Oleamide-Mediated Polarization of M1 Macrophages and IL-1β Production by Regulating NLRP3-Inflammasome Activation in Primary Human Monocyte-Derived Macrophages

Macrophages are a type of innate immune cell that activates the NLRP3 inflammasome, causing the release of the cytokine IL-1 beta, which is a crucial mediator of the inflammatory response. NLRP3 activation that is dysregulated worsens a variety of inflammatory and autoimmune diseases, as well as neurodegenerative diseases. Oleamide is an endogenous fatty acid amide that was first determined as a sleep-inducing molecule and later shown to have wide-ranging beneficial effects on the central nervous system. How oleamide influences human macrophage polarization and NLRP3-inflammasome activation remains unclear. The effect of oleamide on macrophage polarization was explored using an in vitro culture of primary human monocyte-derived macrophages (MDMs) supplemented with human serum-containing media. Cellular and molecular mechanisms of oleamide-regulated MDMs polarization were also investigated. Results showed that oleamide promoted naive macrophages (M0) toward the M1 phenotype by upregulating M1-associated genes (IL-1 beta, iNOS, CXCL10), along with downregulation of M2-associated genes (Arg-1, CD206, CCL22). Cell surface expression indicated that oleamide enhanced CD80 expression in M0 naive macrophages and hider CD206 and CD163 expression in M2 macrophages. Higher production of IL-1 beta cytokine was observed but with no alteration in IL-6 and TNF-alpha levels by MDMs and differentiated THP-1 models. Whether oleamide functioned as a second signal that activated the NLRP3 inflammasome and mediated IL-1 beta production was further investigated using LPS-primed MDMs followed by oleamide treatment that induced activation of inflammasome-related proteins including NLRP3, ASC, cleaved casp-1, and cleaved IL-1 beta. These findings suggested that oleamide promoted M1 macrophage polarization and increased IL-1 beta production by activating the NLRP3 inflammasome in primary MDMs. This research reveals a new function for oleamide as well as prospective targets for treating NLRP3-related inflammatory disorders.

Automated summary

This study investigated the effects of oleamide on macrophage polarization and NLRP3 inflammasome activation. The results showed that oleamide promoted M1 macrophage polarization and increased IL-1 beta production. Additionally, oleamide appeared to activate the NLRP3 inflammasome as a second signal. These findings reveal a new function for oleamide and potential targets for treating NLRP3-related inflammatory disorders.