Metabolipidomic profiling reveals an age‐related deficiency of skeletal muscle pro‐resolving mediators that contributes to maladaptive tissue remodeling

Specialized pro‐resolving mediators actively limit inflammation and support tissue regeneration, but their role in age‐related muscle dysfunction has not been explored. We profiled the mediator lipidome of aging muscle via liquid chromatography‐tandem mass spectrometry and tested whether treatment with the pro‐resolving mediator resolvin D1 (RvD1) could rejuvenate the regenerative ability of aged muscle. Aged mice displayed chronic muscle inflammation and this was associated with a basal deficiency of pro‐resolving mediators 8‐oxo‐RvD1, resolvin E3, and maresin 1, as well as many anti‐inflammatory cytochrome P450‐derived lipid epoxides. Following muscle injury, young and aged mice produced similar amounts of most pro‐inflammatory eicosanoid metabolites of cyclooxygenase (e.g., prostaglandin E₂) and 12‐lipoxygenase (e.g., 12‐hydroxy‐eicosatetraenoic acid), but aged mice produced fewer markers of pro‐resolving mediators including the lipoxins (15‐hydroxy‐eicosatetraenoic acid), D‐resolvins/protectins (17‐hydroxy‐docosahexaenoic acid), E‐resolvins (18‐hydroxy‐eicosapentaenoic acid), and maresins (14‐hydroxy‐docosahexaenoic acid). Similar absences of downstream pro‐resolving mediators including lipoxin A₄, resolvin D6, protectin D1/DX, and maresin 1 in aged muscle were associated with greater inflammation, impaired myofiber regeneration, and delayed recovery of strength. Daily intraperitoneal injection of RvD1 had minimal impact on intramuscular leukocyte infiltration and myofiber regeneration but suppressed inflammatory cytokine expression, limited fibrosis, and improved recovery of muscle function. We conclude that aging results in deficient local biosynthesis of specialized pro‐resolving mediators in muscle and that immunoresolvents may be attractive novel therapeutics for the treatment of muscular injuries and associated pain in the elderly, due to positive effects on recovery of muscle function without the negative side effects on tissue regeneration of non‐steroidal anti‐inflammatory drugs.     

Chronic exposure to biomass ambient particulate matter triggers alveolar macrophage polarization and activation in the rat lung

The role of alveolar macrophages (AMs) in chronic obstructive pulmonary disease is unclear. We characterized the function of AMs in rats chronically exposed to biomass fuel smoke (BMF) and studied the signal pathways that regulate AMs polarization. One hundred and eighty male Sprague‐Dawley rats were divided into BMF group and clean air control (CON) group. After BMF smoke exposure for 4 days, 1 month and 6 months, the cytokine secretion and function of AMs were determined by flow cytometry, quantitative polymerase chain reaction, Western blotting and immunofluorescence. Bone marrow‐derived macrophages were cultured and exposed to particulate matter (PM) from the smoke. Exposure initially promoted pro‐inflammatory factors, but pro‐inflammatory macrophages shared features of anti‐inflammatory macrophages. Consistent with IL‐4 upregulated in bronchoalveolar lavage fluid, p‐Stat6 and peroxisome proliferator‐activated receptor γ (PPARγ) in AMs elevated at 4 days of exposure. After 6 months of exposure, CD206, TGF‐β1 and p‐Smad3 were significantly higher than the control groups. PPARγ reversed the M1 phenotype induced by PM in vitro and drove the macrophages into the M2 phenotype. Altogether, the study demonstrates the dynamic phenotype and functional changes in AMs during exposure to BMF smoke.     

MAIR‐II deficiency ameliorates cardiac remodelling post‐myocardial infarction by suppressing TLR9‐mediated macrophage activation

Macrophages are fundamental components of inflammation in post‐myocardial infarction (MI) and contribute to adverse cardiac remodelling and heart failure. However, the regulatory mechanisms in macrophage activation have not been fully elucidated. Previous studies showed that myeloid‐associated immunoglobulin–like receptor II (MAIR‐II) is involved in inflammatory responses in macrophages. However, its role in MI is unknown. Thus, this study aimed to determine a novel role and mechanism of MAIR‐II in MI. We first identified that MAIR‐II–positive myeloid cells were abundant from post‐MI days 3 to 5 in infarcted hearts of C57BL/6J (WT) mice induced by permanent left coronary artery ligation. Compared to WT, MAIR‐II–deficient (Cd300c2 ^−/−) mice had longer survival, ameliorated cardiac remodelling, improved cardiac function and smaller infarct sizes. Moreover, we detected lower pro‐inflammatory cytokine and fibrotic gene expressions in Cd300c2 ^−/−‐infarcted hearts. These mice also had less infiltrating pro‐inflammatory macrophages following MI. To elucidate a novel molecular mechanism of MAIR‐II, we considered macrophage activation by Toll‐like receptor (TLR) 9–mediated inflammation. In vitro, we observed that Cd300c2 ^−/− bone marrow–derived macrophages stimulated by a TLR9 agonist expressed less pro‐inflammatory cytokines compared to WT. In conclusion, MAIR‐II may enhance inflammation via TLR9‐mediated macrophage activation in MI, leading to adverse cardiac remodelling and poor prognosis.     

Metabolic reprogramming of glycolysis and glutamine metabolism are key events in myofibroblast transition in systemic sclerosis pathogenesis

Systemic Sclerosis (SSc) is a rare fibrotic autoimmune disorder for which no curative treatments currently exist. Metabolic remodelling has recently been implicated in other autoimmune diseases; however, its potential role in SSc has received little attention. Here, we aimed to determine whether changes to glycolysis and glutaminolysis are important features of skin fibrosis. TGF‐β1, the quintessential pro‐fibrotic stimulus, was used to activate fibrotic pathways in NHDFs in vitro. Dermal fibroblasts derived from lesions of SSc patients were also used for in vitro experiments. Parameters of glycolytic function were assessed using by measuring extracellular acidification in response to glycolytic activators/inhibitors, whilst markers of fibrosis were measured by Western blotting following the use of the glycolysis inhibitors 2‐dg and 3PO and the glutaminolysis inhibitor G968. Succinate was also measured after TGF‐β1 stimulation. Itaconate was added to SSc fibroblasts and collagen examined. TGF‐β1 up‐regulates glycolysis in dermal fibroblasts, and inhibition of glycolysis attenuates its pro‐fibrotic effects. Furthermore, inhibition of glutamine metabolism also reverses TGF‐β1‐induced fibrosis, whilst glutaminase expression is up‐regulated in dermal fibroblasts derived from SSc patient skin lesions, suggesting that enhanced glutamine metabolism is another aspect of the pro‐fibrotic metabolic phenotype in skin fibrosis. TGF‐β1 was also able to enhance succinate production, with increased succinate shown to be associated with increased collagen expression. Incubation of SSc cells with itaconate, an important metabolite, reduced collagen expression. TGF‐β1 activation of glycolysis is a key feature of the fibrotic phenotype induced by TGF‐B1 in skin cells, whilst increased glutaminolysis is also evident in SSc fibroblasts.     

Necroptosis contributes to chronic inflammation and fibrosis in aging liver

Inflammaging, characterized by an increase in low‐grade chronic inflammation with age, is a hallmark of aging and is strongly associated with various age‐related diseases, including chronic liver disease (CLD) and hepatocellular carcinoma (HCC). Because necroptosis is a cell death pathway that induces inflammation through the release of DAMPs, we tested the hypothesis that age‐associated increase in necroptosis contributes to chronic inflammation in aging liver. Phosphorylation of MLKL and MLKL oligomers, markers of necroptosis, as well as phosphorylation of RIPK3 and RIPK1 were significantly upregulated in the livers of old mice relative to young mice and this increase occurred in the later half of life (i.e., after 18 months of age). Markers of M1 macrophages, expression of pro‐inflammatory cytokines (TNFα, IL6 and IL1β), and markers of fibrosis were all significantly upregulated in the liver with age and the change in necroptosis paralleled the changes in inflammation and fibrosis. Hepatocytes and liver macrophages isolated from old mice showed elevated levels of necroptosis markers as well as increased expression of pro‐inflammatory cytokines relative to young mice. Short‐term treatment with the necroptosis inhibitor, necrostatin‐1s (Nec‐1s), reduced necroptosis, markers of M1 macrophages, fibrosis, and cell senescence as well as reducing the expression of pro‐inflammatory cytokines in the livers of old mice. Thus, our data show for the first time that liver aging is associated with increased necroptosis and necroptosis contributes to chronic inflammation in the liver, which in turn appears to contribute to liver fibrosis and possibly CLD.     

Alternatively activated macrophages at the recipient site improve fat graft retention by promoting angiogenesis and adipogenesis

The inflammatory response mediated by macrophages plays a role in tissue repair. Macrophages preferentially infiltrate the donor site and subsequently, infiltrate the recipient site after fat grafting. This study aimed to trace host‐derived macrophages and to evaluate the effects of macrophage infiltration at the recipient site during the early stage on long‐term fat graft retention. In our novel mouse model, all mice underwent simulated liposuction and were divided into 2 groups. The fat procurement plus grafting (Pro‐Grafting) group was engrafted with prepared fat (0.3 ml). The pro‐Grafting+M2 group was engrafted with prepared fat (0.3 ml) mixed with 1.0 × 10⁶ GFP+M0 macrophages, and then, 2 ng IL‐4 was injected into the grafts on Day 3. In addition, 1.0 × 10⁶ GFP+M0 macrophages were injected into the tail vein for tracing in the Pro‐Grafting group. As a result, GFP+macrophages first infiltrated the donor site and subsequently infiltrated the recipient site in the Pro‐Grafting group. The long‐term retention rate was higher in the Pro‐Grafting+M2 group (52% ± 6.5%) than in the Pro‐Grafting group (40% ± 3.5%). CD34+ and CD31+ areas were observed earlier, and expression of the adipogenic proteins PPAR‐γ, C/EBP and AP2 was higher in the Pro‐Grafting+M2 group than in the Pro‐Grafting group. The host macrophages preferentially infiltrate the donor site, and then, infiltrate the recipient site after fat grafting. At the early stage, an increase in macrophages at the recipient site may promote vascularization and regeneration, and thereby improve the fat graft retention rate.     

Fractalkine aggravates LPS‐induced macrophage activation and acute kidney injury via Wnt/β‐catenin signalling pathway

Fractalkine (CX3CL1, FKN), a CX3C gene sequence inflammatory chemokine, has been found to have pro‐inflammatory and pro‐adhesion effects. Macrophages are immune cells with a critical role in regulating the inflammatory response. The imbalance of M1/M2 macrophage polarization can lead to aggravated inflammation. This study attempts to investigate the mechanisms through which FKN regulates macrophage activation and the acute kidney injury (AKI) involved in inflammatory response induced by lipopolysaccharide (LPS) by using FKN knockout (FKN‐KO) mice and cultured macrophages. It was found that FKN and Wnt/β‐catenin signalling have a positive interaction in macrophages. FKN overexpression inhibited LPS‐induced macrophage apoptosis. However, it enhanced their cell viability and transformed them into the M2 type. The effects of FKN overexpression were accelerated by activation of Wnt/β‐catenin signalling. In the in vivo experiments, FKN deficiency suppressed macrophage activation and reduced AKI induced by LPS. Inhibition of Wnt/β‐catenin signalling and FKN deficiency further mitigated the pathologic process of AKI. In summary, we provide a novel mechanism underlying activation of macrophages in LPS‐induced AKI. Although LPS‐induced murine AKI was unable to completely recapitulate human AKI, the positive interactions between FKN and Wnt/β‐catenin signalling pathway may be a therapeutic target in the treatment of kidney injury.     

Transplantation of tauroursodeoxycholic acid–inducing M2‐phenotype macrophages promotes an anti‐neuroinflammatory effect and functional recovery after spinal cord injury in rats

ObjectivesIn this study, we study the transplantation of tauroursodeoxycholic acid (TUDCA)‐induced M2‐phenotype (M2) macrophages and their ability to promote anti‐neuroinflammatory effects and functional recovery in a spinal cord injury (SCI) model.MethodsTo this end, compared to the granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), we evaluated whether TUDCA effectively differentiates bone marrow–derived macrophages (BMDMs) into M2 macrophages.ResultsThe M2 expression markers in the TUDCA‐treated BMDM group were increased more than those in the GM‐CSF‐treated BMDM group. After the SCI and transplantation steps, pro‐inflammatory cytokine levels and the mitogen‐activated protein kinase (MAPK) pathway were significantly decreased in the TUDCA‐induced M2 group more than they were in the GM‐CSF‐induced M1 group and in the TUDCA group. Moreover, the TUDCA‐induced M2 group showed significantly enhanced tissue volumes and improved motor functions compared to the GM‐CSF‐induced M1 group and the TUDCA group. In addition, biotinylated dextran amine (BDA)–labelled corticospinal tract (CST) axons and neuronal nuclei marker (NeuN) levels were increased in the TUDCA‐induced M2 group more than those in the GM‐CSF‐induced M1 group and the TUDCA group.ConclusionsThis study demonstrates that the transplantation of TUDCA‐induced M2 macrophages promotes an anti‐neuroinflammatory effect and motor function recovery in SCI. Therefore, we suggest that the transplantation of TUDCA‐induced M2 macrophages represents a possible alternative cell therapy for SCI.     

A novel danshensu derivative ameliorates experimental colitis by modulating NADPH oxidase 4‐dependent NLRP3 inflammasome activation

We have previously reported a novel compound [4‐(2‐acetoxy‐3‐((R)‐3‐(benzylthio)‐1‐methoxy‐1‐oxopropan‐2‐ylamino)‐3‐oxopropyl)‐1,2‐phenylene diacetate (DSC)], derived from danshensu, exhibits cytoprotective activities in vitro. Here, we investigated the effects and underlying mechanisms of DSC on dextran sodium sulphate (DSS)‐induced experimental colitis. We found that DSC treatment afforded significant protection against the development of colitis, evidencing by suppressed inflammatory responses and enhanced barrier integrity. Intriguingly, DSC specifically down‐regulated DSS‐induced colonic NADPH oxidase 4 (Nox4) expression, accompanied by a balanced redox status, suppressed nuclear factor‐κB (NF‐κB) and NLRP3 inflammasome activation and up‐regulated nuclear factor (erythroid‐derived 2)‐like 2 and haeme oxygenase‐1 expression. In vitro study also demonstrated DSC also markedly decreased Nox4 expression and activity associated with inhibiting reactive oxygen species generation, NF‐κB activation and NLRP3 inflammasome activation in bone marrow‐derived macrophages. Either lentiviral Nox4 shRNA‐mediated Nox4 knockdown or Nox4‐specific small‐interfering RNA mimicked effects of DSC by suppressing NLPR3 inflammasome activation to alleviate experimental colitis or inflammatory macrophage response. Collectively, our results provide the first evidence that DSC ameliorates experimental colitis partly through modulating Nox4‐mediated NLRP3 inflammasome activation.     

Delineating the relationship between immune system aging and myogenesis in muscle repair

Recruited immune cells play a critical role in muscle repair, in part by interacting with local stem cell populations to regulate muscle regeneration. How aging affects their communication during myogenesis is unclear. Here, we investigate how aging impacts the cellular function of these two cell types after muscle injury during normal aging or after immune rejuvenation using a young to old (Y‐O) or old to old (O‐O) bone marrow (BM) transplant model. We found that skeletal muscle from old mice (20 months) exhibited elevated basal inflammation and possessed fewer satellite cells compared with young mice (3 months). After cardiotoxin muscle injury (CTX), old mice exhibited a blunted inflammatory response compared with young mice and enhanced M2 macrophage recruitment and IL‐10 expression. Temporal immune and cytokine responses of old mice were partially restored to a young phenotype following reconstitution with young cells (Y‐O chimeras). Improved immune responses in Y‐O chimeras were associated with greater satellite cell proliferation compared with O‐O chimeras. To identify how immune cell aging affects myoblast function, conditioned media (CM) from activated young or old macrophages was applied to cultured C2C12 myoblasts. CM from young macrophages inhibited myogenesis while CM from old macrophages reduced proliferation. These functional differences coincided with age‐related differences in macrophage cytokine expression. Together, this study examines the infiltration and proliferation of immune cells and satellite cells after injury in the context of aging and, using BM chimeras, demonstrates that young immune cells retain cell autonomy in an old host to increase satellite cell proliferation.     

Dysfunction of metabolic activity of bone marrow mesenchymal stem cells in aged mice

ObjectivesEvidences have suggested that the metabolic function is the key regulator to the fate of MSCs, but its function in senescence of MSC and the underlying mechanism is unclear. Therefore, the purpose of this study was to investigate the metabolic activity of MSCs and its possible mechanism during aging.Materials and MethodsWe used the Seahorse XF24 Analyzer to understand OCR and ECAR in BMSCs and used RT‐PCR to analyze the gene expression of mitochondrial biogenesis and key enzymes in glycolysis. We analyzed BMSC mitochondrial activity by MitoTracker Deep Red and JC‐1 staining, and detected NAD+/NADH ratio and ATP levels in BMSCs. Microarray and proteomic analyses were performed to detect differentially expressed genes and proteins in BMSCs. The impact of aging on BMSCs through mitochondrial electron transport chain (ETC) was evaluated by Rotenone and Coenzyme Q10.ResultsOur results demonstrated that the oxidative phosphorylation and glycolytic activity of BMSCs in aged mice were significantly decreased when compared with young mice. BMSCs in aged mice had lower mitochondrial membrane potential, NAD+/NADH ratio, and ATP production than young mice. FABP4 may play a key role in BMSC senescence caused by fatty acid metabolism disorders.ConclusionsTaken together, our results indicated the dysfunction of the metabolic activity of BMSCs in aged mice, which would play the important role in the impaired biological properties. Therefore, the regulation of metabolic activity may be a potential therapeutic target for enhancing the regenerative functions of BMSCs.     

Exosomes as a messager to regulate the crosstalk between macrophages and cardiomyocytes under hypoxia conditions

Recent studies have confirmed that cardiomyocyte‐derived exosomes have many pivotal biological functions, like influencing the progress of coronary artery disease via modulating macrophage phenotypes. However, the mechanisms underlying the crosstalk between cardiomyocytes and macrophages have not been fully characterized. Hence, this study aimed to observe the interaction between cardiomyocytes under hypoxia and macrophages through exosome communication and further evaluate the ability of exosomes derived from cardiomyocytes cultured under hypoxic conditions (Hypo‐Exo) to polarize macrophages, and the effect of alternatively activated macrophages (M2) on hypoxic cardiomyocytes. Our results revealed that hypoxia facilitated the production of transforming growth factor‐beta (TGF‐β) in H9c2 cell‐derived exosomes. Moreover, exosomes derived from cardiomyocytes cultured under normal conditions (Nor‐Exo) and Hypo‐Exo could induce RAW264.7 cells into classically activated macrophages (M1) and M2 macrophages respectively. Likewise, macrophage activation was induced by circulating exosomes isolated from normal human controls (hNor‐Exo) or patients with acute myocardial infarction (hAMI‐Exo). Thus, our findings support that the profiles of hAMI‐Exo have been changed, which could regulate the polarization of macrophages and subsequently the polarized M2 macrophages reduced the apoptosis of cardiomyocytes in return. Based on our findings, we speculate that exosomes have emerged as important inflammatory response modulators regulating cardiac oxidative stress injury.     

Glycogen accumulation in adipocyte precursors from elderly and obese subjects triggers inflammation via SIRT1/6 signaling

Dysfunctional adipocyte precursors have emerged as key determinants for obesity‐ and aging‐related inflammation, but the mechanistic basis remains poorly understood. Here, we explored the dysfunctional adipose tissue of elderly and obese individuals focusing on the metabolic and inflammatory state of human adipose‐derived mesenchymal stromal cells (hASCs), and on sirtuins, which link metabolism and inflammation. Both obesity and aging impaired the differentiation potential of hASCs but had a different impact on their proliferative capacity. hASCs from elderly individuals (≥65 years) showed an upregulation of glycolysis‐related genes, which was accompanied by increased lactate secretion and glycogen storage, a phenotype that was exaggerated by obesity. Multiplex protein profiling revealed that the metabolic switch to glycogenesis was associated with a pro‐inflammatory secretome concomitant with a decrease in the protein expression of SIRT1 and SIRT6. siRNA‐mediated knockdown of SIRT1 and SIRT6 in hASCs from lean adults increased the expression of pro‐inflammatory and glycolysis‐related markers, and enforced glycogen deposition by overexpression of protein targeting to glycogen (PTG) led to a downregulation of SIRT1/6 protein levels, mimicking the inflammatory state of hASCs from elderly subjects. Overall, our data point to a glycogen‐SIRT1/6 signaling axis as a driver of age‐related inflammation in adipocyte precursors.     

Olive phenols preserve lamin B1 expression reducing cGAS/STING/NFκB‐mediated SASP in ionizing radiation‐induced senescence

Senescence occurs upon critical telomere shortening, or following DNA damage, oncogenic activation, hypoxia and oxidative stress, overall referred to stress‐induced premature senescence (SIPS). In response to DNA damage, senescent cells release cytoplasmic chromatin fragments (CCFs), and express an altered secretome, the senescence‐associated secretory phenotype (SASP), which contributes to generate a pro‐inflammatory and pro‐tumoral extracellular milieu. Polyphenols have gained significant attention owing to their anti‐inflammatory and anti‐tumour activities. Here, we studied the effect of oleuropein aglycone (OLE) and hydroxytyrosol (HT) on DNA damage, CCF appearance and SASP in a model of irradiation‐induced senescence. Neonatal human dermal fibroblasts (NHDFs) were γ‐irradiated and incubated with OLE, 5 µM and HT, 1 µM. Cell growth and senescence‐associated (SA)‐β‐Gal‐staining were used as senescence markers. DNA damage was evaluated by Comet assay, lamin B1 expression, release of CCFs, cyclic GMP‐AMP Synthase (cGAS) activation. IL‐6, IL‐8, MCP‐1 and RANTES were measured by ELISA assay. Our results showed that OLE and HT exerted a protective effect on 8 Gy irradiation‐induced senescence, preserving lamin B1 expression and reducing cGAS/STING/NFκB‐mediated SASP. The ability of OLE and HT to mitigate DNA damage, senescence status and the related SASP in normal cells can be exploited to improve the efficacy and safety of cancer radiotherapy.     

Influenza A viruses limit NLRP3‐NEK7‐complex formation and pyroptosis in human macrophages

Pyroptosis is a fulminant form of macrophage cell death, contributing to release of pro‐inflammatory cytokines. In humans, it depends on caspase 1/4‐activation of gasdermin D and is characterized by the release of cytoplasmic content. Pathogens apply strategies to avoid or antagonize this host response. We demonstrate here that a small accessory protein (PB1‐F2) of contemporary H5N1 and H3N2 influenza A viruses (IAV) curtails fulminant cell death of infected human macrophages. Infection of macrophages with a PB1‐F2‐deficient mutant of a contemporary IAV resulted in higher levels of caspase‐1 activation, cleavage of gasdermin D, and release of LDH and IL‐1β. Mechanistically, PB1‐F2 limits transition of NLRP3 from its auto‐repressed and closed confirmation into its active state. Consequently, interaction of a recently identified licensing kinase NEK7 with NLRP3 is diminished, which is required to initiate inflammasome assembly.     

Deletion of SA β‐Gal+ cells using senolytics improves muscle regeneration in old mice

Systemic deletion of senescent cells leads to robust improvements in cognitive, cardiovascular, and whole‐body metabolism, but their role in tissue reparative processes is incompletely understood. We hypothesized that senolytic drugs would enhance regeneration in aged skeletal muscle. Young (3 months) and old (20 months) male C57Bl/6J mice were administered the senolytics dasatinib (5 mg/kg) and quercetin (50 mg/kg) or vehicle bi‐weekly for 4 months. Tibialis anterior (TA) was then injected with 1.2% BaCl₂ or PBS 7‐ or 28 days prior to euthanization. Senescence‐associated β‐Galactosidase positive (SA β‐Gal+) cell abundance was low in muscle from both young and old mice and increased similarly 7 days following injury in both age groups, with no effect of D+Q. Most SA β‐Gal+ cells were also CD11b+ in young and old mice 7‐ and 14 days following injury, suggesting they are infiltrating immune cells. By 14 days, SA β‐Gal+/CD11b+ cells from old mice expressed senescence genes, whereas those from young mice expressed higher levels of genes characteristic of anti‐inflammatory macrophages. SA β‐Gal+ cells remained elevated in old compared to young mice 28 days following injury, which were reduced by D+Q only in the old mice. In D+Q‐treated old mice, muscle regenerated following injury to a greater extent compared to vehicle‐treated old mice, having larger fiber cross‐sectional area after 28 days. Conversely, D+Q blunted regeneration in young mice. In vitro experiments suggested D+Q directly improve myogenic progenitor cell proliferation. Enhanced physical function and improved muscle regeneration demonstrate that senolytics have beneficial effects only in old mice.     

Adipose tissue senescence is mediated by increased ATP content after a short‐term high‐fat diet exposure

In the context of obesity, senescent cells accumulate in white adipose tissue (WAT). The cellular underpinnings of WAT senescence leading to insulin resistance are not fully elucidated. The objective of the current study was to evaluate the presence of WAT senescence early after initiation of high‐fat diet (HFD, 1–10 weeks) in 5‐month‐old male C57BL/6J mice and the potential role of energy metabolism. We first showed that WAT senescence occurred 2 weeks after HFD as evidenced in whole WAT by increased senescence‐associated ß‐galactosidase activity and cyclin‐dependent kinase inhibitor 1A and 2A expression. WAT senescence affected various WAT cell populations, including preadipocytes, adipose tissue progenitors, and immune cells, together with adipocytes. WAT senescence was associated with higher glycolytic and mitochondrial activity leading to enhanced ATP content in HFD‐derived preadipocytes, as compared with chow diet‐derived preadipocytes. One‐month daily exercise, introduced 5 weeks after HFD, was an effective senostatic strategy, since it reversed WAT cellular senescence, while reducing glycolysis and production of ATP. Interestingly, the beneficial effect of exercise was independent of body weight and fat mass loss. We demonstrated that WAT cellular senescence is one of the earliest events occurring after HFD initiation and is intimately linked to the metabolic state of the cells. Our data uncover a critical role for HFD‐induced elevated ATP as a local danger signal inducing WAT senescence. Exercise exerts beneficial effects on adipose tissue bioenergetics in obesity, reversing cellular senescence, and metabolic abnormalities.     

Anti‐inflammatory properties of lemon‐derived extracellular vesicles are achieved through the inhibition of ERK/NF‐κB signalling pathways

Chronic inflammation is associated with the occurrence of several diseases. However, the side effects of anti‐inflammatory drugs prompt the identification of new therapeutic strategies. Plant‐derived extracellular vesicles (PDEVs) are gaining increasing interest in the scientific community for their biological properties. We isolated PDEVs from the juice of Citrus limon L. (LEVs) and characterized their flavonoid, limonoid and lipid contents through reversed‐phase high‐performance liquid chromatography coupled to electrospray ionization quadrupole time‐of‐flight mass spectrometry (RP‐HPLC–ESI‐Q‐TOF‐MS). To investigate whether LEVs have a protective role on the inflammatory process, murine and primary human macrophages were pre‐treated with LEVs for 24 h and then were stimulated with lipopolysaccharide (LPS). We found that pre‐treatment with LEVs decreased gene and protein expression of pro‐inflammatory cytokines, such as IL‐6, IL1‐β and TNF‐α, and reduced the nuclear translocation and phosphorylation of NF‐κB in LPS‐stimulated murine macrophages. The inhibition of NF‐κB activation was associated with the reduction in ERK1‐2 phosphorylation. Furthermore, the ability of LEVs to decrease pro‐inflammatory cytokines and increase anti‐inflammatory molecules was confirmed ex vivo in human primary T lymphocytes. In conclusion, we demonstrated that LEVs exert anti‐inflammatory effects both in vitro and ex vivo by inhibiting the ERK1‐2/NF‐κB signalling pathway.     

Aging‐related cell type‐specific pathophysiologic immune responses that exacerbate disease severity in aged COVID‐19 patients

Coronavirus disease 2019 (COVID‐19) is especially severe in aged patients, defined as 65 years or older, for reasons that are currently unknown. To investigate the underlying basis for this vulnerability, we performed multimodal data analyses on immunity, inflammation, and COVID‐19 incidence and severity as a function of age. Our analysis leveraged age‐specific COVID‐19 mortality and laboratory testing from a large COVID‐19 registry, along with epidemiological data of ~3.4 million individuals, large‐scale deep immune cell profiling data, and single‐cell RNA‐sequencing data from aged COVID‐19 patients across diverse populations. We found that decreased lymphocyte count and elevated inflammatory markers (C‐reactive protein, D‐dimer, and neutrophil–lymphocyte ratio) are significantly associated with age‐specific COVID‐19 severities. We identified the reduced abundance of naïve CD8 T cells with decreased expression of antiviral defense genes (i.e., IFITM3 and TRIM22) in aged severe COVID‐19 patients. Older individuals with severe COVID‐19 displayed type I and II interferon deficiencies, which is correlated with SARS‐CoV‐2 viral load. Elevated expression of SARS‐CoV‐2 entry factors and reduced expression of antiviral defense genes (LY6E and IFNAR1) in the secretory cells are associated with critical COVID‐19 in aged individuals. Mechanistically, we identified strong TGF‐beta‐mediated immune–epithelial cell interactions (i.e., secretory‐non‐resident macrophages) in aged individuals with critical COVID‐19. Taken together, our findings point to immuno‐inflammatory factors that could be targeted therapeutically to reduce morbidity and mortality in aged COVID‐19 patients.