The modulation of hepatic injury and heat shock expression by inhibition of inducible nitric oxide synthase after hemorrhagic shock.

The role of nitric oxide (NO) in maintaining homeostasis and regulating organ function during hemorrhagic shock is complex. The inducible NO synthase (iNOS) has been hypothesized to play a critical role in the pathophysiologic consequences of severe hemorrhage. Heat shock protein (HSP) expression is increased by hemorrhage and is a marker of the magnitude of ischemic injury in the liver. HSP induction is protective against injury in animal models of inflammation and is regulated by NO in hepatocytes. To clarify the role of iNOS in hepatic injury and its relationship to HSP expression in hemorrhagic shock, NOS was inhibited with L-N-6-(1-iminoethyl) lysine (L-NIL), which is reported to be a selective inhibitor of the inducible NOS isoform. Doses of 50 microg/kg or 150 microg/kg were infused over 1 h at the end of compensated shock. Plasma ornithine carbamoyltransferase (OCT), a specific marker of liver injury, was significantly reduced after hemorrhage with low-dose L-NIL (7.1+/-1.5 IU/L) compared to saline-treated control rats (13.0+/-1.5 IU/L, P < 0.005), while high-dose L-NIL significantly increased OCT release (35.9+/-7.2 IU/L, P< 0.05 versus shock alone) despite a greater MAP after resuscitation. HSP expression (HSP-72 and HSP-32) after hemorrhage was increased by L-NIL treatment at the highest dose. We conclude that excessive NO production from iNOS contributes to shock-induced hepatic injury. Our data suggest HSP expression may reflect the degree of ischemic injury after hemorrhage.     

Mechanism of stress ulcer: influence of sodium taurocholate on gastric mucosal energy metabolism during hemorrhagic shock and on mitochondrial respiration and ATPase in gastric mucosa.

In previous reports from this laboratory, we have proposed that stress ulceration complicating hemorrhagic shock results from a gastric mucosal energy deficit due to shock-induced mucosal ischemia. We reasoned that if this hypothesis were correct, an agency known to augment the severity of stress ulceration would be expected to have an adverse effect on gastric mucosal energy metabolism. Others have shown that the severity of stress ulceration developing in animals subjected to hemorrhagic shock is increased by introducing bile salts into the stomach; conversely, the development of stress ulceration can be prevented by ligation of the pylorus or of the common bile duct. We have studied the influence of sodium tauurocholate on the respiration of gastric mucosal mitochondria and on gastric mucosal ATPase.We have also evaluated the influence of the intragastric introduction of taurocholate on the mucosal energy depletion produced by shock. The data presented in this report indicate that taurocholate uncouples oxidative phosphorylation of gastric mucosal mitochondria and inhibits gastric mucosal ATPase. The shock-induced gastric mucosal energy deficit was significantly more severe in the presence of added intragastric taurocholate.     

ghrelin对失血性休克大鼠胃黏膜的保护作用

目的 探讨重组大鼠ghrelin对失血性休克大鼠胃黏膜损伤的影响.方法 18只健康雄性SD大鼠被随机分为对照组、失血性休克组、ghrelin治疗组3组.每组6只.失血性休克组及ghrelin治疗组制备失血性休克模型.ghrelin治疗组休克复苏的同时经颈内静脉推注重组大鼠ghrelin 20μg/kg.于复苏后2 h使用激光多普勒血流仪测定大鼠胃黏膜血流量;用光镜及透射电镜观察胃黏膜损伤情况.结果 失血性休克组胃黏膜血流量较对照组明显降低(260.4±49.6)bpu比(418.6±57.3)bpu,P<0.013,胃黏膜细胞坏死、脱落、溶解,局部溃疡形成.ghrelin治疗组胃黏膜血流量较失血性休克组明显提高((352.9±72.9)bpu比(260.45±49.6)bpu,P<0.05),且与对照组比较差异无统计学意义(P>0.05);胃黏膜损伤显著改善.结论 重组大鼠ghrelin能够提高失血性休克大鼠胃黏膜血流量,改善胃黏膜缺血/再灌注损伤.     

Polymorphonuclear oxidative burst after Helicobacter pylori water extract stimulation is not influenced by the cytotoxic genotype but indicates infection and gastritis grade.

H. pylori-associated gastric mucosal inflammation is characterized by the presence of polymorphonuclear (PMN) leukocyte infiltrate, which is more severe when the infecting strain is cagA positive. After appropriate stimuli, such as bacterial products, PMN release large amounts of oxygen derived free radicals and proteases, to kill the bacterium. H. pylori seems to be particularly resistant to the oxidative machinery of PMN, which can in turn damage the host gastric mucosa. We evaluated peripheral PMN oxidative burst response after stimulation with water extracts from cagA positive (WEcagA+) or negative (WEcagA-) H. pylori strains in infected (n=31) and non-infected patients (n=32) in comparison with healthy controls (n=16); the influence of gastric mucosal inflammatory infiltrate and activity grade on PMN oxidative burst were also assessed. PMN oxidative burst was measured by FACS analysis. H. pylori water extracts were obtained from bacterial culture. H. pylori genotype was determined by means of the polymerase chain reaction. The PMN oxidative burst in H. pylori infected patients was significantly higher than that in H. pylori negative or healthy controls, no differences being found when the results following WEcagA+ and WEcagA- stimulation were compared. The difference in PMN oxidative burst obtained after WEcagA- and E. coli (standard stimulus for PMN oxidative burst) stimulation discriminated H. pylori infected from non-infected patients with a sensitivity of 90% and a specificity of 97%. The grade of PMN oxidative burst correlated with PMN infiltration grade of the gastric mucosa. Our findings allow to conclude that PMN oxidative burst activation by H. pyloriWE is species- but not strain-correlated. PMN priming, probably consequent to the action of soluble mediators released by mononuclear cells, makes PMN hyper-responsive to H. pylori products, thus favoring the release in the gastric mucosa of infected patients of large amounts of oxygen-derived free radicals, which are not enough to eliminate the infection, but may contribute to damaging the gastric mucosa itself. Peripheral PMN oxidative burst response to H. pyloriWE might furthermore be of help in diagnosing H. pylori infection.     

肠淋巴途径在大鼠休克致肝脏炎症反应中的作用

目的 观察结扎肠系膜淋巴管对重症失血性休克不同时期大鼠肝脏炎症介质、自由基的变化,探讨阻断肠淋巴途径对休克大鼠肝脏炎症反应的影响.方法 78只雄性Wistar大鼠被随机分为假手术组(n=6)、休克组(n=42)和结扎组(n=30).休克组与结扎组复制重症失血性休克模型,结扎组于休克复苏后行肠系膜淋巴管结扎术.于休克90 min、输液复苏后0、1、3、6、12和24 h各处死6只大鼠,制备肝组织匀浆,检测肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)、一氧化氮(NO)、一氧化氮合酶(NOS)、丙二醛(MDA)、超氧化物歧化酶(SOD)以及髓过氧化物酶(MPO)水平;采用逆转录-聚合酶链反应(RT-PCR)测定肝组织诱生型一氧化氮合酶(iNOS)mRNA表达.结果 休克组大鼠输液复苏后不同时间点肝组织TNF-α、IL-6、NO、NOS、MDA、MPO以及iNOS mRNA均有不同程度的升高,6～12 h持续在较高水平,均显著高于假手术组,肝组织SOD活性显著低于假手术组(P＜0.05或P＜0.01);结扎组输液复苏后3、6、12和24 h肝组织TNF-α、IL-6、NO、NOS、MDA、MPO以及iNOS mRNA均显著低于休克组相应时间点.SOD活性高于休克组相应时间点(P＜0.05或P＜0.01).结论 肠系膜淋巴管结扎可减少肝脏中性粒细胞扣押,降低TNF-α、IL-6释放,抑制iNOS mRNA表达及NO生成,减少自由基损伤与SOD消耗,从而减轻肝脏的炎症反应.     

Selective inducible nitric oxide synthase inhibition during long-term hyperdynamic porcine bacteremia

We have recently demonstrated that selective inducible nitric oxide (NO) synthase (iNOS) inhibition with 1400W attenuated the hemodynamic and metabolic alterations affiliated with hyperdynamic porcine endotoxemia. In contrast to endotoxemia, limited evidence is available to document a relationship between NO and organ dysfunction in large animal bacteremic models. Therefore, using the same experimental setup, we investigated the role of selective iNOS blockade in porcine bacteremia induced and maintained for 24 h with a continuous infusion of live Pseudomonas aeruginosa. After 12 h of sepsis, animals received either vehicle (Control, n = 8) or continuous infusion of selective iNOS inhibitor, L-N6-(1-iminoethyl)-lysine (L-NIL; n = 8). Measurements were performed before, and 12, 18, and 24 h after P. aeruginosa infusion. L-NIL inhibited sepsis-induced increase in plasma nitrate/nitrite concentrations and prevented hypotension without affecting cardiac output. Despite comparable hepatosplanchnic macrocirculation, L-NIL blunted the progressive deterioration in ileal mucosal microcirculation and prevented mucosal acidosis. L-NIL largely attenuated mesenteric and hepatic venous acidosis, significantly improved P. aeruginosa-induced impairment of hepatosplanchnic redox state, and mitigated the decline in liver lactate clearance. Furthermore, the administration of L-NIL reduced the hepatocellular injury and prevented the development of renal dysfunction. Finally, treatment with L-NIL significantly attenuated the formation of 8-isoprostane concentrations, a direct marker of lipid peroxidation. Thus, selective iNOS inhibition with L-NIL prevented live bacteria from causing key features of metabolic derangements in porcine hyperdynamic sepsis. Underlying mechanisms probably include reduced oxidative stress with improved microcirculatory perfusion and restoration of cellular respiration.     

Increased iNOS activity is essential for intestinal epithelial tight junction dysfunction in endotoxemic mice

We tested the hypothesis that increased production of nitric oxide (NO.) associated with lipopolysaccharide (LPS)-induced systemic inflammation leads to functionally significant alterations in the expression and/or targeting of key tight junction (TJ) proteins in ileal and colonic epithelium. Wild-type or inducible NO. synthase (iNOS) knockout male C57B1/6J mice were injected intraperitoneally with 2 mg/kg Escherichia coli O111:B4 LPS. iNOS was inhibited using intraperitoneal L-N(6)-(1-iminoethyl)lysine (L-NIL; 5 mg/kg). Immunoblotting of total protein and NP-40 insoluble proteins revealed decreased expression and decreased TJ localization, respectively, of the TJ proteins, zonula occludens (ZO)-1, ZO-2, ZO-3, and/or occludin in ileal mucosa and colonic mucosa (total protein only) after injection of C57B1/6J mice with LPS. Immunohistochemistry showed deranged distribution of ZO-1 and occludin in both tissues from endotoxemic mice. Endotoxemia was associated with evidence of gut epithelial barrier dysfunction evidenced by increased ileal mucosal permeability to fluorescein isothiocyanate-dextran (Mr=4 kDa) and increased bacterial translocation to mesenteric lymph nodes. Pharmacologic inhibition of iNOS activity using L-NIL or genetic ablation of the iNOS gene ameliorated LPS-induced changes in TJ protein expression and gut mucosal barrier function. These results support the view that at least one mechanism contributing to the pathogenesis of gastrointestinal epithelial dysfunction secondary to systemic inflammation is increased iNOS-dependent NO. production leading to altered expression and localization of key TJ proteins.     

The role of neostigmine in development of acute gastric mucosal lesion in dogs with live bacterial flora-induced shock

The factors that frequently cause the development of acute gastric mucosal lesions (AGML) were studied in 37 mongrel dogs. Bacterial shock was induced by bolus injection of E. coli live bacterial flora (10(10) cells/kg body weight) under parietal cell-stimulated condition by intravenous administration of 0.008 mg/kg per hour of pentagastrin. In addition, 0.01 mg/kg per hour of neostigmine sulfate was administered intravenously during the experiment. Frequent development of AGML was observed in the neostigmine-administered canines without significant changes in the gastric corporal and antral tissue blood flow. In the neostigmine-administered group, AGML was observed in the antrum, although in the other group AGML was mostly observed in the corpus. These results suggest that a neostigmine-induced systemic vagostimulated condition by intravenous administration of neostigmine plays an important role in the development of AGML in dogs subjected to bacterial shock.     

严重烧伤休克期大鼠胃酸分泌功能的改变及其意义

目的：观察严重烧伤休克期胃酸分泌功能的改变，为烧伤临床急性胃粘膜损害（ＡＧＭＬ）的防治研究提供依据。方法：采用大鼠３０％体表面积（ＴＢＳＡ）全层皮肤３度烧伤模型，对烧伤休克期胃液量、胃液总酸度和总酸排出量进行动态观察。结果：伤后３小时胃液量、胃液总酸度和总酸排出量均显著低于正常对照组（Ｐ均＜０．０１）；伤后６小时上述指标值继续下降，并于伤后１２小时降至最低值；伤后２４小时，胃液量、胃液总酸度和总酸排出量虽有回升，但伤后４８小时仍显著低于正常对照组。结论：烧伤休克期大鼠胃酸分泌功能出现了显著抑制，这是胃粘膜功能障碍重要表现之一；胃酸在严重烧伤诱发的ＡＧＭＬ中，可能不是主导的和决定性因素；目前临床预防性使用抗酸疗法存在着某些不合理性；烧伤后尽快纠正胃粘膜缺血缺氧，可能是防治ＡＧＭＬ更为有效的措施。     

Effect of hemorrhagic shock on bacterial translocation, intestinal morphology, and intestinal permeability in conventional and antibiotic-decontaminated rats

Bacterial translocation and ileal and cecal injury have been shown to occur 24 h after limited periods of hemorrhagic shock. The present studies were performed to determine the temporal sequence of mucosal injury, permeability, and bacterial translocation after hemorrhagic shock. The results indicated that bacterial translocation and mucosal injury have occurred by 2 h after a 30-min episode of shock (mean arterial pressure 30 mm Hg). Although the histologic extent of the intestinal mucosal injury was less at 2 h postshock than at 24 h postshock, at both times intestinal barrier function was lost as measured by permeability to horseradish peroxidase. Since the role of translocating bacteria in potentiating the loss of intestinal barrier function after shock is unclear, the second goal was to determine whether the extent of shock-induced mucosal injury and permeability could be reduced or abrogated by antibiotic decontamination of the gut. The extent of shock-induced mucosal injury and intestinal permeability was similar between rats with a normal gut flora (greater than 10(6) bacteria/g cecum) and antibiotic-decontaminated rats (less than 10(3) bacteria/g cecum) 2 h postshock, although the incidences of bacterial translocation were 67% and 0, respectively. Thus, shock-induced mucosal permeability and injury appear not to be directly related to the presence of translocating bacteria.     

Inducible nitric oxide synthase (iNOS) is not required for IL-2-induced hypotension and vascular leak syndrome in mice

Dose limiting side effects of interleukin-2 (IL-2) include severe hypotension and vascular leak syndrome (VLS). Previous studies have shown that nitric oxide (NO) synthesis is strongly induced after IL-2 treatment of C3H/HeN mice (180,000 IU b.i.d. for 5 d). We employed knockout mice (on C57BL/6 background) to test the role of the inducible NO synthase (iNOS) in mediating IL-2 toxicity. In contrast to C3H/HeN mice, which developed hypotension and VLS after 10 doses of only 180,000 IU IL-2, C57BL/6 mice were far more resistant requiring increased doses of 800,000 IU IL-2 (b.i.d., 5 d) to induce hypotension and VLS. Serum interferon-gamma levels were significantly more elevated by IL-2 treatment in C3H/HeN mice than in C57BL/6, correlating with the severity of hypotension and VLS. Urinary excretion of NO metabolites was markedly reduced in iNOS knockout mice (C57BL/6 iNOS) after IL-2 treatment. A surprising finding was that these mice still developed profound hypotension and VLS. Similar findings were observed after administration of a iNOS specific inhibitor, L-N[6]-(1-iminoethyl)lysine (L-NIL). In contrast, a general NOS inhibitor, N-monomethyl-L-arginine, prevented both hypotension and vascular leak. The superoxide dismutase mimetic, M40403, reversed IL-2-induced hypotension but not VLS in knockout mice. Thus, peroxynitrite-mediated mechanisms are likely responsible for hypotension, whereas NO-induced changes in vascular permeability result in VLS. The iNOS enzyme is not necessary for pathogenesis of IL-2-induced cardiovascular toxicity. These results imply that other NOS isoforms, such as endothelial NOS, may play a major role in the development of IL-2-induced cardiovascular toxicity.     

肠系膜淋巴管结扎对失血性休克大鼠肺组织一氧化氮及其表达的影响

目的 观察结扎肠系膜淋巴管对不同时期重症失血性休克大鼠肺组织一氧化氮（NO）及其表达的影响，探讨肠淋巴途径在休克大鼠急性肺损伤（ALI）中的作用。方法 雄性Wistar大鼠78只，按随机数字表法分为假手术组（n=6）、休克组（n=42）和结扎组（n=30）。休克组与结扎组复制重症失血性休克模型，结扎组于休克复苏后行肠系膜淋巴管结扎术；休克组于休克后90min、输液复苏后0h，休克组及结扎组于输液复苏后1、3、6、12和24h各时间点处死大鼠，制备肺组织匀浆，检测NO及其合酶的变化；用逆转录-聚合酶链反应（RT—PCR）测定各组大鼠肺组织诱生型一氧化氮合酶（iNOS）．mRNA表达。结果 休克组大鼠复苏后3h肺组织NO含量、NOS活性及iNOSmRNA表达开始升高，复苏后6～12h持续在较高水平，均显著高于假手术组、休克后90min及复苏后0h（P〈0．05或P〈0．01）；结扎组仅于3h和6h增高，且结扎组复苏后6、12和24h肺组织NO含量、NOS活性以及iNOSmRNA表达均显著低于休克组相同时间点（P〈0．05或P〈0．01）。结论 肠系膜淋巴管结扎可降低重症失血性休克大鼠肺组织NO生成及iNOSmRNA表达，从而减轻肺损伤。     

Changes in gut mucosal nitric oxide synthase (NOS) activity after thermal injury and its relation with barrier failure

This study was designed to investigate changes in mucosal NOS activity after burns and its relation to barrier failure. In Experiment 1, female specific pathogen free (SPF) Sprague-Dawley rats underwent 35% total body surface area (TBSA) burn. One to six days after burn, intestinal permeability was determined from the plasma leakage of fluorescein isothiocyanate (FITC)-dextran 4400, intestinal mucosal cNOS and iNOS activity were assayed using Griess' reagent, and the cellular localization of iNOS was examined using immunostaining. In Experiment 2, S-methylisothiourea (SMT) was given (5 mg/kg, i.p. every 12 h) for 2 days to suppress inducible NOS (iNOS) activity after thermal injury. On postburn Day 2, the effect of SMT on gut mucosal NOS activity, intestinal permeability, and barrier function were evaluated. The activity of iNOS increased 24 h after the injury and up to a maximum of twofold on postburn Day 2, and decreased thereafter. The increase in iNOS activity in gut mucosa correlated well with the increase in intestinal permeability, an index for barrier failure (r = .776, p = .0002). Results from iNOS immunostaining showed that changes in mucosal iNOS activity after the burn occurred mainly in the enterocytes rather than in the macrophages. Administration of SMT decreased mucosal iNOS activity, intestinal permeability, and bacterial translocation incidence to mesenteric lymph node concurrently. In conclusion, thermal injury induces intestinal mucosal iNOS, which is principally in the enterocytes. The increased intestinal iNOS activity was closely related to barrier failure. SMT inhibited intestinal mucosal iNOS activity and prevented barrier failure as demonstrated by a decrease in BT occurrence and intestinal permeability.     

Cannabinoid antagonist AM 281 reduces mortality rate and neurologic dysfunction after cecal ligation and puncture in rats

OBJECTIVES: The purpose of this study was to examine whether anandamide, an endogenous cannabinoid receptor ligand, is involved in the pathogenesis of septic encephalopathy. DESIGN: Prospective, controlled study. SUBJECTS: Male Wistar rats (7 wks old) were randomly divided into four groups as follows: group 1, control (0.5 mL of saline injected subcutaneously); group 2, sham (surgical abdominal incision and suturing were performed, but ligation and puncture of the cecum were omitted); group 3, cecal ligation and puncture (CLP); group 4, CLP + AM 281 ([N-morpholin-4-yl]-5-[2,4-yl]-5-[2,4-dichlorophenyl]-4-methyl-1H-pyrazole-3-carboxamide) as the cannabinoid receptor antagonist (1 mg/kg intraperitoneally). INTERVENTIONS: Sepsis was induced by CLP under pentobarbital anesthesia (10 mg/kg intraperitoneally) with 1% isoflurane. A 2-Fr high-fidelity micromanometer catheter was inserted into the left ventricle via the right carotid artery to assess hemodynamics. Each of the rats was neurologically assessed at 30 mins and 12, 24, and 48 hrs after the treatment. The cytoplasmic levels of caspase-3 in the hippocampi were assayed before surgery and at 30 mins and 24 and 48 hrs after surgery using Western blotting techniques. To examine the effects of AM 281 on neurologic function and mortality rate, we set another control group treated solely with AM 281. Selective inducible nitric oxide synthase inhibitor, L-N6-(1-iminoethyl)-lysine (4 mg/kg), was injected intraperitoneally immediately after CLP to produce the CLP + L-N6-(1-iminoethyl)-lysine group to exclude the influence of depressed hemodynamics on neurologic impairment. MEASUREMENTS AND MAIN RESULTS: It was found that administration of AM 281 could prevent the hemodynamic changes induced by sepsis. Reflex responses, including the pinna, corneal, paw or tail flexion, and righting reflexes, and the escape response significantly decreased in the CLP and CLP + L-N6-(1-iminoethyl)-lysine groups at 48 hrs after the surgery. In contrast, no changes in these reflex responses were found between the CLP + AM 281 and control and sham groups. In addition, no effects of the administration of AM 281 on neurologic function and mortality rate in the control group were found. Tissue caspase-3 levels were elevated at 48 hrs after CLP in the CLP alone group (means +/- sd: control, 3.9 +/- 0.4; sham, 4.2 +/- 0.4; CLP, 7.1 +/- 1.0 [p < .01]; CLP + AM 281, 4.0 +/- 0.5 densitometric units). In addition, administration of AM 281 also decreased the mortality rate (p < .05). CONCLUSIONS: Administration of AM 281 prevented the hemodynamic changes and development of neurologic dysfunction occurring in association with septic shock, and could decrease the mortality rate in experimentally induced septic shock in rats. Although further studies are necessary to determine whether endogenous cannabinoids cause septic encephalopathy in rats directly or via their effects on systemic hemodynamics, the beneficial effects of AM 281 on these rats might have significant therapeutic implications in cases of septic encephalopathy.