Protection of HepG2 cells against acrolein toxicity by 2-cyano-3,12-dioxooleana-1,9-dien-28-imidazolide via glutathione-mediated mechanism

Abstract

Acrolein is an environmental toxicant, mainly found in smoke released from incomplete combustion of organic matter. Several studies showed that exposure to acrolein can lead to liver damage. The mechanisms involved in acrolein-induced hepatocellular toxicity, however, are not completely understood. This study examined the cytotoxic mechanisms of acrolein on HepG2 cells. Acrolein at pathophysiological concentrations was shown to cause apoptotic cell death and an increase in levels of protein carbonyl and thiobarbituric acid reactive acid substances. Acrolein also rapidly depleted intracellular glutathione (GSH), GSHlinked glutathione-S-transferases, and aldose reductase, three critical cellular defenses that detoxify reactive aldehydes. Results further showed that depletion of cellular GSH by acrolein preceded the loss of cell viability. To further determine the role of cellular GSH in acrolein-mediated cytotoxicity, buthionine sulfoximine (BSO) was used to inhibit cellular GSH biosynthesis. It was observed that depletion of cellular GSH by BSO led to a marked potentiation of acrolein-mediated cytotoxicity in HepG2 cells. To further assess the contribution of these events to acrolein-induced cytotoxicity, triterpenoid compound 2-cyano-3,12-dioxooleana-1,9-dien-28-imidazolide (CDDO-Im) was used for induction of GSH. Induction of GSH by CDDO-Im afforded cytoprotection against acrolein toxicity in HepG2 cells. Furthermore, BSO significantly inhibited CDDO-Im-mediated induction in cellular GSH levels and also reversed cytoprotective effects of CDDO-Im in HepG2 cells. These results suggest that GSH is a predominant mechanism underlying acrolein-induced cytotoxicity as well as CDDO-Im-mediated cytoprotection. This study may provide understanding on the molecular action of acrolein which may be important to develop novel strategies for the prevention of acrolein-mediated toxicity.

Uptake, efflux, and toxicity of inorganic and methyl mercury in the endothelial cells (EA.hy926)

“…MTT assay. The cytotoxicity of HgII and MeHg was determined by modified MTT assay as fully described in our previous studies [28][29][30] . Cells were seeded into 48-well tissue culture plates.…”

“…Annexin V/Dead Cell Apoptosis Kit assay, with the procedures fully described elsewhere 29,31 . In brief, EA.hy926 cells were treated with various concentrations of HgII or MeHg (0.1-10 µM) for 24 h. Cells were then harvested and washed in cold PBS followed by the re-suspension in annexin-binding buffer and dilution of cell density to ~1 × 10 6 cells/ml.…”

Electronic cigarette: A recent update of its toxic effects on humans

“…Further, several chemicals were found to get involved in the interaction between acrolein and GSH. Usage of triterpenoid compound 2‐cyano‐3,12‐dioxooleana‐1,9‐dien‐28‐imidazolide (CDDO‐Im) was corroborated to be an inductor of GSH biosynthesis, and buthionine sulfoximine (BSO) was used to inhibit the inductive function of CDDO—Im, thus inhibiting protective GSH, ultimately leading to acrolein mediated hepatocytotoxicity (Shah et al, ). Experimenting on masculine mice testified that acrolein induced the production of plasma aldosterone via increased angiotensin II (Ang II) and elevated P450cc (enzyme involved in the rate‐limiting step of steroidogenesis) activity (Wang et al, ).…”

“…Experimenting on masculine mice testified that acrolein induced the production of plasma aldosterone via increased angiotensin II (Ang II) and elevated P450cc (enzyme involved in the rate‐limiting step of steroidogenesis) activity (Wang et al, ). In addition, acrolein was found to induce cell apoptosis and liver damage via increasing protein carbonyl and thiobarbituric acid reaction acid substances (TBRAS) (Shah et al, ), and through enhancement of histone modification (histone 3 lysine 4 trimethylation [H3K4me3] and histone 3 lysine 9 acetylation [H3K9ac]) and upregulation of FasL expression (Ghare et al, ). Although acrolein is not classifiable as to its carcinogenicity to humans, in recent years researches have transpired that formation of mutagenic acrolein‐DNA adducts was involved in lung and bladder carcinogenesis (Lee et al, , ; Pan et al, ), implying the carcinogenic property of acrolein to humans.…”

Acrolein is a critical mediator of alcohol-induced liver and intestinal injury in alcoholic liver disease.

“…Acrolein can deplete intracellular glutathione (GSH), GSH-linked glutathione-Stransferases, and aldose reductase rapidly for its detoxification [41], and acrolein can be toxic unless removed or metabolized [42]. The primary pathway of acrolein metabolism is conjugation with glutathione catalyzed by glutathione S-transferase-P (GSTP) [43,44].…”