Carmen González

Nitric oxide mediates tumor necrosis factor-α cytotoxicity in endothelial cells

Summary Tumor necrosis factor alpha (TNF-α) exerts multiple actions on endothelial cells including among others the expression of pro-coagulant activity and adhesion molecules, and secretion of cytokines. We now show that TNF-α induces a time- and dose-dependent cytotoxic effect on cultured bovine aortic endothelial cells. This TNF-induced cytotoxicity, which is preceded by increased production of nitric oxide (NO), is significantly decreased by the NO synthase inhibitor N-iminoethyl-Lornithine (L-NIO). Dexamethasone, which prevents the expression of cytokine-induced NO synthase in endothelial cells, also inhibits TNF-α-dependent cytotoxicity. The results indicate that NO is involved in the cytotoxic effect of TNF-α on endothelial cells.

Local NADPH-diaphorase neurons innervate pial arteries and lie close or project to intracerebral blood vessels: a possible role for nitric oxide in the regulation of cerebral blood flow.

Electrical stimulation of perivascular nerves induced a relaxation of endothelium-denuded cat pial arteries that was significantly reduced by nitric oxide (NO) synthase inhibition, indicating that NO was involved in the neurogenic relaxation of these vessels. Histochemical staining of the pial arteries for NADPH-diaphorase (NADPH-d), used as a marker for NO synthase, showed positive nerve fibers in the adventitial layer. Interestingly, in some restricted areas stained neuronal cell bodies were also observed. These neurons were scattered or distributed in small groups in a ganglion-like manner, and they sent fibers to the vessel wall. No NADPH-d-positive nerve fibers or cell bodies were detected in forelimb, pulmonary, or coronary arteries. Within the brain parenchyma, blood vessels also showed positive fibers around their walls. These fibers were organized in a branching pattern and presented varicosities. NADPH-d-positive neurons were found in the proximity of the intracerebral vascular profiles, sending processes to the vessels and/or being directly apposed to their wall. The neurovascular contacts were preferentially located close to the interface between the cerebral cortex and white matter. The anatomical relationship between NADPH-d-positive neurons and fibers and the cerebral blood vessels, together with the participation of NO in the neurogenic relaxation of pial arteries, suggests that NO is involved in the regulation of cerebral blood flow.

Nitric Oxide Mediates the Neurogenic Vasodilation of Bovine Cerebral Arteries

Nitric oxide (NO) is a mediator of the vasodilation induced by a variety of physiological and pharmacological stimuli. The possible role of NO in the relaxation elicited in cerebral arteries by perivascular nerve stimulation has been investigated. Electrical field stimulation of precontracted bovine cerebral arteries induced a relaxation that was blocked by tetrodotoxin, but not by adrenergic or muscarinic receptor antagonists, suggesting the existence of nonadrenergic, noncholinergic dilator nerves, as has been shown in other species. The relaxation was significantly reduced by the inhibitors of NO synthesis, NG-monomethyl-L-arginine and nitro-L-arginine methyl ester, but not by the enantiomer, NG-monomethyl-D-arginine. Such a reduction was reversed by L-arginine. In addition, transmural nerve stimulation (TNS)-induced relaxation was potentiated by superoxide dismutase. No response to TNS was observed in arteries without endothelium. These results suggested that neurogenic relaxation of bovine cerebral arteries is mediated by endothelium-derived NO.

Neuronal nitric oxide synthase activation by vasoactive intestinal peptide in bovine cerebral arteries.

The participation of nitric oxide and vasoactive intestinal peptide (VIP) in the neurogenic regulation of bovine cerebral arteries was investigated. Nitrergic nerve fibers and ganglion-like groups of neurons were revealed by NADPH-diaphorase staining in the adventitial layer of bovine cerebral arteries. NADPH diaphorase also was present in endothelial cells but not in the smooth muscle layer. Double immunolabeling for neuronal nitric oxide synthase and VIP indicated that both molecules co-localized in the same nerve fibers in these vessels. Transmural nerve stimulation (200 mA, 0.2 milliseconds, 1 to 8 Hz) of endothelium-denuded bovine cerebral artery rings precontracted with prostaglandin F2α, produced tetrodotoxin-sensitive relaxations that were completely suppressed by NG-nitro-l-arginine methyl ester (l-NAME) and by the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline (ODQ), but were not affected by the adenylyl cyclase inhibitor 9-(tetrahydro-2-furanyl)-9H-purin-6-amine (SQ 22,536), nor by VIP tachyphylaxis induced by pretreatment with 1 μmol/L VIP. Transmural nerve stimulation also elicited increases in intracellular cyclic GMP concentration, which were prevented by l-NAME, and small decreases in intracellular cyclic AMP concentration. Addition of VIP to bovine cerebral artery rings without endothelium produced a concentration-dependent relaxation that was partially inhibited by l-NAME, ODQ, and SQ 22,536. The effects of l-NAME and SQ 22,536 were additive. VIP induced a transient increase in intracellular cyclic GMP concentration, which was maximal 1 minute after VIP addition, when the highest relaxation rate was observed, and which was blocked by l-NAME. It is concluded that nitric oxide produced by perivascular neurons and nerve fibers fully accounts for the experimental neurogenic relaxation of bovine cerebral arteries and that VIP, which also is present in the same perivascular fibers, acts as a neuromodulator by activating neuronal nitric oxide synthase.

Nitric oxide from endothelium and smooth muscle modulates responses to sympathetic nerve stimulation: Implications for endotoxin shock

The influence of nitric oxide (NO) on vascular responses to transmural stimulation (TNS) of noradrenergic nerves was studied in isolated rings of rat iliac arteries. TNS produced frequency-dependent contractions in all vessels. The NO synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) significantly enhanced TNS responses in intact vessels, but not in those in which the endothelium had been removed. However, in endothelium-denuded rings incubated for 8 hours, L-NMMA increased the contractions induced by nerve stimulation, an effect which was prevented by treatment with dexamethasone or cycloheximide, and enhanced by incubation with lipopolysaccharide and gamma-interferon. Addition of L-arginine reversed the effect of L-NMMA in intact rings; however, it significantly decreased below control values TNS-induced contractions in vessels without endothelium. The results indicate that a) the arterial response to noradrenergic nerve stimulation is modulated by NO originating either in endothelial cells or in smooth muscle cells after induction of NO synthase activity, and b) once NO synthase is induced, the limiting step in NO production is the availability of the substrate L-arginine. An overproduction of vascular NO in the presence of endotoxin or other inflammatory stimuli may prevent the vascular response to sympathetic stimuli and contribute to the vasodilation observed in inflammation or endotoxic shock.

Albinism and agenesis of the corpus callosum with profound developmental delay : Vici syndrome, evidence for autosomal recessive inheritance

We report on two sibs and two other unrelated patients with agenesis of corpus callosum, oculocutaneous albinism, repeated infections, and cardiomyopathy. All manifested postnatal growth retardation, microcephaly, and profound developmental delay. Additional central nervous system anomalies present in at least one patient included hypoplasia of the cerebellar vermis, white matter neuronal heterotopia, or bilateral schizencephaly. Repeated viral, bacterial, and fungal infections were consistent with a primary immunodeficiency. However, immunological studies showed variable, nonspecific findings. Cardiomyopathy with progressive heart failure or infection led to death before age 2 years in three of the patients. This syndrome was first described by Vici et al. [1988: Am. J. Med. Genet. 29:1-8]. The four patients reported herein confirm this unique disorder. Affected sibs of both sexes born to unaffected parents provide evidence for autosomal recessive inheritance.

Cellular changes induced by chronic nitric oxide inhibition in intact rat basilar arteries revealed by confocal microscopy

Background Cellular aspects of remodelling have not been investigated fully in intact vessels due to lack of appropriate methodology. Objective To determine the cellular alterations induced by chronic inhibition of nitric oxide (NO) production in intact rat basilar arteries by combined use of perfusion myography and a laser scanning confocal microscope. Methods Wistar–Kyoto rats were treated with 10 mg/kg per day NG-nitro-L-arginine methyl ester (L-NAME) for 3 weeks. Basilar arteries from treated and age-matched Wistar–Kyoto rat controls were mounted on a perfusion myograph, stained with the nuclear dye Hoechst 33 342 and fixed under pressure. The segments were mounted on a slide and visualized using the 364 nm line of a laser scanning confocal microscope. MetaMorph software was used to obtain optical sections from the vessel and for morphology determinations. Results L-NAME treatment induced hypertension (systolic blood pressure control 129.2 ± 2.7 mmHg and SBP L-NAME treatment 176.3 ± 5.2 mmHg, P < 0.001). Compared with control rat arteries, arteries from treated rats had a reduced lumen diameter, similar wall thickness and an increased wall: lumen ratio. L-NAME treatment induced specific changes in adventitia, media and intima, namely an increase in number of adventitial cells and in adventitia thickness, a reduction in number of smooth muscle cells with no change in media thickness and reductions in number of endothelial cells, size of nuclei and luminal surface area. Conclusions Hypertension induced by chronic inhibition of NO production is associated with eutrophic remodelling of rat basilar artery. However, within this overall maintenance of constant volume, there are marked cellular changes in adventitia, media and intima. The separate contributions of inhibition of NO production and hypertension to the remodelling process need to be elucidated.

Polymorphism in the type I collagen (COLIA1) gene and risk of fractures in postmenopausal women

Twin and family studies have demonstrated that a large part of a populations variance in bone mineral density (BMD) is attributable to genetic factors. A polymorphism in the collagen type I alpha1 (COLIA1) gene has recently been associated with low bone mass and fracture incidence. We analyzed the relationship between COLIA1 gene polymorphism, lumbar spine and hip BMD, and fracture prevalence in a population of 319 postmenopausal women classified by WHO standards, including 98 nonosteoporotic women (NOPW) and 221 osteoporotic postmenopausal women (OPW), divided into 139 osteoporotic women without fracture (OPWnF) and 82 osteoporotic women with fracture (OPWwF). The COLIA1 genotype was assessed by polymerase chain reaction and BalI endonuclease digestion. Genotype frequencies for the total group were 49.2% GG homozygotes, 39.5% GT heterozygotes, and 11.3% TT homozygotes. We found significant differences in the percentage of homozygous TT between NOPW and OPW (6.1% and 13.6%, respectively). Significantly, the occurrence of genotype TT in OPWnF was 6.2%, and 28% in OPWwF. We observed no associations between the COLIA1 genotype and lumbar spine and hip BMD. The prevalence of fractures varied significantly by genotype: GG, 26.1%; GT, 15.9%; and TT, 58.3%. Logistic regression analysis of fracture prevalence showed that, for prevalent fractures, the women with the TT genotype had a 5.9-fold increased risk when compared with the other genotypes (GG + GT). When prevalence was adjusted for age, body mass index, and BMD, the fracture risk was 4.8 for the TT group vs. the genotype GG, whereas it was 0.6 for the GT genotype. In conclusion, we found the COLIA1 Sp1 TT genotype to be associated with an increased fracture risk in postmenopausal women. Interestingly, this genotype-dependent risk could not be explained completely by BMD differences.

Nitric oxide and the renin-angiotensin system. Is there a physiological interplay between the systems?

Opposed actions for nitric oxide (NO) and angiotensin II (Ang II) in vascular contraction and vascular smooth muscle cell proliferation and apoptosis are well documented. In addition, various experimental approaches have shown that NO negatively modulates the renin-angiotensin system by inhibiting angiotensin-converting enzyme (ACE) activity and down-regulating AT1 receptors. On the other hand, Ang II and Ang-(1-7) positively stimulate NO synthesis and release. In this review, we analyse the data suggesting a mutual regulation between the renin-angiotensin and the nitric oxide-generating systems, and we propose a homeostatic interplay between both factors aimed at regulating cardiovascular function.

Uso de espironolactona o doxazosina en pacientes con hipertensión arterial refractaria

Introduccion y objetivos Valorar el uso de espironolactona o doxazosina en el tratamiento de pacientes con hipertension refractaria (HTAR). Metodos Estudio retrospectivo comparativo de 181 pacientes con HTAR (pacientes tratados con tres farmacos, uno de ellos diuretico, sin alcanzar el control de la presion arterial [PA]) a quienes se anadio espironolactona (88 casos) o doxazosina (93 casos). Resultados La PA sistolica (PAS) se redujo 28 mmHg (intervalo de confianza [IC] del 95%, 24-32 mmHg; p odds ratio multivariable [ORm] = 0,17; IC del 95%, 0,08-0,39; p Conclusiones En los pacientes con hipertension refractaria, tanto al anadir espironolactona como doxazosina se consigue un significativo descenso de la PA, que parece ser mayor con espironolactona. La diabetes dificulta el control de la PA.