N-Formyl-Met-Leu-Phe (fMLP; N-Formyl-MLF) is a chemotactic peptide and a specific ligand of N-formyl peptide receptor (FPR). N-Formyl-Met-Leu-Ph is reported to inhibit TNF-alpha secretion.

Binding of N-Formyl-Met-Leu-Phe to its specific cell surface receptor, N-formyl peptide receptor (FPR), triggers different cascades of biochemical events, eventually leading to cellular activation. FPR is a chemoattractant receptor belonging to the G protein-coupled receptor family. N-Formyl-Met-Leu-Phe promotes osteoblastic commitment and suppresses adipogenic commitment under osteoblastic differentiation conditions. N-Formyl-Met-Leu-Phe stimulates osteogenesis is associated with increased expression of osteogenic markers and mineralization. N-Formyl-Met-Leu-Phe inhibits expression of peroxisome proliferator-activated receptor-γ1. N-Formyl-Met-Leu-Phe-stimulated osteogenic differentiation is mediated via FPR1-phospholipase C/phospholipase D-Ca2+-calmodulin-dependent kinase II-ERK-CREB signaling pathways[1]. N-Formyl-Met-Leu-Phe, a bacterial-derived peptide, induced proinflammatory cytokine gene expression in human peripheral blood monocytes. Bacterial products LPS and N-Formyl-Met-Leu-Phe synergistically induce inflammatory response via multiple signaling pathways. TLR4, IKKβ-IκBα, and NF-κB signaling pathways are involved in the synergistic induction of TNF-α via p65 nuclear translocation-dependent mechanisms[2].

N-Formyl-Met-Leu-Phe promotes bone formation in zebrafish and rabbits. Extensive skeletal development is evident at 5 dpf in over 80% of N-Formyl-Met-Leu-Phe-treated zebrafish. Treatment with N-Formyl-Met-Leu-Phe results in increased expression of Runx2. Bone marrow spaces are widely formed, and connective tissue covering bone is dense, like periosteum, in N-Formyl-Met-Leu-Phe-treated calvaria[1]. N-Formyl-Met-Leu-Phe mediate release of calprotectin from PMN in vitro. It induces release of calprotectin from PMN in a dose dependent manner. A minimum of 10% of total PMN calprotectin is retained at concentrations of 0.1-10.0 nM of N-Formyl-Met-Leu-Phe[3].