Human Inducible Nitric Oxide Synthase Research Articles

New insight on antioxidants and anti-obesity properties of two seagrasses Thalassia hemprichii and Zostera marina: an integrated molecular docking simulation with in vitro study

Background The oceans are teeming with a diverse range of marine organisms that offer unique health benefits, such as seagrass which is one of many key marine products that have garnered attention for their potential therapeutic properties. However, until now there have been few successful reports of seagrass’s metabolites profile and biological activity. Therefore, this work aims to profile metabolites or chemical constituents and assess the potential antioxidants and anti-obesity effects of two seagrasses, Thalassia hemprichii and Zostera marina. Methods Once authenticated, T. hemprichii and Z. marina were extracted with two different solvents, polar (ethanol) and nonpolar (hexane). Metabolite profiling was performed using untargeted metabolomic profiling via liquid chromatography coupled to high-resolution tandem mass spectrometry method analysis, and then antioxidant and anti-obesity capabilities were assessed by molecular docking and in vitro studies on selected receptors. Results A total of 9 and 11 metabolites were observed from T. hemprichii and Z. marina and continued molecular docking. Some of the observed compounds have promising potential as inhibitors of human inducible nitric oxide synthase, reactive oxygen species (ROS) 1 kinase, human pancreatic lipase, and fat mass and obesity-associated (FTO) proteins, including luteolin, 6-hydroxy compounds luteolin O-glucoside, luteolin-O-sulphate, Thalassiolin A, Thalassiolin C, kaempferol-7,4′-dimethylether-3-O-sulfate, apigenin, and diosmetin. T. hemprichii ethanol extract (THE) EC50 value shows antioxidant capabilities via ABTS radical scavenging activity of 76.00 μg/mL, a smaller value than standard antioxidant controls (Trolox, 76.54 μg/mL) and followed by EC50 of lipase inhibition activity by THE which has the same pattern (EC50 THE < EC50 Orlistat). Conclusions This concludes that the two seagrasses have promising biological activity as candidates for functional food and/or drugs in combating free radicals and obesity.

In Silico Analysis of Selected Mikania Constituents As Human HMG-CoA Reductase, Human Inducible Nitric Oxide Synthase, and Human Squalene Synthase Inhibitory Agents.

Background Numerous pharmacological activities have been reportedin Mikania species. In the present investigation, we aimed to evaluate 26 selected constituents of Mikania as potent inhibitory agents of human HMG-CoA reductase (hHMGR), human inducible nitric oxide synthase (hiNOS), and human squalene synthase (hSQS) using the in silico method. Methodology Twenty-six selected constituents of Mikania were investigated based on the docking behavior of three target enzymes, namely hHMGR, hiNOS, and hSQS, using the Cdocker method (Discovery Studio® 3.1, Accelrys, Inc., San Diego, CA). Results Docking analysis showed that methyl-3,5-di-O-caffeoyl quinate (MCQ) has the maximum binding energy (BE) (-39.63, -50.65, and -58.56 kcal/mol) with hHMGR, hiNOS, and hSQS enzymes. On the other hand, six ligands (kaurenoic acid (KAA), stigmasterol (SS), grandifloric acid (GA), kaurenol (KA), spathlenol (SP), and taraxerol (TA)) of Mikania failed to dock with either of the targetenzymes (hHMGR, hiNOS, or hSQS). Conclusions The findings of the current study provide new insight regarding 26 selected ligands of Mikania as potent inhibitory agents of hHMGR, hiNOS, and hSQS.

Anti-inflammatory and Antiphytopathogenic Fungal Activity of 2,3-seco-Tirucallane Triterpenoids Meliadubins A and B from Melia dubia Cav. Barks with ChemGPS-NP and In Silico Prediction.

Two new rearranged 2,3-seco-tirucallane triterpenoids, meliadubins A (1) and B (2), along with four known compounds, 3-6, were isolated from the barks of Melia dubia Cav. Compound 2 exhibited a significant inflammatory inhibition effect toward superoxide anion generation in human neutrophils (EC50 at 5.54 ± 0.36 μM). It bound to active sites of a human inducible nitric oxide synthase (3E7G) through interactions with the residues of GLU377 and PRO350, which may benefit in reducing the neutrophilic inflammation effect. The ChemGPS-NP interpretation combined with bioactivity assay and in silico prediction results suggested 2 to be an agent for targeting iNOS with different mechanisms as compared to a selected set of current approved drugs. Moreover, compounds 1 and 2 showed remarkable inhibition against the rice pathogenic fungus Magnaporthe oryzae in a dose-dependent manner with IC50 values of 137.20 ± 9.55 and 182.50 ± 18.27 μM, respectively. Both 1 and 2 displayed interactions with the residue of TYR223, a key active site of trihydroxynaphthalene reductase (1YBV). The interpretation of 1 and 2 in the ChemGPS-NP physical-chemical property space indicated that both compounds are quite different compared to all members of a selected set of reference compounds. In light of demonstrated biological activity and in silico prediction experiments, both compounds possibly exhibited activity against phytopathogenic fungi via a novel mode of action.

Wound healing potential of Acacia catechu in streptozotocin-induced diabetic mice using invivo and in silico approach.

Acacia catechu Wild. (Fabaceae) barks are traditionally used in the treatment of diabetes and wounds. Therefore, the objective of the present study was to evaluate the wound healing potential of the alcoholic extract of A.catechu (EAC) in streptozotocin-induced diabetic mice. EAC was first subjected to phytochemical estimations and standardization using (-) epicatechin as marker with the help of HPLC. Diabetes was induced in mice using streptozotocin and the wound healing potential of EAC was evaluated using excision and incision wound models on topical and oral treatment. Various biochemical parameters, invivo antioxidants, cytokine profiling, VEGF, and histopathological examination were also performed. Further, molecular docking studies were performed using ligand (-) epicatechin on human inducible nitric oxide synthase. Phytochemically, EAC showed the presence of tannins, flavonoids, phenolic compounds, and saponins, while the content of (-) epicatechin was reported to be 7.81% w/w. The maximum healing of wounds (91.84±1.10%) was observed in mice treated with a combination of both topical (10% gel) and oral (extract at 200mg/kg) followed by topically and orally treated groups respectively after 14 days of treatment. These groups also showed significant restoration of altered biochemical parameters, antioxidant enzymes and cytokines. The molecular docking studies confirmed the role of (-) epicatechin in stabilizing the human inducible nitric oxide synthase with inhibitor showing binding energy of-8.31kcal/mol. The present study confirmed the role of (-) epicatechin as a major marker in diabetic wound healing potential of A.catechu.

New insight on antioxidants and anti-obesity properties of two Indonesian seagrass Thalassia hemprichii and Zostera marina: an integrated molecular docking simulation with in vitro study

Background: The oceans are teeming with a diverse range of marine organisms that offer unique health benefits, such as seagrass which is one of many key marine products that have garnered attention for their potential therapeutic properties. However, until now there have been few successful reports of seagrass’s metabolites profile and biological activity. Therefore, this work aims to profile metabolites or chemical constituents and assess the potential antioxidants and anti-obesity effects of two Indonesian seagrasses, Thalassia hemprichii and Zostera marina. Methods: Once authenticated, T. hemprichii and Z. marina were extracted with two different solvents, polar (ethanol) and nonpolar (hexane). Metabolite profiling was performed using untargeted metabolomic profiling via liquid chromatography coupled to high-resolution tandem mass spectrometry method analysis, and then antioxidant and anti-obesity capabilities were assessed by molecular docking and in vitro studies on selected receptors. Results: A total of 9 and 11 metabolites were observed from T. hemprichii and Z. marina and continued molecular docking. Some of the observed compounds have promising potential as inhibitors of human inducible nitric oxide synthase, reactive oxygen species (ROS) 1 kinase, human pancreatic lipase, and fat mass and obesity-associated (FTO) proteins, including luteolin, 6-hydroxy compounds luteolin O-glucoside, luteolin-O-sulphate, Thalassiolin A, Thalassiolin C, kaempferol-7,4'-dimethylether-3-O-sulfate, apigenin, and diosmetin. T. hemprichii ethanol extract (THE) EC50 value shows antioxidant capabilities via ABTS radical scavenging activity of 76.00 μg/mL, a smaller value than standard antioxidant controls (Trolox, 76.54 μg/mL) and followed by EC50 of lipase inhibition activity by THE which has the same pattern (EC50 THE < EC50 Orlistat). Conclusions: This concludes that the two Indonesian seagrasses have promising biological activity as candidates for functional food and/or drugs in combating free radicals and obesity.

Interdomain Interactions Modulate the Active Site Dynamics of Human Inducible Nitric Oxide Synthase.

Nitric oxide synthase (NOS) is a homodimeric flavohemoprotein responsible for catalyzing the oxidation of l-arginine (l-Arg) to citrulline and nitric oxide. Electrons are supplied for the reaction via interdomain electron transfer between an N-terminal heme-containing oxygenase domain and a FMN-containing (sub)domain of a C-terminal reductase domain. Extensive attention has focused on elucidating how conformational dynamics regulate electron transfer between the domains. Here we investigate the impact of the interdomain FMN-heme interaction on the heme active site dynamics of inducible NOS (iNOS). Steady state linear and time-resolved two-dimensional infrared (2D IR) spectroscopy was applied to probe a CO ligand at the heme within the oxygenase domain for full-length and truncated or mutated constructs of human iNOS. Whereas the linear IR spectra of the CO ligand were identical among the constructs, 2D IR spectroscopy revealed variation in the frequency dynamics. The wild-type constructs that can properly form the FMN/oxygenase docked state due to the presence of both the FMN and oxygenase domains showed slower dynamics than the oxygenase domain alone. Introduction of the mutation (E546N) predicted to perturb electrostatic interactions between the domains resulted in measured dynamics intermediate between those for the full-length and individual oxygenase domain, consistent with perturbation to the docked/undocked equilibrium. These results indicate that docking of the FMN domain to the oxygenase domain not only brings the FMN cofactor within electron transfer distance of the heme domain but also modulates the dynamics sensed by the CO ligand within the active site in a way expected to promote efficient electron transfer.

A specific, non-immune system-related isoform of the human inducible nitric oxide synthase is expressed during differentiation of human stem cells into various cell types

BackgroundNOS2 expression is mostly found in bacteria-exposed or cytokine-treated tissues and is mostly connected to innate immune reactions. There are three isoforms of NOS2 (NOS2-1 to -3). In RNA-seq data sets, analyzing inflammatory gene expression, only expression of the NOS2-1 mRNA isoform is detected. However, the expression of NOS2 in differentiating human pluripotent stems (hPSCs) has not been analyzed yet.MethodsPublic available RNA-seq databases were screened for data of hPSCs during differentiation to different target cells. An isoform specific algorithm was used to analyze NOS2 mRNA isoform expression. In addition, we differentiated four different human iPSC cell lines toward cortical neurons and analyzed NOS2 mRNA expression by qRT-PCR and 5′-RACE. The functionality of the NOS2-2 protein was analyzed by transient transfection of expression clones in human DLD1 cells and nitrate measurement in the supernatant of these cells.ResultsIn RNA-seq databases we detected a transient expression of the NOS2 mRNA during the differentiation of hPSCs to cardiomyocytes, chondrocytes, mesenchymal stromal cells, neurons, syncytiotrophoblast cells, and trophoblasts. NOS2 mRNA isoform specific analyses showed, that the transiently expressed NOS2 mRNA in differentiating hPSC (NOS2-2; “diff-iNOS”) differ remarkably from the already described NOS2 transcript found in colon or induced islets (NOS2-1; “immuno-iNOS”). Also, analysis of the NOS2 mRNA- and protein expression during the differentiation of four different hiPSC lines towards cortical neurons showed a transient expression of the NOS2 mRNA and NOS2 protein on day 18 of the differentiation course. 5′-RACE experiments and isoform specific qRT-PCR analyses revealed that only the NOS2-2 mRNA isoform was expressed in these experiments. To analyze the functionality of the NOS2-2 protein, we transfected human DLD-1 cells with tetracycline inducible expression clones encoding the NOS2-1- or -2 coding sequence. After induction of the NOS2-1 or -2 mRNA expression by tetracycline a similar nitrate production was measured proofing the functionality of the NOS2-2 protein isoform.ConclusionsOur data show that a differentiation specific NOS2 isoform (NOS2-2) is transiently expressed during differentiation of hPSC.1uj3Epc_eyJHiftngx9QfcVideo

Effects of Smokeless Tobacco Samples from Tabuk Saudi Arabia on Nitric Oxide Production: A Potential Risk for Cancer and Cardiovascular Diseases.

Smokeless tobacco (SLT) is traditionally used in Middle East countries. The several toxic constituents with potential carcinogenicity make it a serious human health risk. Literature regarding their effects on cardiac and cancer disease is lacking in Saudi Arabia. This study was conducted to investigate the adverse effect of 11 different samples of widely used SLT varieties from the Tabuk region - Saudi Arabia, on Nitric Oxide (NO) level and their potential risk on cardiovascular health, etiology and/or progression of cancers. Samples were collected from Tabuk, KSA and analyzed by the GC-MS technique. Nitric oxide inhibition was performed using J774.2 macrophages by the Griess method. The retrieved crystallized structure of human inducible nitric oxide synthase (iNOS) from Brookhaven Protein Data Bank Repository PDB I.D: 3E7G with 2.20Å resolution was further prepared by structure using the MOE.2019 tool. The compounds abstracted from 11 different Shammah varieties were sketched by the MOE-Builder tool. Minimization for both receptor and compounds was performed via AMBER99 and MMFF99X force field implemented in MOE. Nine samples (4 - 11) showed a potent suppressive effect on NO production with IC50 values ranging between (16.9-20.4 μg/mL), respectively. The samples (1 & 2) exhibited a moderate level of inhibition with IC50 ranging between 33.2 and 57.4 μg/mL, respectively. Interestingly, sample 4 consisting of compounds (13-15, 19-26, 28) that mostly belongs to the group fatty acid ester and phthalic acid ester showed the most potent suppressive effect. Molecular docking results revealed that the current local SLT constituents presented noticeable potency in different extract samples. Variable suppressive effects on NO were detected in the current SLT samples, where sample 4 was the most potent among all. The extract of the latter exhibited molecular interaction with the first shell amino acid residues of Inducible nitric oxide synthase (iNOS), which may anchor the plasticity and selectivity of the compounds present in it. The samples (4 -11) showed a potent inhibitory effect on the NO, where compound 26 (Phthalic acid ester) is common, and its adequate concentration may account for augmented biological activity. These results may effectively highlight their adverse effects on cardiovascular health and etiology and/or progression of cancer and may help in strengthening the social and governmental efforts in minimizing the use of these substances.

Synthesis, docking and evaluation of in vitro anti-inflammatory activity of novel morpholine capped β-lactam derivatives

This study reports the synthesis and biological investigation of three series of novel monocyclic β-lactam derivatives bearing a morpholine ring substituent on the nitrogen. The resulting β-lactam adducts were synthesized via Staudinger's [2 + 2]-ketene-imine cycloaddition reaction. New synthesized products were fully characterized by spectral data and elemental analyses, and then evaluated for anti-inflammatory activity toward human inducible nitric oxide synthase (iNOS) and cytotoxicity toward HepG2 cell line. The compounds 3e, 3h, 3k, 5c, 5f, 6c, 6d and 6f showed higher activity with anti-inflammatory ratio values of 38, 62, 51, 72, 51, 35, 55 and 99, respectively, in comparison to the reference compound dexamethasone having an anti-inflammatory ratio value of 32. Hence, these compounds can be considered as potent iNOS inhibitors. They also exhibited IC50 values of 0.48 ± 0.04 mM, 0.51 ± 0.01 mM, 0.22 ± 0.02 mM, 0.12 ± 0.00 mM, 0.25 ± 0.05 mM, 0.82 ± 0.07 mM, 0.44 ± 0.04 mM and 0.60 ± 0.04 mM, respectively, in comparison with doxorubicin (IC50 < 0.01 mM) against HepG2 cells, biocompatibility and nontoxic behavior. In silico prediction of drug-likeness characteristic indicated that the compounds are compliant with the Lipinski and Veber rules. Molecular docking experiments showed a good correlation between the experimental activity and the calculated binding affinity to human inducible nitric oxide synthase, the enzymatic target for the anti-inflammatory response.

Cyperane-Type and Related (Nor)Sesquiterpenoids from the Root Bark of Acanthopanax gracilistylus and Their Inhibitory Effects on Nitric Oxide Production.

An enantiomeric pair of rare cyperane-type sesquiterpenoids, (+)- and (-)-gracilistones C (1a, 1b), together with a novel norsesquiterpenoid, gracilistone D (2), bearing a bicyclic lactone system were isolated from the root bark of Acanthopanax gracilistylus using LC-MS-IT-TOF analyses. The structures and absolute configurations of 1a, 1b, and 2 were elucidated by 1D and 2D NMR spectroscopy, X-ray diffraction, and ECD spectroscopic methods. Intermediate 1b suggests a possible biosynthesis process involving compound 2. The bioassay results showed that compounds 1a, 1b, and 2 exhibited significant inhibitory effects against lipopolysaccharide-induced nitric oxide production in RAW 264.7 cells, with IC50 values of 7.7 ± 0.6, 6.8 ± 1.5, and 2.6 ± 0.4 μM, respectively. Additional docking analyses provided some perspective of this activity in human inducible nitric oxide synthase.

Regulation of human inducible nitric oxide synthase expression by an upstream open reading frame

The human inducible nitric oxide synthase (iNOS) gene contains an upstream open reading frame (uORF) in its 5′-untranslated region (5′-UTR) implying a translational regulation of iNOS expression. Transfection experiments in human DLD-1 cells revealed that the uORF although translatable seems not to inhibit the translation start at the bona fide ATG. Our data clearly show that human iNOS translation is cap-dependent and that the 5′-UTR of the iNOS mRNA contains no internal ribosome entry site. Translation of the bona fide coding sequence is most likely mediated by a leaky scanning mechanism.The 5′-UTR is encoded by exon 1 and exon 2 of the iNOS gene with the uORF stop codon located in front of the first intron indicating an involvement of the nonsense mediated RNA decay (NMD) in iNOS regulation. SiRNA-mediated down-regulation of Upf1 resulted in enhanced endogenous cytokine iNOS expression in human DLD-1 cells. Transfection of constructs containing iNOS exon 1, intron 1 and exon 2 in front of a luciferase gene showed a clear effect of the mutation of the uORF-ATG on luciferase reportergene expression.Our data indicate that the uORF in the 5′-UTR sequence of human iNOS gene reduces its expression via the NMD mechanism.

Expression of human inducible nitric oxide synthase in response to cytokines is regulated by hypoxia-inducible factor-1

The production of nitric oxide (NO) by inducible NO synthase (iNOS) and the regulation of gene expression by hypoxia-inducible factors (HIFs) are important for many aspects of human cell biology. However, little is known about whether iNOS expression is controlled by HIFs in human cells. Stimulation of A549 human lung epithelial cells with cytokines (TNF, IL-1 and IFNγ) increased the nuclear accumulation of HIF-1 in normoxic conditions. Activation of HIF-1 by hypoxia or CoCl2 was not sufficient to induce iNOS expression. However, pharmacological inhibition of HIF-1 reduced the induction of iNOS expression in A549 cells and primary human astrocytes. Moreover, elimination of HIF-1α expression and activity by CRISPR/Cas9 gene editing significantly reduced the induction of human iNOS gene promoter, mRNA and protein expression by cytokine stimulation. Three putative hypoxia response elements (HRE) are present within the human iNOS gene promoter and elimination of an HRE at −4981 bp reduced the induction of human iNOS promoter activity in response to cytokine stimulation. These findings establish an important role for HIF-1α in the induction of human iNOS gene expression in response to cytokine stimulation.

Role of an isoform-specific residue at the calmodulin-heme (NO synthase) interface in the FMN - heme electron transfer.

The interface between calmodulin (CaM) and the NO synthase (NOS) heme domain is the least characterized interprotein interface that the NOS isoforms must traverse through during catalysis. Our previous molecular dynamics simulations predicted a salt bridge between K497 in human inducible NOS (iNOS) heme domain and D118(CaM). Herein, the FMN - heme interdomain electron transfer (IET) rate was found to be notably decreased by charge-reversal mutation, while the IET in the iNOS K497D mutant is significantly restored by the CaM D118K mutation. The results of wild-type protein with added synthetic peptides further demonstrate the critical nature of K497 relative to the rest of the peptide sequence in modulating the IET. These data provide definitive evidence supporting the regulatory role of the isoform-specific K497 residue.

Human endogenous retrovirus W env increases nitric oxide production and enhances the migration ability of microglia by regulating the expression of inducible nitric oxide synthase

Human endogenous retrovirus W env (HERV-W env) plays a critical role in many neuropsychological diseases such as schizophrenia and multiple sclerosis (MS). These diseases are accompanied by immunological reactions in the central nervous system (CNS). Microglia are important immunocytes in brain inflammation that can produce a gasotransmitter-nitric oxide (NO). NO not only plays a role in the function of neuronal cells but also participates in the pathogenesis of various neuropsychological diseases. In this study, we reported increased NO production in CHME-5 microglia cells after they were transfected with HERV-W env. Moreover, HERV-W env increased the expression and function of human inducible nitric oxide synthase (hiNOS) and enhanced the promoter activity of hiNOS. Microglial migration was also enhanced. These data revealed that HERV-W env might contribute to increase NO production and microglial migration ability in neuropsychological disorders by regulating the expression of inducible NOS. Results from this study might lead to the identification of novel targets for the treatment of neuropsychological diseases, including neuroinflammatory diseases, stroke, and neurodegenerative diseases.

Selective Nuclear Factor Kappa b (NFkB) Inhibitor, Pyrrolidium Dithiocarbamate Prevents, Long-Term Histologic Damage in Ischemia-Reperfusion Injuries after Delayed Testicular Torsion.

Nuclear factor kapa b (NFKB) is a transcription factor that is required for cytokine-mediated induction of the human inducible nitric oxide synthase (iNOS) gene. Recent studies have shown that in the pathophysiology of ischemia-reperfusion (IR) injuries NFKB is involved. In our study we aimed to determine the efficacy of the selective NFKB inhibitor, pyrrolidium dithiocarbamate (PDTC), on long-term histological damage in testicular IR injuries. Twenty-one adult male Wistar albino rats were divided into 3 equal groups. In groups 1-2, the left testes in rats underwent 4 hours of 720&deg; experimental torsion. In group 2, PDTC (100 mg/kg) was administered intraperitoneally in the last 1 hour before detorsion; and group 3 underwent a sham operation. All rats underwent bilateral orchiectomy 45 days after the experiment. The testes weights were measured and compared to the other groups and their contralateral values. Testes samples were fixed with Bouin solution for histological (Johnsen score) and immunohistochemical examination. Immunohistochemically iNOS and an active subunit of NFKB, p65 were evaluated using mouse primary monoclonal antibodies and were evaluated semi quantitatively. Testicular weights and Johnsen scores in ipsilateral testes were 0.67 &plusmn; 0.85, 1.54 &plusmn; 0.11, 1.84 &plusmn; 0.64 and 1.63 (1-4), 6.94 (4-10), 5.29 (1-9) in the torsion, sham and PDTC groups, respectively. In contralateral testes the same values were 1.74 &plusmn; 0.84, 1.59 &plusmn; 0.13, 1.50 &plusmn; 0.54 and 5.38 (2-8), 7.17 (5-10), 6.30 (4-9). Testicular weights and Johnsen scores were significantly different in the ipsilateral torsion group (P &lt; .05). In the PDTC group testicular weights and Johnsen scores were similar with the control group (P &gt; .05). Immunohistochemically there was marked staining in the iNOS and p65 expressions in the torsion group compared with group 2 and 3. In rats administered PDTC, iNOS and p65 expressions were significantly reduced compared with the torsion group. There were no significant differences between the histological and immunohistochemical results of groups 2 and 3. This data suggests that IR induces iNOS expressions through the activation of NFKB, p65. The NFKB pathway plays major role in testicular reperfusion injuries. It is possible to prevent reperfusion injuries using selective the NFKB inhibitor.&nbsp.

Up-Regulation of Human Inducible Nitric Oxide Synthase by p300 Transcriptional Complex.

p300, a ubiquitous transcription coactivator, plays an important role in gene activation. Our previous work demonstrated that human inducible nitric oxide synthase (hiNOS) expression can be highly induced with the cytokine mixture (CM) of TNF-α + IL-1β + IFN-γ. In this study, we investigated the functional role of p300 in the regulation of hiNOS gene expression. Our initial data showed that overexpression of p300 significantly increased the basal and cytokine-induced hiNOS promoter activities in A549 cells. Interestingly, p300 activated cytokine-induced hiNOS transcriptional activity was completely abrogated by deleting the upstream hiNOS enhancer at -5 kb to -6 kb in the promoter. Furthermore, p300 over-expression increased cytokine-induced transcriptional activity on a heterologous minimal TK promoter with the same hiNOS enhancer. Site-directed mutagenesis of the hiNOS AP-1 motifs revealed that an intact upstream (-5.3kb) AP-1 binding site was critical for p300 mediated cytokine-induced hiNOS transcription. Furthermore, our ChIP analysis demonstrated that p300 was binding to Jun D and Fra-2 proteins at -5.3 kb AP-1 binding site in vivo. Lastly, our 3C assay was able to detect a long DNA loop between the hiNOS enhancer and core promoter site, and ChIP loop assay confirmed that p300 binds to AP-1 and RNA pol II proteins. Overall, our results suggest that coactivator p300 mediates cytokine-induced hiNOS transactivation by forming a distant DNA loop between its enhancer and core promoter region.

Capsaicinoid: A potential antioxidant with close interactions against human iNOS in docking study

Capsicum chinense, popularly known as Bhut jolokia, was collected from three states of North-East India and was studied for variation in its pungency principal viz. capsaicinoid content and antioxidant activity as well as its inter-action affinity with human inducible nitric oxide synthase (iNOS) active sites. HPLC fingerprinting analysis showed capsaicin and dihydrocapsaicin as the major active compounds present in the capsaicinoid extract of C. chinense. In comparison to dihydrocapsaicin, capsaicin was found in high amount. The pungency range was observed between 3, 47,301 SHU to 8, 45,296 SHU in the collected samples. The capsaicinoid extract exhibited antioxidant activity with 46.24 ± 15.34% scavenging of DPPH free radical at 100 ppm. The dock-ing analysis showed that capsaicin interacted more with the active sites of iNOS compared to dihydrocapsaicin. Present investigation revealed considerable difference in capsaicinoid content among the samples collected from three states of North-East India. The capsaicinoid showed noticeable antioxidant activity with potent binding affinity to the active sites of iNOS in the molecular docking analysis.

Chapter Two - microRNA and Human Inducible Nitric Oxide Synthase

Regulation of human inducible nitric oxide synthase (iNOS) expression involves both transcriptional and posttranscriptional mechanisms. Human iNOS gene transcription is controlled in a cell type-specific manner by extracellular cytokines. Transcriptional regulation of human iNOS gene involves transcription factors NF-κB, Stat-1, AP-1, C/EBPβ, KLF6, Oct 1, and NRF. Important posttranscriptional mechanisms also regulate human iNOS mRNA stability through RNA binding proteins HuR, TTP, KSRP, and PABP. Recently, there are several miRNAs that were validated to regulate human and rodent iNOS gene expression. Among them, miR-939 and miR-26a were identified to bind with the human iNOS 3'-UTR and exert a translational blockade of human iNOS protein synthesis.

Post-transcriptional regulation of the human inducible nitric oxide synthase (iNOS) expression by the cytosolic poly(A)-binding protein (PABP)

Affinity purification using the 3′-untranslated region (3′-UTR) of the human inducible nitric oxide synthase (iNOS) mRNA identified the cytosolic poly(A)-binding protein (PABP) as a protein interacting with the human iNOS 3′-UTR. Downregulation of PABP expression by RNA interference resulted in a marked reduction of cytokine-induced iNOS mRNA expression without changes in the expression of mRNAs coding for the major subunit of the RNA polymerase II (Pol 2A) or β2-microglobuline (β2M). Along with the mRNA also iNOS protein expression was reduced by siPABP-treatment, whereas in the same cells protein expression of STAT-1α, NF-κB p65, or GAPDH was not altered. Reporter gene analyses showed no change of the inducibility of the human 16kb iNOS promoter in siPABP cells. In contrast, the siPABP-mediated decline of iNOS expression correlated with a reduction in the stability of the iNOS mRNA. As the stability of the Pol 2A and β2M mRNA was not changed, siPABP-treatment seems to have a specific effect on iNOS mRNA decay. UV-crosslinking experiments revealed that PABP interacts with one binding site in the 5′-UTR and two different binding sites in the 3′-UTR of the human iNOS mRNA. Mutation or deletion of the binding site in the 5′-UTR but not in the 3′-UTR reduced luciferase expression in DLD-1 cells transfected with iNOS-5′-UTR or iNOS-3′-UTR luciferase reporter constructs.In summary, our data demonstrate that PABP by binding to specific sequence elements in the 5′-UTR post-transcriptionally enhances human iNOS mRNA stability and thereby iNOS expression.

Positive Feedback Regulation of Human Inducible Nitric-oxide Synthase Expression by Ras Protein S-Nitrosylation

The production of nitric oxide (NO) by inducible NO synthase (iNOS) regulates many aspects of physiology and pathology. The expression of iNOS needs to be tightly regulated to balance the broad ranging properties of NO. We have investigated the feedback regulation of cytokine-induced iNOS expression by NO in human cells. The pharmacological inhibition of iNOS activity reduced iNOS protein levels in response to cytokine stimulation in a human epithelial cell line (A549 cells) as well as in primary human astrocytes and bronchial epithelial cells. The addition of exogenous NO using a NO donor prevented the reduction in iNOS levels caused by blockade of iNOS activity. Examination of signaling pathways affected by iNOS indicated that NO S-nitrosylated Ras. Transfection of cells with a S-nitrosylation-resistant Ras mutant reduced iNOS protein levels, indicating a role for this Ras modification in the amplification of iNOS levels. Further, the induction of iNOS protein levels correlated with the late activation of the phosphatidylinositol 3-kinase/Akt and mammalian target of rapamycin (mTOR) pathways, and inhibition of these signaling molecules reduced iNOS levels. Altogether, our findings reveal a previously unknown regulatory pathway that amplifies iNOS expression in human cells.