A novel model of megavoltage radiation-induced oral mucositis in hamsters: Role of inflammatory cytokines and nitric oxide

Abstract

Purpose: To design a novel model to study Cobalt-60 (Co-60)-induced radiation mucositis and to describe the pathways involved in its development.

Materials and methods: Hamsters' cheeks were treated with Co-60 radiation (10, 20, 30 or 35 Gy). Three days later, oral mucosa scarification was performed with a needle. The animals were euthanized at day 13 (D + 13) after irradiation. Gross and microscopic alterations were evaluated by a new score system that we developed. Also, neutrophil infiltration, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-10, inducible nitric oxide synthase (iNOS), nitric oxide (NO) and nitrite were assessed in oral mucosa. We also tried to establish the roles of TNF-α and IL-1β and iNOS in our model using pharmacological approaches with pentoxiphylline (PTX) and aminoguanidine (AMG), respectively.

Results: We found that a single administration of 35 Gy of Co-60, followed by mechanical scratches 3 days later, induced oral mucositis in hamsters. Animals with mucositis lost weight and had a survival median of 13 days, the time at which peak inflammation occurs. We noticed increased levels of NO, iNOS, TNF-α and IL-1β and a reduced concentration of IL-10. PTX partially prevented the mucositis phenotype by reducing the levels of inflammatory mediators and iNOS expression. Additionally, AMG, a selective inhibitor of iNOS, reduced Co-60-induced oral mucositis through reducing NO production.

Conclusion: We described a novel model of megavoltage radiation-induced oral mucositis in hamsters. TNF-α, IL-1β and NO seem to play a role in the pathophysiology of this model.

Keywords: Megavoltage radiation; animal model; interleukin-1β; nitric oxide; oral mucositis; tumor necrosis factor-α.