Effects of vitamin E deficiency and glutathione depletion on stress protein heme oxygenase 1 mRNA expression in rat liver and kidney

Resistance of neuroblastoma GI-ME-N cell line to glutathione depletion involves Nrf2 and heme oxygenase-1

Cancer cell survival is known to be related to the ability to counteract oxidative stress, and glutathione (GSH) depletion has been proposed as a mechanism to sensitize cells to anticancer therapy. However, we observed that GI-ME-N cells, a neuroblastoma cell line without MYCN amplification, are able to survive even if GSH-depleted by l-buthionine-(S,R)-sulfoximine (BSO). Here, we show that in GI-ME-N cells, BSO activates Nrf2 and up-regulates heme oxygenase-1 (HO-1). Silencing of Nrf2 restrained HO-1 induction by BSO. Inhibition of HO-1 and silencing of Nrf2 or HO-1 sensitized GI-ME-N cells to BSO, leading to reactive oxygen/nitrogen species overproduction and decreasing viability. Moreover, targeting the Nrf2/HO-1 axis sensitized GI-ME-N cells to etoposide more than GSH depletion. Therefore, we have provided evidence that in GI-ME-N cells, the Nrf2/HO-1 axis plays a crucial role as a protective factor against cellular stress, and we suggest that the inhibition of Nfr2/HO-1 signaling should be considered as a central target in the clinical battle against neuroblastoma.

Glutathione synthesis inhibitor butathione sulfoximine regulates ceruloplasmin by dual but opposite mechanism: Implication in hepatic iron overload

Glutathione (GSH) depletion is often detected in chronic pathological conditions like hepatitis C infection, alcohol consumption or xenobiotic assault with simultaneous reactive oxygen species (ROS) generation and hepatic iron overload. However, relation between GSH depletion and regulators of iron homeostasis is not clear so far. To determine that hepatic HepG2 cells were treated with GSH synthesis inhibitor butathione sulfoximine (BSO) and a dual regulation of ceruloplasmin (Cp) that involves in hepatic iron release was detected unlike other iron homeostasis regulators. BSO treatment that caused marginal GSH deficiency increased Cp synthesis due to increased transcription mediated by activator protein (AP)-1-binding site. In higher GSH deficiency (> 40 %) with increased ROS generation, Cp expression was decreased due to promotion of Cp mRNA decay mediated by 3'untranslated region (3'UTR) as found by transfecting chimera of chloramphenicol acetyl transferase (CAT) gene with Cp 3'UTR. RNA gel shift assay showed significant reduction in 3'UTR binding protein complex in similar condition. Decreased CAT expression and RNA-protein complex binding are reversed by pretreatment with antioxidant N-acetyl cysteine suggesting 3'UTR binding protein complex is redox-sensitive. This unique and opposite regulation of Cp provides a mechanism of hepatic iron-deposition during glutathione deficiency detected in chronic pathological conditions.

Induction of heme oxygenase in guinea-pig stomach: roles in contraction and in single muscle cell ionic currents

The role of heme oxygenase reaction products in modulation of stomach fundus excitability was studied. The presence of constitutive heme oxygenase 2 was verified in myenteric ganglia by immunohistochemistry. The role of inducible heme oxygenase isoenzyme was investigated after invivo treatment of animals with CoCl2 (80 mg kg-1 b.w) injected subcutaneously 24 h before they were killed. This treatment resulted in increased production of bilirubin and positive staining for the inducible isoform in stomach smooth muscle and vast induction in the liver. In both control and treated animals haemin, applied to the bath as a substrate of heme oxygenase caused significant decrease of prostaglandin F2alpha-induced tone, and ameliorated the relaxatory response of the fundic strips to electrical field stimulation. Both effects were antagonized by Sn-protoporphyrin IX, competitive heme oxygenase inhibitor, and were found to be neuronally dependent. In single freshly isolated smooth muscle cells from control animals haemin caused a concentration-dependent increase of the whole cell K+ currents, which was not affected by Sn-protoporphyrin IX, cyclic guanosine monophosphate (cGMP)-dependent protein kinase or guanylyl cyclase antagonists, but was reversed by various antioxidants and abolished by an NO scavenger. In cells from treated animals the K+ current increasing effect of haemin did not depend on the presence of antioxidants, but was abolished by protein kinase G and guanylyl cyclase inhibitors, depletors of intracellular Ca2+ pools or Sn-protoporphyrin IX. Biliverdin did not affect contraction or ionic currents. Thus, this is the first study demonstrating that heme oxygenase is an inducible enzyme in guinea-pigs, which exerts a modulatory role on gastric smooth muscle excitability via carbon monoxide production.

Redox signaling of cardiac HSF1 DNA binding

Experiments involving chemical induction of the heat shock response in simple biological systems have generated the hypothesis that protein denaturation and consequential binding of heat shock transcription factor 1 (HSF1) to proximal heat shock elements (HSEs) on heat shock protein (hsp) genes are the result of oxidation and/or depletion of intracellular thiols. The purpose of the present investigation was to determine the role of redox signaling of HSF1 in the intact animal in response to physiological and pharmacological perturbations. Heat shock and exercise induced HSF1-HSE DNA binding in the rat myocardium (P < 0.001) in the absence of changes in reduced glutathione (GSH), the major nonprotein thiol in the cell. Ischemia-reperfusion, which decreased GSH content (P < 0.05), resulted in nonsignificant HSF1-HSE formation. This dissociation between physiological induction of HSF1 and changes in GSH was not gender dependent. Pharmacological ablation of GSH with L-buthionine-[S,R]-sulfoximine (BSO) treatment increased myocardial HSF1-HSE DNA binding in estrogen-naive animals (P = 0.007). Thus, although physiological induction of HSF1-HSE DNA binding is likely regulated by mediators of protein denaturation other than cellular redox status, the proposed signaling pathway may predominate with pharmacological oxidation and may represent a plausible and accessible strategy in the development of HSP-based therapies.

Enhanced heme oxygenase activity increases the antioxidant defense capacity of guinea pig liver upon acute cobalt chloride loading: comparison with rat liver

Changes in the activity of so-called oxidative stress defensive enzymes, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and heme oxygenase, as well as changes in lipid peroxidation and reduced glutathione levels, were measured in guinea pig and rat liver after acute cobalt loading. Cobalt chloride administration produced a much higher degree of lipid peroxidation in guinea pig than in rat liver compared with the control animals. The intrahepatic reduced glutathione content in control guinea pig was higher than that in rat, but was equally decreased in both species after cobalt administration. The enzymatic scavengers of free radicals, superoxide dismutase, catalase and glutathione peroxidase, were significantly decreased in rat liver after acute cobalt loading, and as a compensatory reaction, the heme oxygenase activity was increased (seven-fold). In guinea pig liver, only superoxide dismutase activity was depleted in response to cobalt-induced oxidative stress, while catalase and glutathione peroxidase were highly activated and the heme oxygenase activity was dramatically increased (13-fold). It is assumed that enhanced heme oxygenase activity may have important antioxidant significance by increasing the liver oxidative-stress defense capacity.

The relationship between stress protein induction and the oxidative defense system in the rat hippocampus following kainic acid administration

The time and dose-dependent effects of kainic acid (KA) induced excitotoxicity on the oxidative defense system and the relationship to the induction of stress proteins were investigated in the rat hippocampus. Male Long-Evans rats were injected subcutaneously with 5.0, 7.5, or 10 mg KA/kg. Rats were sacrificed and the hippocampus removed and processed for biochemical and electrophoretic analysis. The activity of glutathione peroxidase (GPx) increased significantly at the 5 mg KA/kg dose, while malondialdehyde (MDA) levels significantly increased at 7.5 mg KA/kg when measured at 24 h. A dose of 10 mg KA/kg depleted significantly hippocampal glutathione (GSH) levels at 8, 16 and 24 h post-treatment while GPx activity was increased significantly at 2, 4, 8 and 16 hr post-treatment. The 10 mg KA/kg increased significantly hippocampal MDA levels at 2 h post-treatment and decreased significantly thereafter. The induction of stress proteins increased in a dose and time dependent manner. The expression of Hp72 and Hsp32 increased significantly at 16 h with a maximum induction observed at 24 h post-treatment. The data suggests that KA toxicity is mediated through the formation of reactive oxygen species resulting in alterations in the oxidative defense system. The expression of stress proteins following KA administration may reflect a concomitant but alternate response to excitotoxic events.