HAMLET a human milk protein‐lipid complex induces a pro‐inflammatory phenotype of myeloid cells

Abstract

HAMLET is a protein‐lipid complex with a specific and broad bactericidal and tumoricidal activity, that lacks cytotoxic activity against healthy cells. In this study, we show that HAMLET also has general immune‐stimulatory effects on primary human monocyte‐derived dendritic cells and macrophages (Mo‐DC and Mo‐M) and murine RAW264.7 macrophages. HAMLET, but not its components alpha‐lactalbumin or oleic acid, induces mature CD14low/–CD83+ Mo‐DC and M1‐like CD14+CD86++ Mo‐M surface phenotypes. Concomitantly, inflammatory mediators, including IL‐2, IL‐6, IL‐10, IL‐12 and MIP‐1α, were released in the supernatant of HAMLET‐stimulated cells, indicating a mainly pro‐inflammatory phenotype. The HAMLET‐induced phenotype was mediated by calcium, NFκB and p38 MAPK signaling in Mo‐DCs and calcium, NFκB and ERK signaling in Mo‐M as inhibitors of these pathways almost completely blocked the induction of mature Mo‐DCs and M1‐like Mo‐M. Compared to unstimulated Mo‐DCs, HAMLET‐stimulated Mo‐DCs were more potent in inducing T cell proliferation and HAMLET‐stimulated macrophages were more efficient in phagocytosis of Streptococcus pneumoniae in vitro. This indicates a functionally activated phenotype of HAMLET‐stimulated DCs and macrophages. Combined, we propose that HAMLET has a two‐fold anti‐bacterial activity; one inducing direct cytotoxic activity, the other indirectly mediating elimination of bacteria by activation of immune cells of the myeloid lineage.

Cytotoxic Lactalbumin-Oleic Acid Complexes in the Human Milk Diet of Preterm Infants

“…In studies with healthy lymphocytes, HAMLET but not native ALA was shown to significantly upregulate NF-κB expression. HAMLET increased IL-6, IL-8 and TNFα, even localizing in proximity to TLR-4 receptors [60]. The cytokine profile of infants with NEC is similar, demonstrating increased enterocyte apoptosis secondary to upregulation of TLR-4, and subsequent increases in IL-6 and IL-8.…”

“…Activity against Streptococcus pneumoniae, Streptococcus pyogenes and Streptococcus agalactiae (GBS) has been reported [79]. Interestingly, in an attempt to remove adulterated lipopolysaccharides from HAMLET, one laboratory reported that the fatty acid content of HAMLET was reduced by 60%, which also led to reduced bioactivity against streptococcus by 3.75× [60]. It is unknown whether HAMLET may be present in sufficient quantities to significantly affect the gut microbiome or protect the neonate from pathogenic bacteria.…”

Delving into gene-set multiplex networks facilitated by a k-nearest neighbor-based measure of similarity

“…GO:0034368 (protein-lipid complex remodeling) is the gene set with the highest multiplex PageRank centrality (ratio of 30.03). The protein-lipid complex has been reported to be a positive regulator of immune cells [57] . GO:0051240 (positive regulation of multicellular organismal process) is the gene set with the highest PageRank centrality (ratio of 2.74) in the Jaccard layer.…”

Beyond Milk and Nurture: Breastfeeding’s Powerful Impact on Breast Cancer

“…HAMLET (Human a-lactalbumin made lethal to tumor cells), a unique complex formed from alpha-lactalbumin and oleic acid present in human milk, has been shown to induce cell death in both tumor and bacterial cells 91 . Tumor cells experience apoptosis triggered by HAMLET, while well-differentiated normal cells exhibit resilience against its impact 92 . The widespread effectiveness of HAMLET in combating tumors is emphasized by its ability to act against a wide range of tumor cells, including more than 40 different types of lymphoma and in vitro carcinoma cell lines 90 .…”