title: Regulation of monocyte subset proinflammatory responses within the lung microvasculature by the p38 MAPK/MK2 pathway.
abstract: Margination and activation of monocytes within the pulmonary microcirculation contribute substantially to the development of acute lung injury in mice. The enhanced LPS-induced TNF expression exhibited by Gr-1(high) compared with Gr-1(low) monocytes within the lung microvasculature suggests differential roles for these subsets. We investigated the mechanisms responsible for such heterogeneity of lung-marginated monocyte proinflammatory response using a combined in vitro and in vivo approach. The monocyte subset inflammatory response was studied in vitro in mouse peripheral blood mononuclear cell-lung endothelial cell coculture and in vivo in a two-hit model of intravenous LPS-induced monocyte margination and lung inflammation in mice, by flow cytometry-based quantification of proinflammatory genes and intracellular phospho-kinases. With LPS stimulation in vitro, TNF expression was consistently higher in Gr-1(high) than Gr-1(low) monocytes, markedly enhanced by coculture with endothelial cells, and abrogated by p38 MAPK inhibitors. Expression of IL-6, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) was only detectable under coculture conditions, was substantially higher in Gr-1(high) monocytes, and was attenuated by p38 inhibition. Consistent with these differential responses, phosphorylation of p38 and its substrate MAPK-activated protein kinase 2 (MK2) was significantly higher in the Gr-1(high) subset. In vivo, p38 inhibitor treatment significantly attenuated LPS-induced TNF expression in "lung-marginated" Gr-1(high) monocytes. LPS-induced p38/MK2 phosphorylation was higher in lung-marginated Gr-1(high) than Gr-1(low) monocytes and neutrophils, mirroring TNF expression. These results indicate that the p38/MK2 pathway is a critical determinant of elevated Gr-1(high) subset responsiveness within the lung microvasculature, producing a coordinated proinflammatory response that places Gr-1(high) monocytes as key orchestrators of pulmonary microvascular inflammation and injury.
authors.affiliation: Section of Anaesthetics, Pain Medicine and Intensive Care, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital, London, United Kingdom.
authors.forename: Kieran P
authors.initials: KP
authors.lastname: O'Dea
authors.forename: Justina O
authors.initials: JO
authors.lastname: Dokpesi
authors.forename: Kate C
authors.initials: KC
authors.lastname: Tatham
authors.forename: Michael R
authors.initials: MR
authors.lastname: Wilson
authors.forename: Masao
authors.initials: M
authors.lastname: Takata
mesh_terms: D055371:Acute Lung Injury / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D019070:Cell Lineage; D018920:Coculture Techniques; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism; D005434:Flow Cytometry; D007249:Inflammation / Q000276:immunology / Q000378:metabolism* / Q000503:physiopathology; D015850:Interleukin-6 / Q000032:analysis / Q000096:biosynthesis; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000009:adverse effects / Q000494:pharmacology; D008168:Lung / Q000098:blood supply / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D055806:Microvessels / Q000276:immunology* / Q000378:metabolism; D009000:Monocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D015398:Signal Transduction / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000096:biosynthesis; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D051546:Cyclooxygenase 2; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D052247:Nitric Oxide Synthase Type II; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2