Particulate matter air pollution causes oxidant-mediated increase in gut permeability in mice

<p>Abstract</p> <p>Background</p> <p>Exposure to particulate matter (PM) air pollution may be an important environmental factor leading to exacerbations of inflammatory illnesses in the GI tract. PM can gain access to the gastrointestinal (GI) tract via swallowing of air or secretions from the upper airways or mucociliary clearance of inhaled particles.</p> <p>Methods</p> <p>We measured PM-induced cell death and mitochondrial ROS generation in Caco-2 cells stably expressing oxidant sensitive GFP localized to mitochondria in the absence or presence of an antioxidant. C57BL/6 mice were exposed to a very high dose of urban PM from Washington, DC (200 μg/mouse) or saline via gastric gavage and small bowel and colonic tissue were harvested for histologic evaluation, and RNA isolation up to 48 hours. Permeability to 4kD dextran was measured at 48 hours.</p> <p>Results</p> <p>PM induced mitochondrial ROS generation and cell death in Caco-2 cells. PM also caused oxidant-dependent NF-κB activation, disruption of tight junctions and increased permeability of Caco-2 monolayers. Mice exposed to PM had increased intestinal permeability compared with PBS treated mice. In the small bowel, colocalization of the tight junction protein, ZO-1 was lower in the PM treated animals. In the small bowel and colon, PM exposed mice had higher levels of IL-6 mRNA and reduced levels of ZO-1 mRNA. Increased apoptosis was observed in the colon of PM exposed mice.</p> <p>Conclusions</p> <p>Exposure to high doses of urban PM causes oxidant dependent GI epithelial cell death, disruption of tight junction proteins, inflammation and increased permeability in the gut <it>in vitro </it>and <it>in vivo</it>. These PM-induced changes may contribute to exacerbations of inflammatory disorders of the gut.</p

Particulate Matter-Induced Lung Inflammation Increases Systemic Levels of PAI-1 and Activates Coagulation Through Distinct Mechanisms

Exposure of human populations to ambient particulate matter (PM) air pollution significantly contributes to the mortality attributable to ischemic cardiovascular events. We reported that mice treated with intratracheally instilled PM develop a prothrombotic state that requires the release of IL-6 by alveolar macrophages. We sought to determine whether exposure of mice to PM increases the levels of PAI-1, a major regulator of thrombolysis, via a similar or distinct mechanism. mice but was absent in mice treated with etanercept, a TNF-α inhibitor. Treatment with etanercept did not prevent the PM-induced tendency toward thrombus formation.Mice exposed to inhaled PM exhibited a TNF-α-dependent increase in PAI-1 and an IL-6-dependent activation of coagulation. These results suggest that multiple mechanisms link PM-induced lung inflammation with the development of a prothrombotic state

Impaired clearance of influenza A virus in obese, leptin receptor deficient mice is independent of leptin signaling in the lung epithelium and macrophages.

During the recent H1N1 outbreak, obese patients had worsened lung injury and increased mortality. We used a murine model of influenza A pneumonia to test the hypothesis that leptin receptor deficiency might explain the enhanced mortality in obese patients.We infected wild-type, obese mice globally deficient in the leptin receptor (db/db) and non-obese mice with tissue specific deletion of the leptin receptor in the lung epithelium (SPC-Cre/LepR fl/fl) or macrophages and alveolar type II cells (LysM-Cre/Lepr fl/fl) with influenza A virus (A/WSN/33 [H1N1]) (500 and 1500 pfu/mouse) and measured mortality, viral clearance and several markers of lung injury severity.The clearance of influenza A virus from the lungs of mice was impaired in obese mice globally deficient in the leptin receptor (db/db) compared to normal weight wild-type mice. In contrast, non-obese, SP-C-Cre+/+/LepR fl/fl and LysM-Cre+/+/LepR fl/fl had improved viral clearance after influenza A infection. In obese mice, mortality was increased compared with wild-type mice, while the SP-C-Cre+/+/LepR fl/fl and LysM-Cre+/+/LepR fl/fl mice exhibited improved survival.Global loss of the leptin receptor results in reduced viral clearance and worse outcomes following influenza A infection. These findings are not the result of the loss of leptin signaling in lung epithelial cells or macrophages. Our results suggest that factors associated with obesity or with leptin signaling in non-myeloid populations such as natural killer and T cells may be associated with worsened outcomes following influenza A infection

<i>HIF-1α</i> is required for disturbed flow-induced metabolic reprogramming in human and porcine vascular endothelium

Hemodynamic forces regulate vascular functions. Disturbed flow (DF) occurs in arterial bifurcations and curvatures, activates endothelial cells (ECs), and results in vascular inflammation and ultimately atherosclerosis. However, how DF alters EC metabolism, and whether resulting metabolic changes induce EC activation, is unknown. Using transcriptomics and bioenergetic analysis, we discovered that DF induces glycolysis and reduces mitochondrial respiratory capacity in human aortic ECs. DF-induced metabolic reprogramming required hypoxia inducible factor-1α (HIF-1α), downstream of NAD(P)H oxidase-4 (NOX4)-derived reactive oxygen species (ROS). HIF-1α increased glycolytic enzymes and pyruvate dehydrogenase kinase-1 (PDK-1), which reduces mitochondrial respiratory capacity. Swine aortic arch endothelia exhibited elevated ROS, NOX4, HIF-1α, and glycolytic enzyme and PDK1 expression, suggesting that DF leads to metabolic reprogramming in vivo. Inhibition of glycolysis reduced inflammation suggesting a causal relationship between flow-induced metabolic changes and EC activation. These findings highlight a previously uncharacterized role for flow-induced metabolic reprogramming and inflammation in ECs

Effect of the leptin receptor function specifically within lung epithelium and within macrophages and neutrophils on survival, lung injury, and inflammation during influenza A infection.

<p><b>(a)</b> Representative images and <b>(b)</b> weights of <i>db/db</i>, <i>LepR^fl/fl</i>, <i>SP-C-Cre^+/+/LepR^fl/fl</i>, and <i>LysM-Cre^+/+/LepR^fl</i>^/fl mice are shown. Quantitative real-time PCR reveals appropriate knockout of the leptin receptor <b>(c)</b> within the macrophages in <i>LysM-Cre^+/+/LepR^fl</i>^/fl mice and <b>(d)</b> within the lung epithelium in <i>SP-C-Cre^+/+/LepR^fl/fl</i> mice. <i>LepR^fl/fl</i>, <i>SP-C-Cre^+/+/LepR^fl/fl</i>, and <i>LysM-Cre^+/+/LepR^fl</i>^/fl mice were inoculated with influenza A virus (500 pfu/mouse) with assessment of <b>(e)</b> mortality and <b>(f)</b> daily weight. Four days after infection with influenza A virus (500 pfu/mouse), <i>LepR^fl/fl</i>, <i>SP-C-Cre^+/+/LepR^fl/fl</i>, and <i>LysM-Cre^+/+/LepR^fl</i>^/fl mice underwent bronchoalveolar lavage for levels of <b>(g)</b> cell count, <b>(h)</b> total protein, <b>(i–k)</b> inflammatory cytokines and <b>(l)</b> lung pathology (Hematoxylin and Eosin staining).</p

Effect of leptin receptor function specifically within lung epithelium and within macrophages and neutrophils on viral replication.

<p>Plaque forming units (pfu) were counted in MDCK cells treated with lung homogenates from <i>LepR^fl/fl</i>, <i>SP-C-Cre^+/+/LepR^fl/fl</i>, and <i>LysM-Cre^+/+/LepR^fl</i>^/fl mice infected with Influenza A virus 500 pfu/mouse on Day 2 and Day 4. * p<0.05 <i>LysM-Cre^+/+/LepR^fl</i>^/fl and <i>SP-C-Cre^+/+/LepR^fl/fl</i> mice compared to <i>LepR^fl/fl</i> mice.</p

Effect of leptin receptor function on the survival, the degree of lung injury and inflammation during influenza A infection.

<p><i>db/db</i> and C57BL/6 mice were inoculated with influenza A virus (A/WSN/33 [H1N1]) <b>(a)</b> 1500 pfu/mouse or <b>(b)</b> 500 pfu/mouse and mortality was subsequently assessed on a daily basis. Percentage of weight loss was also followed daily for the mice infected with <b>(c)</b> 1500 pfu/mouse or <b>(d)</b> 500 pfu/mouse. Four days after infection with influenza A virus 1500 pfu/mouse, <i>db/db</i> and C57BL/6 mice underwent a bronchoalveolar lavage for <b>(e</b>) assessment of cell count, <b>(f)</b> total protein, <b>(g,h)</b> inflammatory cytokines, <b>(i)</b> flow cytometry, and <b>(j)</b> the assessment of lung pathology (Hematoxylin and Eosin staining). * p<0.05 compared to PBS control. ** p<0.05 <i>db/db</i> compared to wild-type mice.</p