Effects of phosphorothioate oligodeoxynucleotide on hemoglobin-induced damage to intestinal mucosa

Some "blood substitutes," such as human diaspirin cross-linked hemoglobin DBBF-Hb, can damage the intestinal mucosa. This response may be due to release of free iron from Hb leading to production of reactive oxygen species (ROS). Phosphorothioate oligodeoxynucleotides can bind and sequester iron. Therefore experiments were performed to test whether PS-ODN, composed of ten consecutive cytidines "C-10," reduces Hb-induced ROS generation and damage in the mucosa. Anesthetized Sprague-Dawley rats (4-6 per group) were injected arterially with 1 mg C-10, followed two minutes later by 50 mg DBBF-Hb. The positive controls received only DBBF-Hb and the negative controls either saline or PS-ODN followed by saline. Either ROS formation was monitored using a fluorescence technique, or the intestine was fixed for microscopy after 8 or 30 min. Sixty villi per rat were assigned an epithelial integrity index (EI), ranging from 1 (intact) to 3 (some cell-cell and cell-basement membrane separation). Pretreatment with PS-ODN significantly exacerbated DBBF-Hb-induced ROS formation, and PS-ODN groups showed significantly more epithelial damage near Peyer's patches, (EI of 1.93 +/- 0.06 (SEM) at 8 minutes and 1.31 +/- 0.04 at thirty minutes), than the negative controls, (1.11 +/- 0.02 at both 8 and 30 minutes), or the positive controls (1.43 +/- 0.05 at 8 minutes and 1.20 +/- 0.03 at 30 minutes) (p < 0.05). However, mast cell degranulation, eosinophil accumulation and goblet cell secretion were significantly reduced in the DBBF-Hb groups pre-treated with PS-ODN. Thus, PS-ODN, although an iron chelator, can significantly enhance epithelial damage caused by DBBF-Hb in the rat intestinal mucosa near Peyer's patches, possibly by formation of the ferryl component of the hemoglobin.