Background Exercise-induced bronchoconstriction (EIB) is a prototypical feature of indirect airway hyperresponsiveness (AHR). Mast cells are implicated in EIB, but the characteristics, regulation, and function of mast cells in EIB are poorly understood. Objectives To examine mast cell infiltration of the airway epithelium in EIB, and the regulation of mast cell phenotype and function by epithelial-derived cytokines. Methods Endobronchial biopsies, epithelial brushings, and induced sputum were obtained from asthmatics with and without EIB, and normal controls. Mast cell proteases were quantified by qPCR, and mast cell density by design-based stereology. Airway epithelial responses to wounding and osmotic stress were assessed in primary airway epithelial cells and ex vivo murine lung tissue. Mast cell granule development and function were examined in cord blood-derived mast cells. Results Tryptase and carboxypeptidase A3 (CPA3) expression in epithelial brushings and epithelial mast cell density were selectively elevated in the asthma group with EIB. A in vitro scratch wound initiated the release of TSLP that was greater in epithelial cells derived from asthmatics. Osmotic stress induced the release of IL-from explanted murine lung that was increased in allergen-treated mice. TSLP combined with IL-33 increased tryptase and CPA3 immunostaining in mast cell precursors, and selectively increased cysteinyl leukotriene formation by mast cells in a manner that was independent of in vitro sensitization. Conclusions Mast cell infiltration of the epithelium is a critical determinant of indirect AHR, and the airway epithelium may serve as an important regulator of the development and function of this mast cell population.

Rationale: Indirect airway hyperresponsiveness (AHR) is a fundamental feature of asthma that is manifest as exercise-induced bronchoconstriction (EIB). Secreted phospholipase A 2 group X (sPLA 2 -X) plays a key role in regulating eicosanoid formation and the development of inflammation and AHR in murine models. Objectives: We sought to examine sPLA 2 -X in the airway epithelium and airway wall of patients with asthma, the relationship to AHR in humans, and the regulation and function of sPLA 2 -X within the epithelium. Methods: We precisely phenotyped 34 patients with asthma (19 with and 15 without EIB) and 10 normal control subjects to examine in vivo differences in epithelial gene expression, quantitative morphometry of endobronchial biopsies, and levels of secreted protein. The regulation of sPLA 2 -X gene (PLA2G10) expression was examined in primary airway epithelial cell cultures. The function of epithelial sPLA 2 -X in eicosanoid formation was examined using PLA 2 inhibitors and murine tracheal epithelial cells with Pla2g10 deletion. Measurements and Main Results: We found that sPLA 2 -X protein is increased in the airways of patients with asthma and that epithelial-derived sPLA 2 -X may be increased in association with indirect AHR. The expression of sPLA 2 -X increases during in vitro epithelial differentiation; is regulated by inflammatory signals including tumor necrosis factor, IL-13, and IL-17; and is both secreted from the epithelium and directly participates in the release of arachidonic acid by epithelial cells. Conclusions: These data reveal a relationship between epithelialderived sPLA 2 -X and indirect AHR in asthma and that sPLA 2 -X serves as an epithelial regulator of inflammatory eicosanoid formation. Therapies targeting epithelial sPLA 2 -X may be useful in asthma.Keywords: airway hyperresponsiveness; asthma; eicosanoid; epithelial cell; secretory phospholipase A 2Indirect airway hyperresponsiveness (AHR) refers to the propensity to develop airway narrowing in response to stimuli such as exercise, osmotic challenge, or adenosine that cause airflow obstruction via inflammatory or neuronal cells that release mediators (1). Exercise-induced bronchoconstriction (EIB) is a prototypical feature of indirect AHR in asthma that occurs in about 30 to 50% of subjects with asthma in cross-sectional studies (2, 3). Prior studies have identified epithelial shedding into the airway lumen and increased production of inflammatory eicosanoids such as leukotrienes in the airways of patients with EIB (4-8). The basis for the dysregulation of eicosanoids in asthma is incompletely understood. The rate-limiting step in eicosanoid biosynthesis is the release of unesterified arachidonic acid (AA) from the sn-2 position of membrane phospholipids by phospholipase A 2 (PLA 2 ) (9). Recent work has uncovered 10 mammalian secreted PLA 2 s (sPLA 2 s) that may coordinate eicosanoid synthesis with the well-described cytosolic PLA 2 -a (i.e., cPLA 2 a) (10-12). sPLA 2 s have several other inflammatory functions, including ...

Many ecologists have lamented the demise of natural history and have attributed this decline to a misguided view that natural history is outdated and unscientific. Although there is a perception that the focus in ecology and conservation have shifted away from descriptive natural history research and training toward hypothetico-deductive research, we argue that natural history has entered a new phase that we call “next-generation natural history.” This renaissance of natural history is characterized by technological and statistical advances that aid in collecting detailed observations systematically over broad spatial and temporal extents. The technological advances that have increased exponentially in the last decade include electronic sensors such as camera-traps and acoustic recorders, aircraft- and satellite-based remote sensing, animal-borne biologgers, genetics and genomics methods, and community science programs. Advances in statistics and computation have aided in analyzing a growing quantity of observations to reveal patterns in nature. These robust next-generation natural history datasets have transformed the anecdotal perception of natural history observations into systematically collected observations that collectively constitute the foundation for hypothetico-deductive research and can be leveraged and applied to conservation and management. These advances are encouraging scientists to conduct and embrace detailed descriptions of nature that remain a critically important component of the scientific endeavor. Finally, these next-generation natural history observations are engaging scientists and non-scientists alike with new documentations of the wonders of nature. Thus, we celebrate next-generation natural history for encouraging people to experience nature directly.

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