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PloS one2022; 17(3); e0264911; doi: 10.1371/journal.pone.0264911

Effects of equine SALSA on neutrophil phagocytosis and macrophage cytokine production.

Abstract: Salivary scavenger and agglutinin (SALSA) is a secreted protein with various immunomodulatory roles. In humans, the protein agglutinates and inactivates microorganisms, and inhibits the release of pro-inflammatory cytokines. Saliva, which is rich in SALSA, accelerates bacterial phagocytosis, but SALSA's contribution is unclear. In horses, the functions of SALSA in inflammation remain undetermined, so they were investigated through phagocytosis and cytokine assays. Equine SALSA was purified from duodenal tissue, which contains abundant SALSA. To assess phagocytosis, fluorescently-labelled bacteria were incubated with 20, 10, 5, or 2.5 μg/mL of SALSA or phosphate buffered saline (PBS), and then incubated at 37°C or on ice with whole blood from seven healthy horses. Fluorescence was measured by gating on neutrophils using a flow cytometer, and compared between groups. To assess effects on cytokine production, alveolar macrophages were isolated from bronchoalveolar lavage fluid of five healthy horses and cultured in serum-free media for 24 hours with different concentrations of SALSA plus 1 μg/mL lipopolysaccharide (LPS), only LPS, or only media. Cytokines were measured in supernatant using an equine-specific multiplex bead immunoassay. There was significantly greater phagocytosis in samples incubated at 37°C compared to incubation on ice. Samples incubated with 20 μg/mL of SALSA at 37°C had less phagocytosis compared to samples with 10 or 2.5 μg/mL SALSA, or PBS. Alveolar macrophages incubated with SALSA plus LPS released significantly less CXC motif chemokine ligand 1, interleukin-8, interleukin-10, and tumor necrosis factor α, and more granulocyte colony stimulating factor (G-CSF), compared to macrophages incubated with LPS alone. These findings indicate anti-inflammatory effects, which may be due to interference with toll-like receptor 4 recognition of LPS or downstream signaling. Increase in G-CSF following incubation with SALSA suggests a novel mechanism for immunoregulation of alveolar macrophages by SALSA, addressing a knowledge gap regarding its functions in horses.
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Publication Date: 2022-03-14 PubMed ID: 35286327PubMed Central: PMC8920288DOI: 10.1371/journal.pone.0264911Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research explores the immunomodulatory roles of equine SALSA (Salivary scavenger and agglutinin) in promoting bacterial phagocytosis and how it affects the production of specific cytokines in horses.

Overview of the Methodology

  • The study obtained equine SALSA from duodenal tissue, known to be rich in SALSA.
  • For observing phagocytosis, fluorescently-labelled bacteria were treated with various concentrations of SALSA or phosphate-buffered saline (PBS) and then mixed with whole blood harvested from seven healthy horses.
  • The samples were incubated either at 37°C or on ice, and phagocytosis rates were measured using a flow cytometer.
  • For assessing SALSA’s effect on cytokine production, alveolar macrophages were harvested from bronchoalveolar lavage fluid in five horses and were cultured in serum-free media for 24 hours.
  • The media contained varying concentrations of SALSA and 1 μg/mL lipopolysaccharide (LPS), only LPS, or only media, after which cytokine levels were measured using an equine-specific multiplex bead immunoassay.

Findings

  • Samples incubated at 37°C showed significantly greater phagocytosis rates compared to those incubated on ice.
  • Phagocytosis was seen to decrease in samples treated with 20 μg/mL of SALSA compared to those treated with lower concentrations of SALSA or PBS.
  • Alveolar macrophages treated with SALSA and LPS produced significantly lower amounts of certain cytokines, implying anti-inflammatory effects.
  • SALSA induced an increase in granulocyte colony-stimulating factor (G-CSF) production, indicating potential novel mechanisms for immunoregulation by SALSA.

Conclusions and Implications

  • The study’s findings suggest that equine SALSA has anti-inflammatory effects, likely due to inhibition of toll-like receptor 4 recognition of LPS or interference with downstream signaling.
  • The noted increase in G-CSF suggests that SALSA could be a key player in regulating the immune functions of alveolar macrophages, which helps fill knowledge gaps regarding SALSA’s immunomodulatory roles in horses.

Cite This Article

APA
Lee GKC, Kang H, Beeler-Marfisi J, Sears W, Lillie BN, Bienzle D. (2022). Effects of equine SALSA on neutrophil phagocytosis and macrophage cytokine production. PLoS One, 17(3), e0264911. https://doi.org/10.1371/journal.pone.0264911

Publication

PloS one
ISSN: 1932-6203
NlmUniqueID: 101285081
Country: United States
Language: English
Volume: 17
Issue: 3
Pages: e0264911
PII: e0264911

Researcher Affiliations

Lee, Gary Kwok Cheong
  • Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Kang, Heng
  • Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Beeler-Marfisi, Janet
  • Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Sears, William
  • Department of Population Medicine, University of Guelph, Guelph, Ontario, Canada.
Lillie, Brandon N
  • Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
Bienzle, Dorothee
  • Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.

MeSH Terms

  • Animals
  • Cytokines / metabolism
  • Granulocyte Colony-Stimulating Factor / metabolism
  • Horses
  • Ice
  • Lipopolysaccharides / metabolism
  • Lipopolysaccharides / pharmacology
  • Macrophages / metabolism
  • Neutrophils / metabolism
  • Phagocytosis
  • Tumor Necrosis Factor-alpha / metabolism

Conflict of Interest Statement

The authors have declared that no competing interests exist.

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Citations

This article has been cited 1 times.
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