Essential metal ions alter the lactoferrin binding to the erythrocyte plasma membrane receptors.

The effect of metal ions at a concentration of 10(-8) to 10(-5) M [using their salts: ZnCl2, CdCl2, LiCl, CuSO4, NiSO4, Al2(SO4)3, (NH4)2MoO4 on the lactoferrin (Lf) binding to the erythrocyte membrane receptors was studied. In the absence of metal ions, Scatchard's analysis showed the existence of two kinds of binding site: one with high affinity and low capacity, and the another with low affinity and high capacity. All these metals, excluding Zn2+ and Cd2+, at a concentration 10(-5) M decreased the affinity of Lf binding (Ka1) to the high-affinity receptors. In the presence of Zn2+ and Cd2+, only the low-affinity binding site was found. Significant inhibition on the affinity (Ka2) of the low-affinity class of receptors showed Zn2+, Al3+, and Mo6+. Depending on their concentration (10(-8)-10(-5) M), these ions enhanced to a different extent, the binding capacity of the both types receptors, but the effect did not correspond to the applied doses. Several explanations of the mechanism for influence of the metal ions on the Lf-receptor interaction is discussed.

Effect of lactoferrin on the phagocytic activity of polymorphonuclear leucocytes isolated from blood of patients with autoimmune diseases and Staphylococcus aureus allergy.

Phagocytic number (PN) and phagocytic index (PI) of neutrophils isolated from blood of patients with autoimmune diseases, allergy to Staphylococcus aureus and from blood of healthy individuals were examined. Our results concerning the influence of lactoferrin (Lf); (6.7 mg/l) on the PI of PMN showed that: 1) Lf enhances reliable PI of PMN at the 30-th minute starting the phagocytic reaction in patients with autoimmune disease in an active stage, in blood donors treated as healthy with the presence of autoantibodies, in patients with autoimmune diseases and proved autoantibodies against tissue, cell antigens and collagen, 2) Lf influences non-significantly PI of PMN in patients with autoimmune collagen diseases in remission, 3) Lf increases PI of PMN with 19% only in 58% from the assessed patients with Staphylococcus aureus, and 4) Lf decreases non-significantly PI of PMN in the healthy controls. Our studies on the effect of Lf on the phagocytic activity of PMN suggest that Lf has stronger effect on the PN compared to the PI: 1) Lf enhances with 86% the PN in patients with Staphylococcus aureus, 2) Lf increases PN of PMN in all of the assessed patients with autoimmune collagen diseases in active stage (mean with 72%), and 3) Lf increases PN of PMN in 4 from the 5 investigated healthy controls (mean with 22%). Our results show a "corrective" effect of Lf on the phagocytic functions in the investigated groups of patients. The possible mechanisms, by which Lf increases PN and PI of neutrophils, is discussed: 1) they may concern the antioxidative properties of Lf to block the iron ions in their catalytic inactive form or to take part as ferric-Lf in an oxidative-reduction processes on the plasma membrane and controlling transmembrane transport systems, 2) Lf decreases the negative surface charge and thus enhances the adherent ability of the PMN. Probably to this stimulated adherent ability dues the increased ingestion of bacteria in the presence of Lf, and 3) The "changed" membrane of PMN may have higher number receptors for Lf to bind more molecules of exogenous Lf. The increase of Lf binding which enhances the adherence and aggregation of neutrophils, facilitates the phagocytosis.

Superoxide dismutase and lipid-bound sialic acid in sera from children with cancers and juvenile chronic arthritis.

Both experimental and epidemiological studies suggest that patients with autoimmune and other chronic inflammatory diseases are more prone to develop cancer. The aim of the present investigation is to find some typical differences between the content of lipid-bound sialic acid (LSA) and the activity of superoxide dismutase (SOD) in sera from children with neoplastic diseases and juvenile chronic arthritis (JCA). Our results show 30% lower SOD activity in the sera from children with cancer compared with the sera from children with JCA. LSA levels 102% and 166% higher than in children with JCA were observed in the sera from children with blood and solid cancers, respectively. The relation LSA/SOD is about fivefold higher in children with cancers. A negative correlation (r = 0.720, P < 0.001) exists between LSA and SOD in sera from children with cancers. No such correlation was established in the group of children with JCA. We suppose that such differentiation disappears in the beginning of neoplastic process during prolonged therapy of autoimmune diseases. From our findings SOD and LSA appear to be putative markers of malignant disease with potential usefulness not only in JCA but also in other conditions associated with an increased risk of neoplastic development.

Effect of bovine milk antigens and egg lysozyme on the binding of 59Fe-lactoferrin to platelet plasma membranes.

1. Platelets bind specifically to lactoferrin. A significant similarity between human lactoferrin and some bovine milk proteins has been established. 2. Because of the structural homology of lactoferrin and cows milk proteins they are able to influence lactoferrins regulatory function on the level of its binding to membrane receptors on platelets. 3. An inhibitory effect of bovine alpha-lactalbumin and of beta-lactoglobulin on lactoferrin-receptor interaction was shown. 4. Bovine alpha-lactalbumin competes with lactoferrin for the binding sites. 5. Scatchard plot analysis of data shows one binding site for lactoferrin in the presence of alpha-lactalbumin with an affinity constant, Ka = 0.46 x 10(9) mol/l and 335 receptors/cell. 6. The inhibitory effect of beta-lactoglobulin reaches 62% and is different for the common fraction beta-lactoglobulin and the genetic variants beta-lactoglobulin A and B. 7. beta-lactoglobulin does not compete with lactoferrin for the membrane receptors. 8. Bovine casein and egg lysozyme stimulate 59Fe-lactoferrin binding to the receptors. The mechanism of these effects is still unknown. 9. Tested alimentary antigens are able to interact with lactoferrin and also with some platelet membrane structures. 10. Established changes in lactoferrin binding to the platelet membrane might be in relation to lactoferrins regulatory function and (or) eliminating mechanisms of these alimentary antigens.

Lactoferrin binding to human platelets.

1. Platelets bind specifically lactoferrin. 2. The lactoferrin binding to the platelets depends on the concentration of labelled lactoferrin, the number of platelets, the time of incubation and pH. 3. The binding was characterized by two types of binding site: one with high affinity and low capacity, and another with low affinity and high capacity (respectively Kaff1 = 13.6 x 10(9) l/mol and about 40 binding sites, and Kaff2 = 1.23 x 10(9) l/mol and about 135 binding sites per platelet). 4. Both human transferrin and bovine lactoferrin compete with human lactoferrin for the receptors. 5. The presence of lactoferrin receptors on the platelet membrane surface is connected most probably with the effect(s) on the cell function(s) of these cells.

The effect of zinc on [59Fe]lactoferrin binding to blood neutrophilic leucocytes and colostral cells.

Zn2+ inhibits the binding of [59Fe]lactoferrin to neutrophilic leucocytes. The inhibiting effect is proportional to zinc concentration in the range 10-330 mumol/l. Zn2+ inhibits the [59Fe]lactoferrin binding to the colostral cells in the same degree as PMN. The inhibiting effect of Zn2+ on [59Fe]lactoferrin binding to neutrophilic leucocytes is equal to those of non-labelled lactoferrin and transferrin. Fe2+ and Cu2+ does not have such effect on binding of [59Fe]lactoferrin to the PMN leucocytes.

Lactoferrin binding to neutrophilic polymorphonuclear leucocytes.

Neutrophilic polymorphonuclear leukocytes (PMN) bind specifically lactoferrin. This binding was characterized by two types of binding sites: with higher affinity and low capacity and another site with lower affinity and higher capacity (respectively Kaff 1 = 2.2 X 10(9) M-1 and about 39,000 binding sites per cell and Kaff2 = 0.6 X 10(9) M-1 and 76,000 binding sites per cell). The lactoferrin binding to PMN leucocytes depends on the concentration of labelled lactoferrin, the number of cells and the time for incubation. The presence of lactoferrin receptors on the PMN leucocytes is connected most probably with its effect on the cell function of these cells.