RvE1 uses the LTB4 receptor BLT1 to increase [Ca2+]i and stimulate mucin secretion in cultured rat and human conjunctival goblet cells

Purpose: Specialized pro-resolving lipid mediator resolvin (Rv) E1 stimulates secretion including mucins from conjunctival goblet cells. RvE1 can use both its ChemR23 receptor and the LTB4 receptor BLT1 to increase [Ca2+](i). The purpose of this study was to determine the expression of ChemR23 and BLT1 and receptors on conjunctival goblet cells and the respective roles these two receptors play in goblet cell responses to RvE1. Methods: Goblet cells were cultured from male rat or human conjunctiva from both sexes. Western blotting analysis, reverse transcription PCR and immunofluorescence microscopy were used to demonstrate the expression of ChemR23 and BLT1 in conjunctival goblet cells. High molecular weight glycoprotein secretion was determined using an enzyme-linked lectin assay. Signaling pathways were studied by measuring the increase in [Ca2+](i) using fura 2/AM. Results: ChemR23 and BLT1 and receptors were present on both rat and human conjunctival goblet cells. The BLT1 inhibitors LY293111 and U75302 significantly blocked RvE1- and LTB4-stimulated [Ca2+](i) increase. RvE1- and LTB4-stimulated [Ca2+](i) and secretion increases were blocked by BLT1-targeted siRNA. RvE1-stimulated [Ca2+](i) and secretion increases were also blocked by ChemR23-targeted siRNA. Addition of RvE1 2 min before or simultaneously with LTB4 desensitized the LTB4 [Ca2+](i) response. Addition of RvE1 and LTB4 simultaneously caused secretion that was decreased compared to either response alone. Conclusion: RvE1, in addition to the ChemR23 receptor, uses the BLT1 receptor to increase [Ca2+](i) and stimulate secretion in both rat and human cultured conjunctival goblet cells.