A divergent mode of activation of a nitrosyl iron complex with unusual antiangiogenic activity.

Nitric oxide (NO) and nitroxyl (HNO) have gained broad attention due to their roles in several physiological and pathophysiological processes. Remarkably, these sibling species can exhibit opposing effects including the promotion of angiogenic activity by NO compared to HNO, which blocks neovascularization. While many NO donors have been developed over the years, interest in HNO has led to the recent emergence of new donors. However, in both cases there is an expressive lack of iron-based compounds. Herein, we explored the novel chemical reactivity and stability of the trans-[Fe(cyclam)(NO)Cl]Cl2 (cyclam = 1,4,8,11-tetraazacyclotetradecane) complex. Interestingly, the half-life (t1/2) for NO release was 1.8 min upon light irradiation, vs 5.4 h upon thermal activation at 37 °C. Importantly, spectroscopic evidence supported the generation of HNO rather than NO induced by glutathione. Moreover, we observed significant inhibition of NO donor- or hypoxia-induced HIF-1α (hypoxia-inducible factor 1α) accumulation in breast cancer cells, as well as reduced vascular tube formation by endothelial cells pretreated with the trans-[Fe(cyclam)(NO)Cl]Cl2 complex. Together, these studies provide the first example of an iron-nitrosyl complex with anti-angiogenic activity as well as the potential dual activity of this compound as a NO/HNO releasing agent, which warrants further pharmacological investigation.

Stability of Alprostadil in 0.9% Sodium Chloride Stored in Polyvinyl Chloride Containers.

The stability of alprostadil diluted in 0.9% sodium chloride stored in polyvinyl chloride (VIAFLEX) containers at refrigerated temperature, protected from light, is reported. Five solutions of alprostadil 11 mcg/mL were prepared in 250 mL 0.9% sodium chloride polyvinyl chloride (PL146) containers. The final concentration of alcohol was 2%. Samples were stored under refrigeration (2°C to 8°C) with protection from light. Two containers were submitted for potency testing and analyzed in duplicate with the stability-indicating high-performance liquid chromatography assay at specific time points over 14 days. Three containers were submitted for pH and visual testing at specific time points over 14 days. Stability was defined as retention of 90% to 110% of initial alprostadil concentration, with maintenance of the original clear, colorless, and visually particulate-free solution. Study results reported retention of 90% to 110% initial alprostadil concentration at all time points through day 10. One sample exceeded 110% potency at day 14. pH values did not change appreciably over the 14 days. There were no color changes or particle formation detected in the solutions over the study period. This study concluded that during refrigerated, light-protected storage in polyvinyl chloride (VIAFLEX) containers, a commercial alcohol-containing alprostadil formulation diluted to 11 mcg/mL with 0.9% sodium chloride 250 mL was stable for 10 days.

Effect of 1440-nanometer neodymium:yttrium-aluminum-garnet laser irradiation on pain and neuropeptide reduction: a randomized prospective clinical trial.

INTRODUCTION: The purpose of this study was to investigate the efficacy of a 1440-nm neodymium:yttrium-aluminum-garnet (Nd:YAG) laser on relieving pain in relation to the levels of inflammatory cytokine and neuropeptides in the root canal exudates of teeth with persistent symptomatic apical periodontitis. METHODS: Forty teeth with persistent symptomatic apical periodontitis were randomly assigned to treatment groups: group L, intracanal irradiation of 1440-nm Nd:YAG laser with a 300-µm-diameter fiberoptic tip in addition to conventional root canal retreatment, and group C, conventional root canal re-treatment. The degrees of both spontaneous pain and the pain on percussion before and after treatment were recorded, and root canal exudate samples were collected to quantify the associated levels of substance P, calcitonin gene-related peptide (CGRP), and matrix metalloproteinase (MMP)-8 by immunoassay. RESULTS: All of the measured parameters were significantly reduced in group L (P < .05), whereas the level of pain on percussion, CGRP, and MMP-8 were significantly reduced in group C (P < .05). The 1440-nm Nd:YAG laser had significantly better effect on the relief of pain on percussion and the reduction of substance P, CGRP, and MMP-8 levels. The visual analog scale scores of perceived pain correlated with pain-related neuropeptides and inflammatory cytokine levels in root canal exudates. CONCLUSIONS: The 1440-nm Nd:YAG laser irradiation via fiberoptic tip to the teeth with persistent apical periodontitis provided promising consequences of pain and inflammation modulation.

The macrocyclic effect and vasodilation response based on the photoinduced nitric oxide release from trans-[RuCl(tetraazamacrocycle)NO](2+).

Irradiation of trans-[RuCl(cyclam)(NO)](2+), cyclam is 1,4,8,11-tetraazacyclotetradecane, at pHs 1-7.4, with near UV light results in the release of NO and formation of trans-[Ru(III)Cl(OH)(cyclam)](+) with pH dependent quantum yields (from approximately 0.01 to 0.16 mol Einstein(-1)) lower than that for trans-[RuCl([15]aneN(4))(NO)](2+), [15]aneN(4) is 1,4,8,12-tetaazacyclopentadecane, (0.61 mol Einstein(-1)). After irradiation with 355 nm light, the trans-[RuCl([15]aneN(4))(NO)](2+) induces relaxation of the aortic ring, whereas the trans-[RuCl(cyclam)(NO)](2+) complex does not. The relaxation observed with trans-[RuCl([15]aneN(4))(NO)](2+) is consistent with a larger quantum yield of release of NO from this complex.

Biological activity of designed photolabile metal nitrosyls: light-dependent activation of soluble guanylate cyclase and vasorelaxant properties in rat aorta.

The biological and pharmacological utility of nitric oxide (NO) has led to the development of many classes of NO-donor compounds as both research tools and therapeutic agents. Many donors currently in use rely on thermal decomposition or bioactivation for the release of NO. We have developed several photolabile metal-nitrosyl donors that release NO when exposed to either visible or UV light. Herein, we show that these donors are capable of activating the primary "NO receptor", soluble guanylate cyclase (sGC), in a light-dependent fashion leading to increases in cGMP. Moreover, we demonstrate that these donors are capable of eliciting light-dependent increases of cGMP in smooth muscle cells and vasorelaxation of rat aortic smooth muscle tissue, all effects that are attributed to activation of sGC. The potential utility of these compounds as drugs and/or research tools is discussed.

Particular features of photolabile substances in tablets.

Nifedipine and molsidomine tablets are extremely photolabile drug preparations, even at cool room light. Compared to solutions the light spectrum responsible for photodegradation is moved towards the long-wavelength range corresponding to the bathochromic shift of light absorption in the solid state. In the case of nifedipine tablets light up to 500 nm, especially the range between 400-420 nm, is degrading. Molsidomine tablets are affected only by ultraviolet light, but not by visible light. In both cases light penetrates less than 1 mm into the tablets. For nifedipine tablets the exact penetration depth could be determined due to the discolouration of the drug substance upon irradiation. It varied from 360 microm to 880 microm depending on the drug content. Since the decomposition products of nifedipine act as photostabilizers by spectral overlay, light penetration and photodegradation in nifedipine tablets are limited. The formation of gaseous and liquid decomposition products in molsidomine tablets enhances photodegradation. Changes of the tablet structure as well as dissolution and migration processes are discussed. Furthermore the degradation products donot photostabilize the drug substance due to the missing light absorption above 300 nm.

The influence of formulation and manufacturing process on the photostability of tablets.

The formulation and the manufacturing process can significantly influence the photostability of tablets. Investigations of various formulation and manufacturing parameters were done with tablets containing nifedipine and molsidomine as highly light sensitive drugs. The effect of relevant formulation factors are stated. Whereas the particle size of the drug substance and the choice of the lubricant had no effect, the drug content, the compression diluent and geometric alterations significantly affected the photoinstability. Depending on the formulation drug losses varied between 30 and 55% after 12 h irradiation in a light testing cabinet (Suntest CPS+). Manufacturing parameters like compression force and direct compression versus granulation showed less serious influences. Nevertheless, photostability changes up to 10% were registered.

Stability of fenoldopam mesylate in two infusion solutions.

The physical and chemical stability of fenoldopam as the mesylate salt were studied. Test samples of fenoldopam mesylate, with fenoldopam concentrations ranging from 4 to 300 micrograms/mL, were prepared in polyvinyl chloride (PVC) bags of 5% dextrose injection and 0.9% sodium chloride injection and were stored at 4 degrees C in the dark and 23 degrees C in ambient fluorescent light. Physical and chemical stability were evaluated at 0, 24, 48, and 72 hours. Physical stability was assessed by visual observation in fluorescent light and using a high-intensity monodirectional light beam. Turbidity and particle content were measured electronically. Chemical stability of fenoldopam mesylate was evaluated by using a stability-indicating high-performance liquid chromatographic analytical technique. All samples were physically stable throughout the study. Little or no change in particulate burden and haze level was found. Little or no loss of fenoldopam occurred in concentrations of 40 micrograms/mL or greater at either temperature throughout the study period. At the lowest concentrations, minor losses of 3-5% were found. Fenoldopam mesylate, prepared in fenoldopam concentrations ranging from 4 to 300 micrograms/mL, was physically and chemically stable in PVC bags of 5% dextrose and 0.9% sodium chloride injections for 72 hours when stored at 4 degrees C in the dark and 23 degrees C when exposed to ambient fluorescent light.

Local vasodilator response to mobile phones.

OBJECTIVES: The use of mobile phones with the resulting generation of potentially harmful electromagnetic fields (EMF) is the focus of public interest. Heat generation and the activation of the inducible form of nitric oxide (NO) synthase may be possible causes of the biological effects of EMF exposure. We investigated if a mobile telephone conversation can modify skin temperature, NO, and nasal resistance. METHODS: We studied the effect of an EMF (900 MHz) generated by a commercially available cellular phone during a 30-minute telephone conversation on skin temperature, nasal NO measured by chemiluminescence, and nasal minimal cross-sectional area (MCA) measured by rhinometry. Eleven normal subjects (mean age +/- standard error of mean [SEM], 32 +/- 5 y; 10 male) were studied. RESULTS: There was a similar and significant increase in skin temperature of the nostril and occipital area on the same side as the telephone (maximal increase 2.3 +/- 0.2 degrees C at 6 min) as well as a tendency for higher nasal NO levels (maximal increase 12.9 +/- 4.9% at 10 min), whereas the MCA was significantly reduced (maximal decrease -27 +/- 6% at 15 min). Such changes were not recorded when an earpiece was used to avoid the direct exposure to the electromagnetic field. There were no changes in the skin temperature and nasal NO measured on the opposite side to the mobile phone, whereas the MCA was significantly increased (38 +/- 10%). CONCLUSIONS: Exposure to EMF produced by a mobile phone produces biological effects that can be easily measured. Microwaves may increase skin temperature and therefore cause vasodilation and reduce MCA. Further studies are needed to study the long-term effects of mobile phone use and the relation among NO production, vasodilation, and temperature.

Control of NO concentration in solutions of nitrosothiol compounds by light.

We studied the thermal and photolytic decomposition of two S-nitrosothiols, S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylpenicillamine (SNAP), in water or propanol solutions. A "concentration clamp" (relatively constant concentration of NO as a function of time) could be implemented in a closed volume by varying the pH, concentration of nitrovasodilator and intensity of the light source. Depending on the conditions, the light either stimulated NO release or sharply decreased NO concentration in the test solutions. Changes in the absorption spectra of GSNO solutions were monitored as a function of light exposure. Generation of superoxide as a product of a photolytic decomposition reaction of S-nitrosothiols and further oxidation of NO is the most likely mechanism for light suppression of NO concentration.

The effects of a photosensitive nitric oxide donor on basal and electrically-stimulated dopamine efflux from the rat striatum in vitro.

The reported effects of nitric oxide (NO) on dopamine release from the striatum are variable and its precise effect on striatal nerve terminals is unclear. In the present study a novel method of applying NO to brain tissue in situ was employed. Photo-activation of Roussin's Black Salt (RBS), retained in isolated perfused brain tissue, was used to release NO at will upon illumination. Basal and electrically-stimulated dopamine efflux from the rat striatum in vitro was measured in real time using fast cyclic voltammetry. Illumination of an RBS pre-treated brain slice elicited a light intensity-related increase in basal dopamine efflux. Concomitantly there was a decrease in the level of electrically-stimulated dopamine efflux. Illumination in the absence of RBS pre-treatment had no effect on basal or stimulated dopamine efflux. The increase in basal dopamine efflux upon photo-activation of RBS was reduced by the presence of 10 microM oxyhaemoglobin, but was insensitive to the removal of extracellular calcium or the addition of 1 microM sulpiride. The decrease in electrically-stimulated dopamine efflux following illumination was not affected by the presence of either oxyhaemoglobin or sulpiride. It is concluded that NO, produced by photo-activation of RBS, releases dopamine from the rat striatum in vitro by a mechanism independent of extracellular calcium entry.

Laser-induced endothelial damage inhibits endothelium-dependent relaxation in the cerebral microcirculation of the mouse.

This study demonstrates endothelium-dependent relaxation in the surface arterioles of the brain. A helium-neon laser was used to injure endothelium in situ following i.v. injection of Evans blue dye, which sensitizes the bed to the laser. Areas 18 or 36 micron in diameter were injured and no longer relaxed to either 1 ml of acetylcholine chloride or bradykinin triacetate, 80 micrograms/ml delivered for 60 seconds. Dilations to sodium nitroprusside (30 micrograms/ml) were unaffected. Normal responses to nitroprusside, plus electron microscopy, established that vascular smooth muscle was uninjured. Endothelium-dependent relaxation was impaired when only minor ultrastructural damage was present. Dilation was inhibited downstream and upstream as far as 80 micron from the center of the laser beam. This suggests a spread of endothelium injury around the site of laser impact. However, inhibition was somewhat more marked downstream than upstream, implying that a portion of the downstream response was dependent on a substance released from an upstream site. To date, very few studies have reported endothelium-dependent relaxation in vivo, especially in the microcirculation. The present study accomplishes this. Moreover, in contrast to in vitro observations of endothelium-dependent relaxation in large vessels, the in vivo elimination of endothelium-dependent relaxation in the microcirculation required neither removal of endothelium nor injury to large numbers of endothelium cells. Since endothelium-dependent relaxation in the microcirculation has now been demonstrated using three different techniques to injure endothelium, it is reasonable to conclude that the phenomenon is real.