Reactive Oxygen Species Are Involved in Arsenic Trioxide Inhibition of Pyruvate Dehydrogenase Activity

Abstract

Arsenite was shown to inhibit pyruvate dehydrogenase (PDH) activity through binding to vicinal dithiols in pure enzyme and tissue extract. However, no data are available on how arsenite inhibits PDH activity in human cells. The IC(50) values for arsenic trioxide (As(2)O(3)) to inhibit the PDH activity in porcine heart pure enzyme preparation and in human leukemia cell line HL60 cells were estimated to be 182 and 2 microM, respectively. Thus, As(2)O(3) inactivation of PDH activity was about 90 times more potent in HL60 cells than in purified enzyme preparation. The IC(50) values for As(2)O(3) and phenylarsine oxide to reduce the vicinal thiol content in HL60 cells were estimated to be 81.7 and 1.9 microM, respectively. Thus, As(2)O(3) is a potent PDH inhibitor but a weak vicinal thiol reacting agent in HL60 cells. Antioxidants but not dithiol compounds suppressed As(2)O(3) inhibition of PDH activity in HL60 cells. Conversely, dithiol compounds but not antioxidants suppressed the inhibition of PDH activity by phenylarsine oxide. As(2)O(3) increased H(2)O(2) level in HL60 cells, but this was not observed for phenylarsine oxide. Mitochondrial respiration inhibitors suppressed the As(2)O(3)-induced H(2)O(2) production and As(2)O(3) inhibition of PDH activity. Moreover, metal chelators ameliorated whereas Fenton metals aggravated As(2)O(3) inhibition of PDH activity. Treatment with H(2)O(2) plus Fenton metals also decreased the PDH activity in HL60 cells. Therefore, it seems that As(2)O(3) elevates H(2)O(2) production in mitochondria and this may produce hydroxyl through the Fenton reaction and result in oxidative damage to the protein of PDH. The present results suggest that arsenite may cause protein oxidation to inactivate an enzyme and this can occur at a much lower concentration than arsenite binding directly to the critical thiols.

The Yeast Genes ROX1, IXR1, SKY1 and Their Effect upon Enzymatic Activities Related to Oxidative Stress

“…Cd (II) may also displace Zn and Ca ions from metalloproteins (Faller et al, 2005;Schutzendubel & Polle, 2002;Stohs & Bagchi, 1995) and zinc-finger proteins (Hartwig, 2001). As (III) has been shown to interact with TRR, pyruvate dehydrogenase and many other proteins (Kitchin & Wallace, 2008b;Menzel et al, 1999;Samikkannu et al, 2003;Wang et al, 2007). Besides, certain proteins may be more susceptible to As (III)-induced protein oxidation than to direct binding of As (III) to critical thiols (Samikkannu et al, 2003).…”

“…As (III) has been shown to interact with TRR, pyruvate dehydrogenase and many other proteins (Kitchin & Wallace, 2008b;Menzel et al, 1999;Samikkannu et al, 2003;Wang et al, 2007). Besides, certain proteins may be more susceptible to As (III)-induced protein oxidation than to direct binding of As (III) to critical thiols (Samikkannu et al, 2003).…”

Metabolic alterations in liver of fresh water fish, C. punctata exposed to arsenic: an adverse and adaptive response to the environment

“…Arsenic is also shown to inhibit pyruvate dehydrogenase (PDH) activity either via oxidative damage or through binding to vicinal dithiols in both pure enzyme and tissue extract. However, its concentration required to deactivate the enzyme is much lower than what is required for direct binding to thiol groups, suggesting an alternative mechanism (Samikkannu et al, 2003).…”

Arrhythmogenic Effects of Arsenic Trioxide in Patients With Acute Promyelocytic Leukemia and an Electrophysiological Study in Isolated Guinea Pig Papillary Muscles

“…8,9 The decrease in [ATP]i could inhibit Na + /K + ATPase and result in an increase in [Na + ]i, leading to Ca 2+ overload via the Na + /Ca 2+ exchange. The decrease in [ATP]i may also depress SR Ca 2+ -ATPase activity, which causes Ca 2+ overload.…”

“…Previous studies have shown cellular Ca 2+ overload, generation of reactive oxygen species (ROS), and decreased intracellular ATP concentration ([ATP]i), [7][8][9] which may provoke triggered activities because of earlyand delayed afterdepolarization (EAD and DAD). In fact, we have observed not only TdP but also non-sustained monomorphic ventricular tachycardias in patients treated with As2O3.…”