OP 53 Anti-hemolytic effects ofα1-microglobulin – A possible mechanism for pre-eclampsia treatment

Abstract

Introduction The rupture of the red blood cells (RBCs), hemolysis, is followed by leakage of cytosolic components such as hemoglobin (Hb). Free Hb can be toxic to the cells and tissues mainly because of the heme-chelated iron which has strong oxidative reactivity. Oxidative stress is therefore seen in many diseases with hemolysis. One of the characteristics of pre-eclampsia (PE) is the increase of free fetal hemoglobin (HbF) in the maternal circulation, suggesting that fetal hemolysis contributes to the pathogenesis of PE. The tissue and plasma protein α 1-microglobulin (A1M) is a human endogeneous antioxidant protecting against Hb-induced oxidative stress. A1M has previously been shown to prevent heme-induced cell death in vitro and heme-and hemolysis induced damage in different animal models including PE, and has been suggested as a potential treatment of PE. Objectives 1. To compare the susceptibility to stress-induced hemolysis of maternal and fetal RBCs in healthy and pre-eclamptic patients. 2. To determine if A1M has protective effects and can reduce hemolysis when RBCs are subjected to stress. Patients and methods Blood was drawn from healthy, non-pregnant donors. Maternal and fetal (chord) blood was obtained from healthy and pre-eclamptic pregnant patients. Red blood cells were washed and incubated with A1M (recombinantly produced in E. coli) for up to 22 h while exposed to mechanical, osmotic (water-dilution) or oxidative (heme or Fenton-reaction) stress. The amount of hemolysis was assessed by measuring LDH- and Hb-release. Western blotting and transmission electron microscopy (TEM) were also performed to examine hemolysis and A1M-uptake of RBCs. Results A1M significantly reduced hemolysis of RBCs subjected to mechanical, osmotic or oxidative stress, measured by LDH- and Hb-release after 1, 3 and 22 h. Western blotting and TEM showed that A1M was taken up by RBCs. Fetal RBCs showed significantly higher degree of hemolysis (LDH-leakage), after subjection to mechanical or oxidative stress, compared to maternal RBCs, after 22 h incubation. Hemolysis of both maternal and fetal RBCs was significantly reduced with A1M. Conclusion Hemolysis of fetal RBCs may be a novel pathogenic mechanism of PE and our results suggest that the anti-hemolytic effects of A1M may be exploited into a potential treatment of the disease. Download : Download high-res image (355KB) Download : Download full-size image Download : Download high-res image (244KB) Download : Download full-size image