Tumor necrosis factor-α (TNF-α) expression has been documented extensively in animal models of traumatic spinal cord injury (SCI). However, the pathophysiological significance of TNF-α expression in the injured cord remains to be delineated. The TNF receptor (TNFR)-nuclear factor-κB (NF-κB) signal transduction pathway is important for maintaining cell viability. NF-κB exerts anti-apoptotic effects via an endogenous caspase inhibitory system mediated by cellular inhibitor of apoptosis protein 2 (c-IAP2). NF-κB transactivates c-IAP2 to inhibit caspase-3 activation. Progressive cell death, including morphological and biochemical features suggestive of apoptosis, has been noted after SCI. We explored the effects of TNFR1 or TNFR2 deletion on the apoptotic events downstream of NF-κB in relation to SCI pathology and functional recovery. Nuclear proteins from the injured cords of the TNFR1-/- mice had a reduced NF-κB binding activity compared with the wild-type controls. This decrease in NF-κB activation was accompanied by a reduction in c-IAP2 expression and an increase in the active form of caspase-3 protein. After SCI the TNFR1-/- mice had greater numbers of apoptotic cells, a larger lesion size, and worse functional recovery than wild-type mice. TNFR2-deficient mice had a similar, although not as pronounced, consequence as the TNFR1-/- mice. These findings support the argument that the TNFR-NF-κB pathway is beneficial for limiting apoptotic cell death after SCI and that a defective TNFR-NF-κB pathway results in a poorer neurological outcome. A worse functional outcome in TNFR-/- mice suggests that an endogenous apoptosis inhibitory mechanism mediated by TNFR activation, NF-κB, and c-IAP2 may be of pathophysiological importance.
|Number of pages||9|
|Journal||Journal of Neuroscience|
|State||Published - Sep 1 2001|
- Tumor necrosis factor