CR1
Complement receptor type 1 precursor (C3b/C4b receptor) (CD35 antigen) [C3BR]
PublicationsПравить
It is critical to identify individuals at risk for Alzheimer's disease (AD) earlier in the disease time course, such as middle age and preferably well prior to the onset of clinical symptoms, when intervention efforts may be more successful. Genome-wide association and candidate gene studies have identified single nucleotide polymorphisms (SNPs) in APOE, CLU, CR1, PICALM, and SORL1 that confer increased risk of AD. In the current study, we investigated the associations between SNPs in these genes and resting-state functional connectivity within the default mode network (DMN), frontoparietal network (FPN), and executive control network (ECN) in healthy, non-demented middle-aged adults (age 40 -60; N = 123; 74 females). Resting state networks of interest were identified through independent components analysis using a template-matching procedure and individual spatial maps and time courses were extracted using dual regression. Within the posterior DMN, functional connectivity was associated with CR1 rs1408077 and CLU rs9331888 polymorphisms (p's < 0.05). FPN connectivity was associated with CR1 rs1408077, CLU rs1136000, SORL1 rs641120, and SORL1 rs689021 (p's < 0.05). Functional connectivity within the ECN was associated with the CLU rs11136000 (p < 0.05). There were no APOE- or PICALM-related differences in any of the networks investigated (p's > 0.05). This is the first demonstration of the relationship between intrinsic network connectivity and AD risk alleles in CLU, CR1, and SORL1 in healthy, middle-aged adults. These SNPs should be considered in future investigations aimed at identifying potential preclinical biomarkers for AD.
Keywords
- Aging
- Alzheimer’s disease
- middle aged
- neuroimaging
- single nucleotide
polymorphism
The endangered whale shark ([i]Rhincodon typus[/i]) is the largest fish on Earth and a long-lived member of the ancient Elasmobranchii clade. To characterize the relationship between genome features and biological traits, we sequenced and assembled the genome of the whale shark and compared its genomic and physiological features to those of 83 animals and yeast. We examined the scaling relationships between body size, temperature, metabolic rates, and genomic features and found both general correlations across the animal kingdom and features specific to the whale shark genome. Among animals, increased lifespan is positively correlated to body size and metabolic rate. Several genomic traits also significantly correlated with body size, including intron and gene length. Our large-scale comparative genomic analysis uncovered general features of metazoan genome architecture: Guanine and cytosine (GC) content and codon adaptation index are negatively correlated, and neural connectivity genes are longer than average genes in most genomes. Focusing on the whale shark genome, we identified multiple features that significantly correlate with lifespan. Among these were very long gene length, due to introns being highly enriched in repetitive elements such as CR1-like long interspersed nuclear elements, and considerably longer neural genes of several types, including connectivity, activity, and neurodegeneration genes. The whale shark genome also has the second slowest evolutionary rate observed in vertebrates to date. Our comparative genomics approach uncovered multiple genetic features associated with body size, metabolic rate, and lifespan and showed that the whale shark is a promising model for studies of neural architecture and lifespan.
MeSH Terms
- Adaptation, Physiological
- Animals
- Base Sequence
- Body Size
- Genome
- Genomics
- Longevity
- Sharks
- Temperature
Keywords
- body size
- lifespan
- metabolic rate
- neural genes
- whale shark
Multifaceted evidence supports the hypothesis that inflammatory-immune mechanisms contribute to Alzheimer disease (AD) neuropathology and genetic association of several immune specific genes (TREM2, CR1, and CD33) suggests that maladaptive immune responses may be pivotal drivers of AD pathogenesis. We reviewed microglia-related data from postmortem AD studies and examined supporting evidence from AD animal models to answer the following questions: i) What is the temporal sequence of immune activation in AD progression and what is its impact on cognition? ii) Are there discordant, "primed", microglia responses in AD vs successful cognitive aging? iii) Does central nervous system (CNS) repair in aging depend on recruitment of the elements of cellular adaptive immune response such as effector T cells, and can the recruitment of systemic immune cells ameliorate AD neuropathology? iv) How effective are the immune-system-based therapeutic approaches currently employed for the treatment of AD?
MeSH Terms
- Adaptive Immunity
- Aged, 80 and over
- Alzheimer Disease
- Cognition
- Cognitive Aging
- Encephalitis
- Humans
- Microglia
Keywords
- Alzheimer disease
- T cell
- gene expression
- immune response
- inflammation
- macrophage
- microglia
- oldest-old
Vascular dysfunction contributes to the progression and severity of Alzheimer's disease (AD). Patients with AD also sustain larger infarctions after ischemic stroke; however, the responsible mechanisms are unknown. Pial collaterals are the primary source of protection in stroke. Unfortunately, natural aging and other vascular risk factors cause a decline in collateral number and diameter (rarefaction) and an increase in stroke severity. Herein, we tested the hypothesis that AD accelerates age-induced collateral rarefaction and examined potential underlying mechanisms. Triple and double transgenic mouse models of AD both sustained collateral rarefaction by 8 months of age, well before the onset of rarefaction caused by aging alone (16 months of age). Rarefaction, which did not progress further at 18 months of age, was accompanied by a twofold increase in infarct volume after MCA occlusion. AD did not induce rarefaction of similarly sized pial arterioles or penetrating arterioles. Rarefaction was minimal and occurred only at 18 months of age in a parenchymal vascular amyloid-beta model of AD. Rarefaction was not associated with amyloid-beta deposition on collaterals or pial arteries, nor was plaque burden or CD11b cell density greater in brain underlying the collateral zones versus elsewhere. However, rarefaction was accompanied by increased markers of oxidative stress, inflammation, and aging of collateral endothelial and mural cells. Moreover, rarefaction was lessened by deletion of CX CR1 and prevented by overexpression of eNOS. These findings demonstrate that mouse models of AD promote rarefaction of pial collaterals and implicate inflammation-induced accelerated aging of collateral wall cells. Strategies that reduce vascular inflammation and/or increase nitric oxide may preserve collateral function.
MeSH Terms
- Aging
- Alzheimer Disease
- Amyloid beta-Protein Precursor
- Animals
- Arterioles
- Brain Ischemia
- Cell Count
- Cerebral Veins
- Cerebrovascular Circulation
- Collateral Circulation
- Disease Models, Animal
- Humans
- Mice
- Mice, Transgenic
- Neovascularization, Physiologic
- Presenilin-1
- Severity of Illness Index
- Stroke
- tau Proteins
Keywords
- Alzheimer’s disease
- Cerebral amyloid angiopathy
- Collateral circulation
- Stroke
Anemia is a major complication of malaria, driven largely by loss of uninfected RBCs during infection. RBC clearance through loss of complement regulatory proteins (CRPs) is a significant contributor to anemia in Plasmodium falciparum infection, but its role in Plasmodium vivax infection is unknown. CRP loss increases RBC susceptibility to macrophage clearance, a process that is also regulated by CD47. We compared CRPs and CD47 expression on infected and uninfected RBCs in adult patients with vivax and falciparum malaria and different anemia severities from Papua, Indonesia. Complement activation and parasite-specific complement-fixing antibodies were measured by ELISA. Levels of CR1 and CD55 were reduced in severe anemia in both falciparum and vivax malaria. Loss of CRPs and CD47 was restricted to uninfected RBCs, with infected RBCs having higher expression. There was no association among complement-fixing antibodies, complement activation, and CRP loss. Our findings demonstrate that CRP loss is a pan-species, age-independent mechanism of malarial anemia. Higher levels of CRP and CD47 expression on infected RBCs suggest that parasites are protected from complement-mediated destruction and macrophage clearance. Lack of associations between protective antibodies and CRP loss highlight that complement pathogenic and protective pathways are distinct mechanisms during infection.
MeSH Terms
- Adolescent
- Adult
- Aging
- Anemia
- CD47 Antigen
- Complement Activation
- Complement System Proteins
- Erythrocytes
- Female
- Humans
- Malaria, Falciparum
- Malaria, Vivax
- Male
- Plasmodium falciparum
- Plasmodium vivax
- Young Adult
Keywords
- Complement
- Immunology
- Infectious disease
- Malaria
Alzheimer's disease (AD) is one of the most common neurodegenerative disorders mainly affecting elderly people. It is characterized by progressive loss of memory and cognitive function. More than 95% of AD cases are related to sporadic or late-onset AD (LOAD). The etiology of LOAD is still unclear. It has been reported that environmental factors and epigenetic alterations play a significant role in AD pathogenesis. Furthermore, recently, genome-wide association studies (GWAS) identified 10 novel risk genes: ABCA7, APOE, BIN1, CD2AP, CD33, CLU, CR1, MS4A6A, MS4A4E, and PICALM, which play an important role for LOAD. In this review, the therapeutic approaches of AD by epigenetic modifications have been discussed. Nowadays, HDAC inhibitors have clinically proven its activity for epigenetic modifications. Furthermore, we try to establish the relationship between HDAC inhibitors and above mentioned LOAD risk genes. Finally, we are hoping that this review may open new area of research for AD treatment.
MeSH Terms
- Aging
- Alzheimer Disease
- Animals
- Cognition Disorders
- Epigenesis, Genetic
- Genetic Predisposition to Disease
- Genome-Wide Association Study
- Histone Deacetylase Inhibitors
- Histone Deacetylases
- Humans
Keywords
- Alzheimer’s disease
- GWAS
- HDAC inhibitors
- LOAD
- epigenetic modification
With ever-increasing elder populations, age-related cognitive decline, which is characterized as a gradual decline in cognitive capacity in the aging process, has turned out to be a mammoth public health concern. Since genetic information has become increasingly important to explore the biological mechanisms of cognitive decline, the search for genetic biomarkers of cognitive aging has received much attention. There is growing evidence that single-nucleotide polymorphisms (SNPs) within the [i]ADAMTS9, BDNF, CASS4, COMT, CR1, DNMT3A, DTNBP1, REST, SRR, TOMM40[/i], circadian clock, and Alzheimer's diseases-associated genes may contribute to susceptibility to cognitive aging. In this review, we first illustrated evidence of the genetic contribution to disease susceptibility to age-related cognitive decline in recent studies ranging from approaches of candidate genes to genome-wide association studies. We then surveyed a variety of association studies regarding age-related cognitive decline with consideration of gene-gene and gene-environment interactions. Finally, we highlighted their limitations and future directions. In light of advances in precision medicine and multi-omics technologies, future research in genomic medicine promises to lead to innovative ideas that are relevant to disease prevention and novel drugs for cognitive aging.
Keywords
- Alzheimer’s diseases
- SNP–SNP interactions
- age-related cognitive decline
- biomarker
- cognitive aging
- gene–gene interactions
- neurodegeneration
- single-nucleotide polymorphisms
The aim of this study was to assess the relationship between the reproductive management practices and the performance of replacement heifers on large commercial dairy farms. The individual data of 14,763 heifers, first inseminated in 2014, were analysed from 33 Holstein-Friesian dairy herds in Hungary. The relationships between management practices and major reproductive parameters (age at first service, AFS; age at first calving, AFC; conception risk to first insemination, CR1; and pregnancy status at 20 months of age) were examined by mixed-effects models, with the herd as the random effect. The results showed that farms using oestrus detection aids experienced reduced AFS (p<0.001) and AFC (p=0.001). Observation of oestrus for shorter periods instead of continuously showed a tendency towards lower AFC (p=0.057) and was associated with higher odds of pregnancy at 20 months of age (p=0.020). Heifers on farms using sexed semen had younger AFS, but poorer CR1, compared to those using conventional semen exclusively (p<0.05). In addition, the odds of heifers being pregnant by 20 months of age was higher on farms with more experience using sexed semen (p=0.020). Frequent pregnancy diagnosis (i.e. more than once per week) was associated with younger AFC (p=0.023). Our results suggest the use of certain advanced reproductive management practices for heifer reproductive management in large dairy herds (e.g. oestrus detection aids), which can improve reproductive efficiency considerably, but are currently used only to a limited extent.
MeSH Terms
- Aging
- Animal Husbandry
- Animals
- Cattle
- Female
- Insemination, Artificial
- Pregnancy
- Pregnancy, Animal
- Reproduction
Keywords
- Age at first calving
- Dairy heifer
- Oestrus detection
- Pregnancy diagnosis
- Reproductive management
To examine the impact of genetic, inflammatory, cardiovascular, lifestyle, and neuroanatomical factors on cognitive processing speed (CPS) change over time in functionally intact older adults. This observational study conducted over two time points, included 120 community dwelling cognitively normal older adults between the ages of 60 and 80 from the University of California San Francisco Memory and Aging Center. Participants were followed with composite measures of CPS, calculated based on norms for 20-30 year-olds. Variables of interest were AD risk genes (APOE, CR1), markers of inflammation (interleukin 6) and cardiovascular health (BMI, LDL, HDL, mean arterial pressure, fasting insulin), self-reported physical activity, and corpus callosum (CC) volumes. The sample was divided into three groups: 17 "resilient-agers" with fast and stable processing speed; 56 "average-agers" with average and stable processing speed; and 47 "sub-agers" with average baseline speed who were slower at follow-up. Resilient-agers had larger baseline CC volumes than sub-agers ([i]p[/i] < 0.05). Resilient-agers displayed lower levels of interleukin-6 (IL-6) and insulin ([i]p[/i]s < 0.05) than sub-agers, and reported more physical activity than both average- and sub-agers ([i]p[/i]s < 0.01). In a multinomial logistic regression, physical activity and IL-6 predicted average- and sub-ager groups. Resilient-agers displayed a higher frequency of APOE e4 and CR1 AA/AG alleles. Robust and stable CPS is associated with larger baseline CC volumes, lower levels of inflammation and insulin, and greater self-reported physical activity. These findings highlight the relevance of neuroanatomical, biological, and lifestyle factors in the identification and prediction of heterogeneous cognitive aging change over time.
Keywords
- APOE E4 allele
- IL-6
- cognitive aging predictors
- insulin
- physical exercise
- processing speed
- white matter
Genome-wide association studies and meta-analyses implicated that increased risk of developing Alzheimer's diseases (AD) has been associated with the ABCA7, APOE, BIN1, CASS4, CD2AP, CD33, CELF1, CLU, CR1, DSG2, EPHA1, FERMT2, HLA-DRB1, HLA-DRB4, INPP5D, MEF2C, MS4A4A, MS4A4E, MS4A6E, NME8, PICALM, PLD3, PTK2B, RIN3, SLC24A4, SORL1, and ZCWPW1 genes. In this study, we assessed whether single nucleotide polymorphisms (SNPs) within these 27 AD-associatedgenes are linked with cognitive aging independently and/or through complex interactions in an older Taiwanese population. We also analyzed the interactions between lifestyle and these genes in influencing cognitive aging. A total of 634 Taiwanese subjects aged over 60 years from the Taiwan Biobank were analyzed. Mini-Mental State Examination (MMSE) scores were performed for all subjects to evaluate cognitive functions. Out of the 588 SNPs tested in this study, only the association between CASS4-rs911159 and cognitive aging persisted significantly (P = 2.2 x 10-5) after Bonferroni correction. Our data also showed a nominal association of cognitive aging with the SNPs in six more key AD-associated genes, including EPHA1-rs10952552, FERMT2-rs4901317, MEF2C-rs9293506, PLD3-rs11672825, RIN3-rs1885747, and SLC24A4-rs67063100 (P = 0.0018~0.0097). Additionally, we found the interactions among CASS4-rs911159, EPHA-rs10952552, FERMT2-rs4901317, MEF2C-rs9293506, or SLC24A4-rs67063100 on cognitive aging (P = 0.004~0.035). Moreover, our analysis suggested the interactions of SLC24A4-rs67063100 or MEF2C-rs9293506 with lifestyle such as alcohol consumption, smoking status, physical activity, or social support on cognitive aging (P = 0.008~0.041). Our study indicates that the AD-associated genes may contribute to the risk of cognitive aging independently as well as through gene-gene and gene-lifestyle interactions.
MeSH Terms
- Age Factors
- Aged
- Alleles
- Alzheimer Disease
- Cognitive Aging
- Epistasis, Genetic
- Female
- Gene-Environment Interaction
- Genetic Association Studies
- Genetic Predisposition to Disease
- Humans
- Life Style
- Male
- Middle Aged
- Polymorphism, Single Nucleotide
- Risk Factors
- Taiwan
Keywords
- Alzheimer’s diseases
- Gerotarget
- Mini-Mental State Examination
- cognitive aging
- gene-gene and gene-lifestyle interactions
- single nucleotide polymorphisms
Single nucleotide polymorphisms (SNPs) in and near ABCA7, BIN1, CASS4, CD2AP, CD33, CELF1, CLU, complement receptor 1 (CR1), EPHA1, EXOC3L2, FERMT2, HLA cluster (DRB5-DQA), INPP5D, MEF2C, MS4A cluster (MS4A3-MS4A6E), NME8, PICALM, PTK2B, SLC24A4, SORL1, and ZCWPW1 have been associated with Alzheimer's disease (AD) in large meta-analyses. We aimed to determine whether established AD-associated genes are associated with longitudinal cognitive decline by examining aggregate variation across these gene regions. In two single-sex cohorts of older, community-dwelling adults, we examined the association between SNPs in previously implicated gene regions and cognitive decline (age-adjusted person-specific cognitive slopes) using a Sequence Kernel Association Test (SKAT). In regions which showed aggregate significance, we examined the univariate association between individual SNPs in the region and cognitive decline. Only two of the original AD-associated SNPs were significantly associated with cognitive decline in our cohorts. We identified significant aggregate-level associations between cognitive decline and the gene regions BIN1, CD33, CELF1, CR1, HLA cluster, and MEF2C in the all-female cohort and significant associations with ABCA7, HLA cluster, MS4A6E, PICALM, PTK2B, SLC24A4, and SORL1 in the all-male cohort. We also identified a block of eight correlated SNPs in CD33 and several blocks of correlated SNPs in CELF1 that were significantly associated with cognitive decline in univariate analysis in the all-female cohort.
MeSH Terms
- Aged
- Aging
- Alzheimer Disease
- Cognition Disorders
- DNA
- Female
- Genetic Association Studies
- Genetic Predisposition to Disease
- Humans
- Male
- Polymorphism, Single Nucleotide
Keywords
- Candidate AD genes
- Cognitive decline
- SNP associations
The past decade has witnessed a revolution in our understanding of microglia. These immune cells were shown to actively remodel neuronal circuits, leading to propose new pathogenic mechanisms. To study microglial implication in the loss of synapses, the best pathological correlate of cognitive decline across chronic stress, aging, and diseases, we recently conducted ultrastructural analyses. Our work uncovered the existence of a new microglial phenotype that is rarely present under steady state conditions, in hippocampus, cerebral cortex, amygdala, and hypothalamus, but becomes abundant during chronic stress, aging, fractalkine signaling deficiency (CX3 CR1 knockout mice), and Alzheimer's disease pathology (APP-PS1 mice). Even though these cells display ultrastructural features of microglia, they are strikingly distinct from the other phenotypes described so far at the ultrastructural level. They exhibit several signs of oxidative stress, including a condensed, electron-dense cytoplasm and nucleoplasm making them as "dark" as mitochondria, accompanied by a pronounced remodeling of their nuclear chromatin. Dark microglia appear to be much more active than the normal microglia, reaching for synaptic clefts, while extensively encircling axon terminals and dendritic spines with their highly ramified and thin processes. They stain for the myeloid cell markers IBA1 and GFP (in CX3 CR1-GFP mice), and strongly express CD11b and microglia-specific 4D4 in their processes encircling synaptic elements, and TREM2 when they associate with amyloid plaques. Overall, these findings suggest that dark microglia, a new phenotype that we identified based on their unique properties, could play a significant role in the pathological remodeling of neuronal circuits, especially at synapses.
MeSH Terms
- Aging
- Aldehyde Dehydrogenase
- Alzheimer Disease
- Amyloid beta-Protein Precursor
- Animals
- Antigens, CD
- CX3C Chemokine Receptor 1
- Cerebral Cortex
- Disease Models, Animal
- Green Fluorescent Proteins
- Mice
- Mice, Inbred C57BL
- Mice, Transgenic
- Microglia
- Nerve Tissue Proteins
- Oxidoreductases Acting on CH-NH Group Donors
- Phenotype
- Presenilin-1
- Receptors, Chemokine
- Stress, Psychological
Keywords
- aging
- microglia
- neurodegenerative diseases
- stress
- synapses
The rs3818361 single nucleotide polymorphism in complement component (3b/4b) receptor-1 (CR1) is associated with increased risk of Alzheimer's disease (AD). Although this novel variant is associated with a small effect size and is unlikely to be useful as a predictor of AD risk, it might provide insights into AD pathogenesis. We examined the association between rs3818361 and brain amyloid deposition in nondemented older individuals. We used (11)C-Pittsburgh Compound-B positron emission tomography to quantify brain amyloid burden in 57 nondemented older individuals (mean age 78.5 years) in the neuroimaging substudy of the Baltimore Longitudinal Study of Aging. In a replication study, we analyzed (11)C-Pittsburgh Compound-B positron emission tomography data from 22 cognitively normal older individuals (mean age 77.1 years) in the Alzheimer's Disease Neuroimaging Initiative dataset. Risk allele carriers of rs3818361 have lower brain amyloid burden relative to noncarriers. There is a strikingly greater variability in brain amyloid deposition in the noncarrier group relative to risk carriers, an effect explained partly by APOE genotype. In noncarriers of the CR1 risk allele, APOE ε4 individuals showed significantly higher brain amyloid burden relative to APOE ε4 noncarriers. We also independently replicate our observation of lower brain amyloid burden in risk allele carriers of rs3818361 in the Alzheimer's Disease Neuroimaging Initiative sample. Our findings suggest complex mechanisms underlying the interaction of CR1, APOE, and brain amyloid pathways in AD. Our results are relevant to treatments targeting brain Aβ in nondemented individuals at risk for AD and suggest that clinical outcomes of such treatments might be influenced by complex gene-gene interactions.
MeSH Terms
- Aged
- Aged, 80 and over
- Aging
- Alleles
- Alzheimer Disease
- Amyloid
- Apolipoproteins E
- Brain
- Female
- Gene Frequency
- Genetic Predisposition to Disease
- Genotype
- Humans
- Longitudinal Studies
- Male
- Neuropsychological Tests
- Radionuclide Imaging
- Receptors, Complement 3b
Genetics plays a crucial role in human aging with up to 30% of those living to the mid-80s being determined by genetic variation. Survival to older ages likely entails an even greater genetic contribution. There is increasing evidence that genes implicated in age-related diseases, such as cancer and neuronal disease, play a role in affecting human life span. We have selected the 10 most promising late-onset Alzheimer's disease (LOAD) susceptibility genes identified through several recent large genome-wide association studies (GWAS). These 10 LOAD genes (APOE, CLU, PICALM, CR1, BIN1, ABCA7, MS4A6A, CD33, CD2AP, and EPHA1) have been tested for association with human aging in our dataset (1385 samples with documented age at death [AAD], age range: 58-108 years; mean age at death: 80.2) using the most significant single nucleotide polymorphisms (SNPs) found in the previous studies. Apart from the APOE locus (rs2075650) which showed compelling evidence of association with risk on human life span (p = 5.27 × 10(-4)), none of the other LOAD gene loci demonstrated significant evidence of association. In addition to examining the known LOAD genes, we carried out analyses using age at death as a quantitative trait. No genome-wide significant SNPs were discovered. Increasing sample size and statistical power will be imperative to detect genuine aging-associated variants in the future. In this report, we also discuss issues relating to the analysis of genome-wide association studies data from different centers and the bioinformatic approach required to distinguish spurious genome-wide significant signals from real SNP associations.
MeSH Terms
- Age Distribution
- Aging
- Alzheimer Disease
- Chromosome Mapping
- Genetic Markers
- Genetic Predisposition to Disease
- Genetic Variation
- Genome-Wide Association Study
- Humans
- Polymorphism, Single Nucleotide
- Prevalence
Currently there are notable differences in the aging of individuals in modern populations. While some of them enjoy a long healthy aging, others develop neurodegenerative diseases, such as Alzheimer's disease (AD). Environmental factors are critical, but genetics could explain the differences observed. It has recently been postulated that longevity genes might also be neuroprotective. To assess whether certain genetic variants associated with longevity might have a neuroprotective effect. The subjects of this study are people older than 90 years. We will collect sociodemographic and clinical data and multiple assessments, cognitive, functional, anthropometric, nutritional, sensory and physical each participant. In addition, 64 SNPs loci distributed in 13 candidate genes FOXO3, SIRT1, TOMM40, APOE, PICALM, COMT, CETP, CLU, CR1, IL-6, PCK-1, ZNF224 and ACE will be analysed by Taqman array. It is hoped to gain more knowledge about under/over-represented alleles in nonagenarians. Furthermore, comparison of the genetic characteristics of nonagenarians with AD with those free of disease will enable links to be seen between certain alleles with protection or the risk of AD. Associated information on the participants will create subgroups showing the interactions between environment and genetic variation in relation to healthy aging and AD. The study of the genetic variability of nonagenarians can give us information on the alleles associated with longevity and neuroprotection.
MeSH Terms
- Aged, 80 and over
- Aging
- Cognition
- Female
- Humans
- Longevity
- Male
- Prospective Studies
- Spain
Microglia have neuroprotective capacities, yet chronic activation can promote neurotoxic inflammation. Neuronal fractalkine (FKN), acting on CX(3)CR1, has been shown to suppress excessive microglia activation. We found that disruption in FKN/CX(3)CR1 signaling in young adult rodents decreased survival and proliferation of neural progenitor cells through IL-1β. Aged rats were found to have decreased levels of hippocampal FKN protein; moreover, interruption of CX(3)CR1 function in these animals did not affect neurogenesis. The age-related loss of FKN could be restored by exogenous FKN reversing the age-related decrease in hippocampal neurogenesis. There were no measureable changes in young animals by the addition of exogenous FKN. The results suggest that FKN/CX(3)CR1 signaling has a regulatory role in modulating hippocampal neurogenesis via mechanisms that involve indirect modification of the niche environment. As elevated neuroinflammation is associated with many age-related neurodegenerative diseases, enhancing FKN/CX(3)CR1 interactions could provide an alternative therapeutic approach to slow age-related neurodegeneration.
MeSH Terms
- Age Factors
- Aging
- Animals
- CX3C Chemokine Receptor 1
- Chemokine CX3CL1
- Hippocampus
- Interleukin-1beta
- Microglia
- Neurogenesis
- Neurons
- Rats
- Receptors, Chemokine
- Signal Transduction
Data from several laboratories suggest that erythrocyte complement-regulatory proteins, in particular complement receptor 1 (CR1), are important in the pathogenesis of severe malaria. Additional studies suggest that the levels of expression of CR1 and the complement regulator CD55 on erythrocytes vary with age, being low in young children and increasing with age. It is proposed that the interplay between the rate at which immunity develops during malaria exposure and the changes in levels of erythrocyte complement-regulatory proteins that occur with age might contribute to the differences in epidemiology of severe malaria-associated anaemia and cerebral malaria.
MeSH Terms
- Aging
- Anemia
- Animals
- CD55 Antigens
- Disease Susceptibility
- Erythrocytes
- Humans
- Malaria
- Malaria, Cerebral
- Receptors, Complement
- Rosette Formation
Senescence leads to the appearance of atrophic follicular dendritic cells (FDCs) that trap and retain little immune complexes (IC), generate few memory B cells, and induce a reduced number of germinal centers (GC). Deficiencies in antibody responses to T cell dependent exogenous antigens such as pneumonia and influenza vaccines may reflect intrinsic FDC defects or altered FDC-B cell interactions. We recently studied antigen handling capacity and co-stimulatory activity of old FDCs and determined age-related changes in the expression or function of FcgammaRII or CR1 and 2 on FDCs. Here, we present an overview of FDC function in recall responses with known deficiencies in FDCs and GC development. Then, we review our recent work on aged FDCs and discuss age-related changes in molecular interactions between FDCs and B cells. We also discuss the causes underlying the impaired humoral immune response with respect to age-related molecular changes in FDC and B cell interactions. In vitro evidence suggests that FcgammaRII on aged FDCs is regulated abnormally and this in turn might cause the development of a defective FDC-network (reticulum) that retains few ICs, promotes ITIM signaling, prevents B cell proliferation and GC formation, and antibody production.
MeSH Terms
- Aging
- Animals
- Antibody Formation
- Cellular Senescence
- Dendritic Cells, Follicular
- Humans
The low levels of complement receptor 1 (CR1) on erythrocytes in autoimmune diseases and AIDS may be due to accelerated loss in the circulation, or to a diminished expression of CR1 on the red cell lineage. Therefore, we analyzed the expression of CR1 on reticulocytes (R) vs erythrocytes (E). Healthy subjects had a significant higher CR1 number per cell on R (919 /- 99 CR1/cell) than on E (279 /- 30 CR1/cell, n = 23), which corresponded to a 3. 5- /- 1.3-fold loss of CR1. This intravascular loss was confirmed by FACS analysis, which showed that all R expressed CR1, whereas a large fraction of E was negative. The systemic lupus erythematosus (SLE), HIV-infected, and cold hemolytic Ab disease (CHAD) patients had a CR1 number on R identical to the healthy subjects, contrasting with a lower CR1 on their E. The data indicated a significantly higher loss of CR1 in the three diseases, i.e., 7.0- /- 3.8-, 6.1- /- 2.9-, and 9.6- /- 5.6-fold, respectively. The intravascular loss was best exemplified in a patient with factor I deficiency whose CR1 dropped from 520 CR1/R to 28 CR1/E, i.e., 18.6-fold loss. In one SLE patient and in the factor I-deficient patient, the FACS data were consistent with a loss of CR1 already on some R. In conclusion, CR1 is lost progressively from normal E during in vivo aging so that old E are almost devoid of CR1. The low CR1 of RBC in autoimmune diseases and HIV-infection is due to a loss occurring in the circulation by an active process that remains to be defined.
MeSH Terms
- Agglutinins
- Aging
- Anemia, Hemolytic, Autoimmune
- Cryoglobulins
- Enzyme-Linked Immunosorbent Assay
- Erythrocytes
- HIV Infections
- Humans
- Immunoblotting
- Lupus Erythematosus, Systemic
- Receptors, Complement 3b
- Reticulocytes
Human erythrocytes (E) react by exocytosis of membrane vesicles to various stresses including the fixation of the membrane attack complex of Complement. E from normal individuals loose a notable proportion of their initial number of surface CR1 molecules during the ageing process. An acquired decrease of CR1 on E also occurs in pathological conditions such as Systemic Lupus Erythematosus or AIDS. The present study investigated whether calcium ionophore A23187 (Ca-ion) induced vesicle formation of human E in vitro is responsible for a preferential loss of CR1 as well as whether CR1 molecules at the surface of Ca-ion treated E or vesicles are: (i) functional, (ii) native or protease degraded, or (iii) more clustered than CR1 on native E. A study of E from 137 normal individuals showed that a one-hour Ca-ion induced vesicle formation preferentially removed one third of E surface CR1. Kinetic experiments suggested that all surface CR1 could be removed from E upon longer incubation times. CR1 molecules on vesicles were still able to inhibit Complement activation, and were found in larger clusters than on native E. These data suggest that a significant part of surface CR1 molecules may be removed from E by vesicle formation during the life of E in normal individuals. This phenomenon could be exacerbated in pathological conditions.
MeSH Terms
- Aging
- Alleles
- Calcimycin
- Complement C1r
- Complement C4b
- Complement Inactivator Proteins
- Complement Membrane Attack Complex
- Erythrocytes
- Exocytosis
- Flow Cytometry
- Glycoproteins
- Humans
- Immunohistochemistry
- Ionophores
- Microscopy, Electron
- Papain
- Polymorphism, Restriction Fragment Length
- Receptors, Complement
- Receptors, Complement 3b
- Synaptic Vesicles
Caloric restriction (CR), has been shown to extend average and maximum lifespan in rodents and other animals as well as to delay a wide variety of manifestations of aging. The purpose of this study was to further elucidate the relationship between lipofuscin (LF) accumulation and the aging process by examining the effect of lifelong CR on LF accumulation in brain cells. Specifically, 1) we include age groups of CR (CR1 approximately equal to 90 kcal/wk and CR2 approximately equal to 58 kcal/wk) and ad libidum fed (AL; approximately 120 kcal/wk) mice including groups at maximum lifespan; 2) CR was the major dietary manipulation; 3) LF was identified using EM; 4) LF was quantified by areal measurement; and 5) the results were analyzed by inferential statistics. We have found that 1) LF increased with age and 2) that animals in the CR2 group had significantly less overall LF in the perikarya of the granule cells of the dentate gyrus when compared to CR1 or AL animals at equivalent ages. In addition, CR2 mice at maximum lifespan (45 mo.) had slightly less LF than did CR1 or AL mice at their maximum lifespans (36 mo.). Our results clearly demonstrate that CR (at 52%, but not 25% of AL diet) retards the overall accumulation of LF with time and, further, suggest that LF accumulation is not simply a linear function of age.
MeSH Terms
- Aging
- Analysis of Variance
- Animals
- Brain
- Diet, Reducing
- Female
- Lipofuscin
- Mice
- Mice, Inbred Strains
Complement and immunoglobulin have each been claimed to be the major opsonins responsible for sequestration of the effete erythrocyte. Binding of immune complexes to the erythrocyte via CR1 (CD35) provides a model for studying the effects of increments in membrane-bound complement and immunoglobulin on the sequestration of the erythrocyte ('innocent bystander' sequestration). It is possible that C3b-bearing immune complexes (IC-C3b) bound to erythrocyte CR1 contribute to the levels of immunoglobulin and complement fragments detectable on the human erythrocyte. We have, therefore, compared the capacity of erythrocytes from young and elderly donors to bind IC-C3b and the effect of this binding on in vitro sequestration. Erythrocytes from young donors exposed to IC-C3b bind these complexes, as attested by an increment in membrane-bound C3, and undergo 'innocent bystander' sequestration. However, when density-separated erythrocytes are so exposed, it is only the low density (young) erythrocytes from young donors which are susceptible to 'innocent bystander' sequestration. High density (old) erythrocytes from young donors and all erythrocytes from elderly donors show initially high in vitro sequestration and are resistant to the 'innocent bystander' effect. (Those erythrocytes which show initially high in vitro sequestration are referred to collectively as 'in situ aged' erythrocytes.) There is a great similarity between the mechanisms of sequestration of 'in situ aged' and 'innocent bystander' erythrocytes in that they are both inhibited by the integrin binding peptide arginine-glycine-aspartic acid (RGD) and the beta-galactosyl sugar N-acetyl-galactosamine, and unaffected by the Fc-gamma binding protein, Protein-G. Complement is the major opsonin in 'innocent bystander' sequestration since this sequestration occurs whether the isotype of the antibody in the immune complex is IgM or IgG, and Protein-G, which inhibits IgG-dependent erythrophagocytosis, has no effect on 'innocent bystander' sequestration. The present studies demonstrate that in vitro sequestration of 'in situ aged' erythrocytes is similar to complement-dependent 'innocent bystander' sequestration, thus supporting the contention that complement recognition is cardinal in sequestration of 'in situ aged' erythrocytes.
MeSH Terms
- Adolescent
- Adult
- Aged
- Aging
- Antigen-Antibody Complex
- Complement System Proteins
- Erythrocytes
- Female
- Humans
- Male
- Oligopeptides
- Phagocytosis
- Receptors, Complement 3b
Neonatal neutrophils (PMN) show a well-documented defect in chemotaxis that is associated with several abnormalities of PMN structure and function, including deficient surface expression of CR3 (CD11b), a critical adhesion molecule, on chemoattractant-activated PMN. After activation of PMN with additional stimuli including calcium ionophores, we also found deficient surface CR3 (but normal CR1) expression on neonatal PMN suggesting that abnormal signaling mechanisms are not likely to explain the deficient CR3 expression on activated neonatal PMN. Therefore, we hypothesized that deficient surface expression of CR3 on stimulated neonatal neutrophils is caused by a deficiency in total cell content of CR3. We tested this hypothesis using three different methods to compare the total quantity of CR3 in neonatal versus adult PMN. Western blotting of serial twofold dilutions of PMN lysates from five adult and neonatal pairs, using a monoclonal antibody (MoAb) against CR3 (21PM19C), consistently showed diminished CR3 content in neonatal PMN. A sandwich enzyme-linked immunosorbent assay, in which the CR3 heterodimers in PMN lysates were captured by MoAb to the beta-chain, CD18 (R15.7), then detected with a biotinylated MoAb to the alpha-chain, CD11b (anti-Mac-1), showed that neonatal PMN lysates contain about 66% of adult PMN levels of CR3 (P < 0.03; n = 6). PMN fixed with paraformaldehyde and permeabilized with saponin were studied by immunofluorescence flow cytometry to determine total (surface plus intracellular) CR3 content using phycoerythrin-conjugated MoAb to CR3 (anti-Leu15). Mean total cell CR3 content (in relative fluorescence units) was 58 /- 14 for adult PMN and 27 /- 6 for neonatal PMN (n = 5; P = 0.013). In each method, total cell content of CR1 was equivalent for neonatal versus adult PMN. We conclude that neonatal PMN are markedly deficient in total cell CR3 content compared with adult PMN. This result provides a primary explanation for deficient CR3 surface expression on activated neonatal PMN that, in turn, may be important in the chemotactic defect of these cells.
MeSH Terms
- Adult
- Aging
- Antigens, CD
- Blotting, Western
- CD11 Antigens
- Enzyme-Linked Immunosorbent Assay
- Humans
- Infant, Newborn
- Ionomycin
- Kinetics
- N-Formylmethionine Leucyl-Phenylalanine
- Neutrophils
Neonatal neutrophils have Mac-1-related functional abnormalities that may contribute to the enhanced susceptibility of neonates to bacterial infections. We developed a flow cytometric method using differences in light scattering and CD16 expression to distinguish eosinophils from neutrophils and studied their responses to stimulation in vitro. Mean forward light scatter was 20-60% greater for adult neutrophils than eosinophils, p less than or equal to 0.001, and side scatter was 30-60% greater for eosinophils than neutrophils, p less than or equal to 0.01, both before and after stimulation. Light scatter of neonatal and adult eosinophils did not differ. Mac-1 expression on adult eosinophils increased 60% after warming without specific stimulation and further increased 5-fold after incubation with 1 microM A23187, p less than 0.0001. Platelet activating factor and recombinant C5a produced modest increases in eosinophil Mac-1 expression, while N-formyl-met-leu-phe and leukotriene B4 had minimal effects. Histamine and the eosinophil chemotactic factor of anaphylaxis tetrapeptides had no effect on either Mac-1 or CR1 (CD35) expression. After stimulation with 1 microM A23187, eosinophils from eight healthy neonates at term expressed less Mac-1 than eosinophils from eight adults (mean /- SD: 60.0 /- 17.2 versus 89.1 /- 12.8, p = 0.001) by the same ratio as neonatal to adult neutrophils (121.5 /- 17.9 versus 178.2 /- 11.7, p = 0.0004). We conclude that neonatal eosinophils and neutrophils have similar impairments of quantitative Mac-1 up-regulation. Further studies are needed to determine if neonatal eosinophils also have functional abnormalities related to Mac-1.
MeSH Terms
- Adult
- Aging
- Eosinophils
- Humans
- Infant, Newborn
- Macrophage-1 Antigen
- Neutrophils
- Up-Regulation