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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2007;27:2325.)
© 2007 American Heart Association, Inc.

Vascular Biology

Nuclear Redox-Signaling Is Essential for Apoptosis Inhibition in Endothelial Cells—Important Role for Nuclear Thioredoxin-1

Peter Schroeder; Ruediger Popp; Barbara Wiegand; Joachim Altschmied; Judith Haendeler

From the IUF (Institut fuer Umweltmedizinische Forschung) at the University of Duesseldorf gGmbH (P.S., J.H.), Duesseldorf, Germany; the Department of Physiology (R.P.), University of Frankfurt, Germany; the Department of Molecular Cardiology (B.W.), University of Giessen, Germany; and the Department of Molecular Hematology (J.A.), University of Frankfurt, Germany.

Correspondence to Judith Haendeler, PhD, Molecular Cell & Aging Research, Institut fuer Umweltmedizinische Forschung (IUF), at the University of Duesseldorf gGmbH, Auf‘m Hennekamp 50, 40225 Duesseldorf, Germany. E-mail juhae001{at}uni-duesseldorf.de

Objective— The redox regulator thioredoxin-1 (Trx) is a potent antioxidative enzyme and exerts important cellular functions. Physiological concentrations of reactive oxygen species (ROS) and of nitric oxide (NO) act as second messengers. Previously, we demonstrated that ROS and NO reduced apoptosis in a Trx-dependent manner. The aim of this study was to determine the underlying mechanisms.

Methods and Results— First, we investigated the localization of Trx after H₂O₂ and NO. Both induced nuclear import of Trx, which required karyopherin-. siRNA against karyopherin- inhibited nuclear import of Trx. Analysis of the Trx amino acid sequence and subsequent immunoprecipitation studies revealed that Trx(K81/82E) is not imported into the nucleus under H₂O₂ treatment and Trx(K81/82/85E) was retained in the cytosol and induced cell death. Trx(K81/82E) abolished the antiapoptotic capacity of H₂O₂. Glutathione S-transferase P1 (GST-P1) was identified as one major target regulated by H₂O₂. siRNA against GST-P1 abolished the antiapoptotic effect of H₂O₂. Cysteine 69, but not cysteines 32 and 35, which are all required for the complete antiapoptotic function of Trx, is not imported into the nucleus.

Conclusion— H₂O₂-induced nuclear import of Trx depends on karyopherin- and NO. Trx-dependent induction of GST-P1 expression is required for apoptosis inhibition in endothelial cells.

Physiological concentrations of ROS and NO activate signaling pathways. ROS induce karyopherin –dependent nuclear import of Trx, which is enhanced by posttranslational modifications of Trx. Import of Trx modified antioxidant responsive element containing promoters and increased GST-P1 expression. Knocking down GST-P1 abolished the antiapoptotic properties of ROS. Nuclear Trx plays an important role in endothelial cell apoptosis.

Key Words: antioxidants • apoptosis • reactive oxygen species • glutathione S-transferase P1 • thioredoxin-1