Mitochondrial electron transport chain complex dysfunction in the colonic mucosa in ulcerative colitis

Area of Science:

• Biochemistry
• Gastroenterology
• Cell Biology

Background:

• Ulcerative colitis (UC) is associated with energy deficiency in the colonic epithelium.
• Mitochondrial electron transport chain (ETC) complex activity was examined in UC patients and experimental colitis models.
• This study investigates specific ETC complex alterations in both human UC and mouse models.

Purpose of the Study:

• To evaluate mitochondrial ETC complex activity in normal and diseased colonic mucosa of UC patients.
• To investigate alterations in ETC complexes in experimental colitis induced by dextran sodium sulfate (DSS) in mice.
• To determine the role of nitric oxide in mitochondrial dysfunction in colitis.

Main Methods:

• Biochemical assays of ETC complex activity in colonic biopsies from 43 UC patients and 35 controls.
• Assay of ETC complex activities in colonic epithelial cells from DSS-induced colitis mice.
• Measurement of mucosal nitrite and protein carbonyl levels.

Main Results:

• Complex II activity was significantly decreased in UC patients' colonic biopsies compared to controls.
• Complex II activity was reduced in both normal and diseased mucosa in UC patients.
• DSS-induced colitis in mice showed reduced activity of Complex II and Complex IV, which was attenuated by an iNOS inhibitor.

Conclusions:

• Reduced Complex II activity is a specific finding in ulcerative colitis, observed in both active and quiescent disease.
• Mitochondrial complex dysfunction occurs in DSS-induced colitis in mice.
• Nitric oxide appears to mediate mitochondrial dysfunction in experimental colitis.