Differential regulation of HIF-1α isoforms in murine macrophages by TLR4 and adenosine A2A receptor agonists

Madhuri Ramanathan, Wenting Luo, Balázs Csóka, G. Haskó, Dmitry Lukashev, Michail V. Sitkovsky, Samuel Joseph Leibovich

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Adenosine A2AR and TLR agonists synergize to induce an "angiogenic switch" in macrophages, down-regulating TNFα and up-regulating VEGF expression. This switch involves transcriptional regulation of VEGF by HIF-1, transcriptional induction of HIF-1α by LPS (TLR4 agonist), and A2AR-dependent post-transcriptional regulation of HIF-1α stability. Murine HIF-1α is expressed as two mRNA isoforms: HIF-1αI.1 and -I.2, which contain alternative first exons and promoters. HIF-1αI.2 is expressed ubiquitously, and HIF-1αI.1 is tissue-specific. We investigated the regulation of these isoforms in macrophages by TLR4 and A2AR agonists. HIF-1αI.1 is induced strongly compared with HIF-1αI.2 upon costimulation with LPS and A2AR agonists (NECA or CGS21680). In unstimulated cells, the I.1 isoform constituted ∼4% of HIF-1α transcripts; in LPS and NECA- or CGS21680-treated macrophages, this level was ∼15%, indicating a substantial contribution of HIF-1αI.1 to total HIF-1α expression. The promoters of both isoforms were induced by LPS but not enhanced further by NECA, suggesting A 2AR-mediated post-transcriptional regulation. LPS/NECA-induced expression of HIF-1αI.1 was down-regulated by Bay 11-7085 (NF-κB inhibitor) and ZM241385 (A2AR antagonist). Although VEGF and IL-10 expression by HIF-1αI.1-/- macrophages was equivalent to that of wild-type macrophages, TNF-α, MIP-1α, IL-6, IL-12p40, and IL-1β expression was significantly greater, suggesting a role for HIF-1αI.1 in modulating expression of these cytokines. A2AR expression in unstimulated macrophages was low but was induced rapidly by LPS in a NF-κB-dependent manner. LPS-induced expression of A2ARs and HIF-1α and A2AR-dependent HIF-1α mRNA and protein stabilization provide mechanisms for the synergistic effects of LPS and A 2AR agonists on macrophage VEGF expression.

Original languageEnglish
Pages (from-to)681-689
Number of pages9
JournalJournal of Leukocyte Biology
Volume86
Issue number3
DOIs
Publication statusPublished - Sep 1 2009

Fingerprint

Adenosine A2 Receptor Agonists
Protein Isoforms
Adenosine-5'-(N-ethylcarboxamide)
Macrophages
Vascular Endothelial Growth Factor A
Interleukin-12 Subunit p40
RNA Isoforms
Interleukin-1
Interleukin-10
Adenosine
Exons
Interleukin-6
Cytokines
Messenger RNA

Keywords

  • Alternative activation
  • Endotoxin
  • Inflammation
  • TNF-α
  • Transcription factors
  • VEGF

ASJC Scopus subject areas

  • Cell Biology
  • Immunology

Cite this

Differential regulation of HIF-1α isoforms in murine macrophages by TLR4 and adenosine A2A receptor agonists. / Ramanathan, Madhuri; Luo, Wenting; Csóka, Balázs; Haskó, G.; Lukashev, Dmitry; Sitkovsky, Michail V.; Leibovich, Samuel Joseph.

In: Journal of Leukocyte Biology, Vol. 86, No. 3, 01.09.2009, p. 681-689.

Research output: Contribution to journalArticle

Ramanathan, Madhuri ; Luo, Wenting ; Csóka, Balázs ; Haskó, G. ; Lukashev, Dmitry ; Sitkovsky, Michail V. ; Leibovich, Samuel Joseph. / Differential regulation of HIF-1α isoforms in murine macrophages by TLR4 and adenosine A2A receptor agonists. In: Journal of Leukocyte Biology. 2009 ; Vol. 86, No. 3. pp. 681-689.
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