Current Alzheimer Research (v.11, #7)
Editorial (Thematic Issue: Overview of Immunotherapy in Alzheimerµs Disease (AD) and Mechanisms of IVIG Neuroprotection in Preclinical Models of AD) by Scott E. Counts, Debomoy K. Lahiri (623-625).
Epidemiologic studies suggest that we are on the precipiceof a worldwide epidemic of Alzheimer's disease (AD),yet current treatment options are limited to short term symptomaticrelief. Recent advances in our knowledge of the neurobiologyof AD have resulted in the development of severalpotential disease-modifying approaches based on immunotherapy.The present special 'Hot Topic' (HT) issue of “CurrentAlzheimer Research” deals primarily with the mechanismsof passive vaccination with Intravenous Immunoglobulin(IVIG), particularly within the context of neuroprotectionin preclinical models of AD. This HT issue is notmeant to report exhaustively on the many other research effortsin the broader immunotherapy arena. Indeed, this journalhas recently covered various other aspects of immunotherapyrelevant to AD and related disorders. However, wewill briefly overview current immunotherapeutic strategiesfor AD prior to discussing the main topic of IVIG neuroprotection.One of the most significant approaches involves the removalof brain amyloid- β peptide (A β) using anti-A β antibodies.Aβ immunotherapy emerged as a promising treatmentstrategy based on human neuropathology and preclinicalstudies. The hallmark accumulation of parenchymal andvascular Aβ pathology observed in the brains of AD subjectssuggested a logical target, and naturally occurring anti-Aβ antibodies were found to be reduced in the cerebrospinalfluid and blood of AD patients [1, 2]. In addition, both activeand passive amyloid immunization of AD transgenic mousemodels resulted in increased clearance of amyloid plaquelikedeposits and improved cognitive performance [3, 4],whereas brain imaging and neuropathological studies suggestedthe ability of both active and passive anti-A β immunotherapiesto clear Aβ deposits from the AD brain.AN1792 was the first active immunotherapy strategy forAD using full length Aβ 42 as the immunogen; however, aPhase II trial of this anti-amyloid vaccine was halted whenmeningo-encephalitis appeared in a small subset of patients. Despite this setback, long-term follow-up of patientsimmunized with AN1792 showed reduced functional declinein antibody responders , supporting the hypothesis that A βimmunotherapy may have long-term functional benefits. Inthis regard, novel A β immunogens with shorter peptide sequencesare in development which may avoid the autoimmuneresponses to full length A β42 . The first passiveanti-A β immunotherapy for AD focused on bapineuzumab.Bapineuzumab, which is composed of humanized anti-A βmonoclonal antibodies, reduced A β burden in the brains ofAD patients in two Phase II trials. However, bapineuzumabdid not improve clinical outcomes in patients with AD, despitetreatment differences in biomarkers observed in APOEε4 carriers [8, 9]. Other recent approaches, such as systemicco-administration of clioquinol and A β42 vaccines, significantlyreduce A β deposits in the brains of transgenic ADmice . In non-rodent models, a rapid improvement ofcanine cognitive dysfunction with amyloid immunotherapysuggests the important use of the canine model in testingvaccines for AD . So far, the limitations of A β-basedimmunotherapy include the development of encephalitis, thelack of clinical improvement, and the lack of effect on neurofibrillarytangles (NFTs), another major neuropathologicalfeature of AD. Other critical points relate to the study designand several variables in imunotherapy trials, which are essentialfor optimizing trial designs and improving conditionsfor participants .Due to the central role of NFTs in dementia, immunotherapytargeting these tau proteinous aggregates is an importantarea of research [13, 14]. Notably, an active immunotherapytargeting the tau pathological epitope phospho-Ser422 was found to be efficient, resulting in tau clearanceand improved cognitive deficits promoted by tau pathologyin a well-defined tau transgenic model . Like A β oligomers,the putative role of tau oligomers in AD pathophysiologyhas prompted an investigation into tau oligomersas potential immunotherapeutic targets for AD andtauopathies .Taken together, these results suggest that immunotherapiestargeting A β alone may be insufficient for disease modification.To this end, researchers also began testing whetherIVIG might serve as an alternative immunotherapeutic strategy.IVIG is a mixture of naturally occurring human IgGantibodies derived from the plasma of healthy young volunteers.Notably, IVIG has been used for nearly half a centuryfor primary humoral immune deficiencies and autoimmunesyndromes and, more recently, a number of neurologic disorderssuch as chronic inflammatory demyelinating polyradiculoneuropathyand Guillain-Barre syndrome [17, 18].The rationale for using IVIG for the treatment of ADgained traction for a number of reasons. IVIG was found tocontain elevated levels of antibodies against multiple conformations of A β monomers and aggregates [19, 20], yet itsrepertoire of naturally occurring antibodies might also bepredicted to normalize the inflammatory component of AD.The safety profile of IVIG for other diseases also mitigatedconcerns for AD clinical trials. Furthermore, if IVIG wasfound to be beneficial in AD, the potential existed for identifyingtreatment-specific antibodies to elucidate pathogenicmechanisms and allow for more targeted therapeutic designs.However, despite the initial promise of Phase I and II clinicaltrials conducted in Germany and the US, a recent multicenterdouble-blinded Phase III study of 390 subjects, called theGammaglobulin Alzheimer's Partnership (GAP), did notmeet primary endpoints of slowing cognitive and functionaldecline . Then again, the GAP study results continued tosupport IVIG's positive safety profile and showed potentiallybeneficial effects for pre-specified moderate AD and apoE4carrier subgroups. Concurrent with these clinical trials, severalpreclinical studies demonstrated that IVIG was neuroprotectiveagainst A β toxicity in vitro and enhanced microglia-mediated Aβ clearance ex vivo, whereas in vivo IVIGdelivery reduced inflammation in AD transgenic mice [22,23]. Hence, the mechanism of action for IVIG is still of considerableinterest in the field and there remains the opportunityfor testing the extent to which optimized doses of IVIGdelivered early enough in the AD trajectory might yet provebeneficial for modifying disease progression.In the present HT issue, we summarize the state of thefield with respect to IVIG as a potential therapy for AD andexplore further the potential mechanisms of IVIG neuroprotectionin preclinical models of AD. Puli and colleagues reviewour current understanding of the biologic and therapeuticproperties of IVIG relevant to AD therapy and highlighttheir in vitro and in vivo studies on IVIG biological activities,including the suppression of neuroinflammatory microglialactivation and concomitant increase in neurogenesis inAPP/PS1 mice . Gong and colleagues expound uponIVIG immunomodulatory mechanisms by showing that IVIGregulates complement-derived anaphylatoxins, such as C5aand C3, which in turn upregulates AMPA receptor-PKACREBsignaling pathways and improves synaptic functionand cognition in the Tg2576 mouse model of AD . Lahiriand Ray add to the diverse repertoire of IVIG neuroprotectionby reporting that treatment with IVIG protects neuronalviability and synaptic proteins in primary rat hippocampalneurons as well as in primary human brain cultures challengedwith oxidative stress, suggesting a potent neuropreservatoryeffect of IVIG against oxidative insults . Inaddition, although IVIG has been reported to reduce amyloidburden in some AD transgenic models, its potential effectson tau NFT-like pathology in rodent models of disease areunclear. Counts and colleagues show that IVIG reduces hippocampaltau pathology in the 3xTg mouse model of ADthat exhibits NFT as well as plaque-like deposits. In addition,this study reveals that IVIG preserves plasma levels ofmRNAs regulating neuronal cytoskeletal plasticity functionand calcium-mediated signaling compared to placebo . Itis important to note that not all IVIG preclinical studies haveproduced consistently positive results . In this issue,Joly-Amado and colleagues describe how four weeks ofIVIG infusion in Tg2576 mice led to widespread distributionof human IgG in the forebrain, but had no effect on amyloidburden or cognition . However, the authors conclude byagreeing that the beneficial effects of IVIG in mouse modelsof AD are not likely due to its anti-Aβ antibody componentsalone, but must also involve its wide range of antiinflammatory,anti-oxidant, and other prosurvival and neuroprotectiveproperties. Hence, despite the negative toplineresults from the GAP trial, these unique properties of IVIGsuggest that this polyclonal IgG mixture can potentially be asafe and highly effective “top down” therapy for a complexmultifactorial disease like AD. Moreover, the data derivedfrom preclinical study designs may help guide current andfuture IVIG clinical trials targeting early stage patients withmore optimized treatment regimens to prevent or delay theonset of AD symptomology . Finally, since efforts toimmunize against tau  and other AD-related targets havebeen encouraging, these studies would potentially be excellentsubject matters for a future HT issue of the journal.
Intravenous Immunoglobulins for Alzheimer's Disease by Lakshman Puli, Heikki Tanila, Norman Relkin (626-636).
Alzheimer's disease (AD) is a chronic neurodegenerative disease associated with intracerebral accumulation ofaggregated amyloid-beta (Aβ ) and tau proteins, as well as neuroinflammation. Human intravenous immunoglobulin(IVIG) is a mixture of polyclonal IgG antibodies isolated and pooled from thousands of healthy human donors. The scientificrationale for testing IVIG as a potential AD treatment include its natural anti-A β antibody activity, its favorablesafety profile and inherent anti-inflammatory/immunomodulatory properties. Over the past decade, several clinical andpre-clinical experimental findings, advanced our knowledge about biological and therapeutic properties of IVIG that arerelevant to AD therapy. Anti-amyloid antibodies in IVIG show significantly higher binding avidity for amyloid oligomersand fibrils than for Aβ monomers. In a double transgenic murine model of AD, intracerebral injection of IVIG causessuppression of A β fibril pathology whereas long term peripheral IVIG treatments causes elevation of total brain A β levelswith no measurable impact on A β deposits or tendency for inducing cerebral microhemmorhage. Furthermore, chronicIVIG treatment suppressed neuroinflammation and fostered adult hippocampal neurogenesis. In clinical studies with ADpatients, IVIG showed an acceptable safety profile and has not been reported to increase the incidence of amyloid relatedimaging abnormalities. Preliminary studies on small number of patients reported clinical benefits in mild to moderatestage AD patients. However, double blind, placebo controlled studies later did not replicate those initial findings. Interestinglythough, in APOE4 carriers and in moderate disease stage subgroups, positive cognitive signals were reported. Nevertheless,both clinical and experimental (mouse) studies show that antibodies in IVIG can accumulate in CNS and its biologicalactivities include neutralization of Aβ oligomers, suppression of neuroinflammation and immunomodulation. Identifyingmediators of IVIG's effects at the cellular and molecular level is warranted. In light of its favourable safety profileand aforementioned biological properties, IVIG is still an enigmatic experimental candidate with enormous potential forbeing an AD therapeutic.
Role of Complement Systems in IVIG Mediated Attenuation of Cognitive Deterioration in Alzheimer's Disease by Bing Gong, Samara Levine, Scott R. Barnum, Giulio M. Pasinetti (637-644).
Human intravenous immunoglobulin (IVIG) has been indicated as a potential therapy for autoimmune neurologicaldisorders, as well as in many neurodegenerative diseases, with various underlying therapeutic mechanisms such asregulation of T-cell trafficking, cytokines, Fc receptor blocking, and interruption of complement activation cascade. InAlzheimer's disease (AD), IVIG presents naturally occurring antibodies against amyloid-beta (Aβ ) aggregation, thus IVIGimmunotherapy may increase the clearance of Aβ and protect brain function. Recently, we and others reported that besidesAβ clearance, IVIG specifically regulates the levels of complement-derived anaphylatoxins, such as C5a and C3,which play an important role in the regulation of AMPA and NMDA receptor expression in the brain and further upregulatethe AMPA-PKA-CREB signaling pathway and synaptic function in AD mouse models. Since down-regulation ofcomplement components has been linked with deficits of cognitive function in age-related dementia following the declineof innate immunity during aging, the IVIG immunotherapy could be an attractive novel AD therapeutic through its localregulation of C3, C5a component levels in brain.
Intravenous Immunoglobulin Treatment Preserves and Protects Primary Rat Hippocampal Neurons and Primary Human Brain Cultures Against Oxidative Insults by Debomoy K. Lahiri, Balmiki Ray (645-654).
Alzheimer's disease (AD) is characterized by deleterious accumulation of amyloid-β (Aβ ) peptide into senileplaque, neurofibrillary tangles formed from hyperphosphorylated tau protein, and loss of cholinergic synapses in the cerebralcortex. The deposition of Aβ -loaded plaques results in microglial activation and subsequent production of reactiveoxygen species (ROS), including free radicals. Neurons in aging and AD brains are particularly vulnerable to ROS andother toxic stimuli. Therefore, agents that decrease the vulnerability of neurons against ROS may provide therapeutic valuesfor the treatment or prevention of AD. In the present study, our goal was to test whether intravenous immunoglobulin(IVIG) treatment could preserve as well as protect neurons from oxidative damage. We report that treatment with IVIGprotects neuronal viability and synaptic proteins in primary rat hippocampal neurons. Further, we demonstrate the tolerabilityof IVIG treatment in the primary human fetal mixed brain cultures. Indeed, a high dose (20mg/ml) of IVIG treatmentwas well-tolerated by primary human brain cultures that exhibit a normal neuronal phenotype. We also observed apotent neuropreservatory effect of IVIG against ROS-mediated oxidative insults in these human fetal brain cultures. Theseresults indicate that IVIG treatment has great potential to preserve and protect primary human neuronal-enriched culturesand to potentially rescue dying neurons from oxidative insults. Therefore, our findings suggest that IVIG treatment mayrepresent an important therapeutic agent for clinical trials designed to prevent and delay the onset of neurodegeneration aswell as AD pathology.
Intravenous Immunoglobulin Reduces Tau Pathology and Preserves Neuroplastic Gene Expression in the 3xTg Mouse Model of Alzheimer`s Disease by Scott E. Counts, Sylvia E. Perez, Bin He, Elliott J. Mufson (655-663).
Despite recent negative results of the Gammaglobulin Alzheimer's Partnership (GAP) trial, the good tolerabilityto intravenous immunoglobulin (IVIG) and its potential benefit for patient subpopulations have highlighted the importanceof understanding IVIG's mechanism of action. IVIG contains antibodies to amyloid suggesting an amyloid clearancemechanism. However, the suboptimal results of the amyloid immunotherapy trials suggest an additional mechanism.Therefore, we tested whether IVIG alters the expression of tau neurofibrillary tangle (NFT)-like deposits within hippocampalCA1 neurons of the 3xTg mouse model of AD. Three-month-old mice were treated intravenously with IVIG(10%, 400 mg/kg) or placebo (10% BSA/saline) every two weeks for either three or six months. At sacrifice, plasma wasisolated for gene expression profiling and brains were processed for immunohistochemistry using the AT-180 antibody,which recognizes hyperphosphorylated tau in NFTs. Stereologic analysis of CA1 neurons following three months oftreatment revealed no difference in AT-180+ neuron number but a significant 15-20% decrease in AT-180 intraneuronaloptical density with IVIG compared to placebo. By contrast, the number of AT-180+ CA1 neurons was reduced by 25-30% following six months of IVIG treatment compared to placebo. Expression profiling studies showed that IVIG treatmentresulted in a significant 40-50% increase in plasma levels of genes regulating neuronal cytoskeletal plasticity functionand calcium-mediated signaling compared to placebo. Moreover, several transcripts encoding protein phosphatasesubunits were 40-50% higher in IVIG-treated mice. Hence, IVIG reduces hippocampal NFT pathology in the 3xTg mousethrough a mechanism that may involve preservation of neuronal plasticity and tau phosphorylation homeostasis.
Intraventricular Human Immunoglobulin Distributes Extensively but Fails to Modify Amyloid in a Mouse Model of Amyloid Deposition by Aurelie Joly-Amado, Milene Brownlow, Jacob Pierce, Advaitaa Ravipati, Erin Showalter, Qingyou Li, Marcia N Gordon, Dave Morgan (664-671).
Intravenous immunoglobulin infusions into Alzheimer patients have been found to provide cognitive benefitover a period of 6 mo in open label studies. One suggestion has been that these preparations contain small amounts of antibodiesdirected against monomeric and oligomeric A β which underlie their effectiveness in patients. To test this hypothesis,we infused Gammagard®, a version of intravenous immunoglobulin (IVIG), into the lateral ventricle of amyloidprecursor protein (APP) transgenic mice with pre-existing amyloid deposits. Mice were infused over 4 weeks, and testedbehaviorally for the last 2 weeks of treatment. Brains were analyzed for histopathology. We found widespread distributionof human-immunoglobulin G (h-IgG) staining in the mouse forebrain, including cerebral cortices and hippocampus. Somecortical neurons appeared to concentrate the h-IgG, but we did not detect evidence of amyloid plaque labeling by h-IgG.The IVIG-treated mice had no change in phenotype compared to saline-infused animals with respect to activity, learningand memory, or amyloid deposition. APP mice infused with an anti-A β monoclonal antibody did show some reduction inamyloid deposits. These data do not support the argument that anti-A β antibodies in IVIG preparations are responsible forcognitive benefits seen with these preparations.
Fluoxetine Improves Behavioral Performance by Suppressing the Production of Soluble β-Amyloid in APP/PS1 Mice by Junhui Wang, Yanbo Zhang, Haiyun Xu, Shenghua Zhu, Hongxing Wang, Jue He, Handi Zhang, Huining Guo, Jiming Kong, Qingjun Huang, Xin-Min Li (672-680).
Alzheimer's disease (AD) is the most common neurodegenerative disorder of the central nervous system. Currentapproaches for AD treatment only ameliorate symptoms. Therapeutic strategies that target the pathological processesof the disease remain elusive. Fluoxetine (FLX) is one of the most widely used antidepressants for the treatment of depressionand anxiety associated with AD, however, it is unknown if the drug affects the pathogenesis of the disease. Weshowed that FLX improved spatial memory, learning and emotional behaviors of APP/PS1 mice, a well characterizedmodel of AD. In the same mice, FLX effectively prevented the protein loss of synaptophysin (SYP) and microtubuleassociatedprotein 2 (MAP2). FLX was unable to prevent plaque formation, but significantly lowered high levels of solubleβ -amyloid (A β) in brain tissue, cerebrospinal fluid (CSF) and blood sera. FLX also effectively inhibited the phosphorylationof amyloid precursor protein (APP) at T668, which may be a possible mechanism of the reduced A β productionin APP/PS1 mouse after treatment.
Severe Psychiatric Disorders in Mid-Life and Risk of Dementia in Late- Life (Age 65-84 Years): A Population Based Case-Control Study by Renate R. Zilkens, David G. Bruce, Janine Duke, Katrina Spilsbury, James B. Semmens (681-693).
Objective: To examine the association of mid-life exposure to several psychiatric disorders with the developmentof late-life dementia. Methods: A matched case-control study using Western Australian state-wide hospital inpatient,outpatient mental health and emergency records linked to death records. Incident dementia cases (2000-2009) aged 65 to84 years were sex- and age-matched to an electoral roll control. Records as far back as 1970 were used to assess exposureto medical risk factors before age 65 years. Candidate psychiatric risk factors were required to be present at least 10 yearsbefore dementia onset to ensure direction of potential causality. Odds ratios were estimated using conditional logistic regression.Results: 13, 568 dementia cases (median age 78.7 years, 43.4 % male) were matched to a control. Depression,bipolar disorder, schizophrenia, anxiety disorder and alcohol dependence were found to be significant and independentrisk factors for late-life dementia after adjusting for diabetes, heart disease, cerebrovascular disease and smoking risk factors.The effect of a history of depression, schizophrenia and alcohol dependency on dementia risk varied with age, beingstrongest for earlier onset late-life dementia and waning at older ages. Conclusion: Severe depression, anxiety disorder,bipolar disorder, schizophrenia and alcoholic dependency disorder treated by specialists in psychiatric facilities in mid-lifeare important risk factors for late-life dementia. These psychiatric conditions need to be considered in future studies of therisk and prevention of late-life dementia.
Metabotropic Glutamate Receptor 5 in Down's Syndrome Hippocampus During Development: Increased Expression in Astrocytes by A.M. Iyer, J. van Scheppingen, I. Milenkovic, J.J. Anink, D. Lim, A.A. Genazzani, H. Adle-Biassette, G. G. Kovacs, E. Aronica (694-705).
Metabotropic glutamate receptor 5 (mGluR5) is highly expressed throughout the forebrain and hippocampus.Several lines of evidence support the role of this receptor in brain development and developmental disorders, as well as inneurodegenerative disorders like Alzheimer's disease (AD). In the present study, the expression pattern of mGluR5 wasinvestigated by immunocytochemistry in the developing hippocampus from patients with Down's syndrome (DS) and inadults with DS and AD. mGluR5 was expressed in developing human hippocampus from the earliest stages tested (9 gestationalweeks), with strong expression in the ventricular/subventricular zones. We observed a consistent similar temporaland spatial neuronal pattern of expression in DS hippocampus. However, in DS we detected increased prenatal mGluR5expression in white matter astrocytes, which persisted postnatally. In addition, in adult DS patients with widespread ADassociatedneurodegeneration (DS-AD) increased mGluR5 expression was detected in astrocytes around amyloid plaque.In vitro data confirm the existence of a modulatory crosstalk between amyloid-β and mGluR5 in human astrocytes. Thesefindings demonstrate a developmental regulation of mGluR5 in human hippocampus and suggest a role for this receptor inastrocytes during early development in DS hippocampus, as well as a potential contribution to the pathogenesis of ADassociatedpathology.
Bone Loss and Osteoporosis are Associated with Conversion from Mild Cognitive Impairment to Alzheimerµs Disease by Rui Zhou, Huadong Zhou, Li Rui, Jianzhong Xu (706-713).
Objective: The aim of this study was to analyze the relationship between low bone mineral density (BMD) andconversion from mild cognitive impairment (MCI) to Alzheimer's disease (AD) dementia in a Chinese cohort. Methods:Men and women (n=946) aged 60-75 underwent a dual X-ray absorptiometry (DXA) study of the lumbar spine and hipand were followed annually for 5 years. Their cognitive and functional status were assessed using the Chinese version ofthe Mini-Mental State Examination (MMSE) and an assessment of the instrumental activities of daily living (ADL). Results:There was a positive relationship between osteoporosis and a decline in cognition and function (P<0.001) based onMMSE and ADL scores. The subjects with BMD values in the lowest quartile had a 2-fold increased risk of AD conversioncompared with the controls. These results suggest that severe BMD loss is associated with an increased risk of ADconversion in both women and men. Conclusions: Osteoporosis was associated with an increased risk of incident AD dementia.Additionally, low BMD at baseline was associated with an increased risk of AD in both women and men.
CHF5074 Protects SH-SY5Y Human Neuronal-like Cells from Amyloidbeta 25-35 and Tumor Necrosis Factor Related Apoptosis Inducing Ligand Toxicity In Vitro by Nicole Ronsisvalle, Giulia Di Benedetto, Carmela Parenti, Salvatore Amoroso, Renato Bernardini, Giuseppina Cantarella (714-724).
Alzheimer's disease (AD) is contributed by multiple pathogenic causes. The anomalous protein amyloid- β (Aβ )is regarded as a pivotal factor in AD, and originates from enzymatic cleavage of a precursor protein by the secretase family.1-(3',4'-Dichloro-2-fluoro[1,1'-biphenyl]-4-yl)-cyclopropanecarboxylic acid (CHF5074) is a non-steroidal antiinflammatoryderivative able to inhibit A β deposition in the brain of transgenic mouse models of AD. The proapoptoticcytokine TRAIL has been reported to mediate Aβ -dependent neurotoxicity. Here, the effects of CHF5074 on A β25-35-triggered TRAIL toxicity were evaluated in the differentiated human neuroblastoma cell line SH-SY5Y in vitro. Cellswere pre-treated 1h with CHF5074 at graded concentrations (range: 1 nM-1uM) and then challenged for 72 h with eitherAβ 25-35 or TRAIL. Results show that CHF5074 treatment prevented apoptotic death in SH-SY5Y cell line in a concentration-dependent fashion. Its maximally active concentration was 10 nM. Then, investigation of related molecular mechanismsunderlying such protective effect of CHF5074 suggested that the levels of caspases, as well as of various kinases,including stress and MAP kinases, are modulated by CHF5074. Finally, treatment of injured human neuroblastoma cellline SH-SY5Y with CHF5074 resulted in prominent protection from apoptotic death. The bulk of these data suggest thatCHF5074 represents a potential candidate for pharmacological neuroprotective treatment in neurodegenerative disorders.