Regulation of cytokine release from mononuclear cells by the iron- binding protein lactoferrin

Abstract

The iron-binding protein lactoferrin (Lf) is a constituent of neutrophil secondary granules and is discharged into the surrounding medium when neutrophils are activated. Lf released from neutrophils phagocytosing opsonized particles inhibits proliferation of mixed lymphocyte cultures (MLC) and has also been shown to inhibit granulopoiesis, suppress antibody production, and regulate natural killer cell activity. All of these processes are controlled by cytokines, suggesting that Lf may modulate immune responses by inhibiting cytokine activity. When MLC were cultured in round-bottomed wells to crowd the cells together, Lf, 50% saturated with iron, inhibited both proliferation and interleukin-2 (IL-2) release into the supernatants. Inhibition was concentration-dependent and lost at concentrations of Lf greater than 10(-12) mol/L. Lf at 10(-10) mol/L inhibited release of tumor necrosis factor-alpha (TNF) and interleukin- 1 beta (IL-1) into MLC supernatants, as well as inhibiting IL-2 release. TNF in the supernatant was significantly reduced at 5 and 24 hours, becoming less and losing significance by 72 hours. IL-1 in the supernatant was not significantly reduced at 5 and 24 hours, becoming significant at 48 and 72 hours. IL-2 was significantly reduced at 48 and 72 hours and followed the same time course as proliferation. Inhibition was blocked by specific antiserum to Lf, but not by a preimmune serum. Lf, 10(-10) mol/L, also inhibited the production of TNF (49.15% +/- 7.98%; n = 10, P = .032) and IL-1 (42.67% +/- 6.72%; n = 6, P = .032) from endotoxin-stimulated mononuclear cells. As with MLC, inhibition was dose-dependent and abrogated by specific antiserum. Lf did not block the biological action of TNF, IL-1, or IL-2 in specific assays using cytokine-sensitive cell lines. These data suggest that Lf, released from activated neutrophils, acts as a negative feedback mechanism to prevent recruitment and activation of leukocytes in sites of inflammation.

Influence of orally administered bovine lactoferrin on lipid metabolism in lipopolysaccharide‐injected preruminant calves

“…These studies suggest that this prophylactic effect of LF involves the inhibition of the production of several cytokines, including TNF-a and IL-1b, that are key mediators of the inflammatory response leading to death from toxic shock (Lee et al 1998;Conneely 2001). Indeed, LF's anti-inflammatory properties have been demonstrated by its inhibition of LPS-induced TNF-a, IL-1b, and IL-6 activity in vitro and in vivo (Crouch et al 1992;Machnicki et al 1993;Mattsby-Baltzer et al 1996;Wlaszczyk et al 1997). We previously showed that LF given orally inhibited the elevation of LPS-stimulated plasma TNF-a and haptoglobin levels in calves (Kushibiki et al 2008).…”

Lactoferrin a multiple bioactive protein: An overview

“…Similar to its role in inflammation, Lf has the ability to modulate the production of cytokines in cancer. Lf can induce apoptosis and arrest tumor growth in vitro; it can also block the transition from G1 to S in the cell cycle of malignant cells [7,152]. Additionally, treatment of tumors in mice with recombinant human Lf (rhLf) inhibits their growth, increases the levels of anticarcinogenic cytokines such as IL-18, and activates NK cells and CD8+ T lymphocytes [153,154].…”

Oral administration of lactoferrin reduces colitis in rats via modulation of the immune system and correction of cytokine imbalance

“…10 Lactoferrin is stored in secondary granules of neutrophils and is released in response to activation of TNF-α , IL-6, and IL-8. 11 The serum level of lactoferrin, which is very low in the physiological state, increases significantly with infection. 10 Lactoferrin also influences the release of pro-inflammatory cytokines such as IL-1 β , IL-2, IL-6 and TNF-α .…”