Chemokine (C-C Motif) Receptor-Like 2 is not essential for lung injury, lung inflammation, or airway hyperresponsiveness induced by acute exposure to ozone

Abstract

Inhalation of ozone (O3), a gaseous air pollutant, causes lung injury, lung inflammation, and airway hyperresponsiveness. Macrophages, mast cells, and neutrophils contribute to one or more of these sequelae induced by O3. Furthermore, each of these aforementioned cells express chemokine (C‐C motif) receptor‐like 2 (Ccrl2), an atypical chemokine receptor that facilitates leukocyte chemotaxis. Given that Ccrl2 is expressed by cells essential to the development of O3‐induced lung pathology and that chemerin, a Ccrl2 ligand, is increased in bronchoalveolar lavage fluid (BALF) by O3, we hypothesized that Ccrl2 contributes to the development of lung injury, lung inflammation, and airway hyperresponsiveness induced by O3. To that end, we measured indices of lung injury (BALF protein, BALF epithelial cells, and bronchiolar epithelial injury), lung inflammation (BALF cytokines and BALF leukocytes), and airway responsiveness to acetyl‐β‐methylcholine chloride (respiratory system resistance) in wild‐type and mice genetically deficient in Ccrl2 (Ccrl2‐deficient mice) 4 and/or 24 hours following cessation of acute exposure to either filtered room air (air) or O3. In air‐exposed mice, BALF chemerin was greater in Ccrl2‐deficient as compared to wild‐type mice. O3 increased BALF chemerin in mice of both genotypes, yet following O3 exposure, BALF chemerin was greater in Ccrl2‐deficient as compared to wild‐type mice. O3 increased indices of lung injury, lung inflammation, and airway responsiveness. Nevertheless, no indices were different between genotypes following O3 exposure. In conclusion, we demonstrate that Ccrl2 modulates chemerin levels in the epithelial lining fluid of the lungs but does not contribute to the development of O3‐induced lung pathology.

Inconsequential role for chemerin‐like receptor 1 in the manifestation of ozone‐induced lung pathophysiology in male mice

“…Regardless of genotype, chemerin, one of two endogenous ligands for CMKLR1, was significantly greater in BAL fluid obtained from O 3 ‐ as compared to air‐exposed mice (Figure 1b ), which is consistent with our previous data (Malik et al., 2017 ; Razvi et al., 2015 ). However, independent of exposure, BAL chemerin was at least three‐fold greater in CMKLR1‐deficient as compared to wild‐type mice, and this observation is not without precedent.…”

“…Differences exist between 7-and 39-week-old mice with regard to O 3 -lung inflammation and antioxidant gene expression (Shore et al, 2011), and thus, age is another plausible explanation as to the reason differences in lung Cmklr1 mRNA expression exist between our study and that of Kilburg-Basnyat et al (2018). Regardless of genotype, chemerin, one of two endogenous ligands for was significantly greater in BAL fluid obtained from O 3 -as compared to airexposed mice (Figure 1b), which is consistent with our previous data (Malik et al, 2017;Razvi et al, 2015). However, independent of exposure, BAL chemerin was at least three-fold greater in CMKLR1-deficient as compared to wild-type mice, and this observation is not without precedent.…”

“…After airway responsiveness measurements were complete and while the animals remained under anesthesia, each mouse was euthanized by exsanguination after transecting the heart, which was accessed by performing a thoracotomy. Finally, more details concerning these methods have been previously described (Barreno et al., 2013 ; Malik et al., 2017 ).…”

Low‐dose administration of bleomycin leads to early alterations in lung mechanics

“…On days 7, 14, 21, 28 and 33 of the bleomycin treatment regimen, respiratory system mechanics and P–V relationships were measured using the flexiVent (SCIREQ Inc., Montreal, QC, Canada) as previously described (Dahm et al., ; Karmouty‐Quintana et al., , ; Malik et al., ). In brief, the mice were anaesthetized with pentobarbital sodium (50 mg kg −1 , i.p ., Oak Pharmaceuticals, Inc.; Lake Forest, IL, USA) and xylazine hydrochloride (7 mg kg −1 , i.p ., Vedco Inc.; Saint Joseph, MO, USA).…”

Studies with neutralizing antibodies suggest CXCL8-mediated neutrophil activation is independent of C-C motif chemokine receptor-like 2 (CCRL2) ligand binding function

“…CCRL2 genetically deficient mouse models have facilitated research on the function of CCRL2 in homeostasis and disease [16,17,[47][48][49], however, studies demonstrating the functional translation to humans are still lacking. While little is known about the function of CCRL2 in monocytes, previous work showed that human CD14 + monocytes express CCRL2 [35,50].…”