Functional Characterization of beta-defensins in Inflammation
Final Report Abstract
Our previous studies indicated that mouse beta-defensin 14 (mBD14, Defb14), a newly identified member of the beta-defensin super family, interacts with the chemokine receptors CCR2 and CCR6. Our new results demonstrate that pre-stimulation of primary mouse macrophages with mBD14 results in a synergistic, enhanced expression of pro-inflammatory cytokines and chemokines induced by TLR ligand re-stimulation. Experiments using specific inhibitors of Gi-protein-coupled receptor signalling provide evidence that this effect seems to be mediated by a Gi-protein-coupled receptor expressed on bone marrow derived macrophages. However, using primary macrophages derived from CCR6- and CCR2-deficient mice clearly demonstrated that the enhanced pro-inflammatory cytokine and chemokine expression is independent of the chemokine receptors CCR6 and CCR2. Additionally, signalling pathway analysis indicated that mBD14 is capable of inducing MAPK ERK1/2 phosphorylation and the induction of CD86 and F4/80 expression in bone marrowderived macrophages after mBD14 stimulation. Collectively, our data indicate that beta-defensins activate primary macrophages and enhance pro-inflammatory responses by using GiPCRs in order to support inflammatory reactions induced by TLR ligands. Considering a potential relationship between β-defensins and malignancy and our results demonstrating the pro-inflammatory properties of mBD14, we analyzed the expression pattern of mBD14 in fibrosarcoma tissue and its potential role during tumor development. Tumor cells expressing mBD14 demonstrated enhanced solid tumor growth in syngeneic C57BL/6 mice concomitant with increased vascularization of these tumors. Furthermore, mBD14 expressing tumors demonstrated increased expression of pro-angiogenic macrophage inflammatory protein-2 (MIP-2, CXCL2) ex vivo. Cellular analysis of tumor infiltrating leukocytes revealed a significant increase of CCR6+, B220+ lymphocytes in solid tumors derived from mBD14 expressing tumor cells. Enhanced tumor growth of mBD14 expressing fibrosarcomas was abolished in CCR6-deficient mice indicating the requirement of CCR6-expression on host cells. Previously the interaction of activated Lymphotoxin (LT) αβ+ lymphocytes with LTβ-receptor (LTβR) expressing fibrosarcoma tumor cells has been identified as a new CXCL2-dependent pro-angiogenic pathway. Co-expression of a soluble LTβR:Ig fusion protein, an inhibitor of CXCL2-dependent angiogenesis, in mBD14 expressing fibrosarcoma tumor cells prevented enhanced solid tumor growth. Thus, we conclude that mBD14 expression by tumor infiltrating host cells results in the chemoattraction of CCR6+ B220+ lymphocytes, which in turn results in LTβR activation on the tumor cells and initiates a pro-angiogenic pathway leading to enhanced angiogenesis in a CXCL2 dependent manner.
Publications
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Human β-Defensin 2 and 3 and their Mouse Orthologues induce Chemotaxis through Interaction with CCR2. 2010. J. Immunol. 15:184
Röhrl, J., Yang, D., Oppenheim, JJ., and Hehlgans, T.
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Friend or foe: A novel role of B-defensins in tumor development. 2012. Oncoimmunolgy, 1:40
Röhrl, J., Geissler, EK., and Hehlgans, T.
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Mouse β-Defensin 14 (Defb14) Promotes Tumor Growth by Inducing Angiogenesis in a CCR6-Dependent Manner, 2012. J. Immunol. 188: 4931
Röhrl, J., Huber, B., Koehl, GE., Geissler, EK., Hehlgans, T.
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Beta-defensins activate macrophages and synergize in pro-inflammatory cytokine expression induced by TLR ligands. 2013, Immunobiology, 218:1005
Barabas, N., Röhrl, J., Holler, E., Hehlgans T.
