Fungal mycetoma and pregnancy: An association with costly and difficult management, about a case.

Mycetomas are endemic diseases in tropical and sub-tropical countries of Africa, Asia and America, mainly affecting rural populations living below the poverty line. We report a particular case of a mycetoma associated with pregnancy whose evolution was good, but at the cost of significant financial expenses. This was a 39-year-old woman who developed a fungal mycetoma due to Madurella mycetomatis from the ingunocrural region. The patient had to develop several previous pregnancies on this site of mycetoma, the outcome of which was favorable. The last pregnancy was accompanied by an aggravation of the mycetoma in the form of polyfistulized inflammatory swelling of the right inguino-crural region emitting black grains. Magnetic Resonance Imaging (MRI) of the region showed invasion of the adductor muscles at the level of the root of the thigh on its antero-internal side with no sign of pelvic extension or underlying bone lesion. The patient was treated by surgery associated with antifungal treatment. The evolution was favorable for pregnancy and mycetoma.

Impact of the interaction between the polymorphisms and hypermethylation of the CD36 gene on a new biomarker of type 2 diabetes mellitus: circulating soluble CD36 (sCD36) in Senegalese females.

BACKGROUND: Several predisposing factors for diabetes mellitus have been identified, including cluster determinant 36 (CD36) receptor expression. We aimed to determine the effects of CD36 gene polymorphisms and hypermethylation on the plasma CD36 protein levels in type 2 diabetes. MATERIALS AND METHODS: We conducted a cross-sectional study involving 100 females (lean healthy control subjects and subjects with type 2 diabetes). This study was conducted at the Human Physiology Laboratory at the Dakar Faculty of Medicine in Senegal. Circulating sCD36 levels and DNA methyltransferase 3a levels were determined by enzyme-linked immunosorbent assay. The other biological parameters were evaluated in a biochemical laboratory. CD36 gene polymorphisms and methylation were explored by real-time polymerase chain reaction and methylation-specific polymerase chain reaction, respectively. RESULTS: sCD36 was negatively correlated with HDL-cholesterol levels (r = - 0.52 p = 0.0001) and triglyceride levels (r = - 0.36 p = 0.01) in control subjects. However, in the type 2 diabetes group, sCD36 levels were positively correlated with total cholesterol levels (r = 0.28 p = 0.04). For rs3211867, control subjects harboring the CC genotypes had significantly higher sCD36 levels than control subjects harboring the AA/AC genotype (p = 0.02); in the type 2 diabetes group, the sCD36 level was not significantly lower in subjects harboring the AA/AC genotype than in subjects harboring the CC genotype (p = 0.27). CD36 gene methylation reduced the sCD36 level in the control subjects compared to control subjects without CD36 gene methylation (p = 0.03). This difference was not significant in the type 2 diabetes group comparing subjects with diabetes with CD36 gene methylation to subjects with diabetes without CD36 gene methylation (p = 0.09). We noted a nonsignificant increase in sCD36 levels in subjects with diabetes with CD36 gene methylation compared to control subjects with CD36 gene methylation (p = 0.27). A combination of the CD36 polymorphism effect and the CD36 methylation effect did not significantly reduce sCD36 levels in subjects with type 2 diabetes. CONCLUSION: CD36 gene polymorphisms and CD36 gene methylation separately reduce sCD36 levels. Their impacts are compensated for in subjects with type 2 diabetes by an increase in sCD36 levels, the mechanism of which needs to be elucidated.

Heat waves and health risks in the northern part of Senegal: analysing the distribution of temperature-related diseases and associated risk factors.

The Sahelian zone of Senegal experienced heat waves in the previous decades, such as 2013, 2016 and 2018 that were characterised by temperatures exceeding 45°C for up to 3 successive days. The health impacts of these heat waves are not yet analysed in Senegal although their negative effects have been shown in many countries. This study analyses the health impacts of observed extreme temperatures in the Sahelian zone of the country, focusing on morbidity and mortality by combining data from station observation, climate model projections, and household survey to investigate heat wave detection, occurrence of climate-sensitive diseases and risk factors for exposure. To do this, a set of climatic (temperatures) and health (morbidity, mortality) data were collected for the months of April, May and June from 2009 to 2019. These data have been completed with 1246 households' surveys on risk factor exposure. Statistical methods were used to carry out univariate and bivariate analyses while cartographic techniques allowed mapping of the main climatic and health indicators. The results show an increase in temperatures compared to seasonal normal for the 1971-2000 reference period with threshold exceedances of the 90th percentiles (42°C) for the maxima and (27°C) the minima and higher temperatures during the months of May and June. From health perspective, it was noted an increase in cases of consultation in health facilities as well as a rise in declared morbidity by households especially in the departments of Kanel (17.7%), Ranérou (16.1 %), Matam (13.7%) and Bakel (13.7%). The heat waves of May 2013 were also associated with cases of death with a reported mortality (observed by medical staff) of 12.4% unequally distributed according to the departments with a higher number of deaths in Matam (25, 2%) and in Bakel (23.5%) than in Podor (8.4%) and Kanel (0.8%). The morbidity and mortality distribution according to gender shows that women (57%) were more affected than men (43%). These health risks have been associated with a number of factors including age, access to drinkable water, type of fuel, type of housing and construction materials, existence of fan and an air conditioner, and health history.The heat wave recurrence has led to a frequency in certain diseases sensitive to rising temperatures, which is increasingly a public health issue in the Sahelian zone of Senegal.

Neuromyelitis optica spectrum disorders (NMO-SD) in a Sub-Saharan Africa country: A preliminary study of sixteen Senegalese cases.

BACKGROUND: Neuromyelitis optica (NMO) is an autoimmune disease of the central nervous system. In Sub-Saharan Africa, publications are rare and deal with isolated cases. Our goal was to analyze the characteristics of NMO spectrum disorders in a Senegalese cohort compiled in Dakar. PATIENTS AND METHOD: This was a retrospective descriptive study conducted at the Neurology Department of Fann Teaching Hospital. We included all patients with NMO-SD according to the 2014 diagnostic criteria. RESULTS: Sixteen patients were enrolled, 4 men and 12 women with an average age of 30 years. Ten patients (62.5%) presented an acute myelopathy associated with retrobulbar optic neuritis and 5 (31.25%) had isolated spinal cord injury. Spinal MRI showed abnormal cervical (6 patients), dorsal (4 patients), bulbar-cervical (3 patients) or cervico-dorsal (2 patients) signal extended (≥3 vertebral segments) of the spinal cord. Visual evoked potentials (VEP) showed demyelinating optic nerve involvement in 8 patients. Ten patients were positive to AQP-4 IgG. Systemic corticosteroid therapy was the rule in all patients, associated with azathioprine in 10 of them. The clinical course at 3 months was predominantly favourable (10 patients). CONCLUSION: This cohort is the first one compiled in Dakar. African multicentric epidemiological studies are needed.

DNA barcoding and molecular identification of field-collected Culicoides larvae in the Niayes area of Senegal.

BACKGROUND: Biting midge species of the genus Culicoides Latreille (Diptera: Ceratopogonidae) comprise more than 1300 species distributed worldwide. Several species of Culicoides are vectors of various viruses that can affect animals, like the African horse sickness virus (AHSV), known to be endemic in sub-Saharan Africa. The ecological and veterinary interest of Culicoides emphasizes the need for rapid and reliable identification of vector species. However, morphology-based identification has limitations and warrants integration of molecular data. DNA barcoding based on the mitochondrial gene cytochrome c oxidase subunit 1 (cox1) is used as a rapid and authentic tool for species identification in a wide variety of animal taxa across the globe. In this study, our objectives were as follows: (i) establish a reference DNA barcode for Afrotropical Culicoides species; (ii) assess the accuracy of cox1 in identifying Afrotropical Culicoides species; and (iii) test the applicability of DNA barcoding for species identification on a large number of samples of Culicoides larvae from the Niayes area of Senegal, West Africa. RESULTS: A database of 230 cox1 sequences belonging to 42 Afrotropical Culicoides species was found to be reliable for species-level assignments, which enabled us to identify cox1 sequences of Culicoides larvae from the Niayes area of Senegal. Of the 933 cox1 sequences of Culicoides larvae analyzed, 906 were correctly identified by their barcode sequences corresponding to eight species of Culicoides. A total of 1131 cox1 sequences of adult and larval Culicoides were analyzed, and a hierarchical increase in mean divergence was observed according to two taxonomic levels: within species (mean = 1.92%, SE = 0.00), and within genus (mean = 17.82%, SE = 0.00). CONCLUSIONS: Our study proves the efficiency of DNA barcoding for studying Culicoides larval diversity in field samples. Such a diagnostic tool offers great opportunities for investigating Culicoides immature stages ecology and biology, a prerequisite for the implementation of eco-epidemiological studies to better control AHSV in the Niayes region of Senegal, and more generally in sub-Saharan Africa.

Feasibility of utilizing the SD BIOLINE Onchocerciasis IgG4 rapid test in onchocerciasis surveillance in Senegal.

As effective onchocerciasis control efforts in Africa transition to elimination efforts, different diagnostic tools are required to support country programs. Senegal, with its long standing, successful control program, is transitioning to using the SD BIOLINE Onchocerciasis IgG4 (Ov16) rapid test over traditional skin snip microscopy. The aim of this study is to demonstrate the feasibility of integrating the Ov16 rapid test into onchocerciasis surveillance activities in Senegal, based on the following attributes of acceptability, usability, and cost. A cross-sectional study was conducted in 13 villages in southeastern Senegal in May 2016. Individuals 5 years and older were invited to participate in a demographic questionnaire, an Ov16 rapid test, a skin snip biopsy, and an acceptability interview. Rapid test technicians were interviewed and a costing analysis was conducted. Of 1,173 participants, 1,169 (99.7%) agreed to the rapid test while 383 (32.7%) agreed to skin snip microscopy. The sero-positivity rate of the rapid test among those tested was 2.6% with zero positives 10 years and younger. None of the 383 skin snips were positive for Ov microfilaria. Community members appreciated that the rapid test was performed quickly, was not painful, and provided reliable results. The total costs for this surveillance activity was $22,272.83, with a cost per test conducted at $3.14 for rapid test, $7.58 for skin snip microscopy, and $13.43 for shared costs. If no participants had refused skin snip microscopy, the total cost per method with shared costs would have been around $16 per person tested. In this area with low onchocerciasis sero-positivity, there was high acceptability and perceived value of the rapid test by community members and technicians. This study provides evidence of the feasibility of implementing the Ov16 rapid test in Senegal and may be informative to other country programs transitioning to Ov16 serologic tools.

[Hemolytic-uremic syndrome (HUS) in children at the University Hospital Center in Dakar: about four cases]. / Syndrome hémolytique et urémique de l'enfant au Centre Hospitalier Universitaire (CHU) de Dakar: à propos de quatre observations.

Hemolytic-uremic syndrome (HUS) is a common cause of organic acute renal failure (ARF) in children. It is a progressive complication of acute gastroenteritis (AGE), especially caused by Escherichia coli in children. This study aimed to describe the clinical, therapeutic and evolutionary aspects of this affection in four children. We collected four cases of HUS. The average age was 10,5 months (5-15mois), exclusively boys. Clinical examination revealed a hemolytic anemia (pallor and jaundice), oligoanuria and edematous syndrome (2 cases), arterial hypertension (1 patient), AGE associated with severe dehydration and hypovolemic shock (2 patients), consciousness disorders. ARF was found in all patients as well as thrombocytopenia and schizocytes smear. Direct Coombs test was negative. Hyperkalemia was found in 3 patients, of whom 1 with hyperkalemia level of more than 9.2 mmol/L, hyponatremia at 129 mmol/l (1 patient) and hypernatremia at 153 mmol/l (1 patient). HUS was secondary to pneumococcal pneumonia (1 patient) while AGE was secondary to E. coli (1 patient). The treatment was mainly symptomatic and included fluid restriction, transfusion of red cell concentrates, diuretics, peritoneal dialysis and hemodialysis. The evolution was marked by the onset of chronic renal failure (1 patient) after 6 months of follow-up and by recovery (1 case). Three patients died. HUS is the most common cause of organic acute renal failure in newborns. Diagnosis is essentially biological, treatment is mostly symptomatic.

[Congenital hypothyroidism in Dakar: about 28 cases]. / Hypothyroïdie congénitale à Dakar: à propos de 28 cas.

Child hypothyroidism has been little studied in Senegal. The aim of this study was to evaluate the epidemiological, diagnostic and evolutionary aspects of congenital hypothyroidism. We conducted a descriptive-analytical retrospective study of all children treated for congenital hypothyroidism at the Albert-Royer National Children's Hospital Center over the period from 2001 to 2014 (14 years). We collected and analyzed socio-demographic, clinical and evolutionary data from patient medical records. A total of 28 patients were included in the study, an average of 2 cases per year. The average age of discovery of hypothyroidism was 54.25 ± 43 months with a female predominance (Sex-ratio 0.47). Only 2 cases of hypothyroidism were diagnosed in the neonatal period. Consanguinity was present in 68% of patients. Clinical signs were dominated by the delay in psychomotor acquisitions (96%), hypothermia (46%), cranio-facial dysmorphia (43%) and goiter (39%). Growth retardation was constant beyond 6 months. The etiologies were dominated by hormonosynthesis disorders (84.21%). During the study period, mean SD of patients had decreased from -3.5 SD to -2.25 SD for a median treatment duration of 28 months. Mental retardation was present in 73% of cases. Growth retardation and mental retardation were more severe as the diagnosis was late. Our results confirm the inadequacy of early management of patients. It is urgent to implement a routine neonatal screening system in order to improve the mental prognosis of this condition.

An assessment of the predictors of the dynamics in arable production per capita index, arable production and permanent cropland and forest area based on structural equation models.

This study sets out to verify the key predictors of the dynamics of the arable production per capita index, the arable production and permanent crop land and forest area at a national scale in Cameroon. To achieve this objective, data for twelve time series data variables spanning the period 1961-2000 were collected from Oxford University, the United Nations Development program, the World Bank, FAOSTAT and the World Resource Institute. The data were analysed using structural equation models (SEM) based on the two stage least square approach (2SLS). To optimize the results, variables that showed high correlations were dropped because they will not add any new information into the models. The results show that the arable production per capita index is impacted more by population while the influence of rainfall on the arable production per capita index is weak. Arable production and permanent cropland on its part has as the main predictor arable production per capita index. Forest area is seen to be more vulnerable to trade in forest products and logging than any other variable. The models presented in this study are quite reliable because the p and t values are consistent and overall, these results are consistent with previous studies.

Sonic hedgehog carried by microparticles corrects angiotensin II-induced hypertension and endothelial dysfunction in mice.

Microparticles are small fragments of the plasma membrane generated after cell stimulation. We recently showed that Sonic hedgehog (Shh) is present in microparticles generated from activated/apoptotic human T lymphocytes and corrects endothelial injury through nitric oxide (NO) release. This study investigates whether microparticles bearing Shh correct angiotensin II-induced hypertension and endothelial dysfunction in mice. Male Swiss mice were implanted with osmotic minipumps delivering angiotensin II (0.5 mg/kg/day) or NaCl (0.9%). Systolic blood pressure and heart rate were measured daily during 21 days. After 7 day of minipump implantation, mice received i.v. injections of microparticles (10 µg/ml) or i.p. Shh receptor antagonist cyclopamine (10 mg/kg/2 days) during one week. Angiotensin II induced a significant rise in systolic blood pressure without affecting heart rate. Microparticles reversed angiotensin II-induced hypertension, and cyclopamine prevented the effects of microparticles. Microparticles completely corrected the impairment of acetylcholine- and flow-induced relaxation in vessels from angiotensin II-infused mice. The improvement of endothelial function induced by microparticles was completely prevented by cyclopamine treatment. Moreover, microparticles alone did not modify NO and O2 . (-) production in aorta, but significantly increased NO and reduced O2. (-) productions in aorta from angiotensin II-treated mice, and these effects were blocked by cyclopamine. Altogether, these results show that microparticles bearing Shh correct angiotensin II-induced hypertension and endothelial dysfunction in aorta through a mechanism associated with Shh-induced NO production and reduction of oxidative stress. These microparticles may represent a new therapeutic approach in cardiovascular diseases associated with decreased NO production.

Endothelium-derived contracting factors mediate the Ang II-induced endothelial dysfunction in the rat aorta: preventive effect of red wine polyphenols.

Angiotensin II (Ang II)-induced hypertension is associated with vascular oxidative stress and an endothelial dysfunction. This study examined the role of reactive oxygen species (ROS) and endothelium-derived contracting factors in Ang II-induced endothelial dysfunction and whether these effects are prevented by red wine polyphenols (RWPs), a rich source of natural antioxidants. Rats were infused with Ang II for 14 days. RWPs were administered in the drinking water 1 week before and during the Ang II infusion. Arterial pressure was measured in conscious rats. Vascular reactivity was assessed in organ chambers and cyclooxygenase-1 (COX-1) and COX-2 expression by Western blot and immunofluorescence analyses. Ang II-induced hypertension was associated with blunted endothelium-dependent relaxations and induction of endothelium-dependent contractions in the presence of nitro-L-arginine in response to acetylcholine (Ach). These effects were not affected by the combination of membrane permeant analogs of superoxide dismutase and catalase but were abolished by the thromboxane A(2) (TP) receptor antagonist GR32191B and the COX-2 inhibitor NS-398. The COX-1 inhibitor SC-560 also prevented contractile responses to Ach. Ang II increased the expression of COX-1 and COX-2 in the aortic wall. RWPs prevented Ang II-induced hypertension, endothelial dysfunction, and upregulation of COX-1 and COX-2. Thus, Ang II-induced endothelial dysfunction cannot be explained by an acute formation of ROS reducing the bioavailability of nitric oxide but rather by COX-dependent formation of contracting factors acting on TP receptors. RWPs are able to prevent the Ang II-induced endothelial dysfunction mostly due to their antioxidant properties.

In vitro vasorelaxation mechanisms of bioactive compounds extracted from Hibiscus sabdariffa on rat thoracic aorta.

BACKGROUND: In this study, we suggested characterizing the vasodilator effects and the phytochemical characteristics of a plant with food usage also used in traditional treatment of arterial high blood pressure in Senegal. METHODS: Vascular effects of crude extract of dried and powdered calyces of Hibiscus sabdariffa were evaluated on isolated thoracic aorta of male Wistar rats on organ chambers. The crude extract was also enriched by liquid-liquid extraction. The various cyclohexane, dichloromethane, ethyl acetate, butanol extracts obtained as well as the residual marc were subjected to Sephadex LH-20 column chromatography. The different methanolic eluate fractions were then analyzed by Thin Layer (TLC) and High Performance Liquid Chromatography (HPLC) and their vascular effects also evaluated. RESULTS: The H. Sabdariffa crude extract induced mainly endothelium-dependent relaxant effects. The endothelium-dependent relaxations result from NOS activation and those who not dependent to endothelium from activation of smooth muscle potassium channels. The phytochemical analysis revealed the presence of phenolic acids in the ethyl acetate extract and anthocyans in the butanolic extract. The biological efficiency of the various studied extracts, in term of vasorelaxant capacity, showed that: Butanol extract > Crude extract > Residual marc > Ethyl acetate extract. These results suggest that the strong activity of the butanolic extract is essentially due to the presence of anthocyans found in its fractions 43-67. CONCLUSION: These results demonstrate the vasodilator potential of hibiscus sabdariffa and contribute to his valuation as therapeutic alternative.

Statistical modeling of global geogenic fluoride contamination in groundwaters.

The use of groundwater with high fluoride concentrations poses a health threat to millions of people around the world. This study aims at providing a global overview of potentially fluoride-rich groundwaters by modeling fluoride concentration. A large database of worldwide fluoride concentrations as well as available information on related environmental factors such as soil properties, geological settings, and climatic and topographical information on a global scale have all been used in the model. The modeling approach combines geochemical knowledge with statistical methods to devise a rule-based statistical procedure, which divides the world into 8 different "process regions". For each region a separate predictive model was constructed. The end result is a global probability map of fluoride concentration in the groundwater. Comparisons of the modeled and measured data indicate that 60-70% of the fluoride variation could be explained by the models in six process regions, while in two process regions only 30% of the variation in the measured data was explained. Furthermore, the global probability map corresponded well with fluorotic areas described in the international literature. Although the probability map should not replace fluoride testing, it can give a first indication of possible contamination and thus may support the planning process of new drinking water projects.

Angiotensin II induces the vascular expression of VEGF and MMP-2 in vivo: preventive effect of red wine polyphenols.

OBJECTIVE: Previous investigations have indicated that angiotensin II (Ang II)-induced hypertension and endothelial dysfunction are prevented by intake of red wine polyphenols (RWPs). Ang II has also been shown to increase the expression of VEGF and MMP-2, two major pro-inflammatory factors, in vascular diseases. Therefore, the aim of the present study was to determine whether intake of RWPs is able to prevent these effects in rats and, if so, to characterize the underlying mechanism. METHODS: VEGF and endothelial NO synthase (eNOS) expression was assessed by immunofluorescence and Western blotting, MMP-2 activity by zymography, and reactive oxygen species (ROS) formation by dihydroethidine. RESULTS: Ang II increased VEGF expression and MMP-2 activity in the aortic wall. Ang II-induced MMP-2 activation is inhibited by N(G)-nitro-L-arginine and MnTMPyP. Ang II increased the expression of eNOS, the formation of ROS and the nitration of proteins. The stimulatory effects of Ang II on these factors are prevented by RWPs intake. CONCLUSIONS: Infusion of Ang II induced vascular expression of VEGF and peroxynitrite-dependent activation of MMP-2, with both effects being prevented by RWPs intake. Thus, prevention of VEGF and MMP-2 expression might be involved in the protective effect of red wine on coronary heart diseases.

Targeted and persistent effects of NO mediated by S-nitrosation of tissue thiols in arteries with endothelial dysfunction.

We have previously demonstrated that in endothelium-denuded arteries, S-nitrosation of cysteine residues is a mechanism of formation of releasable nitric oxide (NO) stores, accounting for the long-lasting relaxation induced by S-nitrosating agents like S-nitrosoglutathione (GSNO). Here, we have investigated whether such effects could also be obtained in arteries exhibiting oxidative stress-associated endothelial dysfunction. Rats were implanted or not with a minipump delivering saline or angiotensin II for 14 days. As expected, aorta from angiotensin II-infused rats exhibited increased level of superoxide anions (as evaluated with dihydroethidine as fluorescent probe) and a reduced relaxation to acetylcholine in comparison to saline group. Unlike aortic rings with endothelium from controls, those from angiotensin II-infused rats exhibited persistent hyporesponsiveness to phenylephrine after pre-exposure to GSNO, as well as relaxation upon addition of N-acetylcysteine (NAC, which can displace NO from cysteine-NO residues) or HgCl(2) (which cleaves S-NO bonds). In aorta from angiotensin II-infused rats, GSNO also induced a persistent increase in cysteine-NO residues (as determined using anti-cysteine-NO antiserum), which was blunted by NAC and HgCl(2). These data indicate that (i) the vasorelaxant influence of releasable NO stores is unmasked by endothelial dysfunction (ii) S-nitrosation of cysteine residues remains an effective mechanism of formation of releasable NO stores in arteries exhibited oxidative stress-associated endothelial dysfunction. Thus, formation of releasable NO stores by S-nitrosating agents allows targeted vasculoprotective effects of NO at sites of endothelial dysfunction.

Red wine polyphenols prevent angiotensin II-induced hypertension and endothelial dysfunction in rats: role of NADPH oxidase.

OBJECTIVE: Chronic administration of moderate amounts of red wine has been associated with a protective effect on the cardiovascular system. This study examined whether red wine polyphenols prevent the angiotensin II (Ang II)-induced hypertension and endothelial dysfunction in rats, and, if so, to elucidate the underlying mechanism. METHODS: Hypertensive rats were obtained by a 14-day infusion of Ang II. Red wine polyphenols were administered in the drinking water one week before and during the Ang II infusion. Arterial pressure was measured in conscious rats. Ex vivo vascular relaxation was assessed in organ chambers, vascular superoxide anion production by dihydroethidine and vascular NADPH oxidase expression by immunohistochemistry. RESULTS: Ang II-induced hypertension was associated with decreased relaxation to acetylcholine but not to red wine polyphenols. The Ang II treatment also increased vascular superoxide anion production and expression of nox1 and p22phox NADPH oxidase subunits. Intake of red wine polyphenols prevented the Ang II-induced hypertension and endothelial dysfunction and normalized vascular superoxide anion production and NADPH oxidase subunit expression. Red wine polyphenol treatment alone did not affect blood pressure. CONCLUSION: Intake of red wine polyphenols prevents Ang II-induced hypertension and endothelial dysfunction. Prevention of vascular NADPH oxidase induction and preservation of arterial nitric oxide availability during Ang II administration likely contribute to this effect.

Formation of releasable NO stores by S-nitrosoglutathione in arteries exhibiting tolerance to glyceryl-trinitrate.

S-Nitrosating nitric oxide (NO) donors like S-nitrosoglutathione (GSNO) induce a persistent inhibition of vascular tone, through the formation of releasable NO stores. In this study, we investigate whether GSNO also induces NO stores-related effects in vessels exhibiting tolerance to glyceryl-trinitrate. Rat aortic rings treated with glyceryl-trinitrate (100 microM for 1 h) exhibited increased level of superoxide and a decrease in NO elevation and relaxation induced by subsequent addition of glyceryl-trinitrate. In glyceryl-trinitrate-treated rings as in controls, pre-exposure to GSNO (1 microM for 30 min) induced a persistent hyporesponsiveness to noradrenaline and a relaxant response to N-acetylcysteine (a low molecular weight thiol which can displace NO from NO stores), both of which being inhibited by guanylyl-cyclase or cyclic GMP-dependent protein kinase inhibitors. These data indicate that GSNO can promote the formation of releasable NO stores in arteries exhibiting increased superoxide level and tolerance to glyceryl-trinitrate. Formation of releasable NO stores is of potential interest to restore the protective effect of NO in organic nitrate-tolerant blood vessels.

Inhibition of arterial contraction by dinitrosyl-iron complexes: critical role of the thiol ligand in determining rate of nitric oxide (NO) release and formation of releasable NO stores by S-nitrosation.

The inhibition of arterial tone produced by two nitric oxide (NO) derivatives of biological relevance, dinitrosyl-iron complexes with cysteine (DNIC-CYS) or with glutathione (DNIC-GSH), was compared. Both compounds induced vasorelaxation within the same concentration range (3-300 nM) in endothelium-denuded rat aortic rings. Consistent with a faster rate of NO release from DNIC-CYS than from DNIC-GSH, the relaxant effect of DNIC-CYS was rapid in onset and tended to recover with time, whereas the one of DNIC-GSH developed slowly and was sustained. In addition, DNIC-GSH (0.3 and 1 microM) but not DNIC-CYS (1 microM) induced, even after washout of the drug, a persistent hyporesponsiveness to vasoconstrictors and a relaxant effect of low molecular weight thiols like N-acetylcysteine (NAC, which can displace NO from preformed NO stores). Both effects of DNIC-GSH were associated with elevation of cyclic GMP content and were attenuated by NO scavengers or a cyclic GMP-dependent protein kinases inhibitor. In rings previously exposed to DNIC-GSH, addition of mercuric chloride (which can cleave the cysteine-NO bond of S-nitrosothiols) elicited relaxation, completely blunted the one of NAC and also abolished the persistent elevation of NO content. In conclusion, this study shows that whereas both DNIC-CYS and DNIC-GSH elicited a NO release-associated relaxant effect in isolated arteries, only DNIC-GSH induced an inhibition of contraction which persisted after drug removal. The persistent effect of DNIC-GSH was attributed to the formation of releasable NO stores in arterial tissue, most probably as S-nitrosothiols. Thus, the nature of the thiol ligand plays a critical role in determining the mechanisms and duration of the effect of LMW-DNIC in arteries.

Role of S-nitrosation of cysteine residues in long-lasting inhibitory effect of nitric oxide on arterial tone.

S-Nitrosation of cysteine residues plays an important role in nitric oxide (NO) signaling and transport. The aim of the present study was to investigate the role of S-nitrosothiols as a storage form of NO, which may account for the long-lasting effects in the vasculature. Rat aorta exposed to S-nitrosoglutathione (GSNO) displayed, even after washout of the drug, a persistent increase in cysteine-NO residues (detected by immunostaining using an antiserum that selectively recognized S-nitrosoproteins) and in NO content (detected by NO spin-trapping), a persistent attenuation of the effect of vasoconstrictors, and a relaxant response upon addition of low molecular weight (LMW) thiols. Rat mesenteric and porcine coronary artery exposed in vitro to GSNO, as well as aorta and mesenteric arteries removed from rats treated in vivo with GSNO, displayed similar modifications of contraction. In isolated aorta exposed to GSNO, the decrease of the contractile response and the relaxant effect of LMW thiols were both blunted by NO scavengers (oxyhemoglobin or 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) or by a cyclic GMP-dependent protein kinase inhibitor (Rp-8-bromoguanosine-3',5'-cyclic monophosphorothioate). In these arteries, mercuric chloride (which cleaves the cysteine-NO bond) exerted a transient relaxation, completely abolished the one of LMW thiols, and blunted the increase in cysteine-NO residues and NO content. Together, these data support the idea that S-nitrosation of cysteine residues is involved in long-lasting effects of NO on arterial tone. They suggest that S-nitrosation of tissue thiols is a mechanism of formation of local NO stores from which biologically active NO can subsequently be released.