The small bowel is an important dose-limiting organ in abdominal radiotherapy because irradiation can cause acute enteritis that, in turn, leads to progressively reduced motility and finally, in a later phase, to fibrosis. Because these clinical symptoms may be caused by the early stage of an inflammatory process, we characterized the radiation-induced intestinal inflammation in rats. Abdominal γ-irradiation (10-Gy) induced a cascade of inflammatory events characterized by an early (6 h after exposure) increase in IL-1β, TNF-α, and IL-6 mRNA levels in the rat ileal muscularis layer. IL-8 [a cytokine-induced neutrophil chemoattractant (CINC)] mRNA appeared later (at 3 days). The expression of TGF-β (a profibrotic cytokine) was higher in irradiated than control tissue at day 1, whereas IL-10 (an anti-inflammatory cytokine) expression vanished completely. Despite strong IL-1ra expression, the IL-1ra/IL-1β ratio, which is an indicator of inflammatory balance, was -41% at day 1 in irradiated compared with control tissue. The nuclear transcription factors NF-κB and activator protein-1 (AP-1) govern transcription of these genes, directly or indirectly. Although expression of the subunits of NF-κB (p65, p50) and AP-1 (c- fos, c- jun) did not increase, irradiation caused a rapid and persistent translocation of p65 and p50. An imbalance between proinflammatory and anti-inflammatory mediators may contribute to perpetuating intestinal inflammation, thus making it chronic.
Effects of hypothermia on inflammatory cytokine expression in rat liver following asphyxial cardiac arrest
