Coordinate up- and down-regulation of glutathione-dependent prostaglandin E synthase and cyclooxygenase-2 in A549 cells. Inhibition by NS-398 and leukotriene C4.

Recently, a microsomal protein with 38% sequence identity to microsomal glutathione S-transferase 1 was shown to constitute an inducible, glutathione-dependent prostaglandin E synthase (PGES). To investigate the relationship between cyclooxygenase and PGES, a time-course study on protein expression was performed in A549 cells after treatment with interleukin-1beta. The result demonstrated a tandem expression of cyclooxygenase-2 and PGES. The observed induction of PGES protein correlated with microsomal PGES activity. No comparable PGES activity was observed in the absence of glutathione or in the cytosolic fraction. In addition, tumour necrosis factor-alpha was found to induce PGES in these cells. Dexamethasone was found to completely suppress the effect of both cytokines on PGES induction. We also describe a quantitative method, based on RP-HPLC with UV detection for the measurements of PGES activity. This method was used to screen potential PGES inhibitors. Several nonsteroidal anti-inflammatory drugs, stable prostaglandin H2 analogues and cysteinyl leukotrienes were screened for inhibition of PGES activity. NS-398, sulindac sulfide and leukotriene C4 were all found to inhibit PGES activity with IC50 values of 20 microM, 80 microM and 5 microM, respectively. In conclusion, it appears that PGES and cyclooxygenase-2 are functionally coupled in A549 cells and that a required coordinate expression of these enzymes allows for efficient biosynthesis of prostaglandin E2.     

Repression of cytochrome P450 by cytokines: IL-1β counteracts clofibric acid induction of CYP4A in cultured fetal rat hepatocytes

Interleukin-1 is known to repress a number of hepatic drug-metabolizing enzymes in rats and humans. The effect of interleukin-1 on lauric acid 12-hydroxylase (CYP4A family) was studied in cultured fetal rat hepatocytes after clofibric acid induction. Dexamethasone was used as an agent promoting differentiation and long-term maintenance of active hepatocytes. Dexamethasone and clofibric acid in combination allowed maximal (13.5-fold) induction of CYP4A1. Lauric acid 12-hydroxylase activity was found to increase with time in culture. Interleukin-1 adversely affected P4504A clofibric acid-induced activity, totally eliminating the effect of induction at doses exceeding 5 ng/ml. This repression/inhibition was dose-dependent. The mechanism by which interleukin-1 prevents the development of cytochrome P4504A activity is unclear.Abbreviations CA clofibric acid - CM culture medium - d day - D dexamethasone - IL-1 interleukin-1 - LAH lauric acid 12-hydroxylase - PB phenobarbital - PPAR phenobarbital - PPAR peroxisome proliferator activated receptor     

Interleukin-1 beta and transforming growth factor-beta 2 enhance cytosolic high-molecular-mass phospholipase A2 activity and induce prostaglandin E2 formation in rat mesangial cells.

Interleukin-1 beta induces gene expression and secretion of group-II phospholipase A2 and release of prostaglandin E2 from rat mesangial cells. The interleukin-1 beta-induced synthesis of group-II phospholipase A2 is prevented by transforming growth factor-beta 2, whereas transforming growth factor-beta 2 potentiated the interleukin-1 beta-evoked prostaglandin E2 production. Transforming growth factor-beta 2 itself did not induce synthesis of group-II phospholipase A2, although it stimulated prostaglandin E2 formation. Here we describe the effect of interleukin-1 beta and transforming growth factor-beta 2 on a cytosolic phospholipase A2 activity and prostaglandin E2 formation in rat mesangial cells. Based on the resistance to dithiothreitol and migration profiles on a Mono-Q anion-exchange column and a Superose 12 gel-filtration column, the cytosolic phospholipase A2 activity was assigned to a high-molecular-mass phospholipase A2. Measured with 1-stearoyl-2-[1-14C]arachidonoylglycero-phosphocholine as substrate, both interleukin-1 beta and transforming growth factor-beta 2 enhanced the high-molecular-mass phospholipase A2 activity. The stimulation of rat mesangial cells with interleukin-1 beta and transforming growth factor-beta 2 was time- and dose-dependent with maximal cytosolic phospholipase A2 activities at 10 nM and at 10 ng/ml respectively, after 24 h of stimulation. Under these conditions, interleukin-1 beta and transforming growth factor-beta 2 enhanced the cytosolic phospholipase A2 activity 2.2 +/- 0.6-fold and 2.5 +/- 0.6-fold, respectively. These results strongly suggest that an enhanced cytosolic high-molecular-mass phospholipase A2 activity is involved in the formation of prostaglandin E2 mediated by transforming growth factor-beta 2. Whether interleukin-1 beta induced group-II phospholipase A2 and/or interleukin-1 beta-enhanced cytosolic phospholipase A2 activity is involved in prostaglandin E2 formation in rat mesangial cells is discussed.     

The murine DUB-1 gene is specifically induced by the betac subunit of interleukin-3 receptor.

Cytokines regulate cell growth and differentiation by inducing the expression of specific target genes. We have recently isolated a cytokine-inducible, immediate-early cDNA, DUB-1, that encodes a deubiquitinating enzyme. The DUB-1 mRNA was specifically induced by the receptors for interleukin-3, granulocyte-macrophage colony-stimulating factor, and interleukin-5, suggesting a role for the beta common (betac subunit known to be shared by these receptors. In order to identify the mechanism of cytokine induction, we isolated a murine genomic clone for DUB-1 containing a functional promoter region. The DUB-1 gene contains two exons, and the nucleotide sequence of its coding region is identical to the sequence of DUB-1 cDNA. Various regions of the 5' flanking region of the DUB-1 gene were assayed for cytokine-inducible activity. An enhancer region that retains the beta c-specific inducible activity of the DUB-1 gene was identified. Enhancer activity was localized to a 112-bp fragment located 1.4 kb upstream from the ATG start codon. Gel mobility shift assays revealed two specific protein complexes that bound to this minimal enhancer region. One complex was induced by betac signaling, while the other was noninducible. Finally, the membrane-proximal region of human betac was required for DUB-1 induction. In conclusion, DUB-1 is the first example of an immediate-early gene that is induced by a specific subunit of a cytokine receptor. Further analysis of the DUB-1 enhancer element may reveal specific determinants of a betac-specific signaling pathway.     

Acute phase protein response and polymorphonuclear leukocyte cathepsin g release after slow interleukin-1 stimulation in the rat

In this work we have studied the acute phase protein response and degranulation of polymorphonuclear leukocytes in vivo in the rat after a slow interleukin-1beta stimulation. A total dose of 1 mug, 2 mug, 4 mug and 0 mug (controls with only vehicle) of interleukin-1beta was released from osmotic minipumps over a period of 7 days. The pumps were implanted subcutaneously. A cystic formation was formed around the pumps that contained interleukin-1beta whereas no tissue reaction was seen around pumps containing only vehicle. Besides flbroblasts the cyst wall contained numerous polymorphonuclear leukocytes which were positively stained for cathespin G. alpha(2)-macroglobulin, alpha(1)-inhtbitor-3, alpha(1)-proteinase inhibitor, albumin and C3 were measured by electroimmunoassay and all showed plasma concentration patterns that were dose-dependent to the amount of interleuktn-1beta released. Fibrinogen in plasma was elevated in the control group but showed decreased plasma values with higher doses of interleukin-1beta released. All animals showed increased plasma levels of cathespin G but the lowest levels for cathespin G were seen for the highest interleukin-1beta dose released. It was clearly seen that a slow continuous release of interleukin-1beta in vivo caused an inflammatory reaction. Plasma levels for the proteins analysed all showed a similar pattern, namely an initial increase or decrease of plasma concentration followed by a tendency to normalization of plasma values. It was concluded that a long-term interleukin-1beta release could not sustain the acute phase protein response elicited by the initial interleukin-1beta release.     

Tumor necrosis factor-alpha-induced caspase-1 gene expression. Role of p73

Tumour necrosis factor-alpha (TNF-alpha) is a cytokine that is involved in many functions, including the inflammatory response, immunity and apoptosis. Some of the responses of TNF-alpha are mediated by caspase-1, which is involved in the production of the pro-inflammatory cytokines interleukin-1beta, interleukin-18 and interleukin-33. The molecular mechanisms involved in TNF-alpha-induced caspase-1 gene expression remain poorly defined, despite the fact that signaling by TNF-alpha has been well studied. The present study was undertaken to investigate the mechanisms involved in the induction of caspase-1 gene expression by TNF-alpha. Treatment of A549 cells with TNF-alpha resulted in an increase in caspase-1 mRNA and protein expression, which was preceded by an increase in interferon regulatory factor-1 and p73 protein levels. Caspase-1 promoter reporter was activated by the treatment of cells with TNF-alpha. Mutation of the interferon regulatory factor-1 binding site resulted in the almost complete loss of basal as well as of TNF-alpha-induced caspase-1 promoter activity. Mutation of the p53/p73 responsive site resulted in reduced TNF-alpha-induced promoter activity. Blocking of p73 function by a dominant negative mutant or by a p73-directed small hairpin RNA reduced basal as well as TNF-alpha-induced caspase-1 promoter activity. TNF-alpha-induced caspase-1 mRNA and protein levels were reduced when p73 mRNA was down-regulated by small hairpin RNA. Caspase-5 gene expression was induced by TNF-alpha, which was inhibited by the small hairpin RNA-mediated down-regulation of p73. Our results show that TNF-alpha induces p73 gene expression, which, together with interferon regulatory factor-1, plays an important role in mediating caspase-1 promoter activation by TNF-alpha.     

p38 MAPK regulates group IIa phospholipase A2 expression in interleukin-1beta -stimulated rat neonatal cardiomyocytes

Group IIa phospholipase A(2) (GIIa PLA(2)) is released by some cells in response to interleukin-1beta. The purpose of this study was to determine whether interleukin-1beta would stimulate the synthesis and release of GIIa PLA(2) from cardiomyocytes, and to define the role of p38 MAPK and cytosolic PLA(2) in the regulation of this process. Whereas GIIa PLA(2) mRNA was not identified in untreated cells, exposure to interleukin-1beta resulted in the sustained expression of GIIa PLA(2) mRNA. Interleukin-1beta also stimulated a progressive increase in cellular and extracellular GIIa PLA(2) protein levels and increased extracellular PLA(2) activity 70-fold. In addition, interleukin-1beta stimulated the p38 MAPK-dependent activation of the downstream MAPK-activated protein kinase, MAPKAP-K2. Treatment with the p38 MAPK inhibitor, SB202190, decreased interleukin-1beta stimulated MAPKAP-K2 activity, GIIa PLA(2) mRNA expression, GIIa PLA(2) protein synthesis, and the release of extracellular PLA(2) activity. Infection with an adenovirus encoding a constitutively active form of MKK6, MKK6(Glu), which selectively phosphorylates p38 MAPK, induced cellular GIIa PLA(2) protein synthesis and the release of GIIa PLA(2) and increased extracellular PLA(2) activity 3-fold. In contrast, infection with an adenovirus encoding a phosphorylation-resistant MKK6, MKK6(A), did not result in GIIa PLA(2) protein synthesis or release by unstimulated cardiomyocytes. In addition, infection with an adenovirus encoding MKK6(A) abrogated GIIa PLA(2) protein synthesis and release by interleukin-1beta-stimulated cells. These results provide direct evidence that p38 MAPK activation was necessary for interleukin-1beta-induced synthesis and release of GIIa PLA(2) by cardiomyocytes.     

Natural selection and early changes of phenotype of tumor cells in vivo: acquisition of new defense mechanisms

This review summarizes results obtained in the author's and collaborating laboratories within the last decade and is designed to attract the attention of researchers to discrete biochemical mechanisms of protection acquired in vivo by cells of malignant tumors against effectors of innate antitumor immunity. Tumor progression in vivo is associated with the appearance and selection of tumor cells with new specific characteristics: a high level of H(2)O(2)-catabolizing (antioxidant) activity (H(2)O(2)CA) and the ability for immediate release of E2-type prostaglandin (PGES) on contact with natural killers, macrophages, and neutrophils; the expression of the [H(2)O(2)CA + PGES] phenotype provides the tumor cells with two mechanisms of local protection against effectors of innate and acquired antitumor immunity. This results in a 10-100-fold less effective rejection of tumor cells in immune and normal animals and corresponding increase of tumorigenicity. The in vitro transformation of normal fibroblasts, spontaneous or induced by oncogenes LTSV40, E1a,b, Ha-ras, myc, and also by p53(175) and bcl-2 does not result in the [H(2)O(2)CA + PGES] phenotype expression, but during subsequent in vivo growth of the above-mentioned transformants the selection of tumor cells of the [H(2)O(2)CA + PGES] phenotype is correlated with a 30-200-fold increase in their tumorigenicity (accompanied or not accompanied by spontaneous metastatic activity). Unlike the transformation induced by the above-mentioned oncogenes, the transformation of normal cells by the v-src gene results in the [H(2)O(2)CA + PGES] phenotype expression. The data presented confirm the determining role of the v-src gene in the expression of the [H(2)O(2)CA + PGES] phenotype. In various primary viral carcinogenesis (SV40, SA7(C8)) the natural selection of cells expressing the [H(2)O(2)CA + PGES] phenotype begins even within the latent period and can be completed by the appearance of primary tumors.     

Interleukin-1 beta- and forskolin-induced synthesis and secretion of group II phospholipase A2 and prostaglandin E2 in rat mesangial cells is prevented by transforming growth factor-beta 2.

Interleukin-1 beta and forskolin induce prostaglandin E2 release as well as 14-kDa group II phospholipase A2 gene expression and secretion of the enzyme from rat glomerular mesangial cells. We now report that pretreatment of mesangial cells with transforming growth factor-beta 2 prior to stimulation with interleukin-1 beta or forskolin inhibits the induced release of prostaglandin E2. At the same time the secretion of group II phospholipase A2, measured both as enzyme activity with sn-2-labeled phosphatidylethanolamine as substrate and as enzyme protein in immunoblot experiments, is dose-dependently inhibited by pretreatment of the cells with transforming growth factor-beta 2. Analyses of enzyme activity and enzyme protein levels in the cells indicated that this is not due to inhibition of enzyme secretion with a concomitant increase in cellular levels of the enzyme. Rather, pretreatment of the cells with transforming growth factor-beta 2 largely prevented both the interleukin-1 beta- and the forskolin-induced synthesis of phospholipase A2. This is the first report indicating an inhibition of group II phospholipase A2 gene expression by transforming growth factor-beta 2. In line with those results, transforming growth factor-beta 2 did not induce the synthesis and secretion of group II phospholipase A2. However, under conditions where the interleukin-1 beta-induced expression of group II phospholipase A2 is fully suppressed by transforming growth factor-beta 2, the growth factor itself stimulated prostaglandin E2 synthesis by a mechanism apparently not involving group II phospholipase A2. The immunochemical identification of the inducible and secretable phospholipase A2 from rat mesangial cells as a group II enzyme was confirmed by purification and N-terminal amino acid sequence determination.     

A short synthetic peptide fragment of human interleukin-1 beta increases both human and murine natural killer activity

The effect of a short synthetic fragment of human interleukin-1 beta (hu IL-1 beta) on natural killer (NK) activity was examined. Peripheral-blood mononuclear cells (PBMC) from normal donors showed a significant increase in NK activity against K562 leukemia cells after preincubation for 18 h with the IL-1 peptide. A similar augmentation was not observed after culturing the cells in the presence of hu IL-1 beta. The increase in tumor cell lysis could not be ascribed to a cytolytic activity of the synthetic fragment on target cells, since the peptide caused no direct lysis of various tumor cell lines. Although the peptide enhanced NK cytotoxicity of PBMC, highly purified large granular lymphocytes were not susceptible to its stimulatory effect. The addition to the cultures of antibodies to human interleukin-2 (hu IL-2) completely blocked the peptide-induced boost of NK cytotoxicity, suggesting that IL-2 is mainly involved in the activation process. The ability of the IL-1 peptide to increase NK activity was further confirmed in vivo in the mouse. Cytotoxicity against YAC-1 lymphoma cells, which was very low in the spleen of untreated BALB/c mice, was in fact significantly increased after a single inoculation of the peptide. These data thus indicate that a short synthetic peptide fragment of hu IL-1 beta is able to increase both human and murine NK activity.     

The caspase-1 inflammasome: a pilot of innate immune responses

The inflammasome is a large multiprotein complex whose assembly leads to the activation of caspase-1, which promotes the maturation of proinflammatory cytokines interleukin-1beta (IL-1beta) and IL-18. Proteins encoded by the nucleotide-binding domain and leucine-rich repeat (NLR) containing gene family form the central components of inflammasomes and act as intracellular sensors to detect cytosolic microbial components and "danger" signals (such as ATP and toxins). The inflammasome not only plays a pivotal role in innate immune responses toward pathogens but also mediates the activity of aluminum adjuvants. Thus, the inflammasome and associated signaling pathways are attractive targets for new therapeutics and vaccines.