Visit our Expo - Redox and Inflammation signaling 2012

Session XIII : Cell signaling pathways leading to regulated chromatin modifications
Poster XIII, 3
Pharmacological restoration of ROS impaired steroid function: the role of HDAC-2
Paul A. Kirkham, Koremu Meja, Gillian Spooner and John A. Marwick.
Novartis Institutes for Biomedical Research, Horsham, West Sussex, RH12 5AB, UK.
Email: paul.kirkham@novartis.com
HDAC-2 activity plays a major role in regulating steroid function and inflammation. COPD
patients, severe asthmatics and mild asthmatics who smoke are all insensitive to steroid
treatment, as a result of exposure to oxidative stress. Moreover, oxidative stress has a direct
inhibitory effect on HDAC-2 activity through post-translational modification. We
hypothesised that upregulating HDAC activity after exposure to oxidative stress should
restore steroid function. Oxidative stress reduced HDAC-2 but not HDAC-1 activity. Both
theophylline and curcumin specifically restored HDAC-2 activity in pre-ROS stressed cells
only, in both a time and dose dependant manner. Similar effects on restoring HDAC activity
after ROS stress were observed using either JNK or Akt inhibitors, but not p38, cAMP or
calcium modulators. ROS induced reduction of HDAC-2 activity correlated with a decrease
in steroid responsiveness. Co-incubation or theophylline or curcumin with budesonide (1nM)
before stimulation with LPS (10ng/ml) for 16 hours restored steroid responsiveness in ROS
treated cells as assessed by TNFalpha release. Interestingly, neither theophyline or curcumin
alone (upto 10uM) were anti-inflammatory in LPS stimulated pre-ROS stressed U397 cells.
Moreover, theophylline (1µM) also restored the ability of dexamethasone to reduce
inflammatory gene associated histone acetylation in pre-ROS stressed U937 cells as assessed
by chromatin immunoprecipitation (ChIP) assay. Serine phosphorylation on HDAC-2 is
reduced by oxidative stress. However, treatment with curcumin/theophyline (1µM) post ROS
stress increases HDAC-2 serine phosphorylation. In conclusion, our data suggests that
restoring/upregulating HDAC activity and thereby steroid function after prior reduction by
oxidative stress can be achieved through pharmacological intervention. The mechanism of
action for theophyline and curcumin in this process is unclear at present. However, inhibition
of JNK or Akt signaling pathways may play a role. It is therefore likely that both theophyline
and curcumin act on signalling pathways that regulate HDAC protein post-translational status
and hence activity.
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