The Antibiotic Erythromycin Induces Tolerance against Transient Global Cerebral Ischemia in Rats (Pharmacologic Preconditioning)

BACKGROUND: Cerebral ischemic tolerance can be induced by a variety of noxious stimuli, but no clinically applicable regimen for preconditioning has been described. Therefore, the authors tested the ability of a pharmacologic preconditioning strategy using the well-known macrolide antibiotic erythromycin to induce tolerance against transient global cerebral ischemia in vivo. They also investigated whether tolerance induction by erythromycin involves transcriptional and translational changes of cerebral B-cell leukemia/lymphoma-2 (bcl-2) expression. METHODS: Male Wistar rats were treated with erythromycin (25 mg/kg intramuscularly) or vehicle and subjected to 15 min of transient global cerebral ischemia 6, 12, or 24 h after pretreatment. Neurologic deficit was evaluated once daily, and neuronal cell survival was assessed after 7 days of reperfusion. Additional animals were similarly pretreated, and cerebral bcl-2 messenger RNA (mRNA) and protein expression was analyzed 6 and 24 h later. RESULTS: Erythromycin improved postischemic neuronal survival in hippocampal CA1 and CA3 sectors and reduced functional deficit, with 12 h being the most efficient pretreatment interval. Bcl-2 mRNA in hippocampus was transiently up-regulated 6 h after erythromycin, but neuronal Bcl-2 protein remained unchanged. CONCLUSIONS: Erythromycin can induce cerebral ischemic tolerance in vivo (pharmacologic preconditioning), suggesting a potential clinical strategy of preemptive neuroprotection. Changes in bcl-2 expression after erythromycin were small and transient. The induction of bcl-2-related pathways, although important for other preconditioning regimens, may therefore be less relevant for the neuroprotective effects of pharmacologic preconditioning using erythromycin.