Abstract. Acute radiation proctitis is a common complication of pelvic radiation. This study was designed to evaluate the therapeutic effects of topical OzOO on acute radiation proctitis in a rat model. Rats were divided into three groups: control; irradiation+saline (1 mL); and irradiation +OzOO (1 mL). Irradiated rats were euthanised on days 5 and 10 and the mucosal changes evaluated macroscopically and pathologically.

Macroscopic finding scores on the 10th day in the irradiation+saline and irradiation+OzOO groups were different. On pathological examination, radiation-induced mucosal damage was the most prominent 10 days after irradiation in saline-treated rats. On the 10th day, the irradiation+OzOO group showed mild inflammation and slight crypt change, which corresponded to Grade 1 pathological findings.

Introduction. Acute radiation proctitis (ARP) is observed in 50–75% of patients of pelvic radiotherapy, either during treatment or up to 6 weeks after completion of it; suggested therapies of radiation proctitis have not proven to be effective, and their beneficial effects are limited.

The mechanism of action of ozonated oil on wound healing may be connected to its ability to promote the generation of growth factors, activate local antioxidant mechanisms and promote tissue repair, so the topical application of OzOO may produce beneficial effects in the management of ARP.

Results. Only two rats from the IR+OzOO group were apparently healthy on the 5th day, and their clinical finding scores were Grade 0. Grade 2 symptoms were noted in six rats on the 5th day in the IR+saline group, five rats on the 5th day in the IR+OzOO group, and five rats on the 10th day in the IR+OzOO group. On the 10th day, the IR+saline group had a greater frequency of Grade 4 than did the other groups.

Macroscopic changes were maximal in the IR+saline group on the 10th day. The numbers of rats showing Grade 1 and Grade 2 macroscopic findings were similar on the 5th day in the IR+saline and IR+OzOO groups. Treatment with OzOO for 10 days following IR attenuated macroscopic findings in the IR+OzOO group compared with the IR+saline group.

The most significant histopathological changes were observed in the IR+saline group on the 10th day after IR. OzOO attenuated pathological findings of ARP: OzOO treatment for 10 days after IR significantly reduced inflammation and crypt changes, and the difference between the IR+saline and IR+OzOO groups on the 10th day was statistically significant.

Discussion. Radiation therapy results in oxidative stress, and free oxygen radicals have a crucial role in radiation-induced normal tissue toxicity and in inflammation. The increase in antioxidant enzyme levels may prevent damage of IR to normal tissues and reduce the inflammation.

Rectum was examined clinically, macroscopically and pathologically, and the rats that received OzOO tended to show milder rectal damage for all criteria. However, the differences did not reach statistical significance in terms of clinical and macroscopic finding scores. On the 10th day, the IR+saline group had a significantly higher pathological finding score than the IR+OzOO group. The radioprotection observed with ozone is attributed to an increase in the endogenous antioxidative defense enzymes and the inhibition of lipid peroxidation.

We conclude that in the treatment of ARP, OzOO given rectally for 10 days reduced rectal mucosal damage, as shown by macroscopic and histopathological findings in rats.

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