Increase of interleukin-1 beta mRNA and protein in the spinal cord following experimental traumatic injury in the rat

Interleukin-1 beta (IL-1 beta) is a major mediator of inflammation and a growth promoter for many cell types that could play an important role in the consequences of traumatic spinal cord injury (SCI). In the present study, the expression of IL-1 beta and its mRNA was determined in the rat spinal cord following a standardized contusion injury. IL-1 beta mRNA, measured with quantitative RT-PCR, was significantly increased in the lesion site by 1 h after SCI (35.2 +/- 5.9 vs. 9.1 +/- 2.1 pg/mg RNA, n = 3, P < 0.05) and remained significantly higher than in the normal spinal cord for at least 72 h post-injury (p.i.). IL-1 beta mRNA levels in tissue immediately caudal to the lesion site did not change after the injury. IL-1 beta protein levels, measured by an ELISA, were determined at the lesion site and in cerebrospinal fluid (CSF) and serum samples. IL-1 beta levels in the CSF and serum were much lower than in the spinal cord. At the lesion site, IL-1 beta was increased significantly by 1 h p.i., peaked at 8 h (32.3 +/- 0.1 vs. 7.6 +/- 1.9, ng/g tissue, n = 5, P < 0.05) and remained significantly higher than normal through at least 7 days p.i. These results suggest that the increased IL-1 beta mRNA and protein levels are an early and local response at the lesion site that could trigger other, later, responses to traumatic SCI.