Studies comparing endogenous and recombinant serum amyloid A (SAA) have generated conflicting data on the proinflammatory function of these proteins. In exploring this discrepancy, we found that in contrast to commercially sourced recombinant human SAA1 (hSAA1) proteins produced in , hSAA1 produced from eukaryotic cells did not promote proinflammatory cytokine production from human or mouse cells, induce Th17 differentiation, or stimulate TLR2. Proteomic analysis of-derived hSAA1 revealed the presence of numerous bacterial proteins, with several being reported or probable lipoproteins. Treatment of hSAA1 with lipoprotein lipase or addition of a lipopeptide to eukaryotic cell-derived hSAA1 inhibited or induced the production of TNF-α from macrophages, respectively. Our results suggest that a function of SAA is in the binding of TLR2-stimulating bacterial proteins, including lipoproteins, and demand that future studies of SAA employ a recombinant protein derived from eukaryotic cells.

Many mouse models of allergic asthma exhibit eosinophil-predominant cellularity rather than the mixed granulocytic cytology in steroid-unresponsive severe disease. Therefore, we sought to implement a novel mouse model of antigen-driven, mixed-granulocytic, severe allergic asthma to determine biomarkers of the disease process and potential therapeutic targets. C57BL/6J, IL-6-/-, and IL-6R-/- mice were injected with an emulsion of Complete Freund's Adjuvant and House Dust Mite antigen (CFA/HDM) on day 1. Dexamethasone, a lymphocyte-depleting biological, or anti-IL-17A were administered during intranasal HDM challenge on days 19-22. On day 23, the CFA/HDM model elicited mixed bronchoalveolar lavage (BAL) cellularity (typically 80% neutrophils and 10% eosinophils), airway hyperresponsiveness (AHR) to methacholine, diffusion impairment, lung damage, body weight loss, corticosteroid resistance, and elevated levels of serum amyloid A (SAA), pro-inflammatory cytokines, and Th1/Th17 cytokines compared to eosinophilic models of HDM-driven allergic airway disease. BAL cells in IL-6- or IL-6R-deficient mice were predominantly eosinophilic and associated with elevated Th2 and reduced Th1/Th17 cytokine production, along with an absence of SAA. Nevertheless, AHR remained in IL-6-deficient mice even when administered dexamethasone. However, combined administration of anti-IL-17A and systemic corticosteroid significantly attenuated both overall and neutrophilic airway inflammation, and also reduced AHR and body weight loss. Inhibition of IL-17A combined with systemic corticosteroid treatment during antigen-driven exacerbations may provide a novel therapeutic approach to prevent the pathological pulmonary and constitutional changes that greatly impact patients with the mixed-granulocytic endotype of severe asthma.

Obese asthmatics tend to have severe, poorly controlled disease and exhibit methacholine hyperresponsiveness manifesting in proximal airway narrowing and distal lung tissue collapsibility. Substantial weight loss in obese asthmatics or in mouse models of the condition decreases methacholine hyperresponsiveness. Ketone bodies are rapidly elevated during weight loss, coinciding with or preceding relief from asthma-related comorbidities. As ketone bodies may exert numerous potentially therapeutic effects, augmenting their systemic concentrations is being targeted for the treatment of several conditions. Circulating ketone body levels can be increased by feeding a ketogenic diet or by providing a ketone ester dietary supplement, which we hypothesized would exert protective effects in mouse models of inherent obese asthma. Weight loss induced by feeding a low-fat diet to mice previously fed a high-fat diet was preceded by increased urine and blood levels of the ketone body, β-hydroxybutyrate (BHB). Feeding a ketogenic diet for three weeks to high-fat diet-fed obese mice or genetically obese db/db mice increased BHB concentrations and decreased methacholine hyperresponsiveness without substantially decreasing body weight. Acute ketone ester administration decreased methacholine responsiveness of normal mice, and dietary ketone ester supplementation of high-fat diet-fed mice decreased methacholine hyperresponsiveness. Ketone ester supplementation also transiently induced an 'anti-obesogenic' gut microbiome with a decreased Fermicutes/Bacteroidetes ratio. Dietary interventions to increase systemic BHB concentrations could provide symptom relief for obese asthmatics without the need for the substantial weight loss required of patients to elicit benefits to their asthma through bariatric surgery or other diet or lifestyle alterations.

Although recognized as an important endocrine organ, little is known about the mechanisms through which adipose tissue can regulate inflammatory responses in distant tissues, such as lung, that are affected by obesity. To explore potential mechanisms, male C57BL/6J mice were provided either high-fat diet, low-fat diet, or were provided a high-fat diet then switched to the low-fat diet to promote weight loss. Visceral adipocytes were then cultured in vitro to generate conditioned media (CM) that was used to treat both primary (MTEC) and immortalized (MTCC) airway epithelial cells. Adiponectin levels were greatly depressed in the CM from both obese and diet-switched adipocytes relative to mice continually fed the low-fat diet. MTEC from obese mice secreted higher baseline levels of inflammatory cytokines than MTEC from lean or diet-switched mice. MTEC treated with obese adipocyte CM increased their secretion of these cytokines compared to MTEC treated with lean CM. Diet-switched CM modestly decreased the production of cytokines compared to obese CM, and these effects were recapitulated when the CM was used to treat MTCC. Adipose stromal vascular cells from obese mice expressed genes consistent with an M1 macrophage phenotype and decreased eosinophil abundance compared to lean SVF, a profile that persisted in the lean diet-switched mice despite substantial weight loss. Soluble factors secreted from obese adipocytes exert a pro-inflammatory effect on airway epithelial cells, and these alterations are attenuated by diet-induced weight loss, which could have implications for the airway dysfunction related to obese asthma and its mitigation by weight loss.

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