Diospyros lotus is traditionally used for the treatment of diabetes, diarrhea, tumor, and hypertension. The purpose of this study was to investigate the anti-inflammatory effect and underlying molecular mechanisms of myricetin in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Myricetin dose-dependently suppressed the production of pro-inflammatory mediators (NO, iNOS, PGE₂, and COX-2) in LPS-stimulated RAW264.7 macrophages. Myricetin administration decreased the production of NO, iNOS, TNF-α, IL-6, and IL-12 in mice. Myricetin decreased NF-κB activation by suppressing the degradation of IκBα, nuclear translocation of p65 subunit of NF-κB, and NF-κB DNA binding activity in LPS-stimulated RAW264.7 macrophages. Moreover, myricetin attenuated the phosphorylation of STAT1 and the production of IFN-β in LPS-stimulated RAW264.7 macrophages. Furthermore, myricetin induced the expression of HO-1 through Nrf2 translocation. In conclusion, these results suggest that myricetin inhibits the production of pro-inflammatory mediators through the suppression of NF-κB and STAT1 activation and induction of Nrf2-mediated HO-1 expression in LPS-stimulated RAW264.7 macrophages.

Perilla (Perilla frutescens L.) leaves have shown therapeutic efficacy in the treatment of inflammatory disorders, allergies, bronchial asthma, and systemic damage due to free radicals. In the present study we analyzed the active constituents in perilla leaves using high-performance liquid chromatography (HPLC) and isolated luteolin, a polyphenolic flavonoid. We investigated the anti-inflammatory and antipruritic properties of luteolin. Luteolin inhibited the secretion of inflammatory cytokines such as interleukin-1β (IL-1 β) and tumor necrosis factor-α (TNF-α) from human mast cells (HMC-1) stimulated with phorbol myristate acetate plus calcium ionophore A23187 in a dose-dependent manner. Luteolin also significantly reduced the histamine release from rat peritoneal mast cells stimulated by compound 48/80, a potent histamine liberator. Furthermore, the administration of luteolin markedly inhibited the scratching behavior and vascular permeability induced by pruritogens, such as compound 48/80 or serotonin, in ICR mice. These results suggested that luteolin has potential as a therapeutic agent against inflammation and itch-related skin diseases.

Microglia cells are resident cells of the central nervous system (CNS) charged with modulating inflammation in the CNS. Overstimulation of microglia cells continuously releases inflammatory mediators that contribute to neurodegenerative diseases. Apigenin and Luteolin are flavonoids with reported anti-inflammatory activities. However, their effects on IL-31 and IL-33 production in microglial cells are unknown. Here, we investigated the effects of apigenin and luteolin on the production of IL-31 and IL-33 by microglia cells. SIM-A9 microglial cells were pre-treated with apigenin or luteolin and stimulated with lipopolysaccharides to evaluate the production of IL-31 and IL-33. The study revealed that apigenin and luteolin inhibited the production of IL-31 and IL-33 at the gene and protein expressions and the secretion levels. Using potent inhibitors of MAPK, NF-κB, and STAT3 signaling pathways, we demonstrated that apigenin and luteolin’s suppression of ERK and JNK contributed to the inhibition of IL-31 and IL-33 in the MAPK pathway. Luteolin’s suppression of NF-κB and STAT3 also contributed to the inhibition of IL-31 and IL-33. Further analysis revealed that both compounds prevented nuclear translocation of activated NF-κB and STAT3, an act that subsequently prevented their DNA binding activities. Collectively, the study suggested that apigenin and luteolin’s regulation of signaling pathways contributed to the inhibition of IL-31 and IL-33, thus suggesting its importance for the improvement of neurodegenerative diseases involving these two cytokines.