Cytokine-mediated transcriptional induction of the human inducible nitric oxide synthase gene requires both activator protein 1 and nuclear factor kappaB-binding sites

Clinorotation upregulates inducible nitric oxide synthase by inhibiting AP-1 activation in human umbilical vein endothelial cells

Alterations of nitric oxide contribute to post-flight orthostatic intolerance. The aim of this study was to investigate the changes of inducible nitric oxide synthase (iNOS) and the mechanisms underlying regulation of iNOS by simulated microgravity in human umbilical vein endothelial cells (HUVECs). Clinorotation, a simulated-model of microgravity, increased iNOS expression and promoter activity in HUVECs. The transactivations of NF-kappaB and AP-1 were suppressed by 24 h clinorotation. A key role for AP-1, but not NF-kappaB in the regulation of iNOS was shown. (1) PDTC, a NF-kappaB inhibitor, had no effect on clinorotation upregulation of iNOS. (2) SP600125, a JNK-specific inhibitor, which resulted in inhibition of AP-1 activity, enhanced the iNOS expression and promoter activity in clinorotation. (3) Overexpression of AP-1 remarkably attenuated the upregulation effect of clinorotation. These findings indicate that clinorotation upregulates iNOS in HUVECs by a mechanism dependent on suppression of AP-1, but not NF-kappaB. These results support a key role for AP-1 in the signaling of postflight orthostatic intolerance.

A far-upstream Oct-1 motif regulates cytokine-induced transcription of the human inducible nitric oxide synthase gene

Transcriptional regulation of the human inducible nitric oxide synthase (hiNOS) gene is highly complex and requires an orchestrated flow of positive and negative transcription factors that bind to specific cis-acting upstream response elements. Very little specific information exists about the far-upstream region of the hiNOS gene. Oct-1 protein belongs to the Pit-Oct-Unc domain transcription factor family and is constitutively expressed in all dividing cells. It is essential for proliferation, differentiation, and other key cell processes. However, the role of Oct-1 in regulating hiNOS gene expression has not been reported. In this work, the octamer sequence 5'-ATGCAAAT-3' at -10.2 kb in the hiNOS promoter was identified as high-affinity Oct-1 binding by electrophoretic mobility shift assay in vitro and chromatin immunoprecipitation assay in vivo. Mutation of Oct-1 motif at -10.2 kb in the hiNOS promoter decreased cytokine-induced hiNOS promoter activity by 40%. Cytokine-induced hiNOS promoter activity was also significantly reduced by Oct-1 small interfering RNA targeting. Overexpression of Oct-1 increased cytokine-induced hiNOS protein expression in primary human hepatocytes. Furthermore, the Oct-1 motif at -10.2 kb of the hiNOS promoter conferred increased transcriptional activity to the heterologous thymidine kinase promoter irrespective of cytokine induction. Taken together, this work identifies a far-upstream functional Oct-1 enhancer motif at -10.2 kb in the hiNOS promoter that regulates cytokine-induced hiNOS gene transcription and further underscores tight control mechanisms regulating the expression of the hiNOS gene.

Pressure activates epidermal growth factor receptor leading to the induction of iNOS via NFkappaB and STAT3 in human proximal tubule cells

Ureteral obstruction leads to increased pressure and inducible nitric oxide synthase (iNOS) expression. This study examined the involvement of epidermal growth factor (EGF) receptor (EGFR), nuclear factor-kappaB (NFkappaB), and signal transducers and activators of transcription 3 (STAT3) in iNOS induction in human proximal tubule (HKC-8) cells in response to pressure or EGF. HKC-8 cells were subjected to 60 mmHg pressure or treated with EGF for 0-36 h. iNOS was more rapidly induced in response to EGF than pressure. The addition of EGFR, NFkappaB, and STAT3 inhibitors significantly suppressed pressure- or EGF-stimulated iNOS mRNA and protein expression. Analysis of the activated states of EGFR, NFkappaB p65, and STAT3 after exposure to both stimuli demonstrated phosphorylation within 2.5 min. Anti-EGF antibody inhibited iNOS induction in pressurized HKC-8 cells, providing evidence that endogenous EGF mediates the response to pressure. In ureteral obstruction, when pressure is elevated, phosphorylated EGFR was detected in the apical surface of the renal tubules, validating the in vitro findings. These data indicate that EGFR, NFkappaB, and STAT3 are required for human iNOS gene induction in response to pressure or EGF, indicating a similar mechanism of activation.

Effects of cranberry extracts and ursolic acid derivatives on P-fimbriated Escherichia coli, COX-2 activity, pro-inflammatory cytokine release and the NF-kappabeta transcriptional response in vitro

Cranberry, the fresh or dried ripe fruit of Vaccinium macrocarpon Ait. (Ericaceae), is currently used as adjunct therapy for the prevention and symptomatic treatment of urinary tract infections. Data from clinical trials suggest that extracts of cranberry or cranberry juice reduce the bacterial load of E. coli and also suppress the inflammatory symptoms induced by E. coli infections. A methanol extract prepared from 10 kg of dehydrated cranberries did not directly inhibit the growth of E coli strains ATCC 700336 or ATCC 25922 in concentrations up to 256 mug/mL in vitro. However, the methanol extract (CR-ME) inhibited the activity of cyclooxygenase-2, with an IC(50) of 12.8 mug/mL. Moreover, CR-ME also inhibited the NF-kappabeta transcriptional activation in human T lymphocytes with an IC(50) of 19.4 mug/mL, and significantly (p < 0.01) inhibited the release of interleukin (IL)-1beta, IL-6, IL-8 and tumor necrosis factor-alpha from E. coli lipopolysaccharide (LPS)-stimulated human peripheral blood mononuclear cells in vitro, at a concentration of 50 mug/mL. The extract had no effect on inducible nitric oxide synthase activity in the murine macrophage cell line RAW 264.7. The compounds responsible for this activity were identified using a novel LC-MS based assay as ursolic acid and ursolic acid derivatives. Taken together, these data suggest CR-ME and its constituent chemical compounds target specific pathways involved in E. coli-induced inflammation.

Pivotal role of c-Fos in nitric oxide synthase 2 expression in airway epithelial cells

The regulation of nitric oxide synthase 2 (NOS2) in airway epithelial cells plays a key role in the innate host response to a wide variety of microbial agents and also participates in the generation of pathologic airway inflammation. Among the important signalling cascades that direct NOS2 gene expression are nuclear factor kappaB (NFkappaB) and interferon-gamma (IFNgamma)/signal transducer and activator of transcription 1 (STAT-1). Previous studies suggest activator protein-1 (AP-1), in particular c-Fos component of AP-1, influences NOS2 expression. We investigated the effect of c-Fos modulation using RNA interference siRNA on NOS2 gene expression. A549 cells stably transfected with a plasmid overexpressing a c-Fos siRNA construct (FOSi) resulted in a decrease of NOS2 protein inducibility by IFN gamma. In contrast, classical IFN gamma inducible signal transduction pathways interferon regulated factor-1 (IRF-1) and pSTAT-1 were activated at a similar magnitude in FOSi and control cells. DNA-protein binding assays showed that c-Fos binding was present in wild type cells, but reduced in FOSi clones. FOSi clones had activation of NFkappaB detectable by DNA-protein binding assays, which may have contributed to a decrease of NOS2 expression. Overall, these studies indicate that c-Fos is a requisite and specific component for inducible NOS2 expression.

Withaferin A inhibits iNOS expression and nitric oxide production by Akt inactivation and down-regulating LPS-induced activity of NF-kappaB in RAW 264.7 cells

Induction of inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production is thought to have beneficial immunomodulatory effects in acute and chronic inflammatory disorders. In Raw 264.7 cells stimulated with lipopolysaccharide (LPS) to mimic inflammation, withaferin A inhibited LPS-induced expression of both iNOS protein and mRNA in a dose-dependent manner. To investigate the mechanism by which withaferin A inhibits iNOS gene expression, we examined activation of mitogen-activated protein kinases (MAPKs) and Akt in Raw 264.7 cells. We did not observe any significant changes in the phosphorylation of p38 MAPK in cells treated with LPS alone or LPS plus withaferin A. However, LPS-induced Akt phosphorylation was markedly inhibited by withaferin A, while the phosphorylation of p42/p44 extracellular signal-regulated kinases (ERKs) was slightly inhibited by withaferin A treatment. Withaferin A prevented IkappaB phosphorylation, blocking the subsequent nuclear translocation of nuclear factor-kappaB (NF-kappaB) and inhibiting its DNA binding activity. LPS-induced p65 phosphorylation, which is mediated by extracellular signal-regulated kinase (ERK) and Akt pathways, was attenuated by withaferin A treatment. Moreover, LPS-induced NO production and NF-kappaB activation were inhibited by SH-6, a specific inhibitor of Akt. Taken together, these results suggest that withaferin A inhibits inflammation through inhibition of NO production and iNOS expression, at least in part, by blocking Akt and subsequently down-regulating NF-kappaB activity.

Induction of iNOS by Chlamydophila pneumoniae requires MyD88-dependent activation of JNK

Innate immune cells produce NO via inducible NO synthase (iNOS) in response to certain infections or upon stimulation with cytokines such as IFN-gamma and TNF. NO plays an important role in host defense against intracellular bacteria including Chlamydophila pneumoniae as a result of its microbicidal activity. In MyD88-deficient mice, which succumb to C. pneumoniae infection, iNOS induction is impaired 6 days postinfection, although pulmonary levels of IFN-gamma and TNF are elevated as in wild-type mice at this time-point. Here, we demonstrate that induction of iNOS in macrophages upon C. pneumoniae infection is controlled by MyD88 via two pathways: NF-kappaB activation and phosphorylation of the MAPK JNK, which leads to the nuclear translocation of c-Jun, one of the two components of the AP-1 complex. In addition, phosphorylation of STAT1 and expression of IFN regulatory factor 1 (IRF-1) were delayed in the absence of MyD88 after C. pneumoniae infection but not after IFN-gamma stimulation. Taken together, our data show that for optimal induction of iNOS during C. pneumoniae infection, the concerted action of the MyD88-dependent transcription factors NF-kappaB and AP-1 and of the MyD88-independent transcription factors phosphorylated STAT1 and IRF-1 is required.

Silibinin inhibits cytokine-induced signaling cascades and down-regulates inducible nitric oxide synthase in human lung carcinoma A549 cells

Recently, we reported that silibinin inhibits primary lung tumor growth and progression in mice and down-regulates inducible nitric oxide synthase (iNOS) expression in tumors; however, the mechanisms of silibinin action are largely not understood. Also, the activation of signaling pathways inducing various transcription factors are associated with lung carcinogenesis and their inhibition could be an effective strategy to prevent and/or treat lung cancer. Herein, we used human lung epithelial carcinoma A549 cells to explore the potential mechanisms and observed strong iNOS expression by cytokine mixture (containing 100 units/mL IFN-gamma + 0.5 ng/mL interleukin-1beta + 10 ng/mL tumor necrosis factor-alpha). We also examined the cytokine mixture-activated signaling cascades, which could potentially up-regulate iNOS expression, and then examined the effect of silibinin (50-200 mumol/L) on these signaling cascades. Silibinin treatment inhibited, albeit to different extent, the cytokine mixture-induced activation of signal transducer and activator of transcription 1 (Tyr(701)), signal transducer and activator of transcription 3 (Tyr(705)), activator protein-1 family of transcription factors, and nuclear factor-kappaB. The results for activator protein-1 were correlated with the decreased nuclear levels of phosphorylated c-Jun, c-Jun, JunB, JunD, phosphorylated c-Fos, and c-Fos. Further, silibinin also strongly decreased cytokine mixture-induced phosphorylation of extracellular signal-regulated kinase 1/2 but only marginally affected JNK1/2 phosphorylation. Silibinin treatment also decreased constitutive p38 phosphorylation in the presence or absence of cytokine mixture. Downstream of these pathways, silibinin strongly decreased cytokine mixture-induced expression of hypoxia-inducible factor-1alpha without any considerable effect on Akt activation. Cytokine mixture-induced iNOS expression was completely inhibited by silibinin. Overall, these results suggest that silibinin could target multiple cytokine-induced signaling pathways to down-regulate iNOS expression in lung cancer cells and that could contribute to its overall cancer preventive efficacy against lung tumorigenesis.

Dynamic compression counteracts IL-1beta induced inducible nitric oxide synthase and cyclo-oxygenase-2 expression in chondrocyte/agarose constructs

Background

Nitric oxide and prostaglandin E₂ (PGE₂play pivotal roles in both the pathogenesis of osteoarthritis and catabolic processes in articular cartilage. These mediators are influenced by both IL-1β and mechanical loading, and involve alterations in the inducible nitric oxide synthase (iNOS) and cyclo-oxygenase (COX)-2 enzymes. To identify the specific interactions that are activated by both types of stimuli, we examined the effects of dynamic compression on levels of expression of iNOS and COX-2 and involvement of the p38 mitogen-activated protein kinase (MAPK) pathway.

Methods

Chondrocyte/agarose constructs were cultured under free-swelling conditions with or without IL-1β and/or SB203580 (inhibitor of p38 MAPK) for up to 48 hours. Using a fully characterized bioreactor system, constructs were subjected to dynamic compression for 6, 12 and 48 hours under similar treatments. The activation or inhibition of p38 MAPK by IL-1β and/or SB203580 was analyzed by western blotting. iNOS, COX-2, aggrecan and collagen type II signals were assessed utilizing real-time quantitative PCR coupled with molecular beacons. Release of nitrite and PGE₂ was quantified using biochemical assays. Two-way analysis of variance and the post hoc Bonferroni-corrected t-test were used to examine data.

Results

IL-1β activated the phosphorylation of p38 MAPK and this effect was abolished by SB203580. IL-1β induced a transient increase in iNOS expression and stimulated the production of nitrite release. Stimulation by either dynamic compression or SB203580 in isolation reduced the IL-1β induced iNOS expression and nitrite production. However, co-stimulation with both dynamic compression and SB203580 inhibited the expression levels of iNOS and production of nitrite induced by the cytokine. IL-1β induced a transient increase in COX-2 expression and stimulated the cumulative production of PGE₂ release. These effects were inhibited by dynamic compression or SB203580. Co-stimulation with both dynamic compression and SB203580 restored cytokine-induced inhibition of aggrecan expression. This is in contrast to collagen type II, in which we observed no response with the cytokine and/or SB203580.

Conclusion

These data suggest that dynamic compression directly influences the expression levels of iNOS and COX-2. These molecules are current targets for pharmacological intervention, raising the possibility for integrated pharmacological and biophysical therapies for the treatment of cartilage joint disorders.

High mobility group A1 protein mediates human nitric oxide synthase 2 gene expression

Nitric oxide synthase (NOS)2, an inducible enzyme that produces NO during inflammation, is transcriptionally regulated. Our goal was to determine whether high mobility group (HMG)A1 contributes to human (h)NOS2 gene regulation. Using a small molecule inhibitor of HMGA1 binding to DNA, or a dominant-negative form of HMGA1, we blunted the induction of hNOS2 by pro-inflammatory stimuli. Binding of HMGA1 in the region -3506 to -3375 of the hNOS2 promoter, a region not previously known to be involved in hNOS2 regulation, contributed to the induction of hNOS2 promoter in conjunction with upstream enhancer regions. We demonstrate a previously unknown role for HMGA1 in the regulation of hNOS2.

Inhibition of nuclear factor-kappaB by hyaluronan in rheumatoid chondrocytes stimulated with COOH-terminal heparin-binding fibronectin fragment

The aim of this study was to examine the inhibitory effect of high molecular weight hyaluronan (HA) on nuclear factor (NF)-kappaB activation by COOH-terminal heparin-binding fibronectin fragment (HBFN-f) in rheumatoid arthritis (RA) chondrocytes. When RA chondrocytes in monolayer or cartilage explants were cultured with HBFN-f, the fragment stimulated the phosphorylation and nuclear translocation of NF-kappaB, leading to nitric oxide (NO) production in association with inducible form of NO synthase (iNOS) up-regulation. Inhibition studies with NF-kappaB inhibitors indicated the requirement of NF-kappaB for HBFN-f-induced NO production. Pretreatment with 2700 kDa HA resulted in significant suppression of NF-kappaB activation by HBFN-f. HA also inhibited HBFN-f-stimulated NO production with down-regulation of iNOS. The present study clearly demonstrated that high molecular weight HA suppressed HBFN-f-activated NF-kappaB in RA chondrocytes. HA could down-regulate the catabolic action of fibronectin fragments like HBFN-f in RA joints as a potent NF-kappaB inhibitor.

Hepatocyte survival in acute hepatitis is due to c-Jun/AP-1-dependent expression of inducible nitric oxide synthase

Analysis of the molecular factors determining hepatocyte survival or death in response to inflammatory stimuli is essential for understanding the pathogenesis of inflammatory liver disease and for identifying novel therapeutic approaches. c-Jun N-terminal kinase (JNK) is a major mediator of cytokine-induced cell death during hepatitis, but the signaling pathways downstream of JNK remain less well defined. Here we show that the transcription factor c-Jun/AP-1, a prototypic target of JNK, is strongly expressed in the liver of patients with acute liver injury. The molecular function of c-Jun in inflammatory liver disease was analyzed in mice by using the Con A model of T cell-mediated hepatitis. Mice lacking c-Jun in hepatocytes display increased liver cell death and mortality upon Con A injection. This phenotype is caused by impaired expression of inducible nitric oxide synthase (nos2), a direct transcriptional target of c-Jun, and reduced production of hepatoprotective nitric oxide (NO). Moreover, increased hepatotoxicity in mutant mice is likely caused by hypoxia and oxidative stress and can be rescued pharmacologically by liver-specific NO delivery. These findings demonstrate that c-Jun/AP-1 is hepatoprotective during acute hepatitis by regulating nos2/NO expression and thus functionally antagonizes the cell death-promoting functions of JNK.

Transcriptional suppression of cytokine-induced iNOS gene expression by IL-13 through IRF-1/ISRE signaling

IL-13 has been reported as one of the major down-regulators of iNOS expression in various tissues and cells. The molecular mechanism of iNOS suppression by IL-13 remains unclear, especially at the transcriptional stage. In this study, we found that IL-13 inhibited the expression of iNOS mRNA, protein, and NO product in a concentration-dependent manner for cytokine-stimulated rat hepatocytes. The most effective dose for IL-13 inhibitory effect is approximately 5 ng/ml. IL-13 also decreased the rat iNOS transcriptional activity by promoter analysis, but had no effect on iNOS mRNA stability. By using TranSignal Protein/DNA Combo Array, we identified cytokine-stimulated IRF-1/ISRE binding that was decreased by the addition of IL-13. Gel shift assay confirmed that IL-13 reduced the IRF-1/ISRE binding at nucleotides -913 to -923 of the rat iNOS promoter. Western blot revealed that IL-13 diminished the relative amount of IRF-1 protein translocated to the nucleus. Our data demonstrate that IL-13 down-regulates the cytokine-induced iNOS transcription by decreasing iNOS specific IRF-1/ISRE binding activity.

Identification of conserved domains in the promoter regions of nitric oxide synthase 2: implications for the species-specific transcription and evolutionary differences

BACKGROUND

The majority of the genes involved in the inflammatory response are highly conserved in mammals. These genes are not significantly expressed under normal conditions and are mainly regulated at the transcription and prost-transcriptional level. Transcription from the promoters of these genes is very dependent on NF-kappaB activation, which integrates the response to diverse extracellular stresses. However, in spite of the high conservation of the pattern of promoter regulation in kappaB-regulated genes, there is inter-species diversity in some genes. One example is nitric oxide synthase 2 (NOS-2), which exhibits a species-specific pattern of expression in response to infection or pro-inflammatory challenge.

RESULTS

We have conducted a comparative genomic analysis of NOS-2 with different bioinformatic approaches. This analysis shows that in the NOS-2 gene promoter the position and the evolutionary divergence of some conserved regions are different in rodents and non-rodent mammals, and in particular in primates. Two not previously described distal regions in rodents that are similar to the unique upstream region responsible of the NF-kappaB activation of NOS-2 in humans are fragmented and translocated to different locations in the rodent promoters. The rodent sequences moreover lack the functional kappaB sites and IFN-gamma response sites present in the homologous human, rhesus monkey and chimpanzee regions. The absence of kappaB binding in these regions was confirmed by electrophoretic mobility shift assays.

CONCLUSION

The data presented reveal divergence between rodents and other mammals in the location and functionality of conserved regions of the NOS-2 promoter containing NF-kappaB and IFN-gamma response elements.

Attenuation of iNOS in an LPS-stimulated macrophage model by omega-3 fatty acids is independent of COX-2 derived PGE2

BACKGROUND

Omega-3 fatty acids (n-3 FA) demonstrate significant anti-inflammatory properties thought to occur through three principal mechanisms; (1) displacement of arachidonic acid from the cellular membrane, (2) differential prostaglandin E2 (PGE2) and LTB4 production, and (3) molecular level alterations such as diminished nuclear factor kappa B and AP-1 activation. Recently, n-3 FA have been demonstrated to significantly decrease nitric oxide (NO) production in a lipopolysaccharide (LPS)-stimulated M Phi model. We hypothesized that decreased NO production by n-3 FA occurs through inhibition of cyclooxygenase-2 (COX-2) derived PGE2 and that repletion of the system with PGE2 would obliterate these effects. Selective COX-2 inhibitor (L-748,731) experiments and separate PGE2 repletion studies were used to test this hypothesis.

METHODS

NO production was assessed following 24 h with or without LPS/PGE2 in the presence of n-3 FA, L-748,731 (a selective COX-2 inhibitor), or combination (n-3 FA + L-748,731) treatment. Western blots were used to assess inducible NO synthase protein expression.

RESULTS

Independently or in the presence of LPS, treatment with a COX-2 inhibitor significantly increased NO production compared with control, n-3 FA, and combination treatment. NO production in combination treatment is slightly increased compared to n-3 FA treatment. In control cells treated with LPS, PGE2 repletion resulted in a significant decrease in NO. All other treatment groups repleted with PGE2 demonstrated no significant alterations in NO production. Inducible NO synthase protein expression levels were similar to NO production across all treatments.

CONCLUSION

These experiments disproved our original hypothesis that the decrease in NO production associated with n-3 FA treatment occurs through a COX-2 derived PGE2 dependent mechanism. Eliminating COX-2 derived PGE2 by a selective inhibitor actually increased NO production. Exogenous PGE2 repletion did not restore the system. Therefore, mechanisms other than n-3 FA associated alterations in COX-2 derived PGE2 are likely involved in decreasing NO production in LPS stimulated M Phi.

The role of iNOS-derived NO in the antihypertrophic actions of B-type natriuretic peptide in neonatal rat cardiomyocytes

In the infarcted rat heart, the increase of NO occurs in the hypertrophied myocardium of non-infarcted areas and its antihypertrophic efficacy has been well established. As another endogenous regulator and the reliable index of heart pathology, B-type natriuretic peptide also exhibits the antihypertrophic properties in many tissues by elevating intracellular cGMP. Several studies indicate that natriuretic peptides family may exert some actions in part via a nitric oxide pathway following receptor-mediated stimulation of iNOS. Therefore, it raises our great interest to ask what role NO plays in the antihypertrophic actions of B-type natriuretic peptide in cardiomyocytes. Incubation of cardiomyocytes under mild hypoxia for 12 h caused a significant increase in cellular protein content, protein synthesis and cell surface sizes. This growth stimulation was suppressed by exogenous B-type natriuretic peptide in a concentration dependent manner. Furthermore, the generation of intracellular cGMP, the upregulation of iNOS mRNA expression, the increase of iNOS activity and subsequent nitrite generation in hypertrophic cardiomyocytes was also increased by B-type natriuretic peptide. AG, a selective iNOS inhibitor, inhibited the upregulation of iNOS expression and the increase of iNOS activity by the combination of B-type natriuretic peptide/mild hypoxia or by the combination of 8-bromo-cGMP/mild hypoxia. Rp-8-br-cGMP, cGMP dependent protein kinase inhibitor, attenuated the actions of B-type natriuretic peptide and 8-bromo-cGMP which increases intracellular cGMP independent of B-type natriuretic peptide. In conclusion, our present data suggest that B-type natriuretic peptide exerted the antihypertrophic effects in cardiomyocytes, which was partially attributed to induction of iNOS-derived NO by cGMP pathway.

Identification and characterization of the novel human prostate cancer-specific PC-1 gene promoter

Human prostate and colon gene-1 (PC-1, also known as PrLZ) is an androgen-regulated, prostate tissue and prostate cancer cells specifically expressed novel gene. The increased expression of PC-1 gene appears to promote prostate cancer cells androgen-dependent (AD) and androgen-independent (AI) growth. To clone and investigate the expression and regulation elements of PC-1 gene may provide insight into the function of PC-1 and develop a new promoter that targets therapeutic genes to the AD and AI prostate cancer cells. The goal of the present study is cloning and characterization of the PC-1 promoter. A series of luciferase constructs that contain various fragments of the PC-1 5'-genomic region were transfected into human prostate cancer cells for promoter transactivation analysis. 5' deletion analysis identified the -1579 bp promoter region was required for the maximal proximal promoter activity; two transcriptional suppression and a positive regulatory region were identified; -4939 bp promoter fragment of the PC-1 gene retained the characteristic of prostate cancer-specific expression and exhibited higher transcription activity than PSA-6 kb promoter in the medium supplemented with steroid-depleted FBS. An androgen response element (ARE) was located in between -345 and -359 bp of the PC-1 5'-untranslated region relative to the translation initiation site. Thus, our studies not only provide molecular basis of PC-1 transcription regulation, but also define a new regulatory sequence that may be used to restrict expression of therapeutic genes to prostate cancer in the prostate cancer gene therapy.

Pulmonary epithelial cells are a source of interferon-gamma in response to Mycobacterium tuberculosis infection

Recent report from our laboratory showed that A549 cells representing alveolar epithelial cells produce chemokine interleukin-8 and nitric oxide (NO) when challenged with Mycobacterium tuberculosis. Interferon-gamma (IFN-gamma) played a critical role in priming these cells to generate NO in vitro. In the present study, we report that M. tuberculosis-infected A549 cells are capable of elaborating IFN-gamma as shown by enzyme-linked immunosorbent assay and intracellular staining for IFN-gamma. Secretion profile indicated that M. tuberculosis-infected A549 released significantly high concentration of IFN-gamma at 48 and 72 h post-infection. Low level of IFN-gamma release was also seen to be induced by gamma-irradiated M. tuberculosis and subcellular components of M. tuberculosis. Cell surface receptor analysis showed that the M. tuberculosis-infected A549 cells expressed enhanced levels of IFN-gamma receptors. This observation suggests that the endogenously produced IFN-gamma in response to M. tuberculosis infection plays a role in intracellular regulation of innate immunity against intracellular pathogen such as M. tuberculosis. This observation is further strengthened by the fact that infected A549 cells expressed signal transducer and activator of transcription 1 (STAT1), an important mediator for IFN-gamma signaling pathway, leading to expression of inducible NO synthase and subsequent release of NO in sufficient concentration to be mycobactericidal. Our results show that production of IFN-gamma and enhanced expression of IFN-gamma receptors by infected A549 cells is a local phenomenon occurring as de novo intracellular activity, in response to M. tuberculosis infection. To the best of our knowledge, this is the first report to show that A549 cells interact actively with M. tuberculosis to produce IFN-gamma that might play an important role in innate immunity against tuberculosis.

Retinoic acid activates human inducible nitric oxide synthase gene through binding of RARalpha/RXRalpha heterodimer to a novel retinoic acid response element in the promoter

Human inducible nitric oxide synthase (hiNOS) catalyzes nitric oxide (NO) which has a significant effect on tumor suppression and cancer therapy. Here we revealed the detailed molecular mechanism involved in the regulation of hiNOS expression induced by retinoic acid (RA). We showed that RARalpha/RXRalpha heterodimer was important in hiNOS promoter activation, hiNOS protein expression, and NO production. Serial deletion and site-directed mutation analysis revealed two half-sites of retinoic acid response element (RARE) spaced by 5bp located at -172 to -156 in the hiNOS promoter. EMSA and ChIP assays demonstrated that RARalpha/RXRalpha directly bound to this RARE of hiNOS promoter. Our results suggested the identification of a novel RARE in the hiNOS promoter and the roles of the nuclear receptors (RARalpha/RXRalpha) in the induction of hiNOS by RA.

Induction of inducible NO synthase in bystander human T cells increases allogeneic responses in the vasculature

Inducible NO synthase (iNOS) in human T cells is implicated in the pathogenesis of graft arteriosclerosis. Here we analyze the regulation and role of iNOS in human peripheral blood T cells. Allogeneic endothelial cells (EC) or dermal fibroblasts induce iNOS mRNA and protein expression, as well as enzymatic activity in primary human CD8 T cells. Although human EC activate T cells through the presentation of alloantigen, iNOS induction is confined to nonactivated T cells and does not depend on MHC molecules or costimulators. iNOS induction does involve new transcription and depends on NF-kappaB. JAK signaling, initiated during T cell activation, inhibits iNOS expression. Even though iNOS is confined to bystander T cells, inhibition of iNOS activity reduces T cell proliferation in response to allogeneic EC, and addition of low levels of a NO donor rescues T cell responses. Similarly, iNOS is preferentially expressed by nonproliferating T cells within allografted arteries in vivo, and inhibition of iNOS activity reduces the number of activated T cells in these artery segments. These data identify a previously undescribed mechanism for enhanced activation of alloreactive T cells, namely stromal cell-mediated induction of iNOS in bystander T cells.

Novel role of IL-6/SIL-6R signaling in the expression of inducible nitric oxide synthase (iNOS) in murine B16, metastatic melanoma clone F10.9, cells

Inducible nitric oxide synthase (iNOS) has been shown to be frequently expressed in melanomas; up-regulation of this enzyme is though to be associated with tumor progression. In this study, we investigated whether diverse cytokines such as: IL-6, TNF-alpha, IL-1beta, IFN-gamma and IL6RIL6 (a highly active fusion protein of the soluble form of the IL-6R (sIL-6R) and IL-6) enhance the iNOS gene expression in B16/F10.9 murine metastatic melanoma cells. An increase at iNOS expression and NO production was observed with the co-treatment of IL6RIL6 plus TNF-alpha. Gel shift and reporter gene analyses revealed that IL6RIL6 selectively activated AP-1; while TNF-alpha increased the activities of both NF-kappaB and AP-1. Persistent activation of AP-1 was also seen in cells treated with IL6RIL6 plus TNF-alpha. Stimulation of cells with IL6RIL6/TNF-alpha resulted in the activation of mitogen-activated protein kinases (MAPK) such as c-Jun N-terminal kinase (JNK) and p38, and the abrogation by pretreatment with JNK or p38 MAPK inhibitor. IL6RIL6 or IL6RIL6/TNFalpha-inducible AP-1 binding increase was supershifted by anti-c-Jun or c-Fos antibodies, and the activation of c-Jun and c-Fos was dependent on JNK and p38, respectively. These results suggest that IL-6/sIL-6R/gp130 complex signaling has an unexpected positive effect on iNOS gene expression through JNK/p38 MAPK mediated-AP-1 activation in melanoma cells.

Identification of a classic cytokine‐induced enhancer upstream in the human iNOS promoter

The human inducible NOS (iNOS) promoter transcriptionally regulated by 5' flanking region extending 16 kb upstream that contains cytokine-responsive DNA motifs. In this study, we further identified a classic inducible enhancer located between -5 and -6 kb in the hiNOS upstream promoter. This 1 kb promoter sequence functions as a cytokine-inducible enhancer in an orientation- and position-independent manner in human lung A549 and liver AKN1 cells. This DNA enhancer also confers cytokine inducibility to the heterologous thymidine kinase (TK) promoter. Chromatin immunoprecipitation (ChIP) analysis was applied, and confirmed cytokine-inducible in vivo DNA-protein interactions within this enhancer region. In vivo functional binding of both NF-kappaB (p65/p50) and Stat-1alpha at the -5.8 kb human iNOS promoter site was significantly increased in A549 cells after cytokine stimulation, while only Stat-1alpha bound at the -5.2 kb site. These results identify the -5 to -6 kb promoter region as a classic transcriptional enhancer for the human iNOS gene and provide definitive in vivo evidence of specific NF-kappaB and Stat-1 nuclear protein binding that mediates transcription of the hiNOS gene under cytokine stimulation.

Regulation of human nitric oxide synthase 2 expression by Wnt beta-catenin signaling

Nitric oxide (NO.), an important mediator of inflammation, and beta-catenin, a component of the Wnt-adenomatous polyposis coli signaling pathway, contribute to the development of cancer. We have identified two T-cell factor 4 (Tcf-4)-binding elements (TBE1 and TBE2) in the promoter of human inducible NO synthase 2 (NOS2). We tested the hypothesis that beta-catenin regulates human NOS2 gene. Mutation in either of the two TBE sites decreased the basal and cytokine-induced NOS2 promoter activity in different cell lines. The promoter activity was significantly reduced when both TBE1 and TBE2 sites were mutated (P < 0.01). Nuclear extract from HCT116, HepG2, or DLD1 cells bound to NOS2 TBE1 or TBE2 oligonucleotides in electrophoretic mobility shift assays and the specific protein-DNA complexes were supershifted with anti-beta-catenin or anti-Tcf-4 antibody. Overexpression of beta-catenin and Tcf-4 significantly increased both basal and cytokine-induced NOS2 promoter activity (P < 0.01), and the induction was dependent on intact TBE sites. Overexpression of beta-catenin or Tcf-4 increased NOS2 mRNA and protein expression in HCT116 cells. Lithium chloride (LiCl), an inhibitor of glycogen synthase kinase-3beta, increased cytosolic and nuclear beta-catenin level, NOS2 expression, and NO. production in primary human and rat hepatocytes and cancer cell lines. Treatment with Wnt-3A-conditioned medium increased beta-catenin and NOS2 expression in fetal human hepatocytes. When administered in vivo, LiCl increased hepatic beta-catenin level in a dose-dependent manner with simultaneous increase in NOS2 expression. These data are consistent with the hypothesis that beta-catenin up-regulates NOS2 and suggest a novel mechanism by which the Wnt/beta-catenin signaling pathway may contribute to cancer by increasing NO. production.

Role of epithelial nitric oxide in airway viral infection

The airway mucosal epithelium is the first site of virus contact with the host, and the main site of infection and inflammation. Nitric oxide (NO) produced by the airway epithelium is vital to antiviral inflammatory and immune defense in the lung. Multiple mechanisms function coordinately to support high-level basal NO synthesis in healthy airway epithelium and further induction of NO synthesis in the infected airway of normal hosts. Hosts deficient in NO synthesis, such as those patients with cystic fibrosis, have impaired antiviral defense and may benefit from therapies to augment NO levels in the airways.

Reduced nitric oxide synthase 2 (NOS2) promoter activity in the Syrian hamster renders the animal functionally deficient in NOS2 activity and unable to control an intracellular pathogen

Progressive disease in the hamster model of visceral leishmaniasis, caused by Leishmania donovani, in contrast to infection in mice, mimics the progressive disease observed in untreated humans. During progressive infection in hamsters, there was a vigorous type 1 cellular immune response, which is typically associated with control of infection, suggesting that there was ineffective IFN-gamma-mediated macrophage activation. Indeed, at the site of infection, hamsters did not express NO synthase 2 (NOS2), which is the primary mechanism for control of infection in mice. Furthermore, in striking contrast to mouse macrophages, IFN-gamma-activated hamster macrophages did not did not express NOS2 nor generate NO, and were unable to restrict the replication of intracellular L. donovani. The absent hamster NOS2 expression was not the result of NOS2 gene deletion and the NOS2 cDNA had an intact open reading frame. Furthermore, the impaired transcription of NOS2 mRNA was selective and not due to global impairment of IFN-gamma signaling (members of the IFN-gamma-signaling pathway were expressed and functional and IFN-gamma up-regulated several primary and secondary response genes). Strikingly, the proximal hamster NOS2 promoter, like the human ortholog, had >20-fold less basal and IFN-gamma/LPS-inducible activity than the corresponding mouse promoter. Thus, reduced basal and IFN-gamma-induced activity of the hamster NOS2 transcriptional unit, which is unique to this small animal and similar to the human counterpart, accompanies the inability of the animal to control an intracellular pathogen.

Nitric oxide and hormones in breast cancer: allies or enemies?

Unlike other types of cancer, tumors of the breast are greatly influenced by steroid hormones. The effect of estrogen and progesterone depends on the presence of their specific receptors and these constitute important parameters in determining the aggressiveness of the tumor, the feasibility of certain therapies and the prediction of relapse. The molecular mechanisms of steroid hormone action have not been fully elucidated but recent findings implicate the nitric oxide (NO) pathway in some of these effects. Both hormones can regulate the nitric oxide synthases (NOS) and, in turn, the NO produced has profound consequences on tumor cell homeostasis. On one hand, estrogen increases the activity of endothelial NOS (eNOS or NOSIII), while progesterone activates inducible NOS (iNOS or NOSII) expression. The data presented suggest that the low levels of NO produced by NOSIII mediate the proliferative effect of estrogen. On the other hand, the increase in apoptosis in response to progesterone could implicate the high levels of NO produced by induction of NOSII expression. Understanding of the mechanisms and interactions of steroid hormones with the NO pathway could lead to the development of new approaches and strategies for the effective treatment of breast cancer.

Phosphatidylinositol 3-kinase-dependent suppression of the human inducible nitric-oxide synthase promoter is mediated by FKHRL1

The synthesis of nitric oxide by inducible nitric-oxide synthase (iNOS) plays an important role in the innate immune response by promoting microbial killing and cell damage. In response to inflammatory cytokines and bacterial products, the human iNOS (hiNOS) gene undergoes rapid transcriptional activation via binding of stimulatory transcription factors (e.g. AP-1 and NF-kappaB) to its 5'-flanking region. However, maximal hiNOS promoter induction was suppressed via an unknown phosphatidylinositol 3-kinase (PI3K)-dependent mechanism. We hypothesized that inhibition of the transcription factor FKHRL1 by the PI3K/protein kinase B pathway attenuates hiNOS promoter induction by bacterial lipopolysaccharide and interferon-gamma (LPS/IFN-gamma). Human lung epithelial adenocarcinoma (A549) cells were transiently transfected with an 8.3-kb hiNOS promoter luciferase reporter construct. Co-expression of dominant-negative protein kinase B potentiated LPS/IFN-gamma-stimulated hiNOS promoter activity. In response to LPS/IFN-gamma, FKHRL1 was phosphorylated in a PI3K- and time-dependent fashion. Co-expression of constitutively active FKHRL1 increased hiNOS promoter activity and mRNA levels. Dominant-negative siRNA expression showed that FKHRL1 was necessary for the inhibitory effects of PI3K on hiNOS induction. The same effect was observed upon mutation of a consensus FKHRL1-binding site in the hiNOS promoter. By gel-shift analysis, the corresponding oligonucleotide probe bound endogenous FKHRL1 in an LPS/IFN-gamma- and PI3K-sensitive fashion. Regulation of the hiNOS promoter by FKHRL1 represents a potentially important molecular mechanism by which the PI3K pathway might suppress pro-inflammatory and proapoptotic responses to cytokines and bacterial products.

Oregonin inhibits lipopolysaccharide-induced iNOS gene transcription and upregulates HO-1 expression in macrophages and microglia

Oregonin isolated from Alnus formosana is a diarylheptanoid derivative, which appears to have antioxidative and anti-inflammatory activities. In this study, our data demonstrated inhibitory actions of oregonin on the LPS-induced iNOS protein in RAW264.7 macrophages and BV-2 microglial cells. We also suggested that HO-1 induction by oregonin might contribute to this action. Oregonin is able to dose-dependently reduce NO production, iNOS protein and iNOS promoter activity stimulated by LPS in RAW264.7 and BV-2 cells. Oregonin also showed inhibition of LPS-mediated NF-kappaB promoter activity and DNA-binding ability, as well as p65 nuclear translocation and phosphorylation. However, oregonin had no effect on IKK activity. AP-1 promoter activity and p38 MAPK activation but not PKC, ERK and JNK activation induced by LPS were attenuated by oregonin. Accompanying with iNOS protein reduction, moreover, we found that oregonin was able to induce HO-1 protein level. Results using a CO donor, [Ru(CO)(3)Cl(2)](2) further showed the ability of CO in reduction of iNOS protein level induced by LPS through the blockade of NF-kappaB and AP-1. Taken together, these results provide new evidences into the anti-inflammatory actions of oregonin, which include the inhibition of iNOS gene transcription via suppressing transcriptional activity of NF-kappaB and AP-1, as well as the upregulation of anti-inflammatory molecule HO-1. The HO-1-derived CO may also be involved in the suppressive effect on iNOS gene regulation.

Doxycycline modulates nitric oxide production in murine lung epithelial cells

Many effective therapeutic agents exhibit effects that are different from their intended primary mode of action. Antibiotics such as doxycycline and erythromycin A are no exception. They also display anti-inflammatory activity. Using LA4 murine lung alveolar epithelial cells, effects of doxycycline and erythromycin A on inducible NO synthase (iNOS) NO production as well as iNOS protein and mRNA production were investigated. Induction of iNOS was accomplished by treatment with cytomix (TNF-alpha, IL-1beta, and IFN-gamma each at 5 ng/ml). Production of NO or iNOS was not detected in controls with or without erythromycin A. In the presence of cytomix, erythromycin A did not decrease NO, nitrite, iNOS protein, or mRNA production. In contrast, doxycycline caused a dose-dependent decrease in NO, nitrite, iNOS protein, and mRNA production in cytomix-treated cells. Doxycycline at 30 mug/ml produced a 90% decrease in nitrite and NO production and a 52% decrease in iNOS mRNA transcription compared with cytomix treatment alone. Actinomycin D treatment suggests that doxycycline decreases stability of iNOS mRNA in cytomix-treated cells. To determine a mechanism for the decrease in iNOS expression, NF-kappaB and AP-1 transcription regulatory systems and p38 MAPK were examined. Doxycycline treatment gave no statistically significant change in NF-kappaB activation but did decrease p38 MAPK protein in cytomix-treated cells by 50%, suggesting that p38 MAPK may be responsible for stabilization of iNOS mRNA. These results demonstrate that doxycycline decreases NO production from iNOS by destabilization of iNOS mRNA via decreased expression of p38 MAPK.

Acidosis affects tumor cell survival through modulation of nitric oxide release

The influence of environmental pH on the production of tumoricidal free radical nitric oxide (NO) was investigated in mouse fibrosarcoma L929 and rat glioma C6 cell lines. A combination of IFN-gamma and IL-1 induced a significant NO release and subsequent reduction of cell viability in tumor cell lines. Acidification of cell culture medium reduced tumor cell NO production in a pH-dependent manner. While the inhibitory effect of acidosis on NO production in C6 cells was associated with a further decrease in cell viability, it completely rescued L929 cells from NO-dependent apoptotic and necrotic death. Acidic pH diminished IFN-gamma+ IL-1-induced expression of inducible NO synthase (iNOS) mRNA and protein, and abolished the activation of iNOS transcription factor IRF-1 in L929 cells. Moreover, extracellular acidosis significantly impaired cytokine-induced phosphorylation of MAP kinase p44/42 (ERK1/2) and subsequent expression of transcription factor c-Fos in L929 cells. Finally, mild acidosis (pH 6.8) augmented, while severe acidosis (pH 6.0) reduced, IFN-gamma-induced iNOS activation/NO release and NO-dependent anticancer activity of rat and mouse macrophages. Taken together, our findings indicate that modulation of macrophage and tumor cell iNOS by an acidic microenvironment might influence the progression of NO-sensitive solid tumors.

Involvement of TLR4/type I IL-1 receptor signaling in the induction of inflammatory mediators and cell death induced by ethanol in cultured astrocytes

Activated astroglial cells are implicated in neuropathogenesis of many infectious and inflammatory diseases of the brain. A number of inflammatory mediators and cytokines have been proposed to play a key role in glial cell-related brain damage. Cytokine production seems to be initiated by signaling through TLR4/type I IL-1R (IL-1RI) in response to their ligands, LPS and IL-1beta, playing vital roles in innate host defense against infections, inflammation, injury, and stress. We have shown that glial cells are stimulated by ethanol, up-regulating cytokines and inflammatory mediators associated with TLR4 and IL-1RI signaling pathways in brain, suggesting that ethanol may contribute to brain damage via inflammation. We explore the possibility that ethanol, in the absence of LPS or IL-1beta, triggers signaling pathways and inflammatory mediators through TLR4 and/or IL-1RI activation in astrocytes. We show in this study that ethanol, at physiologically relevant concentrations, is capable of inducing rapid phosphorylation within 10 min of IL-1R-associated kinase, ERK1/2, stress-activated protein kinase/JNK, and p38 MAPK in astrocytes. Then an activation of NF-kappaB and AP-1 occurs after 30 min of ethanol treatment along with an up-regulation of inducible NO synthase and cyclooxygenase-2 expression. Finally, we note an increase in cell death after 3 h of treatment. Furthermore, by using either anti-TLR4- or anti-IL-1RI-neutralizing Abs, before and during ethanol treatment, we inhibit ethanol-induced signaling events, including NF-kappaB and AP-1 activation, inducible NO synthase, and cyclooxygenase-2 up-regulation and astrocyte death. In summary, these findings indicate that both TLR4 and IL-1RI activation occur upon ethanol treatment, and suggest that signaling through these receptors mediates ethanol-induced inflammatory events in astrocytes and brain.

The physiology and pathophysiology of nitric oxide in the brain

Nitric oxide (NO) is a molecule with pleiotropic effects in different tissues. NO is synthesized by NO synthases (NOS), a family with four major types: endothelial, neuronal, inducible and mitochondrial. They can be found in almost all the tissues and they can even co-exist in the same tissue. NO is a well-known vasorelaxant agent, but it works as a neurotransmitter when produced by neurons and is also involved in defense functions when it is produced by immune and glial cells. NO is thermodynamically unstable and tends to react with other molecules, resulting in the oxidation, nitrosylation or nitration of proteins, with the concomitant effects on many cellular mechanisms. NO intracellular signaling involves the activation of guanylate cyclase but it also interacts with MAPKs, apoptosis-related proteins, and mitochondrial respiratory chain or anti-proliferative molecules. It also plays a role in post-translational modification of proteins and protein degradation by the proteasome. However, under pathophysiological conditions NO has damaging effects. In disorders involving oxidative stress, such as Alzheimer's disease, stroke and Parkinson's disease, NO increases cell damage through the formation of highly reactive peroxynitrite. The paradox of beneficial and damaging effects of NO will be discussed in this review.

Epigenetic basis for the transcriptional hyporesponsiveness of the human inducible nitric oxide synthase gene in vascular endothelial cells

A marked difference exists in the inducibility of inducible NO synthase (iNOS) between humans and rodents. Although important cis and trans factors in the murine and human iNOS promoters have been characterized using episomal-based approaches, a compelling molecular explanation for why human iNOS is resistant to induction has not been reported. In this study we present evidence that the hyporesponsiveness of the human iNOS promoter is based in part on epigenetic silencing, specifically hypermethylation of CpG dinucleotides and histone H3 lysine 9 methylation. Using bisulfite sequencing, we demonstrated that the iNOS promoter was heavily methylated at CpG dinucleotides in a variety of primary human endothelial cells and vascular smooth muscle cells, all of which are notoriously resistant to iNOS induction. In contrast, in human cell types capable of iNOS induction (e.g., A549 pulmonary adenocarcinoma, DLD-1 colon adenocarcinoma, and primary hepatocytes), the iNOS promoter was relatively hypomethylated. Treatment of human cells, such as DLD-1, with a DNA methyltransferase inhibitor (5-azacytidine) induced global and iNOS promoter DNA hypomethylation. Importantly, 5-azacytidine enhanced the cytokine inducibility of iNOS. Using chromatin immunoprecipitation, we found that the human iNOS promoter was basally enriched with di- and trimethylation of H3 lysine 9 in endothelial cells, and this did not change with cytokine addition. This contrasted with the absence of lysine 9 methylation in inducible cell types. Importantly, chromatin immunoprecipitation demonstrated the selective presence of the methyl-CpG-binding transcriptional repressor MeCP2 at the iNOS promoter in endothelial cells. Collectively, our work defines a role for chromatin-based mechanisms in the control of human iNOS gene expression.

6-(Methylsulfinyl)hexyl isothiocyanate suppresses inducible nitric oxide synthase expression through the inhibition of Janus kinase 2-mediated JNK pathway in lipopolysaccharide-activated murine macrophages

6-(Methylsulfinyl)hexyl isothiocyanate (6-MITC) is an active ingredient of Wasabi (Wasabia japonica (Miq.) Matsumura), which is a very popular pungent spice in Japan. To clarify the cellular signaling mechanism underlying the anti-inflammatory action of 6-MITC, we investigated the effects of 6-MITC on the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated murine macrophage RAW264 cells. 6-MITC showed a dose-dependent inhibition of LPS-induced nitric oxide (NO), iNOS mRNA and protein. LPS caused the c-Jun phosphorylation (a major component of AP-1) and IkappaB-alpha degradation. 6-MITC suppressed LPS-induced c-Jun phosphorylation, but did not inhibit IkappaB-alpha degradation. Cellular signaling analysis using MAPK-(U0126 for MEK1/2, SB203580 for p38 kinase and SP600125 for JNK) and Jak2-specific (AG490) inhibitors demonstrated that LPS stimulated iNOS expression via activating Jak2-mediated JNK, but not ERK and p38, pathway. 6-MITC suppressed iNOS expression through the inhibition of Jak2-mediated JNK signaling cascade with the attendant to AP-1 activation. In addition, the structure-activity study revealed that the inhibitory potency of methylsulfinyl isothiocyanates (MITCs) depended on the methyl chain length. These findings provide the molecular basis for the first time that 6-MITC is an effective agent to attenuate iNOS production.

Differential contribution of hepatitis C virus NS5A and core proteins to the induction of oxidative and nitrosative stress in human hepatocyte-derived cells

BACKGROUND/AIMS

We aimed to explore the effects of hepatitis C virus (HCV) core and NS5A proteins on reactive oxygen (ROS) and nitrogen species (RNS) formation and on gene expression profile of iNOS in human hepatocyte-derived cells.

METHODS

Production of ROS and RNS and nitrotyrosine residues accumulation were determined by flow cytometry and fluorescent microscopy as well as by Western blot, respectively, in NS5A- and core-transfected cells. Northern blot, Western blot, real-time PCR, and luciferase assays were used to assess iNOS gene expression in both transfectants.

RESULTS

Cytokine-activated NS5A- and core-transfected cells induced ROS and RNS production but an earlier and more marked increase was observed in NS5A-expressing cells. Superoxide production was also augmented, showing a similar temporal pattern of appearance in both NS5A- and core-transfected cells. Although both NS5A and core HCV proteins were able to up-regulate iNOS gene expression, accompanied by a nitrotyrosine-containing proteins accumulation, an earlier iNOS overexpression was observed in NS5A-expressing cells, suggesting a different time course of iNOS activation pattern for core and NS5A HCV proteins.

CONCLUSIONS

Our results indicate a differential contribution of both HCV proteins to oxidative and nitrosative stress generation.

Analysis of polymorphic sites in the promoter of the nitric oxide synthase 2 gene

A point mutation (G --> C) in the gene promoter for the human nitric oxide synthase (NOS) 2 at position -954 is associated with protection against severe Plasmodium falciparum malaria in Gabon. Carriers of this mutation show higher basal levels of nitric oxide production than wild type individuals. To obtain information about the possible binding transcription factors, nucleic proteins from the lung carcinoma cell line were enriched by affinity chromatography using DEAE-Sepharose and immobilized oligonucleotides derived from the promoter sequence. A mutational analysis was performed on 30 samples to detect polymorphisms in the NOS2 promoter region that contains important NF-kappaB sites. Three point mutations were identified in this region. In vitro studies with promoter constructs showed an altered expression of the marker gene depending on the promoter variant used.

Hydrogen peroxide stimulates proliferation and migration of human prostate cancer cells through activation of activator protein-1 and up-regulation of the heparin affin regulatory peptide gene

It is becoming increasingly recognized that hydrogen peroxide (HP) plays a role in cell proliferation and migration. In the present study we found that exogenous HP significantly induced human prostate cancer LNCaP cell proliferation and migration. Heparin affin regulatory peptide (HARP) seems to be involved in the stimulatory effect of HP, because the latter had no effect on stably transfected LNCaP cells that did not express HARP. Moreover, HP significantly increased HARP mRNA and protein amounts in a concentration- and time-dependent manner. Curcumin and activator protein-1 (AP-1) decoy oligonucleotides abrogated both HP-induced HARP expression and LNCaP cell proliferation and migration. HP increased luciferase activity of the 5'-flanking region of the HARP gene introduced in a reporter gene vector, an effect that was abolished when even one of the two putative AP-1 binding sites of the HARP promoter was mutated. The effect of HP seems to be due to the binding of Fra-1, JunD, and phospho-c-Jun to the HARP promoter. These results support the notion that HARP is important for human prostate cancer cell proliferation and migration, establish the role of AP-1 in the up-regulation of HARP expression by low concentrations of HP, and characterize the AP-1 dimers involved.

An investigation of NOS2A promoter polymorphisms in Australian multiple sclerosis patients

As with other major autoimmune diseases, susceptibility to multiple sclerosis (MS) is believed to result from the complex interaction of a number of genes, each with modest effect. Extensive research of experimental autoimmune encephalomyelitis in mice and several direct MS studies have implicated NOS2A, which encodes the inducible form of nitric oxide synthase, and the genetic region encoding NOS2A, 17q11.2, has been identified in a number of genome wide screens as being potentially associated with MS. We investigated four single nucleotide polymorphisms in the proximal promoter region of NOS2A, in a case-control group of 100 Australian MS patients and 100 controls and in 203 MS patients and their unaffected parents. We found a trend toward excess transmission of the -277A allele (tag for the AGCC haplotype) to HLA-DRB1*1501-positive MS patients (P (uncorrected)=0.05). We initially discovered a trend toward over-representation of the AGCC haplotype in HLA-DRB1*1501-positive compared to HLA-DRB1*1501-negative MS patients in the case-control cohort. However, when combined with the probands from the transmission disequilibrium analysis, this trend was nullified. Nonetheless, despite the lack of significant evidence of association for the NOS2A promoter polymorphisms with MS, the gene remains an interesting candidate for MS susceptibility, particularly with regard to the HLA-DRB1*1501 haplotype.

AP-1 mediates beta-amyloid-induced iNOS expression in PC12 cells via the ERK2 and p38 MAPK signaling pathways

Nitrosative stress with subsequent inflammatory cell death has been implicated in some neurodegenerative disorders such as Alzheimer's disease (AD). Expression of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO) have been frequently elevated in AD. In this study, we have investigated the molecular mechanisms underlying nitrosative stress induced by beta-amyloid (A beta), a neurotoxic peptide associated with senile plaques formed in the brains of patients with AD. Exposure of rat pheochromocytoma (PC12) cells to the A beta resulted in increased mRNA and protein expression of iNOS and generation of NO. NO can rapidly interact with superoxide anion, forming more reactive peroxynitrite. Treatment of PC12 cells with A beta led to increased peroxynitrite production and nitrotyrosine formation. A beta induced activation of redox sensitive transcription factor activator protein-1 (AP-1), and AP-1 antisense oligonucleotide abolished the A beta-induced iNOS expression. Moreover, A beta transiently activated extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38 MAPK) via phosphorylation. Pharmacologic inhibition of both enzymes or dominant-negative mutation of ERK2 or p38 MAPK effectively down-regulated DNA binding as well as transcriptional activity of AP-1 and subsequent iNOS expression and NO production. The above findings suggest that A beta induces iNOS expression in PC12 cells through activation of AP-1 which is regulated by upstream kinases, such as ERK and p38 MAPK.

Falcarindiol impairs the expression of inducible nitric oxide synthase by abrogating the activation of IKK and JAK in rat primary astrocytes

The effects of falcarindiol on the expression of inducible nitric oxide synthase (iNOS) induced by lipopolysaccharide/interferon-gamma (LPS/IFN-gamma) in rat primary astrocytes were investigated. The molecular mechanisms underlying falcarindiol that confers its effect on iNOS expression were also elucidated. Falcarindiol abrogated the LPS/IFN-gamma-mediated induction of iNOS by about 80%. Falcarindiol attenuated the induction of iNOS in a concentration-dependent manner. The inhibitory effect of falcarindiol on iNOS induction was attributable to decrease in the protein content and the mRNA level of iNOS. Treatment with 50 microM of falcarindiol for 30 min decreased LPS/IFN-gamma-induced nuclear factor-kappaB (NF-kappaB) activation by 32%. Treatment with 50 microM of falcarindiol for 60 min diminished the LPS/IFN-gamma-mediated activation of IkappaB kinase-alpha (IKK-alpha) and IKK-beta by 28.2 and 29.7%, respectively. Falcarindiol modulated the nuclear translocation of signal transducer and activator of transcription 1 (Stat1) in a time-dependent manner. Falcarindiol (50 microM) decreased the tyrosine phosphorylation of janus kinase 1 (JAK1) by 84.8% at 5 min. Falcarindiol also abrogated the tyrosine phoshorylation of JAK2 by 82.3% at 10 min.The present study demonstrates that falcarindiol attenuated the activation of IKK and JAK contributing to the blockade of activation of NF-kappaB and Stat1, thereby leading to the suppression of iNOS expression.

Regulation of the expression of inducible nitric oxide synthase

The role of nitric oxide (NO) generated by the inducible isoform of nitric oxide synthase (iNOS) is very complex. Induction of iNOS expression and hence NO production has been described to have beneficial antiviral, antiparasital, microbicidal, immunomodulatory, and antitumoral effects. However, induced at the wrong place or at the wrong time, iNOS has detrimental consequences and seems to be involved in the pathophysiology of different human diseases. The pathways regulating iNOS expression seem to vary in different cells or different species. In general, activation of the transcription factors nuclear factor (NF)-kappaB and signal transducer and activator of transcription (STAT)-1alpha and thereby activation of the iNOS promoter seems to be an essential step in the regulation of iNOS expression in most cells. Also, post-transcriptional mechanisms are critically involved in the regulation of iNOS expression.

Inducible nitric oxide synthase contributes to ventilator-induced lung injury

RATIONALE

Inducible nitric oxide synthase (iNOS) has been implicated in the development of acute lung injury. Recent studies indicate a role for mechanical stress in iNOS and endothelial NOS (eNOS) regulation.

OBJECTIVES

This study investigated changes in lung NOS expression and activity in a mouse model of ventilator-induced lung injury.

METHODS

C57BL/6J (wild-type [WT]) and iNOS-deficient (iNOS(-/-)) mice received spontaneous ventilation (control) or mechanical ventilation (MV; VT of 7 and 20 ml/kg) for 2 hours, after which NOS gene expression and activity were determined and pulmonary capillary leakage assessed by the Evans blue albumin assay.

RESULTS

iNOS mRNA and protein expression was absent in iNOS(-/-) mice, minimal in WT control mice, but significantly upregulated in response to 2 hours of MV. In contrast, eNOS protein was decreased in WT mice, and nonsignificantly increased in iNOS(-/-) mice, as compared with control animals. iNOS and eNOS activities followed similar patterns in WT and iNOS(-/-) mice. MV caused acute lung injury as suggested by cell infiltration and nitrotyrosine accumulation in the lung, and a significant increase in bronchoalveolar lavage cell count in WT mice, findings that were reduced in iNOS(-/-) mice. Finally, Evans blue albumin accumulation in lungs of WT mice was significant (50 vs. 15% increase in iNOS(-/-) mice compared with control animals) in response to MV and was prevented by treatment of the animals with the iNOS inhibitor aminoguanidine.

CONCLUSION

Taken together, our results indicate that iNOS gene expression and activity are significantly upregulated and contribute to lung edema in ventilator-induced lung injury.

Octacalcium phosphate crystals directly stimulate expression of inducible nitric oxide synthase through p38 and JNK mitogen-activated protein kinases in articular chondrocytes

Basic calcium phosphate (BCP) crystals, including hydroxyapatite, octacalcium phosphate (OCP) and carbonate-apatite, have been associated with severe osteoarthritis and several degenerative arthropathies. Most studies have considered the chondrocyte to be a bystander in the pathogenesis of calcium crystal deposition disease, assuming that synovial cell cytokines were the only triggers of chondrocyte activation. In the present study we identified direct activation of articular chondrocytes by OCP crystals, which are the BCP crystals with the greatest potential for inducing inflammation. OCP crystals induced nitric oxide (NO) production and inducible nitric oxide synthase (NOS) mRNA expression by isolated articular chondrocytes and cartilage fragments, in a dose-dependent manner and with variations over time. OCP crystals also induced IL-1β mRNA expression. Using pharmacological and cytokine inhibitors, we observed that OCP crystals induced NO production and inducible NOS mRNA activation were regulated at both the transcriptional and the translational levels; were independent from IL-1β gene activation; and involved p38 and c-Jun amino-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) pathways, as further confirmed by OCP crystal-induced p38 and JNK MAPK phosphorylation. Taken together, our data suggest that the transcriptional inducible NOS response to OCP crystals involved both the p38 and the JNK MAPK pathways, probably under the control of activator protein-1. NO, a major mediator of cartilage degradation, can be directly produced by BCP crystals in chondrocytes. Together with synovial activation, this direct mechanism may be important in the pathogenesis of destructive arthropathies triggered by microcrystals.

Down-regulation of inducible nitric oxide synthase by lysophosphatidic acid in human respiratory epithelial cells

Viral infection generally results in the activation of inducible nitric oxide synthase (iNOS or NOS2) in respiratory epithelial cells by inflammatory cytokines. Activated NOS2 catalyzes synthesis of nitric oxide (NO), which in excess can cause cellular injury. On the other hand, lysophosphatidic acid (LPA), a lipid mediator released from epithelial cells, platelets, and fibroblasts in injured tissue, functions in repair of cell injury. However, details of the mechanism for repair by LPA remain unknown. We demonstrated one effect of LPA favoring repair, specifically inhibition by LPA of cytokine-induced NOS2 protein and mRNA expression by human respiratory epithelial cells in vitro. NO production by LPA-treated, cytokine-stimulated cells was also reduced. These decreases were prevented by Rho kinase inhibition with Y-27632. Thus, down-regulation by LPA of cytokine-induced increases in NOS2 activity is likely to involve a Rho-dependent signaling pathway. Harmful biologic effects of NO in viral respiratory infection might be modified by therapeutic manipulations involving LPA or Rho.

Inducible heat shock protein 70 kD and inducible nitric oxide synthase in hemorrhage/resuscitation-induced injury

Inducible head shock protein 70 kD (HSP-70i) has been shown to protect cells, tissues, and organs from harmful assaults in vivo and in vitro experimental models. Hemorrhagic shock followed by resuscitation is the principal cause of death among trauma patients and soldiers in the battlefield. Although the underlying mechanisms are still not fully understood, it has been shown that nitric oxide (NO) overproduction and inducible nitric oxide synthase (iNOS) overexpression play important roles in producing injury caused by hemorrhagic shock including increases in polymorphonuclear neutrophils (PMN) infiltration to injured tissues and leukotriene B(4) (LTB(4)) generation. Moreover, transcription factors responsible for iNOS expression are also altered by hemorrhage and resuscitation. It has been evident that either up-regulation of HSP-70i or down-regulation of iNOS can limit tissue injury caused by ischemia/reperfusion or hemorrhage/resuscitation. In our laboratory, geldanamycin, a member of ansamycin family, has been shown to induce HSP- 70i overexpression and then subsequently to inhibit iNOS expression, to reduce cellular caspase-3 activity, and to preserve cellular ATP levels. HSP-70i is found to couple to iNOS and its transcription factor. Therefore, the complex formation between HSP-70i and iNOS may be a novel mechanism for protection from hemorrhage/resuscitation-induced injury.

A synthetic derivative of the natural product rocaglaol is a potent inhibitor of cytokine-mediated signaling and shows neuroprotective activity in vitro and in animal models of Parkinson's disease and traumatic brain injury

Many acute and chronic neurodegenerative diseases are characterized by a localized inflammatory response and constitutive activation of the transcription factors nuclear factor-kappa B (NF-kappa B) and activator protein-1 (AP-1) as well as their upstream activating signaling cascades. Ample evidence indicates the implication of these processes in the pathogenesis of several diseases of the central nervous system. In this study, we show that a synthetic derivative of the natural product rocaglaol (compound A) displays potent anti-inflammatory properties in human endothelial and murine glial cells in vitro. Compound A inhibited cytokine- and lipopolysaccharide-induced release of various cytokines/chemokines and of nitric oxide as well as expression of the adhesion molecule endothelial leukocyte adhesion molecule-1 and the inducible enzymes nitric-oxide synthase and cyclooxygenase-2. As shown by immunocytochemistry and immunoblotting, compound A inhibited NF-kappa B and AP-1 activity in mixed glial cultures. Compound A exhibited neuroprotective activity in vitro and in vivo. 1-Methyl-4-phenylpyridinium-induced damage of mesencephalic dopaminergic neurons was significantly decreased, and long-term treatment of 1-methyl-4-phenyl-1,2,3,6,-tetrahydropyridine-injected mice with compound A significantly and dose-dependently reduced dopaminergic neuronal cell death. In addition, shortterm application of compound A to rats suffering from traumatic brain injury induced by subdural hematoma resulted in a significant reduction of the cerebral infarct volume. These results suggest that by inhibiting NF-kappa B and AP-1 signaling, compound A is able to reduce tissue inflammation and neuronal cell death, resulting in significant neuroprotection in animal models of neurodegeneration.

8-Hydroxyquinoline inhibits iNOS expression and nitric oxide production by down-regulating LPS-induced activity of NF-κB and C/EBPβ in Raw 264.7 cells

In activated macrophage, large amounts of nitric oxide (NO) are generated by inducible nitric oxide synthase (iNOS), resulting in acute or chronic inflammatory disorders. In Raw 264.7 cells stimulated with lipopolysaccharide (LPS) to mimic inflammation, 8-hydroxyquinoline (8HQ) inhibited the LPS-induced expression of both iNOS protein and mRNA in a parallel dose-dependent manner. 8HQ did not enhance the degradation of iNOS mRNA. To investigate the mechanism by which 8HQ inhibits iNOS gene expression, we examined the activation of MAP kinases in Raw 264.7 cells. We did not observe any significant change in the phosphorylation of MAPKs between LPS alone and LPS plus 8HQ-treated cells. Moreover, 8HQ significantly inhibited the DNA-binding activity of nuclear factor-kappaB (NF-kappaB) and CCAAT/enhancer-binding protein beta (C/EBPbeta), but not activator protein-1 and cAMP response element-binding protein. Taken together, these results suggest that 8HQ acts to inhibit inflammation through inhibition of NO production and iNOS expression through blockade of C/EBPbeta DNA-binding activity and NF-kappaB activation.

Regulation of inducible nitric oxide synthase in proinflammatory cytokine-stimulated human primary astrocytes

The present study was undertaken to investigate the mechanism of expression of inducible nitric oxide synthase (iNOS) in human primary astrocytes. Among IL-1beta, TNF-alpha, and IFN-gamma, only IL-1beta alone was capable of inducing iNOS. Similarly, among different cytokine combinations, the combinations involving only IL-1beta as a partner were capable of inducing iNOS. The combination of IL-1beta and IFN-gamma (IL-IF) induced the expression of iNOS at the highest level. All three cytokines alone induced the activation of AP-1 while IL-1beta and TNF-alpha but not IFN-gamma induced the activation of NF-kappaB. However, among the three cytokines, only IL-1beta was capable of inducing the activation of CCAAT/enhancer-binding proteinbeta (C/EBPbeta), suggesting an essential role of C/EBPbeta in the expression of iNOS in astrocytes. Although IL-1beta and IFN-gamma alone induced the activation of AP-1, the combination of these two cytokines (IL-IF) markedly inhibited the activation of AP-1. Consistently, JNK-I, a specific inhibitor of JNK, inhibited IL-1beta-mediated activation of AP-1 and expression of iNOS. On the other hand, JNK-I had no effect on (IL-IF)-induced expression of iNOS, suggesting that the activation of AP-1 is involved only during the low level of iNOS induction by IL-1beta but not during the high level of induction by IL-IF. In contrast, the activation of gamma-activation site (GAS) was involved only during the high level of induction by IL-IF but not during the low level of induction by IL-1beta. However, the activation of NF-kappaB and C/EBPbeta was involved in the induction of iNOS by IL-1beta as well as by IL-IF.

Chronic ethanol treatment enhances inflammatory mediators and cell death in the brain and in astrocytes

Inflammatory processes and cytokine expression have been implicated in the pathogenesis of several neurodegenerative disorders. Chronic ethanol intake induces brain damage, although the mechanisms involved in this effect are not well understood. We tested the hypothesis that activation of glial cells by ethanol would induce stimulation of signaling pathways and inflammatory mediators in brain, and would cause neurotoxicity. We used cerebral cortex from control and chronic ethanol-fed rats, which received ethanol-liquid diet for 5 months and cultured of astrocytes exposed to 75 mM ethanol for 7 days. Our results demonstrate that chronic ethanol treatment up-regulates iNOS, COX-2 and IL-1beta in rat cerebral cortex and in cultured astrocytes. Under both experimental conditions, up-regulation of these inflammatory mediators and IL-1RI concomitantly occurs with the stimulation of IRAK and MAP kinases, including ERK1/2, p-38 and JNK, which trigger the downstream activation of oxidant-sensitive transcription factors NF-KB and AP-1. These effects were associated with an increased in both caspase-3 and apoptosis in ethanol-fed rats and in astrocytes exposed to ethanol. In conclusion, chronic ethanol treatment stimulates glial cells, up-regulating the production and the expression of inflammatory mediators in the brain, and activating signalling pathways and transcription factors involved in inflammatory damage and cell death.