An angiogenic switch in macrophages involving synergy between Toll-like receptors 2, 4, 7, and 9 and adenosine A2A receptors

G Pinhal-Enfield, M Ramanathan, G Hasko… - The American journal of …, 2003 - Elsevier
G Pinhal-Enfield, M Ramanathan, G Hasko, SN Vogel, AL Salzman, GJ Boons, SJ Leibovich
The American journal of pathology, 2003Elsevier
Adenosine A2A receptor (A2AR) agonists synergize with Escherichia coli (E. coli) LPS [toll-
like receptor (TLR) 4 agonist] to up-regulate vascular endothelial growth factor (VEGF)
expression in murine macrophages. Here, we demonstrate that TLR2, TLR7, and TLR9, but
not TLR3 and TLR5 agonists, also synergize with A2AR agonists and adenosine to up-
regulate VEGF, while simultaneously strongly down-regulating TNFα expression. In the
absence of adenosine or A2AR agonists, Porphyromonas gingivalis (P. gingivalis) LPS and …
Adenosine A2A receptor (A2AR) agonists synergize with Escherichia coli (E. coli) LPS [toll-like receptor (TLR)4 agonist] to up-regulate vascular endothelial growth factor (VEGF) expression in murine macrophages. Here, we demonstrate that TLR2, TLR7, and TLR9, but not TLR3 and TLR5 agonists, also synergize with A2AR agonists and adenosine to up-regulate VEGF, while simultaneously strongly down-regulating TNFα expression. In the absence of adenosine or A2AR agonists, Porphyromonas gingivalis (P. gingivalis) LPS and PAM3CAG (TLR2 agonists), resiquimod (R848) (TLR7 agonist), and non-methylated CpG DNA (TLR9 agonist) strongly up-regulate TNFα expression, with no effect on VEGF. In the presence of adenosine or A2AR agonists, but not A1R agonists, TLR2, 4, 7, and 9 agonists strongly up-regulate VEGF expression, while simultaneously down-regulating TNFα. C57BL/10ScN (TLR4 deletion mutant) macrophages produce TNFα in response to TLR2, 3, 7, and 9 agonists, but not the TLR4 agonist E. coli LPS. With adenosine or A2AR agonists, TLR2, 7, and 9, but not TLR4 agonists, also synergistically up-regulate VEGF, while down-regulating TNFα expression. Polyinosinic-polycytidilic acid (poly(I:C)) (TLR3 agonist) stimulates TNFα expression in macrophages from both C57BL/10ScSn and C57BL/10ScN mice, but has little effect on VEGF expression in the presence of adenosine or A2AR agonists. R-flagellins from Serratia marcescens (S. marcescens) and Salmonella muenchen (S. muenchen) do not stimulate TNFα expression in either C57BL/10ScSn or C57BL10/ScN mice, and have no effect on VEGF production in the presence of adenosine or A2AR agonists. While adenosine and A2AR agonists strongly down-regulate TNFα protein expression induced by TLR2, 3, 4, 7, and 9 agonists, TNFα mRNA and NF-κB activation are not reduced. We propose a novel signaling pathway in murine macrophages involving synergy between TLRs 2, 4, 7, and 9 and A2ARs, that up-regulates VEGF and down-regulates TNFα expression, thus acting as an angiogenic switch. This angiogenic switch may play an important role in ischemia when TLR agonists are present, providing an interface between innate immunity and wound healing.
Elsevier