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A Method for Generating Pulmonary Neutrophilia Using Aerosolized Lipopolysaccharide
Published on: December 15, 2014
Parenteral lipids impair pneumococcal elimination by human neutrophils
Michelle W Versleijen1, Hennie M Roelofs, Rene H te Morsche
1Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands.
Insights
Parenteral lipids impair neutrophil function, reducing their ability to eliminate Streptococcus pneumoniae. The lipid emulsion composition significantly impacts this effect, with LCT/MCT being the most detrimental to microbial elimination.
Area of Science:
- Immunology
- Nutrition Science
- Microbiology
Background:
- Parenteral nutrition lipid emulsions may increase infection susceptibility in patients.
- The specific impact of different lipid emulsion structures on phagocyte function is not well understood.
- Neutrophil function, crucial for combating bacterial infections, can be modulated by lipids.
Purpose of the Study:
- To assess the effect of various lipid emulsions on neutrophil's capacity to eliminate Streptococcus pneumoniae.
- To determine if lipid structure influences the impairment of phagocyte function.
Main Methods:
- Neutrophils from healthy volunteers were incubated with different lipid emulsions: soybean (LCT), fish (VLCT), olive (LCT-MUFA), mixed soybean/coconut oils (LCT/MCTs), and structured lipids (SL).
- Streptococcus pneumoniae were opsonized and incubated with neutrophils in the presence of complement.
- Bacterial elimination was quantified by measuring the percentage of bacteria eliminated.
Main Results:
- Neutrophils without lipid exposure eliminated 75% of S. pneumoniae.
- Exposure to LCT-MUFA, VLCT, SL, and LCT reduced elimination capacity to 70%, 67%, 63%, and 66%, respectively.
- The LCT/MCT emulsion significantly reduced bacterial elimination to 47%.
Conclusions:
- Parenteral lipid emulsions impair neutrophil microbial elimination in a structure-dependent manner.
- The LCT/MCT lipid emulsion demonstrated the most potent inhibitory effect on neutrophil function.
- These findings highlight the importance of lipid structure in modulating immune responses during parenteral nutrition.
Background:
Lipid-induced modulation of phagocyte function seems to contribute to increased susceptibility to infections in patients on parenteral nutrition, and an increased risk for development of pneumonia has been observed in this group. The role of various structurally different lipid emulsions, however, remains unclear. In this study, we therefore assessed phagocyte function, as the capacity of neutrophils to eliminate Streptococcus pneumoniae (i.e. combined result of phagocytosis and killing), in the presence of these lipids.
Materials And Methods:
Neutrophils from six healthy volunteers were incubated for 1 h in emulsions (5 mmol L(-1)) derived from soybean- (LCT), fish- (VLCT), olive- (LCT-MUFA), mixed soybean/coconut oils (LCT/MCTs) or structured lipids (SL). After opsonization of the pneumococci (strain OREP-4) by human immunoglobulins, bacteria and neutrophils were incubated in the presence of complement. Next, pneumococcal elimination was evaluated and expressed as the percentage of bacteria eliminated relative to the initial bacterial numbers in neutrophil-free samples.
Results:
Neutrophils that were not exposed to lipids showed a pneumococcal elimination capacity of 75 +/- 3% (mean +/- SD). This significantly decreased after exposure to LCT-MUFA (70 +/- 6%), VLCT (67 +/- 2%), SL (63 +/- 9%), LCT (66 +/- 10%) and LCT/MCT (47 +/- 15%).
Conclusion:
These data demonstrate that parenteral lipids impair the microbial elimination capacity of neutrophils in a structure-dependent manner. In accordance with our previously reported in vitro effect on a range of phagocyte functions, LCT/MCT is by far the most potent in this respect.
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