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Carbon monoxide generated by heme oxygenase 1 suppresses endothelial cell apoptosis.

Brouard S, Otterbein LE, Anrather J, Tobiasch E, Bach FH, Choi AM, Soares MP - J. Exp. Med. (2000)

Bottom Line: Expression of HO-1 or exposure of ECs to exogenous CO enhanced p38 MAPK activation by TNF-alpha.Specific inhibition of p38 MAPK activation by the pyridinyl imidazol SB203580 or through overexpression of a p38 MAPK dominant negative mutant abrogated the antiapoptotic effect of HO-1.Taken together, these data demonstrate that the antiapoptotic effect of HO-1 in ECs is mediated by CO and more specifically via the activation of p38 MAPK by CO.

View Article: PubMed Central - PubMed

Affiliation: Immunobiology Research Center, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.

ABSTRACT
Heme oxygenase 1 (HO-1) inhibits apoptosis by regulating cellular prooxidant iron. We now show that there is an additional mechanism by which HO-1 inhibits apoptosis, namely by generating the gaseous molecule carbon monoxide (CO). Overexpression of HO-1, or induction of HO-1 expression by heme, protects endothelial cells (ECs) from apoptosis. When HO-1 enzymatic activity is blocked by tin protoporphyrin (SnPPIX) or the action of CO is inhibited by hemoglobin (Hb), HO-1 no longer prevents EC apoptosis while these reagents do not affect the antiapoptotic action of bcl-2. Exposure of ECs to exogenous CO, under inhibition of HO-1 activity by SnPPIX, substitutes HO-1 in preventing EC apoptosis. The mechanism of action of HO-1/CO is dependent on the activation of the p38 mitogen-activated protein kinase (MAPK) signaling transduction pathway. Expression of HO-1 or exposure of ECs to exogenous CO enhanced p38 MAPK activation by TNF-alpha. Specific inhibition of p38 MAPK activation by the pyridinyl imidazol SB203580 or through overexpression of a p38 MAPK dominant negative mutant abrogated the antiapoptotic effect of HO-1. Taken together, these data demonstrate that the antiapoptotic effect of HO-1 in ECs is mediated by CO and more specifically via the activation of p38 MAPK by CO.

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HO-1 and CO modulate p38 MAPK activation in ECs. (A) BAECs were either nontransduced (NT), transduced with a β-galactosidase (βgal.), or HO-1 recombinant adenovirus, and were left untreated (−) or treated (+) with TNF-α (10 ng/ml for 15 min). p38 MAPK phosphorylation was monitored by Western blot using antibodies directed against the phosphorylated forms of each MAPK. Results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.), compared with time 0, before TNF-α stimulation. (B) BAECs were stimulated (+) or not (−) by TNF-α (10 ng/ml, 30 min) in the presence or absence of CO (10,000 ppm). Phosphorylation of p38 MAPK was quantified as in A. The results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.).
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Figure 12: HO-1 and CO modulate p38 MAPK activation in ECs. (A) BAECs were either nontransduced (NT), transduced with a β-galactosidase (βgal.), or HO-1 recombinant adenovirus, and were left untreated (−) or treated (+) with TNF-α (10 ng/ml for 15 min). p38 MAPK phosphorylation was monitored by Western blot using antibodies directed against the phosphorylated forms of each MAPK. Results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.), compared with time 0, before TNF-α stimulation. (B) BAECs were stimulated (+) or not (−) by TNF-α (10 ng/ml, 30 min) in the presence or absence of CO (10,000 ppm). Phosphorylation of p38 MAPK was quantified as in A. The results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.).

Mentions: Given that HO-1 and/or CO can modulate p38 MAPK activation in monocyte/macrophages (Mφ [33]), we tested whether HO-1 and/or CO would have similar effects in ECs. Stimulation of ECs with TNF-α resulted in transient activation of JNK and p38 MAPK (Fig. 11), a finding consistent with those of others 41. ERKs (42 and 44 kD) were constitutively active in resting ECs, and no significant upregulation was detectable after TNF-α stimulation (Fig. 11). Recombinant adenovirus–mediated overexpression of HO-1 potentiated the ability of TNF-α to activate p38 MAPK (Fig. 12), but not to activate JNK (data not shown). Overexpression of β-galactosidase had no detectable effect on the activation of either p38 MAPK or JNK by TNF-α. Exposure of ECs to exogenous CO activated p38 MAPK even in the absence of TNF-α (Fig. 12).


Carbon monoxide generated by heme oxygenase 1 suppresses endothelial cell apoptosis.

Brouard S, Otterbein LE, Anrather J, Tobiasch E, Bach FH, Choi AM, Soares MP - J. Exp. Med. (2000)

HO-1 and CO modulate p38 MAPK activation in ECs. (A) BAECs were either nontransduced (NT), transduced with a β-galactosidase (βgal.), or HO-1 recombinant adenovirus, and were left untreated (−) or treated (+) with TNF-α (10 ng/ml for 15 min). p38 MAPK phosphorylation was monitored by Western blot using antibodies directed against the phosphorylated forms of each MAPK. Results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.), compared with time 0, before TNF-α stimulation. (B) BAECs were stimulated (+) or not (−) by TNF-α (10 ng/ml, 30 min) in the presence or absence of CO (10,000 ppm). Phosphorylation of p38 MAPK was quantified as in A. The results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.).
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Figure 12: HO-1 and CO modulate p38 MAPK activation in ECs. (A) BAECs were either nontransduced (NT), transduced with a β-galactosidase (βgal.), or HO-1 recombinant adenovirus, and were left untreated (−) or treated (+) with TNF-α (10 ng/ml for 15 min). p38 MAPK phosphorylation was monitored by Western blot using antibodies directed against the phosphorylated forms of each MAPK. Results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.), compared with time 0, before TNF-α stimulation. (B) BAECs were stimulated (+) or not (−) by TNF-α (10 ng/ml, 30 min) in the presence or absence of CO (10,000 ppm). Phosphorylation of p38 MAPK was quantified as in A. The results are presented as fold induction of MAPK activation by TNF-α in arbitrary units (A.U.).
Mentions: Given that HO-1 and/or CO can modulate p38 MAPK activation in monocyte/macrophages (Mφ [33]), we tested whether HO-1 and/or CO would have similar effects in ECs. Stimulation of ECs with TNF-α resulted in transient activation of JNK and p38 MAPK (Fig. 11), a finding consistent with those of others 41. ERKs (42 and 44 kD) were constitutively active in resting ECs, and no significant upregulation was detectable after TNF-α stimulation (Fig. 11). Recombinant adenovirus–mediated overexpression of HO-1 potentiated the ability of TNF-α to activate p38 MAPK (Fig. 12), but not to activate JNK (data not shown). Overexpression of β-galactosidase had no detectable effect on the activation of either p38 MAPK or JNK by TNF-α. Exposure of ECs to exogenous CO activated p38 MAPK even in the absence of TNF-α (Fig. 12).

Bottom Line: Expression of HO-1 or exposure of ECs to exogenous CO enhanced p38 MAPK activation by TNF-alpha.Specific inhibition of p38 MAPK activation by the pyridinyl imidazol SB203580 or through overexpression of a p38 MAPK dominant negative mutant abrogated the antiapoptotic effect of HO-1.Taken together, these data demonstrate that the antiapoptotic effect of HO-1 in ECs is mediated by CO and more specifically via the activation of p38 MAPK by CO.

View Article: PubMed Central - PubMed

Affiliation: Immunobiology Research Center, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA.

ABSTRACT
Heme oxygenase 1 (HO-1) inhibits apoptosis by regulating cellular prooxidant iron. We now show that there is an additional mechanism by which HO-1 inhibits apoptosis, namely by generating the gaseous molecule carbon monoxide (CO). Overexpression of HO-1, or induction of HO-1 expression by heme, protects endothelial cells (ECs) from apoptosis. When HO-1 enzymatic activity is blocked by tin protoporphyrin (SnPPIX) or the action of CO is inhibited by hemoglobin (Hb), HO-1 no longer prevents EC apoptosis while these reagents do not affect the antiapoptotic action of bcl-2. Exposure of ECs to exogenous CO, under inhibition of HO-1 activity by SnPPIX, substitutes HO-1 in preventing EC apoptosis. The mechanism of action of HO-1/CO is dependent on the activation of the p38 mitogen-activated protein kinase (MAPK) signaling transduction pathway. Expression of HO-1 or exposure of ECs to exogenous CO enhanced p38 MAPK activation by TNF-alpha. Specific inhibition of p38 MAPK activation by the pyridinyl imidazol SB203580 or through overexpression of a p38 MAPK dominant negative mutant abrogated the antiapoptotic effect of HO-1. Taken together, these data demonstrate that the antiapoptotic effect of HO-1 in ECs is mediated by CO and more specifically via the activation of p38 MAPK by CO.

Show MeSH
Related in: MedlinePlus