engleski

Effects of hyperbaric oxygenation on HIF1alpha gene expression in DSS induced colitis in BALB/c mice

INTRODUCTION: Several studies showed that hyperbaric oxygenation (HBO2) can reduce inflammation in the gut mucosa ; however, mechanisms of its actions are not completely elucidated. Based on wound healing experiments, it has been proposed that HBO2 regulates anitioxidative machinery through hypoxia inducible factor alpha (HIF1α)1, 2.The aim of this study was to examine the effects of HBO2 on the gene expression of HIF1α, superoxide dismutase (SOD3) and glutathione peroxidase (GPx2) in dextran sodium sulphate (DSS) induced colitis in BALB/c mice. METHODS: BALB/c mice at the age of 10-12 weeks were randomized into 4 groups (n=9 mice/group): control mice, control mice undergoing HBO2, mice receiving DSS and DSS treated mice undergoing HBO2. Mice were given 5% w/v of DSS (MP Bomedicals, France) in drinking water ad libidum for 7 consecutive days. HBO2 was initiated at day 1 and was administered until the end of experiment, two sessions per day of 100% O2 for 60 minutes at 2.3 bars with additionally 15 minutes for gradual compression and decompression. Disease activity (DAI) was assessed by daily recording of animal body weight, stool consistency and the presence of occult or gross blood per rectum. On day 8, following last HBO2 session, mice were killed by cervical dislocation and distal colon was collected for mRNA expression analysis. Gene expression data were analyzed by REST 2009 software (Qiagen). Results are presented as mean ±S.E.M. The study was approved by the local Ethical Committee. RESULTS: Mice treated with DSS exhibited severe symptoms of colitis, including diarrhea and gross rectal bleeding starting from day 6 whereas DSS treated mice that underwent HBO2 presented with occult bleeding at day 5 and only a loose stool starting at day 7. HIF1α gene expression was significantly higher (2.2 fold) in DSS group of mice compared to both control and control-HBO2 groups (p=0.01). HIF1α gene expression is lower in DSS+HBO2 group compared to DSS group but the difference is not statistically significant. GPx2 was significantly down regulated in DSS and DSS- HBO2 treated mice compared to both control groups (p=0.0001), irrespectively of HBO2 treatment. There were no differences in the SOD3 expression among the groups. CONCLUSION: Consistent to previous reports, HBO2 significantly reduced symptoms of disease and severity of colitis. Inflammation induced by DSS resulted in increased expression of HIF1α and reduced expression of GPx2. HBO2 slightly reduced HIF1α expression. Our data suggest that inflammatory processes per se is capable of up- regulating HIF1α gene, and the mechanisms underlying beneficial effects of HBO2 on the colitis are not indispensably depended on HIF1α and antioxidative genes SOD3 and GPx2.

Hyperbaric oxygenation; DSS; HIF1alpha; gene expression

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