P069 Design and delivery of anti-oxidant inorganic complexes mimicking the superoxide dismutase for inflammatory bowel diseases treatment

Abstract

Abstract Background Oxidative stress (OS), defined by an increased flux of reactive oxygen species (ROS), plays an important role in the pathogenesis, the perpetuation and the amplification of inflammatory bowel diseases. In normal state, enzymatic defenses regulate the concentration of ROS but in IBD, some of them, including the superoxide dismutase (SOD), are weakened. The use of molecules mimicking the SOD activity may compensate for this deficiency and reduce the OS. 4 molecules were characterized for their SOD activity, their stability and their inertness. Their anti-inflammatory activity were assessed in a cellular model of epithelial inflammation and in a murine model of colitis and correlated to their physico-chemical properties. Methods The studied SOD mimics display similar structures differing by the presence of a propyl and a cyclohexyle group aiming to improve their kinetic inertness. To generate an inflammation associated to ROS production, intestinal epithelial (HT29) cells were stably transfected to over-express MD2, a co-receptor for LPS binding to TLR-4 receptor. The cells were stimulated by LPS (0.1µg/mL) and incubated with the SOD mimics (6 hours, 0,1-100µM). The secretion of IL-8 was measured by ELISA and the MnSOD expression by Western Blot. The SOD mimics were administrated to a murine model of colitis chemically-induced by DNBS. To protect them from the gastric acidity, the mimics were encapsulated in delivery vector. The monitoring of weight and the determination of intestinal permeability and macroscopic scores were performed. Results The mimics containing a cyclohexyle group display kinetic rates for metal exchanges that are up to 30-fold lower meaning that they are more inert. At 100µM, the four SOD mimics induced a significative decrease in IL-8 secretion (<35%/positive control (PT), p<0,02) and in MnSOD expression (<20%/PT, p<0,033). At 10µM, only the mimics containing the cyclohexyle group are still able to significatively counteract the LPS-induced secretion in IL-8 (<30/PT, p<0,001) and over-expression of MnSOD (20%/PT, p<0,02). Their bioactivity at lower doses can be correlated to their higher inertness. Concerning in vivo activity, preliminary assays show a faster recovery of the mice, that have received the SOD mimics with the cyclohexyle group. 3 days following DNBS injection, the mice of this group recovered in average 89% of their starting weight while the control mice recovered only 83%. Conclusion The SOD mimics display anti-inflammatory and antioxidant activity on HT29-MD2 cells, which is dependent on their inertness. Assays on a murine model of colitis seems to follow the same trend. The use of antioxidant treatments based on SOD mimics may reduce the inflammation rising from oxidative stress in IBD.