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Background and Aims. Transglutaminases are tissue enzymes involved in different neuronal processes including maintenance and signalling. However, their up-regulation elicited by a variety of noxae contributes to neurodegeneration. This study tested the hypothesis that experimental inflammation evoked transglutaminase up-regulation in myenteric neurons and that this event had an impact on neuronal survival. Methods. Rats with or without trinitro-benzene-sulphonic acid-induced colitis were used. One week after colitis induction, longitudinal muscle-myenteric plexus preparations were obtained from left colon to assess tissue-transglutaminase activity, protein and mRNA expression. Double labelling immunofluorescence using antibodies to neuron-specific enolase and transglutaminase was performed to identify myenteric neurons expressing transglutatninase. Additional sets of experiments evaluated the involvement of transglutaminase in the apoptotic process of cultured myenteric neurons. Results. Compared to controls, rats with colitis showed several tranglutaminase/neuron-specific enolase positive myenteric neurons. Western blot analysis and RT-PCR confirmed that in rats with colitis, the increased neuronal transglutaminase-immunoreactivity was associated with an increased enzyme expression. Similarly, transglutaminase activity was significantly higher than in controls (1100 +/- 280 mU/g vs. 725 +/- 119 mU/g, p

Background and aims: Ulcerative colitis (UC) is characterised by refractory inflammatory ulceration and damage to the colon. The mechanisms underlying impaired healing have yet to be defined. As transglutaminase expression resulting in matrix protein cross linking is associated with increased wound healing in a rat model of colitis, we hypothesised that different types of transglutaminase might also play a role in UC. Patients and methods: Endoscopic and histological indices were studied in 26 patients with UC (10 active and 16 inactive) and in 20 normal controls undergoing colonoscopy. Transglutaminase activity was evaluated in plasma (factor XIIIa) by a radioenzymatic method. Factor XIIIa, tissue and keratinocyte transglutaminase protein content, and mRNA expression in the colon were evaluated by western blot analysis and semiquantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Colonic location of transglutaminases and their reaction products, the e-(γ-glutamyl)lysine bonds, was evaluated by immunohistochemistry using specific monoclonal antibodies. Results: Transglutaminase activity was significantly lower in the plasma of patients with active UC (4.2 (2.4) mU/ml; p v controls) than in those with inactive UC and controls (10.6 (2.2) and 12.1 (1.7) mU/ml). As shown by western blot, protein levels of tissue transglutaminase and factor XIIIa were unchanged in active UC compared with inactive disease and controls, while the keratinocyte form was reduced in active UC. Tissue transglutaminase and factor XIIIa immunostaining was strongly present in damaged areas colocalising with isopeptide bonds. In contrast, the keratinocyte form was almost absent in active UC and localised in the upper part of the crypts in normal subjects. RT-PCR showed upregulation of tissue transglutaminase mRNA in active UC (320% compared with controls) while keratinocyte transglutaminase gene expression was downregulated in active UC. Conclusions: The results of the present study support the concept that, in the damaged colon, transglutaminases are needed in response to chronic injury and underline the key role of these enzymes in mucosal healing.

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

During inflammatory colitis in man and experimental animals, the production of free radicals increases. This study evaluated the histological pattern and biochemical parameters of oxidative damage during acute and chronic colitis induced by 2,4,-trinitrobenzenesulfonic acid + ethanol in rats. On the samples of scraped mucosa of six groups of rats, one not treated, one killed after 1 hr, and those killed one, two, four, and eight weeks after the induced-damage, we determined the histological and superoxide dismutase activity and the concentration of lipoperoxides, malonyldialdheyde, and reduced glutathione. After 1 hr, the mucosal damage and superoxide dismutase activity were slight; glutathione, lipoperoxides, and malonyldialdheyde were significantly increased. At one week, the histological damage was severe, decreasing progressively, and significantly correlated to superoxide dismutase activity. Lipoperoxides and malonyldialdheyde were high throughout the study. Glutathione was significantly increased at one and two weeks and dramatically decreased thereafter. Therefore, in experimental colitis the cascade of free-radical production induces a constant self-maintaining lipoperoxidation and consumes the cellular antioxidant capability.