EVALUATION OF THE EFFECTS OF LACTOFERRINE ON THE HUMAN ERYTHROCYTE MEMBRANE

Lactoferrin. Na,K-ATPase. Ca 2+-ATPase. Erthrocytes. Membrane.

Lactoferrin is a protein involved in iron homeostasis and it is specifically bound to erythrocytes. Previous studies have shown that the iron ion can alter the composition of the plasma membrane of human erythrocytes and stimulate the activity of the enzyme Na,K-ATPase (NKA). Therefore, we sought to identify whether lactoferrin

would also induce changes. Whole blood samples were collected from healthy volunteers and cytoplasm-free membrane preparations (ghost) were obtained. Ghosts were treated with increasing concentrations of lactoferrin (1 nM to 1 µM), for 30 minutes, at 37 ºC. Whole erythrocytes were treated with lactoferrin 1 nM, 50 nM

and 1 µM for 24 hours, at 4 oC. Membranes from pig renal medulla (which has only α1 isoform) and brain cortex membrane preparations of Wistar rats (which have α 1, 2 and 3) were used to evaluate the NKA isoforms involved in lactoferrin effects. A decrease in the content of serum Fe 3+ and the formation of Reactive Substances to Thiobarbituric Acid (TBARS) was observed, demonstrating the antioxidant activity of

lactoferrin on erythrocytes. No morphological changes were observed in the treated erythrocytes, but an increase in cholesterol and total membrane phospholipids was observed. The activation of plasma membrane Ca

2+-ATPase was observed only with treatment with the highest concentrations of lactoferrin, both in membrane

preparations and in erythrocytes. Membrane preparations and lactoferrin-treated whole erythrocytes showed increased NKA activity compared to a control group and this activation is not related to their enzymatic conformation (E1 or E2). Concerning the isoforms of NKA, there was no activation of the α1 isoform and there was activation of the α2 e α3 isoforms. Since erythrocytes do not have α2, these results suggest that its activation may be related to α3 isoform. Since NKA is widely distributed throughout the body and is involved in many signaling processes, the activation of NKA may be one of the mechanisms of action that could explain the

biological activity of lactoferrin, however further studies are needed to elucidate the kinetics involved in this increase and its consequences at the cellular level.