The Role of Interleukin-6 and Tumor Necrosis Factor in an Acute Model of Pelvic Radiation Therapy

Abstract

Cytokines such as tumor necrosis factor alpha (TNFα) and Interleukin-6 (IL-6) play a role in modulating the immune response. The purpose of this study was to document the role of tumor necrosis factor and Interleukin-6 in a model of localized pelvic radiation. Previous studies utilizing this model have shown a reproducible radiation injury to the terminal ileum and distal colon. Female Sprague-Dawley rats (200-250 grams) were anesthetized and received 900 rads of radiation once a week for five weeks for a total of 4500 rads. Control animals received anesthesia only. Both groups had blood drawn from a tail artery prior to radiation and one-half hour, one, two, and four hours post radiation therapy. TNFa was determined by cellular bioassay using the WEHI 160 cell line. IL-6 was determined using a similar method for utilizing the 7TDI biocellular assay. TNFα peaked at one-half to one hour post radiation at each week for both control and treatment groups. Peak values within the treatment group increased with each week and peaked at the fourth week of radiation therapy. These peak values were significantly greater than the controls at weeks three and five. Interleukin-6 values did not show a consistent pattern with no difference between control and treatment groups. In conclusion, we have shown that the tumor necrosis factor is increased with pelvic radiation when compared to controls. These values increase sequentially during a five week course of radiation. Interleukin-6 values do not show a consistent pattern.