Tempol prevents impairment of the endothelial cell wound healing response caused by ionising radiation.

It is known that radiation therapy results in some form of damage to the microcirculation. In support of this view, we found that capillary endothelial cells (EC) treated with X-rays (8 Gy) were defective in their ability to recover a denuded area. A scrape wound of 2 mm width was produced in monolayers 30 min after X-ray or sham treatment. After 48 h, the number of cells migrating into each of five successive 125 microns zones from both sides of the original wound were determined. Greater numbers of sham-treated EC entered zones 3 and 4, compared with irradiated cultures, and only sham-treated EC entered the most distant zone 5. We examined actin fibre orientation within migrating irradiated and sham-treated EC using 2-(D-2-aminobutanoic acid)-7-(N6-((((3,6-bis(dimethylamino)xanthylium-9-yl) carboxyphenyl) amino)thioxomethyl)-L-lysine), chloride (NBD)-phalloidin, immunofluorescent microscopy and computer image analysis. After 48 h, sham-treated, but not irradiated EC, contained actin which was orientated perpendicular to the original wound edge. After 6-9 days, only sham-treated EC closed the wounds. Tempol (4 hydroxy-2,2,6,6-tetra methylpiperidine-1-oxyl)(0.5 or 2 mM)), included in the media during irradiation, prevented this wound healing delay, when measured within the first 24 h. In conclusion, radiation treatment of capillary EC results in a wound healing defect. This defect appears to be related to the EC's inability to realign actin. Tempol protects EC from exhibiting a wound healing delay.