Altered Nitric Oxide Metabolism Research Articles

Oxidative and Inflammatory Imbalance in Placenta and Kidney of sFlt1-Induced Early-Onset Preeclampsia Rat Model.

Preeclampsia (PE) is a pregnancy-specific disorder characterized by the new onset of hypertension plus proteinuria and/or end-organ dysfunction. Here, we investigate the role of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system as a major component of reactive oxygen species generation, in a rodent model of early-onset preeclampsia induced by excess sFlt1 (soluble fms-like tyrosine kinase 1). Placenta and kidney samples were obtained from normal pregnant and PE rats to measure the sFlt1/PlGF (placental growth factor) ratio in addition to oxidative stress-related parameters, including the activities and expressions of NADPH oxidase isoforms (NOX1, NOX2, and NOX4), components of nitric oxide (NO) metabolism, and antioxidant enzymes. Peroxisome proliferator-activated receptors (PPARα, PPARγ) and cytokines IL1β, IL3, IL6, IL10, and IL18 were also measured to evaluate the inflammation status in our experimental setting. Excessive O2●− production was found in rats that were treated with sFlt1; interestingly, this alteration appears to be mediated mainly by NOX2 in the placenta and by NOX4 in the kidney. Altered NO metabolism and antioxidant defense systems, together with mitochondrial dysfunction, were observed in this model of PE. Preeclamptic animals also exhibited overexpression of proinflammatory biomarkers as well as increased collagen deposition. Our results highlight the role of NADPH oxidase in mediating oxidative stress and possibly inflammatory processes in the placenta and kidney of an sFlt1-based model of early-onset preeclampsia.

Periodontal Nitric Oxide Pathway Alteration Due to Precompetition Anxiety in Handball Players

Psychologic and physical stress is known to be related with periodontal disorders. The objective of this study is to investigate salivary and gingival crevicular fluid (GCF) nitric oxide (NO) metabolism and its association with the periodontal reaction to precompetition anxiety in competitive athletes. A total of 18 elite male handball players participated in this study. The anxiety level of participants was determined by using a competitive state anxiety inventory-2 (CSAI-2). Periodontal clinical measurements, saliva, and GCF samples were obtained before the application of the CSAI-2 during the half-season break and just before the league championship match. NO-level, arginase, and NO synthase (NOS) activities were analyzed in saliva samples; NO and basic fibroblast growth factor (FGF-b) levels were analyzed in GCF samples. The CSAI-2 was significantly different between the two evaluation time points. GCF NO and FGF-b levels increased before the championship match, whereas saliva levels did not change. The plaque index and gingival index (GI) increased at the evaluation just before the championship match. The difference in the GI was statistically significant. The competitive stress of athletes may lead to a gingival/periodontal disturbance accompanied by an altered NO metabolism in saliva and GCF.

Asymmetric dimethylarginine, arginine and homoarginine at 11–13 weeks’ gestation and preeclampsia: a case–control study

The aim of this study was to investigate whether the nitric oxide (NO) pathway is altered in pregnancies that develop preeclampsia (PE). This was a nested case-control study of screening for PE, in which plasma asymmetric dimethylarginine (ADMA), L-arginine and L-homoarginine were measured at 11(+0)-13(+6) weeks. In all, 75 pregnancies that developed PE, including 25 requiring delivery before 34 weeks (early PE), and 300 unaffected controls were included. L-arginine and L-homoarginine were measured by gas chromatography-mass spectrometry, whereas ADMA was measured by gas chromatography-tandem mass spectrometry. Multiple regression analysis was used to determine if any maternal characteristics or gestation were significant predictors. In the early-PE group, both L-arginine and L-homoarginine expected medians (MoMs) were significantly reduced (median, IQR: 0.85, 0.76-1.04 vs 0.98, 0.88-1.16, P=0.021 and 0.78, 0.65-0.96 vs 0.99, 0.77-1.31, P=0.006, respectively) but ADMA MoMs were not significantly different (P=0.599). In early PE, compared with controls, the ratios of ADMA to L-arginine MoMs and ADMA to L-homoarginine MoMs were increased (median, IQR: 1.19, 0.94-1.33 vs 1.01, 0.75-1.31, P=0.003 and 1.21, 0.93-1.61 vs 0.99, 0.87-1.16, P=0.012, respectively). There were no significant differences between late PE and controls in ADMA, L-arginine, L-homoarginine or their ratios. In conclusion, development of early PE is associated with altered NO metabolism and/or synthesis apparent from the first trimester.

Molecular basis of hypertension side effects induced by sunitinib

Over the past decade a number of vascular complications have emerged, such as newly developed or worsened hypertension, in patients who were administered with new cancer treatments for several types of cancer that were untreatable earlier. Hypertension is emerging as one of the most common adverse effects of therapy with angiogenesis inhibitors. Small-molecule inhibitors of vascular endothelial growth factor signalling are associated with a high proportion of patients with hypertension. The mechanisms underlying the development of hypertension are not well known, although there seem to be several mechanisms. Physiopathology of hypertension implicates abnormalities in endothelial function and angiogenesis. Several features of hypertensive patients are reduced number of arterioles and capillaries, alterations of the microvascular network, decrease in vascular wall compliance and flexibility, reduced nitric oxide bioactivity and increases in plasma vascular endothelial growth factor. Treatment with tyrosine kinase inhibitors (TKIs) is associated with a significant and sustained increase in blood pressure. We suspect that TKIs exert their hypertensive effects directly at the level of the microvascular network through processes such as vascular rarefaction, endothelial dysfunction and/or altered nitric oxide metabolism. This study shows the vascular complications of treatment with a TKI, sunitinib (SU11248), with special emphasis on hypertension.

Hyperoxia-Induced Lung Injury in Gamma-Glutamyl Transferase Deficiency Is Associated with Alterations in Nitrosative and Nitrative Stress

gamma-Glutamyl transferase (GGT) regulates glutathione metabolism and cysteine supply. GGT inactivation in GGT(enu1) mice limits cysteine availability causing cellular glutathione deficiency. In lung, the resultant oxidant burden is associated with increased nitric oxide (NO) production, yet GGT(enu1) mice still exhibit higher mortality in hyperoxia. We hypothesized that NO metabolism is altered under severe oxidant stress and contributes to lung cellular injury and death. We compared lung injury, NO synthase (NOS) expression, nitrate/nitrite production, nitroso product formation, peroxynitrite accumulation, and cell death in wild-type and GGT(enu1) mice in normoxia and hyperoxia. The role of NOS activity in cell death was determined by NOS inhibition. Exposure of wild-type mice to hyperoxia caused increased lung injury, altered NO metabolism, and induction of cell death compared with normoxia, which was attenuated by NOS inhibition. Each of these lung injury indices were magnified in hyperoxia-exposed GGT(enu1) mice except nitrosation, which showed a diminished decrease compared with wild-type mice. NOS inhibition attenuated cell death only slightly, likely due to further exacerbation of oxidant stress. Taken together, these data suggest that apoptosis in hyperoxia is partially NO-dependent and reiterate the importance of cellular glutathione in lung antioxidant defense. Therefore, reduced denitrosylation of proteins, possibly resulting in impaired cellular repair, and excessive apoptotic cell death likely contribute to increased lung injury and mortality of GGT(enu1) mice in hyperoxia.

Intron 4 polymorphism of the endothelial nitric oxide synthase eNOS gene and early microangiopathy in type 1 diabetes

Nitric oxide (NO) is an endogenous vasodilator involved in inflammatory and autoimmune response, and in the pathophysiology of diabetic vascular disease. Endothelium-derived NO is formed from L-arginine by endothelial NO synthase (eNOS), and earlier studies have provided evidence for altered NO metabolism and impaired endothelial function in diabetes, probably due to polymorphisms in eNOS gene. In the present study we investigated the association of the eNOS gene intron 4 a/b VNTR polymorphism with diabetic microangiopathy in 61 young individuals with type 1 diabetes (T1D), 35 male and 26 female, aged 5.0-29.1 (mean 15.6) years, and followed up for 3.24-11.4 (mean 7.44) years. Ten patients (16.4%) had developed microalbuminuria, three hypertension and two retinopathy. Wild-type b/b homozygosity for eNOS gene intron 4 VNTR was found in 37 (60.7%) and a/b polymorphism in 24 (39.3%). No significant relationship was demonstrated between eNOS gene intron 4 polymorphisms and microalbuminuria, hypertension or retinopathy in these young individuals. Our findings suggest that a/b polymorphism of the intron 4 eNOS gene is not associated with early onset diabetic microangiopathy.

An experimental study of altered nitric oxide metabolism as a mechanism of cyclosporin-induced renal vasoconstriction.

Nephrotoxicity caused by cyclosporin A (CSA) is the result of vasoconstriction of the renal microcirculation. The endothelium-derived relaxing factor nitric oxide (NO) regulates microvascular blood flow in various tissues, and mediates the microcirculatory response during hypertension and sepsis. This study investigated the role of NO in CSA-induced renal vasoconstriction. Hydronephrotic kidneys in rats were suspended in an environmentally controlled tissue bath, and interlobular, afferent and efferent arteriolar diameters and blood flow were measured by in vivo videomicroscopy. CSA was administered alone, with the nitric oxide synthase (NOS) inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) or with exogenous NOS substrate L-arginine. CSA significantly constricted the whole of the renal microvasculature whereas L-NAME alone preferentially constricted the preglomerular vessels. L-Arginine reversed the vasoconstriction induced by CSA whereas L-NAME had no further effect. Preglomerular basal vascular tone is dependent on continuous production of NO and alterations in the L-arginine-NO pathway contribute to CSA-induced renal vasoconstriction.

Surfactant protein-D, a mediator of innate lung immunity, alters the products of nitric oxide metabolism.

Surfactant protein (SP)-D, a 43-kD multifunctional collagen-like lectin, is synthesized and secreted by the airway epithelium. SP-D knockout (SP-D [-/-]) mice exhibit an increase in the number and size of airway macrophages, peribronchiolar inflammation, increases in metalloproteinase activity, and development of emphysema. Nitric oxide (NO) is involved in a variety of signaling processes, and because altered NO metabolism has been observed in inflammation, we hypothesized that alterations in its metabolism would underlie the proinflammatory state observed in SP-D deficiency. Examination of the bronchial alveolar lavage (BAL) from SP-D (-/-) mice reveals a significant increase in protein and phospholipid content and total cell count. NO production and inducible NO synthase expression were increased in the BAL; however, there was a decline in S-nitrosothiol (SNO) content in the BAL and a loss of SNO immunoreactivity within the tissue. This decline in SNO was accompanied by an increase in nitrotyrosine staining. We conclude that inflammation that occurs in SP-D deficiency results in an increase in NO production and a shift in the chemistry and targets of NO. We speculate that the proinflammatory response due to SP-D deficiency results, in part, from a disruption of NO-mediated signaling within the innate immune system.

Special Article Nitric Oxide In Microgravity-Induced Orthostatic Intolerance: Relevance To Spinal Cord Injury

Summary: Prolonged exposure to microgravity results in cardiovascular deconditioning which is marked by orthostatic intolerance in the returning astronauts and recovering bed-ridden patients. Recent studies conducted in our laboratories at University of California, Irvine have revealed marked elevation of nitric oxide (NO) production in the kidney, heart, brain, and systemic arteries coupled with significant reduction of NO production in the cerebral arteries of microgravity-adapted animals. We have further demonstrated that the observed alteration of NO metabolism is primarily responsible for the associated cardiovascular deconditioning. Recovery from acute spinal cord injury (SCI) is frequently complicated by orthostatic intolerance that is due to the combined effects of the disruption of efferent sympathetic pathway and cardiovascular deconditioning occasioned by prolonged confinement to bed. In this presentation, I will review the nature of altered NO metabolism and its role in the pathogenesis of microgravity-induced cardiovascular deconditioning. The possible relevance of the new findings to orthostatic intolerance in patients with acute SCI and its potential therapeutic implications will be discussed.Spinal Cord Med. 2003;26:5-11

Nitric oxide and protein nitration in the cystic fibrosis airway

Cystic fibrosis (CF), characterized by chronic airway infection and inflammation, ultimately leads to respiratory failure. Exhaled nitric oxide (NO), elevated in most inflammatory airway diseases, is decreased in CF, suggesting either decreased production or accelerated metabolism of NO. The present studies performed on two groups of CF patients provide further support for a disordered NO airway metabolism in CF respiratory tract disease. Despite confirmation of subnormal NOS2 in the CF airway epithelium, alternative isoforms NOS1 and NOS3 were present, and inflammatory cells in the CF airway expressed abundant NOS2. Increased immunohistochemical staining for nitrotyrosine was demonstrated in lung tissues from patients with CF as compared to control. To our knowledge, this is the first report localizing nitrotyrosine in diseased CF lung tissue. While the relative NOS2 deficiency in CF respiratory tract epithelium may contribute to the lower expired NO levels, these results suggest that increased metabolism of NO is also present in advanced CF lung disease. The significance of altered NO metabolism and protein nitration in CF remains to be fully elucidated.