Physiological Levels Of Nitric Oxide Research Articles

Redox regulation of m6A methyltransferase METTL3 in β-cells controls the innate immune response in type 1 diabetes.

Type 1 diabetes (T1D) is characterized by the destruction of pancreatic β-cells. Several observations have renewed the interest in β-cell RNA sensors and editors. Here, we report that N6-methyladenosine (m6A) is an adaptive β-cell safeguard mechanism that controls the amplitude and duration of the antiviral innate immune response at T1D onset. m6A writer methyltransferase 3 (METTL3) levels increase drastically in β-cells at T1D onset but rapidly decline with disease progression. m6A sequencing revealed the m6A hypermethylation of several key innate immune mediators, including OAS1, OAS2, OAS3 and ADAR1 in human islets and EndoC-βH1 cells at T1D onset. METTL3 silencing enhanced 2'-5'-oligoadenylate synthetase levels by increasing its mRNA stability. Consistently, in vivo gene therapy to prolong Mettl3 overexpression specifically in β-cells delayed diabetes progression in the non-obese diabetic mouse model of T1D. Mechanistically, the accumulation of reactive oxygen species blocked upregulation of METTL3 in response to cytokines, while physiological levels of nitric oxide enhanced METTL3 levels and activity. Furthermore, we report that the cysteines in position C276 and C326 in the zinc finger domains of the METTL3 protein are sensitive to S-nitrosylation and are important to the METTL3-mediated regulation of oligoadenylate synthase mRNA stability in human β-cells. Collectively, we report that m6A regulates the innate immune response at the β-cell level during the onset of T1D in humans.

Endothelium-Mimicking Bilayer Vascular Grafts with Dual-Releasing of NO/H2S for Anti-Inflammation and Anticalcification.

Vascular complications caused by diabetes impair the activities of endothelial nitric oxide synthase (eNOS) and cystathionine γ-lyase (CSE), resulting in decreased physiological levels of nitric oxide (NO) and hydrogen sulfide (H2S). The low bioavailability of NO and H2S hinders the endothelialization of vascular grafts. In this study, endothelium-mimicking bilayer vascular grafts were designed with spatiotemporally controlled dual releases of NO and H2S for in situ endothelialization and angiogenesis. Keratin-based H2S donor was synthesized and electrospun with poly(l-lactide-co-ε-caprolactone) (PLCL) as the outer layer of the graft to release H2S. Hyaluronic acid, one of the major glycosaminoglycans in endothelial glycocalyx, was complexed with Cu ions as the inner layer to mimic glutathione peroxidase (GPx) and maintain long-term physiological NO flux. The synergistic effects of NO and H2S of bilayer grafts selectively promoted the regeneration and migration of human umbilical vascular endothelial cells (HUVECs), while inhibiting the overproliferation of human umbilical artery smooth muscle cells (HUASMCs). Bilayer grafts could effectively prevent vascular calcification, reduce inflammation, and alleviate endothelial dysfunction. The in vivo study in a rat abdominal aorta replacement model for 1 month showed that the graft had a good patency rate and had potential for vascular remodeling in situ.

Cross-talk between insulin resistance and nitrogen species in hypoxia leads to deterioration of tissue and homeostasis.

Hypoxia has been linked with insulin resistance as it produces changes in the metabolism of the cell; in which the adipocytes impede the insulin receptor tyrosine, phosphorylation, directing at decreased levels of transport of glucose. At this juncture, we are focusing on cross-talk between insulin resistance and nitrogen species in hypoxia, leading to the deterioration of tissue and homeostasis. Physiological levels of nitric oxide play a very crucial role in acting as a priority effector and signaling molecule, arbitrating the body's responses to hypoxia. Both ROS and RNS are associated with a reduction in IRS1 phosphorylation in tyrosine, which leads to reduced levels of IRS1 content and insulin response, which further leads to insulin resistance. Cellular hypoxia is a trigger to inflammatory mediators which signal tissue impairment and initiate survival requirements. But, hypoxia-mediated inflammation act as a protective role by an immune response and promotes wound healing during infection. In this review, we abridge the crosstalk between the inflammation and highlight the dysregulation in physiological consequences due to diabetes mellitus. Finally, we review various treatments available for its related physiological complications.

Smartphone compatible nitric oxide releasing insert to prevent catheter-associated infections.

A large fraction of nosocomial infections is associated with medical devices that are deemed life-threatening in immunocompromised patients. Medical device-related infections are a result of bacterial colonization and biofilm formation on the device surface that affects >1 million people annually in the US alone. Over the past few years, light-based antimicrobial therapy has made substantial advances in tackling microbial colonization. Taking the advantage of light and antibacterial properties of nitric oxide (NO), for the first time, a robust, biocompatible, anti-infective approach to design a universal disposable catheter disinfection insert (DCDI) that can both prevent bacterial adhesion and disinfect indwelling catheters in situ is reported. The DCDI is engineered using a photo-initiated NO donor molecule, incorporated in polymer tubing that is mounted on a side glow fiber optic connected to an LED light source. Using a smartphone application, the NO release from DCDI is photoactivated via white light resulting in tunable physiological levels of NO for up to 24h. When challenged with microorganisms S. aureus and E. coli, the NO-releasing DCDI statistically reduced microbial attachment by >99% versus the controls with just 4h of exposure. The DCDI also eradicated ∼97% of pre-colonized bacteria on the CVC catheter model demonstrating the ability to exterminate an established catheter infection. The smart, mobile-operated novel universal antibacterial device can be used to both prevent catheter infections or can be inserted within an infected catheter to eradicate the bacteria without complex surgical interventions. The therapeutic levels of NO generated via illuminating fiber optics can be the next-generation biocompatible solution for catheter-related bloodstream infections.

Role of nitric oxide in regulating epidermal permeability barrier function.

Nitric oxide (NO), a free radical molecule synthesized by nitric oxide synthases (NOS), regulates multiple cellular functions in a variety of cell types. These NOS, including endothelial NOS (eNOS), inducible NOS (iNOS) and neural NOS (nNOS), are expressed in keratinocytes. Expression levels of both iNOS and nNOS decrease with ageing, and insufficient NO has been linked to the development of a number of disorders such as diabetes and hypertension, and to the severity of atherosclerosis. Conversely, excessive NO levels can induce cellular oxidative stress, but physiological levels of NO are required to maintain the normal functioning of cells, including keratinocytes. NO also regulates cutaneous functions, including epidermal permeability barrier homeostasis and wound healing, through its stimulation of keratinocyte proliferation, differentiation and lipid metabolism. Topical applications of a diverse group of agents which generate nitric oxide (called NO donors) such as S-nitroso-N-acetyl-D,L-penicillamine (SNAP) can delay permeability barrier recovery in barrier-disrupted skin, but iNOS is still required for epidermal permeability barrier homeostasis. This review summarizes the regulatory role that NO plays in epidermal permeability barrier functions and the underlying mechanisms involved.

Diabetoporosis: Role of nitric oxide.

Diabetoporosis, diabetic-related decreased bone quality and quantity, is one of the leading causes of osteoporotic fractures in subjects with type 2 diabetes (T2D). This is associated with lower trabecular and cortical bone quality, lower bone turnover rates, lower rates of bone healing, and abnormal posttranslational modifications of collagen. Decreased nitric oxide (NO) bioavailability has been reported within the bones of T2D patients and can be considered as one of the primary mechanisms by which diabetoporosis is manifested. NO donors increase trabecular and cortical bone quality, increase the rate of bone formation, accelerate the bone healing process, delay osteoporosis, and decrease osteoporotic fractures in T2D patients, suggesting the potential therapeutic implication of NO-based interventions. NO is produced in the osteoblast and osteoclast cells by three isoforms of NO synthase (NOS) enzymes. In this review, the roles of NO in bone remodeling in the normal and diabetic states are discussed. Also, the favorable effects of low physiological levels of NO produced by endothelial NOS (eNOS) versus detrimental effects of high pathological levels of NO produced by inducible NOS (iNOS) in diabetoporosis are summarized. Available data indicates decreased bone NO bioavailability in T2D and decreased expression of eNOS, and increased expression and activity of iNOS. NO donors can be considered novel therapeutic agents in diabetoporosis.

Enhanced Hemocompatibility and In Vivo Analytical Accuracy of Intravascular Potentiometric Carbon Dioxide Sensors via Nitric Oxide Release.

In this letter, the innate ability of nitric oxide (NO) to inhibit platelet activation/adhesion/thrombus formation is employed to improve the hemocompatibility and in vivo accuracy of an intravascular (IV) potentiometric PCO2 (partial pressure of carbon dioxide) sensor. The catheter-type sensor is fabricated by impregnating a segment of dual lumen silicone tubing with a proton ionophore, plasticizer, and lipophilic cation-exchanger. Subsequent filling of bicarbonate and strong buffer solutions and placement of Ag/AgCl reference electrode wires within each lumen, respectively, enables measurement of the membrane potential difference across the inner wall of the tube, with this potential changing as a function of the logarithm of sample PCO2. The dual lumen device is further encapsulated within a S-nitroso-N-acetyl-DL-penicillamine (SNAP)-doped silicone tube that releases physiological levels of NO. The NO releasing sensor exhibits near-Nernstian sensitivity toward PCO2 (slope = 59.31 ± 0.78 mV/decade) and low drift rates (<2 mV/24 h after initial equilibration). In vivo evaluation of the NO releasing sensors, performed in the arteries and veins of anesthetized pigs for 20 h, shows enhanced accuracy (vs non-NO releasing sensors) when benchmarked to measurements of discrete blood samples made with a commercial blood gas analyzer. The accurate, continuous monitoring of blood PCO2 levels achieved with this new IV NO releasing PCO2 sensor configuration could help better manage hospitalized patients in critical care units.

Development of S-Nitroso-N-Acetylpenicillamine Impregnated Medical Grade Polyvinyl Chloride for Antimicrobial Medical Device Interfaces.

In the clinical setting, polyvinyl chloride (PVC) accounts for 25% of all polymers used in medical device applications. However, medical devices fabricated with plasticized PVC, such as endotracheal tubes, extracorporeal circuits (ECCs), or intravenous catheters, can lead to thrombosis and infection complications. Mortality associated with hospital associated infections (HAIs) exceed 100,000 deaths each year. One method to overcome these challenges is to develop bioactive polymers with nitric oxide (NO) release. Nitric oxide exhibits many physiological roles including antibacterial, antithrombic, and anti-inflammatory activity. In this study, plasticized Tygon PVC tubing was impregnated with a NO donor molecule, S-nitroso-N-acetylpenicillamine (SNAP), via a simple solvent-swelling-impregnation method, where polymer samples were submerged in a SNAP impregnation solvent (methanol, acetone, plasticizer), rinsed, and dried. An additional topcoat of a biocompatible CarboSil 2080A (CB) was applied to reduce SNAP leaching. The SNAP-PVC-CB was characterized for NO release using chemiluminescence, leaching with UV-vis spectroscopy, surface characterization with scanning electron microscopy, tensile strength analysis, stability during storage and sterilization, and antimicrobial properties in vitro. The SNAP-PVC-CB exhibited an NO flux of 4.29 ± 0.80 × 10-10 mol cm-2 min-1 over the initial 24 h under physiological conditions and continued to release physiological levels of NO for up to 14 d (incubated in PBS buffer at 37 °C). The addition of the CB topcoat reduced the total SNAP leaching by 60% during incubation. Mechanical properties and surface topography remained similar to the original PVC after SNAP impregnation and application of the CB topcoat. After ethylene oxide sterilization and 1 month of storage, the SNAP-PVC-CB demonstrated excellent SNAP stability (ca. 90% SNAP remaining). In a 24 h antibacterial assay, SNAP-PVC reduced viable bacteria colonization (ca. 1 log reduction) of S.aureus and E.coli compared to PVC controls. This simple method for SNAP impregnation of medical grade plasticized PVC holds great potential for improving the biocompatibility of postfabricated, plasticized PVC medical devices.

Modulation of Nitric Oxide Synthases by Oxidized LDLs: Role in Vascular Inflammation and Atherosclerosis Development.

The maintenance of physiological levels of nitric oxide (NO) produced by eNOS represents a key element for vascular endothelial homeostasis. On the other hand, NO overproduction, due to the activation of iNOS under different stress conditions, leads to endothelial dysfunction and, in the late stages, to the development of atherosclerosis. Oxidized LDLs (oxLDLs) represent the major candidates to trigger biomolecular processes accompanying endothelial dysfunction and vascular inflammation leading to atherosclerosis, though the pathophysiological mechanism still remains to be elucidated. Here, we summarize recent evidence suggesting that oxLDLs produce significant impairment in the modulation of the eNOS/iNOS machinery, downregulating eNOS via the HMGB1-TLR4-Caveolin-1 pathway. On the other hand, increased oxLDLs lead to sustained activation of the scavenger receptor LOX-1 and, subsequently, to NFkB activation, which, in turn, increases iNOS, leading to EC oxidative stress. Finally, these events are associated with reduced protective autophagic response and accelerated apoptotic EC death, which activates atherosclerotic development. Taken together, this information sheds new light on the pathophysiological mechanisms of oxLDL-related impairment of EC functionality and opens new perspectives in atherothrombosis prevention.

Development of Cu-Modified PVC and PU for Catalytic Generation of Nitric Oxide

Nitric oxide (NO) generating surfaces are potentially promising for improving haemocompatibility of blood-contacting biomaterials. In the present report, Cu-modified poly(vinyl chloride) (PVC) and polyurethane (PU) were prepared via polydopamine (pDA)-assisted chelation. The copper content on the PVC and PU modified surfaces, assessed by inductively coupled plasma - optical emission spectrometry (ICP-OES), were about 3.86 and 6.04 nmol·cm−2, respectively. The Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) data suggest that copper is attached to the polymer surface through complex formation with pDA. The cumulative leaching of copper from modified PVC and PU during the five day incubation in phosphate buffered saline (PBS), measured by inductively coupled plasma mass spectrometry (ICP-MS), was about 50.7 ppb and 48 ppb, respectively which is within its physiological level. Modified polymers were tested for their ability to catalytically generate NO by decomposing of endogenous S-nitrosothiol (GSNO). The obtained data show that Cu-modified PVC and PU exhibited the capacity to generate physiological levels of NO which could be a foundation for developing new biocompatible materials with NO-based therapeutics.

Physiological Levels of Nitric Oxide Diminish Mitochondrial Superoxide. Potential Role of Mitochondrial Dinitrosyl Iron Complexes and Nitrosothiols.

Mitochondria are the major source of superoxide radicals and superoxide overproduction contributes to cardiovascular diseases and metabolic disorders. Endothelial dysfunction and diminished nitric oxide levels are early steps in the development of these pathological conditions. It is known that physiological production of nitric oxide reduces oxidative stress and inflammation, however, the precise mechanism of “antioxidant” effect of nitric oxide is not clear. In this work we tested the hypothesis that physiological levels of nitric oxide diminish mitochondrial superoxide production without inhibition of mitochondrial respiration. In order to test this hypothesis we analyzed effect of low physiological fluxes of nitric oxide (20 nM/min) on superoxide and hydrogen peroxide production by ESR spin probes and Amplex Red in isolated rat brain mitochondria. Indeed, low levels of nitric oxide substantially attenuated both basal and antimycin A-stimulated production of reactive oxygen species in the presence of succinate or glutamate/malate as mitochondrial substrates. Furthermore, slow releasing NO donor DPTA-NONOate (100 μM) did not change oxygen consumption in State 4 and State 3. However, the NO-donor strongly inhibited oxygen consumption in the presence of uncoupling agent CCCP, which is likely associated with inhibition of the over-reduced complex IV in uncoupled mitochondria. We have examined accumulation of dinitrosyl iron complexes and nitrosothiols in mitochondria treated with fast-releasing NO donor MAHMA NONOate (10 μM) for 30 min until complete release of NO. Following treatment with NO donor, mitochondria were frozen for direct detection of dinitrosyl iron complexes using Electron Spin Resonance (ESR) while accumulation of nitrosothiols was measured by ferrous-N-Methyl-D-glucamine dithiocarbamate complex, Fe(MGD)2, in lysed mitochondria. Treatment of mitochondria with NO-donor gave rise to ESR signal of dinitrosyl iron complexes while ESR spectra of Fe(MGD)2 supplemented mitochondrial lysates showed presence of both dinitrosyl iron complexes and nitrosothiols. We suggest that nitric oxide attenuates production of mitochondrial superoxide by post-translational modifications by nitrosylation of protein cysteine residues and formation of protein dinitrosyl iron complexes with thiol-containing ligands and, therefore, nitric oxide reduction in pathological conditions associated with endothelial dysfunction may increase mitochondrial oxidative stress.

Regulation of mitochondrial function and endoplasmic reticulum stress by nitric oxide in pluripotent stem cells.

Mitochondrial dysfunction and endoplasmic reticulum stress (ERS) are global processes that are interrelated and regulated by several stress factors. Nitric oxide (NO) is a multifunctional biomolecule with many varieties of physiological and pathological functions, such as the regulation of cytochrome c inhibition and activation of the immune response, ERS and DNA damage; these actions are dose-dependent. It has been reported that in embryonic stem cells, NO has a dual role, controlling differentiation, survival and pluripotency, but the molecular mechanisms by which it modulates these functions are not yet known. Low levels of NO maintain pluripotency and induce mitochondrial biogenesis. It is well established that NO disrupts the mitochondrial respiratory chain and causes changes in mitochondrial Ca2+ flux that induce ERS. Thus, at high concentrations, NO becomes a potential differentiation agent due to the relationship between ERS and the unfolded protein response in many differentiated cell lines. Nevertheless, many studies have demonstrated the need for physiological levels of NO for a proper ERS response. In this review, we stress the importance of the relationships between NO levels, ERS and mitochondrial dysfunction that control stem cell fate as a new approach to possible cell therapy strategies.

Improved Hemocompatibility of Multilumen Catheters via Nitric Oxide (NO) Release from S-Nitroso-N-acetylpenicillamine (SNAP) Composite Filled Lumen.

Blood-contacting devices, such as intravascular catheters, suffer from challenges related to thrombus formation and infection. Nitric oxide (NO) is an endogenous antiplatelet and antimicrobial agent. Exogenous release of NO from various polymer matrices has been shown to reduce thrombosis and infection of/on implantable medical devices. However, the clinical applications of such materials have been hindered due to factors such as NO donor leaching and thermal instability. In this study, a novel approach is demonstrated in which one lumen of commercial dual lumen catheters is dedicated to the NO release chemistry, allowing the other lumen to be available for clinical vascular access. A composite consisting of poly(ethylene glycol) (PEG) and S-nitroso-N-acetylpenicillamine (SNAP) is used to fill the NO-releasing lumen of commercial 7 French silicone catheters. Physiological levels of NO are released from the SNAP-PEG catheters for up to 14 d, as measured by chemiluminescence NO analyzer (in PBS buffer at 37 °C). PEG facilitates the NO release from SNAP within the lumen by increasing the water absorption and slowly dissolving the solid SNAP-PEG composite. In a CDC biofilm bioreactor, the SNAP-PEG catheters are found to reduce >97% bacterial adhesion as compared to the PEG controls for single bacterial species including E. coli and S. aureus. SNAP-PEG and PEG control catheters were implanted in rabbit veins for 7 h (single lumen) and 11 d (dual lumen) to evaluate their hemocompatibility properties. Significant reductions in thrombus formation on the SNAP-PEG vs PEG controls were observed, with ca. 85% reduction for 7 h single lumen catheters and ca. 55% reduction for 11 d dual lumen catheters.

Efficient Eradication of Mature Pseudomonas aeruginosa Biofilm via Controlled Delivery of Nitric Oxide Combined with Antimicrobial Peptide and Antibiotics.

Fast eradication of mature biofilms is the ‘holy grail’ in the clinical management of device-related infections. Endogenous nitric oxide (NO) produced by macrophages plays an important role in host defense against intracellular pathogens, and NO is a promising agent in preventing biofilms formation in vitro. However, the rate of delivery of NO by various NO donors (e.g., diazeniumdiolates, S-nitrosothiols, etc.) is difficult to control, which hinders fundamental studies aimed at understanding the role of NO in biofilm control. In this study, by using a novel precisely controlled electrochemical NO releasing catheter device, we examine the effect of physiological levels of NO on eradicating mature Pseudomonas aeruginosa biofilm (7 days), as well as the potential application of the combination of NO with antimicrobial agents. It is shown that physiological levels of NO exhibit mixed effects of killing bacteria and dispersing ambient biofilm. The overall biofilm-eradicating effect of NO is quite efficient in a dose-dependent manner over a 3 h period of NO treatment. Moreover, NO also greatly enhances the efficacy of antimicrobial agents, including human beta-defensin 2 (BD-2) and several antibiotics, in eradicating biofilm and its detached cells, which otherwise exhibited high recalcitrance to these antimicrobial agents. The electrochemical NO release technology offers a powerful tool in evaluating the role of NO in biofilm control as well as a promising approach when combined with antimicrobial agents to treat biofilm-associated infections in hospital settings, especially infections resulting from intravascular catheters.

Development of glycine-α-methyl-proline-containing tripeptides with neuroprotective properties

Herein is described the synthesis of novel glycine-α-methyl-proline-containing tripeptides (GPMeX tripeptides namely GPMeR, GPMeK, and GPMeH) with the aim of obtaining derivatives highly stable in human plasma and able to counteract neuroinflammatory processes that are distinctive of neurodegenerative pathologies. The syntheses of GPMeR, GPMeK, and GPMeH were all achieved both by introducing the ProMe residue into the Gly-Pro-Arg (GPR) sequence in place of the native Pro in P2 position and replacing the basic amino acid Arg in P3 position by Lys or His.Results showed that all novel GPMeX tripeptides are stable in human plasma (t1/2 > 51 h) and that GPMeH – generating stable intramolecular H-bond in a C11-turn by interaction of His imidazole ring and Gly carbonyl group – restored physiological levels of nitric oxide deriving from neuronal NOS (nNOS) activity, thus preventing the inflammatory response by suppression of the NF-kB activity and, consequently, the expression of inflammatory genes such as inducibile NOS (iNOS). Therefore, GPMeH could be a lead compound for further development of peptidomimetics able to contrast neuroinflammatory processes.

Curcumin and folic acid abrogated methotrexate induced vascular endothelial dysfunction.

Methotrexate, an antifolate drug widely used in rheumatoid arthritis, psoriasis, and cancer, is known to cause vascular endothelial dysfunction by causing hyperhomocysteinemia, direct injury to endothelium or by increasing the oxidative stress (raising levels of 7,8-dihydrobiopterin). Curcumin is a naturally occurring polyphenol with strong antioxidant and anti-inflammatory action and therapeutic spectra similar to that of methotrexate. This study was performed to evaluate the effects of curcumin on methotrexate induced vascular endothelial dysfunction and also compare its effect with that produced by folic acid (0.072 μg·g(-1)·day(-1), p.o., 2 weeks) per se and in combination. Male Wistar rats were exposed to methotrexate (0.35 mg·kg(-1)·day(-1), i.p.) for 2 weeks to induce endothelial dysfunction. Methotrexate exposure led to shedding of endothelium, decreased vascular reactivity, increased oxidative stress, decreased serum nitrite levels, and increase in aortic collagen deposition. Curcumin (200 mg·kg(-1)·day(-1) and 400 mg·kg(-1)·day(-1), p.o.) for 4 weeks prevented the increase in oxidative stress, decrease in serum nitrite, aortic collagen deposition, and also vascular reactivity. The effects were comparable with those produced by folic acid therapy. The study shows that curcumin, when concomitantly administered with methotrexate, abrogated its vascular side effects by preventing an increase in oxidative stress and abating any reduction in physiological nitric oxide levels.

The Effects of Cu-doped TiO2 Thin Films on Hyperplasia, Inflammation and Bacteria Infection

In the present work, different concentrations of Cu ion (1, 2, 5 and 10 wt %) were doped in the TiO2 film by a sol-gel method and dip coating process. The morphology of the Cu-doped TiO2 films were characterized by scanning electron microscopy (SEM) and the results showed that the doped Cu made no change to the TiO2 films. The nitric oxide (NO) release experiment showed that these Cu-doped surfaces showed the ability of catalytic decomposition of exogenous donor S-nitroso-N-acetyl-penicillamine (SNAP) to generate (NO). Based on fluorescence analysis and CCK-8 quantitative results, such films had the ability to inhibit smooth muscle cells adhesion, proliferation and migration with SNAP in vitro. The macrophage adhesion assay and anti-bacterial test proved that such Cu-doped TiO2 films also possessed anti-inflammatory and anti-bacterial abilities. All the abilities above showed positive correlation with the amounts of the doped Cu. This study suggested that the Cu-doped TiO2 films were capable of generating physiological levels of NO in the presence of endogenous donor S-nitrosothiols (RSNO), endowing the TiO2 films with anti-hyperplasia, anti-inflammatory and anti-bacterial abilities.

Development and therapeutic applications of nitric oxide-releasing materials.

Prior to the truly seismic revelation that nitric oxide (NO) was the elusive endothelium-derived relaxing factor, NO was considered simply a reactive pollutant for the vast majority of the biology and biomedical research community – there was essentially no linkage to actual in vivo functional processes, let alone therapeutic applications. Even the relationship between NO and the therapeutic efficacy of nitroglycerin was at this point still unknown. The abrupt change in the research status of NO, initiated by the monumental discovery of the NO-elusive endothelium-derived relaxing factor connection, heralded a new era of investigation that continues to dramatically expand every year. Research on NO has now expanded to include: mechanisms of physiological and biochemical action; the importance of temporal and site-specific NO generation under both normal and pathological conditions; the nature, properties and synthesis of longer lived NO-related molecules that preserve and extend NO bioactivity; the role of nitrite as a stable source of physiological levels of NO; potential therapeutic targets for NO and other NO-related molecules; food and supplements to enhance levels of NO in the circulation; and development of topical and systemic delivery vehicles for therapeutic levels of NO and NO-releasing molecules. In fact, it is becoming ever more apparent that many of the current drugs being developed to address numerous disease conditions are in effect elegant methods of stimulating NO in the appropriate locations and amount. What is also clear is with every new discovery and shift of the research landscape, new NO-related questions emerge at an equally steady pace. Issues seemingly as fundamental as to whether NO promotes or inhibits cancer growth remain controversial. Limitations in addressing not only basic questions relating to how NO participates in both physiological and pathophysiological processes but also how to utilize NO therapeutically arise from an inability to appropriately and effectively deliver and monitor NO in vivo. This issue is an attempt to update overviews of where we are with respect to several of these rapidly evolving NO associated foci of research with an emphasis on delivery and detection strategies. We are fully cognizant that with the level of activity and the rate at which new insights are emerging, we can at best provide but a transient depiction that represents at least a breath catching pause for researchers to take stock of what has been accomplished and where we might be headed. The contributors to this effort are all at the cutting edge of NO research and represent a cohesive effort to encompass many of the important issues that pertain to the ultimate biomedical objective of harnessing the extraordinary therapeutic potential of this seemingly simple molecule.

Reduction in Thrombosis and Bacterial Adhesion with 7 Day Implantation of S-Nitroso-N-acetylpenicillamine (SNAP)-Doped Elast-eon E2As Catheters in Sheep.

Thrombosis and infection are two common problems associated with blood-contacting medical devices such as catheters. Nitric oxide (NO) is known to be a potent antimicrobial agent as well as an inhibitor of platelet activation and adhesion. Healthy endothelial cells that line the inner walls of all blood vessels exhibit a NO flux of 0.5~4×10-10 mol cm-2 min-1 that helps prevent thrombosis. Materials with a NO flux that is equivalent to this level are expected to exhibit similar anti-thrombotic properties. In this study, NO-releasing catheters were fabricated by incorporating S-nitroso-N-acetylpenicillamine (SNAP) in the Elast-eon E2As polymer. The SNAP/E2As catheters release physiological levels of NO for up to 20 d, as measured by chemiluminescence. Furthermore, SNAP is stable in the E2As polymer, retaining 89% of the initial SNAP after ethylene oxide (EO) sterilization. The SNAP/E2As and E2As control catheters were implanted in sheep veins for 7 d to examine the effect on thrombosis and bacterial adhesion. The SNAP/E2As catheters reduced the thrombus area when compared to the control (1.56 ± 0.76 and 5.06 ± 1.44 cm2, respectively). A 90% reduction in bacterial adhesion was also observed for the SNAP/E2As catheters as compared to the controls. The results suggest that the SNAP/E2As polymer has the potential to improve the hemocompatibility and bactericidal activity of intravascular catheters, as well as other blood-contacting medical devices (e.g., vascular grafts, extracorporeal circuits).

Addition of a Nitric Oxide Donor to an Angiotensin II Type 1 Receptor Blocker May Cancel Its Blood Pressure-Lowering Effects

While physiological levels of nitric oxide (NO) protect the endothelium and have vasodilatory effects, excessive NO has adverse effects on the cardiovascular system. Recently, new NO-releasing pharmacodynamic hybrids of angiotensin II (Ang II) type 1 (AT1) receptor blockers (ARBs) have been developed.We analyzed whether olmesartan with NO-donor side chains (Olm-NO) was superior to olmesartan (Olm) for the control of blood pressure (BP). Although there was no significant difference in binding affinity to AT1 wild-type (WT) receptor between Olm and Olm-NO in a cell-based binding assay, the suppressive effect of Olm-NO on Ang II-induced inositol phosphate (IP) production was significantly weaker than that of Olm in AT1 WT receptor-expressing cells. While Olm had a strong inverse agonistic effect on IP production, Olm-NO did not. Next, we divided 18 C57BL mice into 3 groups: Ang II (infusion using an osmotic mini-pump) as a control group, Ang II (n = 6) + Olm, and Ang II (n = 6) + Olm-NO groups (n = 6). Olm-NO did not block Ang II-induced high BP after 10 days, whereas Olm significantly decreased BP. In addition, Olm, but not Olm-NO, significantly reduced the ratio of heart weight to body weight (HW/BW) with downregulation of the mRNA levels of atrial natriuretic peptide.An ARB with a NO-donor may cancel BP-lowering effects probably due to excessive NO and a weak blocking effect by Olm-NO toward AT1 receptor activation.