The cysteinyl leukotriene 2 receptor mediates retinal edema and pathological neovascularization in a murine model of oxygen‐induced retinopathy

Abstract

Leukotrienes have been implicated in the pathogenesis of degenerative diabetic retinopathy, with research focusing primarily on leukotriene B(4), with little attention devoted to the cysteinyl leukotrienes (cysLTs), which act through cysLT receptors (CysLT(1)R and CysLT(2)R). We demonstrate here the presence of CysLT(2)R in pericytes and endothelial cells of superficial retinal vasculature using an indirect assay by assessment of β-galactosidase expression in CysLT(2)R-knockout (KO) mice. Retinal damage was induced in KO and wild-type (WT) mice using an established oxygen-induced retinopathy (OIR) model. CysLT(2)R expression following OIR was intensely up-regulated compared to sham-treated controls. Staining with Griffonia simplicifolia lectin revealed enhanced tissue damage (as assessed by vasoobliteration/vasoproliferation) in KO mice compared to WT controls, yet the opposite was true with respect to retinal edema. However, vascular endothelial growth factor receptor 1 (VEGFR1) transcripts were increased by OIR similarly with respect to genotype. Intravitreal application of exogenous cysLTs elicited greater vasculature leakage (assessed ex vivo) in eyes from WT mice compared to KO mice. While mRNA encoding enzymes for various components of the leukotriene cascade were detected in sham- and OIR-treated retinas, only prostaglandins and hydroxyeicosatetraenoic acids, but not leukotrienes, were detected in A23187-treated retina preparations. Together, these results implicate the CysLT(2)R in the progression of ischemic retinopathy.

Phenotype-based Discovery of 2-[(E)-2-(Quinolin-2-yl)vinyl]phenol as a Novel Regulator of Ocular Angiogenesis

“…This may be due to the drug targeting one specific CysLT receptor at lower concentrations and more than one CysLT receptor at higher concentrations. In agreement, Barajas-Espinosa et al (37) reported a similar finding when Cyslt2r knockout mice were exposed to the OIR experimental paradigm. P17 flat-mount retinas, the same time point analyzed in our study, exhibited both reduced revascularization and increased neovascularization.…”

“…5B). Previous studies have confirmed retinal expression of CysLT 1 in rodent models of retinal neovascularization (37), and we demonstrated here ocular expression of the zebrafish cysltr1 and cysltr2 genes during hyaloid vessel development (Fig. 5D) and expression of cysteinyl leukotriene receptors 1 and 2 in human endothelial cells (HMEC-1), human retinal microvascular endothelial cells (ACBRI-181), and human RPE cells (ARPE-19) (Fig.…”

“…Adult Cysltr2 knockout mice show no retinal vascular phenotype compared with wild types (37). In agreement, preliminary analysis of isolectin-stained retinal flat mounts from P8 Cysltr1 or Cysltr2 knockout mice suggest that neither receptor alone is required for retinal developmental angiogenesis (data not shown).…”

“…Recently montelukast has been reported to reduce neuroinflammation in an aged rat model, acting via inhibition of a separate cysteinyl leukotriene receptor, GPR17 (56), and a fourth cysteinyl leukotriene receptor, GPR99, has been proposed (26). In genetic loss-of function models, cysteinyl leukotriene receptors demonstrate cognate compensatory up-regulation (37,39,57). Thus, there are exciting future opportunities to decipher the cysLT receptors exhibiting co-regulatory expression to understand the underlying control mechanisms and to determine the combinations of cysLT receptors that regulate physiological phenotypes.…”

“…Previous studies have reported a role for CysLTs in inflammation, vascular permeability, immune responses, tissue repair, and regeneration (28,(33)(34)(35)(36). CysLT 2 and CysLT 1 are expressed in the murine retina, and exogenous cysLTs are sufficient to induce retinal edema (37). Here quininib inhibits known cysteinyl leukotriene receptor signaling pathways, reducing ERK phosphorylation in response to leukotriene D4 agonism (38,39).…”