Histone deacetylases (HDACs) are key molecules involved in epigenetic regulation of gene expression. We have previously demonstrated that oxidative stress Caused a reduction in HDAC2, resulting in amplified inflammation and reduced corticosteroid responsiveness. Here we showed nitrative/oxidative stress reduced HDAC2 expression via nitration of distinct tyrosine residues. Peroxynitrite, hydrogen peroxide and cigarette smoke-conditioned medium reduced HDAC2 expression in A549 epithelial cells in vitro. This reduction was due to increased proteasomal degradation following ubiquitination rather than reduction of mRNA expression or stability. HDAC2 was nitrated under nitrative/oxidative Stress and in the peripheral lung tissues of smokers and patients with chronic obstructive Pulmonary disease. Mutagenesis studies replacing tyrosine (Y) residues with alanine revealed that Y253 is at least partly responsible for the proteasomal degradation of HDAC2 under nitrative stress. Thus, nitration of distinct tyrosine residues modifies both the expression and activity of HDAC2, having an impact on epigenetic regulation. (C) 2009 Elsevier Inc. All rights reserved.