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Tissue injury triggers a complex network of cellular and molecular responses. Although cell migration and proliferation are the most conspicuous, several other responses, such as apoptosis and increased protease activity, are necessary for a proper restitution of the tissue. In this work, we study the leukocyte elastase inhibitor (LEI) expression during wound healing of bovine corneal endothelial monolayers in culture. LEI is a multifunctional protein with anti-protease and anti-apoptotic activity. When properly cleaved, it is transformed into L-DNase II, a pro-apoptotic enzyme and translocated to the nucleus. We found that early after injury LEI increases its protein and mRNA expressions, without nuclear translocation and returns to basal levels immediately after wound closure. This increase is blocked by N-acetylcysteine, suggesting that production of reactive oxygen species immediately after wounding is involved in the LEI increase. Another finding of this work is that there is an acidification of the cells at the wound border which, in contrast to other cell types, does not determine nuclear translocation of the protein. Taken together, the results of this work suggest that the function of LEI during wound healing is related to its activity as a protease inhibitor and/or to its anti-apoptotic activity.

Previous work from our laboratory and others has shown that, in some epithelia, the epithelial sodium channel (ENaC) increases its expression during wound healing. In these cases, inhibition of the channel determines a decrease in the healing rate, a result suggesting a role for ENaC in the overall healing process. To understand further this role of ENaC in epithelia, we explored the participation of ENaC in wound healing in four cultured epithelial cell lines selected on the basis of their different embryonic origins, function and modality of healing, i.e., by lamellipodial cell crawling or by actin cable formation. Three of the cell lines (bovine corneal endothelial cells, rabbit corneal epithelial cells and Madin-Darby canine kidney cells) exhibited an increase in ENaC expression and consequent membrane potential depolarization and an increase in cytosolic sodium and calcium, whereas one line (bovine aortal endothelial cells, BAEC) did not exhibit any of these changes. In all of the cell lines, however, ENaC inhibition determined a similar decrease in the rate of wound healing. In BAEC monolayers, the increase in ENaC activity produced plasma membrane depolarization, increased cytosolic sodium and calcium, and augmented the velocity of healing. These novel findings contribute to the idea that ENaC plays a critical role in wound healing in various epithelia, independently of the modality of healing and of any increase in the expression of the channel.