Inflammatory M1-like macrophages polarized by NK-4 undergo enhanced phenotypic switching to an anti-inflammatory M2-like phenotype upon co-culture with apoptotic cells

Abstract

Background NK-4 has been used to promote wound healing since the early-1950s; however, the mechanism of action of NK-4 is unknown. In this study, we examined whether NK-4 exerts a regulatory effect on macrophages, which play multiple roles during wound healing from the initial inflammatory phase until the tissue regeneration phase. Results NK-4 treatment of THP-1 macrophages induced morphological features characteristic of classically-activated M1 macrophages, an inflammatory cytokine profile, and increased expression of the M1 macrophage-associated molecules CD38 and CD86. Interestingly, NK-4 augmented TNF-α production by THP-1 macrophages in combination with LPS, Pam3CSK4, or poly(I:C). Furthermore, NK-4 treatment enhanced THP-1 macrophage phagocytosis of latex beads. These results indicate that NK-4 drives macrophage polarization toward an inflammatory M1-like phenotype with increased phagocytic activity. Efferocytosis is a crucial event for resolution of the inflammatory phase in wound healing. NK-4-treated THP-1 macrophages co-cultured with apoptotic Jurkat E6.1 (Apo-J) cells switched from an M1-like phenotype to an M2-like phenotype, as seen in the inverted ratio of TNF-α to IL-10 produced in response to LPS. We identified two separate mechanisms that are involved in this phenotypic switch. First, recognition of phosphatidylserine molecules on Apo-J cells by THP-1 macrophages downregulates TNF-α production. Second, phagocytosis of Apo-J cells by THP-1 macrophages and activation of PI3K/Akt signaling pathway upregulates IL-10 production. Conclusion It is postulated that the phenotypic switch from a proinflammatory M1-like phenotype to an anti-inflammatory M2-like phenotype is dysregulated due to impaired efferocytosis of apoptotic neutrophils at the wound site. Our results demonstrate that NK-4 improves phagocytosis of apoptotic cells, suggesting its potential as a therapeutic strategy to resolve sustained inflammation in chronic wounds.

Tilapia Piscidin 4 (TP4) Reprograms M1 Macrophages to M2 Phenotypes in Cell Models of Gardnerella vaginalis-Induced Vaginosis

“…Impairments in vaginal epithelium function are associated with higher inflammatory status driven by M1 macrophage accumulation ( 72 ). The M1 macrophage accumulation usually prolongs the inflammatory phase and increases disease severity via cytokine production ( 73 ).…”

Immunology of Acute and Chronic Wound Healing

“…The failure of macrophages to polarize from a pro-inflammatory M1 towards a pro-healing reparative M2 phenotype is strongly associated with poorly healing wounds ( Figure 2 ) [ 24 ]. This failure is due to an overexpression of pro-inflammatory cytokines in the wound microenvironment as well as impaired clearance of apoptotic neutrophils by macrophages [ 122 ]. A study comparing macrophages derived from wounds of healthy people to patients suffering from diabetes revealed a distinctive expression of the methyltransferase Setdb2, of which production in wound macrophages is under the control of IFN-β.…”

“…NK-4 is a cyanine dye, which was shown to activate differentiation of tumor-derived macrophages into M1 pro-inflammatory phenotype and stimulate their phagocytic activity. Interestingly, NK-4 treated M1 macrophages, when incubated together with apoptotic Jurkat E6.1 (Apo-J) cells, switched into M2 phenotype through the downregulation of TNF-α secretion and stimulation of IL-10 production [ 122 ]. Finally, treatment of diabetic mice with docosahexaenoic acid significantly improved the healing of ulcers by stimulating macrophage polarization toward M2 phenotype [ 144 ].…”

CD38: A Significant Regulator of Macrophage Function

“…Increased expression of CD38 can reduce the number of osteoclasts and bone resorption. Through Ca 2+ , cAMP, and cytokines (such as tumor necrosis factor alpha (TNF-α), regulating the expression of the NAD + sensitive enzyme CD38 might help to couple the strong metabolic activity of osteoclasts and osteoblasts with their respective bone resorption and bone shaping functions ( 19 , 20 ). In the tumor microenvironment (TME), CD38 regulates the activation of tumor associated microglia/macrophages (TMMs) through the increase of calcium concentration mediated by cADPR.…”