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.

Anthocyanins from the petals of Hibiscus syriacus L. (PS) possess anti-inflammatory, antioxidant, and antimelanogenic activities. However, it remains unclear whether PS inhibit the NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation and assembly. This study is aimed at investigating whether PS downregulate NLRP3-mediated inflammasome by inhibiting nuclear factor-κB (NF-κB) and endoplasmic reticulum (ER) stress. BV2 microglia cells were treated with PS in the presence of lipopolysaccharide and adenosine triphosphate (LPS/ATP), and the NLRP3-related signaling pathway was investigated. In this study, we found that LPS/ATP treatment activated the NLRP3 inflammasome, which resulted in the release of interleukin-1β (IL-1β) and IL-18. Meanwhile, PS reduced LPS/ATP-mediated NLRP3 inflammasome at 12 h by inhibiting ER stress-mediated Ca2+ accumulation and subsequent mitochondrial reactive oxygen species (mtROS) production, which, in turn, decreased IL-1β and IL-18 release. Furthermore, PS inhibited the NLRP3 inflammasome 1 h after LPS/ATP treatment by suppressing the NF-κB pathway, which downregulated Ca2+ accumulation and mtROS production. These data showed that PS negatively regulated activation of the NLRP3 inflammasome in a time-different manner by inhibiting the NF-κB signaling pathway in the early stage and the ER stress response in the late stage. The pathways shared Ca2+ accumulation-mediated mtROS production, which was significantly inhibited in the presence of PS. In conclusion, our results suggested that PS has potential as a supplement against NLRP3 inflammasome-related inflammatory disorders; nevertheless, further studies are needed to determine the effect of PS in the noncanonical NLRP3 inflammasome pathways and pathological conditions in vivo.

Fermented oyster (Crassostrea gigas) extract (FO) prevents ovariectomy-induced osteoporosis by inhibiting osteoclastogenesis and activating osteogenesis. However, the molecular mechanisms underlying FO-mediated bone formation and growth rate are unclear. In the current study, we found that FO significantly upregulated the expression of growth-promoting genes in zebrafish larvae including insulin-like growth factor 1 (zigf-1), insulin-like growth factor binding protein 3 (zigfbp-3), growth hormone-1 (zgh-1), growth hormone receptor-1 (zghr-1), growth hormone receptor alpha (zghra), glucokinase (zgck), and cholecystokinin (zccka). In addition, zebrafish larvae treated with 100 μg/mL FO increased in total body length (3.89 ± 0.13 mm) at 12 days post fertilization (dpf) compared to untreated larvae (3.69 ± 0.02 mm); this effect was comparable to that of the β-glycerophosphate-treated zebrafish larvae (4.00 ± 0.02 mm). Furthermore, FO time- and dose-dependently increased the extracellular release of IGF-1 from preosteoblast MC3T3-E1 cells, which was accompanied by high expression of IGF-1. Pharmacological inhibition of IGF-1 receptor (IGF-1R) using picropodophyllin (PPP) significantly reduced FO-mediated vertebrae formation (from 9.19 ± 0.31 to 5.53 ± 0.35) and growth performance (from 3.91 ± 0.02 to 3.69 ± 0.01 mm) in zebrafish larvae at 9 dpf. Similarly, PPP significantly decreased FO-induced calcium deposition in MC3T3-E1 cells by inhibiting GSK-3β phosphorylation at Ser9. Additionally, DOI hydrochloride, a potent stabilizer of GSK-3β, reduced FO-induced nuclear translocation of RUNX2. Transient knockdown of IGF-1Rα/β using specific silencing RNA also resulted in a significant decrease in calcium deposition and reduction in GSK-3β phosphorylation at Ser9 in MC3T3-E1 cells. Altogether, these results indicate that FO increased phosphorylated GSK-3β at Ser9 by activating the autocrine IGF-1-mediated IGF-1R signaling pathway, thereby promoting osteogenesis and growth performance. Therefore, FO is a potential nutritional supplement for bone formation and growth.

To identify potent plant extracts with strong antioxidant activity, we evaluated the free radical scavenging activity of 184 plant extracts obtained from the Freshwater Bioresources Culture Collection (FBCC) of Nakdonggang National Institute of Biological Resources (Republic of Korea), as various plant extracts have been used therapeutically to prevent chronic diseases associated with oxidative stress. From them, three plant extracts (FBCC-EP858 from Ammannia multiflora, FBCC-EP920 from Ammannia coccinea, and FBCC-EP1014 from Salix gracilistyla) were selected based on their abilities to scavenge the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical with more than 80% efficiency. We found that these extracts had in vitro half maximal inhibitory concentration (IC50) values ranging from 11.89 to 14.26 μg/mL and strong total antioxidant activity (corresponding to approximately 0.18, 0.22, and 0.23 mM Trolox, respectively). We also studied the effect of these extracts on RAW 264.7 macrophages and found that FBCC-EP920 significantly downregulated relative cell viability at a concentration of 100 μg/mL. However, the other two extracts, FBCC-EP858 and FBCC-EP1014, did not affect cell viability at the same concentration. Additionally, all three extracts inhibited hydrogen peroxide (H2O2)-induced reactive oxygen species (ROS) production and depolarization of mitochondrial membrane potential in RAW 264.7 macrophages. An additional experiment in zebrafish larvae showed that the three extracts reduced 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA) fluorescent intensity induced by H2O2. The extracts also upregulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expression, and an HO-1 inhibitor, zinc protoporphyrin (ZnPP), attenuated the extract-induced antioxidant activity both in vivo and in vitro. Taken together, these findings suggest that the extracts from A. multiflora, A. coccinea, and S. gracilistyla have potential free radical scavenging and antioxidant capacities both in vivo and in vitro by activating the Nrf2/HO-1 signaling pathway. These results could be useful for the prevention and treatment of various oxidative stress-mediated human diseases.