Effect of 5-ASA on DSS-induced colitis in Nat1/2 WT and KO mice. DSS colitis was induced by adding 3.5% DSS to drinking water for 5 days followed by regular drinking water for two days. During this 7 day DSS and regular water treatment, mice were gavaged daily with vehicle (Veh) or 75 mg/kg/day 5-ASA (ASA). Control (Con) mice did not receive DSS or any treatment. (A) Whole colon lengths of excised mouse colon at day 7. Values are mean ± SEM, **P < 0.01, ***P < 0.001 vs. corresponding control, #P < 0.05 Nat1/2 KO Veh vs. Nat1/2 KO ASA. (B) Percent baseline weight changes at day zero (all mice at 100 %) and day 7. **P < 0.01, ***P < 0.001 vs. corresponding control. (C) MPO activity of distal colon in response to DSS. Values are mean ± SEM. *P < 0.05, **P < 0.01 vs. corresponding control; #P < 0.05 Nat1/2 KO Veh vs. Nat1/2 KO ASA. (D) NAT enzyme activity of distal colon. Values are mean ± SEM. ***P < 0.001 vs. control. (E) Correlation of NAT versus MPO enzyme activity of WT control (○) with no DSS, and vehicle treated (), or ASA treated (◆) during DSS. Each point represents one mouse. Linear regression with 95 % confidence levels (dotted line).