Ascofuranone inhibits lipopolysaccharide–induced inflammatory response via NF-kappaB and AP-1, p-ERK, TNF-α, IL-6 and IL-1β in RAW 264.7 macrophages

Abstract

The natural fungal compound ascofuranone (5-chloro-3-[(2E,6E)-7-[(2S)-5,5-dimethyl-4-oxo-tetrahydrofuran-2-yl]-3-methyl-octa-2,6-dienyl]-2,4-dihydroxy-6-methyl-benzaldehyde, MW 420.93) (AF) isolated from Ascochyta viciae has been known to promote cell cycle arrest and inhibit invasion of tumor cells. We have previously studied a structurally similar compound ascochlorin (ASC; MW 404.93) with regard to its anti-inflammatory activity in LPS- stimulated RAW 264.7 macrophages. In order to examine the relationship between the anti-inflammatory activities and the molecular differences between AF and ASC, the activity of AF is herein studied, because ASC has a unique trimethyl oxocyclohexyl structure, while AF has a unique dimethyl-oxo-tetrahydrofuran structure. AF dose-dependently inhibited the production of NO and iNOS and the COX-2 mRNA and protein levels in RAW 264.7 cells. In addition, AF suppressed mRNA expression levels of inflammatory cytokines such as TNF-α, IL-6, and IL-1β, as assessed by RT-PCR. AF (30–50 μg/ml) treatment clearly inhibited the nuclear translocation of NF-κB, AP-1 (p-c-Jun) from the cytosolic space. Phosphorylation of IκB, which functions to maintain the activity of NF-κB, was decreased by AF treatment. Moreover, AF suppressed the binding of NF-κB (p65). Inhibition of IkBa phosphorylation and degradation inhibits nuclear translocation of p65. Immunofluorescence confocal microscopy analysis also revealed that translocation of NF-κB and AP-1 (p-c-Jun) was decreased upon AF treatment. AF specifically decreased the expression level of p-ERK, but not the expression level of p-p38 or p-JNK. Given these results, we suggest that AF suppresses the inflammatory response by targeting p-ERK. This indicates that AF is a negative regulator of LPS-stimulated nuclear translocation of NF-κB and AP-1 (p-c-Jun) in RAW 264.7 macrophages, and specifically it targets p-ERK. Therefore, AF and ASC exert their effects in different ways, most probably because their structural differences allow for specific recognition and inhibition of their target MAPKs. Our results further suggest that AF could be a natural bioactive compound useful for treating inflammation-mediated pathological diseases.

Curcumin alleviates macrophage activation and lung inflammation induced by influenza virus infection through inhibiting the NF‐κB signaling pathway

“…Previous studies have revealed that NF‐κB signaling pathway is one of the most important pathways that are activated in macrophages under the pathogen challenge . Thus, we aimed to study whether the anti‐inflammatory ability of curcumin is associated with NF‐κB signaling pathway.…”

“…Previous studies have revealed that NF-κB signaling pathway is one of the most important pathways that are activated in macrophages under the pathogen challenge. [34][35][36][37][38] Thus, we aimed to study whether the anti-inflammatory ability of curcumin is associated with NF-κB signaling pathway. By examining the protein expression levels via Western Blotting, we found that IAV infection leads to the decrease in IκBα and cytosolic p65, while enhanced the levels of p-IκBα and nuclear p65.…”

Orostachys japonicus extract inhibits the lipopolysaccharide‐induced pro‐inflammatory factors by suppression of transcription factors

“…The inflammatory response activates macrophages and pro‐inflammatory mediators, and cytokines are expressed, such as inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)‐2, interleukin (IL)‐1β, IL‐2, IL‐6, and interferon‐gamma inducible protein 10 kDa (IP‐10). Their overproduction of these molecules is a common marker of the inflammatory response, resulting in various adverse effects (Park et al, ; Yao et al, ). Inhibiting the expression in these inflammatory mediators is important to verify the anti‐inflammatory activity of a natural substance.…”

“…Pro‐inflammatory mediators and cytokines were expressed in LPS‐stimulated cells after the transcription factors are translocated to the nucleus. Inhibiting translocation into the nucleus is an important mechanism to regulate inflammation (Kim, Han, Kil, Seo, & Jin, ; Park et al, ; Takeda & Akira, ). To conform for inhibits of solvent fractions, cells were pretreated with the highest concentration of solvent fractions (100 μg/ml) for 2 hr and LPS‐induced inflammatory for 1.5 hr.…”

Gaudichaudione H Inhibits Inflammatory Responses in Macrophages and Dextran Sodium Sulfate-Induced Colitis in Mice

“…Factor-kB and Mitogen-Activated Protein Kinase Pathways Activation in RAW 264.7 Cells It is well-known that NF-kB is an important signaling molecule in the development of inflammatory diseases. In its inactive form, NF-kB exists in the cytoplasm and binds to its inhibitor IkB (Park et al, 2017). Upon activation by LPS, IkB is phosphorylated by IKKa/b, leading to its degradation and NF-kB activation (Qi et al, 2012).…”