Intracellular Nitric Oxide Concentration Research Articles

Investigation of artificial intelligence integrated fluorescence endoscopy image analysis with indocyanine green for interpretation of precancerous lesions in colon cancer.

Indocyanine green (ICG) has been used in clinical practice for more than 40 years and its safety and preferential accumulation in tumors has been reported for various tumor types, including colon cancer. However, reports on clinical assessments of ICG-based molecular endoscopy imaging for precancerous lesions are scarce. We determined visualization ability of ICG fluorescence endoscopy in colitis-associated colon cancer using 30 lesions from an azoxymethane/dextran sulfate sodium (AOM/DSS) mouse model and 16 colon cancer patient tissue-samples. With a total of 60 images (optical, fluorescence) obtained during endoscopy observation of mouse colon cancer, we used deep learning network to predict four classes (Normal, Dysplasia, Adenoma, and Carcinoma) of colorectal cancer development. ICG could detect 100% of carcinoma, 90% of adenoma, and 57% of dysplasia, with little background signal at 30 min after injection via real-time fluorescence endoscopy. Correlation analysis with immunohistochemistry revealed a positive correlation of ICG with inducible nitric oxide synthase (iNOS; r > 0.5). Increased expression of iNOS resulted in increased levels of cellular nitric oxide in cancer cells compared to that in normal cells, which was related to the inhibition of drug efflux via the ABCB1 transporter down-regulation resulting in delayed retention of intracellular ICG. With artificial intelligence training, the accuracy of image classification into four classes using data sets, such as fluorescence, optical, and fluorescence/optical images was assessed. Fluorescence images obtained the highest accuracy (AUC of 0.8125) than optical and fluorescence/optical images (AUC of 0.75 and 0.6667, respectively). These findings highlight the clinical feasibility of ICG as a detector of precancerous lesions in real-time fluorescence endoscopy with artificial intelligence training and suggest that the mechanism of ICG retention in cancer cells is related to intracellular nitric oxide concentration.

Peptide Sodium Channels Modulator Mu-Agatoxin-Aa1a Prevents Ischemia-Reperfusion Injury of Cells

Ischemia-reperfusion injury (IRI) is an irreversible functional and structural injury. Restoration of normal oxygen concentration exacerbates the emergence and development of deadly cells. One of the possible moments of reperfusion damage to cells is an increase in the intracellular concentration of sodium ions. In this article, we study the mu-agatoxin-Aa1a, a modulator of sodium channels, on the processes of IRI cells damage. The toxin was synthesized using an automatic peptide synthesizer. Hypoxia was induced by reducing the content of serum and oxygen in the CHO-K1 culture. The influence of the toxin on the level of apoptosis; intracellular concentration of sodium, calcium, and potassium ions; intracellular pH; totality of reactive oxygen species (ROS), nitric oxide (NO), and ATP; and changes in the mitochondrial potential were studied. The experiments performed show that mu-agatoxin-Aa1a effectively prevents IRI of cells. Toxin reduces the level of apoptosis and prevents a decrease in the intracellular concentration of sodium and calcium ions during IRI. Mu-agatoxin-Aa1a contributes to the maintenance of elevated intracellular pH, reduces the intracellular concentration of ROS, and prevents the decrease in intracellular NO concentration and mitochondrial potential under conditions of reoxygenation/reperfusion. An analysis of experimental data shows that the mu-agatoxin-Aa1a peptide has adaptogenic properties. In the future, this peptide can be used to prevent ischemia/reperfusion tissue damage different genesis.

Gold nanoparticle-based two-photon fluorescent nanoprobe for monitoring intracellular nitric oxide levels.

Nitric oxide (NO) plays an important role in the regulation of the immune, cardiovascular and nervous systems. Consequently, being able to monitor and quantify intracellular NO levels would provide a greater understanding of the implications of this molecule in the different biological processes, including, for example, in cancer. Here, we report a broadly applicable two-photon excitable fluorescent nanoprobe able to detect and potentially quantify NO levels in an extensive range of cellular environments. The nanoprobe consists of a thiolated photoinduced electron transfer-based two=photon fluorescent probe attached onto the surface of 2.4 ± 0.7 nm gold nanoparticles (DANPY-NO@AuNPs). The nanoprobe, which can be synthesised in a reproducible manner and exhibits great stability when stored at room temperature, is able to selectively detect NO in solution, with a dynamic range up to 150 μM, and at pH values of biological relevance. DANPY-NO@AuNPs were able to selectively detect endogenous NO in RAW264.7γ NO- macrophages and THP-1 human leukemic cells; and endogenous and exogenous NO in endothelial cells. The nanoprobe accumulated in the acidic organelles of the tested cell lines showing negligible toxicity. Importantly, DANPY-NO@AuNPs showed potential to quantify intracellular NO concentrations in MDA-MB-231 breast cancer cells. The biological evaluation of the nanoprobe was undertaken using confocal laser scanning (images and intracellular emission spectra) and multiphoton microscopies, and flow cytometry. Based on their excellent sensitivity and stability, and outstanding versatility, DANPY-NO@AuNPs can be applied for the spatiotemporal monitoring of in vitro and in vivo NO levels.

A highly photostable and versatile two-photon fluorescent probe for the detection of a wide range of intracellular nitric oxide concentrations in macrophages and endothelial cells.

Nitric oxide (NO) is involved in many biological processes affecting the cardiovascular, nervous and immune systems. Intracellular NO can be monitored using fluorescent probes in combination with fluorescence imaging techniques. Most of the currently available NO fluorescent molecular probes are excited via one-photon excitation using UV or Vis light, which results in poor penetration and high photodamage to living tissues. Here, we report a two-photon fluorescent molecular probe, DANPY-NO, able to detect NO in live cells. The probe consists of an o-phenylenediamine linked to a naphthalimide core; and operates via photoinduced electron transfer. DANPY-NO exhibits good sensitivity (LOD of 77.8nM) and high selectivity towards NO, and is stable over a broad range of pHs. The probe targeted acidic organelles within macrophages and endothelial cells, and demonstrated enhanced photostability over a commercially available NO probe. DANPY-NO was used to selectively detect endogenous NO in RAW264.7ϒ NO- macrophages, THP-1 human leukemic cells, primary mouse (bone marrow-derived) macrophages and endothelial cells. The probe was also able to detect exogenous NO in endothelial cells and distinguish between increasing concentrations of NO. The NO detection was evidenced using confocal laser scanning and two-photon microscopies, and flow cytometry. Further evidence was obtained by recording the changes in the intracellular fluorescence emission spectrum of the probe. Importantly, the probe displayed negligible toxicity to the analysed biological samples. The excellent sensitivity, selectivity, stability and versatility of DANPY-NO confirm its potential for in vitro and in vivo imaging of NO.

Development of a microtiter plate-based analysis method of nitric oxide dioxygenase activity.

Nitric oxide (NO) functions in cell protection or cell death, depending on its concentration. Therefore, regulation of the intracellular concentrations of NO by its degradation systems is important for cellular functions. One of the NO degrading enzymes, flavohemoglobin (FHb), which has NO dioxygenase (NOD) activity, is a promising target for antibiotics, based on the finding that FHb-deficient pathogens exhibited reduced host toxicity. Here, we developed a high-throughput method to measure the NOD activity. Our newly developed method could contribute to the screening of potential antibiotics with NOD inhibitory activity.

Knockdown of the inducible nitric oxide synthase (NOS2) splicing variant S3 promotes autophagic cell death from nitrosative stress in SW480 human colon cancer cells.

Low levels of nitric oxide (NO) produced by constitutively expressed inducible NO synthase (NOS2) in tumor cells may be an important factor in their development. NOS2 expression is associated with high mortality rates for various cancers. Alternative splicing of NOS2 down-regulates its enzymatic activity, resulting in decreased intracellular NO concentrations. Specific probes to detect alternative splicing of NOS2 were used in two isogenic human colon cancer cell lines derived either from the primary tumor (SW480) or from a lymph node metastasis (SW620). Splicing variant of NOS2 S3, lacking exons 9, 10, and 11, was overexpressed in SW480 cells. NOS2 S3 was silenced in SW480 cells. Flow-cytometry analysis was used to estimate the intracellular NO levels and to analyze the cell cycle of the studied cell lines. Western blot analysis and quantitativereal-time polymerase chain reaction(qRT-PCR) were used to determine apoptosis and autophagy markers. SW480 and SW620 cells expressed NOS2 S3. Overexpression of the NOS2 S3 in SW480 cells downregulated intracellular NO levels. SW480 cells with knocked down NOS2 S3 (referred to as S3C9 cells) had higher intracellular levels of NO compared to the wild-type SW480 cells under serum restriction. Higher NO levels resulted in the loss of viability of S3C9 cells, which was associated with autophagy. Induction of autophagy by elevated intracellular NO levels in S3C9 cells under serum restriction, suggests that autophagy operates as a cytotoxic response to nitrosative stress. The expression of NOS2 S3 plays an important role in regulating intracellular NO production and maintaining viability in SW480 cells under serum restriction. These findings may prove significant in the design of NOS2/NO-based therapies for colon cancer.

L-Arginine Reduces Nitro-Oxidative Stress in Cultured Cells with Mitochondrial Deficiency.

L-Arginine (L-ARG) supplementation has been suggested as a therapeutic option in several diseases, including Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like syndrome (MELAS), arguably the most common mitochondrial disease. It is suggested that L-ARG, a nitric oxide (NO) precursor, can restore NO levels in blood vessels, improving cerebral blood flow. However, NO also participates in mitochondrial processes, such as mitochondrial biogenesis, the regulation of the respiratory chain, and oxidative stress. This study investigated the effects of L-ARG on mitochondrial function, nitric oxide synthesis, and nitro-oxidative stress in cell lines harboring the MELAS mitochondrial DNA (mtDNA) mutation (m.3243A>G). We evaluated mitochondrial enzyme activity, mitochondrial mass, NO concentration, and nitro-oxidative stress. Our results showed that m.3243A>G cells had increased NO levels and protein nitration at basal conditions. Treatment with L-ARG did not affect the mitochondrial function and mass but reduced the intracellular NO concentration and nitrated proteins in m.3243A>G cells. The same treatment led to opposite effects in control cells. In conclusion, we showed that the main effect of L-ARG was on protein nitration. Lowering protein nitration is probably involved in the mechanism related to L-ARG supplementation benefits in MELAS patients.

A Novel Mechanism for Nitrosative Stress Tolerance Dependent on GTP Cyclohydrolase II Activity Involved in Riboflavin Synthesis of Yeast

The biological functions of nitric oxide (NO) depend on its concentration, and excessive levels of NO induce various harmful situations known as nitrosative stress. Therefore, organisms possess many kinds of strategies to regulate the intracellular NO concentration and/or to detoxify excess NO. Here, we used genetic screening to identify a novel nitrosative stress tolerance gene, RIB1, encoding GTP cyclohydrolase II (GTPCH2), which catalyzes the first step in riboflavin biosynthesis. Our further analyses demonstrated that the GTPCH2 enzymatic activity of Rib1 is essential for RIB1-dependent nitrosative stress tolerance, but that riboflavin itself is not required for this tolerance. Furthermore, the reaction mixture of a recombinant purified Rib1 was shown to quench NO or its derivatives, even though formate or pyrophosphate, which are byproducts of the Rib1 reaction, did not, suggesting that the reaction product of Rib1, 2,5-diamino-6-(5-phospo-d-ribosylamino)-pyrimidin-4(3 H)-one (DARP), scavenges NO or its derivatives. Finally, it was revealed that 2,4,5-triamino-1H-pyrimidin-6-one, which is identical to a pyrimidine moiety of DARP, scavenged NO or its derivatives, suggesting that DARP reacts with N2O3 generated via its pyrimidine moiety.

Detection system of the intracellular nitric oxide in yeast by HPLC with a fluorescence detector

Nitric oxide (NO) is an important signaling molecule involved in various biological phenomena in many organisms. The physiological functions and metabolism of NO in yeast, a unicellular microorganism, are still unknown, mainly because it is difficult to analyze the intracellular NO levels accurately. Here, we developed a new method of more accurately measuring NO content in yeast cells with the detection limit of 6 nM, by treating the cells with an NO-specific fluorescence probe followed by high-performance liquid chromatography with fluorescence detection (HPLC/FLD). This approach successfully detected and quantified the NO content inside yeast cells treated with an NO donor. Moreover, the HPLC/FLD analysis indicates that the fluorescence induced under some environmental stress conditions, such as ethanol, vanillin, and heat-shock, was not derived from NO. The HPLC/FLD method developed in this study provides a new strategy for measuring the intracellular NO concentration with higher accuracy.

Fluorescence imaging of nitric oxide in living cells using o-phenylenediamine-rhodamine based polymeric nanosensors.

Direct real-time measurement of nitric oxide (NO) in living cells has proven quite challenging, owing in part to the lack of tools that are selective and sensitive to measure intracellular concentrations of NO. Herein we report the synthesis and characterization of polyvinyl alcohol (PVA) based nanosensors for fluorescence imaging of cytosolic NO using an o-phenylenediamine-rhodamine (OPD-RhB) platform. More specifically, thiol-functionalized PVA incorporating RhB conjugated OPD was disulfide crosslinked to yield NO-responsive nanosensors. The polymeric nanosensors were anionic, averaged 170nm in hydrodynamic size, and exhibited linear increases in fluorescence intensity (FLI) to micro- and nanomolar concentrations of NO in a sodium nitroprusside (SNP) concentration-dependent manner. In the presence of SNP, the engineered nanosensors demonstrated physical stability at extracellular glutathione (GSH) conditions, while favoring NO detection at cytoplasmic GSH conditions. In addition, the PVA-based nanosensors were non-cytotoxic, cell membrane-permeable and demonstrated hydrogen peroxide-dependent FL increases upon incubation with activated synoviocytes in vitro. Most notably, NO-induced cell FLIs correlated strongly with total nitrite/nitrate content of conventional Griess assays with Pearson correlation coefficients of 0.96. Comprehensively, our results show that OPD-RhB-conjugated PVA nanosensors offer real-time imaging of NO with high sensitivity in living cells that can be employed for direct quantification of NO.

Nitric oxide regulates the expression of heme carrier protein-1 via hypoxia inducible factor-1α stabilization.

Photodynamic therapy (PDT) is a cancer therapy that capitalizes on cancer-specific porphyrin accumulation. We have investigated this phenomenon to propose the following three conclusions: 1) the mechanism underlying this phenomenon is closely related to both nitric oxide (NO) and heme carrier protein-1 (HCP-1), 2) NO inactivates ferrochelatase, and thus, the intracellular porphyrin levels in the cells are increased by the administration of an NO donor after 5-aminolevulinic acid treatment, 3) HCP-1 transports not only heme but also other porphyrins. Since NO stabilizes hypoxia-inducible factor (HIF)-1α, resulting in the upregulation of heme biosynthesis, HCP-1 expression can be increased by HIF-1α stabilization. In this study, we determined whether NO regulates HCP-1 expression by stabilizing HIF-1α expression. For this purpose, rat gastric cancer cell line RGK36 was treated with L-arginine or N6-(1-iminoethyl)-L-lysine (L-NIL). L-arginine treatment increased the intracellular NO concentration, and both HCP-1 and HIF-1α expression, while L-NIL treatment decreased them. Cytotoxicity of PDT was enhanced by L-arginine, following intracellular hemato-porphyrin dihydrochloride (HpD) accumulation. Both Cytotoxicity of PDT and HpD accumulation were decreased by L-NIL. The HCP-1 and HIF-1α expression, intracellular HpD accumulation and PDT cytotoxicity were decreased by 2-methoxyestradiol, which is a HIF-1α inhibitor. Moreover, these phenomena were not increased by a combination of both L-arginine and 2-Me. Thus, HCP-1 can be a downstream target of HIF-1α. These effects were also induced in the human gastric cancer cell line MKN45. Taken together, we conclude that HCP-1 expression is regulated by NO via HIF-1α stabilization.

Stimuli-responsive nitric oxide generator for light-triggered synergistic cancer photothermal/gas therapy

As a minimally invasive local cancer therapy, photothermal therapy (PTT) has aroused intensive interests in recent years. However, the therapeutic effect of PTT is still unsatisfying due to the production of heat shock proteins. Combination therapy has been regarded as a promising strategy to enhance therapeutic efficiency. In this study, a novel intelligent protoporphyrin (PpIX)-based polymer nanoplatform is developed for synergistic enhancement of cancer treatment through combined PTT and nitric oxide (NO) therapy. The core of the nanoparticle is composed of closely packed porphyrin-based NO donors and PpIX branches of the block copolymer. The prepared nanoparticles exhibit good photothermal conversion capability and high sensitivity to release NO under light illumination. And the produced high localized temperature and intracellular NO concentration could efficiently inhibit cancer cells both in vitro and in vivo. More important, this therapeutic nanoplatform can fundamentally eliminate the emergence of multidrug resistance and overcome the hypoxia microenvironment in tumors because of the absence of chemotherapeutic drugs and the oxygen-independent process, thus opening up new ideas for multifunctional therapeutic agent design for treatment of multidrug-resistant cancer.

Investigation of the mechanism of enhanced and directed differentiation of neural stem cells by an atmospheric plasma jet: A gene-level study

Cold atmospheric plasmas (CAPs) have been shown to be capable of enhancing stem cell differentiation, especially directed differentiation of neural stem cells (NSCs). Consequently, one-step CAP treatment shows promise as an aid to tissue transplantation. However, the mechanisms involved in the enhancement of NSCs differentiation by CAP treatment are not yet fully understood. We have previously shown that in atmospheric helium plasma jet treatment, nitric oxide (NO) is the main factor involved in promoting NSC differentiation. This article further investigated the possible signaling pathways stimulated by NO in the neuronal differentiation of C17.2-NSCs after plasma treatment. Extracellular and intracellular NO concentrations were measured at different time points of incubation to monitor NO production. Meanwhile, the expressions of related genes and proteins were detected by quantitative real-time polymerase chain reaction and western blot, respectively. It is found that plasma treatment could both generate extracellular NO and increase extracellular NO concentration by inducing inducible nitric oxide synthase expression. The synergetic effect of extracellular and intracellular NO then downregulated Notch1 and Id2, and upregulated Ngn2 and Ascl1, thereby activating downstream NeuroD expression and finally enhancing and directing differentiation of NSCs into neurons.Cold atmospheric plasmas (CAPs) have been shown to be capable of enhancing stem cell differentiation, especially directed differentiation of neural stem cells (NSCs). Consequently, one-step CAP treatment shows promise as an aid to tissue transplantation. However, the mechanisms involved in the enhancement of NSCs differentiation by CAP treatment are not yet fully understood. We have previously shown that in atmospheric helium plasma jet treatment, nitric oxide (NO) is the main factor involved in promoting NSC differentiation. This article further investigated the possible signaling pathways stimulated by NO in the neuronal differentiation of C17.2-NSCs after plasma treatment. Extracellular and intracellular NO concentrations were measured at different time points of incubation to monitor NO production. Meanwhile, the expressions of related genes and proteins were detected by quantitative real-time polymerase chain reaction and western blot, respectively. It is found that plasma treatment could both genera...

Effect of nerve growth factor on sperm quality in asthenozoosprmic men during cryopreservation.

BackgroundAlthough routinely used in assisted reproductive technology, human sperm cryopreservation is not an entirely successful procedure. This study determined the effect of nerve growth factor (NGF) supplementation of cryopreservation medium on post-thaw viability, motility, intracellular nitric oxide (NO) concentration, and DNA fragmentation of human spermatozoa in asthenozoospermic men.MethodsSemen samples were collected from 25 asthenozoosprmic men and divided into the following groups (n = 5/group): fresh semen (control); frozen-thawed semen without treatment; frozen-thawed semen with NGF treatment (0.5, 1, and 5 ng/ml). Prior to dividing the asthenozoospermic samples, 200 μl of each sample was collected for NGF content assessment by ELISA and then compared with normozoospermic semen samples (25 normozoospermic men). Sperm motility and viability were assessed according to WHO criteria. Furthermore, intracellular nitric oxide and DNA fragmentation were evaluated by Flow Cytometry.ResultsNGF content was significantly higher in normozoospermic compared with asthenozoospermic men. Cryopreservation of asthenozoospermic semen samples significantly decreased sperm viability and motility, and increased intracellular nitric oxide concentration and DNA damage (p < 0.01). In asthenozoospermic frozen–thawed samples treated with 0.5 ng/ml exogenous NGF, we observed a significantly increased viability, motility, and decreased DNA fragmentation (p < 0.05), but intracellular nitric oxide concentration was not reduced. The other high doses (1 and 5 ng/ml) had no significant effect on the variables.ConclusionSupplementation with exogenous NGF could have partial and limited protective effect during cryopreservation of human spermatozoa but further research is needed to evaluate the possible clinical applications.

Doxorubicin chemotherapy affects intracellular and interstitial nitric oxide concentrations in skeletal muscle : Effect of doxorubicin on intracellular and interstitial NO in skeletal muscle.

The role of nitric oxide (NO) in doxorubicin (DOX; cancer chemotherapeutic)-induced cardiotoxicity is well established. In skeletal muscle (SM), NO regulation plays a critical role in health, biogenesis, and function. Despite the increasing evidence that indicates the negative impact of DOX on SM function, the effect of DOX on NO production in SM has yet to be examined. The purpose of the current study was to simultaneously examine intracellular and interstitial NO concentrations in the SM following the administration of DOX. A single dose of 1.5 or 4.5mg/kg was administered intraperitoneally to male Sprague Dawley rats, and interstitial (IS) and intracellular (IC) NO was quantified every 24 up to 192h post-injection. There was no significant difference in IC NO following the injection of 1.5mg/kg DOX when compared to the control; however, the administration of 4.5mg/kg DOX resulted in lower (P < 0.05) concentrations of NO in the IC. Interestingly, a consistently higher (P < 0.05) concentration of NO in the IS was established following the administration of 1.5mg/kg compared to the control while no significant changes in IS NO resulted from the administration of the 4.5mg/kg dose. The fluctuation of IS and IC NO was not a result of substrate availability as arginine concentrations remained stable throughout the experiment. By utilizing the microdialysis technique, we have simultaneously quantified for the first time the IS and IC concentrations of NO in SM following DOX administration. These data provide important insight in the possible mechanisms leading to DOX-related SM dysfunction.

Nerve growth factor in human semen: Effect of nerve growth factor on the normozoospermic men during cryopreservation process.

Although routinely applied in assisted reproductive technology, human sperm cryopreservation is not a completely successful procedure. Adverse effects of cryopreservation on the fertilization capacity, motility, morphology, and viability of spermatozoa have been proven; cryopreservation has also shown a role in sperm DNA fragmentation and infertility. The post-thaw survival of spermatozoa improved after addition of supplementation of antioxidant molecules to freezing media. Nerve growth factor (NGF) as one of the prosurvival substances has gained great attention in recent years. The aim of this study was the usage of NGF as prosurvival factor after cryopreservation process of human semen samples to assess the motility and viability of sperm, nitric oxide (NO) concentration, and DNA fragmentation in normozoospermic men. Semen samples were collected from 25 normozoospermic men and were divided into fresh semen samples as control group, frozen-thawed semen samples without addition of exogenous NGF, and three groups of semen samples cryopreserved with addition of exogenous NGF (0.5, 1, and 5 ng/ml) in freezing medium. Viability was assessed by eosin-negrosin staining technique. Motility was evaluated with inverted microscope. NO concentration and apoptosis content were measured with flow cytometry. Results showed that exogenous NGF at 0.5 ng/ml could significantly (P-value <0.05) influence viability, motility, nitric oxide, and DNA fragmentation content. Exogenous NGF as cryoprotectant improved sperm viability and motility, increased intracellular NO concentration, and decreased apoptosis content in normal human spermatozoa.

Pharmacological characterization of the vasodilating effect induced by the ruthenium complex cis-[Ru(NO)(NO2)(bpy)2].(PF6)2.

Nitric oxide (NO) can be found in different species and is a potent vasodilator. The ruthenium compound cis-[Ru(NO)(NO2)(bpy)2].(PF6)2 (BPY) can generate NO. This study aimed to investigate the BPY stability at physiological pH, the cellular mechanisms involved in BPY effect, NO species originating from BPY, and to verify how BPY affects blood pressure. Our results has shown that at pH 7.4 and 9.4, the NO coordinated to ruthenium (Ru-NO) is converted to nitrite (Ru-NO2) and remains stable. In aortic rings, the stable configuration of BPY (Ru-NO2) induces vascular relaxation in a concentration-dependent manner. Thus, further experiments were made with stable configuration of BPY (Ru-NO2). The relaxation induced by BPY was abolished in the presence of guanylyl cyclase inhibitor and decreased in the presence of potassium channel blocker. By using radicalar (NO) and nitroxyl (NO) scavenger, our results suggest that the BPY mainly release the radicalar species. By using fluorescence probes to detect intracellular NO concentration ([NO]i) and cytosolic Ca concentration ([Ca]c), we verified that in smooth muscle cells, BPY induces an increase in [NO]i and a decrease in [Ca]c. The intravenous bolus injection of 1.25, 2.5, and 5.0 mg/kg from stable configuration of BPY results in a decrease on basal blood pressure values. Taken together, our results indicated that the stable configuration of the compound BPY induces vascular relaxation in aorta because of NO release and decrease of [Ca]c in vascular smooth muscle cells. Also, the stable configuration is able to reduce the blood pressure in a dose-dependent manner.

Urocortin 2 stimulates nitric oxide production in ventricular myocytes via Akt- and PKA-mediated phosphorylation of eNOS at serine 1177

Urocortin 2 (Ucn2) is a cardioactive peptide exhibiting beneficial effects in normal and failing heart. In cardiomyocytes, it elicits cAMP- and Ca(2+)-dependent positive inotropic and lusitropic effects. We tested the hypothesis that, in addition, Ucn2 activates cardiac nitric oxide (NO) signaling and elucidated the underlying signaling pathways and mechanisms. In isolated rabbit ventricular myocytes, Ucn2 caused concentration- and time-dependent increases in phosphorylation of Akt (Ser473, Thr308), endothelial NO synthase (eNOS) (Ser1177), and ERK1/2 (Thr202/Tyr204). ERK1/2 phosphorylation, but not Akt and eNOS phosphorylation, was suppressed by inhibition of MEK1/2. Increased Akt phosphorylation resulted in increased Akt kinase activity and was mediated by corticotropin-releasing factor 2 (CRF2) receptors (astressin-2B sensitive). Inhibition of phosphatidylinositol 3-kinase (PI3K) diminished both Akt as well as eNOS phosphorylation mediated by Ucn2. Inhibition of protein kinase A (PKA) reduced Ucn2-induced phosphorylation of eNOS but did not affect the increase in phosphorylation of Akt. Conversely, direct receptor-independent elevation of cAMP via forskolin increased phosphorylation of eNOS but not of Akt. Ucn2 increased intracellular NO concentration ([NO]i), [cGMP], [cAMP], and cell shortening. Inhibition of eNOS suppressed the increases in [NO]i and cell shortening. When both PI3K-Akt and cAMP-PKA signaling were inhibited, the Ucn2-induced increases in [NO]i and cell shortening were attenuated. Thus, in rabbit ventricular myocytes, Ucn2 causes activation of cAMP-PKA, PI3K-Akt, and MEK1/2-ERK1/2 signaling. The MEK1/2-ERK1/2 pathway is not required for stimulation of NO signaling in these cells. The other two pathways, cAMP-PKA and PI3K-Akt, converge on eNOS phosphorylation at Ser1177 and result in pronounced and sustained cellular NO production with subsequent stimulation of cGMP signaling.

Generation of nitric oxide gradients in microfluidic devices for cell culture using spatially controlled chemical reactions

In this paper, we develop a microfluidic device capable of generating nitric oxide (NO) gradients for cell culture using spatially controlled chemical reactions. NO plays an essential role in various biological activities, including nervous, immune, and cardiovascular systems. The device developed in this paper can control NO gradients without utilizing expensive and hazardous high purity NO gas sources or direct addition of NO donors. Consequently, the device provides an efficient, cost-effective, robust, and stable platform to generate NO gradients for cell culture studies. In the experiments, NO gradients are first characterized using a NO-sensitive fluorescence dye, and cell experiments using aortic smooth muscle cells are conducted. The results demonstrate that the device can alter the intracellular NO concentrations and further affect the Ca(2+) concentration oscillation for the cells. The device developed in this paper provides a powerful platform for researchers better study the biological roles of NO and its spatial distribution using in vitro cell models with minimal instrumentation.

Role of Size and Shape on Biofilm Eradication for Nitric Oxide-Releasing Silica Nanoparticles

Nitric oxide (NO), a reactive free radical, has proven effective in eradicating bacterial biofilms with reduced risk of fostering antibacterial resistance. Herein, we evaluated the efficacy of NO-releasing silica nanoparticles against Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus biofilms as a function of particle size and shape. Three sizes of NO-releasing silica nanoparticles (i.e., 14, 50, and 150 nm) with identical total NO release (∼0.3 μmol/mg) were utilized to study antibiofilm eradication as a function of size. To observe the role of particle shape on biofilm killing, we varied the aspect ratio of the NO-releasing silica particles from 1 to 8 while maintaining constant particle volume (∼0.02 μm(3)) and NO-release totals (∼0.7 μmol/mg). Nitric oxide-releasing particles with decreased size and increased aspect ratio were more effective against both P. aeruginosa and S. aureus biofilms, with the Gram-negative species exhibiting the greatest susceptibility to NO. To further understand the influence of these nanoparticle properties on NO-mediated antibacterial activity, we visualized intracellular NO concentrations and cell death with confocal microscopy. Smaller NO-releasing particles (14 nm) exhibited better NO delivery and enhanced bacteria killing compared to the larger (50 and 150 nm) particles. Likewise, the rod-like NO-releasing particles proved more effective than spherical particles in delivering NO and inducing greater antibacterial action throughout the biofilm.