TABLE 5.

The effects of endogenous opioid peptides on macrophage’s function.

Endogenous opioid peptides	Animal models/cell types	Effects on macrophages	References
Endomorphin	Rat peritoneal macrophages	Enhances the adhesion of macrophages and the expression of the adhesion molecule Mac-1; inhibits the chemotaxis and superoxide anion production of macrophages; inhibits the production of TNF-α, IL-10, and IL-12	Inui et al. (2002)
	Murine macrophage cell line, J774; mice peritoneal macrophages	Activates NOS2 activity, downregulate NOS2 gene expression, and inhibit the release of NO	Sarić et al. (2007); Balog et al. (2010)
	Human lipid-laden macrophages	Regulates the release of cytokines by human lipid macrophages by downregulating CD36	Chiurchiù et al. (2011)
β-endorphin	THP-1 monocyte-derived macrophages	Increases oxLDL uptake by macrophages and promote oxLDL-induced macrophages to form foam cells; transforms the macrophage phenotype into pro-inflammatory M1 through NF-κB phosphorylation; increases macrophage migration and apoptosis	Okano et al. (2020)
Dynorphin A	Murine IC-21 macrophages	Enhances Mac-1-mediated phagocytosis of macrophages	Podolnikova et al. (2015)

NOS2: Nitric oxide synthase 2; oxLDL: oxidized low-density lipoprote.