Thromb Haemost 2014; 111(01): 67-78
DOI: 10.1160/TH13-03-0220
Blood Coagulation, Fibrinolysis and Cellular Haemostasis
Schattauer GmbH

Extracellular haemoglobin upregulates and binds to tissue factor on macrophages: Implications for coagulation and oxidative stress

Neha Bahl
1   Computational and Systems Biology, Singapore-Massachusetts Institute of Technology Alliance, Singapore
,
Imelda Winarsih
2   Department of Biological Sciences, National University of Singapore, Singapore
,
Lisa Tucker-Kellogg*
1   Computational and Systems Biology, Singapore-Massachusetts Institute of Technology Alliance, Singapore
3   Mechanobiology Institute, National University of Singapore, T-Lab, Singapore
,
Jeak Ling Ding*
1   Computational and Systems Biology, Singapore-Massachusetts Institute of Technology Alliance, Singapore
2   Department of Biological Sciences, National University of Singapore, Singapore
› Author Affiliations

Financial support: This work was supported by the Computational and Systems Biology Programme, Singapore-MIT Alliance, and by Tier 2 Grant [T208B3109] from the Ministry of Education, Singapore.
Further Information

Publication History

Received: 14 March 2013

Accepted after major revision: 02 September 2013

Publication Date:
29 November 2017 (online)

Preview

Summary

The mechanisms of crosstalk between haemolysis, coagulation and innate immunity are evolutionarily conserved from the invertebrate haemocyanin to the vertebrate haemoglobin (Hb). In vertebrates, extracellular Hb resulting from haemolytic infections binds bacterial lipopolysaccharide (LPS) to unleash the antimicrobial redox activity of Hb. Because bacterial invasion also upregulates tissue factor (TF), the vertebrate coagulation initiator, we asked whether there may be functional interplay between the redox activity of Hb and the procoagulant activity of TF. Using real-time PCR, TF-specific ELISA, flow cytometry and TF activity assay, we found that Hb upregulated the expression of functional TF in macrophages. ELISA, flow cytometry and immunofluorescence microscopy showed binding between Hb and TF, in isolation and in situ. Bioinformatic analysis of Hb and TF protein sequences showed co-evolution across species, suggesting that Hbβ binds TF. Empirically, TF suppressed the LPS-induced activation of Hb redox activity. Furthermore, Hb desensitised TF to the effects of antioxidants like glutathione or serum. This bi-directional regulation between Hb and TF constitutes a novel link between coagulation and innate immunity. In addition, induction of TF by Hb is a potentially central mechanism for haemolysis to trigger coagulation.

* Co-senior authors.