Monocytes present age-related changes in phospholipid concentration and decreased energy metabolism

Elucidating the role of chemokines in inflammaging associated atherosclerotic cardiovascular diseases

Age-related inflammation or inflammaging is a critical deciding factor of physiological homeostasis during aging. Cardiovascular diseases (CVDs) are exquisitely associated with aging and inflammation and are one of the leading causes of high mortality in the elderly population. Inflammaging comprises dysregulation of crosstalk between the vascular and cardiac tissues that deteriorates the vasculature network leading to development of atherosclerosis and atherosclerotic-associated CVDs in elderly populations. Leukocyte differentiation, migration and recruitment holds a crucial position in both inflammaging and atherosclerotic CVDs through relaying the activity of an intricate network of inflammation-associated protein-protein interactions. Among these interactions, small immunoproteins such as chemokines play a major role in the progression of inflammaging and atherosclerosis. Chemokines are actively involved in lymphocyte migration and severe inflammatory response at the site of injury. They relay their functions via chemokine-G protein-coupled receptors-glycosaminoglycan signaling axis and is a principal part for the detection of age-related atherosclerosis and related CVDs. This review focuses on highlighting the detailed intricacies of the effects of chemokine-receptor interaction and chemokine oligomerization on lymphocyte recruitment and its evident role in clinical manifestations of atherosclerosis and related CVDs. Further, the role of chemokine mediated signaling for formulating next-generation therapeutics against atherosclerosis has also been discussed.

Arachidonic acid in aging: New roles for old players

BACKGROUND

Arachidonic acid (AA), one of the most ubiquitous polyunsaturated fatty acids (PUFAs), provides fluidity to mammalian cell membranes. It is derived from linoleic acid (LA) and can be transformed into various bioactive metabolites, including prostaglandins (PGs), thromboxanes (TXs), lipoxins (LXs), hydroxy-eicosatetraenoic acids (HETEs), leukotrienes (LTs), and epoxyeicosatrienoic acids (EETs), by different pathways. All these processes are involved in AA metabolism. Currently, in the context of an increasingly visible aging world population, several scholars have revealed the essential role of AA metabolism in osteoporosis, chronic obstructive pulmonary disease, and many other aging diseases.

AIM OF REVIEW

Although there are some reviews describing the role of AA in some specific diseases, there seems to be no or little information on the role of AA metabolism in aging tissues or organs. This review scrutinizes and highlights the role of AA metabolism in aging and provides a new idea for strategies for treating aging-related diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

As a member of lipid metabolism, AA metabolism regulates the important lipids that interfere with the aging in several ways. We present a comprehensivereviewofthe role ofAA metabolism in aging, with the aim of relieving the extreme suffering of families and the heavy economic burden on society caused by age-related diseases. We also collected and summarized data on anti-aging therapies associated with AA metabolism, with the expectation of identifying a novel and efficient way to protect against aging.

Human monocyte subtype expression of neuroinflammation and regeneration-related genes is linked to age and sex

Stroke is a leading cause of disability and the third cause of death. The immune system plays an essential role in post-stroke recovery. After an ischemic stroke, monocytes infiltrate the injured brain tissue and can exacerbate or mitigate the damage. Ischemic stroke is more prevalent in the aged population, and the aging brain exhibits an altered immune response. There are also sex disparities in ischemic stroke incidence, outcomes, and recovery, and these differences may be hormone-driven and determined by genetic and epigenetic factors. Here, we studied whether human peripheral blood monocyte subtype (classical, intermediate, and non-classical) expression of neuronal inflammation- and regeneration-related genes depends on age and sex. A FACS analysis of blood samples from 44 volunteers (male and female, aged 28 to 98) showed that in contrast to other immune cells, the proportion of natural killer cells increased in females. The proportion of B-cells decreased in both sexes with age, and subtypes of monocytes were not linked to age or sex. Gene expression analysis by qPCR identified several genes differentially correlating with age and sex within different monocyte subtypes. Interestingly, ANXA1 and CD36 showed a consistent increase with aging in all monocytes, specifically in intermediate (CD36) and intermediate and non-classical (ANXA1) subtypes. Other genes (IL-1β, S100A8, TNFα, CD64, CD33, TGFβ1, TLR8, CD91) were differentially changed in monocyte subtypes with increased aging. Most age-dependent gene changes were differentially expressed in female monocytes. Our data shed light on the nuanced interplay of age and sex in shaping the expression of inflammation- and regeneration-related genes within distinct monocyte subtypes. Understanding these dynamics could pave the way for targeted interventions and personalized approaches in post-stroke care, particularly for the aging population and individuals of different sexes.

Alterations in metabolic pathways: a bridge between aging and weaker innate immune response

Aging is a time-dependent progressive physiological process, which results in impaired immune system function. Age-related changes in immune function increase the susceptibility to many diseases such as infections, autoimmune diseases, and cancer. Different metabolic pathways including glycolysis, tricarboxylic acid cycle, amino acid metabolism, pentose phosphate pathway, fatty acid oxidation and fatty acid synthesis regulate the development, differentiation, and response of adaptive and innate immune cells. During aging all these pathways change in the immune cells. In addition to the changes in metabolic pathways, the function and structure of mitochondria also have changed in the immune cells. Thereby, we will review changes in the metabolism of different innate immune cells during the aging process.

Immunity in the Progeroid Model of Cockayne Syndrome: Biomarkers of Pathological Aging

Cockayne syndrome (CS) is a rare autosomal recessive disorder that affects the DNA repair process. It is a progeroid syndrome predisposing patients to accelerated aging and to increased susceptibility to respiratory infections. Here, we studied the immune status of CS patients to determine potential biomarkers associated with pathological aging. CS patients, as well as elderly and young, healthy donors, were enrolled in this study. Complete blood counts for patients and donors were assessed, immune cell subsets were analyzed using flow cytometry, and candidate cytokines were analyzed via multi-analyte ELISArray kits. In CS patients, we noticed a high percentage of lymphocytes, an increased rate of intermediate and non-classical monocytes, and a high level of pro-inflammatory cytokine IL-8. In addition, we identified an increased rate of particular subtypes of T Lymphocyte CD8+ CD28- CD27-, which are senescent T cells. Thus, an inflammatory state was found in CS patients that is similar to that observed in the elderly donors and is associated with an immunosenescence status in both groups. This could explain the CS patients' increased susceptibility to infections, which is partly due to an aging-associated inflammation process.

ARID5B-mediated LINC01128 epigenetically activated pyroptosis and apoptosis by promoting the formation of the BTF3/STAT3 complex in β2GPI/anti-β2GPI-treated monocytes

BACKGROUND

Alterations of the trimethylation of histone 3 lysine 4 (H3K4me3) mark in monocytes are implicated in the development of autoimmune diseases. Therefore, the purpose of our study was to elucidate the role of H3K4me3-mediated epigenetics in the pathogenesis of antiphospholipid syndrome (APS).

METHODS

H3K4me3 Cleavage Under Targets and Tagmentation and Assay for Transposase-Accessible Chromatin were performed to determine the epigenetic profiles. Luciferase reporter assay, RNA immunoprecipitation, RNA pull-down, co-immunoprecipitation and chromatin immunoprecipitation were performed for mechanistic studies. Transmission electron microscopy and propidium iodide staining confirmed cell pyroptosis. Primary monocytes from patients with primary APS (PAPS) and healthy donors were utilised to test the levels of key molecules. A mouse model mimicked APS was constructed with beta2-glycoprotein I (β2GPI) injection. Blood velocity was detected using murine Doppler ultrasound.

RESULTS

H3K4me3 signal and open chromatin at the ARID5B promoter were increased in an in vitro model of APS. The epigenetic factor ARID5B directly activated LINC01128 transcription at its promoter. LINC01128 promoted the formation of the BTF3/STAT3 complex to enhance STAT3 phosphorylation. Activated STAT3 interacted with the NLRP3 promoter and subsequently stimulated pyroptosis and apoptosis. ARID5B or BTF3 depletion compensated for LINC01128-induced pyroptosis and apoptosis by inhibiting STAT3 phosphorylation. In mice with APS, β2GPI exposure elevated the levels of key proteins of pyroptosis and apoptosis pathways in bone marrow-derived monocytes, reduced the blood velocity of the ascending aorta, increased the thrombus size of the carotid artery, and promoted the release of interleukin (IL)-18, IL-1β and tissue factor. Patients with PAPS had the high-expressed ARID5B and LINC01128, especially those with triple positivity for antiphospholipid antibodies. Moreover, there was a positive correlation between ARID5B and LINC01128 expression.

CONCLUSION

This study indicated that ARID5B/LINC01128 was synergistically upregulated in APS, and they aggravated disease pathogenesis by enhancing the formation of the BTF3/STAT3 complex and boosting p-STAT3-mediated pyroptosis and apoptosis, thereby providing candidate therapeutic targets for APS.

HIGHLIGHTS

The H3K4me3 mark and chromatin accessibility at the ARID5B promoter are increased in vitro model mimicked APS. ARID5B-mediated LINC01128 induces pyroptosis and apoptosis via p-STAT3 by binding to BTF3. ARID5B is high- expressed in patients with primary APS and positively correlated with LINC01128 expression. OICR-9429 treatment mitigates pyroptosis and related inflammation in vivo and in vitro models mimicked APS.

Improving Blood Monocyte Energy Metabolism Enhances Its Ability to Phagocytose Amyloid-β and Prevents Alzheimer's Disease-Type Pathology and Cognitive Deficits

Deficiencies in the clearance of peripheral amyloid β (Aβ) play a crucial role in the progression of Alzheimer's disease (AD). Previous studies have shown that the ability of blood monocytes to phagocytose Aβ is decreased in AD. However, the exact mechanism of Aβ clearance dysfunction in AD monocytes remains unclear. In the present study, we found that blood monocytes in AD mice exhibited decreases in energy metabolism, which was accompanied by cellular senescence, a senescence-associated secretory phenotype, and dysfunctional phagocytosis of Aβ. Improving energy metabolism rejuvenated monocytes and enhanced their ability to phagocytose Aβ in vivo and in vitro. Moreover, enhancing blood monocyte Aβ phagocytosis by improving energy metabolism alleviated brain Aβ deposition and neuroinflammation and eventually improved cognitive function in AD mice. This study reveals a new mechanism of impaired Aβ phagocytosis in monocytes and provides evidence that restoring their energy metabolism may be a novel therapeutic strategy for AD.

Myeloid Cells As a Promising Target for Brain-Bone Degenerative Diseases from a Metabolic Point of View

Brain and bone degenerative diseases such as Alzheimer's disease and osteoporosis are common in the aging population and lack efficient pharmacotherapies. Myeloid cells are a diverse group of mononuclear cells that plays important roles in development, immune defense, and tissue homeostasis. Aging drastically alters the expansion and function of myeloid cells, which might be a common pathogenesis of the brain-bone degenerative diseases. From this perspective, the role of myeloid cells in brain-bone degenerative diseases is discussed, with a particular focus on metabolic alterations in myeloid cells. Furthermore, targeting myeloid cells through metabolic regulation via drugs such as metformin and melatonin is proposed as a potential therapy for the clinical treatment of brain-bone diseases.

Lipids and the hallmarks of ageing: From pathology to interventions

Lipids are critical structural and functional architects of cellular homeostasis. Change in systemic lipid profile is a clinical indicator of underlying metabolic pathologies, and emerging evidence is now defining novel roles of lipids in modulating organismal ageing. Characteristic alterations in lipid metabolism correlate with age, and impaired systemic lipid profile can also accelerate the development of ageing phenotype. The present work provides a comprehensive review of the extent of lipids as regulators of the modern hallmarks of ageing viz., cellular senescence, chronic inflammation, gut dysbiosis, telomere attrition, genome instability, proteostasis and autophagy, epigenetic alterations, and stem cells dysfunctions. Current evidence on the modulation of each of these hallmarks has been discussed with emphasis on inherent age-dependent deficiencies in lipid metabolism as well as exogenous lipid changes. There appears to be sufficient evidence to consider impaired lipid metabolism as key driver of the ageing process although much of knowledge is yet fragmented. Considering dietary lipids, the type and quantity of lipids in the diet is a significant, but often overlooked determinant that governs the effects of lipids on ageing. Further research using integrative approaches amidst the known aging hallmarks is highly desirable for understanding the therapeutics of lipids associated with ageing.

Peripheral blood monocyte status is a predictor for judging occurrence and development on sepsis in older adult population: a case control study

BACKGROUND

Peripheral blood monocytes are important immune modulatory cells that change during aging. Previous studies on sepsis and monocytes did not distinguish between age groups, especially in the older adult population. The mechanisms of monocyte subsets and function are not well-understood in the aging context with sepsis.

METHODS

Monocyte subsets were measured using flow cytometry in 80 sepsis patients and 40 healthy controls. Plasma cytokine levels were measured using cytokine antibody arrays.

RESULTS

The percentage of MO3 (CD14 + CD16 + +)/monocytes was higher in sepsis patients than in controls (P = 0.011), whereas the percentage of MO1 (CD14 +  + CD16 -)/monocytes was higher in septic shock patients and 28-day death group than in those without shock and 28-day survival group (P = 0.034, 0.038). Logistic regression analysis showed that the percentage of MO3/monocytes (OR = 1.120, P = 0.046) and plasma level of monocyte chemoattractant protein (MCP)-1 (OR = 1.006, P = 0.023) were independently associated with the occurrence of sepsis, whereas the percentage of MO1/monocytes (OR = 1.255, P = 0.048) was independently associated with septic shock. The receiver operating characteristic (ROC) curve showed that the area under the curve (AUC) of MO3/monocyte percentage in combination with MCP-1 plasma level (AUC = 0.799) for predicting sepsis was higher than that of each parameter alone (P < 0.001). The AUC of MO1/monocyte percentage with the value 0.706 (P = 0.003) was lower than the AUC of SOFA (sequential organ failure assessment) score with the value 0.966 (P < 0.001) for predicting septic shock, but the value of the two AUCs were similar for predicting 28-day mortality (AUC = 0.705, 0.827; P = 0.020, P < 0.001). The AUC of MO1/monocytes percentage in combination with SOFA score for predicting 28-day mortality was higher than that of each parameter alone (AUC = 0.867, P < 0.001). Using a cut-off of 58.5% (for MO1/monocytes determined by ROC) could discriminate between survivors and non-survivors on Kaplan-Meier curves for 28-day mortality with a positive predictive value of 77.4%.

CONCLUSION

The MO3/monocyte percentage and plasma MCP-1 level were independent predictors of sepsis occurrence, whereas the percentage of MO1/monocytes was an independent predictor of prognosis in the Chinese Han older adult population.

TRIAL REGISTRATION

Registration number: ChiCTR2200061490, date of registration: 2022-6-26 (retrospectively registered).

Single-cell RNA sequencing reveals the molecular features of peripheral blood immune cells in children, adults and centenarians

Peripheral blood immune cells have different molecular characteristics at different stages of the whole lifespan. Knowledge of circulating immune cell types and states from children to centenarians remains incomplete. We profiled peripheral blood mononuclear cells (PBMCs) of multiple age groups with single-cell RNA sequencing (scRNA-seq), involving the age ranges of 1-12 (G1), 20-30(G2), 30-60(G3), 60-80(G4), and >110 years (G5). The proportion and states of myeloid cells change significantly from G1 to G2. We identified a novel CD8⁺CCR7⁺GZMB⁺ cytotoxic T cell subtype specific in G1, expressing naive and cytotoxic genes, and validated by flow cytometry. CD8⁺ T cells showed significant changes in the early stage (G1 to G2), while CD4⁺ T cells changed in the late stage (G4 to G5). Moreover, the intercellular crosstalk among PBMCs in G1 is very dynamic. Susceptibility genes for a variety of autoimmune diseases (AIDs) have different cell-specific expression localization, and the expression of susceptibility genes for AIDs changes with age. Notably, the CD3⁺ undefined T cells clearly expressed susceptibility genes for multiple AIDs, especially in G3. ETS1 and FLI1, susceptibility genes associated with systemic lupus erythematosus, were differentially expressed in CD4⁺ and CD8⁺ effector cells in G1 and G3. These results provided a valuable basis for future research on the unique immune system of the whole lifespan and AIDs.

Exploration of the Mechanism of Linoleic Acid Metabolism Dysregulation in Metabolic Syndrome

We aimed to explore the mechanism of the linoleic acid metabolism in metabolic syndrome (MetS). RNA-seq data for 16 samples with or without MetS from the GSE145412 dataset were collected. Gene set variation analysis (GSVA), gene set enrichment analysis (GSEA), and gene differential expression analysis were performed. Expression data of differentially expressed genes (DEGs) involved in the linoleic acid metabolism pathway were mapped to the pathway by using Pathview for visualization. There were 19 and 10 differentially expressed biological processes in the disease group and healthy group, respectively. 9 KEGG pathways were differentially expressed in the disease group. Linoleic acid metabolism was the only differentially expressed pathway in the healthy group. The GSVA enrichment score of the linoleic acid metabolism pathway in the disease group was markedly lower than that in the healthy group. The GSEA result showed that the linoleic acid metabolism pathway was significantly downregulated in the disease group. JMJD7-PLA2G4B, PLA2G1B, PLA2G2D, CYP2C8, and CYP2J2 involved in the pathway were significantly downregulated in the disease group. This study may provide novel insight into MetS from the point of linoleic acid metabolism dysregulation.

Production of MHCII-expressing classical monocytes increases during aging in mice and humans

Aging is associated with increased monocyte production and altered monocyte function. Classical monocytes are heterogenous and a shift in their subset composition may underlie some of their apparent functional changes during aging. We have previously shown that mouse granulocyte-monocyte progenitors (GMPs) produce "neutrophil-like" monocytes (NeuMo), whereas monocyte-dendritic cell progenitors (MDPs) produce monocyte-derived dendritic cell (moDC)-producing monocytes (DCMo). Here, we demonstrate that classical monocytes from the bone marrow of old male and female mice have higher expression of DCMo signature genes (H2-Aa, H2-Ab1, H2-Eb1, Cd74), and that more classical monocytes express MHCII and CD74 protein. Moreover, we show that bone marrow MDPs and classical monocytes from old mice yield more moDC. We also demonstrate higher expression of Aw112010 in old monocytes and that Aw112010 lncRNA activity regulates MHCII induction in macrophages, which suggests that elevated Aw112010 levels may underlie increased MHCII expression during monocyte aging. Finally, we show that classical monocyte expression of MHCII is also elevated during healthy aging in humans. Thus, aging-associated changes in monocyte production may underlie altered monocyte function and have implications for aging-associated disorders.

A new monocyte epigenetic clock reveals nonlinear effects of alcohol consumption on biological aging in three independent cohorts (N = 2242)

BACKGROUND

Assessing the effect of alcohol consumption on biological age is essential for understanding alcohol use-related comorbidities and mortality. Previously developed epigenetic clocks are mainly based on DNA methylation in heterogeneous cell types, which provide limited knowledge on the impacts of alcohol consumption at the individual cellular level. Evidence shows that monocytes play an important role in both alcohol-induced pathophysiology and the aging process. In this study, we developed a novel monocyte-based DNA methylation clock (MonoDNAmAge) to assess the impact of alcohol consumption on monocyte age.

METHODS

A machine learning method was applied to select a set of chronological age-associated DNA methylation CpG sites from 1202 monocyte methylomes. Pearson correlation was tested between MonoDNAmAge and chronological age in three independent cohorts (N_total  = 2242). Using the MonoDNAmAge clock and four established clocks (i.e., HorvathDNAmAge, HannumDNAmAge, PhenoDNAmAge, GrimDNAmAge), we then evaluated the effect of alcohol consumption on epigenetic aging in the three cohorts [i.e., Yale Stress Center Community Study (YSCCS), Veteran Aging Cohort Study (VACS), Women's Interagency HIV Study (WIHS)] using linear and quadratic models.

RESULTS

The MonoDNAmAge, comprised of 186 CpG sites, was moderately to strongly correlated with chronological age in the three cohorts (r = 0.90, p = 3.12E-181 in YSCCS; r = 0.54, p = 1.75E-96 in VACS; r = 0.66, p = 1.50E-60 in WIHS). More importantly, we found a nonlinear association between MonoDNAmAge and alcohol consumption (p_model  = 4.55E-08, px2  = 7.80E-08 in YSCCS; p_model  = 1.85E-02, px2  = 3.46E-02 in VACS). Heavy alcohol consumption increased EAA_MonoDNAmAge up to 1.60 years while light alcohol consumption decreased EAA_MonoDNAmAge up to 2.66 years. These results were corroborated by the four established epigenetic clocks (i.e., HorvathDNAmAge, HannumDNAmAge, PhenoDNAmAge, GrimDNAmAge).

CONCLUSIONS

The results suggest a nonlinear relationship between alcohol consumption and its effects on epigenetic age. Considering adverse effects of alcohol consumption on health, nonlinear effects of alcohol use should be interpreted with caution. The findings, for the first time, highlight the complex effects of alcohol consumption on biological aging.

DNA Methylation Aberrant in Atherosclerosis

Atherosclerosis (AS) is a pathological process involving lipid oxidation, immune system activation, and endothelial dysfunction. The activated immune system could lead to inflammation and oxidative stress. Risk factors like aging and hyperhomocysteinemia also promote the progression of AS. Epigenetic modifications, including DNA methylation, histone modification, and non-coding RNA, are involved in the modulation of genes between the environment and AS formation. DNA methylation is one of the most important epigenetic mechanisms in the pathogenesis of AS. However, the relationship between the progression of AS and DNA methylation is not completely understood. This review will discuss the abnormal changes of DNA methylation in AS, including genome-wide hypermethylation dominating in AS with an increase of age, hypermethylation links with methyl supply and generating hyperhomocysteinemia, and the influence of oxidative stress with the demethylation process by interfering with the hydroxyl-methylation of TET proteins. The review will also summarize the current status of epigenetic treatment, which may provide new direction and potential therapeutic targets for AS.

Pannexin Channel Regulation of Cell Migration: Focus on Immune Cells

The role of Pannexin (PANX) channels during collective and single cell migration is increasingly recognized. Amongst many functions that are relevant to cell migration, here we focus on the role of PANX-mediated adenine nucleotide release and associated autocrine and paracrine signaling. We also summarize the contribution of PANXs with the cytoskeleton, which is also key regulator of cell migration. PANXs, as mechanosensitive ATP releasing channels, provide a unique link between cell migration and purinergic communication. The functional association with several purinergic receptors, together with a plethora of signals that modulate their opening, allows PANX channels to integrate physical and chemical cues during inflammation. Ubiquitously expressed in almost all immune cells, PANX1 opening has been reported in different immunological contexts. Immune activation is the epitome coordination between cell communication and migration, as leukocytes (i.e., T cells, dendritic cells) exchange information while migrating towards the injury site. In the current review, we summarized the contribution of PANX channels during immune cell migration and recruitment; although we also compile the available evidence for non-immune cells (including fibroblasts, keratinocytes, astrocytes, and cancer cells). Finally, we discuss the current evidence of PANX1 and PANX3 channels as a both positive and/or negative regulator in different inflammatory conditions, proposing a general mechanism of these channels contribution during cell migration.

Monocytes in HIV and SIV Infection and Aging: Implications for Inflamm-Aging and Accelerated Aging

Before the antiretroviral therapy (ART) era, people living with HIV (PLWH) experienced complications due to AIDS more so than aging. With ART and the extended lifespan of PLWH, HIV comorbidities also include aging—most likely due to accelerated aging—as well as a cardiovascular, neurocognitive disorders, lung and kidney disease, and malignancies. The broad evidence suggests that HIV with ART is associated with accentuated aging, and that the age-related comorbidities occur earlier, due in part to chronic immune activation, co-infections, and possibly the effects of ART alone. Normally the immune system undergoes alterations of lymphocyte and monocyte populations with aging, that include diminished naïve T- and B-lymphocyte numbers, a reliance on memory lymphocytes, and a skewed production of myeloid cells leading to age-related inflammation, termed “inflamm-aging”. Specifically, absolute numbers and relative proportions of monocytes and monocyte subpopulations are skewed with age along with myeloid mitochondrial dysfunction, resulting in increased accumulation of reactive oxygen species (ROS). Additionally, an increase in biomarkers of myeloid activation (IL-6, sCD14, and sCD163) occurs with chronic HIV infection and with age, and may contribute to immunosenescence. Chronic HIV infection accelerates aging; meanwhile, ART treatment may slow age-related acceleration, but is not sufficient to stop aging or age-related comorbidities. Overall, a better understanding of the mechanisms behind accentuated aging with HIV and the effects of myeloid activation and turnover is needed for future therapies.

Age Related Differences in Monocyte Subsets and Cytokine Pattern during Acute COVID-19-A Prospective Observational Longitudinal Study

The COVID-19 pandemic drastically highlighted the vulnerability of the elderly population towards viral and other infectious threats, illustrating that aging is accompanied by dysregulated immune responses currently summarized in terms like inflammaging and immunoparalysis. To gain a better understanding on the underlying mechanisms of the age-associated risk of adverse outcome in individuals experiencing a SARS-CoV-2 infection, we analyzed the impact of age on circulating monocyte phenotypes, activation markers and inflammatory cytokines including interleukin 6 (IL-6), IL-8 and tumor necrosis factor (TNF) in the context of COVID-19 disease progression and outcome in 110 patients. Our data indicate no age-associated differences in peripheral monocyte counts or subset composition. However, age and outcome are associated with differences in monocyte activation status. Moreover, a distinct cytokine pattern of IL-6, IL-8 and TNF in elderly survivors versus non-survivors, which consolidates over the time of hospitalization, suggests that older patients with adverse outcomes experience an inappropriate immune response, reminiscent of an inflammaging driven immunoparalysis. Our study underscores the value, necessity and importance of longitudinal monitoring in elderly COVID-19 patients, as dynamic changes after symptom onset can be observed, which allow for a differentiated insight into confounding factors that impact the complex pathogenesis following an infection with SARS-CoV-2.

Type I Interferon signaling controls the accumulation and transcriptomes of monocytes in the aged lung

Aging is paradoxically associated with a deteriorated immune defense (immunosenescence) and increased basal levels of tissue inflammation (inflammaging). The lung is particularly sensitive to the effects of aging. The immune cell mechanisms underlying physiological lung aging remain poorly understood. Here we reveal that aging leads to increased interferon signaling and elevated concentrations of chemokines in the lung, which is associated with infiltration of monocytes into the lung parenchyma. scRNA‐seq identified a novel Type‐1 interferon signaling dependent monocyte subset (MO‐ifn) that upregulated IFNAR1 expression and exhibited greater transcriptomal changes with aging than the other monocytes. Blockade of type‐1 interferon signaling by treatment with anti‐IFNAR1 neutralizing antibodies rapidly ablated MO‐ifn cells. Treatment with anti‐IFNAR1 antibodies also reduced airway chemokine concentrations and repressed the accumulation of the overall monocyte population in the parenchyma of the aged lung. Together, our work suggests that physiological aging is associated with increased basal level of airway monocyte infiltration and inflammation in part due to elevated type‐1 interferon signaling.

Resveratrol as an Adjunctive Therapy for Excessive Oxidative Stress in Aging COVID-19 Patients

The coronavirus disease 2019 (COVID-19) pandemic continues to burden healthcare systems worldwide. COVID-19 symptoms are highly heterogeneous, and the patient may be asymptomatic or may present with mild to severe or fatal symptoms. Factors, such as age, sex, and comorbidities, are key determinants of illness severity and progression. Aging is accompanied by multiple deficiencies in interferon production by dendritic cells or macrophages in response to viral infections, resulting in dysregulation of inflammatory immune responses and excess oxidative stress. Age-related dysregulation of immune function may cause a more obvious pathophysiological response to SARS-CoV-2 infection in elderly patients and may accelerate the risk of biological aging, even after recovery. For more favorable treatment outcomes, inhibiting viral replication and dampening inflammatory and oxidative responses before induction of an overt cytokine storm is crucial. Resveratrol is a potent antioxidant with antiviral activity. Herein, we describe the reasons for impaired interferon production, owing to aging, and the impact of aging on innate and adaptive immune responses to infection, which leads to inflammation distress and immunosuppression, thereby causing fulminant disease. Additionally, the molecular mechanism by which resveratrol could reverse a state of excessive basal inflammatory and oxidative stress and low antiviral immunity is discussed.

Jejunal Transcriptomic Profiling for Differences in Feed Conversion Ratio in Slow-Growing Chickens

Simple Summary

The slow-growing Korat chicken (KR) is economically attractive, as KR meat has a high selling price and has thus been used in Thailand to support smallholder farmers. However, low feed efficiency in KR stockbreeding makes the product less competitive and improving KR feed efficiency is central to increasing KR profitability. Using RNA sequencing, we compared the jejunal transcriptomic profiles of low- and high-feed conversion ratio (FCR) KR chickens, to identify FCR-related transcriptional variation and biological pathways. Gene Ontology and Kyoto Encyclopedia of Gene and Genome analysis revealed that the main pathways involved in KR FCR variation are related to immune response, glutathione metabolism, vitamin transport and metabolism, lipid metabolism, and neuronal and cardiac maturation, development, and growth. This is the first study to investigate, in the jejunum, the molecular genetic mechanisms affecting the FCR of slow-growing chickens. These findings will be useful in line-breeding programs to improve feed efficiency and profitability in slow-growing chicken stockbreeding.

Abstract

Improving feed efficiency is an important breeding target for the poultry industry; to achieve this, it is necessary to understand the molecular basis of feed efficiency. We compared the jejunal transcriptomes of low- and high-feed conversion ratio (FCR) slow-growing Korat chickens (KRs). Using an original sample of 75 isolated 10-week-old KR males, we took jejunal samples from six individuals in two groups: those with extremely low FCR (n = 3; FCR = 1.93 ± 0.05) and those with extremely high FCR (n = 3; FCR = 3.29 ± 0.06). Jejunal transcriptome profiling via RNA sequencing revealed 56 genes that were differentially expressed (p < 0.01, FC > 2): 31 were upregulated, and 25 were downregulated, in the low-FCR group relative to the high-FCR group. Functional annotation revealed that these differentially expressed genes were enriched in biological processes related to immune response, glutathione metabolism, vitamin transport and metabolism, lipid metabolism, and neuronal and cardiac maturation, development, and growth, suggesting that these are important mechanisms governing jejunal feed conversion. These findings provide an important molecular basis for future breeding strategies to improve slow-growing chicken feed efficiency.

New Pharmacological Tools to Target Leukocyte Trafficking in Lung Disease

Infection and inflammation of the lung results in the recruitment of non-resident immune cells, including neutrophils, eosinophils and monocytes. This swift response should ensure clearance of the threat and resolution of stimuli which drive inflammation. However, once the threat is subdued this influx of immune cells should be followed by clearance of recruited cells through apoptosis and subsequent efferocytosis, expectoration or retrograde migration back into the circulation. This cycle of cell recruitment, containment of threat and then clearance of immune cells and repair is held in exquisite balance to limit host damage. Advanced age is often associated with detrimental changes to the balance described above. Cellular functions are altered including a reduced ability to traffic accurately towards inflammation, a reduced ability to clear pathogens and sustained inflammation. These changes, seen with age, are heightened in lung disease, and most chronic and acute lung diseases are associated with an exaggerated influx of immune cells, such as neutrophils, to the airways as well as considerable inflammation. Indeed, across many lung diseases, pathogenesis and progression has been associated with the sustained presence of trafficking cells, with examples including chronic diseases such as Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis and acute infections such as Pneumonia and Pneumonitis. In these instances, there is evidence that dysfunctional and sustained recruitment of cells to the airways not only increases host damage but impairs the hosts ability to effectively respond to microbial invasion. Targeting leukocyte migration in these instances, to normalise cellular responses, has therapeutic promise. In this review we discuss the current evidence to support the trafficking cell as an immunotherapeutic target in lung disease, and which potential mechanisms or pathways have shown promise in early drug trials, with a focus on the neutrophil, as the quintessential trafficking immune cell.

Immunometabolic responses according to physical fitness status and lifelong exercise during aging: New roads for exercise immunology

Molecules such as cytokines, energetic substrates, and hormones found in the immune cell environment, especially lymphocytes and monocytes, are crucial for directing energy metabolism. In turn, changes in energy metabolism occur in a synchronized manner with the activation of certain signaling pathways, thereby this crosstalk is responsible for determining the functionality of immune cells. The immunometabolism field has grown over time and that is becoming increasingly promising in several populations; here we discuss the mechanisms involved in sedentary and physically active middle-aged individuals and master athletes. In this context, this review shows that the physical activity status and lifelong exercise seems to be good strategies for the promotion of metabolic and functional adaptations in T lymphocytes and monocytes, counteracting inflammatory environments caused by expanded adipose tissue and sedentary behavior, as well as delaying the immunosenescence caused by aging.

Programmed PPAR-α downregulation induces inflammaging by suppressing fatty acid catabolism in monocytes

Inflammaging is associated with an increased risk of chronic disease. Monocytes are the principal immune cells for the production of inflammatory cytokines and contribute to inflammaging in the elderly. However, the underlying mechanisms remain largely unknown. Here, we found that monocytes from aged individuals contained high levels of lipid droplets (LDs), and this increase was correlated with impaired fatty acid oxidation. Downregulated peroxisome proliferator-activated receptor (PPAR)-α may be responsible for the pro-inflammatory phenotype of monocytes in aged individuals, as it was positively correlated with LD accumulation and increasing TNF-α concentration. Interestingly, interventions that result in PPAR-α upregulation, such as fenofibrate treatment, TNF-α neutralization, or calorie restriction, reversed the effect of aging on monocytes. Thus the downregulation of PPAR-α and LD levels in monocytes represents a novel biomarker for inflammaging. Furthermore, PPAR-α activation in the elderly may also alleviate long-term inflammaging, preventing the development of life-limiting chronic diseases.

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Monocytes from aged individuals contained high levels of lipid droplets (LDs)

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Downregulated PPAR-α is responsible for the aged monocytes profiles

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TNF-α might accelerate monocyte aging by downregulating PPAR-α expression

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PPAR-α activation in the elderly may also alleviate long-term inflammaging

Inhibition of phospholipases suppresses progression of psoriasis through modulation of inflammation

Abnormal lipid metabolism is regarded as a crucial cause of psoriasis. The specific mechanism of how phospholipase PLA2G4B mediates local immune dysfunction and skin lesions remains unclear. The aim of this study was to explore the mechanisms of anti-psoriasis and immune suppression effect by inhibiting PLA2G4B in psoriasis progression. We successfully transfected si-PLA2G4B in a murine keratinocyte cell-line PAM212 to verify the effect of progression by PLA2G4B. The Imiquimod psoriasis mouse model was then successfully constructed, followed by emulsion wrapped PLA2G4B-siRNA applied to the skin lesions. The phenotype, pathology, immunofluorescence staining of PLA2G4B, IL17, CD3, and CD1b, and bulk transcriptome analysis were performed to decipher the effect and mechanism of si-PLA2G4B. Interfering with PLA2G4B significantly inhibited the proliferation and migration of PAM212. The interference of PLA2G4B in vivo showed a therapeutic effect on psoriasis, comparable to that of betamethasone. The phenotype and pathology revealed reduced keratinocytes in the si-PLA2G4B group compared to the model mice. Immunofluorescence showed that CD1b, CD3+ T cells, and IL17 were suppressed in the skin lesions. RNA-seq and deconvolution revealed that immune cells such as myeloid dendritic cell and T cell CD8+ naive were inactivated. Th17 reduce the release of inflammatory factors such as IL17 and IL36. Pathway analysis revealed the potential therapeutic mechanism involved in the inhibition of sphingolipid or ceramide secretion. This study verified the anti-psoriatic effect of using si-PLA2G4B. The immune response was alleviated after administration. This phospholipase inhibition-based therapy sheds light on the pharmaceutical potential against psoriasis.

Age-related differences in monocyte DNA methylation and immune function in healthy Kenyan adults and children

BACKGROUND

Age-related changes in adaptive and innate immune cells have been associated with a decline in effective immunity and chronic, low-grade inflammation. Epigenetic, transcriptional, and functional changes in monocytes occur with aging, though most studies to date have focused on differences between young adults and the elderly in populations with European ancestry; few data exist regarding changes that occur in circulating monocytes during the first few decades of life or in African populations. We analyzed DNA methylation profiles, cytokine production, and inflammatory gene expression profiles in monocytes from young adults and children from western Kenya.

RESULTS

We identified several hypo- and hyper-methylated CpG sites in monocytes from Kenyan young adults vs. children that replicated findings in the current literature of differential DNA methylation in monocytes from elderly persons vs. young adults across diverse populations. Differentially methylated CpG sites were also noted in gene regions important to inflammation and innate immune responses. Monocytes from Kenyan young adults vs. children displayed increased production of IL-8, IL-10, and IL-12p70 in response to TLR4 and TLR2/1 stimulation as well as distinct inflammatory gene expression profiles.

CONCLUSIONS

These findings complement previous reports of age-related methylation changes in isolated monocytes and provide novel insights into the role of age-associated changes in innate immune functions.

Recent developments and future perspectives in aging and macrophage immunometabolism

<abstract> <p>Aging is the strongest contributor to the development and severity of many chronic and infectious diseases, primarily through age-related increases in low-grade inflammation (inflammaging) and decreases in immune function (immunosenescence). Metabolic reprogramming in immune cells is a significant contributor to functional and phenotypic changes in these cells, but little is known about the direct effect of aging on immunometabolism. This review highlights several recent advances in this field, focusing on mitochondrial dysfunction, NAD+ metabolism, and therapeutic reprogramming in aged monocytes and macrophages. Perspectives on opportunities for future research in this area are also provided. Targeting immunometabolism is a promising strategy for designing therapeutics for a wide variety of age-related diseases.</p> </abstract>

The impact of ageing on monocytes and macrophages

Ageing is a global burden. Increasing age is associated with increased incidence of infections and cancer and decreased vaccine efficacy. This increased morbidity observed with age, is believed to be due in part to a decline in adaptive immunity, termed immunosenescence. However not all aspects of immunity decrease with age as ageing presents with systemic low grade chronic inflammation, characterised by elevated concentrations of mediators such as IL-6, TNFα and C Reactive protein (CRP). Inflammation is a strong predictor of morbidity and mortality, and chronic inflammation is known to be detrimental to a functioning immune system. Although the source of the inflammation is much discussed, the key cells which are believed to facilitate the inflammageing phenomenon are the monocytes and macrophages. In this review we detail how macrophage and monocyte phenotype and function change with age. The impact of ageing on macrophages includes decreased phagocytosis and immune resolution, increased senescent-associated markers, increased inflammatory cytokine production, reduced autophagy, and a decrease in TLR expression. With monocytes there is an increase in circulating CD16⁺ monocytes, decreased type I IFN production, and decreased efferocytosis. In conclusion, we believe that monocytes and macrophages contribute to immunosenescence and inflammageing and as a result have an important role in defective immunity with age.

Updating Phospholipase A2 Biology

The phospholipase A₂ (PLA₂) superfamily contains more than 50 enzymes in mammals that are subdivided into several distinct families on a structural and biochemical basis. In principle, PLA₂ has the capacity to hydrolyze the sn-2 position of glycerophospholipids to release fatty acids and lysophospholipids, yet several enzymes in this superfamily catalyze other reactions rather than or in addition to the PLA₂ reaction. PLA₂ enzymes play crucial roles in not only the production of lipid mediators, but also membrane remodeling, bioenergetics, and body surface barrier, thereby participating in a number of biological events. Accordingly, disturbance of PLA₂-regulated lipid metabolism is often associated with various diseases. This review updates the current state of understanding of the classification, enzymatic properties, and biological functions of various enzymes belonging to the PLA₂ superfamily, focusing particularly on the novel roles of PLA₂s in vivo.

Novel roles of immunometabolism and nonmyocyte metabolism in cardiac remodeling and injury

Changes in cardiomyocyte metabolism have been heavily implicated in cardiac injury and heart failure (HF). However, there is emerging evidence that metabolism in nonmyocyte populations, including cardiac fibroblasts, immune cells, and endothelial cells, plays an important role in cardiac remodeling and adaptation to injury. Here, we discuss recent advances and insights into nonmyocyte metabolism in the healthy and injured heart. Metabolic switching from mitochondrial oxidative phosphorylation to glycolysis is critical for immune cell (macrophage and T lymphocyte) and fibroblast phenotypic switching in the inflamed and fibrotic heart. On the other hand, cardiac endothelial cells are heavily reliant on glycolytic metabolism, and thus impairments in glycolytic metabolism underlie endothelial cell dysfunction. Finally, we review current and ongoing metabolic therapies for HF and the potential implications for nonmyocyte metabolism.

Implication of Aging Related Chronic Neuroinflammation on COVID-19 Pandemic

SARS-CoV-2, the virus responsible for the COVID-19 pandemic, leads to a respiratory syndrome and other manifestations. Most affected people show no or mild symptoms, but the risk of severe disease and death increases in older people. Here, we report a narrative review on selected studies targeting aging-related chronic neuroinflammation in the COVID-19 pandemic. A hyperactivation of the innate immune system with elevated levels of pro-inflammatory cytokines occurs during severe COVID-19, pointing to an important role of the innate immune dysregulation in the disease outcome. Aging is characterized by a general condition of low-grade inflammation, also connected to chronic inflammation of the brain (neuroinflammation), which is involved in frailty syndrome and contributes to several age-associated diseases, including neurodegenerative and neuropsychiatric disorders. Since neuroinflammation can be induced or worsened by the virus infection itself, as well as by stressful conditions like those linked to the recent pandemic, the role of neuroinflammatory mechanisms could be central in a vicious circle leading to an increase in the mortality risk in aged COVID-19 patients. Furthermore, triggered neuroinflammatory pathways and consequent neurodegenerative and neuropsychiatric conditions might be potential long-term complications of COVID-19. In order to provide insights to help clinicians in identifying patients who progress to a more severe case of the disease, this review underlines the potential implications of aging-related neuroinflammation in COVID-19 pandemic.

Severe COVID-19 and aging: are monocytes the key?

The ongoing pandemic severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes a disproportionate number of severe cases and deaths in older adults. Severe SARS-CoV-2-associated disease (coronavirus disease 2019 (COVID-19)) was declared a pandemic by the World Health Organization in March 2020 and is characterized by cytokine storm, acute respiratory distress syndrome, and in some cases by systemic inflammation-related pathology. Currently, our knowledge of the determinants of severe COVID-19 is primarily observational. Here, I review emerging evidence to argue that monocytes, a circulating innate immune cell, are principal players in cytokine storm and associated pathologies in COVID-19. I also describe changes in monocyte function and phenotype that are characteristic of both aging and severe COVID-19, which suggests a potential mechanism underlying increased morbidity and mortality due to SARS-CoV-2 infection in older adults. The innate immune system is therefore a potentially important target for therapeutic treatment of COVID-19, but experimental studies are needed, and SARS-CoV-2 presents unique challenges for pre-clinical and mechanistic studies in vivo. The immediate establishment of colonies of SARS-CoV-2-susceptible animal models for aging studies, as well as strong collaborative efforts in the geroscience community, will be required in order to develop the therapies needed to combat severe COVID-19 in older adult populations.

Fanning the Flames of Inflammaging: Impact of Monocyte Metabolic Reprogramming

Monocytes are circulating innate immune cells that are functionally dysregulated during aging. However, while metabolic regulation of innate immune cell function is now well-established, only a handful of studies have examined this in the context of aging. In a recent article published in Aging Cell, Saare et al. observe comprehensive metabolic reprogramming of otherwise unstimulated monocytes isolated from older adults. These cells display increased glucose uptake and dysregulation of mitochondrial function, concomitant with activation of signaling pathways contributing to increased inflammation. These findings suggest a mechanism whereby metabolic reprogramming in aged monocytes contributes to chronic low-grade inflammation and open new avenues of investigation into the biological underpinning of inflammaging.

Monocytes present age-related changes in phospholipid concentration and decreased energy metabolism

Age‐related changes at the cellular level include the dysregulation of metabolic and signaling pathways. Analyses of blood leukocytes have revealed a set of alterations that collectively lower their ability to fight infections and resolve inflammation later in life. We studied the transcriptomic, epigenetic, and metabolomic profiles of monocytes extracted from younger adults and individuals over the age of 65 years to map major age‐dependent changes in their cellular physiology. We found that the monocytes from older persons displayed a decrease in the expression of ribosomal and mitochondrial protein genes and exhibited hypomethylation at the HLA class I locus. Additionally, we found elevated gene expression associated with cell motility, including the CX3CR1 and ARID5B genes, which have been associated with the development of atherosclerosis. Furthermore, the downregulation of two genes, PLA2G4B and ALOX15B, which belong to the arachidonic acid metabolism pathway involved in phosphatidylcholine conversion to anti‐inflammatory lipoxins, correlated with increased phosphatidylcholine content in monocytes from older individuals. We found age‐related changes in monocyte metabolic fitness, including reduced mitochondrial function and increased glycose consumption without the capacity to upregulate it during increased metabolic needs, and signs of increased oxidative stress and DNA damage. In conclusion, our results complement existing findings and elucidate the metabolic alterations that occur in monocytes during aging.