Effects of Exposure to Mild Hyperbaric Oxygen on DSS-Induced Colonic Inflammation and Diarrhea in Rats

Abstract

Purpose: In rodents, dextran sulfate sodium (DSS)-induced diarrhea and colonic inflammation have similar symptoms to those of ulcerative colitis in humans. We examined the effects of exposure to mild hyperbaric oxygen (MHO) at an atmospheric pressure of 1317 hPa with 40% oxygen on DSS-induced diarrhea and colonic inflammation in rats.

Methods: Five-week-old male Kyoto Apc Delta (KAD) rats (n = 12) were administered 2% DSS through drinking water for 1 week. Subsequently, DSS-treated male rats were not subjected to any further treatment (n = 6) or exposed to MHO (n = 6) for 2 weeks. Age-matched KAD rats not subjected to DSS treatment or exposed to MHO were used as the control group (n = 6).

Results: Control rats did not exhibit diarrhea and colonic inflammation. However, DSS-treated rats exhibited diarrhea and colonic inflammation, regardless of exposure to MHO. Exposure to MHO for 2 weeks led to decreased incidence of diarrhea in DSS-treated rats (p < 0.05). Exposure to MHO had no effect on colonic inflammation in DSS-treated rats (p = 0.12).

Conclusion: Exposure to MHO for 2 weeks can improve diarrhea but cannot attenuate colonic inflammation, possibly due to the short exposure duration (2 weeks) used in this study.

Keywords: Kyoto Apc Delta rats; colonic inflammation; dextran sulfate sodium; mild hyperbaric oxygen; oxidative metabolism.

Figure 1

Body weights of KAD rats in the CON, DSS, and DSS + MHO groups from 5 to 8 weeks of age. Values are expressed as mean ± standard deviation (n = 6). ^ap < 0.05 compared with the age-matched CON group. Abbreviations: CON, control; DSS, dextran sulfate sodium; MHO, mild hyperbaric oxygen.

Figure 2

Incidences of diarrhea in DSS-induced KAD rats in the DSS and DSS + MHO groups from 6 to 8 weeks of age. Values are expressed as mean ± standard deviation (n = 6). ^bp < 0.05 compared with the age-matched DSS group. Abbreviations: DSS, dextran sulfate sodium; MHO, mild hyperbaric oxygen.

Figure 3

Macroscopic view of the distal colon in KAD rats in the CON (A), DSS (B), and DSS + MHO (C) groups at 8 weeks of age. The distal colon was cut longitudinally along the main axis. Scale bar indicates 1 cm. Abbreviations: CON, control; DSS, dextran sulfate sodium; MHO, mild hyperbaric oxygen.

Figure 4

(A) Histology of the distal colon in KAD rats of the CON (a), DSS (b), and DSS + MHO (c) groups at 8 weeks of age. Hematoxylin-eosin staining was used. Scale bar on c indicates 100 μm. (B) Colonic inflammation scores in the DSS and DSS + MHO groups at 8 weeks of age. Values are expressed as mean ± standard deviation (n = 6). Abbreviations: CON, control; DSS, dextran sulfate sodium; MHO, mild hyperbaric oxygen.

Figure 5

mRNA levels of Il10 (A), Il1β (B), Tnfα (C), and Wif1 (D) in the colonic mucosa of the distal colon in KAD rats in the CON, DSS, and DSS + MHO groups at 8 weeks of age. Values are expressed as mean ± standard deviation (n = 6). Abbreviations: CON, control; DSS, dextran sulfate sodium; MHO, mild hyperbaric oxygen.