TY - JOUR
T1 - Distinct protective mechanisms of HO-1 and HO-2 against hydroperoxide-induced cytotoxicity
AU - Kim, Yun Sook
AU - Zhuang, Hean
AU - Koehler, Raymond C.
AU - Doré, Sylvain
N1 - Funding Information:
This work was supported in part by a postdoctoral fellowship from the Mid-Atlantic American Heart Association (YSK) and grants from NIH-NS38684 (RCK), the American Health Assistance Foundation (SD), the American Heart Association (SD), the Alzheimer's Association (SD), NIH-NS046400 (SD), and NIH-AT002113 (SD). We thank Tzipora Sofare, MA, for her assistance in preparing this manuscript.
Copyright:
Copyright 2012 Elsevier B.V., All rights reserved.
PY - 2005/1/1
Y1 - 2005/1/1
N2 - Heme oxygenases (HO-1 and HO-2) catalyze the NADPH-cytochrome P 450 reductase (CPR)-dependent degradation of heme into iron, carbon monoxide, and biliverdin, which is reduced into bilirubin. Under basal conditions, HO-1 is often undetected and can be induced by numerous stress conditions. Although HO-2 is constitutively expressed, its activity appears to be regulated by post-translational modifications. HO activity has been associated with cellular protection, by which it degrades heme, a prooxidant, into bioactive metabolites. Under given circumstances, overexpression of HO-1 can render cells more sensitive to free radicals. Here, we investigated the properties of human HO isoforms that protect against oxidative stress. Considering that CPR can be a limiting factor for optimal HO activity, we tested stable HO-1 and HO-2 cell lines that derived from the CPR cells. Results indicate that the HO-1 and HO-2 cells are more resistant than controls to hemin and to the organic tert-butyl hydroperoxide, t-BuOOH. However, HO-1 cells are less resistant than HO-2 cells to hydrogen peroxide (H 2O 2). The levels of oxidatively modified proteins of HO-1 and HO-2 cells in response to t-BuOOH toxicity are identical, but the level of oxidatively modified proteins of HO-2 cells is less than that of HO-1 cells in response to H 2O 2 toxicity. Performing subcellular fractionations revealed that HO-2 and CPR are found together in the microsomal fractions, whereas HO-1 is partially present in the microsome and also found in other fractions, such as the cytosol. These same findings were observed in non-transfected primary neurons where HO-1 proteins were chemically induced with 15-deoxy-Δ 12,14-prostaglandin J 2 (15dPGJ 2). The differences in subcellular localization of HO-1 and HO-2 could explain some of the discrepancies in their cellular activity and enzymatic protective mechanisms.
AB - Heme oxygenases (HO-1 and HO-2) catalyze the NADPH-cytochrome P 450 reductase (CPR)-dependent degradation of heme into iron, carbon monoxide, and biliverdin, which is reduced into bilirubin. Under basal conditions, HO-1 is often undetected and can be induced by numerous stress conditions. Although HO-2 is constitutively expressed, its activity appears to be regulated by post-translational modifications. HO activity has been associated with cellular protection, by which it degrades heme, a prooxidant, into bioactive metabolites. Under given circumstances, overexpression of HO-1 can render cells more sensitive to free radicals. Here, we investigated the properties of human HO isoforms that protect against oxidative stress. Considering that CPR can be a limiting factor for optimal HO activity, we tested stable HO-1 and HO-2 cell lines that derived from the CPR cells. Results indicate that the HO-1 and HO-2 cells are more resistant than controls to hemin and to the organic tert-butyl hydroperoxide, t-BuOOH. However, HO-1 cells are less resistant than HO-2 cells to hydrogen peroxide (H 2O 2). The levels of oxidatively modified proteins of HO-1 and HO-2 cells in response to t-BuOOH toxicity are identical, but the level of oxidatively modified proteins of HO-2 cells is less than that of HO-1 cells in response to H 2O 2 toxicity. Performing subcellular fractionations revealed that HO-2 and CPR are found together in the microsomal fractions, whereas HO-1 is partially present in the microsome and also found in other fractions, such as the cytosol. These same findings were observed in non-transfected primary neurons where HO-1 proteins were chemically induced with 15-deoxy-Δ 12,14-prostaglandin J 2 (15dPGJ 2). The differences in subcellular localization of HO-1 and HO-2 could explain some of the discrepancies in their cellular activity and enzymatic protective mechanisms.
KW - Cytochrome P reductase
KW - Endoplasmic reticulum
KW - Free radicals
KW - Heme oxygenase
KW - Microsome
KW - Prostaglandins
KW - Subcellular localization
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U2 - 10.1016/j.freeradbiomed.2004.09.031
DO - 10.1016/j.freeradbiomed.2004.09.031
M3 - Article
C2 - 15589375
AN - SCOPUS:10344219952
SN - 0891-5849
VL - 38
SP - 85
EP - 92
JO - Free Radical Biology and Medicine
JF - Free Radical Biology and Medicine
IS - 1
ER -