Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Our objective in experiments reported here was to identify myofilament proteins of rat hearts either lost or degraded by cardiac ischemia (15- or 60-minute duration) with and without 45 minutes of reperfusion. We correlated these changes with alterations in myofilament sensitivity to Ca2+ and maximum force generation. Protein degradation and loss were assessed by high-performance liquid chromatography, SDS-PAGE, Western blotting analysis, and amino acid sequencing. Compared with nonischemic control hearts, bundles of skinned fibers from hearts subjected to ischemia alone demonstrated a decrease in maximum force generation and an increase in sensitivity to Ca2+. These changes in function were increased with the duration of the ischemia and with reperfusion. With increasing duration of ischemia, there was an increased loss and degradation of myofibrillar alpha-actinin and troponin I (TnI) at its C-terminus. Alpha-actinin and TnI were most susceptible to ischemia, but with 60 minutes of ischemia/reperfusion, there was also degradation of myosin light chain-1 (MLC1) involving a clip of residues 1 to 19. The MLC1 degradation product was detected in the reperfusion effluent (along with troponin T, tropomyosin, and alpha-actinin) but not in the tissue with 60 minutes of ischemia with no reperfusion. Moreover, with ischemia the following proteins became associated with the myofibrils: GAPDH and proteins of the mitochondrial ATP synthase complex. Our results provide new evidence regarding the mechanism by which ischemia/reperfusion causes myocardial injury and support the hypothesis that an important element in the injury is altered activity and structure of the myofilaments.
 ...
PMID:Breakdown and release of myofilament proteins during ischemia and ischemia/reperfusion in rat hearts: identification of degradation products and effects on the pCa-force relation. 946 97

The effects of tacrolimus (FK 506) on brain phosphorylation have been investigated in vitro using mitochondria isolated from rat brain. Respiratory control ratio (RCR), oxygen consumption, ATP synthesis and enzymatic activities of involved complexes have been measured to assess the mechanisms of action of tacrolimus. Our data show that this drug decreases RCR and ATP synthesis. This effect is quantitatively limited after a single application of the drug (14%), concentration-dependent and biphasic, the respective effect 50%-concentration (EC50) being 0.129 and 247 nM, each step corresponding to 50% of the total oxygen consumption inhibition. Tacrolimus acts mainly as an inhibitor of ubiquinol-cytochrome c reductase (complex III), competing at least partly with antimycin A or myxothiazol, the corresponding EC50 being 0.27 and 103 nM respectively. Tacrolimus inhibits also complex V i.e. ATPase activity (40%) and ATP synthase activity (30%) in a concentration-dependent manner, the relevant EC50 being 78 and 394 nM respectively. These data may be relevant for the protective effect of tacrolimus observed in ischemia-reperfusion, which may be due to its inhibition of both complex III, where Reactive Oxygen Species (ROS) are generated, and complex V, where ATP is depleted by ATPase activation. It may also be related to neurotoxicity occurring along chronic administration of tacrolimus in humans.
 ...
PMID:Tacrolimus decreases in vitro oxidative phosphorylation of mitochondria from rat forebrain. 971 23

A short period of ischemia followed by reperfusion produces a state of affairs in which the cells' potential for surviving longer ischemia is enhanced. This is called ischemic preconditioning. The effects of preconditioning are also related to the reperfusion damage which ensues upon tissue oxygenation. The role of the cellular energy state in reperfusion damage remains an enigma, although ischemic preconditioning is known to trigger mechanisms which contribute to the prevention of unnecessary ATP waste. In some species up to 80% of ATP hydrolysis in ischemia can be attributed to mitochondrial F1-F0-ATPase (ATP synthase), and a role for its inhibitor protein (IF1) in ATP preservation has been proposed. Although originally regarded as limited to large animals with a slow heart beat, inhibition by IF1 is probably a universal phenomenon. Coincidentally with ATPase inhibition, the decline in cellular ATP slows down, but even so the difference in ATP concentration between preconditioned and non-conditioned hearts is still small at the final stages of a long ischemia, when the beneficial effect of preconditioning is observable, although the energy state during reperfusion remains low in hearts which do not recover.
 ...
PMID:Role of cellular energetics in ischemia-reperfusion and ischemic preconditioning of myocardium. 974 33

A short period of ischemia followed by reperfusion (ischemic preconditioning) is known to trigger mechanisms that contribute to the prevention of ATP depletion. In ischemic conditions, most of the ATP hydrolysis can be attributed to mitochondrial F1F0-ATPase (ATP synthase). The purpose of the present study was to examine the effect of myocardial ischemic preconditioning on the kinetics of ATP hydrolysis by F1F0-ATPase. Preconditioning was accomplished by three 3-min periods of global ischemia separated by 3 min of reperfusion. Steady state ATP hydrolysis rates in both control and preconditioned mitochondria were not significantly different. This suggests that a large influence of the enzyme on the preconditioning mechanism may be excluded. However, the time required by the reaction to reach the steady state rate was increased in the preconditioned group before sustained ischemia, and it was even more enhanced in the first 5 min of reperfusion (101 +/- 3.0 sec in preconditioned vs. 83.4 +/- 4.4 sec in controls, p < 0.05). These results suggest that this transient increase in activation time may contribute to the cardioprotection by slowing the ATP depletion in the very critical early phase of post-ischemic reperfusion.
 ...
PMID:Myocardial ischemic preconditioning and mitochondrial F1F0-ATPase activity. 1120 53

Cell survival is critically dependent on the preservation of cellular bioenergetics. However, the metabolic mechanisms that confer resistance to injury are poorly understood. Phosphotransfer reactions integrate ATP-consuming with ATP-producing processes and could thereby contribute to the generation of a protective phenotype. Here, we used ischemic preconditioning to induce a stress-tolerant state and (18)O-assisted (31)P nuclear magnetic resonance spectroscopy to capture intracellular phosphotransfer dynamics. Preconditioning of isolated perfused hearts triggered a redistribution in phosphotransfer flux with significant increase in creatine kinase and glycolytic rates. High energy phosphoryl fluxes through creatine kinase, adenylate kinase, and glycolysis in preconditioned hearts correlated tightly with post-ischemic functional recovery. This was associated with enhanced metabolite exchange between subcellular compartments, manifested by augmented transfer of inorganic phosphate from cellular ATPases to mitochondrial ATP synthase. Preconditioning-induced energetic remodeling protected cellular ATP synthesis and ATP consumption, improving contractile performance following ischemia-reperfusion insult. Thus, the plasticity of phosphotransfer networks contributes to the effective functioning of the cellular energetic system, providing a mechanism for increased tolerance toward injury.
 ...
PMID:Cellular energetics in the preconditioned state: protective role for phosphotransfer reactions captured by 18O-assisted 31P NMR. 1158 91

A cDNA library constructed from kidney of the thirteen-lined squirrel, Spermophilus tridecemlineatus, was differentially screened for genes that were upregulated during hibernation. A clone encoding cytochrome c oxidase subunit 1 was found and confirmed to have been upregulated by northern blotting. Differential expression of Cox1 mRNA occurred in multiple organs during hibernation; in hibernating animals transcript levels were twofold higher in kidney and fourfold higher in heart and brown adipose tissue than in euthermic animals, but were unchanged in skeletal muscle. Transcript levels of mitochondrial-encoded ATP synthase 6/8 were similarly upregulated in these tissues whereas transcript levels of the nuclear encoded subunits Cox4 and ATP synthase alpha did not change during hibernation. Immunoblot analysis revealed a 2.4-fold increase in Cox 1 protein and a slight decrease in Cox 4 protein in kidney of hibernating squirrels, compared with euthermic controls. Hibernating mammals may increase the expression of the mitochondrial genome in general, and Cox1 specifically, to prevent or minimize the damage to the electron transport chain caused by the cold and ischemia experienced during a hibernation bout.
 ...
PMID:Differential expression of mitochondria-encoded genes in a hibernating mammal. 1200 Aug 7

Ischemia limits the delivery of oxygen and glucose to cells and disturbs the maintenance of mitochondrial membrane potential (MMP). MMP regulates the production of high-energy phosphate and apoptotic cascading. Thus, MMP is an important parameter determining the fate of neurons. Differences in the time course of MMP according to the grading of the ischemic impact have not been clarified. MMP and intracellular ATP contents were monitored before and after short-term oxygen-glucose deprivation. A primary hippocampal culture seeded in a 35 mm fenestrated dish for fluorescence microscopy was mounted in a sealed chamber for an anaerobic incubation. A continuous flow of 100% nitrogen into the chamber and a replacement of glucose-free medium allowed the condition of oxygen-glucose deprivation (OGD), thereby extrapolating ischemia. MMP was evaluated by the fluorescence of a voltage-dependent dye, JC-1, under fluorescence microscopy. The intracellular ATP content was evaluated in a hippocampal culture seeded in a 96-well plate by the luciferin-luciferase reaction after a designated period of OGD. During OGD, MMP decreased to 0.72+/-0.03 (normalized JC-1 fluorescence), then increased to the hyperpolarized level 1.99+/-0.12 during 60 min reoxygenation after 30 min OGD. MMP after 60 min OGD decreased and recovered occasionally during reoxygenation. After 90 min OGD and reoxygenation, MMP was reduced and never recovered. The intracellular ATP content was 8.1+/-6.6 and 3.2+/-1.9% after 30 min OGD and 30 min reoxygenation following 30 min OGD, respectively; 60 min OGD did not significantly change these levels (7.1+/-5.8, 2.6+/-0.5%). Hyperpolarization after OGD did not accompany ATP production. This observation suggests the inhibition of electron reentry into an inner membrane during reoxygenation and the disturbance of FoF1-ATP synthase. This pathological finding of an energy-producing system after OGD may provide a clue to explain post-ischemic energy failure.
 ...
PMID:Mitochondrial membrane potential and intracellular ATP content after transient experimental ischemia in the cultured hippocampal neuron. 1268 6

Biotin-cysteine was used to study protein S-thiolation in isolated rat kidneys subjected to ischemia and reperfusion. After 40 min of ischemia, total protein S-thiolation increased significantly (P < 0.05), by 311%, and remained significantly elevated (P < 0.05), 221% above control, after 5 min of postischemic reperfusion. Treatment of protein samples with 2-mercaptoethanol abolished the S-thiolation signals detected, consistent with the dependence of the signal on the presence of a disulfide bond. With the use of gel filtration chromatography followed by affinity purification with streptavidin-agarose, S-thiolated proteins were purified from CHAPS-soluble kidney homogenate. The proteins were then separated by SDS-PAGE and stained with Coomassie blue. With a combination of matrix-assisted laser desorption ionization time of flight mass spectrometry and LC/MS/MS analysis of protein bands digested with trypsin, a number of S-thiolation substrates were identified. These included the LDL receptor-related protein 2, ATP synthase alpha chain, heat shock protein 90 beta, hydroxyacid oxidase 3, serum albumin precursor, triose phosphate isomerase, and lamin. These represent proteins that may be functionally regulated by S-thiolation and thus could undergo a change in activity or function after renal ischemia and reperfusion.
 ...
PMID:Reversible cysteine-targeted oxidation of proteins during renal oxidative stress. 1287 48

Excitotoxic neuronal injury related to excessive glutamate release is believed to play a key role in the pathogenesis of focal cerebral ischemia. Reversal of neuronal glutamate transporters caused by ATP fall and subsequent imbalance of membrane ionic gradients accounts for most glutamate release after cerebral ischemia. ATP synthesis from oxidative phosphorylation derives from the coupled functioning of the mitochondrial respiratory chain (MRC) and the ATP synthase; interestingly, the MRC is one of the main sites of cellular reactive oxygen species (ROS) generation even in physiological circumstances. Hence, we have studied the effect of the antioxidants glutathione, superoxide dismutase, and alpha-tocopherol on infarct outcome, brain ATP, and glutamate levels after permanent middle cerebral artery occlusion (MCAO) in Fischer rats; we have also characterized the actions of antioxidants on MRC complexes. Our results show that intraperitoneal administration of antioxidants 2 h before MCAO enhances ATP synthesis and causes a neuroprotective effect concomitant to inhibition of ischemia-induced increase in brain glutamate. Antioxidants also increased mitochondrial ATP and MRC complex I-III activity and respiration, suggesting that these actions are due to removal of the inhibition caused by endogenous ROS on MRC. These findings may possess important therapeutic repercussions in the management of ischemic stroke.
 ...
PMID:Inhibition of glutamate release by delaying ATP fall accounts for neuroprotective effects of antioxidants in experimental stroke. 1450 May 56

The amplitude of coronary reactive hyperemia (CRH), elicited by 15 s of ischemia, is reduced in hearts subjected to 5 min of ischemic preconditioning (IP). F0F1 ATP synthase activity and ATP concentration are also altered by IP. We hypothesized that F0F1 ATP synthase is differently modulated by the inhibitor protein IF(1) during CRH elicited before (CRHnp) and after (CRHprec) IP. Hemodynamic parameters were recorded in 10 anesthetized goats. Myocardial biopsies were obtained before IP (Cnp), during CRHnp, 4 and 6 min after the onset of CRHnp, after IP (Cprec), during CRHprec, and 4 min after CRHprec. F0F1 ATP synthase activity, ATP concentration, and ATP-to-ADP ratio (ATP/ADP) were determined. Compared with CRHnp, IP blunted CRHprec. F0F1 ATP synthase activity transiently increased during CRHnp, decreased 4 min after CRHnp, and returned to control 2 min later; it was lower after IP (Cprec) and did not change during and after CRHprec. All these changes in activity were modulated by IF1. During CRHnp, ATP concentration and ATP/ADP were reduced compared with Cnp and began to rise 6 min thereafter. During Cprec, both parameters were transiently reduced but increased during and after CRHprec. Hence, during CRHnp, F0F1 ATP synthase activity transiently increases and then decreases significantly. The short-lasting inhibition of the enzyme may explain why a few seconds of occlusion do not induce IP. After IP, F0F1 ATP synthase activity is blunted, and it is not affected by a subsequent 15 s of occlusion, which induces a blunted CRHprec. These results suggest that postischemic long-lasting inhibition of F0F1 ATP synthase activity may be a feature of the preconditioned heart. The increase in ATP concentration after preconditioning is in agreement with previous reports of reduced ATP hydrolysis by cytoplasmic ATPases.
 ...
PMID:F0F1 ATP synthase activity is differently modulated by coronary reactive hyperemia before and after ischemic preconditioning in the goat. 1521 95


1 2 3 4 5 6 7 8 Next >>