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Hoffmann, R. A wiki for the life sciences where authorship matters. Nature Genetics (2008)
 
 
 
 
 

Expression of Tie-2 by human monocytes and their responses to angiopoietin-2.

Angiopoietins 1 and 2 bind to Tie-2 expressed on endothelial cells and regulate vessel stabilization and angiogenesis. Tie-2(+) monocytes have been shown to be recruited to experimental tumors where they promote tumor angiogenesis. In this study, we show that 20% of CD14(+) human blood monocytes express Tie-2, and that these cells coexpress CD16 (FcgammaRIII) and are predominantly CD34 negative. Ang-2 is up-regulated by endothelial cells in malignant tumors and inflamed tissues, so our finding that Ang-2 is a chemoattractant for human Tie-2(+) monocytes and macrophages, suggests that it may help to recruit and regulate their distribution in such tissues. Ang-2 was also found to markedly inhibit release of the important proinflammatory cytokine, TNF-alpha, by monocytes in vitro. Following extravasation of monocytes, and their differentiation into macrophages, many accumulate in the hypoxic areas of inflamed and malignant tissues. Ang-2 is known to be up-regulated by hypoxia and we show that monocytes and macrophages up-regulate Tie-2 when exposed to hypoxia. Furthermore, hypoxia augmented the inhibitory effect of Ang-2 on the release of the anti-angiogenic cytokine, IL-12 by monocytes. In sum, our data indicate that Ang-2 may recruit Tie-2(+) monocytes to tumors and sites of inflammation, modulate their release of important cytokines and stimulate them to express a proangiogenic phenotype.[1]

References

  1. Expression of Tie-2 by human monocytes and their responses to angiopoietin-2. Murdoch, C., Tazzyman, S., Webster, S., Lewis, C.E. J. Immunol. (2007) [Pubmed]
 
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