AMPK Signaling Involvement for the Repression of the IL-1β-Induced Group IIA Secretory Phospholipase A2 Expression in VSMCs

PLoS One. 2015 Jul 10;10(7):e0132498. doi: 10.1371/journal.pone.0132498. eCollection 2015.

Abstract

Secretory Phospholipase A2 of type IIA (sPLA2 IIA) plays a crucial role in the production of lipid mediators by amplifying the neointimal inflammatory context of the vascular smooth muscle cells (VSMCs), especially during atherogenesis. Phenformin, a biguanide family member, by its anti-inflammatory properties presents potential for promoting beneficial effects upon vascular cells, however its impact upon the IL-1β-induced sPLA2 gene expression has not been deeply investigated so far. The present study was designed to determine the relationship between phenformin coupling AMP-activated protein kinase (AMPK) function and the molecular mechanism by which the sPLA2 IIA expression was modulated in VSMCs. Here we find that 5-aminoimidazole-4-carboxamide-1-β-D-ribonucleotide (AICAR) treatment strongly repressed IL-1β-induced sPLA2 expression at least at the transcriptional level. Our study reveals that phenformin elicited a dose-dependent inhibition of the sPLA2 IIA expression and transient overexpression experiments of constitutively active AMPK demonstrate clearly that AMPK signaling is involved in the transcriptional inhibition of sPLA2-IIA gene expression. Furthermore, although the expression of the transcriptional repressor B-cell lymphoma-6 protein (BCL-6) was markedly enhanced by phenformin and AICAR, the repression of sPLA2 gene occurs through a mechanism independent of BCL-6 DNA binding site. In addition we show that activation of AMPK limits IL-1β-induced NF-κB pathway activation. Our results indicate that BCL-6, once activated by AMPK, functions as a competitor of the IL-1β induced NF-κB transcription complex. Our findings provide insights on a new anti-inflammatory pathway linking phenformin, AMPK and molecular control of sPLA2 IIA gene expression in VSMCs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • AMP-Activated Protein Kinases / metabolism*
  • Aminoimidazole Carboxamide / analogs & derivatives
  • Aminoimidazole Carboxamide / pharmacology
  • Animals
  • Binding Sites
  • Cattle
  • Cell Separation
  • Cells, Cultured
  • Enzyme Activation / drug effects
  • Gene Expression Regulation, Enzymologic / drug effects
  • Group II Phospholipases A2 / genetics*
  • Group II Phospholipases A2 / metabolism
  • Interleukin-1beta / pharmacology*
  • Male
  • Muscle, Smooth, Vascular / cytology*
  • Myocytes, Smooth Muscle / drug effects
  • Myocytes, Smooth Muscle / enzymology*
  • NF-kappa B / metabolism
  • Phenformin / pharmacology
  • Phosphorylation / drug effects
  • Promoter Regions, Genetic / genetics
  • Protein Subunits / metabolism
  • Proto-Oncogene Proteins c-bcl-6 / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rats, Wistar
  • Ribonucleotides / pharmacology
  • Signal Transduction / drug effects*
  • Transcriptional Activation / drug effects

Substances

  • Interleukin-1beta
  • NF-kappa B
  • Protein Subunits
  • Proto-Oncogene Proteins c-bcl-6
  • RNA, Messenger
  • Ribonucleotides
  • Aminoimidazole Carboxamide
  • Phenformin
  • AMP-Activated Protein Kinases
  • Group II Phospholipases A2
  • AICA ribonucleotide

Grants and funding

This work was supported by the Université Pierre et Marie Curie (University Paris 6) and by grants from the “Leg Poix-2007” and "Leg Poix-2009" of the Chancellerie des Universités de Paris. Dr. Lucas Ravaux was supported by doctoral fellowships from the Ministère de l’Education Nationale de la Recherche et de la Technologie.