Cysteinyl leukotriene 2 receptor characterization

Two classes of cysteinyl leukotriene (CysLT) receptors, CysLT1R and CysLT2R, have been identified and pharmacologically characterized in human tissues. While the CysLT1R mediates the proinflammatory effects of leukotrienes in human asthma, the physiological roles of CysLT 2R are not defined and a suitable mouse model would be useful in delineating function. We cloned the mouse CysLT2R (mCysLT2R) from heart tissue. mCysLT2R cDNA encodes a protein of 309 amino acids, truncated at both ends compared to the human ortholog (hCysLT2R). The gene resides on the central region of mouse chromosome 14 and is composed of 6 exons with the entire coding region located in the last exon. Two 5 ′UTR splice variants were identified with the short form lacking exon 3 as the predominant transcript. Expression of mCysLT2R was detected in spleen, thymus, adrenal gland, and discrete sites in heart including Purkinje cells and endothelial cells. CysLTs elicited intracellular calcium mobilization in HEK 293T cells transfected with recombinant mCysLT2R with a rank order potency of LTC4 = LTD4 [special characters omitted] LTE4. [3H]LTD4 binding to membranes expressing mCysLT2R could be effectively competed by LTC4 and LTD4, and only partially inhibited by LTE4 and BAYu9773. The identification of mCysLT2R will be useful for establishing transgenic mouse models. Pharmacological studies demonstrated the functional existence of CysLT 2R in vascular wall. We generated an endothelial cell-specific human CysLT2R (EC-hCysLT2R) transgenic (TG) mouse model using the Tie2 promoter/enhancer. Strong expression of hCysLT2R in TG lung and endothelial cells, detected by real time PCR, markedly enhanced CysLT-stimulated intracellular calcium mobilization when compared to the endogenous expression in cells from nontransgenic (NTG) mice. TG mice displayed an augmented vascular permeability response to LTC4 applied exogenously and also to CysLTs produced endogenously during passive cutaneous anaphylaxis as measured by Evans blue dye leakage in ear vasculature. The rapid, systemic pressor response to intravenous LTC4 was also diminished in TG mice, coincidental with augmented production of nitric oxide. These results indicated that CysLT 2R plays important vascular modulatory roles that can be explored in depth using EC-hCysLT2R mice