Leader: Natascha Leleu
Recently, we have shown that NOD1 is an essential intrinsic regulator in polymorphonuclear leukocyte (PMN) migration and phagocytosis. It modulates the expression of adhesion molecules on hepatocytes, and regulates the interaction between PMNs and hepatocytes. In the context of hepatic I/R, it has been demonstrated that Nod1-/- mice are protected from the occurrence of lesions, and the administration of a NOD1 inhibitor in an I/R mice model significantly reduced the necrosis area and the serum level of alanine transaminase (a biomarker of liver health). These results provide proof of concept and suggest that NOD1 antagonists have therapeutic potential in the treatment of I/R injury - a public health problem in these times of graft shortage. In France, a treatment to prevent I/R lesions in the liver would potentially provide 120 additional transplants, which corresponds to 10% of the annual level of activity.
Today, NOD1’s natural ligand binding site has been partially described via a site-directed mutagenesis approach. The ligand is bound by amino acids in the leucine-rich repeat (LRR) domain. We recently built a theoretical 3D model of the LRR domain by homology with a porcine ribonuclease inhibitor. This provides good accuracy because of the ribonuclease inhibitor’s high degree of sequence identity with the NOD1 LRR. We therefore have an atomic model of ligand-NOD1 interactions.
Thanks to a novel molecular modeling method and a rational drug design approach, we have been able to design molecules capable of interacting with amino acids that block NOD1’s pharmacological activity. These strategies have generated a panel of several hundred potential NOD1 antagonists, from which we shall pick out the most promising. To date, about 60 molecules have been synthesized, and some have been tested in cellulo to evaluate their ability to block the NOD1 signaling pathway NF-κB. The preliminary results are very promising, and have identified the first structure-activity relationships. This ambitious project is based on solid preliminary data, and is now mature enough for the development of new medicinal tools in the prevention of I/R lesions. The novelty of our work is based on the compounds’ dual action (i.e. effects on both hepatocytes and PMNs).