FIG. 13.

Accumulation of PEox hydrolysis products and lipid mediators in the ileum of mice exposed to TBI (9.5 Gy). LPE species and oxygenated free fatty acids were analyzed by normal-phase and reverse-phase LC-MS, respectively, by using a Q-Exactive mass spectrometer (ThermoFisher Scientific). Accumulation of total LPE (A, left panel) and LPE molecular species (A, right panel) in the ileum of naïve mice (blue) and irradiated mice (1 day after irradiation, red). Data are mean ± SD, n = 4. The content of free HXA₃ in the ileum of naive mice (blue) and irradiated mice (1 day after irradiation, red), (B, left panel). Data are mean ± SD, n = 4. MS/MS spectrum of molecular ion with m/z 334.22 at HXA₃ retention time (B, right panel). Characteristic HXA₃ fragments formed during MS/MS analysis (m/z 127, m/z 151, m/z 179 and m/z 183) are shown in red. Accumulation of free HXA₃ in the ileum of irradiated mice might be due to hydrolysis of PE-HXA₃ species by phospholipase A₂ and liberation HXA₃ from the sn-2 position of PE. Notably, the LPE species originated from alkenyl and alkyl PE species. The content of free LTB₄ in the ileum of naive mice (blue) and irradiated mice (1 day after irradiation, red). Data are mean ± SD, n = 5 (C, left panel). MS/MS spectrum of the molecular ion with m/z 334.22 at LTB₄ retention time (C, right panel). Characteristic LTB₄ fragment formed during MS/MS analysis (m/z 195) is shown in red. Cytokine production in the ileum of irradiated mice (D). Cytokine production was by Luminex immunoassays run on the intestine for each group (n = 4–5 each data point) at serial time points at days 0 (before irradiation), 1, 2, 3, 4, 5, 6, or 7 after TBI. Shown are “heat maps” for three proteins (RANTES that plays an important role in the recruitment of neutrophils to the inflammatory sites), KC (a homolog of a neutrophil recruiting human pro-inflammatory cytokine, IL-8) along with MCP1 (a monocyte chemoattractant protein 1). LPE, lyso-phosphatidylethanolamine species; LTB₄, leukotriene B₄. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/ars