Influence of hypoxia on protease expression and function in inflammation

Principal Investigator

Associated Principal Investigator

Background and current state of research

Hypoxia and inflammation are intimately linked. Hypoxia can influence the environment of the tissue, particularly by regulating oxygen-dependent gene expression. Several inflammatory diseases, such as rheumatoid arthritis (RA), inflammatory bowel disease (IBD), and atherosclerosis are linked to the deregulation of the hypoxia and inflammation pathways. In IBD, the entire mucosa becomes even more hypoxic, accordingly surgical specimens of the inflamed intestine were found to contain elevated levels of the transcriptional factor, HIF (hypoxia-inducible factor)-1α and HIF-2α. T cells present in inflammatory lesions in IBD and RA also express Hif-1α suggesting that T cell responses in the context of inflammation are likely influenced by hypoxia. HIF-1 exerts its effect on the pathogenesis of inflammatory diseases via a variety of molecular and cellular events. In particular, different target cells and effector cells (e.g. macrophages, T cells) are affected, highlighting the environmental cues that control HIF-1 expression/activation.
Disintegrin-like metalloproteases (ADAMs) comprise the major family of ubiquitously expressed ectodomain sheddases. In inflammatory settings, ADAMs mediate signalling of cytokines including TNFα and IL-6 and control leukocyte recruitment by the cleavage of cell adhesion molecules. ADAM17 and ADAM10 have been implicated in diverse diseases associated with inflammation including RA, IBD, atherosclerosis, psoriasis, asthma, inflammation associated tumors, and diabetes. ADAM17 controls both TNF-alpha production by inflammatory/immune cells and the bioavailability of TNF-alpha receptors (TNFRs) on target cells, i.e. epithelial cells. Although ADAM10 and ADAM17 are well characterized, almost all analyses were performed using normal oxygen concentration (21%). We recently obtained evidence that these important proteases behave quite differently under hypoxia. Thus, there is an urgent need to re-address transmembrane protease function under conditions reflecting the hypoxic inflammatory environment.

Our goals

The overall goal of the project is to learn more about how hypoxia might influence metalloprotease-driven inflammation. Since ADAMs are central regulators of inflammatory processes their function is tightly controlled at different levels. Preliminary data suggest that striking differences exist under hypoxic conditions shedding new light on the role of these proteases for inflammation.

How to get there

Different cell types of target cells and effector cells (colonic cell lines, primary endothelial cells, smooth muscle cells, macrophages, T cells) will be cultured for different time periods under normoxic or diverse hypoxic conditions in the presence of absence of LPS-induced inflammatory responses. Hypoxia-induced upregulation of HIF will be analyzed using RT-PCR and Western blot analyses. These methods will also be used to analyze the expression of ADAM10, ADAM17, related metalloproteases, and their respective substrates. Substrate release (e.g. TNFR, L-selectin, TNF-alpha, IL-6R) will be measured via ELISA. Metalloproteases are key player in the control of epithelial/endothelial barrier function. The
influence of metalloproteases on barrier function and leukocyte transmigration will be analyzed under normoxic and hypoxic conditions using different functional assays. Protease overexpression, siRNA experiments and pharmacological approaches will ensure the direct link to the respective protease.

More information

Requirements for the position:
Preferably excellent Master / “Diplom” graduates from the field of Biochemistry, Cell Biology or Medical Life Sciences.

References:
Reiss K, Bhakdi S (2017) The plasma membrane: Penultimate regulator of ADAM sheddase function. Biochim Biophys Acta. 1864:2082-2087. Saftig P, Reiss K (2011) The "A Disintegrin And Metalloproteases" ADAM10 and ADAM17: novel drug targets with therapeutic potential? Eur. J. Cell Biol., 90, 527-535.