Nitric oxide: new evidence for novel therapeutic indications

Evaluation of Anticancer Activity of Nucleoside-Nitric Oxide Photo-Donor Hybrids

Herein, we report the synthesis of a new hybrid compound based on a 2'-deoxyuridine nucleoside conjugated with a NO photo-donor moiety (dU-t-NO) via CuAAC click chemistry. Hybrid dU-t-NO, as well as two previously reported 2'-deoxyadenosine based hybrids (dAdo-S-NO and dAdo-t-NO), were evaluated for their cytotoxic and cytostatic activities in selected cancer cell lines. dAdo-S-NO and dAdo-t-NO hybrids displayed higher activity with respect to dU-t-NO. All hybrids showed effective release of NO in the micromolar range. The photochemical behavior of the newly reported hybrid, dU-t-NO, was studied in the RKO colon carcinoma cell line, whereas the dAdo-t-NO hybrid was tested in both colon carcinoma RKO and hepatocarcinoma Hep 3B2.1-7 cell lines to evaluate the potential effect of NO released upon irradiation on cell viability. A customized irradiation apparatus for in vitro experiments was also designed.

Which patients with coronary artery disease should include oral nitrates on their discharge medication list?

BACKGROUND

Which patients with coronary artery disease (CAD) should have oral nitrates on their discharge medication list after coronary angiography (CAG)? To assess the relationship between oral nitrates included in the discharge medication list and major adverse cardiovascular events (MACEs) among CAD patients, we designed this retrospective cohort study.

METHODS

A total of 2979 CAD patients hospitalised in the Department of Cardiology, Affiliated Hospital of Jining Medical University from May 2013 to October 2015 were enrolled, grouped according to whether oral nitrates were included at discharge after CAG, and followed up for MACEs for a mean of 4.42 years after discharge. The primary endpoint was MACEs. Multivariate Cox proportional hazards models were used to analyses potential confounding factors. Stratified analysis was used to observe the relationship between oral nitrates and MACEs by different covariates.

RESULTS

The median follow-up time was 4.61 years, and 296 (9.94%) patients experienced MACEs. Multivariate Cox proportional hazards model analysis showed no association between oral nitrates on the discharge medication list and the occurrence of MACEs among patients with CAD (p > 0.05) after adjusting for some covariates, such as SYNTAX score (hazard ratio (HR): 1.18, 95% confidence interval (CI): 0.90-1.55, p = 0.2420). Stratified analysis revealed a higher incidence of MACEs among hypertensive patients prescribed oral nitrates at discharge (HR: 1.67, 95% confidence CI: 1.13-2.46, p = 0.0046). However, prescribing nitrates at discharge for patients with low uric acid levels increased the incidence of MACEs, which showed a possible trend towards significance (HR: 1.44, 95% CI: 0.99-2.09, p = 0.0525).

CONCLUSION

There was no association between oral nitrates included in the discharge medication list and the development of MACEs among patients with CAD after adjusting for some covariates, such as SYNTAX score. Oral nitrates after discharge for CAD patients combined with hypertension increased the occurrence of MACEs. Oral nitrates after discharge for CAD patients combined with low uric acid levels may increase theoccurrence of MACEs, and close monitoring for any adverse events is recommended.

Endogenous stimulus-responsive nitric oxide releasing bioactive liposome for a multilayered drug-eluting balloon

Drug-eluting balloon (DEB) system has been widely utilized for percutaneous coronary intervention (PCI), treating atherosclerosis to overcome the limitations of cardiovascular stents. With the anti-proliferative drug, everolimus (EVL), nitric oxide (NO) plays a key bioregulator role to facilitate the angiogenesis of endothelial cells (ECs) and inhibit the cell proliferation of smooth muscle cells (SMCs) in the lesions of cardiovascular diseases. Due to the very short lifetime and limited exposure area of NO in the body, the continuous release and efficient delivery of NO must be carefully considered. In this respect, a liposome-containing disulfide bonding group was introduced as a delivery vehicle of EVL and NO with the continuous release of NO via successive reaction cycles with GSH and SNAP in the blood vessel without the need for exogenous stimulations. With a multilayer coating platform consisting of a polyvinylpyrrolidone (PVP)/EVL-laden liposome with NO (EVL-NO-Lipo)/PVP, we precluded the loss of the EVL-encapsulated liposome with NO release during the transition time and maximized the transfer rate from the surface of DEB to the tissues. The sustained release of NO was monitored using a nitric oxide analyzer (NOA), and the synergistic bioactivities of EVL and NO were proved in EC and SMC with angiogenesis and cell proliferation-related assays. From the results of hemocompatibility and ex vivo studies, the feasibility was provided for future in vivo applications of the multilayer-coated DEB system.

Biodegradable hyaluronic acid-based, nitric oxide-releasing nanofibers for potential wound healing applications

Nitric oxide (NO) is one of the smallest gas molecules with pharmaceutical and potential wound therapeutic effects due to its ability to regulate inflammation and eradicate bacterial infections. Recently, NO-releasing synthetic polymer-based nanofibers have become promising candidates for wound healing due to their facile functionalisation, tunable mechanical properties, and large effective surface areas. However, synthetic polymer-based nanofibers suffer from poor degradability in the physiological milieu, which restricts their use in in vivo applications. In this study, we developed biodegradable and nitric oxide-releasing nanofibers for potential wound healing applications. We synthesised dual-functionalised hyaluronic acid (HA) containing methacrylate groups and N-diazeniumdiolate (NONOate)-NO donor groups and capable of forming crosslinked, electrospun nanofibers, with an effective NO payload, through an electrospinning process and photoinitiated polymerisation. Nuclear magnetic resonance, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroscopy confirmed the successful synthesis of the functionalised HA. Control over both the NO donor and HA concentrations allowed for the preparation of NO-releasing, HA-based nanofibers of varying diameters (240-490 nm), NO payloads (10-620 nmol mg^-1), maximum amounts of NO released (160-8920 ppb mg^-1), and NO release durations (1.5-20.2 h). Moreover, the NO-releasing nanofibers had good biodegradability and potential wound healing effects without any observed cytotoxicity. The biodegradable and NO-releasing HA-based nanofibers developed in this study have the potential application in wound healing.

The effects of extended nitric oxide release on responses of the human non-pregnant myometrium to endothelin-1 or vasopressin

BACKGROUND

Uterotonic mediators: endothelin-1 (ET-1), arginine vasopressin (AVP), and nitric oxide (NO) play important roles in the regulation of uterine contractility. We hypothesize that NO affects both ET-1 or AVP. Therefore, this study investigated the involvement of extended exogenous NO release in the regulation of responses of the human non-pregnant myometrium to ET-1 and AVP.

METHODS

Specimens were obtained from 10 premenopausal women, undergoing hysterectomy for benign gynecological disorders. Responses of the myometrial strips to ET-1 or AVP in the absence and presence of an exogenous NO donor (diethylenetriamine; DETA/NO; 10-4 mol/L) were recorded under isometric conditions. To inhibit endogenous NO, a competitive inhibitor of NO synthase, L-NG-nitroarginine (L-NNA) was added to the organ bath.

RESULTS

ET-1 enhanced the spontaneous contractile activity of the myometrium more powerfully (p < 0.01) than AVP. Preincubation with exogenous NO weakened ET-1- or AVP-induced increases in this contractile activity (p < 0.05). However, unexpected results were obtained after preincubation with L-NNA and with DETA/NO then added. Both ET-1 and AVP induced augmented contractile effects in almost all concentrations compared with the responses to these peptides alone or after NOS synthase inhibition (both p < 0.01).

CONCLUSIONS

This study demonstrated for the first time that extended incubation with a NO donor influences the uterine muscle response evoked by ET-1 and AVP. Both endogenous and exogenous NO is involved in the control of the uterine responses to ET-1 or AVP of non-pregnant myometrium. Furthermore, both peptides stimulate increased uterine contractility when the local imbalance between the constrictive and relaxing mediators takes place.

Intracellular NO-Releasing Hyaluronic Acid-Based Nanocarriers: A Potential Chemosensitizing Agent for Cancer Chemotherapy

In this work, we investigate whether S-nitrosoglutathione (GSNO)-conjugated hyaluronic acid-based self-assembled nanoparticles (GSNO-HANPs) can be useful as a chemosensitizing agent to improve the anticancer activity of doxorubicin (DOX). The GSNO-HANPs were prepared by aqueous assembly of GSNO-conjugated HA with grafted poly(lactide- co-glycolide). Aqueous GSNO stability shielded within the assembled environments of the GSNO-HANPs was greatly enhanced, compared to that of free GSNO. The NO release from the GSNO-HANPs was facilitated in the presence of hyaluronidase-1 (Hyal-1) and ascorbic acid at intracellular concentrations. Microscopic analysis showed GSNO-HANPs effectively generated NO within the cells. We observed that NO made the human MCF-7 breast cancer cells vulnerable to DOX. This chemosensitizing activity was supported by the observation of an increased level of ONOO^- (peroxynitrite), a highly reactive oxygen species, upon co-treatment with the GSNO-HANPs and DOX. Apoptosis assays showed that GSNO-HANP alone exhibited negligible cytotoxic effects and reinforced apoptotic activity of DOX. Animal experiments demonstrated the effective accumulation of GSNO-HANPs in solid MCF-7 tumors and effectively suppressed tumor growth in combination with DOX. This hyaluronic acid-based intracellularly NO-releasing nanoparticles may serve as a significant chemosensitizing agent in treatments of various cancers.

Synthesis and Characterization of Nitric Oxide-Releasing Platinum(IV) Prodrug and Polymeric Micelle Triggered by Light

Herein, we report the proof of concept of photoresponsive chemotherapeutics comprising nitric oxide-releasing platinum prodrugs and polymeric micelles. Photoactivatable nitric oxide-releasing donors were integrated into the axial positions of a platinum(IV) prodrug, and the photolabile hydrophobic groups were grafted in the block copolymers. The hydrophobic interaction between nitric oxide donors and the photolabile groups allowed for the loading of platinum drugs and nitric oxide-releasing donors in the photolabile polymeric micelles. After cellular uptake of micelles, light irradiation induced the release of nitric oxide, which sensitized the cancer cells. Simultaneously, photolabile hydrophobic groups were cleaved from micelles, and the nitric oxide-releasing donor was altered to be more hydrophilic, resulting in the rapid release of platinum(IV) prodrugs. The strategy of using platinum(IV) prodrugs and nitric oxide led to enhanced anticancer effects.

Vitamin D and cardiovascular diseases: Causality

Vitamin D regulates blood pressure, cardiac functions, and endothelial and smooth muscle cell functions, thus, playing an important role in cardiovascular health. Observational studies report associations between vitamin D deficiency with hypertension and cardiovascular-related deaths. Peer-reviewed papers were examined in several research databases as per the guidelines of the Preferred Reporting Items for Systematic Reviews, using key words that address the relationship between vitamin D and cardiovascular disease. Correlations and interpretations were made considering the risks-benefits, broader evidence, and implications. This review analyzed current knowledge regarding the effects of vitamin D on the cardiovascular system. 1,25(OH)₂D and related epigenetic modifications subdue cellular inflammation, improve overall endothelial functions, reduce age-related systolic hypertension and vascular rigidity, and attenuate the actions of the renin-angiotensin-aldosterone system. Most observational and ecological studies support 25(OH)vitamin D having protective effects on the cardiovascular system. However, the association of vitamin D deficiency with cardiovascular diseases is based primarily on observational and ecological studies and thus, is a matter of controversy. Adequately powered, randomized controlled clinical trial data are not available to confirm these associations. Thus, to test the hypothesis that correction of vitamin D deficiency protects the cardiovascular system, well-designed, statistically powered, longer-term clinical trials are needed in persons with vitamin D deficiency. Nevertheless, the available data support that adequate vitamin D supplementation and/or sensible sunlight exposure to achieve optimal vitamin D status are important in the prevention of cardiovascular disease and other chronic diseases.

Controlling the Uptake and Regulating the Release of Nitric Oxide in Microporous Solids

Representative compounds from three classes of microporous solids, namely, metal-organic frameworks (MOFs), hybrid ultra-microporous materials (HUMs), and porous-organic polymers (POPs), were investigated for their nitric oxide gas uptake and release behavior. Low-pressure sorption studies indicated strong chemisorption of NO on the free amine groups decorating the MOF UiO-66-NH₂ when compared to its non-amine-functionalized parent. The HUMs demonstrated reversible physisorption within the low-pressure regime, but interestingly in one case there was evidence for chemisorption following pressurization with NO at 10 bar. Significant release of chemisorbed NO from the UiO-66-NH₂ and one of the HUMs was triggered by addition of acid to the medium, a pH change from 7.4 to 5.4 being sufficient to trigger NO release. An imidazole-based POP exhibited chemisorption of NO at high pressure wherein the ring basicity facilitated both NO uptake and spontaneous release upon contact with the aqueous release medium.

Nitrite enhances liver graft protection against cold ischemia reperfusion injury through a NOS independent pathway

INTRODUCTION

Nitrite has been found to protect liver graft from cold preservation injury. However, the cell signaling pathway involved in this protection remains unclear. Here, we attempt to clarify if the NOS pathway by using the NOS inhibitor, L-NAME (L-NG-Nitroarginine methyl ester).

ANIMALS AND METHODS

Rat livers were conserved for 24 h at 4°C in (IGL-1) solution enriched or not with nitrite at 50 nM. In a third group, rats were pretreated with 50 mg/kg of L-NAME before their liver procurement and preservation in IGL-1 supplemented with nitrite (50 nM) and L-NAME (1 mM). After 24 h of cold storage, rat livers were ex-vivo perfused at 37°C during 2 h. Control livers were perfused without cold storage.

RESULTS

Nitrite effectively protected the rat liver grafts from the onset of cold I/R injury. L-NAME treatment did not abolish the beneficial effects of nitrite. Liver damage, protein oxidation and lipid peroxidation remained at low levels in both nitrite-treated groups when compared to IGL-1 group. Antioxidant enzyme activities and functional parameters were unchanged after NOS inhibition.

CONCLUSION

Despite NOS inhibition by L-NAME, nitrite can still provide hepatic protection during cold I/R preservation. This suggests that nitrite acts through a NOS-independent pathway.

The latest advances in the discovery of nitric oxide hybrid drug compounds

INTRODUCTION

There is a great interest in Nitric oxide (NO) within medicinal chemistry since it's involved in human signaling pathways. Prodrugs or hybrid compounds containing NO-donor scaffolds linked to an active compound are valuable, due to their potential for modulating many pathological conditions due to NO's biological properties when released in addition to the native drug. Compounds that selectively inhibit nitric oxide synthase isoforms (NOS) can also increase therapeutic capacity, particularly in the treatment of chronic diseases. However, search for bioactive compounds to efficiently and selectively modulate NO is still a challenge in drug discovery. Areas covered: In this review, the authors highlight the recent advances in the strategies used to discover NO-hybrid derivatives, especially those related to anti-inflammatory, cardiovascular, anticancer and anti-microorganism activities. They also focus on: nitric oxide synthase inhibitors, NO delivery materials and other related activities. Expert opinion: The process of molecular hybridization can be used to obtain NO-releasing compounds that also interact with different targets. The main problem with this approach is to control NO multiple actions in the right biological system. However, the use of NO-releasing groups with many different scaffolds leads to new molecular structures for bioactive compounds, suggesting synergies.

Influence of NO and (NO)2 adsorption on the properties of Fe-N4 porphyrin-like graphene sheets

Fe-N4 porphyrin-like graphene catalysis and spin filter characteristics toward NO and (NO)₂ dimer adsorption.

NO Photoreleaser-Deoxyadenosine and -Bile Acid Derivative Bioconjugates as Novel Potential Photochemotherapeutics

This contribution reports the synthesis of some novel bioconjugates with anticancer activity and able to release nitric oxide (NO) under visible light excitation. The 4-nitro-2-(trifluoromethyl)aniline derivative, a suitable NO photodonor, was conjugated with 2'-deoxyadenosine and urso- and cheno-deoxycholic acid derivatives, through a thioalkylic chain or the 4-alkyl-1,2,3-triazole moiety. Photochemical experiments demonstrated the effective release of NO from 2'-deoxyadenosine and ursodeoxycholic acid conjugates under the exclusive control of visible light inputs. Studies for the in vitro antiproliferative activity against leukemic K562 and colon carcinoma HCT116 cell lines are reported for all the compounds as well as a case study of photocytotoxicity against HCT116.

Light-Tunable Generation of Singlet Oxygen and Nitric Oxide with a Bichromophoric Molecular Hybrid: a Bimodal Approach to Killing Cancer Cells

The design, synthesis, photochemical properties, and biological evaluation of a novel photoactivatable bichromophoric conjugate are reported. The compound 1, [4-(4,4-difluoro-2,6-diiodo-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacen-8-yl)-N-(3-((4-nitro-3-(trifluoromethyl)phenyl)amino)propyl)butanamide] combines a 2,6-diiodo-1,3,5,7-tetramethyl BODIPY derivative as singlet oxygen ((1) O2 ) photosensitizer and 4-nitro-3-(trifluoromethyl)aniline (NOPD) as nitric oxide (NO) photodonor, joined by an alkyl spacer. These two chromogenic units absorb in distinct regions of the visible spectrum, and their individual photochemical properties are conserved in the molecular conjugate. Irradiation of the bichromophoric conjugate with green light afforded (1) O2 in high quantum yields, whereas (1) O2 production was negligible with the use of blue light; under this latter condition, NO was released. Photogeneration of NO and cytotoxic (1) O2 can therefore be regulated by appropriately tuning the excitation light wavelength and intensity. Tested on melanoma cancer cells, this resulted in amplified photomortality relative to that of a structurally correlated model compound 2 [4-(4,4-difluoro-2,6-diiodo-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacen-8-yl)-N-(3-(p-tolylamino)propyl)butanamide] deprived of the NO-release capacity. The cellular uptake of 1, evaluated by confocal fluorescence microscopy, showed that the product is localized in the cytoplasm.

de Oliveira M, Brito GAC. Topical HPMC/S-Nitrosoglutathione Solution Decreases Inflammation and Bone Resorption in Experimental Periodontal Disease in Rats

S-nitrosoglutathione (GSNO) is a nitric oxide (NO) donor, which exerts antioxidant, anti-inflammatory, and microbicidal actions. Intragingival application of GSNO was already shown to decrease alveolar bone loss, inflammation and oxidative stress in an experimental periodontal disease (EPD) model. In the present study, we evaluated the potential therapeutic effect of topical applications of hydroxypropylmethylcellulose (HPMC)/GSNO solutions on EPD in Wistar rats. EPD was induced by placing a sterilized nylon (3.0) thread ligature around the cervix of the second left upper molar of the animals, which received topical applications of a HPMC solutions containing GSNO 2 or 10 mM or vehicle (HPMC solution), 1 h prior to the placement of the ligature and then twice daily until sacrifice on day 11. Treatment with HPMC/GSNO 10 mM solution significantly reduced alveolar bone loss, oxidative stress and TNF-α e IL-1β levels in the surrounding gingival tissue, and led to a decreased transcription of RANK and TNF-α genes and elevated bone alkaline phosphatase, compared to the HPMC group. In conclusion, topical application of HPMC/GSNO solution is a potential treatment to reduce inflammation and bone loss in periodontal disease.

Light-Induced Acid Generation on a Gatekeeper for Smart Nitric Oxide Delivery

We report herein the design of a light-responsive gatekeeper for smart nitric oxide (NO) delivery. The gatekeeper is composed of a pH-jump reagent as an intermediary of stimulus and a calcium phosphate (CaP) coating as a shielding layer for NO release. The light irradiation and subsequent acid generation are used as triggers for uncapping the gatekeeper and releasing NO. The acids generated from a light-activated pH-jump agent loaded in the mesoporous nanoparticles accelerated the degradation of the CaP-coating layers on the nanoparticles, facilitating the light-responsive NO release from diazeniumdiolate by exposing a NO donor to physiological conditions. Using the combination of the pH-jump reagent and CaP coating, we successfully developed a light-responsive gatekeeper system for spatiotemporal-controlled NO delivery.

Inhibitory Effects of JEUD-38, a New Sesquiterpene Lactone from Inula japonica Thunb, on LPS-Induced iNOS Expression in RAW264.7 Cells

We isolated JEUD-38, a new sesquiterpene lactone from Inula japonica Thunb. JEUD-38 dramatically attenuated lipopolysaccharide (LPS)-induced nitric oxide (NO) production. Consistent with this finding, the protein expression of inducible nitric oxide synthase (iNOS) was blocked by JEUD-38 in a concentration-dependent manner. To elucidate the mechanism, we examined the effect of JEUD-38 on LPS-stimulated nuclear factor-κB (NF-κB) nuclear translocation, inhibitory factor-κB (IκB) phosphorylation, and degradation. JEUD-38 reduced the translocation of p65, via abrogating IκB-α phosphorylation and degradation. In addition, JEUD-38 inhibited LPS-stimulated phosphorylation of mitogen-activated protein kinases (MAPKs) including extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38. Since iNOS as well as the upstream NF-κB and MAPKs are known to be closely involved in inflammation, these results suggest that JEUD-38 is a promising candidate for prevention and therapy of inflammatory diseases.

The Protective and Therapeutic Effect of Exclusive and Combined Treatment with Alpha-ketoglutarate Sodium Salt and Ipriflavone on Bone Loss in Orchidectomized Rats

OBJECTIVE

This study investigated the effect of alpha-ketoglutarate sodium salt (AKG) and ipriflavone (IP) treatment on the mineralization of the tibia in male rats during the development and after the establishment of osteopenia.

DESIGN

One hundred and twenty eight male rats were randomly selected and submitted to either sham-operation (SHO) or orchidectomy (ORX), after which each group were then randomly divided between the two experiments. In Experiment-1, treatment with AKG or/and IP started after a 7-day recovery period, whereas in Experiment-2, the experimental protocol proceeded after a 60-day period of osteopenia establishment. AKG was then administered as an experimental drinking, at a concentration of 1.0 mol/l. As a control, a placebo solution was administered. IP at 50 mg/kg b.w., and physiological saline - PhS (as a control for IP) were applied daily via gavage.

MEASUREMENTS

After 60 days of experimental treatment, in both experiments, the rats were sacrificed, their body weight recorded, while blood serum (Osteocalcin, CTX) and isolated tibia (weight, length, pQCT, DXA, 3-point bending test) were stored for further analysis.

RESULTS AND CONCLUSIONS

Our results show that during the development of osteopenia, AKG and IP when applied exclusively, counteracts osteopenia development, whereas their usage after the establishment of osteopenia, significantly limits the development of bone disorders. Furthermore, combined treatment of AKG and IP exceeded the effects of their sole usage. In addition, during the development of osteopenia, AKG and IP not only inhibited bone resorption, but markedly stimulated the formation of bone tissue. Finally, after the development of osteopenia, combined treatment with AKG and IP protected the bone tissue against orchidectomy-induced bone loss.

Anti-Inflammatory Activity of Triterpenes Isolated from Protium paniculatum Oil-Resins

Protium is the main genus of the Burseraceae family and one of the most common genera in South America, with an important species called “breu.” Gum and oil-resins of this species are used as tonic and stimulant and for the treatment of ulcers and inflammation. The present study aims to isolate and investigate the anti-inflammatory activity of triterpene compounds isolated from oil-resin of Protium paniculatum. The pentacyclic triterpenes α,β-amyrin, acetylated α,β-amyrin, α,β-amyrone, and brein/maniladiol did not alter the viability of murine J774 macrophages (IC₅₀ > 20 µg/mL), with the exception of mixture of brein/maniladiol which showed moderate cytotoxic activity. Also it was observed that compounds at 10 µg/mL inhibited more than 80% of production of NO^•, although only α,β-amyrin was able to inhibit the production of TNF-α (52.03 ± 2.4%). The compounds inhibited the production of IL-6 and induced the production of IL-10 in murine J774 macrophages stimulated by LPS. α,β-Amyrone inhibited the expression of COX-2 and also inhibited the formation of paw or ear edema in rats and mice, having a quick and immediate effect. This study may provide the basis for future investigations on the therapeutic role of α,β-amyrone in treating inflammation.

Is beetroot juice more effective than sodium nitrate? The effects of equimolar nitrate dosages of nitrate-rich beetroot juice and sodium nitrate on oxygen consumption during exercise

Dietary nitrate has been reported to lower oxygen consumption in moderate- and severe-intensity exercise. To date, it is unproven that sodium nitrate (NaNO3(-); NIT) and nitrate-rich beetroot juice (BR) have the same effects on oxygen consumption, blood pressure, and plasma nitrate and nitrite concentrations or not. The aim of this study was to compare the effects of different dosages of NIT and BR on oxygen consumption in male athletes. Twelve healthy, well-trained men (median [minimum; maximum]; peak oxygen consumption: 59.4 mL·min(-1)·kg(-1) [40.5; 67.0]) performed 7 trials on different days, ingesting different nitrate dosages and placebo (PLC). Dosages were 3, 6, and 12 mmol nitrate as concentrated BR or NIT dissolved in plain water. Plasma nitrate and nitrite concentrations were measured before, 3 h after ingestion, and postexercise. Participants cycled for 5 min at moderate intensity and further 8 min at severe intensity. End-exercise oxygen consumption at moderate intensity was not significantly different between the 7 trials (p = 0.08). At severe-intensity exercise, end-exercise oxygen consumption was ~4% lower in the 6-mmol BR trial compared with the 6-mmol NIT (p = 0.003) trial as well as compared with PLC (p = 0.010). Plasma nitrite and nitrate concentrations were significantly increased after the ingestion of BR and NIT with the highest concentrations in the 12-mmol trials. Plasma nitrite concentration between NIT and BR did not significantly differ in the 6-mmol (p = 0.27) and in the 12-mmol (p = 0.75) trials. In conclusion, BR might reduce oxygen consumption to a greater extent compared with NIT.

Prophylactic treatment for preeclampsia in high-risk teenage primigravidae with nitric oxide donors: a pilot study

OBJECTIVES

Preeclampsia is associated with significant morbidity and mortality especially in high-risk groups. Impairment of endogenous nitric oxide has been shown to be associated with the disease and prophylactic therapy may ameliorate this condition and improve pregnancy outcome. This study valuated nitric oxide donors prophylactic treatment for preeclampsia in high-risk teenage primigravidae.

METHODS

The study included three hundred primigravidae aged ≤ 20 years with singleton pregnancy. Abdominal pulsed color Doppler ultrasound was done at 24 weeks gestation and pregnancies with uterine artery diastolic notch were randomly allocated to a control group received placebo vaginal tablets and a study group received isosorbid mononitrate 20 mg tablet once daily applied vaginally until delivery.

OUTCOMES

Incidence of preeclampsia and maternal, fetal, and neonatal outcome in both groups.

RESULTS

The study group had significant lower incidence of preeclampsia, preterm birth, intrauterine growth restriction and of neonatal admission to the intensive care (p < 0.05).

CONCLUSIONS

Nitric oxide donors prophylactic treatment for preeclampsia in high-risk teenage pregnancies decrease the incidence of preeclampsia and improve maternal, fetal, and neonatal outcomes. Further studies on larger sample size are required to confirm these results.

Nitric oxide therapy for dermatologic disease

Nitric oxide (NO) plays an important role in the maintenance and regulation of the skin and the integrity of its environment. Derangement of NO production is implicated in the etiology of a multitude of dermatologic diseases, indicating future therapeutic directions. In an era of increasing resistance rates to available antibiotics and subpar development of new agents, NO is promising as a prospective topical broad-spectrum antimicrobial agent with small likelihood of resistance development. Because the greatest strides have been made in the setting of infectious disease and skin and soft-tissue infection, this will be a major focus of this article. In addition, we will review NO's role in skin regulation and dysregulation, immune function, the various topical release systems that have been devised and tested, NO's relation to UV radiation and skin pigmentation, and finally, its potential applications as a cosmeceutical.

Oximes induce erection and are resistant to oxidative stress

INTRODUCTION

Because of their nitric oxide (NO)-donating capacities, oxime derivatives have shown to offer some therapeutic perspective for the treatment of erectile dysfunction (ED) as well as cardiovascular diseases. However, to date the in vivo effect of these oximes on erectile function remains unknown. In many disease states oxidative stress occurs, impairing NO-mediated relaxations. Hence the influence of oxidative stress on oxime-induced effects is also of interest.

AIMS

This study aimed to evaluate the in vivo effect of formaldoxime (FAL) and formamidoxime (FAM) on blood pressure and intracavernosal pressure (ICP); and to examine the role of soluble guanylyl cyclase (sGC) and the influence of oxidative stress on the FAL and FAM responses.

METHODS

Blood pressure and ICP were monitored in vivo after resp. intravenous or intracavernosal injection of FAL and FAM. Moreover isometric tension was measured in vitro on isolated mice corpora cavernosa (CC), thoracic aorta, and femoral artery in organ baths. The role of sGC was investigated using transgenic mice lacking the alpha 1 subunit of sGC.

MAIN OUTCOME MEASURES

Mean arterial pressure (MAP) and ICP were measured after FAL/FAM injection. In vitro relaxation of CC strips was evaluated in response to addition of FAL/FAM.

RESULTS

In vivo both FAL and FAM elicit a dose-dependent lowering of blood pressure (maximal ΔMAP: 33.66 ± 4.07 mm Hg [FAL] and 20.43 ± 2.06 mm Hg [FAM] ) as well as an increase of ICP (maximal increase of ICP/MAP: 70.29 ± 2.88% [FAL] and 52.91 ± 8.61% [FAM] ). The FAL/FAM effect is significantly lower in knockout vs. wild-type mice. Oxidative stress has an inhibitory effect on corporal NO-mediated relaxations induced by electrical field stimulation, acetylcholine, and sodium nitroprusside whereas the responses to 8-(4-chlorophenylthio)-guanosine 3',5'-cyclic monophosphate sodium salt, FAL and FAM were not influenced.

CONCLUSIONS

Oximes induce erection which is mediated by sGC. The oxime-induced relaxations are resistant to oxidative stress, which increases their therapeutic potential for the treatment of ED.

The regulation of BK channel activity by pre- and post-translational modifications

Large conductance, Ca²⁺-activated K⁺ (BK) channels represent an important pathway for the outward flux of K⁺ ions from the intracellular compartment in response to membrane depolarization, and/or an elevation in cytosolic free [Ca²⁺]. They are functionally expressed in a range of mammalian tissues (e.g., nerve and smooth muscles), where they can either enhance or dampen membrane excitability. The diversity of BK channel activity results from the considerable alternative mRNA splicing and post-translational modification (e.g., phosphorylation) of key domains within the pore-forming α subunit of the channel complex. Most of these modifications are regulated by distinct upstream cell signaling pathways that influence the structure and/or gating properties of the holo-channel and ultimately, cellular function. The channel complex may also contain auxiliary subunits that further affect channel gating and behavior, often in a tissue-specific manner. Recent studies in human and animal models have provided strong evidence that abnormal BK channel expression/function contributes to a range of pathologies in nerve and smooth muscle. By targeting the upstream regulatory events modulating BK channel behavior, it may be possible to therapeutically intervene and alter BK channel expression/function in a beneficial manner.

Effect of topically applied sildenafil citrate on wound healing: experimental study

Wound healing is a complex process that necessitates organization of different cell types and several signalling molecules. The aim of this study is to evaluate the effect of different concentrations of sildenafil citrate, which decreases cGMP degradation, on wound healing by secondary intention.This study was performed using 25 Sprague Dawley rats weighing 200-250 grams. 4 dorsal defects were created. Four different treatment modalities which were 1% and 5% sildenafil citrate gel prepared with carbopol, pure carbopol gel without any drug in it and 0,9% NaCl solution; were applied to each lesion of the same rat. Randomly selected five rats (25 rats in total) were sacrificed on 3rd, 5th, 7th, 10th, and 14th days; and the effect of each modality was evaluated by means of defect area measurement, histopathological examination and measurement of tissue hydroxyproline levels.Sildenafil citrate gel application decreased the defect areas in a dose independent manner starting from 3rd day and dose dependent manner after 7th day. By means of vascularization, sildenafil citrate increased vascularity starting from 3rd day. The strength of acute inflammation was superior in sildenafil groups starting from 5th day; and the amount and maturation of granulation in the wound bed, as well as the strength of chronic inflammation were superior in defects treated with sildenafil citrate as early as 7th day.

A spontaneous animal model of intestinal dysmotility evoked by inflammatory nitrergic dysfunction

Background and Aims

Recent reports indicate the presence of low grade inflammation in functional gastrointestinal disorders (FGID), in these cases often called “post-inflammatory” FGIDs. However, suitable animal models to study these disorders are not available. The Biobreeding (BB) rat consists of a diabetes-resistant (BBDR) and a diabetes-prone (BBDP) strain. In the diabetes-prone strain, 40–60% of the animals develop diabetes and concomitant nitrergic dysfunction. Our aim was to investigate the occurrence of intestinal inflammation, nitrergic dysfunction and intestinal dysmotility in non-diabetic animals.

Methods

Jejunal inflammation (MPO assay, Hematoxylin&Eosin staining and inducible nitric oxide synthase (iNOS) mRNA expression), in vitro jejunal motility (video analysis) and myenteric neuronal numbers (immunohistochemistry) were assessed in control, normoglycaemic BBDP and diabetic BBDP rats. To study the impact of iNOS inhibition on these parameters, normoglycaemic BBDP rats were treated with aminoguanidine.

Results

Compared to control, significant polymorphonuclear (PMN) cell infiltration, enhanced MPO activity, increased iNOS mRNA expression and a decreased ratio of nNOS to Hu-C/D positive neurons were observed in both normoglycaemic and diabetic BBDP rats. Aminoguanidine treatment decreased PMN infiltration, iNOS mRNA expression and MPO activity. Moreover, it restored the ratio of nNOS to Hu-C/D positive nerves in the myenteric plexus and decreased the abnormal jejunal elongation and dilation observed in normoglycaemic BBDP rats.

Conclusions

Aminoguanidine treatment counteracts the inflammation-induced nitrergic dysfunction and prevents dysmotility, both of which are independent of hyperglycaemia in BB rats. Nitrergic dysfunction may contribute to the pathophysiology of “low-grade inflammatory” FGIDs. Normoglycaemic BBDP rats may be considered a suitable animal model to study the pathogenesis of FGIDs.

Inhibitory effects of a spinasterol glycoside on lipopolysaccharide-induced production of nitric oxide and proinflammatory cytokines via down-regulating MAP kinase pathways and NF-κB activation in RAW264.7 macrophage cells

Extracts from the leaves of Stewartia koreana are known to exhibit strong anti-inflammatory activity. Investigation of bioactive compounds from S. koreana has led to the isolation of 3-O-β-d-glucopyanosylspinasterol (spinasterol-Glc), a spinasterol glycoside. In the present study, we examined the effects of spinasterol-Glc on production of nitric oxide (NO) and proinflammatory cytokines in LPS-treated RAW264.7 macrophage cells and in mouse models. Our results showed that spinasterol-Glc inhibited the production of NO and proinflammatory cytokines such as TNF-α, IL-6 and IL-1β in dose-dependent manners in LPS-treated RAW264.7 cells. Spinasterol-Glc inhibited the expression of iNOS and the proinflammatory cytokine genes. Spinasterol-Glc also inhibited phosphorylation of IκB-α and IKKα/β as well as translocation of NF-κB to the nucleus. We demonstrated that spinasterol-Glc reduced transcription of the NF-κB minimal promoter and NF-κB DNA binding activity. Administration of the spinasterol-Glc significantly decreased the plasma levels of these inflammatory mediators including TNF-α, IL-6 and IL-1β in LPS-injected mice and improved survival of septic mice with lethal endotoxemia. These results suggest that spinasterol-Glc has effective inhibitory effects on production of inflammatory mediators via inhibition of MAP kinases/NF-κB activities, and can be used as a potential anti-inflammatory agent for the prevention and treatment of inflammatory diseases.

Cucurbitacin L 2-O-β-Glucoside Demonstrates Apoptogenesis in Colon Adenocarcinoma Cells (HT-29): Involvement of Reactive Oxygen and Nitrogen Species Regulation

Emerging evidence suggests that reactive oxygen (ROS) and nitrogen (RNS) species can contribute to diverse signalling pathways of inflammatory and tumour cells. Cucurbitacins are a group of highly oxygenated triterpenes. Many plants used in folk medicine to treat cancer have been found to contain cucurbitacins displaying potentially important anti-inflammatory actions. The current study was designed to investigate the anti-ROS and -RNS effects of cucurbitacin L 2-O-β-glucoside (CLG) and the role of these signaling factors in the apoptogenic effects of CLG on human colon cancer cells (HT-29). This natural cucurbitacin was isolated purely from Citrullus lanatus var. citroides (Cucurbitaceae). The results revealed that CLG was cytotoxic to HT-29. CLG increased significantly (P < 0.05) RNA and protein levels of caspase-3 in HT-29 cells when verified using a colorimetric assay and realtime qPCR, respectively. The results showed that lipopolysaccharide/interferon-gamma (LPS/INF-γ) increased nitrous oxide (NO) production inR AW264.7macrophages, whereas N(G)-nitro-L-argininemethyl ester (L-NAME) and CLG curtailed it. This compound did not reveal any cytotoxicity on RAW264.7 macrophages and human normal liver cells (WRL-68) when tested using the MTT assay. Findings of ferric reducing antioxidant power (FRAP) and oxygen radical absorption capacity (ORAC) assays demonstrate the antioxidant properties of CLG. The apoptogenic property of CLG on HT-29 cells is thus related to inhibition of reactive nitrogen and oxygen reactive species and the triggering of caspase-3-regulated apoptosis.

Emerging therapies for osteoporosis

This article reviews the conceptual framework for agents that are antiresorptive or anabolic, including pathways that affect bone formation and resorption, and the steps in those pathways that are targets for new therapeutic agents. This article discusses novel antiresorptive and anabolic agents in development. Recent developments that link bone remodeling with serotonin in the gastrointestinal system and the central nervous system via the sympathetic nervous system may change the paradigm for skeletal remodeling. Novel anabolic agents in development include antibodies that target molecules involved in Wnt signaling.

Effects of slow, sustained, and rate-tunable nitric oxide donors on human aortic smooth muscle cells proliferation

Smooth muscle cell (SMC) proliferation has been accepted as a common event in the pathophysiology of vascular diseases, including atherogenesis and intimal hyperplasia. Delivery of the nitric oxide synthase (NOS) substrate l-arginine, pharmacological nitric oxide (NO) donors, NO gas or overexpression of NOS proteins can inhibit SMC proliferation and reduce the injury responses within the blood vessel wall. Although commercial development of NO donors that attempt to provide exogenous delivery of NO has accelerated over the last few years, none of the currently available products can provide controlled, sustained, time-tunable release of NO. Nitrosamine-based NO donors, prepared in our laboratory, present a unique and innovative alternative for possible treatments for long-term NO deficiency-related diseases, including atherosclerosis, asthma, erectile dysfunction, cancer, and neurodegenerative diseases. A family of secondary amines prepared via nucleophilic aromatic displacement reactions could be readily N-nitrosated to produce NO donors. NO release takes place in three distinct phases. During the initial phase, the release rate is extremely fast. In the second phase, the release is slower and the rate remains essentially the same during the final stage. These compounds inhibited up to 35% human aortic smooth muscle cell proliferation in a concentration-dependent manner.

Hepatic gene expression profiling of 5'-AMP-induced hypometabolism in mice

There is currently much interest in clinical applications of therapeutic hypothermia. Hypothermia can be a consequence of hypometabolism. We have recently established a procedure for the induction of a reversible deep hypometabolic state in mice using 5'-adenosine monophosphate (5'-AMP) in conjunction with moderate ambient temperature. The current study aims at investigating the impact of this technology at the gene expression level in a major metabolic organ, the liver. Our findings reveal that expression levels of the majority of genes in liver are not significantly altered by deep hypometabolism. However, among those affected by hypometabolism, more genes are differentially upregulated than downregulated both in a deep hypometabolic state and in the early arousal state. These altered gene expression levels during 5'-AMP induced hypometabolism are largely restored to normal levels within 2 days of the treatment. Our data also suggest that temporal control of circadian genes is largely stalled during deep hypometabolism.

Systemic nitric oxide clamping in normal humans guided by total peripheral resistance

AIM

We wanted to stabilize the availability of nitric oxide (NO) at levels compatible with normal systemic haemodynamics to provide a model for studies of complex regulations in the absence of changes in NO levels.

METHODS

Normal volunteers (23-28 years) were infused i.v. with the nitric oxide synthase (NOS) inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME) at 0.5 mg kg(-1) h(-1). One hour later, the NO donor sodium nitroprusside (SNP) was co-infused in doses eliminating the haemodynamic effects of l-NAME. Haemodynamic measurements included blood pressure (MABP) and cardiac output (CO) by impedance cardiography.

RESULTS

l-NAME increased MABP and total peripheral resistance (TPR, 1.02 + or - 0.05 to 1.36 + or - 0.07 mmHg s mL(-1), mean + or - SEM, P < 0.001). With SNP, TPR fell to a stable value slightly below control (0.92 + or - 0.05 mmHg s mL(-1), P < 0.05). CO decreased with l-NAME (5.8 + or - 0.3 to 4.7 + or - 0.3 L min(-1), P < 0.01) and returned to control when SNP was added (6.0 + or - 0.3 L min(-1)). A decrease in plasma noradrenaline (42%, P < 0.01) during l-NAME administration was completely reversed by SNP. Plasma renin activity decreased during l-NAME administration and returned towards normal after addition of SNP. In contrast, plasma aldosterone was increased by l-NAME and remained elevated.

CONCLUSIONS

Concomitant NOS inhibition and NO donor administration can be adjusted to maintain TPR at control level for hours. This approach may be useful in protocols in which stabilization of the peripheral supply of NO is required. However, the dissociation between renin and aldosterone secretion needs further investigation.

Transdermal nitroglycerin therapy may not prevent early postmenopausal bone loss

CONTEXT

Osteoporosis is common among postmenopausal women; animal studies and human pilot studies support the concept of nitric oxide (NO) donors reducing bone mineral density loss.

OBJECTIVE

The objective of the study was to evaluate whether NO donor, nitroglycerin, prevents postmenopausal bone loss.

DESIGN

This was a 3-yr randomized, double blinded, single-center, placebo-controlled clinical trial.

SETTING

The single-center study was conducted at the University of Medicine and Dentistry-Robert Wood Johnson Medical School (New Brunswick, NJ).

PARTICIPANTS

Participants included 186 postmenopausal women aged 40-65 yr, with lumbar bone mineral density (BMD) T-scores of 0 to -2.5.

INTERVENTION

Women, stratified by lumbar T-score (<-1.50 and >or=-1.50) and years since menopause (5 yr), were randomized to receive nitroglycerin ointment (22.5 mg as Nitro-Bid) or placebo ointment received daily for 3 yr. Both groups took 630 mg daily calcium plus 400 IU vitamin D supplements.

MEASUREMENTS

BMD was measured at 6 months and annually by dual-energy x-ray absorptiometry. Percent change in lumbar vertebrae BMD was the primary outcome. Hip BMD, total body bone mineral content, and height were secondary outcomes.

RESULTS

After 36 months of therapy, changes of -2.1% in the active group (n = 88) and -2.5% in the placebo group (n = 82) in lumbar spine BMD were seen (P = 0.59; 95% confidence interval -1.001, 1.975). Secondary outcomes also did not differ by intervention arm. The active group reported more headaches compared with the placebo group (57 vs. 14%, P < 0.001). Other adverse and serious adverse events were not different.

CONCLUSIONS

BMD changes did not substantially differ between postmenopausal women who received the dose of nitroglycerin tested, in comparison with a placebo. Once-daily dosing with 22.5 mg of transdermal-administered nitroglycerin was not effective (compliance adjusted dose was only approximately 16 mg/d); a sub-therapeutic dose.

Nitric oxide-loaded echogenic liposomes for nitric oxide delivery and inhibition of intimal hyperplasia

OBJECTIVES

We sought to develop a new bioactive gas-delivery method by the use of echogenic liposomes (ELIP) as the gas carrier.

BACKGROUND

Nitric oxide (NO) is a bioactive gas with potent therapeutic effects. The bioavailability of NO by systemic delivery is low with potential systemic effects.

METHODS

Liposomes containing phospholipids and cholesterol were prepared by the use of a new method, freezing under pressure. The encapsulation and release profile of NO from NO-containing ELIP (NO-ELIP) or a mixture of NO/argon (NO/Ar-ELIP) was studied. The uptake of NO from NO-ELIP by cultured vascular smooth muscle cells (VSMCs) both in the absence and presence of hemoglobin was determined. The effect of NO-ELIP delivery to attenuate intimal hyperplasia in a balloon-injured artery was determined.

RESULTS

Coencapsulation of NO with Ar enabled us to adjust the amount of encapsulated NO. A total of 10 microl of gas can be encapsulated into 1 mg of liposomes. The release profile of NO from NO-ELIP demonstrated an initial rapid release followed by a slower release during the course of 8 h. Sixty-eight percent of cells remained viable when incubated with 80 microg/ml of NO/Ar-ELIP for 4 h. The delivery agent of NO to VSMCs by the use of NO/Ar-ELIP was 7-fold greater than unencapsulated NO. We discovered that NO/Ar-ELIP remained an effective delivery agent of NO to VSMCs even in the presence of hemoglobin. Local NO-ELIP administration to balloon-injured carotid arteries attenuated the development of intimal hyperplasia and reduced arterial wall thickening by 41 +/- 9%.

CONCLUSIONS

Liposomes can protect and deliver a bioactive gas to target tissues with the potential for both visualization of gas delivery and controlled therapeutic gas release.

Hydrogen sulfide and the vasculature: a novel vasculoprotective entity and regulator of nitric oxide bioavailability?

Hydrogen sulfide (H₂S) is a well known and pungent toxic gas that has recently been shown to be synthesised in man from the amino acids cystathionine, homocysteine and cysteine by at least two distinct enzymes; cystathionine-γ-lyase and cystathionine-β-synthase. In the past few years, H₂S has emerged as a novel and increasingly important mediator in the cardiovascular system but delineating the precise physiology and pathophysiology of H₂S is proving to be complex and difficult to unravel with disparate findings reported with cell types, tissue types and animal species reported. Therefore, in this review we summarize the mechanisms by which H₂S has been proposed to regulate blood pressure and cardiac function, discuss the mechanistic discrepancies reported in the literature as well as the therapeutic potential of H₂S. We also examine the methods of H₂S detection in biological fluids, processes for H₂S removal and discuss the reported blood levels of H₂S in man and animal models of cardiovascular pathology. We also highlight the complex interaction of H₂S with nitric oxide in regulating cardiovascular function in health and disease.