Aqueous Extract from Leaves of Citrus unshiu Attenuates Lipopolysaccharide-Induced Inflammatory Responses in a Mouse Model of Systemic Inflammation

Abstract

Inflammation is related to various life-threatening diseases including cancer, neurodegenerative diseases, and metabolic syndrome. Because macrophages are prominent inflammatory cells, regulation of macrophage activation is a key issue to control the onset of inflammation-associated diseases. In this study, we aimed to evaluate the potential anti-inflammatory activity of Citrus unshiu leaf extract (CLE) and to elucidate the mechanism underlying its anti-inflammatory effect. We found the inhibitory activity of CLE on the secretion of proinflammatory cytokines and a chemokine from mouse macrophage-like RAW 264.7 cells and mouse peritoneal macrophages. The inhibitory activity of CLE was attributed to downregulated JNK, p38 MAPK, and NF-κB signaling pathways, leading to suppressed gene expression of inflammation-associated proteins. Oral administration of CLE significantly decreased the serum level of proinflammatory cytokines IL-6 and TNFα and increased that of anti-inflammatory cytokine IL-10 in lipopolysaccharide-induced systemic inflammation mice. In addition, oral administration of CLE decreased secretion and gene expression of several proinflammatory proteins in the liver and spleen of the model mice. Overall results revealed that C. unshiu leaf is effective to attenuate inflammatory responses in vitro and in vivo.

Exploring the anti-inflammatory effect of clove water extract in lipopolysaccharide-stimulated RAW264.7 cells and mouse peritoneal macrophages

“…Based on previous research (Pandey et al, 2024) which mentions several components contained in clove and following the method by Nishi et al (2021), the water extraction of clove components was performed as followings. Clove powder was suspended in distilled water at 100 mg/mL and homogenized overnight at 12°C.…”

“…Inflammatory signaling pathways such as MAPK and NF-κB are important transcription factors in the inflammation-regulating system (Nishi et al, 2021). Therefore, to investigate the potential mechanism of the anti-inflammatory effect of CWE, the effect of CWE on the essential intracellular signaling pathways such as MAPK and NF-κB, and the protein expression level of iNOS, were investigated using Western blot analysis.…”

Biometabolites of Citrus unshiu Peel Enhance Intestinal Permeability and Alter Gut Commensal Bacteria

“…In particular, the therapeutic effects of the peel covering C. unshiu have received more attention than other parts of the plant, because it exerts outstanding antioxidant effects compared to the pulp owing to its high mineral composition [ 13 , 14 ]. C. unshiu peel is widely used as a therapeutic agent for clinical purposes, such as neuropathic pain [ 15 ], cervical cancer [ 16 ], nonalcoholic fatty liver [ 17 ], hyperglycemia [ 18 ], pancreatic cancer [ 19 ], and systemic inflammation [ 20 ]. This raw material can also be processed using various extraction protocols, as mentioned above.…”

“…Especially, water or ethanol extraction is a commonly used method to extract flavonoids from natural substances, hence, many studies employing solvent-extracted CUP have been conducted. For example, the ethanol derivative of CUP ameliorated oxidative stress by suppressing nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 expression (NOX2) in a chemotherapy-induced neuropathic pain animal model [ 15 ] and decreasing the expression levels of pro-inflammatory cytokines, such as interleukin (IL)-6, interferon (IFN)-γ, and tumor necrosis factor-alpha (TNFα), in a type 2 diabetes and systemic inflammation mouse model [ 18 , 20 ]. Moreover, water extracts of CUP have been reported to attenuate dextran sulfate sodium-induced colitis by regulating the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway [ 21 ].…”

Citrus unshiu Peel Attenuates Dextran Sulfate Sodium-Induced Ulcerative Colitis in Mice due to Modulation of the PI3K/Akt Signaling Pathway and MAPK and NF-κB

“…Also, in a recent study, Citrus unshiu peel was shown to have various pharmacological effects against viral infection, depression, obesity, and inflammation [ 11 – 14 ]. In the studies of Noh et al and Karthikeyan et al, it was reported that the Citrus unshiu peel exhibits anti-inflammatory effects in LPS stimulated RAW264.7 [ 15 , 16 ], and in the study of Nishi et al, the Citrus unshiu peel relieves inflammation through the NF- κ Bp65 and MAPK pathways in the model of systemic inflammation [ 17 ].…”