Transglutaminase expression in myenteric plexus of rat with TNBS-induced colitis.

Background: Transglutaminases (TGs) are ubiquitous enzymes whose increased or defective activity contributes to many pathological processes. In the central nervous system (CNS), TGs may be involved in neuronal signalling and maintenance of neuronal structure and function and, recently, evidence has emerged about its role in neurodegenerative dLqeases. In enteric nervous system (ENS) a wide range of neuronal alterations have been repotted during bowel inflammation, but the role of TGs has never been investigated. Aim of our study was to investigate tissue TG (tTG) expression and activity in myenteric plexus in an experimental model of colitis. Methods: Ten male Wistar rats were studied (5 controls and 5 with TNBS-induced colitis). One week after saline or ethanol/TNBS administration, longitudinal muscle-myemeric plexus preparations (LMMP) were prepared from left colon and fresh tissue was used to assess tTG activity and protein levels by radioenzymatic method and western blot analysis respectively. A double labelling immunofluorescence of LMMP was also performed to stain myenteric neurons for neuronal specific enolase (NSE) and tTG. Results: One week after TNBS-induced colitis, a mild to moderate inflammation was observed at mucosal/submucosal levels. In LMMP of TNBS treated rats, a higher number of NSE/tTG positive neurons were counted compared to controls (3.5-+ 0.3 vs 1.2 _+ 0.2 neurons per ganglion, p<0 0l). Western blot analysis confirmed that in TNBS-rats the increased neuronal tTG-immunoreactivity was associated with an increased protein expression. Similarly, TGase activity in LMMP of rats with colitis was significantly higher than in controls (1434+ 112 vs. 918_+8 mU/g, p=0.05). Conclusions: we showed for the first time that myenteric neurons express tTG, and that tTG expression and activity are both increased during bowel inflammation. Our findings strongly suggest that TGs may play a role in the damage or repairing mechanisms occurring in myenteric neurons during bowel inflammation.