Beneficial effects of melatonin in a rat model of splanchnic artery occlusion and reperfusion

The aim of the present study was to investigate the protective effect of the pineal secretary product melatonin in a model of splanchnic artery occlusion shock (SAO). SAO shock was induced in rats by clamping both the superior mesenteric artery and the celiac trunk for 45 min, followed thereafter by release of the clamp (reperfusion). At 60 min after reperfusion, animals were sacrificed for tissue histological examination and biochemical studies. There was a marked increase in the oxidation of dihydrorhodamine 123 to rhodamine (a marker of peroxynitrite-induced oxidative processes) in the plasma of the SAO-shocked rats after reperfusion, but not during ischemia alone. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine, an index of nitrogen species such as peroxynitrite, in the necrotic ileum in shocked rats. SAO-shocked rats developed a significant increase of tissue myeloperoxidase and malondialdehyde activity, and marked histological injury to the distal ileum. SAO shock was also associated with a significant mortality (0% survival at 2 hr after reperfusion). Reperfused ileum tissue sections from SAO-shocked rats showed positive staining for P-selectin, which was mainly localized in the vascular endothelial cells. Ileum tissue sections obtained from SAO-shocked rats with anti-intercellular adhesion molecule (ICAM-1) antibody showed a diffuse staining. Melatonin (applied at 3 mg/kg, 5 min prior to reperfusion, followed by an infusion of 3 mg/kg per hr), significantly reduced ischemia reperfusion injury in the bowel as evaluated by histological examination. This prevented the infiltration of neutrophils into the reperfused intestine, is evidenced by reduced myeloperoxidase activity and reduced lipid peroxidation. This was evaluated by malondialdehyde activity which reduced the production of peroxynitrite during reperfusion, markedly reduced the intensity and degree of P-selectin and ICAM-1 in tissue section from SAO-shocked rats and improved their survival. Taken together, our results clearly demonstrate that melatonin treatment exerts a protective effect and part of this effect may be due to inhibition of the expression of adhesion molecule and peroxynitrite-related pathways and subsequent reduction of neutrophil-mediated cellular injury.     

Nitrosation of melatonin by nitric oxide: a computational study

Melatonin is being increasingly promoted as a therapeutic agent for the treatment of jet lag and insomnia, and is an efficient free radical scavenger. We have recently characterized a product for the reaction of melatonin with nitric oxide (NO), N-nitrosomelatonin. In the present work, reaction pathways with N1, C2, C4, C6 and C7 as possible targets for its reaction with NO that yield the respective nitroso derivatives have been investigated using semiempirical AM1 computational tools, both in vacuo and aqueous solution. Specifically, two different pathways were studied: a radical mechanism involving the hydrogen atom abstraction to yield a neutral radical followed by NO addition, and an ionic mechanism involving addition of nitrosonium ion to the indolic moiety. Our results show that the indolic nitrogen is the most probable site for nitrosation by the radical mechanism, whereas different targets are probable considering the ionic pathway. These results are in good agreement with previous experimental findings and provide a coherent picture for the interaction of melatonin with NO.     

一氧化氮和自由基对大鼠急性肝损伤的作用

目的用硫代乙酰胺（ＴＡＡ）诱发大鼠急性肝损伤,观察肝损伤过程中一氧化氮与自由基的变化．方法实验Ⅰ：大鼠２４只分为４组,一组为正常组,其余３组为损伤组．ＴＡＡ６００ｍｇ／ｋｇｓｃ２４,４８,７２ｈ测定内毒素及ＮＯ３－／ＮＯ２－,ＡＬＴ,ＡＳＴ含量．取肝组织匀浆,测定蛋白含量．脂质过氧化物歧化酶（ＳＯＤ）及谷胱甘肽过氧化物酶（ＧＳＨＰＸ）活性,并观察肝组织学变化．实验Ⅱ：大鼠３２只分为４组,Ａ组为正常组,Ｂ,Ｃ,Ｄ组ＴＡＡ６００ｍｇ／ｋｇｓｃ;同时给予Ｂ组生理盐水０４ｍＬ／ｋｇ,Ｃ组７５％ＬＡｒｇ３００ｍｇ／ｋｇ,Ｄ组２５％ＬＮＮＡ１０ｍｇ／ｋｇ．２４ｈ后重复注射１次．２４ｈ后按实验Ⅰ取血、肝组织,测定有关指标．结果大鼠注射ＬＡｒｇ后,ＮＯ的合成增多,转氨酶及肝组织损伤程度明显降低,注射ＬＮＮＡ组大鼠肝损伤程度加重,肝组织自由基的测定表明,抑制肝损伤大鼠ＮＯ合成,肝组织ＬＰＯ含量增高而ＳＯＤ,ＧＳＰＨＸ活性降低,ＳＯＤ,ＧＳＨＰＸ协同作用可清除体内自由基．结论抑制ＮＯ的生物合成,自由基水平增高,从而加重了肝损伤     

Beneficial effects of supplemental nitric oxide donor given during reperfusion period in reperfusion-induced lung injury

BACKGROUND: Reperfusion injury is a perplexing cause of early graft failure after lung transplantation and today we know that reperfusion may be more harmful to tissues than the preceding ischemia. We hypothesized that administration of the nitric oxide donor nitroglycerin (NTG) during flush perfusion and reperfusion periods would ameliorate reperfusion-induced lung injury. METHODS: Using an IN SITU normothermic ischemic lung rabbit model, three groups were studied (n = 7/group): (1) NTG given during flush perfusion (ischemia group); (2) NTG given in the flush perfusion and the reperfusion period (reperfusion group); and (3) no NTG (control group). All groups were flushed with low potassium dextran glucose solution. Blood gas analysis, tissue nitrite (nitric oxide metabolite) level analysis, bronchoalveolar lavage (BAL) fluid examination and morphological examinations were performed. RESULTS: Compared with the ischemia group, the reperfusion group had significantly improved arterial oxygenation (318 +/- 31.4 mmHg vs. 180 +/- 14.7 mmHg, P < 0.05), decreased BAL fluid neutrophil percentage (21 +/- 1.9 % vs. 30 +/- 5.6 %, P < 0.05), increased tissue nitrite level (32.55 +/- 4.12 nmol/g vs. 27.81 +/- 1.05 nmol/g, P < 0.05), and decreased tissue histopathological lesion scores (0.42 +/- 0.53 vs. 1.14 +/- 0.37, P < 0.05). CONCLUSIONS: This study suggests that nitric oxide donors supplemented during flush perfusion and reperfusion have more beneficial effects on lung functions against reperfusion injury than any other treatment modalities during IN SITU normothermic ischemic lung model.     

Long-term treatment in vivo with NOX-101, a scavenger of nitric oxide, prevents diabetes-induced endothelial dysfunction

Summary Substantial evidence exists that diabetes results in impaired endothelial dysfunction suggesting diminished nitric oxide production from diabetic endothelium. It is not known what factors contribute to the development of this defect. In this study, we tested whether chronic treatment in vivo with NOX-101, a water-soluble nitric oxide scavenger, prevents endothelial dysfunction in diabetes. Sprague-Dawley rats were made diabetic by an intravenous injection of streptozotocin. A subgroup of control or diabetic animals received twice daily subcutaneous injections of 80 mg/kg NOX-101 beginning at 48 h after streptozotocin was injected and throughout 8 weeks of diabetes. Body weights and glucose concentrations were monitored weekly. At the end of 8 weeks, blood glucose and glycosylated haemoglobin was raised in diabetic rats but serum insulin concentrations were reduced. Treatment with NOX-101 did not alter glucose or insulin concentrations in control or diabetic rats; however, total glycosylated haemoglobin was partially reduced compared with untreated rats. In a subgroup of 2-week diabetic and age-matched rats fasted for 24 h, NOX-101 abolished total urinary nitrate plus nitrite (an index of nitric oxide production in vivo). In isolated tissue baths, relaxation to the endothelium-dependent vasodilator, acetylcholine, was impaired in diabetic aortic rings and relaxation to nitroglycerin was unaltered. Treatment of control rats with NOX-101 did not alter maximum relaxation to acetylcholine but shifted the response curve slightly to the right. In contrast in diabetic rats, NOX-101 prevented the impairment in endothelium-dependent relaxation but had no effect on relaxation induced by nitroglycerin. These data suggest the possibility that diabetes-induced endothelial dysfunction in diabetes results, in part, from a paradoxical increase in nitric oxide production during the course of the disease. This suggests a novel pathway of vascular complications. [Diabetologia (1998) 41: 1220–1226] Received: 12 January 1998 and in revised form: 9 May 1998     

Pancreatic enzymes and microvascular cell activation in multiorgan failure

Cell activation in the microcirculation leads to an inflammatory cascade and is accompanied by many cardiovascular complications. There is a need to identify the trigger mechanisms that lead to the production of in vivo activating factors. We review here mechanisms for cell activation in the microcirculation and specifically the production of humoral cell activators in physiological shock. The elevated levels of activating factors in plasma could be traced to the action of pancreatic enzymes in the ischemic intestine. New interventions against the production of the activators are proposed. The evidence suggests that pancreatic enzymes in the ischemic intestine may attack several tissue components and generate cellular activators that are associated with multiorgan dysfunction in physiological shock.     

Role of nitric oxide in endotoxin-induced hepatic microvascular dysfunction in rats chronically fed ethanol

BACKGROUND: Nitric oxide (NO) appears to be involved in the pathogenesis of endotoxin-induced liver injury. However, little is known about how NO acts on the hepatic microcirculation, especially in alcohol-fed animals. We examined the roles of NO in endotoxin-induced hepatic microvascular dysfunction in control and ethanol-fed rats. METHODS: One lobe of the liver was observed with an intravital microscope. Flow velocity of fluorescein isothiocyanate-labeled erythrocytes in sinusoids was measured with an off-line velocimeter. Portal pressure and mean arterial pressure also were measured. RESULTS: After administration of endotoxin to control, the flow velocity decreased after 30 min. Portal pressure increased after 45 min. However, in ethanol-fed rats, both the flow velocity and portal pressure temporarily increased in the early phase. Thereafter, the flow velocity decreased and portal pressure increased. At 30 min after administration of the endotoxin, pretreatment with 10 mg/kg of an NO synthase inhibitor, NG-monomethyl-L-arginine (L-NMMA), enhanced the endotoxin-induced decrease in the velocity of erythrocytes in the midzonal region of both control and ethanol-fed rats. Although 0.5 mg/kg of L-NMMA enhanced the endotoxin-induced reduction of erythrocyte velocity in the midzonal region of ethanol-fed rats, L-NMMA enhanced the endotoxin-induced reduction of erythrocyte velocity in the pericentral region of control rats. At 60 min after the endotoxin administration, L-NMMA did not affect the endotoxin-induced decrease of erythrocyte velocity in either control or ethanol-fed rats. Although 10 mg/kg of L-NMMA increased mean arterial pressure both in control and ethanol-fed rats, 0.5 mg/kg of L-NMMA did not change mean arterial pressure in either control or ethanol-fed rats. CONCLUSIONS: These results suggest that NO is involved in endotoxin-induced hepatic microvascular dysfunction, which may contribute to the sequential liver injury, especially in alcohol-fed animals.     

伊贝沙坦对糖尿病大鼠一氧化氮系统及肾脏的影响

目的　研究伊贝沙坦对糖尿病大鼠一氧化氮 (NO)系统及肾脏的影响。　方法　随机将 4 0只Wistar大鼠分为 4组 ,每组 10只 ,分别为正常对照组、糖尿病组、伊贝沙坦组和开搏通组。病程 12周时处死大鼠 ,取血、尿和肾脏标本 ,测定尿量、体重、肾重 /体重比值、血糖、糖化血红蛋白(HbA1c) ;测定血清、尿液和肾组织的NO水平 ,通过免疫组化方法 ,检测肾脏组织诱导型一氧化氮合酶 (iNOS)蛋白的合成 ,并通过光镜和电镜观察肾脏的病理结构变化。　结果　治疗 12周后 ,糖尿病各组大鼠的尿量、肾重 /体重比值、血糖、HbA1c、血清、尿液和肾脏组织的NO水平、肾脏组织iNOS蛋白的合成、肾小球体积和肾小球基底膜厚度明显高于或大于正常组 ,体重明显低于正常组 (P <0 .0 1) ;伊贝沙坦组大鼠的血清、尿液和肾脏组织的NO水平、肾脏组织iNOS蛋白的合成、肾小球体积和肾小球基底膜厚度比糖尿病组明显减少 (P <0 .0 5 ) ;血清、尿液和肾组织NO水平与肾小球体积和肾小球基底膜厚度呈正相关。　结论　伊贝沙坦能延缓糖尿病大鼠肾脏功能损害的进展 ,其机制可能与伊贝沙坦不同程度地抑制糖尿病大鼠NO的产生有关。     

Therapeutic effects of melatonin on heatstroke-induced multiple organ dysfunction syndrome in rats

Abstract: Melatonin reportedly exerts beneficial effects to attenuate multiple organ dysfunction syndrome (MODS) in septic shock. Heatstroke resembles septic shock in many aspects. Thus, this study was performed on the anesthetized rats by using heat exposure to induce heatstroke‐associated MODS. We evaluated the effect of melatonin, a versatile molecule synthesized in the pineal gland and in many organs, in heatstroke rats and showed that melatonin (0.2–5.0 mg/kg of body weight, i.v., immediately after the start of heat stress) significantly (i) attenuated hyperthermia, hypotension and hypothalamic ischemia and hypoxia, (ii) reduced plasma index of the toxic oxidizing radicals like nitric oxide metabolites and hydroxyl radicals, (iii) diminished plasma index of hepatic and renal dysfunction like creatinine, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase, (iv) attenuated plasma systemic inflammation response molecules like soluble intercellular and lesion molecule‐1, E‐selectin, tumor necrosis factor‐alpha, interleukin (IL)‐1β, and IL‐6, (v) promoted plasma levels of an anti‐inflammatory cytokine IL‐10, (vi) reduced an index of infiltration of polymorphonuclear neutrophils in the lung like myeloperoxidase activity, and (vii) promoted the survival time to fourfold compared with the heatstroke alone group. Thus, melatonin could be a novel agent for the treatment of heatstroke animals or patients in the early stage.     

Reversal by L-arginine of a dysfunctional arginine/nitric oxide pathway in the endothelium of the genetic diabetic BB rat

Summary We examined the effects of acute supplementation with arginine in vitro on endothelium-dependent relaxation in aortic rings taken from female genetic, diabetes-prone BB rats. Sensitivity to norepinephrine-induced contraction was unaltered in rings of diabetic BB rats compared to rings from non-diabetic littermates. In precontracted rings, acetylcholine produced a concentration-dependent relaxation which was impaired by diabetes. This relaxation was blocked by l-nitroarginine in both control and diabetic rings. Addition of 3 mmol/l l-arginine (but not d-arginine) enhanced relaxation in diabetic rings similar to that seen in control rings without arginine. l-arginine had no effect on acetylcholine-induced relaxation in control rings. In contrast, relaxation-induced by nitroglycerin in diabetic rings without endothelium was not altered by l-arginine treatment. Thus, a defect in the utilization of arginine by nitric oxide synthase exists in the endothelium of the diabetic BB rat. [Diabetologia (1997) 40: 910–915] Received: 24 February 1997 and in revised form: 17 April 1997     

Role of leukocyte-endothelial cell adhesion in radiation-induced microvascular dysfunction in rats

Recent evidence suggests an active role of endothelial cells and inflammatory cells in radiation-induced vascular dysfunction and organ damage. The aim of this study was to characterize the endothelial cell-leukocyte interactions, their molecular mechanisms, and the associated microvascular dysfunction in postcapillary venules exposed to ionizing radiation. Leukocyte rolling, adherence, and emigration and leakage of fluorescein isothiocyanate albumin in rat mesenteric venules were measured in control conditions and at 2, 4, and 6 hours after abdominal irradiation. Some animals were treated with monoclonal antibodies against leukocyte (CD18) or endothelial cell (intercellular adhesion molecule 1, P-selectin) adhesion molecules before radiation and 5 hours thereafter. In comparison with controls, irradiated animals had a marked increase in the number of rolling leukocytes at 2 hours after radiation. In animals studied 6 hours after radiation, a significant increment in the number of adherent and emigrated leukocytes was observed. This was associated with an increased permeability to fluorescein isothiocyanate albumin. Treatment with antibodies against either CD18 or intercellular adhesion molecule 1, but not P-selectin, significantly attenuated leukocyte adherence, emigration, and the increase in permeability induced by radiation. Radiation-induced leukocyte adherence and emigration involves an interaction between CD11/CD18 on leukocytes and intercellular adhesion molecule 1 on vascular endothelium. These interactions are implicated in the early increase in vascular permeability after irradiation.     

L-精氨酸对离体心肌细胞和心脏微血管内皮细胞一氧化氮合酶活性的影响

目的 :探讨 L-精氨酸对体外培养的心肌细胞和内皮细胞一氧化氮合酶 (NOS)活性的影响。方法 :体外培养 SD大鼠的心肌细胞和心脏微血管内皮细胞 ,72 h后分组 ,实验组在生长液中加入 1 mol/L的 L-精氨酸 ,分别在加入 L-精氨酸后 1 /2、1、2、4h取细胞 ,反复冻融 3次使细胞破裂 ,用分光光度法测细胞内 NOS活性。结果 :加入 1 mol/L的 L-精氨酸后 ,心肌细胞的 NOS活性在 1 /2 h升高至对照组的 1 2 8% (P <0 .0 5) ,2 h时升高至 1 37% (P <0 .0 5) ,4h后下降 ;而内皮细胞在加入 L-精氨酸后 1 /2、1、2、4h时的 NOS活性分别为对照组的 1 2 2 %、1 38%、1 2 8%和1 0 3% ,且内皮细胞 NOS活性较心肌细胞为高。结论 :L-精氨酸可升高心肌细胞和心脏微血管内皮细胞的 NOS活性     

一氧化氮、内皮素及氧自由基对大鼠酒精性胃损害的作用研究

目的研究大鼠酒精性胃损害中,一氧化氮(NO)、内皮素(ET)和氧自由基的作用,以及NO对ET-1、丙二醛(MDA)水平的影响.方法以酒精给大鼠灌胃制备急性胃粘膜损害模型,实验分为五组,应用L-NAME或/和L-Arg依不同分组行尾静脉注射.取门脉血测定NO、ET-1和MDA水平,并取出胃进行形态学观察.结果酒精灌胃后,大鼠门脉血NO含量降低,ET-1和MDA量升高,粘膜损伤加重.L-NAME组NO进一步减少,ET-1和MDA更加升高,粘膜损伤明显加重.L-Arg与L-NAME合用后NO、ET-1及MDA水平均有不同程度恢复,粘膜损伤亦减轻.NO与ET-1及MDA水平呈负相关.结论在酒精性胃损害中,ET-1与氧自由基生成增加,起损害作用,内源性NO可调节ET-1的生成,清除氧自由基而发挥保护作用.     

一氧化氮在肝硬化大鼠睾丸功能障碍发生中的作用

目的探讨一氧化氮(NO)在肝硬化睾丸功能障碍发生中的作用. 方法采用胆管结扎(BDL)复制肝硬化模型,应用硝酸酶还原法测定大鼠血清和睾丸组织匀浆的NO浓度,应用放射免疫分析法测定血清睾酮浓度,同时检测大鼠附睾精子密度和精子活率. 结果肝硬化(HC)组大鼠血清和睾丸组织匀浆NO水平分别为(4.165±1.162)μmol/L和(1.305±0.087)μmol/g,假手术(SO)组大鼠血清和睾丸组织匀浆NO水平分别为(0.535±0.237)μmol/L和(0.720±0.063)μmol/g,HC组显著高于SO组.HC组血清睾酮水平[(0.049±0.020)μg/L]、附睾精子活率(16.46%±4.84%)及精子密度[(86.89±33.17)×106个/ml]均显著低于SO组[分别为(2.680±0.403)μg/L、62.45%±9.21%和(299.43±53.85)×106个/ml],而持续给予小剂量NOS抑制剂L-NAME(HC-NAME组)(0.5mg@kg-1@d-1)达一周,HC-NAME组大鼠血清及睾丸组织NO水平分别为(1.975±0.406)μmol/L和(0.950±0.057)μmol/g,较HC组显著降低.同时HC-NAME组血清睾酮水平、附睾精子活率和精子密度较HC组均显著增高,分别为(0.993±0.179)μg/L、33.85%±4.93%和(188.94±38.34)×106个/ml. 结论 NO在肝硬化大鼠睾丸功能障碍发生中起重要作用,小剂量应用NOS抑制剂L-NAME,肝硬化大鼠NOS持续抑制引起的睾丸功能障碍得到不同程度改善,表明在治疗肝硬化睾丸功能障碍患者时体内给予NOS抑制剂的可能性.     

Expression of nitric oxide synthase in macula densa in streptozotocin diabetic rats

Summary Renal haemodynamic changes are suggested to be an early sign of diabetic glomerulopathy. The juxtaglomerular apparatus relevant to the renin-angiotensin system, known to be the site of nitric oxide (NO) production, is considered to play a role in the regulation of glomerular blood flow. This study was therefore designed to clarify whether in situ expression of nitric oxide synthase (NOS) is altered in the kidney of diabetic rats. Streptozotocin-induced diabetic rats with 6, 8, 12 and 32 weeks' diabetes duration and age-matched normal control rats were used. The expression of a constitutive form of NOS (cNOS, neural type) and NADPH diaphorase activity in the renal cortex were studied immunohistochemically and histochemically. Diabetic rats had lower body weight and heavier kidney mass compared to control rats at each time point examined. Mean glomerular surface area was greater in 6, 8 and 12-week diabetic rats compared to age-matched control rats. cNOS reaction was localized in the macula densa and appeared less intense in diabetic rats compared to age-matched control rats. The mean number of macula densa cells positive for cNOS in each glomerulus and in each glomerular area was significantly lower in diabetic rats compared to control rats at any time examined. In contrast, NADPH diaphorase activity was detected in both juxtaglomerular arterioles and macula densa cells. The staining reaction of NADPH diaphorase in the arterioles remained positive but appeared less intense in macula densa cells in diabetic rats. These results suggest that NO production in macula densa cells may be reduced in diabetic rats, modulating the vasodilatory function of afferent arterioles. Further investigation on the changes in inducible NOS as well as endothelial cNOS are necessary to clarify mechanisms of haemodynamic changes in the diabetic kidney. [Diabetologia (1996) 39: 793–799] Received: 27 September 1995 and in final revised form: 13 February 1996     

Gene transfer of endothelial nitric oxide synthase alters endothelium-dependent relaxations in aortas from diabetic rabbits

Aims/hypothesis. Cardiovascular disease is the leading cause of death in diabetes mellitus. Abnormal endothelium-dependent relaxation is observed both in humans and in animal models of diabetes mellitus and decreased bioavailability of nitric oxide (NO) is thought to be involved in this defect. Therefore, the aim of this study was to test whether adenovirus-mediated gene transfer of endothelial nitric oxide synthase (eNOS) alters vascular reactivity of diabetic vessels.¶Methods. Vascular reactivity was first assessed in thoracic aortas and carotid arteries from nine alloxan-induced diabetic (plasma glucose, 26.5 ± 1.2 mmol/l; HbA_{1 c}, 6.4 ± 0.3 %) and nine control rabbits (plasma glucose, 11.1 ± 1.3 mmol/l; HbA_{1 c}, 2.1 ± 0.1 %). Vascular reactivity was next examined in thoracic aortas of diabetic animals after ex vivo transduction with replication-deficient adenovirus encoding gene for eNOS (AdeNOS) or β-galactosidase (Adβ gal).¶Results. After 10 weeks of hyperglycaemia, endothelium-dependent relaxation to acetylcholine was impaired in diabetic aorta, but was normal in carotid arteries from diabetic rabbits. In contrast, responses of both vessels to calcium ionophore and nitric oxide donor were normal. Histochemical staining for β-galactosidase and immunohistochemistry for eNOS showed transgene expression in the endothelium and adventitia in Adβ gal and AdeNOS transduced vessels, respectively. During submaximum contractions with phenylephrine, relaxations to low concentrations of acetylcholine (3 × 10^–8 to 10^–7 mol/l) were augmented in AdeNOS transduced diabetic vessels.¶Conclusion/interpretation. These findings suggest that adenovirus-mediated gene transfer of eNOS to diabetic aorta alters vascular reactivity. [Diabetologia (2000) 43: 340–347]     

Relationship between protective effects of rosiglitazone on endothelium and endogenous nitric oxide synthase inhibitor in streptozotocin-induced diabetic rats and cultured endothelial cells

BACKGROUND: Previous investigations have indicated that the level of asymmetric dimethylarginine (ADMA) is increased in diabetic patients and animals, and rosiglitazone has a protective effect on the endothelium. In the present study, we tested the relationship between protective effects of rosiglitazone and ADMA in streptozotocin (STZ)-induced diabetic rats and cultured endothelial cells. METHODS: Blood samples were collected from carotid artery. Vasodilator responses to acetylcholine (ACh) in the isolated aortic rings were measured, and serum concentrations of glucose, lipid, nitrite/nitrate, ADMA and tumour necrosis factor-alpha (TNF-alpha) were determined. Cultured endothelial cells were treated with ADMA, and the concentrations of intercellular adhesion molecule (ICAM-1), TNF-alpha, and the activity of nuclear factor-kappaB (NF-kappaB) were determined. RESULTS: Vasodilator responses to ACh were decreased markedly and the serum concentrations of TNF-alpha, nitrite/nitrate and ADMA were increased significantly in diabetic rats. Rosiglitazone (3, 10 or 30 mg/kg) produced a significant reduction of the inhibition of vasodilator responses to ACh, but had no effect on the serum concentrations of glucose, lipid, nitrite/nitrate and ADMA in diabetic rats. ADMA (30 microM) significantly increased the activity of NF-kappaB and elevated the levels of ICAM-1 and TNF-alpha, and pre-treatment with rosiglitazone (10 or 30 microM) markedly inhibited the increased activity of NF-kappaB and reduced the elevated levels of TNF-alpha and ICAM-1 induced by ADMA in cultured endothelial cells. CONCLUSIONS: Rosiglitazone improves endothelial function in diabetic rats, which is related to the reduction of the inflammatory response induced by ADMA.     

Therapeutic effects of melatonin on peritonitis-induced septic shock with multiple organ dysfunction syndrome in rats

Abstract:  The pathogenesis of multiple organ dysfunction syndrome (MODS) in septic shock is complicated and not fully understood. Some studies show that an overproduction of nitric oxide (NO) leads to the refractory hypotension and multiple organ failure, while other studies suggest that free radicals, e.g. superoxide (O₂⁻), contribute to the detrimental effect on vascular responsiveness and tissue/organ damage. Thus, this study was performed on the Wistar rat by using cecal ligation and puncture (CLP) to induce septic shock-associated MODS. We evaluated the effect of an antioxidant melatonin in CLP-induced septic rats and demonstrated that melatonin (3 mg/kg, i.v. at 3, 6, 12 hr after CLP) significantly (a) attenuated hyporeactivity to norepinephrine and delayed hypotension, (b) reduced plasma index of hepatic and renal dysfunction, (c) diminished plasma NO and interleukin-1β (IL-1β) concentrations as well as aortic O₂⁻ levels, (d) reduced marked infiltration of polymorphonuclear neutrophils (PMNs) in the lung and liver tissues, and (e) promoted the survival rate at 18 hr to twofold compared with the CLP alone group. The current study underlined the inhibition of plasma NO and IL-1β as well as aortic O₂⁻ production and the reduction of PMN infiltration may lead to the amelioration of MODS, which may contribute to the beneficial effect of antioxidants (e.g. melatonin in this study) in conscious rats with peritonitis-induced lethality. Thus, the antioxidant could be a novel agent for the treatment of septic animals or patients in the early stage.     

Upregulation of hypothalamic nitric oxide synthase gene expression in streptozotocin-induced diabetic rats

Summary Plasma arginine vasopressin (AVP) is known to be elevated in patients with uncontrolled insulin-dependent diabetes mellitus who have plasma hyperosmolality with hyperglycaemia. Although osmotic stimuli cause an increase in nitric oxide synthase (NOS) activity as well as synthesis of AVP and oxytocin in the paraventricular (PVN) and supraoptic nuclei (SON), it is not known whether NOS activity in the hypothalamus changes in the diabetic patients who have plasma hyperosmolality with hyperglycaemia caused by insulin deficiency. Expression of the neuronal (n) NOS gene in the PVN and SON in streptozotocin (STZ)-induced diabetic rats was investigated by using in situ hybridization histochemistry and NADPH-diaphorase histochemical staining. Four weeks after intraperitoneal (i. p.) administration of STZ, male Wistar rats developed hyperglycaemia and plasma hyperosmolality. The expression of nNOS gene and NADPH-diaphorase staining in the PVN and SON remarkably increased in STZ-induced diabetic rats compared to control rats. Three weeks after administration of STZ, the diabetic rats were subcutaneously treated with insulin for 1 week, which resulted in significant suppression of the induction of nNOS, AVP and oxytocin gene expression in the PVN and SON. Furthermore, the induction of nNOS gene expression in the PVN and SON was suppressed in STZ-induced diabetic rats treated with phlorizin and diet to normalize hyperglycaemia without insulin treatment. These results suggest that upregulation of nNOS gene expression as well as AVP and oxytocin gene expression in the PVN and SON in STZ-induced diabetic rats may be associated with hyperglycaemia and plamsa hyperosmolality. [Diabetologia (1998) 41: 640–648] Received: 16 September 1997 and in revised form: 9 February 1998