Abstract
Fisetin is a naturally occurring flavonoid that possesses several pharmacological benefits including anti-inflammatory activity. However, its precise anti-inflammatory mechanism is not clear. In the present study, we found that fisetin significantly inhibited the expression of proinflammatory mediators, such as nitric oxide (NO) and prostaglandin E2 (PGE2), and cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Additionally, fisetin attenuated LPS-induced mortality and abnormalities in zebrafish larvae and normalized the heart rate. Fisetin decreased the recruitment of macrophages and neutrophils to the LPS-microinjected inflammatory site in zebrafish larvae, concomitant with a significant downregulation of proinflammatory genes, such as inducible NO synthase (iNOS), cyclooxygenase-2a (COX-2a), IL-6, and TNF-α. Fisetin inhibited the nuclear localization of nuclear factor-kappa B (NF-κB), which reduced the expression of pro-inflammatory genes. Further, fisetin inactivated glycogen synthase kinase 3β (GSK-3β) via phosphorylation at Ser9, and inhibited the degradation of β-catenin, which consequently promoted the localization of β-catenin into the nucleus. The pharmacological inhibition of β-catenin with FH535 reversed the fisetin-induced anti-inflammatory activity and restored NF-κB activity, which indicated that fisetin-mediated activation of β-catenin results in the inhibition of LPS-induced NF-κB activity. In LPS-microinjected zebrafish larvae, FH535 promoted the migration of macrophages to the yolk sac and decreased resident neutrophil counts in the posterior blood island and induced high expression of iNOS and COX-2a, which was accompanied by the inhibition of fisetin-induced anti-inflammatory activity. Altogether, the current study confirmed that the dietary flavonoid, fisetin, inhibited LPS-induced inflammation and endotoxic shock through crosstalk between GSK-3β/β-catenin and the NF-κB signaling pathways.
Highlights
Fisetin is a naturally occurring flavonoid that possesses several pharmacological benefits including anti-inflammatory activity
No significant change in cell viability was observed at concentrations of up to 8 μM fisetin compared to that of the untreated cells (97.8 ± 1.6%, 97.3 ± 1.7%, 97.5 ± 1.5%, 96.2 ± 1.9% at 1, 2, 4, and 8 μM fisetin); higher concentrations of fisetin significantly decreased the viability of RAW 264.7 macrophages (89.5 ± 1.3% and 78.8 ± 5.7% at 10 and 20 μM, respectively) (Fig. 1A)
We found that LPS alone decreased the percentage of viable cell populations (75.0 ± 0.4%) and increased dead cell populations (25.0 ± 0.4%, Fig. 1D). Both 10 μM and 20 μM fisetin decreased viability to 62.28 ± 0.77% and 55.05 ± 0.98%, and increased dead cell populations up to 37.71 ± 0.77% and 44.95 ± 0.97%. These results indicate that high concentrations of fisetin exhibit cytotoxicity in RAW 264.7 macrophages; cytotoxicity was not observed below a concentration of 8 μM
Summary
Fisetin is a naturally occurring flavonoid that possesses several pharmacological benefits including anti-inflammatory activity. Fisetin decreased the recruitment of macrophages and neutrophils to the LPS-microinjected inflammatory site in zebrafish larvae, concomitant with a significant downregulation of proinflammatory genes, such as inducible NO synthase (iNOS), cyclooxygenase-2a (COX-2a), IL-6, and TNF-α. In LPS-microinjected zebrafish larvae, FH535 promoted the migration of macrophages to the yolk sac and decreased resident neutrophil counts in the posterior blood island and induced high expression of iNOS and COX-2a, which was accompanied by the inhibition of fisetin-induced anti-inflammatory activity. The current study confirmed that the dietary flavonoid, fisetin, inhibited LPS-induced inflammation and endotoxic shock through crosstalk between GSK-3β/β-catenin and the NF-κB signaling pathways. NF-κB is a well-characterized ubiquitous transcription factor that positively regulates the expression of inflammatory genes, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α)[8,9]. Agonists of the Wnt/β-catenin signaling pathway could serve as promising anti-inflammatory candidates in NF-κB-induced inflammatory disorders, such as septic shock
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
