Novel Pathway of Adenosine Generation in the Lungs from NAD+: Relevance to Allergic Airway Disease.

Richard Graeff,Erin Wendt-Hornickle,Mathur Kannan,Alonso Guedes,Timothy Walseth,Scott O’Grady,Ruth Quintana,Caroline Baldo

doi:10.3390/molecules25214966

Richard Graeff, Erin Wendt-Hornickle + Show 6 more

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https://doi.org/10.3390/molecules25214966

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Abstract

Adenosine and uric acid (UA) play a pivotal role in lung diseases such as asthma and chronic obstructive pulmonary disease (COPD). In the present experiments, we measured adenosine synthesis from nicotinamide adenine dinucleotide (NAD+) in membranes prepared from wild type (WT) and CD38 knockout (CD38KO) mouse lungs, from cultured airway smooth muscle and epithelial cells, and in bronchoalveolar lavage fluid after airway challenge with epidemiologically relevant allergens. Adenosine was determined using an enzymatically coupled assay that produces ATP and is detected by luminescence. Uric acid was determined by ELISA. Exposure of cultured airway epithelial cells to Alternaria alternata extract caused significant nucleotide (NAD+ and ATP) release in the culture media. The addition of NAD+ to membranes prepared from WT mice resulted in faster generation of adenosine compared to membranes from CD38KO mice. Formation of adenosine from NAD+ affected UA and ATP concentrations, its main downstream molecules. Furthermore, NAD+ and adenosine concentrations in the bronchoalveolar lavage fluid decreased significantly following airway challenge with house-dust mite extract in WT but not in CD38KO mice. Thus, NAD+ is a significant source of adenosine and UA in the airways in mouse models of allergic airway disease, and the capacity for their generation from NAD+ is augmented by CD38, a major NADase with high affinity for NAD+. This novel non-canonical NAD+-adenosine-UA pathway that is triggered by allergens has not been previously described in the airways.

Highlights

Chronic obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are the most common chronic respiratory inflammatory diseases and are among the leading causes of morbidity and mortality worldwide [1]
We found that 16HBE cells, which are widely used as surrogates for native human airway epithelium, exposed to Alternaria alternata extract rapidly released large amounts of NAD+ and ATP indicating that exposure to aeroallergens would increase substrate availability for local adenosine synthesis
The role of CD38-mediated events in the pulmonary epithelium is mostly unknown, but our results suggest that the presence of CD38 in airway smooth muscle (ASM) or the airway epithelium could influence mucous hypersecretion during allergic airway disease via autocrine and paracrine adenosinergic signaling mechanisms, similar to that previously described for NAD+ and cyclic ADP ribose (cADPR) in other model systems [50,51,52]

Summary

Introduction

Chronic obstructive lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD), are the most common chronic respiratory inflammatory diseases and are among the leading causes of morbidity and mortality worldwide [1]. Our laboratory was the first to report the contribution of CD38, a type II transmembrane glycoprotein, to the regulation of intracellular calcium in airway smooth muscle (ASM) and airway hyperresponsiveness (AHR) in a series of studies employing cellular imaging, molecular and biochemical techniques in cells, tissues and animal models (e.g., [5]). Our previous studies revealed a prominent role of the CD38/cADPR signaling in heightened intracellular calcium responsiveness and contractile properties of human and mouse ASM cells exposed to inflammatory cytokines such as TNF-α, IFN-γ and IL-1β as well as the Th2 cytokine IL-13 [7,8,9,10,11]. CD38 activity in resident airway cells, rather than in inflammatory cell infiltrate, significantly contributes to airway hyperresponsiveness in mouse models of cytokine- and allergen-induced inflammatory airway disease [12,13,14]

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