Macrophage NOX2 NADPH oxidase maintains alveolar homeostasis in mice.

The leukocyte NADPH oxidase 2 (NOX2) plays a key role in pathogen killing and immunoregulation. Genetic defects in NOX2 result in chronic granulomatous disease (CGD), associated with microbial infections and inflammatory disorders, often involving the lung. Alveolar macrophages (AMs) are the predominant immune cell in the airways at steady state, and limiting their activation is important, given the constant exposure to inhaled materials, yet the importance of NOX2 in this process is not well understood. In this study, we showed a previously undescribed role for NOX2 in maintaining lung homeostasis by suppressing AM activation, in CGD mice or mice with selective loss of NOX2 preferentially in macrophages. AMs lacking NOX2 had increased cytokine responses to Toll-like receptor-2 (TLR2) and TLR4 stimulation ex vivo. Moreover, between 4 and 12 week of age, mice with global NOX2 deletion developed an activated CD11bhigh subset of AMs with epigenetic and transcriptional profiles reflecting immune activation compared with WT AMs. The presence of CD11bhigh AMs in CGD mice correlated with an increased number of alveolar neutrophils and proinflammatory cytokines at steady state and increased lung inflammation after insults. Moreover, deletion of NOX2 preferentially in macrophages was sufficient for mice to develop an activated CD11bhigh AM subset and accompanying proinflammatory sequelae. In addition, we showed that the altered resident macrophage transcriptional profile in the absence of NOX2 is tissue specific, as those changes were not seen in resident peritoneal macrophages. Thus, these data demonstrate that the absence of NOX2 in alveolar macrophages leads to their proinflammatory remodeling and dysregulates alveolar homeostasis.

Cutting Edge: NOX2 NADPH Oxidase Controls Infection by an Intracellular Bacterial Pathogen through Limiting the Type 1 IFN Response.

The NOX2 NADPH oxidase (NOX2) produces reactive oxygen species to kill phagosome-confined bacteria. However, we previously showed that Listeria monocytogenes is able to avoid the NOX2 activity in phagosomes and escape to the cytosol. Thus, despite the established role of NOX2 limiting L. monocytogenes infection in mice, the underlying mechanisms of this antibacterial activity remain unclear. In this article, we report that NOX2 controls systemic L. monocytogenes spread through modulation of the type I IFN response, which is known to be exploited by L. monocytogenes during infection. NOX2 deficiency results in increased expression of IFN-stimulated genes in response to type I IFN and leads to 1) promotion of cell-to-cell spread by L. monocytogenes, 2) defective leukocyte recruitment to infection foci, and 3) production of anti-inflammatory effectors IL-10 and thioredoxin 1. Our findings report a novel antimicrobial role for NOX2 through modulation of type I IFN responses to control bacterial dissemination.

Argentinean Puna Plants with In Vitro Antioxidant and Anti-Inflammatory Activities as a Potential Nutraceutical.

Parastrephia lucida (Compositae), Tessaria absinthioides (Compositae), and Ephedra multiflora (Ephedraceae), three plant species from the Argentinean Puna (3600 m.a.s.l.) were selected for their anti-inflammatory and antioxidant properties to prepare mixtures to evaluate their use as nutraceuticals. Seven binary and ternary herbal mixtures made of ethanol 20% extracts of the selected plant species were prepared (Mixtures A to G), and they were analyzed for their effect on proinflammatory enzymes and their antioxidant activity in two cellular systems and in cell free systems. Toxicity tests were also carried out, and they were analyzed by high-performance liquid chromatography with a diode-array detector (HPLC-DAD) to quantify chemical markers. Mix A (equal parts of the three selected plant species) showed an important inhibitory capacity of different proinflammatory enzymes. Its potency on COX-2 was also higher than that of ibuprofen. Mix A and Mix G (P. lucida and T. absinthioides 1:1) showed a high antioxidant capacity in cellular and in cell-free systems. Toxicity assays further demonstrated their safety. This work shows the potential use of herbal mixtures made of medicinal plant species from the Argentinean Puna as nutraceutical or dietary supplements with antioxidant and anti-inflammatory activities. PRACTICAL APPLICATION: P. lucida, T. absinthioides, and E. multiflora are three plant species that are commonly used by Argentinean Puna inhabitants with medicinal purposes. Their proven safety, their antioxidant activity as well as their capacity to inhibit different proinflammatory enzymes make them attractive candidates to be used in combination as part of a dietary supplement aimed to prevent or palliate gastrointestinal and systemic inflammatory diseases. The use of native plant species as an alternative to more common and commercial plant species would have a positive impact on local communities' economies.

Mammalian Target of Rapamycin Inhibition in Trypanosoma cruzi-Infected Macrophages Leads to an Intracellular Profile That Is Detrimental for Infection.

The causative agent of Chagas' disease, Trypanosoma cruzi, affects approximately 10 million people living mainly in Latin America, with macrophages being one of the first cellular actors confronting the invasion during T. cruzi infection and their function depending on their proper activation and polarization into distinct M1 and M2 subtypes. Macrophage polarization is thought to be regulated not only by cytokines and growth factors but also by environmental signals. The metabolic checkpoint kinase mammalian target of rapamycin (mTOR)-mediated sensing of environmental and metabolic cues influences macrophage polarization in a complex and as of yet incompletely understood manner. Here, we studied the role of the mTOR pathway in macrophages during T. cruzi infection. We demonstrated that the parasite activated mTOR, which was beneficial for its replication since inhibition of mTOR in macrophages by different inhibitors decreased parasite replication. Moreover, in rapamycin pretreated and infected macrophages, we observed a decreased arginase activity and expression, reduced IL-10 and increased interleukin-12 production, compared to control infected macrophages treated with DMSO. Surprisingly, we also found a reduced iNOS activity and expression in these macrophages. Therefore, we investigated possible alternative mechanisms involved in controlling parasite replication in rapamycin pretreated and infected macrophages. Although, cytoplasmic ROS and the enzyme indoleamine 2, 3-dioxygenase (IDO) were not involved, we observed a significant increase in IL-6, TNF-α, and IL-1ß production. Taking into account that IL-1ß is produced by activation of the cytoplasmic receptor NLRP3, which is one of the main components of the inflammasome, we evaluated NLRP3 expression during mTOR inhibition and T. cruzi infection. We observed that rapamycin-pretreated and infected macrophages showed a significant increase in NLRP3 expression and produced higher levels of mitochondrial ROS (mtROS) compared with control cells. Moreover, inhibition of mtROS production partially reversed the effect of rapamycin on parasite replication, with there being a significant increase in parasite load in rapamycin pretreated and infected macrophages from NLRP3 KO mice compared to wild-type control cells. Our findings strongly suggest that mTOR inhibition during T. cruzi infection induces NLRP3 inflammasome activation and mtROS production, resulting in an inflammatory-like macrophage profile that controls T. cruzi replication.