Evidence for a possible inhibitory interaction between the HO-1/CO- and Akt/NO-pathways in human endothelial cells.
OBJECTIVE
The protective properties of heme oxygenase 1 (HO-1) give reason to study this mechanism as a potential therapeutic target for inflammatory and cardiovascular diseases. Recent evidence suggests a possible interaction between the HO-1/CO- and the protein kinase Akt/NO-pathway. This study was designed to examine the effects of continuous HO-1 overexpression in endothelial cells.


METHODS
Oncoretroviral vectors were constructed to achieve constitutive overexpression of HO-1, Akt, and green fluorescence protein in human umbilical vein endothelial cells. [(3)H]thymidine-incorporation and lipid-peroxidation were measured following exposure to heme and H(2)O(2). Expression of HO-1, Akt and its downstream-target endothelial NO-synthase were quantified by Western blot analysis. NO-synthase-activity was measured using the citrulline-conversion-assay.


RESULTS
HO-1-overexpression reduced proliferative rates and DNA-synthesis of HUVEC, but provided potent protection from oxidative stress induced by heme and H(2)O(2). Phosphorylated-Akt and eNOS was downregulated in HO-1-HUVEC. eNOS-activity was reduced in HO-1-HUVEC. Co-infection with the Akt-retrovirus restored proliferative rates and eNOS-expression and -activity.


CONCLUSIONS
Continuously elevated HO-1-activity protects EC from oxidative stress but inhibits Akt-mediated proliferation and eNOS-expression. This inhibitory feedback mechanism could be a limitation of HO-1 as a target for the treatment of vascular disease.
Batzlsperger
Christian A
CA
Department of Internal Medicine II, Regensburg University Medical Center, Franz Josef Strauss Allee 11, 93053 Regensburg, Germany.
Achatz
Stefan
S
Spreng
Josefine
J
Riegger
Guenter A J
GA
Griese
Daniel P
DP
D002248:Carbon Monoxide / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D015536:Down-Regulation; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation; D005822:Genetic Vectors / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000096:biosynthesis; D006418:Heme / Q000494:pharmacology; D051547:Heme Oxygenase-1 / Q000096:biosynthesis / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000032:analysis / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000096:biosynthesis / Q000378:metabolism*; D012190:Retroviridae / Q000235:genetics; D014779:Virus Replication / Q000235:genetics
D049452:Green Fluorescent Proteins; D009569:Nitric Oxide; D006418:Heme; D002248:Carbon Monoxide; D004247:DNA; D006861:Hydrogen Peroxide; D052250:Nitric Oxide Synthase Type III; D051547:Heme Oxygenase-1; D051057:Proto-Oncogene Proteins c-akt