INTESTINAL MOTILITY DISORDER INDUCED BY FREE RADICALS: A NEW MODEL MIMICKING OXIDATIVE STRESS IN GUT

Literature data suggest that the inflamed intestine may be subjected to a considerable oxidative stress. Therefore, the aim of the present study was to simulate the oxidative stress in the gastrointestinal tract and to explore its effect on intestinal motility. This was attained by treating isolated segments from the rabbit jejunum and from the guinea pig ileum with 2,2'-Azobis (2-amidinopropane) dihydrochloride (ABAP), which generates peroxyl radicals by thermal decomposition. Treatment of intestinal segments with ABAP reduced the muscarinic cholinergic response to acetylcholine in both preparations and induced a dose-dependent inhibition of the spontaneous contractions in the jejunum, also in the presence of tetrodotoxin. ABAP was found to inhibit the contractile response induced by BaCl(2) in guinea pig ileum preparations. This effect was not dose-dependent and it was reversed by Bay-K 8644, which activates voltage operated L-type calcium channels. The rapid and reversible effects of ABAP suggest that it might directly affect L-type calcium channels before lipoperoxidation induction. In conclusion, the results of the present study show that ABAP could be a useful tool to simulate early contractility dysfunctions mediated by oxidative stress.     

DECREASED RENAL RESPONSES TO ATRIAL NATRIURETIC PEPTIDE IN RENAL WRAP HYPERTENSION

1. The effects of atrial natriuretic polypeptide (ANP) on renal function were examined in renal wrap hypertensive rabbits and sham operated rabbits. 2. ANP (2 micrograms/min) induced hypotension, but did not produce significant diuresis, natriuresis or change in the glomerular filtration rate (GFR) in renal wrap hypertensive rabbits (n = 8). 3. In sham operated normotensive rabbits (n = 4), ANP induced significant diuresis (230%) and increased GFR by about 40%. 4. Thus, ANP was markedly less effective in the impaired kidneys of renal wrapped rabbits than in normal kidneys.     

APOPTOTIC AN IN AN IN VITRO MODEL OF NEURONAL OXIDATIVE STRESS

1. Oxidative stress is believed to be an important mediator of neuronal cell death but the precise mechanism by which this accurs is unknown. 2. We have developed an in vitro model of neuronal oxidative stress to study the pathways by which free radicals kill neurones. 3. We have shown that oxidative stress, cystine deprivation and glutathione depletion results in cell death with the morphological and biochemical features of apoptosis. 4. Neuronal apoptosis induced by oxidative stress can be inhibited by macromolecular synthesis inhibitors. 5. This in vitro model will be a valuable tool for defining the molecular targets of toxic free radicals in neurones and, in turn, in designing rational new therapies for free radical mediated diseases.     

ENDOPLASMIC RETICULUM STRESS INVOLVED IN HEART AND LIVER INJURY IN IRON-LOADED RATS

• 1 Iron overload contributes to the pathogenesis of various diseases and directly induces tissue injury. In the present study, we investigated the relationship between heart and liver injury induced by iron overload and cellular endoplasmic reticulum (ER) stress to explore the molecular mechanism of iron overload‐induced cellular injury.
• 2 Iron overload in rats was generated by intraperitoneal injection of iron–dextran chronically (30 mg/kg per day for 9 weeks) or acutely (300 mg/kg once). Tissue injury was assessed by determining serum lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity, as well as malondialdehyde (MDA) content in the heart and liver. The ER stress response was analysed by expression of glucose‐response protein 78 (GRP78) and activation of caspase 12.
• 3 In chronic iron‐loaded rats, iron levels in the heart and liver were higher, by approximately 2‐and 7.8‐fold, respectively (P < 0.01), compared with control. Serum LDH, ALT and AST activity, as well as MDA content, GRP78 expression and caspase 12 activity in the heart and liver, were upregulated in chronically iron‐loaded rats. In acute iron‐loaded rats, iron content in the heart and liver was 51% and 63% higher than in controls (both P < 0.01). Serum LDH, ALT and AST activity, MDA content in the heart and liver and levels of ER stress markers were all increased in acute iron‐loaded rats. N‐Acetylcysteine (150 mg/kg, s.c.) lowered the levels of these parameters in acute iron‐loaded rats.
• 4 The results of the present study indicate that ER stress may play an important role in iron‐induced tissue injury and that reactive oxygen species may mediate the ER stress response in the pathogenesis of iron‐overload cellular injury.

     

PSYCHOSOCIAL STRESS INDUCES TUBULOINTERSTITIAL NEPHRITIS UNRELATED TO HYPERTENSION IN CBA MICE

1. Groups of mice interacting socially in complex population cages become hypertensive. Some also develop fatal chronic tubulointerstitial nephritis. 2. Long-term administration of the cardioselective β-blocker metoprolol controls stress-induced elevation of plasma renin and adrenal tyrosine hydroxylase. It also normalizes blood pressure. Despite the effectiveness of this sympathetic blockade, the incidence of nephritis was not diminished. 3. The fact that stress-induced increases of adrenal weight and plasma cortico-sterone persist during metoprolol treatment points to the independence of the pituitary-adrenal cortical system and its possible role in the aetiology of renal disease.     

GENES OF STRESS IN EXPERIMENTAL HYPERTENSION

1. A significant portion of blood pressure variance is modified by the environment. 2. The present report summarizes evidence that: (i) the environmental response is genetically determined; (ii) various stressors can evoke a differential response in hypertensive animals and constitute its intermediate phenotypes; (iii) the response to heat stress can be assigned to a single ‘thermosensitivity’ locus; (iv) candidate genes of susceptibility to environmental stresses are member(s) of the heat stress gene (HSP) gene families; (v) a restriction fragment length polymorphism ofhsp70 and a single base mutation in the 3′-untranslated region of hsp27 are associated with hypertension in recombinant inbred strains. 3. In conclusion, HSP gene variants may be causative in susceptibility to hypertension.     

亚硒酸钠诱导人急性早幼粒细胞白血病细胞株NB4细胞氧化应激和细胞凋亡

目的研究亚硒酸钠诱导NB4细胞的氧化应激和细胞凋亡。方法MTT比色法检测亚硒酸钠对NB4细胞的生长抑制;用形态学、DNA琼脂糖电泳和流式细胞术研究亚硒酸钠诱导NB4细胞凋亡的作用;用化学发光法和比色法研究亚硒酸钠对NB4细胞内氧化应激的影响。 结果亚硒酸钠可以时间和剂量依赖性地抑制NB4细胞生长和诱导NB4细胞凋亡。亚硒酸钠(≥5 μmol·L^-1)提高了NB4细胞内ROS水平,同时伴有细胞内还原型谷胱甘肽含量下降,而抗氧化剂NAC可抑制亚硒酸钠诱导的NB4细胞氧化应激和细胞凋亡。结论亚硒酸钠诱导NB4细胞氧化应激可能是其诱导NB4细胞凋亡的重要机理。     

HYPOTHESIS: GLUCAGON RECEPTOR GLYCINE TO SERINE MISSENSE MUTATION CONTRIBUTES TO ONE IN 20 CASES OF ESSENTIAL HYPERTENSION*

1. A missense mutation leading to reduced ligand affinity in the glucagon receptor (GCG-R) has been found recently to be five-fold more common in essential hypertensives than normotensives. The present paper provides additional information on patients that harbour this variant and proposes a possible mechanism by which this may lead to hypertension. 2. The seven hypertensives with the mutation were all female, had a later age of onset of the disease and a slightly higher body mass index. 3. Glucagon is involved in the regulation of fluid and electrolyte excretion. Mutant GCG-R results in reduced ligand affinity and cAMP response which, in the kidney, would reduce the normal natriuretic effect of glucagon. This could lead to enhanced fluid reabsorption, expansion of extracellular fluid volume and hypertension via long-term autoregulation of blood pressure.     

CARDIOVASCULAR HABITUATION TO EMOTIONAL STRESS IN LYON HYPERTENSIVE RATS

1. Intra-aortic blood pressure was recorded continuously in freely moving genetically hypertensive (LH), normotensive (LN) and low blood pressure (LL) rats of the Lyon strain during two 11 h periods (08:00-19:00 h). During the first period (control), the animals were left undisturbed and during the second period (stress), a jet of air was applied for 20 min every hour. Urine was collected simultaneously and analysed for its content in norepinephrine and epinephrine. 2. The first exposure to the stressor induced larger increases in blood pressure and heart rate in LH than in LN and LL rats. However blood pressure and heart rate responses to the 10 following stressors decreased in LH rats while they remained stable in LN and LL animals. 3. Repeated stress exposure induced significant increases in epinephrine excretion in both LN and LL but not in LH rats. 4. It is concluded that LH rats exhibit marked cardiovascular habituation to repeated stress. Taken together with the lack of stress-induced sympathoadrenal activation, this suggests a reduced level of emotional responsiveness in Lyon hypertensive rats.     

PRESSOR SENSITIVITY TO ANGIOTENSIN I AND ANGIOTENSIN II DURING THE DEVELOPMENT OF EXPERIMENTAL RENAL HYPERTENSION IN THE RAT

Treatment with the potent angiotensin converting enzyme inhibitor perindopril completely prevented any rise in blood pressure in the 2-kidney, 1-clip (2K1C) model of renal hypertension in rats. Withdrawal of this inhibitor was followed by a slow rise in blood pressure. In 2K1C rats treated with perindopril, pressor responses to angiotensin I fell during the treatment period, but returned to normal after the inhibitor was stopped. Pressor responses to angiotensin II (AII) increased during treatment with perindopril; this was presumably due to increased receptor sensitivity consequent on the falls in endogenous AII levels. Responses to AII fell to control levels after the inhibitor was stopped. It is concluded that an increased pressor sensitivity to AII is not the cause of the slowly developing hypertension in the 2K1C model of hypertension, and that the slow pressor response to AII must be due to other factors.     

INVOLVEMENT OF OXIDATIVE AND L-ARGININE-NO PATHWAYS IN THE NEUROTOXICITY OF DRUGS OF ABUSE IN VITRO

1. Inhibitors of nitric oxide (NO) formation or ADP-ribosylation attenuate methamphetamine (METH)- and methyl-enedioxymetamphetamine (MDMA)-induced neurotoxicity on dopaminergic and serotonergic cells in primary cultures. 2. They also prevent METH-induced reactive gliosis in dopaminergic cultures. 3. Overexpression of superoxide dismutase (SOD) in cells obtained from SOD-transgenic mice also attenuates drug-induced toxicity. 4. These data indicate a role for oxygen-based and NO free radicals in the mechanisms of cell death associated with drugs of abuse in vitro.     

HIGH-CHOLESTEROL DIET AUGMENTS ENDOTHELIAL DYSFUNCTION VIA ELEVATED OXIDATIVE STRESS AND REDUCED TETRAHYDROBIOPTERIN IN INS2AKITA MICE, AN AUTOSOMAL DOMINANT MUTANT TYPE 1 DIABETIC MODEL

• 1 Oxidative stress contributes to endothelial dysfunction and atherogenesis in diabetes. The present study tested the hypothesis that a high‐cholesterol diet accelerates endothelial dysfunction in Ins2^Akita mice, a Type 1 diabetic model with a spontaneous autosomal preproinsulin gene (Ins2 gene) mutation, through further increase of superoxide production.
• 2 The Ins2^Akita diabetic mice were fed a high‐cholesterol diet (1.25% cholesterol) for 4 months. Some Ins2^Akita mice were also treated for 4 months with the selective NADPH oxidase inhibitor apocynin (4 mg/kg per day in drinking water). Oxidative stress markers, tetrahydrobiopterin (BH₄) levels, GTP cyclohydrolase I activity and endothelial function were determined in serum or arteries afterwards.
• 3 Serum lipid peroxidation and arterial superoxide levels were increased, whereas arterial BH₄ levels and GTP cyclohydrolase I activity were decreased, in Ins2^Akita mice on a high‐cholesterol diet, resulting in impaired endothelium‐dependent nitric oxide‐mediated relaxation in response to acetylcholine.
• 4 In vivo treatment with apocynin not only blunted serum lipid peroxidation and arterial superoxide levels, but also increased BH₄ levels and GTP cyclohydrolase I activity, resulting in improved endothelium‐dependent relaxation.
• 5 These results suggest that NADPH oxidase may play a potential role in oxidative stress‐induced arterial BH₄ and GTP cyclohydrolase I deficiency, resulting in endothelial dysfunction in Ins2^Akita Type 1 diabetic mice fed a high‐cholesterol diet.

     

UPLC-Q-Exactive-Orbitrap-MS法鉴定白花蛇舌草注射液中化学成分

目的采用超高效液相色谱–四级杆–静电场轨道阱联用技术(UPLC-Q-Exactive-Orbitrap-MS)辨别分析白花蛇舌草注射液中化学成分。方法采用Waters Acquity UPLC HSS T3 C18色谱柱(100 mm×2.1 mm,1.8μm),以0.1%甲酸水溶液–乙腈为流动相,梯度洗脱,柱温30℃,体积流量0.30 mL/min,样品室温度10℃,进样体积10μL。采用电喷雾离子源(ESI),正、负离子模式下采集数据。通过NIST质谱数据库检索,结合保留时间、分子离子、主要碎片,并根据文献资料,推测其化学成分。结果白花蛇舌草注射液中共鉴定出22个化合物,其中包括黄酮类7个、有机酸类7个,糖类3个、萜类2个、嘌呤2个、丁香脂素和酚苷各1个。结论建立的方法能快速、准确、高效鉴定白花蛇舌草注射液中多种化学成分,为阐明白花蛇舌草的药效物质基础提供参考。