Glutamine enema regulates colonic ubiquitinated proteins but not proteasome activities during TNBS‐induced colitis leading to increased mitochondrial activity

Abstract

Ubiquitin proteasome system contributes to the regulation of intestinal inflammatory response as its inhibition is associated with tissue damage improvement. We aimed to evaluate whether glutamine is able to limit inflammation by targeting ubiquitin proteasome system in experimental colitis. Colitis was induced in male rats by intrarectal instillation of 2-4-6-trinitrobenzen sulfonic acid (TNBS) at day 1. From day 2 to day 6, rats daily received either an intrarectal instillation of PBS (TNBS/PBS group) or glutamine (TNBS/Gln). Rats were euthanized at day 7 and colonic samples were taken to evaluate ubiqutinated proteins by proteomic approach combining 2D electrophoresis and immunoblots directed against ubiquitin. Results were then confirmed by evaluating total expression of proteins and mRNA levels. Survival rate, TNFα, and IL-1β mRNA were improved in TNBS/Gln compared with TNBS/PBS (p < 0.05). Proteasome activities were affected by TNBS but not by glutamine. We identified eight proteins that were less ubiquitinated in TNBS/PBS compared with controls with no effect of glutamine. Four proteins were more ubiquitinated in TNBS/PBS group and restored in TNBS/Gln group. Finally, 12 ubiquitinated proteins were only affected by glutamine. Among proteins affected by glutamine, eight proteins (GFPT1, Gapdh, Pkm2, LDH, Bcat2, ATP5a1, Vdac1, and Vdac2) were involved in metabolic pathways. In conclusion, glutamine may regulate ubiquitination process during intestinal inflammation.

Pyruvate Kinase M2: A Potential Target for Regulating Inflammation

“…Moreover, elevated levels of PKM2 were found in stool samples from patients with active Crohn’s disease, suggesting that this protein can be a useful non-invasive marker for inflammatory bowel disease ( 63 , 64 ). In accordance with this, expression of PKM2 was progressively increased in intestinal tissue of mice undergoing TNBS-induced colitis ( 62 , 65 ). Finally, proteomic analysis revealed that PKM2 was one of the 33 over-expressed proteins found in synovial tissue from patients with rheumatoid arthritis ( 66 ).…”

SPECT-computed tomography in rats with TNBS-induced colitis: A first step toward functional imaging

“…Similarly to previous studies[13-15,17-20], we observed colon inflammation demonstrated by stiffened colon, histological inflammatory score or increased inflammatory markers. We also noted SPECT signs of inflammation such as an increased maximal thickness of colon.…”

Glutamine Restores Tight Junction Protein Claudin‐1 Expression in Colonic Mucosa of Patients With Diarrhea‐Predominant Irritable Bowel Syndrome

“…By using a rectal route or targeted delivery of glutamine, high concentrations of glutamine can be easily achieved in the colonic lumen. Even if luminal amino acids are not considered to be able to enter the colonocytes, 25 , 26 previous data reported reduced colonic inflammatory response after a rectal supply of glutamine in both animals 27 , 28 and humans 29 . More interestingly, we observed that the effects of glutamine depended on the basal expression of claudin‐1, suggesting that the lower the basal claudin‐1 expression, the greater the glutamine effects.…”