Methanol extract of Euphorbia cotinifolia L. leaf attenuates inflammation and oxidative stress in RAW 264.7 macrophages via TAK1-mediated suppression of NF-κB/MAPK and activation of Nrf2 pathways

Euphorbia cotinifolia L. (E. cotinifolia L.) is distributed in temperate and tropical regions. It exhibits various biological activities, including antioxidant, antimicrobial, and antiviral properties. Although its antioxidant properties have been described, its regulatory molecular mechanisms remain poorly understood and its anti-inflammatory effects have not been studied yet. This study investigated the effects of methanol extract of E. cotinifolia L. (MECL) on inflammation and oxidative stress in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. MECL significantly suppressed the production of inflammatory mediators, including nitric oxide (NO) and prostaglandin E₂ (PGE₂), by downregulating inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). In addition, MECL inhibited the production of key pro-inflammatory cytokines, including interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α (TNF-α), by suppressing of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways. It suppressed TAK1 phosphorylation, thereby inhibiting IKKα/β. Consequently, IκBα was stabilized, preventing its degradation and thereby suppressing NF-κB p65 phosphorylation and nuclear translocation. Additionally, MECL attenuated the activation of JNK, ERK, and p38 MAPK signaling. It also activated nuclear factor erythroid 2-related factor 2 (Nrf2), which is a key antioxidant transcription factor, upregulating its target genes, heme oxygenase-1 and NAD(P)H quinone dehydrogenase 1, which are essential for oxidative stress defense. These findings suggested that MECL mitigated inflammation and oxidative stress by regulating TAK1-mediated NF-κB/MAPK signaling and Nrf2 activation. Therefore, it showed potential as a natural therapeutic candidate for inflammatory diseases.