Aging brain: exploring the interplay between bone marrow aging, immunosenescence, and neuroinflammation

Aging is a complex process characterized by a myriad of physiological changes, including alterations in the immune system termed immunosenescence. It exerts profound effects on both the bone marrow and the central nervous system, with significant implications for immunosenescence in neurological contexts. Our mini-review explores the complex relationship between bone marrow aging and its impact on immunosenescence, specifically within the context of neurological diseases. The bone marrow serves as a crucial hub for hematopoiesis and immune cell production, yet with age, it undergoes significant alterations, including alterations in hematopoietic stem cell function, niche composition, and inflammatory signaling. These age-related shifts in the bone marrow microenvironment contribute to dysregulation of immune cell homeostasis and function, impacting neuroinflammatory processes and neuronal health. In our review, we aim to explore the complex cellular and molecular mechanisms that link bone marrow aging to immunosenescence, inflammaging, and neuroinflammation, with a specific focus on their relevance to the pathophysiology of age-related neurological disorders. By exploring this interplay, we strive to provide a comprehensive understanding of how bone marrow aging impacts immune function and contributes to the progression of neurological diseases in aging individuals. Ultimately, this knowledge can hold substantial promise for the development of innovative therapeutic interventions aimed at preserving immune function and mitigating the progression of neurological disorders in the elderly population.

Senescent cell-derived extracellular vesicles as potential mediators of innate immunosenescence and inflammaging

Ageing is accompanied by a decline in immune function (immunosenescence), increased inflammation (inflammaging), and more senescent cells which together contribute to age-related disease and infection susceptibility. The innate immune system is the front-line defence against infection and cancer and is also involved in the removal of senescent cells, so preventing innate immunosenescence and inflammaging is vital for health in older age. Extracellular vesicles (EVs) modulate many aspects of innate immune function, including chemotaxis, anti-microbial responses, and immune regulation. Senescent cell derived EVs (SEVs) have different cargo to that of non-senescent cell derived EVs, suggesting alterations in EV cargo across the lifespan may influence innate immune function, possibly contributing to immunosenescence and inflammaging. Here we review current understanding of the potential impact of miRNAs, lipids and proteins, found in higher concentrations in SEVs, on innate immune functions and inflammation to consider whether SEVs are potential influencers of innate immunosenescence and inflammaging. Furthermore, senolytics have demonstrated an ability to return plasma EV content closer to that of non-senescent EVs, therefore the potential use of senotherapeutics (senolytics and senostatics) to ameliorate the effects of SEVs on immunosenescence and inflammaging is also considered as a possible strategy for extending health-span in older adults.

The Impact of T-cell Aging on Alloimmunity and Inflammaging

Aging affects immunity broadly through changes caused by immunosenescence, clinically resulting in augmented susceptibility to infections, autoimmunity, and cancer. The most striking alterations associated with immunosenescence have been observed in the T-cell compartment with a significant shift toward a terminally differentiated memory phenotype taking on features of innate immune cells. At the same time, cellular senescence impairs T-cell activation, proliferation, and effector functions, compromising the effectiveness of immunity. In clinical transplantation, T-cell immunosenescence has been the main driver of less frequent acute rejections in older transplant recipients. This patient population, at the same time, suffers more frequently from the side effects of immunosuppressive therapy including higher rates of infections, malignancies, and chronic allograft failure. T-cell senescence has also been identified as an instigator of age-specific organ dysfunction through a process that has been coined "inflammaging," accelerating organ injury and potentially contributing to the limited lifetime of organ transplants. Here, we provide a summary of the latest evidence on molecular characteristics of T-cell senescence affecting alloimmunity and organ quality while dissecting the consequences of unspecific organ injury and immunosuppression on T-cell senescence. Rather than conceptualizing immunosenescence as a broad and general "weaker" alloimmune response, it appears critical to understand both mechanisms and clinical effects in detail as a basis to refine treatment.

[Research advances in immunosenescence and inflammation in lung diseases]

The world's population is ageing at a rate unprecedented in human history. As the number of older people increases, so does the prevalence of lung disease in the elderly, making it essential to understand the pathophysiology of elderly patients with lung disease. Age-related changes in immune system function and lung parenchyma occur throughout a person's life. Immunosenescence refers to the tendency for innate and adaptive immunity to decline in the elderly. As we age, changes in the innate and adaptive immune systems can lead to dysregulation and reduced immune function. A low-level chronic inflammatory state is known as inflamm-aging and is driven by immunosenescence. This review discusses the role of immunosenescence and inflamm-aging in pulmonary diseases such as chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis, asthma, and lung infections. Understanding the different manifestations of lung diseases between the elderly and the young, finding new therapeutic sites, or improving clinical outcomes in hospitalized patients will provide clinicians with new ideas.

A silver bullet for ageing medicine?: clinical relevance of T-cell checkpoint receptors in normal human ageing

Immunosenescence describes dysregulation of the immune system with ageing manifested in both the innate and adaptive immunity, including changes in T-cell checkpoint signaling. Through complex and nuanced process, T-cells lose excitatory signaling pathways and upregulate their inhibitory signaling, leading to ineffective immune responses that contribute to the formation of the ageing phenotype. Here we expand on the expression, function, and clinical potential of targeting the T-cell checkpoint signaling in age and highlight interventions offering the most benefits to older adults' health. Notably, modifications in vaccination such as with mTOR inhibitors show immediate clinical relevance and good tolerability. Other proposed treatments, including therapies with monoclonal antibodies fail to show clinical efficacy or tolerability needed for implementation at present. Although T-cell co-signaling fits a valuable niche for translational scientists to manage immunosenescence, future study would benefit from the inclusion of older adults with multiple long-term conditions and polypharmacy, ensuring better applicability to actual patients seen in clinical settings.

Natural killer cells immunosenescence and the impact of lifestyle management

Natural killer cells (NKs) are lymphocytes of the innate immune system that quickly respond to viruses, infections, and tumors during their short cell life cycle. However, it was recently found that NKs undergo quantitative, distributional, structural, and functional phenotypic changes during aging that suppress immune responses, which is known as immunosenescence. The aging host environment, cytokine regulation, cytomegalovirus status, and hypothalamic‒pituitary‒adrenal axis have significant effects on NK function. Different lifestyle management interventions modulate the number and cytotoxic activity of NKs, which are essential for rebuilding the immune barrier against pathogens in elderly individuals. Based on recent studies, we review the phenotypic changes of and potential threats of NKs during aging and explore the underlying mechanisms. By summarizing the effects of lifestyle management on NKs and their application prospects, we aim to provide evidence for enhancing immune system function against immune diseases in elderly individuals.

Immunosenescence and cancer: Opportunities and challenges

As individuals age, cancer becomes increasingly common. This continually rising risk can be attributed to various interconnected factors that influence the body's susceptibility to cancer. Among these factors, the accumulation of senescent cells in tissues and the subsequent decline in immune cell function and proliferative potential are collectively referred to as immunosenescence. Reduced T-cell production, changes in secretory phenotypes, increased glycolysis, and the generation of reactive oxygen species are characteristics of immunosenescence that contribute to cancer susceptibility. In the tumor microenvironment, senescent immune cells may promote the growth and spread of tumors through multiple pathways, thereby affecting the effectiveness of immunotherapy. In recent years, immunosenescence has gained increasing attention due to its critical role in tumor development. However, our understanding of how immunosenescence specifically impacts cancer immunotherapy remains limited, primarily due to the underrepresentation of elderly patients in clinical trials. Furthermore, there are several age-related intervention methods, including metformin and rapamycin, which involve genetic and pharmaceutical approaches. This article aims to elucidate the defining characteristics of immunosenescence and its impact on malignant tumors and immunotherapy. We particularly focus on the future directions of cancer treatment, exploring the complex interplay between immunosenescence, cancer, and potential interventions.

Immunosenescence and Inflammaging in COVID-19

Despite knowledge gaps in understanding the full spectrum of the hyperinflammatory phase caused by SARS-CoV-2, according to the World Health Organization (WHO), COVID-19 is still the leading cause of death worldwide. Susceptible people to severe COVID-19 are those with underlying medical conditions or those with dysregulated and senescence-associated immune responses. As the immune system undergoes aging in the elderly, such drastic changes predispose them to various diseases and affect their responsiveness to infections, as seen in COVID-19. At-risk groups experience poor prognosis in terms of disease recovery. Changes in the quantity and quality of immune cell function have been described in numerous literature sites. Impaired immune cell function along with age-related metabolic changes can lead to features such as hyperinflammatory response, immunosenescence, and inflammaging in COVID-19. Inflammaging is related to the increased activity of the most inflammatory factors and is the main cause of age-related diseases and tissue failure in the elderly. Since hyperinflammation is a common feature of most severe cases of COVID-19, this pathway, which is not fully understood, leads to immunosenescence and inflammaging in some individuals, especially in the elderly and those with comorbidities. In this review, we shed some light on the age-related abnormalities of innate and adaptive immune cells and how hyperinflammatory immune responses contribute to the inflammaging process, leading to clinical deterioration. Further, we provide insights into immunomodulation-based therapeutic approaches, which are potentially important considerations in vaccine design for elderly populations.

Immunosenescence as a convergence pathway in neurodegeneration

Immunity refers to the body's defense mechanism to protect itself against illness or to produce antibodies against pathogens. Senescence is a cellular phenomenon that integrates a sustainable growth restriction, other phenotypic abnormalities and including a pro-inflammatory secretome. It is highly involved in regulating developmental stages, tissue homeostasis, and tumor proliferation monitoring. Contemporary experimental reports imply that abolition of senescent cells employing evolved genetic and therapeutic approaches augment the chances of survival and boosts the health span of an individual. Immunosenescence is considered as a process in which dysfunction of the immune system occurs with aging and greatly includes remodeling of lymphoid organs. This in turn causes fluctuations in the immune function of the elderly that has strict relation with the expansion of autoimmune diseases, infections, malignant tumors and neurodegenerative disorders. The interaction of the nervous and immune systems during aging is marked by bi-directional influence and mutual correlation of variations. The enhanced systemic inflammatory condition in the elderly, and the neuronal immune cell activity can be modulated by inflamm-aging and peripheral immunosenescence resulting in chronic low-grade inflammatory processes in the central Nervous system known as neuro-inflammaging. For example, glia excitation by cytokines and glia pro-inflammatory productions contribute significantly to memory injury as well as in acute systemic inflammation, which is associated with high levels of Tumor necrosis factor -α and a rise in cognitive decline. In recent years its role in the pathology of Alzheimer's disease has caught research interest to a large extent. This article reviews the connection concerning the immune and nervous systems and highlights how immunosenescence and inflamm-aging can affect neurodegenerative disorders.

Immunosenescence, Inflammaging, and Frailty: Role of Myeloid Cells in Age-Related Diseases

The immune system is the central regulator of tissue homeostasis, ensuring tissue regeneration and protection against both pathogens and the neoformation of cancer cells. Its proper functioning requires homeostatic properties, which are maintained by an adequate balance of myeloid and lymphoid responses. Aging progressively undermines this ability and compromises the correct activation of immune responses, as well as the resolution of the inflammatory response. A subclinical syndrome of "homeostatic frailty" appears as a distinctive trait of the elderly, which predisposes to immune debilitation and chronic low-grade inflammation (inflammaging), causing the uncontrolled development of chronic and degenerative diseases. The innate immune compartment, in particular, undergoes to a sequela of age-dependent functional alterations, encompassing steps of myeloid progenitor differentiation and altered responses to endogenous and exogenous threats. Here, we will review the age-dependent evolution of myeloid populations, as well as their impact on frailty and diseases of the elderly.

[Aging of the immune system]

Mit zunehmendem Alter sind ein Anstieg der Inzidenz von Infektionen, inflammatorischen Erkrankungen, wie Arteriosklerose, und Tumoren sowie parallel eine Reduktion des Impferfolgs zu beobachten. Dafür ist ein dysfunktionelles Immunsystem verantwortlich. Das Immunsystem kann in 3 Bereiche eingeteilt werden. Die erste Barriere, die epitheloide Schutzschicht der Haut und der Schleimhäute, verliert mit dem Alter ihre Schutzfunktion. Die zweite Barriere, das angeborene Immunsystem, wird im Alter durch eine chronische niedriggradige Entzündung bei gleichzeitiger Reduktion einer adäquaten Antwort auf Pathogene charakterisiert. Die reduzierte Bildung neuer naiver Lymphozyten und eine Abnahme der Diversität kennzeichnen das adaptive Immunsystem, die dritte Barriere, im Alter. Diese als Immunseneszenz zusammengefassten Veränderungen sind für eine Vielzahl von degenerativen Erkrankungen mitverantwortlich.

Aging of the Immune System: Focus on Natural Killer Cells Phenotype and Functions

Aging is the greatest risk factor for nearly all major chronic diseases, including cardiovascular diseases, cancer, Alzheimer’s and other neurodegenerative diseases of aging. Age-related impairment of immune function (immunosenescence) is one important cause of age-related morbidity and mortality, which may extend beyond its role in infectious disease. One aspect of immunosenescence that has received less attention is age-related natural killer (NK) cell dysfunction, characterized by reduced cytokine secretion and decreased target cell cytotoxicity, accompanied by and despite an increase in NK cell numbers with age. Moreover, recent studies have revealed that NK cells are the central actors in the immunosurveillance of senescent cells, whose age-related accumulation is itself a probable contributor to the chronic sterile low-grade inflammation developed with aging (“inflammaging”). NK cell dysfunction is therefore implicated in the increasing burden of infection, malignancy, inflammatory disorders, and senescent cells with age. This review will focus on recent advances and open questions in understanding the interplay between systemic inflammation, senescence burden, and NK cell dysfunction in the context of aging. Understanding the factors driving and enforcing NK cell aging may potentially lead to therapies countering age-related diseases and underlying drivers of the biological aging process itself.

Aging Leukocytes and the Inflammatory Microenvironment of the Adipose Tissue

Age-related immunosenescence, defined as an increase in inflammaging and the decline of the immune system, leads to tissue dysfunction and increased risk for metabolic disease. The elderly population is expanding, leading to a heightened need for therapeutics to improve health span. With age, many alterations of the immune system are observed, including shifts in the tissue-resident immune cells, increased expression of inflammatory factors, and the accumulation of senescent cells, all of which are responsible for a chronic inflammatory loop. Adipose tissue and the immune cell activation within are of particular interest for their well-known roles in metabolic disease. Recent literature reveals that adipose tissue is an organ in which signs of initial aging occur, including immune cell activation. Aged adipose tissue reveals changes in many innate and adaptive immune cell subsets, revealing a complex interaction that contributes to inflammation, increased senescence, impaired catecholamine-induced lipolysis, and impaired insulin sensitivity. Here, we will describe current knowledge surrounding age-related changes in immune cells while relating those findings to recent discoveries regarding immune cells in aged adipose tissue.

Retinal drusen in patients with chronic myeloproliferative blood cancers are associated with an increased proportion of senescent T cells and signs of an aging immune system

The cause of age-related macular degeneration (AMD) is unknown, but evidence indicates that both innate and adaptive immunity play a role in the pathogenesis. Our recent work has investigated AMD in patients with myeloproliferative neoplasms (MPNs) since they have increased drusen and AMD prevalence. We have previously found increased levels of chronic low-grade inflammation (CLI) in MPN patients with drusen (MPNd) compared to MPN patients with normal retinas (MPNn). CLI and AMD are both associated with aging, and we, therefore, wanted to study immunosenescence markers in MPNd, MPNn, and AMD. The purpose was to identify differences between MPNd and MPNn, which might reveal novel information relevant to drusen pathophysiology and thereby the AMD pathogenesis. Our results suggest that MPNd have a T cell differentiation profile resembling AMD and more effector memory T cells than MPNn. The senescence-associated-secretory-phenotype (SASP) is associated with effector T cells. SASP is thought to play a role in driving CLI seen with advancing age. Senescent cells with SASP may damage healthy tissue, including the eye tissues affected in AMD. The finding of increased effector cells in MPNd could implicate a role for adaptive immunity and senescent T cells together with increased CLI in drusen pathophysiology.

T Cell Immunosenescence in Aging, Obesity, and Cardiovascular Disease

Although advances in preventive medicine have greatly improved prognosis, cardiovascular disease (CVD) remains the leading cause of death worldwide. This clearly indicates that there remain residual cardiovascular risks that have not been targeted by conventional therapies. The results of multiple animal studies and clinical trials clearly indicate that inflammation is the most important residual risk and a potential target for CVD prevention. The immune cell network is intricately regulated to maintain homeostasis. Ageing associated changes to the immune system occurs in both innate and adaptive immune cells, however T cells are most susceptible to this process. T-cell changes due to thymic degeneration and homeostatic proliferation, metabolic abnormalities, telomere length shortening, and epigenetic changes associated with aging and obesity may not only reduce normal immune function, but also induce inflammatory tendencies, a process referred to as immunosenescence. Since the disruption of biological homeostasis by T cell immunosenescence is closely related to the development and progression of CVD via inflammation, senescent T cells are attracting attention as a new therapeutic target. In this review, we discuss the relationship between CVD and T cell immunosenescence associated with aging and obesity.

Is It "Aging" or Immunosenescence? The COVID-19 Biopsychosocial Risk Factors Aggravating Immunosenescence as Another Risk Factor of the Morbus. A Developmental-clinical Social Work Perspective

COVID-19 has proliferated ageism. The impetus of this article is to show that immunosenescence is a risk factor to COVID-19 and not aging per se. Based on the idea that some older people are also healthier than younger ones, the emphasis of this article is on immunosenescence and not aging as a risk factor of COVID-19 complications. The paper utilizes a biopsychosocial approach to expound on the link between immunosenescence and COVID-19 risk factors. The article explores biological factors such as malnutrition, comorbidities, substance abuse, and sex. It also expands on psychosocial factors such as mental health disorders, homelessness, unemployment, lack of physical exercises, stigma, and discrimination. The article calls for gerontological social work to assume a developmental-clinical social work perspective to prevent the early onset and progression of immunosenescence. It calls for gerontological social work to prevent factors that promote unhealthy aging. The article promotes a preventative stance to practice and not just curative approaches. Treatment involves primary prevention which emphasizes on avoiding the onset of unhealthy aging. It is this approach that gerontological social work should aim also to address in building resilience in the face of pandemics.

An aged immune system drives senescence and ageing of solid organs

Ageing of the immune system, or immunosenescence, contributes to the morbidity and mortality of the elderly1,2. To define the contribution of immune system ageing to organism ageing, here we selectively deleted Ercc1, which encodes a crucial DNA repair protein3,4, in mouse haematopoietic cells to increase the burden of endogenous DNA damage and thereby senescence5-7 in the immune system only. We show that Vav-iCre+/-;Ercc1-/fl mice were healthy into adulthood, then displayed premature onset of immunosenescence characterized by attrition and senescence of specific immune cell populations and impaired immune function, similar to changes that occur during ageing in wild-type mice8-10. Notably, non-lymphoid organs also showed increased senescence and damage, which suggests that senescent, aged immune cells can promote systemic ageing. The transplantation of splenocytes from Vav-iCre+/-;Ercc1-/fl or aged wild-type mice into young mice induced senescence in trans, whereas the transplantation of young immune cells attenuated senescence. The treatment of Vav-iCre+/-;Ercc1-/fl mice with rapamycin reduced markers of senescence in immune cells and improved immune function11,12. These data demonstrate that an aged, senescent immune system has a causal role in driving systemic ageing and therefore represents a key therapeutic target to extend healthy ageing.

Immune response to vaccination in the elderly

The immune system develops from childhood until the late age. Each of these periods has its own specialities. Aging is typical for immunity, depending on the conversion of hematogenous bone marrow to adipose, involution of the thymus and persistent viral infections (e.g. CMV). In the elderly, whose numbers have been increasing in recent decades, there is a need to understand the changes in the immune system also called as immunosenescence. The substantial remodeling of the immune system during aging leads to a decline in its functional activity in both innate (complement, cytokines, granulocytes, NK cells, macrophages) and adaptive immunity (B lymphocytes and antibody production, T lymphocytes, cytokine production and cytotoxic response, NKT cells, regulatory T lymphocytes with suppressor activity) with advancing age, resulting in increased risk of chronic diseases, infections, autoimmunity and vaccination failure.

Coronavirus disease-2019: A tocsin to our aging, unfit, corpulent, and immunodeficient society

Acute and chronic respiratory illnesses cause widespread morbidity and mortality, and this class of illness now includes the novel coronavirus severe acute respiratory syndrome that is causing coronavirus disease-2019 (COVID-19). The world is experiencing a major demographic shift toward an older, obese, and physically inactive populace. Risk factor assessments based on pandemic data indicate that those at higher risk for severe illness from COVID-19 include older males, and people of all ages with obesity and related comorbidities such as hypertension and type 2 diabetes. Aging in and of itself leads to negative changes in innate and adaptive immunity, a process termed immunosenescence. Obesity causes systemic inflammation and adversely impacts immune function and host defense in a way that patterns immunosenescence. Two primary prevention strategies to reduce the risk for COVID-19 at both the community and individual levels include mitigation activities and the adoption of lifestyle practices consistent with good immune health. Animal and human studies support the idea that, in contrast to high exercise workloads, regular moderate-intensity physical activity improves immunosurveillance against pathogens and reduces morbidity and mortality from viral infection and respiratory illnesses including the common cold, pneumonia, and influenza. The odds are high that infectious disease pandemics spawned by novel pathogens will continue to inflict morbidity and mortality as the world's population becomes older and more obese. COVID-19 is indeed a wake-up call, a tocsin, to the world that primary prevention countermeasures focused on health behaviors and hygiene demand our full attention and support.

Elderly at time of COronaVIrus disease 2019 (COVID-19): possible role of immunosenescence and malnutrition

The unprecedented COVID-19 pandemic is rapidly and unpredictably evolving and the majority of deaths are occurring in older people. A partial description of the magnitude of the scenario is provided by numbers and statistics, which probably underestimate the ongoing tragedy. In the present opinion paper, we have focused our attention on the evidence of the relationship among malnutrition, immunosenescence, and the higher morbidity and mortality in elderly patients. In particular, we propose the intriguing hypothesis that correction of nutritional deficits may attenuate the age-dependent alterations of the innate and adaptive immune system which participate in the increased susceptibility and worse outcome observed in the elderly COVID-19 patients.

Mitochondrial mass governs the extent of human T cell senescence

The susceptibility of human CD4+ and CD8+ T cells to senesce differs, with CD8+ T cells acquiring an immunosenescent phenotype faster than the CD4+ T cell compartment. We show here that it is the inherent difference in mitochondrial content that drives this phenotype, with senescent human CD4+ T cells displaying a higher mitochondrial mass. The loss of mitochondria in the senescent human CD8+ T cells has knock-on consequences for nutrient usage, metabolism and function. Senescent CD4+ T cells uptake more lipid and glucose than their CD8+ counterparts, leading to a greater metabolic versatility engaging either an oxidative or a glycolytic metabolism. The enhanced metabolic advantage of senescent CD4+ T cells allows for more proliferation and migration than observed in the senescent CD8+ subset. Mitochondrial dysfunction has been linked to both cellular senescence and aging; however, it is still unclear whether mitochondria play a causal role in senescence. Our data show that reducing mitochondrial function in human CD4+ T cells, through the addition of low-dose rotenone, causes the generation of a CD4+ T cell with a CD8+ -like phenotype. Therefore, we wish to propose that it is the inherent metabolic stability that governs the susceptibility to an immunosenescent phenotype.

Impact of mesenchymal stem cell senescence on inflammaging

Life expectancy has dramatically increased around the world over the last few decades, and staying healthier longer, without chronic disease, has become an important issue. Although understanding aging is a grand challenge, our understanding of the mechanisms underlying the degeneration of cell and tissue functions with age and its contribution to chronic disease has greatly advanced during the past decade. As our immune system alters with aging, abnormal activation of immune cells leads to imbalance of innate and adaptive immunity and develops a persistent and mild systemic inflammation, inflammaging. With their unique therapeutic properties, such as immunomodulation and tissue regeneration, mesenchymal stem cells (MSCs) have been considered to be a promising source for treating autoimmune disease or as anti-aging therapy. Although direct evidence of the role of MSCs in inflammaging has not been thoroughly studied, features reported in senescent MSCs or the aging process of MSCs are associated with inflammaging; MSC niche-driven skewing of hematopoiesis toward the myeloid lineage or oncogenesis, production of pro-inflammatory cytokines, and weakening their modulative property on macrophage polarization, which plays a central role on inflammaging development. This review explores the role of senescent MSCs as an important regulator for onset and progression of inflammaging and as an effective target for anti-aging strategies. [BMB Reports 2020; 53(2): 65-73].

Regulatory Effect of Anwulignan on the Immune Function Through Its Antioxidation and Anti-Apoptosis in D-Galactose-Induced Aging Mice

BACKGROUND

Aging is a spontaneous and inevitable phenomenon of biology, which can lead to the gradual deterioration of tissues and organs. One of the age-related deterioration processes is immunosenescence, which leads to changes in the function of immune systems, including immune cells and associated cytokines. A proper modulation of immune responses can improve the age-related immunosenescence process and then reach healthy aging. Schisandra sphenanthera, a traditional Chinese medicine, has been used as both a medicine and a nutritional supplement for thousands of years. Anwulignan, a monomer compound of Schisandra sphenanthera lignans, has been reported to possess an immunomodulatory effect. Therefore, this study was designed to further explore whether Anwulignan could also modulate the immune functions in aging model mice and the underlying mechanism.

METHODS

D-galactose (D-gal) is often used as an inducer of immunosenescence in animals. In this study, a mice model was created by subcutaneous D-gal (220 mg kg-1) for successive 42 days. Then, the blood and spleen tissue samples were taken for the analysis and observation of cytokine levels, immunoglobulin levels, leukocyte numbers, and the phagocytic activity of macrophages, as well as the histological changes, the proliferation ability of lymphocytes, and the biochemical parameters in the spleen tissue.

RESULTS

Anwulignan significantly increased the serum levels of IL-2, IL-4, IFN-γ, lgG, lgM, and lgA, decreased the content of TNF-α and IL-6 in the aging mice, and increased the blood leukocyte number, the phagocytic activity, the lymphocyte proliferation, and the spleen index in vitro. Anwulignan also significantly increased the activities of SOD and GSH-Px, decreased the contents of MDA and 8-OHdG in the spleen tissue, up-regulated the expressions of Nrf2, HO-1, and Bcl2, down-regulated the expressions of Keap1, Caspase-3, and Bax in the spleen cells, and reduced the apoptosis of spleen lymphocytes.

CONCLUSION

Anwulignan can restore the immune function that is declined in D-gal-induced aging mice partly related to its antioxidant capacity by activating the Nrf2/ARE pathway and downstream enzymes, as well as its anti-apoptotic effect by regulating Caspase-3 and the ratio of Bcl2 to Bax in the spleen.

Mechanisms underlying T cell ageing

T cell ageing has a pivotal role in rendering older individuals vulnerable to infections and cancer and in impairing the response to vaccination. Easy accessibility to peripheral human T cells as well as an expanding array of tools to examine T cell biology have provided opportunities to examine major ageing pathways and their consequences for T cell function. Here, we review emerging concepts of how the body attempts to maintain a functional T cell compartment with advancing age, focusing on three fundamental domains of the ageing process, namely self-renewal, control of cellular quiescence and cellular senescence. Understanding these critical elements in successful T cell ageing will allow the design of interventions to prevent or reverse ageing-related T cell failure.

A longitudinal study of the stability, variability, and interdependencies among late-differentiated T and NK cell subsets in older adults

The stability and variability of older adults' late-differentiated peripheral blood T and natural killer (NK) cells over time remains incompletely quantified or understood. We examined the variability and change over time in T and NK cell subsets in a longitudinal sample of older adults; the effects of sex, cytomegalovirus (CMV) serostatus, and chronic disease severity on immune levels and trajectories; and interdependencies among T and NK cell subsets. Older adults (N = 149, age 64-94 years, 42% male) provided blood every 6 months for 2.5 years (up to 5 waves) to evaluate late-differentiated CD8 T cells (CD28-, CD57+) and CD56dimNK cells (CD57+, NKG2C+, FcɛRIγ-). In multilevel models, most of the variance in immune subsets reflected stable differences between people. However, CD56dimNK cell subsets (CD57+ and FcɛRIγ-) also increased with age, whereas T cell subsets did not. Independent of age, all subsets examined were higher in CMV-positive older adults. Men had higher levels of CD56dim CD57+ than women. Chronic disease was not associated with any immune subset investigated. T and NK cell subsets correlated within each cell type, but interdependencies differed by CMV serostatus. Our results suggest the accumulation of these stable cell populations may be driven less by chronological aging, even less by chronic disease severity, and more by CMV, which may differentially skew T and NK cell differentiation.

Age-Associated Changes in the Respiratory Epithelial Response to Influenza Infection

Older adults suffer a disproportionate burden of influenza-related morbidity and mortality typically attributed to defects in the aging immune system collectively known as immunosenescence. While the age-related decline in the adaptive immune system has been well characterized, little is known about how aging affects the principal site of influenza infection-the nasal epithelium. In human nasal epithelial cell cultures (hNECs) from older adults, we found similar or increased levels of cytokines during influenza infection compared with hNECs from younger individuals. However, hNECs from older individuals demonstrated decreased mRNA expression for several key proteins that affect clearance of infected cells, including MHC-I and transporter associated with antigen presentation (TAP). These findings were confirmed at the level of protein expression. In vivo studies corroborated the in vitro differences in MHC-I and TAP gene expression and also revealed important decreases in the expression of key influenza-specific antiviral mediators MX1 and IFITM1. Furthermore, epithelial cell-cytotoxic T lymphocyte co-cultures demonstrate that CTL cytotoxic activity is dose-dependent on MHC-I antigen presentation. Taken together, these results indicate that aging is associated with important changes in the nasal epithelium, including antigen presentation and antiviral pathways, which may contribute to increased severity of disease in older adults through impaired clearance of infected cells.

Diversity of aging of the immune system classified in the cotton rat (Sigmodon hispidus) model of human infectious diseases

Susceptibility and declined resistance to human pathogens like respiratory syncytial virus (RSV) at old age is well represented in the cotton rat (Sigmodon hispidus). Despite providing a preferred model of human infectious diseases, little is known about aging of its adaptive immune system. We aimed to define aging-related changes of the immune system of this species. Concomitantly, we asked whether the rate of immunological alterations may be stratified by physiological aberrations encountered during aging. With increasing age, cotton rats showed reduced frequencies of T cells, impaired induction of antibodies to RSV, higher incidence of aberrations of organs and signs of lipemia. Moreover, old animals expressed high biological heterogeneity, but the age-related reduction of T cell frequency was only observed in those specimens that displayed aberrant organs. Thus, cotton rats show age-related alterations of lymphocytes that can be classified by links with health status.

Aging, inflammation, immunity and periodontal disease

The increased prevalence and severity of periodontal disease have long been associated with aging, such that this oral condition affects the majority of the adult population over 50 years of age. Although the immune system is a critical component for maintaining health, aging can be characterized by quantitative and qualitative modifications of the immune system. This process, termed 'immunosenescence', is a progressive modification of the immune system that leads to greater susceptibility to infections, neoplasia and autoimmunity, presumably reflecting the prolonged antigenic stimulation and/or stress responses that occur across the lifespan. Interestingly, the global reduction in the host capability to respond effectively to these challenges is coupled with a progressive increase in the general proinflammatory status, termed 'inflammaging'. Consistent with the definition of immunosenescence, it has been suggested that the cumulative effect of prolonged exposure of the periodontium to microbial challenge is, at least in part, a contributor to the effects of aging on these tissues. Thus, it has also been hypothesized that alterations in the function of resident immune and nonimmune cells of the periodontium contribute to the expression of inflammaging in periodontal disease. Although the majority of aging research has focused on the adaptive immune response, it is becoming increasingly clear that the innate immune compartment is also highly affected by aging. Thus, the phenomenon of immunosenescence and inflammaging, expressed as age-associated changes within the periodontium, needs to be more fully understood in this era of precision and personalized medicine and dentistry.

Immunosenescence patterns differ between populations but not between sexes in a long-lived mammal

In animals, physiological mechanisms underlying reproductive and actuarial senescence remain poorly understood. Immunosenescence, the decline in the ability to display an efficient immune response with increasing age, is likely to influence both reproductive and actuarial senescence through increased risk of disease. Evidence for such a link has been reported from laboratory animal models but has been poorly investigated in the wild, where variation in resource acquisitions usually drives life-history trade-offs. We investigated immunosenescence patterns over 7 years in both sexes of two contrasting roe deer populations (Capreolus capreolus). We first measured twelve immune markers to obtain a thorough identification of innate and adaptive components of immunity and assessed, from the same individuals, the age-dependent variation observed in parasitic infections. Although the level of innate traits was maintained at old age, the functional innate immune traits declined with increasing age in one of two populations. In both populations, the production of inflammatory markers increased with advancing age. Finally, the adaptive response declined in late adulthood. The increasing parasite burden with age we reported suggests the effective existence of immunosenescence. Age-specific patterns differed between populations but not between sexes, which indicate that habitat quality could shape age-dependent immune phenotype in the wild.

Traumatic Stress and Accelerated Cellular Aging: From Epigenetics to Cardiometabolic Disease

PURPOSE OF REVIEW

The aim of this paper is to review the recent literature on traumatic stress-related accelerated aging, including a focus on cellular mechanisms and biomarkers of cellular aging and on the clinical manifestations of accelerated biological aging.

RECENT FINDINGS

Multiple lines of research converge to suggest that PTSD is associated with accelerated aging in the epigenome, and the immune and inflammation systems, and this may be reflected in premature onset of cardiometabolic and cardiovascular disease. The current state of research paves the way for future work focused on identifying the peripheral and central biological mechanisms linking traumatic stress to accelerated biological aging and medical morbidity, with an emphasis on processes involved in inflammation, immune functioning, oxidative stress, autonomic arousal, and stress response. Ultimately, such work could help reduce the pace of biological aging and improve health and wellness.

Effects of Physical Exercise on Markers of Cellular Immunosenescence: A Systematic Review

Aging affects negatively the immune system, defined as immunosenescence, which increases the susceptibility of elderly persons to infection, autoimmune disease, and cancer. There are strong indications that physical exercise in elderly persons may prevent the age-related decline in immune response without significant side effects. Consequently, exercise is being considered as a safe mode of intervention to reduce immunosenescence. The aim of this review was to appraise the existing evidence regarding the impact of exercise on surface markers of cellular immunosenescence in either young and old humans or animals. PubMed and Web of Science were systematically screened, and 28 relevant articles in humans or animals were retrieved. Most of the intervention studies demonstrated that an acute bout of exercise induced increases in senescent, naïve, memory CD4⁺ and CD8⁺ T-lymphocytes and significantly elevated apoptotic lymphocytes in peripheral blood. As regards long-term effects, exercise induced increased levels of T-lymphocytes expressing CD28⁺ in both young and elderly subjects. Few studies found an increase in natural killer cell activity following a period of training. We can conclude that exercise has considerable effects on markers of cellular aspects of the immune system. However, very few studies have been conducted so far to investigate the effects of exercise on markers of cellular immunosenescence in elderly persons. Implications for immunosenescence need further investigation.

The Role of Immunosenescence in the Development of Age-Related Diseases

Aging is a complex phenomenon leading to numerous changes in the physiological systems of the body. One of the most important changes, called immunosenescence, occurs in the immune system. Immunosenescence covers changes in the innate and the adaptive immune systems and is associated with a low-grade inflammation called inflammaging. Aging, likely via inflammaging, is also associated with the emergence of chronic diseases including cardiovascular and neurodegenerative diseases, cancer, and diabetes mellitus type 2. The origin of this inflammaging is not known with certainty, but several concurrent contributing factors have been suggested, such as aging-associated changes in the innate and adaptive immune response, chronic antigenic stimulation, the appearance of endogenous macromolecular changes, and the presence of senescent cells exhibiting a senescence-associated secretory phenotype. A better understanding of the multiple biological phenomena leading to these diseases via the immunosenescence associated with inflammaging provides a powerful target for interventions to increase the healthspan of elderly subjects.

Biomarkers related to immunosenescence: relationships with therapy and survival in lung cancer patients

PURPOSE

There are well-known alterations occurring within the immune system with aging. Collectively, these changes are known as immunosenescence. The incidence of malignancies also increases with age. The aim of this study was to determine the presence of immunosenescence biomarkers in non-small cell lung cancer (NSCLC) patients and to evaluate some of them as predictive biomarkers of CIMAvax-EGF cancer vaccine efficacy.

METHODS

Sixty-six NSCLC patients, vaccinated or not with CIMAvax-EGF cancer vaccine, and 37 age-matched controls were enrolled. Peripheral blood samples were studied for CD19+, CD4+, CD8+, CD28-, CD57+ and CD45RA+ subpopulations by flow cytometry.

RESULTS

Absolute count of CD19+ and the CD4/CD8 ratio were significantly lower in NSCLC patients than in age-paired controls, while highly differentiated T cells increased in NSCLC patients treated with platinum-based chemotherapy. Using Cox regression, we were able to dichotomize the patient population according to biomarkers. Vaccinated patients with frequency <24 % of CD8 + CD28- T cells, >40 % of CD4 T cells and CD4/CD8 ratio higher than two at the beginning of immunotherapy achieved a 20-month increase in median survival regarding control patients.

CONCLUSIONS

Distribution of lymphocyte subsets was influenced by cancer and chemotherapy in NSCLC patients. CD19 + B cells decrease by cancer disease and not by chemotherapy, and CD28- subpopulations increase by chemotherapy and not by cancer. The proportion of CD8 + CD28- T cells, CD4+ T cells and CD4/CD8 ratio can be used as predictive biomarkers of CIMAvax-EGF efficacy in NSCLC patients and thereby could, be a useful tool for a personalized treatment.

Young and old animals use various strategies of metabolic adaptation to Cu-induced liver fibrosis

The role of the prooxidant-antioxidant and immune systems in formation of age-related adaptive responses to chronic effects of toxic substances (copper ions) was studied. In this purpose in young and old animals by multiple sequential administration of copper sulfate was induced liver fibrosis. Using this model the characteristics of prooxidant-antioxidant and immune systems, and physiological characteristics of were assessed. The Cu-induced liver fibrosis was accompanied by the oxidative stress and a significant reduction in cell immune activity. In the case of elimination of oxidative stress by introducing exogenous antioxidants (mix factor) in animals with fibrosis was recovered efficiency, body weight, the content of red blood cells. In old animals the restoring of the changed parameters of cellular immunity was more effective than in the young. Young and old animals used different metabolic strategies of adaptation to toxic environmental factors.

Imaging Immunosenescence

To demonstrate effects of aging visually requires a robust technique that can reproducibly detect small differences in efficiency or kinetics between groups. Investigators of aging will greatly appreciate the benefits of Amnis ImageStream technology ( www.amnis.com/), which combines quantitative flow cytometry with simultaneous high-resolution digital imaging. Imagestream is quantitative, reproducible, feasible with limited samples, and it facilitates in-depth examination of cellular mechanisms between cohorts of samples.

Frailty, Inflammation and Immunosenescence

Frailty is a still-evolving concept of a complex phenomenon. There are several algorithms and strategies for assessing frailty syndrome, but currently, no universally accepted definition or measurement protocol has been determined. Consequently, the biological cause(s) of frailty are also poorly defined. Much circumstantial experimental data point to the dysregulation of several key physiological systems, including the neuroendocrine, musculoskeletal, metabolic and immune/inflammatory systems, resulting from alterations in functional reserves. Immune dysregulation and inflammation as causes of frailty have gained some support from the results of longitudinal studies, but a true causal relationship has not been established. This chapter will describe the immune/inflammatory alterations found in frailty and their putative causal relationships with this state.