Dichloromethane fraction of Laminaria japonica ethanolic extract inhibits lipopolysaccharide-induced nitric oxide synthase and cyclooxygenase-2 expression in RAW 264.7 cells via NF-κB pathway

Effects of laminarin on growth performance and resistance against Pseudomonas plecoglossicida of large yellow croaker （Larimichthys crocea）

Laminarin (LAM) is widely used as an immunopotentiator in aquaculture, but its protective mechanism is still unclear. In this study, the effects of LAM on the growth performance and resistance against Pseudomonas plecoglossicida of large yellow croaker were studied in vitro and in vivo. The 42 d-feeding trial in large yellow croaker showed that dietary LAM could obviously promote the fish growth by improving the weight gain rate (WGR), specific growth rate (SGR), and feed conversion rate (FCR). Dietary LAM could also improve the survival rate of large yellow croakers subjected to P. plecoglossicida infection, and 500 mg/kg LAM produced the highest relative percent survival (RPS) of 35.00 %. LAM improved fish antioxidant level by enhancing serum total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activity, and reducing malondialdehyde (MDA) content. In addition, LAM also improved fish innate immunity by increasing serum acid phosphatase (ACP) and alkaline phosphatase (AKP) activities and complement 3 (C3) content under P. plecoglossicida infection. What is more, on 9 d post P. plecoglossicida challenge, LAM could significantly decrease the bacteria load in head kidneys, spleens and livers of fish, and the lowest bacterial load was found in 500 mg/kg LAM group. In vitro, LAM exerted a protective role against inactivated P. plecoglossicida-triggered inflammatory injury in primary head kidney macrophages (PKM) of large yellow croaker by recovering cell viability, suppressing NO production, and reversing pro-inflammatory cytokine expression (IL-1β, IL-6, and IL-8). All these findings therefore will provide insights into the protection mechanism of LAM in fish, facilitating its application in prevention and control of fish bacteriosis.

Euryfuranyl compounds from edible species of cuttlefish as potential anti-inflammatory leads attenuating NF-κB signaling cascade in lipopolysaccharide-activated macrophages

Nuclear factor-kappa B is an inducible transcription element, which was considered as an important regulator of immune functions, and plays a critical role to induce inflammatory reactions. In this study, we have demonstrated the anti-inflammatory potentials of previously undescribed (4 → 13)-abeo-euryfuranyls (1-2) from the spineless cuttlefish Sepiella inermis in lipopolysaccharide-stimulated macrophages. The euryfuranyl bearing (4 → 13)-abeo-euryfuranyl-2-ene-6-hydroxymethyl-propanoate framework (compound 1) displayed prominent inhibitory effects against pro-inflammatory cyclooxygenase-2 (IC₅₀ 0.36 mM) and 5-lipoxygenase (IC₅₀ 0.70 mM). Additionally, it suppressed the generation of inducible nitric oxide synthase along with cyclooxygenase-2 and 5-lipoxygenase in lipopolysaccharide-stimulated macrophages. The euryfuranyl analogue (1) down-regulated the mRNA expression of cyclooxygenase-2 and nuclear factor-κB signaling pathway in lipopolysaccharide-activated macrophage cells by hindering the degradation of inhibitor-κB proteins, and transfer of the subunit NF-κB p⁶⁵ to the nucleus from the cytosol. These results demonstrated that the euryfuranyl analogue could be explored as a promising anti-inflammatory therapeutic lead attenuating nuclear factor-κB signaling cascade.

Anti-Inflammatory Potential of Carpomitra costata Ethanolic Extracts via Inhibition of NF-κB and AP-1 Activation in LPS-Stimulated RAW264.7 Macrophages

Marine algae have valuable health and dietary benefits. The present study aimed to investigate whether an ethanol extract of Carpomitra costata (CCE) could inhibit the inflammatory response to LPS. CCE attenuated the production of proinflammatory mediators, such as prostaglandin E₂ (PGE₂) and nitric oxide (NO), by inhibiting inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in LPS-induced RAW264.7 macrophages. CCE also inhibited the expression of proinflammatory cytokines such as IL-1β, TNF-α, and IL-6. CCE suppressed the LPS-induced DNA-binding activity of (NF-κB) and activator protein-1 (AP-1). In addition, CCE attenuated the LPS-stimulated phosphorylation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK) and phosphatidylinositol 3′-kinase/Akt (PI3K/Akt). Functional aspects of the JNK and Akt signaling pathways were analyzed using specific inhibitors, which attenuated the LPS-induced production of proinflammatory cytokines, and NO and PGE₂ expression by suppressing AP-1 and NF-κB activity. In particular, the AP-1 signaling pathway is not involved in the production of inflammatory cytokines, such as IL-6, TNF-α, and IL-1β. These results suggested that CCE might exert its anti-inflammatory action by downregulating transcriptional factors (NF-κB and AP-1) through JNK and Akt signaling pathways. The current study suggested that CCE might be a valuable candidate for the treatment of inflammatory disorders.

Anti-inflammatory activity of edible brown alga Saccharina japonica and its constituents pheophorbide a and pheophytin a in LPS-stimulated RAW 264.7 macrophage cells

Anti-inflammatory activity of Saccharina japonica and its active components was evaluated via in vitro inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) expression in RAW 264.7 murine macrophage cells. Since the methanolic extract of S. japonica showed strong anti-inflammatory activity, it was fractionated with several solvents. Among the fractions, the ethyl acetate fraction demonstrated the highest inhibition of LPS-induced NO production (IC50=25.32μg/mL), followed by the CH2Cl2 fraction (IC50=75.86μg/mL). Considering the yield and anti-inflammatory potential together, the CH2Cl2 fraction was selected for chromatographic separation to yield two active porphyrin derivatives, pheophorbide a and pheophytin a, together with an inactive fucoxanthin. In contrast to fucoxanthin, pheophorbide a and pheophytin a showed dose-dependent inhibition against LPS-induced NO production at nontoxic concentrations in RAW 264.7 cells. Both compounds also suppressed the expression of iNOS proteins, while they did not inhibit the COX-2 expression in LPS-stimulated macrophages. These results indicate that pheophorbide a and pheophytin a are two important candidates of S. japonica as anti-inflammatory agents which can inhibit the production of NO via inhibition of iNOS protein expression. Thus, these compounds hold great promise for use in the treatment of various inflammatory diseases.

Anti-inflammatory effect of hexane fraction from Myagropsis myagroides ethanolic extract in lipopolysaccharide-stimulated BV-2 microglial cells

OBJECTIVES

Microglial activation has been implicated in neurological disorders for its inflammatory and neurotrophic effects. We investigated the anti-inflammatory effect of the hexane fraction from Myagropsis myagroides (Mertens ex Turner) Fensholt ethanolic extract and its underlying molecular mechanism in lipopolysaccharide-stimulated microglia.

METHODS

Various solvent fractions prepared from the ethanolic extract of M. myagroides were analysed for total phenolic content, 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity and inhibitory effect on nitric oxide (NO) production in activated BV-2 microglia. We measured prostaglandin E2 (PGE2 ) and pro-inflammatory cytokine levels by enzyme-linked immunosorbent assay. Expression of inflammatory enzymes was analysed by Western blot. Nuclear translocation and activation of nuclear factor-kappaB (NF-κB) were determined by immunofluorescence and reporter gene assay, respectively.

KEY FINDINGS

Among the fractions, the hexane fraction (MMH), rich in fatty acid, showed the highest inhibitory activity on NO generation. Pretreatment with MMH decreased mRNA and protein levels of inducible NO synthase and cyclooxygenase-2, resulting in a decrease in NO and PGE2 in LPS-stimulated BV-2 cells. Furthermore, MMH inhibited the production of inducible pro-inflammatory cytokines at their transcriptional level via inactivation of NF-κB. MMH inhibited the activation of extracellular signal-regulated kinase and c-Jun N-terminal kinase.

CONCLUSIONS

These results indicate that MMH has a strong anti-inflammatory activity in LPS-stimulated microglia, suggesting that MMH can be used as a therapeutic agent against neuroinflammatory diseases.

Hexane fraction from Sargassum fulvellum inhibits lipopolysaccharide-induced inducible nitric oxide synthase expression in RAW 264.7 cells via NF-κB pathways

Sargassum fulvellum (Turner) C. Agardh has been used to treat various inflammatory diseases, including lump, dropsy, swollen and painful scrotum, and urination problems for several centuries with no side effects. This study aims to investigate the anti-inflammatory effect of the hexane fraction of S. fulvellum (HFS) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and phorbol 12-myristate 13-acetate (PMA)-induced mouse-ear edema. The anti-inflammatory activity of HFS in LPS-stimulated RAW 264.7 cells was investigated by assessing the inhibition of nitric oxide (NO) and pro-inflammatory cytokine production during Griess reaction and enzyme-linked immunosorbent assay (ELISA), respectively. The molecular mechanisms that underlie the anti-inflammatory action of HFS were investigated by analyzing the activation of transcription factor and its upstream signaling proteins. Additionally, an in vivo study of the anti-inflammatory effect of HFS was carried out using PMA-induced mouse-ear edema. HFS inhibited LPS-induced NO production in a dose-dependent manner and suppressed the expression of inducible NO synthase (iNOS) in the RAW 264.7 cells. Further, HFS reduced the production of pro-inflammatory cytokines in the LPS-stimulated RAW 264.7 cells. HFS significantly inhibited LPS-induced nuclear factor kappa B (NF-κB) transcriptional activity and NF-κB translocation into the nucleus by preventing degradation of inhibitor κB-α. Moreover, HFS inhibited the activation of Akt and mitogen-activated protein kinases (MAPKs) in the LPS-stimulated RAW 264.7 cells. Furthermore, HFS suppressed PMA-induced mouse-ear edema. The above data indicate that the anti-inflammatory effects of HFS on LPS-stimulated cells are associated with the suppression of NF-κB through the inhibition of MAPKs and Akt phosphorylation.