NF-kappaB involvement in the induction of high affinity CAT-2 in lipopolysaccharide-stimulated rat lungs

BACKGROUND: Endotoxemia stimulates nitric oxide (NO) biosynthesis through induction of inducible NO synthase (iNOS). Cellular uptake of L-arginine, the sole substrate for iNOS, is an important mechanism regulating NO biosynthesis by iNOS. The isozymes of type-2 cationic amino acid transporters, including CAT-2, CAT-2A, and CAT-2B, constitute the most important pathways responsible for trans-membrane L-arginine transportation. Therefore, regulation of CAT-2 isozymes expression may constitute one of the downstream regulatory pathways that control iNOS activity. We investigated the time course of enzyme induction and the role of nuclear factor-kappaB (NF-kappaB) in CAT-2 isozymes expression in lipopolysaccharide-(LPS) treated rat lungs. METHODS: Adult male Sprague-Dawley rats were randomly given intravenous injections of normal saline (N/S), LPS, LPS plus NF-kappaB inhibitor pre-treatment (PDTC, dexamethasone, or salicylate), or an NF-kappaB inhibitor alone. The rats were sacrificed at different times after injection and enzyme expression and lung injury were examined. Pulmonary and systemic NO production were also measured. RESULTS: LPS co-induced iNOS, CAT-2, and CAT-2B but not CAT-2A expression in the lungs. Furthermore, NF-kappaB actively participated in LPS-induction of iNOS, CAT-2, and CAT-2B. LPS induced pulmonary and systemic NO overproduction and resulted in lung injuries. Attenuation of LPS-induced iNOS, CAT-2, and CAT-2B induction significantly inhibited NO biosynthesis and lessened lung injury. CONCLUSION: NF-kappaB actively participates in the induction of CAT-2 and CAT-2B in intact animals. Our data further support the idea that CAT-2 and CAT-2B are crucial in regulating iNOS activity.     

Catecholamines' enhancement of inducible nitric oxide synthase-induced nitric oxide biosynthesis involves CAT-1 and CAT-2A

Catecholamines enhance inducible nitric oxide synthase (iNOS) expression that results in nitric oxide (NO) overproduction in lipopolysaccharide (LPS)-stimulated macrophages. L-arginine transport mediated by cationic amino acid transporters (including CAT-1, CAT-2, CAT-2A, and CAT-2B) is crucial in regulating iNOS activity. We sought to assess the effects of catecholamines on L-arginine transport and CAT isozyme expression in stimulated macrophages. Confluent RAW264.7 cells were cultured with LPS with or without catecholamines (epinephrine or norepinephrine, 5 x 10(-6) M) for 18 h. NO production, L-arginine transport, and enzyme expression were determined. Our data revealed that LPS co-induced iNOS, CAT-2, and CAT-2B expression, whereas CAT-1 and CAT-2A expression remained unaffected. Significant increases in NO production and L-arginine transport (approximately eight-fold and three-fold increases, respectively) were found in activated macrophages. Catecholamines significantly enhanced NO production and L-arginine transport (approximately 30% and 20% increases, respectively) in activated macrophages. Catecholamines also enhanced the expression of iNOS, CAT-1, and CAT-2A but not CAT-2 or CAT-2B in LPS-stimulated macrophages. Furthermore, the enhancement effects of catecholamines were inhibited by either dexamethasone or propranolol. We provide the first evidence to indicate that L-arginine transport in activated macrophages could be enhanced by catecholamines. Furthermore, this catecholamine-enhanced L-arginine transport might involve CAT-1 and CAT-2A but not CAT-2 or CAT-2B.     

Platonin attenuates LPS-induced CAT-2 and CAT-2B induction in stimulated murine macrophages

BACKGROUND: Platonin, a cyanine photosensitizing dye, is a potent immunomodulator that suppresses acute inflammation. Platonin not only inhibits interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha production but also improves circulatory failure in septic rats. In addition, platonin reduces plasma nitric oxide (NO) formation during sepsis. However, the effects of platonin on inducible NO synthase (iNOS) and cationic amino-acid transporter (including CAT-2, CAT-2 A, and CAT-2B) expressions during sepsis remain uninvestigated. METHODS: Five groups of confluent murine macrophages (RAW264.7 cells) were randomly allocated to receive a 1-h pretreatment of one of five doses of platonin (0.1 microM, 1 microM, 10 microM, 100 microM, or 1000 microM) followed by lipopolysaccharide (LPS; 100 ng ml(-1)). For negative, positive, and platonin control, three other groups of cell cultures were randomly allocated to receive phosphate-buffered saline, LPS, or platonin (1000 microM). The cultures were harvested after exposing them to LPS for 18 h or a comparable duration in those groups without LPS. NO production, L-arginine transport, and expression of the relevant enzymes were then evaluated. RESULTS: Platonin significantly attenuated LPS-induced up-regulation of iNOS expression and NO production in stimulated murine macrophages in a dose-dependent manner. Platonin also significantly inhibited up-regulation of CAT-2 and CAT-2B expression as well as L-arginine transport in LPS-stimulated murine macrophages in a dose-dependent manner. In contrast, CAT-2 A expression in murine macrophages was not affected by LPS and/or platonin. CONCLUSIONS: Platonin attenuates NO production and L-arginine transport in LPS-stimulated murine macrophages possibly through inhibiting iNOS, CAT-2, and CAT-2B expression.     

细胞外信号调节激酶在内毒素休克大鼠生物喋呤诱生中的作用机制探讨

目的观察细胞外信号调节激酶（ERK）通路抑制剂对生物喋呤（BH4）和一氧化氮（NO）表达及核因子-kB（NF-kB）活化的影响,探讨内毒素休克时ERK信号通路与NF-kB的交汇作用及其对BH4诱生NO的调控机制。方法采用内毒素休克模型,60只大鼠随机分为正常对照组（n=8）、内毒素休克组（n=32）和ERK抑制剂PD98059拮抗组（n=20）。留取动物肝、肺、肾组织进行NF-kB活性分析以及三磷酸鸟苷环水解酶I（GTP—CHⅠ）、诱生型一氧化氮合酶（iNOS）基因表达的检测,并测定组织及血浆中BH4、NO水平。结果内毒素攻击可导致动物肝、肺、肾组织GTP-CHⅠ基因表达和BH4水平明显升高,至伤后24h仍持续于较高水平;与之相应,组织iNOS基因表达和NO水平亦明显升高;各组织NF-kB迅速活化,并于2h达峰值。采用PD98059处理后,内毒素休克动物肾组织GTP—CHⅠ mRNA表达明显受抑,肝、肺组织GTP—CHⅠmRNA表达仅呈现降低趋势;血浆及肝、肾组织中BH4水平12h显著降低;同样,各组织iNOS mRNA表达及NO水平早期亦显著降低。此外,PD98059处理组动物肝组织2～6h、肺组织2h、24h和肾组织24h时相点NF-KB活性显著降低。结论内毒素休克时抑制ERK通路,能部分下调BH4和NO表达与NF-kB的活化,表明ERK与NF-kB通路间可能存在交汇作用,共同参与了BH4诱生NO的调控作用。     

Ketamine attenuates liver injury attributed to endotoxemia: role of cyclooxygenase-2

BACKGROUND: Endotoxic shock can cause end-organ dysfunction and liver injury. Critically ill patients frequently require surgical intervention under general anesthesia for source control. However, the effects of anesthetics on organ function during sepsis and their influence on inflammatory mediators such as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) remain to be fully elucidated. Because ketamine anesthesia has anti-inflammatory effects in some tissues, we hypothesized that it would attenuate lipopolysaccharide (LPS)-induced liver injury. METHODS: Adult rats were given no anesthesia (saline), continuous isoflurane inhalation, or intraperitoneal (i.p.) injection of ketamine 70 mg/kg. One hour later, the rats received saline or LPS (20 mg/kg i.p.) for 5 hours. The rats were killed, and serum hepatocellular enzymes, liver COX-2, iNOS protein (Western immunoblot), and nuclear factor kappa B (NF-kappaB)-binding activity (electrophoretic mobility shift assay) determined. In a separate study, the role of COX-2 in LPS-induced liver injury was examined by pretreating rats with the selective COX-2 inhibitor NS-398 (3 mg/kg, i.p.) and the role of iNOS examined with the use of the selective inhibitor aminoguanidine (45 mg/kg, i.p.) 1 hour before LPS. RESULTS: LPS increased serum aspartate aminotransferase and alanine aminotransferase levels, hepatic iNOS and COX-2 protein, and nuclear factor NF-kappaB. Ketamine, but not isoflurane, attenuated these effects caused by LPS. COX-2 inhibition with NS-398 as well as iNOS inhibition with aminoguanidine diminished LPS-induced changes in aspartate aminotransferase and alanine aminotransferase levels. CONCLUSIONS: These data indicate that anesthetics differ in their effects on liver injury caused by LPS. Ketamine has hepatoprotective effects, while isoflurane does not. Moreover, the protective effects of ketamine are mediated, at least in part, through a reduction in COX-2 and iNOS protein that could be regulated via changes in NF-kappaB-binding activity.     

Hyperbaric oxygen attenuation of lipopolysaccharide-induced acute lung injury involves heme oxygenase-1

BACKGROUND: Hyperbaric oxygen (HBO) attenuates lipopolysaccharide (LPS)-induced acute lung injury. This beneficial effect of HBO involves inhibition of inducible nitric oxide synthase (iNOS) expression and subsequent nitric oxide (NO) biosynthesis. We sought to investigate the role of heme oxygenase-1 (HO-1) on this HBO inhibition of iNOS induction and acute lung injury in septic rat lungs. METHODS: Before the experiment, 72 rats were randomly allocated to receive HBO or air treatment. With or without HBO pre-treatment, the rats were further divided into the following subgroups (n = 6): (i) LPS injection, (ii) normal saline (N/S) injection, (iii) hemin (a HO-1 inducer) plus LPS, (iv) hemin alone, (v) tin protoporphyrin (SnPP; a HO-1 inhibitor) plus LPS, and (vi) SnPP alone. All rats were maintained for 6 h and then sacrificed with a high-dose pentobarbital injection. Lung injuries and relevant enzymes expression were thus assayed. RESULTS: Histological analysis, PMNs/alveoli ratio, and wet/dry weight ratio measurements demonstrated that LPS caused significant lung injury and HBO and/or hemin significantly attenuated this LPS-induced lung injury. Increased pulmonary iNOS expression and NO production were associated with lung injury. Induction of HO-1, by HBO and/or hemin, significantly attenuated this LPS-induced iNOS expression and acute lung injury. SnPP, on the contrary, offset the effects of HBO and worsened the LPS-induced lung injury. CONCLUSIONS: HBO may act through inhibiting pulmonary iNOS expression to attenuate LPS-induced acute lung injury in septic rats. Furthermore, this HBO attenuation of iNOS expression involves HO-1 induction.     

内毒素休克大鼠核因子κB活化规律及其在生物蝶呤诱生中的作用

目的观察内毒素休克大鼠血浆及主要脏器核因子(NF)κB活化规律及其对生物蝶呤(BH4)和一氧化氮(NO)表达水平的影响,探讨内毒素休克时NF-κB信号通路对BH4诱生NO的分子调控机制及其与多器官功能损害的关系。方法将47只大鼠按表格随机法分为正常组(8只)、内毒素／脂多糖(LPS)组(24只,每观察时相点8只,均同时注射LPS制成休克模型)和拮抗组[15只,每观察时相点5只,均同时注射LPS并以吡咯烷二硫代氨基甲酸盐(PDTC)拮抗]。休克及拮抗组于注射LPS后2、6、12 h观察,并与正常组同法处死,无菌留取大鼠血标本及肝、肺、肾组织,测定组织中NF-κB活性和三磷酸鸟苷环水解酶Ⅰ(GTP-CHⅠ)和诱导型一氧化氮合酶(iNOS)mRNA表达水平、血浆和组织中的BH4含量及NO水平、肝脏和肾脏功能指标、肺组织髓过氧化物酶活性。结果与正常组(例如肺组织中NF-κB活性为26±6)比较,LPS组大鼠组织中NF-κB迅速活化(P<0．01),并于注射后2 h达峰值(肺组织中为291±44);LPS组各组织中GTP-CHⅠ和iNOS mRNA表达、BH4和NO水平也较正常组明显升高(P<0．05或0．01),至伤后12 h仍持续较高水平。此外,该组相应器官功能均受到不同程度的损害。应用PDTC的拮抗组大鼠各组织中NF-κB活性均较LPS组有所降低,GTP-CHⅠ、iNOS mRNA表达及BH4、NO水平显著受抑,肝、肺、肾功能明显改善。结论内毒素休克时机体内NF-κB通路高度活化,并对BH4／NO系统具有明显调节效应;可通过下调BH4介导的iNOS的过度活化抑制NF-κB信号途径,从而减轻组织炎性反应,对机体脏器功能起到保护作用。     

L-Arginine transport is augmented through up-regulation of tubular CAT-2 mRNA in ischemic acute renal failure in rats

BACKGROUND: Ischemic acute renal failure (iARF) is associated with increased nitric oxide (NO) production during the reperfusion period, as endothelial nitric oxide synthase (eNOS) is maximally activated, and renal tubular inducible NOS (iNOS) is stimulated. Increased NO production leads to augmented tubular injury, probably through the formation of peroxynitrite. l-Arginine (l-Arg), the only precursor for NO, is transported into cells by cationic amino acid transporters, CAT-1 and CAT-2. We hypothesized that the increased NO production observed in iARF may result from increased l-Arg uptake, which would be reflected in the augmented expression of l-Arg transporter(s). METHODS: Ischemic acute renal failure was induced in rats by right nephrectomy + left renal artery clamping for 60 minutes. l-Arg uptake was examined in freshly harvested glomeruli and tubuli from control, sham operated, and animals subjected to 15, 30, and 60 minutes, and 24 hours of reperfusion, following 60 minutes of ischemia. Using RT-PCR, renal tissues were examined further for the expression of iNOS, CAT-1, CAT-2, arginase I and arginase II. RESULTS: Tubular expression of iNOS mRNA was initiated by ischemia, continued to increase after 60 minutes of reperfusion, and decreased after 24 hours. l-Arg transport into glomeruli was similar in all experimental groups. l-Arg uptake into tubuli was markedly augmented following the 60-minute reperfusion, while it moderately increased after 24 hours of reperfusion. This was accompanied by a parallel, preferential increase in tubular CAT-2 mRNA expression at 60 minutes of reperfusion. CAT-1 mRNA expression was unchanged, as detected by RT-PCR. In addition, the expression of arginase II and arginase I mRNA was attenuated by 30 minutes and one hour of reperfusion, and returned to baseline values after 24 hours of reperfusion. CONCLUSIONS: Ischemic ARF is associated with augmented tubular CAT-2 mRNA expression, which leads to enhanced l-Arg transport and increased NO production. This may contribute to the renal injury exhibited in iARF.     

Microdialysis for measurement of hepatic and systemic nitric oxide biosynthesis in septic rats

BACKGROUND: We sought to compare two techniques, microdialysis and repeated blood withdrawal, for serial assessment of hepatic and systemic nitric oxide (NO) biosynthesis in septic rats. METHODS: Rats were randomly allocated to either microdialysis or blood withdrawal groups. Two microdialysis probes, one in liver and the other in right atrium, were placed in rats in the microdialysis group. Half of the rats from each group were then given lipopolysaccharide (LPS) to induce NO production. The other half of the rats from each group were injected with vehicle (normal saline) to serve as controls. In the microdialysis group, dialysate (30 microl) was collected every 30 min. In the blood withdrawal group, 0.3 ml of blood was drawn every 30 min. Sampling was performed up to 6 h after injection of LPS or vehicle. Hemodynamics, hepatic and systemic NO concentrations, and iNOS expression in harvested liver tissues were assayed. RESULTS: Repeated blood withdrawal by itself caused a significant decrease in blood pressure and induced hepatic iNOS expression. Microdialysis, on the contrary, reliably detected LPS-induced NO production without resulting either in hemodynamic changes or in iNOS induction in liver tissue. CONCLUSIONS: Microdialysis provides serial measure of hepatic and systemic NO concentrations in LPS-treated rats without the need for removal of tissue.     

Glycochenodeoxycholate (GCDC) inhibits cytokine induced iNOS expression in rat hepatocytes

BACKGROUND: Although the accumulation of hydrophobic bile acid (e.g., glycine conjugated chenodeoxycholic acid, GCDC) is considered to be an important factor contributing to cholestatic liver dysfunction, its pathogenesis is poorly understood. The purpose of this study was to examine the effect of the bile salt GCDC on the regulation of iNOS expression, a key immune modulator during liver inflammation. MATERIALS AND METHODS: GCDC significantly decreased cytokine-stimulated iNOS promoter activity, and both iNOS mRNA and protein expression. GCDC decreased iNOS promoter activity by preventing IkappaB degradation and inhibiting NF-kappaB DNA-binding activity. To explore the role of iNOS in bile salt induced apoptosis, we also examined the effect of NO on caspase-3 activity. RESULTS: GCDC strongly induced caspase-3 activity, and this increase was abrogated by both exogenous NO exposure and endogenous NO synthesis. Furthermore, adenoviral iNOS (AdiNOS) pre-treatment decreased acute cholestatic-induced liver injury in a rat bile duct ligation model. CONCLUSIONS: These findings indicate a novel signaling pathway where potentially toxic bile salts down-regulate hepatic iNOS expression. This blockade of the iNOS mediated antiapoptotic phenotype may have important implications in certain liver disorders.     

Effect of NO donor sodium nitroprusside on lipopolysaccharide induced acute lung injury in rats

Nitric oxide (NO) donor-sodium nitroprusside (SNP) mitigates acute lung injury (ALI), but the mechanism of this protection is incompletely known. We investigated the effect of SNP on lipopolysaccharide (LPS)-induced ALI in rats. Forty-eight male Wistar rats were randomly assigned into six groups: the sham-operation group (S group), the LPS instillation group (LPS group), the haemin, a haeme oxygenase-1 (HO-1) inducer, pretreatment group (HM group), the haemin pretreatment plus LPS instillation group (HM+LPS group), the SNP alone and SNP plus LPS treatment groups. Macroscopic and histopathological examinations and immunohistochemistry analysis were performed for the lung specimens 8h after LPS instillation. Intratracheal administration of LPS induced significant expressions of the inducible isoform of NO synthase (iNOS) and HO-1, while both haemin pretreatment and SNP treatment increased the expression of HO-1 and prevented the expression of iNOS. In the LPS group, the wet-dry weight ratio (W/D), bronchoalveolar lavage fluid (BALF) protein, and lung malondialdehyde (MDA) content were significantly higher than those in the sham-operation group, which were reversed by the pretreatment with haemin or administration of SNP. These results suggest that HO-1 plays a protective role against LPS-induced acute lung injury, which may be achieved at least in part, via inactivating the iNOS/NO system that is involved in the pathophysiological process of LPS-induced acute lung injury. The nitric oxide (NO) donor-SNP ameliorates LPS-induced ALI, which may be related to the induction of HO-1 and the subsequent inhibition of iNOS.     

Differential regulation of L-arginine transporters (cationic amino acid transporter-1 and -2) by peroxynitrite in rat mesangial cells.

BACKGROUND: It has become evident that increased nitric oxide (NO) generation may be associated with production of reactive oxygen species, such as peroxynitrite (ONOO-). Peroxynitrite has been postulated to be responsible for several of the cytotoxic effects previously ascribed to NO. Since cellular arginine uptake has been shown to modulate nitric oxide synthase activity, we were intrigued to study the effect of ONOO- on arginine traffic in renal mesangial cells. METHODS: Arginine uptake, CAT-1 and CAT-2 mRNA expression by northern blotting analysis, and CAT-1 protein content using western blotting were determined in mesangial cells pre-treated with peroxynitrite (0.1 and 0.5 mM) for 2 h. RESULTS: Peroxynitrite induced a significant increase in arginine uptake and CAT-2 mRNA expression compared with untreated cells. In contrast, CAT-1 mRNA expression and protein abundance were diminished. CONCLUSIONS: In rat mesangial cells, peroxynitrite augments arginine uptake via augmentation of CAT-2 while decreasing CAT-1 expression.     

Ketamine/xylazine attenuates LPS-induced iNOS expression in various rat tissues

Ketamine and xylazine (K/X) are commonly used in combination as an anesthetic agent in experimental animal models. We previously noted that K/X attenuated lipopolysaccharide (LPS)-induced liver injury, gastric stasis, and reduced symptoms of endotoxemia. Because ketamine attenuates expression of several proinflammatory genes, we examined the effects of K/X on inducible nitric oxide synthase (iNOS), which has been implicated in endotoxin-induced tissue injury. We hypothesized that K/X would attenuate LPS-induced expression of iNOS in various organs in the rat. Rats were given either intraperitoneal saline or ketamine (70 mg/kg) and xylazine (6 mg/kg) 1 h before saline or LPS (20 mg/kg). Rats were sacrificed 5 h later and stomach, duodenum, jejunum, ileum, colon, liver, lung, kidney, and spleen were collected for determination of iNOS protein immunoreactivity by Western immunoblot. Data reported in densitometric units (DU) as mean +/- SEM (n >/= 5; ANOVA). LPS significantly increased iNOS protein immunoreactivity in all tissues examined versus saline controls (P 相似文献   

Overexpression of inducible nitric oxide synthase in gastric mucosa of rats with portal hypertension: correlation with gastric mucosal damage

BACKGROUND: An increased biosynthesis of nitric oxide (NO) has been implicated in the hyperdynamic circulation and development of collaterals of portal hypertension (PHT) because of its potent vasodilatory effects. NO is synthesized from L-arginine by three different isozymes of nitric oxide synthase (nNOS, iNOS and eNOS). Thus, the expression of inducible NOS (iNOS) might account for NO overproduction in PHT. However, in previous investigations, the role of iNOS in the pathogenesis of PHT gastropathy remained controversial. Our current study was in both molecular and protein levels to determine whether the expression of iNOS is responsible for PHT gastropathy. MATERIALS AND METHODS: PHT was induced experimentally by partial ligation of the portal vein. Fourteen days after partial ligation of the portal vein, the rats were randomly assigned to receive either vehicle or L-NAME (NOS inhibitor) at doses of 5 mg/kg/day, 10 mg/kg/day, or 25 mg/kg/day by gastric lavage twice a day for 1 week. Sham operated rats served as controls. Northern hybridization and in situ hybridization are used to compare the expression of gastric mucosa iNOS mRNA in the PHT rats and the controls. NO was measured by the Griess method after reduction of nitrate to nitrite with nitrate reductase. Immunohistochemical staining was carried out to detect the iNOS protein. In addition, the severity of gross gastric mucosal lesions was evaluated macroscopically by a gross ulcer index. RESULTS: The iNOS expression at both mRNA and protein was prominently increased in PHT rats, accompanied with the enhanced NO production. The gastric mucosa iNOS mRNA and serum NO levels were significantly decreased after L-NAME administration (P < 0.05). However, the markedly reduced gastric mucosal damage in PHT rats was observed only at high does of L-NAME (25 mg/kg/day) administration. CONCLUSION: PHT triggers overexpression of iNOS mRNA and proteins in rat gastric mucosa, but that this alone does not account for PHT gastropathy.     

HO-1 mediates the effects of HBO pretreatment against sepsis

BACKGROUND: We have recently shown that attenuation of sepsis-induced lung injury by hyperbaric oxygen (HBO) pretreatment involves expression regulation of inducible nitric oxide synthase (iNOS) and heme oxygenase (HO)-1. This study was performed to determine the effects of HBO pretreatment on acute kidney and liver injuries in septic rats and the roles of iNOS and HO-1. MATERIALS AND METHODS: One group of adult male rats (n = 48) were pretreated with HBO. The other group of rats (n = 48) breathed air at normal atmospheric pressure instead. Rats in each group were randomly allocated to receive injection of lipopolysaccharide (LPS), normal saline (N/S), LPS plus hemin (a HO-1 inducer), hemin, LPS plus SnPP (a HO-1 inhibitor), SnPP, LPS plus hemin plus SnPP, or hemin plus SnPP. Hemin and SnPP were injected at 1 h before HBO or air pretreatment. Rats were maintained for 6 h before sacrifice. RESULTS: LPS caused prominent kidney and liver injuries as well as iNOS and HO-1 expression in stimulated rats. HBO pretreatment significantly attenuated LPS-induced kidney but not liver injury. However, in conjunction with hemin (a HO-1 inducer), HBO pretreatment did attenuate LPS-induced liver injury. In addition, the inhibition of iNOS expression by HBO pretreatment was associated with "super-induction" (i.e., further enhancement) of LPS-induced HO-1 expression. Furthermore, the therapeutic effect of HBO could be counteracted by SnPP (a HO-1 inhibitor). CONCLUSIONS: HBO pretreatment significantly attenuates LPS-induced acute organ injuries in septic rats. The beneficial effect of HBO pretreatment against sepsis is mediated, at least in part, by "super-induction" of HO-1.     

氯化镧对内毒素/脂多糖诱导巨噬细胞株一氧化氮合酶表达的抑制作用

目的了解氯化镧（LaCl3）对内毒素／脂多糖（LPS）刺激的巨噬细胞诱导型一氧化氮合酶（iNOS）表达的影响，并探讨其机制。方法将小鼠巨噬细胞株RAW264．7分为空白对照组、LaCl、组、LPS组和LaCl3＋LPS组。前3组细胞分别用常规培养液、含2．50μmol／L LaCl3的培养液、含1mg／L LPS的培养液培养24h，LaCl3＋LPS组用含2．5μmol／LLaCl，的培养液培养24h后，换为含1mg／L LPS的培养液培养24h。采用免疫细胞化学染色法检测iNOS在各组细胞中的表达强度；蛋白质印迹法检测iNOS的蛋白表达水平；反转录一PCR测定iNOS的mRNA表达水平；硝酸还原酶法测定各组细胞培养上清液中一氧化氮（NO）含量。结果免疫细胞化学染色结果显示，iNOS主要分布于各组细胞的胞质中，空白对照组和LaCl3组荧光强度极弱；LPS组荧光强度最强，阳性细胞百分率为44．4％，明显高于LaCl3＋LPS组（11．8％，P〈0．05）。LPS组iNOS蛋白及其mRNA表达量和细胞培养上清液中NO含量均高于其余各组（P〈0．05）。结论LaCl3可在mRNA水平和蛋白水平抑制LPS诱导的iNOS过度表达，减少NO生成，提示LaCl3能拮抗LPS诱导的iNOS过度活化。