Abstract TP333: Lactoferrin as Contributor to Beneficial Effect of Neutrophil After Intracerebral Hemorrhage

Abstract

Background: Lactoferrin (LTF) is an essential, high-affinity iron-binding protein that is abundant in the secondary granules of neutrophils. After intracerebral hemorrhage (ICH), circulating blood neutrophils (PMNs) enter the ICH-afflicted brain and secrete LTF into the damaged tissue. This LTF can bind to iron and hemoglobin (key toxic components of the hematoma) thereby neutralizing toxicity of the hematoma. Here we study the role of LTF in the rodent brain after ICH. Methods and Results: In an autologous blood injection model of ICH in rats using RT-PCR and Western blotting, we measured the expression of LTF in ICH-affected brain. We found that LTF mRNA is virtually undetectable in the naïve rats’ brains and brains of rats at 3h to 7d after ICH. These findings suggest that LTF is not synthesized in the brain. LTF protein was not detectable in the naïve rat brain; however, the LTF protein is increased starting 3-6h post-ICH in the hematoma-affected hemispheres, reached maximum by 24-48h, and remained elevated for about 7d. Double immunofluorescence for LTF and RP-1 antigen (a biomarker for PMNs) shows that most LTF + -cells in the ICH-affected brains are PMNs. The locations of LTF + -cells in the brain were primarily peri-hematoma and the hematomas, which are loci of PMNs infiltration. Also, the temporal profile of LTF level and the number of PMNs in the brain were similar. We also detected a similar progression of LTF changes in the peripheral blood after ICH. Finally, in the ICH model in rats, administration of the recombinant LTF (rLTF) after the onset of ICH significantly reduced brain edema, oxidative damage, and neurological deficits, as assessed on day 3. Interestingly, in neuron-glial co-culture, after exposing these cells to red blood cells (RBCs; to simulate ICH-mediated injury), rLTF reduced the neurotoxic effect of RBCs and accelerated the removal of RBCs by microglia. This suggests that the cytoprotective effect of LTF and the modulation of microglia’s phenotype could underlie the beneficial role of LTF, with neutrophils being a primary source of LTF production. Conclusion: We propose that LTF delivered to the ICH-affected brain by infiltrating activated PMNS could be beneficial for hematoma detoxification, which may be a potential target for ICH therapy.