Showing papers by "Arthur I. Cederbaum published in 2013"
TL;DR: Results show that autophagy was protective against the toxicity produced by several agents known to be activated by CYP2E1 and chemical inhibitors of p38 MAPK and JNK lowered the elevated toxicity of AA produced by 3-MA.
Abstract: Autophagy has been shown to be protective against drug and alcohol-induced liver injury. CYP2E1 plays a role in the toxicity of ethanol, carcinogens and certain drugs. Inhibition of autophagy increased ethanol-toxicity and accumulation of fat in wild type and CYP2E1 knockin mice but not in CYP2E1 knockout mice as well as in HepG2 cells expressing CYP2E1 (E47 cells) but not HepG2 cells lacking CYP2E1 (C34 cells). The goal of the current study was to evaluate whether modulation of autophagy can affect CYP2E1-dependent cytotoxicity in the E47 cells. The agents used to promote CYP2E1 -dependent toxicity were a polyunsaturated fatty acid, arachidonic acid (AA), buthionine sulfoximine (BSO), which depletes GSH, and CCl4, which is metabolized to the CCl3 radical. These three agents produced a decrease in E47 cell viability which was enhanced upon inhibition of autophagy by 3-methyladenine (3-MA) or Atg 7 siRNA. Toxicity was lowered by rapamycin which increased autophagy and was much lower to the C34 cells which do not express CYP2E1. Toxicity was mainly necrotic and was associated with an increase in reactive oxygen production and oxidative stress; 3-MA increased while rapamycin blunted the oxidative stress. The enhanced toxicity and ROS formation produced when autophagy was inhibited was prevented by the antioxidant N-Acetyl cysteine. AA, BSO and CCl4 produced mitochondrial dysfunction, lowered cellular ATP levels and elevated mitochondrial production of ROS. This mitochondrial dysfunction was enhanced by inhibition of autophagy with 3-MA but decreased when autophagy was increased by rapamycin. The mitogen activated protein kinases p38 MAPK and JNK were activated by AA especially when autophagy was inhibited and chemical inhibitors of p38 MAPK and JNK lowered the elevated toxicity of AA produced by 3-MA. These results show that autophagy was protective against the toxicity produced by several agents known to be activated by CYP2E1. Since CYP2E1 plays an important role in the toxicity of ethanol, drugs and carcinogens and is activated under various pathophysiological conditions such as diabetes, NASH and obesity, attempts to stimulate autophagy may be beneficial in preventing/lowering CYP2E1/ethanol liver injury.
72 citations
TL;DR: The data support a novel role for intestinal CYP2E1 in alcohol-induced intestinal hyperpermeability via a mechanism involving CYP 2E1-dependent induction of oxidative stress and upregulation of circadian clock proteins CLOCK and PER2.
Abstract: We have shown that alcohol increases Caco-2 intestinal epithelial cell monolayer permeability in vitro by inducing the expression of redox-sensitive circadian clock proteins CLOCK and PER2 and that...
60 citations
TL;DR: It is suggested that CYP2E1 plays a role in ethanol-induced hypoxia, oxidative stress, and activation of HIF-1 α in vivo and that Hif-1α contributes to CYP 2E1-dependent ethanol- induced toxicity.
46 citations
TL;DR: Nrf2 plays a key role in the adaptive response against increased oxidative stress caused by CYP2E1 in the HepG2 cells, and blocking Nrf2 by siRNAs decreases GSH and increases ROS and lipid peroxidation, resulting in decreased mitochondrial membrane potential and loss of cell viability.
Abstract: The transcription factor Nrf2 regulates the expression of important cytoprotective enzymes. Induction of cytochrome P450 2E1(CYP2E1) is one of the central pathways by which ethanol generates oxidative stress. CYP2E1 can be induced by ethanol and several low molecular weight chemicals such as pyrazole. The chapter discusses biochemical and toxicological effects of CYP2E1 and the effects of Nrf2 in modulating these actions of CYP2E1.Besides ethanol, CYP2E1 metabolizes and activates many other important toxicological compounds. One approach to try to understand basic effects and actions of CYP2E1 was to establish HepG2 cell lines that constitutively express human CYP2E1. Ethanol, polyunsaturated fatty acids and iron were toxic to the HepG2 cells which express CYP2E1 (E47 cells) but not control C34HepG2 cells which do not express CYP2E1.Toxicity was associated with enhanced oxidant stress and could be prevented by antioxidants and potentiated if glutathione (GSH) was removed. The E47 cells had higher GSH levels and a Twofold increase in catalase, cytosolic and microsomal glutathione transferase, and heme oxygenase-1 (HO-1) than control HepG2 cells due to activation of their respective genes. These activations were prevented by antioxidants, suggesting that reactive oxygen species (ROS) generated by CYP2E1 were responsible for the up-regulation of these antioxidant genes. This upregulation of antioxidant genes may reflect an adaptive mechanism to remove CYP2E1-derived oxidants. Increases in Nrf2 protein and mRNA were observed in livers of chronic alcohol-fed mice or rats and of pyrazole-treated rats or mice, conditions known to elevate CYP2E1. E47 cells showed increased Nrf2 mRNA and protein expression compared with control HepG2 C34 cells. Upregulation of antioxidant genes in E47 cells is dependent on Nrf2 and is prevented by siRNA-Nrf2. Blocking Nrf2 by siRNA-Nrf2 decreases GSH and increases ROS and lipid peroxidation, resulting in decreased mitochondrial membrane potential and loss of cell viability of E47 cells but not C34 cells. Nrf2 is activated and levels of Nrf2 protein and mRNA are increased when CYP2E1 is elevated. These results suggest that Nrf2 plays a key role in the adaptive response against increased oxidative stress caused by CYP2E1 in the HepG2 cells.
26 citations
TL;DR: It is suggested that nicotine enhances ethanol-induced steatosis and collagen deposition, but nicotine has no effect onanol-induced inflammation.
17 citations