Protection from diclofenac-induced small intestinal injury by the JNK

39 40 Small intestinal ulceration, bleeding, and inflammation are major adverse effects 41 associated with the use of diclofenac (DCF) or other nonsteroidal anti-inflammatory 42 drugs (NSAIDs). The underlying mechanisms of DCF enteropathy are poorly understood, 43 but there is increasing evidence that topical effects are involved. The aim of this study 44 was to explore the role of c-Jun-N-terminal kinase (JNK) in DCF-induced enterocyte 45 death because JNK not only regulates mitochondria-mediated apoptosis but also is a key 46 node where many of the proximal stress signals converge. Male C57BL/6 mice were 47 injected intraperitoneally with DCF or vehicle (solutol HS-15), and the extent of small 48 intestinal ulceration was determined. A single dose of DCF (60 mg/kg) produced 49 numerous ulcers in the third and fourth quartiles of the jejunum/ileum, with maximal 50 effects after 18 h and extensive recovery after 48 h. To study the molecular pathways 51 leading to enterocyte injury, we isolated villi-enriched mucosal fractions from DCF52 treated mice. Immunoblot studies with a phosphospecific JNK antibody revealed that 53 JNK1/2 (p46) was activated at 6 h, leading to phosphorylation of the downstream target 54 c-Jun. The levels of the JNK-regulated proapoptotic transcription factor CHOP were also 55 increased after DCF. The selective JNK inhibitor, SP600125 (30 mg/kg, ip), given both 1 56 h before and 1 h after DCF, blocked JNK kinase activity and afforded significant 57 protection against DCF enteropathy. In conclusion, these data demonstrate that the JNK 58 pathway is critically involved in the pathogenesis of DCF-induced enteropathy and 59 suggest a potential application of JNK inhibitors in the prevention of NSAID-induced 60 enteropathy. 61 62 63 64