ADENINE-NUCLEOTIDE AND PROTEIN-KINASE-C REGULATION OF RENAL TUBULAR EPITHELIAL-CELL WOUND-HEALING

The present studies were done to determine the effect of selected aden ine nucleotides on healing of wounds made by mechanically denuding are as in confluent monolayers of renal tubular epithelial cells. We found that hydrolyzable and nonhydrolyzable forms of ATP but not UTP stimul ated healing of LLC-PK1 cell wounds, while both ATP and UTP promoted h ealing of MDCK cell wounds, suggesting that different subtypes of puri noceptors regulated wound healing in these cells. Stimulation of wound healing by ATP was equivalent in control cells and in cells in which irradiation suppressed proliferation, suggesting a prominent role for cell migration in the healing process. Since ATP receptors are often l inked to activation of protein kinase C, the effect of a protein kinas e C activator (4 beta-phorbol 12-myristate 13-acetate, PMA) on wound h ealing was studied. Long-term (24 hr) exposure to PMA inhibited while short-term (30-120 min) exposure to PMA enhanced cell wound healing. T wo chemically and mechanistically dissimilar protein kinase C inhibito rs (calphostin C and chelerythrine) inhibited LLC-PK1 and MDCK cell wo und healing, and calphostin C prevented ATP enhancement of LLC-PK1 hea ling. These observations suggest a role for protein kinase C in regula tion of basal and adenine nucleotide-stimulated wound healing. Adenosi ne triphosphate did not affect cell-cell adhesion of either LLC-PK1 or MDCK cells. Adenine nucleotides and PMA enhanced and calphostin C inh ibited short-term adhesion of LLC-PK1 and MDCK cells to plastic and to other substrates such as fibronectin, laminin and collagen type IV. T hese results demonstrate that ATP and protein kinase C can stimulate h ealing of two types of renal tubular epithelial cell wounds. The effec ts of ATP to promote wound healing appear to occur by purinoceptors wh ich stimulate cell migration, and a protein kinase C mechanism may be involved in this migration.