Ethanol inhibition of phagocytosis and superoxide anion production by microglia

A case of a symptomatic colonic lipoma causing recurrent abdominal pain and intestinal obstruction, not treated is reported. Lipomas are the most common mesenchymal benign tumors that can be found in the colon and are second as frequence only to the adenomatous polyps. In 65% of cases the lipomas are located in the large bowel and represent the most common cause of intestinal intussusception in the adult. Lipomas are most frequent in the right colon (40%-68%) an opposite distribution in comparison with adenocarcinomas and adenomatous polyps. When their diameter is more than 3 cm, lipomas become symtomatic. In lipomas less then 2 cm in diameter it is possible an endoscopic removal while for bigger sizes the surgical laparoscopic approach is recommended.     

Involvement of the reductase domain of neuronal nitric oxide synthase in superoxide anion production

Neuronal nitric oxide synthase (nNOS) is a modular enzyme which consists of a flavin-containing reductase domain and a heme-containing oxygenase domain, linked by a stretch of amino acids which contains a calmodulin (CaM) binding site. CaM binding to nNOS facilitates the transfer of NADPH-derived electrons from the reductase domain to the oxygenase domain, resulting in the conversion of L-arginine to L-citrulline with the concomitant formation of a guanylate cyclase activating factor, putatively nitric oxide. Numerous studies have established that peroxynitrite-derived nitrogen oxides are present following nNOS turnover. Since peroxynitrite is formed by the diffusion-limited reaction between the two radical species, nitric oxide and O2.-, we employed the adrenochrome assay to examine whether nNOS was capable of producing O2.- during catalytic turnover in the presence of L-arginine. To differentiate between the role played by the reductase domain and that of the oxygenase domain in O2.- production, we compared its production by nNOS against that of a nNOS mutant (CYS-331), which was unable to transfer NADPH-derived electrons efficiently to the heme iron under special conditions, and against that of a flavoprotein module construct of nNOS. We report that O2.- production by nNOS and the CYS-331 mutant is CaM-dependent and that O2.- production can be modulated by substrates and inhibitors of nNOS. O2.- was also produced by the reductase domain of nNOS; however, it did not display the same CaM dependency. We conclude that both the reductase and oxygenase domains of nNOS produce O2.-, but that the reductase domain is both necessary and sufficient for O2.- production.     

Morphine stimulates nitric oxide release from invertebrate microglia

Analysis of chromosomal DNA restriction patterns produced by pulsed field gel electrophoresis (PFGE) was used to investigate an outbreak of human salmonellosis caused by Salmonella enterica ssp. enterica serovar Infantis (S. Infantis) involving more than 500 registered human cases. The outbreak had been tentatively traced back to a single pig slaughterhouse. A total of 135 isolates from various sources produced 21 different PFGE patterns with the restriction endonuclease XbaI. All human isolates from the outbreak belonged to a single type, the 'EPI-type', whereas human isolates recovered before and after the outbreak belonged to several different types. All isolates investigated from the suspect pig slaughterhouse and its supplier pig herds belonged to the EPI-type. Isolates from pork from the central meat market in Copenhagen, which received most of the carcasses from the suspect slaughterhouse, also belonged to the EPI-type. This was furthermore, the case for isolates from beef from the same market, indicating that cross-contamination had taken place. All isolates from pork and some, but not all, isolates from beef, collected in butchers' shops during the outbreak belonged to the EPI-type. The typing results supported that the outbreak was a common source outbreak, probably originating from a limited number of supplier pig herds supplying animals to a single slaughterhouse.     

The changes of plasma nitric oxide in patients with pregnancy induced hypertension

OBJECTIVE: To determine whether the antepartum and postpartum plasma nitric oxide (NO) levels were changed in pregnancy induced hypertension (PIH). METHODS: 30 patients with PIH and 30 healthy women in their late pregnancy were studied. The antepartum and postpartum plasma NO2-/NO2- levels, the stable metabolic end products of NO, and cyclic guanosine monophosphate (cGMP) were measured with greiss reagent. RESULTS: (1) The plasma concentration of NO2-/NO2- and cGMP in patients with PIH decreased significantly when compared with that of healthy pregnant women (P < 0.01). (2) The concentration of antepartum plasma NO2-/NO2- was markedly lower than that of postpartum one in PIH patients (P < 0.01). (3) There was a negative correlation between the plasma NO2-/NO3- level and systolic blood pressure in PIH (P < 0.01). (4) A positive correlation was seen between plasma NO2-/NO3- levels and cGMP levels in PIH patients (P < 0.01). CONCLUSION: The decrease of NO synthesis may be one of the important factors responsible for PIH.     

Basal and induced nitric oxide and cGMP productions are decreased in senescent cultured rat articular chondrocytes

The effects of interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), and lipopolysaccharide (LPS) on the productions of nitric oxide (NO) and cGMP by cultured articular chondrocyte (AC) monolayers from 1-, 8- and 18-month old male Wistar rats were studied. It was found that basal NO and cGMP productions decrease with the age of animals. The productions were more than 2-fold greater in cells from 1-month old rats then in cells from older animals. IL-1, TNF-alpha, and LPS stimulated all three types of cells to produce NO and cGMP in a time- and concentration-dependent manner. Although the cells from young animals produced more NO per microg DNA, the older counterparts were more sensitive to these agents since they produced more NO upon stimulation then the corresponding non-stimulated controls. At the concentration of 10(-3) M, the nitric oxide synthase (NOS) inhibitor, Ng-monomethyl-L-arginine (L-NMA), blocked, although incompletely, both the basal and stimulated NO and cGMP productions in cells from the 1 and 8-month old rats and only induced productions in 18-month old counterparts. These results show a decreased capacity of unstimulated- and stimulated-AC from old rats to produce NO and cGMP in culture, which may affect the ageing cells in some yet unknown way.     

Involvement of superoxide and nitric oxide on airway inflammation and hyperresponsiveness induced by diesel exhaust particles in mice

We previously demonstrated that chronic intratracheal instillation of diesel exhaust particles (DEP) induces airway inflammation and hyperresponsiveness in the mouse, and that these effects were partially reversed by the administration of superoxide dismutase (SOD). In the present study, we have investigated the involvement of superoxide in DEP-induced airway response by analyzing the localization and activity of two enzymes: (1) a superoxide producer, NADPH cytochrome P-450 reductase (P-450 reductase), and (2) a superoxide scavenger, SOD, in the lungs of the exposed mice and controls. P-450 reductase was detected mainly in ciliated cells and clara cells: its activity was increased by the repeated intratracheal instillation of DEP. While CuZn-SOD and Mn-SOD were also present in the airway epithelium, their activity was significantly decreased following DEP instillation. Exposure to DEP doubled the level of nitric oxide (NO) in the exhaled air. DEP exposure also increased the level of constitutive NO synthase (cNOS) in the airway epithelium and inducible NO synthase (iNOS) in the macrophages. Pretreatment with N-G-monomethyl L-arginine, a nonspecific inhibitor of NO synthase, significantly reduced the airway hyperresponsiveness induced by DEP. These results indicate that superoxide and NO may each contribute to the airway inflammation and hyperresponsiveness induced by the repeated intratracheal instillation of DEP in mice.     

Role of nitric oxide and superoxide anion in elimination of low metastatic human colorectal carcinomas by unstimulated hepatic sinusoidal endothelial cells

Human colorectal carcinoma (CRC) cell survival for the first 24 h after implantation in the hepatic sinusoid determines its potential to colonize the liver. Nearly 10-fold more highly metastatic CX-1 cells survive within the livers of nude mice 24 h after intrasplenic injection than weakly metastatic clone A cells. Because CRCs contact sinusoidal endothelial cells (SECs) during implantation, we sought to determine whether SECs were more toxic to clone A than to CX-1 cells. When 2 x 10(4) vital dye-labeled CRC cells were added to murine SEC monolayers, more than 30% of clone A cells lost calcein AM fluorescence compared to fewer than 5% of CX-1 cells after 24 h of coculture with SECs. Kupffer cells did not mediate this effect, because neither enriched Kupffer cells nor SECs treated with a Kupffer cell inhibitor altered the SEC-mediated toxic effect to clone A cells. Pretreatment with a nitric oxide synthase inhibitor, N(G)-monomethyl-L-arginine, superoxide dismutase, or dexamethasone, blocked SEC-mediated toxicity to clone A cells, whereas calcium chelation and catalase did not. In addition, clone A cells were more sensitive to a superoxide donor, 3-morpholinosydnonimine N-ethylcarbamide, than were CX-1 cells, and neither cell line was sensitive to sodium nitroprusside, a nitric oxide donor. Thus, unstimulated murine SECs produce reactive oxygen species that are selectively toxic to weakly metastatic clone A cells. This may be a mechanism by which host liver cells eliminate weakly metastatic neoplastic cells.     

Helicobacter pylori generates superoxide radicals and modulates nitric oxide metabolism

During studies of the bactericidal action of nitric oxide (NO), we found that it reversibly inhibited the respiration of Escherichia coli and irreversibly inhibited the respiration of Helicobacter pylori. Peroxynitrite, a reaction product of NO and superoxide, irreversibly inhibited the respiration of both H. pylori and E. coli. H. pylori, but not E. coli, generated substantial amounts of superoxide radicals. These results suggest that NO directly inhibits the respiration of E. coli whereas it rapidly reacts with endogenously generated superoxide radicals in H. pylori. The resulting peroxynitrite inactivates the respiration of H. pylori.     

Morphine-induced conformational changes in human monocytes, granulocytes, and endothelial cells and in invertebrate immunocytes and microglia are mediated by nitric oxide

We evaluated the contribution of nitric oxide (NO) to morphine-induced rounding of spontaneously activated (mobile) ameboid human monocytes, granulocytes, or arterial endothelial cells and invertebrate immunocytes and microglia. Morphine induced significant rounding and inactivation of ameboid cells within 20 min except for arterial endothelial cells, which became rounded 24 h after morphine exposure. The effects of morphine on cell conformation were blocked in the presence of N-nitro-L-arginine, a nitric oxide synthase inhibitor. Treatment of cells with the NO donor, sodium nitroprusside, induced cell rounding similar to that observed following morphine exposure, suggesting that NO release may mediate morphine-induced changes in cell conformation. The contribution of NO release to morphine-induced cell rounding was determined by direct evaluation of NO concentration in real-time using a NO-specific amperometric probe. Significant increases in NO concentration were observed 2 min after morphine stimulation, whereas morphine-induced NO release was markedly impaired by pretreatment with N-nitro-L-arginine or the opiate alkaloid antagonist, naloxone. In contrast, opioid peptides failed to induce NO release, consistent with our previous observations that demonstrated the failure of opioid peptides to promote cell rounding. Taken together, these data suggest that morphine-induced NO release may be mediated by activation of the opiate alkaloid-selective, opioid peptide-insensitive micro3 receptor, and that functional coupling of morphine to NO production has been conserved during evolution and may modulate cellular activation.     

Melanocortin peptides inhibit production of proinflammatory cytokines and nitric oxide by activated microglia

This brief history of the dental diamond bur is intended to provide both a historical perspective and an evaluation of the current state of bur technology. An understanding of the origins of dental diamonds and the issues facing manufacturers transforms the dentist from a simple user into an informed consumer. The author contends that this can improve dental care and enable the dentist to collaborate with manufacturers in developing improved dental burs.     

Renal changes induced by nitric oxide and prostaglandin synthesis reduction: effects of trandolapril and verapamil

The benefits of the simultaneous administration of low doses of a calcium antagonist and a converting enzyme inhibitor in the treatment of hypertension and renal vasoconstriction are well established. The objective of this study was to evaluate whether the administration of low doses of a calcium antagonist and a converting-enzyme inhibitor have beneficial effects in treating the renal alterations induced by the acute administration of a cyclooxygenase inhibitor when nitric oxide synthesis is reduced. These effects were examined in anesthetized dogs before and during an acute sodium load. It was found that the intrarenal infusion of meclofenamate (5 microg x kg[-1] x min[-1]), simultaneously with a low dose of NG-nitro-L-arginine methyl ester (1 microg x kg[-1] x min[-1]), produced a 40% decrease of renal blood flow and glomerular filtration rate and a reduction in the renal excretory response to the sodium load. In a second group of dogs, intrarenal verapamil (0.5 microg x kg[-1] x min[-1]) was effective in blocking the effects of nitric oxide and prostaglandin synthesis inhibition on sodium excretion and glomerular filtration rate but did not modify the effects on renal blood flow. An intrarenal infusion of trandolapril (0.3 microg x kg[-1] x min[-1]) was effective in a third group of dogs in reducing the renal hemodynamic effects but not in preventing the antinatriuretic effect observed in the first group. Finally, in a fourth group, the simultaneous administration of verapamil and trandolapril was effective in treating all the renal changes induced by the cyclooxygenase inhibitor when nitric oxide synthesis was reduced. These results suggest that the combination of low doses of trandolapril and verapamil has additive effects in treating the renal vasoconstriction and antinatriuresis induced by the acute administration of a cyclooxygenase inhibitor, when nitric oxide synthesis is reduced.     

Effects of nitric oxide in cultured prevertebral sympathetic ganglion neurons

The effects of the nitric oxide donor, S-nitrosoacetylpenicillamine (SNAP), were tested on cultured dissociated guinea pig celiac ganglion neurons using whole cell patch-clamp recordings. S-nitrosoacetylpenicillamine induced a concentration- and voltage-dependent inwardly directed shift in holding current (inward current shift) in 89% of neurons. The inward current shift was prevented by pre-treatment with the nitric oxide scavenger reduced hemoglobin and was abolished by intra- or extracellular cesium. The amplitude of the inward current shift was also sensitive to the extracellular potassium concentration. The S-nitrosoacetylpenicillamine-induced inward current shift was mediated by a decrease in calcium-dependent potassium currents (IAHPs); apamin (100 nM), charybdotoxin (10 nM) or tetraethylammonium (5 mM) reduced but did not abolish the amplitude of its inward current shift and a combination of apamin and tetraethylammonium abolished the S-nitrosoacetylpenicillamine-induced inward current response. In the presence of extracellular cobalt, SNAP produced an outward current that was concentration- and voltage-dependent, abolished by reduced hemoglobin and extracellular cesium and reduced by 4-AP (1 mM); in the absence of cobalt, 4-AP increased the SNAP-induced inward current shift. These data indicate that NO exerts dual opposing effects on neuronal potassium conductances, namely an inward current shift mediated through an inhibition of IAHP and induction of an outward current mediated by activation of the potassium delayed rectifier.     

Antioxidant and pro-oxidant actions of flavonoids: effects on DNA damage induced by nitric oxide, peroxynitrite and nitroxyl anion

Antioxidant and pro-oxidant activities of flavonoids have been reported. We have studied the effects of 18 flavonoids and related phenolic compounds on DNA damage induced by nitric oxide (NO), peroxynitrite, and nitroxyl anion (NO-). Similarly to our previous findings with catecholamines and catechol-estrogens, DNA single-strand breakage was induced synergistically when pBR322 plasmid was incubated in the presence of an NO-releasing compound (diethylamine NONOate) and a flavonoid having an ortho-trihydroxyl group in either the B ring (e.g., epigallocatechin gallate) or the A ring (e.g., quercetagetin). Either NO or any of the above flavonoids alone did not induce strand breakage significantly. However, most of the tested flavonoids inhibited the peroxynitrite-mediated formation of 8-nitroguanine in calf-thymus DNA, measured by a new HPLC-electrochemical detection method, as well as the peroxynitrite-induced strand breakage. NO- generated from Angeli's salt caused DNA strand breakage, which was also inhibited by flavonoids but at only high concentrations. On the basis of these findings, we propose that NO- and/or peroxynitrite could be responsible for DNA strand breakage induced by NO and a flavonoid having an ortho-trihydroxyl group. Our results indicate that flavonoids have antioxidant properties, but some act as pro-oxidants in the presence of NO.     

Angiotensin-converting enzyme inhibition alters nitric oxide and superoxide release in normotensive and hypertensive rats

Young (approximately 1 month old) male normotensive Wistar-Kyoto rats (n=26) and spontaneously hypertensive rats (n=38) were randomized into three groups treated via drinking water for approximately 2 years with, respectively, placebo, low doses, or high doses of an angiotensin-converting enzyme inhibitor, ramipril (10 microg x kg[-1] x d[-1], non-blood pressure-lowering dose, or 1 mg x kg[-1] x d[-1], blood pressure-lowering dose). Relative to placebo treatment in each respective rat strain, both ramipril dosages increased endothelial constitutive nitric oxide synthase expression (Western blot) and resultant synthesis of nitric oxide (porphyrinic sensor) in freshly excised carotids and thoracic aortas, respectively. Paradoxically, this activity was associated with an increased/decreased superoxide accumulation (chemiluminescence) in freshly excised aortas from 24-/22-month-old normotensive/hypertensive rats. In normotensive rats, relative to placebo treatment, the threefold increase in superoxide accumulation with antihypertensive ramipril treatment is most likely from the >300% increase in endothelial constitutive nitric oxide synthase expression (some of which may be disarranged by local insufficiencies in L-arginine or tetrahydrobiopterin). In hypertensive rats, relative to placebo treatment, the 35% increase in nitric oxide availability by long-term antihypertensive ramipril treatment may contribute to the preservation of the endothelium and prevent its dysfunction by inhibiting superoxide production. Increased nitric oxide production with concomitant decreased superoxide accumulation (approximately one third of placebo levels) correlates positively with the previously reported +40% life span extension for rats with genetic hypertension that were treated with antihypertensive doses of ramipril.     

High glucose inhibits nitric oxide production in cultured rat mesangial cells

Hyperglycemia directly contributes to the development of diabetic nephropathy. A high-serum glucose concentration alters intraglomerular hemodynamics and promotes deposition of extracellular matrix in the kidney. Nitric oxide (NO) is a short-lived messenger molecule that participates in the regulation of renal blood flow, GFR, and mesangial matrix accumulation. Therefore, in this study it was tested whether high glucose directly modulates NO synthesis by rat mesangial cells in vitro by measuring the accumulation of nitrite, the stable metabolite of NO, in the incubation media. Raising the external glucose concentration to 33.3 mM for 24 to 72 h reduced nitrite levels in cell supernatants in a time-dependent manner to a nadir of 14 +/- 3% of the amount in normal glucose media (5.6 mM) (P < 0.01). The decline in NO synthesis in high glucose media was paralleled by decreased cyclic guanosine monophosphate generation; however, there was no alteration in rat mesangial cell expression of inducible NO synthase protein. The suppressive effect of high glucose on NO production by mesangial cells was not modified by inhibition of protein kinase C (H-7), the addition of antioxidants (vitamin E or superoxide dismutase), or a pan-specific anti-transforming growth factor-beta antibody. An elevated ambient glucose caused a time-dependent reduction in mesangial cell L-arginine content. Addition of L-arginine (10 to 20 mM) to external media partially reversed the inhibitory effect of high glucose on mesangial cell NO production in a dose-dependent manner. The highest dose of L-arginine (20 mM) increased mesangial cell L-arginine content to comparable levels in normal and high glucose media. These results indicate that high glucose causes depletion of L-arginine in mesangial cells and compromises NO synthesis. Limitation in the metabolic precursor and other, as yet unidentified, factors act to reduce NO production by mesangial cells in the presence of an elevated ambient glucose level, a change that may play a role in the development of diabetic glomerulosclerosis.     

Cyclosporin inhibits nitric oxide production in medullary ascending limb cultured cells

BACKGROUND: Nitric oxide (NO) has been shown to play a role in cyclosporin (CsA) nephrotoxicity, but its mechanism of action is still unclear. As inducible NO synthase (iNOS) mRNA has been found to be expressed in rat medullary thick ascending limb (mTAL) cells, we investigated the effects of CsA on NO production in a model of mouse cultured mTAL cells. MATERIALS AND METHODS: The experiments were carried out on sub-cultured cells derived from isolated mTAL microdissected from the kidney of C57BL/6 mice. The identification of the iNOS mRNA in mTAL microdissected segment and cultured cell was confirmed by RT PCR and RsaI digestion. Nitrite (NO2) released by mTAL cells was determined using the modified Griess reagent method and taken as an index of nitric oxide production. The cultured cells were treated with various concentrations of CsA and different signal transduction regulators to assess the effect and possible pathway(s) of action of CsA on NO production in mTAL cells. RESULTS: The basal production of NO by mTAL cells increased by 1.8-fold following incubation with bacterial lipopolysaccaride (LPS). Both aminoguanidine and L-NAME inhibited NO production. CsA (10-300 ng/ml) also inhibited NO production in a dose-dependent manner and prevented its increase induced by LPS. Phorbol 12-myristate 13-acetate (PMA), a PKC stimulator, enhanced slightly the production of NO under basal conditions and prevented the inhibitory action of CsA on NO production. These results suggest that the NO secreted by mouse cultured mTAL cells is dependent on the PKC pathway. CONCLUSION: These results show that CsA may down-regulate the production of NO by cultured mTAL cells expressing iNOS mRNA and that the PKC pathway is involved in this process.