The protective effect of ceramide in immature rat brain hypoxia-ischemia involves up-regulation of Bcl-2 and reduction of TUNEL-positive cells

Preconditioning brain with tumor necrosis factor alpha (TNF-alpha) can indu ce tolerance to experimental hypoxia and stroke and ceramide is a downstrea m messenger in the TNF-alpha signaling pathway. A hypoxic-ischemic (HI) ins ult in the immature rat injures brain primarily through apoptosis. Apoptosi s is regulated by Bcl-2 family proteins. The authors explored whether ceram ide protects against HI in the immature rat, and whether Bcl-2 family prote in expression is involved. Hypoxia-ischemia was produced in seven-day-old r ats by ligating the right carotid artery, followed by 2 hours of 8% oxygen exposure. Thirty minutes after HI, C-2-ceramide (150 mug/kg) was injected i ntraventricularly. Infarct volume was measured 5 days later. C-2-ceramide r educed HI-induced brain damage by 45% to 65% compared with HI/dimethyl sulf oxide (DMSO) (vehicle control) or HI only groups. In separate experiments, brains of sham-operated control and HI only animals and animals subjected t o HI plus C-2-ceramide or DMSO infusion were sampled 6 hours, 24 hours, and 5 days after treatments and analyzed for Bcl-2, Bcl-xl, and Bax expression (Western blotting), and apoptosis (TUNEL assay). Augmented Bcl-2 and Bcl-x l levels in the C-2-ceramide treated group were associated with a significa nt decrease in TUNEL-positive cells. The results support a protective role for ceramide in neonatal.