Anti-Inflammatory Mechanisms of <i>Pleurotus citrinopileatus</i>: Inhibition of MAPK and NF-κB Signaling Pathways, and Activation of ROS/PI3K/Nrf2/HO-1 Signaling Pathway in LPS-Stimulated RAW264.7 Cells
Hyeok Jin Choi, Jeong Won Choi, So Jung Park, Sang Hun Lee, Jin Hyuk Hwang, Youngki Park, Kyoung Tae Lee, Jin Boo Jeong
Abstract
by examining its impact on inflammation-related signaling pathways in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Fractions obtained using hexane (HE), dichloromethane (DCM), and ethyl acetate (EA) were found to suppress LPS-induced nitric oxide (NO) production and the expression of inducible nitric oxide synthase (iNOS). Additionally, these fractions inhibited the phosphorylation of key mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinases 1/2 (ERK1/2), p38, and c-Jun N-terminal kinase (JNK), as well as the nuclear factor kappa B (NF-κB) subunit p65. The HE, DCM, and EA fractions also promoted the nuclear accumulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and increased the expression of heme oxygenase-1 (HO-1). Notably, the suppression of HO-1 activity using zinc (II) protoporphyrin IX (ZnPP) reversed the NO-inhibitory effects of these fractions. Furthermore, treatment with the HE, DCM, and EA fractions enhanced phosphoinositide 3-kinase (PI3K) activation, whereas PI3K inhibition by LY294002 attenuated HO-1 expression and nuclear Nrf2 translocation. Reactive oxygen species (ROS) scavenging by N-acetyl-L-cysteine (NAC) similarly reduced PI3K activation and the upregulation of HO-1 and nuclear Nrf2. Collectively, these findings indicate that the HE, DCM, and EA fractions mitigate NO production by downregulating iNOS expression through the suppression of MAPK and NF-κB signaling, while also engaging the ROS/PI3K/Nrf2/HO-1 pathway to exert anti-inflammatory effects.