function of age, ApoE ε4 status, response type, and electrode site. These findings highlight the potential of OERPs to distinguish ε4- and ε4+ individuals and to contribute to an earlier diagnosis of AD.

Apolipoprotein E as a β-amyloid-independent factor in Alzheimer's disease

APOE, which encodes apolipoprotein E, is the most prevalent and best established genetic risk factor for late-onset Alzheimer’s disease. Current understanding of Alzheimer’s disease pathophysiology posits an important role for apolipoprotein E in the disease cascade via its interplay with β-amyloid. However, evidence is also emerging for roles of apolipoprotein E in the disease process that are independent of β-amyloid. Particular areas of interest are lipid metabolism, tau pathology, neuroenergetics, neurodevelopment, synaptic plasticity, the neurovasculature, and neuroinflammation. The intent of this article is to review the literature in each of these areas.

Western-type diet modulates inflammatory responses and impairs functional outcome following permanent middle cerebral artery occlusion in aged mice expressing the human apolipoprotein E4 allele

Background

Numerous clinical trials in stroke have failed, most probably partially due to preclinical studies using young, healthy male rodents with little relevance to the heterogenic conditions of human stroke. Co-morbid conditions such as atherosclerosis and infections coupled with advanced age are known to contribute to increased risk of cerebrovascular diseases. Clinical and preclinical studies have shown that the E4 allele of human apolipoprotein (ApoE4) is linked to poorer outcome in various conditions of brain injury and neurodegeneration, including cerebral ischemia. Since ApoE is a known regulator of lipid homeostasis, we studied the impact of a high-cholesterol diet in aged mice in the context of relevant human ApoE isoforms on the outcome of focal brain ischemia.

Methods

Aged mice expressing human E3 and E4 isoforms of ApoE in C57BL/6J background and C57BL/6J mice fed on either a high-fat diet or a normal diet underwent permanent middle cerebral artery occlusion. The impact of a high-cholesterol diet was assessed by measuring the serum cholesterol level and the infarction volume was determined by magnetic resonance imaging. Sensorimotor deficits were assessed using an adhesive removal test and the findings were correlated with inflammatory markers.

Results

We show that expression of human ApoE4 renders aged mice fed with a western-type diet more susceptible to sensorimotor deficits upon stroke. These deficits are not associated with atherosclerosis but are accompanied with altered astroglial activation, neurogenesis, cyclooxygenase-2 immunoreactivity and increased plasma IL-6.

Conclusions

Our results support the hypothesis that ApoE alleles modify the inflammatory responses in the brain and the periphery, thus contributing to altered functional outcome following stroke.

Molecular links between Alzheimer's disease and diabetes mellitus

Substantial epidemiological evidence shows an increased risk for developing Alzheimer's disease (AD) in people with diabetes. Yet the underlying molecular mechanisms still remain to be elucidated. This article reviews the current studies on common pathological processes of Alzheimer's disease and diabetes with particular focus on potential mechanisms through which diabetes affects the initiation and progression of Alzheimer's disease. Impairment of insulin signaling, inflammation, oxidative stress, mitochondrial dysfunction, advanced glycation end products, APOEε4 and cholesterol appear to be important mediators and are likely to act synergistically in promoting AD pathology.

Study on potential role of apolipoprotein E in recurrent pregnancy loss

The role of apolipoprotein E (Apo E) gene polymorphisms in the etiology of recurrent pregnancy loss (RPL) is not clearly understood. We evaluated this polymorphism in unexplained pregnancy losses in a group of Turkish women. In our prospective case-control study, 45 well-characterized RPL cases were examined for their Apo E genotypes, based on restriction fragment length polymorphism analysis of polymerase chain reaction (PCR)-amplified fragments. The observed genotypes were compared with those obtained from equal number matched controls. We observed similar Apo E genotypes and E2, E3 and E4 allele frequency distribution among RPL patients and controls. The allele frequencies obtained in patients and controls, respectively, were as follows: E2=8 (9%) and 12 (13.4%) (P=0.342), E3=66 (73.3%) and 60 (66.6%) (P=0.328) and E4=16 (17.7%) and 18 (20%) (P=0.703). Our data did not support the association of Apo E gene polymorphisms with RPL as reported by previous studies. We endorse adequate characterization of RPL cases and adequate sample size prior to addressing such studies.

Apolipoprotein E and its mimetic peptide suppress Th1 and Th17 responses in experimental autoimmune encephalomyelitis

Apolipoprotein E (apoE) has been detected to possess anti-inflammatory properties that can contribute to protection against experimental autoimmune encephalomyelitis (EAE). However, its impact on Th1 and Th17 responses in EAE is unclear. In this study, we induced EAE in apoE-/- mice and wild-type mice. We observed that the absence of apoE resulted in the increased proportion of Th1 and Th17 cells in the spleens and brains, as well as up-regulated expressions of proinflammatory cytokines (IL-17, IFN-γ, TNF-α, IL-12, IL-1β and IL-6) and transcription factors (RORγt and T-bet) in the CNS. ApoE-/- mice also showed the increased release of proinflammatory cytokines by macrophages in vitro. In addition, we used a mimetic peptide of apoE, which mimic the functions of apoE except for lipid transport. ApoE mimetic peptide could reverse the above negative effect in EAE. Thus, apoE can modulate Th1 and Th17 responses, likely through its inhibitory effect on the secretion of cytokines by macrophages. Our result also suggests that apoE mimetic peptide might be developed into a therapeutic agent for multiple sclerosis.

Combination of plasma tumor necrosis factor receptors signaling proteins, beta-amyloid and apolipoprotein E for the detection of Alzheimer's disease

Activation of inflammatory processes has been observed within the brain as well as periphery of subjects with Alzheimer's disease (AD). Among several putative neuroinflammatory mechanisms, the tumor necrosis factor-α (TNF-α) signaling system plays a central role. TNF-α converting enzyme (TACE) does not only cleave pro-TNF-α but also TNF receptors, however, whether the TACE activity and soluble TNF receptors (sTNFRs) were changed in the plasma were not clear. The aim of this study was to determine whether the levels of TACE activity and sTNFRs are sufficiently altered in the plasma of AD patients to be helpful in AD diagnosis. We examined TACE levels in the plasma of 153 patients with AD, 98 patients with amnestic mild cognitive impairment (aMCI), 53 patients with vascular dementia (VaD), and 120 age-matched healthy control subjects, and found TACE activity and sTNFRs were significantly higher in patients with AD and aMCI compared with control subjects (TACE: P<0.001, P<0.01; sTNFR1: P<0.001, P<0.001; sTNFR2: P<0.001, P<0.01, respectively). The TACE activity and sTNFRs levels in VaD patients were significantly higher than the levels observed in AD patients (TACE activity: P<0.001, sTNFR1: P<0.01, sTNFR2: P<0.01). In the plasma of AD patients, the levels of both TACE activity and sTNFRs positively correlated with the levels of Aβ40 and negatively correlated with the ratio of Aβ42/Aβ40. AD patients with at least one copy of the ApoEε4 allele showed higher TACE activity and sTNFR plasma levels compared with patients without the ApoEε4 allele. We then combined the data on plasma TACE activity, sTNFRs, and Aβ with the presence of the APOEε4 allele and found that this biomarker panel exhibited a high sensitivity and specificity for discriminating AD patients from non-demented control subjects and VaD patients.

Apolipoprotein e sets the stage: response to injury triggers neuropathology

Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer's disease and is associated with poor clinical outcome following traumatic brain injury and other neuropathological disorders. Protein instability and an isoform-specific apoE property called domain interaction are responsible for these neuropathological effects. ApoE4 is the most neurotoxic isoform and can induce neuropathology through various cellular pathways. Neuronal damage or stress induces apoE synthesis as part of the repair response; however, when apoE4 is expressed in neurons, its unique conformation makes it susceptible to proteolysis, resulting in the generation of neurotoxic fragments. These fragments cause pathological mitochondrial dysfunction and cytoskeletal alterations. Here, we review data supporting the hypothesis that apoE4 (> apoE3 > apoE2) has direct neurotoxic effects and highlight studies showing that blocking domain interaction reverses these detrimental effects.

Associations of ABCB1 and IL-10 genetic polymorphisms with sirolimus-induced dyslipidemia in renal transplant recipients

BACKGROUND

Hyperlipidemia is a common adverse effect of sirolimus (SRL). We previously showed significant associations of ABCB1 3435C>T and IL-10 -1082G>A with log-transformed SRL dose-adjusted weighted-normalized trough. We further examined to see whether these polymorphisms were also associated with SRL-induced dyslipidemia.

METHODS

Genotyping was performed for ABCB1 1236C>T, 2677 G>T/A, and 3435C>T; CYP3A4 -392A>G; CYP3A5 6986A>G and 14690G>A; IL-10 -1082G>A; TNF -308G>A; and ApoE ε2, ε3, and ε4 alleles. The longitudinal changes of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and triglyceride (TG) levels after SRL treatment before statin therapy were analyzed by a linear mixed-effects model, with adjustments for selected covariates for each lipid.

RESULTS

Under the dominant genetic model, ABCB1 3435C>T was associated with TC (P=0.0001) and LDL-C (P<0.0001) values after SRL administration. Mean TC and LDL-C levels were 26.9 and 24.9 mg/dL higher, respectively, in ABCB1 3435T carriers than 3435CC homozygotes at an average SRL trough concentration of 4 ng/mL without concomitant medication. ABCB1 1236C>T under the recessive model and IL-10 -1082G>A under the dominant model were associated with log-transformed TG values (P=0.0051 and 0.0436, respectively). Mean TG value was 25.1% higher in ABCB1 1236TT homozygotes compared with ABCB1 1236C carriers and was 12.4% higher in IL-10 -1082AA homozygotes than -1082G carriers.

CONCLUSIONS

ABCB1 polymorphisms were found to be associated with lipid responses to SRL treatment, confirming the role of ABCB1 gene in SRL pharmacokinetics and pharmacodynamics. Further studies are necessary to define the role of ABCB1 and IL-10 polymorphisms on SRL-induced dyslipidemia in renal transplantation.

Apolipoprotein E and Alzheimer disease: risk, mechanisms and therapy

Apolipoprotein E (Apo-E) is a major cholesterol carrier that supports lipid transport and injury repair in the brain. APOE polymorphic alleles are the main genetic determinants of Alzheimer disease (AD) risk: individuals carrying the ε4 allele are at increased risk of AD compared with those carrying the more common ε3 allele, whereas the ε2 allele decreases risk. Presence of the APOE ε4 allele is also associated with increased risk of cerebral amyloid angiopathy and age-related cognitive decline during normal ageing. Apo-E-lipoproteins bind to several cell-surface receptors to deliver lipids, and also to hydrophobic amyloid-β (Aβ) peptide, which is thought to initiate toxic events that lead to synaptic dysfunction and neurodegeneration in AD. Apo-E isoforms differentially regulate Aβ aggregation and clearance in the brain, and have distinct functions in regulating brain lipid transport, glucose metabolism, neuronal signalling, neuroinflammation, and mitochondrial function. In this Review, we describe current knowledge on Apo-E in the CNS, with a particular emphasis on the clinical and pathological features associated with carriers of different Apo-E isoforms. We also discuss Aβ-dependent and Aβ-independent mechanisms that link Apo-E4 status with AD risk, and consider how to design effective strategies for AD therapy by targeting Apo-E.

Apolipoprotein E Mimetic Promotes Functional and Histological Recovery in Lysolecithin-Induced Spinal Cord Demyelination in Mice

Objective

Considering demyelination is the pathological hallmark of multiple sclerosis (MS), reducing demyelination and/or promoting remyelination is a practical therapeutic strategy to improve functional recovery for MS. An apolipoprotein E (apoE)-mimetic peptide COG112 has previously demonstrated therapeutic efficacy on functional and histological recovery in a mouse experimental autoimmune encephalomyelitis (EAE) model of human MS. In the current study, we further investigated whether COG112 promotes remyelination and improves functional recovery in lysolecithin induced focal demyelination in the white matter of spinal cord in mice.

Methods

A focal demyelination model was created by stereotaxically injecting lysolecithin into the bilateral ventrolateral funiculus (VLF) of T8 and T9 mouse spinal cords. Immediately after lysolecithin injection mice were treated with COG112, prefix peptide control or vehicle control for 21 days. The locomotor function of the mice was measured by the beam walking test and Basso Mouse Scale (BMS) assessment. The nerve transmission of the VLF of mice was assessed in vivo by transcranial magnetic motor evoked potentials (tcMMEPs). The histological changes were also examined by by eriochrome cyanine staining, immunohistochemistry staining and electron microscopy (EM) method.

Results

The area of demyelination in the spinal cord was significantly reduced in the COG112 group. EM examination showed that treatment with COG112 increased the thickness of myelin sheaths and the numbers of surviving axons in the lesion epicenter. Locomotor function was improved in COG112 treated animals when measured by the beam walking test and BMS assessment compared to controls. TcMMEPs also demonstrated the COG112-mediated enhancement of amplitude of evoked responses.

Conclusion

The apoE-mimetic COG112 demonstrates a favorable combination of activities in suppressing inflammatory response, mitigating demyelination and in promoting remyelination and associated functional recovery in animal model of CNS demyelination. These data support that apoE-mimetic strategy may represent a promising therapy for MS and other demyelination disorders.

ApolipoproteinE mimetic peptides improve outcome after focal ischemia

Growing clinical evidence implicates isoform-specific effects of apolipoprotein E (apoE) in reducing neuroinflammation and mediating adaptive responses following ischemic and traumatic brain injury. However, the intact apoE holoprotein does not cross the blood-brain barrier and thus has limited therapeutic potential. We have created a small peptide, COG1410 (acetyl-AS-Aib-LRKL-Aib-KRLL-amide), derived from the apoE receptor-binding region. COG1410 retains the anti-inflammatory and neuroprotective biological properties of the intact holoprotein and penetrates the blood-brain barrier. In the current study, we utilized a murine model of transient focal cerebral ischemia and reperfusion to demonstrate that intravenous (IV) administration of COG1410 reduces infarct volume and radiographic progression of infarct, and improves functional outcome as assessed by rotarod when delivered up to 4h after ischemia onset.

Connections between apolipoprotein E genotypes and the development of cardiovascular diseases

Elevated plasma lipid level is one of the main risk factors for cardiovascular diseases, which are considered to be pimary causes of death. Apolipoprotein E plays a part in the lipid transport in the blood, thus polimophisms of that affect the lipid composition of the plasma. The three most common alleles of apolipoprotein E are e2, e3, e4. Out of the two non-wild type alleles, the e2 and e4, the latter was shown to play a role in the development of cardiovascular diseases and Alzheimer’s disease. Some studies mention the e2/e2 homozygote genotype as one of the causes of hyperlipoproteinemia type III. Besides lipid metabolism, apolipoprotein E also influences the manifestation of cardiovascular diseases through other biochemical pathways, therefore it is essential to explore the molecular background of these metabolic pathways. Orv. Hetil., 2012, 153, 2070–2076.

Gene by neuroticism interaction and cognitive function among older adults

OBJECTIVES

Both apolipoprotein E (ApoE) ε-4 allele(s) and elevated trait neuroticism, the tendency to experience distress, are associated with cognitive function among older adults. We predicted that neuroticism moderates the association between ApoE and cognitive function and also explored whether other personality dimensions (openness to experience, agreeableness, extraversion, and conscientiousness) affect the association between ApoE status and cognitive function.

METHOD

Five-hundred and ninety-seven older adults (mean age of 78 years) enrolled in the Ginkgo Evaluation of Memory study completed the NEO five-factor inventory of personality. Cognitive function was assessed via the cognitive portion of the Alzheimer's Disease Assessment Scale, and a blood sample for ApoE genotyping was drawn.

RESULTS

As hypothesized, regression analysis indicated that neuroticism moderated the relationship between the presence of ApoE ε-4 and cognitive function. Individuals with high neuroticism scores had significantly lower scores on the cognitive portion of the Alzheimer's Disease Assessment Scale compared with individuals with low neuroticism scores, but this was true only among carriers of ApoE ε-4 (interaction effect β = 0.124, p = 0.028). There was scant evidence that other personality dimensions moderate the association between ApoE ε-4 and cognitive function.

CONCLUSIONS

Cognitive function may be affected by ApoE and neuroticism acting in tandem. Research on the underlying physiological mechanisms by which neuroticism amplifies the effect of ApoE ε-4 is warranted. The study of genotype by phenotype interactions provides an important and useful direction for the study of cognitive function among older adults and for the development of novel prevention programs.

Cholesterol: its regulation and role in central nervous system disorders

Cholesterol is a major constituent of the human brain, and the brain is the most cholesterol-rich organ. Numerous lipoprotein receptors and apolipoproteins are expressed in the brain. Cholesterol is tightly regulated between the major brain cells and is essential for normal brain development. The metabolism of brain cholesterol differs markedly from that of other tissues. Brain cholesterol is primarily derived by de novo synthesis and the blood brain barrier prevents the uptake of lipoprotein cholesterol from the circulation. Defects in cholesterol metabolism lead to structural and functional central nervous system diseases such as Smith-Lemli-Opitz syndrome, Niemann-Pick type C disease, and Alzheimer's disease. These diseases affect different metabolic pathways (cholesterol biosynthesis, lipid transport and lipoprotein assembly, apolipoproteins, lipoprotein receptors, and signaling molecules). We review the metabolic pathways of cholesterol in the CNS and its cell-specific and microdomain-specific interaction with other pathways such as the amyloid precursor protein and discuss potential treatment strategies as well as the effects of the widespread use of LDL cholesterol-lowering drugs on brain functions.

Human apolipoprotein E peptides inhibit hepatitis C virus entry by blocking virus binding

Hepatitis C virus (HCV) entry is a multiple-step process involving a number of host factors and hence represents a promising target for new antiviral drug development. In search of novel inhibitors of HCV infection, we found that a human apolipoprotein E (apoE) peptide, hEP, containing both a receptor binding fragment and a lipid binding fragment of apoE specifically blocked the entry of cell culture grown HCV (HCVcc) at submicromolar concentrations. hEP caused little cytotoxicity in vitro and remained active even if left 24 hours in cell culture. Interestingly, hEP inhibited neither human immunodeficiency virus (HIV)-HCV pseudotypes (HCVpp) nor HIV and Dengue virus (DENV) infection. Further characterization mapped the anti-HCV activity to a 32-residue region that harbors the receptor binding domain of apoE, but this fragment must contain a cysteine residue at the N-terminus to mediate dimer formation. The anti-HCV activity of the peptide appears to be dependent on both its length and sequence and correlates with its ability to bind lipids. Finally, we demonstrated that the apoE-derived peptides directly blocked the binding of both HCVcc and patient serum-derived virus to hepatoma cells as well as primary human hepatocytes.

CONCLUSION

apoE peptides potently inhibit HCV infection and suggest a direct role of apoE in mediating HCV entry. Our findings also highlight the potential of developing apoE mimetic peptides as novel HCV entry inhibitors by targeting HCV-host interactions.

The apoE-mimetic peptide, COG1410, improves functional recovery in a murine model of intracerebral hemorrhage

BACKGROUND

Apolipoprotein E has previously been demonstrated to modulate acute brain injury responses, and administration of COG1410, an apoE-mimetic peptide derived from the receptor-binding region of apoE, improves outcome in preclinical models of acute neurological injury. In the current study, we sought to establish the optimal dose and timing of peptide administration associated with improved functional outcome in a murine model of intracerebral hemorrhage (ICH).

METHODS

Ten to twelve-week-old C57/BL6 male mice were injured by collagenase-induced ICH and randomly selected to receive either vehicle or one of four doses of COG1410 (0.5, 1, 2, or 4 mg/kg) via tail vein injection at 30 min after injury and then daily for 5 days. The injured mice were euthanized at various time points to assess inflammatory mediators, cerebral edema, and hematoma volume. Over the first 5 days following injury, vestibulomotor function was tested via Rotorod (RR) latency. After an optimal dose was demonstrated, a final cohort of animals was injured with ICH and randomly assigned to receive the first dose of COG1410 or vehicle at increasingly longer treatment initiation times after injury. The mice were then assessed for functional deficit via RR testing over the first 5 days following injury.

RESULTS

The mice receiving 2 mg/kg of COG1410 after injury demonstrated reduced functional deficit, decreased brain concentrations of inflammatory proteins, and less cerebral edema, although hematoma volume did not vary. The improved RR performance was maintained when peptide administration was delayed for up to 2 h after ICH.

CONCLUSIONS

COG1410 administered at a dose of 2 mg/kg within 2 h after injury improves functional recovery in a murine model of ICH.

Apolipoprotein E COG 133 mimetic peptide improves 5-fluorouracil-induced intestinal mucositis

Background

Intestinal mucositis is one of the major troublesome side effects of anticancer chemotherapy leading to poor patient compliance. In this study we addressed the role of the novel apolipoprotein E (ApoE) COG 133 mimetic peptide in 5-fluorouracil (5-FU)-challenged Swiss mice and IEC-6 cell monolayers. Experiments were also conducted in C57BL6J ApoE knock-out mice to assess the effects of apoE peptide treatment.

Methods

Experimental groups were as follows: unchallenged controls, 5-FU-challenged mice (450 mg/kg, i.p) with or without the ApoE peptide (0.3, 1, and 3 μM, given twice daily i.p. for 4 days). Mice were sacrificed 3 days after 5-FU challenge. Proximal small intestinal samples were harvested for molecular biology and histological processing. We conducted ELISA assays and RT-PCR to target IL-1β, TNF-α, IL-10, iNOS, and myeloperoxidase (MPO) to assess intestinal inflammation. Cell death and NF-κB assays were also conducted in apoE knock-out mice. In our in vitro models, IEC-6 cells were exposed to 1 mM of 5-FU in glutamine free media with or without the ApoE peptide (0.02, 0.2, 2, 5, 10, and 20 μM). We investigated IEC-6 cell proliferation and migration, 24 h after the 5-FU challenge. Additionally, apoptotic IEC-6 cells were measured by Tunel and flow cytometry. Equimolar doses of the ApoA-I (D4-F) peptide were also used in some experiments for comparative studies.

Results

Villus blunting and heavy inflammatory infiltrates were seen in the 5-FU-challenged group, findings that were partially ameliorated by the ApoE peptide. We found increased intestinal MPO and pro-inflammatory IL-1β and TNF-α levels, and TNF-α and iNOS transcripts, and reduction of IL-10 following 5-FU treatment, each of which were partially abrogated by the peptide. Improvements were also found in IEC-6 cell apoptosis and migration following ApoE and D-4F treatment.

Conclusion

Altogether, these findings suggest that the novel ApoE COG 133 mimetic peptide can reduce 5-FU-induced intestinal changes and potentially benefit mucositis.

Administration of COG1410 reduces axonal amyloid precursor protein immunoreactivity and microglial activation after controlled cortical impact in mice

Traumatic axonal injury (TAI) accounts for at least 35% of the morbidity and mortality in traumatic brain injury (TBI) patients without space-occupying lesions. It is also believed to be a key determinant of adverse outcomes such as cognitive dysfunction across the spectrum of TBI severity. Previous studies have shown that COG1410, a synthetic peptide derived from the apolipoprotein E (apoE) receptor binding region, has anti-inflammatory effects after experimental TBI, with improvements in cognitive recovery. However, the effects of COG1410 on axonal injury following TBI are not known. The current study evaluated the effects of 1 mg/kg daily COG1410 versus saline administered intravenously starting 30 min after controlled cortical impact (CCI) injury on pericontusional TAI in young, wild-type C57BL6/J male mice. We found that COG1410 did not affect the number of amyloid precursor protein (APP)-immunoreactive axonal varicosities in the pericontusional corpus callosum and external capsule at 24 h, but reduced APP-immunoreactive varicosities by 31% at 3 days (p=0.0023), and 36% at 7 days (p=0.0009). COG1410 significantly reduced the number of Iba1-positive cells with activated microglial morphology at all three time points by 21-30%. There was no effect of COG1410 on pericontusional white matter volume or silver staining at any time point. This indicates a possible effect of COG1410 on delayed but not immediate TAI. Future studies are needed to investigate the underlying mechanisms, therapeutic time window, and physiological implications of this effect.

Apo E4 and lipoprotein-associated phospholipase A2 synergistically increase cardiovascular risk

OBJECTIVE

Apolipoprotein E (apoE) has been implicated as conveying increased risk for coronary artery disease (CAD). Previous studies suggest a role of apoE as a modulator of immune response and inflammatory properties. We hypothesized that the presence of apo E4 is associated with an increased inflammatory burden in subjects with CAD as compared to subjects without CAD.

METHODS

ApoE genotypes, systemic (C-reactive protein [CRP], fibrinogen, serum amyloid-A [SAA]) and vascular inflammatory markers (Lipoprotein-associated phospholipase A(2) [Lp-PLA(2)] and pentraxin-3 [PTX-3]) were assessed in 324 Caucasians and 208 African Americans, undergoing coronary angiography.

RESULTS

For both ethnic groups, Lp-PLA(2) index, an integrated measure of Lp-PLA(2) mass and activity, increased significantly and stepwise across apoE isoforms (P = 0.009 and P = 0.026 for African Americans and Caucasians respectively). No differences were found for other inflammatory markers tested (CRP, fibrinogen, SAA and PTX-3). For the top cardiovascular score tertile, apo E4 carriers had a significantly higher level of Lp-PLA(2) index in both ethnic groups (P = 0.027 and P = 0.010, respectively).

CONCLUSION

The presence of the apo E4 isoform was associated with a higher level of Lp-PLA(2) index, a marker of vascular inflammation. Our results suggest that genetic variation at the apoE locus may impact cardiovascular disease risk through enhanced vascular inflammation.

An apolipoprotein E4 fragment affects matrix metalloproteinase 9, tissue inhibitor of metalloproteinase 1 and cytokine levels in brain cell lines

Apolipoprotein (apo) E4 isoform, a major risk factor for Alzheimer disease (AD), is more susceptible to proteolysis than apoE2 and apoE3 isoforms. ApoE4 fragments have been found in AD patients' brain. In the present study, we examined the effect of full-length apoE4 and apoE4 fragments apoE4[Δ(186-299)] and apoE4[Δ(166-299)] on inflammation in human neuroblastoma SK-N-SH and human astrocytoma SW-1783 cells. Western blot and zymography analysis showed that treatment of SK-N-SH cells with apoE4[Δ(186-299)], but not full-length apoE4 or the shorter apoE4[Δ(166-299)] fragment, leads to increased extracellular levels of matrix metalloproteinase 9 (MMP9) and tissue inhibitor of metalloproteinase 1 (TIMP1). Real-time PCR showed that interleukin (IL)-1β gene expression is also increased in SK-N-SH cells treated with apoE4[Δ(186-299)]. Treatment of SK-N-SH cells with IL-1β leads to increased MMP9 and TIMP1 extracellular levels, suggesting that the induction of IL-1β may be the mechanism by which apoE4[Δ(186-299)] regulates MMP9 and TIMP1 levels in these cells. In contrast to SK-N-SH cells, treatment of SW-1783 cells with apoE4[Δ(186-299)], and to a lesser extent with apoE4, leads to increased TIMP1 extracellular levels without affecting MMP9 levels. Additionally, apoE4[Δ(186-299)] leads to decreased IL-10 gene expression in SK-N-SH cells, whereas both apoE4 and apoE4[Δ(186-299)] lead to decreased TNFα gene expression without affecting IL-1β and IL-10 gene expression in SW-1783 cells. Overall, our findings indicate that a specific apoE4 fragment (apoE4[Δ(186-299)]), with molecular mass similar that of apoE4 fragments detected in AD patients' brain, can influence the level of inflammatory molecules in brain cell lines. It is possible that these phenomena contribute to AD pathogenesis.

Apolipoprotein mimetic peptides: a new approach for the treatment of asthma

New treatments are needed for severe asthmatics to improve disease control and avoid severe toxicities associated with oral corticosteroids. We have used a murine model of house dust mite (HDM)-induced asthma to identify steroid-unresponsive genes that might represent targets for new therapeutic approaches for severe asthma. This strategy identified apolipoprotein E as a steroid-unresponsive gene with increased mRNA expression in the lungs of HDM-challenged mice. Furthermore, apolipoprotein E functioned as an endogenous negative regulator of airway hyperreactivity and goblet cell hyperplasia in experimental HDM-induced asthma. The ability of apolipoprotein E, which is expressed by lung macrophages, to attenuate AHR, and goblet cell hyperplasia is mediated by low density lipoprotein (LDL) receptors expressed by airway epithelial cells. Consistent with this, administration of an apolipoprotein E mimetic peptide, corresponding to amino acids 130–149 of the LDL receptor-binding domain of the holo-apoE protein, significantly reduced AHR and goblet cell hyperplasia in HDM-challenged apoE^−/− mice. These findings identified the apolipoprotein E – LDL receptor pathway as a new druggable target for asthma that can be activated by administration of apoE-mimetic peptides. Similarly, apolipoprotein A-I may have therapeutic potential in asthma based upon its anti-inflammatory, anti-oxidative, and anti-fibrotic properties. Furthermore, administration of apolipoprotein A-I mimetic peptides has attenuated airway inflammation, airway remodeling, and airway hyperreactivity in murine models of experimental asthma. Thus, site-directed delivery of inhaled apolipoprotein E or apolipoprotein A-I mimetic peptides may represent novel treatment approaches that can be developed for asthma, including severe disease.

APOE-mimetic peptides reduce behavioral deficits, plaques and tangles in Alzheimer's disease transgenics

BACKGROUND

After age, the second largest risk factor for Alzheimer's disease (AD) is apolipoprotein E (APOE) genotype, where APOE4 is associated with lower apoE protein levels, more severer brain pathology, enhanced inflammation and disease. Small peptides corresponding to the receptor-binding region of apoE mimic the anti-inflammatory activity of the apoE holoprotein. These apoE mimetics greatly improve behavioral outcomes and neuronal survival in head trauma models that display AD pathology and neuronal loss.

OBJECTIVE

To determine whether apoE mimetics change behavior, inflammation and pathology in CVND-AD (SwDI-APP/NOS2(-/-)) transgenic mice.

METHODS

Starting at 9 months, apoE peptides were subcutaneously administered 3 times per week for 3 months followed by behavioral, histochemical and biochemical testing.

RESULTS

Treatment with apoE mimetics significantly improved behavior while decreasing the inflammatory cytokine IL-6, neurofibrillary tangle-like and amyloid plaque-like structures. Biochemical measures matched the visible pathological results.

CONCLUSIONS

Treatment with apoE mimetics significantly improved behavior, reduced inflammation and reduced pathology in CVND-AD mice. These improvements are associated with apoE-mimetic-mediated increases in protein phosphatase 2A activity. Testing in additional AD models showed similar benefits, reinforcing this novel mechanism of action of apoE mimetics. These data suggest that the combination of anti-inflammatory and neuroprotective activities of apoE mimetics represents a new generation of potential therapeutics for AD.

Neuroinflammation: modulation by flavonoids and mechanisms of action

Neuroinflammatory processes are known to contribute to the cascade of events culminating in the neuronal damage that underpins neurodegenerative disorders such as Parkinson's and Alzheimer's disease. Recently, there has been much interest in the potential neuroprotective effects of flavonoids, a group of plant secondary metabolites known to have diverse biological activity in vivo. With respect to the brain, flavonoids, such as those found in cocoa, tea, berries and citrus, have been shown to be highly effective in preventing age-related cognitive decline and neurodegeneration in both animals and humans. Evidence suggests that flavonoids may express such ability through a multitude of physiological functions, including an ability to modulate the brains immune system. This review will highlight the evidence for their potential to inhibit neuroinflammation through an attenuation of microglial activation and associated cytokine release, iNOS expression, nitric oxide production and NADPH oxidase activity. We will also detail the current evidence indicting that their regulation of these immune events appear to be mediated by their actions on intracellular signaling pathways, including the nuclear factor-κB (NF-κB) cascade and mitogen-activated protein kinase (MAPK) pathway. As such, flavonoids represent important precursor molecules in the quest to develop of a new generation of drugs capable of counteracting neuroinflammation and neurodegenerative disease.

APOE genotype alters glial activation and loss of synaptic markers in mice

The ε4 allele of the Apolipoprotein E (APOE) gene is the strongest genetic risk factor for late-onset Alzheimer's disease (AD), and affects clinical outcomes of chronic and acute brain damages. The mechanisms by which apoE affect diverse diseases and disorders may involve modulation of the glial response to various types of brain damage. We examined glial activation in a mouse model where each of the human APOE alleles are expressed under the endogenous mouse APOE promoter, as well as in APOE knock-out mice. APOE4 mice displayed increased glial activation in response to intracerebroventricular lipopolysaccharide (LPS) compared to APOE2 and APOE3 mice by several measures. There were higher levels of microglia/macrophage, astrocytes, and invading T-cells after LPS injection in APOE4 mice. APOE4 mice also displayed greater and more prolonged increases of cytokines (IL-1β, IL-6, TNF-α) than APOE2 and APOE3 mice. We found that APOE4 mice had greater synaptic protein loss after LPS injection, as measured by three markers: PSD-95, drebin, and synaptophysin. In all assays, APOE knock-out mice responded similar to APOE4 mice, suggesting that the apoE4 protein may lack anti-inflammatory characteristics of apoE2 and apoE3. Together, these findings demonstrate that APOE4 predisposes to inflammation, which could contribute to its association with Alzheimer's disease and other disorders.

Apolipoprotein E gene polymorphisms are strong predictors of inflammation and dyslipidemia in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA), a condition with a strong genetic etiology, is associated with excess cardiovascular disease (CVD). Dyslipidemia in RA may be driven by inflammation and genetic factors. Apolipoprotein E (ApoE) is important for the regulation of lipid levels and CVD risk and immune function in the general population. We compared the frequency of 2 ApoE single-nucleotide polymorphisms (SNP) in patients with RA and controls, and studied the relationship of ApoE genotypes with lipids and inflammation in RA.

METHODS

A total of 387 patients with well-characterized RA and 420 non-RA controls were studied. Two ApoE SNP, rs7412 (ApoE2) and rs429358 (ApoE4), were identified.

RESULTS

Genotypic (p = 0.908) and allelic (p = 0.894) frequencies did not differ between RA and controls. Within RA, the E2 allele was associated with the lowest and E4 allele with the highest levels of total cholesterol (p = 0.007), low-density lipoproteins (p = 0.004), and apolipoprotein B (p = 0.009). The E4 allele was also associated with lower C-reactive protein (p = 0.007), erythrocyte sedimentation rate (p = 0.001), and Disease Activity Score (p = 0.015) compared to the E3 allele. E2 or E4 alleles were not associated with CVD in RA, although a trend was observed (p = 0.074).

CONCLUSION

The frequency of ApoE polymorphisms did not differ between patients with RA and controls. ApoE genotypes are strongly linked to inflammation and lipid levels in RA, raising interest in the prognostic implications of ApoE genotypes.

New kids on the block: the emerging role of apolipoproteins in the pathogenesis and treatment of asthma

New treatments are needed for patients with severe asthma. We hypothesized that a clinically relevant experimental model of house dust mite (HDM)-induced murine asthma could be used to discover new pathways that regulate disease severity. In HDM-challenged mice, genome-wide expression profiling of the asthmatic lung transcriptome identified apolipoprotein E (apoE) as a steroid-unresponsive gene with persistently upregulated expression despite dexamethasone treatment. ApoE and low-density lipoprotein receptor (LDLR) knockout mice were used to demonstrate that apoE, which is produced by lung macrophages, functions in a paracrine fashion by binding to LDLRs expressed on ciliated airway epithelial cells, to negatively modulate airway hyperreactivity, mucin gene expression, and goblet cell hyperplasia. Furthermore, administration of an apoE mimetic peptide, which corresponded to the LDLR-binding domain of apoE, prevented the induction of airway inflammation, airway hyperreactivity, and goblet cell hyperplasia in HDM-challenged apoE knockout mice. This suggests that therapeutic strategies that activate the apoE-LDLR pathway, such as apoE mimetic peptides, may represent a novel treatment approach for patients with asthma. Similarly, we showed that administration of a 5A apolipoprotein A-I mimetic peptide attenuated the induction of HDM-mediated asthma in mice. These preclinical data suggest that apoE and apoA-I mimetic peptides might be developed into alternative treatments for patients with severe asthma. Future clinical trials will be required to determine whether inhaled apolipoprotein E or apolipoprotein A-I mimetic peptides are effective for the treatment of severe asthma, including patients with phenotypes that lack effective therapeutic options.

Genetic polymorphisms in sepsis

The number of genetic polymorphisms shown to play a role in sepsis continues to increase. At the same time, platforms for genetic sequencing and expression analysis are being refined, allowing unprecedented data generation. International databases may soon facilitate synchrony of genotypic and phenotypic data using enormous numbers of septic patients. If this occurs, 2 strategies for investigating polymorphisms in sepsis are likely to gain favor. In the first strategy, sepsis will continue to be viewed as a single entity. High-throughput genetic techniques will be used to evaluate numerous polymorphisms, each with fractional disease responsibility. Nongenetic variables, such as pathogen characteristics, underlying host medical conditions, and type and timing of resuscitation, will be considered cofactors. Using this approach, principal components that predict susceptibility to and outcomes during sepsis are likely to be identified. In the second strategy, sepsis will be divided into subtypes based on the concentration of specific variables. Categories will be based on features like the presence or absence of specific polymorphisms, gram-positive or gram-negative staining of causative organisms, age and comorbid conditions of the host, recent administration of chemotherapeutic agents, and hospital setting (ie, community vs teaching institution). Each category will be used to create homogenous sepsis subgroups for detailed evaluation. This approach will increase the odds of finding single dominant factors responsible for predilection and/or outcome within well-defined groups among those with sepsis. Several elements will be essential for the success of both these strategies. Firstly, databases that are extremely detailed will have to be generated. Secondly, better clinical information technology systems will be needed to facilitate large-scale phenotyping. Thirdly, standardization of protocols will need to take place to ensure uniformity of data sets. If the rapid advances in technology and informatics continue, they may catalyze paradigm shifts with regard to how clinicians address sepsis. Clinicians may change their focus from aggressive uniform treatment strategies to rapid stratification and subcategorization, with subsequent aggressive targeted therapeutic interventions. Advances in technology have the potential to change our primary goal in sepsis from rapid treatment to prevention for those most at risk. The cost savings to the US health care systems from such changes could be substantial.

Cross-talk between apolipoprotein E and cytokines

Apolipoprotein E (apoE) is a multifunctional glycosylated protein characterized by its wide tissue distribution. Despite its importance in lipid transport and atherosclerosis pathogenesis, apoE is associated with neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson disease, and autoimmune disorders such as multiple sclerosis and psoriasis. Among others, the role of apoE in modulating inflammation and oxidation is crucial in elucidating the risk factors of the above diseases since the function of apoE is closely linked with both proinflammatory and antiinflammatory cytokines. Moreover, apoE modulates inflammatory and immune responses in an isoform-dependent manner. Correspondingly, inflammatory cytokines can either upregulate or downregulate the production of apoE in various tissue types. However, studies on the interactions between apoE and cytokines occasionally yield conflicting results, highlighting the complex roles of apoE and cytokines in various disorders. The present paper summarizes the current knowledge about the cross-talk between apoE and cytokines, with emphasis on the effects of apoE on the Th1/Th2 balance.

Exacerbation of type II collagen-induced arthritis in apolipoprotein E-deficient mice in association with the expansion of Th1 and Th17 cells

OBJECTIVE

To explore the bidirectional relationship between the development of rheumatoid arthritis (RA) and atherosclerosis using bovine type II collagen (CII)-immunized B10.RIII apoE(-/-) mice, a murine model of spontaneous atherosclerosis and collagen-induced arthritis (CIA).

METHODS

Male B10.RIII apoE(-/-) mice and wild-type controls were immunized with 150 μg of CII emulsified in Freund's complete adjuvant (CFA). The clinical, radiologic, and histopathologic severity of CIA, the levels of circulating IgG1 and IgG2a anti-CII antibodies, the expression of proinflammatory and antiinflammatory cytokines in the joints, and the percentages of Th1, Th17, and Treg lymphocytes in the draining lymph nodes were evaluated during CIA induction. In addition, the size of atherosclerotic lesions was assessed in these mice 8 weeks after CIA induction.

RESULTS

B10.RIII apoE(-/-) mice that were immunized with CII and CFA developed an exacerbated CIA that was accompanied by increased joint expression of multiple proinflammatory cytokines and by the expansion in the draining lymph nodes of Th1 and Th17 cells. In contrast, the size of vascular lesions in B10.RIII apoE(-/-) mice was not affected by the development of CIA.

CONCLUSION

Our findings indicate that a deficiency in apolipoprotein E and/or its consequences in cholesterol metabolism act as accelerating factors in autoimmunity by promoting Th1 and Th17 inflammatory responses.

Apolipoprotein E and peptide mimetics modulate inflammation by binding the SET protein and activating protein phosphatase 2A

The molecular mechanism by which apolipoprotein E (apoE) suppresses inflammatory cytokine and NO production is unknown. Using an affinity purification approach, we found that peptide mimetics of apoE, derived from its receptor binding domain residues 130-150, bound to the SET protein, which is a potent physiological inhibitor of protein phosphatase 2A (PP2A). Both holo-apoE protein and apoE-mimetic peptides bound to the C-terminal region of SET, which is then associated with an increase in PP2A-mediated phosphatase activity. As physiological substrates for PP2A, the LPS-induced phosphorylation status of signaling MAPK and Akt kinase is reduced following treatment with apoE-mimetic peptides. On the basis of our previous report, in which apoE-mimetic peptides reduced I-κB kinase and NF-κB activation, we also demonstrate a mechanism for reduced production of inducible NO synthase protein and its NO product. These data provide evidence for a novel molecular mechanism by which apoE and apoE-mimetic peptides antagonize SET, thereby enhancing endogenous PP2A phosphatase activity, which reduces levels of phosphorylated kinases, signaling, and inflammatory response.