Nitric oxide-mediated regulation of transepithelial sodium and chloride transport in murine nasal epithelium. (73/20782)

Transepithelial ion transport is regulated by a variety of cellular factors. In light of recent evidence that nitric oxide (NO) production is decreased in cystic fibrosis airways, we examined the role of NO in regulating sodium and chloride transport in murine nasal epithelium. Acute intervention with the inducible NO synthase (iNOS)-selective inhibitor S-methylisothiourea resulted in an increase of amiloride-sensitive sodium absorption observed as a hyperpolarization of nasal transepithelial potential difference. Inhibition of iNOS expression with dexamethasone also hyperpolarized transepithelial potential difference, but only a portion of this increase proved to be amiloride sensitive. Chloride secretion was significantly inhibited in C57BL/6J mice by the addition of both S-methylisothiourea and dexamethasone. Mice lacking iNOS expression [NOS2(-/-)] also had a decreased chloride-secretory response compared with control mice. These data suggest that constitutive NO production likely plays some role in the downregulation of sodium absorption and leads to an increase in transepithelial chloride secretion.  (+info)

Adenosine-induced renal vasoconstriction in diabetes mellitus rats: role of nitric oxide. (74/20782)

In rats with streptozotocin (STZ)-induced diabetes, the renal vasoconstrictor effect of adenosine is enhanced. We investigated the role of nitric oxide (NO) in the renal vascular response to exogenous and endogenous adenosine in control and STZ diabetic rats. Exogenous adenosine (0.01-100 nmol) injected into the abdominal aorta decreased renal blood flow (RBF) in a dose-dependent manner to a much greater extent in STZ rats than in control rats (P < 0.001). Inhibition of NO synthesis with Nomega-nitro-L-arginine (L-NNA, 30 micromol/kg iv) and with renal perfusion pressure controlled potentiated the adenosine-induced renal vasoconstriction to a significantly greater extent in control rats than in STZ rats. In control rats, L-NNA shifted the dose-response curve of exogenous adenosine-induced RBF reductions to the left by a factor of 32 [half-maximal effective dose (ED50), from 5.5 to 0.17 nmol adenosine, n = 6] and in STZ rats only by a factor of 4.6 (ED50, from 0.32 to 0.07 nmol adenosine, n = 6). The renal response to endogenous adenosine was assessed by the magnitude of the postocclusive reduction of RBF (POR) after a 30-s renal artery occlusion. POR was markedly enhanced in STZ rats (-67.8 +/- 3.8%, P < 0.001) compared with control rats (-38.8 +/- 4.3%). L-NNA markedly enhanced POR in control rats but did not increase POR in STZ rats. These findings demonstrate a greater potentiation of the adenosine-induced renal vasoconstriction in the presence of L-NNA infusion in control rats compared with STZ rats. We conclude that the increased vasoconstrictor sensitivity of the diabetic renal vasculature to adenosine is caused by a defective NO-dependent renal vasodilation of the afferent arteriole in diabetic rats.  (+info)

AVP inhibits LPS- and IL-1beta-stimulated NO and cGMP via V1 receptor in cultured rat mesangial cells. (75/20782)

The present study examined how arginine vasopressin (AVP) affects nitric oxide (NO) metabolism in cultured rat glomerular mesangial cells (GMC). GMC were incubated with test agents and nitrite, and intracellular cGMP content, inducible nitric oxide synthase (iNOS) mRNA, and iNOS protein were analyzed by the Griess method, enzyme immunoassay, and Northern and Western blotting, respectively. AVP inhibited lipopolysaccharide (LPS)- and interleukin-1beta (IL-1beta)-induced nitrite production in a dose- and time-dependent manner, with concomitant changes in cGMP content, iNOS mRNA, and iNOS protein. This inhibition by AVP was reversed by V1- but not by oxytocin-receptor antagonist. Inhibition by AVP was also reproduced on LPS and interferon-gamma (IFN-gamma). Protein kinase C (PKC) inhibitors reversed AVP inhibition, whereas PKC activator inhibited nitrite production. Although dexamethasone and pyrrolidinedithiocarbamate (PDTC), inhibitors of nuclear factor-kappaB, inhibited nitrite production, further inhibition by AVP was not observed. AVP did not show further inhibition of nitrite production with actinomycin D, an inhibitor of transcription, or cycloheximide, an inhibitor of protein synthesis. In conclusion, AVP inhibits LPS- and IL-1beta-induced NO production through a V1 receptor. The inhibitory action of AVP involves both the activation of PKC and the transcription of iNOS mRNA in cultured rat GMC.  (+info)

Tonic and phasic influences of nitric oxide on renal blood flow autoregulation in conscious dogs. (76/20782)

The aim of this study was to investigate the influence of the mean level and phasic modulation of NO on the dynamic autoregulation of renal blood flow (RBF). Transfer functions were calculated from spontaneous fluctuations of RBF and arterial pressure (AP) in conscious resting dogs for 2 h under control conditions, after NO synthase (NOS) inhibition [NG-nitro-L-arginine methyl ester hydrochloride (L-NAME)] and after L-NAME followed by a continuous infusion of an NO donor [S-nitroso-N-acetyl-DL-penicillamine (SNAP)]. After L-NAME (n = 7) AP was elevated, heart rate (HR) and RBF were reduced. The gain of the transfer function above 0.08 Hz was increased, compatible with enhanced resonance of the myogenic response. A peak of high gain around 0.03 Hz, reflecting oscillations of the tubuloglomerular feedback (TGF), was not affected. The gain below 0.01 Hz, was elevated, but still less than 0 dB, indicating diminished but not abolished autoregulation. After L-NAME and SNAP (n = 5), mean AP and RBF were not changed, but HR was slightly elevated. The gain above 0.08 Hz and the peak of high gain at 0.03 Hz were not affected. The gain below 0.01 Hz was elevated, but smaller than 0 dB. It is concluded that NO may help to prevent resonance of the myogenic response depending on the mean level of NO. The feedback oscillations of the TGF are not affected by NO. NO contributes to the autoregulation below 0.01 Hz due to phasic modulation independent of its mean level.  (+info)

Exhaled nitric oxide; relationship to clinicophysiological markers of asthma severity. (77/20782)

Bronchial asthma is an airway disorder associated with bronchial hyperresponsiveness, variable airflow obstruction and elevated levels of nitric oxide (NO) in exhaled air. The variables all reflect, in part, the underlying airway inflammation in this disease. To understand their interrelationships we have investigated the relationship between exhaled NO levels and clinicophysiological markers of asthma severity. Twenty-six steroid naive atopic asthmatics participated in the analysis. All were given diary cards and were asked to record their peak expiratory flow (PEF) rates twice daily together with their asthma symptom scores and beta-agonist use. Diary cards were collected 2 weeks later and measurements of exhaled NO levels, FEV1 and histamine bronchial hyperreactivity (PC20 histamine) were undertaken. Exhaled NO levels were significantly higher in our study population than in normal control subjects and correlated negatively with PC20 histamine (r = -0.51; P = 0.008) and positively with PEF diurnal variability (r = 0.58; P = 0.002), but not with symptom scores, beta-agonist use of FEV1 (%). We conclude that a significant relationship exists between exhaled NO levels and the two characteristic features and markers of asthma severity, namely bronchial hyperreactivity and PEF diurnal variability. The lack of correlation between symptom score and beta-agonist use, of FEV1 (%) predicted and exhaled NO suggests that these measures are reflective of differing aspects of asthma.  (+info)

Macrophage control of herpes simplex virus type 1 replication in the peripheral nervous system. (78/20782)

After corneal infection, herpes simplex virus type 1 (HSV-1) invades sensory neurons with cell bodies in the trigeminal ganglion (TG), replicates briefly, and then establishes a latent infection in these neurons. HSV-1 replication in the TG can be detected as early as 2 days after corneal infection, reaches peak titers by 3-5 days after infection, and is undetectable by 7-10 days. During the period of HSV-1 replication, macrophages and gammadelta TCR+ T lymphocytes infiltrate the TG, and TNF-alpha, IFN-gamma, the inducible nitric oxide synthase (iNOS) enzyme, and IL-12 are expressed. TNF-alpha, IFN-gamma, and the iNOS product nitric oxide (NO) all inhibit HSV-1 replication in vitro. Macrophage and gammadelta TCR+ T cell depletion studies demonstrated that macrophages are the main source of TNF-alpha and iNOS, whereas gammadelta TCR+ T cells produce IFN-gamma. Macrophage depletion, aminoguanidine inhibition of iNOS, and neutralization of TNF-alpha or IFN-gamma all individually and synergistically increased HSV-1 titers in the TG after HSV-1 corneal infection. Moreover, individually depleting macrophages or neutralizing TNF-alpha or IFN-gamma markedly reduced the accumulation of both macrophages and gammadelta TCR+ T cells in the TG. Our findings establish that after primary HSV-1 infection, the bulk of virus replication in the sensory ganglia is controlled by macrophages and gammadelta TCR+ T lymphocytes through their production of antiviral molecules TNF-alpha, NO, and IFN-gamma. Our findings also strongly suggest that cross-regulation between these two cell types is necessary for their accumulation and function in the infected TG.  (+info)

Blockade of nitric oxide-induced relaxation of rabbit aorta by cysteine and homocysteine. (79/20782)

AIM: To examine the inhibition by L-cysteine (Cys) and L-homocysteine (HoCys) of NO-induced relaxation of aorta. METHODS: The tension of rabbit aortic rings in oxygenated Krebs' solution was recorded isometrically. RESULTS: Pretreatment of endothelium-denuded rings with Cys or HoCys inhibited the NO-induced increase in cGMP. The inhibitory effects of Cys or HoCys on relaxation responses to subsequent additions of NO 75 nmol.L-1 gradually diminished with time, which was consistent with the loss of the sulfhydryl concentration of Cys and HoCys. Superoxide dismutase (SOD) 35 kU.L-1 attenuated the inhibition by Cys and HoCys of NO-induced relaxation. Neither boiled SOD nor catalase 100 kU.L-1 antagonized the inhibitory effects of Cys. Preaddition of SOD 35 kU.L-1 inhibited the reduction of cytochrome C by Cys. Increasing concentrations of SOD from 35 to 350 kU.L-1 intensified the cytochrome C reduction. Addition of xanthine 300 mumol.L-1 plus xanthine oxidase 1 U.L-1 to the mixture of cytochrome C 60 mumol.L-1 and Cys 100 mumol.L-1 produced an additional augmentation of SOD-inhibitable reduction of cytochrome C. The rate of the reduction of cytochrome C induced by HoCys 100 mumol.L-1 was much slower than with Cys. Addition of NO reduced the SH concentrations of both the supernatant of aortic homogenate and Cys in Krebs' solution. CONCLUSION: The inhibition by the SH compounds of NO is mediated partly by the superoxide generated by the auto-oxidation of these compounds, and partly by a direct reaction of SH groups with NO.  (+info)

Intrahippocampal infusion of interleukin-6 impairs avoidance learning in rats. (80/20782)

AIM: To study the effect of intrahippocampal infusion of interleukin-6 (IL-6) on active avoidance in rats and the possible involvement of nitric oxide (NO). METHODS: Using a shuttle-box model, the effects of bilaterally intrahippocampal infusion of IL-6 3.2, 16, and 80 ng as well as sodium nitroprusside (SNP) 400 ng on active avoidance were studied on d 8 after administration. The levels of nitrite as an index of NO in the hippocampus were detected using a fluorometric assay 24 h after infusion of IL-6 3.2 or 80 ng. RESULTS: IL-6 16 and 80 ng impaired the acquisition performance of active avoidance by prolonging the latency of avoidance in training, but not the retention performance in testing. IL-680 ng and SNP 400 ng also resulted in a marked impairment in acquisition performances by decreasing the rate of avoidance, but not in retention performances. IL-680 ng markedly elevated the nitrite levels from 10.6 +/- 0.7 in control rats to 13.6 +/- 2.0 (nmol/g wet wt) (P < 0.01). IL-6 3.2 ng had no effect on active avoidance nor on nitrite levels. CONCLUSION: Intrahippocampal infusion of IL-6 impaired learning acquisition of active avoidance in rats.  (+info)