Bovine lactoferrin free of lipopolysaccharide can induce a proinflammatory response of macrophages

Abstract

BackgroundLactoferrin (LF) is an 80 kDa glycoprotein which is known for its effects against bacteria, viruses and other pathogens. It also has a high potential in nutrition therapy and welfare of people and a variety of animals, including piglets. The ability to bind lipopolysaccharide (LPS) is one of the described anti-inflammatory mechanisms of LF. Previous studies suggested that cells can be stimulated even by LPS-free LF. Therefore, the aim of our study was to bring additional information about this possibility. Porcine monocyte derived macrophages (MDMF) and human embryonic kidney (HEK) cells were stimulated with unpurified LF in complex with LPS and with purified LF without bound LPS.ResultsBoth cell types were stimulated with unpurified as well as purified LF. On the other hand, neither HEK0 cells not expressing any TLR nor HEK4a cells transfected with TLR4 produced any pro-inflammatory cytokine transcripts after stimulation with purified LF. This suggests that purified LF without LPS stimulates cells via another receptor than TLR4. An alternative, TLR4-independent, pathway was further confirmed by analyses of the NF-kappa-B-inducing kinase (NIK) activation. Western blot analyses showed NIK which activates different NFκB subunits compared to LF-LPS signaling via TLR4. Though, this confirmed an alternative pathway which is used by the purified LF free of LPS. This stimulation of MDMF led to low, but significant amounts of pro-inflammatory cytokines, which can be considered as a positive stimulation of the immune system.ConclusionOur results suggest that LF’s ability is not only to bind LPS, but LF itself may be a stimulant of pro-inflammatory pathways.

Lactoferrin-induced myeloid-derived suppressor cell therapy attenuates pathologic inflammatory conditions in newborn mice

“…LF induced potent antibacterial activity in MDSCs, which could be exploited in future therapeutic applications. Activation of NF-κB transcription factor is a known downstream target of LF (36,37). We confirmed upregulation of NF-κB in neonate myeloid cells by LF and demonstrated that selective inhibition of NF-κB abrogated the effect of LF.…”

Lactoferrin in a Context of Inflammation-Induced Pathology

“…It is therefore likely that LTF also plays an indirect role through other “sensing” receptors, such as the receptor for advanced glycation end products (RAGE) and the myeloid cell triggering receptor TREM-1. These are less prominent, but stimulation through these receptors also triggers NF-κB activation and subsequent transcription of genes for inflammatory cytokines and chemokines ( 60 , 61 ). This includes expression of IL-1α and β, IL-6, IL-8, TNF-α, IL-12, IL-15, IFN-α, and IFN-β, cyclooxygenases (COX1 and COX2), and inducible nitric oxide (nitric oxide) synthase; they also include the gene products important for initiation of adaptive immune responses (such as CD80, CD86, and CD40) ( 62 ).…”

“…This includes expression of IL-1α and β, IL-6, IL-8, TNF-α, IL-12, IL-15, IFN-α, and IFN-β, cyclooxygenases (COX1 and COX2), and inducible nitric oxide (nitric oxide) synthase; they also include the gene products important for initiation of adaptive immune responses (such as CD80, CD86, and CD40) ( 62 ). These diverse mediators initiate a cascade of specific and non-specific responses including bone marrow stimulation for the production of monocyte and neutrophil precursors (Figure 1 ) ( 61 ). Finally, it should be mentioned that LTF can also activate complement, through the classical pathway, which assists in mediating attraction of innate cells to inflammatory sites ( 63 ).…”

Bovine Lactoferrin Inhibits Dengue Virus Infectivity by Interacting with Heparan Sulfate, Low-Density Lipoprotein Receptor, and DC-SIGN

“…These results are consistent with our previous JEV study showing that bLF inhibits dengue virus infection mainly at the steps of virus attachment [ 6 ]. Also, bLF added after viral attachment inhibited DENV-2, and that might associate with the multiple enzymatic activities of internalized lactoferrin, especially RNase, [ 25 ] or with innate immunity triggered by bLF through a Toll-like receptor [ 26 ].…”