Neuroprotective and Anti-Inflammatory Activities of Hybrid Small-Molecule SA-10 in Ischemia/Reperfusion-Induced Retinal Neuronal Injury Models

Embolism, hyperglycemia, high intraocular pressure-induced increased reactive oxygen species (ROS) production, and microglial activation result in endothelial/retinal ganglion cell death. Here, we conducted in vitro and in vivo ischemia/reperfusion (I/R) efficacy studies of a hybrid antioxidant-nitric oxide donor small molecule, SA-10, to assess its therapeutic potential for ocular stroke.

METHODS

To induce I/R injury and inflammation, we subjected R28 and primary microglial cells to oxygen glucose deprivation (OGD) for 6 h in vitro or treated these cells with a cocktail of TNF-α, IL-1β and IFN-γ for 1 h, followed by the addition of SA-10 (10 µM). Inhibition of microglial activation, ROS scavenging, cytoprotective and anti-inflammatory activities were measured. In vivo I/R-injured mouse retinas were treated with either PBS or SA-10 (2%) intravitreally, and pattern electroretinogram (ERG), spectral-domain optical coherence tomography, flash ERG and retinal immunocytochemistry were performed.

RESULTS

SA-10 significantly inhibited microglial activation and inflammation in vitro. Compared to the control, the compound SA-10 significantly attenuated cell death in both microglia (43% vs. 13%) and R28 cells (52% vs. 17%), decreased ROS (38% vs. 68%) production in retinal microglia cells, preserved neural retinal function and increased SOD1 in mouse eyes.

CONCLUSION

SA-10 is protective to retinal neurons by decreasing oxidative stress and inflammatory cytokines.

Porous Molybdenum Nitride Nanosphere as Carrier-Free and Efficient Nitric Oxide Donor for Synergistic Nitric Oxide and Chemo/Sonodynamic Therapy

Given its abundant physiological functions, nitric oxide (NO) has attracted much attention as a cancer therapy. The sensitive release and great supply capacity are significant indicators of NO donors and their performance. Here, a transition metal nitride (TMN) MoN@PEG is adopted as an efficient NO donor. The release process starts with H+-triggered denitrogen owing to the high electronegativity of the N atom and weak Mo-N bond. Then, these active NHx are oxidized by O2 and other reactive oxygen species (ROS) to form NO, endowing specific release to the tumor microenvironment (TME). With a porous nanosphere structure (80 nm), MoN@PEG does not require an extra carrier for NO delivery, contributing to ultrahigh atomic utilization for outstanding release ability (94.1 ± 5.6 μM). In addition, it can also serve as a peroxidase and sonosensitizer for anticancer treatment. To further improve the charge separation, MoN-Pt@PEG was prepared to enhance the sonodynamic therapy (SDT) effect. Accordingly, ultrasound (US) further promotes NO generation due to more ROS generation, facilitating in situ peroxynitrite (·ONOO-) generation with great cytotoxicity. At the same time, the nanostructure also degrades gradually, leading to high elimination (94.6%) via feces and urine within 14-day. The synergistic NO and chemo-/sono-dynamic therapy brings prominent antitumor efficiency and further activates the immune response to inhibit metastasis and recurrence. This work develops a family of NO donors that would further widen the application of NO therapy in other fields.

Soluble guanylate cyclase mediates the relaxation of healthy and inflamed bladder smooth muscle by aqueous nitric oxide

Introduction: Due to its chemical properties, functional responses to nitric oxide (NO) are often difficult to examine. In the present study, we established a method to produce NO in an aqueous solution and validated its capacity to evoke functional responses in isolated rat bladders. Furthermore, we compared the NO responses to the commonly used NO donor sodium nitroprusside (SNP). We also investigated the impact of ongoing inflammation on the involvement of soluble guanylate cyclase (sGC) dependent signaling in NO relaxation. Methods: A setup to produce an aqueous NO solution was established, allowing the production of an aqueous solution containing a calculated NO concentration of 2 mM. Sixty male Sprague-Dawley rats received either no treatment (controls) or cyclophosphamide (CYP; 100 mg*kg-1 i.p., 60 h prior to the experiment) to induce experimental cystitis. Bladder strip preparations were mounted in organ baths and studied at basal tension or pre-contracted with methacholine (3 μM). Aqueous NO solution (40-400 μL; 2 mM corresponding to 4-40 μM) or SNP (1-1,000 μM) was added cumulatively in increasing concentrations. Relaxation to aqueous NO was also studied in the presence of the sGC inhibitor ODQ (0.25-25 μM). The expression of sGC was investigated by immunohistochemical analysis. Results: The NO solution caused functional relaxations in both controls and inflamed bladder preparations. NO-induced relaxations were significantly greater in inflamed bladder strips at basal tension, whereas no differences were seen in methacholine pre-contracted strips. In the presence of the sGC inhibitor ODQ in a high concentration, the NO-evoked relaxations were abolished in both control and inflamed preparations. At a lower concentration of ODQ, only NO relaxations in inflamed preparations were attenuated. Immunohistochemical analysis showed that sGC was expressed in the detrusor and mucosa, with a significantly lower expression in the inflamed detrusor. Conclusion: In the present study, we found that aqueous NO solution induces relaxation of the rat detrusor by activating soluble guanylate cyclase in both control and inflamed bladder strips. Induction of inflammation conceivably leads to decreased sGC expression in the detrusor, which may explain the different susceptibility towards inhibition of sGC in inflamed versus control tissue. The use of an aqueous NO solution should be further considered as a valuable complement to the pharmacological tools currently used.

Record-High Ultrasound-Sensitive NO Nanogenerators for Cascade Tumor Pyroptosis and Immunotherapy

Pyroptosis is a pro-inflammatory cell death that is associated with innate immunity promotion against tumors. Excess nitric oxide (NO)-triggered nitric stress has potential to induce pyroptosis, but the precise delivery of NO is challenging. Ultrasound (US)-responsive NO production has dominant priority due to its deep penetration, low side effects, noninvasion, and local activation manner. In this work, US-sensitive NO donor N-methyl-N-nitrosoaniline (NMA) with thermodynamically favorable structure is selected and loaded into hyaluronic acid (HA)-modified hollow manganese dioxide nanoparticles (hMnO2 NPs) to fabricate hMnO2 @HA@NMA (MHN) nanogenerators (NGs). The obtained NGs have a record-high NO generation efficiency under US irradiation and can release Mn2+ after targeting the tumor sites. Later on, cascade tumor pyroptosis and cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING)-based immunotherapy is achieved and tumor growth is effectively inhibited.

Discovery of novel hybrids of mTOR inhibitor and NO donor as potential anti-tumor therapeutics

Nitric oxide (NO) may be beneficial to overcoming drug resistance resulting from mutation of mTOR kinases and bypass mechanisms. In this study, a novel structural series of hybrids of mTOR inhibitor and NO donor were designed and synthesized via structure-based drug design (SBDD). Throughout the 20 target compounds, half of the compounds (13a, 13b, 19a-19d, 19f-19j) demonstrated attractive mTOR inhibitory activity with IC₅₀ at single-digit nanomolar level. In particular, 19f exerted superior anti-proliferative activity against HepG2, MCF-7, HL-60 cells (HepG2, IC₅₀ = 0.24 μM; MCF-7, IC₅₀ = 0.88 μM; HL-60, IC₅₀ = 0.02 μM) to that of the clinical investigated mTOR inhibitor MLN0128, and show mild cytotoxicity against normal cells with IC₅₀ over 10 μM. 19a, with the most potent mTOR inhibitory activity in this series (IC₅₀ = 3.31 nM), also displayed attractive cellular potency. In addition, 19f treatment in HL-60 reduces the levels of Phos-Akt and Phos-S6 in a dose-dependent manner, and releases NO in cells. In summary, 19f deserves further development as a novel mTOR-based multi-target anti-cancer agent.

Novel nitric oxide donor, nitrated phenylbutyrate, induces cell death of human pancreatic cancer cells and suppresses tumor growth of cancer xenografts

Pancreatic cancer has a low response rate to chemotherapy due to the low drug transferability caused by the low blood flow around the tumor. In the present study, focusing on nitric oxide (NO) for its vasodilatory and antitumor effects, a novel NO donor, a nitrated form of phenylbutyrate (NPB) was synthesized and the antitumor effect on human pancreatic cancer cells (AsPC1 and BxPC3) and xenografts was examined. Using Annexin V, NPB was confirmed to induce cell death against AsPC1 and BxPC3 in a time‑ and concentration‑dependent manner. In NPB‑exposed cells, DAF‑FM DA (a probe to detect intracellular NO) derived fluorescence was observed. Release of nitrite and nitrate from NPB in aqueous solution was very gradual until even 72 h after dissolution. Phenylbutyrate (PB) and hydroxy PB in which the nitro group of NPB was replaced with a hydroxyl group did not have the cell death‑inducing effect as observed in NPB. These results suggest that the effect of NPB was dependent on NO release form NPB. Apoptosis inhibitor, Z‑VAD FMK, had no effect on the cell death‑inducing effect of NPB, and NPB did not show significant activation of caspase‑3/7. In addition, NPB significantly decreased cellular ATP levels, suggesting that necrosis is involved in the effect of NPB. NPB also accumulated cells specifically at the S phase of the cell cycle. A single dose of NPB (10 mg/kg) into mice with established BxPC3 xenografts significantly suppressed tumor growth for at least 7 weeks without apparent toxicity. The findings of the present study indicate that NPB has potential as a novel therapeutic agent for NO‑based therapy of pancreatic cancer.

Therapeutic Potency of NO Loaded into Anticancer Copper Metal-Organic Framework through Nonclassical Hydrogen Bonding

Metal-organic frameworks (MOFs) are potential exogenous scaffolds for therapeutic nitric oxide (NO) delivery because they can store drug or bioactive gas molecules within pores or on active metal sites. Herein, we employed a Cu-MOF coordinated with glutarate (glu) and 1,2-bis(4-pyridyl)ethane (bpa) to obtain NO-loaded Cu-MOF (NO⊂Cu-MOF). NO loading transformed the space group of Cu-MOF from monoclinic C2/c to triclinic P-1 through nonclassical hydrogen bonding with glu and bpa. Cu-MOF showed good stability in deionized water and phosphate-buffered saline. NO⊂Cu-MOF released up to 1.10 μmol mg-1 NO over 14.6 h at 37 °C, which is suitable for therapeutic applications. NO⊂Cu-MOF showed moderate biocompatibility with L-929 cells and significant anticancer activity against HeLa cells, suggesting an apoptosis-mediated cell death mechanism. These insights into NO bonding modes with Cu-MOF that enable controlled NO release can inspire the design of functional MOFs as hybrid NO donors for drug delivery.

Syntheses and high selective cytotoxicity of dehydroabietylamine C-ring nitration derivatives

To find more effective anticancer agents, a series of novel dehydroabietylamine (DA) derivatives were synthesized, focusing on C-ring nitro modifications and C-18 imide introduction. Their cytotoxic activities against human tumor cell line HeLa (cervix), MCF-7 (breast), A549 (lung), HepG2 (liver), and nonmalignant cell line HUVEC (umbilical vein) in vitro were screened. The C-18 imide heterocyclic compounds 1, 2, and C-ring 14-nitro substituted 14 exhibited moderate to good cytotoxic activities and significant selectivity towards malignant cell lines. More importantly, they were significantly less cytotoxic to nonmalignant cells (HUVEC) than the parent compound and positive control doxorubicin hydrochloride (DOX). Meantime the mechanism of cytotoxicity of DA derivatives was studied. Annexin V-FITC/PI double-staining analysis suggested that cytotoxicity of compounds 2 and 14 was associated with early apoptosis induction. The interaction between compounds and DNA (herring sperm DNA) was studied using absorption spectral analysis and ethidium bromide (EB) fluorescence displacement experiments, the results exhibited that the binding of the compound to DNA was in the intercalative mode. The structure-activity relationship discussion implied that introduction of the nitro-group, especially the 14-nitro group, can significantly improve the cytotoxicity of dehydroabietylimide compounds. The relatively high cytotoxicity and significant high selectivity of compounds 2 and 14 indicated that they were particularly noteworthy. NO released amounts indicated that the amounts of NO released by the compounds bearing nitro-group were quite well associated positive correlation with their cytotoxic activity, which provide a new strategy for structure design of DA anticancer agents in the future.

Nitric oxide-releasing nanomaterials: from basic research to potential biotechnological applications in agriculture

Nitric oxide (NO) is a multifunctional gaseous signal that modulates the growth, development and stress tolerance of higher plants. NO donors have been used to boost plant endogenous NO levels and to activate NO-related responses, but this strategy is often hindered by the relative instability of donors. Alternatively, nanoscience offers a new, promising way to enhance NO delivery to plants, as NO-releasing nanomaterials (e.g. S-nitrosothiol-containing chitosan nanoparticles) have many beneficial physicochemical and biochemical properties compared to non-encapsulated NO donors. Nano NO donors are effective in increasing tissue NO levels and enhancing NO effects both in animal and human systems. The authors believe, and would like to emphasize, that new trends and technologies are essential for advancing plant NO research and nanotechnology may represent a breakthrough in traditional agriculture and environmental science. Herein, we aim to draw the attention of the scientific community to the potential of NO-releasing nanomaterials in both basic and applied plant research as alternatives to conventional NO donors, providing a brief overview of the current knowledge and identifying future research directions. We also express our opinion about the challenges for the application of nano NO donors, such as the environmental footprint and stakeholder's acceptance of these materials.

Nitric Oxide Release and Antibacterial Efficacy Analyses of S-Nitroso-N-Acetyl-Penicillamine Conjugated to Titanium Dioxide Nanoparticles

Therapeutic agents can be linked to nanoparticles to fortify their selectivity and targeted delivery while impeding systemic toxicity and efficacy loss. Titanium dioxide nanoparticles (TiNPs) owe their rise in biomedical sciences to their versatile applicability, although the lack of inherent antibacterial properties limits its application and necessitates the addition of bactericidal agents along with TiNPs. Structural modifications can improve TiNP's antibacterial impact. The antibacterial efficacy of nitric oxide (NO) against a broad spectrum of bacterial strains is well established. For the first time, S-nitroso-N-acetylpenicillamine (SNAP), an NO donor molecule, was covalently immobilized on TiNPs to form the NO-releasing TiNP-SNAP nanoparticles. The TiNPs were silanized with 3-aminopropyl triethoxysilane, and N-acetyl-d-penicillamine was grafted to them via an amide bond. The nitrosation was carried out by t-butyl nitrite to conjugate the NO-rich SNAP moiety to the surface. The total NO immobilization was measured to be 127.55 ± 4.68 nmol mg^-1 using the gold standard chemiluminescence NO analyzer. The NO payload can be released from the TiNP-SNAP under physiological conditions for up to 20 h. The TiNP-SNAP exhibited a concentration-dependent antimicrobial efficiency. At 5 mg mL^-1, more than 99.99 and 99.70% reduction in viable Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria, respectively, were observed. No significant cytotoxicity was observed against 3T3 mouse fibroblast cells at all the test concentrations determined by the CCK-8 assay. TiNP-SNAP is a promising and versatile nanoparticle that can significantly impact the usage of TiNPs in a wide variety of applications, such as biomaterial coatings, tissue engineering scaffolds, or wound dressings.

Design and synthesis of novel aza-ursolic acid derivatives: in vitro cytotoxicity and nitric oxide release inhibitory activity

Aim: Inducible nitric oxide synthase (iNOS) is a validated target for anti-inflammatory treatment. Based on the authors' previous work, novel aza-ursolic acid derivatives were designed and synthesized and their inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) release from RAW264.7 cells was evaluated. Materials & results: 16 novel derivatives were screened for their in vitro inhibitory activity against NO release using Griess assays and the cytotoxicity was evaluated using MTT assays. The presence of furoxan joined to the A-ring of ursolic acid and N-methylpiperazine groups in the lead compound was identified for anti-inflammatory activity, and compound 21b showed 94.96% inhibition of NO release at 100 μM with an IC50 value of 8.58 μM. Conclusion: Compound 21b has potential anti-inflammatory activity with low cytotoxicity that warrants further preclinical study and evaluation.

Second generation β-elemene nitric oxide derivatives with reasonable linkers: potential hybrids against malignant brain glioma

Elemene is a second-line broad-spectrum anti-tumour drug that has been used in China for more than two decades. However, its main anti-tumour ingredient, β-elemene, has disadvantages, including excessive lipophilicity and relatively weak anti-tumour efficacy. To improve the anti-tumour activity of β-elemene, based on its minor molecular weight character, we introduced furoxan nitric oxide (NO) donors into the β-elemene structure and designed six series of new generation β-elemene NO donor hybrids. The synthesised compounds could effectively release NO in vitro, displayed significant anti-proliferative effects on U87MG, NCI-H520, and SW620 cell lines. In the orthotopic glioma model, compound Id significantly and continuously suppressed the growth of gliomas in nude mice, and the brain glioma of the treatment group was markedly inhibited (>90%). In short, the structural fusion design of NO donor and β-elemene is a feasible strategy to improve the in vivo anti-tumour activity of β-elemene.

Synthesis and biological evaluation of N, N-dialkylcarboxy coumarin-NO donor conjugates as potential anticancer agents

A series of nitric oxide (NO) donor furoxan conjugates of N, N-dialkylcarboxy coumarins have been synthesized as potential anticancer agents. The synthesized compounds have been tested for their in vitro antiproliferative activities on various cancer and noncancerous cell lines. The candidate derivatives exhibit selectivity towards cancer cells with excellent activities in low nM to µM concentrations. In vitro mechanistic studies indicate that the candidate compounds generate substantial NO, inhibit colony formation, and cause apoptosis in cancer cells. A preliminary in vivo tolerance study of the lead candidate 10 in mice indicates that it is well-tolerated, evidenced by zero mortality and normal body weight gains in treated mice. Further translation of the lead derivative 10 using MDA-MB-231 based tumor xenograft model shows good tumor growth reduction.

Synthesis and biological evaluation of NO-donor containing photosensitizers to induce ferroptosis of cancer cells

Photodynamic therapy (PDT) is a non-invasive treatment method for tumors by exciting photosensitizers (PS) upon light irradiation to generate cytotoxic reactive oxygen species (ROS). However, the low oxygen concentration near the tumor tissue limits the therapeutic effect of PDT. Herein, we synthesized six chlorin e6 derivatives containing NO-donors to enhance their antitumor activity by synergistic effect of ROS and NO. The results revealed that the new NO-donor containing photosensitizers (PS-NO) exhibited more potent photodynamic activity than chlorin e6, and the introduction of NO donor moieties to chlorin e6 increased the level of NO and ROS in cells. The addition of Ferrostatin-1, a ferroptosis inhibitor, markedly reduced the photodynamic activity of PS-NO as well as the level of NO and ROS in cells. Mechanism studies further showed that PS-NO could reduce intracellular GSH level, inhibit GPX4 activity and promote malondialdehyde (MDA) accumulation upon light irradiation, which suggested the ferroptosis mechanism underlying the PDT effect of PS-NO.

Hybrids as NO Donors

Cinnamic acid and its derivatives have been studied for a variety of biological properties, including anti-inflammatory, antioxidant, anticancer, antihypertensive, and antibacterial. Many hybrids of cinnamic derivatives with other bioactive molecules have been synthesized and evaluated as nitric oxide (NO) donors. Since NO plays a significant role in various biological processes, including vasodilation, inflammation, and neurotransmission, NO donor groups are incorporated into the structures of already-known bioactive molecules to enhance their biological properties. In this review, we present cinnamic hybrids with NO-donating ability useful in the treatment of several diseases.

O2-(2,4-dinitrophenyl) diazeniumdiolate derivative induces G2/M arrest via PTEN-mediated inhibition of PI3K/Akt pathway in hepatocellular carcinoma cells

OBJECTIVES

The study aimed to investigate whether G2/M arrest caused by O2-(2,4-dinitrophenyl) diazeniumdiolate derivative (JS-K) was related to PTEN-mediated inhibition of PI3K/Akt pathway in hepatocellular carcinoma cells.

METHODS

The cell apoptosis was detected by DAPI staining and Annexin V-FITC/PI dual staining. The cell cycle was analysed by PI staining. The expressions of cell cycle-related proteins, PTEN and PI3K/AKT pathway were measured by Western blot. The rat model of primary hepatic carcinoma was established with diethylnitrosamine to verify the antitumour effects of JS-K.

KEY FINDINGS

The morphological features of apoptosis were obviously reversed when the cells were pre-treated with bpv(pic), followed by treatment with JS-K. JS-K mediated G2/M arrest and down-regulated expressions of cyclin B1. Meanwhile, it up-regulated the expression of p-Cdk1, p-Chk2 and p-CDC25C while down-regulated that of Cdk1 and CDC25C. Furthermore, JS-K also enhanced the expressions of p21 and p27, PTEN and p53 while decreased the expressions of p-PTEN, PI3K and p-AKT. However, bpv(pic) and Carboxy-PTIO could reverse JS-K-induced G2/M cell arrest and PTEN-mediated inhibition of the PI3K/AKT pathway. The same results were also testified in the rat model of primary hepatic carcinoma.

CONCLUSIONS

JS-K caused G2/M arrest through PTEN-mediated inhibition of the PI3K/AKT pathway involving Chk2/CDC25C/Cdk1 checkpoint.

N-Nitrosomelatonin, an efficient nitric oxide donor and transporter in Arabidopsis seedlings

Nitric oxide (NO) produced in plant cells has the unique ability to interact with various other biomolecules, thereby facilitating its own as well as their signaling and associated actions at their sites of biosynthesis and at other sites via transcellular long distance transport of the molecular complexes. Melatonin (Mel) is one such biomolecule produced in plant cells which has fascinated plant biologists with regard to its molecular crosstalk with other molecules to serve its roles as a growth regulator. Present work reports the synthesis of N-nitrosomelatonin (NOMela) and its preferential uptake by Arabidopsis seedlings roots and long distance transport to the leaves through vascular strands. Equimolar (250 μM) concentrations of NOMela and S-nitrosoglutathione (GSNO) in aqueous solutions bring about 52.8% more release of NO from NOMela than from GSNO. Following confocal laser scanning microscopic (CLSM) imaging, Pearson's correlation coefficient analysis of the Scatter gram of endogenously taken up NOMela demonstrates significant NO signal in roots emanating from mitochondria. NOMela (250 μM) taken up by Arabidopsis seedling roots also proved more efficient as a NO transporter from primary root to leaves than 250 μM of GSNO. These novel observations on NOMela thus hold promise to decipher its crucial role as a NO carrier and reservoir in plant cells, and also as a facilitator of melatonin action in plant development.

Nanochemistry Modulates Intracellular Decomposition Routes of S-Nitrosothiol Modified Silica-Based Nanoparticles

Cellular delivery of nitric oxide (NO) using NO donor moieties such as S-nitrosothiol (SNO) is of great interest for various applications. However, understandings of the intracellular decomposition routes of SNO toward either NO or ammonia (NH₃ ) production are surprisingly scarce. Herein, the first report of SNO modified mesoporous organosilica nanoparticles with tetrasulfide bonds for enhanced intracellular NO delivery, ≈10 times higher than a commercial NO donor, is presented. The tetrasulfide chemistry modulates the SNO decomposition by shifting from NH₃ to NO production in glutathione rich cancer cells. This study provides a new strategy to control the NO level in biological systems.

A review of the synthesis of nitric oxide donor and donor derivatives with pharmacological activities

Endogenous nitric oxide (NO) is an important effector molecule and signal transduction molecule, which participates in the regulation of multiple functions in organisms, involving a variety of physiological and pathological processes, especially playing a very important role in the cardiovascular, immune, and nervous systems. NO is a gaseous substance with a short half-life in the body and is unstable in aqueous solutions. Therefore, many researchers focus on the release and activity of NO donors and their derivatives. However, NO donors can release free NO or NO analogues under physiological conditions to meet the human need. NO donors can be coupled with the corresponding active basic nucleus, so that they have the biological activity derived from both the basic nucleus and the NO donors, thus performing better bioactivity. This paper reviewed the routes of synthesis and advance activities of NO donor derivatives.

Low Nitric Oxide Bioavailability Increases Renin Production in the Collecting Duct

In the kidney, the stimulation of renin production by the collecting duct (CD-renin) contributes to the development of hypertension. The CD is a major nephron segment for the synthesis of nitric oxide (NO), and low NO bioavailability in the renal medulla is associated with hypertension. However, it is unknown whether NO regulates renin production in the CD. To test the hypothesis that low intrarenal NO levels stimulate the production of CD-renin, we first examined renin expression in the distal nephron segments of CD-eNOS deficient mice. In these mice, specific CD-renin immunoreactivity was increased compared to wild-type littermates; however, juxtaglomerular (JG) renin was not altered. To further assess the intracellular mechanisms involved, we then treated M-1 cells with either 1 mM L-NAME (L-arginine analog), an inhibitor of NO synthase activity, or 1 mM NONOate, a NO donor. Both treatments increased intracellular renin protein levels in M-1 cells. However, only the inhibition of NOS with L-NAME stimulated renin synthesis and secretion as reflected by the increase in Ren1C transcript and renin protein levels in the extracellular media, respectively. In addition, NONOate induced a fast mobilization of cGMP and intracellular renin accumulation. These response was partially prevented by guanylyl cyclase inhibition with ODQ (1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1]. Accumulation of intracellular renin was blocked by protein kinase G (PKG) and protein kinase C (PKC) inhibitors. Our data indicate that low NO bioavailability increases CD-renin synthesis and secretion, which may contribute to the activation of intrarenal renin angiotensin system.

Structure, photodynamic reaction and DNA photocleavage properties of a nitrosyl iron-sulfur cluster (Me4N)2[Fe2S2(NO)4]: A DFT calculation and experimental study

Density functional theory calculations were performed on the structure of the nitrosyl iron-sulfur cluster (Me₄N)₂[Fe₂S₂(NO)₄]. The IR spectra were assigned and the electronic ground-state properties in different solvents were analyzed. Dynamic conversion of [Fe₂S₂(NO)₄]^2- was analyzed quantitatively using the time-resolved IR spectra in different solvents. Photo irradiation and polarity of solvent obviously affect the reaction rates, which are faster in CH₃CN and CH₃OH than those in DMSO and water. The calculated orbital energies of HOMOs are higher and those of LUMO-HOMO gap are smaller in CH₃CN and CH₃OH than those in DMSO and water, which is consistent with the reaction rate and explains the experimental observation. Moreover, the photo-induced nitric oxide (NO) release and cluster conversion was identified using EPR spectra. The photocleavage of pBR322 DNA was observed, both NO and oxygen related free radicals play key roles in the process. The study provides an effective method to monitor the photodynamic reactions for better understanding of the physiological activity of nitrosyl iron-sulfur clusters.

The Possible Role of the Nitroso-Sulfide Signaling Pathway in the Vasomotoric Effect of Garlic Juice

The beneficial cardiovascular effects of garlic have been reported in numerous studies. The major bioactive properties of garlic are related to organic sulfides. This study aimed to investigate whether garlic juice works exclusively due to its sulfur compounds or rather via the formation of new products of the nitroso-sulfide signaling pathway. Changes in isometric tension were measured on the precontracted aortic rings of adult normotensive Wistar rats. We evaluated NO-donor (S-nitrosoglutathione, GSNO)-induced vasorelaxation and compare it with effects of hydrogen sulfide (H₂S)/GSNO and garlic/GSNO. Incubation with garlic juice increased the maximal GSNO-induced relaxation and markedly changed the character of the relaxant response. Although incubation with an H₂S donor enhanced the maximal vasorelaxant response of GSNO, neither the absolute nor the relative relaxation changed over time. The mixture of GSNO with an H₂S donor evoked a response similar to GSNO-induced relaxation after incubation with garlic juice. This relaxation of the H₂S and GSNO mixture was soluble guanylyl cyclase (sGC) dependent, partially reduced by HNO scavenger and it was adenosine triphosphate-sensitive potassium channels (K_ATP) independent. In this study, we demonstrate for the first time the suggestion that H₂S itself is probably not the crucial bioactive compound of garlic juice but rather potentiates the production of new signaling molecules during the GSNO-H₂S interaction.

Sodium nitroprusside prevents the detrimental effects of glucose on the neurovascular unit and behaviour in zebrafish

Diabetes is associated with dysfunction of the neurovascular unit, although the mechanisms of this are incompletely understood and currently no treatment exists to prevent these negative effects. We previously found that the nitric oxide (NO) donor sodium nitroprusside (SNP) prevents the detrimental effect of glucose on neurovascular coupling in zebrafish. We therefore sought to establish the wider effects of glucose exposure on both the neurovascular unit and on behaviour in zebrafish, and the ability of SNP to prevent these. We incubated 4-days post-fertilisation (dpf) zebrafish embryos in 20 mM glucose or mannitol for 5 days until 9 dpf, with or without 0.1 mM SNP co-treatment for 24 h (8-9 dpf), and quantified vascular NO reactivity, vascular mural cell number, expression of a klf2a reporter, glial fibrillary acidic protein (GFAP) and transient receptor potential cation channel subfamily V member 4 (TRPV4), as well as spontaneous neuronal activation at 9 dpf, all in the optic tectum. We also assessed the effect on light/dark preference and locomotory characteristics during free-swimming studies. We find that glucose exposure significantly reduced NO reactivity, klf2a reporter expression, vascular mural cell number and TRPV4 expression, while significantly increasing spontaneous neuronal activation and GFAP expression (all in the optic tectum). Furthermore, when we examined larval behaviour, we found that glucose exposure significantly altered light/dark preference and high and low speed locomotion while in light. Co-treatment with SNP reversed all these molecular and behavioural effects of glucose exposure. Our findings comprehensively describe the negative effects of glucose exposure on the vascular anatomy, molecular phenotype and function of the optic tectum, and on whole-organism behaviour. We also show that SNP or other NO donors may represent a therapeutic strategy to ameliorate the complications of diabetes on the neurovascular unit.This article has an associated First Person interview with the first author of the paper.

Effect of nitric oxide on boar sperm motility, membrane integrity, and acrosomal status during semen storage

Nitric oxide (NO) is a major gasotransmitter involved in several physiological processes of male reproduction. There is, nevertheless, little information concerning the role of NO during semen storage. The aim of this study was to evaluate the effect of NO on boar semen stored at 17oC for 72 h. For this purporse, sperm samples were treated with 0.625, 1.25, 2.5, 5, and 10 mM aminoguanidine (AG) or Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME), a selective and non-selective NO synthase (NOS) inhibitor, respectively. Moreover, sodium nitroprusside (SNP), a NO donor, was used at the dose of 18.75, 37.5, 75, and 150 μM. Sperm motility, membrane integrity, and acrosomal status were evaluated at 0, 4, 24, 48, and 72 h of semen storage. A significant increase of the amplitude of lateral sperm head displacement (ALH), and both curvilinear and straight-line velocity (VCL and VSL, respectively) was observed at 72 h of semen storage in samples treated with 0.625 mM AG, probably because of the antioxidant properties of this NOS inhibitor. Contrarily, 0.625 mM L-NAME showed no effect on boar sperm parameters during the entire period of semen storage. Moreover, AG and L-NAME at 10 mM negatively affected sperm kinetics and acrosome integrity, which may provide further support to the notion that low NO levels are necessary for a normal sperm function. The concentrations of SNP used in this study had mostly no or negative effects on boar sperm parameters during semen storage. In conclusion, the results from this study increase the understanding of the role of NO on boar sperm physiology.

Design, Synthesis and Biological Evaluation of Nitrate Derivatives of Sauropunol A and B as Potent Vasodilatory Agents

A group of nitrate derivatives of naturally occurring sauropunol A and B were designed and synthesized. Nitric oxide (NO) releasing capacity and vasodilatory capacity studies were performed to explore the structure-activity relationship of resulted nitrates. Biological evaluation of these compounds revealed that most of the synthesized mononitrate derivatives demonstrated superior releasing capacity than isosorbide mononitrate (ISMN), and 2MNS-6 even demonstrated stronger NO releasing capacity than isosorbide dinitrate (ISDN). Two dinitrates, DNS-1 and DNS-2, showed higher NO releasing capacity than ISDN. Evaluation of inhibitory activities to the contractions in mesenteric artery rings revealed that 2MNS-8 and DNS-2 showed stronger vasorelaxation activities than ISDN. High level of NO and soluble guanylyl cyclase (sGC) may be essential for the potent vasodilatory effect of DNS-2. The vasodilatory effects of DNS-2 may result from cellular signal transduction of NO-sGC-cGMP. DNS-2 was found to be the most potent sauropunol-derived nitrate vasodilatory agent for further pharmaceutical investigation against cardiovascular diseases.

Signaling and physiological activity of the NO-donating agent TNICthio in human blood lymphocytes, Jurkat and MCF7 cell lines

Signaling and physiological activities of the crystalline tetranitrosyl iron complex with thiosulfate-a NO-donor (TNICthio) were first studied on human cells in conditions of mono and combined application of H₂S and antioxidants. Comparative studies were performed on three cell lines: normal and leukemic T lymphocytes (Jurkat cells) and breast cancer MCF-7 cells (human breast adenocarcinoma). Also established was a high biological activity of TNICthio, as well as correlation between the levels of reactive oxygen species generation, the formation of double-strand breaks (DSB) in DNA and cell proliferation. The amount of DNA DSB repair in normal lymphocytes was tenfold higher than in leukemic cells. Inorganic H₂S donor sodium hydrosulfide (NaHS) had insignificant effects on the production of reactive oxygen species and generation of DNA DSB in the cells of all the lines under study. However, H₂S increased the tolerance of cells to the stress response after combined cell treatment with NO + H₂S. 0.5 mM NO-donor and 0.1 mM antitumor antibiotic doxorubicin were equally effective generators of reactive oxygen species in MCF-7 cells; however, antiproliferative activity of the NO-donor, in this case, proved to be twice higher. The results obtained in this work may be promising for the prediction of pro- and antioxidant properties of the new NO and H₂S donating compounds, as well as for the development of methods for complex anticancer therapy.

Synthesis, hepatotoxic evaluation and antipyretic activity of nitrate ester analogs of the acetaminophen derivative SCP-1

A series of nitrate ester analogues of the acetaminophen derivative SCP-1 were prepared by triflic acid catalyzed O-acylation of SCP-1 with chloroalkanoyl chlorides followed by nitration with silver nitrate. The chloroesters and corresponding nitrate esters were obtained in high yields. Preliminary hepatotoxicity studies revealed nitrate esters 5b (MD-38) and 5c (MD-39) to be well tolerated by human hepatocytes and had little effect on the three cytochrome P450 enzymes tested (CYP3A4, CYP2E1 and CYP2D6). In addition, the nitrate ester 5c (MD-39) exhibited antipyretic activity similar to acetaminophen.

Pentaerythrityltetranitrate (PETN) improves utero- and feto-placental Doppler parameters in pregnancies with impaired utero-placental perfusion in mid-gestation - a secondary analysis of the PETN-pilot trial

AIM

In pregnancies complicated by impaired utero-placental perfusion, pentaeritrithyltetranitrate (PETN) has been shown to reduce the risk of severe fetal growth restriction (FGR) and perinatal death by 39%. The effect is most likely related to the vasodilatative influence of PETN. To assess its impact on utero-placental and fetal perfusion, we analyzed the Doppler parameters measured during the PETN pilot-trial.

METHODS

One hundred and eleven pregnancies presenting impaired utero-placental resistance at mid-gestation were included in the trial. Fifty-four women received PETN, while 57 received a placebo. Doppler velocimetry measurements were monitored biweekly. Statistical analysis was performed using a mixed linear model.

RESULTS

Within the first week of treatment, the mean pulsatility index (PI) of the uterine artery (UtA) dropped more prominently in the PETN group [-0.20, 95% confidence interval (CI): -0.34 to -0.05, P=0.007). The adjusted relative risk (RR) for abnormal cerebro-placental ratio (CPR) was significantly reduced by PETN [RR 0.412 (95% CI: 0.181-0.941)]. Kaplan-Meier analysis demonstrates the postponement of absent end-diastolic flow (AED), absent or reverse end-diastolic flow (ARED), brain sparing and abnormal cerebroplacental ratio (CPR) in the PETN group.

CONCLUSION

The demonstrated effect of PETN on utero-placental and feto-placental perfusion strengthens the evidence for a positive impact in pregnancies complicated by impaired placental perfusion and might explain the effect on neonatal outcome, as shown in the PETN-pilot trial.

Antioxidant Properties of a Pharmaceutical Substance Hypocard, a Potential Drug for Ischemic Disease

Antioxidant activity of a pharmaceutical substance hypocard was compared with activity of nitromalic acid and well-known agents nicorandil and Mexidol. The ability of these substances to inhibit spontaneous and oxidant-induced LPO process in rat brain homogenate was analyzed. The mechanisms of these effects were studied. The antioxidant properties of hypocard manifested in the inhibition of Fe(II)-induced LPO were significantly more pronounced in comparison with Mexidol and nicorandil.

Coadministration of iRGD with Multistage Responsive Nanoparticles Enhanced Tumor Targeting and Penetration Abilities for Breast Cancer Therapy

Limited tumor targeting and poor penetration of nanoparticles are two major obstacles to improving the outcome of tumor therapy. Herein, coadministration of tumor-homing peptide iRGD and multistage-responsive penetrating nanoparticles for the treatment of breast cancer are reported. This multistage-responsive nanoparticle, IDDHN, was comprised of an NO donor-modified hyaluronic acid (HN) shell and a small-sized dendrimer, namely, dendri-graft-l-lysine conjugated with doxorubicin and indocyanine (IDD). The results showed that IDDHN could be degraded rapidly from about 330 nm to a smaller size that was in a size range of 35 to 150 nm (most at 35-60 nm) after hyaluronidase (HAase) incubation for 4 h; in vitro cellular uptake demonstrated that iRGD could mediate more endocytosis of IDDHN into 4T1 cells, which was attributed to the overexpression of α_vβ₃ integrin receptor. Multicellular spheroids penetration results showed synergistically enhanced deeper distribution of IDDHN into tumors, with the presence of iRGD, HAase incubation, and NO release upon laser irradiation. In vivo imaging indicated that coadministration with iRGD markedly enhanced the tumor targeting and penetration abilities of IDDHN. Surprisingly, coadministration of IDDHN with iRGD plus 808 nm laser irradiation nearly suppressed all tumor growth. These results systematically revealed the excellent potential of coadministration of iRGD with multistage-responsive nanoparticles for enhancing drug delivery efficiency and overcoming the 4T1 breast cancer.

Design, synthesis and biological evaluation of nitric oxide releasing derivatives of dapagliflozin as potential anti-diabetic and anti-thrombotic agents

The cardiovascular complications were highly prevalent in type 2 diabetes mellitus (T2DM), even at the early stage of T2DM or the state of intensive glycemic control. Therefore, there is an urgent need for the intervention of cardiovascular complications in T2DM. Herein, the new hybrids of NO donor and SGLT2 inhibitor were design to achieve dual effects of anti-hyperglycemic and anti-thrombosis. As expected, the preferred hybrid 2 exhibited moderate SGLT2 inhibitory effects and anti-platelet aggregation activities, and its anti-platelet effect mediated by NO was also confirmed in the presence of NO scavenger. Moreover, compound 2 revealed significantly hypoglycemic effects and excretion of urinary glucose during an oral glucose tolerance test in mice. Potent and multifunctional hybrid, such as compound 2, is expected as a potential candidate for the intervention of cardiovascular complications in T2DM.

Effect of a nitric oxide donor on maternal hemodynamics in fetal growth restriction

OBJECTIVE

To evaluate the effect on maternal cardiovascular parameters of treatment with a nitric oxide (NO) donor and plasma volume expansion in pregnancies complicated by fetal growth restriction (FGR).

METHODS

Twenty-six pregnant women with a diagnosis of FGR were treated with transdermal patches of a NO donor and plasma volume expansion by co-administration of oral fluids. We compared the treated group to a historical control group of untreated FGR patients. Hemodynamic indices were obtained using the UltraSonic Cardiac Output Monitor system.

RESULTS

At diagnosis, the two groups were similar in terms of maternal and hemodynamic characteristics. In the treated group, we found a significant increase in maternal cardiac output and stroke volume and a decrease in systemic vascular resistance after 2 weeks of therapy. No significant differences were found 2 weeks after diagnosis in the untreated group. The treated group delivered infants with higher birth-weight centile than did the untreated control group.

CONCLUSIONS

The combined therapeutic approach of NO donor administration and plasma volume expansion in FGR apparently improves significantly maternal hemodynamic indices. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Biological properties of nitro-fatty acids in plants

Nitro-fatty acids (NO2-FAs) are formed from the reaction between nitrogen dioxide (NO2) and mono and polyunsaturated fatty acids. Knowledge concerning NO2-FAs has significantly increased within a few years ago and the beneficial actions of these species uncovered in animal systems have led to consider them as molecules with therapeutic potential. Based on their nature and structure, NO2-FAs have the ability to release nitric oxide (NO) in aqueous environments and the capacity to mediate post-translational modifications (PTM) by nitroalkylation. Recently, based on the potential of these NO-derived molecules in the animal field, the endogenous occurrence of nitrated-derivatives of linolenic acid (NO2-Ln) was assessed in plant species. Moreover and through RNA-seq technology, it was shown that NO2-Ln can induce a large set of heat-shock proteins (HSPs) and different antioxidant systems suggesting this molecule may launch antioxidant and defence responses in plants. Furthermore, the capacity of this nitro-fatty acid to release NO has also been demonstrated. In view of this background, here we offer an overview on the biological properties described for NO2-FAs in plants and the potential of these molecules to be considered new key intermediaries of NO metabolism in the plant field.

Nitric oxide donor [Ru(terpy)(bdq)NO]3+ induces uncoupling and phosphorylation of endothelial nitric oxide synthase promoting oxidant production

[Ru(terpy)(bdq)NO]3+ (TERPY) is a nitric oxide (NO) donor that promotes relaxation of the mesenteric artery and aorta in rats. We sought to investigate whether it acts as both an NO donor and endothelial NO synthase (eNOS) activator, as shown previously for nitroglycerin. Human umbilical vein endothelial cells (HUVECs) and human embryonic kidney 293 cells transfected with empty vector (HEK) or eNOS cDNA (HEK-eNOS) were treated with TERPY (1µM) for different lengths of time. eNOS expression, dimerization, and Ser1177 phosphorylation, caveolin-1 (Cav-1) oligomerization, Cav-1 Tyr14 phosphorylation were evaluated by Western blotting. Studies also assessed the production of reactive oxygen/nitrogen species (ROS/RNS) in HUVECs and HEK-eNOS cells. In HEK cells devoid of eNOS, TERPY released NO without additional stimulus indicating that is an NO donor. Moreover, in HEK-eNOS cells, TERPY-induced NO production that was blocked by L-NAME. In addition, TERPY increased ROS and ONOO- production which were blocked by more than 80% by BH4 (essential eNOS co-factor) and eNOS siRNA. These results suggest that TERPY-induced ROS and ONOO- production were originated from eNOS. HUVECs stimulated with TERPY showed increased eNOS Ser1177 and Cav-1 Tyr14 phosphorylation, and decreased eNOS dimerization, Cav-1 oligomerization, and Cav-1/eNOS interaction after 20min. It suggests that TERPY induces eNOS hyperactivation and uncoupling by disrupting Cav-1/eNOS interaction and depleting BH4. Endothelium-dependent vasodilation in response to NO donor TERPY is associated with eNOS activation and uncoupling, and thereby appears to be mediated, at least in part, via eNOS-dependent ROS/RNS production.

NO-Donor Iron Nitrosyl Complex with N-Ethylthiourea Ligand Exhibits Selective Toxicity to Glioma A172 Cells

We studied effects of NO-donor iron nitrosyl complex with N-ethylthiourea ligand (ETM) on normal or tumor-derived cell lines. ETM was mildly toxic to most cell lines studied except the human glioma cell line A172 that proved to be highly sensitive to the complex and underwent cell death after ETM exposure. The high susceptibility of A172 cells to ETM was attributed to its NO-donor properties since no toxicity was detected for the N-ethylthiourea ligand.

Hypotensive Effect and Accumulation of Dinitrosyl Iron Complexes in Blood and Tissues after Intravenous and Subcutaneous Injection

Subcutaneous injection of Oxacom with glutathione-bound dinitrosyl iron complex as the active principle produced a slower drop of mean BP and longer accumulation of protein-bound dinitrosyl iron complexes in whole blood and tissues than intravenous injection of this drug, while durations of hypotensive effect in both cases were practically identical. In contrast to intravenous injection of the drug, its subcutaneous administration was not characterized by a high concentration of protein-bound dinitrosyl iron complexes in the blood at the onset of experiment; in addition, accumulation of these NO forms in the lungs was more pronounced after subcutaneous injection than after intravenous one.

NO-Releasing Enmein-Type Diterpenoid Derivatives with Selective Antiproliferative Activity and Effects on Apoptosis-Related Proteins

A series of nine enmein-type ent-kaurane diterpenoid and furoxan-based nitric oxide (NO) donor hybrids (10a-i) were designed and synthesized from commercially available oridonin (1). These hybrids were evaluated for their antiproliferative activity against Bel-7402, K562, MGC-803, and CaEs-17 human cancer cell lines and L-02 normal liver cells. The antiproliferative activity against tumor cells was stronger than the lead compound 1 and parent molecule 9 in most cases. Especially, compound 10f showed the strongest activity against human hepatocarcinoma Bel-7402 cell line with an IC50 of 0.81 μM and could also release 33.7 μmol/L NO at the time point of 60 min. Compounds 10a-i also showed cytotoxic selectivity between tumor and normal liver cells with IC50 ranging from 22.1 to 33.9 μM. Furthermore, the apoptotic properties on Bel-7402 cells revealed that 10f could induce S phase cell cycle arrest and apoptosis at low micromolar concentrations. The effects of 10f on apoptosis-related proteins were also investigated. The potent antiproliferative activities and mechanistic studies warrant further preclinical investigations.

Increasing the availability of l-arginine and nitric oxide increases sensitivity of nitrous oxide (N2O)-insensitive inbred mice to N2O-induced antinociception

Nitrous oxide (N2O)-induced antinociception in mice is dependent on the neuromodulator nitric oxide (NO). In contrast to C57BL/6J (B6) mice, DBA/2J (D2) mice fail to respond to N2O with a robust antinociceptive response or with an increase in brain nitric oxide synthase (NOS) enzyme activity, suggesting that failure of D2 mice to respond to N2O might result from a deficit of NO function. Therefore, it was of interest to determine whether increasing the availability of NO might increase sensitivity of D2 mice to N2O. Male D2 mice were pretreated with sub-antinociceptive intracerebroventricular doses of the NO donor 3-morpholinosydnoimine or the NO precursor l-arginine then assessed for responsiveness to N2O-induced antinociception using the acetic acid abdominal constriction test. Both pretreatments increased the antinociceptive responsiveness of D2 mice to N2O. These results indicate that the NOS enzyme in D2 mice is functional and that the deficit in NO function that obstructs sensitivity to N2O-induced antinociception may lie in availability or utilization of l-arginine.

A Case of Hyperacute Onset of Vasospasm After Aneurysmal Subarachnoid Hemorrhage and Refractory Vasospasm Treated with Intravenous and Intraventricular Nitric Oxide: A Mini Review

BACKGROUND

A case of hyperacute vasospasm, indicating a poor prognosis after aneurysmal subarachnoid hemorrhage (SAH), is reported, and a review is presented of the literature addressing use of nitric oxide (NO) donors in cases of refractory vasospasm and recurrent delayed cortical ischemias (DCI).

CASE DESCRIPTION

A 65-year-old woman was admitted within 1 hour after aneurysmal SAH (Hunt and Hess grade III, Fisher modified by Frontera grade IV). A hyperacute vasospasm had been confirmed arteriographically, the right middle cerebral artery (MCA) aneurysm was immediately coiled and a standard antivasospastic therapy was started. Within 48 hours, the patient developed cerebral vasospasm with DCI. Because the standard therapy failed to control clinical symptoms and to address severe vasospasm, an individualized rescue treatment with NO donors was initiated. A continuous intravenous molsidomine infusion was started and clinical stabilization was achieved for a week (Hunt and Hess grade I; World Federation of Neurological Surgeons grade I; Glasgow Coma Scale score, 15) after which vasospasm and DCI recurred. During a subsequent DCI, we escalated NO donor therapy by adding intraventricular boluses of sodium nitroprusside (SNP). Over the course of the following 22 days, 7 transient DCIs (Glasgow Coma Scale score, 8) were treated with boluses of SNP during continued molsidomine therapy and each time vasospasm and DCI were completely reversed. Despite initial poor prognosis, the clinical outcome was excellent; at 3, 6, and 12 months follow-up the patient's modified National Institutes of Health-Stroke Scale and modified Rankin Scale scores were 0, with no cognitive deficits.

CONCLUSIONS

The review of the literature suggested that combined intravenous molsidomine with intraventricular SNP treatment reversed refractory, recurrent vasospasm and DCIs probably by addressing the hemoglobin NO sink effect, NO depletion, and decreased NO availability after aneurysmal SAH.

A Novel Compound Analgesic Cream (Ketamine, Pentoxifylline, Clonidine, DMSO) for Complex Regional Pain Syndrome Patients

BACKGROUND

Evidence suggests that complex regional pain syndrome (CRPS) is a manifestation of microvascular dysfunction. Topical combinations of α2-adrenergic receptor agonists or nitric oxide donors with phosphodiesterase or phosphatidic acid inhibitors formulated to treat microvascular dysfunction have been shown to reduce allodynia in a rat model of CRPS-I. Driven by these findings, we assessed the outcomes of CRPS patients treated with a compound analgesic cream (CAC) consisting of ketamine 10%, pentoxifylline 6%, clonidine 0.2%, and dimethyl sulfoxide 6% to 10%.

METHODS

An audit was conducted on 13 CRPS patients who trialed the CAC. A detailed report was compiled for each patient which comprised baseline characteristics, including CRPS description, previous treatments, and pain scores (numerical pain rating scale; 0 to 10). Recorded outcomes consisted of pain scores, descriptive outcomes, and concurrent medications/treatments, for which basic analysis was performed to determine the effectiveness of the CAC. Case reports are presented for 3 patients with varying outcomes.

RESULTS

Nine patients (69%) reported pain/symptom reduction (4.4 ± 2.1 vs. 6.3 ± 1.9) with use of the CAC. Six patients reported sustained benefits after 2 months of CAC use, and 2 patients reported complete resolution of pain/symptoms: one had early CRPS-I and the other received a partial CRPS diagnosis. An otherwise medication refractory and intolerant patient found partial benefit with the CAC.

CONCLUSIONS

These results demonstrate promise for this topical combination as a useful treatment in multimodal therapy for patients with CRPS, with the potential to resolve pain/symptoms in early CRPS patients.

Characterisation and comparison of temporal release profiles of nitric oxide generating donors

•

Nitric oxide release profiles were characterised for commonly used donors.

•

Released NO differs greatly between donors and depends on storage conditions.

•

High release donors (NOC-5, PAPA NONOate) decay quickly.

•

SNP and GSNO show greater stability releasing consistent lower NO levels.

•

This comprehensive characterisation provides knowledge to define NO concentrations released in vitro.

Background

Nitric oxide (NO) is a vital signalling molecule in a variety of tissues including the neuronal, vascular and reproductive system. However, its high diffusibility and inactivation make characterisation of nitrergic signalling difficult. The use of NO donors is essential to characterise downstream signalling pathways but knowledge of donor release capacities is lacking, thus making comparisons of donor responses difficult.

New method

This study characterises NO profiles of commonly used NO donors. Donors were stored under defined conditions and temporal release profiles detected to allow determination of released NO concentrations.

Results

Using NO-sensitive microsensors we assessed release profiles of NO donors following different storage times and conditions. We found that donors such as NOC-5 and PAPA-NONOate decayed substantially within days, whereas SNP and GSNO showed greater stability releasing consistent levels of NO over days. In all donors tested, the amount of released NO differs between frozen and unfrozen stocks.

Comparison with existing method(s)

Fluorescent and amperometric approaches to measure NO concentrations yield a wide range of levels. However, due to a lack of characterisation of the release profiles, inconsistent effects on NO signalling have been widely documented. Our systematic assessment of release profiles of a range of NO donors therefore provides new essential data allowing for improved and defined investigations of nitrergic signalling.

Conclusions

This is the first systematic comparison of temporal release profiles of different NO donors allowing researchers to compare conditions across different studies and the use of defined NO levels by choosing specific donors and concentrations.

Visible light-induced nitric oxide release from a novel nitrobenzene derivative cross-conjugated with a coumarin fluorophore

Nitric oxide (NO) is a well-known free-radical molecule which is endogenously biosynthesised and shows various functions in mammals. To investigate NO functions, photocontrollable NO donors, compounds which release NO in response to light, are expected to be potentially useful. However, most of the conventional NO donors require harmful ultra-violet light for NO release. In this study, two dimethylnitrobenzene derivatives conjugated with coumarins were designed, synthesized and evaluated as photocontrollable NO donors. The optical properties and efficiency of photo-induced NO release were dependent upon the nature of the conjugation system. One of these compounds, Bhc-DNB (1), showed spatiotemporally well-controlled NO release in cultured cells upon exposure to light in the less-cytotoxic visible wavelength range (400-430 nm).

Nitric oxide donors rescue diabetic nephropathy through oxidative-stress-and nitrosative-stress-mediated Wnt signaling pathways

AIMS/INTRODUCTION

The role of the renal nitric oxide (NO) system in the pathophysiology of diabetic nephropathy constitutes a very challenging and fertile field for future investigation. The purpose of the present study was to investigate whether NO donors can attenuate diabetic renal fibrosis and apoptosis through modulating oxidative-and nitrosative-stress, and Wnt signaling using in vivo diabetic models.

MATERIALS AND METHODS

Diabetic rat was induced by a single intraperitoneal injection of streptozotocin. Rats in each group were intraperitoneally given 2,2'-(hydroxynitrosohydrazino)bis-ethanamine (1 U/kg/day) and vehicle for 28 and 56 consecutive days. Expression of the oxidative-and nitrosative-stress, and Wnt signaling components were examined in kidneys from diabetic animals by quantitative reverse transcription polymerase chain reaction, western blot analysis and immunohistochemical staining.

RESULTS

NO donor treatment significantly reduced the ratio of kidney weight to bodyweight and proteinuria. This treatment also significantly restored the suppressive effect of diabetes on urinary NO2 + NO3 levels. Immunohistochemistry showed that NO donor treatment significantly reduced transforming growth factor (TGF)-β1, fibronectin, cleaved caspase-3 and triphosphate-biotin nick end-labeling expression in the glomeruli of diabetic rats. We found that diabetes promoted 8-hydroxy-2'-deoxyguanosine, and peroxynitrite expression coincided with reduced endothelial NO synthase expression in glomeruli. Interestingly, NO donor treatment completely removed oxidative stress and nitrosative stress, and restored endothelial NO synthase expression in diabetic renal glomeruli. Immunohistomorphometry results showed that NO donor treatment significantly restored suppressed Wnt5a expression and β-catenin immunoreactivities in glomeruli. Based on laser-captured microdissection for quantitative reverse transcription polymerase chain reaction, diabetes significantly increased TGF-β1, and fibronectin expression coincided with depressed Wnt5a expression. NO donor treatment reduced TGF-β1, fibronectin activation, and the suppressing effect of diabetes on Wnt5a and β-catenin expression in renal glomeruli.

CONCLUSIONS

NO donor treatment alleviates extracellular matrix accumulation and apoptosis in diabetic nephropathy in vivo by not only preventing the diabetes-mediated oxidative and nitrostative stress, but also restoring downregulation of endothelial NO synthase expression and Wnt/β-catenin signaling. These findings suggest that modulation of NO is a viable alternative strategy for rescuing diabetic renal injury.

Specific inhibitory effects of the NO donor MAHMA/NONOate on human platelets

Nitric oxide (NO) is a physiological inhibitor of platelet function and has vaso-dilating effects. Therefore, synthesized NO releasing agents are used e.g. in cardiovascular medicine. The aim of this study was to characterise specific effects of the short living agent MAHMA/NONOate, a NO donor of the diazeniumdiolate class, on human platelets. Whole blood was obtained from healthy volunteers. In washed human platelets, the MAHMA/NONOate induced phosphorylation of the vasodilator-stimulated phosphoprotein (VASP) and cyclic nucleotide production were studied by Western Blot and by enzyme immunoassay kits. Agonist induced aggregation was measured in platelet rich plasma. Paired Student׳s t-test was used for statistical analysis. MAHMA/NONOate significantly stimulated platelet VASP phosphorylation in a concentration dependent manner and increased intracellular cGMP, but not cAMP levels, transiently. ODQ, a specific inhibitor of the soluble guanylyl cyclase, completely prevented VASP phosphorylation induced by low MAHMA/NONOate concentrations (5nM-15nM). The effects of higher concentrations (30-200nM) were only partially inhibited by ODQ. MAHMA/NONOate reduced platelet aggregation induced by low doses of agonists (2µM ADP, 0.5µg/mL collagen, 5µM TRAP-6) in a concentration dependent manner. MAHMA/NONOate leads to a rapid and transient activation of platelet inhibitory systems, accompanied by decreased platelet aggregation induced by low dose agonists. At low MAHMA/NONOate concentrations, the effects are cGMP dependent and at higher concentrations additionally cGMP independent. The substance could be of interest for clinical situations requiring transient and subtotal inhibition of platelet function.

In vitro inflammatory/anti-inflammatory effects of nitrate esters of purines

Six purine analogues bearing a nitrate ester group (potential NO donor) were tested on human THP-1 macrophages to investigate their effects on the inflammatory response. Only three analogues increased the basal level of IL-1β. Two analogues exacerbated the inflammatory response induced by ATP but not that induced by H2O2. Only 6-[4-(6-nitroxyacetyl)piperazin-1-yl]-9H-purine (compound MK128) abolished ATP or H2O2-induced IL-1β production in the culture medium. Similar results were reproduced on macrophages differentiated from buffy coats and stimulated with LPS. MK128 was the only analogue to release NO and leading to nitrite formation in the culture medium. The EC50 for inhibition of induced IL-1β production by the cells was estimated to be 10-12µg/ml (about 36µM) and corresponded to the production of around 30µM nitrites in the culture medium. This anti-inflammatory effect of MK128 was mimicked by trinitrin used in 10 fold higher concentrations. Preincubation of cells with NO trapper cPTIO partially abolished the beneficial effect of MK128 while MK137, a ONO2 deprived analogue of MK128, was not able to inhibit induced IL-1β production and proved to be inflammatory. Moreover, purinergic channel inhibitors (oATP and U73122) inhibited the MK137 inflammatory effect. Finally, MK128 reduced the quantity of p20 caspase-1 produced in the culture medium. We suggest that MK128 inhibits IL-1β production via NO production and subsequent inflammasome component nitrosylation. On the opposite MK137, deprived from ONO2 group, could act as agonist of purinergic receptors and could thus activate inflammasome.

Synthesis, nitric oxide release, and α-glucosidase inhibition of nitric oxide donating apigenin and chrysin derivatives

α-Glucosidase (AG) play crucial roles in the digestion of carbohydrates. Inhibitors of α-glucosidase (AGIs) are promising candidates for the development of anti-diabetic drugs. Here, five series of apigenin and chrysin nitric oxide (NO)-donating derivatives were synthesised and evaluated for their AG inhibitory activity and NO releasing capacity in vitro. Except for 9a-c, twelve compounds showed remarkable inhibitory activity against α-glucosidase, with potency being better than that of acarbose and 1-deoxynojirimycin. All organic nitrate derivatives released low concentrations of NO in the presence of l-cysteine. Structure activity relationship studies indicated that 5-OH, hydrophobic coupling chain, and carbonyl groups of the coupling chain could enhance the inhibitory activity. Apigenin and chrysin derivatives therefore represents a new class of promising compounds that can inhibit α-glucosidase activity and supply moderate NO for preventing the development of diabetic complications.