The design of nitric oxide donor drugs: s-nitrosothiol tDodSNO is a superior photoactivated donor in comparison to GSNO and SNAP

SMA-BmobaSNO: an intelligent photoresponsive nitric oxide releasing polymer for drug nanoencapsulation and targeted delivery

Nitric oxide (NO) is an important biological signalling molecule that acts to vasodilate blood vessels and change the permeability of the blood vessel wall. Due to these cardiovascular actions, co-administering NO with a therapeutic could enhance drug uptake. However current NO donors are not suitable for targeted drug delivery as they systemically release NO. To overcome this limitation we report the development of a smart polymer, SMA-BmobaSNO, designed to release NO in response to a photostimulus. The polymer's NO releasing functionality is an S-nitrosothiol group that, at 10 mg ml^-1, is highly resistant to both thermal (t_1/216 d) and metabolic (t_1/232 h) decomposition, but rapidly brakes down under photoactivation (2700 W m^-2, halogen source) to release NO (t_1/225 min). Photoresponsive NO release from SMA-BmobaSNO was confirmed in a cardiovascular preparation, where irradiation resulted in a 12-fold decrease in vasorelaxation EC₅₀(from 5.2μM to 420 nM). To demonstrate the polymer's utility for drug delivery we then used SMA-BmobaSNO to fabricate a nanoparticle containing the probe Nile Red (NR). The resulting SMA-BmobaSNO-NR nanoparticle exhibited spherical morphology (180 nm diameter) and sustained NR release (≈20% over 5 d). Targeted delivery was characterised in an abdominal preparation, where photoactivation (450 W m^-2) caused localized increases in vasodilation and blood vessel permeability, resulting in a 3-fold increase in NR uptake into photoactivated tissue. Nanoparticles fabricated from SMA-BmobaSNO therefore display highly photoresponsive NO release and can apply the Trojan Horse paradigm by using endogenous NO signalling pathways to smuggle a therapeutic cargo into target tissue.

Recent Developments in Nitric Oxide Donors and Delivery for Antimicrobial and Anti-Biofilm Applications

The use of nitric oxide (NO) is emerging as a promising, novel approach for the treatment of antibiotic resistant bacteria and biofilm infections. Depending on the concentration, NO can induce biofilm dispersal, increase bacteria susceptibility to antibiotic treatment, and induce cell damage or cell death via the formation of reactive oxygen or reactive nitrogen species. The use of NO is, however, limited by its reactivity, which can affect NO delivery to its target site and result in off-target effects. To overcome these issues, and enable spatial or temporal control over NO release, various strategies for the design of NO-releasing materials, including the incorporation of photo-activable, charge-switchable, or bacteria-targeting groups, have been developed. Other strategies have focused on increased NO storage and delivery by encapsulation or conjugation of NO donors within a single polymeric framework. This review compiles recent developments in NO drugs and NO-releasing materials designed for applications in antimicrobial or anti-biofilm treatment and discusses limitations and variability in biological responses in response to the use of NO for bacterial eradiation.

Inhibition of nitric oxide production enhances the activity of facial nerve tubulin polymerization and the ability of tau to promote microtubule assembly after neurorrhaphy

We previously reported that inhibition of nitric oxide (NO) production promotes rat reconnected facial nerve regeneration. However, the underlying mechanism is obscure. Microtubule assembly is known to be essential to axon regeneration; nevertheless, tubulins and microtubule-associated proteins (MAPs) have been demonstrated as targets for NO and peroxynitrite. Thus, we hypothesized that NO and/or peroxynitrite may affect facial nerve regeneration via influencing on microtubule assembly. First, tubulins and tau (a MAP) were extracted from facial nerves of normal rats, treated with NO donor or peroxynitrite, and processed for microtubule assembly assay. We found that peroxynitrite, DEA NONOate, and Angeli's salt reduced the tubulin polymerization activity to a greater extent than GSNO, SIN-1, and SNAP. Additionally, SIN-1, peroxynitrite, and Angeli's salt impaired the ability of tau to promote microtubule assembly. Next, nitrosative stress biomarkers 3-nitrotyrosine (3-NT) and S-nitrosylated cysteine (SNO-Cys) were immunolabeled in facial nerves. Both biomarkers were highly upregulated in proximal and distal stumps of reconnected facial nerves at 3 days and 1 week after neurorrhaphy. Notably, the expression of 3-NT was greatly reduced at 2 weeks, whereas that of SNO-Cys was maintained. Conversely, inhibition of NO production with L-NAME prevented the upregulation of SNO-Cys. Further, we used tubulins and tau extracted from facial nerves of sham-operated, nerve suture + vehicle treatment, and nerve suture + L-NAME treatment rats to perform microtubule assembly assay. We found that L-NAME treatment enhanced polymerization activity of tubulins and ability of tau to promote microtubule assembly. It is noteworthy that α-tubulin plays a more important role than β-tubulin since the activity of microtubule assembly using α-tubulin extracted from L-NAME-treated rats was greatly elevated, whereas that using β-tubulin extracted from L-NAME-treated rats was not. Overall, our findings support that inhibition of NO production reduces nitrosative stress, and may thus facilitate microtubule assembly and facial nerve regeneration.

Nitric oxide and viral infection: Recent developments in antiviral therapies and platforms

Nitric oxide (NO) is a gasotransmitter of great significance to developing the innate immune response to many bacterial and viral infections, while also modulating vascular physiology. The generation of NO from the upregulation of endogenous nitric oxide synthases serves as an efficacious method for inhibiting viral replication in host defense and warrants investigation for the development of antiviral therapeutics. With increased incidence of global pandemics concerning several respiratory-based viral infections, it is necessary to develop broad therapeutic platforms for inhibiting viral replication and enabling more efficient host clearance, as well as to fabricate new materials for deterring viral transmission from medical devices. Recent developments in creating stabilized NO donor compounds and their incorporation into macromolecular scaffolds and polymeric substrates has created a new paradigm for developing NO-based therapeutics for long-term NO release in applications for bactericidal and blood-contacting surfaces. Despite this abundance of research, there has been little consideration of NO-releasing scaffolds and substrates for reducing passive transmission of viral infections or for treating several respiratory viral infections. The aim of this review is to highlight the recent advances in developing gaseous NO, NO prodrugs, and NO donor compounds for antiviral therapies; discuss the limitations of NO as an antiviral agent; and outline future prospects for guiding materials design of a next generation of NO-releasing antiviral platforms.

Molecular mechanisms by which iNOS uncoupling can induce cardiovascular dysfunction during sepsis: Role of posttranslational modifications (PTMs)

Human sepsis is the result of a multifaceted pathological process causing marked dysregulation of cardiovascular responses. A more sophisticated understanding of the pathogenesis of sepsis is certainly prerequisite. Evidence from studies provide further insight into the role of inducible nitric oxide synthase (iNOS) isoform. Results on inhibition of iNOS in sepsis models remain inconclusive. Concern has been devoted to improving our knowledge and understanding of the role of iNOS. The aim of this review is to define the role of iNOS in redox homeostasis disturbance, the detailed mechanisms linking iNOS and posttranslational modifications (PTMs) to cardiovascular dysfunctions, and their future implications in sepsis settings. Many questions related to the iNOS and PTMs still remain open, and much more work is needed on this.

Encapsulation of tDodSNO generates a photoactivated nitric oxide releasing nanoparticle for localized control of vasodilation and vascular hyperpermeability

We report the synthesis and characterization of a photoactive nitric oxide (NO) releasing nanoparticle (NP) by encapsulation of the NO donor tert-dodecane S-nitrosothiol (tDodSNO) into a co-polymer of styrene and maleic anhydride (SMA) to afford SMA-tDodSNO. Encapsulation did not affect tDodSNO's stability or NO release profile, but imparted water solubility and protection from degradation reactions with glutathione. Under photoactivation the NP acted as a potent NO donor, with photoactivation acting as a switch to induce localized vasodilation in aortic rings (EC₅₀^* 660 nM at 2700 W/m²) and cause vascular hyperpermeability in mesenteric beds (8-fold increase in dye uptake at 1 µM SMA-tDodSNO with 460 W/m² photoactivation). The NP was markedly superior as a photoactive NO donor in comparison to the S-nitrosothiols GSNO and SNAP, which are commonly used in experimental studies, as well as sodium nitroprusside, a clinically used vasodilator. Future development of this NP may find wide ranging therapeutic applications for treating cardiovascular disease and other disorders related to NO signaling, as well as enhancing macromolecular drug delivery to target organs through selective hyperpermeability. Supporting information describing the biophysical characterization of SMA-tDodSNO is supplied in an accompanying Data in Brief article (Alimoradi et al., doi: 10.1016/j.dib.2018.10.149).

Nitric oxide-releasing nanoparticles improve doxorubicin anticancer activity

Purpose

Anticancer drug delivery systems are often limited by hurdles, such as off-target distribution, slow cellular internalization, limited lysosomal escape, and drug resistance. To overcome these limitations, we have developed a stable nitric oxide (NO)-releasing nanoparticle (polystyrene-maleic acid [SMA]-tert-dodecane S-nitrosothiol [tDodSNO]) with the aim of enhancing the anticancer properties of doxorubicin (Dox) and a Dox-loaded nanoparticle (SMA-Dox) carrier.

Materials and methods

Effects of SMA-tDodSNO and/or in combination with Dox or SMA-Dox on cell viability, apoptosis, mitochondrial membrane potential, lysosomal membrane permeability, tumor tissue, and tumor growth were studied using in vitro and in vivo model of triple-negative breast cancer (TNBC). In addition, the concentrations of SMA-Dox and Dox in combination with SMA-tDodSNO were measured in cells and tumor tissues.

Results

Combination of SMA-tDodSNO and Dox synergistically decreased cell viability and induced apoptosis in 4T1 (TNBC cells). Incubation of 4T1 cells with SMA-tDodSNO (40 µM) significantly enhanced the cellular uptake of SMA-Dox and increased Dox concentration in the cells resulting in a twofold increase (P<0.001). Lysosomal membrane integrity, evaluated by acridine orange (AO) staining, was impaired by 40 µM SMA-tDodSNO (P<0.05 vs control) and when combined with SMA-Dox, this effect was significantly potentiated (P<0.001 vs SMA-Dox). Subcutaneous administration of SMA-tDodSNO (1 mg/kg) to xenografted mice bearing 4T1 cells showed that SMA-tDodSNO alone caused a twofold decrease in the tumor size compared to the control group. SMA-tDodSNO in combination with SMA-Dox resulted in a statistically significant 4.7-fold reduction in the tumor volume (P<0.001 vs control), without causing significant toxicity as monitored through body weight loss.

Conclusion

Taken together, these results suggest that SMA-tDodSNO can be used as a successful strategy to increase the efficacy of Dox and SMA-Dox in a model of TNBC.

Don't just say no: Differential pathways and pharmacological responses to diverse nitric oxide donors

Nitric oxide (NO) is a gaseous free radical molecule with a short half-life (∼1 s), which can gain or lose an electron into three interchangeable redox-dependent forms, the radical (NO), the nitrosonium cation (NO⁺), and nitroxyl anion (HNO). NO acts as an intra and extracellular signaling molecule regulating a wide range of functions in the cardiovascular, immune, and nervous system. NO donors are collectively known by their ability to release NOin vitro and in vivo, being proposed as therapeutic pharmacological tools for the treatment of several pathologies, such as cardiovascular disease. The highly reactive NO molecule is easily oxidized under physiological conditions to N-oxides, nitrate/nitrite and nitrogen dioxide. Different cellular responses are triggered depending on: 1) NO concentration [e.g., nanomolar for heme coordination in the allosteric site of guanylate cyclase (sGC) enzyme]; 2) the type of chemical bound to the nitrosated group (i.e., bound to nitrogen, N-nitro, or bound to sulphur atom, S-nitro) determining post-translational cysteine nitrosation; 3) the time-dependent availability of molecular targets. Classic NO donors are: organic nitrates (e.g., nitroglycerin, or glyceryl trinitrate, GTN; isosorbide mononitrate, ISMN), diazeniumdiolates having a diolate group [or NONOates, e.g., 2-(N,N-diethylamino)-diazenolate-2-oxide], S-nitrosothiols (e.g., S-nitroso glutathione, GSNO; S-nitroso-N-acetylpenicillamine, SNAP) or the organic salt sodium nitroprusside (SNP). In addition, nitroxyl (HNO) donors such as Piloty's acid and Angeli's salt can also be considered. The specific NO form released, as well as its differential reactivity to thiols, could act on different molecular targets and should be discussed in the context of: a) the type and amount of NO species determining the sensitivity of molecular targets (e.g., heme coordination, or S-nitrosation); b) the cellular redox state that could gate different effects. Experimental designs should take special care when choosing which NO donors to use, since different outcomes are to be expected. This article will comment recent findings regarding physiological responses involving NO species and their pharmacological modulation with donor drugs, especially in the context of the photic transduction pathways at the hypothalamic circadian clock.

Nitric oxide regulates chlorophyllide biosynthesis and singlet oxygen generation differently between Arabidopsis and barley

Nitric oxide (NO) has a general inhibitory effects on chlorophyll biosynthesis, especially to the step of 5-aminolevulinic acid (ALA) biosynthesis and protochlorophyllide (Pchlide) to chlorophyllide (Chlide) conversion (responsible by the NADPH:Pchlide oxidoreductase POR). Previous study suggested that barley large POR aggregates may be generated by dithiol oxidation of cysteines of two POR monomers, which can be disconnected by some reducing agents. POR aggregate assembly may be correlated with seedling greening in barley, but not in Arabidopsis. Thus, NO may affect POR activity and seedling greening differently between Arabidopsis and barley. We proved this assumption by non-denaturing gel-analysis and reactive oxygen species (ROS) monitoring during the greening. NO treatments cause S-nitrosylation to POR cysteine residues and disassembly of POR aggregates. This modification reduces POR activity and induces Pchlide accumulation and singlet oxygen generation upon dark-to-high-light shift (and therefore inducing photobleaching lesions) in barley leaf apex, but not in Arabidopsis seedlings. ROS staining and ROS-related-gene expression detection confirmed that superoxide anion and singlet oxygen accumulated in barley etiolated seedlings after the NO treatments, when exposed to a fluctuating light. The data suggest that POR aggregate assembly may be correlated with barley chlorophyll biosynthesis and redox homeostasis during greening. Cysteine S-nitrosylation may be one of the key reasons for the NO-induced inhibition to chlorophyll biosynthetic enzymes.

Delivery of Antioxidant and Anti-inflammatory Agents for Tissue Engineered Vascular Grafts

The treatment of patients with severe coronary and peripheral artery disease represents a significant clinical need, especially for those patients that require a bypass graft and do not have viable veins for autologous grafting. Tissue engineering is being investigated to generate an alternative graft. While tissue engineering requires surgical intervention, the release of pharmacological agents is also an important part of many tissue engineering strategies. Delivery of these agents offers the potential to overcome the major concerns for graft patency and viability. These concerns are related to an extended inflammatory response and its impact on vascular cells such as endothelial cells. This review discusses the drugs that have been released from vascular tissue engineering scaffolds and some of the non-traditional ways that the drugs are presented to the cells. The impact of antioxidant compounds and gasotransmitters, such as nitric oxide and carbon monoxide, are discussed in detail. The application of tissue engineering and drug delivery principles to biodegradable stents is also briefly discussed. Overall, there are scaffold-based drug delivery techniques that have shown promise for vascular tissue engineering, but much of this work is in the early stages and there are still opportunities to incorporate additional drugs to modulate the inflammatory process.

Nitric oxide induces monosaccharide accumulation through enzyme S-nitrosylation

Nitric oxide (NO) is extensively involved in various growth processes and stress responses in plants; however, the regulatory mechanism of NO-modulated cellular sugar metabolism is still largely unknown. Here, we report that NO significantly inhibited monosaccharide catabolism by modulating sugar metabolic enzymes through S-nitrosylation (mainly by oxidizing dihydrolipoamide, a cofactor of pyruvate dehydrogenase). These S-nitrosylation modifications led to a decrease in cellular glycolysis enzymes and ATP synthase activities as well as declines in the content of acetyl coenzyme A, ATP, ADP-glucose and UDP-glucose, which eventually caused polysaccharide-biosynthesis inhibition and monosaccharide accumulation. Plant developmental defects that were caused by high levels of NO included delayed flowering time, retarded root growth and reduced starch granule formation. These phenotypic defects could be mediated by sucrose supplementation, suggesting an essential role of NO-sugar cross-talks in plant growth and development. Our findings suggest that molecular manipulations could be used to improve fruit and vegetable sweetness.

The preparation and characterization of nitric oxide releasing silicone rubber materials impregnated with S-nitroso-tert-dodecyl mercaptan

Recently, considerable research efforts have focused on increasing the biocompatibility a nd bactericidal activity of biomedical polymeric devices (e.g., catheters, etc.) through incorporation of nitric oxide (NO) releasing molecules. NO is an important endogenous molecule that is well known for enhancing blood flow via its vasodilatory activity, but it also exhibits potent antithrombotic and antimicrobial properties. In this work, we demonstrate that silicone rubber tubing can be impregnated with a tertiary S-nitrosothiol (RSNO), S-nitroso-tert-dodecylmercaptan, via a simple solvent swelling method. We further characterize the NO release and RSNO leaching from the tubing over time via use of chemiluminescence and UV/Vis spectroscopy, respectively. The tubing is shown to maintain an NO flux above the physiological levels released by endothelial cells, 0.5-4.0 × 10-10 molcm-2min-1, for more than 3 weeks while stored at 37 °C and exhibit minimal leaching. Finally, the RSNO impregnated tu bing exhibits significant antimicrobial activity over a 21 d period (vs. controls) during incubation in a CDC bioreactor after inoculation of media with S. aureus bacteria. The use of such lipophilic RSNO impregnated silicone rubber tubing could dramatically reduce the risk of catheter-related infections, which are a common problem associated with placement of intravascular or urinary catheters.

Dual roles of nitric oxide in the regulation of tumor cell response and resistance to photodynamic therapy

Photodynamic therapy (PDT) against cancer has gained attention due to the successful outcome in some cancers, particularly those on the skin. However, there have been limitations to PDT applications in deep cancers and, occasionally, PDT treatment resulted in tumor recurrence. A better understanding of the underlying molecular mechanisms of PDT-induced cytotoxicity and cytoprotection should facilitate the development of better approaches to inhibit the cytoprotective effects and also augment PDT-mediated cytotoxicity. PDT treatment results in the induction of iNOS/NO in both the tumor and the microenvironment. The role of NO in cytotoxicity and cytoprotection was examined. The findings revealed that NO mediates its effects by interfering with a dysregulated pro-survival/anti-apoptotic NF-κB/Snail/YY1/RKIP loop which is often expressed in cancer cells. The cytoprotective effect of PDT-induced NO was the result of low levels of NO that activates the pro-survival/anti-apoptotic NF-κB, Snail, and YY1 and inhibits the anti-survival/pro-apoptotic and metastasis suppressor RKIP. In contrast, PDT-induced high levels of NO result in the inhibition of NF-kB, Snail, and YY1 and the induction of RKIP, all of which result in significant anti-tumor cytotoxicity. The direct role of PDT-induced NO effects was corroborated by the use of the NO inhibitor, l-NAME, which reversed the PDT-mediated cytotoxic and cytoprotective effects. In addition, the combination of the NO donor, DETANONOate, and PDT potentiated the PDT-mediated cytotoxic effects. These findings revealed a new mechanism of PDT-induced NO effects and suggested the potential therapeutic application of the combination of NO donors/iNOS inducers and PDT in the treatment of various cancers. In addition, the study suggested that the combination of PDT with subtoxic cytotoxic drugs will result in significant synergy since NO has been shown to be a significant chemo-immunosensitizing agent to apoptosis.

•

PDT-mediated cytotoxic and cytoprotective effects depend also by the induction of NO from tumor.

•

The PDT-induced NO modulates the dysregulated NF-kB/Snail/RKIP loop.

•

The direct role of NO induction by PDT was corroborated by the use of the NO inhibitor, l-NAME.

•

The combination of an NO donor and PDT resulted in a increased cytotoxic effect, in vitro and in vivo.

•

Novel potential therapeutic applications are proposed for the use of PDT combined with NO donors.

Synergistic activations of REG I α and REG I β promoters by IL-6 and Glucocorticoids through JAK/STAT pathway in human pancreatic β cells

Reg (Regenerating gene) gene was originally isolated from rat regenerating islets and its encoding protein was revealed as an autocrine/paracrine growth factor for β cells. Rat Reg gene is activated in inflammatory conditions for β cell regeneration. In human, although five functional REG family genes (REG Iα, REG Iβ, REG III, HIP/PAP, and REG IV) were isolated, their expressions in β cells under inflammatory conditions remained unclear. In this study, we found that combined addition of IL-6 and dexamethasone (Dx) induced REG Iα and REG Iβ expression in human 1.1B4 β cells. Promoter assay revealed that a signal transducer and activator of transcription- (STAT-) binding site in each promoter of REG Iα (TGCCGGGAA) and REG Iβ (TGCCAGGAA) was essential for the IL-6+Dx-induced promoter activation. A Janus kinase 2 (JAK2) inhibitor significantly inhibited the IL-6+Dx-induced REG Iα and REG Iβ transcription. Electrophoretic mobility shift assay and chromatin immunoprecipitation revealed that IL-6+Dx stimulation increased STAT3 binding to the REG Iα promoter. Furthermore, small interfering RNA-mediated targeting of STAT3 blocked the IL-6+Dx-induced expression of REG Iα and REG Iβ. These results indicate that the expression of REG Iα and REG Iβ should be upregulated in human β cells under inflammatory conditions through the JAK/STAT pathway.