Iron chelation with a deferoxamine conjugate in hemorrhagic shock

Abstract

Oxygen-derived radicals are cytotoxic, highly reactive molecules that contribute to cellular death and injury in hemorrhagic shock. Iron released into the plasma in hemorrhagic shock may contribute to cellular damage by catalyzing lipid peroxidation of cell membranes. Deferoxamine (DFO) chelation of transitional metal ions prevents formation of these radicals and may diminish reperfusion injury. The conjugation of DFO to pentastarch (PS) decreases DFO toxicity and extends its half-life making it a potentially useful resuscitative fluid. A porcine hemorrhagic shock model was used to evaluate the effects of five resuscitative fluids on survival and hepatic function. Swine (11–16 kg) underwent splenectomy, liver biopsy, and placement of arterial and venous catheters. Awake animals were bled at 1 ml/kg/min to a MAP of 45 mm Hg, maintained for 1 hr, and resuscitated over 30 min with one of five fluids: Lactated Ringer's (LR); LR + free DFO 2.5 mg/ml (LR + DFO) ( n = 6); 5% PS in LR (PS) ( n = 6); 5% PS + free DFO (PS + DFO) 7.5 mg/ml ( n = 6); 5% PS/DFO conjugate (7.5 mg/ml) in LR ( n = 6). LR and LR + DFO received 3 ml/ml shed blood; PS, PS + DFO, and PS/DFO received 1 ml/ml shed blood. No shed blood was returned to the animals. There were no significant differences between groups in MAP, HR, CVP, and T pre- and post-resuscitation. No LR lived to sacrifice at 24 hr. Thirty-three percent of LR + DFO and PS + DFO animals died within minutes of receiving the free DFO containing resuscitative fluid, presumably from acute DFO toxicity. All other animals survived to sacrifice at 24 hr. Aspartate aminotransferase (AST) levels at 24 hr were significantly lower ( P < 0.05) for the PS/DFO animals compared to all other groups and there was no significant difference between the baseline and 24-hr AST level for the PS/DFO group ( P < 0.05). Serum iron levels were significantly decreased in all DFO groups post-resuscitation, and iron levels in the PS/DFO and PS + DFO groups remained decreased at 24 hr ( P < 0.05). Malonyldialdehyde (MDA), a marker of lipid peroxidation, was measured in liver homogenates in the PS and PS/DFO groups. The PS animals showed a 72.5 ± 32.9% increase from baseline MDA levels at 24 hr, but PS/DFO conjugate animals were essentially identical at baseline and 24 hr (−1.6 ± 14.1%, P < 0.001). These data suggest that iron chelation with a deferoxamine-hetastarch conjugate limits lipid peroxidation and may diminish reperfusion injury.