Effect of targeted deletion of the heme oxygenase-2 gene on hemoglobin toxicity in the striatum.
The heme oxygenase (HO) enzymes catalyze the rate-limiting step in the breakdown of heme to iron, carbon monoxide, and biliverdin. A prior cell culture study demonstrated that deletion of HO-2, the isoform constitutively expressed in neurons, attenuated hemoglobin (Hb) neurotoxicity. The present study tested the hypothesis that HO-2 gene deletion is cytoprotective in a model of Hb toxicity in vivo. Stereotactic injection of 6 microL stroma-free Hb (SFHb) into the striatum significantly increased protein oxidation in wild-type mice at 24 to 72 h, as detected by an assay for carbonyl groups. At 72 h, carbonylation was increased 2.5-fold compared with that in the contralateral striatum. In HO-2 knockout mice, protein oxidation was not increased at 24 h, and was increased by only 1.7-fold at 72 h. Similarly, striatal lipid peroxidation, as detected by the malondialdehyde assay, was significantly greater in the SFHb-injected striata of wild-type mice than in knockout mice. Striatal cell viability, determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, was 45.0%+/-6.3% of that in contralateral striata in wild-type mice at 72 h; it was increased to 85%+/-8% in knockouts. Heme oxygenase-2 gene deletion did not alter weight loss or mortality after SFHb injection. Baseline striatal HO-1 expression was similar in knockout and wild-type mice; induction after SFHb injection occurred more rapidly in the latter. These results suggest that HO-2 gene deletion protects striatal cells from the oxidative toxicity of Hb in vivo. Pharmacologic or genetic strategies that target HO-2 may be beneficial after central nervous system hemorrhage, and warrant further investigation.
Qu
Yan
Y
Department of Emergency Medicine, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Chen
Jing
J
Benvenisti-Zarom
Luna
L
Ma
Xin
X
Regan
Raymond F
RF
D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D002543:Cerebral Hemorrhage / Q000201:enzymology / Q000473:pathology / Q000628:therapy; D003342:Corpus Striatum / Q000201:enzymology* / Q000473:pathology; D017353:Gene Deletion; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006419:Heme Oxygenase (Decyclizing) / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism / Q000633:toxicity*; D015227:Lipid Peroxidation / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D010084:Oxidation-Reduction / Q000187:drug effects
D006454:Hemoglobins; D006419:Heme Oxygenase (Decyclizing); C105245:heme oxygenase-2