Induction of nitric oxide synthase by protein synthesis inhibition in aortic smooth muscle cells

Stress Activation of Mammary Epithelial Cell Xanthine Oxidoreductase Is Mediated by p38 MAPK and CCAAT/Enhancer-binding Protein-β

Xanthine oxidoreductase (XOR) catalyzes the formation of uric acid from xanthine and hypoxanthine and is recognized as a source of reactive oxygen and nitrogen species. Unexpectedly, XOR was found to play an essential role in milk secretion in the differentiating mammary gland, where it is an integral component of the milk fat globule. XOR gene expression in both mammary glands and differentiating mammary epithelial cells in culture is regulated by the lactogenic hormones prolactin and cortisol. Expression in mammary epithelial cells is also regulated by inflammatory cytokines and induced by cycloheximide. Cycloheximide was found to stimulate XOR gene expression in differentiating HC11 mouse mammary epithelial cells. Activation of XOR gene expression by both cycloheximide and inflammatory cytokines suggested that XOR may be regulated by stress-activated protein kinases, the MAPKs. We demonstrate here that XOR was induced in HC11 cells by low dose cycloheximide and that expression was blocked by inhibitors of p38 MAPK. Accumulation of phospho-p38 was stimulated by low dose cycloheximide. Low dose cycloheximide stress promoted phosphorylation and nuclear accumulation of the CCAAT/enhancer-binding protein-beta (C/EBPbeta) transcription factor, which was blocked by inhibition of p38. Furthermore, C/EBPbeta was found to activate the mouse XOR promoter, and XOR promoter-C/EBPbeta protein complexes were induced by low dose cycloheximide stress. These data demonstrate, for the first time, that mouse mammary epithelial cell XOR is regulated by p38 MAPK. They identify an essential function of the C/EBPbeta transcription factor in mouse XOR expression and suggest a potential role for p38 MAPK activation of C/EBPbeta in mammary epithelial cells.

The biology of exhaled nitric oxide (NO) in ischemia–reperfusion-induced lung injury: A tale of dynamism of NO production and consumption

The main objective of this paper is to review the potential diagnostic roles of exhaled nitric oxide (NO) in evaluating ischemia-reperfusion-induced lung injury associated with cardiac surgery. We shall start by elaborating on current clinical practice of cardiac surgery and to arrive at the conclusion that clinically important ischemia-reperfusion injury is a common scenario of many forms of these surgical procedures. We shall conclude this part by establishing the clinical need for biomarkers of inflammation in cardiothoracic surgery and by proposing that exhaled NO could be an important new addition to our anaesthetic monitoring repertoire based on our expertise with exhaled breath monitoring. We shall then take a closer look at mechanisms of ischemia-reperfusion injury and will propose the role of reactive oxygen and nitrogen species as mediators and biomarkers of acute lung injury. This analysis will provide a good opportunity to highlight major potential mechanisms of altered NO production and bioactivity of NO. We shall conclude that multiple relevant mechanisms may either lead to increased production of NO or enhance consumption of NO, leaving us with the paradigm that NO maybe used either as a positive or negative biomarker of inflammation. In order to explore this dilemma further, we will investigate the predominant effect of oxidative stress on NO bioactivity in cell culture models of ischemia-reperfusion injury. We will then turn to animal models of ischemia-reperfusion injury to elucidate the ultimate effects of this condition on lung NO production and concentrations of NO in the lung. Finally, we shall complete this journey by highlighting the human relevance of these observations by reviewing our own experience at Harefield Hospital, UK, and that of others, regarding exhaled NO in ischemia-reperfusion injury associated with cardiac surgery and lung transplantation.

Inhibitory mechanisms of YC-1 and PMC in the induction of iNOS expression by lipoteichoic acid in RAW 264.7 macrophages

In the present study, the signal pathways involved in NO formation and iNOS expression in RAW 264.7 macrophages stimulated by LTA were investigated. We also compared the relative inhibitory activities and mechanisms of PMC, a novel potent antioxidant of alpha-tocopherol derivatives, with those of YC-1, an sGC activator, on the induction of iNOS expression by LTA in cultured macrophages in vitro and LTA-induced hypotension in vivo. LTA induced concentration (0.1-50 microg/mL)- and time (4-24 hr)-dependent increases in nitrite (an indicator of NO biosynthesis) in macrophages. Both PMC (50 microM) and YC-1 (10 microM) inhibited NO production, iNOS protein, mRNA expression, and IkappaBalpha degradation upon stimulation by LTA (20 microg/mL) in macrophages. On the other hand, PMC (50 microM) almost completely suppressed JNK/SAPK activation, whereas YC-1 (10 microM) only partially inhibited its activation in LTA-stimulated macrophages. Moreover, PMC (10 mg/kg, i.v.) and YC-1 (5 mg/kg, i.v.) significantly inhibited the fall in MAP stimulated by LTA (10 mg/kg, i.v.) in rats. In conclusion, we demonstrate that YC-1 shows more-potent activity than PMC at abrogating the expression of iNOS in macrophages in vitro and reversing delayed hypotension in rats with endotoxic shock stimulated by LTA. The inhibitory mechanisms of PMC may be due to its antioxidative properties, with a resulting influence on JNK/SAPK and NF-kappaB activations. YC-1 may be mediated by increasing cyclic GMP, followed by, at least partly, inhibition of JNK/SAPK and NF-kappaB activations, thereby leading to inhibition of iNOS expression.

A novel antioxidant, octyl caffeate, suppression of LPS/IFN-gamma-induced inducible nitric oxide synthase gene expression in rat aortic smooth muscle cells

In the present study, we investigated the effects and mechanisms of a novel potent antioxidant, octyl caffeate, on the induction of iNOS expression by lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) in cultured primary rat aortic smooth muscle cells (RASMCs) in vitro and LPS-induced hypotension in vivo. Octyl caffeate (0.1-1.0 microM) exerted a concentration-dependent inhibition of iron-catalyzed lipid peroxidation in rat brain homogenates. Furthermore, octyl caffeate (20, 50, and 100 microM) concentration-dependently diminished the initial rate of superoxide-induced NBT reduction and the enzymatic activity of xanthine oxidase. It also concentration-dependently (1-50 microM) inhibited the NO production, iNOS protein and messenger RNA expressions upon stimulation by LPS (100 microg/mL)/IFN-gamma (100U/mL) in RASMCs. In addition, we found that octyl caffeate did not significantly affect IkappaBalpha degradation stimulated by LPS/IFN-gamma in RASMCs. On the other hand, octyl caffeate (10 and 50 microM) significantly suppressed activation of c-Jun-N-terminal kinase and extracellular signal-regulated kinase. Moreover, octyl caffeate (10mg/kg, i.v.) significantly inhibited the fall in mean arterial pressure stimulated by LPS (7.5mg/kg) in rats. In conclusion, we demonstrate that a novel potent antioxidant, octyl caffeate, significantly ameliorates circulatory failure of endotoxemia in vivo by a mechanism involving suppression of iNOS expression through inactivation of mitogen-activated protein kinases in RASMCs.

p38 Triggers late preconditioning elicited by anisomycin in heart: involvement of NF-kappaB and iNOS

We investigated the role of stress-activated p38 MAP kinase (p38/SAPK-2) signaling in delayed preconditioning of the heart. Adult male out-bred ICR mice were treated with p38 activator, anisomycin (0.1 mg/kg IP), or vehicle (5% DMSO). Twenty-four hours later, hearts were perfused in Langendorff mode and subjected to 30 minutes of ischemia and 30 minutes of reperfusion. Improvement in postischemic recovery of end-diastolic pressure and reduction in infarct size was observed, which was abolished by SB203580, a specific p38 inhibitor, and pyrrolidinediethyldithiocarbamate (PDTC), the NF-kappaB inhibitor, but not by PD 98059, a specific inhibitor for MEK1 or 2. Transient increase in p38 phosphorylation was observed 15 minutes after anisomycin treatment which subsided by 30 minutes. Electrophoretic mobility shift assay demonstrated rapid activation of NF-kappaB DNA binding with anisomycin, peaking at 30 minutes. Western blot confirmed the accumulation of p50 and p65 in nuclear extracts after anisomycin treatment. Anisomycin-induced NF-kappaB DNA binding activity was inhibited by SB203580 and PDTC. Expression of inducible nitric oxide synthase (iNOS) mRNA, protein, and nitric oxide (NO) synthesis were enhanced in anisomycin-treated mice. SB203580 and PDTC blocked the increased expression of iNOS and increase in synthesis of NO. Selective iNOS inhibitor S-methylisothiourea abolished the protective effect of anisomycin. Furthermore, postischemic cardioprotective effect of anisomycin was absent in mice with targeted ablation of iNOS gene but not in the wild-type B6.129 mice. For the first time, these results suggest that direct pharmacological activation of p38 triggers delayed preconditioning by signaling mechanism involving NF-kappaB activation and synthesis of NO from iNOS.

Molecular cloning and analysis of the rat inducible nitric oxide synthase gene promoter in aortic smooth muscle cells

We have cloned five DNA fragments (-0.32, -0.48, -1.7, -3.2, and -5.1 kb) of the 5'-flanking region of the rat inducible nitric oxide synthase (iNOS) gene from rat genomic DNA. The functional importance of the 5'-flanking region was determined by transient expression of iNOS promoter-luciferase constructs in cultures of rat aortic smooth muscle cells. The -0.48 kb construct, containing one nuclear factor kappaB (NF-kappaB) binding site, expressed basal promoter activity but showed only a 1.5- and 1.7-fold increase in luciferase activity in response to lipopolysaccharide (LPS) or a cytokine mixture, respectively. However, the -3.2 kb construct (containing a second NF-kappaB binding site) showed full promoter activity with a 24-fold increase in response to LPS or cytokine mixture. The -5.1 kb construct showed no further increase in luciferase activity, suggesting that the 1.9 kb upstream of -3.2 kb may not be important in rat iNOS regulation. Rat iNOS promoter induction did not appear to be transcriptionally regulated by NO since NOS inhibitors did not affect induction. These data are in marked contrast to the mouse iNOS promoter in which a DNA sequence as short as a -85 bp, containing one NF-kappaB site, confers 10-fold inducibility by LPS. The present findings demonstrate that the rat iNOS gene is transcriptionally regulated by cytokines and LPS, but, unlike the mouse gene, the downstream NF-kappaB site does not appear to be a key region in responses to cytokines and LPS. These data suggest that the regulation of the rat gene may require the coexistence of at least two NF-kappaB sites or other elements upstream of -0.48 kb of the 5'-flanking region.