RESUMO
Lactoferrin is a milk protein that reportedly protects infants from gut-related, systemic infection. Proof for this concept is limited and was addressed during in vivo and in vitro studies. Neonatal rats pretreated orally with recombinant human lactoferrin (rh-LF) had less bacteremia and lower disease severity scores (P < 0.001) after intestinal infection with Escherichia coli. Control animals had 1,000-fold more colony-forming units of E. coli per milliliter of blood than treated animals (P < 0.001). Liver cultures from control animals had a twofold increase in bacterial counts compared with cultures from rh-LF-treated pups (P < 0.02). Oral therapy with rh-LF + FeSO(4) did not alter the protective effect. In vitro studies confirmed that rh-LF interacted with the infecting bacterium and rat macrophages. An in vitro assay showed that rh-LF did not kill E. coli, but a combination of rh-LF + lysozyme was microbicidal. In vitro studies showed that rat macrophages released escalating amounts of nitric oxide and tumor necrosis factor-alpha when stimulated with increasing concentrations of rh-LF. The in vitro studies suggest that rh-LF may act with other "natural peptide antibiotics" or may prime macrophages to kill E. coli in vivo.
Assuntos
Animais Recém-Nascidos/fisiologia , Infecções por Escherichia coli/prevenção & controle , Proteínas Imediatamente Precoces , Intestinos/microbiologia , Lactoferrina/farmacologia , Animais , Morte Celular , Contagem de Colônia Microbiana , Proteínas de Ligação a DNA/metabolismo , Combinação de Medicamentos , Proteína 1 de Resposta de Crescimento Precoce , Escherichia coli/efeitos dos fármacos , Escherichia coli/isolamento & purificação , Escherichia coli/fisiologia , Infecções por Escherichia coli/fisiopatologia , Feminino , Humanos , Fígado/microbiologia , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Muramidase/farmacologia , NF-kappa B/efeitos dos fármacos , NF-kappa B/fisiologia , Óxido Nítrico/metabolismo , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/farmacologia , Índice de Gravidade de Doença , Fatores de Transcrição/metabolismo , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Intravenous fructose-1,6-diphosphate (FDP) is reported to reverse shock and improves survival in animals given systemic lipopolysaccharide (LPS), although the mechanism is incompletely understood. Since endotoxin-related shock is associated with increased nitric oxide (NO) production, LPS-stimulated macrophages were treated with FDP, and the NO metabolite, nitrite, was measured 24 h later. Treatment of LPS-stimulated macrophages with 1, 5, or 10 mM FDP caused a dose-dependent reduction in mRNA expression for inducible NO synthase by Northern analysis and decreased the micromolar concentrations of nitrite produced by 17, 42, and 68%, respectively. Neither fructose nor sodium phosphate had these effects in LPS-exposed macrophages. Electrophoretic mobility shift assays revealed that FDP did not inhibit LPS-mediated activation of nuclear factor kappa B. Viability analysis showed that the FDP effect was not caused by cytotoxicity. Overall, these results suggest that fructose-1,6-diphosphate, a glycolytic intermediate with potential clinical use, may mitigate the adverse effects of LPS by regulating the generation of NO.
