Principle investigator: Julia Mayerle
Co-supervisor: M. Lalk

The onset and severity of acute pancreatitis is determined by premature intracellular activation of proteases which eventually will lead to necrosis of pancreatic acinar cells and subsequently to systemic inflammation [1;2;3]. Recently, we were able to show that the proinflammatory cytokine TNF alpha alone is able to induce premature intracellular activation of the serine protease trypsin. The effect of TNF alpha was entirely dependent on the activity of the lysosomal protease cathepsin B but the underlying signalling mechanism is unclear at present [4]. Lysosomal cysteine proteases such as cathepsin B and L are co-localised with serine proteases in the secretory compartment of the pancreas [4;5;6]. Knockout of cathepsin B reduces activation of serine proteases by 80% and knockout of cathepsin L results in decreased severity of acute pancreatitis5. However, cysteine proteases are constitutively co-localised with serine proteases but the development of pancreatitis is a rare event suggesting that fail safe mechanisms are in place. Micromilieu changes resulting in optimal catalytic conditions of cathepsin B and L depend on radicals, pH and endogenous inhibitors. We aim to determine the role of reactive oxygen species on enzyme activity of cysteine proteases in the secretory compartment and their effect on the earliest disease processes in pancreatitis. It is a well-established fact that necrotic cell death induced by TNF alpha requires ROS. The source of these radicals as well as the subcellular compartment in which they are generated needs to be determined. Radical scavengers such as NAC or more specific inhibitors such as L-Nil or L-Name will be used to specify the nature of ROS. In NADPH knock-out animals as well as in cyclophillin-D knock-out animals we aim to study whether ROS production is a mainly mitochondria dependent process or whether the secretory compartment has its own anti-oxidative defence capacity. In collaboration with B2 (Scholz) we will employ microelectrodes to quantify ROS generation in subcellular compartments. Furthermore, together with C1 (Antelmann) we will work on the ROS-proteome and together with B4 (Lalk/Kahlert) we will investigate metabolomic changes upon supramaximal caerulein stimulation to induce pancreatitis. Furthermore, mechanisms in the exocrine and endocrine pancreas might be driven by a similar pathomechanism. Therefore in close collaboration with A4 (Lenzen & Elsner), we will work on the identification of different ROS and sources of generation in pancreatic acinar cells with respect to pancreatitis. In conclusion, the micromilieu in the secretory compartment of acini determines the enzymatic activity of disease relevant proteases. The effect of ROS generated by TNF  alpha stimulation on enzyme activity of cathepsins is likely to be disease causing and could be influenced therapeutically.

Literature

1 Ruthenbürger, M., Mayerle, J., Lerch, M.M.: Endocrinol. Metab. Clin. North Am. (2006) 35, 313.

2 Mayerle, J.: Gut (2009) 58, 1440.

3 Mayerle,J., Schnekenburger, J., Krüger, B., Kellermann, J., Ruthenbürger, M., Weiss, F.U., Nalli, A., Domschke, W., Lerch, M.M.: Gastroenterology (2005) 129, 1251.

4 Sendler, M., Dummer, A., Weiss, F.U., Krüger, B., Wartmann, T., Scharffetter-Kochanek, K., van Rooijen, N., Malla, S.R., Aghdassi, A., Halangk, W., Lerch, M.M., Mayerle, J.: Gut (2013) 62, 430. 

5 Halangk, W., Lerch, M.M., Brandt-Nedelev, B., Roth, W., Ruthenbuerger, M., Reinheckel, T., Domschke, W., Lippert, H., Peters, C., Deussing, J.: J Clin Invest. (2000) 106, 773.

6 Wartmann, T., Mayerle, J., Kähne,T., Sahin-Tóth, M., Ruthenbürger, M., Matthias, R., Kruse, A., Reinheckel, T., Peters, C., Weiss, F.U., Sendler, M., Lippert, H., Schulz, H.U., Aghdassi, A., Dummer, A., Teller, S., Halangk, W., Lerch, M.M.: Gastroenterology. (2010) 138, 726.