Airway mast cells in a rhesus model of childhood allergic airways disease

Use of nonhuman primates in obstructive lung disease research - is it required?

In times of increasing costs for health insurances, obstructive lung diseases are a burden for both the patients and the economy. Pulmonary symptoms of asthma and chronic obstructive pulmonary disease (COPD) are similar; nevertheless, the diseases differ in pathophysiology and therapeutic approaches. Novel therapeutics are continuously developed, and nonhuman primates (NHPs) provide valuable models for investigating novel biologicals regarding efficacy and safety.

This review discusses the role of nonhuman primate models for drug development in asthma and COPD and investigates whether alternative methods are able to prevent animal experiments.

Immunopathology of the Respiratory System

Respiratory immunity is accomplished using multiple mechanisms including structure/anatomy of the respiratory tract, mucosal defense in the form of the mucociliary apparatus, innate immunity using cells and molecules and acquired immunity. There are species differences of the respiratory immune system that influence the response to environmental challenges and pharmaceutical, industrial and agricultural compounds assessed in nonclinical safety testing and hazard identification. These differences influence the interpretation of respiratory system changes after exposure to these challenges and compounds in nonclinical safety assessment and hazard identification and their relevance to humans.

Mast cell-derived neurotrophin 4 mediates allergen-induced airway hyperinnervation in early life

Asthma often progresses from early episodes of insults. How early-life events connect to long-term airway dysfunction remains poorly understood. We demonstrated previously that increased neurotrophin 4 (NT4) levels following early-life allergen exposure cause persistent changes in airway smooth muscle (ASM) innervation and airway hyper-reactivity (AHR) in mice. Herein, we identify pulmonary mast cells as a key source of aberrant NT4 expression following early insults. NT4 is selectively expressed by ASM and mast cells in mice, nonhuman primates, and humans. We show in mice that mast cell-derived NT4 is dispensable for ASM innervation during development. However, upon insults, mast cells expand in number and degranulate to release NT4 and thus become the major source of NT4 under pathological condition. Adoptive transfer of wild-type mast cells, but not NT4^-/- mast cells restores ASM hyperinnervation and AHR in Kit^W-sh/W-sh mice following early-life insults. Notably, an infant nonhuman primate model of asthma also exhibits ASM hyperinnervation associated with the expansion and degranulation of mast cells. Together, these findings identify an essential role of mast cells in mediating ASM hyperinnervation following early-life insults by producing NT4. This role may be evolutionarily conserved in linking early insults to long-term airway dysfunction.

Increased CCL24/eotaxin-2 with postnatal ozone exposure in allergen-sensitized infant monkeys is not associated with recruitment of eosinophils to airway mucosa

Epidemiology supports a causal link between air pollutant exposure and childhood asthma, but the mechanisms are unknown. We have previously reported that ozone exposure can alter the anatomic distribution of CD25+ lymphocytes in airways of allergen-sensitized infant rhesus monkeys. Here, we hypothesized that ozone may also affect eosinophil trafficking to allergen-sensitized infant airways. To test this hypothesis, we measured blood, lavage, and airway mucosa eosinophils in 3-month old monkeys following cyclical ozone and house dust mite (HDM) aerosol exposures. We also determined if eotaxin family members (CCL11, CCL24, CCL26) are associated with eosinophil location in response to exposures. In lavage, eosinophil numbers increased in animals exposed to ozone and/or HDM. Ozone+HDM animals showed significantly increased CCL24 and CCL26 protein in lavage, but the concentration of CCL11, CCL24, and CCL26 was independent of eosinophil number for all exposure groups. In airway mucosa, eosinophils increased with exposure to HDM alone; comparatively, ozone and ozone+HDM resulted in reduced eosinophils. CCL26 mRNA and immunofluorescence staining increased in airway mucosa of HDM alone animals and correlated with eosinophil volume. In ozone+HDM animal groups, CCL24 mRNA and immunofluorescence increased along with CCR3 mRNA, but did not correlate with airway mucosa eosinophils. Cumulatively, our data indicate that ozone exposure results in a profile of airway eosinophil migration that is distinct from HDM mediated pathways. CCL24 was found to be induced only by combined ozone and HDM exposure, however expression was not associated with the presence of eosinophils within the airway mucosa.

Lung gene expression in a rhesus allergic asthma model correlates with physiologic parameters of disease and exhibits common and distinct pathways with human asthma and a mouse asthma model

Experimental nonhuman primate models of asthma exhibit multiple features that are characteristic of an eosinophilic/T helper 2 (Th2)-high asthma subtype, characterized by the increased expression of Th2 cytokines and responsive genes, in humans. Here, we determine the molecular pathways that are present in a house dust mite-induced rhesus asthma model by analyzing the genomewide lung gene expression profile of the rhesus model and comparing it with that of human Th2-high asthma. We find that a prespecified human Th2 inflammation gene set from human Th2-high asthma is also present in rhesus asthma and that the expression of the genes comprising this gene set is positively correlated in human and rhesus asthma. In addition, as in human Th2-high asthma, the Th2 gene set correlates with physiologic markers of allergic inflammation and disease in rhesus asthma. Comparison of lung gene expression profiles from human Th2-high asthma, the rhesus asthma model, and a common mouse asthma model indicates that genes associated with Th2 inflammation are shared by all three species. However, some pathophysiologic aspects of human asthma (ie, subepithelial fibrosis, angiogenesis, neural biology, and immune host defense biology) are better represented in the gene expression profile of the rhesus model than in the mouse model. Further study of the rhesus asthma model may yield novel insights into the pathogenesis of human Th2-high asthma.

Biochemical effects of ozone on asthma during postnatal development

BACKGROUND

Ozone exposure during early life has the potential to contribute to the development of asthma as well as to exacerbate underlying allergic asthma.

SCOPE OF REVIEW

Developmentally regulated aspects of sensitivity to ozone exposure and downstream biochemical and cellular responses.

MAJOR CONCLUSIONS

Developmental differences in antioxidant defense responses, respiratory physiology, and vulnerabilities to cellular injury during particular developmental stages all contribute to disparities in the health effects of ozone exposure between children and adults.

GENERAL SIGNIFICANCE

Ozone exposure has the capacity to affect multiple aspects of the "effector arc" of airway hyperresponsiveness, ranging from initial epithelial damage and neural excitation to neural reprogramming during infancy. This article is part of a Special Issue entitled: Biochemistry of Asthma.

Anatomical and immunohistochemical considerations on the microinnervation of trachea in humans

The anatomy of the tracheal microinnervation is understudied in humans; the purpose of our study was to fill this gap by working on human adult tracheas, to compare the results with those obtained from animal studies, and to checking whether or not these studies are suitable to be translated from comparative to the human anatomy. The study was designed as a qualitative one. The present work was performed on human adult tracheas dissected out in 15 human adult cadavers. Microdissections were performed in eight tracheas and revealed the outer peritracheal plexus, segmentally supplied and distributed to trachea and esophagus, with longitudinal intersegmentary anastomoses but also with bilateral interrecurrential anastomoses previously undescribed in anatomy. Seven different tracheas were transversally cut and paraffin embedded. Histological stains (HE, toluidine blue, luxol fast blue, Giemsa on tissues and trichrome Gieson) and immunohistochemistry using primary antibodies for nNOS, neurofilament, SMA and the cocktail of citokeratines CK AE1-AE3+8/18 were done. According to the histological individual variation, the neural layers of the posterior wall of the human trachea could be considered as it follows: (a) an outer neural layer, ganglionated, associated with the connective covering layers, adventitia and the posterior fibroelastic membrane (external elastic lamina); (b) a submucosal ganglionated neural layer, mainly with juxtaglandular microganglia that may expand, as glands do, through the outer covering layers; (c) intrinsic nerves of the transverse trachealis muscle; (d) the neural layer intrinsic to the longitudinal elastic band (internal elastic lamina) and supplied from the inner submucosa; (e) the neural plexus of the lamina propria, with scarcely distributed neurons. We also bring here the first evidences for the in vivo nNOS phenotype of mast cells that were identified, but not exclusively, within the trachealis muscle.