Selective inhibition of nuclear factor-κB activation after hypoxia/ischemia in neonatal rats is not neuroprotective

Activated nuclear factor-kappa B (NF kappa B) has been shown to increase transcription of several genes that could potentially contribute to neuronal damage, such as proinflammatory cytokines, chemokines, and inducible nitric oxide synthase. The aim of our study was to investigate whether inhibition of NF kappa B activation could prevent hypoxia/ischemia (HI)-induced cerebral damage in neonatal rats. We used a cell permeable peptide (NEMO binding domain [NBD] peptide) that is known to prevent the association of the regulatory protein NEMO with IKK, the kinase that activates NF kappa B. Via this mechanism, the NBD peptide can specifically block the activation of NF kappa B, without inhibiting basal NFKB activity. Cerebral HI was induced in neonatal rats by occlusion of the right carotid artery followed by 90 min of hypoxia (Fi(O2) = 0.08). Immediately upon reoxygenation, as well as 6 and 12 h later, rats were treated with vehicle or NBD peptide (20 mg/kg i.p.). Histologic analysis of brain damage was performed at 6 wk after HI. To assess NF kappa B activation, electromobility shift assays (EMSAs) were performed on brain nuclear extracts obtained 6 h after reoxygenation. Increased NF kappa B activity could be shown at 6 h after HI in both hemispheres. Peripheral administration of NBD peptide prevented this HI-induced increase in NF kappa B activity in both hemispheres. Histologic analysis of Iona-term cerebral damage revealed that inhibition of NF kappa B activation by administration of NBD peptide at 0, 6, and 12 h after HI resulted in an increment of neuronal damage. In conclusion, our data suggest that inhibition of NF kappa B activation using NBD peptide early after HI increases brain damage in neonatal rats.