Bovine Lactoferrin (bLf) possessing an high homology of sequence with human Lf, is classified as Generally Recognized As Save and is used in vitro models and in clinical trials on humans. It is a multifunctional glycoprotein able i) to chelate two ferric ions/molecule, ii) to interact with cellular and molecular components due to its high pI >9 , iii) to enter inside the nucleus where, by binding to specific DNA sequences, inhibits pro-inflammatory cytokine synthesis and iv) to bind at high affinity to Lf receptor (LfR) and at low affinity to low density lipoprotein receptor related protein (LRP). We assumed that LfR or LRP could differently influence bLf internalization, localization into the nucleus, and consequently, anti-inflammatory activity and cell damage repair. As prolonged inflammation leads to non-repairing cell damages, the bLf anti-inflammatory activity could neutralize overabundant immune response and promote the cell damage repair. The cell damage repaired by bLf has been investigated only in intestinal cell model. Here, for the first time, bLf efficacy on cell damage repair, probably associated to LfR or LRP, has been studied in vitro on human cholangiocytes and in vivo on pregnant women with membrane premature rupture and in the patients affected from osteonecrosis. The preliminary positive results in healing both membrane premature ruptures and wounds following osteonecrosis treatments, respectively, have been obtained through intravaginal and oral bLf administration. A further deep study is required to unequivocally ascertain this new important bLf therapeutic potential in repairing cell damages promoted by severe and prolonged inflammations.
Of note, lactoferrin is one of the few (if not the only?) proteins that has its own dedicated scientific meeting. The biennial `Lactoferrin Conference' provides an important forum for the dissemination and the promotion of research on this protein and for discussions about new insights into the benefits of Lf as a mediator of general health and its potential therapeutic applications. Piera Valenti as Member of International Committee on Lactoferrin, for the third time, will organized the International Conference on Lactoferrin - Rome, 6-11 November 2017. Currently, a Pubmed search in the NCBI Medline database identifies almost 8,000 publications for this topic and this number increases by about 400 publications each year in consideration of the availability, in large quantities and at low cost of bovine Lf (bLf) suitable for clinical trials. The purified bLf is used for several applications, such as a supplement to infant formula, as a health-promoting additive to various foods, as a nutraceutical, or as an immune-stimulating, anti-inflammatory and bone-growth-promoting dietary supplement. The in vivo emerging results confirm not only the in vitro data on human Lf and bLf multiple functions but also highlight the potential for its therapeutic or health-promoting applications. BLf is a biologic therapeutic protein for the treatment of diarrhea, inflammatory bowel diseases, anemia, sepsis and certain forms of cancer. Typically in all these clinical studies the protein is very well tolerated, and clearly this bodes well for its therapeutic use. Despite the multi-functionality of bLf, we found that
-therapeutic successful applications are mainly related to bLf potent anti-inflammatory activity -the nuclear localization of bLf is associated to its anti-inflammatory activity
-the anti-inflammatory activity consists in the down-regulation of pro-inflammatory cytokines including IL-1, IL-6, and IL-8, involved in cell damage repair, anaemia of inflammation and recruiment of neutrophils.
Therefore, the nuclear localization and anti-inflammatory activity could be underlie of the bLf several functions.
In our previous paper (Puddu et al Plosone 2011), we demonstrated that bLF enters the nucleus of monocytes, while monocyte-derived dendritic cells failed to internalize bLF. This difference was related to down or up-expression of IL-6 by bLf in these two cell models. However, at the time, these differences fell within the conflicting data reported by the International Literature on the bLf as pro or anti-inflammatory protein. Currently, we are assuming, as mentioned in the project objectives, that the presence of different receptors at high or low bLf affinity, as LfR or LRP, could be related to the bLf internalization and localization into the nucleus as well as to its anti-inflammatory function related to several activities as cell growth, proliferation, and cell damage repair. For the first time, the different functions of bLf on cell growth, proliferation and cell damage repairing could be associated to an unique occurrence represented by the ability of bLf to enter into the nucleus and inhibit pro-inflammatory cytokine synthesis as IL-1 (involved in apoptosis and wound healing) and IL-6 (involved in inflammatory disorders and wound healing). Understanding the molecular mechanisms underlying these activities as well as identifying cell targets and receptors involved hold the promise of a better exploitation of bLf therapeutic potential. The depth study of this complex mechanism will contribute to clarify the conflicting data on this multifunctional protein. Surprisingly, the bLf biological functions seems to be related to cell targets and receptors in the treatment of premature rupture of membranes and PTD, of wound healing in patients suffering from osteonecrosis. The research on inflamed cholangiocytes will be critical to identify the type of Lf receptors (LfR or LRP-1) as well as their influence on Lf internalization, nuclear localization and multifunctionality. Successively, the influence of bLf on growth and proliferation of cholangiocytes will be studied . Finally, the effect of bLf in repairing cell damages through the synthesis of IL-1, Il-6 and the number of infiltrating cells and histological observations will be studied in ex vivo samples collected from mice with cholestasis or humans suffering from primary biliary cirrhosis. Interestingly, the efficacy of bLf on growth, development and repairing cell damages will be tested on the patients after osteonecrosis surgical resection of jaw.