The role of the MAPK pathway alterations in GM-CSF modulated human neutrophil apoptosis with aging

Role of depression, suicide attempt history and childhood trauma in neutrophil-to-lymphocyte ratio dynamics: A 30-week prospective study

Studying the biology of suicidal behaviour and developing blood-based biomarkers may help stratify individuals with suicidal behaviors into clinically relevant categories. Literature suggests that people diagnosed with mood disorders and suicidal behaviour show an increased neutrophil to lymphocyte ratio (NLR). For the first time, we investigated NLR variability in mood disorders, a critical aspect of biomarker development. Our study provides a result on the influence of our variables on the NLR and also on the intrinsic properties of the ratio. Consequently, our objective was to analyse the differences in NLR between healthy subjects and patients diagnosed with mood disorder with suicidal behaviour or mood disorder without suicidal attempt. A prospective study was conducted on 97 healthy subjects, 63 patients with mood disorder without suicidal behaviour and 61 patients with mood disorder with suicidal behaviour (mean age [SD] = 44.2 [14.31]; 66.1 % female). Participants were assessed four times over 30 weeks, where blood samples and clinical data were collected. After controlling for confounding factors such as smoking and medical history, we found that NLR stability was low but NLR was significantly associated with a history of suicide attempt (mixed linear model, F = 4.044; p = 0.018). We also observed a significant interaction between NLR values and childhood trauma (p = 0.002). Furthermore, our results demonstrate that NLR is influenced by childhood trauma, including in controls (p = 0.014). Finally, NLR expression differs between patients with and without suicidal behaviour, but only in those without a history of childhood trauma (p = 0.026). Despite its variability over time, our data suggest that NLR may be a promising biomarker for identifying individuals at high risk of suicidal behaviour among patients with mood disorders.

Disrupting Smad3 potentiates immunostimulatory function of NK cells against lung carcinoma by promoting GM-CSF production

Through Smad3-dependent signalings, transforming growth factor-β (TGF-β) suppresses the development, maturation, cytokine productions and cytolytic functions of NK cells in cancer. Silencing Smad3 remarkably restores the cytotoxicity of NK-92 against cancer in TGF-β-rich microenvironment, but its effects on the immunoregulatory functions of NK cells remain obscure. In this study, we identified Smad3 functioned as a transcriptional repressor for CSF2 (GM-CSF) in NK cells. Therefore, disrupting Smad3 largely mitigated TGF-β-mediated suppression on GM-CSF production by NK cells. Furthermore, silencing GM-CSF in Smad3 knockout NK cells substantially impaired their anti-lung carcinoma effects. In-depth study demonstrated that NK-derived GM-CSF strengthened T cell immune responses by stimulating dendritic cell differentiation and M1 macrophage polarization. Meanwhile, NK-derived GM-CSF promoted the survival of neutrophils, which in turn facilitated the terminal maturation of NK cells, and subsequently boosted NK-cell mediated cytotoxicity against lung carcinoma. Thus, Smad3-silenced NK-92 (NK-92-S3KD) may serve as a promising immunoadjuvant therapy with clinical translational value given its robust cytotoxicity against malignant cells and immunostimulatory functions to reinforce the therapeutic effects of other immunotherapies.

The Regulation of Neutrophil Migration in Patients with Sepsis: The Complexity of the Molecular Mechanisms and Their Modulation in Sepsis and the Heterogeneity of Sepsis Patients

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Common causes include gram-negative and gram-positive bacteria as well as fungi. Neutrophils are among the first cells to arrive at an infection site where they function as important effector cells of the innate immune system and as regulators of the host immune response. The regulation of neutrophil migration is therefore important both for the infection-directed host response and for the development of organ dysfunctions in sepsis. Downregulation of CXCR4/CXCL12 stimulates neutrophil migration from the bone marrow. This is followed by transmigration/extravasation across the endothelial cell barrier at the infection site; this process is directed by adhesion molecules and various chemotactic gradients created by chemotactic cytokines, lipid mediators, bacterial peptides, and peptides from damaged cells. These mechanisms of neutrophil migration are modulated by sepsis, leading to reduced neutrophil migration and even reversed migration that contributes to distant organ failure. The sepsis-induced modulation seems to differ between neutrophil subsets. Furthermore, sepsis patients should be regarded as heterogeneous because neutrophil migration will possibly be further modulated by the infecting microorganisms, antimicrobial treatment, patient age/frailty/sex, other diseases (e.g., hematological malignancies and stem cell transplantation), and the metabolic status. The present review describes molecular mechanisms involved in the regulation of neutrophil migration; how these mechanisms are altered during sepsis; and how bacteria/fungi, antimicrobial treatment, and aging/frailty/comorbidity influence the regulation of neutrophil migration.

Convergence of signalling pathways in innate immune responses and genetic forms of Parkinson's disease

In recent years progress in molecular biology and genetics have advanced our understanding of neurological disorders and highlighted synergistic relationships with inflammatory and age-related processes. Parkinson's disease (PD) is a common neurodegenerative disorder that is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc). Increasing extensive evidence supports the contribution of genetic risk variants and inflammation in the pathobiology of this disease. Functional and genetic studies demonstrate an overlap between genes linked to increased risk for PD and autoimmune diseases. Variants identified in loci adjacent to LRRK2, GBA, and HLA establish a crosstalk between the pathobiologies of the two disease spectra. Furthermore, common signalling pathways associated with the pathogenesis of genetic PD are also relevant to inflammatory signaling include MAPK, NF-κB, Wnt and inflammasome signaling. Importantly, post-mortem analyses of brain and cerebrospinal fluid from PD patients show the accumulation of proinflammatory cytokines. In this review we will focus on the principal mechanisms of genetic, inflammatory and age-related risk that intersect in the pathogenesis of PD.

The Role of Zinc in GM-CSF-Induced Signaling in Human Polymorphonuclear Leukocytes

SCOPE

Zinc is suggested to be necessary for functional signaling induced by certain growth factors. The granulocyte-macrophage colony-stimulating factor (GM-CSF) is a key factor for differentiation and activation of myeloid cells. This report analyses the impact of different zinc concentrations on GM-CSF-induced signaling in mature polymorphonuclear leukocytes (PMN).

METHODS AND RESULTS

As measured by flow cytometry, zinc increases surface GM-CSF receptor (GM-CSFR) in PMN, whereas monocytes respond with decreased GM-CSFR surface expression. Since total cellular GM-CSFR expression remains unaffected, the observed zinc-induced GM-CSFR surface dynamics may be explained by receptor redistribution. In PMN, zinc enhanced phosphorylation of mitogen-activated protein kinases (MAPK) in a dose-dependent manner as found in western blot. Zinc-induced MAPK phosphorylation is additionally augmented by moderate GM-CSF stimulation.

CONCLUSION

The present study demonstrates the opposing influence of zinc on GM-CSFR surface expression in monocytes and PMN. Zinc and GM-CSF, use in optimized concentrations, augment MAPK signaling, and increase expression of MAPK-induced myeloid cell leukemia-1 (Mcl-1) in PMN. Thus, this study concludes that zinc strengthens growth factor-induced signaling. Hence, the study provides a basis for further in vivo studies, focusing on the therapeutic value of zinc in patients with a disturbed GM-CSF signaling.

Transcriptome Profiling Reveals CD73 and Age-Driven Changes in Neutrophil Responses against Streptococcus pneumoniae

Neutrophils are required for host resistance against Streptococcus pneumoniae, but their function declines with age. We previously found that CD73, an enzyme required for antimicrobial activity, is downregulated in neutrophils (also known as polymorphonuclear leukocytes [PMNs]) from aged mice. This study explored transcriptional changes in neutrophils induced by S. pneumoniae to identify pathways controlled by CD73 and dysregulated with age. Pure bone marrow-derived neutrophils isolated from wild-type (WT) young and old and CD73 knockout (CD73KO) young mice were mock challenged or infected with S. pneumoniae ex vivo. RNA sequencing (RNA-Seq) was performed to identify differentially expressed genes (DEGs). We found that infection triggered distinct global transcriptional changes across hosts that were strongest in CD73KO neutrophils. Surprisingly, there were more downregulated than upregulated genes in all groups upon infection. Downregulated DEGs indicated a dampening of immune responses in old and CD73KO hosts. Further analysis revealed that CD73KO neutrophils expressed higher numbers of long noncoding RNAs (lncRNAs) than those in WT controls. Predicted network analysis indicated that CD73KO-specific lncRNAs control several signaling pathways. We found that genes in the c-Jun N-terminal kinase (JNK)-mitogen-activated protein kinase (MAPK) pathway were upregulated upon infection in CD73KO mice and in WT old mice, but not in WT young mice. This corresponded to functional differences, as phosphorylation of the downstream AP-1 transcription factor component c-Jun was significantly higher in neutrophils from infected CD73KO mice and old mice. Importantly, inhibition of JNK/AP-1 rescued the ability of these neutrophils to kill S. pneumoniae. Together, our findings revealed that the ability of neutrophils to modify their gene expression to better adapt to bacterial infection is in part regulated by CD73 and declines with age.

Older but Not Wiser: the Age-Driven Changes in Neutrophil Responses during Pulmonary Infections

Elderly individuals are at increased risk of life-threatening pulmonary infections. Neutrophils are a key determinant of the disease course of pathogen-induced pneumonia. Optimal host defense balances initial robust pulmonary neutrophil responses to control pathogen numbers, ultimately followed by the resolution of inflammation to prevent pulmonary damage. Recent evidence suggests that phenotypic and functional heterogeneity in neutrophils impacts host resistance to pulmonary pathogens. Apart from their apparent role in innate immunity, neutrophils also orchestrate subsequent adaptive immune responses during infection. Thus, the outcome of pulmonary infections can be shaped by neutrophils. This review summarizes the age-driven impairment of neutrophil responses and the contribution of these cells to the susceptibility of the elderly to pneumonia. We describe how aging is accompanied by changes in neutrophil recruitment, resolution, and function. We discuss how systemic and local changes alter the neutrophil phenotype in aged hosts. We highlight the gap in knowledge of whether these changes in neutrophils also contribute to the decline in adaptive immunity seen with age. We further detail the factors that drive dysregulated neutrophil responses in the elderly and the pathways that may be targeted to rebalance neutrophil activity and boost host resistance to pulmonary infections.

Effect of Age on Bleeding on Probing (BOP) as an Indicator of Periodontal Inflammation in Patients Enrolled in Supportive Periodontal Therapy

PURPOSE

To assess the effect of age on the mean percentage of bleeding on probing (BOP) during supportive periodontal therapy (SPT) in patients enrolled in SPT for at least 5 years. Materials and Methods: This study was performed as a retrospective analysis of data collected from SPT patients initially diagnosed with gingivitis or mild to severe periodontitis. Two groups of patients were selected: in group A, younger adults (age ≤ 35 years) were included while group B consisted of older SPT patients (age ≥ 65 years). BOP in the two groups was compared according to both disease severity and % compliance with SPT visits. Results: BOP in all patients (n = 236) was 19.2% (± 12.4). Group A (n = 110) presented mean BOP levels of 19.7% (± 11.8), while lower BOP levels of 18.7% (± 13.0) were found in group B (n = 126; p = 0.5272). Older patients demonstrating high % compliance had lower mean BOP levels (14.2% ± 9.5) than younger patients (18.0% ±  11.7; p = 0.0841). Similarly, BOP was lower in older patients with moderate (group B: 18.4% ± 12.1, group A: 19.3% ± 14.6, p = 0.0541) or severe periodontitis (group B: 22.4% ± 11.4, group A: 23.2% ±  14.0; p = 0.3440). In patients with moderate or severe periodontitis and higher % compliance with SPT, the mean BOP was statistically significantly lower in older patients than in younger patients (moderate: 14.4% ± 11.9 vs 19.4% ± 15.1, p < 0.0001; severe: 13.2% ± 11.1 vs 18.3% ± 17.5, p = 0.0170). Conclusion: Older patients enrolled in SPT may present lower levels of BOP. This finding should be considered when determining SPT intervals with elderly patients.

Antioxidant effect of Resveratrol: Change in MAPK cell signaling pathway during the aging process

Aging is characterized by a progressive loss of physiological integrity. One common denominator is the increase of reactive oxygen species (ROS) caused by inhibition of important antioxidant pathways. Resveratrol is a polyphenol known for its potent antioxidant activity. However, antioxidant pathways activated by them change with aging. The objective of our study was to verify the antioxidant effect of resveratrol in an oxidative stress environment in Human Mononuclear Cells (PBMC) from donors with different ages. Resveratrol (5 μM), a stimulus with H₂O₂ (0,64 % v/v) in addition to inhibitors of PKA, AkT/PKB and MAPK signaling pathways were used in chemiluminescence assay. An incresed basal production of ROS was observed in the elderly than in the middle-aged group. Resveratrol was able to reduce ROS in both groups, but with greater efficiency in the middle-aged group. By inhibiting PKA, Akt/PKB and MAPK signaling pathways we observed that resveratrol presented an altered performance in the aging process, changing signaling pattern of MAPK pathway.

Blocking elevated p38 MAPK restores efferocytosis and inflammatory resolution in the elderly

Increasing age alters innate immune-mediated responses; however, the mechanisms underpinning these changes in humans are not fully understood. Using a human dermal model of acute inflammation, we found that, although inflammatory onset is similar between young and elderly individuals, the resolution phase was substantially impaired in elderly individuals. This arose from a reduction in T cell immunoglobulin mucin receptor-4 (TIM-4), a phosphatidylserine receptor expressed on macrophages that enables the engulfment of apoptotic bodies, so-called efferocytosis. Reduced TIM-4 in elderly individuals was caused by an elevation in macrophage p38 mitogen-activated protein kinase (MAPK) activity. Administering an orally active p38 inhibitor to elderly individuals rescued TIM-4 expression, cleared apoptotic bodies and restored a macrophage resolution phenotype. Thus, inhibiting p38 in elderly individuals rejuvenated their resolution response to be more similar to that of younger people. This is the first resolution defect identified in humans that has been successfully reversed, thereby highlighting the tractability of targeting pro-resolution biology to treat diseases driven by chronic inflammation.

Antioxidant hesperetin improves the quality of porcine oocytes during aging in vitro

The citrus flavonoid hesperetin has a variety of pharmacological actions, including antioxidant, antiinflammatory, and anticancer activities. This study investigated whether hesperetin prevents aging of oocytes in vitro in which it determined the maturation of nuclear and cytoplasm and the developmental capacity of embryo by modulating the reactive oxygen species (ROS) level. Porcine oocytes were matured in vitro for 44 hr (control) and for an additional 24 hr in the presence of 0, 1, 10, 100, and 250 μM hesperetin (aging, H-1, H-10, H-100, and H-250, respectively). Although there was no difference in the rate of maturation among all the groups, both the control and H-100 groups significantly increased in the rate of cleavage and blastocyst formation compared to the aging group. The H-100 group significantly decreased ROS activity and increases the level of glutathione (GSH) and expression of the antioxidant genes (PRDX5, NFE2L, SOD1, and SOD2) compared with the aging group. The H-100 groups prevented aberrant spindle organization and chromosomal misalignment, blocked the decrease in the level of phosphorylated-p44/42 mitogen-activated protein kinase and increased the messenger RNA expression of cytoplasmic maturation factor genes (GDF9, CCNB1, BMP15, and MOS). Subsequently, both the control and H-100 groups significantly increased the total cell number and decreased the apoptosis cells at the blastocyst stage compared with aging group. The results indicate that hesperetin improves the quality of porcine oocytes by protecting them against oxidative stress during aging in vitro.

Neutrophil-mediated enhancement of angiogenesis and osteogenesis in a novel triple cell co-culture model with endothelial cells and osteoblasts

Repair and regeneration of critical-sized bone defects remain a major challenge in orthopaedic and craniomaxillofacial surgery. Until now, attempts to bioengineer bone tissue have been hindered by the inability to establish proper angiogenesis and osteogenesis in the tissue construct. In the present study, we established a novel triple cell co-culture model consisting of osteoblasts, endothelial cells, and neutrophils and conducted a systematic investigation of the effects of neutrophils on angiogenesis and osteogenesis. Neutrophils significantly increased angiogenesis in the tissue construct, evidenced by the formation of microvessel-like structures with an extensive lattice-like, stable tubular network in the co-culture model. Moreover, neutrophils significantly induced the expression of pro-angiogenic markers, such as VEGF-A, CD34, EGF, and FGF-2 in a dose- and time-dependent manner. Subsequently, PCR arrays corroborated that neutrophils upregulate the important angiogenic markers and MMPs. Moreover, neutrophils also enhanced osteogenic markers, such as ALP, OCN, OPN, and COL-1 compared with the controls. As shown by the osteogenic gene arrays, neutrophils significantly regulated major osteogenic markers such as BMP2, BMP3, BMP4, BMP5, TGF-β2, RUNX2, and ECM proteins. Significantly higher mineralization was observed in triple cell co-culture compared with controls. Foregoing data indicate that the triple cell co-culture model can be used to stimulate the growth of microvasculature within a bone bioengineering construct to improve cell viability. Neutrophil-mediated enhancement of angiogenesis and osteogenesis could be a viable, clinically relevant tissue engineering strategy to obtain optimal bone growth in defect sites, in the field of oral and maxillofacial surgery.

Neutrophil and Monocyte Bactericidal Responses to 10 Weeks of Low-Volume High-Intensity Interval or Moderate-Intensity Continuous Training in Sedentary Adults

Neutrophils and monocytes are key components of the innate immune system that undergo age-associated declines in function. This study compared the impact of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on immune function in sedentary adults. Twenty-seven (43 ± 11 years) healthy sedentary adults were randomized into ten weeks of either a HIIT (>90% maximum heart rate) or MICT (70% maximum heart rate) group training program. Aerobic capacity (VO_2peak), neutrophil and monocyte bacterial phagocytosis and oxidative burst, cell surface receptor expression, and systemic inflammation were measured before and after the training. Total exercise time commitment was 57% less for HIIT compared to that for MICT while both significantly improved VO_2peak similarly. Neutrophil phagocytosis and oxidative burst and monocyte phagocytosis and percentage of monocytes producing an oxidative burst were improved by training similarly in both groups. Expression of monocyte but not neutrophil CD16, TLR2, and TLR4 was reduced by training similarly in both groups. No differences in systemic inflammation were observed for training; however, leptin was reduced in the MICT group only. With similar immune-enhancing effects for HIIT compared to those for MICT at 50% of the time commitment, our results support HIIT as a time efficient exercise option to improve neutrophil and monocyte function.

Mycoplasma ovipneumoniae induces sheep airway epithelial cell apoptosis through an ERK signalling-mediated mitochondria pathway

Background

Mycoplasma ovipneumoniae (M. ovipneumoniae) is a species of Mycoplasma bacteria that specifically infects sheep and goat, causing ovine infectious pleuropneumonia. However, the mechanism underlying the pathogen-host interaction between M. ovipneumoniae and airway epithelial cells is unknown.

Methods

A primary air-liquid interface (ALI) epithelial culture model generated from the bronchial epithelial cells of Ningxia Tan sheep (ovis aries) was employed to explore the potential mechanism of M. ovipneumoniae-induced cell apoptosis by characterizing the production of reactive oxygen species (ROS), methane dicarboxylic aldehyde (MDA) and anti-oxidative enzymes, as well as the mitochondrial membrane potentials, cytochrome C release, and activities of ERK and caspase signalling pathways.

Results

Increased ROS production and MDA concentration with mitochondrial membrane dysfunction and apoptotic cell death but decreased expression of the antioxidant enzymes catalase (CAT), glutathione synthetase (GSS), total superoxide dismutaes (T-SOD) and Mn-SOD were observed in sheep airway epithelial cells infected with M. ovipneumoniae. Mechanistically, the M. ovipneumoniae-induced cell apoptosis and disruption of mitochondrial integrity reflected mechanisms by which pathogen-activated mitogen-activated protein kinase (MAPK) signalling sequentially led to mitochondrial damage and release of Cyt-C into the cytoplasm, which in turn triggered the activation of caspase signalling cascade, resulting in the apoptosis of host cells.

Conclusions

These results suggest that M. ovipneumoniae-induced ROS and MAPK signalling-mediated mitochondrial apoptotic pathways might play key roles in the pathogenesis of M. ovipneumoniae infection in sheep lungs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0842-0) contains supplementary material, which is available to authorized users.

Epigenetic drift in the aging genome: a ten-year follow-up in an elderly twin cohort

BACKGROUND

Current epigenetic studies on aging are dominated by the cross-sectional design that correlates subjects' ages or age groups with their measured epigenetic profiles. Such studies have been more aimed at age prediction or building up the epigenetic clock of age rather than focusing on the dynamic patterns in epigenetic changes during the aging process.

METHODS

We performed an epigenome-wide association study of intra-individual longitudinal changes in DNA methylation at CpG (cytosine-phosphate-guanine) sites measured in whole-blood samples of a cohort of 43 elderly twin pairs followed for 10 years (age at intake 73-82 years). Biological pathway analysis and survival analysis were also conducted on CpGs showing longitudinal change in their DNA-methylation levels. Classical twin models were fitted to each CpG site to estimate the genetic and environmental effects on DNA-methylation.

RESULTS

Our analysis identified 2284 CpG sites whose DNA-methylation levels changed longitudinally over the follow-up. Twin modelling revealed that the longitudinal change for 90% of these CpG sites was explained solely by individual unique environmental factors and only for 10% of these sites was it influenced by familial factors (genetic or shared environment). Over 60% of the identified CpG sites were replicated (same direction and replication P < 0.05) in an independent cross-sectional sample of 300 twins aged from 30 to 74 years. The replication rate went up to 91% for the top 53 CpGs with P < 1 × 10-07. Pathway analysis of genes linked to these CpGs identified biologically meaningful gene-sets involved in cellular-signalling events and in transmission across chemical synapses, which are important molecular underpinnings of aging-related degenerative disorders.

CONCLUSION

Our epigenome-wide association studies on a cohort of old twins followed up for 10 years identified highly replicable epigenetic biomarkers predominantly implicated in signalling pathways of degenerative disorders and survival in the elderly.

Intracellular signalling pathways: targets to reverse immunosenescence

Ageing is a very complex process, the result of the dysregulation of multiple systems interacting in many ways. A prominent change occurring with ageing is related to the architecture and functioning of the immune system, viewed commonly as detrimental and termed 'immunosenescence'. However, age-associated changes may also lead to increased function in certain respects, which can be viewed as adaptive. None the less, on balance it is well-recognized that immunosenescence is accompanied by the low-grade inflammation observed commonly in elderly people, which has been dubbed 'inflamm-ageing'. The exact cause and significance of all these changes is not clear, but there is a consensus that they are related to the occurrence of chronic non-infectious age-associated disease, as well as increased susceptibility to infections. Alterations to immune cell signalling may be a prominent cause of malfunctioning immunity. Emerging attempts to reverse immunosenescence have recently targeted the signalling pathways in various different cell types of the immune system. Here, we review and discuss alterations in the signalling pathways of immune cells with ageing and consider current targets and means to modulate altered functions. We discuss the potential dangers as well as the benefits of these interventions, and consider future approaches to this problem.

Role of Immune Aging in Susceptibility to West Nile Virus

West Nile virus (WNV) can cause severe neuroinvasive disease in humans and currently no vaccine or specific treatments are available. As aging is the most prominent risk factor for WNV, age-related immune dysregulation likely plays an essential role in host susceptibility to infection with WNV. In this review, we summarize recent findings in effects of aging on immune responses to WNV infection. In particular, we focus on the age-dependent dysregulation of innate immune cell types-neutrophils, macrophages, and dendritic cells-in response to WNV infection, as well as age-related alterations in NK cells and γδ T cells that may associate with increased WNV susceptibility in older people. We also highlight two advanced technologies, i.e., mass cytometry and microRNA profiling, which significantly contribute to systems-level study of immune dysregulation in aging and should facilitate new discoveries for therapeutic intervention against WNV.

Altered neutrophil functions in elderly patients during a 6-month follow-up period after a hip fracture

BACKGROUND

Fracture of the hip (HF) is a significant cause of morbidity and mortality in elderly individuals. HF is an acute stress that triggers a state of inflammation which may affect immune responses and physical recovery.

METHODS

Longitudinal study of the impact of HF on the functions of polymorphonuclear neutrophils (PMNs) in elderly subjects. Data were recorded prior to surgery, 6weeks and 6months later.

RESULTS

PMN functions were severely impaired shortly after HF (chemotaxis, phagocytosis, superoxide production) but there was a time-related recovery of some PMN functions (chemotaxis, phagocytosis) over time, except in the case of superoxide production. Whereas FcγRII (CD32) expression remained unchanged, FcγRIII (CD16) increased from low values before surgery to levels of controls 6months post-surgery. This was also the case for the C5a complement receptor and CD11b. TLR2 and TLR4 expressions were unchanged. Cytokine and chemokine secretions by stimulated PMN were altered. TNFα and IL-10 secretions were increased following HF but IL-8 secretion was decreased. Impaired PMN functions prior to surgery were related to alterations in PI3K and NF-κB signaling pathways. Recovery of these functions paralleled increased PI3K activity, although superoxide production remained low. Sustained activation of the NF-κB pathway by TNFα has been reported to involve upregulation of IKKβ kinase activity. Activated IKKβ kinase inhibits ERK1/2 and results in concomitant downstream inhibition of NADPH oxidase complex which can account for sustained impaired production of ROS in HF patients.

CONCLUSION

Our data showed that the stress caused by HF negatively affects initial PMN responses shortly after the event and that may negatively influence clinical outcomes such as resolving long-term inflammation and recovery, as well as explaining susceptibility to opportunistic infections.

Inhibitory mechanism of Korean Red Ginseng on GM-CSF expression in UVB-irradiated keratinocytes

Background

UV-irradiated keratinocytes secrete various proinflammatory cytokines. UV-induced skin damage is mediated by growth factors and proinflammatory cytokines such as granulocyte macrophage colony stimulating factor (GM-CSF). In a previous study, we found that the saponin of Korean Red Ginseng (SKRG) decreased the expression of GM-CSF in UVB-irradiated SP-1 keratinocytes. In this study, we attempted to find the inhibitory mechanism of SKRG on UVB-induced GM-CSF expression in SP-1 keratinocytes.

Methods

We investigated the inhibitory mechanism of SKRG and ginsenosides from Panax ginseng on UVB-induced GM-CSF expression in SP-1 keratinocytes.

Results

Treatment with SKRG decreased the expression of GM-CSF mRNA and protein induced by irradiation of UVB in SP-1 keratinocytes. The phosphorylation of ERK was induced by UVB at 10 min, and decreased with SKRG treatment in SP-1 keratinocytes. In addition, treatment with SKRG inhibited the UVB-induced phosphorylation of epidermal growth factor receptor (EGFR), which is known to be an upstream signal of ERK. From these results, we found that the inhibition of GM-CSF expression by SKRG was derived from the decreased phosphorylation of EGFR. To identify the specific compound composing SKRG, we tested fifteen kinds of ginsenosides. Among these compounds, ginsenoside-Rh3 decreased the expression of GM-CSF protein and mRNA in SP-1 keratinocytes.

Conclusion

Taken together, we found that treatment with SKRG decreased the phosphorylation of EGFR and ERK in UVB-irradiated SP-1 keratinocytes and subsequently inhibited the expression of GM-CSF. Furthermore, we identified ginsenoside-Rh3 as the active saponin in Korean Red Ginseng.

Natural compounds and aging: between autophagy and inflammasome

Aging, a natural physiological process, is characterized by a progressive loss of physiological integrity. Loss of cellular homeostasis in the aging process results from different sources, including changes in genes, cell imbalance, and dysregulation of the host-defense systems. Innate immunity dysfunctions during aging are connected with several human pathologies, including metabolic disorders and cardiovascular diseases. Recent studies have clearly indicated that the decline in autophagic capacity that accompanies aging results in the accumulation of dysfunctional mitochondria, reactive oxygen species (ROS) production, and further process dysfunction of the NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome activation in the macrophages, which produce the proinflammatory cytokines. These factors impair cellular housekeeping and expose cells to higher risk in many age-related diseases, such as atherosclerosis and type 2 diabetes. In this review, we investigated the relationship between dysregulation of the inflammasome activation and perturbed autophagy with aging as well as the possible molecular mechanisms. We also summarized the natural compounds from food intake, which have potential to reduce the inflammasome activation and enhance autophagy and can further improve the age-related diseases discussed in this paper.

Cellular signaling in the aging immune system

Causes for immunosenescence and inflamm-aging have to be established. Efficient function of the immune system requires homeostatic regulation from receptor recognition of antigenic challenge to cell responses and adaptation to its changing environment. It is reasonable to assume that one of the most important molecular causes of immunosenescence is alteration in the regulation of signaling pathways. Indeed, alterations in feed-forward and negative feedback (inhibitory) signaling have been highlighted in all cells involved in the immune response including short-lived (neutrophils) and long-lived (T lymphocytes) cells. These dysregulations tip the balance in favor of altered (less efficient) function of the immune system. In this review, we summarize our knowledge on signal transduction changes in the aging immune system and propose a unifying mechanism as one of the causes of immunosenescence. Modulation of these pathways with aging represents a major challenge to restore the immune response to functional levels.

Age-related activation of MKK/p38/NF-κB signaling pathway in lung: from mouse to human

We and others previously reported that the pro-inflammatory cytokine tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and IL-6 significantly accumulate with age in mouse lung. This is accompanied by elevated phosphorylation of p38. Here, we further investigate whether aging affects activation of p38 signaling and the inflammatory reaction after exposure to lipopolysaccharide (LPS) in the lungs of mice in vivo and humans ex vivo. The data showed that activation of p38 peaked at 0.5h and then rapidly declined in young (2-month-old) mouse lung, after intranasal inhalation challenge with LPS. In contract, activation of p38 peaked at 24h and was sustained longer in aged (20-month-old) mice. As well as altered p38, activations of its upstream activator MKK and downstream substrate NF-κB were also changed in the lungs of aged mice, which corresponded with the absence in the early phase but delayed increases in concentrations of TNF-α, IL-1β and IL-6. Consistent with the above observations in mice, similar patterns of p38 signaling also occurred in human lungs. Compared with younger lungs from adult-middle aged subjects, the activation of p38, MKK and NF-κB, as well as the production of pro-inflammatory cytokines were significantly increased in the lungs of older subjects ex vivo. Exposure of human lung cells to LPS induced rapid activation of p38, MKK and NF-κB in these cells from adult-middle aged subjects, but not older subjects, with increases in the production of the pro-inflammatory cytokines. The LPS-induced rapid activation in the lung cells from adult-middle aged subjects occurred as early as 0.25h after exposure, and then declined. Compared with adult-middle aged subjects, the LPS exposure did not induce marked changes in the early phase, either in the activation of p38, MKK and NF-κB, or in the production of TNF-α, IL-1β or IL-6 in the lung cells from older subjects. In contrast, these changes occurred relatively late, peaked at 16h and were sustained longer in the lungs of older subjects. These data support the hypothesis that the sustained activation of the p38 signaling pathway at baseline and the absence in the early phase but delayed of p38 signaling pathway response to LPS in the elderly may play important roles in increased susceptibility of aged lungs to inflammatory injury.

Increased oxidative stress response in granulocytes from older patients with a hip fracture may account for slow regeneration

Proximal femur fracture, a typical fracture of the elderly, is often associated with morbidity, reduced quality of life, impaired physical function and increased mortality. There exists evidence that responses of the hematopoietic microenvironment to fractures change with age. Therefore, we investigated oxidative stress markers and oxidative stress-related MAPK activation in granulocytes from the young and the elderly with and without fractured long bones. Lipid peroxidation levels were increased in the elderly controls and patients. Aged granulocytes were more sensitive towards oxidative stress induced damage than young granulocytes. This might be due to the basally increased expression of SOD-1 in the elderly, which was not further induced by fractures, as observed in young patients. This might be caused by an altered MAPK activation. In aged granulocytes basal p38 and JNK activities were increased and basal ERK1/2 activity was decreased. Following fracture, JNK activity decreased, while ERK1/2 and p38 activities increased in both age groups. Control experiments with HL60 cells revealed that the observed p38 activation depends strongly on age. Summarizing, we observed age-dependent changes in the oxidative stress response system of granulocytes after fractures, for example, altered MAPK activation and SOD-1 expression. This makes aged granulocytes vulnerable to the stress stimuli of the fracture and following surgery.

Aging and its Impact on Innate Immunity and Inflammation: Implications for Periodontitis

The elderly exhibit increased susceptibility to a number of inflammatory or degenerative pathologies. Aging is similarly thought to be associated with increased prevalence and severity of periodontitis, although the underlying causes are poorly understood. Among the plausible mechanisms whereby aging could contribute to increased susceptibility to periodontitis are age-dependent alterations in the innate immune and inflammatory status of the host. This hypothesis is supported by studies in humans and animal models outlined in this Review. Indeed, innate immune cells isolated from elderly subjects exhibit age-related cell-intrinsic defects that could predispose the elderly to deregulated immune and inflammatory responses. Moreover, the investigation of age-related alterations in the tissue environment where recruited inflammatory cells ultimately function could provide complementary, if not better, insights into the impact of aging on periodontitis. Integrative approaches combining in vitro and in vivo mechanistic models are underway and can potentially contribute to targeted molecular therapies that can reverse or mitigate the effects of aging on periodontitis and other inflammatory diseases.

Nutrition, diet and immunosenescence

Ageing is characterized by immunosenescence and the progressive decline in immunity in association with an increased frequency of infections and chronic disease. This complex process affects both the innate and adaptive immune systems with a progressive decline in most immune cell populations and defects in activation resulting in loss of function. Although host genetics and environmental factors, such as stress, exercise and diet can impact on the onset or course of immunosenescence, the mechanisms involved are largely unknown. This review focusses on identifying the most significant aspects of immunosenescence and on the evidence that nutritional intervention might delay this process, and consequently improve the quality of life of the elderly.

Immunosenescence, aging, and systemic lupus erythematous

Senescence is a normal biological process that occurs in all organisms and involves a decline in cell functions. This process is caused by molecular regulatory machinery alterations, and it is closely related to telomere erosion in chromosomes. In the context of the immune system, this phenomenon is known as immunosenescence and refers to the immune function deregulation. Therefore, functions of several cells involved in the innate and adaptive immune responses are severely compromised with age progression (e.g., changes in lymphocyte subsets, decreased proliferative responses, chronic inflammatory states, etc.). These alterations make elderly individuals prone to not only infectious diseases but also to malignancy and autoimmunity. This review will explore the molecular aspects of processes related to cell aging, their importance in the context of the immune system, and their participation in elderly SLE patients.

The emerging role of epigenetics in rheumatic diseases

Epigenetics is a key mechanism regulating the expression of genes. There are three main and interrelated mechanisms: DNA methylation, post-translational modification of histone proteins and non-coding RNA. Gene activation is generally associated with lower levels of DNA methylation in promoters and with distinct histone marks such as acetylation of amino acids in histones. Unlike the genetic code, the epigenome is altered by endogenous (e.g. hormonal) and environmental (e.g. diet, exercise) factors and changes with age. Recent evidence implicates epigenetic mechanisms in the pathogenesis of common rheumatic disease, including RA, OA, SLE and scleroderma. Epigenetic drift has been implicated in age-related changes in the immune system that result in the development of a pro-inflammatory status termed inflammageing, potentially increasing the risk of age-related conditions such as polymyalgia rheumatica. Therapeutic targeting of the epigenome has shown promise in animal models of rheumatic diseases. Rapid advances in computational biology and DNA sequencing technology will lead to a more comprehensive understanding of the roles of epigenetics in the pathogenesis of common rheumatic diseases.

Neutrophil heterogeneity in health and disease: a revitalized avenue in inflammation and immunity

Leucocytes form the principal cellular components of immunity and inflammation, existing as multiple subsets defined by distinct phenotypic and functional profiles. To date, this has most notably been documented for lymphocytes and monocytes. In contrast, as neutrophils are traditionally considered, to be short-lived, terminally differentiated cells that do not re-circulate, the potential existence of distinct neutrophil subsets with functional and phenotypic heterogeneity has not been widely considered or explored. A growing body of evidence is now challenging this scenario, and there is significant evidence for the existence of different neutrophil subsets under both physiological and pathological conditions. This review will summarize the key findings that have triggered a renewed interest in neutrophil phenotypic changes, both in terms of functional implications and consequences within disease models. Special emphasis will be placed on the potential pro- and anti-inflammatory roles of neutrophil subsets, as indicated by the recent works in models of ischaemia–reperfusion injury, trauma, cancer and sepsis.

G-CSF activation of AKT is not sufficient to prolong neutrophil survival

Neutrophils play an important role in the innate immune response against bacterial and fungal infections. They have a short lifespan in circulation, and their survival can be modulated by several cytokines, including G-CSF. Previous studies have implicated AKT as a critical signaling intermediary in the regulation of neutrophil survival. Our results demonstrate that G-CSF activation of AKT is not sufficient to prolong neutrophil survival. Neutrophils treated with G-CSF undergo apoptosis, even in the presence of high levels of p-AKT. In addition, inhibitors of AKT and downstream targets failed to alter neutrophil survival. In contrast, neutrophil precursors appear to be dependent on AKT signaling pathways for survival, whereas high levels of p-AKT inhibit proliferation. Our data suggest that the AKT/mTOR pathway, although important in G-CSF-driven myeloid differentiation, proliferation, and survival of early hematopoietic progenitors, is less essential in G-CSF suppression of neutrophil apoptosis. Whereas basal AKT levels may be required for the brief life of neutrophils, further p-AKT expression is not able to extend the neutrophil lifespan in the presence of G-CSF.

Innate immunosenescence: effect of aging on cells and receptors of the innate immune system in humans

Components of the innate immune response, including neutrophils and macrophages, are the first line of defense against infections. Their role is to initiate an inflammatory response, phagocyte and kill pathogens, recruit natural killer cells (NK), and facilitate the maturation and migration of dendritic cells that will initiate the adaptive immune response. Extraordinary advances have been made in the last decade on the knowledge of the receptors and mechanisms used by cells of the innate immunity not only to sense and eliminate the pathogen but also to communicate each other and collaborate with cells of adaptive immunity to mount an effective immune response. The analysis of innate immunity in elderly humans has evidenced that aging has a profound impact on the phenotype and functions of these cells. Thus altered expression and/or function of innate immunity receptors and signal transduction leading to defective activation and decreased chemotaxis, phagocytosis and intracellular killing of pathogens have been described. The phenotype and function of NK cells from elderly individuals show significant changes that are compatible with remodeling of the different NK subsets, with a decrease in the CD56bright subpopulation and accumulation of the CD56dim cells, in particular those differentiated NK cells that co-express CD57, as well as a decreased expression of activating natural cytotoxicity receptors. These alterations can be responsible of the decreased production of cytokines and the lower per-cell cytotoxicity observed in the elderly. Considering the relevance of these cells in the initiation of the immune response, the possibility to reactivate the function of innate immune cells should be considered in order to improve the response to pathogens and to vaccination in the elderly.

Melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in leukocytes from elderly humans

The mechanisms regulating neutrophil apoptosis are basically unaffected by the aging process. However, a significant impairment of cell survival occurs in elderly individuals following neutrophil challenge with pro-inflammatory stimuli, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). The goal of the present study was to prove the effects of melatonin supplementation on apoptosis induced by calcium signaling in human leukocytes from elderly volunteers. Treatments with the specific inhibitor of cytosolic calcium re-uptake, thapsigargin, and/or the calcium mobilizing agonist, N-formyl-methionyl-leucyl-phenylalanine (fMLP), induced mitochondrial membrane depolarization, caspase activation, phosphatidylserine (PS) externalization, and DNA fragmentation in leukocytes from both young and elderly volunteers, although such effects were much more evident in aged leukocytes. Importantly, melatonin treatment substantially preserved mitochondrial membrane potential, reversed caspase activation, reduced PS exposure and forestalled DNA fragmentation in leukocytes from both age groups. In conclusion, melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in aged leukocytes and may counteract, at the cellular level, age-related degenerative phenomena linked to oxidative stress.

Reactive oxygen intermediate-induced pathomechanisms contribute to immunosenescence, chronic inflammation and autoimmunity

Deregulation of reactive oxygen intermediates (ROI) resulting in either too high or too low concentrations are commonly recognized to be at least in part responsible for many changes associated with aging. This article reviews ROI-dependent mechanisms critically contributing to the decline of immune function during physiologic - or premature - aging. While ROI serve important effector functions in cellular metabolism, signalling and host defence, their fine-tuned generation declines over time, and ROI-mediated damage to several cellular components and/or signalling deviations become increasingly prevalent. Although distinct ROI-associated pathomechanisms contribute to immunosenescence of the innate and adaptive immune system, mutual amplification of dysfunctions may often result in hyporesponsiveness and immunodeficiency, or in chronic inflammation with hyperresponsiveness/deregulation, or both. In this context, we point out how imbalanced ROI contribute ambiguously to driving immunosenescence, chronic inflammation and autoimmunity. Although ROI may offer a distinct potential for therapeutic targeting along with the charming opportunity to rescue from deleterious processes of aging and chronic inflammatory diseases, such modifications, owing to the complexity of metabolic interactions, may carry a marked risk of unforeseen side effects.

Aging and neutrophils: there is still much to do

Human neutrophils are activated by a wide array of compounds through their receptors. This elicits their classical functions, such as chemotaxis, phagocytosis, and the production of reactive oxygen species (ROS). Upon stimulation, neutrophils also produce lipid and immune mediators and can present antigen through the major histocompatibility complex I (MHC-I). The age-related impairment of the classical functions of neutrophils is well described, but experimental evidence showing alterations in the production of mediators and antigen presentation with aging are lacking. This review highlights the role of neutrophils in age-related pathologies such as Alzheimer's disease, atherosclerosis, cancer, and autoimmune diseases. Furthermore, we discuss how aging potentially affects the production and release of mediators by human neutrophils in ways that may contribute to the development of these pathologies.

Granulocyte macrophage--colony-stimulating factor-dependent proliferation is impaired in macrophages from senescence-accelerated mice

A senescence-accelerated (SAMP8) mouse model was used to determine the effect of aging on the immune system. We produced in vitro bone marrow-derived macrophages from SAMP8 mice and compared them against senescence-resistant, long-lived mice (SAMR1). Although macrophages from both strains of mice proliferated in a similar manner in response to monocyte-colony-stimulating factor (M-CSF), SAMP8 macrophages showed an impaired response to granulocyte macrophage-colony-stimulating factor (GM-CSF). Similar levels of external regulated kinases (ERK)1/2 and signaling transducer and activator of transcription 5 (STAT5) phosphorylation were observed in macrophages from both strains of mice. The lack of proliferation was not caused by the induction of apoptosis. Differentiation of bone marrow cells into dendritic cells was similar in both strains of mice, as was the induction of major histocompatibility complex (MHC) class II molecules by interferon-gamma (IFN-gamma). Finally, we determined the density of Langerhans cells in vivo in the skin of the two mouse strains, but no differences were found.

Innate immunity and aging

Advanced age is associated with defects in all of the cells of the innate immune system, including numbers, function, and early stages of activation. This review, presents the current state of the field on the impact of age on the innate immune system. The analysis of the literature suggests that a dysfunctional innate immune system is a contributing factor to aberrant outcomes after injury or infection and to the development of many of the diseases observed in the elderly. Gaining an understanding of the nature of the defects in innate immune cells may allow the development of therapeutic strategies aimed to restore innate immune function in aged individuals.

Innate immunity and aging

Advanced age is associated with defects in all of the cells of the innate immune system, including numbers, function, and early stages of activation. This review, presents the current state of the field on the impact of age on the innate immune system. The analysis of the literature suggests that a dysfunctional innate immune system is a contributing factor to aberrant outcomes after injury or infection and to the development of many of the diseases observed in the elderly. Gaining an understanding of the nature of the defects in innate immune cells may allow the development of therapeutic strategies aimed to restore innate immune function in aged individuals.

Neutrophil depletion delays wound repair in aged mice

One of the most important clinical problems in caring for elderly patients is treatment of pressure ulcers. One component of normal wound healing is the generation of an inflammatory reaction, which is characterized by the sequential infiltration of neutrophils, macrophages and lymphocytes. Neutrophils migrate early in the wound healing process. In aged C57BL/6 mice, wound healing is relatively inefficient. We examined the effects of neutrophil numbers on wound healing in both young and aged mice. We found that the depletion of neutrophils by anti-Gr-1 antibody dramatically delayed wound healing in aged mice. The depletion of neutrophils in young mice had less effect on the kinetics of wound healing. Intravenous G-CSF injection increased the migration of neutrophils to the wound site. While the rate of wound repair did not change significantly in young mice following G-CSF injection, it increased significantly in old mice.

Immunosupportive therapies in aging

The primary role of the immune system is to protect the organism against pathogens, but age-associated alterations to immunity increase the susceptibility of the elderly to infectious disease. The exact nature of these changes is still controversial, but the use of screening procedures, such as the SENIEUR protocol to exclude underlying illness, helped to better characterize the changes actually related to physiological aging rather than pathology. It is generally agreed that the most marked changes occur in the cellular immune response reflecting profound alterations in T cells. Much of this is due to thymic involution as well as changes in the proportions of T cell subpopulations resulting from antigen exposure, and altered T cell activation pathways. However, a body of data indicates that innate immune responses, including the critical bridge between innate and adaptive immunity, and antigen presenting capacity are not completely resistant to senescence processes. The consequences of all these alterations are an increased incidence of infections, as well as possibly cancers, autoimmune disorders, and chronic inflammatory diseases. The leading question is what, if anything, can we do to prevent these deleterious changes without dangerously dysregulating the precarious balance of productive immunity versus immunopathology? There are many potential new therapeutic means now available to modulate immunosenescence and many others are expected to be available shortly. One main problem in applying these experimental therapies is ethical: there is a common feeling that as ageing is not a disease; the elderly are not sick and therefore do not require adventurous therapies with unpredictable side-effects in mostly frail individuals. Animal models are not helpful in this context. In this chapter we will first briefly review what we think we know about human immunosenescence and its consequences for the health status of elderly individuals. We will then discuss possible interventions that might one day become applicable in an appropriate ethical environment.

Age-related impairment of GM-CSF-induced signalling in neutrophils: role of SHP-1 and SOCS proteins

Functional activities of mature human neutrophils are strongly influenced by the pro-inflammatory cytokine granulocyte macrophage-colony stimulating factor (GM-CSF). Accordingly, a defective response to GM-CSF might have dramatic consequences for neutrophil functions and the host defence against infections. Such an event is most likely to occur in senescence. A number of studies have, in fact, reported an impairment of the GM-CSF capacity to prime and/or to activate respiratory burst, as well as to delay apoptotic events, in neutrophils from elderly individuals. In the last 2 decades many efforts have been made to explore at molecular levels the mechanism underlying these defects. Recent studies let us depict a scenario in which an increased activity of inhibitory molecules, such as Src homology domain-containing protein tyrosine phosphatase-1 (SHP-1) and suppressors of cytokine signalling (SOCS), is responsible for the age-related failure of GM-CSF to stimulate neutrophil functions via inhibition of Lyn-, phosphoinositide 3-kinase (PI3-K)/extracellular signal-regulated kinase (ERK)- and signal transducers and activators of transcription (STAT)-dependent pathways. The control of SHP-1 and/or SOCS activity might therefore be an important therapeutic target for the restoration of normal immune responses during senescence.

Host resistance and immune responses in advanced age

Immunosenescence results in populating immune tissues with less functional T cells, and perhaps B cells dendritic cells, that do not function well and produce more type 2 cytokines and fewer type 1 cytokines. Impaired immunity, distinct from immunosenescence, correlates more with disease burden than chronologic age. Older adults who have chronic diseases or chronic infections are more susceptible to common infections and have poor vaccine responses. Understanding specific mechanisms and targeting interventions are dependent on research to resolve the relationship between frailty-associated impaired immunity and the role of chronic infection versus immunosenescence in developing impaired immunity.

Role of phosphoinositide 3-kinase and extracellular signal-regulated kinase pathways in granulocyte macrophage-colony-stimulating factor failure to delay fas-induced neutrophil apoptosis in elderly humans

Fas-stimulated neutrophils from elderly individuals show impaired granulocyte macrophage-colony-stimulating factor (GM-CSF)-induced apoptosis cell rescue. Herein, this defect was found to be associated with a significant reduction in GM-CSF-mediated Akt and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. Using Akt and ERK1/2 inhibitors, we demonstrated that both kinases were critical for GM-CSF antiapoptotic effects. Whereas Akt inhibition also affected GM-CSF-dependent ERK1/2 phosphorylation, ERK1/2 inhibition did not affect GM-CSF-induced Akt phosphorylation, suggesting that phosphoinositide 3-kinase (PI3-K)/Akt and ERK1/2 are activated in series and that PI3-K is located upstream of ERK1/2 along the GM-CSF-dependent signaling pathway. No age-associated changes in GM-CSF receptor expression were observed. Interestingly, both suppressors of cytokine signaling (SOCS)1 and SOCS3 proteins were significantly higher in unstimulated neutrophils from elderly individuals and, unlike in young individuals, did not further increase following GM-CSF cell triggering. These results indicate that defective PI3-K/Akt/ERK1/2 activation, likely dependent on elevated SOCS1 and SOCS3 levels, may affect the GM-CSF capacity to delay neutrophil apoptosis in elderly persons.

Effects of aging on triggering receptor expressed on myeloid cells (TREM)-1-induced PMN functions

Triggering receptor expressed on myeloid cell-1 (TREM-1) is a recently described receptor that has many effects on polymorphonuclear neutrophil (PMN), as the engagement of this receptor on PMN can induce phagocytosis, respiratory burst and degranulation. We studied the effects of aging on TREM-1 engagement in human PMN. PMN from elderly were found to have impaired response following TREM-1 engagement. Notably they were not able to modulate the TREM-1-induced respiratory burst as PMN from young did. TREM-1 engagement could not reverse PMN survival following incubation with LPS or GM-CSF in the elderly whereas it did in the young. The phosphorylation of TREM-1 signal transduction molecules was altered with aging. Finally, TREM-1 engagement could not drive the recruitment of TREM-1 in the lipid-rafts of the elderly explaining in part the altered response. The observed alterations in TREM-1 response are possibly an important contributing factor in the higher incidence of sepsis-related deaths in the elderly population.

PKC signaling deficits: a mechanistic hypothesis for the origins of Alzheimer's disease

There is strong evidence that protein kinase C (PKC) isozyme signaling pathways are causally involved in associative memory storage. Other observations have indicated that PKC signaling pathways regulate important molecular events in the neurodegenerative pathophysiology of Alzheimer's disease (AD), which is a progressive dementia that is characterized by loss of recent memory. This parallel involvement of PKC signaling in both memory and neurodegeneration indicates a common basis for the origins of both the symptoms and the pathology of AD. Here, we discuss this conceptual framework as a basis for an autopsy-validated peripheral biomarker--and for AD drug design targeting drugs (bryostatin and bryologs) that activate PKC isozymes--that has already demonstrated significant promise for treating both AD neurodegeneration and its symptomatic memory loss.

GM-CSF activates the Jak/STAT pathway to rescue polymorphonuclear neutrophils from spontaneous apoptosis in young but not elderly individuals

Polymorphonuclear neutrophils (PMN) are the first cells to be recruited to the site of tissular aggression. They have a short-life span and die by spontaneous apoptosis. However, their life span and functional activities can be extended in vitro by a number of proinflammatory cytokines, including the granulocyte-macrophage colony stimulating factor (GM-CSF). We have reported that the protective effect of GM-CSF did not occur in PMN of elderly subjects. Data reported here showed that this difference was not due to a change in the expression of the GM-CSF receptor in the PMN of elderly individuals compared to young subjects. Furthermore, we showed here that GM-CSF activated the Janus kinase/signal transducer and activator of transcription (Jak/STAT) pathway and this activation appeared to be maintained for an extended period of time (18 h) playing an important role in the GM-CSF induced delayed PMN apoptosis. In marked contrast, GM-CSF had no effects on Jak2 activation in PMN of elderly individuals. We found that an inhibitor of Jak2 activation (AG490) abolished the protective effect of GM-CSF in PMN from young donors, however had no effect in PMN of elderly subjects. GM-CSF induced a transient activation of STAT3 and STAT5 in PMN of young donors but failed to activate to the same extent these signal transducers in PMN of elderly donors. The levels of proCaspase-3 were reduced in PMN of young donors treated with GM-CSF for 18 h but remained unchanged in PMN of elderly subjects treated under the same conditions compared to the untreated PMN. Our data are consistent with the interpretation that, at least in part (1) the protective effect of GM-CSF against apoptosis results from the activation of the Jak/STAT pathway and (2) decreased rescue from apoptosis in PMN of elderly is related to a failure of GM-CSF to activate this pathway in these cells.

Nampt/PBEF/Visfatin: a regulator of mammalian health and longevity?

Eukaryotes have evolved elaborate mechanisms to survive periods of adversity. By manipulating genes that control these mechanisms, researchers have found they can generate more stress resistant, longer-lived organisms. One of these is the PNC1 gene of Saccharomyces cerevisiae, a master "longevity regulatory gene" that translates a variety of environmental stresses into lifespan extension by activating the sirtuin family of longevity deacetylases. Master longevity genes such as PNC1 are highly adaptive because they allow organisms to respond in a concerted way to adversity and to rapidly evolve life strategies to compensate for a changing environment. Hence, they should be well conserved. We propose that there is a functional equivalent of PNC1 in mammals called Nampt (a.k.a. PBEF/Visfatin), a stress-responsive gene that would coordinately regulate metabolism, cell defenses, and resistance to diseases of aging.

Cytokine receptor signalling and aging

With ageing the immune system is deregulated and this leads to the development of immunosenescence mainly affecting the adaptive immune response. There is much knowledge accumulated concerning various receptor functions and signalling with ageing such as TCR, FcRs, TLRs. Cytokines are playing a major role in haematopoietic cell functions and in the harmonious and integrated coordination of the innate and adaptive immune response. There exists a large amount of data on cytokine production changes with ageing, as IL-2 production is decreasing, while IL-6 production is increasing. In contrast, there is only scarce knowledge concerning the cytokine receptors and their signalling in ageing. However, there is some evidence that the signalling of IL-2 receptors is altered in T cells and macrophages, mainly in relation to the JAK/STAT pathway. We present here evidence that the IL-6 induced signalling is also altered in T cells with ageing. An alteration in the JAKs and STATs activations in T cells and macrophages was demonstrated. The exact cause of these altered activations is not known and future studies are needed to elucidate them. In this review we summarise our present knowledge on cytokine signalling with ageing, mainly focusing on IL-2 and IL-6 receptors signalling.