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Tauopathies, including frontotemporal dementia (FTD) and Alzheimer’s disease (AD) are progressive neurodegenerative diseases clinically characterized by cognitive decline and could be caused by the aggregation of hyperphosphorylated pathological tau (pTau) as neurofibrillary tangles (NFTs) inside neurons. There is currently no FDA-approved treatment that cures, slows or prevents tauopathies. Current immunotherapy strategies targeting pTau have generated encouraging data but may pose concerns about scalability, affordability, and efficacy. Here, we engineered a virus-like particle (VLP)-based vaccine in which tau peptide, phosphorylated at threonine 181, was linked at high valency to Qß bacteriophage VLPs (pT181-Qß). We demonstrate that vaccination with pT181-Qß is sufficient to induce a robust and long-lived anti-pT181 antibody response in the sera and the brains of both Non-Tg and rTg4510 mice. Only sera from pT181-Qß vaccinated mice are reactive to classical somatodendritic pTau in human FTD and AD post-mortem brain sections. Finally, we demonstrate that pT181-Qß vaccination reduces both soluble and insoluble species of hyperphosphorylated pTau in the hippocampus and cortex, avoids a Th1-mediated pro-inflammatory cell response, prevents hippocampal and corpus callosum atrophy and rescues cognitive dysfunction in a 4-month-old rTg4510 mouse model of FTD. These studies provide a valid scientific premise for the development of VLP-based immunotherapy to target pTau and potentially prevent Alzheimer’s diseases and related tauopathies., Tauopathies: Active vaccination of mouse tauopathy Tauopathies such as fronto-temporal dementia or Alzheimer’s disease are characterized by the accumulation of phosphorylated Tau (pTau) protein into pathogenic neurofibrillary tangles (NFT). Kiran Bhaskar and colleagues at the University of New Mexico investigate the efficacy of an active vaccine approach in the treatment of rTg4510 mice—an aggressive model of tauopathy. Mice receive 3 intramuscular doses of a disease-relevant pTau peptide (pT181) multivalently conjugated to an immunostimulatory bacteriophage virus-like particle (pT181-Qß). Vaccination induces high titers of anti-pTau—stable to at least 20 weeks—that is also able to bind human disease samples, but importantly does not react to unphosphorylated physiological Tau protein. Antibody can enter the brain and bind both soluble and intraneuronal pTau. Vaccination of mice reduces brain NFT, pathology, indicators of neuroinflammation and improves cognitive function in two different models of memory.

Pathological aggregation of tau (pTau) and neuroinflammation, driven by interleukin-1β (IL-1β), are the major hallmarks of tauopathies. Here, we show that pTau primes and activates IL-1s. First, pTau burden correlates with increased IL-1β and inflammasome proteins (NLRP3 and ASC) in autopsy brains of human tauopathies. Suppression of human tau blocks both priming and activation of ASC and NLRP3 in the rTg4510 mouse model of tauopathy. Treating microglia with pTau-containing neuronal media, exosomes or purified tau tangles from human tauopathy brains causes IL-1β activation, which is NLRP3, ASC, and caspase-1-dependent. While the microglia-restricted deletion of a common innate immune adaptor protein, MyD88 prevents both IL-1β expression and activation in the hTau mouse model of tauopathy, genetic deficiency of ASC within microglia reduces pTau-induced IL-1β activation and improves cognitive function in the hTau mice. Together, our results suggest that pTau activates IL-1β via MyD88- and NLRP3-ASC-dependent pathways and lead to neuroinflammation in tauopathies.

SUMMARY Pathological hyperphosphorylation and aggregation of tau (pTau) and neuroinflammation, driven by interleukin-1β (IL-1β), are the major hallmarks of tauopathies. Here, we show that pTau primes and activates IL-1β. First, RNA-sequence analysis suggests paired-helical filaments (PHFs) from human tauopathy brain primes nuclear factor κB (NF-κB), chemokine, and IL-1β signaling clusters in human primary microglia. Treating microglia with pTau-containing neuronal media, exosomes, or PHFs causes IL-1β activation, which is NLRP3, ASC, and caspase-1 dependent. Suppression of pTau or ASC reduces tau pathology and inflammasome activation in rTg4510 and hTau mice, respectively. Although the deletion of MyD88 prevents both IL-1β expression and activation in the hTau mouse model of tauopathy, ASC deficiency in myeloid cells reduces pTau-induced IL-1β activation and improves cognitive function in hTau mice. Finally, pTau burden co-exists with elevated IL-1β and ASC in autopsy brains of human tauopathies. Together, our results suggest pTau activates IL-1β via MyD88- and NLRP3-ASC-dependent pathways in myeloid cells, including microglia., Graphical Abstract, In brief Jiang et al. show pathological tau primes and activates interleukin-1β in microglia via MyD88-, NLRP3-, and ASC-dependent pathways. Suppressing tau, MyD88, or ASC reduces tau pathology and inflammasome activation and improves cognitive function in the hTau mice. Tau burden co-exists with elevated IL-1β and ASC in human tauopathy brains.

Background Fractalkine (CX3CL1) and its receptor (CX3CR1) play an important role in regulating microglial function. We have previously shown that Cx 3 cr1 deficiency exacerbated tau pathology and led to cognitive impairment. However, it is still unclear if the chemokine domain of the ligand CX3CL1 is essential in regulating neuronal tau pathology. Methods We used transgenic mice lacking endogenous Cx 3 cl1 (Cx 3 cl1 −/−) and expressing only obligatory soluble form (with only chemokine domain) and lacking the mucin stalk of CX3CL1 (referred to as Cx 3 cl1 105Δ mice) to assess tau pathology and behavioral function in both lipopolysaccharide (LPS) and genetic (hTau) mouse models of tauopathy. Results First, increased basal tau levels accompanied microglial activation in Cx 3 cl1 105Δ mice compared to control groups. Second, increased CD45+ and F4/80+ neuroinflammation and tau phosphorylation were observed in LPS, hTau/Cx 3 cl1 −/−, and hTau/Cx 3 cl1 105Δ mouse models of tau pathology, which correlated with impaired spatial learning. Finally, microglial cell surface expression of CX3CR1 was reduced in Cx 3 cl1 105Δ mice, suggesting enhanced fractalkine receptor internalization (mimicking Cx 3 cr1 deletion), which likely contributes to the elevated tau pathology. Conclusions Collectively, our data suggest that overexpression of only chemokine domain of CX3CL1 does not protect against tau pathology.

BACKGROUND: Hypertension-induced microvascular brain injury is a major vascular contributor to cognitive im-pairment and dementia. We hypothesized that chronic hypoxia promotes the hyperphosphorylation of tau and cell death in an accelerated spontaneously hypertensive stroke prone rat model of vascular cognitive impairment. METHODS: Hypertensive male rats (n = 13) were fed a high salt, low protein Japanese permissive diet and were compared to Wistar Kyoto control rats (n = 5). RESULTS: Using electron paramagnetic resonance oximetry to measure in vivo tissue oxygen levels and magnetic resonance imaging to assess structural brain damage, we found compromised gray (dorsolateral cortex: p = .018) and white matter (corpus callosum: p = .016; external capsule: p = .049) structural integrity, reduced cerebral blood flow (dorsolateral cortex: p = .005; hippocampus: p < .001; corpus callosum: p = .001; external capsule: p < .001) and a significant drop in cortical oxygen levels (p < .05). Consistently, we found reduced oxygen carrying neuronal neuroglobin (p = .008), suggestive of chronic cerebral hypoperfusion in high salt-fed rats. We also observed a corresponding increase in free radicals (NADPH oxidase: p = .013), p-Tau (pThr231) in dorsolateral cortex (p = .011) and hippocampus (p = .003), active interleukin-1β (p < .001) and neurode generation (dorsolateral cortex: p = .043, hippocampus: p = .044). Human patients with subcortical ischemic vascular disease, a type of vascular dementia (n = 38; mean age = 68; male/female ratio = 23/15) showed reduced hippocampal volumes and cortical shrinking (p < .05) consistent with the neuronal cell death observed in our hypertensive rat model as compared to healthy controls (n = 47; mean age = 63; male/female ratio = 18/29). CONCLUSIONS: Our data support an association between hypertension-induced vascular dysfunction and the sporadic occurrence of phosphorylated tau and cell death in the rat model, correlating with patient brain atrophy, which is relevant to vascular disease.

Pathological aggregation of tau is a hallmark of Alzheimer's disease and related tauopathies. We have previously shown that the deficiency of the microglial fractalkine receptor (CX3CR1) led to the acceleration of tau pathology and memory impairment in an hTau mouse model of tauopathy. Here, we show that microglia drive tau pathology in a cell-autonomous manner. First, tau hyperphosphorylation and aggregation occur as early as 2 months of age in hTauCx3cr1(-/-) mice. Second, CD45(+) microglial activation correlates with the spatial memory deficit and spread of tau pathology in the anatomically connected regions of the hippocampus. Third, adoptive transfer of purified microglia derived from hTauCx3cr1(-/-) mice induces tau hyperphosphorylation within the brains of non-transgenic recipient mice. Finally, inclusion of interleukin 1 receptor antagonist (Kineret®) in the adoptive transfer inoculum significantly reduces microglia-induced tau pathology. Together, our results suggest that reactive microglia are sufficient to drive tau pathology and correlate with the spread of pathological tau in the brain.

Increasing evidence suggests that hyperphosphorylation and aggregation of microtubule-associated protein tau (MAPT or tau) correlates with the development of cognitive impairment in Alzheimer’s disease (AD) and related tauopathies. While numerous attempts have been made to model AD-relevant tau pathology in various animal models, there has been very limited success for these models to fully recapitulate the progression of disease as seen in human tauopathies. Here, we performed whole genome gene expression in a genomic mouse model of tauopathy that expressed human MAPT gene under the control of endogenous human MAPT promoter and also were complete knockout for endogenous mouse tau [referred to as ‘hTauMaptKO(Duke)′ mice]. First, whole genome expression analysis revealed 64 genes, which were differentially expressed (32 up-regulated and 32 down-regulated) in the hippocampus of 6-month-old hTauMaptKO(Duke) mice compared to age-matched non-transgenic controls. Genes relevant to neuronal function or neurological disease include up-regulated genes: PKC-alpha (Prkca), MECP2 (Mecp2), STRN4 (Strn4), SLC40a1 (Slc40a1), POLD2 (Pold2), PCSK2 (Pcsk2), and down-regulated genes: KRT12 (Krt12), LASS1 (Cers1), PLAT (Plat), and NRXN1 (Nrxn1). Second, network analysis suggested anatomical structure development, cellular metabolic process, cell death, signal transduction, and stress response were significantly altered biological processes in the hTauMaptKO(Duke) mice as compared to age-matched non-transgenic controls. Further characterization of a sub-group of significantly altered genes revealed elevated phosphorylation of MECP2 (methyl-CpG-binding protein-2), which binds to methylated CpGs and associates with chromatin, in hTauMaptKO(Duke) mice compared to age-matched controls. Third, phoshpho-MECP2 was elevated in autopsy brain samples from human AD compared to healthy controls. Finally, siRNA-mediated knockdown of MECP2 in human tau expressing N2a cells resulted in a significant decrease in total and phosphorylated tau. Together, these results suggest that MECP2 is a potential novel regulator of tau pathology relevant to AD and tauopathies.

Neuroinflammation is one of the neuropathological hallmarks of Alzheimer's disease (AD) and related tauopathies. Activated microglia spatially coexist with microtubule-associated protein tau (Mapt or tau)-burdened neurons in the brains of human AD and non-AD tauopathies. Numerous studies have suggested that neuroinflammation precedes tau pathology and that induction or blockage of neuroinflammation via lipopolysaccharide (LPS) or anti-inflammatory compounds (such as FK506) accelerate or block tau pathology, respectively in several animal models of tauopathy. We have previously demonstrated that microglia-mediated neuroinflammation via deficiency of the microglia-specific chemokine (fractalkine) receptor, CX3CR1, promotes tau pathology and neurodegeneration in a mouse model of LPS-induced systemic inflammation. Here, we demonstrate that tau mediates the neurotoxic effects of LPS in Cx3cr1 (-/-) mice. First, Mapt (+/+) neurons displayed elevated levels of Annexin V (A5) and TUNEL (markers of neurodegeneration) when co-cultured with LPS-treated Cx3cr1 (-/-)microglia, which is rescued in Mapt (-/-) neurons. Second, a neuronal population positive for phospho-S199 (AT8) tau in the dentate gyrus is also positive for activated or cleaved caspase (CC3) in the LPS-treated Cx3cr1 (-/-) mice. Third, genetic deficiency for tau in Cx3cr1 (-/-) mice resulted in reduced microglial activation, altered expression of inflammatory genes and a significant reduction in the number of neurons positive for CC3 compared to Cx3cr1 (-/-)mice. Finally, Cx3cr1 (-/-)mice exposed to LPS displayed a lack of inhibition in an open field exploratory behavioral test, which is rescued by tau deficiency. Taken together, our results suggest that pathological alterations in tau mediate inflammation-induced neurotoxicity and that deficiency of Mapt is neuroprotective. Thus, therapeutic approaches toward either reducing tau levels or blocking neuroinflammatory pathways may serve as a potential strategy in treating tauopathies.

Massive neuronal loss is a key pathological hallmark of Alzheimer's disease (AD). However, the mechanisms are still unclear. Here we demonstrate that neuroinflammation, cell autonomous to microglia, is capable of inducing neuronal cell cycle events (CCEs), which are toxic for terminally differentiated neurons. First, oligomeric amyloid-beta peptide (AβO)-mediated microglial activation induced neuronal CCEs via the tumor-necrosis factor-α (TNFα) and the c-Jun Kinase (JNK) signaling pathway. Second, adoptive transfer of CD11b+ microglia from AD transgenic mice (R1.40) induced neuronal cyclin D1 expression via TNFα signaling pathway. Third, genetic deficiency of TNFα in R1.40 mice (R1.40-Tnfα(-/-)) failed to induce neuronal CCEs. Finally, the mitotically active neurons spatially co-exist with F4/80+ activated microglia in the human AD brain and that a portion of these neurons are apoptotic. Together our data suggest a cell-autonomous role of microglia, and identify TNFα as the responsible cytokine, in promoting neuronal CCEs in the pathogenesis of AD.

Improved fluorescent detection of amyloid protein aggregates would accelerate research into the biology of amyloid formation, implicated in Alzheimer's and Parkinson's diseases, among other neurodegenerative conditions. We report the development of a fluorescent sensor OPE1 for amyloids, competent for one- and two-photon imaging, with a strong binding-activated increase in emission based on formation of superluminescent J aggregates and dequenching in a hydrophobic environment. OPE1 stains neurofibrillary tangles and beta-amyloid plaques with low background in murine and human brain tissue, and detects a wide variety of in vitro-formed amyloid aggregates. Unlike conventional sensors such as thioflavin T, OPE1 exhibits static quenching in water based on interactions with chromophore-attached ethyl ester moieties as well as a propensity to form highly emissive J-type aggregates. We provide evidence that both these mechanisms are at work in the large increase in fluorescence intensity observed for OPE1 with amyloid fibrils. We hope that these novel mechanisms will lead to the development of improved self-assembling fluorescent probes for amyloid and other relevant analytes.

Background Tangle pathology (hyperphosphorylated and aggregation of tau) is a major neuropathological hallmark of Alzheimer’s disease (AD) and related tauopathies. Increasing evidence suggests that inflammatory processes in the brain precede tau pathology. A previous study from our group has demonstrated that enhancing neuroinflammation either via a Toll-Like Receptor-4 (TLR-4) ligand lipopolysaccharide (LPS) or genetic ablation of the Cx3cr1 (fractalkine receptor) led to increased tau phosphorylation, aggregation and working memory impairment in a manner dependent upon the activation of interleukin-1 receptor (IL-1R)-p38 mitogen activated protein kinase (p38 MAPK) pathway. Aims and methods To block IL-1R and TLR-4 receptor signaling, we targeted and performed cell-specific deletion of MyD88 – a common adapter protein of IL-1 and TLR-4 receptors using Cre-LoxP technology. Results and conclusions First, in contrast to what was expected, microglia-restricted deletion of MyD88 (in CD11bCreMyD88f/fmice) led to enhanced AT8- and AT180-site tau phosphorylation. Notably, this effect was exacerbated upon LPS administration, suggesting the MyD88 may be required for homeostasis of tau. Second, infiltration of CD45 + peripheral monocytes was increased within the brains of CD11bCreMyD88f/f mice compared to MyD88f/f mice. Third, gene expression analysis comparing the CD11bCreMyD88f/f to MyD88f/f suggested alterations in key inflammatory cytokines. Finally, neuronal-restricted deletion of MyD88 in hTau mouse model of tauopathy (hTau-Mapt−/−/CamKII α CreMyD88f/f) showed drastic reduction in the levels of truncated neurotoxic tau in the cortex of hTauMapt−/−/CamKII α CreMyD88f/f mice compared to hTauMapt−/− mice, suggesting neuron-restricted deletion of MyD88 is neuroprotective. Further studies on the characterization of truncated tau species and the effect of hTau on microglia-restricted (CD11b) deletion of MyD88 on tangle pathology and cognitive function are ongoing.

Introduction Massive neuronal loss is the prominent pathological hallmark feature of Alzheimer’s disease (AD). One of the ways post-mitotic neurons die is via their ectopic entry into cell-cycle, which often occurs at very early stages of the disease [1] . We have previously demonstrated occurrence of neuronal cell cycle events (CCEs) in a transgenic mouse model of AD (R1.40) similar to those occur in human AD [1] . Furthermore, these events were dependent upon amyloidogenic processing of amyloid-precursor protein [2] , precede deposition of senile plaques and coincide with elevated neuroinflammation. While we have also demonstrated that Tool-Like Receptor-4 (TLR4) mediated induction of neuroinflammation accelerated neuronal CCEs, and blocking inflammation via NSAIDs completely blocked neuronal CCEs and reduced microglial activation [3] , the source of neuroinflammation and molecular mechanisms for the induction of neuronal CCEs is unclear. Methods We utilized following methods: immunohistochemistry, purification and adoptive transfer of microglia, primary neurons and microglial cultures and generation and analysis of R1.40- Tnf α −/− mice. Results Here we demonstrate that neuroinflammation, cell autonomous to microglia, is capable of inducing neuronal CCEs. First, CD45+ microglia is present at six months of age in the affected region of R1.40 mouse brain and increases with age. Second, the F4/80+ microglia spatially co-exist with cyclin D1+ neurons in the temporal cortex of human AD brain. Notably, these cyclin D1+ neurons in the human brain are also TUNEL positive, suggesting that a portion of them is apoptotic. Third, purification and adoptive transfer of CD11b+ microglia derived form R1.40, but not from non-transgenic mice, was sufficient to induce cyclin D1 expression within the neurons of non-transgenic recipient mouse brain. Fourth, conditioned media (CM) derived from amyloid beta activated primary microglia significantly induced dose-dependent increase in DNA replication within primary cortical neurons and strongly correlated with increased levels of tumor-necrosis factor-α(TNFα) in the CM. Notably, blocking or activating TNFα pathway either via anti-TNFα antibody or recombinant human TNFα, significantly induced cyclin D1 expression and/or DNA replication in in vitro as well as in adoptive transfer studies. Generation of R1.40 mice deficient for TNFα (R1.40- Tnfa −/− ) displayed decreased microglial activation and showed significantly lower levels of cyclin D1+ neurons at six months of age. Finally, analysis of downstream molecules of TNFα receptor pathway suggested that neuronal CCEs is mediated via activation of JNK signaling pathway. Conclusion Together, our results provide first direct evidence that the neuroinflammation, cell-autonomous to microglia, induces AD-related neuronal CCEs and neurodegeneration via alteration of TNFR-MAPK signaling pathway.

PURPOSE. To determine the molecular basis and the pathologic consequences of a chemically induced mutation in a mouse model of photoreceptor degeneration, nmf240. METHODS. Mice from a G3 N-ethyl-N-nitrosourea mutagenesis program were screened by indirect ophthalmoscopy for abnormal fundi. A chromosomal position for the recessive nmf240 mutation was determined by a genome-wide linkage analysis by use of simple sequence length polymorphic markers in an F2 intercross. The critical region was refined, and candidate genes were screened by direct sequencing. The nmf240 phenotype was characterized by histologic analysis of the retina, brain, and male reproductive organs and by electroretinogram (ERG)-based studies of the retina and retinal pigment epithelium (RPE). RESULTS. Clinically, homozygous nmf240 mutants exhibit a grainy retina that progresses to panretinal patches of depigmentation. The mutation was localized to a region on chromosome 16 containing Clcn2, a gene associated with retinal degeneration. Sequencing identified a missense C-T mutation at nucleotide 1063 in Clcn2 that converts a glutamine to a stop codon. Mice homozygous for the Clcn2 nmf240 mutation experience a severe loss of photoreceptor cells at 14 days of age that is preceded by an elongation of RPE apical microvilli. Homozygous mutants also experience leukoencephalopathy in multiple brain areas and male sterility. Despite a normal retinal histology in nmf240 heterozygotes, the ERG light peak, generated by the RPE, is reduced. CONCLUSIONS. The nmf240 phenotype closely resembles that reported for Clcn2 knockout mice. The observation that heterozygous nmf240 mice present with a reduced ERG light peak component suggests that CLCN2 is necessary for the generation of this response component. (Invest Ophthalmol Vis Sci. 2010;51:3264‐3272) DOI:10.1167/iovs.09-4887

Background Hyperphosphorylation and aggregation of tau protein are the pathological hallmarks of Alzheimer’s disease and related tauopathies. We previously demonstrated that the microglial activation induces tau hyperphosphorylation and cognitive impairment via activation of p38 mitogen-activated protein kinase (p38 MAPK) in the hTau mouse model of tauopathy that was deficient for microglial fractalkine receptor CX3CR1. Method We report an isoform-selective, brain-permeable, and orally bioavailable small molecule inhibitor of p38α MAPK (MW181) and its effects on tau phosphorylation in vitro and in hTau mice. Results First, pretreatment of mouse primary cortical neurons with MW181 completely blocked inflammation-induced p38α MAPK activation and AT8 (pS199/pS202) site tau phosphorylation, with the maximum effect peaking at 60–90 min after stimulation. Second, treatment of old (~20 months of age) hTau mice with MW181 (1 mg/kg body weight; 14 days via oral gavage) significantly reduced p38α MAPK activation compared with vehicle-administered hTau mice. This also resulted in a significant reduction in AT180 (pT231) site tau phosphorylation and Sarkosyl-insoluble tau aggregates. Third, MW181 treatment significantly increased synaptophysin protein expression and resulted in improved working memory. Fourth, MW181 administration reduced phosphorylated MAPK-activated protein kinase 2 (pMK2) and phosphorylated activating transcription factor 2 (pATF2), which are known substrates of p38α MAPK. Finally, MW181 reduced the expression of interferon-γ and interleukin-1β. Conclusions Taken together, these studies support p38α MAPK as a valid therapeutic target for the treatment of tauopathies.