Nitrative Inactivation of Thioredoxin-1 and Its Role in Postischemic Myocardial Apoptosis

Abstract

Background-Intracellular proteins involved in oxidative stress and apoptosis are nitrated in diseased tissues but not in normal tissues; definitive evidence to support a causative link between a specific protein that is nitratively modified with tissue injury in a specific disease is limited, however. The aims of the present study were to determine whether thioredoxin (Trx), a novel antioxidant and antiapoptotic molecule, is susceptible to nitrative inactivation and to establish a causative link between Trx nitration and postischemic myocardial apoptosis. Methods and Results-In vitro exposure of human Trx-1 to 3-morpholinosydnonimine resulted in significant Trx-1 nitration and almost abolished Trx-1 activity. 3-morpholinosydnonimine-induced nitrative Trx-1 inactivation was completely blocked by MnTE-2-PyP 5ϩ (a superoxide dismutase mimetic) and markedly attenuated by PTIO (a nitric oxide scavenger). Administration of either reduced or oxidized Trx-1 in vivo attenuated myocardial ischemia/ reperfusion injury (Ͼ50% reduction in apoptosis and infarct size, PϽ0.01). However, administration of nitrated Trx-1 failed to exert a cardioprotective effect. In cardiac tissues obtained from ischemic/reperfused heart, significant Trx-1 nitration was detected, Trx activity was markedly inhibited, Trx-1/ASK1 (apoptosis signal-regulating kinase-1) complex formation was abolished, and apoptosis signal-regulating kinase-1 activity was increased. Treatment with either FP15 (a peroxynitrite decomposition catalyst) or MnTE-2-PyP 5ϩ 10 minutes before reperfusion blocked nitrative Trx inactivation, attenuated apoptosis signal-regulating kinase-1 activation, and reduced postischemic myocardial apoptosis. Conclusions-These results strongly suggest that nitrative inactivation of Trx plays a proapoptotic role under those pathological conditions in which production of reactive nitrogen species is increased and that antinitrating treatment may have therapeutic value in those diseases, such as myocardial ischemia/reperfusion, in which pathological apoptosis is increased.

Nitrative thioredoxin inactivation as a cause of enhanced myocardial ischemia/reperfusion injury in the aging heart

“…In a recent study, we have demonstrated that besides three previously reported posttranslational Trx modifications which all occur at the cysteine residue, Trx can also be modified at the tyrosine residue (protein nitration) in a peroxynitrite-dependent fashion [28]. More interestingly, in contrast to the reversible (by Trx reductase) oxidative Trx inactivation, nitrative modification of Trx results in an irreversible inactivation [28].…”

“…More interestingly, in contrast to the reversible (by Trx reductase) oxidative Trx inactivation, nitrative modification of Trx results in an irreversible inactivation [28]. Therefore, nitric oxide and its secondary reaction products, particularly peroxynitrite, exert opposite effect on Trx activity.…”

“…In a recent study, we have demonstrated that Trx is susceptible to nitrative modification by peroxynitrite, and its activity is irreversibly inhibited by this novel post-translational modification [28]. To determine whether reduced Trx activity observed in the aging heart is caused by increased nitrative stress and subsequent Trx nitration, two additional experiments were performed.…”

Thioredoxin system – a novel therapeutic target

“…In addition, Trx is able to interact with transcription factors and to undergo the posttranslational modifications such as: oxidation of the thiol groups of Cys-32 and -35, glutathionylation at Cys-73 (Casagrande et al 2002), Snitrosylation at Cys-69 or Cys-73 (Haendeler et al 2002), nitrative modification at Tyr-49 (Tao et al 2006) and also glycation (Yuan et al 2010). This capability is also consistent with the role of Trx system in angiogenesis signaling.…”

Cell death: protein misfolding and neurodegenerative diseases

“…Additionally, NO can possibly mediate cell death or injury via S-nitrosylation or nitration reactions on other TRX-like proteins, such as TRX itself and glutaredoxin [71,157,158]. In addition to PDI, S-nitrosylation is likely to affect critical thiol groups on other chaperones, such as HSP90 in the cytoplasm [159] and possibly GRP in the ER.…”