Objective: The cysteinyl leukotrienes (CysLTs) are lipid mediators that have been implicated in the pathogenesis of allergic rhinitis. Pharmacological studies of CysLTs indicate that two classes of receptors, CysLT1R and CysLT2R exist. CysLT1R is a high affinity LTD4 receptor with lower affinity for LTC4, and a CysLT1R antagonist is currently used to treat asthma and allergic rhinitis. CysLT2R binds to LTC4 and LTD4 with equal affinity. GPR99 (also called GPR80), previously described as an oxoglutarate receptor (OXGR1), has recently emerged as a potential novel receptor with LTE4. The purpose of this study was to determine the expression and localization of GPR99 protein in the human nasal mucosa.
Methods: Human turbinates were obtained after turbinectomy from 12 patients with nasal obstruction refractory to medical therapy. GPR99 protein expression was evaluated by western blotting, and the specific cells expressing GPR99 protein identified by immunostaining using a commercial anti-GPR99 (OXGR1) monoclonal antibody.
Results: A 38-kDa band was detected in the western blots of human nasal samples by using the anti-GPR99 monoclonal antibody. We did not find any differences in GPR99 protein levels between allergic and non-allergic nasal mucosa. The immunohistochemical studies revealed that the anti-GPR99 monoclonal antibody mainly labeled vascular smooth muscle cells in the nasal mucosa.
Conclusion: These immunohistochemical results suggest that GPR99 may play some roles in the vascular response. Further functional studies will be necessary to clarify the biological significance of the GPR99 receptor in nasal vasculature.
Keywords: GPR99; Human turbinate; Immunohistochemistry; Leukotriene E4; OXGR1.
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