Genetic Deletion of β-Arrestin-2 and the Mitigation of Established Airway Hyperresponsiveness in a Murine Asthma Model

Abstract

b-Arrestin-2 (barr2) is a ubiquitously expressed cytosolic protein that terminates G protein-coupled receptor signaling and transduces G protein-independent signaling. We previously showed that mice lacking barr2 do not develop an asthma phenotype when sensitized to, and challenged with, allergens. The current study evaluates if an established asthma phenotype can be mitigated by deletion of barr2 using an inducible Cre recombinase. We sensitized and challenged mice to ovalbumin (OVA) and demonstrated that on Day (d) 24 the allergic asthma phenotype was apparent in uninduced barr2 and wild-type (WT) mice. In a second group of OVA-treated mice, tamoxifen was injected on d24 to d28 to activate Cre recombinase, and OVA aerosol challenge was continued through d44. The asthma phenotype was assessed using lung mechanics measurements, bronchoalveolar lavage cell analysis, and histological assessment of mucin and airway inflammation. Compared with their respective saline-treated controls, OVA-treated WT mice and mice expressing the inducible Cre recombinase displayed a significant asthma phenotype at d45. Whereas tamoxifen treatment had no significant effect on the asthma phenotype in WT mice, it inhibited barr2 expression and caused a significant reduction in airway hyperresponsiveness (AHR) in Cre-inducible mice. These findings suggest that barr2 is actively required for perpetuation of the AHR component of the allergic asthma phenotype. Our finding that barr2 participates in the perpetuation of AHR in an asthma model means that targeting barr2 may provide immediate and potentially longterm relief from daily asthma symptoms due to AHR irrespective of inflammation.

FoxO1 is a critical regulator of M2‐like macrophage activation in allergic asthma

“…Once this was determined, we subjected the mice to the DRA protocol (Figure E) to evaluate whether or not tamoxifen‐induced FoxO1 depletion was associated with changes in the asthmatic phenotype. Tamoxifen treatment had no significant effect on the asthma phenotype in WT mice . Interestingly, we found that loss of FoxO1 by tamoxifen caused an additional decline in total BAL cells and the percentage of eosinophils (from 60.5% to 48.9%) in BAL was reduced in the FoxO1 fl/fl Csf1rcre mice.…”

Circulating Exosomes Induced by Cardiac Pressure Overload Contain Functional Angiotensin II Type 1 Receptors

“…21 β-arrestin2 flox/flox mice were generated by flanking exon 2 of the mouse β-arrestin2 gene ( Arrb2 ) with LoxP sites 21 and subsequent backcrossing into a C57/B6 genetic background for 7 generations. Conditional cardiomyocyte deletion of β-arrestin2 was generated by crossing β-arrestin2 flox/flox mice with transgenic mice expressing a tamoxifen-inducible Mer-Cre-Mer recombinase under the control of the α-myosin heavy chain promoter, 22 (Jackson lab, stock #005650) to generate β-arrestin2 flox/+ /αMHC MerCreMer mice and then crossed with β-arrestin2 flox/flox to yield the genotypes used in the study (Figure S3).…”

Phosphodiesterase 4 Inhibitors Attenuate the Asthma Phenotype Produced by β2-Adrenoceptor Agonists in Phenylethanolamine N-Methyltransferase–Knockout Mice

“…For example, barrestin-2 null mice show an attenuated asthma-like phenotype (14), and, as shown by a recent study, where barrestin-2 was deleted after the asthma-like phenotype had been established, barrestin-2 is essential for perpetuation of AHR (15). Furthermore, we have recently identified that certain "b-blockers" (such as carvedilol) that lack agonism toward the Gas signaling pathway, yet activate ERK1/2 in cell-based assays, restore the asthma-like phenotype in PNMT-KO mice, and are ineffective at attenuating the phenotype in wild-type (WT) mice (16).…”