Cellular senescence: the good, the bad and the unknown

Cellular senescence is a ubiquitous process with roles in tissue remodelling, including wound repair and embryogenesis. However, prolonged senescence can be maladaptive, leading to cancer development and age-related diseases. Cellular senescence involves cell-cycle arrest and the release of inflammatory cytokines with autocrine, paracrine and endocrine activities. Senescent cells also exhibit morphological alterations, including flattened cell bodies, vacuolization and granularity in the cytoplasm and abnormal organelles. Several biomarkers of cellular senescence have been identified, including SA-βgal, p16 and p21; however, few markers have high sensitivity and specificity. In addition to driving ageing, senescence of immune and parenchymal cells contributes to the development of a variety of diseases and metabolic disorders. In the kidney, senescence might have beneficial roles during development and recovery from injury, but can also contribute to the progression of acute kidney injury and chronic kidney disease. Therapies that target senescence, including senolytic and senomorphic drugs, stem cell therapies and other interventions, have been shown to extend lifespan and reduce tissue injury in various animal models. Early clinical trials confirm that senotherapeutic approaches could be beneficial in human disease. However, larger clinical trials are needed to translate these approaches to patient care.

Prevalence and Loads of Torquetenovirus in the European MARK-AGE Study Population

Torquetenovirus (TTV) viremia has been associated with increased mortality risk in the elderly population. This work aims to investigate TTV viremia as a potential biomarker of immunosenescence. We compared levels of circulating TTV in 1813 participants of the MARK-AGE project, including human models of delayed (offspring of centenarians [GO]) and premature (Down syndrome [DS]) immunosenescence. The TTV load was positively associated with age, cytomegalovirus (CMV) antibody levels, and the Cu/Zn ratio and negatively associated with platelets, total cholesterol, and total IgM. TTV viremia was highest in DS and lowest in GO, with intermediate levels in the SGO (spouses of GO) and RASIG (Randomly Recruited Age-Stratified Individuals From The General Population) populations. In the RASIG population, TTV DNA loads showed a slight negative association with CD3+T-cells and CD4+T-cells. Finally, males with ≥4log TTV copies/mL had a higher risk of having a CD4/CD8 ratio<1 than those with lower viremia (odds ratio [OR] = 2.85, 95% confidence interval [CI]: 1.06-7.62), as well as reduced CD3+ and CD4+T-cells compared to males with lower replication rates (<4log), even after adjusting for CMV infection. In summary, differences in immune system preservation are reflected in the models of delayed and premature immunosenescence, displaying the best and worst control over TTV replication, respectively. In the general population, TTV loads were negatively associated with CD4+ cell counts, with an increased predisposition for an inverted CD4/CD8 ratio for individuals with TTV loads ≥4log copies/mL, thus promoting an immune risk phenotype.

Nutritional Factors Modulating Alu Methylation in an Italian Sample from The Mark-Age Study Including Offspring of Healthy Nonagenarians

Alu hypomethylation promotes genomic instability and is associated with aging and age-related diseases. Dietary factors affect global DNA methylation, leading to changes in genomic stability and gene expression with an impact on longevity and the risk of disease. This preliminary study aims to investigate the relationship between nutritional factors, such as circulating trace elements, lipids and antioxidants, and Alu methylation in elderly subjects and offspring of healthy nonagenarians. Alu DNA methylation was analyzed in sixty RASIG (randomly recruited age-stratified individuals from the general population) and thirty-two GO (GeHA offspring) enrolled in Italy in the framework of the MARK-AGE project. Factor analysis revealed a different clustering between Alu CpG1 and the other CpG sites. RASIG over 65 years showed lower Alu CpG1 methylation than those of GO subjects in the same age class. Moreover, Alu CpG1 methylation was associated with fruit and whole-grain bread consumption, LDL2-Cholesterol and plasma copper. The preserved Alu methylation status in GO, suggests Alu epigenetic changes as a potential marker of aging. Our preliminary investigation shows that Alu methylation may be affected by food rich in fibers and antioxidants, or circulating LDL subfractions and plasma copper.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Supplementation with Bifidobacterium longum Bar33 and Lactobacillus helveticus Bar13 mixture improves immunity in elderly humans (over 75 years) and aged mice

OBJECTIVE

Aging induces several physiologic and immune changes. The usefulness of probiotics in ameliorating age-related disorders remains largely unexplored. The aim of this study was to evaluate the effectiveness of a Bifidobacterium longum Bar33 and Lactobacillus helveticus Bar13 mixture in improving the physiologic status and immunity of older adults (over 75 years). Furthermore, the possible role of such mixture in ameliorating gut immunity in aged mice was investigated.

METHODS

A randomized, double-blind, placebo-controlled trial was conducted with 98 adults (84.6 ± 7.8 y), supplemented for 30 d with a biscuit containing a probiotic mixture of B. longum Bar33 and L. helveticus Bar13 (1:1), or no probiotics, as placebo. Blood was collected for analysis of biochemical parameters, lymphocyte subpopulations, natural killer activity, and cytokine release. Aged Balb/c mice received the same probiotic mixture or placebo daily for 28 d, then blood and intestinal lymphocyte subpopulations were analyzed.

RESULTS

The probiotic mixture ameliorated immune response in older adults by increasing naive, activated memory, regulatory T cells, B cells, and natural killer activity and decreasing memory T cells compared with placebo (P < 0.05). The biochemical parameters did not change after probiotic supplementation. In the gut of old mice, the two probiotics modulated cells crucial for gut immune homeostasis by increasing regulatory T (Treg and Tr1) and decreasing γδ T cells compared with control mice (P < 0.05). In addition, B cells increased in the gut and blood of probiotic-treated mice.

CONCLUSION

Results from the present study data indicated that B. longum Bar33 and L. helveticus Bar13 improve immune function at intestinal and peripheral sites in aging.

Sicilian centenarian offspring are more resistant to immune ageing

BACKGROUND

Immunosenescence constitutes a major indirect cause of morbidity and mortality in the elderly. Previous analysis of immune signatures in a cohort of centenarian offspring showed an intermediate immunophenotype between age-matched and younger controls.

AIMS

To confirm and extend the previous studies performing further phenotypical analysis in centenarian offspring and controls.

METHODS

Analysis of Treg cells, γδ T cells, mucosal-associated invariant T cells, and senescent immune T cells was performed in centenarian offspring and controls.

RESULTS

We report significant differences between elderly and centenarian offspring in most of the studied subsets, showing that centenarian offspring subsets present an intermediate phenotyping between elderly and younger people.

CONCLUSION

The whole present data confirm and extend the previous results showing that centenarian offspring retain more youthful immunological parameters and that the exhaustion of the immune system is less evident than in elderly without centenarian parents, though further investigations are warranted.

Activation-Induced Autophagy Is Preserved in CD4+ T-Cells in Familial Longevity

As with many other tissues and organs, the immune system is also affected by age. Immunosenescence is characterized by a decreased ability of immune cells to mount a productive response upon exposure to new antigens. Several studies have reported that members of families with exceptional longevity show improved immune function, which might contribute to the increased life- and health-span observed in those families. Autophagy is a catabolic process that delivers cytoplasmic material to the lysosomes for degradation. Defective autophagy is known to be associated with age in several cell types and tissues and its dysregulation is related to age-associated diseases. In T-cells, autophagy has an essential role in modulating protein and organelle homeostasis and in the regulation of activation-induced responses. In this study, using two different cohorts of individuals belonging to families with exceptional longevity, we show that CD4+ T-cells isolated from the offspring of parents with exceptional longevity show improved activation-induced autophagic activity compared with age-matched controls. Interestingly, increased autophagy is positively correlated with increased interferon-γ production. In conclusion, autophagy appears to be better maintained in members of families with extended longevity and positively correlates with improved T-cell function.

Phenome and genome based studies into human ageing and longevity: An overview

Human ageing is an extremely personal process leading across the life course of individuals to large population heterogeneity in the decline of functional capacity, health and lifespan. The extremes of this process are witnessed by the healthy vital 100-year-olds on one end and the 60-year-olds suffering from multiple morbid conditions on the other end of the spectrum. Molecular studies into the basis of this heterogeneity have focused on a range of endpoints and methodological approaches. The phenotype definitions most prominently investigated in these studies are either lifespan-related or biomarker based indices of the biological ageing rate of individuals and their tissues. Unlike for many complex, age-related diseases, consensus on the ultimate set of multi-biomarker ageing or lifespan-related phenotypes for genetic and genomic studies has not been reached yet. Comparable to animal models, hallmarks of age-related disease risk, healthy ageing and longevity include immune and metabolic pathways. Potentially novel genomic regions and pathways have been identified among many (epi)genomic studies into chronological age and studies into human lifespan regulation, with APOE and FOXO3A representing yet the most robust loci. Functional analysis of a handful of genes in cell-based and animal models is ongoing. The way forward in human ageing and longevity studies seems through improvements in the interpretation of the biology of the genome, in application of computational and systems biology, integration with animal models and by harmonization of repeated phenotypic and omics measures in longitudinal and intervention studies. This article is part of a Special Issue entitled: Model Systems of Aging - edited by "Houtkooper Riekelt".

Differential DNA methylation and lymphocyte proportions in a Costa Rican high longevity region

Background

The Nicoya Peninsula in Costa Rica has one of the highest old-age life expectancies in the world, but the underlying biological mechanisms of this longevity are not well understood. As DNA methylation is hypothesized to be a component of biological aging, we focused on this malleable epigenetic mark to determine its association with current residence in Nicoya versus elsewhere in Costa Rica. Examining a population’s unique DNA methylation pattern allows us to differentiate hallmarks of longevity from individual stochastic variation. These differences may be characteristic of a combination of social, biological, and environmental contexts.

Methods

In a cross-sectional subsample of the Costa Rican Longevity and Healthy Aging Study, we compared whole blood DNA methylation profiles of residents from Nicoya (n = 48) and non-Nicoya (other Costa Rican regions, n = 47) using the Infinium HumanMethylation450 microarray.

Results

We observed a number of differences that may be markers of delayed aging, such as bioinformatically derived differential CD8+ T cell proportions. Additionally, both site- and region-specific analyses revealed DNA methylation patterns unique to Nicoyans. We also observed lower overall variability in DNA methylation in the Nicoyan population, another hallmark of younger biological age.

Conclusions

Nicoyans represent an interesting group of individuals who may possess unique immune cell proportions as well as distinct differences in their epigenome, at the level of DNA methylation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13072-017-0128-2) contains supplementary material, which is available to authorized users.

The Survival of Spouses Marrying Into Longevity-Enriched Families

BACKGROUND

Studies of longevity-enriched families are an important tool to gain insight into the mechanisms of exceptionally long and healthy lives. In the Long Life Family Study, the spouses of the members of the longevity-enriched families are often used as a control group. These spouses could be expected to have better health than the background population due to shared family environment with the longevity-enriched family members and due to assortative mating.

METHODS

A Danish cohort study of 5,363 offspring of long-lived siblings, born 1917-1982, and 4,498 "first spouses" of these offspring. For each offspring and spouse, 10 controls were drawn from a 5% random sample of the Danish population matched on birth year and sex. Mortality was assessed for ages 20-69 years during 1968-2013 based on prospectively collected registry data.

RESULTS

During the 45-year follow-up period, 437 offspring deaths and 502 offspring spouse deaths were observed. Compared with the background population, the hazard ratio for male offspring was 0.44 (95% confidence interval [CI]: 0.38-0.50) and for female offspring it was 0.57 (95% CI: 0.49-0.66). For male spouses, the hazard ratio was 0.66 (95% CI: 0.59-0.74), whereas for female spouses it was 0.64 (95% CI: 0.54-0.76). Sensitivity analyses in restricted samples gave similar results.

CONCLUSION

The mortality for ages 20-69 years of spouses marrying into longevity-enriched families is substantially lower than the mortality in the background population, although long-lived siblings participation bias may have contributed to the difference. This finding has implications for the use of spouses as controls in healthy aging and longevity studies, as environmental and/or genetic overmatching may occur.

Genetic Influence on the Peripheral Blood CD4+ T-cell Differentiation Status in CMV Infection

A latent infection with cytomegalovirus (CMV), a ubiquitous beta herpesvirus, is associated with an accumulation of late-differentiated memory T-cells, often accompanied by a reciprocal reduced frequency of early-differentiated cells (commonly also referred to as "naïve"). However, this impact of CMV on T-cell phenotypes is variable between individuals. Our previous findings in a subgroup of participants in the Leiden familial Longevity Study indicated an important role of genetics. For further testing, we have analyzed middle-aged monozygotic (MZ, n = 42) and dizygotic (DZ, n = 39) twin pairs from the Danish Twin Registry for their T-cell differentiation status, assessed by surface expression of CD27, CD28, CD57, and KLRG-1. We observed a significant intraclass correlation between cotwins of MZ, but not DZ pairs for the differentiation status of CD4⁺ and CD8⁺ subsets. Classical heritability analysis confirmed a substantial contribution of genetics to the differentiation status of T-cells in CMV infection. The humoral (IgG) response to different CMV antigens also seems to be genetically influenced, suggesting that a similar degree of immune control of the virus in MZ twins might be responsible for their similar T-cell differentiation status. Thus, the way T-cells differentiate in the face of a latent CMV infection, and the parallel humoral responses, both controlling the virus, are genetically influenced.

IFNγ⁻TNFα⁻IL2⁻MIP1α⁻CD107a⁺PRF1⁺ CD8 pp65-Specific T-Cell Response Is Independently Associated With Time to Death in Elderly Humans

Persistent cytomegalovirus (CMV) infection has been suggested to be a major driving force in the immune deterioration and an underlying source of age-related diseases in the elderly. CMV antibody titers are associated with lower responses to vaccination, cardiovascular diseases, frailty, and mortality. CMV infection is also associated with shorter T-cell telomeres and replicative senescence. Although an age-related deregulation of CMV-specific T-cell responses could be an underlying cause of the relationship between CMV and immune defects, strong and polyfunctional responses are observed in elderly individuals, casting uncertainty on their direct role in age-related immune frailty. In this study, we longitudinally followed a cohort of healthy donors aged over 50 years, assessing their mortality rates and time to death during a 2-year period. Specific T-cell responses to the immunodominant antigen pp65 (IFNγ, TNFα, IL2, MIP1α, CD107a, and perforin production) were analyzed at the beginning of the 2-year observation period. A cytotoxic CD8 pp65-specific T-cell response, without cytokine or chemokine coexpression, was independently associated with all-cause mortality in these elderly individuals. This pp65-specific CD8 T-cell response could be a useful tool to identify individuals with depressed immune function and a higher risk of death.