Protective effect of mesalamine against oxidativeinjury in a rat model of radiation rectitis

Radiation rectitis is a major problem associated with high-doseirradiation used for pelvic malignancies.

The aim of this study was to investigate the possible protectiveeffect of mesalamine against irradiation-induced oxidative tissue damage in an experimental model.

THREE GROUPS OF FEMALE SPRAGUE DAWLEY RATS WERE ASSIGNED TO RECEIVE TREATMENT AS FOLLOWS: mesalamine enema (60 mg/mL) BID + irradiation (IR) was given to the mesalamine + IR group, and isotonic saline enema BID + irradiation to the control group. Treatments were given from the day before irradiation until euthanization (72 hours after the irradiation). Sham control rats received isotonic saline enema BID but no irradiation. On the third day of treatment, all animals were euthanized, and reduced glutathione (GSH) level, malondialdehyde (MDA) level, and myeloperoxidase (MPO) activity were measured in the rectal, intestinal, and hepatic tissue of the rats.

The sham group comprised 7 rats; the control and mesalamine + IRgroups, 16 rats each. The median GSH levels of rectal and intestinal specimens were lower in the control group compared with the sham group. The rectal and intestinal MDA levels were higher in the control group compared with the sham group. The rectal and intestinal MPO activities were higher in the control group compared with the sham group. All of these differences were statistically significant (P < 0.001) and indicated oxidative stress. With the topical application of mesalamine, the GSH and MDA levels and MPO activities were similar to those of the sham group.

The pelvic irradiation of rats caused oxidative rectal, intestinal,and hepatic tissue damage, which was ameliorated with the use of mesalamine.