Cellular senescence is a double-edged sword in regulating aged immune responses to influenza

Clearance of senescent cells has demonstrated therapeutic potential in the context of chronic age-related diseases. Little is known, however, how clearing senescent cells affects the ability to respond to an acute infection and form quality immunological memory. We aimed to probe the effects of clearing senescent cells in aged mice on the immune response to influenza (flu) infection. We utilized a p16 trimodality reporter mouse model (p16-3MR) to allow for identification and selective clearance of p16-expressing cells upon administration of ganciclovir (GCV). While p16-expressing cells may exacerbate dysfunctional responses to a primary infection, our data suggest they may play a role in fostering memory cell generation. We demonstrate that although clearance of p16-expressing cells enhanced viral clearance, this also severely limited antibody production in the lungs of flu-infected aged mice. 30 days later, there were fewer flu-specific CD8 memory T cells and lower levels of flu-specific antibodies in the lungs of GCV-treated mice. Furthermore, GCV-treated mice were unable to mount an optimal memory response and demonstrated increased viral load following heterosubtypic challenge. These results suggest that targeting senescent cells may potentiate primary responses while limiting the ability to form durable and protective immune memory with age.

Unraveling the association between major depressive disorder and senescent biomarkers in immune cells of older adults: a single-cell phenotypic analysis

Background: Little is known about the prevalence of cellular senescence among immune cells (i.e., immune cells expressing senescence markers, iSCs) nor is there a gold-standard to efficiently measure iSCs. Major depressive disorder (MDD) in older adults has been associated with many hallmarks of senescence in whole blood, leukocytes, and plasma, supporting a strong connection between iSCs and MDD. Here, we investigated the prevalence and phenotype of iSCs in older adults with MDD. Using a single-cell phenotypic approach, circulating immune cells were examined for iSC biomarkers and their relationship to depression and inflammation. Results: PBMCs from older adults with MDD (aged 69.75 ± 5.23 years) and healthy controls (aged 71.25 ± 8.8 years) were examined for immune subset distribution and senescence biomarkers (i.e., lack of proliferation, senescence-associated heterochromatin foci (SAHF), and DNA damage). Dual-expression of SAHF and DNA damage was categorized by low, intermediate, and high expression. A significant increase in the number of high expressing total PBMCs (p = 0.01), monocytes (p = 0.008), a trending increase in the number of high expressing CD4 T cells (p = 0.06) was observed overall in those with MDD. There was also a significantly lower proportion of intermediate expressing cells in monocytes and CD4 T cells in MDD (p = 0.01 and p = 0.05, respectively). Correlation analysis revealed associations between iSCs and mRNA expression of factors related to SASP and immune cell function. Conclusion: MDD is associated with increased senescent cell biomarkers in immune cell populations delineated by distinct levels of SAHF and DNA damage. Inflammatory markers might serve as potent indicators of iSC burden in MDD.

Respiratory viral infection promotes the awakening and outgrowth of dormant metastatic breast cancer cells in lungs

Breast cancer is the second most common cancer globally. Most deaths from breast cancer are due to metastatic disease which often follows long periods of clinical dormancy1. Understanding the mechanisms that disrupt the quiescence of dormant disseminated cancer cells (DCC) is crucial for addressing metastatic progression. Infection with respiratory viruses (e.g. influenza or SARS-CoV-2) is common and triggers an inflammatory response locally and systemically2,3. Here we show that influenza virus infection leads to loss of the pro-dormancy mesenchymal phenotype in breast DCC in the lung, causing DCC proliferation within days of infection, and a greater than 100-fold expansion of carcinoma cells into metastatic lesions within two weeks. Such DCC phenotypic change and expansion is interleukin-6 (IL-6)-dependent. We further show that CD4 T cells are required for the maintenance of pulmonary metastatic burden post-influenza virus infection, in part through attenuation of CD8 cell responses in the lungs. Single-cell RNA-seq analyses reveal DCC-dependent impairment of T-cell activation in the lungs of infected mice. SARS-CoV-2 infected mice also showed increased breast DCC expansion in lungs post-infection. Expanding our findings to human observational data, we observed that cancer survivors contracting a SARS-CoV-2 infection have substantially increased risks of lung metastatic progression and cancer-related death compared to cancer survivors who did not. These discoveries underscore the significant impact of respiratory viral infections on the resurgence of metastatic cancer, offering novel insights into the interconnection between infectious diseases and cancer metastasis.

Unleashing CAR T cells to delay metabolic aging

Amor and colleagues previously developed chimeric antigen receptor (CAR) T cells that can target and eliminate senescent cells. The utility of these senolytic CAR T cells is now expanded to show that they can combat age-related metabolic dysfunction, and that they can be used prophylactically and have effects that persist for months, thus opening the door to the development of long-term senolytic approaches.

Patient-derived organoids recapitulate glioma-intrinsic immune program and progenitor populations of glioblastoma

Glioblastoma multiforme (GBM) is a highly lethal human cancer thought to originate from a self-renewing and therapeutically-resistant population of glioblastoma stem cells (GSCs). The intrinsic mechanisms enacted by GSCs during 3D tumor formation, however, remain unclear, especially in the stages prior to angiogenic/immunological infiltration. In this study, we performed a deep characterization of the genetic, immune, and metabolic profiles of GBM organoids from several patient-derived GSCs (GBMO). Despite being devoid of immune cells, transcriptomic analysis across GBMO revealed a surprising immune-like molecular program, enriched in cytokine, antigen presentation and processing, T-cell receptor inhibitors, and interferon genes. We find two important cell populations thought to drive GBM progression, Special AT-rich sequence-binding protein 2 (SATB2+) and homeodomain-only protein homeobox (HOPX+) progenitors, contribute to this immune landscape in GBMO and GBM in vivo. These progenitors, but not other cell types in GBMO, are resistant to conventional GBM therapies, temozolomide and irradiation. Our work defines a novel intrinsic immune-like landscape in GBMO driven, in part, by SATB2+ and HOPX+ progenitors and deepens our understanding of the intrinsic mechanisms utilized by GSCs in early GBM formation.

Dysfunctional Bladder Morphology and Functional Impairments Are Identified in the Alzheimer's Disease APPNL-G-F/NL-G-F Murine Model

BACKGROUND

While symptoms related to lower urinary tract dysfunction (LUTD) are common in individuals with Alzheimer's disease (AD), pathophysiological links between AD and LUTD remain unclear.

OBJECTIVE

This study aimed to investigate whether AD neuropathology would cause autonomic dysfunction along the spinal cord-bladder axis, which could result in alterations in bladder muscle kinetics.

METHODS

We utilized APPNL-G-F/NL-G-F knock-in (APP KI) and APPwt/wt (wild-type) mice at two different ages, 4- and 10-month-old, to investigate how AD impacts bladder tissue function by immunohistochemistry, western blotting, and pharmacomyography.

RESULTS

We showed that the mucosal layer partially separated from the detrusor in 10-month-old APP KI mouse bladders. Although there was no detectable amyloid deposition in the APP KI bladder, we found amyloid plaques in APP KI lumbar spinal cord. Further immunoblot analysis revealed that tyrosine hydroxylase protein levels were significantly reduced in both 4- and 10-month-old bladder tissues, suggesting reduction of norepinephrine synthesis in APP KI mouse bladders. In contrast, the level of β2 adrenergic receptor was increased in 4-month-old but not 10-month-old APP KI bladders. In bladder strips, the adrenergic agonist isoproterenol induced increased relaxation in 4- but not 10-month-old APP KI bladders. With 10 Hz electrical field stimulation, 10-month-old APP KI bladder strips were more responsive than wild-type controls, with no differences observed in 4-month-old APP KI bladders.

CONCLUSIONS

APP KI mice exhibit LUTD, which is likely arising from amyloid pathology in the spinal cord, and results in maturational declines in presynaptic activity combined with compensatory postsynaptic upregulation.

Old drug, new tricks: the utility of metformin in infection and vaccination responses to influenza and SARS-CoV-2 in older adults

In the face of global pathogens such as influenza (flu) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), strategies beyond standard vaccines and virus-specific treatments are critically needed for older populations who are more susceptible to severe disease and death from these infections due to age-related immune dysregulation. Thus, complimentary therapeutics are needed to address the increased risk of complications and death in older adults. Metformin, an FDA approved diabetes drug, is an attractive therapeutic candidate to improve immune defenses and resilience in older adults facing viral challenge. Metformin is already a candidate anti-aging drug, but its benefits have potential to span beyond this and improve specific immune responses. Metformin can target multiple aging hallmarks as well as directly impact innate and adaptive immune cell subsets. Both retrospective and prospective studies have demonstrated metformin's efficacy in improving outcomes after SARS-CoV-2 or flu infections. Moreover, evidence from clinical trials has also suggested that metformin treatment can improve vaccination responses. In totality, these findings suggest that metformin can improve age-related declines in immunological resilience. Strategies to improve outcomes after infection or improve vaccine-induced protection are invaluable for older adults. Moreover, the ability to repurpose an already FDA approved drug has significant advantages in terms of necessary time and resources. Thus, metformin has great potential as a therapeutic to improve age-related immune dysregulation during flu and SARS-CoV-2 infections and should be further explored to confirm its ability to improve overall immunological resilience in older adults.

Metformin for Treatment of Acute COVID-19: Systematic Review of Clinical Trial Data Against SARS-CoV-2

BACKGROUND

Observational and preclinical data suggest metformin may prevent severe coronavirus disease 2019 (COVID-19) outcomes.

PURPOSE

We conducted a systematic review of randomized, placebo-controlled clinical trials of metformin treatment for COVID-19 to determine whether metformin affects clinical or laboratory outcomes in individuals infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and present a structured summary of preclinical data.

STUDY SELECTION

Two independent reviewers searched PubMed, Scopus, Cochrane COVID-19 Study Register, and ClinicalTrials.gov on 1 February 2023 with no date restrictions for trials where investigators randomized adults with COVID-19 to metformin versus control and assessed clinical and/or laboratory outcomes of interest. The Cochrane Risk of Bias 2 tool was used to assess bias.

DATA EXTRACTION

Two reviewers extracted data pertaining to prespecified outcomes of each interest from each included trial.

DATA SYNTHESIS

The synthesis plan was developed a priori and was guided by Synthesis Without Meta-analysis (SWiM) guidelines. Summary tables and narrative synthesis were used (PROSPERO, 2022, CRD42022349896). Three randomized trials met inclusion criteria. In two of the trials investigators found that metformin improved clinical outcomes (prevented need for oxygen and prevented need for acute health care use), and in the third trial a larger portion of adults with diabetes were enrolled but results did show a direction of benefit similar to that of the other trials in the per-protocol group. In the largest trial, subjects were enrolled during the delta and omicron waves and vaccinated individuals were included. The certainty of evidence that metformin prevents health care use due to COVID-19 was moderate per Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria. Many preclinical studies have shown metformin to be effective against SARS-CoV-2.

LIMITATIONS

Limitations include inclusion of only three trials and heterogeneity between trials.

CONCLUSIONS

Future trials will help define the role of metformin in COVID-19 treatment guidelines.

Senolytic treatment with dasatinib and quercetin does not improve overall influenza responses in aged mice

Age is the greatest risk factor for adverse outcomes following influenza (flu) infection. The increased burden of senescent cells with age has been identified as a root cause in many diseases of aging and targeting these cells with drugs termed senolytics has shown promise in alleviating many age-related declines across organ systems. However, there is little known whether targeting these cells will improve age-related deficits in the immune system. Here, we utilized a well characterized senolytic treatment with a combination of dasatinib and quercetin (D + Q) to clear aged (18-20 months) mice of senescent cells prior to a flu infection. We comprehensively profiled immune responses during the primary infection as well as development of immune memory and protection following pathogen reencounter. Senolytic treatment did not improve any aspects of the immune response that were assayed for including: weight loss, viral load, CD8 T-cell infiltration, antibody production, memory T cell development, or recall ability. These results indicate that D + Q may not be an appropriate senolytic to improve aged immune responses to flu infection.

A pilot metabolomic study of drug interaction with the immune response to seasonal influenza vaccination

Many human diseases, including metabolic diseases, are intertwined with the immune system. The understanding of how the human immune system interacts with pharmaceutical drugs is still limited, and epidemiological studies only start to emerge. As the metabolomics technology matures, both drug metabolites and biological responses can be measured in the same global profiling data. Therefore, a new opportunity presents itself to study the interactions between pharmaceutical drugs and immune system in the high-resolution mass spectrometry data. We report here a double-blinded pilot study of seasonal influenza vaccination, where half of the participants received daily metformin administration. Global metabolomics was measured in the plasma samples at six timepoints. Metformin signatures were successfully identified in the metabolomics data. Statistically significant metabolite features were found both for the vaccination effect and for the drug-vaccine interactions. This study demonstrates the concept of using metabolomics to investigate drug interaction with the immune response in human samples directly at molecular levels.

Targeting the hallmarks of aging to improve influenza vaccine responses in older adults

Age-related declines in immune response pose a challenge in combating diseases later in life. Influenza (flu) infection remains a significant burden on older populations and often results in catastrophic disability in those who survive infection. Despite having vaccines designed specifically for older adults, the burden of flu remains high and overall flu vaccine efficacy remains inadequate in this population. Recent geroscience research has highlighted the utility in targeting biological aging to improve multiple age-related declines. Indeed, the response to vaccination is highly coordinated, and diminished responses in older adults are likely not due to a singular deficit, but rather a multitude of age-related declines. In this review we highlight deficits in the aged vaccine responses and potential geroscience guided approaches to overcome these deficits. More specifically, we propose that alternative vaccine platforms and interventions that target the hallmarks of aging, including inflammation, cellular senescence, microbiome disturbances, and mitochondrial dysfunction, may improve vaccine responses and overall immunological resilience in older adults. Elucidating novel interventions and approaches that enhance immunological protection from vaccination is crucial to minimize the disproportionate effect of flu and other infectious diseases on older adults.

The effect of metformin on influenza vaccine responses in nondiabetic older adults: a pilot trial

BACKGROUND

Aging is associated with progressive declines in immune responses leading to increased risk of severe infection and diminished vaccination responses. Influenza (flu) is a leading killer of older adults despite availability of seasonal vaccines. Geroscience-guided interventions targeting biological aging could offer transformational approaches to reverse broad declines in immune responses with aging. Here, we evaluated effects of metformin, an FDA approved diabetes drug and candidate anti-aging drug, on flu vaccination responses and markers of immunological resilience in a pilot and feasibility double-blinded placebo-controlled study.

RESULTS

Healthy older adults (non-diabetic/non-prediabetic, age: 74.4 ± 1.7 years) were randomized to metformin (n = 8, 1500 mg extended release/daily) or placebo (n = 7) treatment for 20 weeks and were vaccinated with high-dose flu vaccine after 10 weeks of treatment. Peripheral blood mononuclear cells (PBMCs), serum, and plasma were collected prior to treatment, immediately prior to vaccination, and 1, 5, and 10 weeks post vaccination. Increased serum antibody titers were observed post vaccination with no significant differences between groups. Metformin treatment led to trending increases in circulating T follicular helper cells post-vaccination. Furthermore, 20 weeks of metformin treatment reduced expression of exhaustion marker CD57 in circulating CD4 T cells.

CONCLUSIONS

Pre-vaccination metformin treatment improved some components of flu vaccine responses and reduced some markers of T cell exhaustion without serious adverse events in nondiabetic older adults. Thus, our findings highlight the potential utility of metformin to improve flu vaccine responses and reduce age-related immune exhaustion in older adults, providing improved immunological resilience in nondiabetic older adults.

Cellular Senescence is a Double-Edged Sword in Regulating Aged Immune Responses to Influenza

Clearance of senescent cells has demonstrated therapeutic potential in the context of chronic age-related diseases. Little is known, however, how clearing senescent cells affects the ability to respond to an acute infection and form quality immunological memory. We aimed to probe the effects of clearing senescent cells in aged mice on the immune response to influenza (flu) infection. We utilized a p16 trimodality reporter mouse model (p16-3MR) to allow for identification and selective deletion of p16-expressing senescent cells upon administration of ganciclovir (GCV). While p16-expressing senescent cells may exacerbate dysfunctional responses to a primary infection, our data suggest they may play a role in fostering memory cell generation. We demonstrate that although deletion of p16-expressing cells enhanced viral clearance, this also severely limited antibody production in the lungs of flu-infected aged mice. 30 days later, there were fewer flu-specific CD8 memory T cells and lower levels of flu-specific antibodies in the lungs of GCV treated mice. GCV treated mice were unable to mount an optimal memory response and demonstrated increased viral load following a heterosubtypic challenge. These results suggest that targeting senescent cells may potentiate primary responses while limiting the ability to form durable and protective immune memory with age.

Loss of resilience contributes to detrusor underactivity in advanced age

Volume hyposensitivity resulting from impaired sympathetic detrusor relaxation during bladder filling contributes to detrusor underactivity (DU) associated with aging. Detrusor tension regulation provides an adaptive sensory input of bladder volume to the brainstem and is challenged by physiological stressors superimposed upon biological aging. We recently showed that HCN channels have a stabilizing role in detrusor sympathetic relaxation. While mature mice maintain homeostasis in the face of stressors, old mice are not always capable. In old mice, there is a dichotomous phenotype, in which resilient mice adapt and maintain homeostasis, while non-resilient mice fail to maintain physiologic homeostasis. In this DU model, we used cystometry as a stressor to categorize mice as old-responders (old-R, develop a filling/voiding cycle) or old-non-responders (old-NR, fail to develop a filling/voiding cycle; fluctuating high pressures and continuous leaking), while also assessing functional and molecular differences. Lamotrigine (HCN activator)-induced bladder relaxation is diminished in old-NR mice following HCN-blockade. Relaxation responses to NS 1619 were reduced in old-NR mice, with the effect lost following HCN-blockade. However, RNA-sequencing revealed no differences in HCN gene expression and electrophysiology studies showed similar percentage of detrusor myocytes expressing HCN (I_h) current between old-R and old-NR mice. Our murine model of DU further defines a role for HCN, with failure of adaptive recalibration of HCN participation and intensity of HCN-mediated stabilization, while genomic studies show upregulated myofibroblast and fibrosis pathways and downregulated neurotransmitter-degradation pathways in old-NR mice. Thus, the DU phenotype is multifactorial and represents the accumulation of age-associated loss in homeostatic mechanisms.

Altered T cell infiltration and enrichment of leukocyte regulating pathways within aged skeletal muscle are associated impaired muscle function following influenza infection

Older adults have diminished immune responses that increase susceptibility to infectious diseases, such as influenza (flu). In older adults, flu infection can lead to hospitalization, catastrophic disability, and mortality. We previously demonstrated severe and prolonged muscle degradation and atrophy in aged mice during flu infection. Here, we utilized an unbiased transcriptomic analysis to elucidate mechanisms of flu-induced muscular declines in a mouse model. Our results showed age-related gene expression differences including downregulation of genes associated with muscle regeneration and organization and upregulation of genes associated with pro-inflammatory cytokines and migratory immune pathways in aged mice when compared to young. Pathway analysis revealed significant enrichment of leukocyte migration and T cell activation pathways in the aged muscle during infection. Intramuscular CD4 T cells increased in both young and aged mice during infection, while intramuscular CD8 T cells increased exclusively in aged muscle. CD4 T cells in young muscle were regulatory T cells (Treg), while those in aged were T follicular helper (Tfh) and Th2 cells. Correspondingly, IL-33, an important cytokine for Treg accumulation within tissue, increased only in young flu-infected muscle. Conversely, CXCL10 (IP-10) increased only in aged muscle suggesting a continued recruitment of CD8 T cells into the aged muscle during flu infection. Overall, our findings elucidate a link between flu-induced disability and dysregulated intracellular T cell recruitment into flu-injured muscle with aging. Furthermore, we uncovered potential pathways involved that can be targeted to develop preventative and therapeutic interventions to avert disability and maintain independence following infection.

Mechanisms of impaired muscle repair following influenza infection in aged mice

Older adults are susceptible to infectious diseases including Influenza (flu), due to widely accepted declines in immune response with age. Flu infection in older adults commonly results in hospitalization and catastrophic disability, leading to loss of independence. Previous findings demonstrate that flu infection induces severe and prolonged muscle injury in aged mice. We aimed to explore the effects of flu infection on skeletal muscle gene expression and immune cell populations to elucidate mechanisms of flu-induced disability in older adults. Young and aged C57BL/6 male mice were infected with a sublethal dose of PR8 (H1N1) influenza. Gastrocnemius muscles were harvested for RNA sequencing, confocal microscopy, and flow cytometry. Our findings showed differential gene expression changes between young and aged mice, including downregulation of muscle regeneration and organization genes and upregulation proinflammatory cytokine and migratory cell pathways in aged muscle. Pathway analysis revealed significant increases in T cell activation pathways in the aged muscle. Confocal microcopy confirmed increased leukocytes (CD45+) and T cells (CD3+) intramuscularly following flu infection. Flow cytometric analyses confirmed that aged mice have increased infiltrating CD8 T cells during infection compared to young mice, while young muscle have increased infiltrating regulatory T cells (Tregs) compared to their aged counterparts. Further analysis suggested that differences in IL-33 levels between young and aged mice influence these infiltrating populations. Future research is necessary to determine if IL-33 supplementation may prevent or ameliorate flu-induced disability in older adults.

Supported by NIH/NIA R01 AG051647 (Co-I) NIH/NIA R01 AR075346 (Co-I) NIH/NIA R33 AG061456 (Co-I) NIH/NIA R21 AG071292 (Co-I) American Federation for Aging Research Reboot (PI)

Role of p16 expressing cells in formation and function of T cell memory with age

Aging results in the accumulation of senescent cells that have been shown to cause dysfunction in many contexts but the effect on the function of T cell immunity is still unclear. Here, we aimed to probe the effects of clearing senescent cells on T cell responses to influenza infection. We utilized a powerful p16 trimodality reporter mouse model (p16-3MR) that includes cassettes encoding luciferase, RFP, as well as herpesvirus thymidine kinase (HSV-TK) all under the control of p16 promoter. p16 is commonly upregulated in senescent cells so this model allows us to detect senescent cells via luciferase activity, RFP expression, and selectively delete those cells by treating with ganciclovir (GCV). In aged p16-3MR mice following flu infection, we observed a transient induction of RFP+ p16 expressing cells at two weeks post infection. We hypothesized that p16 expressing cells are important for resolution of inflammation and fostering the effector to memory transition. Aged p16-3MR mice lacking p16 expressing cells following GCV treatment developed fewer flu-specific tissue resident memory CD8 T cells (Trm, CD103+ CD69+) in the lung compared to control treated aged counterparts. Interestingly, deletion of p16 expressing cells also increased the proportion of flu-specific Trm cells in the draining lymph node 30 days post infection. As a result, these mice were less effective in controlling viral burden following a secondary challenge. Conversely, during primary infection, deletion of p16 expressing cells induced a more youthful response in aged mice. This suggests that targeting senescent cells is a double-edged sword that may potentiate primary responses to infection while severely limiting the ability to form durable and protective memory.

Supported by grants from NIH (R21 AG060707, R21 AG071292)

The effects of metformin on influenza vaccination responses in healthy older adults

With aging, there is a progressive decline in the immune system leading to increased risk of infection and diminished vaccination responses. Concurrently, there are age-related changes to systemic and cellular metabolism. Influenza (flu) is a leading killer of older adults despite availability of a seasonal vaccine. Metabolic adjuvants may target metabolic deficits in immune cells and have potential to increase vaccination efficacy. Here we aimed to determine the effects of metformin, an FDA approved diabetes drug that targets AMPK and modulates cellular metabolism, on flu vaccination responses. In this study, healthy older adults (non-diabetic/non-prediabetic, age: 74.4±1.7 years) were randomized to metformin (n=8, 1500mg XR/daily) or placebo (n=7) treatment for 20 weeks. 10 weeks after the start of treatment, subjects were vaccinated with High Dose Flu Vaccine. Blood was obtained prior to treatment, prior to vaccination, and 1, 5, and 10 weeks post vaccination. To evaluate the effect of metformin treatment on vaccination responses, peripheral blood mononuclear cells (PBMCs), serum, and plasma were collected from each visit. Serum antibodies titers were quantified and PBMCs were stimulated with live flu virus to assess cell-mediated responses. Clear responses to vaccination were seen in T and B cell subsets via flow cytometry. There were trending increases in antibody fold changes with metformin, indicating a need to further explore the effects of metformin on humoral responses. Overall, metformin had no negative effects, but requires additional studies to determine if it has favorable effects on flu vaccine responses in healthy older adults.

Supported by American Federation for Aging Research (AFAR Diamond 18155, Bartley) and J. Bartley start up funds

Senescence-induced changes in CD4 T cell differentiation can be alleviated by treatment with senolytics

Aging and senescence impact CD4 T helper cell (Th) subset differentiation during influenza infection. In the lungs of infected aged mice, there were significantly greater percentages of Th cells expressing the transcription factor FoxP3, indicative of regulatory CD4 T cells (Treg), when compared to young. TGF‐beta levels, which drive FoxP3 expression, were also higher in the bronchoalveolar lavage of aged mice and blocking TGF‐beta reduced the percentage of FoxP3⁺ Th in aged lungs during influenza infection. Since TGF‐beta can be the product of senescent cells, these were targeted by treatment with senolytic drugs. Treatment of aged mice with senolytics prior to influenza infection restored the differentiation of Th cells in those aged mice to a more youthful phenotype with fewer Th cells expressing FoxP3. In addition, treatment with senolytic drugs induced differentiation of aged Th toward a healing Type 2 phenotype, which promotes a return to homeostasis. These results suggest that senescent cells, via production of cytokines such as TGF‐beta, have a significant impact on Th differentiation.

Better, Faster, Stronger: mRNA Vaccines Show Promise for Influenza Vaccination in Older Adults

Older adults have diminished immune responses that lead to increased susceptibility and severity of infectious diseases. Influenza is a leading killer of older adults despite the availability of seasonal influenza vaccination. Influenza vaccines are strain specific, and their efficacy varies greatly year to year based on how well the vaccine virus matches the circulating strains. Additionally, older adults have reduced vaccination responses. The COVID-19 pandemic highlighted the increased mortality rate in older adults for infectious disease, and brought vaccine development to the forefront. The speed of vaccine development was met with an equally impressive vaccine efficacy. Interestingly, both mRNA-based COVID-19 vaccines currently available have shown similar efficacy in both young and older adults. mRNA vaccine production has significantly reduced the production timeline compared to current influenza vaccines, making them particularly attractive for influenza vaccine development. Faster production coupled with improved efficacy would be a tremendous advancement in protecting older adults from influenza morbidity and mortality.

Targeting Aging: Lessons Learned From Immunometabolism and Cellular Senescence

It is well known that aging is associated with dysregulated metabolism. This is seen both in terms of systemic metabolism, as well as at the cellular level with clear mitochondrial dysfunction. More recently, the importance of cellular metabolism in immune cells, or immunometabolism, has been highlighted as a major modifier of immune cell function. Indeed, T cell activation, differentiation, and effector function partly depend on alterations in metabolic pathways with different cell types and functionality favoring either glycolysis or oxidative phosphorylation. While immune system dysfunction with aging is well described, what remains less elucidated is how the integral networks that control immune cell metabolism are specifically affected by age. In recent years, this significant gap has been identified and work has begun to investigate the various ways immunometabolism could be impacted by both chronological age and age-associated symptoms, such as the systemic accumulation of senescent cells. Here, in this mini-review, we will examine immunometabolism with a focus on T cells, aging, and interventions, such as mTOR modulators and senolytics. This review also covers a timely perspective on how immunometabolism may be an ideal target for immunomodulation with aging.

Network Topology of Biological Aging and Geroscience-Guided Approaches to COVID-19

Aging has emerged as the greatest and most prevalent risk factor for the development of severe COVID-19 infection and death following exposure to the SARS-CoV-2 virus. The presence of multiple co-existing chronic diseases and conditions of aging further enhances this risk. Biological aging not only enhances the risk of chronic diseases, but the presence of such conditions further accelerates varied biological processes or "hallmarks" implicated in aging. Given growing evidence that it is possible to slow the rate of many biological aging processes using pharmacological compounds has led to the proposal that such geroscience-guided interventions may help enhance immune resilience and improve outcomes in the face of SARS-CoV-2 infection. Our review of the literature indicates that most, if not all, hallmarks of aging may contribute to the enhanced COVID-19 vulnerability seen in frail older adults. Moreover, varied biological mechanisms implicated in aging do not function in isolation from each other, and exhibit intricate effects on each other. With all of these considerations in mind, we highlight limitations of current strategies mostly focused on individual single mechanisms, and we propose an approach which is far more multidisciplinary and systems-based emphasizing network topology of biological aging and geroscience-guided approaches to COVID-19.

Biopolymer-nanotube nerve guidance conduit drug delivery for peripheral nerve regeneration: In vivo structural and functional assessment

Peripheral nerve injuries account for roughly 3% of all trauma patients with over 900,000 repair procedures annually in the US. Of all extremity peripheral nerve injuries, 51% require nerve repair with a transected gap. The current gold-standard treatment for peripheral nerve injuries, autograft repair, has several shortcomings. Engineered constructs are currently only suitable for short gaps or small diameter nerves. Here, we investigate novel nerve guidance conduits with aligned microchannel porosity that deliver sustained-release of neurogenic 4-aminopyridine (4-AP) for peripheral nerve regeneration in a critical-size (15 mm) rat sciatic nerve transection model. The results of functional walking track analysis, morphometric evaluations of myelin development, and histological assessments of various markers confirmed the equivalency of our drug-conduit with autograft controls. Repaired nerves showed formation of thick myelin, presence of S100 and neurofilament markers, and promising functional recovery. The conduit's aligned microchannel architecture may play a vital role in physically guiding axons for distal target reinnervation, while the sustained release of 4-AP may increase nerve conduction, and in turn synaptic neurotransmitter release and upregulation of critical Schwann cell neurotrophic factors. Overall, our nerve construct design facilitates efficient and efficacious peripheral nerve regeneration via a drug delivery system that is feasible for clinical applications.

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Nerve guidance conduit platform with tunable scaffold properties for repair and regeneration of large-gap nerve injuries.

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Sustained 4-aminopyridine release amplifies neurotrophic factor release by Schwann cells to promote axon regeneration.

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Longitudinally aligned scaffold pores and controllable physicochemical properties provide guidance for axon regeneration.

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Critical-size rat sciatic nerve defect healing both structurally and functionally resembled autograft control treatment.

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Innovative and transformative scaffold technology imbued with structural and functional features for tissue regeneration.

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Scaffold enable tailorable release profiles for small molecules proteins and electrical stimulation for tissue regeneration.

Effects of cold water immersion on circulating inflammatory markers at the Kona Ironman World Championship

Cold water immersion (CWI) purportedly reduces inflammation and improves muscle recovery after exercise, yet its effectiveness in specific contexts (ultraendurance) remains unclear. Thus, our aim was to study hematological profiles, systemic inflammation, and muscle damage responses to a specific post-race CWI (vs. control) during recovery after the Ironman World Championship, a culmination of ∼100 000 athletes competing in global qualifying Ironman events each year. Twenty-nine competitors were randomized into either a CWI or control (CON) group. Physiological parameters and blood samples were taken at pre-race, after intervention (POST), and 24 (+1DAY) and 48 hours (+2DAY) following the race. Muscle damage markers (plasma myoglobin, serum creatine kinase) were elevated at POST, +1DAY, and +2DAY, while inflammatory cytokines interleukin (IL)-6, IL-8, and IL-10 and total leukocyte counts were increased only at POST. CWI had no effect on these markers. Numbers of the most abundant circulating cell type, neutrophils, were elevated at POST more so in CWI (p < 0.05, vs. CON). Despite that neutrophil counts may be a sensitive marker to detect subtle effects, CWI does not affect recovery markers 24- and 48-hours post-race (vs. CON). Overall, we determined that our short CWI protocol was not sufficient to improve recovery. Novelty: Ironman World Championship event increased circulating muscle damage markers, inflammatory markers, and hematological parameters, including circulating immune cell sub-populations that recover 24-48 hours after the race. 12-min CWI post-ultraendurance event affects the absolute numbers of neutrophils acutely, post-race (vs. CON), but does not impact recovery 24- and 48-hours post-race.

Influenza Infection has Fiber Type-Specific Effects on Cellular and Molecular Skeletal Muscle Function in Aged Mice

Skeletal muscle myopathies represent a common non-pulmonary manifestation of influenza infection, leading to reduced physical function and hospitalization in older adults. However, underlying mechanisms remain poorly understood. Our study examined the effects of influenza virus A pulmonary infection on contractile function at the cellular (single fiber) and molecular (myosin-actin interactions and myofilament properties) levels in soleus and extensor digitorum longus muscles of aged (20 months) C57BL/6 male mice that were healthy or flu-infected for 7 (7-days post-infection; 7-DPI) or 12 days (12-DPI). Cross-sectional area (CSA) of myosin heavy chain (MHC) IIA and IIB fibers was reduced at 12-DPI relative to 7-DPI and healthy. Maximal isometric force in MHC IIA fibers was also reduced at 12-DPI relative to 7-DPI and healthy, resulting in no change in specific force (maximal isometric force divided by CSA). In contrast, MHC IIB fibers produced greater isometric force and specific force at 7-DPI compared to 12-DPI or healthy. The increased specific force in MHC IIB fibers was likely due to greater myofilament lattice stiffness and/or an increased number or stiffness of strongly bound myosin-actin cross-bridges. At the molecular level, cross-bridge kinetics were slower in MHC IIA fibers with infection, while changes in MHC IIB fibers were largely absent. In both fiber types, greater myofilament lattice stiffness was positively related to specific force. This study provides novel evidence that cellular and molecular contractile function is impacted by influenza infection in a fiber type-specific manner, suggesting potential molecular mechanisms to help explain the impact of flu-induced myopathies.

Assessment of Lymph Node Stromal Cells as an Underlying Factor in Age-Related Immune Impairment

Aging negatively impacts immunity, resulting in inefficient responses to vaccinations and infections. Fibroblastic reticular cells (FRCs) are the major stromal cell subset in lymph nodes (LNs) and play an intricate role in the orchestration and control of adaptive immune responses. Although stromal cells have a major impact on immune responses, the impact of aging on LN stromal cells remains unclear. Quantitative analysis of LN stromal cells by flow cytometry revealed that there are no significant differences in the number of stromal cells in young and aged LN at steady state but after influenza infection aged FRCs have delayed expansion as a result of reduced proliferation. Aged LNs also produce reduced levels of homeostatic chemokines, which correlates with reduced homing of naive T cells. Image analysis reveals that young and aged T-cell zone FRCs have similar morphology at steady state and after infection. Furthermore, aged FRCs did not appear to be a contributing factor in the reduced proliferation of young T cells transferred into aged LNs after influenza infection. These results demonstrate that aging alters LN stromal cell response to challenge and these age-related changes may be an underlying contributor to impaired immune responses in the elderly people.

Vaccination mitigates influenza-induced muscular declines in aged mice

Influenza (flu) infection increases the risk for disability, falls, and broken bones in older adults. We have employed a preclinical model to examine the impact of flu on muscle function, which has a direct impact on fall risk. In mice, flu causes mobility and strength impairments with induction of inflammatory and muscle degradation genes that are increased and prolonged with aging. To determine if vaccination could reduce flu-induced muscle decrements, mice were vaccinated with flu nucleoprotein, infected, and muscle parameters were measured. Vaccination of aged mice resulted in significant protection from functional decrements, muscle gene expressions alterations, and morphological damage. Vaccination also improved protection from lung localized and systemic inflammation in aged mice. Despite documented decreased vaccine efficacy with aging, vaccination still provided partial protection to aged mice and represents a potential strategy to prevent flu-induced disability. These findings provide translational insight on ways to reduce flu-induced disability with aging. Graphical abstract .

Diminished immune responses with aging predispose older adults to common and uncommon influenza complications

Influenza (flu) is a serious disease for older adults, with increased severity of infection and greater risk for hospitalization and death. Flu infection is limited to pulmonary epithelial cells, yet there are many systemic symptoms and older adults are more susceptible to flu-related complications. In older adults, flu rarely comes without additional complications and there is a perfect storm for enhanced disease due to multiple factors including existing co-morbidities, plus impaired lung function and dysregulated immune responses that occur with even healthy aging. Commonly, opportunistic secondary bacterial infections prosper in damaged lungs. Intensified systemic inflammation with aging can cause dysfunction in extra-pulmonary organs and tissues such as cardiovascular, musculoskeletal, neuropathologic, hepatic, and renal complications. Often overlooked is the underappreciated connections between many of these conditions, which exacerbate one another when in parallel. This review focuses on flu infection and the numerous complications in older adults associated with diminished immune responses.

Aging augments the impact of influenza respiratory tract infection on mobility impairments, muscle-localized inflammation, and muscle atrophy

Although the influenza virus only infects the respiratory system, myalgias are commonly experienced during infection. In addition to a greater risk of hospitalization and death, older adults are more likely to develop disability following influenza infection; however, this relationship is understudied. We hypothesized that upon challenge with influenza, aging would be associated with functional impairments, as well as upregulation of skeletal muscle inflammatory and atrophy genes. Infected young and aged mice demonstrated decreased mobility and altered gait kinetics. These declines were more prominent in hind limbs and in aged mice. Skeletal muscle expression of genes involved in inflammation, as well as muscle atrophy and proteolysis, increased during influenza infection with an elevated and prolonged peak in aged mice. Infection also decreased expression of positive regulators of muscle mass and myogenesis components to a greater degree in aged mice. Gene expression correlated to influenza-induced body mass loss, although evidence did not support direct muscle infection. Overall, influenza leads to mobility impairments with induction of inflammatory and muscle degradation genes and downregulation of positive regulators of muscle. These effects are augmented and prolonged with aging, providing a molecular link between influenza infection, decreased resilience and increased risk of disability in the elderly.

Impact of Age, Caloric Restriction, and Influenza Infection on Mouse Gut Microbiome: An Exploratory Study of the Role of Age-Related Microbiome Changes on Influenza Responses

Immunosenescence refers to age-related declines in the capacity to respond to infections such as influenza (flu). Caloric restriction represents a known strategy to slow many aging processes, including those involving the immune system. More recently, some changes in the microbiome have been described with aging, while the gut microbiome appears to influence responses to flu vaccination and infection. With these considerations in mind, we used a well-established mouse model of flu infection to explore the impact of flu infection, aging, and caloric restriction on the gut microbiome. Young, middle-aged, and aged caloric restricted (CR) and ad lib fed (AL) mice were examined after a sublethal flu infection. All mice lost 10–20% body weight and, as expected for these early time points, losses were similar at different ages and between diet groups. Cytokine and chemokine levels were also similar with the notable exception of IL-1α, which rose more than fivefold in aged AL mouse serum, while it remained unchanged in aged CR serum. Fecal microbiome phyla abundance profiles were similar in young, middle-aged, and aged AL mice at baseline and at 4 days post flu infection, while increases in Proteobacteria were evident at 7 days post flu infection in all three age groups. CR mice, compared to AL mice in each age group, had increased abundance of Proteobacteria and Verrucomicrobia at all time points. Interestingly, principal coordinate analysis determined that diet exerts a greater effect on the microbiome than age or flu infection. Percentage body weight loss correlated with the relative abundance of Proteobacteria regardless of age, suggesting flu pathogenicity is related to Proteobacteria abundance. Further, several microbial Operational Taxonomic Units from the Bacteroidetes phyla correlated with serum chemokine/cytokines regardless of both diet and age suggesting an interplay between flu-induced systemic inflammation and gut microbiota. These exploratory studies highlight the impact of caloric restriction on fecal microbiome in both young and aged animals, as well as the many complex relationships between flu responses and gut microbiota. Thus, these preliminary studies provide the necessary groundwork to examine how gut microbiota alterations may be leveraged to influence declining immune responses with aging.

Report: NIA Workshop on Measures of Physiologic Resiliencies in Human Aging

BACKGROUND/OBJECTIVES

Resilience, the ability to resist or recover from adverse effects of a stressor, is of widespread interest in social, psychologic, biologic, and medical research and particularly salient as the capacity to respond to stressors becomes diminished with aging. To date, research on human resilience responses to and factors influencing these responses has been limited.

METHODS

The National Institute on Aging convened a workshop in August 2015 on needs for research to improve measures to predict and assess resilience in human aging. Effects of aging-related factors in impairing homeostatic responses were developed from examples illustrating multiple determinants of clinical resilience outcomes. Research directions were identified by workshop participants.

RESULTS

Research needs identified included expanded uses of clinical data and specimens in predicting or assessing resilience, and contributions from epidemiological studies in identifying long-term predictors. Better measures, including simulation tests, are needed to assess resilience and its determinants. Mechanistic studies should include exploration of influences of biologic aging processes on human resiliencies. Important resource and infrastructure needs include consensus phenotype definitions of specific resiliencies, capacity to link epidemiological and clinical resilience data, sensor technology to capture responses to stressors, better laboratory animal models of human resiliencies, and new analytic methods to understand the effects of multiple determinants of stress responses.

CONCLUSIONS

Extending the focus of care and research to improving the capacity to respond to stressors could benefit older adults in promoting a healthier life span.

Metabolic characteristics of keto-adapted ultra-endurance runners

BACKGROUND

Many successful ultra-endurance athletes have switched from a high-carbohydrate to a low-carbohydrate diet, but they have not previously been studied to determine the extent of metabolic adaptations.

METHODS

Twenty elite ultra-marathoners and ironman distance triathletes performed a maximal graded exercise test and a 180 min submaximal run at 64% VO2max on a treadmill to determine metabolic responses. One group habitually consumed a traditional high-carbohydrate (HC: n=10, %carbohydrate:protein:fat=59:14:25) diet, and the other a low-carbohydrate (LC; n=10, 10:19:70) diet for an average of 20 months (range 9 to 36 months).

RESULTS

Peak fat oxidation was 2.3-fold higher in the LC group (1.54±0.18 vs 0.67±0.14 g/min; P=0.000) and it occurred at a higher percentage of VO2max (70.3±6.3 vs 54.9±7.8%; P=0.000). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21±0.02 vs 0.76±0.11 g/min; P=0.000) corresponding to a greater relative contribution of fat (88±2 vs 56±8%; P=0.000). Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (-64% from pre-exercise) and 120 min of recovery (-36% from pre-exercise).

CONCLUSION

Compared to highly trained ultra-endurance athletes consuming an HC diet, long-term keto-adaptation results in extraordinarily high rates of fat oxidation, whereas muscle glycogen utilization and repletion patterns during and after a 3 hour run are similar.

APIC state-of-the-Art report: the role of infection control during construction in health care facilities

The Association for Professionals in Infection Control and Epidemiology, Inc (APIC), is a multidisciplinary organization of more than 12,000 health care professionals who practice infection control and epidemiology within a variety of health care settings. This report reviews issues the infection control professional should consider related to construction and renovation projects in health care facilities. Preventing transmission of infectious agents to vulnerable patient populations, health care workers, and visitors remains an important component of infection control programs. Environmental dispersal of microorganisms during construction, resulting in nosocomial infections, has been described previously, and select examples are provided in Table I as a reminder that there is a solid, scientific basis for these concerns. Environmental airborne contaminants and infectious agents are closely related to water and moisture-related conditions and figure prominently in construction activity. Weems et al have established construction activity as an independent variable for infectious risks in such circumstances. Construction-related outbreak literature will not be revisited in detail; however, pertinent citations will identify resources as appropriate.

Environmental control: operating room air quality

1. OR staff members should familiarize themselves with basic air handling system terminology to better manage their own environment (eg, HVAC, air changes, air balancing, HEPA filtration). A working relationship with building engineers is an important skill for the OR nurse. 2. Knowledge of the standards on which air quality in the OR is based should assist in the process of planning for improved design--as well as in monitoring existing air quality. 3. Current standards balance energy savings with air changes and high levels of filtration to achieve optimum outcomes. Recommendations from design and engineering authorities (even for implant surgery) are based on average air changes and HEPA filtration, not laminar air flow. 4. The daily, operational role of the OR staff in maintaining high air quality includes managing traffic, using low-lint barrier materials, monitoring air quality indicators, and investigating unusual variances with the engineering staff for appropriate follow-up (eg, filter changes).

North-South Contraction of the Mojave Block and Strike-Slip Tectonics in Southern California

The Mojave block of southern California has undergone significant late Cenozoic north-south contraction. This previously unappreciated deformation may account for part of the discrepancy between neotectonic and plate-tectonic estimates of Pacific-North American plate motion, and for part of the Big Bend in the San Andreas fault. In the eastern Mojave block, contraction is superimposed on early Miocene crustal extension. In the western Mojave block, contractional folds and reverse faults have been mistaken for extensional structures. The three-dimensional complexity of the contractional structures may mean that rigid-block tectonic models of the region based primarily on paleomagnetic data are unreliable.