Strong neuroprotection by inhibition of NF-kappaB after neonatal hypoxia-ischemia involves apoptotic mechanisms but is independent of cytokines.
OBJECTIVE
Interactions between excitotoxic, inflammatory, and apoptotic pathways determine outcome in hypoxic-ischemic brain damage. The transcription factor NF-kappaB has been suggested to enhance brain damage via stimulation of cytokine production. There is also evidence that NF-kappaB activity is required for neuronal survival. We used the NF-kappaB inhibitor NBD, coupled to TAT to facilitate cerebral uptake, to determine the neuroprotective capacity of NF-kappaB inhibition in neonatal hypoxia-ischemia (HI) and to identify its contribution to cerebral inflammation and damage.


METHODS
Brain damage was induced in neonatal rats by unilateral carotid artery occlusion and hypoxia and analyzed immunohistochemically; NF-kappaB activity was analyzed by EMSA. We analyzed cytokine mRNA levels and activation of apoptotic pathways by Western blotting. In vitro effects of TAT-NBD were determined in a neuronal cell line.


RESULTS
Inhibition of cerebral NF-kappaB activity by TAT-NBD had a significant neuroprotective effect; brain damage was reduced by more than 80% with a therapeutic window of at least 6 hours. In contrast to earlier suggestions, the protective effect of TAT-NBD did not involve suppression of early cytokine upregulation after HI. Moreover, NF-kappaB inhibition prevented HI-induced upregulation and nuclear as well as mitochondrial accumulation of p53, prevented mitochondrial cytochrome-c release and activation of caspase-3. Finally, TAT-NBD could directly increase neuronal survival because TAT-NBD was sufficient to inhibit death in a neuronal cell line. A nonactive mutant peptide did not have any effect.


CONCLUSIONS
Inhibition of NF-kappaB has strong neuroprotective effects that involve downregulation of apoptotic molecules but are independent of inhibition of cytokine production.
Nijboer
Cora H A
CH
University Medical Center Utrecht, Laboratory of Psychoneuroimmunology, Lundlaan 6, KC 03.068.0, 3584 EA Utrecht, The Netherlands.
Heijnen
Cobi J
CJ
Groenendaal
Floris
F
May
Michael J
MJ
van Bel
Frank
F
Kavelaars
Annemieke
A
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D001921:Brain / Q000378:metabolism / Q000473:pathology; D016207:Cytokines / Q000096:biosynthesis*; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology*; D007249:Inflammation; D007700:Kinetics; D008954:Models, Biological; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D013997:Time Factors
D016207:Cytokines; D016328:NF-kappa B; D018696:Neuroprotective Agents