Harvesting murine alveolar macrophages and evaluating cellular activation induced by polyanhydride nanoparticles

Coevolution of furA-Regulated Hyper-Inflammation and Mycobacterial Resistance to Oxidative Killing through Adaptation to Hydrogen Peroxide

Mycobacterium tuberculosis (Mtb) is highly resistant to host oxidative killing. We hypothesized that the evolutionary adaptation of M. smegmatis to hydrogen peroxide (H2O2) would endow the nonpathogenic Mycobacterium persistent in a host. In the study, we screened a highly H2O2-resistant strain (mc2114) via evolutionary H2O2 adaptation in vitro. The MIC of mc2114 to H2O2 is 320 times that of wild-type mc2155. Mouse infection experiments showed that mc2114, similar to Mtb, was persistent in the lungs and caused high lethality in mice with restricted responses of NOX2, ROS, IFN-γ, decreased macrophage apoptosis, and overexpressed inflammatory cytokines in the lungs. Whole-genome sequencing analysis revealed that mc2114 harbored 29 single nucleotide polymorphisms in multiple genes; one of them was on the furA gene that caused FurA deficiency-mediated overexpression of KatG, a catalase-peroxidase to detoxify ROS. Complementation of mc2114 with a wild-type furA gene reversed lethality and hyper-inflammatory response in mice with rescued overexpression of KatG and inflammatory cytokines, whereas NOX2, ROS, IFN-γ, and macrophage apoptosis remained reduced. The results indicate that although FurA regulates KatG expression, it does not contribute significantly to the restriction of ROS response. Instead, FurA deficiency is responsible for the detrimental pulmonary inflammation that contributes to the severity of the infection, a previously nonrecognized function of FurA in mycobacterial pathogenesis. The study also indicates that mycobacterial resistance to oxidative burst results from complex mechanisms involving adaptive genetic changes in multiple genes. IMPORTANCE Mycobacterium tuberculosis (Mtb) causes human tuberculosis (TB), which has killed more people in human history than any other microorganism. However, the mechanisms underlying Mtb pathogenesis and related genes have not yet been fully elucidated, which impedes the development of effective strategies for containing and eradicating TB. In the study, we generated a mutant of M. smegmatis (mc2114) with multiple mutations by an adaptive evolutionary screen with H2O2. One of the mutations in furA caused a deficiency of FurA, which mediated severe inflammatory lung injury and higher lethality in mice by overexpression of inflammatory cytokines. Our results indicate that FurA-regulated pulmonary inflammation plays a critical role in mycobacterial pathogenesis in addition to the known downregulation of NOX2, ROS, IFN-γ responses, and macrophage apoptosis. Further analysis of the mutations in mc2114 would identify more genes related to the increased pathogenicity and help in devising new strategies for containing and eradicating TB.

Downregulation of calponin 2 contributes to the quiescence of lung macrophages

Calponin 2 is an actin cytoskeleton-associated regulatory protein that inhibits the activity of myosin-ATPase and cytoskeleton dynamics. Recent studies have demonstrated that deletion of calponin 2 restricts the proinflammatory activation of macrophages in atherosclerosis and arthritis to attenuate the disease progression in mice. Here we demonstrate that the levels of calponin 2 vary among different macrophage populations, which may reflect their adaptation to specific tissue microenvironment corresponding to specific functional states. Interestingly, lung resident macrophages express significantly lower calponin 2 than peritoneal resident macrophages, which correlates with decreased substrate adhesion and reduced expression of proinflammatory cytokines and a proresolution phenotype. Deletion of calponin 2 in peritoneal macrophages also decreased substrate adhesion and downregulated the expression of proinflammatory cytokines. Providing the first line of defense against microbial invasion while receiving constant exposure to extrinsic antigens, lung macrophages need to maintain a necessary level of activity while limiting exaggerated inflammatory reaction. Therefore, their low level of calponin 2 may reflect an important physiological adaption. Downregulation of calponin 2 in macrophages may be targeted as a cytoskeleton-based novel mechanism, possibly via endoplasmic reticulum stress altering the processing and secretion of cytokines, to regulate immune response and promote quiescence for the treatment of inflammatory diseases.

A critical role for ABC transporters in persistent lung inflammation in the development of emphysema after smoke exposure

Macrophage infiltration is common to both emphysema and atherosclerosis, and cigarette smoke down-regulates the macrophage cholesterol efflux transporter ATP binding cassette (ABC)A1. This decreased cholesterol efflux results in lipid-laden macrophages. We hypothesize that cigarette smoke adversely affects cholesterol transport via an ABCA1-dependent mechanism in macrophages, enhancing TLR4/myeloid differentiation primary response gene 88 (Myd88) signaling and resulting in matrix metalloproteinase (MMP) up-regulation and exacerbation of pulmonary inflammation. ABCA1 is significantly down-regulated in the lung upon smoke exposure conditions. Macrophages exposed to cigarette smoke in vivo and in vitro exhibit impaired cholesterol efflux correlating with significantly decreased ABCA1 expression, up-regulation of the TLR4/Myd88 pathway, and downstream MMP-9 and MMP-13 expression. Treatment with liver X receptor (LXR) agonist restores ABCA1 expression after short-term smoke exposure and attenuates the inflammatory response; after long-term smoke exposure, there is also attenuated physiologic and morphologic changes of emphysema. In vitro, treatment with LXR agonist decreases macrophage inflammatory activation in wild-type but not ABCA1 knockout mice, suggesting an ABCA1-dependent mechanism of action. These studies demonstrate an important association between cigarette smoke exposure and cholesterol-mediated pathways in the macrophage inflammatory response. Modulation of these pathways through manipulation of ABCA1 activity effectively blocks cigarette smoke-induced inflammation and provides a potential novel therapeutic approach for the treatment of chronic obstructive pulmonary disease.-Sonett, J., Goldklang, M., Sklepkiewicz, P., Gerber, A., Trischler, J., Zelonina, T., Westerterp, M., Lemaître, V., Okada, V., D'Armiento, J. A critical role for ABC transporters in persistent lung inflammation in the development of emphysema after smoke exposure.

Soluble mucus component CLCA1 modulates expression of leukotactic cytokines and BPIFA1 in murine alveolar macrophages but not in bone marrow-derived macrophages

The secreted airway mucus cell protein chloride channel regulator, calcium-activated 1, CLCA1, plays a role in inflammatory respiratory diseases via as yet unidentified pathways. For example, deficiency of CLCA1 in a mouse model of acute pneumonia resulted in reduced cytokine expression with less leukocyte recruitment and the human CLCA1 was shown to be capable of activating macrophages in vitro. Translation of experimental data between human and mouse models has proven problematic due to several CLCA species-specific differences. We therefore characterized activation of macrophages by CLCA1 in detail in solely murine ex vivo and in vitro models. Only alveolar but not bone marrow-derived macrophages freshly isolated from C57BL6/J mice increased their expression levels of several pro-inflammatory and leukotactic cytokines upon CLCA1 stimulation. Among the most strongly regulated genes, we identified the host-protective and immunomodulatory airway mucus component BPIFA1, previously unknown to be expressed by airway macrophages. Furthermore, evidence from an in vivo Staphylococcus aureus pneumonia mouse model suggests that CLCA1 may also modify BPIFA1 expression in airway epithelial cells. Our data underscore and specify the role of mouse CLCA1 in inflammatory airway disease to activate airway macrophages. In addition to its ability to upregulate cytokine expression which explains previous observations in the Clca1-deficient S. aureus pneumonia mouse model, modulation of BPIFA1 expression expands the role of CLCA1 in airway disease to involvement in more complex downstream pathways, possibly including liquid homeostasis, airway protection, and antimicrobial defense.

Effect of anti-podoplanin antibody administration during lipopolysaccharide-induced lung injury in mice

Introduction

Acute respiratory distress syndrome (ARDS) is a devastating pulmonary condition in the critically ill patient. A therapeutic intervention is yet to be found that can prevent progression to ARDS. We recently demonstrated that the interaction between podoplanin expressed on inflammatory alveolar macrophages (iAMs) and its endogenous ligand, platelet C-type lectin-like 2 (CLEC-2), protects against exaggerated lung inflammation during a mouse model of ARDS. In this study, we aim to investigate the therapeutic use of a crosslinking/activating anti-podoplanin antibody (α-PDPN, clone 8.1.1) during lipopolysaccharide (LPS)-induced lung inflammation in mice.

Methods

Intravenous administration of α-PDPN was performed 6 hours after intratracheal LPS in wildtype, C57Bl/6 mice. Lung function decline was measured by pulse oximetry as well as markers of local inflammation including bronchoalveolar lavage neutrophilia and cytokine/chemokine expression. In parallel, alveolar macrophages were isolated and cultured in vitro from haematopoietic-specific podoplanin-deficient mice (Pdpn^fl/flVAV1cre⁺) and floxed-only controls treated with or without LPS in the presence or absence of α-PDPN.

Results

Lung function decline as well as alveolar neutrophil recruitment was significantly decreased in mice treated with the crosslinking/activating α-PDPN in vivo. Furthermore, we demonstrate that, in vitro, activation of podoplanin on iAMs regulates their secretion of proinflammatory cytokines and chemokines.

Conclusions

These data confirm the importance of the CLEC-2–podoplanin pathway during intratracheal (IT)-LPS and demonstrate the beneficial effect of targeting podoplanin during IT-LPS in mice possibly via modulation of local cytokine/chemokine expression. Moreover, these data suggest that podoplanin-targeted therapies may have a beneficial effect in patients at risk of developing ARDS.

Transintestinal transport of the anti-inflammatory drug 4F and the modulation of transintestinal cholesterol efflux

The site and mechanism of action of the apoA-I mimetic peptide 4F are incompletely understood. Transintestinal cholesterol efflux (TICE) is a process involved in the clearance of excess cholesterol from the body. While TICE is responsible for at least 30% of the clearance of neutral sterols from the circulation into the intestinal lumen, few pharmacological agents have been identified that modulate this pathway. We show first that circulating 4F selectively targets the small intestine (SI) and that it is predominantly transported into the intestinal lumen. This transport of 4F into the SI lumen is transintestinal in nature, and it is modulated by TICE. We also show that circulating 4F increases reverse cholesterol transport from macrophages and cholesterol efflux from lipoproteins via the TICE pathway. We identify the cause of this modulation of TICE either as 4F being a cholesterol acceptor with respect to enterocytes, from which 4F enhances cholesterol efflux, or as 4F being an intestinal chaperone with respect to TICE. Our results assign a novel role for 4F as a modulator of the TICE pathway and suggest that the anti-inflammatory functions of 4F may be a partial consequence of the codependent intestinal transport of both 4F and cholesterol.

Hemagglutinin-based polyanhydride nanovaccines against H5N1 influenza elicit protective virus neutralizing titers and cell-mediated immunity

H5N1 avian influenza is a significant global concern with the potential to become the next pandemic threat. Recombinant subunit vaccines are an attractive alternative for pandemic vaccines compared to traditional vaccine technologies. In particular, polyanhydride nanoparticles encapsulating subunit proteins have been shown to enhance humoral and cell-mediated immunity and provide protection upon lethal challenge. In this work, a recombinant H5 hemagglutinin trimer (H5₃) was produced and encapsulated into polyanhydride nanoparticles. The studies performed indicated that the recombinant H5₃ antigen was a robust immunogen. Immunizing mice with H5₃ encapsulated into polyanhydride nanoparticles induced high neutralizing antibody titers and enhanced CD4(+) T cell recall responses in mice. Finally, the H5₃-based polyanhydride nanovaccine induced protective immunity against a low-pathogenic H5N1 viral challenge. Informatics analyses indicated that mice receiving the nanovaccine formulations and subsequently challenged with virus were similar to naïve mice that were not challenged. The current studies provide a basis to further exploit the advantages of polyanhydride nanovaccines in pandemic scenarios.