Corneal disease and injury remain a major cause of blindness affecting over 10 million people worldwide according to the W.H.O.. Diabetes further complicates wound repair by slowing the healing process and impairing regeneration. We postulate that defective diabetic healing is in part due to changes in the regulation of signaling pathways including ion and G-protein coupled receptors and the composition of their underlying matrix. To study this problem we will examine the role of purinoreceptors in wound repair in a diabetic animal model and examine the changes in YAP (yes associated protein), a transcriptional regulator that is activated by changes in composition of the matrix that occur with diabetes. In the past grant period we made the novel observation that P2X7, an ion channel purinoreceptor, is significantly upregulated in the unwounded human diabetic corneal epithelium. A similar elevation in expression was detected in the corneal epithelium of diabetic rodents. We then made the novel observation that both the P2X7 transcript and protein drop rapidly after injury to control corneas, however the decrease in P2X7 levels does not occur in wounded diabetic epithelium. Furthermore, we have shown that P2Y2, a G-protein coupled purinoreceptor, is inversely correlated with levels of P2X7. We predict that this regulation of P2X7 and P2Y2 are required for proper healing in normal corneas and that impaired regulation is involved in defective diabetic healing. The P2X and P2Y purinoreceptor families are two classes of receptors that respond to changes in extracellular ATP due to cellular stress and trigger the phosphorylation of kinases in distinct downstream signaling pathways including paxillin, FAK, Src, and MAPK . Collectively these data indicate that the decrease in P2X7 may be one of the key regulatory events that mediate the early wound response and successful wound repair in the cornea and that this control does not occur in diabetic corneas. While it is known that the composition of the basement membrane zone (BMZ) changes in diabetic tissue, it is not understood how cells sense that change and respond. Previously investigators proposed that the release of soluble factors promote remodeling leading to changes in activation of YAP. Our preliminary data demonstrate that YAP is present in the cytoplasm of unwounded mouse corneal epithelium and moves to the nucleus in cells at the wound margin; however it remains cytoplasmic in epithelial wound margin epithelium from DIO mice. These indicate that the mechanoregulation which links signaling with cell adhesion and cell migration that occurs during wound repair is altered in diabetic epithelia.
Injury to the cornea can be both painful and compromise vision. We are investigating a protein called P2X7 that is present at higher levels in diabetic corneas than control corneas. As wound repair in diabetic eyes is often impaired, our goal is to determine the role of the P2X7 receptor in the repair of injured tissue.
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