Lack of the E3 Ubiquitin Ligase March1 Affects CD8 T Cell Fate and Exacerbates Insulin Resistance in Obese Mice.

Obesity is a major risk factor for the development of insulin resistance and type 2 diabetes. However, the mechanisms that trigger the underlying adipose tissues inflammation are not completely understood. Here, we show that the E3 ubiquitin ligase March1 controls the phenotypic and functional properties of CD8+ T cells in mice white adipose tissue. In a diet-induced obesity model, mice lacking March1 [March1 knockout (KO)] show increased insulin resistance compared to their WT counterparts. Also, in obese March1 KO mice, the proportions of effector/memory (Tem) and resident/memory (Trm) CD8+ T cells were higher in the visceral adipose tissue, but not in the spleen. The effect of March1 on insulin resistance and on the phenotype of adipose tissue CD8+ T cells was independent of major histocompatibility complex class II ubiquitination. Interestingly, we adoptively transferred either WT or March1 KO splenic CD8+ T cells into obese WT chimeras that had been reconstituted with Rag1-deficient bone marrow. We observed an enrichment of Tem and Trm cells and exacerbated insulin resistance in mice that received March1 KO CD8 T cells. Mechanistically, we found that March1 deficiency alters the metabolic activity of CD8+ T cells. Our results provide additional evidence of the involvement of CD8+ T cells in adipose tissue inflammation and suggest that March1 controls the metabolic reprogramming of these cells.

A silent agonist of α7 nicotinic acetylcholine receptors modulates inflammation ex vivo and attenuates EAE.

Nicotinic acetylcholine receptors (nAChRs) are best known to function as ligand-gated ion channels in the nervous system. However, recent evidence suggests that nicotine modulates inflammation by desensitizing non-neuronal nAChRs, rather than by inducing channel opening. Silent agonists are molecules that selectively induce the desensitized state of nAChRs while producing little or no channel opening. A silent agonist of α7 nAChRs has recently been shown to reduce inflammation in an animal model of inflammatory pain. The objective of this study was to determine whether a silent agonist of α7 nAChRs can also effectively modulate inflammation and disease manifestation in an animal model of multiple sclerosis. We first evaluated the effects of various nAChR ligands and of an α7 nAChR-selective silent agonist, 1-ethyl-4-(3-(bromo)phenyl)piperazine (m-bromo PEP), on the modulation of mouse bone marrow-derived monocyte/macrophage (BMDM) numbers, phenotype and cytokine production. The non-competitive antagonist mecamylamine and the silent agonist m-bromo PEP reduced pro-inflammatory BMDM numbers by affecting their viability and proliferation. Both molecules also significantly reduced cytokine production by mouse BMDMs and significantly ameliorated disease in experimental autoimmune encephalomyelitis. Finally, m-bromo PEP also reduced chronic inflammatory pain in mice. Taken together, our results further support the hypothesis that nAChRs may modulate inflammation via receptor desensitization rather than channel opening. α7 nAChR-selective silent agonists may thus be a novel source of anti-inflammatory compounds that could be used for the treatment of inflammatory disorders.

Downregulation of MHC Class II by Ubiquitination Is Required for the Migration of CD206+ Dendritic Cells to Skin-Draining Lymph Nodes.

Dendritic cells (DCs) are critical players in skin homeostasis. A subset of mannose receptor (CD206)-expressing monocyte-derived DCs was found in skin, and their migratory counterpart is present in skin-draining lymph nodes (sdLNs). Skin CD206+ DCs were shown to upregulate MHC class II (MHCII) progressively, raising the question of whether this feature affects their biology. In this study, we assessed the role of MHCII regulation in the development and migration of these cells in mouse models expressing differential MHCII levels. Using CD206 as a surrogate marker, we found that skin CD206+ DCs develop in an MHCII-independent manner. However, their migration to sdLNs was affected by overexpression rather than absence or lower expression of MHCII. Accordingly, B16 tumor growth was exacerbated in mice overexpressing MHCII in the absence of ubiquitination. Mechanistically, CD206+ DCs from these mice showed decreased IRF4 and CCR7 expression. LPS, which is known to promote monocyte-derived DC recruitment to sdLNs, partially improved these defects. However, GM-CSF delivery restored CD206+ DC migration by promoting IRF4 expression. Collectively, these data show that MHCII downregulation is crucial for IRF4-dependent migration of CD206+ DCs to sdLNs in health and disease.

March1 E3 Ubiquitin Ligase Modulates Features of Allergic Asthma in an Ovalbumin-Induced Mouse Model of Lung Inflammation.

Membrane-associated RING-CH-1 (March1) is a member of the March family of E3 ubiquitin ligases. March1 downregulates cell surface expression of MHC II and CD86 by targeting them to lysosomal degradation. Given the key roles of MHC class II and CD86 in T cell activation and to get further insights into the development of allergic inflammation, we asked whether March1 deficiency exacerbates or attenuates features of allergic asthma in mice. Herein, we used an acute model of allergy to compare the asthmatic phenotype of March1-deficient and -sufficient mice immunized with ovalbumin (OVA) and later challenged by intranasal instillation of OVA in the lungs. We found that eosinophilic inflammation in airways and lung tissue was similar between WT and March1-/- allergic mice, whereas neutrophilic inflammation was significant only in March1-/- mice. Airway hyperresponsiveness as well as levels of IFN-γ, IL-13, IL-6, and IL-10 was lower in the lungs of asthmatic March1-/- mice compared to WT, whereas lung levels of TNF-α, IL-4, and IL-5 were not significantly different. Interestingly, in the serum, levels of total and ova-specific IgE were reduced in March1-deficient mice as compared to WT mice. Taken together, our results demonstrate a role of March1 E3 ubiquitin ligase in modulating allergic responses.

Pulmonary Pseudomonas aeruginosa infection induces autophagy and proteasome proteolytic pathways in skeletal muscles: effects of a pressurized whey protein-based diet in mice.

Background: Pulmonary Pseudomonas aeruginosa infection in cystic fibrosis patients is associated with skeletal muscle atrophy. In this study, we investigated the effects of P. aeurginosa infection and a whey protein-rich diet on skeletal muscle proteolytic pathways. Design: An agar bead model of pulmonary P. aeurginosa infection was established in adult C57/Bl6 mice. Protein ubiquitinaiton, lipidation of LC3B protein and expressions of autophagy-related genes and ubiquitin E3 ligases were quantified using immunoblotting and qPCR. The effects of pressure-treated whey protein diet on muscle proteolysis were also evaluated. Results: Pulmonary P. aeurginosa infection reduced diaphragm, tibialis anterior, and soleus muscle weights and increased protein ubiquitination, LC3B protein lipidation, and the expressions of Lc3b, Gabarapl1, Bnip3, Parkin, Atrogin-1, and MuRF1 genes in each muscle. These changes were greater in the tibialis as compared to soleus and diaphragm. Proteolysis indicators increased within one day of infection but were not evident after seven days of infection. A pressurized whey diet attenuated LC3B protein lipidation, expressions of autophagy-related genes (BNIP3), pro-inflammatory cytokines, and protein ubiquitination. Conclusions: We conclude that pulmonary P. aeruginosa infection activates the autophagy, and the proteasome pathways in skeletal muscles and that a pressurized whey protein diet attenuates muscle proteolysis in this model.

Role of antigen presentation in the production of pro-inflammatory cytokines in obese adipose tissue.

Type II diabetes regroups different physiological anomalies that ultimately lead to low-grade chronic inflammation, insulin resistance and loss of pancreatic ß-cells. Obesity is one of the best examples of such a condition that can develop into Metabolic Syndrome, causing serious health problems of great socio-economic consequences. The pathological outcome of obesity has a genetic basis and depends on the delicate balance between pro- and anti-inflammatory effectors of the immune system. The causal link between obesity and inflammation is well established. While innate immunity plays a key role in the development of a pro-inflammatory state in obese adipose tissues, it has now become clear that adaptive immune cells are also involved and participate in the cascade of events that lead to metabolic perturbations. The efficacy of some immunotherapeutic protocols in reducing the symptoms of obesity-driven metabolic syndrome in mice implicated all arms of the immune response. Recently, the production of pathogenic immunoglobulins and pro-inflammatory cytokines by B and T lymphocytes suggested an auto-immune basis for the establishment of a non-healthy obese state. Understanding the cellular landscape of obese adipose tissues and how immune cells sustain chronic inflammation holds the key to the development of targeted therapies. In this review, we emphasize the role of antigen-presenting cells and MHC molecules in obese adipose tissue and the general contribution of the adaptive arm of the immune system in inflammation-induced insulin resistance.

Pressurized whey protein can limit bacterial burden and protein oxidation in Pseudomonas aeruginosa lung infection.

BACKGROUND: Lung infection caused by Pseudomonas aeruginosa is associated with an exuberant inflammatory response, oxidative stress, and lung damage. Whey protein is a rich source of cysteine, and anti-inflammatory and immune-enhancing peptides. Anti-inflammatory and antioxidant properties of whey are augmented by hyperbaric pressure treatment. In this study, we tested whether dietary supplementation with pressurized whey protein enhances the host ability to clear P. aeruginosa infection compared with native (i.e., unpressurized) whey. METHODS: Using a minimally invasive, non-lethal model of murine (female C57Bl/6) model of P. aeruginosa infection (mucoid strain embedded in agar beads), we studied kinetics of infection, inflammation, and oxidative stress at d 1, 3, and 7 postinfection. A parallel set of mice were fed for 4 wk a semipurified diet containing either native or pressurized whey and subsequently infected with P. aeruginosa. In these mice, the parameters mentioned previously were studied at d 1 and 3 postinfection. RESULTS: Infection with P. aeruginosa resulted in inflammation and protein oxidation sustained beyond bacterial clearance. Animals that were fed pressurized whey had fewer bacteria at day 3 than mice on native whey. Weight loss or broncho-alveolar lavage cell content were comparable. Airway protein oxidation was attenuated, whereas airway leukocyte bacterial killing ability and oxidative burst in response to opsonized bacteria were increased in the pressurized whey-fed animals. CONCLUSIONS: Use of nutritionally derived substances with anti-inflammatory and antioxidant properties, such as pressurized whey, aids in limiting airway bacterial infection, particularly, under conditions of ongoing oxidative stress.

Gadolinium chloride attenuates sepsis-induced pulmonary apoptosis and acute lung injury.

Gadolinium chloride (GdCl3), a Kupffer cells inhibitor, attenuates acute lung injury; however, the mechanisms behind this effect are not completely elucidated. We tested the hypothesis that GdCl3 acts through the inhibition of lung parenchymal cellular apoptosis. Two groups of rats were injected intraperitoneally with saline or E. coli lipopolysaccharide. In two additional groups, rats were injected with GdCl3 24 hrs prior to saline or LPS administration. At 12 hrs, lung injury, inflammation, and apoptosis were studied. Lung water content, myeloperoxidase activity, pulmonary apoptosis and mRNA levels of interleukin-1 ß , -2, -5, -6, -10 and TNF- α rose significantly in LPS-injected animals. Pretreatment with GdCl3 significantly reduced LPS-induced elevation of pulmonary water content, myeloperoxidase activity, cleaved caspase-3 intensity, and attenuated pulmonary TUNEL-positive cells. GdCl3 pre-treatment upregulated IL-1 ß , -2 and -10 pulmonary gene expression without significantly affecting the others. These results suggest that GdCl3 attenuates acute lung injury through its effects on pulmonary parenchymal apoptosis.