Direct evidence of nitric oxide production induced by lactoferrin and its enhancement by magnesium ions in cultured endothelial cells.

Bovine lactoferrin (BLF) reportedly lowers blood pressure and induces vasorelaxation, but its effect on nitric oxide (NO) production has not been established. Accordingly, we aimed to determine whether BLF induces NO production in bovine aortic endothelial cells, and the effects of extracellular free magnesium (Mg) ion concentrations on this NO production. BLF induced NO production time-dependently. NO production was markedly inhibited by the NO synthase inhibitor, NG-nitro-L-arginine methyl ester, in an effect abolished by L-arginine, but not D-arginine. NO production was suppressed at low concentrations, and enhanced at high concentrations, of Mg ions in culture medium. These results suggest that BLF has an important role in hypotensive effects. Mg ions may affect BLF-induced NO production.

Protection against infections by oral lactoferrin: evaluation in animal models.

It has been reported previously that oral administration of lactoferrin (LF) provides some host-protective effects against infections, cancers, and inflammations. In this review, we focus on the effect of oral LF on various infectious diseases and discuss the mechanism as elucidated in animal models. In the case of infections occurring at sites other than the digestive canal, it is unclear whether oral LF is absorbed from the intestine and exerts its protective effect at the site of infection. In preterm human infants, neonatal pigs, and rats with colitis, it was reported that LF is detectable in various body fluids after oral administration. We could not detect the transport of oral bovine LF into the blood of adult rats without gastrointestinal illness using several techniques, suggesting that there is an extremely low level of transport of LF, if any. Orally administered LF may act at the oro-gastro-intestinal mucosa and aid the defense system against infections through a network of mucosal immunity and systemic immunity. Indeed, it is reported that oral LF increases the number of cells in the leukocyte subset and cytokine (IFN-gamma and IL-18) production in the intestinal mucosa of mice. Regarding systemic immunity, we have observed an increase of leukocyte number, cytokine (IFN-gamma, TNF-alpha, IL-12, and IL-18) production, and effector activity of macrophages in response to LF administration in several animal models. These enhanced immune responses may contribute to eradication of the pathogen, resolution of the symptoms, and maintenance of the homeostasis during infectious diseases.

No detectable transfer of dietary lactoferrin or its functional fragments to portal blood in healthy adult rats.

We investigated the transfer of dietary bovine lactoferrin (LF) and its functional lactoferricin (LFcin) B-containing fragments to the portal blood of healthy adult rats by using several techniques. After a single administration of (125)I-labeled LF, radioactive bands were detected in autoradioluminograms of the portal blood, but similar bands were also observed after the administration of [(125)I]NaI. Although ovalbumin was detected by ELISA at 3-18 ng/ml in the portal blood plasma after an overnight administration, no LF was detected (< or =1.5 ng/ml). The antibody-captured ovalbumin fragments, but not the LF fragments, were detected in the plasma by surface-enhanced laser desorption/ionization affinity mass spectrometry (SELDI affinity MS). We finally attempted to detect the LFcin B-containing fragments by SELDI affinity MS with on-chip LFcin B-conversion, but could not detect them (< or =1 ng/ml) in the portal blood after the LF ingestion. The level of LF or its functional fragments transferred to the portal blood was therefore extremely low, if any.