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INTRODUCTION: Triggering receptor expressed on myeloid cells 2 (TREM2) agonists are being clinically evaluated as disease-modifying therapeutics for Alzheimer's disease. Clinically translatable pharmacodynamic (PD) biomarkers are needed to confirm drug activity and select the appropriate therapeutic dose in clinical trials. METHODS: We conducted multi-omic analyses on paired non-human primate brain and cerebrospinal fluid (CSF), and stimulation of human induced pluripotent stem cell-derived microglia cultures after TREM2 agonist treatment, followed by validation of candidate fluid PD biomarkers using immunoassays. We immunostained microglia to characterize proliferation and clustering. RESULTS: We report CSF soluble TREM2 (sTREM2) and CSF chitinase-3-like protein 1 (CHI3L1/YKL-40) as PD biomarkers for the TREM2 agonist hPara.09. The respective reduction of sTREM2 and elevation of CHI3L1 in brain and CSF after TREM2 agonist treatment correlated with transient microglia proliferation and clustering. DISCUSSION: CSF CHI3L1 and sTREM2 reflect microglial TREM2 agonism and can be used as clinical PD biomarkers to monitor TREM2 activity in the brain. HIGHLIGHTS: CSF soluble triggering receptor expressed on myeloid cells 2 (sTREM2) reflects brain target engagement for a novel TREM2 agonist, hPara.09. CSF chitinase-3-like protein 1 reflects microglial TREM2 agonism. Both can be used as clinical fluid biomarkers to monitor TREM2 activity in brain.
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Chronic kidney disease (CKD) is characterized by inflammation and fibrosis in the kidney. Renal biopsies and estimated glomerular filtration rate (eGFR) remain the standard of care, but these endpoints have limitations in detecting the stage, progression, and spatial distribution of fibrotic pathology in the kidney. MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo both in clinical and preclinical studies. However, these imaging studies have not systematically identified fibrosis particularly deeper in the kidney where biopsy sampling is limited, or completed an extensive analysis of whole organ histology, blood biomarkers, and gene expression to evaluate the relative strengths and weaknesses of MRI for evaluating renal fibrosis. In this study, we performed DTI in the sodium oxalate mouse model of CKD. The DTI parameters fractional anisotropy, apparent diffusion coefficient, and axial diffusivity were compared between the control and oxalate groups with region of interest (ROI) analysis to determine changes in the cortex and medulla. In addition, voxel-based analysis (VBA) was implemented to systematically identify local regions of injury over the whole kidney. DTI parameters were found to be significantly different in the medulla by both ROI analysis and VBA, which also spatially matched with collagen III immunohistochemistry (IHC). The DTI parameters in this medullary region exhibited moderate to strong correlations with histology, blood biomarkers, hydroxyproline, and gene expression. Our results thus highlight the sensitivity of DTI to the heterogeneity of renal fibrosis and importance of whole kidney noninvasive imaging.NEW & NOTEWORTHY Chronic kidney disease (CKD) can be characterized by inflammation and fibrosis of the kidney. Although standard of care methods have been limited in scope, safety, and spatial distribution, MRI diffusion tensor imaging (DTI) has emerged as a promising noninvasive technology to evaluate renal fibrosis in vivo. In this study, we performed DTI in an oxalate mouse model of CKD to systematically identify local kidney injury. DTI parameters strongly correlated with histology, blood biomarkers, hydroxyproline, and gene expression.
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Imagen de Difusión Tensora , Modelos Animales de Enfermedad , Fibrosis , Ratones Endogámicos C57BL , Insuficiencia Renal Crónica , Animales , Insuficiencia Renal Crónica/patología , Insuficiencia Renal Crónica/diagnóstico por imagen , Masculino , Oxalatos/metabolismo , Riñón/patología , Riñón/diagnóstico por imagen , Riñón/metabolismo , RatonesRESUMEN
Human genetics and preclinical studies have identified key contributions of TREM2 to several neurodegenerative conditions, inspiring efforts to modulate TREM2 therapeutically. Here, we characterize the activities of three TREM2 agonist antibodies in multiple mixed-sex mouse models of Alzheimer's disease (AD) pathology and remyelination. Receptor activation and downstream signaling are explored in vitro, and active dose ranges are determined in vivo based on pharmacodynamic responses from microglia. For mice bearing amyloid-ß (Aß) pathology (PS2APP) or combined Aß and tau pathology (TauPS2APP), chronic TREM2 agonist antibody treatment had limited impact on microglia engagement with pathology, overall pathology burden, or downstream neuronal damage. For mice with demyelinating injuries triggered acutely with lysolecithin, TREM2 agonist antibodies unexpectedly disrupted injury resolution. Likewise, TREM2 agonist antibodies limited myelin recovery for mice experiencing chronic demyelination from cuprizone. We highlight the contributions of dose timing and frequency across models. These results introduce important considerations for future TREM2-targeting approaches.
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Enfermedad de Alzheimer , Glicoproteínas de Membrana , Microglía , Esclerosis Múltiple , Receptores Inmunológicos , Animales , Receptores Inmunológicos/agonistas , Receptores Inmunológicos/metabolismo , Receptores Inmunológicos/genética , Glicoproteínas de Membrana/agonistas , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/metabolismo , Ratones , Esclerosis Múltiple/tratamiento farmacológico , Esclerosis Múltiple/inmunología , Femenino , Masculino , Microglía/efectos de los fármacos , Microglía/metabolismo , Modelos Animales de Enfermedad , Ratones Endogámicos C57BL , Ratones Transgénicos , Anticuerpos/farmacología , Humanos , Péptidos beta-Amiloides/metabolismo , Proteínas tau/metabolismoRESUMEN
BACKGROUND: Understanding patterns of association between CSF phosphorylated tau (p-tau) species and clinical disease severity will aid Alzheimer's disease (AD) diagnosis and treatment. OBJECTIVE: To evaluate changes in tau phosphorylation ratios to brain imaging (amyloid PET, [18F]GTP1 PET, and MRI) and cognition across clinical stages of AD in two different cohorts. METHODS: A mass spectrometry (MS)-based method was used to evaluate the relationship between p-tau/tau phosphorylation ratios on 11 sites in CSF and AD pathology measured by tau PET ([18F]GTP1) and amyloid PET ([18F]florbetapir or [18F]florbetaben). Cohort A included cognitively normal amyloid negative (nâ=â6) and positive (nâ=â5) individuals, and amyloid positive prodromal (nâ=â13), mild (nâ=â12), and moderate AD patients (nâ=â10); and Cohort B included amyloid positive prodromal (nâ=â24) and mild (nâ=â40) AD patients. RESULTS: In this cross-sectional analysis, we identified clusters of phosphosites with different profiles of phosphorylation ratios across stages of disease. Eight of 11 investigated sites were hyperphosphorylated and associated with SUVR measures from [18F]GTP1 and amyloid PET. Novel sites 111, 153, and 208 may be relevant biomarkers for AD diagnosis to complement tau hyperphosphorylation measures on previously established sites 181, 205, 217, and 231. Hypophosphorylation was detected on residues 175, 199, and 202, and was inversely associated with [18F]GTP1 and amyloid PET. CONCLUSION: Hyperphosphorylated and hypophosphorylated forms of tau are associated with AD pathologies, and due to their different site-specific profiles, they may be used in combination to assist with staging of disease.
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Enfermedad de Alzheimer/líquido cefalorraquídeo , Enfermedad de Alzheimer/patología , Encéfalo/patología , Tomografía de Emisión de Positrones , Proteínas tau/líquido cefalorraquídeo , Anciano , Enfermedad de Alzheimer/diagnóstico por imagen , Biomarcadores/líquido cefalorraquídeo , Encéfalo/diagnóstico por imagen , Cognición , Estudios Transversales , Femenino , Radioisótopos de Flúor/metabolismo , Humanos , Masculino , Espectrometría de Masas , Persona de Mediana Edad , Radiofármacos/metabolismoRESUMEN
BACKGROUND: The role and implementation of tau PET imaging for predicting subsequent cognitive decline in Alzheimer's disease (AD) remains uncertain. This study was designed to evaluate the relationship between baseline [18F]GTP1 tau PET and subsequent longitudinal change across multiple cognitive measures over 18 months. METHODS: Our analyses incorporated data from 67 participants, including cognitively normal controls (n = 10) and ß-amyloid (Aß)-positive individuals ([18F] florbetapir Aß PET) with prodromal (n = 26), mild (n = 16), or moderate (n = 15) AD. Baseline measurements included cortical volume (MRI), tau burden ([18F]GTP1 tau PET), and cognitive assessments [Mini-Mental State Examination (MMSE), Clinical Dementia Rating (CDR), 13-item version of the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog13), and Repeatable Battery for the Assessment of Neuropsychological Status (RBANS)]. Cognitive assessments were repeated at 6-month intervals over an 18-month period. Associations between baseline [18F]GTP1 tau PET indices and longitudinal cognitive performance were assessed via univariate (Spearman correlations) and multivariate (linear mixed effects models) approaches. The utility of potential prognostic tau PET cut points was assessed with ROC curves. RESULTS: Univariate analyses indicated that greater baseline [18F]GTP1 tau PET signal was associated with faster rates of subsequent decline on the MMSE, CDR, and ADAS-Cog13 across regions of interest (ROIs). In multivariate analyses adjusted for baseline age, cognitive performance, cortical volume, and Aß PET SUVR, the prognostic performance of [18F]GTP1 SUVR was most robust in the whole cortical gray ROI. When AD participants were dichotomized into low versus high tau subgroups based on baseline [18F]GTP1 PET standardized uptake value ratios (SUVR) in the temporal (cutoff = 1.325) or whole cortical gray (cutoff = 1.245) ROIs, high tau subgroups demonstrated significantly more decline on the MMSE, CDR, and ADAS-Cog13. CONCLUSIONS: Our results suggest that [18F]GTP1 tau PET represents a prognostic biomarker in AD and are consistent with data from other tau PET tracers. Tau PET imaging may have utility for identifying AD patients at risk for more rapid cognitive decline and for stratification and/or enrichment of participant selection in AD clinical trials. Trial registration ClinicalTrials.gov NCT02640092 . Registered on December 28, 2015.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Enfermedad de Alzheimer/diagnóstico por imagen , Enfermedad de Alzheimer/psicología , Péptidos beta-Amiloides , Disfunción Cognitiva/diagnóstico por imagen , Disfunción Cognitiva/psicología , Humanos , Tomografía de Emisión de Positrones/métodos , Proteínas tauRESUMEN
BACKGROUND AND PURPOSE: Develop a translational assay of Transient Receptor Potential Ankyrin 1 (TRPA1) activity for use as a preclinical and clinical biomarker. EXPERIMENTAL APPROACH: Allyl isothiocyanate (AITC), capsaicin or citric acid were applied to ears of wildtype and Trpa1-knock out (Trpa1 KO) rats, and changes in dermal blood flow (DBF) were measured by laser speckle contrast imaging. In humans, the DBF, pain and itch responses to 5-20% AITC applied to the forearm were measured and safety was evaluated. Reproducibility of the DBF, pain and itch responses to topically applied 10% and 15% AITC were assessed at two visits separated by 13-15 days. DBF changes were summarized at 5-minute intervals as areas under the curve (AUC) and maxima. Intraclass correlation coefficient (ICC) was calculated to assess arm-arm and period-period reproducibility. KEY RESULTS: AITC- and citric acid-induced DBF were significantly reduced in Trpa1 KO rats compared to wildtype (90 ± 2% and 65 ± 11% reduction, respectively), whereas capsaicin response did not differ. In humans, each AITC concentration significantly increased DBF compared to vehicle with the maximal increase occurring 5 minutes post application. Ten percent and 15% AITC were selected as safe and effective stimuli. AUC from 0 to 5 minutes was the most reproducible metric of AITC-induced DBF across arms (ICC = 0.92) and periods (ICC = 0.85). Subject-reported pain was more reproducible than itch across visits (ICC = 0.76 vs 0.17, respectively). CONCLUSION AND IMPLICATIONS: AITC-induced DBF is a suitable target engagement biomarker of TRPA1 activity for preclinical and clinical studies of TRPA1 antagonists.
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Roedores , Animales , Biomarcadores , Humanos , Isotiocianatos , Ratas , Reproducibilidad de los Resultados , Canal Catiónico TRPA1RESUMEN
Vascular leakage, or edema, is a serious complication of acute allergic reactions. Vascular leakage is triggered by the release of histamine and serotonin from granules within tissue-resident mast cells. Here, we show that expression of Neutrophil Serine Protease 4 (NSP4) during the early stages of mast cell development regulates mast cell-mediated vascular leakage. In myeloid precursors, the granulocyte-macrophage progenitors (GMPs), loss of NSP4 results in the decrease of cellular levels of histamine, serotonin and heparin/heparan sulfate. Mast cells that are derived from NSP4-deficient GMPs have abnormal secretory granule morphology and a sustained reduction in histamine and serotonin levels. Consequently, in passive cutaneous anaphylaxis and acute arthritis models, mast cell-mediated vascular leakage in the skin and joints is substantially reduced in NSP4-deficient mice. Our findings reveal that NSP4 is required for the proper storage of vasoactive amines in mast cell granules, which impacts mast cell-dependent vascular leakage in mouse models of immune complex-mediated diseases.
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Mastocitos/enzimología , Serina Proteasas/metabolismo , Traslado Adoptivo , Animales , Complejo Antígeno-Anticuerpo , Regulación Enzimológica de la Expresión Génica , Histamina/metabolismo , Ratones , Ratones Noqueados , Neutrófilos , Serina Proteasas/genética , Serotonina/metabolismoRESUMEN
NMDA receptors (NMDARs) play subunit-specific roles in synaptic function and are implicated in neuropsychiatric and neurodegenerative disorders. However, the in vivo consequences and therapeutic potential of pharmacologically enhancing NMDAR function via allosteric modulation are largely unknown. We examine the in vivo effects of GNE-0723, a positive allosteric modulator of GluN2A-subunit-containing NMDARs, on brain network and cognitive functions in mouse models of Dravet syndrome (DS) and Alzheimer's disease (AD). GNE-0723 use dependently potentiates synaptic NMDA receptor currents and reduces brain oscillation power with a predominant effect on low-frequency (12-20 Hz) oscillations. Interestingly, DS and AD mouse models display aberrant low-frequency oscillatory power that is tightly correlated with network hypersynchrony. GNE-0723 treatment reduces aberrant low-frequency oscillations and epileptiform discharges and improves cognitive functions in DS and AD mouse models. GluN2A-subunit-containing NMDAR enhancers may have therapeutic benefits in brain disorders with network hypersynchrony and cognitive impairments.
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Enfermedad de Alzheimer/tratamiento farmacológico , Encéfalo/metabolismo , Cognición/efectos de los fármacos , Ciclopropanos/farmacología , Epilepsias Mioclónicas/tratamiento farmacológico , Nitrilos/farmacología , Receptores de N-Metil-D-Aspartato/metabolismo , Tiazoles/farmacología , Regulación Alostérica/efectos de los fármacos , Enfermedad de Alzheimer/genética , Enfermedad de Alzheimer/metabolismo , Animales , Conducta Animal/efectos de los fármacos , Encéfalo/efectos de los fármacos , Células CHO , Cricetulus , Modelos Animales de Enfermedad , Epilepsias Mioclónicas/genética , Epilepsias Mioclónicas/metabolismo , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Pirazoles/farmacología , Receptores de N-Metil-D-Aspartato/agonistasRESUMEN
To date, there is no validated fluid biomarker for tau pathology in Alzheimer's disease, with contradictory results from studies evaluating the correlation between phosphorylated tau in CSF with tau PET imaging. Tau protein is subjected to proteolytic processing into fragments before being secreted to the CSF. A recent study suggested that tau cleavage after amino acid 368 by asparagine endopeptidase (AEP) is upregulated in Alzheimer's disease. We used immunoprecipitation followed by mass spectrometric analyses to evaluate the presence of tau368 species in CSF. A novel Simoa® assay for quantification of tau368 in CSF was developed, while total tau (t-tau) was measured by ELISA and the presence of tau368 in tangles was evaluated using immunohistochemistry. The diagnostic utility of tau368 was first evaluated in a pilot study (Alzheimer's disease = 20, control = 20), then in a second cohort where the IWG-2 biomarker criteria were applied (Alzheimer's disease = 37, control = 45), and finally in a third cohort where the correlation with 18F-GTP1 tau PET was evaluated (Alzheimer's disease = 38, control = 11). The tau368/t-tau ratio was significantly decreased in Alzheimer's disease (P < 0.001) in all cohorts. Immunohistochemical staining demonstrated that tau fragments ending at 368 are present in tangles. There was a strong negative correlation between the CSF tau368/t-tau ratio and 18F-GTP1 retention. Our data suggest that tau368 is a tangle-enriched fragment and that the CSF ratio tau368/t-tau reflects tangle pathology. This novel tau biomarker could be used to improve diagnosis of Alzheimer's disease and to facilitate the development of drug candidates targeting tau pathology. Furthermore, future longitudinal studies will increase our understanding of tau pathophysiology in Alzheimer's disease and other tauopathies.
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Enfermedad de Alzheimer/líquido cefalorraquídeo , Péptidos beta-Amiloides/líquido cefalorraquídeo , Fragmentos de Péptidos/líquido cefalorraquídeo , Proteínas tau/líquido cefalorraquídeo , Adulto , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/patología , Biomarcadores/líquido cefalorraquídeo , Estudios de Cohortes , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana EdadRESUMEN
Microglia are specialized brain macrophages that play numerous roles in tissue homeostasis and response to injury. Colony stimulating factor 1 receptor (CSF1R) is a receptor tyrosine kinase required for the development, maintenance, and proliferation of microglia. Here we show that in adult mice peripheral dosing of function-blocking antibodies to the two known ligands of CSF1R, CSF1, and IL-34, can deplete microglia differentially in white and gray matter regions of the brain, respectively. The regional patterns of depletion correspond to the differential expression of CSF1 and IL-34. In addition, we show that while CSF1 is required to establish microglia in the developing embryo, both CSF1 and IL-34 are required beginning in early postnatal development. These results not only clarify the roles of CSF1 and IL-34 in microglia maintenance, but also suggest that signaling through these two ligands might support distinct sub-populations of microglia, an insight that may impact drug development for neurodegenerative and other diseases.
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Sustancia Gris/inmunología , Interleucinas/inmunología , Factor Estimulante de Colonias de Macrófagos/inmunología , Microglía/inmunología , Receptores de Factor Estimulante de Colonias de Granulocitos y Macrófagos/inmunología , Sustancia Blanca/inmunología , Animales , Interleucinas/genética , Factor Estimulante de Colonias de Macrófagos/genética , Ratones , Ratones Transgénicos , Receptores de Factor Estimulante de Colonias de Granulocitos y Macrófagos/genética , Transducción de Señal/genética , Transducción de Señal/inmunologíaRESUMEN
Colony-stimulating factor 1 (CSF1) and interleukin 34 (IL34) signal via the CSF1 receptor to regulate macrophage differentiation. Studies in IL34- or CSF1-deficient mice have revealed that IL34 function is limited to the central nervous system and skin during development. However, the roles of IL34 and CSF1 at homeostasis or in the context of inflammatory diseases or cancer in wild-type mice have not been clarified in vivo. By neutralizing CSF1 and/or IL34 in adult mice, we identified that they play important roles in macrophage differentiation, specifically in steady-state microglia, Langerhans cells, and kidney macrophages. In several inflammatory models, neutralization of both CSF1 and IL34 contributed to maximal disease protection. However, in a myeloid cell-rich tumor model, CSF1 but not IL34 was required for tumor-associated macrophage accumulation and immune homeostasis. Analysis of human inflammatory conditions reveals IL34 upregulation that may account for the protection requirement of IL34 blockade. Furthermore, evaluation of IL34 and CSF1 blockade treatment during Listeria infection reveals no substantial safety concerns. Thus, IL34 and CSF1 play non-redundant roles in macrophage differentiation, and therapeutic intervention targeting IL34 and/or CSF1 may provide an effective treatment in macrophage-driven immune-pathologies.
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Homeostasis/inmunología , Inflamación/inmunología , Interleucinas/inmunología , Factor Estimulante de Colonias de Macrófagos/inmunología , Macrófagos/inmunología , Neoplasias/inmunología , Animales , Diferenciación Celular/genética , Diferenciación Celular/inmunología , Modelos Animales de Enfermedad , Homeostasis/genética , Humanos , Inflamación/genética , Inflamación/metabolismo , Interleucinas/genética , Interleucinas/metabolismo , Factor Estimulante de Colonias de Macrófagos/genética , Factor Estimulante de Colonias de Macrófagos/metabolismo , Macrófagos/metabolismo , Masculino , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Endogámicos DBA , Ratones Endogámicos NZB , Ratones Noqueados , Células Mieloides/inmunología , Células Mieloides/metabolismo , Neoplasias/genética , Neoplasias/metabolismoRESUMEN
Multiple myeloma (MM) arises from malignant immunoglobulin (Ig)-secreting plasma cells and remains an incurable, often lethal disease despite therapeutic advances. The unfolded-protein response sensor IRE1α supports protein secretion by deploying a kinase-endoribonuclease module to activate the transcription factor XBP1s. MM cells may co-opt the IRE1α-XBP1s pathway; however, the validity of IRE1α as a potential MM therapeutic target is controversial. Genetic disruption of IRE1α or XBP1s, or pharmacologic IRE1α kinase inhibition, attenuated subcutaneous or orthometastatic growth of MM tumors in mice and augmented efficacy of two established frontline antimyeloma agents, bortezomib and lenalidomide. Mechanistically, IRE1α perturbation inhibited expression of key components of the endoplasmic reticulum-associated degradation machinery, as well as secretion of Ig light chains and of cytokines and chemokines known to promote MM growth. Selective IRE1α kinase inhibition reduced viability of CD138+ plasma cells while sparing CD138- cells derived from bone marrows of newly diagnosed or posttreatment-relapsed MM patients, in both US- and European Union-based cohorts. Effective IRE1α inhibition preserved glucose-induced insulin secretion by pancreatic microislets and viability of primary hepatocytes in vitro, as well as normal tissue homeostasis in mice. These results establish a strong rationale for developing kinase-directed inhibitors of IRE1α for MM therapy.
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Endorribonucleasas/genética , Mieloma Múltiple/tratamiento farmacológico , Inhibidores de Proteínas Quinasas/farmacología , Proteínas Serina-Treonina Quinasas/genética , Anciano , Animales , Bortezomib/farmacología , Estrés del Retículo Endoplásmico/genética , Endorribonucleasas/antagonistas & inhibidores , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Lenalidomida/farmacología , Masculino , Ratones , Persona de Mediana Edad , Mieloma Múltiple/genética , Mieloma Múltiple/patología , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Transducción de Señal/efectos de los fármacos , Respuesta de Proteína Desplegada/genética , Proteína 1 de Unión a la X-Box/genética , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
The regional relationships between tau positron emission tomography (PET) imaging and cognitive impairment in Alzheimer's disease (AD) remain uncertain. We examined cross-sectional associations between cognitive performance, cerebral uptake of the novel tau PET tracer [18F]GTP1, and other neuroimaging indices ([18F]florbetapir amyloid PET, magnetic resonance imaging) in 71 participants with normal cognition, prodromal AD, or AD dementia. Greater [18F]GTP1 uptake was seen with increasing clinical severity and correlated with poorer cognition. [18F]GTP1 uptake and cortical volume (but not [18F]florbetapir uptake) were independently associated with cognitive performance, particularly within the temporal lobe. Delayed memory was more specifically associated with temporal [18F]GTP1 uptake; other domains correlated with a broader range of regional [18F]GTP1 uptake. These data confirm that [18F]GTP1 tau PET uptake significantly correlates with cognitive performance in AD, but regional correlations between performance in non-memory cognitive domains were less specific than reported by tau PET imaging studies that included participants with atypical focal cortical AD syndromes. Tau PET imaging may have utility as a surrogate biomarker for clinical AD progression in therapeutic trials of disease-modifying interventions.
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Enfermedad de Alzheimer/diagnóstico por imagen , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Cognición , Disfunción Cognitiva/diagnóstico por imagen , Radioisótopos de Flúor/metabolismo , Tomografía de Emisión de Positrones , Radiofármacos/metabolismo , Proteínas tau/metabolismo , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/psicología , Disfunción Cognitiva/psicología , Estudios Transversales , Femenino , Humanos , Masculino , Persona de Mediana Edad , Neuroimagen , Índice de Severidad de la EnfermedadRESUMEN
OBJECTIVE: Neurofibrillary tangles (NFTs), consisting of intracellular aggregates of the tau protein, are a pathological hallmark of Alzheimer's disease (AD). Here we report the identification and initial characterization of Genentech Tau Probe 1 ([18F]GTP1), a small-molecule PET probe for imaging tau pathology in AD patients. METHODS: Autoradiography using human brain tissues from AD donors and protein binding panels were used to determine [18F]GTP1 binding characteristics. Stability was evaluated in vitro and in vivo in mice and rhesus monkey. In the clinic, whole-body imaging was performed to assess biodistribution and dosimetry. Dynamic [18F]GTP1 brain imaging and input function measurement were performed on two separate days in 5 ß-amyloid plaque positive (Aß+) AD and 5 ß-amyloid plaque negative (Aß-) cognitive normal (CN) participants. Tracer kinetic modeling was applied and reproducibility was evaluated. SUVR was calculated and compared to [18F]GTP1-specific binding parameters derived from the kinetic modeling. [18F]GTP1 performance in a larger cross-sectional group of 60 Aß+ AD participants and ten (Aß- or Aß+) CN was evaluated with images acquired 60 to 90 min post tracer administration. RESULTS: [18F]GTP1 exhibited high affinity and selectivity for tau pathology with no measurable binding to ß-amyloid plaques or MAO-B in AD tissues, or binding to other tested proteins at an affinity predicted to impede image data interpretation. In human, [18F]GTP1 exhibited favorable dosimetry and brain kinetics, and no evidence of defluorination. [18F]GTP1-specific binding was observed in cortical regions of the brain predicted to contain tau pathology in AD and exhibited low (< 4%) test-retest variability. SUVR measured in the 60 to 90-min interval post injection correlated with tracer-specific binding (slope = 1.36, r2 = 0.98). Furthermore, in a cross-sectional population, the degree of [18F]GTP1-specific binding increased with AD severity and could differentiate diagnostic cohorts. CONCLUSIONS: [18F]GTP1 is a promising PET probe for the study of tau pathology in AD.
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Enfermedad de Alzheimer/diagnóstico por imagen , Radioisótopos de Flúor/farmacocinética , Tomografía de Emisión de Positrones/métodos , Radiofármacos/farmacocinética , Proteínas tau/metabolismo , Adulto , Anciano , Anciano de 80 o más Años , Enfermedad de Alzheimer/metabolismo , Enfermedad de Alzheimer/patología , Animales , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Femenino , Radioisótopos de Flúor/administración & dosificación , Humanos , Cinética , Macaca mulatta , Masculino , Ratones , Ratones Endogámicos C57BL , Persona de Mediana Edad , Ovillos Neurofibrilares/metabolismo , Tomografía de Emisión de Positrones/normas , Unión Proteica , Radiofármacos/administración & dosificación , Sensibilidad y EspecificidadRESUMEN
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.
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Geographic atrophy (GA), the advanced form of dry age-related macular degeneration (AMD), is characterized by progressive loss of retinal pigment epithelium cells and photoreceptors in the setting of characteristic extracellular deposits and remains a serious unmet medical need. While genetic predisposition to AMD is dominated by polymorphisms in complement genes, it remains unclear how complement activation contributes to retinal atrophy. Here we demonstrate that complement is activated on photoreceptor outer segments (POS) in the retina peripheral to atrophic lesions associated with GA. When exposed to human serum following outer blood-retinal barrier breakdown, POS act as potent activators of the classical and alternative complement pathway. In mouse models of retinal degeneration, classical and alternative pathway complement activation on photoreceptors contributed to the loss of photoreceptor function. This was dependent on C5a-mediated recruitment of peripheral blood monocytes but independent of resident microglia. Genetic or pharmacologic inhibition of both classical and alternative complement C3 and C5 convertases was required to reduce progressive degeneration of photoreceptor rods and cones. Our study implicates systemic classical and alternative complement proteins and peripheral blood monocytes as critical effectors of localized retinal degeneration with potential relevance for the contribution of complement activation to GA.
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Activación de Complemento/genética , Atrofia Geográfica/fisiopatología , Células Fotorreceptoras Retinianas Bastones/metabolismo , Animales , Atrofia/patología , Activación de Complemento/fisiología , Complemento C3/genética , Complemento C3/fisiología , Complemento C4/genética , Complemento C4/fisiología , Atrofia Geográfica/genética , Humanos , Degeneración Macular/fisiopatología , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Monocitos/metabolismo , Células Fotorreceptoras/metabolismo , Retina/metabolismo , Degeneración Retiniana/patología , Epitelio Pigmentado de la Retina/metabolismoRESUMEN
18F-AV-1451 is currently the most widely used of several experimental tau PET tracers. The objective of this study was to evaluate 18F-AV-1451 binding with full kinetic analysis using a metabolite-corrected arterial input function and to compare parameters derived from kinetic analysis with SUV ratio (SUVR) calculated over different imaging time intervals. Methods:18F-AV-1451 PET brain imaging was completed in 16 subjects: 4 young healthy volunteers (YHV), 4 aged healthy volunteers (AHV), and 8 Alzheimer disease (AD) subjects. Subjects were imaged for 3.5 h, with arterial blood samples obtained throughout. PET data were analyzed using plasma and reference tissue-based methods to estimate the distribution volume, binding potential (BPND), and SUVR. BPND and SUVR were calculated using the cerebellar cortex as a reference region and were compared across the different methods and across the 3 groups (YHV, AHV, and AD). Results: AD demonstrated increased 18F-AV-1451 retention compared with YHV and AHV based on both invasive and noninvasive analyses in cortical regions in which paired helical filament tau accumulation is expected in AD. A correlation of R2 > 0.93 was found between BPND (130 min) and SUVR-1 at all time intervals. Cortical SUVR curves reached a relative plateau around 1.0-1.2 for YHV and AHV by approximately 50 min, but increased in AD by up to approximately 20% at 110-130 min and approximately 30% at 160-180 min relative to 80-100 min. Distribution volume (130 min) was lower by 30%-35% in the YHV than AHV. Conclusion: Our data suggest that although 18F-AV-1451 SUVR curves do not reach a plateau and are still increasing in AD, an SUVR calculated over an imaging window of 80-100 min (as currently used in clinical studies) provides estimates of paired helical filament tau burden in good correlation with BPND, whereas SUVR sensitivity to regional cerebral blood changes needs further investigation.
Asunto(s)
Enfermedad de Alzheimer/metabolismo , Encéfalo/metabolismo , Carbolinas/farmacocinética , Modelos Biológicos , Tomografía de Emisión de Positrones , Proteínas tau/metabolismo , Anciano , Enfermedad de Alzheimer/diagnóstico por imagen , Biomarcadores/metabolismo , Encéfalo/diagnóstico por imagen , Simulación por Computador , Femenino , Humanos , Interpretación de Imagen Asistida por Computador , Cinética , Masculino , Tasa de Depuración Metabólica , Persona de Mediana Edad , Radiofármacos/farmacocinética , Valores de Referencia , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Distribución TisularRESUMEN
Age-related macular degeneration (AMD), a leading cause of vision impairment in the ageing population, is characterized by irreversible loss of retinal pigment epithelial (RPE) cells and photoreceptors and can be associated with choroidal neovascularization. Mononuclear phagocytes are often present in AMD lesions, but the processes that direct myeloid cell recruitment remain unclear. Here, we identify IL-33 as a key regulator of inflammation and photoreceptor degeneration after retina stress or injury. IL-33(+) Müller cells were more abundant and IL-33 cytokine was elevated in advanced AMD cases compared with age-matched controls with no AMD. In rodents, retina stress resulted in release of bioactive IL-33 that in turn increased inflammatory chemokine and cytokine expression in activated Müller cells. Deletion of ST2, the IL-33 receptor α chain, or treatment with a soluble IL-33 decoy receptor significantly reduced release of inflammatory mediators from Müller cells, inhibited accumulation of mononuclear phagocytes in the outer retina, and protected photoreceptor rods and cones after a retina insult. This study demonstrates a central role for IL-33 in regulating mononuclear phagocyte recruitment to the photoreceptor layer and positions IL-33 signaling as a potential therapeutic target in macular degenerative diseases.
Asunto(s)
Inmunidad Innata , Interleucina-33/metabolismo , Degeneración Macular/inmunología , Anciano , Anciano de 80 o más Años , Animales , Estudios de Casos y Controles , Núcleo Celular/inmunología , Citocinas/metabolismo , Células Ependimogliales/inmunología , Células Ependimogliales/patología , Femenino , Humanos , Técnicas In Vitro , Proteína 1 Similar al Receptor de Interleucina-1 , Interleucina-33/química , Interleucina-33/deficiencia , Interleucina-33/genética , Mácula Lútea/inmunología , Mácula Lútea/patología , Degeneración Macular/genética , Degeneración Macular/patología , Masculino , Ratones , Ratones Endogámicos BALB C , Ratones Endogámicos C57BL , Ratones Noqueados , Procesamiento Proteico-Postraduccional , Ratas , Receptores de Superficie Celular/genética , Receptores de Superficie Celular/metabolismo , Receptores de Interleucina/deficiencia , Receptores de Interleucina/genética , Receptores de Interleucina/metabolismo , Epitelio Pigmentado de la Retina/inmunología , Epitelio Pigmentado de la Retina/patologíaRESUMEN
The blood-brain barrier (BBB) poses a major challenge for developing effective antibody therapies for neurological diseases. Using transcriptomic and proteomic profiling, we searched for proteins in mouse brain endothelial cells (BECs) that could potentially be exploited to transport antibodies across the BBB. Due to their limited protein abundance, neither antibodies against literature-identified targets nor BBB-enriched proteins identified by microarray facilitated significant antibody brain uptake. Using proteomic analysis of isolated mouse BECs, we identified multiple highly expressed proteins, including basigin, Glut1, and CD98hc. Antibodies to each of these targets were significantly enriched in the brain after administration in vivo. In particular, antibodies against CD98hc showed robust accumulation in brain after systemic dosing, and a significant pharmacodynamic response as measured by brain Aß reduction. The discovery of CD98hc as a robust receptor-mediated transcytosis pathway for antibody delivery to the brain expands the current approaches available for enhancing brain uptake of therapeutic antibodies.