Inhibitory effects of alternaramide on inflammatory mediator expression through TLR4-MyD88-mediated inhibition of NF-кB and MAPK pathway signaling in lipopolysaccharide-stimulated RAW264.7 and BV2 cells

Chem Biol Interact. 2016 Jan 25:244:16-26. doi: 10.1016/j.cbi.2015.11.024. Epub 2015 Nov 24.

Abstract

Alternaramide (1), a novel lipophilic depsipeptide, has been isolated from the extract of the marine-derived fungus Alternaria sp. SF-5016. In the course of extensive biological evaluation of 1, its anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated RAW264.7 and BV2 cells were observed. In our initial study of the anti-inflammatory effects of 1, the compound suppressed production of nitric oxide (NO) and prostaglandin E2 (PGE2) in LPS-stimulated RAW264.7 and BV2 cells. Suppression of NO and PGE2 production was correlated with the inhibitory effect of 1 on expression of LPS-induced inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the protein level in RAW264.7 and BV2 cells. In addition, 1 reduced production of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, and IL-12 in LPS-stimulated RAW264.7 and BV2 cells. In the evaluation of the molecular mechanisms underlying the anti-inflammatory effects of 1, the compound was found to suppress the nuclear factor-kappa B (NF-κB) signaling pathway in RAW264.7 and BV2 cells stimulated with LPS. This suppression was mediated by disruption of phosphorylation and degradation of IκBα, an inhibitor of NF-κB, in the cytoplasm, and blocking of nuclear translocation of the NF-κB p50-p65 heterodimer. Furthermore, 1 inhibited phosphorylation of c-Jun N-terminal kinases (JNKs) and p38 mitogen-activated protein kinase (MAPK), demonstrating its capacity to inhibit MAPK signaling. Finally, 1 markedly reduced expression of Toll-like receptor 4 (TLR4) and myeloid differentiation primary response gene 88 (MyD88) at the mRNA and protein levels in LPS-stimulated RAW264.7 and BV2 cells. Taken together, the results of the present study suggest that 1 modulates several TLR4-mediated inflammatory pathways, demonstrating its potential in the treatment of inflammatory and neuroinflammatory conditions.

Keywords: Alternaramide; Anti-inflammation; MAPK; Marine-derived fungus; Nuclear factor-kappa B; Toll-like receptor 4.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternaria / chemistry
  • Animals
  • Anti-Inflammatory Agents, Non-Steroidal / chemistry
  • Anti-Inflammatory Agents, Non-Steroidal / isolation & purification
  • Anti-Inflammatory Agents, Non-Steroidal / pharmacology*
  • Cell Line
  • Depsipeptides / chemistry
  • Depsipeptides / isolation & purification
  • Depsipeptides / pharmacology*
  • Dose-Response Relationship, Drug
  • Humans
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Lipopolysaccharides / pharmacology*
  • MAP Kinase Signaling System / drug effects*
  • Mice
  • Molecular Conformation
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / metabolism*
  • NF-kappa B / metabolism*
  • Structure-Activity Relationship
  • Toll-Like Receptor 4 / biosynthesis
  • Toll-Like Receptor 4 / metabolism*
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Anti-Inflammatory Agents, Non-Steroidal
  • Depsipeptides
  • Lipopolysaccharides
  • MYD88 protein, human
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • NF-kappa B
  • TLR4 protein, human
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • alternaramide
  • JNK Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases