Expression of prostaglandin receptors EP₄ and FP in human lens epithelial cells

Purpose. To examine the expression of prostaglandin (PG) receptors EP₂, EP₄, and FP in a human lens epithelial cell line (HLE-B3) at molecular and pharmacologic levels. Methods. Reverse transcription-polymerase chain reactions (RT-PCR) were performed with total RNA preparations from HLE-B3 cells using sense and antisense primers for each of the three prostaglandin receptors. The PCR products were hybridized with specific ³²P-labeled probes and, for further confirmation, digested with appropriate restriction enzymes. At the pharmacologic level, the expression of EP₄ receptors was determined by measuring intracellular cyclic adenosine monophosphate (cAMP) formation in response to PGE₂ (EP₁, EP₂, EP₃, and EP₄ agonist) and the EP₄ receptor-selective antagonist AH23848. The expression of FP receptors in HLE-B3 cells was explored by measuring intracellular [Ca²⁺](i) mobilization. Results. RT-PCR generated DNA products of predicted sizes corresponding to the EP₂, EP₄, and FP receptors. Hybridization of the PCR products with specific ³²P-labeled probes and restriction digestion of the PCR products further confirmed that they were generated from the respective EP₂, EP₄, and FP mRNAs. The EP receptor agonist PGE₂ significantly increased the cAMP level in HLE-B3 cells. The formation of cAMP by PGE₂ was concentration-dependently inhibited by the EP₄ receptor-selective antagonist AH23848. Stimulation of HLE-B3 cells by the FP receptor agonist fluprostenol increased [Ca²⁺](i) in the time-dependent manner. Conclusions. The results of the molecular biologic and pharmacologic experiments showed conclusively the presence of EP₄ and FP receptor messenger RNAs and proteins, respectively, in HLE-B3 cells.