Targeted Gene Disruption Reveals the Role of the Cysteinyl Leukotriene 2 Receptor in Increased Vascular Permeability and in Bleomycin-induced Pulmonary Fibrosis in Mice

Abstract

The cysteinyl leukotrienes (cys-LTs) mediate both acute and chronic inflammatory responses in mice, as demonstrated by the attenuation of the IgE/antigen-mediated increase in microvascular permeability and of bleomycin-induced pulmonary fibrosis, respectively, in a strain with targeted disruption of leukotriene C 4 synthase to prevent cys-LT synthesis. Our earlier finding that the acute, but not the chronic, injury was attenuated in a strain with targeted disruption of the cysteinyl leukotriene 1 (CysLT 1 ) receptor suggested that the chronic injury might be mediated through the CysLT 2 receptor. Thus, we generated CysLT 2 receptor-deficient mice by targeted gene disruption. These mice developed normally and were fertile. The increased vascular permeability associated with IgE-dependent passive cutaneous anaphylaxis was significantly reduced in CysLT 2 receptor-null mice as compared with wild-type mice, whereas plasma protein extravasation in response to zymosan A-induced peritoneal inflammation was not altered. Alveolar septal thickening after intratracheal injection of bleomycin, characterized by interstitial infiltration with macrophages and fibroblasts and the accumulation of collagen fibers, was significantly reduced in CysLT 2 receptor-null mice as compared with the wild-type mice. The amounts of cys-LTs in bronchoalveolar lavage fluid after bleomycin injection were similar in the CysLT 2 receptor-null mice and the wildtype mice. Thus, in response to a particular pathobiologic event the CysLT 2 receptor can mediate an increase in vascular permeability in some tissues or promote chronic pulmonary inflammation with fibrosis.The cysteinyl leukotrienes (cys-LTs), 1 leukotriene (LT) C 4 , LTD 4 , and LTE 4 , are lipid mediators (1, 2) that have been implicated in the pathobiology of allergic and asthmatic inflammatory responses on the basis of the efficacy of specific intervention with a biosynthetic inhibitor (3) or antagonists to a receptor subsequently shown to be the cysteinyl leukotriene 1 (CysLT 1 ) receptor (4). Two types of human receptors for cys-LTs, designated CysLT 1 receptor and CysLT 2 receptor, belonging to the seventransmembrane, G protein-coupled receptor family, were cloned and shown to be 38% homologous in their amino acid sequences (5-9). The rank order of affinities of the cys-LTs for the CysLT 1 and CysLT 2 receptors is LTD 4 Ͼ LTC 4 Ͼ LTE 4 Ͼ Ͼ LTB 4 and LTC 4 ϭ LTD 4 Ͼ Ͼ LTE 4 Ͼ Ͼ LTB 4 , respectively. The CysLT 1 receptor is expressed on airway smooth muscle, monocytes/ macrophages, eosinophils (5, 10, 11), a subset of neutrophils (11), mast cells (12, 13), and endothelial cells (14). The CysLT 2 receptor is expressed on monocyte/macrophages, airway smooth muscle, cardiac Purkinje cells, adrenal medulla cells, peripheral blood leukocytes, brain cells (7), eosinophils (11, 15), mast cells (16), and endothelial cells (17,18). We and others have reported that the mouse CysLT 1 receptor can function as a receptor for LTD 4 in transfected cells with a ligand preference similar to that of the...

GPR17 is a negative regulator of the cysteinyl leukotriene 1 receptor response to leukotriene D 4

“…We and others subsequently reported that the mouse CysLT 1 R can function as a receptor for LTD 4 in transfected cells with a ligand preference similar to that of the human CysLT 1 R (20, 21) and that the mouse CysLT 2 R exhibits a ligand profile of LTC 4 Ն LTD 4 Ͼ LTE 4 (21, 22). Targeted disruption of LTC 4 synthase, CysLT 1 R, and CysLT 2 R in mice confirmed the function of the cys-LTs in vascular smooth muscle and in the cellular aspects of allergic or chronic fibrotic pulmonary injury (23)(24)(25)(26)(27)). An additional receptor in porcine pulmonary arterial rings that is responsive to LTC 4 and LTD 4 , but not LTE 4 , has been recognized by differential pharmacologic responses or resistance to available receptor antagonists on various smooth muscle preparations (28,29).…”

Cysteinyl leukotriene 2 receptor and protease-activated receptor 1 activate strongly correlated early genes in human endothelial cells

“…However, these proinflammatory activities may be attenuated by COX-2 and DSCR1 up-regulation, as noted above. That the cysLT 2 -R mediates subacute types of fibroproliferative lung injury in vivo in response to bleomycin has recently been reported in cysLT 2 -R-deficient mice (40,41). Our data are consistent with the possibility that biological activities of the 5-LO pathway may result in lasting alterations of the EC phenotype, such as increased platelet-EC interactions, promotion of blood monocyte adhesion to the endothelium, participation in extracellular matrix remodeling, and reperfusion injury of the heart (40,41).…”

“…That the cysLT 2 -R mediates subacute types of fibroproliferative lung injury in vivo in response to bleomycin has recently been reported in cysLT 2 -R-deficient mice (40,41). Our data are consistent with the possibility that biological activities of the 5-LO pathway may result in lasting alterations of the EC phenotype, such as increased platelet-EC interactions, promotion of blood monocyte adhesion to the endothelium, participation in extracellular matrix remodeling, and reperfusion injury of the heart (40,41). The shared activities of LTD 4 and thrombin invite examination of the possibility that still further actions of thrombin in vivo may also be relevant for LTD 4 actions on EC cysLT 2 -R (20,42).…”

Leukotriene E4elicits respiratory epithelial cell mucin release through the G-protein–coupled receptor, GPR99

“…Ltc4s -/-mice were generated on a 129Sv background (37) and backcrossed for 15 generations onto the C57BL/6 background. Cysltr1 -/-and Cysltr2 -/-mice were generated on a C57BL/6 background as reported previously (38,39). C57BL/6 Gpr99 +/-mice were obtained from the National Institutes of Health Knock-Out Mouse Project and intercrossed to obtain Gpr99 -/-mice (25).…”