Spred-2 Deficiency Exacerbates Lipopolysaccharide-Induced Acute Lung Inflammation in Mice

Abstract

BackgroundAcute respiratory distress syndrome (ARDS) is a severe and life-threatening acute lung injury (ALI) that is caused by noxious stimuli and pathogens. ALI is characterized by marked acute inflammation with elevated alveolar cytokine levels. Mitogen-activated protein kinase (MAPK) pathways are involved in cytokine production, but the mechanisms that regulate these pathways remain poorly characterized. Here, we focused on the role of Sprouty-related EVH1-domain-containing protein (Spred)-2, a negative regulator of the Ras-Raf-extracellular signal-regulated kinase (ERK)-MAPK pathway, in lipopolysaccharide (LPS)-induced acute lung inflammation.MethodsWild-type (WT) mice and Spred-2−/− mice were exposed to intratracheal LPS (50 µg in 50 µL PBS) to induce pulmonary inflammation. After LPS-injection, the lungs were harvested to assess leukocyte infiltration, cytokine and chemokine production, ERK-MAPK activation and immunopathology. For ex vivo experiments, alveolar macrophages were harvested from untreated WT and Spred-2−/− mice and stimulated with LPS. In in vitro experiments, specific knock down of Spred-2 by siRNA or overexpression of Spred-2 by transfection with a plasmid encoding the Spred-2 sense sequence was introduced into murine RAW264.7 macrophage cells or MLE-12 lung epithelial cells.ResultsLPS-induced acute lung inflammation was significantly exacerbated in Spred-2−/− mice compared with WT mice, as indicated by the numbers of infiltrating leukocytes, levels of alveolar TNF-α, CXCL2 and CCL2 in a later phase, and lung pathology. U0126, a selective MEK/ERK inhibitor, reduced the augmented LPS-induced inflammation in Spred-2−/− mice. Specific knock down of Spred-2 augmented LPS-induced cytokine and chemokine responses in RAW264.7 cells and MLE-12 cells, whereas Spred-2 overexpression decreased this response in RAW264.7 cells.ConclusionsThe ERK-MAPK pathway is involved in LPS-induced acute lung inflammation. Spred-2 controls the development of LPS-induced lung inflammation by negatively regulating the ERK-MAPK pathway. Thus, Spred-2 may represent a therapeutic target for the treatment of ALI.

MEK1 regulates pulmonary macrophage inflammatory responses and resolution of acute lung injury

“…There was no significant difference in the levels of MEK2 between the groups (Figure 1, A and B), and there was no significant difference in the total number of alveolar macrophages recovered from Mek1 fl and Mek1 fl LysM Cre mice ( Figure 1C). We predicted that loss of MEK1 would decrease the macrophage proinflammatory response to LPS stimulation, which would be consistent with results demonstrated by use of pharmacological MEK1/2 inhibitor compounds (19). To test this hypothesis, we stimulated alveolar macrophages ex vivo with LPS for 4 hours and measured proinflammatory gene expression.…”

A Novel Role of Spred2 in the Colonic Epithelial Cell Homeostasis and Inflammation

“…Particularly, in DSS-induced colitis, bacteria that translocated to the mucosa interact with mucosal cells, such as macrophages, via toll-like receptors and promote the production of pro-inflammatory cytokines, resulting in overwhelming inflammatory responses48. We previously reported that Spred2-deficiency increased the production of pro-inflammatory cytokines by LPS-activated alveolar macrophages, and exacerbated LPS-induced lung injury59. In this study, however, the inflammatory response in the colonic mucosa of Spred2 mice was milder than WT mice, and only a small number of leukocytes infiltrated the mucosa of Spred2 KO mice; thus, the effect of Spred2-deficiency on macrophages cannot explain the decreased inflammatory responses detected in the colon of Spred2 KO mice.…”

Sex-specific variation in signaling pathways and gene expression patterns in human leukocytes in response to endotoxin and exercise

“…Their activation became only apparent in LPS-stimulated cultures, and men showed highly significant activation while women showed only a trend. Similarly, the central protective gene IL-6, the tumorigenesis controlling gene HIVEP1[25], and SPRED2 [26] which are all clearly anti-inflammatory in their effects were significantly more highly expressed in men than women.…”