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Osteopontin mediates Stat1 degradation to inhibit iNOS transcription in a cecal ligation and puncture model of sepsis.

ABSTRACT: Osteopontin (OPN) represses inducible nitric oxide synthase (iNOS) expression by increasing ubiquitin (Ub)-proteasome degradation of Stat1, a critical transcription factor for iNOS expression. We investigated the in vivo relevance of our findings in a cecal ligation and puncture model.A total of 129 wild-type (WT; n = 24) and OPN null (n = 24) mice were used. Bone marrow macrophages and whole liver tissue were isolated. iNOS and phosphorylated Stat-1 (P-Stat1) protein were significantly greater in OPN null than WT. Cecal ligation and puncture increased Ub-P-Stat1; Ub-P-Stat1 was significantly less in OPN null than WT. In chromatin immunoprecipitation assays, P-Stat1 binding to the iNOS promoter was increased in OPN null. Ex vivo studies with bone marrow macrophages were performed with MG132 (10 microM), an inhibitor of 26S proteasome function, and/or exogenous OPN (50 microM). Ub-P-Stat1 was decreased in OPN null bone marrow macrophages treated with LPS; iNOS was increased. Exogenous OPN or MG132 restored Ub-P-Stat1 and iNOS to levels seen in WT. Our results indicate that absence of OPN does the following: (1) increases iNOS and P-Stat1 protein, (2) decreases ubiquitination and degradation of P-Stat1, and (3) increases iNOS transcription.We conclude that OPN downregulates iNOS expression by accelerating ubiquitination and degradation of Stat1.

SUBMITTER: Guo H

PROVIDER: S-EPMC2525867 | biostudies-literature | 2008 Aug

REPOSITORIES: biostudies-literature

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Osteopontin mediates Stat1 degradation to inhibit iNOS transcription in a cecal ligation and puncture model of sepsis.

Guo Hongtao H Wai Philip Y PY Mi Zhiyong Z Gao Chengjiang C Zhang Jinping J Kuo Paul C PC

Surgery 20080516 2

<h4>Background</h4>Osteopontin (OPN) represses inducible nitric oxide synthase (iNOS) expression by increasing ubiquitin (Ub)-proteasome degradation of Stat1, a critical transcription factor for iNOS expression. We investigated the in vivo relevance of our findings in a cecal ligation and puncture model.<h4>Methods and results</h4>A total of 129 wild-type (WT; n = 24) and OPN null (n = 24) mice were used. Bone marrow macrophages and whole liver tissue were isolated. iNOS and phosphorylated Stat- ...[more]

PMID: 18656624

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Project description:BACKGROUND:The paradigm shift from crystalloid to plasma resuscitation of traumatic hemorrhagic shock has improved patient outcomes due in part to plasma-mediated reversal of catecholamine and inflammation-induced endothelial injury, decreasing vascular permeability and attenuating organ injury. Since sepsis induces a similar endothelial injury as seen in hemorrhage, we hypothesized that plasma resuscitation would increase 48-h survival in a rat sepsis model. METHODS:Adult male Sprague-Dawley rats (375-425?g) were subjected to 35% cecal ligation and puncture (CLP) (t?=?0?h). Twenty-two hours post-CLP and prior to resuscitation (t?=?22?h), animals were randomized to resuscitation with normal saline (NS, 10?cc/kg/h) or pooled rat fresh frozen plasma (FFP, 3.33?cc/kg/h). Resuscitation under general anesthesia proceeded for the next 6 h (t?=?22?h to t?=?28?h); lactate was checked every 2?h, and fluid volumes were titrated based on lactate clearance. Blood samples were obtained before (t?=?22?h) and after resuscitation (t?=?28?h), and at death or study conclusion. Lung specimens were obtained for calculation of wet-to-dry weight ratio. Fisher exact test was used to analyze the primary outcome of 48-h survival. ANOVA with repeated measures was used to analyze the effect of FFP versus NS resuscitation on blood gas, electrolytes, blood urea nitrogen (BUN), creatinine, interleukin (IL)-6, IL-10, catecholamines, and syndecan-1 (marker for endothelial injury). A two-tailed alpha level of <0.05 was used for all statistical tests. RESULTS:Thirty-three animals were studied: 14 FFP, 14 NS, and 5 sham. Post-CLP but preresuscitation (t?=?22?h) variables between FFP and NS animals were similar and significantly deranged compared with sham animals. FFP significantly increased 48-h survival compared to NS (n?=?8 [57%] vs n?=?2 [14%]), attenuated the post-resuscitation (t?=?28?h) levels of epinephrine (mean 2.2 vs 7.0?ng/mL), norepinephrine, (3.8 vs 8.9?ng/mL), IL-6 (3.8 vs 18.7?ng/mL), and syndecan-1 (21.8 vs 31.0?ng/mL) (all P?<?0.05), improved the post-resuscitation PO2 to FiO2 ratio (353 vs 151), and reduced the pulmonary wet-to-dry weight ratio (5.28 vs 5.94) (all P?<?0.05). CONCLUSION:Compared to crystalloid, plasma resuscitation increased 48-h survival in a rat sepsis model, improved pulmonary function and decreased pulmonary edema, and attenuated markers for inflammation, endothelial injury, and catecholamines.

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Osteopontin mediates Stat1 degradation to inhibit iNOS transcription in a cecal ligation and puncture model of sepsis.

Publications

Osteopontin mediates Stat1 degradation to inhibit iNOS transcription in a cecal ligation and puncture model of sepsis.

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