Induced iNOS Expression Research Articles

PIAS1 and STAT-3 impair the tumoricidal potential of IFN-γ-stimulated mouse dendritic cells generated with IL-15.

Primarily defined by their antigen-presenting property, dendritic cells (DCs) are being implemented as cancer vaccines in immunotherapeutic interventions. DCs can also function as direct tumor cell killers. How DC cytotoxic activity can be efficiently harnessed and the mechanisms controlling this nonconventional property are not fully understood. We report here that the tumoricidal potential of mouse DCs generated from myeloid precursors with GM-CSF and IL-15 (IL-15 DCs) can be triggered with the Toll-like receptor (TLR) 4 ligand lipopolysaccharide to a similar extent compared with that of their counterparts, conventionally generated with IL-4 (IL-4 DCs). The mechanism of tumor cell killing depends on the induction of iNOS expression by DCs. In contrast, interferon (IFN)-γ induces the cytotoxic activity of IL-4 but not IL-15 DCs. Although the IFN-γ-STAT-1 signaling pathway is overall functional in IL-15 DCs, IFN-γ fails to induce iNOS expression in these cells. iNOS expression is negatively controlled in IFN-γ-stimulated IL-15 DCs by the cooperation between the E3 SUMO ligase PIAS1 and STAT-3, and can be partially restored with PIAS1 siRNA and STAT-3 inhibitors.

Induction of inducible nitric oxide synthase (iNOS) expression by oxLDL inhibits macrophage derived foam cell migration

ObjectiveDeletion of inducible nitric oxide synthase (iNOS) in apolipoprotein E knockout mice was shown to mitigate the extent of arteriosclerosis. Oxidized low density lipoprotein (oxLDL) inhibits macrophage migration and traps foam cells, possibly through a mechanism involving oxidative stress. Here, we addressed whether a reduction of iNOS-mediated oxidative stress remobilizes macrophage-derived foam cells and may reverse plaque formation. MethodsMigration of RAW264.7 cells and bone marrow cells was quantified using a modified Boyden chamber. iNOS expression, phalloidin staining, focal adhesion kinase phosphorylation, lipid peroxides, nitric oxide (NO) and reactive oxygen species (ROS) production were assessed. ResultsoxLDL treatment significantly reduced cell migration compared to unstimulated cells (p < 0.05). This migratory arrest was reversed by co-incubation with a pharmacologic iNOS inhibitor 1400W (p < 0.05) and iNOS-siRNA (p > 0.05). Furthermore, apoE/iNOS double knockout macrophages do not show migratory arrest in response to oxLDL uptake, compared to apoE knockout controls (p > 0.05). We documented significantly increased iNOS expression following oxLDL treatment and downregulation using 1400W and small inhibitory RNA (siRNA). iNOS inhibition was associated with a reduction in NO and peroxynitrite (ONOO–)– and increased superoxide generation. Trolox treatment of RAW264.7 cells restored migration indicating that peroxynitrite mediated lipid peroxide formation is involved in the signaling pathway mediating cell arrest.. ConclusionsHere, we provide pharmacologic and genetic evidence that oxLDL induced iNOS expression inhibits macrophage-derived foam cell migration. Therefore, reduction of peroxynitrite and possibly lipid hydroperoxide levels in plaques represents a valuable therapeutic approach to reverse migratory arrest of macrophage-derived foam cells and to impair plaque formation.

IGF-1 induces iNOS expression via the p38 MAPK signal pathway in the anti-apoptotic process in pulmonary artery smooth muscle cells during PAH

Apoptosis and cell proliferation are two important cellular processes that determine the accumulation of pulmonary artery smooth muscle cells (PASMC) during pulmonary arterial hypertension (PAH). Insulin-like growth factor 1 (IGF-1) is an endocrine and autocrine/paracrine growth factor that circulates at high levels in the plasma and is expressed in most cell types. IGF-1 has major effects on development, cell growth and differentiation, also tissue repair. Inducible nitric oxide synthase (iNOS) has been shown to serve many vasoprotective roles in vascular smooth muscle cells (VSMCs) including inhibition of VSMC proliferation and migration and stimulation of endothelial cell growth. In this study, we investigated the involvement of iNOS in the process of IGF-1-induced inhibition of PASMC apoptosis. We also examined the role of p38 mitogen-activated protein kinase (MAPK) in the IGF-1-induced iNOS activation. Our results show that exogenous IGF-1 induced the up-regulation of iNOS in PASMC. Immunofluorescence of IGF-1 and iNOS showed a decreased immunostaining of both IGF-1 and iNOS in the cytoplasm and the perinucleus under serum deprivation condition. iNOS inhibition in PASMC in vitro markedly induced IGF-1-mediated anti-apoptosis as assessed by the cell viability measurement, Western blot, mitochondrial potential analysis and nuclear morphology determination. A p38 MAPK inhibitor blocked all the effects of IGF-1 on iNOS. Our findings suggest that IGF-1 inhibits cells apoptosis in PASMC by activating the p38 MAPK–iNOS transduction pathway. This mechanism may contribute to the accumulation of PASMC in early human PAH.

Guanosine protects C6 astroglial cells against azide‐induced oxidative damage: a putative role of heme oxygenase 1

Guanosine, a guanine-based purine, is an extracellular signaling molecule that is released from astrocytes and shows neuroprotective effects in several in vivo and in vitro studies. Our group recently showed that guanosine presents antioxidant properties in C6 astroglial cells. The heme oxygenase 1 signaling pathway is associated with protection against oxidative stress. Azide, an inhibitor of the respiratory chain, is frequently used in experimental models to induce oxidative and nitrosative stress. Thus, the goal of this study was to investigate the effect of guanosine on azide-induced oxidative damage in C6 astroglial cells. Azide treatment of these cells resulted in several detrimental effects, including induction of cytotoxicity and mitochondrial dysfunction, increased levels of reactive oxygen/nitrogen species, inducible nitric oxide synthase expression and NADPH oxidase, decreased glutamate uptake and EAAC1 glutamate transporter expression, decreased glutathione (GSH) levels, and decreased activities of glutamine synthetase (GS), superoxide dismutase and catalase (CAT). The treatment also increased nuclear factor-κB activation and the release of proinflammatory cytokines tumor necrosis factor α and IL-1β. Guanosine strongly prevented these effects, protecting glial cells against azide-induced cytotoxicity and modulating glial, oxidative and inflammatory responses through the activation of the heme oxygenase 1 pathway. These observations reinforce and support the role of guanosine as an antioxidant molecule against oxidative damage. Guanosine protects against azide-induced oxidative damage in C6 astroglial cells. Azide-induced mitochondrial dysfunction (1); increased reactive oxygen species/reactive nitrogen species levels (2); decreased glutamate uptake (3), GS activity (4), GSH levels (5), and SOD (6) and CAT (7) activities; increased glutathione peroxidase (GPx) (8) and NADPH oxidase (9) activities and cellular superoxide levels (10); increased NF-κB activation (11), TNF-α and IL-1β levels (12); and induced iNOS expression (13). Guanosine prevented these effects through the HO1 signaling pathway, thus our findings support the antioxidant effects of guanosine.

Chronic moderate alcohol consumption induces iNOS expression in the penis: An immunohistochemical study.

To investigate the effect of moderate alcohol consumption on metabolic alterations, inducible nitric oxide synthase (iNOS), immunohistochemical distribution, and morphological damage to penile erectile tissue in rats. Male Wistar albino rats were divided into 2 groups. Group 1 rats (control group, n = 8) received tap water ad libitum, and group 2 rats (n = 8) were fed with 20% ethanol. Increasing levels of alcohol were given to the rats over 12 weeks. Immunohistochemistry was then performed using the avidin-biotin-peroxidase technique on 5-pm thickness tissue sections. Stained sections were examined by imaging microscope. Alcohol consumption resulted in a significant increase in iNOS immunoreactivity in the penile erectile tissue. Increased iNOS expression was determined in the tunica albuginea, cavernosal smooth muscle cells, trabeculae of connective tissue, arterioles, and the urethral epithelium. Moreover, chronic alcohol consumption resulted in decreasing serum testosterone and high density lipoprotein (HDL) levels with increasing cholesterol and triglyceride levels. Chronic moderate alcohol consumption can affect penile erectile tissue by increasing iNOS immunoreactivity and induce histopathological damage such as penile fibrosis. These abnormalities are also related to the defense mechanism against morphological damage.

The role of MAP kinases in the induction of iNOS expression in neutrophils exposed to NDMA: the involvement transcription factors

The role of MAP kinases in the activation of AP-1 (c-Jun, c-Fos) and NF-κB p65 engaged in the regulation of iNOS expression in human neutrophils (PMNs) exposed to N-nitrosodimethylamine (NDMA) was analyzed in the study. The study included a group of 20 healthy individuals. Isolated human PMN were incubated in the presence of NDMA. Selective MAP kinases inhibitors were used. The expression of proteins in the cytoplasmic and nuclear fractions was assessed using Western blot method. The results show that NDMA intensifies iNOS, c-Jun, NF-κB p65 and IκB-α expression in the analyzed PMNs. The blocking of the p38 pathway led to lower iNOS expression, and higher expression of c-Jun and c-Fos in the cytoplasmic fraction, and also lower c-Jun expression in the nuclear fraction of PMNs exposed to NDMA. A decrease in iNOS expression in the cytoplasmic fraction, and also c-Jun in both fractions of the examined cells, was observed as a result of JNK pathway inhibition. The blocking of the ERK5 pathway led to higher iNOS, c-Jun and c-Fos expression in the cytoplasmic fraction, and higher c-Jun expression in the nuclear fraction of PMNs exposed to NDMA. The study also demonstrated that blocking of the p38 and JNK pathways resulted in higher expression of NF-κB p65 and IκB-α in the cytoplasmic fraction and their lower expression in the nuclear fraction of these cells. Our data indicate the role of MAP kinases p38 and JNK in the activation of c-Jun and NF-κB p65 transcription factors engaged in the regulation of iNOS expression in human neutrophils exposed to NDMA. However ERK5 kinase is not involved in the regulation of iNOS and NO production by those cells.

Anti-diabetic and anti-inflammatory effect of a novel selective 11β-HSD1 inhibitor in the diet-induced obese mice

It has been reported that the selective inhibitors of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) have considerable potential for treating type 2 diabetes mellitus, metabolic syndrome and inflammation. In the present study, we investigated the anti-diabetic and anti-inflammatory effects of N-(5-carbamoyladamantan-2-yl)-3-((2-fluorophenyl) sulfonyl)thiazolidine-2-carboxamide (KR-67105), a novel 11β-HSD1 inhibitor, in diabetic mice model and preadipocyte model. KR-67105 concentration dependently inhibited 11β-HSD1 activity in human and mouse 11β-HSD1 overexpressing cells and mouse 3T3-L1 adipocytes. Furthermore, KR-67105 concentration-dependently inhibited 11β-HSD1 activity in the ex vivo assay of C57BL/6 mice. In the study with diet-induced obese (DIO) mice, the administration of KR-67105 (100mg/kg/day, orally for 28 days) improved the glucose tolerance and insulin sensitivity as determined by the oral glucose tolerance test and the insulin tolerance test. Anti-diabetic effect by KR-67105 was associated with the suppression of diabetic related genes expression in liver and fat. Furthermore, KR-67105 suppressed 11β-HSD1 activity in liver and fat of diabetic mice, but showed no effect on adrenal grand weight/body weight ratio and plasma corticosterone concentration in diabetic mice. In 3T3-L1 preadipocytes, cortisone induced the mRNA of inflammatory cytokines and 11β-HSD1 and reactive oxygen species formation. This effect was abolished by co-incubation with KR-67105 in a concentration-dependent manner. Moreover, KR-67105 attenuated cortisone induced iNOS expression and phosphorylation of NF-κB p65, p38 MAPK, and ERK1/2 in preadipocytes. Taken together, it is concluded that a selective 11β-HSD1 inhibitor, KR-67105, may provide a new therapeutic window in the prevention and treatment of type 2 diabetes with chronic inflammation without toxicity.

Citrus nobiletin suppresses inducible nitric oxide synthase gene expression in interleukin-1β-treated hepatocytes

BackgroundNobiletin is a polymethoxylated flavone that is abundant in the peels of citrus fruits, such as Citrus unshiu (Satsuma mandarin) and Citrus sinensis. The dried peels of C. unshiu (chinpi) have been included in several formulae of Japanese Kampo medicines. Nobiletin may suppress the induction of inducible nitric oxide synthase (iNOS), which synthesizes the inflammatory mediator nitric oxide (NO) in hepatocytes. MethodsA C. unshiu peel (CUP) extract was prepared. Primary cultured rat hepatocytes were treated with the CUP extract or nobiletin in the presence of interleukin 1β (IL-1β), which induces iNOS expression. NO production and iNOS gene expression were analyzed. ResultsHigh-performance liquid chromatography analyses revealed that the nobiletin content in the CUP extract was 0.14%. Nobiletin dose-dependently reduced the NO levels and decreased iNOS expression at the protein, mRNA and antisense transcript levels. Flavone, which does not contain any methoxy groups, also suppressed iNOS induction. Nobiletin reduced the transcriptional activity of iNOS promoter-luciferase constructs and the DNA-binding activity of nuclear factor κB (NF-κB) in the nuclei. ConclusionsThe suppression of iNOS induction by nobiletin suggests that nobiletin may be responsible for the anti-inflammatory effects of citrus peels and have a therapeutic potential for liver diseases.

Metal Allergens Induce Nitric Oxide Production by Mouse Dermal Fibroblasts via the Hypoxia-Inducible Factor-2α–Dependent Pathway

Nickel (Ni) has been shown to be one of the most frequent metal allergens. We have already reported a murine metal allergy model with pathogen-associated molecular patterns (PAMPs) as adjuvants. Interleukin (IL)-1β plays a critical role in our mouse model. Because nonimmune cells, including fibroblasts, play important roles in local allergic inflammation, we investigated whether Ni induces inflammatory responses in mouse dermal fibroblasts (MDF). We also analyzed the synergistic effects between Ni, PAMPs, and IL-1β. MDF stimulated with Ni produced a significantly higher amount of nitric oxide (NO) in a dose-dependent manner. NO production was augmented by costimulation with IL-1β but not with PAMPs. On the other hand, IL-1β or PAMPs induced a significantly higher amount of IL-6 production by MDF, but no augmentation was detected in the presence of Ni. A specific inhibitor for inducible nitric oxide synthase (iNOS) inhibited Ni-induced NO production. iNOS mRNA expression was significantly higher in MDF stimulated with Ni, IL-1β, or both. A specific inhibitor for hypoxia-inducible factor (HIF)-2α, but not HIF-1α, inhibited NO production. Another frequent metal allergen, cobalt, also induced iNOS expression and NO production by MDF via the HIF-2α-dependent pathway. The inhibitor for iNOS augmented ear swelling in Ni allergy mouse model. On the other hand, HIF-2α inhibitor attenuates allergic inflammation. These results indicate that metal allergens induce NO production in MDF via the HIF-2α-dependent pathway and IL-1β augments NO production, which suggests that the NO induced by metal allergens plays a pathological role in metal allergies.

P3: iNOS/NO upregulates Wnt/β-catenin signaling through dickkopf-1 (DKK1) inhibition

Wnt signaling contributes to carcinogenesis and tumor progression but the detailed mechanism of constitutive activation or silencing of Wnt signaling is not well-established. We have shown that human iNOS (hiNOS) gene is a target of Wnt/ β -catenin signaling pathway, and Wnt/ β -catenin signaling regulates hiNOS by inhibiting NF- κ B activity in cancer cells. DKK1 is a potent secreted Wnt antagonist that plays a key role in the negative regulation of the canonical Wnt system, by interacting with Wnt co-receptor proteins in the LRP family to inhibit Wnt signaling. However, the relationship between induced NO synthesis and DKK1-mediated inhibition of Wnt signaling has not been examined. The purpose of this study was to determine if iNOS expression and NO influence Wnt/ β -catenin activity, and if so whether this was mediated by an effect on DKK1 expression. Stable cell lines transfected with human iNOS (hiNOS) or DKK-1genes were established in the SW480 colon cancer cell line. Stable cell lines transfected with shRNA-iNOS were established in SW480 colon and MCF7 breast cancer cell lines. A Wnt signaling pathway microarray analysis (SuperArray) was employed to study the global transcriptional response to hiNOS gene expression. The Greiss reaction was used for the detection of NO production. RT-PCR and Western blotting were used for gene expression analysis. Banked cancer tissues were examined for hiNOS and DKK1 expression. Human iNOS (hiNOS) gene expression was inversely correlated with DKK1 expression in human colon and breast cancer tumor samples and intestinal adenoma tumors from Min ( APC min /+ ) mice. HiNOS gene expression promoted canonical Wnt signaling in cancer cells. HiNOS expression transcriptionally downregulated DKK1 gene expression in the Wnt-related gene superarray, and in cancer cell lines stably expressing hiNOS. Cytokines that induced iNOS expression in cancer cells and primary human hepatocytes decreased constitutive DKK1 protein levels. Knocking down hiNOS gene by shRNA restored DKK1 expression and inhibitory effect on Wnt signaling. These findings demonstrate that iNOS/NO down-regulate DKK1 gene expression at the transcriptional level in vitro, and are consistent with the in vivo findings in cancer tissues where iNOS and DKK1 expression are inversely correlated. These data identify a previously unrecognized mechanism by which the iNOS/NO pathway promotes cancer by inhibiting DKK1 which unleashes Wnt/ β -catenin signaling leading to enhanced β -catenin target gene activation. The findings provide new insight into the complex control mechanisms of iNOS/NO, DKK1, and Wnt/ β -catenin during carcinogenesis. Nothing to disclose.

Glucosamine inhibits lipopolysaccharide-stimulated inducible nitric oxide synthase induction by inhibiting expression of NF-kappaB/Rel proteins at the mRNA and protein levels

Expression of inducible nitric oxide synthase (iNOS) protein by lipopolysaccharide (LPS) in BV2 microglia cells increased in a biphasic manner. Glucosamine (GlcN) selectively suppressed the late- but not early-stage iNOS response to LPS. Prolonged induction of iNOS expression by LPS was inhibited by cycloheximide, suggesting that de novo protein synthesis was required. Late-phase activation of nuclear factor-kappaB (NF-κB) activity required for sustained iNOS induction. Nuclear translocation and DNA binding of NF-κB, and Rel proteins expressions were inhibited by GlcN at later time points but not upon immediate early-stage activation by LPS. We show that GlcN selectively inhibits sustained iNOS induction by inhibiting Rel protein expression at both the mRNA and protein levels; such expression is required for prolonged iNOS induction by LPS. Our results provide mechanistic evidence that GlcN regulates inflammation, represented by iNOS. The implication of these results is that GlcN may be a potent transcriptional regulator of iNOS and other genes involved in the general inflammation process.

Exendin‐4 inhibits iNOS expression at the protein level in LPS‐stimulated Raw264.7 macrophage by the activation of cAMP/PKA pathway

Glucagon-like peptide-1 (GLP-1) and its potent agonists have been widely studied in pancreatic islet β-cells. However, GLP-1 receptors are present in many extrapancreatic tissues including macrophages, and thus GLP-1 may have diverse actions in these tissues and cells. Therefore, we examined the mechanism by which exendin-4 (EX-4), a potent GLP-1 receptor agonist, inhibits lipopolysaccharide (LPS)-induced iNOS expression in Raw264.7 macrophage cells. EX-4 significantly inhibited LPS-induced iNOS protein expression and nitrite production. However, Northern blot and promoter analyses demonstrated that EX-4 did not inhibit LPS-induced iNOS mRNA expression and iNOS promoter activity. Electrophoretic mobility shift assay (EMSA) showed that EX-4 did not alter the binding activity of NF-κB to the iNOS promoter. Consistent with the result of EMSA, LPS-induced IκBα phosphorylation and nuclear translocation of p65 were not inhibited by EX-4. Also, actinomycin D chase study and the promoter assay using the construct containing 3'-untranslated region of iNOS showed that EX-4 did not affect iNOS mRNA stability. Meanwhile, cycloheximide chase study demonstrated that EX-4 significantly accelerated iNOS protein degradation. The EX-4 inhibition of LPS-induced iNOS protein was significantly reversed by adenylate cyclase inhibitors (MDL-12330A and SQ 22536), a PKA inhibitor (H-89) and PKAα gene silencing. These findings suggest that EX-4 inhibited LPS-induced iNOS expression at protein level, but not at transcriptional mechanism of iNOS gene and this inhibitory effect of EX-4 was mainly dependent on cAMP/PKA system.

INOS inhibitor, L-NIL, reverses burn-induced glycogen synthase kinase-3β activation in skeletal muscle of rats

ObjectivesRecent studies suggest that activation of glycogen synthase kinase (GSK)-3β may be involved in burn injury-induced metabolic derangements and protein breakdown in skeletal muscle. However, the mechanism for GSK-3β activation after burn injury is unknown. To investigate the role of inducible nitric oxide synthase (iNOS) in this scenario, a major mediator of inflammation, we examined the effects of a specific inhibitor for iNOS, L-NIL, on GSK-3β activity in skeletal muscle of burned rats. Materials/MethodsFull-thickness third degree burn injury comprising 40% of total body surface area was produced under anesthesia in male Sprague–Dawley rats (160–190g) by immersing the back of the trunk for 15s and the abdomen for 8s in 80°C water. Burned and sham-burned rats were treated with L-NIL (60mg/kg BW, b.i.d., IP) or phosphate-buffered saline for three days. GSK-3β activity in skeletal muscle was evaluated by immune complex kinase assay, and by phosphorylation status of GSK-3β and its endogenous substrate, glycogen synthase. ResultsGSK-3β activity was increased in a time-dependent manner in skeletal muscle after burn injury, concomitant with the induction of iNOS expression. iNOS inhibitor, L-NIL, reverted the elevated GSK-3β activity in skeletal muscle of burned rats, although L-NIL did not alter GSK-3β activity in sham-burned rats. ConclusionsOur results clearly indicate that iNOS plays an important role in burn injury-induced GSK-3β activation in skeletal muscle. These findings suggest that iNOS may contribute to burn injury-induced metabolic derangements, in part, by activating GSK-3β.

Leukaemia inhibitory factor stimulates proliferation of olfactory neuronal progenitors via inducible nitric oxide synthase.

Neurogenesis continues in the adult brain and in the adult olfactory epithelium. The cytokine, leukaemia inhibitory factor and nitric oxide are both known to stimulate neuronal progenitor cell proliferation in the olfactory epithelium after injury. Our aim here was to determine whether these observations are independent, specifically, whether leukaemia inhibitory factor triggers neural precursor proliferation via the inducible nitric oxide synthase pathway. We evaluated the effects of leukaemia inhibitory factor on inducible form of nitric oxide synthase (iNOS) expression, and cell proliferation in olfactory epithelial cell cultures and olfactory neurosphere-derived cells. Leukaemia inhibitory factor induced expression of iNOS and increased cell proliferation. An iNOS inhibitor and an anti-leukaemia inhibitory factor receptor blocking antibody inhibited leukaemia inhibitory factor-induced cell proliferation, an effect that was reversed by a NO donor. Altogether, the results strongly suggest that leukaemia inhibitory factor induces iNOS expression, increasing nitric oxide levels, to stimulate proliferation of olfactory neural precursor cells. This finding sheds light on neuronal regeneration occurring after injury of the olfactory epithelium.

PP026-MON HEPCIDIN STORM AFTER ABDOMINAL SURGERY

Rationale: Glucagon-like peptide-1 (GLP-1) and its potent agonists have been widely studied in pancreatic islet b-cells. However, GLP-1 receptors are present in many extrapancreatic tissues including macrophages, and thus GLP-1 may have diverse actions on these tissues and cells. Therefore, we examined the mechanism by which exendin-4 (EX-4), a potent GLP-1 receptor agonist, inhibits lipopolysaccharide (LPS)-induced iNOS expression in Raw264.7 macrophage cells. Methods: The expression of iNOS, p-IuBa and p65 were detected by Western blot analysis and content of nitrite was measured using Griess reagent. Additionally, iNOS mRNA expression and promoter activity were observed by Northern blot analysis and luciferase assay, respectively. To observe the stability of iNOS mRNA and protein, actinomycin D chase and cycloheximide chase studies were performed, respectively. Also, we examined using adenylate cyclase inhibitor, PKA inhibitor and PKA gene silencing. Results: EX-4 significantly inhibited LPS-induced iNOS protein expression and nitrite production. However, EX-4 did not inhibit LPS-induced iNOS mRNA expression and iNOS promoter activity. Consistent with the result of iNOS promoter, LPS-induced IuBa phosphorylation and nuclear translocation of p65 were not inhibited by EX-4. Also, actinomycin D chase study showed that EX-4 did not affect iNOS mRNA stability. Meanwhile, cycloheximide chase study demonstrated that EX-4 significantly accelerated iNOS protein degradation. The EX-4 inhibition of LPS-induced iNOS protein was significantly reversed by adenylate cyclase inhibitors (MDL-12330A and SQ 22536), a PKA inhibitor (H-89) and PKAa gene silencing. Conclusion: These findings suggest that EX-4 inhibited LPS-induced iNOS protein expression at protein level, but not at transcriptional mechanism of iNOS gene and this inhibitory effect of EX-4 was mainly dependent on cAMP/PKA system.

Chronic inhibition of nitric oxide synthase activity by NG-nitro-l-arginine induces nitric oxide synthase expression in the developing rat cerebellum

Studies on chronic inhibition of NO synthase (NOS) in the CNS suggest a plastic change in NO synthesis in areas related to motor control, which might protect the animal from the functional and behavioral consequences of NO deficiency. In the present study, the acute and chronic effect of the substrate analogue inhibitor N G -nitro- l -arginine (L-NNA) was examined on NO production, NO-sensitive cGMP levels and the expression of NOS isoforms in the developing rat cerebellum. Acute intraperitoneal administration of the inhibitor (5–200 mg/kg) to 21-day old rats reduced NOS activity and NO concentration dose dependently by 70–90% and the tissue cGMP level by 60–80%. By contrast, chronic application of L-NNA between postnatal days 4–21 diminished the total NOS activity and NO concentration only by 30%, and the tissue cGMP level by 10–50%. Chronic treatment of 10 mg/kg L-NNA induced nNOS expression in granule cells, as revealed by in situ hybridization, NADPH-diaphorase histochemistry and Western-blot, but it had no significant influence on tissue cGMP level or on layer formation of the cerebellum. However, a higher concentration (50 mg/kg) of L-NNA decreased the intensity of the NADPH-diaphorase reaction in granule cells, significantly reduced cGMP production, and retarded layer formation and induced iNOS expression and activity in glial cells. Treatments did not affect eNOS expression. The present findings suggest the existence of a concentration-dependent compensatory mechanism against experimentally-induced chronic inhibition of NOS, including nNOS or iNOS up-regulation, which might maintain a steady-state NO level in the developing cerebellum.

Interferon γ Stimulates Accumulation of Gas Phase Nitric Oxide in Differentiated Cultures of Normal and Cystic Fibrosis Airway Epithelial Cells

Exhaled nitric oxide (NO) levels have been reported to be lower in patients with cystic fibrosis (CF) than in controls; however the mechanism(s) responsible and the effect on pathogenesis are unclear. The objective of these studies was to determine if the low levels of gas phase NO (gNO) could be reproduced in well-differentiated air-liquid interface (ALI) cultures of normal and CF cells. Human bronchial epithelial (HBE) cells from CF and control tissues were cultured under ALI conditions that promote differentiation into a mostly ciliated, pseudostratified epithelium similar to that of the in vivo airway. Cultures were incubated in gas tight chambers and the concentration of gNO was measured using a Sievers nitric oxide analyzer. In CF and control cultures the level of accumulated gNO under baseline conditions was low (<20ppb). Treatment with interferon gamma (IFNγ) induced iNOS expression and increased gNO significantly in differentiated cultures, while having no significant effect on undifferentiated cultures. Submersion of the apical surface with fluid drastically reduced the level of gNO. Importantly, the average level of gNO measured after IFNγ treatment of control cells (576ppb) was threefold greater than that from CF cells (192ppb). The results demonstrate that the lower level of exhaled NO observed in CF patients is reproduced in well-differentiated primary cultures of HBE cells treated with IFNγ, supporting the hypothesis that the regulation of NO production is altered in CF. The results also demonstrate that IFNγ treatment of differentiated cells results in higher levels of gNO than treatment of undifferentiated cells, and that a layer of fluid on the apical surface drastically reduces the amount of gNO, possibly by limiting the availability of oxygen.

IL-17A Synergizes with IFN-γ to Upregulate iNOS and NO Production and Inhibit Chlamydial Growth

IFN-γ-mediated inducible nitric oxide synthase (iNOS) expression is critical for controlling chlamydial infection through microbicidal nitric oxide (NO) production. Interleukin-17A (IL-17A), as a new proinflammatory cytokine, has been shown to play a protective role in host defense against Chlamydia muridarum (Cm) infection. To define the related mechanism, we investigated, in the present study, the effect of IL-17A on IFN-γ induced iNOS expression and NO production during Cm infection in vitro and in vivo. Our data showed that IL-17A significantly enhanced IFN-γ-induced iNOS expression and NO production and inhibited Cm growth in Cm-infected murine lung epithelial (TC-1) cells. The synergistic effect of IL-17A and IFN-γ on Chlamydia clearance from TC-1 cells correlated with iNOS induction. Since one of the main antimicrobial mechanisms of activated macrophages is the release of NO, we also examined the inhibitory effect of IL-17A and IFN-γ on Cm growth in peritoneal macrophages. IL-17A (10 ng/ml) synergizes with IFN-γ (200 U/ml) in macrophages to inhibit Cm growth. This effect was largely reversed by aminoguanidine (AG), an iNOS inhibitor. Finally, neutralization of IL-17A in Cm infected mice resulted in reduced iNOS expression in the lung and higher Cm growth. Taken together, the results indicate that IL-17A and IFN-γ play a synergistic role in inhibiting chlamydial lung infection, at least partially through enhancing iNOS expression and NO production in epithelial cells and macrophages.

SOD1 suppresses maternal hyperglycemia-increased iNOS expression and consequent nitrosative stress in diabetic embryopathy

Hyperglycemia induces oxidative stress and increases inducible nitric oxide synthase (iNOS) expression. We hypothesized that oxidative stress is responsible for hyperglycemia-induced iNOS expression. iNOS-luciferase activities, nitrosylated protein, and lipid peroxidation markers 4-hydroxynonenal and malondialdehyde were determined in parietal yolk sac-2 cells exposed to 5 mmol/L glucose or high glucose (25 mmol/L) with or without copper zinc superoxide dismutase 1 (SOD1) treatment. Levels of iNOS protein and messenger RNA, nitrosylated protein, and cleaved caspase-3 and -8 were assessed in wild-type embryos and SOD1-overexpressing embryos from nondiabetic and diabetic dams. SOD1 treatment diminished high glucose-induced oxidative stress, as evidenced by 4-hydroxynonenal and malondialdehyde reductions, and it blocked high glucose-increased iNOS expression, iNOS-luciferase activities, and nitrosylated protein. In vivo SOD1 overexpression suppressed hyperglycemia-increased iNOS expression and nitrosylated protein, and it blocked caspase-3 and -8 cleavage. We conclude that oxidative stress induces iNOS expression, nitrosative stress, and apoptosis in diabetic embryopathy.

The expression of inducible nitric oxide synthase in human retinal pigment epithelial cells under stimulation of proinflammatory cytokine tumor necrosis factor-α

PurposeTo elucidate the effects of tumor necrosis factor (TNF)-α on the expression of inducible nitric oxide synthase (iNOS) in retinal pigment epithelial cells in vitro. MethodsARPE-19 cell lines were cultured with TNF-α stimulation, and then treated with proteasome inhibitors (MG132 or lactacystin) for 30 minutes. The expression of iNOS was determined by RT-PCR and Western blot. The expression of nitric oxide (NO) was determined by an enzyme-linked immunosorbent assay. The interaction of nuclear factor kappa-B (NF-κB) activation and iNOS induction was assessed by electrophoretic mobility shift assay. ResultsThe expression of iNOS in ARPE-19 was induced by TNF-α in a dose-dependent manner. Upregulation of iNOS resulted in increased production of NO. iNOS induced by TNF-α could be inhibited by MG-132 and lactacystin. Supershift assay revealed that NF-κB activation was responsible for iNOS induction. ConclusionTNF-α could induce iNOS expression and NO production in RPE cells, at least in part, via an NF-κB signal pathway.