Nitric oxide (NO) is now known to control both mitochondrial respiration and organelle biogenesis. Under conditions of ethanol-dependent hepatic dysfunction, steatosis is increased, and this is associated with increased expression of inducible nitric oxide synthase (iNOS). We have previously shown that after chronic exposure to ethanol, the sensitivity of mitochondrial respiration to inhibition by NO is enhanced, and we have proposed that this contributes to ethanol-dependent hypoxia. This study examines the role of iNOS in controlling the NO-dependent modification of mitochondrial function. Mitochondria were isolated from the livers of both wild-type (WT) and iNOS knockout (iNOS ؊/؊ ) mice that were fed an isocaloric ethanol-containing diet for a period of 5 weeks. All animals that consumed ethanol showed some evidence of fatty liver; however, this was to a lesser extent in the iNOS ؊/؊ mice compared to controls. At this early stage in ethanol-dependent hepatic dysfunction, infiltration of inflammatory cells and the formation of nitrated proteins was also decreased in response to ethanol feeding in the iNOS ؊/؊ animals. Mitochondria isolated from wild-type ethanol-fed mice showed a significant decrease in respiratory control ratio and an increased sensitivity to NO-dependent inhibition of respiration relative to their pair-fed controls. In contrast, liver mitochondria isolated from iNOS ؊/؊ mice fed ethanol showed no change in the sensitivity to NO-dependent inhibition of respiration. In conclusion, the hepatic response to chronic alcohol-dependent cytotoxicity involves a change in mitochondrial function dependent on the induction of iNOS. (HEPATOLOGY 2004;40:565-573.)

No abstract

Adaptation to oxidative and nitrosative stress occurs in cells first exposed to a nontoxic stress, resulting in the ability to tolerate a toxic challenge of the same or a related oxidant. Adaptation is observed in a wide variety of cells including endothelial cells on exposure to nitric oxide or oxidized lipids, and lung epithelial cells exposed to air-borne pollutants and toxicants. This acquired characteristic has been related to the regulation of a family of stress responding proteins including those that control the synthesis of the intracellular antioxidant glutathione. The focus of this article, which includes a review of recent results along with new data, is the regulation and signaling of glutathione biosynthesis, especially those relating to adaptive mechanisms. These concepts are illustrated with examples using nitric oxide and oxidized low density lipoprotein mediated adaptation to oxidative stress. These data are discussed in the context of other adaptive mechanisms relating to glutathione synthesis including those from dietary constituents such as curcumin.

Heme oxygenase-1 (HO-1) is a key cytoprotective enzyme and an established marker of oxidative stress. Increased HO-1 expression has been found in the resident macrophages in the alveolar spaces of smokers. The lipid peroxidation product 4-hydroxynonenal (HNE) is also increased in the bronchial and alveolar epithelium in response to cigarette smoke. This suggests a link between a chronic environmental stress, HNE formation, and HO-1 induction. HNE is both an agent of oxidative stress in vivo and a potent cell signaling molecule. We hypothesize that HNE acts as an endogenously produced pulmonary signaling molecule that elicits an adaptive response culminating in the induction of HO-1. Here we demonstrate that HNE increases HO-1 mRNA, protein, and activity in pulmonary epithelial cells and identify ERK as a key pathway involved. Treatment with HNE increased ERK phosphorylation, c-Fos protein, JNK phosphorylation, c-Jun phosphorylation, and AP-1 binding. Whereas inhibiting the ERK pathway with the MEK inhibitor PD98059 significantly decreased HNEmediated ERK phosphorylation, c-Fos protein induction, AP-1 binding, and HO-1 protein induction, inhibition of the ERK pathway had no effect on HNE-induced HO-1 mRNA. This suggests that ERK is involved in the increase in HO-1 through regulation of translation rather than transcription. Keywords 4-Hydroxynonenal; Oxidative stress; HO-1; MAPK signaling; Free radicals Heme oxygenase-1 (HO-1) is an important cytoprotective enzyme and widely accepted marker of oxidative stress. HO-1 catalyzes the first and rate-limiting step in the catabolism of heme, which generates equimolar amounts of biliverdin, ferrous iron, and carbon monoxide [1][2][3]. Although heme is the major substrate of HO-1, a variety of non-heme-containing agents are also strong inducers of HO-1. HO-1 has been shown to respond to a number of proinflammatory cytokines, including TNF-α, . HO-1 is also induced by a variety of agents NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript that cause oxidative stress and/or in response to environmental stress [5][6][7][8]. For example, increased HO-1 expression has recently been found in the alveolar spaces in the resident macrophages of smokers [9]. Once induced, HO-1 provides protection against multiple types of tissue injury [10][11][12][13]; specific to the lung, overexpression of HO-1 in pulmonary epithelial cells has been shown to protect against oxygen toxicity [14]. In contrast, HO-1 deficiency in mice (HO-1 −/− ) increases susceptibility to inflammatory lung injury [15], as does HO-1 deficiency in humans [16]. Although the precise mechanisms by which HO-1 exerts its cytoprotective effects are not known, there is mounting evidence that carbon monoxide plays a key role in this process. For thorough reviews of the recent literature see [17,18].Another characteristic of oxidative stress is the formation of the lipid peroxidation product 4-hydroxy-2-nonenal (HNE). HNE has been shown to increase HO-1 in the cell [19,20], but the mechanism(s...

cOspZ is an effector protein of the type III secretion system in Shigella spp. that downregulates the human inflammatory response during bacterial infection. The ospZ gene is located on the large virulence plasmid of Shigella. Many genes on this plasmid are transcriptionally repressed by the nucleoid structuring protein H-NS and derepressed by VirB, a DNA-binding protein that displays homology to the plasmid partitioning proteins ParB and SopB. In this study, we characterized the ospZ promoter and investigated its regulation by H-NS and VirB in Shigella flexneri. We show that H-NS represses and VirB partially derepresses the ospZ promoter. H-NS-mediated repression requires sequences located between ؊731 and ؊412 relative to the beginning of the ospZ gene. Notably, the VirB-dependent derepression of ospZ requires the same VirB binding sites as are required for the VirBdependent derepression of the divergent icsP gene. These sites are centered 425 bp upstream of the ospZ gene but over 1 kb upstream of the icsP transcription start site. Although these VirB binding sites lie closer to ospZ than icsP, the VirB-dependent increase in ospZ promoter activity is lower than that observed at the icsP promoter. This indicates that the proximity of VirB binding sites to Shigella promoters does not necessarily correlate with the level of VirB-dependent derepression. These findings have implications for virulence gene regulation in Shigella and other pathogens that control gene expression using mechanisms of transcriptional repression and derepression.