CAT and colitis: To investigate the role of HIF-1α in the regulation of the antioxidative response/capacity during DSS-induced colitis and HBO2 treatment, HIF-1α, CAT, GPx1, and SOD1 mRNA expressions were determined using quantitative PCR method. HIF-1α mRNA expression was significantly changed by the HBO2 treatment and the inflammatory microenvironment in the gut mucosa.