<p> In the presence of arachidonic acid (AA), <i>Saccharomyces cerevisiae </i> produces prostaglandin E<sub>2</sub> (PGE<sub>2</sub>). <i> S. cerevisiae</i> and its metabolites may be consumed in products manufactured using the yeast (e.g. beer). Neutrophils are immune cells present in the gastrointestinal (GI) tract during inflammation. As a lipid-signaling molecule, PGE<sub>2</sub> can potentially modify neutrophil functions and exacerbate pre-existing inflammation. As neutrophil migration is a hallmark of inflammation, we investigated the impact of PGE<sub>2</sub> on neutrophil chemotaxis. Chemotaxis assays were performed on neutrophils isolated from human whole blood using the chemotactic agents f-Met-Leu-Phe (fMLP) or interleukin-8 (IL-8). Neutrophil chemotaxis was concentration dependent as it was enhanced 3.5-fold at low concentrations of PGE<sub>2</sub> (0.1 nM-10 nM) and reduced 3.0-fold at higher concentrations of PGE<sub>2</sub> (100 nM).</p><p> The biochemical pathway utilized by <i>S. cerevisiae</i> to produce PGE<sub>2</sub> is unknown. Identifying enzymes that metabolize AA may direct approaches to reduce the impact that yeast PGE<sub>2</sub> may have on neutrophils. <i>S. cerevisiae</i> does not have genes homologous to those involved in mammalian AA metabolism. We employed RNAseq transcriptome sequencing to study the lipid biosynthetic pathway in <i>S. cerevisiae </i> and observed 1248 genes upregulated in yeast that were cultured in the presence of AA relative to yeast that were cultured without AA. Notably, genes that mediate beta-oxidation of fatty acids (<i>Pot1, Pox1, Faa1 and Faa2</i>) were upregulated up to 2.3-fold.</p><p> The results demonstrate that low concentrations of PGE<sub>2</sub> enhance neutrophil chemotaxis that is mediated by fMLP or IL-8, suggesting that PGE<sub> 2</sub> may aid in recruiting neutrophils from regions that are distant to a site of inflammation. Once a higher concentration of PGE<sub>2</sub> is encountered by neutrophils, neutrophils may halt their migration and engage effector functions such as phagocytosis and superoxide production. Increased expression of genes involved with fatty acid metabolism points to enzymes that may utilize AA to produce PGE<sub>2</sub> in <i>S. cerevisiae</i>. Experiments testing PGE<sub>2</sub> levels in knock-out strains of yeast will identify genes involved in PGE<sub>2</sub> production. Results of this study have implications to reduce potential off-target effects caused by yeast PGE<sub> 2</sub> in consumables.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1526893 |
| Date | 31 October 2014 |
| Creators | Batugedara, Hashini Maneesha |
| Publisher | California State University, Long Beach |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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