AGTR2 absence or antagonism prevents cystic fibrosis pulmonary manifestations

Abstract

Background: Pulmonary disease remains the primary cause of morbidity and mortality for individuals with cystic fibrosis (CF). Variants at a locus on the X-chromosome containing the type 2 angiotensin II receptor gene (AGTR2) were identified by a large GWAS as significantly associating with lung function in CF patients. We hypothesized that manipulating the angiotensin-signaling pathway may yield clinical benefit in CF.

Methods: Genetic subset analysis was conducted on a local CF cohort to extend the GWAS findings. Next, we evaluated pulmonary function in CF mice with a deleted AGTR2 gene, and in those who were given subcutaneous injections of PD123,319, a selective AGTR2 antagonist for 12 weeks beginning at weaning.

Results: The genetic subset analysis replicated the initial GWAS identified association, and confirmed the association of this locus with additional lung function parameters. Studies in genetically modified mice established that absence of the AGTR2 gene normalized pulmonary function indices in two independent CF mouse models. Further, we determined that pharmacologic antagonism of AGTR2 improved overall pulmonary function in CF mice to near wild-type levels.

Conclusions: These results identify that reduced AGTR2 signaling is beneficial to CF lung function, and suggest the potential of manipulating the angiotensin-signaling pathway for treatment and/or prevention of CF pulmonary disease. Importantly, the beneficial effects were not CF gene mutation dependent, and were able to be reproduced with pharmacologic antagonism. As there are clinically approved drugs available to target the renin-angiotensin signaling system, these findings may be quickly translated to human clinical trials.

Keywords: Angiotensin signaling; GWAS follow up; Mouse models of airway disease; Pulmonary function.

Figure 1.

An inactivating deletion in AGTR2 prevents aspects of pulmonary dysfunction in F508del CF mice. (A-E) Lung function and (F-J) distal airspace size were quantified in F508del CF mice, F508del CF mice with the genetic deletion of the AGTR2 gene (double knockout: AT/F508del), wild type C57bl/6 mice and AGTR2 knockout mice with wild type CFTR (AT KO). (G-J) Representative histologic images are displayed (size bars indicate 100 microns). Data are presented as means, with error bars denoting standard deviations. *P<0.05 compared to wild type; #P<0.05 compared to AT/F508del.

Figure 2.

An inactivating deletion in AGTR2 aspects of pulmonary dysfunction in R117H CF mice. (A-E) Lung function and (F-J) distal airspace size were also quantified in CF mice homozygous for the R117H CFTR mutation (R117H), and compared to CF mice with the genetic deletion of the AGTR2 gene (double knockout: AT/R117H), wild type C57bl/6 mice and AGTR2 knockout mice with wild type CFTR (AT KO). (G-J) Representative histologic images are displayed (size bars indicate 100 microns). Data are presented as means, with error bars denoting standard deviations. *P<0.05 compared to wild type; #P<0.05 compared to AT/F508del.

Figure 3.

Pharmacologic antagonism of AGTR2 prevents the development of CF-related pulmonary dysfunction. (A-E) Lung function was quantified in drug treated F508del CF mice and compared to untreated CF mice and wild type C57bl/6 mice (both treated and untreated). *P<0.05 compared to wild type; #P<0.05 compared to AT/F508del.