Catalase and estradiol inhibit mitochondrial protein S-glutathionylation.

Regulation and downstream effects of mitochondrial protein S-glutathionylation in response to oxidative stress are poorly understood. The study aim was to determine whether anti-oxidants such as catalase and estradiol alter mitochondrial protein S-glutathionylation and in turn affect apoptosis following ultraviolet B (UV-B) light irradiation. HeLa cells were transduced with increasing amounts of adenovirus encoding catalase (Ad-Cat) and β-galactosidase (Ad-Lac Z) or pre-incubated with estradiol before induction of apoptosis by UV-B light exposure.

A genome-wide deletion mutant screen identifies pathways affected by nickel sulfate in Saccharomyces cerevisiae.

Background: The understanding of the biological function, regulation, and cellular interactions of the yeast genome and proteome, along with the high conservation in gene function found between yeast genes and their human homologues, has allowed for Saccharomyces cerevisiae to be used as a model organism to deduce biological processes in human cells. Here, we have completed a systematic screen of the entire set of 4,733 haploid S. cerevisiae gene deletion strains (the entire set of nonessential genes for this organism) to identify gene products that modulate cellular toxicity to nickel sulfate (NiSO(4)).

Covalent modifications of histones during mitosis and meiosis.

Higher order chromosome structures are the hallmark of mitotic and meiotic cells. Chromatin condensation and compaction are essential for rapid chromosome congression and accurate chromosome segregation during cell division. The core histones possess tails at their amino-termini.

A genome-wide screen in Saccharomyces cerevisiae reveals pathways affected by arsenic toxicity.

We have used Saccharomyces cerevisiae to identify toxicologically important proteins and pathways involved in arsenic-induced toxicity and carcinogenicity in humans. We performed a systemic screen of the complete set of 4733 haploid S. cerevisiae single-gene-deletion mutants to identify those that have decreased or increased growth, relative to wild type, after exposure to sodium arsenite (NaAsO(2)).

Polo-like kinase 3 functions as a tumor suppressor and is a negative regulator of hypoxia-inducible factor-1 alpha under hypoxic conditions.

Polo-like kinase 3 (Plk3) is an important mediator of the cellular responses to genotoxic stresses. In this study, we examined the physiologic function of Plk3 by generating Plk3-deficient mice. Plk3(-/-) mice displayed an increase in weight and developed tumors in various organs at advanced age.

Cytochrome P450 2E1 contributes to ethanol-induced fatty liver in mice.

Cytochrome P450 2E1 (CYP2E1) is suggested to play a role in alcoholic liver disease, which includes alcoholic fatty liver, alcoholic hepatitis, and alcoholic cirrhosis. In this study, we investigated whether CYP2E1 plays a role in experimental alcoholic fatty liver in an oral ethanol-feeding model. After 4 weeks of ethanol feeding, macrovesicular fat accumulation and accumulation of triglyceride in liver were observed in wild-type mice but not in CYP2E1-knockout mice.

Cycloheximide protects HepG2 cells from serum withdrawal-induced apoptosis by decreasing p53 and phosphorylated p53 levels.

Cycloheximide (CHX), an inhibitor of protein synthesis, has been reported to prevent cell death in a wide variety of cell types and produced by different apoptotic stimuli. However, the mechanisms by which CHX protects cells from apoptosis are still unclear. In this study, we investigated whether p53 plays a role in the protection by CHX against serum withdrawal-induced apoptosis.

Adenovirus-mediated expression of CYP2E1 produces liver toxicity in mice.

Induction of cytochrome P450 2E1 by ethanol is believed to be one of the central pathways by which ethanol generates a state of oxidative stress and causes hepatotoxicity. In order to evaluate the biochemical and toxicological actions of CYP2E1 and its sensitization of hepatotoxin-induced injury, an adenovirus which can mediate overexpression of CYP2E1 was constructed. Injecting this virus into mice through the tail vein elevated CYP2E1 protein and activity twofold in the liver of the mice compared with the mice injected with Ad-LacZ or saline.

Overexpression of CYP2E1 in mitochondria sensitizes HepG2 cells to the toxicity caused by depletion of glutathione.

Induction of CYP2E1 by ethanol is one mechanism by which ethanol causes oxidative stress and alcohol liver disease. Although CYP2E1 is predominantly found in the endoplasmic reticulum, it is also located in rat hepatic mitochondria. In the current study, chronic alcohol consumption induced rat hepatic mitochondrial CYP2E1.

Adenovirus mediated overexpression of CYP2E1 increases sensitivity of HepG2 cells to acetaminophen induced cytotoxicity.

To study the biochemical and toxicological properties of cytochrome P450 2E1 (CYP2E1), an adenovirus containing human CYP2E1 cDNA (Ad-CYP2E1) was constructed and was shown to successfully mediate the overexpression of CYP2E1 in HepG2 cells. Acetaminophen (APAP) toxicity to HepG2 cells infected with Ad-CYP2E1 was characterized as a preliminary proof of principle experiment to validate the functionality of the CYP2E1 adenovirus. Compared with cells infected with Ad-LacZ, HepG2 cells infected with Ad-CYP2E1 were more sensitive to APAP induced necrosis and apoptosis when the cells were depleted of intracellular reduced glutathione (GSH).

Apoptosis and the liver: relation to autoimmunity and related conditions.

Apoptosis is a normal physiologic form of cell death that follows activation of either an intrinsic or extrinsic pathway. In the intrinsic, various stimuli, such as oxidative stress, lead to mitochondrial dysfunction and the release of pro-apoptotic factors. Ligand binding to cell surface death receptors, such as Fas, activates the extrinsic pathway.

Catalase protects HepG2 cells from apoptosis induced by DNA-damaging agents by accelerating the degradation of p53.

Oxidants such as H(2)O(2) play a role in the toxicity of certain DNA-damaging agents, a process that often involves the tumor suppressor p53. H(2)O(2) is rapidly degraded by catalase, which protects cells against oxidant injury. To study the effect of catalase on apoptosis induced by DNA-damaging agents, HepG2 cells were infected with adenovirus containing the cDNA of catalase (Ad-Cat).

Adenovirus-mediated overexpression of catalase in the cytosolic or mitochondrial compartment protects against toxicity caused by glutathione depletion in HepG2 cells expressing CYP2E1.

Induction of cytochrome P450 CYP2E1 by ethanol appears to be one of the mechanisms by which ethanol creates a state of oxidative stress. Glutathione (GSH) is a key cellular antioxidant that detoxifies reactive oxygen species. Depletion of GSH, especially mitochondrial GSH, is believed to play a role in the ethanol-induced liver injury.

Toxicity by pyruvate in HepG2 cells depleted of glutathione: role of mitochondria.

Several studies have shown that pyruvate can scavenge H(2)O(2) and protect from H(2)O(2)-mediated cell injury. Mitochondria are critical participants in the control of apoptotic and necrotic cell death. Mitochondrial GSH plays an important role in the maintenance of cell functions and viability by metabolism of oxygen free radicals generated by the respiratory chain.