High salt intake inhibits nitric oxide synthase expression and aggravates hypertension in rats with chronic renal failure

The pathophysiology of hypertension in chronic renal failure is complex, but sodium retention and volume expansion play an important role. High salt intake may aggravate hypertension in chronic renal failure, but the mechanisms of this action are not well established. In this study, we have tested the hypothesis that high salt intake aggravates hypertension in rats with chronic renal failure by decreasing nitric oxide synthase (NOS) expression and by increasing sympathetic nervous system activity. Sprague-Dawley rats were subjected to 5/6 nephrectomy (CRF) or sham-operation and fed a regular rat chow. Half of the rats were allowed to drink distilled water and half water containing 1% NaCl. Blood pressure was measured weekly by tail-cuff. Four weeks after nephrectomy or sham-surgery, animals were sacrificed and brains immediately separated and frozen. Norepinephrine (NE) content and NOS-mRNA gene expression were measured in the posterior hypothalamic (PH) nuclei, the locus coeruleus (LC), the paraventricular nuclei (PVN), and in the mesenteric vessels. The endogenous concentration of NE was greater in the PH, LC, and PVN of CRF rats than it was in control animals both during a normal and a high dietary salt intake. In control and CRF rats, the concentration of NE was greater (p < 0.01) during a high than during a normal salt intake in the PH, LC, PVN, and in the mesenteric vessels. A high salt intake reduced the nNOS-mRNA gene expression in the PH (from 100 +/- 2.4 to 46 +/- 1.0;p < 0.01), LC (from 92 +/- 1.9 to 69 +/- 1.2; p < 0.01) and PVN (from 63 +/- 0.8 to 46 +/- 1.3) of CRF rats. A similar reduction occurred in the PH (from 36 +/- 0.8 to 23.6 +/- 1.2), LC (from 33 +/- 1.4 to 24 +/- 1.1) and PVN (from 37 +/- 1. to 27 +/- 1.0) of control rats. High salt intake significantly reduced the nNOS-mRNA gene expression in the mesenteric arteries of control rats, but not in those of CRF rats. In conclusion, these studies provide evidence that in control and CRF rats, high salt intake inhibits nNOS-mRNA expression in the brain, resulting in activation of the sympathetic nervous system and higher blood pressure.     

Inducible nitric oxide synthase in renal transplantation

The importance of the endothelial isoform of nitric oxide synthase (eNOS) has been well established. Endothelium-derived nitric oxide has been shown to be essential for vascular homeostasis and modulation of eNOS has thus become a target in prevention of cardiovascular disease. The role of the inducible form of nitric oxide synthase (iNOS) in vascular biology, however, is less clear. Classically, iNOS has been regarded as an enzyme that produces nmolar amounts of the nitric oxide radical, thereby leading to cellular damage. More recent data, however, have shown that the iNOS can be a superoxide, peroxynitrite as well as a nitric oxide-producing enzyme, while the biological effects of iNOS probably depend upon the sort of radical species released by the enzyme as well as the anti-oxidant capacity of the cellular microenvironment of the enzyme. This brief review discusses these aspects in relation to renal transplantation.     

Nitric oxide production and nitric oxide synthase expression in acute human renal allograft rejection

BACKGROUND: Nitric oxide (NO) is produced by nitric oxide synthases (NOS), which are either constitutively expressed in the kidney or inducible, in resident and infiltrating cells during inflammation and allograft rejection. NO is rapidly degraded to the stable end products nitrite and nitrate, which can be measured in serum and urine, and may serve as noninvasive markers of kidney allograft rejection. METHODS: Total nitrite and nitrate levels (NOx) were measured in serum and urine thrice weekly after an overnight fast in 18 consecutive patients following renal cadaveric transplantation. Inducible NOS (iNOS) and endothelial NOS (eNOS) expression was immunochemically determined in renal biopsy specimens with or without acute rejection (AR). RESULTS: Serum NOx levels increased days before AR and were significantly higher at the moment of AR (27+/-12.4 micromol/L) compared with recipients with an uncomplicated course (13+/-7.6 micromol/L), but not compared with recipients with cyclosporine (CsA) toxicity (20+/-13.0 micromol/L). Urinary NOx levels were significantly lower during AR (20+/-13.6 micromol/mmol creatinine) compared with an uncomplicated course (64+/-25.2 micromol/mmol creatinine) or CsA toxicity (53.8+/-28.3 micromol/mmol creatinine). Interstitial and glomerular iNOS expression was significantly increased in biopsy specimens showing AR. Unexpectedly, glomerular eNOS expression was significantly decreased in patients with AR. CONCLUSIONS: This study reports differences in NOx levels in serum and urine, which may help discriminate AR episodes from an uncomplicated course or CsA toxicity. As expected, renal iNOS expression is increased in acute allograft rejection. The decrease in glomerular eNOS expression suggests an intriguing link between acute and chronic rejection.     

抗氧化剂抑制内毒素性休克大鼠诱导型一氧化氮合酶基因表达

感染性休克时循环机能障碍的显著特点表现为进行性、顽固性低血压,伴对血管活性药物敏感性降低,以至组织器官灌注不足、重要器官机能代谢障碍,病死率仍高达30％～70％。休克时循环机能障碍所涉及的病理生理机制极其复杂,脂质过氧化物的堆积和NO的爆发生成是其中的关键病理因素之一。我们以往的研究中发现抗氧化剂能部分逆转内毒素休克大鼠的血管低反应性,为了进一步探讨其治疗学机制,本实验对抗氧化剂在内毒素性休克大鼠iNOS mRNA表达中的作用进行了观察。     

左旋精氨酸恢复eNOS和iNOS平衡并抑制肺动脉高压的研究

目的 探讨诱导型一氧化氮合酶(iNOS)在中、晚期肺动脉高压(PH)发病中的作用机制及左旋精氨酸 (L-Arg)对其产生的影响.方法 30只雄性SD大鼠随机均分为5组,对照组(C组)、MCT3组(M3组)、MCT5组(M5组)、L-Arg3/MCT3组(L3组)、L-Arg5/MCT5组(L5组).除C组外其他组大鼠均用野百合碱一次性腹腔注射诱导PH模型.此后L3组和L5组分别连续每天腹腔注射L-Arg 3周和5周,M3组和M5组分别连续每天腹腔注射与L-Arg等量的生理盐水3周和5周,C组连续每天腹腔注射与L-Arg等量的生理盐水共5周.实验周期结束则用右心导管法测定右心室收缩压(RVSP),间接反映肺动脉压力,然后取大鼠肺组织做免疫组化,检测各组iNOS、内皮一氧化氮合酶(eNOS)和弹性蛋白(elastin)的表达变化.结果 M3和M5组中iNOS和elastin的表达明显高于C组,而eNOS表达明显少于C组;L3和L5组iNOS和elastin的表达少于相应M3和M5组,但L5组两种蛋白表达仍高于C组,L3和L5组eNOS的减少明显比相应M3和M5组少,但不及C组.结论 PH形成的中、晚期,肺组织中eNOS表达减少,而此时iNOS的表达增高可能产生大量一氧化氮(NO),但并没有改善PH的病情,而L-Arg能够恢复eNOS和iNOS之间的平衡并有效抑制PH的进展.     

Endothelial nitric oxide synthase expression in ischemia-reperfusion injury after living related-donor renal transplantation

Ischemia-reperfusion injury during renal transplantation has been linked to early graft dysfunction and late graft failure. Nitric oxide (NO), produced by NO synthase (NOS), participates in the recovery from ischemia. We correlated the intensity of graft immunoreactivity for the endothelial NOS isoform (eNOS) during early reperfusion with graft function in 25 children receiving grafts from related donors. Renal allograft biopsy specimens were obtained before transplantation, 1 h after renal artery reperfusion, and 1 year after transplantation. Immunohistochemical staining for eNOS occurred mainly within the endothelium of glomerular capillaries and peritubular capillaries as well as in tubule cells. The mean intensity score for eNOS staining (0-9) was 3.0+/-1.4 before transplantation, 4.5+/-1.9 at 1 h, and 3.3+/-1.9 at 1 year (baseline vs 1 h, P<0.05). Creatinine clearance (ml/min) in patients with a 1-h eNOS score of below 5 and of at least 5, respectively, was 77.1+/-28.4 vs 104.3+/-25.3 at 1 month, 78.7+/-33.4 vs 105.2+/-24.4 at 3 months, 64.7+/-30.1 vs 100.1+/-25.3 at 1 year, 58.2+/-31.3 vs 84.7+/-18.8 at 3 years, and 71.2+/-19.7 vs 78.3+/-23.1 at 5 years ( P<0.05 for 1 month, 1 year, and 3 years). We concluded that elevated eNOS expression after reperfusion in living related-donor renal transplantation enhances the recovery from renal ischemia and, consequently, reduces late graft deterioration.     

Renal neuronal nitric oxide synthase protein expression as a marker of renal injury

BACKGROUND: Animal studies suggest that nitric oxide deficiency occurs in the remnant after 5/6 removal of renal mass. The present studies investigated the time course in relation to progression of renal disease, as well as the impact on individual renal nitric oxide synthase (NOS) isoforms. METHODS: Rats were studied from 2 to 11 weeks after 5/6 ablation/infarction (A/I) of renal mass, with acceleration of progression by high protein and salt intake, in some groups. Measurements were made before sacrifice of 24-hour protein and creatinine excretion, blood was taken for creatinine and blood urea nitrogen (BUN) determination and the kidneys were investigated histologically for structural damage, abundance of endothelial NOS (eNOS) and neuronal NOS (nNOS), and in some groups for in vitro NOS activity. RESULTS: A time-dependent fall in glomerular filtration rate (GFR) and rise in proteinuria and glomerular sclerosis developed after 5/6 A/I. The nNOS abundance in cortex and medulla was decreased relative to shams, in all but the mildest injury and there was a strong, steep correlation between level of glomerular sclerosis and the degree of reduction in renal nNOS. Where measured, cortical NOS activity correlated with the nNOS abundance. In contrast, the eNOS abundance was either increased or unchanged in rats post A/I. CONCLUSION: Renal nNOS abundance was reduced in the 5/6 A/I model of renal disease when plasma creatinine> approximately 1 mg/dL and when> approximately 20% of remaining glomeruli were sclerosed.     

核因子κB诱捕物寡核苷酸对肾小管上皮细胞炎症因子表达的影响

目的 研究核因子(NF)κB结合位点诱捕物寡核苷酸(NF—κBdecoyODN)对肾小管上皮细胞的NF-κB活性及下游炎症因子表达的影响。方法 (1)鱼精蛋白-脂质体法转染NF-κBdecoy ODN：将NF-κBdecoyODN与鱼精蛋白、脂质体混合，转染至TNF—α刺激培养的大鼠肾小管上皮细胞内，测定转染率。(2)凝胶电泳迟滞分析测定转染NF-κBdecoy ODN后细胞NF-κB活性。(3)RT—PCR方法检测转染NF-κB decoy ODN后细胞ET-1、iNOS、ICAM-1、VCAM-1以及MCP-1mRNA表达水平。结果 当 ／一比例为4时，鱼精蛋白-脂质体法转染率高达93．20％；转染NF-κB decoy ODN可抑制TNF—α激活的NF-κB活性，从而进一步抑制ET-1、iNOS、ICAM-1、VCAM-1和MCP-1的mRNA表达。结论 (1)鱼精蛋白-脂质体法是一种不受血清影响的高效率转染方法。(2)NF—κBdecoy ODN在体外通过抑制NF-κB活性，进而影响肾小管上皮细胞炎症因子的表达。     

Ketamine inhibits nitric oxide synthase in lipopolysaccharide-treated rat alveolar macrophages

Purpose  To evaluate the effects of ketamine on the activity and protein expression of inducible nitric oxide synthase (iNOS) induced by lipopolysaccharide (LPS) in rat alveolar macrophages. Methods  Pulmonary alveolar macrophages isolated from Wistar-Kyoto rats were used. After incubation of macrophages with ketamine (1,10, or 100μM) and LPS (1μg· ml⁻¹) for 24 hr, the cell-free medium was removed for measuring the nitrite and tumour necrosis factor-α (TNF-α) levels by Griess reaction and ELISA kit, respectively. The harvested macrophages were also used to determine the activity of iNOS by using the conversion of [³H]-Larginine to [³H]-L-citruliine method. In addition, the protein expression of iNOS was detected by Western blot analysis. Results  In rat alveolar macrophages, (1) ketamine (1 to 100 μM) caused a dose-dependent suppression of the production of nitrite and TNF-α induced by LPS and (ii) ketamine (100 μM) inhibited the activity (46.5 ± 4.8%, P < 0.05) and protein expression (35 ± 11%, P < 0.05) of iNOS in response to LPS. Conclusion  These results show that ketamine inhibits the activity and expression of iNOS in LPS-activated alveolar macrophages, which may be associated with the reduction of the release of TNF-α following LPS treatment.

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Résumé Objectif  évaluer les effets de la ketamine sur l’activité et la production de l’oxyde nitrique synthase inductible (iNOS) par le lipopolysaccharide (LPS) sur des macrophages alvéolaires de rats. Méthodes  Des macrophages alvéolaires pulmonaires isolés chez des rats Wistar-Kyoto ont été utilisés. Après l’incubation des macrophages dans la kétamine (1,10 ou 100 μM) et le LPS (1 μ/g· kg⁻¹) pendant 24 h, le médium libre de cellules a été extrait pour mesurer les niveaux nitriques et de TNF-α (tumour necrosing factor- α) avec la réaction de Griess et par ELISA. La méthode de conversion de la [3H]-L-arginine à la [3H]-L-citnjlline à servi à déterminer l’activité iNOS des macrophages recueillis. En outre, l’analyseWestern blot décelait l’expression protéinique de iNOS. Résultats  Dans les macrophages alvéolaires de rats, (i) la kétamine (là 100 μM) a provoqué une suppression dépendante de la dose de la production de nitrite et de TNF-α induite par LPS et (ii) la kétamine (100 μM) inhibait l’activité (46,5 ± 4,8%, P < 0,05) et l’expression protéinique (35 = 11%, P < 0,05) de l’iNOS en réponse au LPS. Conclusion  Ces résultats montrent que la kétamine inhibe l’activité et la production de l’iNOS dans des macrophages alvéolaires activés par LPS, ce qui peut être associé a une réduction de la libération de TNF-α à la suite d’un traitement par LPS.

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Supported by a grant of the Tri-servke General Hospital, Taipei, Taiwan, R. O. C. (TSGH-C86-50).     

Stat1 acetylation inhibits inducible nitric oxide synthase expression in interferon-gamma-treated RAW264.7 murine macrophages

BACKGROUND: We hypothesized that acetylation of the Stat1 regulates interferon-gamma (IFN-gamma) mediated macrophage expression of inducible nitric oxide synthase (iNOS). METHODS: RAW 264.7 iNOS expression was induced with IFN-gamma. Deacetylase inhibitors trichostatin A (TSA) or valproic acid (VPA) were added. Stat1 and iNOS mRNA and protein were measured. Acetylated Stat1 was determined by immunoprecipitation. Chromatin immunoprecipitation assessed in vivo binding of Stat1 to the iNOS promoter. RESULTS: IFN-gamma significantly increased nitrite, iNOS protein and iNOS mRNA, and iNOS promoter activation. (P < .01 vs control for nitrite, protein, and mRNA). TSA-mediated acetylation decreased these to levels that were not different from controls. IFN-gamma increased acetylated Stat1 by 5-fold (P < .02 vs control); TSA + IFN-gamma caused an additional 4-fold increase in acetylated Stat1 (P < .05 vs IFN alone). Stat1 binding to the iNOS promoter increased 8-fold with IFN-gamma (P < .01 vs control). In TSA + IFN-gamma, Stat1 binding was not different from controls. Although less potent than TSA, VPA also significantly decreased nitrite, iNOS protein, iNOS mRNA, Stat1 acetylation, and Stat1 binding. CONCLUSIONS: Acetylation of Stat1 protein correlates with decreased Stat1 binding to the iNOS promoter with resultant inhibition of IFN-gamma-mediated iNOS expression. Acetylation of the Stat1 protein may downregulate iNOS expression in proinflammatory states.     

Inducible nitric oxide synthase attenuates endothelium-dependent renal microvascular vasodilation

Previous studies have demonstrated that inducible nitric oxide synthase (iNOS) plays a key pathophysiologic role during sepsis. The present study was designed to delineate the consequences of iNOS activation on renal microvascular function. Male Sprague-Dawley rats were given intraperitoneal injections of lipopolysaccharide (LPS; 4 mg/kg) at 16 h and 4 h before experimentation. Afferent and efferent arteriolar diameters from LPS-treated and control rats were assessed in vitro with the use of the blood perfused juxtamedullary nephron technique. Basal afferent and efferent arteriolar diameters of LPS-treated rats averaged 19.7 +/- 0.9 (n = 7) and 18.3 +/- 1.0 microm (n = 5), respectively, and were similar to those of control rats (20.8 +/- 0.3 [n = 6] and 18.4 +/- 0.6 microm [n = 6], respectively). Superfusion with the selective iNOS inhibitor S,S'-(1,3-phenylenebis[1,2-ethanediyl]) bisisothiourea (PBIT), at the doses of 0.01, 0.1, and 1 microM, significantly decreased afferent and efferent arteriolar diameters in a dose-dependent manner, whereas afferent or efferent arteriolar diameters of control rats were not altered in response to the same doses of PBIT. In the second series of experiments, superfusion with 10 microM acetylcholine (ACh) significantly increased afferent and efferent arteriolar diameters of LPS-treated rats by 14.9 +/- 1.6% (n = 9) and 6.6 +/- 1.1% (n = 6), respectively. The ACh-induced afferent and efferent arteriolar dilator responses were inhibited by superfusion with the nonselective NOS inhibitor N:(omega)-nitro-L-arginine (100 microM). However, afferent and efferent arteriolar dilator responses to ACh were significantly enhanced during selective iNOS inhibition with 1 microM PBIT (40.1 +/- 0.7% and 25.2 +/- 1.3%, respectively). These results suggest that activation of iNOS by LPS increases the influence of nitric oxide on afferent and efferent arteriolar tone and impairs endothelium-dependent nitric oxide effects.     

诱导型一氧化氮合酶在单侧输尿管梗阻大鼠肾脏的表达

目的:探讨诱导型一氧化氮合酶(iNOS)在单侧输尿管梗阻(UUO)大鼠术侧肾脏的表达.方法:建立左侧输尿管梗阻模型(UUO组),设假手术组为对照.3 d后应用逆转录-聚合酶链反应(RT-PCR)检测iNOS的mRNA水平.结果:与对照组相比,UUO组大鼠肾脏出现明显病理变化,并且其iNOS mRNA表达明显增加.结论:iNOS参与UUO的发生和发展的病理过程.     

Differential nitric oxide synthase expression during hepatic ischemia-reperfusion

BACKGROUND: In recent years the important role of nitric oxide in hepatic ischemia-reperfusion injury has been increasingly recognised. The prevailing consensus is that reperfusion injury may be partly the result of decreased production of nitric oxide from endothelial nitric oxide synthase and excessive production of nitric oxide from the inducible isoform. We therefore undertook this study to characterize the expression of different nitric oxide synthase isoforms during hepatic reperfusion. METHODS: Male Wistar rats (n = 6) were subjected to 45 minutes of partial hepatic ischemia (left lateral and median lobes) followed by 6 hours of reperfusion. Control animals (n = 6) were subjected to sham laparotomy. The expression of endothelial and inducible nitric oxide synthase was examined using immunohistochemistry and Western blotting. Liver sections were also stained with nitrotyrosine antibody, a specific marker of protein damage induced by peroxynitrite (a highly reactive free radical formed from nitric oxide). RESULTS: Liver sections from all the control animals showed normal expression of the endothelial isoform and no expression of inducible nitric oxide synthase. Livers from all the animals subjected to hepatic ischemia showed decreased expression of endothelial nitric oxide synthase, and all but one animal from this group showed expression of the inducible isoform both in inflammatory cells and in hepatocytes. Western blotting confirmed these findings. Staining with the antinitrotyrosine antibody was also confined to five liver sections from animals subjected to hepatic ischemia. CONCLUSIONS: During the reperfusion period after hepatic ischemia, endothelial nitric oxide synthase is downregulated while inducible nitric oxide synthase is expressed in both hepatocytes and inflammatory cells. The presence of nitrotyrosine in livers subjected to hepatic ischemia-reperfusion suggests that the expression of inducible nitric oxide synthase plays an important role in mediating reperfusion injury in this model.     

Increased expression of nitric oxide synthase in human lung transplants after nitric oxide inhalation

BACKGROUND: The effects of the ischemia-reperfusion process of organ transplantation on nitric oxide (NO) synthase (NOS) in humans are unknown. The effects of NO inhalation on endogenous NOS expression and activity are controversial. The authors hypothesized that NO inhalation may affect ischemia-reperfusion-induced alterations of the endogenous NOS system. METHODS: The authors performed lung biopsy on patients in a randomized phase II clinical trial of NO inhalation during lung transplantation. After lung implantation, 20 ppm of NO or placebo gas was administered 10 min after the start of reperfusion. Lung tissues were collected from 20 patients (NO, n=9; placebo, n=11) after cold and warm ischemia, 1 hr and 2 hr after reperfusion. The protein levels of NOS isoforms were analyzed by Western blotting and the total NOS activity was measured. RESULTS: The protein levels of inducible NOS did not change significantly in either of the groups. In contrast, during the 2-hr reperfusion period, constitutive NOS (neuronal NOS [nNOS] and endothelial NOS) tended to decrease in the placebo group, but gradually increased in the NO group. After 2 hr of reperfusion, the nNOS protein in the NO group was significantly higher than that in the placebo group (P <0.05). However, the total NOS activity remained at low levels in both groups. CONCLUSIONS: NO inhalation-induced increase of constitutive NOS proteins indicates the interaction between inhaled NO molecules and lung tissues. However, the activity of these newly synthesized NOS proteins remains suppressed during the ischemia-reperfusion period of lung transplantation.     

Effect of severe aortic banding above the renal arteries on nitric oxide synthase isotype expression

BACKGROUND: Severe aortic stenosis above the renal arteries leads to a reduction in renal perfusion, increased renin secretion, and elevation of arterial blood pressure above the stenotic site. Nitric oxide (NO) plays an important role in regulation of renal and systemic vascular resistance, renal blood flow, and Na(+) handling. Abdominal aortic banding provides an excellent model for simultaneous testing of the effects of increased and decreased pressure, flow, and shear stress in the same animal. METHODS: We studied protein expressions of endothelial NO synthase (eNOS), inducible NOS (iNOS), and neuroneal NOS (nNOS) isotypes in the renal cortex, renal medulla, heart, brain, and aorta segments above and below the stenosis site three weeks after abdominal aortic banding above the renal arteries. The results were compared with those obtained in the sham-operated controls. NOS isotype proteins were measured by Western blot. RESULTS: Compared with the control group, the banded group showed significant up-regulations of eNOS, iNOS, and nNOS in renal cortex and medulla. Likewise, heart eNOS, brain nNOS, and thoracic aorta eNOS proteins were significantly increased in the banded group. However, eNOS and iNOS expressions were unchanged in the aorta segment below the stenotic site. Likewise, iNOS expression in the heart and thoracic aorta remained unchanged in the banded animals. No significant difference was found in creatinine clearance or urinary protein excretion between the two groups. CONCLUSIONS: These findings clearly demonstrate the up-regulatory action of increased pressure on eNOS expression in the thoracic aorta and heart and of nNOS expression in the brain. These data further show up-regulation of all NOS isotypes in the kidney, which must have helped to mitigate the associated hypoperfusion.