title: Soluble heparan sulfate fragments generated by heparanase trigger the release of pro-inflammatory cytokines through TLR-4.
abstract: Heparanase is a β-D-endoglucuronidase that cleaves heparan sulfate (HS), facilitating degradation of the extracellular matrix (ECM) and the release of HS-bound biomolecules including cytokines. The remodeling of the ECM by heparanase is important for various physiological and pathological processes, including inflammation, wound healing, tumour angiogenesis and metastasis. Although heparanase has been proposed to facilitate leukocyte migration through degradation of the ECM, its role in inflammation by regulating the expression and release of cytokines has not been fully defined. In this study, the role of heparanase in regulating the expression and release of cytokines from human and murine immune cells was examined. Human peripheral blood mononuclear cells treated ex vivo with heparanase resulted in the release of a range of pro-inflammatory cytokines including IL-1β, IL-6, IL-8, IL-10 and TNF. In addition, mouse splenocytes treated ex vivo with heparanase resulted in the release of IL-6, MCP-1 and TNF. A similar pattern of cytokine release was also observed when cells were treated with soluble HS. Furthermore, heparanase-induced cytokine release was abolished by enzymatic-inhibitors of heparanase, suggesting this process is mediated via the enzymatic release of cell surface HS fragments. As soluble HS can signal through the Toll-like receptor (TLR) pathway, heparanase may promote the upregulation of cytokines through the generation of heparanase-cleaved fragments of HS. In support of this hypothesis, mouse spleen cells lacking the key TLR adaptor molecule MyD88 demonstrated an abolition of cytokine release after heparanase stimulation. Furthermore, TLR4-deficient spleen cells showed reduced cytokine release in response to heparanase treatment, suggesting that TLR4 is involved in this response. Consistent with these observations, the pathway involved in cytokine upregulation was identified as being NF-κB-dependent. These data identify a new mechanism for heparanase in promoting the release of pro-inflammatory cytokines that is likely to be important in regulating cell migration and inflammation.
authors.affiliation: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia; Cooperative Research Centre for Biomarker Translation, Melbourne, Victoria, Australia.
authors.forename: Katharine J
authors.initials: KJ
authors.lastname: Goodall
authors.affiliation: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.
authors.forename: Ivan K H
authors.initials: IK
authors.lastname: Poon
authors.affiliation: School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Phipps
authors.affiliation: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Melbourne, Victoria, Australia.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Hulett
mesh_terms: D000818:Animals; D016207:Cytokines / Q000378:metabolism*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D005966:Glucuronidase / Q000378:metabolism*; D006497:Heparan Sulfate / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012995:Solubility; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D000099175:Heparanase
chemical_list: D016207:Cytokines; D005966:Glucuronidase; D006497:Heparan Sulfate; D053594:Myeloid Differentiation Factor 88; D051197:Toll-Like Receptor 4; D000099175:Heparanase; C495345:TLR4 protein, human