Person:

Levy, Bruce

Resolvins are generated from omega-3 fatty acids during inflammatory responses in the lung. These natural mediators interact with specific receptors to decrease lung inflammation and promote its resolution in healthy tissues. There are several lung diseases of chronic inflammation that fail to resolve, most notable asthma. This common disorder has a lifetime prevalence of nearly 10% and is characterized, in part, by chronic, non-resolving inflammation of the airway. Pro-resolving mediators are generated during asthma; however, their biosynthesis is decreased in severe and uncontrolled asthma, suggesting that the chronic, adaptive inflammation in asthmatic airways may result from a resolution defect. This article focuses on recent insights into the cellular and molecular mechanisms for resolvins that limit adaptive immune responses in healthy airways.

Objective—Both asthma and abdominal aortic aneurysms (AAA) involve inflammation. It remains unknown whether these diseases interact.

Approach and Results—Databases analyzed included Danish National Registry of Patients, a population-based nationwide case–control study included all patients with ruptured AAA and age- and sex-matched AAA controls without rupture in Denmark from 1996 to 2012; Viborg vascular trial, subgroup study of participants from the population-based randomized Viborg vascular screening trial. Patients with asthma were categorized by hospital diagnosis, bronchodilator use, and the recorded use of other anti-asthma prescription medications. Logistic regression models were fitted to determine whether asthma associated with the risk of ruptured AAA in Danish National Registry of Patients and an independent risk of having an AAA at screening in the Viborg vascular trial. From the Danish National Registry of Patients study, asthma diagnosed <1 year or 6 months before the index date increased the risk of AAA rupture before (odds ratio [OR]=1.60–2.12) and after (OR=1.51–2.06) adjusting for AAA comorbidities. Use of bronchodilators elevated the risk of AAA rupture from ever use to within 90 days from the index date, before (OR=1.10–1.37) and after (OR=1.10–1.31) adjustment. Patients prescribed anti-asthma drugs also showed an increased risk of rupture before (OR=1.12–1.79) and after (OR=1.09–1.48) the same adjustment. In Viborg vascular trial, anti-asthmatic medication use associated with increased risk of AAA before (OR=1.45) or after adjustment for smoking (OR=1.45) or other risk factors (OR=1.46).

Conclusions—Recent active asthma increased risk of AAA and ruptured AAA. These findings document and furnish novel links between airway disease and AAA, 2 common diseases that share inflammatory aspects.

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 KitW-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.