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Exposure of glia to pro‐oxidant agents revealed selective Stat1 activation by H 2 O 2 and Jak2‐independent antioxidant features of the Jak2 inhibitor AG490
Author(s) -
Gorina Roser,
Sanfeliu Coral,
Galitó Aida,
Messeguer Àngel,
Planas Anna M.
Publication year - 2007
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.20542
Subject(s) - oxidative stress , reactive oxygen species , trolox , paraquat , phosphorylation , stat1 , biology , tyrosine phosphorylation , antioxidant , microbiology and biotechnology , biochemistry , antioxidant capacity
The JAK/STAT pathway is activated in response to cytokines and growth factors. In addition, oxidative stress can activate this pathway, but the causative pro‐oxidant forms are not well identified. We exposed cultures of rat glia to H 2 O 2 , FeSO 4 , nitroprussiate, or paraquat. We assessed oxidative stress by measuring reactive oxygen species (ROS) and oxidated proteins, we determined phosphorylated Stat1 (pStat1), and we evaluated the effect of antioxidants (trolox, propyl gallate, and N ‐acetylcysteine) and of Jak2 (Janus tyrosine kinases) inhibitors (AG490 and Jak2‐Inhibitor‐II). Pro‐oxidant agents induced ROS and protein oxidation, excluding nitroprussiate that induced protein nitrosylation. H 2 O 2 , and to a lesser extent FeSO 4 , increased the level of pStat1, whereas nitroprussiate and paraquat did not. Trolox and propyl gallate strongly prevented ROS formation but they did not abolish H 2 O 2 ‐induced pStat1. In contrast, NAC did not reduce the level of ROS but it prevented the increase of pStat1 induced by H 2 O 2 , evidencing a differential effect on ROS formation and on Stat1 phosphorylation. H 2 O 2 induced pStat1 in mixed glia cultures and, to a lesser extent, in purified astroglia, but not in microglia. Jak2 inhibitors reduced H 2 O 2 ‐induced pStat1, suggesting the involvement of this kinase in the increased phosphorylation of Stat1 by peroxide. Unexpectedly, AG490, but not Jak2‐Inhibitor‐II, reduced ROS formation, and it abrogated lipid peroxidation in microsomal preparations. Furthermore, AG490 reduced ROS in glial cells that were transfected with siRNA to silence Jak2 expression. These findings reveal previously unrecognized Jak2‐independent antioxidant properties of AG490, and show that Jak2‐dependent Stat1 activation by peroxide is dissociated from ROS generation. © 2007 Wiley‐Liss, Inc.