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Endotoxin recognition in fish results in inflammatory cytokine secretion not gene expression

Nerea Roher1, Agnes Callol, Josep V Planas

  • 1Departament Biologia Cellular, Immunologia i Fisiologia Animal Universitat Autónoma de Barcelona, Barcelona, Spain.

Innate Immunity
|January 20, 2010
PubMed

Insights

Rainbow trout macrophages secrete tumor necrosis factor-alpha (TNF-α) in response to pathogen-associated molecular patterns (PAMPs). This secretion is triggered by contaminants in lipopolysaccharide (LPS) and involves specific signaling pathways.

Area of Science:

  • Immunology
  • Fish Biology
  • Cellular Signaling

Background:

  • Macrophages are key immune cells recognizing pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs).
  • While immune gene expression in fish macrophages is studied, cytokine release mechanisms remain unclear.
  • Tumor necrosis factor-alpha (TNF-α) plays a crucial role in immune responses.

Purpose of the Study:

  • To characterize TNF-α secretion in rainbow trout macrophages stimulated with various PAMPs.
  • To compare TNF-α secretion with gene expression of TNF-α, IL-1β, IL-6, INF-α, and Mx protein.
  • To investigate the signaling pathways and TNF-α converting enzyme (TACE) involvement in TNF-α secretion.

Main Methods:

  • Primary macrophage cultures from rainbow trout (Oncorhynchus mykiss).
  • Stimulation with lipopolysaccharide (LPS), ultrapure LPS, and zymosan.
  • Western blot analysis for TNF-α secretion.
  • Gene expression analysis for cytokines (TNF-α, IL-1β, IL-6) and antiviral proteins (INF-α, Mx).
  • Analysis of signaling pathways (ERK, p38MAPK, JNK) and TACE activity.

Main Results:

  • LPS and zymosan significantly induce TNF-α secretion, independent of initial TNF-α mRNA induction.
  • Ultrapure LPS stimulates TNF-α secretion but not expression, suggesting contaminants in commercial LPS are potent inducers.
  • TNF-α secretion is mediated by TACE-like activity, dependent on ERK, p38MAPK, and JNK pathway activation by LPS.

Conclusions:

  • Rainbow trout macrophages exhibit PAMP-induced TNF-α secretion, with contaminants in LPS being key drivers.
  • TNF-α shedding in fish macrophages is a regulated process involving TACE-like activity and specific MAPK pathways.
  • This study provides novel insights into fish innate immune responses and cytokine regulation.

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