TEMPOL PREVENTS IMPAIRMENT OF THE ENDOTHELIAL-CELL WOUND-HEALING RESPONSE CAUSED BY IONIZING-RADIATION

It is known that radiation therapy results in some form of damage to t he microcirculation. In support of this view, we found that capillary endothelial cells (EC) treated with X-rays (8 Gy) were defective in th eir ability to recover a denuded area. A scrape wound of 2 mm width wa s produced in monolayers 30 min after X-ray or sham treatment. After 4 8 h, the number of cells migrating into each of five successive 125 mu m zones from both sides of the original wound were determined. Greate r numbers of sham-treated EC entered zones 3 and 4, compared with irra diated cultures, and only sham-treated EC entered the most distant zon e 5. We examined actin fibre orientation within migrating irradiated a nd sham-treated EC using 2-(D-2-aminobutanoic -9-yl)carboxyphenyl)amin o)thioxomethyl)-L-lysine), chloride (NBD)-phalloidin, immunofluorescen t microscopy and computer image analysis. After 48 h, sham-treated, bu t not irradiated EC, contained actin which was orientated perpendicula r to the original wound edge. After 6-9 days, only sham-treated EC clo sed the wounds. Tempol (4 hydroxy-2,2,6,6-tetra methylpiperidine-1-oxy )(0.5 or 2 mM)), included in the media during irradiation, prevented t his wound healing delay, when measured within the first 24 h. In concl usion, radiation treatment of capillary EC results in a wound healing defect. This defect appears to be related to the EC's inability to rea lign actin. Tempol protects EC from exhibiting a wound healing delay.