Significant Increase In Nitric Oxide Synthase Activity Research Articles

Asymmetrical dimethylarginine: the Uber marker?

The traditional risk factors of hypercholesterolemia, hypertension, diabetes mellitus, and tobacco exposure identify a subset of patients at greater cardiovascular risk. A variety of clinical phenotypes, biochemical markers, and genetic polymorphisms have been proposed to explain the variance in risk not explained by the traditional factors. Notably, all of the traditional risk factors, as well as the great majority of new risk markers, are associated with endothelial vasodilator dysfunction. Because the end points (endothelial dysfunction leading to plaque formation, progression, and rupture) are the same, it follows that diverse risk factors ultimately share common pathways(s) of pathobiology. We and others have provided evidence for a ubiquitous mechanism of endothelial pathobiology shared by all risk factors and markers examined to date. This mechanism of endothelial derangement is mediated by an endogenous inhibitor of nitric oxide synthase (NOS), a molecule known as asymmetrical dimethylarginine (ADMA). Risk factors impair endothelial vasodilator function by causing the accumulation of ADMA. Furthermore, by blocking NO generation, ADMA initiates and promotes processes involved in atherogenesis, plaque progression. and plaque rupture. This review examines the burgeoning body of literature that supports ADMA as an “Uber marker,” a biochemical factor mediating the adverse vascular effects of many other risk factors and markers. Endothelial NOS converts the amino acid l-arginine into l-citrulline and NO. The importance of NO in vascular homeostasis has been discussed elsewhere.1 In addition to its vasodilator activity, NO inhibits key processes involved in vascular disease, including leukocyte adhesion, platelet aggregation, and vascular smooth muscle cell proliferation. In animal models, alterations in vascular NO synthesis profoundly influence the progression of atherosclerosis and restenosis.2–6 These experimental observations have gained greater significance with recent reports that impairment of the NOS pathway independently predicts cardiovascular events.7–11 Major causes of impairment of the NOS pathway are …

The effect of cauda equina constriction on nitric oxide synthase activity.

Nitric oxide synthase (NOS) activity was studied in the gray and white matter regions of the spinal cord 2 and 5 days after multiple cauda equina constrictions of the central processes of L7-Co5 dorsal root ganglia neurons. The results show considerable differences in enzyme activity in the thoracic, upper lumbar, lower lumbar, and sacral segments. Increased NOS activity was observed at 2 days after multiple cauda equina constrictions in the dorsal, lateral, and ventral columns of the lower lumbar segments and in the ventral column of the upper lumbar segments. The values returned to control levels within 5 postconstriction days. In the lateral columns of thoracic segments taken 2 and 5 days after surgery, NOS activity was enhanced by 54% and 55% and in the upper lumbar segments by 130% and 163%, respectively. Multiple cauda equina constrictions performed surgically for 2 and 5 days caused a significant increase in NOS activity predominantly in the gray matter regions of thoracic segments. A quite different response was found 5 days postconstriction in the upper lumbar segments, where the enzyme activity was significantly decreased in the dorsal horn, intermediate zone, and ventral horn. No such extreme differences could be seen in the lower lumbar segments, where NOS activity was significantly enhanced only in the ventral horn. The data correspond with a higher number of NOS immunoreactive somata, quantitatively evaluated in the ventral horn of the lower lumbar segments at 5 days after multiple cauda equina constrictions. While the great region-dependent heterogeneity in NOS activity seen 2 and 5 days after multiple cauda equina constrictions is quite apparent and suggestive of an active role played by nitric oxide in neuroprotective or neurotoxic processes occurring in the gray and white matter of the spinal cord, the extent of damage or the degree of neuroprotection caused by nitric oxide in compartmentalized gray and white matter in this experimental paradigm would be possible only using longer postconstriction periods.

The effect of cauda equina constriction on nitric oxide synthase activity

The effect of cauda equina constriction (CEC) on nitric oxide synthase (NOS) activity has been studied in spinal cord of the dog. CEC lasting for 2 days caused significant increase in NOS activity in white matter of lumbar segments. The enzyme activity decreased to basal levels 5 days after injury. An extreme reduction of NO formation has been seen in sacral segments at 2 day of postsurgery. At 5 day, the enzyme activity greatly increased and in gray matter significantly exceeded baseline. Quantitative measurement of NOS activity produced a rise in gray matter of thoracic segments and indicated a decrease in gray matter of upper lumbar segments. The results indicate a time‐dependent formation of nitric oxide after CEC in spinal cord segments and regions.Acknowledgements: Supported by VEGA Grants no. 2/2079/22 and 2/3217/23PS9, STAA Grant no. 51‐013002 and by NIH grants NS 32794 and NS 40386 to M.M.

Age-dependent changes in nitric oxide synthase activity and protein expression in striata of mice transgenic for the Huntington’s disease mutation

Huntington’s disease (HD) is an autosomal hereditary neurodegenerative disorder caused by an abnormal expansion of the CAG repeats that code for a polyglutamine tract in a novel protein called huntingtin (htt). Both patients and experimental animals exhibit oxidative damage in specific areas of the brain, particularly the striatum. Nitric oxide (NO) is involved in many different physiological processes, and under pathological conditions it may promote oxidative damage through the formation of the highly reactive metabolite peroxynitrite; however, it may also play a role protecting cells from oxidative damage. We previously showed a correlation between the progression of the neurological phenotype and striatal oxidative damage in a line of transgenic mice, R6/1, which expresses a human mutated htt exon 1 with 116 CAG repeats. The purpose of the present work was to explore the participation of NO in the progressive oxidative damage that occurs in the striata of R6/1 mice. We analyzed the role of NO by measuring the activity of nitric oxide synthase (NOS) in the striata of transgenic and control mice at different ages. There was no difference in NOS activity between transgenic and wild-type mice at 11 weeks of age. In contrast, 19-week-old transgenic mice showed a significant increase in NOS activity, compared with same age controls. By 35 weeks of age, there was a decrease in NOS activity in transgenic mice when compared with wild-type controls. NOS protein expression was also determined in 11-, 19- and 35-week-old transgenic mice and wild-type littermates. Our results show increased neuronal NOS expression in 19-week-old transgenic mice, followed by a decreased level in 35-week-old mice, compared with controls, a phenomenon that parallels the changes in NOS enzyme activity. The present results suggest that NO is involved in the process leading to striatal oxidative damage and that it is associated with the onset of the progressive neurological phenotype in mice transgenic for the HD mutation.

Pulsed magnetic fields enhance nitric oxide synthase activity in rat cerebellum

The effect of pulsed magnetic fields on nitric oxide synthase (NOS) activity in the rat brain was investigated. Sprague–Dawley rats (male, 200–250 g body weight) brain were dissected regionally, and the crude enzyme solutions were treated with pulsed DC, AC or static DC magnetic fields at 0°C for 1 h. After exposure, NOS activity was measured as nitrite and nitrate levels generated from incubation with arginine, CaCl 2 and β-nicotinamide adenine dinucleotide phosphate. Under these experimental conditions, neither AC nor static DC field treatment showed any significant change in NOS activity. A significant increase in NOS activity was observed in the cerebellum (111.2±2.0%, P<0.05, five separate experiments) for a 1 Gauss (0.1 mT) pulsed DC field. Under the same experimental condition, only a slight change or no effect was observed in the hippocampus, cortex, medulla oblongata, hypothalamus, striatum and midbrain. These studies suggest that pulsed magnetic fields result in a different effect on NOS activity in the cerebellum of the rats.

A study on human umbilical cord endothelial cells: Functional modifications induced by plasma from insulin-dependent diabetes mellitus patients

The aim of the present study was to evaluate the action of plasma from insulin-dependent diabetic (IDDM) pregnant women on nitric oxide synthase (NOS) activity in cultured human umbilical vein endothelial cells (HUVECs). We also studied the effect of the plasma on cytosolic calcium and on Na + K + -adenosine triphosphatase (ATPase) activity. Dynamic fluorescence studies of membrane fluidity were contemporarily performed to detect a direct effect of plasma on the endothelial cell membrane. We observed a significant increase in NOS activity, intracellular calcium, and Na + K + -ATPase activity in cultured HUVECs exposed to IDDM plasma. Our dynamic fluorescence study showed a different microenvironmental organization of the cellular membrane after incubation with plasma from IDDM pregnant women, with a marked decrease in microheterogeneity as evaluated in terms of 1-(4-trimethylaminophenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH) lifetime distribution width. The present investigation suggests that plasma from IDDM pregnant women can cause a generalized disturbance in the function of endothelial cells cultured from healthy subjects. Such a modification might play a central role in the pathogenesis of the vascular complications of the disease.

L-Arginine Metabolites Regulate DNA Synthesis and Nitric Oxide Synthase Activity in Cultured Human Dermal Microvascular Endothelial Cells—Potential Positive and Negative Regulators of Angiogenesis Derived from l-Arginine

Human dermal microvascular endothelial cell (HDMVEC) growth and proliferation is important for skin angiogenesis. Our data support the hypothesis that a regulator?, switch from an angiogenic to a nonangiogenic stimulus involves a change in 1-arginine metabolism from polyamines (PAS) to nitric oxide (NO) and, conversely, a change to an angiogenic stimulus is expected to drive I-arginine metabolism in favor of PA synthesis. Current studies with cultured HDMVECs demonstrated that NO inhibited, whereas the PA putrescine stimulated DNA synthesis. The nitric oxide synthase (NOS) inhibitor NG-nitro I-arginine methyl ester stimulated DNA synthesis with a signifcant increase from control at 2.5 and 5 mM (p < 0.05); in contrast, the ornithine decarboxylase (ODC) inhibitor α-difluoromethyl ornithine (DFMO) inhibited DNA synthesis with a signifcant decrease from control at 19.65, 29.48, and 39.48 μM (p < 0.05). NO donors sodium nitroprusside dihydrate, S-nitroso-N-penicillamine, and l-hydroxy-2-oxo-3(3-aminopropyl)-3-propyl-triazine all inhibited DNA synthesis. There was a significant increase in NOS activity with DFMO treatment (p < 0.05) and a less pronounced decrease in NOS activity with direct PA treatment. In summary, NO and PAS are important mediators of HDMVEC growth and PAS downregulate NOS activity in these cells. NOS and ODC enzyme products may not only be important components in the regulation of angiogenesis in the skin but they may also regulate their own synthesis via feedback mechanisms.

Increase in nitric oxide synthase and NADPH-diaphorase in the adrenal gland of streptozotocin-diabetic Wistar rats and its prevention by ganglioside

Levels of nitric oxide synthase (NOS) and NADPH-diaphorase in adrenal glands of streptozotocin-diabetic rats of 8 and 12 weeks' duration compared with control rats were assessed with histochemical and biochemical techniques. Adrenal glands from streptozotocin-diabetic rats of 8 weeks' duration treated with ganglioside were examined also. In the adrenal medulla of 8-weeks- and 12-weeks-diabetic rats, NOS-immunoreactive nerve fibres were increased and decreased, respectively; additional NOS-immunoreactive and NADPH-diaphorase stained cells, which appeared to be cortical cells, were located in medulla and cortex compared with controls. Increased intensity in NADPH-diaphorase staining of the cortical cells of diabetic rats was observed also. Ganglioside treatment of the 8-weeks-diabetic rats prevented the diabetic-induced increase in NOS-immunoreactive nerve fibres. Also, it reduced most of the increase in the NOS-immunoreactive and NADPH-diaphorase stained cells and the intensity of NADPH-diaphorase staining of cortical cells. With biochemical assay, a significant increase in NOS activity was found in the adrenal glands from 8-weeks-diabetic rats, and this increase was reduced by ganglioside treatment in four out of six diabetic rats.In summary, streptozotocin-induced diabetes causes an initial increase in the levels of NOS and NADPH-diaphorase in the adrenal gland of rat, which was prevented by ganglioside treatment.

Nitric Oxide Synthase Activity Is Elevated in Brain Microvessels in Alzheimer′s Disease

The cerebral microcirculation undergoes specific biochemical changes in Alzheimer′s disease. In this study, we have compared the nitric oxide synthase (NOS) activity of brain microvessels isolated from Alzheimer and control brains. L-[3H]-citrulline, the stable co-product generated with nitric oxide (NO) from L-[3H]-arginine, was measured as an indicator of NOS activity. The results indicated a significant increase in NOS activity in microvessels isolated from Alzheimer brains. In addition, using antibodies to both the endothelial and inducible NOS isoforms, we demonstrated a significant increase in enzyme level in Alzheimer-derived vessels. Elevated vascular production of NO, a potentially neurotoxic mediator in the CNS, may contribute to the susceptibility of neurons to injury and cell death in Alzheimer′s disease.