Upregulation of type I interleukin-1 receptor after traumatic spinal cord injury in adult rats

Post-traumatic inflammation response has been implicated in secondary injury mechanisms after spinal cord injury (SCI). Interleukin-1 (IL-1) is a key inflammatory mediator that is increasingly expressed after SCI. The action of IL-1 is mediated through its functional receptor, type I interleukin-1 receptor (IL-1RI). However, whether this receptor is expressed after SCI remains to be elucidated. In the present study, the temporospatial expression of IL-1RI was detected in rats that received a moderate contusive SCI (a 10 g rod dropped at a height of 12.5 mm) at the ninth to tenth thoracic vertebral level using a widely used New York University impact device. Our study demonstrated that IL-1RI was slightly increased at 4 h post-injury compared to the normal or sham-operated controls, reached the peak at 8 h at mRNA level (4.44-fold, P < 0.01) and 1 d at protein level (2.62-fold, P < 0.01). IL-1RI remained at its elevated levels for a relatively long duration (4 h-7 days). Spatially, IL-1RI was observed throughout the entire length of a 10 mm-long cord segment containing the injury epicenter. Colocalization of IL-1RI was found in neurons, oligodendrocytes, astrocytes, and activated microglia. Our results suggest that the elevated expression of IL-1RI after SCI may contribute to posttraumatic inflammation responses of IL-1.