Chemokine production by peripheral blood mononuclear cells in elderly subjects

Global analyses revealed age-related alterations in innate immune responses after stimulation of pathogen recognition receptors

Aging leads to dysregulation of multiple components of the immune system that results in increased susceptibility to infections and poor response to vaccines in the aging population. The dysfunctions of adaptive B and T cells are well documented, but the effect of aging on innate immunity remains incompletely understood. Using a heterogeneous population of peripheral blood mononuclear cells (PBMCs), we first undertook transcriptional profiling and found that PBMCs isolated from old individuals (≥ 65 years) exhibited a delayed and altered response to stimulation with TLR4, TLR7/8, and RIG-I agonists compared to cells obtained from adults (≤ 40 years). This delayed response to innate immune agonists resulted in the reduced production of pro-inflammatory and antiviral cytokines and chemokines including TNFα, IL-6, IL-1β, IFNα, IFNγ, CCL2, and CCL7. While the major monocyte and dendritic cell subsets did not change numerically with aging, activation of specific cell types was altered. PBMCs from old subjects also had a lower frequency of CD40+ monocytes, impaired up-regulation of PD-L1 on monocytes and T cells, and increased expression of PD-L2 and B7-H4 on B cells. The defective immune response to innate agonists adversely affected adaptive immunity as TLR-stimulated PBMCs (minus CD3 T cells) from old subjects elicited significantly lower levels of adult T-cell proliferation than those from adult subjects in an allogeneic mixed lymphocyte reaction (MLR). Collectively, these age-associated changes in cytokine, chemokine and interferon production, as well as co-stimulatory protein expression could contribute to the blunted memory B- and T-cell immune responses to vaccines and infections.

Pulmonary effects of inhaled diesel exhaust in aged mice

Pulmonary morbidity and mortality resulting from exposure to fine particulate matter (PM) increases with age. The present studies analyzed potential mechanisms underlying increased susceptibility of the elderly to PM using diesel exhaust (DE) as a model. Mice (2 m and 18 m) were exposed to DE (0, 300, and 1000 microg/m(3)) for 3 h once (single) or 3 h/day for 3 days (repeated). Bronchoalveolar lavage fluid (BAL), serum and lung tissue were collected 0 and 24 h later. Exposure to DE resulted in structural alterations in the lungs of older but not younger mice, including patchy thickening of the alveolar septa and inflammatory cell localization in alveolar spaces. These effects were most pronounced 24 h after a single exposure to the higher dose of DE. Significant increases in BAL nitrogen oxides were also noted in older mice, as well as expression of lipocalin 24p3, an oxidative stress marker in the lung with no effects in younger mice. Following DE inhalation, expression of Tumor Necrosis Factor alpha (TNFalpha) was upregulated in lungs of both younger and older mice; however, this was attenuated in older animals. Whereas exposure to DE resulted in increases in lung Interleukin-6 (IL-6) expression in both older and younger mice, IL-8 increased only in older animals. In younger mice, constitutive expression of manganese superoxide dismutase (MnSOD) decreased after DE exposure, while in older mice, constitutive MnSOD was not detectable and DE had no effect on expression of this antioxidant. Taken together, these results suggest that altered generation of inflammatory mediators and MnSOD may contribute to increased susceptibility of older mice to inhaled DE.

Aging and lung injury repair: a role for bone marrow derived mesenchymal stem cells

The incidence of lung fibrosis increases with age. Aging is associated with modifications in the intracellular and extracellular environment including alteration of the extracellular matrix, imbalance of the redox state, accumulation of senescent cells and potential alteration of the recruitment of bone marrow mesenchymal stem cells. The combination of these senescence-related alterations in the lung and in bone marrow progenitor cells might be responsible of the higher susceptibility to lung fibrosis in elderly individuals. The understanding of these age related changes must be considered in the rationale for the development of therapeutic interventions to control lung injury and fibrosis.

Aging-related defects are associated with adverse cardiac remodeling in a mouse model of reperfused myocardial infarction

OBJECTIVES

The purpose of this study was to study aging-associated alterations in the inflammatory and reparative response after myocardial infarction (MI) and their involvement in adverse post-infarction remodeling of the senescent heart.

BACKGROUND

Advanced age is a predictor of death and ventricular dilation in patients with MI; however, the cellular mechanisms responsible for increased remodeling of the infarcted senescent heart remain poorly understood.

METHODS

Histomorphometric, molecular, and echocardiographic end points were compared between young and senescent mice undergoing reperfused infarction protocols. The response of young and senescent mouse cardiac fibroblasts to transforming growth factor (TGF)-beta stimulation was examined.

RESULTS

Senescence was associated with decreased and delayed neutrophil and macrophage infiltration, markedly reduced cytokine and chemokine expression in the infarcted myocardium, and impaired phagocytosis of dead cardiomyocytes. Reduced inflammation in senescent mouse infarcts was followed by decreased myofibroblast density and markedly diminished collagen deposition in the scar. The healing defects in senescent animals were associated with enhanced dilative and hypertrophic remodeling and worse systolic dysfunction. Fibroblasts isolated from senescent mouse hearts showed a blunted response to TGF-beta1.

CONCLUSIONS

Although young mice exhibit a robust post-infarction inflammatory response and form dense collagenous scars, senescent mice show suppressed inflammation, delayed granulation tissue formation, and markedly reduced collagen deposition. These defects might contribute to adverse remodeling. These observations suggest that caution is necessary when attempting to therapeutically target the post-infarction inflammatory response in patients with reperfused MI. The injurious potential of inflammatory mediators might have been overstated, owing to extrapolation of experimental findings from young animals to older human patients.

Toll-like receptors in older adults

Toll-like receptors (TLRs) recognize a limited number of conserved elements in pathogens and, by activating antigen-presenting cells such as dendritic cells and monocytes and macrophages, play a crucial role in the immune response to infection and vaccination. Most data on TLR function in the context of human aging focus on responses to lipopolysaccharide, an integral component of gram-negative bacteria, which signals through TLR4. However, such studies have not led to a consensus conclusion and are limited by differences in epidemiological and laboratory methods. A recent comprehensive evaluation of TLR function in monocytes from older adults was conducted using a multivariable mixed statistical model to account for covariates. It was found that cytokine production after TLR1/2 engagement, which is essential for the recognition of triacylated lipopeptides found in a variety of bacteria, is substantially lower in monocytes from older adults. The upregulation of costimulatory proteins such as CD80, essential for optimal activation of T cells, on monocytes from older adults was less for all TLR ligands tested than for cells from young individuals, and the extent of CD80 upregulation predicted subsequent antibody response to influenza immunization. These and other consequences of aging on human TLR function may impair activation of the immune response and contribute to poorer vaccine responses and greater morbidity and mortality from infectious diseases in older adults. Such age-associated alterations have particular relevance in view of the interest in TLR agonists as therapeutic agents not only for infections, but also for allergic, autoimmune, and malignant disease.

Simultaneous evaluation of circulating chemokine and cytokine profiles in elderly subjects by multiplex technology: relationship with zinc status

Cellular components of both adaptive and innate immune systems produce different chemokines and cytokines, involved in different signalling pathways among cells, and modulate effector function during immune response, playing a key role in the regulation of the type and extent of the immune response in the elderly. We evaluated the circulating concentration of selected chemokines: MCP-1, MIP-1alpha, IL-8, RANTES together with IL-6 and TNF-alpha in plasma obtained from a group of healthy old subjects, in order to highlight possible differences in the synthesis of these factors, assuming that both the cytokine and the chemokine networks are remodelled with ageing. The simultaneous evaluation was performed by a multiplex analysis system. In addition, since micronutrient deficiency may underlie an inflammatory response, the association between chemokine levels and a nutritional element such as zinc was also evaluated, since the immune system is the first system to be affected by changing zinc levels, due to its high cell turnover. A progressive age-related increase of plasma concentrations of all soluble factors was observed. The increment was particularly evident for IL-6, IL-8, MCP-1 and TNF-alpha in the over 85-year-old group in concomitance with increasing percentages of subjects with low circulating levels of zinc. In conclusion, the remodelling of chemokine profiles, skewed to Th2 response by both advanced ages and circulating levels of zinc, might reflect different states of activation and/or responsiveness of the human immune cell/mediator network, thus influencing the ability to develop rapid innate and long-lasting adaptive immune responses with advancing age.

Role of chemokines in endocrine autoimmune diseases

Chemokines are a group of peptides of low molecular weight that induce the chemotaxis of different leukocyte subtypes. The major function of chemokines is the recruitment of leukocytes to inflammation sites, but they also play a role in tumoral growth, angiogenesis, and organ sclerosis. In the last few years, experimental evidence accumulated supporting the concept that interferon-gamma (IFN-gamma) inducible chemokines (CXCL9, CXCL10, and CXCL11) and their receptor, CXCR3, play an important role in the initial stage of autoimmune disorders involving endocrine glands. The fact that, after IFN-gamma stimulation, endocrine epithelial cells secrete CXCL10, which in turn recruits type 1 T helper lymphocytes expressing CXCR3 and secreting IFN-gamma, thus perpetuating autoimmune inflammation, strongly supports the concept that chemokines play an important role in endocrine autoimmunity. This article reviews the recent literature including basic science, animal models, and clinical studies, regarding the role of these chemokines in autoimmune endocrine diseases. The potential clinical applications of assaying the serum levels of CXCL10 and the value of such measurements are reviewed. Clinical studies addressing the issue of a role for serum CXCL10 measurement in Graves' disease, Graves' ophthalmopathy, chronic autoimmune thyroiditis, type 1 diabetes mellitus, and Addison's disease have been considered. The principal aim was to propose that chemokines, and in particular CXCL10, should no longer be considered as belonging exclusively to basic science, but rather should be used for providing new insights in the clinical management of patients with endocrine autoimmune diseases.

Zinc, oxidative stress, genetic background and immunosenescence: implications for healthy ageing

The relevance of zinc for proper functioning of the entire immune system is already well documented. However, the identification of individuals who really need zinc supplementation is still debated in view of the fact that excessive zinc may also be toxic. The risk of developing zinc deficiency in people from industrialized countries is relatively low, except for elderly subjects where zinc intake may be suboptimal and inflammation is chronic. Thus, the role of zinc on the immune system and on the health of European elderly people is becoming of paramount importance, considering also that the elderly population is rapidly increasing. In particular, the factors contributing to and the biochemical markers of zinc deficiency in the elderly are still remain to be established. Epidemiological, functional, and genetic studies aimed at formulating a rationale for the promotion of healthy ageing through zinc supplementation was the subject of an International Conference held in Madrid from 11-13 February 2006 (3rd ZincAge Meeting) at the CNIO Institute (local organizer: Maria Blasco, partner of ZincAge).

Expression and production of two selected beta-chemokines in peripheral blood mononuclear cells from patients with Alzheimer's disease

MCP-1 and RANTES are molecules that regulate monocyte and T-lymphocyte recruitment towards sites of inflammation. We sought to evaluate the role of these chemokines in Alzheimer's disease (AD), and the effect of acetylcholinesterase inhibitor (AchEI) therapy on their release from peripheral blood mononuclear cells (PBMC). MCP-1 and RANTES mRNA expressions were determined by RT-PCR and the amount of secreted chemokines was assayed using specific ELISA methods from purified PBMC from each AD patients (n = 40) at the time of enrolment (T0) and after 1 month of treatment with AchEI (T1) and from 20 healthy age and sex-matched subjects (HC). We found that expression and production of MCP-1 in AD patients was significantly lower than in HC subjects. After 1 month of therapy with AchEI (Donepezil), MCP-1 levels increased in each patient. However, higher levels were detected for RANTES in AD patients compared to control subjects and in AD patients treated with Donepezil. MCP-1 and RANTES have a compensatory role in balancing the impaired mechanisms involved in immune response during ageing. Our present findings suggest that these two chemokines are both involved in AD pathogenesis and might reflect different states of activation and/or responsiveness of PBMC from AD patients, contributing to the impaired of the peripheral immune system in these patients.

Age-dependent changes in CXC chemokine ligand 10 serum levels in euthyroid subjects

Circulating levels of cytokines are deeply influenced by aging, and few data about serum chemokines are available. The aim of this study was to evaluate the influence of aging on circulating CXCL10. One hundred forty healthy subjects (70 males and 70 females), 10-79 years of age, underwent fasting plasma glucose, total cholesterol, high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglyceride, and CXCL8 serum assay. Thyroid hormone testing for thyroid-stimulating hormone (TSH), antithyroglobulin (AbTg), and antithyroperoxidase (AbTPO) autoantibodies and thyroid ultrasonography were performed in all subjects to exclude the presence of clinical or subclinical thyroid disease. Serum CXCL10 levels were assayed in all subjects and found to be increased in 14 of 70 females (20%) and in 4 of 70 males (5.7%) (p = 0.01). In a multiple linear regression model including age, body mass index (BMI), systolic and diastolic blood pressure, glycemia, total cholesterol, HDL, LDL, triglycerides, TSH, AbTPO, AbTg, and CXCL8, only age was significantly related to CXCL10 [C.R. 1.30 (0.28-2.33), p = 0.001]. No relationship was present between CXCL8 serum levels and age, suggesting a specificity of CXCL10 elevation as a function of age. Results of this study, performed in healthy subjects on an age gradient, demonstrate an increase in serum CXCL10 with advancing age overall in females, supporting the hypothesis of enhanced Th1 immune responses in aging.

Increase of interferon-gamma inducible alpha chemokine CXCL10 but not beta chemokine CCL2 serum levels in chronic autoimmune thyroiditis

OBJECTIVE

To measure serum levels of CXCL10 and CCL2 prototype chemokines of the two major subclass (CXC and CC) in patients with newly diagnosed chronic autoimmune thyroiditis (AT), and relate the findings to the clinical phenotype.

DESIGN AND METHODS

Serum CXCL10 and CCL2 were assayed in 70 consecutive patients with newly diagnosed chronic AT, in sex- and age-matched healthy volunteers (n = 37) and in 20 patients with non-toxic multinodular goiter, extracted from a random sample of the general population from the same geographic area.

RESULTS

CXCL10 serum levels were significantly higher in patients with thyroiditis than in controls or multinodular goiter patients, while comparable CCL2 levels were found between groups. CXCL10 levels were significantly increased in hypothyroid patients and in those with an hypoechoic pattern (P = 0.0004 and P = 0.0001, respectively) while serum CCL2 levels were significantly increased in patients older than 50 years and in those with hypothyroidism (P = 0.0001 and P = 0.03, respectively). No correlation between CXCL10 and CCL2 serum levels could be demonstrated. CXCL10 and CCL2 were studied separately in relation to clinical features of AT patients. Two separate multiple linear regression models for CXCL10 and CCL2 were performed, including age, thyroid volume, thyroid stimulating hormone (TSH), FT4, anti-thyroid peroxidase (AbTPO), hypoechoic pattern, and the presence of hypervascularity, demonstrating that ln of serum CXCL10 levels was associated with TSH independently of other possible confounders levels [regression coefficient (R.C.) 0.143 confidence interval (C.I.) (0.042-0.245); P = 0.0059], while serum CCL2 were significantly associated only with age [R.C. 5.412 C.I. (3.838-6.986); P < 0.0001].

CONCLUSION

Our results, obtained in a large cohort of newly diagnosed AT patients demonstrate increased CXCL10 especially in hypothyroid patients with a more aggressive disorder, and normal CCL2 serum levels in AT.

Aging Is Associated With Increased T-Cell Chemokine Expression in C57Bl/6 Mice

To better understand the contribution of the chemokine system in immune senescence, we determined the aging effect on CD4+ and CD8+ T-cell chemokine expression by microarray screening and ribonuclease protection assays. Compared with young C57BL/6 mice, freshly isolated CD4+ cells from aged mice express increased level of interferon-gamma-inducible protein 10 (IP-10), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, regulated upon activation, normal T-cell expressed and secreted (RANTES), and lymphotactin (Ltn). T-cell receptor (TCR)/coreceptor stimulation up-regulates MIP-1alpha, MIP-1beta, and Ltn, and down-regulates IP-10 and RANTES expression in CD4+ T cells. A similar increase in chemokine expression was demonstrated in the CD8+ T cell. Enzyme-linked immunosorbent assays confirmed increased T-cell chemokine protein production in old CD4+ and CD8+ T cells. Finally, supernatant of cultured T cells from old animals caused an enhanced leukocyte chemotaxis response compared with that from young animals, suggesting that the age-related difference in T-cell chemokine expression has an important functional consequence.

Oxygen supply modulates MCP-1 release in monocytes from young and aged rats: decrease of MCP-1 transcription and translation is age-related

Hyper or hypoxia may affect the immune system's chemokine production. Monocyte chemotactic protein-1 (MCP-1), an important chemotactic cytokine can be activated by active oxygen species. Groups of rats were exposed to hypoxic and hyperoxic environmental conditions for 60 h and MCP-1 was determined in their peripheral blood mononuclear cells by Elisa and Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). In this study we evaluated if the ability of monocytes to produce MCP-1 under basal conditions or after stimulation with lipopolysaccharide (LPS) or phytohaemagglutinin (PHA) was differently affected by exposure to hyper or hypoxic conditions in young and aged rats. MCP-1 expression and production in monocyte/macrophages from rats at normoxic conditions was reduced in aged subjects. However, spontaneous, LPS or PHA-induced MCP-1 production was up-regulated by exposure to hyperoxic conditions in both young (62 +/- 8, 99 +/- 7, 102 +/- 8 pg/ml, respectively) and aged rats (79 +/- 4, 112 +/- 9, 117 +/- 10 pg/ ml, respectively). We conclude that hyperoxia is an important regulator of MCP-1 release and support the hypothesis that increased % of O2 may serve to initiate MCP-1 production which then serves to recruit and regulate the distribution of mononuclear cells to the sites of inflammation.

T cell chemokine receptor expression in aging

Changes in chemokine receptor expression are important in determining T cell migration and the subsequent immune response. To better understand the contribution of the chemokine system in immune senescence we determined the effect of aging on CD4(+) T cell chemokine receptor function using microarray, RNase protection assays, Western blot, and in vitro chemokine transmigration assays. Freshly isolated CD4(+) cells from aged (20-22 mo) mice were found to express a higher level of CCR1, 2, 4, 5, 6, and 8 and CXCR2-5, and a lower level of CCR7 and 9 than those from young (3-4 mo) animals. Caloric restriction partially or completely restored the aging effects on CCR1, 7, and 8 and CXCR2, 4, and 5. The aging-associated differences in chemokine receptor expression cannot be adequately explained by the age-associated shift in the naive/memory or Th1/Th2 profile. CD4(+) cells from aged animals have increased chemotactic response to stromal cell-derived factor-1 and macrophage-inflammatory protein-1alpha, suggesting that the observed chemokine receptor changes have important functional consequences. We propose that the aging-associated changes in T cell chemokine receptor expression may contribute to the different clinical outcome in T cell chemokine receptor-dependent diseases in the elderly.

RANTES and MIP-1alpha production by T lymphocytes, monocytes and NK cells from nonagenarian subjects

While numerous previous studies have investigated age-related changes of cytokine production, little is known about chemokines, the importance of which in regulating immune response is becoming increasingly evident. In this study, a group of healthy subjects over 90 years old is compared to a group of young subjects, we evaluated the ability of monocytes, T lymphocytes and NK cells: (1) to produce RANTES and MIP-1alpha, either in basal conditions or after stimulation with, respectively, LPS, anti-CD3 MoAb and IL-2; (2) to express the corresponding chemokine receptors (CCR1, CCR3, CCR5). We demonstrate that: (a) monocytes, T lymphocytes and NK cells spontaneously produced detectable amounts of chemokines, both in young and old subjects; (b) monocyte-dependent RANTES and MIP-1alpha production induced by LPS was up-regulated in nonagenarian subjects as anti-CD3-induced secretion from T cells; (c) RANTES and MIP-1alpha production by IL-2 stimulated NK cells was reduced in elderly subjects; (d) CCR1, CCR3 and CCR5 were widely expressed on monocytes, but less expressed on T lymphocytes and NK cells. The diversity within PBMC might reflect their different states of activation and/or responsiveness, influencing the ability to develop rapid innate and long-lasting adaptive immune responses.