Involvement of nitric oxide in the pathogenesis of cyclophosphamide-induced hemorrhagic cystitis.

The involvement of nitric oxide (NO) and the potential modulation of NO synthase (NOS) activity by platelet-activating factor were investigated in a rat model of cyclophosphamide-induced hemorrhagic cystitis. Male Wistar rats received a single intraperitoneal injection of cyclophosphamide, and cystitis was evaluated 6, 12, 24, 48, and 72 hours later by determining the changes in bladder wet weight and plasma protein extravasation and the macro- and microscopic morphological alterations. In addition, NOS activity and NADPH-diaphorase histochemistry were studied in bladder tissues. Normal bladders showed extensive NADPH-diaphorase staining and a high level of constitutive NOS whereas the activity of inducible NOS was almost undetectable. Cyclophosphamide dose- and time-dependently increased the bladder wet weight and bladder plasma protein extravasation. These events were accompanied at a microscopic level by urothelial necrosis, sloughing, ulceration, hemorrhage, and leukocyte infiltration. Cyclophosphamide also increased the levels of inducible NOS but reduced those of constitutive NOS. The NOS inhibitors L-NG-nitroarginine methyl ester and L-NG-nitroarginine significantly reduced the cyclophosphamide-induced plasma protein extravasation and urothelial damage. This reduction was completely reversed by L-arginine but not by D-arginine. The administration of the platelet-activating factor antagonist BN 52021 decreased the cyclophosphamide-induced plasma protein extravasation as well as the rise in inducible NOS activity but had no effect on the fall in constitutive NOS activity. These results suggest that endogenous NO participates in the urothelial damage and in the inflammatory events leading to cyclophosphamide-induced hemorrhagic cystitis. Platelet-activating factor also seems to be involved in the pathogenesis of this condition, possibly by inducing NOS.     

Arrest of B16 melanoma cells in the mouse pulmonary microcirculation induces endothelial nitric oxide synthase-dependent nitric oxide release that is cytotoxic to the tumor cells

Metastatic cancer cells seed the lung via blood vessels. Because endothelial cells generate nitric oxide (NO) in response to shear stress, we postulated that the arrest of cancer cells in the pulmonary microcirculation causes the release of NO in the lung. After intravenous injection of B16F1 melanoma cells, pulmonary NO increased sevenfold throughout 20 minutes and approached basal levels by 4 hours. NO induction was blocked by N(G)-nitro-L-arginine methyl ester (L-NAME) and was not observed in endothelial nitric oxide synthase (eNOS)-deficient mice. NO production, visualized ex vivo with the fluorescent NO probe diaminofluorescein diacetate, increased rapidly at the site of tumor cell arrest, and continued to increase throughout 20 minutes. Arrested tumor cells underwent apoptosis with apoptotic counts more than threefold over baseline at 8 and 48 hours. Neither the NO signals nor increased apoptosis were seen in eNOS knockout mice or mice pretreated with L-NAME. At 48 hours, 83% of the arrested cells had cleared from the lungs of wild-type mice but only approximately 55% of the cells cleared from eNOS-deficient or L-NAME pretreated mice. eNOS knockout and L-NAME-treated mice had twofold to fivefold more metastases than wild-type mice, measured by the number of surface nodules or by histomorphometry. We conclude that tumor cell arrest in the pulmonary microcirculation induces eNOS-dependent NO release by the endothelium adjacent to the arrested tumor cells and that NO is one factor that causes tumor cell apoptosis, clearance from the lung, and inhibition of metastasis.     

Phosphorylation of extracellular signal-regulated kinases in bladder afferent pathways with cyclophosphamide-induced cystitis

Extracellular signal-regulated kinases (ERK1 and ERK2) are phosphorylated in the nervous system after somatic or visceral stimulation or inflammation and play roles in central sensitization and pain hypersensitivity. ERK1/2 activation with cyclophosphamide (CYP)-induced cystitis has been demonstrated in urinary bladder and inhibitors of ERK1/2 phosphorylation reduce CYP-induced bladder hyperreflexia. In this study, we determined pERK1/2 expression and regulation in lumbosacral dorsal root ganglia (DRG) and spinal cord with CYP-induced cystitis (4 h, 48 h, chronic) using Western blotting and immunohistochemical techniques. Phosphorylated extracellular signal-regulated kinases (pERK1/2) expression was significantly (P≤0.01) upregulated in L6 and S1 DRG with CYP-induced cystitis with the greatest upregulation occurring at 4 h. No changes in pERK1/2 expression were observed in L1, L2 or L5 DRG or in any spinal cord segment examined (L1, L2, L5–S1) with CYP-induced cystitis. Cytoplasmic pERK1/2–immunoreactivity (IR) and pericellular pERK1/2–IR was observed in all DRG examined from control rats and cytoplasmic pERK1/2–IR was significantly (P≤0.01) increased in L6 and S1 DRG with 4 and 48 h CYP-induced cystitis. In contrast, pericellular pERK1/2–IR in DRG was not regulated by CYP-induced cystitis. A small percentage of bladder afferent cells in lumbosacral DRG expressed pERK1/2-IR in control rats; however, CYP-induced cystitis (48 h) significantly (P≤0.01) increased the percentage of bladder afferent cells in the L6 and S1 DRG exhibiting pERK1/2–IR. These studies suggest that activation of the ERK pathway in lumbosacral DRG may play a role in neuroplasticity in micturition reflexes with CYP-induced cystitis.     

Isosorbide dinitrate improves the efficacy of bone mesenchymal stem cell transplantation via endothelial nitric oxide synthase-dependent mechanism

This study investigated the effect of treatment wientry isosorbide dinitrate (Isoket) on bone mesenchymal stem cell (BMSC) transplantation in a rat model of myocardial infarction (MI) and its possible mechanism. Sprague-Dawley (SD) rats were randomized to a sham operation group, MI control group, BMSC transplantation group, and Isoket-BMSCs transplantation group. Isosorbide dinitrate (Isoket, 5?μg/m) was administered by intraperitoneal injection (10?ml/kg) at 0, 12, and 24?hours following ischemia/reperfusion induction of MI models. Left ventricular function, myocardial infarct size (MIS), the survival of engrafted BMSCs, and expression of vascular endothelial growentry factor (VEGF), inducible nitric oxide synthase (iNOS), and endothelial nitric oxide synthase (eNOS) proteins were detected 2?weeks post-transplantation. The results showed isosorbide dinitrate attenuated cardiac dysfunction, increased the survival of engrafted cells in the ischemic heart and promoted iNOS, eNOS, and VEGF protein expression. It is suggested that isosorbide dinitrate enhances mesenchymal stem cell therapy for MI via an eNOS-dependent mechanism.     

Role of nitric oxide in haemodialysis hypotension

To investigate the possible involvement of nitric oxide (NO) in haemodialysis hypotension, we measured plasma concentrations of nitrate anion (NO3-), a metabolite of NO, in 114 patients undergoing maintenance haemodialysis. Mean plasma NO3- concentrations before dialysis were greater in subjects with lower blood pressure (155 +/- 16 micromol L-1) than in those with middle (117 +/- 8 micromol L-1) or higher blood pressure (105 +/- 12 micromol L-1) before dialysis. Further, mean plasma NO3- concentrations before dialysis were greater in subjects with lower blood pressure (186 +/- 13 micromol L-1) than in those with middle (112 +/- 7 micromol L-1) or higher blood pressure (64 +/- 11 micromol L-1) after dialysis. Plasma NO3- concentrations before dialysis were inversely correlated with mean blood pressure before dialysis (r=0.318, P=0.0006), and showed a strong inverse correlation with mean blood pressure after dialysis (r=0.608, P=0.0001). In the selected participants who had equal range of mean blood pressure before dialysis, mean plasma NO3- concentrations were greater in subjects with severe hypotension during dialysis (180 +/- 14 micromol L-1) than in those with mild hypotension (99 +/- 11 micromol L-1) or without hypotension (53 +/- 12 micromol L-1); plasma NO3- concentrations before dialysis were inversely correlated with changes in mean blood pressure during dialysis and mean blood pressure after dialysis. Results indicate that enhanced NO production may be involved in acute hypotension during dialysis, and suggest the possible involvement of NO in the pathogenesis of chronic hypotension associated with maintenance haemodialysis.     

Role of nitric oxide in inflammation.

A number of laboratories have sought to elucidate the role of nitric oxide (NO) in both acute and chronic inflammatory diseases. It is now well appreciated that NO can influence many aspects of the inflammatory cascade ranging from its own expression to recruitment of leucocytes to the effected tissue. With the advent of mice selectively deficient in the various isoforms of nitric oxide synthase (NOS), the role that NO may play in various disease states can now be examined in vivo. One such syndrome that has gained much attention in recent years is ischaemia and reperfusion-induced tissue injury. Ischaemia-reperfusion (I/R) injury is an important clinical consideration in situations such as transplantation, trauma, liver or bowel resection and haemorrhagic shock. A hallmark of I/R is the production of reactive oxygen species (ROS) during the reperfusion phase and it is thought that the production of ROS mediate much of the post-ischaemic tissue injury. This review will examine the current state of knowledge regarding the regulatory mechanisms by which NO can influence various aspects of the inflammatory cascade as well as its role in a model of I/R injury in vivo.     

Role of nitric oxide in anaphylactic shock

Nitric oxide, synthesized from the guanidino group ofl-arginine by nitric oxide synthase, has an important role in pathophysiological changes associated with anaphylaxis. Nitric oxide production due to activation of constitutive nitric oxide synthase is detected using a nitric oxide-selective electrode in anaphylactic rabbitsin vivo. A nitric oxide synthase inhibitor attenuates hypotension and hemoconcentration and decreases venous return but does not improve cardiac depression. Nitric oxide functionally antagonizes the effects of vasoconstrictors released by anaphylaxisin vitro. In animals pretreated with a nitric oxide synthase inhibitor, the cardiac output falls significantly, although venous return is increased. Pulmonary resistance is significantly increased with a nitric oxide synthase inhibitor, andl-arginine attenuates the bronchospasm. These findings suggest that production of nitric oxide may reduce the pathophysiologic changes, except for vasodilatation, associated with anaphylaxis.     

Role of nitric oxide in mast cells

Mast cells (MC) are important effector cells in allergic disorders. Recenty, the role of MC in innate and adaptive immunity is gaining prominence. Nitric oxide is an important signaling molecule and its production in mast cell has been reported widely. However, controversy exists about whether MC produce NO. This review addresses the role of NO in MC biology and the reasons behind the controversy and discusses effects of NO in regulation of MC phenotype and function.     

Role of nitric oxide in implantation and menstruation

Nitric oxide (NO) is a major paracrine mediator of various biological processes, including vascular functions and inflammation. In blood vessels, NO is produced by the low-input constitutive endothelial NO synthase (eNOS) and is a potent vasodilator and platelet aggregation inhibitor. The inducible NOS isoform (iNOS) is capable of producing NO at high concentrations which have pro-inflammatory properties. Immunohistochemical and molecular studies of endometrial NOS expression, as well as animal experiments with NOS inhibitors, indicate that NO plays an important role in endometrial functions such as endometrial receptivity, implantation and menstruation. In rodents, both iNOS and eNOS are highly up-regulated in the implantation sites, and NOS inhibitors show synergistic effects with antiprogestins in inhibiting the establishment of pregnancy. In the human endometrium, eNOS have been localized in the glandular epithelium and in endometrial microvascular endothelium, primarily during the luteal phase. iNOS has been found in the endometrial epithelium during menstruation, in immunocompetent endometrial cells, and in decidualized stromal cells. In primates, NO may be involved in the initiation and maintenance of menstrual bleeding by inducing tissue breakdown and vascular relaxation as well as by inhibiting platelet aggregation. Endometrium-derived NO may also play a role in myometrial relaxation during menstruation. These studies open up new applications for NO-donating and -inhibiting agents in uterine disorders. NO donors may be useful in the treatment of dysmenorrhoea and for promoting fertility. Antiprogestins, progesterone receptor modulators and iNOS inhibitors may find applications in the treatment and prevention of abnormal uterine bleeding.     

Role of nitric oxide synthases in elastase-induced emphysema

Nitric oxide (NO) in combination with superoxide produces peroxynitrites and induces protein nitration, which participates in a number of chronic degenerative diseases. NO is produced at high levels in the human emphysematous lung, but its role in this disease is unknown. The aim of this study was to determine whether the NO synthases contribute to the development of elastase-induced emphysema in mice. nNOS, iNOS, and eNOS were quantified and immunolocalized in the lung after a tracheal instillation of elastase in mice. To determine whether eNOS or iNOS had a role in the development of emphysema, mice bearing a germline deletion of the eNOS and iNOS genes and mice treated with a pharmacological iNOS inhibitor were exposed to elastase. Protein nitration was determined by immunofluorescence, protein oxidation was determined by ELISA. Inflammation and MMP activity were quantified by cell counts, RT-PCR and zymography in bronchoalveolar lavage fluid. Cell proliferation was determined by Ki67 immunostaining. Emphysema was quantified morphometrically. iNOS and eNOS were diffusely upregulated in the lung of elastase-treated mice and a 12-fold increase in the number of 3-nitrotyrosine-expressing cells was observed. Over 80% of these cells were alveolar type 2 cells. In elastase-instilled mice, iNOS inactivation reduced protein nitration and increased protein oxidation but had no effect on inflammation, MMP activity, cell proliferation or the subsequent development of emphysema. eNOS inactivation had no effect. In conclusion, in the elastase-injured lung, iNOS mediates protein nitration in alveolar type 2 cells and alleviates oxidative injury. Neither eNOS nor iNOS are required for the development of elastase-induced emphysema.     

Exhaled nitric oxide is associated with allergic inflammation in children

Exhaled nitric oxide (eNO) has been proposed as a noninvasive marker of airway inflammation in asthma. In asthmatic patients, exhaled NO levels have been shown to relate with other markers of eosinophilic recruitment, which are detected in blood, sputum, bronchoalveolar lavage fluid and bronchial biopsy samples. The purpose of this study was to assess the possible relationship between eNO and allergic inflammation or sensitization in childhood asthma and allergic rhinitis. Subjects consisted of 118 asthmatic children, 79 patients with allergic rhinitis, and 74 controls. Their age ranged from 6 to 15 yr old. eNO level, peripheral blood eosinophil count, eosinophil cationic protein (ECP), serum total IgE level and specific IgE levels were measured. Methacholine challenge test and allergic skin prick test for common allergens were performed in all subjects. Atopic group (n = 206, 44.48 ± 30.45 ppb) had higher eNO values than non-atopic group (n = 65, 20.54 ± 16.57 ppb, P < 0.001). eNO level was significantly higher in patients with asthma (42.84 ± 31.92 ppb) and in those with allergic rhinitis (43.59 ± 29.84 ppb) than in healthy controls (27.01 ± 21.34 ppb, P < 0.001) but there was no difference between asthma and allergic rhinitis group. eNO also had significant positive correlations with Dermatophagoides pteronyssinus IgE level (r = 0.348, P < 0.001), Dermatophagoides farinae IgE level (r = 0.376, P < 0.001), and the number of positive allergens in skin prick test (r = 0.329, P = 0.001). eNO had significant positive correlations with peripheral blood eosinophil count (r = 0.356, P < 0.001), serum total IgE level (r = 0.221, P < 0.001), and ECP (r = 0.436, P < 0.001). This study reveals that eNO level is associated with allergic inflammation and the degree of allergic sensitization.     

Role of nitric oxide in the mechanisms of Verograffin nephrotoxicity

Nephrotoxicity of radiopaque agents and the role of nitric oxide in its realization are studied in Wistar rats with Verograffin-induced acute renal insufficiency. Experiments demonstrate a significant decrease in nitric oxide production in the kidneys due to inhibition of constitutive NO-synthetase and disturbances of renal function, hemodynamics, and electrolyte balance. These changes are prevented by simultaneous injection of verapamil. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 10, pp. 396–399, October, 1997     

Role of nitric oxide during rotavirus infection

The pathophysiological mechanisms behind rotavirus-induced diarrhoea still remain incomplete. Current views suggest that the non-structural protein 4 (NSP4) of rotavirus and the enteric nervous system (ENS) participate in water secretion and diarrhoea. In the present work the role of nitric oxide (NO) in rotavirus infection and disease has been studied in vitro, mice and humans. Incubation of human intestinal epithelial cells (HT-29) with purified NSP4 but not with infectious virus produced NO2/NO3 accumulation in the incubation media. The NSP4-induced release of NO metabolites occurred within the first minutes after the addition of the toxin. Mice infected with murine rotavirus (strain EDIM) accumulated NO2/NO3 in the urine at the onset for diarrhoea. Following rotavirus infection, inducible nitric oxide synthetase (iNOS) mRNA was upregulated in ileum, but not in duodenum or jejunum of newborn pups within 5 days post-infection. A prospective clinical study including 46 children with acute rotavirus infection and age-matched controls concluded that rotavirus infection stimulates NO production during the course of the disease (P < 0.001). These observations identify NO as an important mediator of host responses during rotavirus infection.     

Role for nitric oxide in hookworm-associated immune suppression

Hookworm infection is a major cause of anemia and malnutrition in resource-poor countries. Human and animal studies suggest that infection with these intestinal nematodes is associated with impaired cellular immunity, characterized by reduced lymphocyte proliferation in response to both parasite and heterologous antigens. We report here data from studies aimed at defining mechanisms through which hookworms modulate the host cellular immune response. Splenocytes and mesenteric lymph node (MLN) cells from hamsters infected with Ancylostoma ceylanicum showed minimal proliferation in response to mitogen at days 20 and 30 postinfection (p.i.), with partial recovery noted at day 70 p.i. The proliferative capacity of enriched splenocyte T-cell preparations from infected animals following stimulation with hookworm antigens was partially restored in the presence of antigen-presenting cells from uninfected hamsters. Analysis by fluorescence-activated cell sorting revealed that hookworm infection is associated with reduced percentages of both CD4⁺ and surface immunoglobulin G-positive lymphocytes in the spleen and MLN cells. Splenocytes from infected hamsters also secreted more nitric oxide (NO) in culture than did those from naïve animals. Inhibition of NO secretion was associated with partial restoration of the proliferative capacity of splenocytes from infected animals in response to concanavalin A, suggesting a role for NO in mediating this effect. Together, these data demonstrate that hookworm infection is associated with impaired function of antigen-presenting cells and depletion of important lymphocyte subpopulations and also suggests a role for NO in parasite-induced immunosuppression.It is estimated that more than 700 million people in resource-poor countries are infected with hookworms, bloodfeeding intestinal nematodes that cause anemia and malnutrition (8, 14). Together with Ascaris lumbricoides and Trichuris trichiura, the hookworms Ancylostoma duodenale and Necator americanus comprise the group of soil-transmitted nematodes that are now recognized as a major cause of global morbidity (2, 56). Significant clinical features of hookworm infection in humans include iron-deficiency anemia, hypoproteinemia, and growth delay (13, 53). Although control strategies relying on targeted delivery of benzimidazole antihelminthics are generally effective at eliminating adult worms, reinfection occurs quickly and frequent treatments may be necessary for sustained improvement in the health of at-risk populations (50, 52).Although sterile immunity does not appear to develop following natural infection, data from human and animal studies confirm that hookworms elicit humoral and cellular immune responses in mammalian hosts (18). Although the nature of this response has yet to be elucidated fully, infection appears to be associated with a mixed Th1/Th2 host cytokine profile (22, 49). It has also been reported that hookworm infection is associated with suppression of host cellular responses to hookworm-specific and heterologous antigens (22, 45, 49). These studies suggest that hookworms, like other parasites, effectively downregulate host cell-mediated responses, blunting development of protective immunity (1, 41, 51).We report here results of studies designed to characterize the effect of hookworm infection on cellular immune responses. These data, which were acquired using the hamster model of Ancylostoma ceylanicum infection, confirm that hookworm infection is associated with reduced lymphocyte proliferation following stimulation with parasite antigens or T-cell mitogen. These studies also demonstrate for the first time impaired antigen presentation, a reduction in CD4⁺ T-lymphocyte number, and a role of nitric oxide (NO) in downregulation of the hamster cellular immune response. Together, the data provide new insights into how hookworms modulate immune responses in their mammalian hosts.     

Benefit of Satureja khuzestanica in subchronically rat model of cyclophosphamide-induced hemorrhagic cystitis

Cyclophosphamide (CP) as a widely used antineoplastic drug causes hemorrhagic cystitis (HC) mainly via induction of oxidative stress. Regarding established antioxidant potential of Satureja khuzestanica (Lamiaceae) essential oil (SKEO), we aimed to investigate its protective effects in a subchronic rat model of CP-induced HC. CP (6 mg/kg/day) and SKEO (225 mg/kg/day) were administered alone or in combination by gavage for 28 days. Histopathological changes were investigated by light microscopy. Plasma samples were assayed for lipid peroxidation and total antioxidant power as biomarkers of toxic stress.In the CP-treated animals, irregular mucus layer, severe hemorrhage and edema, infiltration of inflammatory cells, and accumulation of mast cells were observed. In the CP+SKEO group, a relatively normal urothelial topography with decreased number of mucosal mast cells and inflammatory cells were observed. Increased lipid peroxidation along with decreased total antioxidant capacity resulting from CP treatment was significantly recovered by SKEO co-treatment.It is concluded that SKEO protects rats from CP-induced HC by reduction of free radical-induced toxic stress. It is strongly recommended to examine SKEO in the clinic to approve its benefit in patients undertaking CP.     

Alteration of muscarinic and purinergic receptors in urinary bladder of rats with cyclophosphamide-induced interstitial cystitis

We characterized muscarnic and purinergic receptors and urodynamic parameters in the bladder of cyclophosphamide (CYP)-treated rats to clarify the mechanisms involved in the pathophysiology of interstitial cystitis (IC). In the cystometry of CYP-treated rats compared with control rats, the micturition interval and micturition volume were significantly (55% and 77%, respectively) decreased and the frequency of micturition and basal pressure were significantly (3 and 2.3 times, respectively) increased. These changes in urodynamic parameters may characterize the detrusor overactivity occurring in CYP-treated rats. The maximal number of binding sites (B(max)) for specific binding of [N-methyl-(3)H]scopolamine methyl chloride ([(3)H]NMS) and alphabeta-methylene ATP [2,8-(3)H]tetrasodium salt ([(3)H]alphabeta-MeATP) was significantly (43% and 31%, respectively) decreased in the bladder of CYP-treated rats compared with control rats. On the other hand, the apparent dissociation constant (K(d)) for neither radioligand was significantly altered by the CYP treatment. K(i) value for the inhibition of bladder [(3)H]NMS binding by antimuscarinic agents (oxybutynin, tolterodine, darifenacin, and AF-DX 116) did not differ significantly between control and CYP-treated rats. The inhibition constant (K(i)) for the inhibition of bladder [(3)H]alphabeta-MeATP binding by purinergic antagonists (A-317491, PPADS) was significantly higher in CYP-treated rats than control rats. In conclusion, CYP treatment has been shown to cause down-regulation of pharmacologically relevant (muscarinic and purinergic) receptors in the bladder of rats. Thus, the present study offers further pharmacological evidence that both muscarinic and purinergic mechanisms contribute significantly to the urinary dysfunction due to IC.     

内皮素和一氧化氮的失平衡在哮喘发病中的作用

目的:探讨内皮素和一氧化氮的平衡在哮喘发病中的作用。方法:用卵白蛋白作为致敏原制备哮喘大鼠模型,建立大鼠离体气管环的张力测定并用内皮素-1(ET-1)作用观察张力的变化和JKC302及L-亚硝基精氨酸甲酯(L-NAME)对ET-1作用的影响。结果:ET-1对正常大鼠和哮喘大鼠离体气道均有强大的收缩作用,对哮喘组的作用明显高于正常对照组(P＜0.01)。在哮喘大鼠ET-1的收缩气道作用只能被ET_A拮抗剂JKC302部分阻断,比例为13.5%。L-NAME孵育哮喘大鼠气管环后,ET-1的气道收缩反应明显升高(P＜0.05)。结论:哮喘大鼠气道对ET-1的反应性明显提高,一氧化氮可影响ET-1的作用,在大鼠介导ET-1气道收缩作用主要是ET_B受体。气道ET-1和NO平衡失调是引起哮喘发生的机制之一。     

Role of nitric oxide in the gastro-protective effect of lithium.

Background and aim: Lithium is widely used for the management of neuropsychiatric symptoms in bipolar disorders. A few studies have shown that lithium has a protective effect against gastric damage with an unknown mechanism. Some of the actions of lithium are mediated through nitric oxide (NO), which has an important role in the regulation of gastric wall blood flow as well as gastric mucosal integrity. The aim of this study was to test the hypothesis if the gastro-protective effect of lithium is mediated through NO. Methods: Male Wistar rats were pre-treated with either a non-selective NO synthase inhibitor (N(G)-nitro-l-arginine, 10mg/kg), a selective inducible NO synthase inhibitor (aminoguanidine, 100mg/kg) or saline. Lithium carbonate (10, 20, 50 and 100mg/kg) was then administered intraperitoneally 1h before the induction of gastric mucosal damage. Gastric damage was induced by either water immersion stress or ethanol gavage in rats. Results: Lithium had a significant protective effect in both stress and ethanol-induced gastric damage, but it needed in ethanol-induced gastric damage a higher dose than in the stress induced lesion. Lithium carbonate doses 20 and 50mg/kg produced plasma concentrations that were in the range of human therapeutic Li levels (0.6-1.0muM). Pre-treatment of animals with N(G)-nitro-l-arginine (20 and 40mg/kg) reduced the protective effect of lithium against ethanol-induced gastric damage, but not in stress-induced damage. Aminoguanidine administration showed no effect on the damage reduction either in control or lithium treated rats. Conclusions: The results indicate that NO might play a role in the gastro-protective effect of lithium against ethanol-induced gastric damage in rats.     

Role of nitric oxide in the pathogenesis of chronic pulmonary hypertension

Chronic pulmonary hypertension is a serious complication of a number of chronic lung and heart diseases. In addition to vasoconstriction, its pathogenesis includes injury to the peripheral pulmonary arteries leading to their structural remodeling. Increased pulmonary vascular synthesis of an endogenous vasodilator, nitric oxide (NO), opposes excessive increases of intravascular pressure during acute pulmonary vasoconstriction and chronic pulmonary hypertension, although evidence for reduced NO activity in pulmonary hypertension has also been presented. NO can modulate the degree of vascular injury and subsequent fibroproduction, which both underlie the development of chronic pulmonary hypertension. On one hand, NO can interrupt vascular wall injury by oxygen radicals produced in increased amounts in pulmonary hypertension. NO can also inhibit pulmonary vascular smooth muscle and fibroblast proliferative response to the injury. On the other hand, NO may combine with oxygen radicals to yield peroxynitrite and other related, highly reactive compounds. The oxidants formed in this manner may exert cytotoxic and collagenolytic effects and, therefore, promote the process of reparative vascular remodeling. The balance between the protective and adverse effects of NO is determined by the relative amounts of NO and reactive oxygen species. We speculate that this balance may be shifted toward more severe injury especially during exacerbations of chronic diseases associated with pulmonary hypertension. Targeting these adverse effects of NO-derived radicals on vascular structure represents a potential novel therapeutic approach to pulmonary hypertension in chronic lung diseases.     

Long-term administration of the histone deacetylase inhibitor vorinostat attenuates renal injury in experimental diabetes through an endothelial nitric oxide synthase-dependent mechanism

Epigenetic changes in gene expression play a role in the development of diabetic complications, including nephropathy. Histone deacetylases (HDACs) are a group of enzymes that exert epigenetic effects by altering the acetylation status of histone and nonhistone proteins. In the current study, we investigated the action of the clinically available HDAC inhibitor vorinostat in a mouse model of diabetic nephropathy, with the following aims: to define its effect on the progression of renal injury and to explore its mechanism of action by focusing on its role in regulating the expression of endothelial nitric oxide synthase (eNOS). Control and streptozotocin-diabetic wild-type and eNOS(-/-) mice were treated with vorinostat by daily oral dosing for 18 weeks. Without affecting either blood glucose concentration or blood pressure, vorinostat decreased albuminuria, mesangial collagen IV deposition, and oxidative-nitrosative stress in streptozotocin-wild-type mice. These attenuating effects were associated with a >50% reduction in eNOS expression in mouse kidneys and in cultured human umbilical vein endothelial cells. Vorinostat treatment had no effect on albuminuria, glomerular collagen IV concentration, or mesangiolysis in diabetic mice genetically deficient in eNOS. These observations illustrate the therapeutic efficacy of long-term HDAC inhibition in diabetic nephropathy and emphasize the importance of the interplay between eNOS activity and oxidative stress in mediating these effects.