Inhibition Of Nitric Oxide Synthase Activity Research Articles

Anti-cancer effect of in vivo inhibition of nitric oxide synthase in a rat model of breast cancer.

Increased expression of nitric oxide synthase (NOS) is associated with different cancers such as cervical, breast, lung, brain, and spinal cord. Inhibition of NOS activity has been suggested as potential tool to prevent breast cancer. The anti-tumor therapeutic effect of L-nitro arginine methyl ester (L-NAME), NOS inhibitor, using in vivo models is currently under investigation. We hypothesized that L-NAME will show an anti-tumor effect by delaying a progression of breast cancer via a modulation of cell death and proliferation, and angiogenesis. We used a novel model of anti-cancer treatment by the administration of L-NAME (30mg/kg in a day, intraperitoneal) injected every third day for five weeks to rat model of 7,12-dimethylbenz[a]anthracene (DMBA)-induced breast tumor. Concentrations of nitrite anions, polyamines, malondialdehyde, NH4+ levels, and arginase activity in the blood were decreased in DMBA + L-NAME-treated rats compared with DMBA rats. The mortality rates, tumor number, weight, and volume, as well as the histopathological grade of breast cancer were also significantly reduced. In addition, L-NAME treatment showed a delay in tumor formation, and in body weight compared with rats administrated only with DMBA. In conclusion, our data show that L-NAME is a promising anti-cancer agent to treat breast cancer, which can lead to development of anti-tumor therapeutic tools in future.

Nitric oxide modulates tapentadol antinociceptive tolerance and physical dependence

Tapentadol, an analgesic with a dual mechanism of action, involving both μ-opioid receptor agonism and noradrenaline reuptake inhibition (MOP-NRI), was designed for the treatment of moderate to severe pain. However, the widely acknowledged risk of analgesic tolerance and development of physical dependence following sustained opioid use may hinder their effectiveness. One of the possible mechanisms behind these phenomena are alterations in nitric oxide synthase (NOS) system activity. The aim of the study was to investigate the tolerance and dependence potential of tapentadol in rodent models and to evaluate the possible role of nitric oxide (NO) in these processes. Our study showed that chronic tapentadol treatment resulted in tolerance to its antinociceptive effects to an extent similar to tramadol, but much less than morphine. A single injection of a non-selective NOS inhibitor, NG-nitro-L-arginine (L-NOArg), reversed the tapentadol tolerance. In dependence studies, repeated administration of L-NOArg attenuated naloxone-precipitated withdrawal in tapentadol-treated mice, whereas a single injection of L-NOArg was ineffective. Biochemical analysis revealed that tapentadol decreased nNOS protein levels in the dorsal root ganglia of rats following 31 days of treatment, while no significant changes were found in iNOS and eNOS protein expression. Moreover, pre-treatment with L-NOArg augmented tapentadol antinociception in an opioid- and α2-adrenoceptor-dependent manner. In conclusion, our data suggest that the NOS system plays an important role in the attenuation of tapentadol-induced tolerance and withdrawal. Thus, inhibition of NOS activity can serve as a promising treatment option for long-term tapentadol use by extending its effectiveness and improving the side-effects profile.

Age-associated bladder and urethral coordination impairment and changes in urethral oxidative stress in rats

AimsWe examined age-associated changes in bladder and urethral coordination involving the nitric oxide (NO)/soluble guanylyl cyclase (sGC) system, which induces urethral smooth muscle relaxation, and urethral ischemic/oxidative stress changes in rats. Main methodsSixteen female Sprague-Dawley rats were divided into young (3 months old) and middle-aged (12–15 months old) groups. Urethral activity was evaluated by simultaneously recording intravesical pressure under isovolumetric conditions and urethral perfusion pressure (UPP) under urethane anesthesia. Sodium nitroprusside (SNP, 0.1 mg/kg), an NO donor, and BAY 41-2272, a novel NO-independent stimulator of sGC (0.1 mg/kg), were administered intravenously to both groups. N-nitro-l-arginine methyl ester hydrochloride (l-NAME, 100 mg/kg) was also injected intravenously, to inhibit NO synthase activity in both groups. Staining for the ischemic marker, hypoxia-inducible factor-1α (HIF-1α), and the oxidative stress markers, 8-hydroxy-2′-deoxyguanosine (8-OHdG) and malondialdehyde (MDA), was performed on tissue sections of the urethra, in both groups. Key findingsBaseline UPP and UPP changes were significantly lower in middle-aged rats than in young rats. After administration of SNP and BAY 41-2272, baseline UPP and UPP nadir were significantly decreased in both groups. After administration of l-NAME, UPP change/bladder contraction amplitude in young rats was still lower than at baseline but was completely restored to control levels in middle-aged rats. Immunoreactivity of HIF-1α, 8-OHdG, and MDA was higher in middle-aged rats than in young rats. SignificanceAge-associated ischemic and oxidative stress in the urethra might be correlated with impairment of the NO/sGC system and with coordination of the bladder and urethra.

Low Nitric Oxide Bioavailability Increases Renin Production in the Collecting Duct.

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

The Effect of Chronic NO Synthase Inhibition on the Vasoactive and Structural Properties of Thoracic Aorta, NO Synthase Activity, and Oxidative Stress Biomarkers in Young SHR.

Although the role of nitric oxide (NO) in essential hypertension is still unclear, the effects of long-term NO deficiency have not yet been investigated during the critical juvenile period in spontaneously hypertensive rats (SHR). We aimed to analyze the effects of chronic NO synthase (NOS) inhibition on systolic blood pressure (sBP), vasoactivity, morphological changes and superoxide level in the thoracic aorta (TA), NOS activity in different tissues, and general biomarkers of oxidative stress in plasma of young SHR. Four-week-old SHR were treated with NG-nitro-L-arginine methyl ester (L-NAME, 50 mg/kg/day, p.o.) for 4-5 weeks. L-NAME treatment induced a transient sBP increase only, and surprisingly, slightly inhibited endothelium-dependent relaxation of TA. Hereby, the inhibition of NOS activity varied from tissue to tissue, ranging from the lowest in the TA and the kidney to the highest in the brain stem. In spite of an increased sensitivity of adrenergic receptors, the maximal adrenergic contraction of TA was unchanged, which was associated with changes in elastin arrangement and an increase in wall thickness. The production of reactive oxygen species in the TA was increased; however, the level of selected biomarkers of oxidative stress did not change. Our findings proved that the TA of young SHR responded to chronic NO deficiency by the development of adaptive mechanisms on the functional (preserved NO-derived vasorelaxation, unincreased contraction) and molecular (preserved NOS activity) level.

Age-associated urethral dysfunction in urethane-anesthetized rats.

We aimed to investigate the age-associated changes in movement coordination between the urinary bladder and the urethra in rats. A total of 17 female Sprague-Dawley rats were used. The rats were divided into young (3 months old) and middle-aged (12-15 months old) groups. In both groups, isovolumetric cystometry and urethral perfusion pressure (UPP) measurements were performed under urethane anesthesia. After the rhythmic bladder contractions stabilized, L-arginine, a nitric oxide (NO) substrate (100 mg/kg), was administered intravenously in both groups. Subsequently, N-nitro-L-arginine methyl ester hydrochloride (L-NAME) (50 mg/kg) was injected intravenously to inhibit NO synthase activity in both groups. UPP change, defined as UPP nadir minus baseline UPP, was significantly smaller in middle-aged rats (64%) than in young rats (P < 0.05). The mean amplitude of high-frequency oscillations (HFOs) of the external urethral sphincter was also significantly lower (62%) in middle-aged rats than that in young rats (P < 0.05). Urethral contraction during UPP change was also noted in middle-aged rats. This urethral contraction disappeared after L-arginine administration. UPP nadir during bladder contraction was inhibited by L-NAME in both groups. UPP change was greater in middle-aged rats than in young rats, and 3 out of 9 middle-aged rats showed a detrusor-sphincter dyssynergia pattern after L-NAME. The results indicated that aging induces dysfunction in movement coordination between the urinary bladder and the urethra. Thus, age-associated urethral dysfunctions may lead to inefficient voiding with increased post-void residual urine volume, which is often observed in elderly populations.

NOX2-Induced Activation of Arginase and Diabetes-Induced Retinal Endothelial Cell Senescence.

Increases in reactive oxygen species (ROS) and decreases in nitric oxide (NO) have been linked to vascular dysfunction during diabetic retinopathy (DR). Diabetes can reduce NO by increasing ROS and by increasing activity of arginase, which competes with nitric oxide synthase (NOS) for their commons substrate l-arginine. Increased ROS and decreased NO can cause premature endothelial cell (EC) senescence leading to defective vascular repair. We have previously demonstrated the involvement of NADPH oxidase 2 (NOX2)-derived ROS, decreased NO and overactive arginase in DR. Here, we investigated their impact on diabetes-induced EC senescence. Studies using diabetic mice and retinal ECs treated with high glucose or H2O2 showed that increases in ROS formation, elevated arginase expression and activity, and decreased NO formation led to premature EC senescence. NOX2 blockade or arginase inhibition prevented these effects. EC senescence was also increased by inhibition of NOS activity and this was prevented by treatment with a NO donor. These results indicate that diabetes/high glucose-induced activation of arginase and decreases in NO bioavailability accelerate EC senescence. NOX2-generated ROS contribute importantly to this process. Blockade of NOX2 or arginase represents a strategy to prevent diabetes-induced premature EC senescence by preserving NO bioavailability.

Doxorubicin-induced oxidative stress: The protective effect of nicorandil on HL-1 cardiomyocytes

The primary cardiotoxic action of doxorubicin when used as antitumor drug is attributed to the generation of reactive oxygen species (ROS) therefore effective cardioprotection therapies are needed. In this sense, the antianginal drug nicorandil has been shown to be effective in cardioprotection from ischemic conditions but the underlying molecular mechanism to cope with doxorubicin-induced ROS is unclear. Our in vitro study using the HL-1 cardiomyocyte cell line derived from mouse atria reveals that the endogenous nitric oxide (NO) production was stimulated by nicorandil and arrested by NO synthase inhibition. Moreover, while the NO synthase activity was inhibited by doxorubicin-induced ROS, the NO synthase inhibition did not affect doxorubicin-induced ROS. The inhibition of NO synthase activity by doxorubicin was totally prevented by preincubation with nicorandil. Nicorandil also concentration-dependently (10 to 100 μM) decreased doxorubicin-induced ROS and the effect was antagonized by 5-hydroxydecanoate. The inhibition profile of doxorubicin-induced ROS by nicorandil was unaltered when an L-arginine derivative or a protein kinase G inhibitor was present. Preincubation with pinacidil mimicked the effect of nicorandil and the protection was eliminated by glibenclamide. Quantitative colocalization of fluorescence indicated that the mitochondrion was the target organelle of nicorandil and the observed response was a decrease in the mitochondrial inner membrane potential. Interference with H+ movement across the mitochondrial inner membrane, leading to depolarization, also protected from doxorubicin-induced ROS. The data indicate that activation of the mitochondrial ATP-sensitive K+ channel by nicorandil causing mitochondrial depolarization, without participation of the NO donor activity, was responsible for inhibition of the mitochondrial NADPH oxidase that is the main contributor to ROS production in cardiomyocytes. Impairment of the cytosolic Ca2+ signal induced by caffeine and the increase in lipid peroxidation, both of which are indicators of doxorubicin-induced oxidative stress, were also prevented by nicorandil.

Jaburetox affects gene expression and enzyme activities in Rhodnius prolixus, a Chagas’ disease vector

Jaburetox, a recombinant peptide of ∼11kDa derived from one of the Canavalia ensiformis (Jack Bean) urease isoforms, is toxic and lethal to insects belonging to different orders when administered orally or via injection. Previous findings indicated that Jaburetox acts on insects in a complex fashion, inhibiting diuresis and the transmembrane potential of Malpighian tubules, interfering with muscle contractility and affecting the immune system. In vitro, Jaburetox forms ionic channels and alters permeability of artificial lipid membranes. Moreover, recent data suggested that the central nervous system (CNS) is a target organ for ureases and Jaburetox. In this work, we employed biochemical, molecular and cellular approaches to explore the mode of action of Jaburetox using Rhodnius prolixus, one of the main Chagas’ disease vectors, as experimental model. In vitro incubations with fluorescently labeled Jaburetox indicated a high affinity of the peptide for the CNS but not for salivary glands (SG). The in vitro treatment of CNS or SG homogenates with Jaburetox partially inhibited the activity of nitric oxide synthase (NOS), thus disrupting nitrinergic signaling. This inhibitory effect was also observed in vivo (by feeding) for CNS but not for SG, implying differential modulation of NOS in these organs. The inhibition of NOS activity did not correlate to a decrease in expression of its mRNA, as assessed by qPCR. UDP-N-acetylglucosamine pyrophosphorylase (UAP), a key enzyme in chitin synthesis and glycosylation pathways and a known target of Jaburetox in insect CNS, was also affected in SG, with activation of the enzyme seen after both in vivo or in vitro treatments with the peptide. Unexpectedly, incubation of Jaburetox with a recombinant R. prolixus UAP had no effect on its activity, implying that the enzyme’s modulation by the peptide requires the participation of other factor(s) present in CNS or SG homogenates. Feeding Jaburetox to R. prolixus decreased the mRNA levels of UAP and chitin synthase, indicating a complex regulation exerted by the peptide on these enzymes. No changes were observed upon Jaburetox treatment in vivo and in vitro on the activity of the enzyme acid phosphatase, a possible link between UAP and NOS. Here we have demonstrated for the first time that the Jaburetox induces changes in gene expression and that SG are another target for the toxic action of the peptide. Taken together, these findings contribute to a better understanding of the mechanism of action of Jaburetox as well as to the knowledge on basic aspects of the biochemistry and neurophysiology of insects, and might help in the development of optimized strategies for insect control.

An arginase-1 SNP that protects against the development of pulmonary hypertension in bronchopulmonary dysplasia enhances NO-mediated apoptosis in lymphocytes.

Arginase and nitric oxide synthase (NOS) share a common substrate, l‐arginine, and have opposing effects on vascular remodeling. Arginase is the first step in polyamine and proline synthesis necessary for cellular proliferation, while NO produced from NOS promotes apoptosis. Previously, we identified a single nucleotide polymorphism (SNP) in the arginase‐1 (ARG1) gene, rs2781666 (T‐allele) that was associated with a decreased risk for developing pulmonary hypertension (PH) in a cohort of infants with bronchopulmonary dysplasia (BPD). In this study, we utilized lymphocytes from neonates (the only readily available cells from these patients expressing the two genotypes of interest) with either the rs2781666 SNP (TT) or wild type (GG) to test the hypothesis that the protection of the ARG1 SNP against the development of PH in BPD would involve augmented NO production leading to more apoptosis. Lymphocytes were stimulated with IL‐4, IL‐13, and phorbol myristate acetate (PMA). We found that TT lymphocytes had similar levels of arginase I and arginase II expression, but there was a tendency for lower urea production (a surrogate marker of arginase activity), than in the GG lymphocytes. The TT lymphocytes also had significantly greater NO production than did GG lymphocytes despite no differences in iNOS expression between genotypes. Furthermore, the TT lymphocytes had lower numbers of viable cells, and higher levels of cleaved caspase‐3 than did GG lymphocytes. Inhibiting NOS activity using N ω‐Nitro‐l‐arginine methyl ester hydrochloride (l‐NAME) significantly decreased cleaved caspase‐3 levels in the TT lymphocytes. These data demonstrate that the TT genotype results in greater levels of NO production leading to more apoptosis, which is consistent with the concept that BPD patients with the TT genotype are protected against the development of PH by producing greater basal levels of endogenous NO.

The role of nitric oxide in the epigenetic regulation of THP-1 induced by lipopolysaccharide

AimsChanges in the gene expression are one of the molecular events involved in the Systemic of Inflammatory Response Syndrome during sepsis. The preconditioning with low doses of lipopolysaccharide (LPS) reduces the expression of pro-inflammatory genes leading to less tissue damage and better outcome. This hyporesponsive state called tolerance is associated to alterations in chromatin structure and nitric oxide (NO) production. In the current study, we demonstrated that tolerance induced by LPS was found to be NO-dependent and related to epigenetic changes. Main methodsTHP-1 cells were cultivated in RPMI medium (Control), submitted to tolerance (500ng/mL of LPS 24h before challenge with 1000ng/mL of LPS during 24h Tolerant group) and challenge (1000ng/mL of LPS during 24h Directly challenged group). The analyses performed were: cytokines production, histone acetyl transferases/histone deacetylases (HAT/HDAC) activity, nitrosylation of HDAC-2 and -3, expression of acetylated histones H3 and H4. HDAC and Nitric Oxide Synthases (NOS) activities were inhibited with 30mM trichostatin (TSA) and 100μM LNAME, respectively. Key findingsAdministration of low doses of LPS repressed the production of IL-6 and IL-10, however this effect was abolished with the inhibition of NOS activity and by TSA in the case of IL-10. Tolerance modulates the activity of HAT and, consequently, the acetylation of histones H3 and H4. Inhibition of NO decreases acetylation of Histones. The HDACs 2 and 3 were nitrosylated after the tolerance induction. SignificanceThe tolerance to LPS regulates the cytokine production by modulating chromatin structure and this event is NO dependent.

Protective effect of a polysaccharide from Rhizoma Atractylodis Macrocephalae on acute liver injury in mice

A homogeneous polysaccharide was isolated and purified from Rhizoma Atractylodis Macrocephalae (RAM) and named PRAM2. Its average molecular weight was 19.6×103Da and it was composed of rhamnose, xylose, arabinose, glucose, mannose and galactose in a ratio of 1: 1.3: 1.5: 1.8: 2.1: 3.2. In vitro experiments confirmed that PRAM2 presented an obvious effect to scavenge 1,1-diphenyl-2-picrylhydrazyl radical 2,2-diphenyl-1-(2,4,6-trinitrophenyl) (DPPH), superoxide anion and hydroxyl radical. In vivo experiments confirmed that PRAM2 could reduce the liver weight, liver index, aspartate transaminase (AST) and alanine aminotransferase (ALT) activities in the serum; meanwhile, PRAM2 could significantly reduce nitric oxide synthase (NOS) activity, and nitric oxide (NO) and malonaldehyde (MDA) contents in the liver tissues, and increase superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. These results suggest that PRAM2 has a significant in vitro antioxidant activity and a protective effect on CCl4-induced liver injury in mice; the protective effect may be related to its anti-oxidation, its inhibition of NOS activity and NO level and its reduction of the production of free radicals.

Enhanced nitric oxide generation in root transition zone during the early stage of cadmium stress is required for maintaining root growth in barley

The objective of this study was to analyse the role of nitric oxide (NO) in relation to reactive oxygen species (ROS) production and root growth inhibition in the early response of barley root tip to cadmium. We used cell-permeable NO-binding dye DAF-2DA for the NO localization and cell-impermeable dye DAR-4M for the quantification of NO in barley root apex. A considerable increase in NO production was detected in the transition zone of root tips already 30 min after the immersion of barley roots into 15 μM Cd. This Cd-induced NO generation further increased during the recovery period and reached its maximum level 2 h after the short-term treatment. At this stage an enhanced Cd-induced NO generation was observed in the meristematic, transition and in the beginning of elongation zone in comparison with control roots. Inhibitor of NO synthase activity markedly reduced root growth in control seedlings and had a synergistic growth inhibitory effect with Cd. On the contrary, this Cd-induced root growth inhibition was markedly alleviated by the NO donor. Exposure of roots to Cd markedly increased the production of ROS in the proximal elongation zone of root. While NO did not affect ROS generation, inhibition of its synthesis slightly decreased ROS generation in both control and Cd-treated roots. Our results revealed that enhanced NO production is a very early response of barley root to Cd stress and it is involved in the regulation of root growth mitigating Cd-induced root growth inhibition.

Evidence that reduced nitric oxide signal contributes to cutaneous microvascular dysfunction in peripheral arterial disease.

Peripheral arterial disease (PAD) is associated with cutaneous microvascular dysfunction and an increased risk of arterial ulceration in the affected lower-limb(s). The purpose of this study was to investigate the role of nitric oxide (NO) in cutaneous microvascular dysfunction in patients with PAD. Using laser-Doppler flowmetry, we measured skin blood flow (SkBF) in 5 patients with unilateral symptomatic PAD and 10 age-matched healthy controls at baseline and during 40 min of local skin heating to 42°C at 1) untreated lower-leg sites, and 2) lower-leg sites treated with 20 mM N(G)-nitro-L-arginine methyl ester (L-NAME) to inhibit NO synthase activity. SkBF was expressed as laser-Doppler flux (LDF) and normalized to maximal LDF (%LDF(max)) achieved through localized heating to 44°C and concomitant infusion of 56 mM sodium nitroprusside. Pharmacological agents and control treatments (lactated Ringer's) were administered using intradermal microdialysis. The plateau LDF response to local skin warming at the untreated skin sites was significantly (P<0.05) lower in the diseased limb of the PAD patients (70.3±13.6 %max) compared to the non-diseased contralateral limb (85.0±10.2 %max) and the response observed for the control participants (89.0±5.2 %max). The NO contribution to the plateau SkBF response tended to be lower in the diseased limb of the PAD patients (45.1±16.4% versus 56.1±10.7% [P=0.12] and 55.4±11.5% [P=0.13], respectively). The results suggest that PAD impairs downstream cutaneous microvascular vasodilatory function and that the microvascular dysfunction is probably explained, at least in part, by a reduced NO signal.

Obesity-induced cerebral hypoperfusion derived from endothelial dysfunction: one of the risk factors for Alzheimer's disease.

Increasing evidence supports the idea that chronic hypoperfusion in the brain is responsible for the pathogenesis underling Alzheimer's disease (AD). Obesity at midlife is associated with the risk of cognitive loss and AD at later life. Obesity decreases cerebral blood flow that is associated with decreased synthesis and actions of nitric oxide (NO) derived from the endothelium and also increases the production of oxidative stress. Increased plasma levels of asymmetric dimethylarginine decreases the production of NO by inhibiting NO synthase activity, leading to cerebral hypoperfusion and cognitive and neurodegenerative changes in AD. Adiponectin has a cerebroprotective action through an eNOSdependent mechanism. Obesity-induced endothelial dysfunction and cerebral hypoperfusion enhance the production of β-amyloid that in turn impairs endothelial function; this vicious cycle promotes the pathogenic changes leading to AD. Interrupting this cycle by enhancement of NO-mediated cerebral blood flow is expected to promote prophylaxis against AD pathogenesis. This review summarizes recent advances in prophylactic or therapeutic measures, including physical exercise, nutritionally adequate dietary intake, pharmacological treatments such as acetylcholinesterase inhibitors and antioxidants, and bariatric surgery that are efficient in protecting and retarding the progress of cognitive failure and neurodegeneration.

Endothelial arginine resynthesis contributes to the maintenance of vasomotor function in male diabetic mice.

AimArgininosuccinate synthetase (ASS) is essential for recycling L-citrulline, the by-product of NO synthase (NOS), to the NOS substrate L-arginine. Here, we assessed whether disturbed arginine resynthesis modulates endothelium-dependent vasodilatation in normal and diabetic male mice.Methods and ResultsEndothelium-selective Ass-deficient mice (Assfl/fl/Tie2Cretg/− = Ass-KOTie2) were generated by crossing Assfl/fl mice ( = control) with Tie2Cre mice. Gene ablation in endothelial cells was confirmed by immunohistochemistry. Blood pressure (MAP) was recorded in 34-week-old male mice. Vasomotor responses were studied in isolated saphenous arteries of 12- and 34-week-old Ass-KOTie2 and control animals. At the age of 10 weeks, diabetes was induced in control and Ass-KOTie2 mice by streptozotocin injections. Vasomotor responses of diabetic animals were studied 10 weeks later. MAP was similar in control and Ass-KOTie2 mice. Depletion of circulating L-arginine by arginase 1 infusion or inhibition of NOS activity with L-NAME resulted in an increased MAP (10 and 30 mmHg, respectively) in control and Ass-KOTie2 mice. Optimal arterial diameter, contractile responses to phenylephrine, and relaxing responses to acetylcholine and sodium nitroprusside were similar in healthy control and Ass-KOTie2 mice. However, in diabetic Ass-KOTie2 mice, relaxation responses to acetylcholine and endothelium-derived NO (EDNO) were significantly reduced when compared to diabetic control mice.ConclusionsAbsence of endothelial citrulline recycling to arginine did not affect blood pressure and systemic arterial vasomotor responses in healthy mice. EDNO-mediated vasodilatation was significantly more impaired in diabetic Ass-KOTie2 than in control mice demonstrating that endothelial arginine recycling becomes a limiting endothelial function in diabetes.

Taras Shevchenko National University of Kyiv, Ukraine

It was established in experiments on the rats in the acute period of modeling pituitrin-isadrin myocardial infarction the formation of nitrogen monoxide decreases along with its accelerated transformation into peroxynitrite. It was evidenced by more than double inhibition of NO synthase activity in the myocardium and by decreasing the amount of nitrates on the background of the increasing level of peroxynitrites' marker--nitrotyrosine by 246.6% at an average. Experimental therapy of rats by ademol which is a derivate of adamantan (1-adamantiloxy-3-morpholino-2 propanol hydrochloride) better than by corvitin normalizes the processes of synthesis of nitric oxide. At the same time ademol probably exceeded the reference drug in ability to increase NO synthase activity and amount of nitrate, and promoted a decrease of the level of nitrotyrosine in the myocardium on the average by 36.3; 50.6 and 12.7%, respectively. Corrective influence of ademol on indicators of metabolism in NO system under the conditions of acute cardiac ischemia indicates to promicing development of domestic cardioprotector on its base.

Excessive nitric oxide impairs wound collagen accumulation

BackgroundNitric oxide (NO) plays a major regulatory role in wound collagen synthesis. We hypothesized that this regulatory role is tightly controlled by the levels of NO in the wound environment and that supranormal wound NO generation impairs wound collagen accumulation. Materials and methodsWe used the model of turpentine-induced granuloma in male Sprague–Dawley rats as a sterile inflammatory stimulus generating large amounts of NO. In this environment, NO generation increased by 260%, whereas collagen deposition was significantly reduced by 38.5% (729.7 ± 81.5 versus 449.4 ± 76.3 μg hydroxyproline/100 mg sponge, P<0.05). Inhibition of NO synthase activity using 300 mM L-N6-(1-iminoethyl)-lysine, a highly potent and selective inhibitor of inducible NO synthase, significantly reduced NO elevation by 43.3% and increased wound collagen deposition by 37.3% (P<0.05). These effects occurred without any anti-inflammatory effects of L-N6-(1-iminoethyl)-lysine as assessed by the white blood cell counts and levels of interleukins 1 and 6. ConclusionsThe data show that high levels of NO within the wound environment significantly reduce wound collagen deposition. Inhibition of NO generation restores collagen levels to normal levels. The regulatory effects of NO on wound collagen appear to be highly correlated with the amount of NO generated.

Effects of Red Light-emitting Diode Irradiation on Dental Pulp Cells

Light irradiation activates a range of cellular processes in a variety of cell types, including stem cells, and can promote tissue repair. This study investigated the effects of light-emitting diode (LED) exposure on dental pulp cells (DPCs). Dose response analysis at 20-second intervals up to 120 seconds demonstrated that a LED array emitting 653-nm red light stimulated significantly increased cell growth at 3 and 7 days post-irradiation with 40 (149 mJ/cm2) and 60 (224 mJ/cm2) seconds of radiant exposure. Double-dosing cells at days 1 and 4 of a 7-day culture period with 60-second (224 mJ/cm2) LED exposure significantly increased cell growth compared with a single dosing regime. BrdU analysis demonstrated significantly increased proliferation rates associated with significantly increased ATP, nitric oxide (NO), and mitochondrial metabolic activity. LED-stimulated NO levels were not reduced by inhibition of NO-synthase activity. Light exposure also rescued the inhibition of mitochondrial dysfunction and increased levels of in vitro mineralization compared with control. Media exchange experiments indicated that autocrine signaling was not likely responsible for red-light-induced DPC activity. In conclusion, data analysis indicated that 653-nm LED irradiation promoted DPC responses relevant to tissue repair, and this is likely mediated by increased mitochondrial activity.

Cyclooxygenase-2 prostaglandins mediate anandamide-inhibitory action on nitric oxide synthase activity in the receptive rat uterus

Anandamide, an endocannabinoid, prostaglandins derived from cyclooxygenase-2 and nitric oxide synthesized by nitric oxide synthase (NOS), are relevant mediators of embryo implantation. We adopted a pharmacological approach to investigate if anandamide modulated NOS activity in the receptive rat uterus and if prostaglandins mediated this effect. As we were interested in studying the changes that occur at the maternal side of the fetal–maternal interface, we worked with uteri obtained from pseudopregnant rats. Females were sacrificed on day 5 of pseudopregnancy, the day in which implantation would occur, and the uterus was obtained. Anandamide (2ng/kg, i.p.) inhibited NOS activity (P<0.001) and increased the levels of prostaglandin E2 (P<0.001) and prostaglandin F2α (P<0.01). These effects were mediated via cannabinoid receptor type 2, as the pre-treatment with SR144528 (10mg/kg, i.p.), a selective cannabinoid receptor type 2 antagonist, completely reverted anandamide effect on NOS activity and prostaglandin levels. The pre-treatment with a non-selective cyclooxygenase inhibitor (indomethacin 2.5mg/kg, i.p.) or with selective cyclooxygenase-2 inhibitors (meloxicam 4mg/kg, celecoxib 3mg/kg, i.p.) reverted anandamide inhibition on NOS, suggesting that prostaglandins are derived from cyclooxygenase-2 mediated anandamide effect. Thus, anandamide levels seemed to modulate NOS activity, fundamental for implantation, via cannabinoid receptor type 2 receptors, in the receptive uterus. This modulation depends on the production of cyclooxygenase-2 derivatives. These data establish cannabinoid receptors and cyclooxygenase enzymes as an interesting target for the treatment of implantation deficiencies.