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. 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. 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.

中文翻译：

---

与凋亡细胞共培养时，由NK-4极化的炎性M1样巨噬细胞经历了增强的表型转换，转变为抗炎M2样表型

自1950年代初以来，NK-4就一直用于促进伤口愈合。但是，NK-4的作用机理尚不清楚。在这项研究中，我们检查了NK-4是否对巨噬细胞发挥调节作用，巨噬细胞在伤口愈合过程中（从最初的炎症阶段到组织再生阶段）起着多种作用。NK-4处理THP-1巨噬细胞诱导了经典激活的M1巨噬细胞的形态特征，炎性细胞因子谱以及M1巨噬细胞相关分子CD38和CD86的表达增加。有趣的是，NK-4通过与TPS-1巨噬细胞结合LPS，Pam3CSK4或poly（I：C）增强TNF-α的产生。此外，NK-4处理增强了乳胶珠的THP-1巨噬细胞吞噬作用。这些结果表明NK-4驱动巨噬细胞极化向具有吞噬活性增加的炎性M1样表型。泡腾病是伤口愈合中炎症相消退的关键事件。从TNF-α与IL的倒置比例可以看出，与凋亡的Jurkat E6.1（Apo-J）细胞共培养的NK-4处理的THP-1巨噬细胞从M1型转变为M2型。对LPS产生-10。我们确定了与该表型转换有关的两种独立机制。首先，THP-1巨噬细胞识别Apo-J细胞上的磷脂酰丝氨酸分子会下调TNF-α的产生。第二，THP-1巨噬细胞吞噬Apo-J细胞并激活PI3K / Akt信号通路上调IL-10的产生。据推测，由于创伤部位的凋亡性中性粒细胞的胞吞作用减弱，导致表型从促炎性M1样表型向抗炎性M2样表型的调节失调。我们的结果表明，NK-4改善了凋亡细胞的吞噬作用，表明其作为解决慢性伤口持续炎症的治疗策略的潜力。