The P2X7 Receptor in the Cornea

The P2X7 Receptor in the Cornea

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Abstract: The cornea is an integral part of the eye whose role is to refract light to the retina for vision. Therefore, the healing of a corneal wound needs to occur quickly and with negligible scarring to prevent vision impairment. The organization of collagen fibrils in the corneal stroma is essential for unimpeded refraction of light. Previous work demonstrated that Ca 2+ waves mediated by purinergic receptors propagate away from a wound, signaling that injury has occurred. The overall goal is to determine the role of the ATP activated ion gating P2X 7 receptor in mediating corneal epithelial wound healing and regulating the organization of collagen in the stroma. Corneal epithelial cells express C-terminal truncated P2X 7 splice variants that respond to the P2X 7 agonist, 3'-O-(4-benzoyl)benzoyl adenosine triphosphate (BzATP), but do not induce apoptosis, pore formation, or membrane blebbing, all of which are activated by the full-length receptor. Therefore, we hypothesize that P2X 7 mediates corneal wound healing, that co-regulation occurs between P2X 7 and P2Y receptors that mediate migration, and that P2X 7 is necessary for proper stromal ultrastructure. Upon P2X 7 down-regulation, corneal epithelial cell migration in response to BzATP was abolished. Additionally, healing of epithelial debridement wounds was delayed and the expression of pro-migratory proteins was altered in P2X 7 null (P2X 7 -/- ) mice. The interaction between P2X 7 and P2Y receptors was examined using Ca 2+ experiments in which pre-stimulation with BzATP resulted in an attenuated response to UTP, the agonist for P2Y 2 and P2Y 4 . In addition, when P2X 7 was down-regulated, the expression of P2Y 2 increased significantly, indicating compensatory regulation of P2X 7 and P2Y 2 . In the stroma, the expression of P2X 7 was shown to be required for collagen organization. The collagen in P2X 7 -/- mice exhibited decreased fibril diameters and increased interfibrillar spacing along with decreased expression of collagen types I and V and increased expression of collagen type III and lysyl oxidase. Decreases in lumican, decorin, and keratocan, with a contrasting increase in perlecan, were also detected in the P2X 7 -/- stromas. These results indicate that P2X 7 can mediate the activity and expression of P2Y 2 , and is required for corneal epithelial cell migration and maintenance of stromal collagen organization.Abstract: The cornea is an integral part of the eye whose role is to refract light to the retina for vision.

Title:The P2X7 Receptor in the Cornea
Author:Courtney Elizabeth Mayo
Publisher: - 2009


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