Xanthine oxidoreductase promotes the inflammatory state of mononuclear phagocytes through effects on chemokine expression, peroxisome proliferator-activated receptor-{gamma} sumoylation, and HIF-1{alpha}.

The protective effects of pharmacological inhibitors of xanthine oxidoreductase (XOR) have implicated XOR in many inflammatory diseases. Nonetheless, the role played by XOR during inflammation is poorly understood. We previously observed that inhibition of XOR within the inflammatory mononuclear phagocytes (MNP) prevented neutrophil recruitment during adoptive transfer demonstrating the role of XOR in MNP-mediated neutrophil recruitment. To further explore the role of XOR in the inflammatory state of MNP, we studied MNP isolated from inflammatory lungs combined with analyses of MNP cell lines. We demonstrated that XOR activity was increased in inflammatory MNP following insufflation of Th-1 cytokines in vivo and that activity was specifically increased by MNP differentiation. Inhibition of XOR reduced levels of CINC-1 secreted by MNP. Expression of peroxisome proliferator-activated receptor γ (PPARγ) in purified rat lung MNP and MNP cell lines reflected both the presence of PPARγ isoforms and PPARγ SUMOylation, and XOR inhibitors increased levels of SUMO-PPARγ in MNP cell lines. Both ectopic overexpression of XOR cDNA and uric acid supplementation reduced SUMO-PPARγ in MNP cells. Levels of the M2 markers CD36, CD206, and arginase-1 were modulated by uric acid and oxonic acid, whereas siRNA to SUMO-1 or PIAS-1 also reduced arginase-1 in RAW264.7 cells. We also observed that HIF-1α was increased by XOR inhibitors in inflammatory MNP and in MNP cell lines. These data demonstrate that XOR promotes the inflammatory state of MNP through effects on chemokine expression, PPARγ SUMOylation, and HIF-1α and suggest that strategies for inhibiting XOR may be valuable in modulating lung inflammatory disorders.

Effect of ergothioneine on acute lung injury and inflammation in cytokine insufflated rats.

OBJECTIVE: The Acute Respiratory Distress Syndrome (ARDS), the most severe form of Acute Lung Injury (ALI), is a highly-fatal, diffuse non-cardiogenic edematous lung disorder. The pathogenesis of ARDS is unknown but lung inflammation and lung oxidative stress are likely contributing factors. Since no specific pharmacologic intervention exists for ARDS, our objective was to determine the effect of treatment with ergothioneine-a safe agent with multiple anti-inflammatory and antioxidant properties on the development of lung injury and inflammation in rats insufflated with cytokines found in lung lavages of ARDS patients. METHOD: Sprague-Dawley rats (3-10/group) were given 15 mg/kg or 150 mg/kg l-ergothioneine intravenously 1h before or 18 h after cytokine (IL-1 and IFNγ) insufflation. Lung injury (lavage LDH levels) and lung inflammation (lavage neutrophil numbers) were measured 24h after cytokine insufflation. RESULTS: Ergothioneine pre- and post-treatment generally decreased lung injury and lung inflammation in cytokine insufflated rats. CONCLUSION: Ergothioneine should be considered for additional testing as a potential therapy for treating and preventing ARDS.

Preventing the acute respiratory distress syndrome.

Laudable supportive advances have been made to improve the care of patients with the Acute Respiratory Distress Syndrome (ARDS) but no pharmacologic interventions are known to reduce the high mortality of this disorder once it is established. This commentary discusses some of the challenges that arise in preventing ARDS in at-risk individuals and the likely dependence of this approach on biomarker panels that can be done in real time.

Early increase in alveolar macrophage prostaglandin 15d-PGJ2 precedes neutrophil recruitment into lungs of cytokine-insufflated rats.

Early detection and prevention is an important goal in acute respiratory distress syndrome research. We determined the concentration of the anti-inflammatory 15-deoxy-Δ(12,14)-prostaglandin-J2 (15d-PGJ2) and other components of the cyclopentenone prostaglandin cascade in relation to lung inflammation in cytokine (IL-1/LPS)-insufflated rats. We found that 15d-PGJ2 levels increase in the bronchoalveolar lavage (BAL) fluid of rats insufflated with cytokines 2 h before. BAL 15d-PGJ2 increases preceded neutrophil recruitment, lung injury, and oxidative stress in the lungs of cytokine-insufflated rats. 15d-PGJ2 was localized in alveolar macrophages that decreased following cytokine insufflation. 15d-PGJ2 may constitute an early biomarker of lung inflammation and may reflect an endogenous attempt to regulate ongoing inflammation in macrophages and elsewhere after cytokine insufflation.

Hyperpolarized 83Kr MRI of lungs.

Hyperpolarized (hp) (83)Kr (spin I=9/2) is a promising gas-phase contrast agent that displays sensitivity to the surface chemistry, surface-to-volume ratio, and surface temperature of the surrounding environment. This proof-of-principle study demonstrates the feasibility of ex vivo hp (83)Kr magnetic resonance imaging (MRI) of lungs using natural abundance krypton gas (11.5% (83)Kr) and excised, but otherwise intact, rat lungs located within a custom designed ventilation chamber. Experiments comparing the (83)Kr MR signal intensity from lungs to that arising from a balloon with no internal structure inflated to the same volume with krypton gas mixture suggest that most of the observed signal originated from the alveoli and not merely the conducting airways. The (83)Kr longitudinal relaxation times in the rat lungs ranged from 0.7 to 3.7s but were reproducible for a given lung. Although the source of these variations was not explored in this work, hp (83)Kr T(1) differences may ultimately lead to a novel form of MRI contrast in lungs. The currently obtained 1200-fold signal enhancement for hp (83)Kr at 9.4T field strength is found to be 180 times below the theoretical upper limit.

Mononuclear phagocyte xanthine oxidoreductase contributes to cytokine-induced acute lung injury.

Acute lung injury (ALI) is characterized by increased alveolar cytokines, inflammatory cell infiltration, oxidative stress, and alveolar cell apoptosis. Previous work suggested that xanthine oxidoreductase (XOR) may contribute to oxidative stress in ALI as a product of the vascular endothelial cell. We present evidence that cytokine induced lung inflammation and injury involves activation of XOR in the newly recruited mononuclear phagocytes (MNP). We found that XOR was increased predominantly in the MNP that increase rapidly in the lungs of rats that develop ALI following intratracheal cytokine insufflation. XOR was recovered from the MNP largely converted to its oxygen radical generating, reversible O-form, and alveolar MNP exhibited increased oxidative stress as evidenced by increased nitrotyrosine staining. Cytokine insufflation also increased alveolar cell apoptosis. A functional role for XOR in cytokine-induced inflammation was demonstrated when feeding rats two different XOR inhibitors, tungsten and allopurinol, decreased MNP XOR induction, nitrotyrosine staining, inflammatory cell infiltration, and alveolar cell apoptosis. Transfer of control or allopurinol treated MNP into rat lungs confirmed a specific role for MNP XOR in promoting lung inflammation. These data indicate that XOR can contribute to lung inflammation by its expression and conversion in a highly mobile inflammatory cell population.