Calcium-sensing receptor antagonists abrogate airway hyperresponsiveness and inflammation in allergic asthma

Abstract

Airway hyperresponsiveness and inflammation are fundamental hallmarks of allergic asthma that are accompanied by increases in certain polycations, such as eosinophil cationic protein. Levels of these cations in body fluids correlate with asthma severity. We show that polycations and elevated extracellular calcium activate the human recombinant and native calcium-sensing receptor (CaSR), leading to intracellular calcium mobilization, cyclic adenosine monophosphate breakdown, and p38 mitogen-activated protein kinase phosphorylation in airway smooth muscle (ASM) cells. These effects can be prevented by CaSR antagonists, termed calcilytics. Moreover, asthmatic patients and allergen-sensitized mice expressed more CaSR in ASMs than did their healthy counterparts. Indeed, polycations induced hyper-reactivity in mouse bronchi, and this effect was prevented by calcilytics and absent in mice with CaSR ablation from ASM. Calcilytics also reduced airway hyperresponsiveness and inflammation in allergen-sensitized mice in vivo. These data show that a functional CaSR is up-regulated in asthmatic ASM and targeted by locally produced polycations to induce hyperresponsiveness and inflammation. Thus, calcilytics may represent effective asthma therapeutics.

The vascular Ca2+-sensing receptor regulates blood vessel tone and blood pressure

“…CaSR-LoxP ϫ SM22␣-Cre mice were inbred for at least three generations before being used for experiments. Genotyping for CaSR-LoxP sites and Cre was performed as described elsewhere (13,25,56). All animal work was conducted according to UK legislation and all procedures were independently reviewed and approved by the UK Home Office (Home Office Project License 30/3007) and conformed to the guidelines from directive 2010/63/EU of the European Parliament on the protection of animals used for scientific purposes.…”

“…Age-and sex-matched mice expressing only floxed CaSR alleles but no Cre-recombinase (SM22␣-Cre Ϫ/Ϫ -LoxP-CaSR ϩ/ϩ ) were used as controls for all experiments (termed WT). The resulting truncated ⌬exon7 product was shown to be nonfunctional (13), and these animals were viable and fertile (56). Representative genotyping is shown in Fig.…”

“…For this purpose, we generated animals with targeted CaSR ablation from smooth muscle cells by breeding mice with LoxP sites flanking exon seven of the CaSR (13) with mice in which Cre recombinase expression is transcriptionally regulated by the SM22␣ promoter (30). This approach allowed us to study animals with targeted deletion of the CaSR from VSMC throughout the vascular system, visceral smooth muscle, and cardiac cells but not skeletal muscle cells (30,56).…”

GENETICS IN ENDOCRINOLOGY: Gain and loss of function mutations of the calcium-sensing receptor and associated proteins: current treatment concepts

“…In addition, cinacalcet has been used for treatment of hyperparathyroidism related to hereditary vitamin D-resistant rickets (43) and X-linked hypophosphatemia (44). Allosteric CASR inhibitors called calcilytics (45,46,47) are currently investigated as a way to stimulate endogenous PTH secretion for the treatment of osteoporosis (48,49,50) and they have been proposed as a novel therapeutic strategy to treat allergic asthma (51), pulmonary hypertension (52) and Alzheimer's disease (53).…”

Heat Shock–Related Protein 20 Peptide Decreases Human Airway Constriction Downstream of β2-Adrenergic Receptor

“…Along with its ability to reduce methacholine-induced hyperresponsiveness in the OVA mouse model (Figure 3), the development of the P20 peptide into an effective bronchodilator in clinical settings has promising potential. Thus, P20 peptide emerges as a potential asthma therapeutic that causes ASM relaxation, joining other bronchodilators that can cause relaxation of ASM, such as bitter taste receptor activators (37), chloride channel blockers (38), and calcium-sensing receptor antagonists (calcilytics) (39). One of the limitations of this study is that the HASM used did not constitute samples from patients with asthma.…”