EP3 Expression and Functions in Human Ocular Surface Epithelium

Abstract

Purpose: : We previously reported that prostaglandin (PG) E receptor subtype EP3 is constitutively expressed in the ocular surface epithelium of mice, and that PGE₂ acts on EP3 in conjunctival epithelium and down-regulates the progression of murine experimental allergic conjunctivitis. In this study, we examined the expression of EP3 in human ocular surface epithelium and compared the EP3 expression in conjunctival epithelium between various ocular surface diseases. Furthermore, we also examined the function of EP3 using an EP3 agonist.

Methods: : The expression of EP3 was examined by RT-PCR and immunohistochemistry in normal conjunctival epithelium and corneal epithelium. Moreover, EP3 expression was examined in conjunctival epithelium from various ocular surface diseases by immunohistochemistry. Next, to examine the function of EP3, primary cultivated human conjunctival epithelial cells (PHCjE) were either left untreated or pre-treated by the EP3 agonist, 10ug/ml of AE248, and then incubated for 24 hrs with 10ug/ml polyI:C. The amount of CXCL10, CXCL11, RANTES, CCL20, IL-6, and IL-8 proteins was determined by ELISA.

Results: : The ocular surface epithelium, both corneal and conjunctival epithelium, expressed EP3-specific mRNA. Immunohistochemistry of ocular surface tissues revealed that conjunctival epithelial cells expressed the EP3 protein, while we could not find the positive signal in corneal epithelium, presumably because of decreased expression of the EP3 protein. Although we could clearly find the positive signal in conjunctival epithelium from conjunctivochalasis and pterygium patients, we could not find the positive signal in conjunctival epithelium from Steven`s-Johnson Syndrome (SJS), Toxic Epidermal Necrolysis(TEN), or Ocular Cicatricial Pemphigoid (OCP) patients. In PHCjE stimulated with polyI:C, pre-treatment by the EP3 agonist significantly suppressed the production of CXCL10, CXCL11, RANTES, CCL20, IL-6, but not IL-8.

Conclusions: : EP3 was expressed in conjunctival epithelium from non-inflammatory ocular surface diseases such as conjunctivochalasis and pterygium, but not from inflammatory ocular surface diseases such as SJS and OCP. EP3 in conjunctival epithelium might regulate ocular surface inflammation.

Keywords: conjunctiva • inflammation • immunohistochemistry