S-nitrosothiols inhibit cytokine-mediated induction of matrix metalloproteinase-9 in airway epithelial cells

Facilitating Nitrite-Derived S-Nitrosothiol Formation in the Upper Gastrointestinal Tract in the Therapy of Cardiovascular Diseases

Cardiovascular diseases (CVDs) are often associated with impaired nitric oxide (NO) bioavailability, a critical pathophysiological alteration in CVDs and an important target for therapeutic interventions. Recent studies have revealed the potential of inorganic nitrite and nitrate as sources of NO, offering promising alternatives for managing various cardiovascular conditions. It is now becoming clear that taking advantage of enzymatic pathways involved in nitrite reduction to NO is very relevant in new therapeutics. However, recent studies have shown that nitrite may be bioactivated in the acidic gastric environment, where nitrite generates NO and a variety of S-nitrosating compounds that result in increased circulating S-nitrosothiol concentrations and S-nitrosation of tissue pharmacological targets. Moreover, transnitrosation reactions may further nitrosate other targets, resulting in improved cardiovascular function in patients with CVDs. In this review, we comprehensively address the mechanisms and relevant effects of nitrate and nitrite-stimulated gastric S-nitrosothiol formation that may promote S-nitrosation of pharmacological targets in various CVDs. Recently identified interfering factors that may inhibit these mechanisms and prevent the beneficial responses to nitrate and nitrite therapy were also taken into consideration.

Nitrate and nitrite-based therapy to attenuate cardiovascular remodelling in arterial hypertension

Hypertension is a highly prevalent disease marked by vascular and cardiac maladaptive remodelling induced mainly by renin-angiotensin system activation followed by oxidative stress. Here, we briefly describe these damages and review the current evidence supporting a potential role for nitrate and nitrite as antihypertensive molecules that act via nitric oxide (NO) formation-dependent and NO formation-independent mechanisms and how nitrate/nitrite inhibits cardiovascular remodelling in hypertension. The renin-angiotensin system activation and oxidative stress converge to activate proteases involved in cardiovascular remodelling in hypertension. Besides these proteases, several investigations have demonstrated that reduced endogenous NO bioavailability is a central pathological event in hypertension. In this regard, nitrate/nitrite, long considered inert products of NO, is now known as physiological molecules able to reduce blood pressure in hypertensive patients and in different experimental models of hypertension. These effects are associated with the formation of NO and other NO-related molecules, which could induce S-nitrosylation of target proteins. However, it remains unclear whether S-nitrosylation is an essential mechanism for the anti-remodelling effects of nitrate/nitrite in hypertension. Moreover, nitrate/nitrite produces antioxidant effects associated with the inhibition of signalling pathways involved in cardiovascular remodelling. Together, these findings may help to establish nitrate and nitrite as effective therapies in hypertension-induced cardiovascular remodelling.

NO-Donor Nitrosyl Iron Complex with 2-Aminophenolyl Ligand Induces Apoptosis and Inhibits NF-κB Function in HeLa Cells

NO donating iron nitrosyl complex with 2-aminothiophenyl ligand (2-AmPh complex) was studied for its ability to cause cell death and affect nuclear factor kappa B (NF-κB) signaling. The complex inhibited viability of HeLa cells and induced cell death that was accompanied by loss of mitochondrial membrane potential and characteristic for apoptosis phosphatidylserine externalization. At IC50, 2-AmPh caused decrease in nuclear content of NF-κB p65 polypeptide and mRNA expression of NF-κB target genes encoding interleukin-8 and anti-apoptotic protein BIRC3. mRNA levels of interleukin-6 and anti-apoptotic protein BIRC2 encoding genes were not affected. Our data demonstrate that NO donating iron nitrosyl complex 2-AmPh can inhibit tumor cell viability and induce apoptosis that is preceded by impairment of NF-κB function and suppression of a subset of NF-κB target genes.

Inhibition of matrix metalloproteinase-9 by a barbiturate-nitrate hybrid ameliorates dextran sulphate sodium-induced colitis: effect on inflammation-related genes

BACKGROUND AND PURPOSE

Matrix metalloproteinase-9 (MMP-9) is up-regulated in ulcerative colitis and implicated in the pathology of the disease. In this study, we have examined the effects of a barbiturate-based MMP inhibitor incorporating a nitric oxide donor/mimetic group (dinitrate-barbiturate) on the intestinal injury induced by dextran sulphate sodium (DSS).

EXPERIMENTAL APPROACH

In vivo experiments were carried out using male Wistar rats given 5% DSS ad libitum in drinking water. The dinitrate-barbiturate, non-nitrate equivalent, nitrate side chains alone or vehicle were administered rectally, twice daily. MMP-9 release was measured by gelatin zymography, and analysis of gene expression was carried out using RT-qPCR. TaqMan low density arrays were used to evaluate the expression of 91 inflammatory genes in the rat colon.

KEY RESULTS

The dinitrate-barbiturate inhibited the induction and activity of MMP-9 during DSS colitis in the rat. This occurred in association with significant reductions in the colitic response to DSS as assessed by an established clinical disease activity index and a pathological colitis grade score. The compound modified expression rates of numerous inflammation-related genes in the colon.

CONCLUSIONS AND IMPLICATIONS

This study demonstrated the efficacy of the dinitrate-barbiturate in DSS-induced colitis. Therefore, barbiturate-nitrate hybrids may be developed as a promising anti-inflammatory approach to the treatment of inflammatory bowel disease.

Mechanisms and targets of the modulatory action of S-nitrosoglutathione (GSNO) on inflammatory cytokines expression

A number of experimental studies has documented that S-nitrosoglutathione (GSNO), the main endogenous low-molecular-weight S-nitrosothiol, can exert modulatory effects on inflammatory processes, thus supporting its potential employment in medicine for the treatment of important disease conditions. At molecular level, GSNO effects have been shown to modulate the activity of a series of transcription factors (notably NF-κB, AP-1, CREB and others) as well as other components of signal transduction chains (e.g. IKK-β, caspase 1, calpain and others), resulting in the modulation of several cytokines and chemokines expression (TNFα, IL-1β, IFN-γ, IL-4, IL-8, RANTES, MCP-1 and others). Results reported to date are however not univocal, and a single main mechanism of action for the observed anti-inflammatory effects of GSNO has not been identified. Conflicting observations can be explained by differences among the various cell types studies as to the relative abundance of enzymes in charge of GSNO metabolism (GSNO reductase, γ-glutamyltransferase, protein disulfide isomerase and others), as well as by variables associated with the individual experimental models employed. Altogether, anti-inflammatory properties of GSNO seem however to prevail, and exploration of the therapeutic potential of GSNO and analogues appears therefore warranted.

Promotion of lung tumor growth by interleukin-17

Recent findings demonstrate that inhaled cigarette smoke, the predominant lung carcinogen, elicits a T helper 17 (Th17) inflammatory phenotype. Interleukin-17A (IL-17), the hallmark cytokine of Th17 inflammation, displays pro- and antitumorigenic properties in a manner that varies according to tumor type and assay system. To investigate the role of IL-17 in lung tumor growth, we used an autochthonous tumor model (K-Ras(LA1) mice) with lung delivery of a recombinant adenovirus that expresses IL-17A. Virus-mediated expression of IL-17A in K-Ras(LA1) mice at 8-10 wk of age doubled lung tumor growth in 3 wk relative to littermates that received a green fluorescent protein-expressing control adenovirus. IL-17 induced matrix metalloproteinase-9 (MMP-9) expression in vivo and in vitro. In accord with this finding, selective and specific inhibitors of MMP-9 repressed the increased motility and invasiveness of IL-17-treated lung tumor cells in culture. Knockdown or mutation of p53 promoted the motility of murine lung tumor cells and abrogated the promigratory role of IL-17. Coexpression of siRNA-resistant wild-type, but not mutant, human p53 rescued both IL-17-mediated migration and MMP-9 mRNA induction in p53 knockdown lung tumor cells. IL-17 increased MMP-9 mRNA stability by reducing interaction with the mRNA destabilizing serine/arginine-rich splicing factor 1 (SRSF1). Taken together, our results indicate that IL-17 stimulates lung tumor growth and regulates MMP-9 mRNA levels in a p53- and SRSF1-dependent manner.

Nitric oxide-matrix metaloproteinase-9 interactions: biological and pharmacological significance--NO and MMP-9 interactions

Nitric oxide (NO) and matrix metalloproteinase 9 (MMP-9) levels are found to increase in inflammation states and in cancer, and their levels may be reciprocally modulated. Understanding interactions between NO and MMP-9 is of biological and pharmacological relevance and may prove crucial in designing new therapeutics. The reciprocal interaction between NO and MMP-9 have been studied for nearly twenty years but to our knowledge, are yet to be the subject of a review. This review provides a summary of published data regarding the complex and sometimes contradictory effects of NO on MMP-9. We also analyse molecular mechanisms modulating and mediating NO-MMP-9 interactions. Finally, a potential therapeutic relevance of these interactions is presented.

Radiation-induced TNFα cross signaling-dependent nuclear import of NFκB favors metastasis in neuroblastoma

Ascertaining function-specific orchestration of NFκB in response to radiation may reveal a molecular blue-print that dictates induced relapse and metastasis of the neuroblastoma. We recently demonstrated that sustained activation of NFκB caused by ionizing radiation (IR)-initiated TNFα-NFκB feedback signaling leads to radioresistance and recurrence of neuroblastoma. We investigated whether muting IR-triggered or TNFα-dependent second-signaling feedback-dependent NFκB nuclear import results in limiting IR-altered invasion and metastasis. Neuroblastoma cells were exposed to 2 Gy and incubated for 1 h or 24 h. The cells were then treated with an NFκB-targeting peptide blocker, SN50. Upon confirming the blockade in DNA-binding activity, transcription driven transactivation of NFκB and secretion of soluble TNFα, transcriptional alterations of 93 tumor invasion/metastasis genes were assessed by using QPCR profiling and then were selectively validated at the protein level. Exposure to 2 Gy induced 63, 42 and 71 genes in surviving SH-SY5Y, IMR-32 and SK-N-MC cells, respectively. Blocking post-translational nuclear import of NFκB comprehensively inhibited both initial activation of genes (62/63, 34/42 and 65/71) triggered by IR and also TNFα-mediated second signaling-dependent sustained (59/63, 32/42 and 71/71) activation of tumor invasion and metastasis signaling molecules. Furthermore, alterations in the proteins MMP9, MMP2, PYK-2, SPA-1, Dnmt3b, Ask-1, CTGF, MMP10, MTA-2, NF-2, E-Cadherin, TIMP-2 and ADAMTS1 and the results of our scratch-wound assay validate the role of post-translational NFκB in IR-regulated invasion/metastasis. These data demonstrate that IR-induced second-phase (post-translational) NFκB activation mediates TNFα-dependent second signaling and further implies that IR induced NFκB in cells that survive after treatment regulates tumor invasion/metastasis signaling.

Inducible nitric oxide synthase inhibition increases MMP-2 activity leading to imbalance between extracellular matrix deposition and degradation after polypropylene mesh implant

Prosthetic mesh implants are commonly used to correct abdominal wall defects. However, success of the procedure is conditioned by an adequate inflammatory response to the device. We hypothesized that nitric oxide produced by nitric oxide synthase 2 (NOS2) and MMP-2 and -9 participate in response induced by mesh implants in the abdominal wall and, consequently, affect the outcome of the surgical procedure. In the first step, temporal inflammatory markers profile was evaluated. Polypropylene meshes were implanted in the peritoneal side of the abdominal wall of C57Black mice. After 2, 4, 7, 15, and 30 days, tissues around the mesh implant were collected and inflammatory markers were analyzed. In the second step, NOS2 activity was inhibited with nitro-L-arginine methyl ester (L-NAME). Samples were collected after 15 days (when inflammation was reduced), and the inflammatory and tissue remodeling markers were investigated. Polypropylene mesh implant induced a pro-inflammatory environment mediated by intense MMP-2 and -9 activities, NO release, and interleukin-1β production peaking in 7 days and gradually decreasing after 15 days. NOS2 inhibition increased MMP-2 activity and resulted in a higher visceral adhesion incidence at the mesh implantation site when compared with non-treated animals that underwent the same procedure. We conclude that NOS2-derived NO is crucial for adequate response to polypropylene mesh implant integration in the peritoneum. NO deficiency results in an imbalance between extracellular matrix deposition/degradation contributing to visceral adhesions incidence.

Nitric oxide regulates cytokine induction in the diaphragm in response to inspiratory resistive breathing

Resistive breathing (encountered in chronic obstructive pulmonary disease and asthma) results in cytokine upregulation and decreased nitric oxide (NO) levels in the strenuously contracting diaphragm. NO can regulate gene expression. We hypothesized that endogenously produced NO downregulates cytokine production triggered by strenuous diaphragmatic contraction. Wistar rats treated with vehicle, the nonselective NO synthase inhibitor NG-nitro-l-arginine-methylester (l-NAME), or the NO donor diethylenetriamine-NONOate (DETA) were subjected to inspiratory resistive breathing (IRB; 50% of maximal inspiratory pressure) for 6 h or sham operation. Additional groups of rats were subjected to IRB for 6 h with concurrent administration of l-NAME and inhibitors of NF-κB (BAY-11-7082), ERK1/2 (PD98059), or P38 (SB203580). Inhibition of NO production (with l-NAME) resulted in upregulation of IRB-induced diaphragmatic IL-6, IL-10, IL-2, TNF-α, and IL-1β levels by 50%, 53%, 60%, 47%, and 45%, respectively. In contrast, the NO donor (DETA) attenuated the IRB-induced cytokine upregulation to levels characteristic of quietly breathing animals. l-NAME augmented IRB-induced activation of MAPKs (P38 and ERK1/2) and NF-κB, whereas DETA triggered the opposite effect. NF-κB and ERK1/2 inhibition in l-NAME-treated animals blunted the l-NAME-induced cytokine upregulation except IL-6, whereas P38 inhibition blunted all (including IL-6) cytokine upregulation. NO downregulates IRB-induced cytokine production in the strenuously contracting diaphragm through its action on MAPKs and NF-κB.

Smoke decreases reversible oxidations S-glutathionylation and S-nitrosylation in mice

Cigarette smoke causes irreversible oxidations in lungs, but its impact on reversible and physiologically relevant redox-dependent protein modifications remains to be investigated. Here the effect of cigarette smoke exposure in mice was investigated on the covalent binding of glutathione to protein thiols, known as S-glutathionylation (PSSG), which can be reversed by glutaredoxins (Grx). Also, protein S-nitrosylation (PSNO) which is the modification of protein thiols by NO and which is reversed by the enzyme alcohol dehydrogenase (ADH) 5 was examined. Both PSSG and PSNO levels in lung tissue were markedly decreased after 4 weeks of cigarette smoke exposure. This coincided with attenuated protein free thiol levels and increased protein carbonylation. The expression of NOX4, DHE sensitive oxidant production and iNOS levels were induced by smoke, whereas Grx1 mRNA expression and activity were attenuated. Free GSH levels, protein expression and activity of ADH5 were unaffected by smoke. Taken together, smoke exposure decreases reversible cysteine oxidations PSSG and PSNO and enhances protein carbonylation. These alterations are not associated with differences in some of the regulatory enzymes, but are likely the result of oxidative stress.

Novel insights into interactions between mitochondria and xanthine oxidase in acute cardiac volume overload

Xanthine oxidoreductase (XOR) is increased in the left ventricle (LV) of humans with volume overload (VO), and mitochondrial inhibition of the respiratory chain occurs in animal models of VO. Because mitochondria are both a source and a target of reactive oxygen and nitrogen species, we hypothesized that activation of XOR and mitochondrial dysfunction are interdependent. To test this we used the aortocaval fistula (ACF) rat model of VO and a simulation of the stretch response in isolated adult cardiomyocytes with and without the inhibitor of XOR, allopurinol, or the mitochondrially targeted antioxidant MitoQ. Xanthine oxidase (XO) activity was increased in cardiomyocytes from ACF vs sham rats (24h) without an increase in XO protein. A twofold increase in LV end-diastolic pressure/wall stress and a decrease in LV systolic elastance with ACF were improved when allopurinol treatment (100mg/kg) was started at ACF induction. Subsarcolemmal State 3 mitochondrial respiration was significantly decreased in ACF and normalized by allopurinol. Cardiomyocytes subjected to 3h cyclical stretch resulted in an increase in XO activity and mitochondrial swelling, which was prevented by allopurinol or MitoQ pretreatment. These studies establish an early interplay between cardiomyocyte XO activation and bioenergetic dysfunction that may provide a new target that prevents progression to heart failure in VO.

Purinergic signaling in wound healing and airway remodeling

Airway epithelia are continuously damaged by airborne pollutants, pathogens and allergens, and they rely on intrinsic mechanisms to restore barrier integrity. Epithelial repair is a multi-step process including cell migration into the wounded area, proliferation, differentiation and matrix deposition. Each step requires the secretion of various molecules, including growth factors, integrins and matrix metalloproteinases. Evidence is emerging that purinergic signaling promotes repair in human airway epithelia. An injury induces ATP release, which binds P2Y(2) receptors (P2Y(2)Rs) to initiate protein kinase C (PKC)-dependent oxidative activation of TNFα-converting enzyme (TACE), which then releases the membrane-bound ligands of the epidermal growth factor receptor (EGFR). The P2Y(2)R- and EGFR-dependent signaling cascades converge to induce mediator release, whereas the latter also induces cytoskeletal rearrangement for cell migration and proliferation. Similar roles for purinergic signaling are reported in pulmonary endothelial cells, smooth muscle cells and fibroblasts. In chronic airway diseases, the aberrant regulation of extracellular purines is implicated in the development of airway remodeling by mucus cell metaplasia and hypersecretion, excess collagen deposition, fibrosis and neovascularization. This chapter describes the crosstalk between these signaling cascades and discusses the impact of deregulated purinergic signaling in chronic lung diseases.

Cutaneous MMPs are differently modulated by environmental stressors in old and young mice

Skin is frequently exposed to pro-oxidative insults such as UV light, ozone (O(3)) and cigarette smoke (CS), which are able to deplete antioxidants and induce oxidation products affecting skin pathophysiology. Skin turnover and regeneration are largely dependent on extracellular matrix metabolism, which is under the control of matrix metalloproteinases, MMPs. The present study evaluated cutaneous MMPs activity upon environmental pollutants exposure and analyzed the response of old and young animals. For this purpose, SKH-1 hairless mice (8 weeks and 18 months old) were exposed for 6h/day to 0.25ppm of O(3) or to UV radiation (0.3 MED) or to CS for 4 days. Gelatin zymography revealed an increase of MMP-2 in both young and old animals, after exposure to pollutants, while MMP-9, undetectable in unexposed subjects, was strongly induced only in old mice. Casein zymography and Western blot analysis showed an increase of MMP-12 in the aged group after environmental stressors exposure. TIMP-1 and -2 expression levels did not change. The current study demonstrates the ability of certain environmental pollutants to affect the ECM turnover through modulation of specific MMPs, and confirms the higher susceptibility of old subjects to exogenous pro-oxidant insults.

Synergistic up-regulation of epithelial cell matrix metalloproteinase-9 secretion in tuberculosis

Mycobacterium tuberculosis (MTb) kills approximately 2 million people each year. MTb must drive host tissue destruction to disseminate and also to cause pulmonary cavitation. Matrix metalloproteinase-9 (MMP-9, gelatinase B) is implicated in this Tb-related immunopathology. We demonstrate that conditioned media from MTb-infected monocytes (CoMTb), but not direct infection with MTb, up-regulates MMP-9 gene expression and secretion from primary human bronchial epithelial cells (NHBE). MMP-9 secretion was increased 8.7-fold by CoMTb (P < 0.05) as assayed by gelatin zymography. A549 and 16HBE14o epithelial cell MMP secretion was significantly less than primary NHBE secretion. MMP-9 secretion was decreased 53.2% by inhibition of the p38 mitogen-activated protein kinase (MAPK) by SB203580 (P < 0.01) and 48.3% by inhibition of extracellular signal-regulated kinase with PD98059 (P < 0.05). MMP-9 secretion was prostaglandin independent. TNF-alpha was necessary but not sufficient for MMP-9 up-regulation by the monocyte-epithelial cell network. Soluble factors derived from Tb culture synergized with TNF-alpha to increase MMP-9 secretion by NHBE 6-fold (P < 0.01 compared with either stimulus alone). Together, these data reveal a new mechanism by which host- and pathogen-derived factors act together in MTb infection to drive MAPK-dependent MMP-9 secretion from respiratory epithelial cells.

Proteomic analysis of the airway surface liquid: modulation by proinflammatory cytokines

The airway surface is covered by a fluid, the airway surface liquid, interposed between the mucous layer and the epithelium. The airway surface liquid contains proteins, secreted by different cell types, that may have pro-/anti-inflammatory or bactericidal functions or have a role in the mucociliary clearance. We have used a proteomics approach to identify the proteins secreted by an isolated in vitro model of human airway epithelium, at resting and under proinflammatory conditions, as a strategy to define the factors involved in epithelial barrier function. To this aim, we have analyzed the airway surface liquid from human bronchial epithelial cells grown as polarized monolayers in the presence and absence of inflammatory stimuli such as IL-4, IL-1β, TNF-α, and IFN-γ. Two-dimensional electrophoresis followed by mass spectrometry analysis has allowed the identification of ∼175 secreted protein spots, among which are immune-related proteins, structural proteins, an actin severer, some protease inhibitors, and a metalloproteinase. Comparisons between treated and untreated conditions have shown that the expression of several proteins was significantly modified by the different cytokines. Our results indicate that the surface epithelium is an active player in the epithelial barrier function and that inflammatory conditions may modulate protein secretion.

Airway epithelial cell migration and wound repair by ATP-mediated activation of dual oxidase 1

The airway epithelium is continuously subjected to environmental pollutants, airborne pathogens, and allergens and relies on several intrinsic mechanisms to maintain barrier integrity and to promote epithelial repair processes following injury. Here, we report a critical role for dual oxidase 1 (Duox1), a newly identified NADPH oxidase homolog within the tracheobronchial epithelium, in airway epithelial cell migration and repair following injury. Activation of Duox1 during epithelial injury is mediated by cellular release of ATP, which signals through purinergic receptors expressed on the epithelial cell surface. Purinergic receptor stimulation by extracellular ATP is a critical determinant of epithelial cell migration and repair following injury and is associated with activation of extracellular signal-regulated kinases (ERK1/2) and matrix metalloproteinase-9 (MMP-9). Stimulation of these integral features of epithelial cell migration and repair processes was found to require the activation of Duox1. Our findings demonstrate a novel role for Duox1 in the tracheobronchial epithelium, in addition to its proposed role in antimicrobial host defense, by participating in epithelial repair processes to maintain epithelial integrity and barrier function in the face of environmental stress.

AUF-1 mediates inhibition by nitric oxide of lipopolysaccharide-induced matrix metalloproteinase-9 expression in cultured astrocytes

Neuroinflammatory diseases are associated with increased production of matrix metalloproteinase-9 (MMP-9) and excessive generation of nitric oxide (NO). NO has been reported to have variable effects on MMP-9 gene expression and activation in various cell types. In the present study, we investigated the effect of NOon MMP-9 expression in primary cortical astrocytes. Zymography and real-time PCR showed that lipopolysaccharide (LPS) dramatically increased latent MMP-9 gelatinolytic activity and MMP-9 mRNA expression. By using the NO donor DETA NONOate, we observed a dose-dependent inhibition of MMP-9 induction by LPS. Active forms of MMP-9 were not found by zymography after NO treatment. The MEK1/2 inhibitor U0126 completely inhibited LPS-induced MMP-9, which was partially inhibited by the p38 MAPK inhibitor SB203580. NO had no effect on LPS-stimulated ERK1/2 and p38 MAPK activation, suggesting that the inhibitory action of NO occurs downstream of MAPK cascades. Real-time PCR analysis showed that NO accelerated the degradation of MMP-9 mRNA after LPS induction. Western blotting and pull-down assay demonstrated that NO increased AUF-1 expression as well as its specific binding to the MMP-9 gene 3'-untranslated region. Knockdown of AUF-1 with siRNA partially reversed the inhibitory action of NO on LPS-stimulated MMP-9 induction. We conclude that NO does not activate MMP-9 in astrocyte cultures but reduces LPS-induced MMP-9 expression via accelerating MMP-9 mRNA degradation, which is partially mediated by AUF-1. Our results suggest that elevated NO concentrations may suppress MMP-9 and restrict the inflammatory response in neurodegenerative diseases.

Nitric oxide promotes airway epithelial wound repair through enhanced activation of MMP-9

The airway epithelium provides a protective barrier against inhaled environmental toxins and microorganisms, and epithelial injury initiates a number of processes to restore its barrier integrity, including activation of matrix metalloproteinases such as MMP-9 (92-kD gelatinase B). Airway epithelial cells continuously produce nitric oxide (NO), which has been linked to cell migration and MMP-9 regulation in several cell types, but the importance of epithelial NO in mediating airway epithelial repair or MMP-9 activation is unknown. Using primary or immortalized human bronchial epithelial cells, we demonstrate that low concentrations of NO promote epithelial cell migration and wound repair in an in vitro wound assay, which was associated with increased localized expression and activation of MMP-9. In addition, in HBE1 cells that were stably transfected with inducible NOS (NOS2), to mimic constitutive epithelial NOS2 expression in vivo, NOS inhibition decreased epithelial wound repair and MMP-9 expression. The stimulatory effects of NO on epithelial wound repair and MMP-9 expression were dependent on cGMP-mediated pathways and were inhibited by 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ), an inhibitor of soluble guanylyl cyclase. Inhibition of cGMP-dependent protein kinase (PKG) attenuated NO-mediated epithelial wound closure, but did not affect MMP-9 expression. However, pharmacologic MMP inhibition and siRNA knockdown of MMP-9 expression demonstrated the contribution of MMP-9 to NO-mediated wound closure. Overall, our results demonstrate that NOS2-derived NO contributes to airway epithelial repair by both PKG-dependent and -independent mechanisms, and involves NO-dependent expression and activation of MMP-9.

Increased Alveolar and Plasma Gelatinases Activity during Postpump Syndrome: Inhibition by Inhaled Nitric Oxide

Postpump syndrome is associated with systemic inflammation. Matrix metalloproteinases (MMP)-2 and -9 contribute to proinflammatory and platelet-activator reactions. Nitric oxide (NO) is involved in the regulation of MMPs. The objectives of our study were to investigate the intensity of inflammation induced by 3 different surgical procedures, the effects of inflammation on the activity of MMPs, and the regulation of inflammation by inhaled NO (20 ppm). Inhaled NO was initiated immediately after tracheal intubation and maintained for the total duration of the experiments. Thirty pigs were equally randomized into 6 groups [sham; sham + NO; cardiopulmonary bypass; bypass + NO; bypass + lipopolysaccharide (1 microg/kg for 50 min); bypass + lipopolysaccharide + NO] and animals were subjected to anesthesia and mechanical ventilation up to 24 h. The levels of MMP-2 and MMP-9 in plasma and bronchoalveolar lavage were measured using zymography. Bypass resulted in a time-dependent rise in MMP activity, an effect potentiated by lipopolysaccharide. Inhaled NO attenuated the effects of bypass + lipopolysaccharide. These results confirm that MMP-2 and MMP-9 are associated with the inflammatory process causing the postpump syndrome. Preemptive and continuous administration of inhaled NO helps to prevent increased MMP-2 and MMP-9 activity.

Overexpression of nitric oxide synthase by the endothelium attenuates bleomycin-induced lung fibrosis and impairs MMP-9/TIMP-1 balance

BACKGROUND

Nitric oxide (NO) produced by endothelial NO synthase (eNOS) is thought to effect an anti-inflammatory response, but its mechanism is still unknown.

METHODS

eNOS transgenic (eNOS-TG) mice and their littermate controls (C57/BL6) were used to clarify the role of NO derived from eNOS. Bleomycin hydrochloride (1 U/body/day) or PBS was injected intraperitoneally.

RESULTS

Subpleural fibrotic changes and hydroxyproline content in the eNOS-TG mice were significantly reduced compared with those of the wild-type (WT) mice by day 56. Administration of N(omega)-nitro-L-arginine methyl ester, a potent inhibitor of NO synthase, worsened the fibrotic response in bleomycin-treated eNOS-TG mice. Gelatinolytic activity in lung homogenates, corresponding to metalloproteinase-9 (MMP-9), was significantly increased in bleomycin-injured WT mice on day 14. In contrast, the level of tissue inhibitor of metalloproteinases-1 (TIMP-1), an endogenous MMP-9 inhibitor, was increased in the bleomycin-treated eNOS-TG mice compared with WT. Immunohistochemical analysis demonstrated that MMP-9 and TIMP-1 were strongly expressed in inflammatory cells, including subpleural fibrotic lesions.

CONCLUSION

These data suggested that eNOS overexpression attenuates bleomycin-induced lung injury by ameliorating the MMP-9/TIMP-1 balance.

Relevance of tenascin-C and matrix metalloproteinases in vascular abnormalities in murine hypoplastic lungs

BACKGROUND

Tenascin-C (TN-C), an extracellular matrix glycoprotein, is crucial to cell-migration, proliferation, apoptosis and remodeling of tissues, with a potential role in pathobiology of pulmonary hypertension. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are crucial to the integrity of the extracellular matrix. TN-C and MMPs are counter-regulatory molecules, which influence the vascular integrity through modulations of elastin. We have a murine model of pulmonary hypoplasia with coexistent diaphragmatic hernia, vascular abnormalities and excessive arterial smooth muscle cell (SMC) proliferation.

OBJECTIVES

Our objective was to investigate modulations of TN-C and MMPs in hypoplastic lungs and their possible contribution to the observed pulmonary vascular abnormalities.

METHODS

We addressed our objectives by pursing immunoblotting and immunohistochemistry and zymography/reverse zymography to assess the alterations in activities of MMPs and their inhibitors.

RESULTS

We observed significant down-regulation of MMP-9 activity in hypoplastic lungs at the later fetal developmental stages, whereas MMP-2 activity assessed by gelatin zymography remained unaltered. Reverse zymography revealed up-regulation of activities of TIMP-1, -2, -3 and -4 in hypoplastic lungs during later fetal development, with pronounced increases in TIMP-3 and -4 activities. Furthermore, immunoblot analyses and immunohistochemistry revealed that TN-C protein was down-regulated in developing hypoplastic lungs, compared to normal lungs.

CONCLUSIONS

(1)TN-C is known to inhibit vascular SMC proliferation. But, decrease in TN-C in hypoplastic lungs may support the observed arterial SMC proliferation. (2) Our studies showed that in hypoplastic lungs the SMC apoptosis is not affected, thus suggesting that SMC proliferation and apoptosis may be two separate processes in pulmonary hypoplasia with coexistent diaphragmatic hernia. Together, our data showed an imbalance in the extracellular matrix proteins, which may contribute to the pulmonary vascular abnormalities.

Correlations of epidermal growth factor-mediated nuclear factor-kappa B and matrix proteinase activity with invasions of cholangiocarcinoma cells

AIM: To explore the mechanism of epidermal growth factor (EGF) in the promotion of human cholangiocarcinoma cell invasion.

METHODS: Invasion assay and cell proliferation assay were performed in human cholangiocarcinoma cell line HuCCT1 treated with different concentrations of EGF. Reverse transcription polymerase chain reaction (RT-PCR) and Western blot were used to detect the expression of matrix metalloproteinases (MMPs), urokinase type plasminogen activator (uPA) and plasminogen activator inhibitor (PAI-1) in HuCCT1 cells. The activity of nuclear factor-kappa B (NF-κB) was determined by electrophoretic mobility shift assay (EMSA). After pretreatment with pyrrolidine dithiocarbamate or ibuprofen, the invasion of HuCCT1 cells was observed.

RESULTS: EGF treatment resulted in increased invasions of HuCCT1 cells in a dose-dependent manner (cell number as EGF at 10, 100 μg/L vs 0 μg/L: 35.4 ± 6.2, 57.2 ± 7.6 vs 16.3 ± 3.1; t = 4.77, P = 0.009; t = 8.63, P = 0.001, respectively). However, EGF did not affect the proliferation in HuCCT1 cells. RT-PCR and Western blot showed that EGF dramatically increased the expression of MMP-9, uPA and PAI-1 mRNA and protein in HuCCT1 cells, but it did not change the expression of MMP-2. The activity of NF-κB was significantly increased after EGF treatment, while EGF-induced invasion of HuCCT1 cells was markedly inhibited by pretreatment with PDTC or ibuprofen (cell number: 46.6 ± 4.6 vs 62.3 ± 5.2, t = 3.168, P = 0.037; 35.3 ± 5.4 vs62.3 ± 5.2, t = 6.30, P = 0.003).

CONCLUSION: EGF promotes the invasion of human cholangiocarcinoma cells, and the up-regulation of MMP-9, uPA , PAI-1 and NF-κB activity is involved in this process.

Regulation of MMP-9 gene expression for the development of novel molecular targets against cancer and inflammatory diseases

The need to pharmacologically control the proteolytic activity of matrix metalloproteinases (MMPs) has been commonly acknowledged, despite its limited efficacy in clinical trials. Among the reasons that explain this failure is our limited understanding of the signals that control the expression of MMPs in different cell types during different pathological conditions. Thus, future therapies must rely on more selective approaches. With the continually increasing body of proof implicating MMPs in a large number of diseases, it has become a priority to establish the pertinence of molecules involved in the signalling pathways leading to the expression of these enzymes. MMP-9 is a case in point: its dramatic overexpression in cancer and various inflammatory conditions clearly points to the molecular mechanisms controlling its expression as a potential target for eventual rational therapeutic intervention. In this article, recent progress in the signalling pathways that regulate MMP-9 expression is reviewed, and the latest strategies to be considered in the search for a specific inhibitor of its expression are presented.

Molecular mechanism for activation and regulation of matrix metalloproteinases during bacterial infections and respiratory inflammation

Matrix metalloproteinases (MMPs) are critical mediators of tissue remodeling. Inappropriate regulation of MMPs causes many pathological events, including microbial invasion and inflammatory tissue damage. Some of the bacterial exoproteinases can effectively activate pro-MMPs (inactive zymogens) via limited proteolysis around their autoinhibitory domains. In addition, overproduction of nitric oxide (NO) may contribute to respiratory inflammation via the formation of reactive nitrogen species (RNS). Several studies have identified regulatory properties of NO/RNS on biomolecules due to functional modification of their cysteine residues. In fact, NO/RNS can mediate activation and expression of MMPs, because RNS can interact with a cysteine switch in the autoinhibitory domain, thus converting proMMPs into their active forms without proteolysis. Many studies have indicated that NO/RNS can participate in expression of various genes that affect immune-inflammatory responses, including MMPs. Although NO in some cases upregulates MMPs, S -nitrosothiols downregulate MMP-9 expression by suppressing the NF-kappaB pathway. While microbial proteinases cause excessive activation of MMPs and contribute to microbial pathogenesis, NO/RNS may modulate expression and activation of MMPs as well as various inflammatory mediators, depending on the redox status at sites of inflammation. Therefore, appropriate regulation of MMPs may be of potential therapeutic value for various infections and inflammatory lung diseases.

Bradykinin stimulates MMP-2 production in guinea pig tracheal smooth muscle cells

The implication of bradykinin (BK) receptors in the release of the matrix metalloproteinase-2 (MMP-2; gelatinase A) was studied in guinea pig tracheal smooth muscle cells (GP-TSMC). Bradykinin (10(-8)-10(-4) M) induced a time- and concentration-dependent upregulation of MMP-2 production from cultured GP-TSMC. Pretreatment of the GP-TSMC with the bradykinin B2 receptor (BKB2-R) antagonist Hpp-HOE-140 (Hpp-D-Arg0-Hyp3-Thi5-D-Tic7-Oic8-BK; 10(-8)-10(-4) M) significantly inhibited the BK-stimulated upregulation of MMP-2 in GP-TSMC in a concentration-related manner. Conversely, GP-TSMC pretreated with the selective bradykinin B1 receptor (BKB1-R) antagonist R-954 (Ac-Om[Oic2, alpha-MePhe5, D-betaNal7, Ile8]desArg9BK; 10(-8)-10(-4) M) did not show any change in the response to BK. Moreover, the selective BKB2-R agonist Lys0BK (kallidin; 10(-8)-10(-4) M) stimulated whereas the selective BKB1-R agonist desArg9BK (DBK; 10(-8)-10(-4) M) had no effect on MMP-2 release from GP-TSMC. Further, the nonselective cyclooxygenase (COX) enzyme inhibitor indomethacin (IND; 10(-5) M), the glucocorticosteroid dexamethasone (DEX; 1 ng/mL) and the protein synthesis inhibitors, cycloheximide (CHX; 10(-6) M) and actinomycin D (ACT-D; 10(-8) M) also inhibited BK-induced MMP-2 release from GP-TSMC. These results provide the first evidence for the involvement of BK in the release of MMP-2 from airway smooth muscle cells through activation of the BKB2-R. Such response is mostly mediated by the induction of COX and the subsequent production of endogenous prostaglandins (PGs). It could therefore be suggested that MMP-2 might play a role in the process of airway remodeling.

Inhibition of NFkappaB activation and IL-8 expression in human bronchial epithelial cells by acrolein

Lipid oxidation and environmental pollutants are major sources of alpha,beta-unsaturated aldehydes such as acrolein and 4-hydroxynonenal. Acrolein (2-propenal), a major product of organic combustion such as tobacco smoke, represents the most reactive alpha,beta-unsaturated aldehyde, with high reactivity toward nucleophilic targets such as sulfhydryl groups. To investigate how acrolein affects respiratory tract cell activation, we exposed either primary (NHBE) or immortalized human bronchial epithelial cells (HBE1) to 0-25 microM acrolein, and determined effects on basal and tumor necrosis factor-alpha (TNFalpha)-induced production of the chemokine interleukin (IL)-8. Cell exposure to acrolein dose-dependently suppressed IL-8 mRNA levels in HBE1 cells (26, 40, and 79% at 5, 10, and 25 microM acrolein concentrations, respectively) and resulted in corresponding decreases in IL-8 production. Studies of nuclear factor-kappaB (NFkappaB) activation, an essential event in IL-8 production, showed decreased TNFalpha-induced NFkappaB activation by acrolein, illustrated by inhibition of nuclear translocation of NFkappaB and reduced IkappaBalpha degradation. Immunochemical analysis of IkappaB kinase (IKK), a redox-sensitive regulator of NFkappaB activation, indicated direct modification of the IKK beta-subunit by acrolein, suggesting that acrolein may act directly on IKK. In summary, our results demonstrate that acrolein can suppress inflammatory processes in the airways by inhibiting epithelial IL-8 production through direct or indirect inhibitory effects on NFkappaB activation.

Nitric oxide in health and disease of the respiratory system

During the past decade a plethora of studies have unravelled the multiple roles of nitric oxide (NO) in airway physiology and pathophysiology. In the respiratory tract, NO is produced by a wide variety of cell types and is generated via oxidation of l-arginine that is catalyzed by the enzyme NO synthase (NOS). NOS exists in three distinct isoforms: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS). NO derived from the constitutive isoforms of NOS (nNOS and eNOS) and other NO-adduct molecules (nitrosothiols) have been shown to be modulators of bronchomotor tone. On the other hand, NO derived from iNOS seems to be a proinflammatory mediator with immunomodulatory effects. The concentration of this molecule in exhaled air is abnormal in activated states of different inflammatory airway diseases, and its monitoring is potentially a major advance in the management of, e.g., asthma. Finally, the production of NO under oxidative stress conditions secondarily generates strong oxidizing agents (reactive nitrogen species) that may modulate the development of chronic inflammatory airway diseases and/or amplify the inflammatory response. The fundamental mechanisms driving the altered NO bioactivity under pathological conditions still need to be fully clarified, because their regulation provides a novel target in the prevention and treatment of chronic inflammatory diseases of the airways.

Nitric oxide represses inhibitory kappaB kinase through S-nitrosylation

Nitric oxide (NO) possesses antiinflammatory effects, which may be exerted via its ability to inhibit the transcription factor, NF-kappaB. A commonly proposed mode of action for inhibition of NF-kappaBbyNO involves interference with NF-kappaB binding to DNA. Because activation of inhibitory kappaB kinase (IKK), the prerequisite enzyme complex necessary to induce NF-kappaB, is subject to redox regulation, we assessed whether IKK could present a more proximal target for NO to inhibit NF-kappaB activation. We demonstrate here that S-nitrosothiols (SNO) caused a dose-dependent inhibition of the enzymatic activity of IKK, in lung epithelial cells and in Jurkat T cells, which was associated with S-nitrosylation of the IKK complex. Using biotin derivatization of SNO, we revealed that IKKbeta, the catalytic subunit required for NF-kappaB activation, was a direct target for S-nitrosylation. A mutant version of IKKbeta containing a Cys-179-to-Ala mutation was refractory to inhibition by SNO or to increases in S-nitrosylation, in contrast to wild-type IKKbeta, demonstrating that Cys-179 is the main target for attack by SNO. Importantly, inhibition of NO synthase activity in Jurkat T cells resulted in activation of IKK, in association with its denitrosylation. Moreover, NO synthase inhibition enhanced the ability of tumor necrosis factor alpha to activate IKK, illustrating the importance of endogenous NO in regulating the extent of NF-kappaB activation by cytokines. Collectively, our findings demonstrate that IKKbeta is an important target for the redox regulation of NF-kappaB by endogenous or exogenous NO, providing an additional mechanism for its antiinflammatory properties.

Regulation of matrix metalloproteinases by cytokines and reactive oxygen/nitrogen species in the myocardium

Dysregulation of the myocardial extracellular matrix contributes to abnormal cardiac muscle function. Changes in the balance between matrix deposition and matrix degradation by matrix metalloproteinases (MMPs) can lead to cardiac fibrosis and dilation. In this review, we discuss the regulation of MMPs, their endogenous inhibitors (TIMPs) and collagen synthesis by inflammatory cytokines and reactive oxygen/nitrogen species (ROS/RNS). Inflammatory cytokines, such as interleukin-1beta and tumor necrosis factor-alpha, and ROS activate mitogen-activated protein kinases and stress-responsive protein kinases in cardiac cells. In non-cardiac tissues, inflammatory cytokine activation of these kinases is redox sensitive, suggesting ROS may also be involved in cytokine signaling in the heart. Subsequent activation of transcription factors including AP-1, Ets, and nuclear factor kappa-B leads to increased transcription of MMPs. ROS also directly activate MMPs post-translationally. In addition, inflammatory cytokines and ROS lead to decreased TIMP levels and collagen synthesis. Work in animal models suggests that inhibition of inflammatory cytokine or ROS signaling leads to less myocardial remodeling. Further study of the signaling of regulation of the cardiac extracellular matrix may lead to new approaches for the treatment of myocardial remodeling and failure.

Ultrastructural study of pleural lymphatic drainage unit and effect of nitric oxide on the drainage capacity of pleural lymphatic stomata in the rat

The objective of this study was twofold: first to investigate the ultrastructure of the lymphatic drainage unit on the costal pleura of rats by electron microscopy, and secondly to examine the effect of nitric oxide on the pleural lymphatic stomata and fluid absorption from the pleural cavity. The lymphatic drainage unit of the rat costal pleura is composed of three special components: the lymphatic stomata between the mesothelial cells, the initial part of the lymphatic vessels and the underlying connective tissue containing many foramina. The unit is the main passage to drainage fluid, particles and cells in the pleural space. To investigate the regulator of the lymph drainage, nitric oxide synthase inhibitor and nitric oxide donor were injected into the peritoneal cavity of the rats, respectively. Trypan blue was used as tracer. The ultrastructural changes of pleural lymphatic stomata were observed under scanning electron microscope and analyzed by a computer image processing system. It turned out that the area and density of the pleural lymphatic stomata were positively correlated with the nitric oxide quantity (p < 0.05). After the tracer was injected into the pleural cavity, the nitric oxide donor group exhibited a higher trypan blue concentration than the control group (p < 0.05). The ability of the pleura to absorb trypan blue was enhanced because of the larger opening of the lymphatic stomata (p < 0.05). It is suggested that nitric oxide can increase lymphatic absorption of the pleura by opening pleural lymphatic stomata.

A Nitric Oxide-Releasing Salbutamol Elicits Potent Relaxant and Anti-Inflammatory Activities

Beta2-adrenoceptor agonists are widely used in the treatment of pulmonary diseases. We have investigated the relaxant and anti-inflammatory activities of NCX-950 (alpha'-[[(1,1-dimethylethy)amino]methyl]-4-hydroxy-1,3-benzenedimethanol nitrate) (a nitric oxide-releasing salbutamol) in human isolated bronchi and on lipopolysaccharide (LPS)-induced acute airway inflammation in mice. NCX-950 (10(-8)-10(-5) M) elicited a relaxation of human isolated bronchi moderately higher than salbutamol, which was reduced by a beta-adrenergic blocking drug, propranolol, but not by an inhibitor of guanylate cyclase, ODQ (1H-[1,2,4]oxadiazolo[4,3-] quinolaxin-1-one). The treatment of mice with NCX-950 (1, 10, and 100 microM aerosol) markedly inhibited the neutrophil influx induced by LPS aerosol in bronchoalveolar lavage (BAL) fluid, whereas salbutamol at equimolar doses elicited a moderate inhibition. Pretreatment of mice with NCX-950 (100 microM) also significantly reduced tumor necrosis factor-alpha, interleukin-6 (IL-6), transforming growth factor-beta, and matrix metalloproteinase-9 release in BAL fluid, whereas salbutamol was ineffective. Propranolol, but not ODQ, suppressed the inhibitory activity of NCX-950 on neutrophil influx and IL-6 release in BAL fluids. A nitric oxide-releasing sildenafil NCX-911 [(5-[2-ethoxy-5-(4-methylpiperidinylsulfonyl)phenyl]-1-methyl-3-n-propyl-1,6-dihydro-7H-pyrazolo[4,3-d]pyrimidin-7-one nitrate)], but not sildenafil (100 microM) also reduced the neutrophil influx following LPS exposure in mice. This study reported that NCX-950 elicits potent relaxant and anti-inflammatory activities compared with salbutamol, and these effects may be mainly due to the activation of the beta2-adrenoceptor rather than the cGMP pathway.

Multiple contributing roles for NOS2 in LPS-induced acute airway inflammation in mice

Acute lung inflammation and injury were induced by intranasal instillation of lipopolysaccharide (LPS) in normal and type 2 nitric oxide synthase (NOS2)-deficient (NOS2-/-) C57BL/6 mice. LPS-induced increases in extravasated airway neutrophils and in lung lavage fluid of TNF-alpha and macrophage inflammatory protein-2 were markedly lower in NOS2-/- than in wild-type mice, indicating that NOS2-derived nitric oxide (NO.) participates in inflammatory cytokine production and neutrophil recruitment. Instillation of LPS also increased total lung lavage protein and induced matrix metalloproteinase-9 and mucin 5AC, as indexes of lung epithelial injury and/or mucus hyperplasia, and increased tyrosine nitration of lung lavage proteins, a marker of oxidative injury. All these responses were less pronounced in NOS2-/- than in wild-type mice. Inhibition of NOS activity also suppressed production of TNF-alpha and macrophage inflammatory protein-2 by LPS-stimulated mouse alveolar MH-S macrophages, and this was restored by NO. donors, illustrating involvement of NO. in macrophage cytokine signaling. Oligonucleotide microarray (GeneChip) analysis of global lung gene expression revealed that LPS inhalation induced a range of transcripts encoding proinflammatory cytokines and chemokines, stress-inducible factors, and other extracellular factors and suppressed mRNAs encoding certain cytoskeletal proteins and signaling proteins, responses that were generally attenuated in NOS2-/- mice. Comparison of both mouse strains revealed altered expression of several cytoskeletal proteins, cell surface proteins, and signaling proteins in NOS2-/- mice, changes that may partly explain the reduced responsiveness to LPS. Collectively, our results suggest that NOS2 participates in the acute inflammatory response to LPS by multiple mechanisms: involvement in proinflammatory cytokine signaling and alteration of the expression of various genes that affect inflammatory-immune responses to LPS.

Induction of stress proteins and MMP-9 by 0.8 ppm of ozone in murine skin

Ozone (O(3)) is among the most reactive environmental oxidant pollutants to which cutaneous tissues are exposed. O(3) exposure has been shown to induce antioxidant depletion as well as the oxidation of lipids and proteins within the outermost skin layer, the stratum corneum. However, relatively little is known regarding the potential effects of O(3) on the cellular constituents of the underlying skin epidermis and dermis. In the present study, hairless mice exposed for 6 h to 0.8 ppm O(3) showed increases in lipid peroxidation, as quantitated by increases in 4-hydroxynonenal-protein adducts. O(3) exposure caused an induction of the stress proteins HSP27 and heme oxygenase-1 (HO-1), starting at 6 h and increasing up to 18 h after O(3) exposure. This was accompanied by an increase in matrix metalloproteinase-9 (MMP-9) mRNA and activity levels, indicative of possible injurious-reparative processes. Collectively, our data demonstrate that skin exposure to O(3) not only affects antioxidant levels and oxidation markers in the outermost stratum corneum layer, but also induces cellular stress responses in the deeper cellular layers of the skin.