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Simvastatin attenuates lung vascular leak and inflammation in a murine model of radiation-induced lung injury

ABSTRACT: Background: Microvascular injury and increased vascular leakage are prominent features of the radiation-induced lung injury (RILI) which follows cancer–associated thoracic irradiation. The mechanisms of RILI are incompletely understood and therapeutic strategies to limit RILI are currently unavailable. We established a murine model of radiation pneumonitis in order to assess mechanism-based therapies for RILI-induced inflammation and vascular barrier dysfunction. Based on prior studies, we investigated the therapeutic potential of simvastatin as a vascular barrier protective agent in RILI. Methods: C57BL6/J mice receiving single dose exposure to 18, 20, 22, or 25 Gy, (n=10/group) were temporally assessed (4-12 weeks) for cellular and biochemical indices of injury present in both bronchoalveolar lavage (BAL) and lung tissues (cytokines, tyrosine nitrosylated proteins, leukocytes, extravasation of Evans blue dye or EBD, BAL albumin, histology). In specific experiments, irradiated mice (25Gy) received simvastatin (10 mg/kg) via intraperitoneal injection three times a week (pre and post irradiation) for 2- 6 weeks post irradiation. Results. Acute RILI evolved in a dose- and time-dependent fashion. Mice irradiated with 25Gy exhibited modest increases in BAL leukocytes but significant increases in BAL IL-6 (p=0.03) and TNF-a (p=0.01) at 4 weeks compared to controls. Increases in BAL nitrotyrosine content peaked at 6 weeks (p=0.03) and was accompanied by marked nitrotyrosine immunostaining in lung tissues. Indices of increase lung vascular permeability such as EBD extravasation, BAL protein and BAL albumin significantly increased over time beginning at 6 weeks (p>0.002 all) with histological evidence of severe edema formation and airway inflammation. Simvastatin- treated irradiated mice were noted to exhibit marked attenuation of vascular leak with significantly decreased BAL protein (p=0.01) and inflammatory cell infiltration (50% reduction). Conclusion: Simvastatin is a potentially important therapeutic strategy to limit RILI and may influence radiation associated morbidity and mortality. We used microarrays to detail the global programme of gene expression induced by radiation in Wild type and the protection of SIMVA

ORGANISM(S): Mus musculus

PROVIDER: GSE14431 | GEO | 2009/03/02

SECONDARY ACCESSION(S): PRJNA111761

REPOSITORIES: GEO

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Project description:Background: Microvascular injury and increased vascular leakage are prominent features of the radiation-induced lung injury (RILI) which follows cancerâ??associated thoracic irradiation. The mechanisms of RILI are incompletely understood and therapeutic strategies to limit RILI are currently unavailable. We established a murine model of radiation pneumonitis in order to assess mechanism-based therapies for RILI-induced inflammation and vascular barrier dysfunction. Based on prior studies, we investigated the therapeutic potential of simvastatin as a vascular barrier protective agent in RILI. Methods: C57BL6/J mice receiving single dose exposure to 18, 20, 22, or 25 Gy, (n=10/group) were temporally assessed (4-12 weeks) for cellular and biochemical indices of injury present in both bronchoalveolar lavage (BAL) and lung tissues (cytokines, tyrosine nitrosylated proteins, leukocytes, extravasation of Evans blue dye or EBD, BAL albumin, histology). In specific experiments, irradiated mice (25Gy) received simvastatin (10 mg/kg) via intraperitoneal injection three times a week (pre and post irradiation) for 2- 6 weeks post irradiation. Results. Acute RILI evolved in a dose- and time-dependent fashion. Mice irradiated with 25Gy exhibited modest increases in BAL leukocytes but significant increases in BAL IL-6 (p=0.03) and TNF-a (p=0.01) at 4 weeks compared to controls. Increases in BAL nitrotyrosine content peaked at 6 weeks (p=0.03) and was accompanied by marked nitrotyrosine immunostaining in lung tissues. Indices of increase lung vascular permeability such as EBD extravasation, BAL protein and BAL albumin significantly increased over time beginning at 6 weeks (p>0.002 all) with histological evidence of severe edema formation and airway inflammation. Simvastatin- treated irradiated mice were noted to exhibit marked attenuation of vascular leak with significantly decreased BAL protein (p=0.01) and inflammatory cell infiltration (50% reduction). Conclusion: Simvastatin is a potentially important therapeutic strategy to limit RILI and may influence radiation associated morbidity and mortality. We used microarrays to detail the global programme of gene expression induced by radiation in Wild type and the protection of SIMVA Experiment Overall Design: animals were treated by Vehical, Radiation (25Gy), SIMVA(10mg/kg), or both.

Project description:Clinically significant radiation-induced lung injury (RILI) is associated with significant morbidity and mortality and a common toxicity in patients administered thoracic radiotherapy. While the molecular etiology of RILI is poorly understood, we previously characterized a murine model of RILI in which alterations in lung endothelial barrier integrity surfaced as a potentially important pathobiologic event. In these studies, inhibition of HMG-CoA reductase activity (simvastatin) reduced murine RILI-associated lung inflammation and vascular leak and attenuated radiation-induced dysregulation of sphingolipid metabolic pathway genes identified by genome-wide lung gene expression profiling. In the present study, we test the hypothesis that sphingolipid signaling components serve as important modulators of RILI pathobiology and novel therapeutic targets. Sphingolipid involvement in murine RILI was confirmed by radiation-induced increases in lung expression of sphingosine kinase (SphK) isoforms 1 and 2 and increases in the ratio of ceramide to cumulative sphingosine-1-phosphate (S1P) and dihydro-S1P (DHS1P) levels in plasma, bronchoalveolar lavage (BAL) fluid and lung tissue following 25 Gy exposure (6 weeks). Moreover, genetically-engineered mice with either targeted deletion of SphK1 (SphK1-/-), or with reduced expression of selective members of the S1P receptor family (S1PR1+/-, S1PR2-/-, S1PR3-/-,), exhibited marked susceptibility to RILI-mediated lung inflammation. Finally, we assessed the efficacy of three potent vascular barrier-protective S1P analogues FTY720 (FTY), fTysiponate (fTyS) and SEW-2871 (SEW) in attenuating indices of RILI. The phosphonate analogue, fTyS, and to a lesser degree SEW, exhibited significant attenuation of RILI and RILI-induced gene dysregulation compared to control RILI-challenged mice (6 weeks). In contrast, FTY failed to significantly alter physiologic or genomic changes compared to RILI-challenged controls. Together, these results support the targeting of sphingolipid components as a novel and effective therapeutic strategy in RILI. Four mice were treated with PBS as a control. Three mice were treated with (S)-FTY-phosphonate (0.1mg/kg) as a drug control. Three mice were treated with SEW-2871 (0.1mg/kg) as a drug control. Three mice were treated with FTY720 (0.1mg/kg) as a drug control. Three mice were treated with administered radiation (25 Gy) alone. Three mice were treated with both administered radiation (25 Gy) and (S)-FTY-phosphonate (0.1mg/kg). Three mice were treated with both administered radiation (25 Gy) and SEW-2871 (0.1mg/kg). Three mice were treated with both administered radiation (25 Gy) and FTY720 (0.1mg/kg).

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Simvastatin attenuates lung vascular leak and inflammation in a murine model of radiation-induced lung injury

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