Angiopoietins 1 and 2 increased in severe refractory asthma
MedWire News: Patients with severe refractory asthma (SRA) show increased sputum levels of angiopoietin (Ang)-1 and -2, which play a role in vascular remodeling of the airways, researchers report.
Writing in Allergy, Stelios Loukides (University of Athens Medical School, Greece) and team explain: "Increased angiogenesis has been observed in SRA, and along with other components of tissue repair and airway inflammation, they may account for the poor steroid response in SRA."
They add that "Ang-1 is an essential mediator of angiogenesis by establishing vascular integrity, whereas Ang-2 acts as its natural inhibitor."
To investigate levels of these angiopoietins in patients with SRA, and to determine possible associations with mediators and cells involved in inflammation and vascular remodeling processes, the team studied 38 patients with SRA, 35 with moderate asthma, and 20 nonatopic, nonsmoking healthy individuals (controls). The three groups were similar in terms of mean age, body mass index (BMI), and gender distribution.
Sputum samples were collected from all of the participants and assessed for levels of Ang-1, Ang-2, vascular endothelial growth factor (VEGF), transforming growth factor (TGF)-β1, cysteinyl leukotrienes (Cys-LTs), matrix metalloproteinase (MMP)-2, interleukin (IL)-13, eosinophilic cationic protein (ECP), and IL-8.
The participants also underwent lung function and bronchial hyperresponsiveness tests, and their airway vascular permeability (AVP) index was determined.
The researchers found that Ang-1 levels were significantly higher in SRA patients than in those with moderate asthma and controls, at 30.0 versus 7.5 and 4.7 ng/mL, respectively, as were levels of Ang-2, at 506 versus 190 and 96 pg/mL, respectively.
The differences in Ang-1 and Ang-2 levels between patients with moderate asthma and controls were also significant, the researchers note.
Regression analysis that adjusted for age, gender, BMI, duration of disease, atopy, and treatment regimens revealed significant positive associations between Ang-2 levels and AVP index, MMP-2, Ang-1, and VEGF levels in patients with SRA, and a weak association between Ang-1 and eosinophil levels.
There were no significant associations between Ang-1 or Ang-2 levels and mediators related to inflammation and vascular remodeling or sputum inflammatory cells in patients with moderate asthma and controls.
There were also no significant associations between Ang-1 or Ang-2 levels and lung function test variables in any of the groups.
Loukides and team conclude: "This study indicates that Ang-1 and Ang-2 levels are higher in SRA compared with moderate asthma and healthy subjects. In patients with SRA, Ang-2 is associated with mediators involved in the vascular permeability process."
They add: "Our results provide suggestions for possible mechanisms involving angiopoietins in the pathogenesis of SRA."
By Mark Cowen