Enriched dietary saturated fatty acids induce trained immunity via ceramide production that enhances severity of endotoxemia and clearance of infection

  1. Amy L Seufert
  2. James W Hickman
  3. Ste K Traxler
  4. Rachael M Peterson
  5. Trent A Waugh
  6. Sydney J Lashley
  7. Natalia Shulzhenko
  8. Ruth J Napier
  9. Brooke A Napier  Is a corresponding author
  1. Portland State University, United States
  2. VA Portland Health Care System, United States
  3. Oregon State University, United States

Abstract

Trained immunity is an innate immune memory response that is induced by primary microbial or sterile stimuli that sensitizes monocytes and macrophages to a secondary pathogenic challenge, reprogramming the host response to infection and inflammatory disease. Nutritional components, such as dietary fatty acids, can act as inflammatory stimuli, but it is unknown if they can act as the primary stimuli in the context of innate immune memory. Here we find mice fed a diet enriched exclusively in saturated fatty acids (SFAs; ketogenic diet; KD) confer a hyper-inflammatory response to systemic lipopolysaccharide (LPS) and increased mortality, independent of diet-induced microbiome and glycemic modulation. We find KD mediates the composition of the hematopoietic stem cell (HSC) compartment, and macrophages derived from the bone marrow of mice fed KD do not have altered baseline inflammation, but enhanced responses to a secondary inflammatory challenge. Lipidomics identified enhanced free palmitic acid (PA) and PA-associated lipids in KD-fed mice serum. We found pre-treatment with physiologically relevant concentrations of PA alone reprograms macrophages to induce a hyper-inflammatory response to secondary challenge with LPS. This response was found to be dependent on the synthesis of ceramide, and reversible when treated with a ceramide synthase inhibitor. In vivo, we found systemic PA confers enhanced inflammation and mortality during an acute inflammatory response to systemic LPS, and this phenotype was not reversible for up to 7 days post-PA-exposure. While PA-treatment is harmful for endotoxemia outcome, we find PA exposure enhanced clearance of Candida albicans in Rag1-/- mice. Further, we show that oleic acid (OA), a mono-unsaturated FA that depletes intracellular ceramide, reverses the PA-induced hyper-inflammatory response shown in macrophages treated with LPS, and reduces severity and mortality of LPS endotoxin stimulation, highlighting the plasticity of SFA-dependent enhanced endotoxemia severity in vivo. These are the first data to implicate enriched dietary SFAs, and specifically PA, in the induction of long-lived innate immune memory that is detrimental during an acute inflammatory response, but beneficial for clearance of pathogens.

Data availability

All data generated or analyzed during this study are included in the manuscript and supporting file.

Article and author information

Author details

  1. Amy L Seufert

    Department of Biology, Portland State University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. James W Hickman

    Department of Biology, Portland State University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Ste K Traxler

    Department of Biology, Portland State University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Rachael M Peterson

    Department of Biology, Portland State University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Trent A Waugh

    Department of Biology, Portland State University, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  6. Sydney J Lashley

    VA Portland Health Care System, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  7. Natalia Shulzhenko

    Department of 9Biomedical Sciences, Oregon State University, Corvallis, United States
    Competing interests
    The authors declare that no competing interests exist.
  8. Ruth J Napier

    VA Portland Health Care System, Portland, United States
    Competing interests
    The authors declare that no competing interests exist.
  9. Brooke A Napier

    Department of Biology, Portland State University, Portland, United States
    For correspondence
    brnapier@pdx.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-6409-4750

Funding

NIGMS/NIH (R35GM133804)

  • Brooke A Napier

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Jos W van der Meer, Radboud University Medical Centre, Netherlands

Ethics

Animal experimentation: This study was performed in strict accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. All of the animals were handled according to approved institutional animal care and use committee (IACUC) protocols (#IP00002661 & IP00001903) of Oregon Health & Sciences University and Oregon State University (#5091). All animal experiments were approved by the Oregon Health and Sciences University (OHSU) Department of Comparative Medicine or Oregon State University (OSU) Animal Program Office and were overseen by the Institutional Care and Use Committee (IACUC).

Version history

  1. Preprint posted: June 16, 2021 (view preprint)
  2. Received: January 4, 2022
  3. Accepted: October 19, 2022
  4. Accepted Manuscript published: October 20, 2022 (version 1)
  5. Version of Record published: November 8, 2022 (version 2)

Copyright

This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

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  1. Amy L Seufert
  2. James W Hickman
  3. Ste K Traxler
  4. Rachael M Peterson
  5. Trent A Waugh
  6. Sydney J Lashley
  7. Natalia Shulzhenko
  8. Ruth J Napier
  9. Brooke A Napier
(2022)
Enriched dietary saturated fatty acids induce trained immunity via ceramide production that enhances severity of endotoxemia and clearance of infection
eLife 11:e76744.
https://doi.org/10.7554/eLife.76744

Share this article

https://doi.org/10.7554/eLife.76744

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    1. Immunology and Inflammation
    2. Medicine
    Joanna C Porter, Jamie Inshaw ... Venizelos Papayannopoulos
    Research Article

    Background:

    Prinflammatory extracellular chromatin from neutrophil extracellular traps (NETs) and other cellular sources is found in COVID-19 patients and may promote pathology. We determined whether pulmonary administration of the endonuclease dornase alfa reduced systemic inflammation by clearing extracellular chromatin.

    Methods:

    Eligible patients were randomized (3:1) to the best available care including dexamethasone (R-BAC) or to BAC with twice-daily nebulized dornase alfa (R-BAC + DA) for seven days or until discharge. A 2:1 ratio of matched contemporary controls (CC-BAC) provided additional comparators. The primary endpoint was the improvement in C-reactive protein (CRP) over time, analyzed using a repeated-measures mixed model, adjusted for baseline factors.

    Results:

    We recruited 39 evaluable participants: 30 randomized to dornase alfa (R-BAC +DA), 9 randomized to BAC (R-BAC), and included 60 CC-BAC participants. Dornase alfa was well tolerated and reduced CRP by 33% compared to the combined BAC groups (T-BAC). Least squares (LS) mean post-dexamethasone CRP fell from 101.9 mg/L to 23.23 mg/L in R-BAC +DA participants versus a 99.5 mg/L to 34.82 mg/L reduction in the T-BAC group at 7 days; p=0.01. The anti-inflammatory effect of dornase alfa was further confirmed with subgroup and sensitivity analyses on randomised participants only, mitigating potential biases associated with the use of CC-BAC participants. Dornase alfa increased live discharge rates by 63% (HR 1.63, 95% CI 1.01–2.61, p=0.03), increased lymphocyte counts (LS mean: 1.08 vs 0.87, p=0.02) and reduced circulating cf-DNA and the coagulopathy marker D-dimer (LS mean: 570.78 vs 1656.96 μg/mL, p=0.004).

    Conclusions:

    Dornase alfa reduces pathogenic inflammation in COVID-19 pneumonia, demonstrating the benefit of cost-effective therapies that target extracellular chromatin.

    Funding:

    LifeArc, Breathing Matters, The Francis Crick Institute (CRUK, Medical Research Council, Wellcome Trust).

    Clinical trial number:

    NCT04359654.

    1. Immunology and Inflammation
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    Trained immunity is the long-term functional reprogramming of innate immune cells, which results in altered responses toward a secondary challenge. Despite indoxyl sulfate (IS) being a potent stimulus associated with chronic kidney disease (CKD)-related inflammation, its impact on trained immunity has not been explored. Here, we demonstrate that IS induces trained immunity in monocytes via epigenetic and metabolic reprogramming, resulting in augmented cytokine production. Mechanistically, the aryl hydrocarbon receptor (AhR) contributes to IS-trained immunity by enhancing the expression of arachidonic acid (AA) metabolism-related genes such as arachidonate 5-lipoxygenase (ALOX5) and ALOX5 activating protein (ALOX5AP). Inhibition of AhR during IS training suppresses the induction of IS-trained immunity. Monocytes from end-stage renal disease (ESRD) patients have increased ALOX5 expression and after 6 days training, they exhibit enhanced TNF-α and IL-6 production to lipopolysaccharide (LPS). Furthermore, healthy control-derived monocytes trained with uremic sera from ESRD patients exhibit increased production of TNF-α and IL-6. Consistently, IS-trained mice and their splenic myeloid cells had increased production of TNF-α after in vivo and ex vivo LPS stimulation compared to that of control mice. These results provide insight into the role of IS in the induction of trained immunity, which is critical during inflammatory immune responses in CKD patients.