The Journal of immunology : official journal of the American Association of Immunologists
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Peroxisome proliferator activator receptor-gamma (PPARgamma) is a nuclear receptor that controls the expression of several genes involved in metabolic homeostasis. We investigated the role of PPARgamma during the inflammatory response in sepsis by the use of the PPARgamma ligands, 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) and ciglitazone. Polymicrobial sepsis was induced by cecal ligation and puncture in rats and was associated with hypotension, multiple organ failure, and 50% mortality. ⋯ These beneficial effects of the PPARgamma ligands were associated with the reduction of IkappaB kinase complex and c-Jun NH(2)-terminal kinase activation and the reduction of NF-kappaB and AP-1 DNA binding in the lung. Furthermore, treatment with ciglitazone or 15d-PGJ(2) up-regulated the expression of PPARgamma in lung and thoracic aorta and abolished nitrotyrosine formation and poly(ADP-ribose) expression in aorta. Our data suggest that PPARgamma ligands attenuate the inflammatory response in sepsis through regulation of the NF-kappaB and AP-1 pathways.
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Evasion of host immune responses is well documented for viruses and may also occur during tumor immunosurveillance. The mechanisms involve alterations in MHC class I expression, Ag processing and presentation, chemokine and cytokine production, and lymphocyte receptor expression. Epithelial tumors overexpress MHC class I chain-related (MIC) molecules, which are ligands for the activating receptor NKG2D on NK and T cells. ⋯ The patients' NK cells up-regulate expression of NKG2D, NKp44, CXCR1, and CCR7 when cultured in normal serum or anti-MIC Ab-treated autologous serum. NKG2D(+) but not NKG2D(-) NK cells are tumoricidal in vitro, and in vivo they selectively traffic to the xenografted carcinoma, form immunological synapse with tumor cells, and significantly retard tumor growth in the SCID mice. These results suggest that circulating sMIC in the cancer patients deactivates NK immunity by down-modulating important activating and chemokine receptors.
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Aside from its mechanical barrier function, bronchial epithelium plays an important role both in the host defense and in the pathogenesis of inflammatory airway disorders. To investigate its role in lung defense, the effect of a bacterial cell wall protein, the outer membrane protein A from Klebsiella pneumoniae (kpOmpA) on bronchial epithelial cells (BEC) was evaluated on adhesion molecule expression and cytokine production. Moreover, the potential implication of this mechanism in kpOmpA-induced lung inflammation was also determined. ⋯ In vivo kpOmpA priming induced bronchial epithelium activation as evaluated by ICAM-1 and CXCL1 expression, associated with the secretion of CXCL1 and CXCL5 in bronchoalveolar lavage fluids. In the lung, an increased level of the IL-6, CXCL1, CXCL5, CXCL10 mRNA was observed with a maximum at 6 h. These data showed that kpOmpA is involved in host defense mechanism by its ability to activate not only APC but also BEC, resulting in a lung neutrophilia.
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To determine whether p300 is involved in inducible NO synthase (iNOS) transcriptional regulation, we evaluated the effect of p300 overexpression on iNOS expression and characterized p300 binding to iNOS promoter in RAW 264.7 cells. p300 overexpression increased iNOS expression which was abrogated by deletion of the histone acetyltransferase (HAT) domain (Delta1472-1522). DNA-binding and chromatin immunoprecipitation assays revealed binding of p300 to several DNA-bound transactivators at basal state. Following stimulation with LPS plus IFN-gamma, binding of p300, p50/p65 NF-kappaB, and IFN-regulatory factor-1 was increased by approximately 2-fold. ⋯ Co-overexpression of E1A abolished the augmentation of p50 acetylation and p50 binding induced by p300 overexpression, and a correlative suppression of p300 recruitment to the complex. We conclude that p300 is essential for iNOS transcription. Our results suggest that p300 HAT acetylates the p50 subunit of NF-kappaB, thereby increasing NF-kappaB binding and NF-kappaB mediated transactivation.
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Stat3 is a transcription factor mediating anti-inflammatory properties of IL-10. In the present study, we demonstrate a pivotal role of Stat3 expressed in innate immune cells during septic peritonitis induced by cecal ligation and puncture (CLP). Mice with targeted disruption of Stat3 in macrophages and neutrophils were succumbed to septic peritonitis induced by CLP. ⋯ Elicited macrophages and neutrophils with Stat3 deficiency also impaired bactericidal activity as compared with those with Stat3. Lysosomal enzyme release, an effector molecule for bacterial clearance, was significantly decreased in elicited leukocytes with Stat3 deficiency while increasing the production of inflammatory cytokines. Altogether, these results suggest that macrophage/neutrophil-specific STAT3 is crucial in not only modulating multiple organ failure associated with systemic inflammation but also intensifying the bactericidal activity, which highlight the significance of cell-specific Stat3 in the protective immunity during sepsis.