Pharmacological Induction of Heme Oxygenase-1 by a Triterpenoid Protects Neurons Against Ischemic Injury

• DOI: 10.1161/strokeaha.111.647420
• Publication Date: 2012-03-30T04:43:00Z
• Authors: Feng Zhang; Suping Wang; Meijuan Zhang; Zhongfang Weng; Peiying Li; Yu Gan; Lili Zhang; Guodong Cao; Yanqin Gao; Rehana K. Leak; Michael B. Sporn; Jun Chen
• Keywords: Brain Infarction; Neurons; 0303 health sciences; NF-E2-Related Factor 2; Imidazoles; Protoporphyrins; Protective Agents; Hippocampus; Triterpenes; Brain Ischemia; Rats; Up-Regulation; 3. Good health; Mice; 03 medical and health sciences; Infusions, Intraventricular; Models, Animal; Animals; Oleanolic Acid; Hypoxia; Cells, Cultured; Heme Oxygenase-1; Injections, Intraperitoneal

Background and Purpose— Heme oxygenase-1 (HO-1) is an inducible Phase 2 enzyme that degrades toxic heme; its role in cerebral ischemia is not fully understood. We hypothesize that chemically induced HO-1 upregulation with the novel triterpenoid CDDO-Im (2-cyano-3,12 dioxooleana-1,9 dien-28-oyl imidazoline), a robust inducer of Phase 2 genes, protects neurons against ischemic injury.

Methods— Using 3 different models of ischemia, including oxygen–glucose deprivation in neuronal cultures, global ischemia in rats, and focal ischemia in mice, we determined (1) whether CDDO-Im induces HO-1 expression and protects against ischemic injury; and (2) whether HO-1 inhibition disrupts the neuroprotective effect of CDDO-Im.

Results— CDDO-Im treatment (50–300 nmol/L) resulted in 8-fold HO-1 upregulation in cultured neurons and protected against oxygen–glucose deprivation. The protection was abolished when the cultures were transfected with nuclear factor (erythroid-derived 2) like-2–shRNA or coincubated with tin protoporphyrin IX, a specific HO-1 inhibitor. In the rat model of global ischemia, intracerebroventricular infusion of CDDO-Im (0.5–1.5 μg) augmented HO-1 expression in hippocampal neurons and resulted in significant increases in CA1 neuronal survival after global ischemia. To further strengthen the clinical relevance of the CDDO-Im treatment, we tested its effects in the mouse model of temporary focal ischemia (60 minutes). Postischemic intraperitoneal injection of CDDO-Im (10–100 μg) enhanced HO-1 expression and significantly reduced neurological dysfunction and infarct volume. Intracerebroventricular infusion of tin protoporphyrin IX reduced the neuroprotective effect of CDDO-Im against global and focal ischemia.

Conclusions— CDDO-Im confers neuroprotection against ischemic injury by upregulating HO-1, suggesting that enhance of HO-1 expression may be a legitimate strategy for therapeutic intervention of stroke.