Anti-inflammatory and polarization-modulating effects of Houttuynia cordata in LPS-stimulated RAW264.7 macrophages

Inflammation is a fundamental component of the immune response in host defense against pathogens and during tissue repair. Houttuynia cordata (HC), a herbaceous plant used in traditional Asian medicine, has significant anti-inflammatory and antimicrobial properties. However, the underlying mechanisms of the anti-inflammatory effects of HC are not fully understood. In this study, the immunomodulatory potential and macrophage polarization-modulating effects of HC were evaluated with a focus on cell signaling molecule expression, inflammatory cytokine production and macrophage polarization, with the aim of revealing the molecular mechanisms underlying the effects and therapeutic potential of HC.

We investigated the effects of HC extract on proinflammatory cytokine production, signaling pathway activity, macrophage surface marker expression, morphology, and phagocytic activity under different treatment conditions in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages.

Compared with LPS alone, HC treatment before LPS stimulation significantly reduced IL-1β, TNF-α, nuclear NF-κB, and pERK levels while increasing TGF-β levels. Compared with HC pretreatment, HC treatment after LPS stimulation further decreased the IL-6, TNF-α, nuclear NF-κB, and pERK levels. LPS resulted in a trend toward increased CD80 expression in macrophages. Both HC pretreatment and HC posttreatment tended to increase CD163 expression in macrophages. Our study demonstrated that HC, particularly when administered after inflammation onset, effectively reduces proinflammatory cytokine levels, modulates key signaling pathways, and polarizes macrophages toward an anti-inflammatory phenotype. These effects suggest that HC has significant therapeutic potential in treating inflammatory diseases by modulating macrophage activity.