Enhanced antioxidant defense due to extracellular catalase activity in Syrian hamster during arousal from hibernation

Mammalian hibernators are considered a natural model for resistance to ischemia-reperfusion injuries, and protective mechanisms against oxidative stress evoked by repeated hibernation-arousal cycles in these animals are increasingly the focus of experimental investigation. Here we show that extracellular catalase activity provides protection against oxidative stress during arousal from hibernation in Syrian hamster. To examine the serum antioxidant defense system, we first assessed the hibernation-arousal state-dependent change in serum attenuation of cytotoxicity induced by hydrogen peroxide. Serum obtained from hamsters during arousal from hibernation at a rectal temperature of 32 degrees C, concomitant with the period of increased oxidative stress, attenuated the cytotoxicity four-fold more effectively than serum from cenothermic control hamsters. Serum catalase activity significantly increased during arousal, whereas glutathione peroxidase activity decreased by 50%, compared with cenothermic controls. The cytoprotective effect of purified catalase at the concentration found in serum was also confirmed in a hydrogen peroxide-induced cytotoxicity model. Moreover, inhibition of catalase by aminotriazole led to an 80% loss of serum hydrogen peroxide scavenging activity. These results suggest that extracellular catalase is effective for protecting hibernators from oxidative stress evoked by arousal from hibernation.     

Allopurinol-Enhanced Postischemic Recovery in the Isolated Pat Heart Involves Repletion of High-Energy Phosphates

The effects of allopurinol (AP) on functional and metabolic recovery of the isolated rat heart after global ischemia were studied. Hearts were subjected to aerobic perfusion (30 min), cardioplegic infusion (5 min), normothermic ischemia (37 min), and reperfusion (50 min) which was started with secondary cardioplegic infusion (10 min). AP was injected into rats (44 mg/kg body wt ip 2 h before heart excision) and added to cardioplegic solution (2 mM) prior and after ischemia. AP treatment significantly improved postischemic recovery of the function and reduced the leakage of lactate dehydrogenase from reperfused hearts. These beneficial effects were accompanied by a better preservation of tissue content of ATP, the total adenine nucleotides, phosphocreatine, and the total creatine at the end of reperfusion. Inhibition of xanthine oxidase by AP substantially decreased pre- and postischemic release of xanthine and uric acid and increased postischemic release of hypoxanthine into the coronary effluent. Despite this, AP treated hearts did not exhibit a reduction in hydroxyl radical adduct formation in the effluents at reperfusion assessed by the spin-trap measurements. The results suggest that AP may protect the heart from ischemia/reperfusion injury due to enhanced energy provision rather than by prevention of oxygen-derived free radical formation.     

Targeted disruption of peroxiredoxin 6 gene renders the heart vulnerable to ischemia-reperfusion injury

Peroxiredoxin 6 (Prdx6) is a novel peroxidase enzyme belonging to the Prdx family, which in mammals contains five more peroxiredoxins (Prdx1-Prdx5). Like glutathione peroxidase (GSHPx) and catalase, Prdx6 possesses H(2)O(2)-scavenging activities, and, like the former, it also removes hydroperoxides. Since significant amounts of catalase and GSHPx are present in the heart contributing toward the attenuation of H(2)O(2) and hydroperoxides formed during ischemia-reperfusion injury and thereby providing cardioprotection, we asked whether Prdx6 also has any role in this process. In the present study we used Prdx6(-/-) mice to assess the role of Prdx6 in ischemic injury. Western blot analysis revealed the absence of any Prdx activity in the Prdx6(-/-) mouse heart, while the GSHPx-1 and catalase levels remained unchanged. Randomly selected hearts from Prdx6(-/-) mice and wild-type mice were subjected to 30 min of global ischemia followed by 120 min of reperfusion at normothermia. The hearts from the Prdx6(-/-) mice were more susceptible to ischemic reperfusion injury as evidenced by reduced recovery of left ventricular function, increased myocardial infarct size, and higher amount of apoptotic cardiomyocytes compared with wild-type mouse hearts. These Prdx6(-/-) hearts were also subjected to a higher amount of oxidative stress as evidenced by the presence of higher amount of malondialdehyde. The present study thus indicates a nonredundant role of Prdx6 in myocardial ischemic reperfusion injury as catalase, and GSHPx could not make up for the deficiency of Prdx6 activities.     

尾加压素Ⅱ对正常及缺血-再灌注离体大鼠心脏的影响

在正常Langendorff灌流与缺血-再灌注(停灌20 min-复灌20 min)离体大鼠心脏模型,观察尾加压素Ⅱ(urotensin Ⅱ,UⅡ)对冠脉流量、心功能和心肌代谢的影响以及心肌UⅡ受体的功能,以探讨UⅡ的心脏效应。对正常心脏给予0.1、1和10 nmol/L UⅡ各5 min,然后换洗5 min,对停灌缺血-再灌注心脏在再灌注期给予1或10nmol/L UⅡ。监测心率、左室内压和左室内压升降的最大变化率等心功能指标,计算冠脉流量,测定冠脉流出液中总蛋白和肌红蛋白含量以及乳酸脱氢酶(LDH)活性。灌流结束后,测定心肌丙二醛(MDA)含量和质膜UⅡ结合位点(放射性配基结合法)。结果如下:(1)正常心脏灌流UⅡ后,冠脉流量和心功能呈浓度依赖下降,换洗后没有完全恢复。心肌蛋白、肌红蛋白和LDH漏出随UⅡ浓度的增加而增加,换洗后迅速减少。UⅡ组心肌MDA含量与对照组差异无显著性。(2)缺血-再灌注后,冠脉流量显著减少,心功能显著抑制,再灌注期心肌蛋白、肌红蛋白和LDH明显漏出;给予UⅡ后,上述变化增强,且高浓度组更强,与对照组差异有显著性(P<<0.01),再灌注后心肌MDA含量亦显著高于对照(P<0.01)。(3)缺血-再灌注心肌质膜UⅡ受体的B_(max)显著高于正常对照心肌(14.65±1.78vs20.53±1.98 fmol/mg pr,P<0.01),Kd值变化无统计学意义。上述结果表明,在正常     

Prevention of H2O2 generation by monoamine oxidase protects against CNS O2 toxicity.

Toxicity to the central nervous system (CNS) by hyperbaric oxygen (HBO) presumably relates to increased production of reactive oxygen species. The sites of generation of reactive oxygen species during HBO, however, have not been fully characterized in the brain. We investigated the relationship between regional generation of hydrogen peroxide (H2O2) in the brain in the presence of an irreversible inhibitor of catalase, aminotriazole (ATZ), and protection from CNS O2 toxicity by a monoamine oxidase (MAO) inhibitor, pargyline. At 6 ATA of oxygen, pargyline significantly protected rats from CNS O2 toxicity whereas ATZ enhanced O2 toxicity. In animals pretreated with ATZ, HBO inactivated 21-40% more catalase than air exposure in the six brain regions studied. Because ATZ-mediated inactivation of catalase was H2O2 dependent, the decrease in catalase activity during hyperoxia was proportional to the intracellular production of H2O2. Pargyline, administered 30 min before HBO, inhibited MAO by greater than 90%, prevented ATZ inhibition of catalase activity during HBO, and reversed the augmentation of CNS O2 toxicity by ATZ. These findings indicate that H2O2 generated by MAO during hyperoxia is important to the pathogenesis of CNS O2 toxicity in rats.     

间歇性低压低氧对过氧化氢心肌细胞损伤的保护作用

目的:观察慢性间歇性低压低氧对过氧化氢所致心肌细胞损伤的保护作用及其机制。方法:雄性豚鼠20只,随机分为两组(n=10):对照组(non-IHH)、低氧组(IHH)。低氧组豚鼠于低压氧舱接受28 d(海拔5 000 m、每天6 h)的低压低氧处理。胶原酶方法急性分离心肌细胞。细胞动缘探测系统测定过氧化氢对各组细胞收缩力的变化。生化方法测定各组丙二醛(MDA)、乳酸脱氢酶(LDH)及超氧化物歧化酶(SOD)和过氧化氢酶(CAT)的变化。结果:①过氧化氢可使心肌细胞出现收缩、舒张紊乱,但IHH处理使其出现的潜伏期明显延长。②给予过氧化氢(300μmol/L,10 min)使来自于non-IHH或IHH的心肌细胞LDH、MDA含量均明显增加,但IHH心肌细胞LDH、MDA含量明显低于non-IHH心肌细胞的LDH、MDA含量。③经IHH处理组的心肌细胞SOD,CAT活性均明显高于non-IHH组。给予过氧化氢使来自于non-IHH或IHH的心肌细胞SOD,CAT活性均明显降低,但IHH心肌细胞SOD,CAT活性明显高于non-IHH心肌细胞的SOD,CAT活性。结论:IHH具有对抗过氧化氢心肌细胞损伤的作用,可能与其增强抗氧化酶活性有关。     

Effects of ischemia on the metabolism of cardiac enkephalins

The effect of ischemia on cardiac Leucine enkephalin (Leu-enk) content, degradation and coronary release was studied in the isolated perfused hearts of male Sprague Dawley rats. Hearts were electrically stimulated at 180 beats/min. Cardiac Leu-enk concentrations were increased when hearts were perfused (635 +/- 41 vs 301 +/- 60 fmol/g in control non-perfused hearts,) or during ischemia-reperfusion (520 +/- 78 vs 277 +/- 42 fmol/g in heart submitted to ischemia alone). The quantity of leucine-enkephalin released by the heart during perfusion was four times higher than the initial content measured in the heart tissue. The rate of this release was the same throughout the experiment (25.9 +/- 2.9 fmol/min/g during perfusion vs. 19.2 +/- 1.6 during ischemia-reperfusion). These findings suggested that cardiac enkephalin metabolism is regulated by cardiac events. In fact, enzymes involved in enkephalin degradation were decreased during perfusion (39%) and increased during ischemia (50%). The decrease in the enzyme activity during coronary perfusion depended on a reduced activity in the membrane fraction only while membrane and soluble fractions were interested in the increased enzyme activity after ischemia. Ischemia-reperfusion induced a larger release of Leu-enk than perfusion without ischemia. In view of the protective actions of enkephalin peptides against oxidative stress, we can infer from our results an implication of Leu-enk in ischemia-reperfusion and thus eventually in preconditioning phenomenon.     

Hydrogen peroxide and ischemic renal injury: effect of catalase inhibition.

Although reactive oxygen species are believed to participate in postischemic renal injury, the actual chemical species involved and the role of endogenous scavenging systems in protecting against injury requires additional study. Hydrogen peroxide, which derives from superoxide radical, is toxic and also yields toxic hydroxyl radical. 3-amino-1,2,4-triazole reacts with catalase to form irreversibly inactivated catalase only in the presence of hydrogen peroxide. We made use of this chemical reaction both to determine whether inhibition of the hydrogen peroxide-scavenging enzyme catalase would influence ischemic renal injury and to measure hydrogen peroxide production rates after ischemia. Sprague-Dawley rats were given aminotriazole (100 mg/kg) one hour before 40 min of renal ischemia. Twenty-four h after ischemia GFR had decreased to 300 microL/min in control animals and to 50 microL/min in aminotriazole-treated animals. Histologic evidence of injury was also worse in catalase-inhibited animals. To measure hydrogen peroxide production rates aminotriazole was given 60 min before measurement of renal catalase activity. In control animals, aminotriazole caused a 53.4% decrease in catalase activity. In animals subjected to 40 min of ischemia plus either 10 or 60 min of reflow catalase activity decreased by 33.9 and 49.5% (not significantly different from control). Thus, when measured by this method total renal hydrogen peroxide production was considerable but was not increased by ischemia. However, in isolated proximal tubule segments 60 min of anoxia and 30 min of reoxygenation caused a 42% increase in H2O2 released into the incubation medium. In summary, inhibition of catalase before ischemia led to exacerbation of ischemic injury.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of hydrogen peroxide on CO2 fixation of isolated intact chloroplasts

Low concentrations of hydrogen peroxide strongly inhibit CO₂ fixation of isolated intact chloroplasts (50% inhibition at 10⁻⁵ M hydrogen peroxide). Addition of catalase to a suspension of intact chloroplasts stimulates CO₂ fixation 2–6 fold, indicating that this process is partially inhibited by endogenous hydrogen peroxide formed in a Mehler reaction.

The rate of CO₂ fixation is strongly increased by addition of Calvin cycle intermediates if the catalase activity of the preparation is low. However, at high catalase activity addition of Calvin cycle intermediates remains without effect. Obviously the hydrogen peroxide formed at low catalase activity leads to a loss of Calvin cycle substrates which reduces the rate of CO₂ fixation.

3-Phosphoglycerate-dependent O₂-evolution is not influenced by hydrogen peroxide at a concentration (5 · 10⁻⁴ M) which inhibits CO₂ fixation almost completely. Therefore the inhibition site of hydrogen peroxide cannot be at the step of 3-phosphoglycerate reduction. Dark CO₂ fixation of lysed chloroplasts in a hypotonic medium is not or only slightly inhibited by hydrogen peroxide (2.5 · 10⁻⁴ M), if ribulose-1,5-diphosphate, ribose 5-phosphate or xylulose 5-phosphate were added as substrates. However, there is a strong inhibition of CO₂ fixation by hydrogen peroxide, if fructose 6-phosphate together with triose phosphate are used as substrates. This indicates that hydrogen peroxide interrupts the Calvin cycle at the transketolase step, leading to a reduced supply of the CO₂-acceptor ribulose 1,5-diphosphate.     

A thrombocyte-induced myocardial dysfunction in the ischemic and reperfused guinea pig heart is mediated by reactive oxygen species

In recent investigations, we could demonstrate that thrombocytes are able to contribute to ischemia- and reperfusion-induced injury of the heart. The aim of the current study was to investigate whether reactive oxygen species are responsible for induction of myocardial dysfunction under these conditions. Isolated, perfused, and pressure-volume work–performing guinea pig hearts were exposed to a 30-min low-flow ischemia (1 ml/min) and were reperfused (5 ml/min). Washed, homologous blood platelets were administered as a 1-min bolus (20,000 per microliter of perfusion buffer), either during the 15th minute of ischemia or in the first or fifth minute of reperfusion in the presence of thrombin (0.3 U/ml perfusion buffer)). The radical scavengers superoxide dismutase (SOD; 10 U/ml perfusate) and catalase (30 U/ml perfusate) were added during ischemia or in the first or fifth minute of reperfusion, respectively. Intracoronary platelet retention (in percentage of platelets applied) and recovery of EHW (postischemic EHW in percentage of preischemic EHW) were quantified. Ischemic and reperfused hearts with time-matched application of platelets but without administration of SOD or catalase served as controls. Interestingly, both administration of SOD during ischemia and in reperfusion significantly improved recovery of EHW (88.4 ± 2%, 82.6 ± 1%, and 90 ± 3%, respectively) as compared with the case of controls (56.2 ± 3%, 42 ± 2%, and 75 ± 2%, respectively). Platelet retention, however, was not significantly influenced by administration of SOD during ischemia or reperfusion (26 ± 2%, 31 ± 2%, and 26 ± 2%) compared with controls (30.5 ± 3%, 33 ± 2%, and 22 ± 3%, respectively). Coadministration of catalase, on the other hand, exhibited some cardioprotective potential only in the first minute of reperfusion (recovery, 61% ± 4%) as compared with the case of control (42 ± 2%). We conclude that thrombocytes under conditions of ischemia and reperfusion are able to induce a myocardial dysfunction mediated by reactive oxygen species. Superoxide seems to play a major role in this respect.     

Free-radical formation by mitomycin C and its novel analogs in cardiac microsomes and the perfused rat heart

Using a spin-trapping technique, we have examined free-radical formation by mitomycin C and its analogs, BMY 25282 and BMY 25067, in rat cardiac microsomes and isolated perfused rat hearts. All three drugs stimulated 2--4-fold OH radical formation in cardiac microsomes which was inhibited by SOD and catalase. Superoxide anion radical was also detected in the presence of diethylenetetraaminopentaacetic acid. Addition of DMSO yielded methyl radicals, thus indicating the production of free OH under these conditions. Similar stimulation of OH formation (2--3-fold) in the perfusates from rat hearts was detected with all three drugs. Perfusion with catalase (550 U/ml) completely suppressed the OH signal both in the presence and absence of the drugs, thus suggesting the intermediacy of hydrogen peroxide. However, BMY 25067-induced OH formation was more sensitive to inhibition by superoxide dismutase (SOD) and the iron chelator ICRF-187. Perfusion with DMSO produced methyl radicals at the expense of OH in the presence of all three drugs. SOD and catalase inhibited DMPO-OH signals, indicating that most of the OH formation was extracellular in this setting. While mitomycin C and BMY 25067 (up to 10 microM) did not affect the heart rate, perfusion with 10 microM BMY 25282 caused acute arrhythmia and cardiac standstill within 20 min. An initial surge in OH formation (2-fold) accompanied this cardiotoxic effect. Both the arrhythmia and the free radical signal were partially blocked by SOD, catalase and ICRF-187, indicating that iron-dependent oxygen radical formation from BMY-25282 (and possibly other compounds) is involved, in part, in inducing toxic manifestations in the rat heart and possibly in clinic.     

Basic fibroblast growth factor is cardioprotective in ischemia-reperfusion injury

To examine whether basic fibroblast growth factor (bFGF) administered to the heart by perfusion can improve cardiac resistance to injury we employed an isolated rat heart model of ischemia-reperfusion injury and determined the extent of functional recovery in bFGF-treated and control hearts. Global ischemia was simulated by interruption of flow for 60 min. Recovery of developed force of contraction (DF), recorded after reestablishment of flow for 30 min, reached 63.8±1.5% and 96.5±3.5% of preischemic levels in control and bFGF-treated hearts (10 g/heart), respectively, indicating that bFGF induced significantly improved recovery of mechanical function. Recoveries of the rates of contraction or relaxation were also significantly improved in bFGF-treated hearts. Extent of myocardial injury, assessed by determination of phosphocreatine kinase in the effluent, was reduced as a result of bFGF treatment. As a first step towards understanding the mechanism and direct cellular target(s) of bFGF-induced cardioprotection, we investigated its fate after perfusion. Perfusion of 10 g bFGF/heart resulted in a 4-fold increase in bFGF associated with the heart compared to control levels, as estimated by biochemical fractionation and immunoblotting. Immunofluorescent staining of the bFGF-perfused hearts revealed intense anti-bFGF staining in association with blood vessels as well as the periphery of cardiomyocytes, suggesting that the latter may be a target for direct bFGF action. In conclusion, our findings of bFGF-induced increases in cardiac resistance to, and improved functional recovery from, ischemia-reperfusion injury indicate that bFGF may have clinical applications in the treatment of ischemic heart disease.     

Physiological characterization of Haemophilus influenzae Rd deficient in its glutathione-dependent peroxidase PGdx

The chimeric peroxidase PGdx of Haemophilus influenzae Rd belongs to a recently identified family of thiol peroxidases capable of reducing hydrogen peroxide as well as alkylhydroperoxides by means of glutathione redox cycling. In the present study, we constructed a H. influenzae Rd strain, deficient in its PGdx encoding gene (open reading frame HI0572). The mutant was shown by disk inhibition and liquid culture growth assays to exhibit increased susceptibility to organic hydroperoxides. The hampered growth was restored by complementing the interrupted gene on the genome with a replicating plasmid bearing an intact copy of the gene, hereby rejecting the possible influences of polar effects. Elevated levels of hydrogen peroxide scavenging activity, due to the catalase HktE, were measured in the absence of a functional pgdx gene rendering the mutant more resilient against hydrogen peroxide. On the other hand, after initiation of the stationary phase, aerobic cultures of the pgdx mutant were practically devoid of living cells, whereas wild-type counterparts retained viability. This observed feature was alleviated by complementation with the functional gene or with the addition of catalase.     

Relationship between mechanical dysfunction and depression of sarcolemmal Ca2+-pump activity in hearts perfused with oxygen free radicals

Although in vitro studies have shown that oxygen free radicals depress the sarcolemmal Ca²⁺-pump activity and thereby may cause the occurrence of intracellular Ca²⁺ overload for the genesis of contractile failure, the exact relationship between changes in sarcolemmal Ca²⁺-pump activity and cardiac function due to these radicals is not clear. In this study we examined the effects of oxygen radicals on sarcolemmal Ca²⁺ uptake and Ca²⁺-stimulated ATPase activities as well as contractile force development by employing isolated rat heart preparations. When hearts were perfused with medium containing xanthine plus xanthine oxidase, the sarcolemmal Ca²⁺-stimulated ATPase activity and ATP-dependent Ca²⁺ accumulation were depressed within 1 min whereas the developed contractile force, rate of contraction and rate of relaxation were increased at 1 min and decreased over 3–20 min of perfusion. The resting tension started increasing at 2 min of perfusion with xanthine plus xanthine oxidase. Catalase showed protective effects against these alterations in heart function and sarcolemmal Ca²⁺-pump activities upon perfusion with xanthine plus xanthine oxidase whereas superoxide dismutase did not exert such effects. The combination of catalase and superoxide dismutase did not produce greater effects in comparison to catalase alone. These results are consistent with the view that the depression of heart sarcolemmal Ca²⁺ pump activities may result in myocardial dysfunction due to the formation of hydrogen peroxide and/or hydroxyl radicals upon perfusing the hearts with xanthine plus xanthine oxidase.     

异丙酚和氯胺酮对大鼠离体缺血再灌注损伤心肌脂质过氧化的影响

目的：比较异丙酚和氯胺酮对大鼠离体缺血再灌注损伤心肌脂质过氧化的影响。方法：成年Wistar大鼠18只,雌雄不拘。体重240-300g,随机分为3组（T1=6）：心肌缺血再灌注损伤组（I／R组）,异丙酚组（P组）,氯胺酮组（K组）。采用Langendorff灌装置建立离体心脏缺血再灌注模型,将心脏连接至Langendorff逆灌装置,3组均以K-H液平衡灌注10min后,再分别以K．H液、含30μmol/L。异丙酚的K-H液、含10μmol-L-1氯胺酮的K-H液灌注10min,然后全心停灌25min,再分别以停灌前相同的灌注液恢复灌注30min。留取冠脉流出液测定总LDH活性;灌注末取左室心肌组织置于2．5％的戊二醛固定,观察心肌的超微结构;心尖部心肌组织留待检测8-异前列腺素和SOD活性。结果：与I／R组比较,P组8-异前列腺素含量降低,SOD活性升高,LDH活性降低（P〈0．05）;K组8-异前列腺素含量,SOD及LDH活性均无统计学意义（P〉0．05）;与P组比较,K组8-异前列腺素含量升高,SOD及LDH活性降低（P〈0．05）;P组心肌超微结构损伤较m组和K组也明显改善。结论：异丙酚可显著减轻心肌缺血再灌注损伤大鼠的脂质过氧化和心肌缺血再灌注损伤,而氯胺酮没有抗心肌缺血再灌注损伤心肌脂质过氧化的作用。     

Cardioprotection from oxidative stress in the newborn heart by activation of PPARγ is mediated by catalase

Regulation of catalase (CAT) by peroxisome proliferator-activated receptor-γ (PPARγ) was investigated to determine if PPARγ activation provides cardioprotection from oxidative stress caused by hydrogen peroxide (H(2)O(2)) in an age-dependent manner. Left ventricular developed pressure (LVDP) was measured in Langendorff perfused newborn or adult rabbit hearts, exposed to 200μM H(2)O(2), with perfusion of rosiglitazone (RGZ) or pioglitazone (PGZ), PPARγ agonists. We found: (1) H(2)O(2) significantly decreased sarcomere shortening in newborn ventricular cells but not in adult cells. Lactate dehydrogenase (LDH) release occurred earlier in newborn than in adult heart, which may be due, in part, to the lower expression of CAT in newborn heart. (2) RGZ increased CAT mRNA and protein as well as activity in newborn but not in adult heart. GW9662 (PPARγ blocker) eliminated the increased CAT mRNA by RGZ. (3) In newborn heart, RGZ and PGZ treatment inhibited release of LDH in response to H(2)O(2) compared to H(2)O(2) alone. GW9662 decreased this inhibition. (4) LVDP was significantly higher in both RGZ+H(2)O(2) and PGZ+H(2)O(2) groups than in the H(2)O(2) group. Block of PPARγ abolished this effect. In contrast, there was no effect of RGZ in adult. (5) The cardioprotective effects of RGZ were abolished by inhibition of CAT. In conclusion, PPARγ activation is cardioprotective to H(2)O(2)-induced stress in the newborn heart by upregulation of catalase. These data suggest that PPARγ activation may be an effective therapy for the young cardiac patient.     

高铁血红素对心肌缺血／再灌注损伤的防护作用及其机制

目的：在大鼠急性心肌缺血／再灌ii（I／R）模型上,观察高铁血红素在钙激活中性蛋白酶（calpain）介导的心肌I／R损伤中的作用。并初步探讨其可能的机制。方法：64只雄性SD大鼠随机8组（n：8）：假手术组（sham组）、（I／R）组、MDL28170＋I／R组、单纯MDL28170组、高铁血红素＋I／R组、单纯高铁血红素组、锌原卟啉Ⅸ＋高铁血红素＋I／R组、单纯锌原卟啉Ⅸ组。采用大鼠离体心脏Langendorff灌流技术,心脏I／R后,测定左室发展压（LVDP）、心肌梗死面积、冠脉流出液中的乳酸脱氢酶（LDH）释放量。检测calpain、血红素氧化酶（HO）、和半胱氨酸天冬氨酸蛋白酶3（caspase3）活性。Westernblot观察心肌钙蛋白酶抑制蛋白（calpastatin）蛋白表达。结果：①心肌I／R后,calpain、caspase3活性明显增高。calpain抑制剂MDL28170可抑制I／R诱导的LDH释放量增加,增高LVDP,缩小心肌梗死面积。②与单纯I／R组相比,大鼠预先给予高铁血红素后,心脏HO-1活性增加,calpain和caspase3活性下降。同时,LDH释放量减少,LVDP明显增高,心肌梗死面积缩小。③I／R组心肌calpastatin表达量明显低于对照组,高铁血红素组大鼠calpastatin表达量增高。HO-1的抑制剂锌原卟啉Ⅸ可取消高铁血红素对calpastain表达量的影响,并取消其心肌保护作用。结论：高铁血红素预处理可通过抑制calpain的激活,减轻大鼠心肌I／R损伤,其机制可能与增加calpastatin蛋白表达有关。     

Tumor necrosis factor-alpha pretreatment is protective in a rat model of myocardial ischemia-reperfusion injury.

We have demonstrated that tumor necrosis factor-alpha (TNF-alpha) pretreatment protected the rat heart from ischemia-reperfusion injury. This effect was monitored by assaying for lactate dehydrogenase (LDH), an enzyme whose release correlates with loss of cell membrane integrity. Intact hearts removed from rats pretreated with TNF-released significantly lower amounts of LDH compared to control hearts after 20 min. of total global ischemia followed by reperfusion. Hearts from TNF-alpha-pretreated animals contained higher levels of manganous superoxide dismutase (MnSOD) mRNA than hearts from untreated rats. Because oxygen free radicals have been implicated as a major cause of reperfusion damage and the function of MnSOD is to detoxify superoxide anions in the mitochondria, a possible protective mechanism for TNF-alpha may be to induce expression of MnSOD in the heart and thus confer resistance to oxygen free radicals generated during reperfusion.     

Construction and Physiological Analysis of a Xanthomonas Mutant To Examine the Role of the oxyR Gene in Oxidant-Induced Protection against Peroxide Killing

We constructed and characterized a Xanthomonas campestris pv. phaseoli oxyR mutant. The mutant was hypersensitive to H₂O₂ and menadione killing and had reduced aerobic plating efficiency. The oxidants’ induction of the catalase and ahpC genes was also abolished in the mutant. Analysis of the adaptive responses showed that hydrogen peroxide-induced protection against hydrogen peroxide was lost, while menadione-induced protection against hydrogen peroxide was retained in the oxyR mutant. These results show that X. campestris pv. phaseoli oxyR is essential to peroxide adaptation and revealed the existence of a novel superoxide-inducible peroxide protection system that is independent of OxyR.     

Preparation of Labeled Casein fron Goat Milk after Lysine-14C Injection

Hydrogen peroxide in methylotrophic yeasts can be metabolized in at least two distinct ways. Addition of exogenous hydrogen peroxide removes the dependance of catalase on endogenously-produced hydrogen peroxide resulting enhanced rates of alcohol oxidation. Exogenous hydrogen peroxide is also efficiently degraded by cytochrome c peroxidase (CCP), a competitive reaction which does not result in enhanced alcohol oxidation. To overcome the influence of cytochrome c peroxidase, artificial peroxisomes were prepared by coimmobilization of alcohol oxidase and catalase. These artificial peroxisomes mimic the peroxide-induced rate enhancement observed with whole cells.