The pathogenic profile of Pseudomonas aeruginosa is related to its ability to secrete a variety of virulence factors. Quorum sensing (QS) is a mechanism wherein small diffusible molecules, specifically acyl-homoserine lactones, are produced by P. aeruginosa to promote virulence. We show here that macrophage clearance of P. aeruginosa (PAO1) is enhanced by activation of the nuclear hormone receptor peroxisome proliferator-activated receptor gamma (PPARγ). Macrophages treated with a PPARγ agonist (pioglitazone) showed enhanced phagocytosis and bacterial killing of PAO1. It is known that PAO1 QS molecules are inactivated by PON-2. QS molecules are also known to inhibit activation of PPARγ by competitively binding PPARγ receptors. In accord with this observation, we found that infection of macrophages with PAO1 inhibited expression of PPARγ and PON-2. Mechanistically, we show that PPARγ induces macrophage paraoxonase 2 (PON-2), an enzyme that degrades QS molecules produced by P. aeruginosa. Gene silencing studies confirmed that enhanced clearance of PAO1 in macrophages by PPARγ is PON-2 dependent. Further, we show that PPARγ agonists also enhance clearance of P. aeruginosa from lungs of mice infected with PAO1. Together, these data demonstrate that P. aeruginosa impairs the ability of host cells to mount an immune response by inhibiting PPARγ through secretion of QS molecules. These studies define a novel mechanism by which PPARγ contributes to the host immunoprotective effects during bacterial infection and suggest a role for PPARγ immunotherapy for P. aeruginosa infections.
Vitamin D deficiency is highly prevalent in children and adults with cystic fibrosis (CF). Recent studies have found an association between vitamin D status and risk of pulmonary exacerbations in children and adults with CF. The ongoing Vitamin D for enhancing the Immune System in Cystic fibrosis (DISC) study, a multi-center, double-blind, randomized, placebo-controlled trial, will test the hypothesis of whether high dose vitamin D given as a single oral bolus of 250,000 IU to adults with CF during a pulmonary exacerbation followed by a maintenance dose of vitamin D will improve time to next pulmonary exacerbation and re-hospitalization, improve survival and lung function compared to placebo and reduce the rates of pulmonary exacerbation. Subjects will be randomized 1:1 at each clinical site to vitamin D or placebo within 72 h of hospital admission for pulmonary exacerbation. Clinical follow-up visits will occur at 1, 2, 3, and 7 days, and 1, 3, 6 and 12 months after randomization. Blood and sputum will be collected and determination of clinical outcomes will be assessed at each visit. The primary endpoint will be the time to next pulmonary exacerbation requiring antibiotics, re-hospitalization or death. The secondary endpoints will include lung function assessed by forced expiratory volume in 1 s (FEV 1 ), blood markers of inflammatory cytokines, anti-microbial peptide expression by peripheral blood mononuclear cells and circulating concentrations in blood. Other exploratory endpoints will examine the phenotype of neutrophils and monocyte/macrophages in sputum. Nutritional status will be assessed by 3 day food records and food frequency questionnaire.
Background Cystic fibrosis (CF) is a chronic catabolic disease often requiring hospitalization for acute episodes of worsening pulmonary exacerbations. Limited data suggest that vitamin D may have beneficial clinical effects, but the impact of vitamin D on systemic metabolism in this setting is unknown. Objective We used high-resolution metabolomics (HRM) to assess the impact of baseline vitamin D status and high-dose vitamin D 3 administration on systemic metabolism in adults with CF with an acute pulmonary exacerbation. Design Twenty-five hospitalized adults with CF were enrolled in a randomized trial of high-dose vitamin D 3 (250,000 IU vitamin D 3 bolus) versus placebo. Age-matched healthy subjects served as a reference group for baseline comparisons. Plasma was analyzed with liquid chromatography/ultra-high resolution mass spectrometry. Using recent HRM bioinformatics and metabolic pathway enrichment methods, we examined associations with baseline vitamin D status (sufficient vs. deficient per serum 25-hydroxyvitamin D concentrations) and the 7-day response to vitamin D 3 supplementation. Results Several amino acids and lipid metabolites differed between CF and healthy control subjects, indicative of an overall catabolic state. In CF subjects, 343 metabolites differed (P < 0.05) by baseline vitamin D status and were enriched within 7 metabolic pathways including fatty acid, amino acid, and carbohydrate metabolism. A total of 316 metabolites, which showed enrichment for 15 metabolic pathways—predominantly representing amino acid pathways—differed between the vitamin D 3 - and placebo-treated CF subjects over time (P < 0.05). In the placebo group, several tricarboxylic acid cycle intermediates increased while several amino acid-related metabolites decreased; in contrast, little change in these metabolites occurred with vitamin D 3 treatment. Conclusions Numerous metabolic pathways detected by HRM varied in association with vitamin D status and high-dose vitamin D 3 supplementation in adults with CF experiencing a pulmonary exacerbation. Overall, these pilot data suggest an anti-catabolic effect of high-dose vitamin D 3 in this clinical setting.
by
Ignacio Sanz;
Rabindra Tirouvanziam;
Mary Galinski;
Hao Wu;
Dean Jones;
Eberhard Voit;
Frances Lee;
C. Moreno;
Shuzhao Li;
Jan Pohl;
David Anderson;
CJ Joyner;
CFA Brito;
CL Saney;
RJ Cordy;
ML Smith;
SA Lapp;
M Cabrera-Mora;
S Kyu;
N Lackman;
M Nural;
JD DeBarry;
JC Kissinger;
MP Styczynski;
TJ Lamb;
C Ibegbu;
SE Bosinger;
A Garcia;
AK Stout;
J Jiang;
A Hankus;
S Soderberg;
JB Gutierrez;
J-T Chien;
SB Pakala;
M Nural;
J Humphrey;
N Lackman;
LL Fonseca;
Y Tang;
JW Barnwell;
A Kong;
D Nace;
GK Tharp;
MS Peterson;
EVS Meyer