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

The mechanisms by which long-chain dietary polyunsaturated fatty acids (PUFAs) protect against cardiovascular disease are largely unknown. The present study determines the effects of eicosapentaenoic acid (EPA) and arachidonic acid (ARA) on the response of neonatal rat cardiomyocytes to simulated ischaemia (SI) and reperfusion (R). Myocytes isolated from 1-2 day old Wistar rat hearts were cultured with or without EPA or ARA and exposed to 1 h SI followed by 30 minutes reperfusion. Apoptosis was evaluated by caspase-3 activation, poly-(ADP-ribose) polymerase (PARP) cleavage and nuclear condensation. EPA (20microM) and ARA (20microM) significantly inhibited caspase-3 activation and PARP-cleavage and reduced the apoptotic index during reperfusion. Both fatty acids significantly increased ERK phosphorylation and decreased p38 phosphorylation during reperfusion. The mechanism of action of ARA on the MAPKs was further investigated with okadaic acid (to inhibit serine-threonine phosphatases) and orthovanadate (to inhibit tyrosine phosphatases). Vanadate, but not okadaic acid, significantly reduced ARA-induced inhibition of p38 phosphorylation, suggesting the involvement a tyrosine phosphatase during SI/R. Mitogen-activated protein kinase phosphatase-1 (MKP-1), a dual-specificity phosphatase, was targeted and a significant induction of MKP-1 by ARA and EPA was observed. It was demonstrated for the first time that EPA and ARA protect neonatal cardiac myocytes from ischaemia/reperfusion-induced apoptosis through activation of ERK as well as induction of a dual-specific phosphatase, causing dephosphorylation of the pro-apoptotic kinase, p38. The cardioprotective effects of EPA and ARA could also be demonstrated on the functional recovery of isolated perfused hearts subjected to global ischemia.
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PMID:Long-chain polyunsaturated fatty acids protect the heart against ischemia/reperfusion-induced injury via a MAPK dependent pathway. 1621 66

Previous studies showed that insulin antagonizes AMP-activated protein kinase activation by ischemia and that protein kinase B might be implicated. Here we investigated whether the direct phosphorylation of AMP-activated protein kinase by protein kinase B might participate in this effect. Protein kinase B phosphorylated recombinant bacterially expressed AMP-activated protein kinase heterotrimers at Ser(485) of the alpha1-subunits. In perfused rat hearts, phosphorylation of the alpha1/alpha2 AMP-activated protein kinase subunits on Ser(485)/Ser(491) was increased by insulin and insulin pretreatment decreased the phosphorylation of the alpha-subunits at Thr(172) in a subsequent ischemic episode. It is proposed that the effect of insulin to antagonize AMP-activated protein kinase activation involves a hierarchical mechanism whereby Ser(485)/Ser(491) phosphorylation by protein kinase B reduces subsequent phosphorylation of Thr(172) by LKB1 and the resulting activation of AMP-activated protein kinase.
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PMID:Insulin antagonizes ischemia-induced Thr172 phosphorylation of AMP-activated protein kinase alpha-subunits in heart via hierarchical phosphorylation of Ser485/491. 1634 11

Differential neurological outcomes due to prostaglandin E2 activating G-protein-coupled prostaglandin E (EP) receptors have been observed. Here, we investigated the action of the EP4/EP3 agonist 1-hydroxyPGE1 (1-OHPGE1) in modulating transient ischemic brain damage. C57BL/6 mice were pretreated 50 min before transient occlusion of the middle cerebral artery with an intraventricular injection of 1-OHPGE1 (0.1, 0.2, 2.0 nmol/0.2 microL). Brain damage 4 days after reperfusion, as estimated by infarct volume, was significantly reduced by more than 19% with 1-OHPGE1 in the two higher-dose groups (P < 0.05). To further address whether protection also was extended to neurons, primary mouse cultured neuronal cells were exposed to N-methyl-D-aspartate. Co-treatment with 1-OHPGE1 resulted in significant neuroprotection (P < 0.05). To better understand potential mechanisms of action and to test whether changes in cyclic adenosine monophosphate (cAMP) levels and downstream signaling would be neuroprotective, we measured cAMP levels in primary neuronal cells. Brief exposure to 1-OHPGE1 increased cAMP levels more than twofold and increased the phosphorylation of extracellular-regulated kinases at positions Thr-202/Tyr-204. In a separate cohort of animals, 1-OHPGE1 at all doses tested produced no significant effect on the physiological parameters of core body temperature, mean arterial pressure and relative cerebral blood flow observed following drug treatment. Together, these results suggest that modulation of PGE2 receptors that increase cAMP levels and activate extracellular-regulated kinases 1/2 caused by treatment with 1-OHPGE1 can be protective against neuronal injury induced by focal ischemia.
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PMID:1-hydroxyPGE reduces infarction volume in mouse transient cerebral ischemia. 1642 Apr 13

Testicular torsion followed by torsion repair induces an ischemia-reperfusion injury to the testis that can render the testis aspermatogenic. Previous results have demonstrated this loss of spermatogenesis to be the result of germ cell apoptosis induced by oxidative stress. The present work reports protein changes occurring in the mouse testis 24 hours after repair of a testicular torsion known to induce germ cell apoptosis and severe seminiferous impairment. Total proteins were extracted from sham-operated testes and testes having had 2-hour 720 degrees torsion 24 hours previously. Testicular proteins were separated by 2-dimensional electrophoresis and the resulting gel images were analyzed with image analysis software. Of the over 1100 proteins detected on the average gel, over 700 were consistently appearing in multiple gels, and those protein spot intensities were averaged within sham and torsion groups and compared between the 2 groups. Twenty-three proteins were consistently increased after torsion repair and 48 were decreased. Six proteins, 3 of which increased and 3 of which decreased after torsion repair, were identified by mass spectrometry. The 3 proteins that increased after torsion repair, beta2-tubulin and 2 isoforms of serum albumin, as well as the 3 proteins that decreased after torsion repair, vimentin, phosphoglycerate kinase, and t-complex protein 1beta, were for the most part associated with various aspects of cell stress responses. The number of proteins phosphorylated on tyrosine residues exceeded the number of proteins phosphorylated on serine/threonine residues, but among 6 stress-related proteins specifically examined for phosphorylation in sham testes and those examined after torsion repair, increases in threonine phosphorylation of c-Jun NH2 terminal kinase and activating transcription factor 2 were the most prominent. Knowing these proteins and the pathways to which they point will aid in the search for new therapies of oxidative stress in the testis.
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PMID:Testicular torsion alters the presence of specific proteins in the mouse testis as well as the phosphorylation status of specific proteins. 1647 26

Apoptosis repressor with a CARD domain (ARC) has been demonstrated to protect heart cells against ischemia/reperfusion (I/R) injury. In this study, we investigated the mechanism by which ARC protects heart cells against oxidative stress. We monitored the extent of apoptosis and activity of multiple components of the intrinsic apoptotic pathway in rat cardiac myoblast cell line H9c2 with either reduced or increased expression of ARC during oxidative stress. Overexpression of ARC-inhibited oxidative stress-induced caspase-2/3 activation, cytochrome c release, and translocation of Bax to mitochondria. Furthermore, phosphorylation of ARC at threonine 149 was found to be critical to its function. ARC containing a T149A mutation failed to translocate to mitochondria, did not inhibit caspase-2 activation, and had a dominant negative effect against the protective effect of endogenous ARC during oxidative stress. In addition, wild-type ARC but not the T149A mutant inhibited cell death induced by overexpression of caspase-2. Using a yeast two-hybrid (YTH) screening approach and co-immunoprecipitation (Co-IP), we found that protein phosphatase 2C (PP2C) interacted with ARC and that PP2C mediated-dephosphorylation of ARC inhibited its anti-apoptotic activity. Eliminating either the N-terminal CARD domain or the C-terminal P/E domain also abolished the anti-apoptotic function of ARC, suggesting that full-length ARC is required for its apoptotic inhibition. These results indicate that ARC plays an important role in protection of H9c2 cells against oxidative stress-induced apoptosis by phosphorylation-dependent suppression of the mitochondria-mediated intrinsic pathway, partially initiated through the activation of caspase-2.
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PMID:ARC protects rat cardiomyocytes against oxidative stress through inhibition of caspase-2 mediated mitochondrial pathway. 1663 14

AMP-activated protein kinase (AMPK) plays a key role in modulating cellular metabolic processes. AMPK, a serine-threonine kinase, is a heterotrimeric complex of catalytic alpha-subunits and regulatory beta- and gamma-subunits with multiple isoforms. Mutations in the cardiac gamma(2)-isoform have been associated with hypertrophic cardiomyopathy and pre-excitation syndromes. However, physiological regulation of AMPK complexes containing different subunit isoforms is not well defined and is important for an understanding of the function of this signaling pathway in the intact heart. We evaluated the kinase activity associated with heart AMPK complexes containing specific alpha- and gamma-subunit isoforms of AMPK in an in vivo rat model of regional ischemia. Left coronary artery occlusion activated the immunoprecipitated alpha(1)-isoform (6-fold, P < 0.01) and alpha(2)-isoform (9-fold, P < 0.01) in the ischemic left ventricle compared with sham controls. The degree of alpha-subunit activation depended on the extent of ischemia and paralleled echocardiographic contractile dysfunction. The regulatory gamma(1)- and gamma(2)-isoforms were expressed in the heart. The gamma(1)- and gamma(2)-isoforms coimmunoprecipitated with alpha(1)- and alpha(2)-isoforms in proportion to alpha-subunit content. gamma(1)-Isoform immunocomplexes accounted for 70% of AMPK activity and AMPK phosphorylation (Thr(172)) in hearts. Ischemia similarly increased AMPK activity associated with the gamma(1)- and gamma(2)-isoform complexes threefold (P < 0.01 for each). Thus AMPK catalytic alpha(1)- and alpha(2)-isoforms are activated by regional ischemia in vivo in the heart, irrespective of the regulatory gamma(1)- or gamma(2)-isoforms to which they are complexed. Despite the pathophysiological importance of gamma(2)-isoform mutations, gamma(1)-isoform complexes account for most of the AMPK activity in the ischemic heart.
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PMID:Activation of AMPK alpha- and gamma-isoform complexes in the intact ischemic rat heart. 1664 75

In this study, we examined the phosphorylation of ASK1, Akt and PTEN and the effects of sodium orthovanadate on these signal proteins during ischemia. Transient (15 min) brain ischemia was induced by the four-vessel occlusion in Sprague-Dawley rats. The following results were observed: (1) the decreased tyrosine phosphorylation of PTEN and the decreased serine phosphorylation of Akt induced by ischemia were suppressed by sodium orthovanadate, respectively. (2) The phosphorylation of ASK1 at serine 83 was decreased and the phosphorylation of ASK1 at threonine 845 was increased during ischemia. Sodium orthovanadate could alter the phosphorylation status of ASK1 at serine 83 and threonine 845 induced by ischemia. However, LY294002 could reverse the effect of sodium orthovanadate on the phosphorylation of ASK1 at threonine 845, namely, sodium orthovanadate inhibited ASK1 through the PI3-K/Akt-dependent pathway. Taken together, we concluded that sodium orthovanadate could increase the tyrosine posphorylation of PTEN and further inhibit the activation of ASK1 via activating Akt during cerebral ischemia.
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PMID:Down-regulation of PTEN by sodium orthovanadate inhibits ASK1 activation via PI3-K/Akt during cerebral ischemia in rat hippocampus. 1676 4

Rho-kinase is a serine threonine kinase that increases vasomotor tone via its effects on both endothelium and smooth muscle. Rho-kinase inhibition reduces cerebral infarct size in wild type, but not endothelial nitric oxide synthase deficient (eNOS-/-) mice. The mechanism may be related to Rho-kinase activation under hypoxic/ischemic conditions and impaired vasodilation because of downregulation of eNOS activity. To further implicate Rho-kinase in impaired vascular relaxation during hypoxia/ischemia, we exposed isolated vessels from rat and mouse to 60 mins of hypoxia, and showed that hypoxia reversibly abolished acetylcholine-induced eNOS-dependent relaxation, and that Rho-kinase inhibitor hydroxyfasudil partially preserved this relaxation during hypoxia. We, therefore, hypothesized that if hypoxia-induced Rho-kinase activation acutely impairs vasodilation in ischemic cortex, in vivo, then Rho-kinase inhibitors would acutely augment cerebral blood flow (CBF) as a mechanism by which they reduce infarct size. To test this, we studied the acute cerebral hemodynamic effects of Rho-kinase inhibitors in ischemic core and penumbra during distal middle cerebral artery occlusion (dMCAO) in wild-type and eNOS-/- mice using laser speckle flowmetry. When administered 60 mins before or immediately after dMCAO, Rho-kinase inhibitors hydroxyfasudil and Y-27632 reduced the area of severely ischemic cortex. However, hydroxyfasudil did not reduce the area of CBF deficit in eNOS-/- mice, suggesting that its effect on CBF within the ischemic cortex is primarily endothelium-dependent, and not mediated by its direct vasodilator effect on vascular smooth muscle. Our results suggest that Rho-kinase negatively regulates eNOS activity in acutely ischemic brain, thereby worsening the CBF deficit. Therefore, rapid nontranscriptional upregulation of eNOS activity by small molecule inhibitors of Rho-kinase may be a viable therapeutic approach in acute stroke.
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PMID:Rho-kinase inhibition acutely augments blood flow in focal cerebral ischemia via endothelial mechanisms. 1703 91

Cerebral ischemia and reperfusion induces rapid accumulation of oxidative DNA lesions in the brain, which, if not repaired promptly, may trigger cell death. The base-excision repair (BER) pathway is the main mechanism employed by neurons to repair various types of oxidative DNA damage. Recent studies have suggested that the cellular activity of BER is highly regulated (up- or down-regulated) after ischemic brain injury, and this regulation may contribute to the outcome of cell injury. The mechanism through which cellular BER is regulated in response to neuronal injury is currently poorly understood. In the present study, we have examined BER regulation in the rat model of focal ischemic brain injury induced by 2 hr of middle cerebral artery occlusion and 0-72 hr of reperfusion. As determined using cerebral nuclear extracts, focal ischemia resulted in a marked reduction in BER activities, including the overall BER activity, AP endonuclease activity and DNA polymerase-beta activity, indicating functional impairment of the BER pathway. BER reduction occurred as early as 0.5 hr after the onset of reperfusion. Thereafter, BER activity failed to recover, and there were persistent accumulations of apurinic/apyrimidinic abasic sites and DNA single-strand breaks in ischemic tissues. The reduction in BER during the early reperfusion phase (less than 6 hr) was not accompanied by any alterations in the levels of essential BER enzymes in brain extracts. However, increased serine- and threonine-specific phosphorylation was detected for both AP endonuclease and DNA polymerase-beta after ischemia, with the time course of serine phosphorylation closely correlated to that of changes in BER activity. Furthermore, dephosphorylation of nuclear extracts with alkaline phosphatase largely restored AP endonuclease and DNA polymerase-beta activities. Taking advantage of the neuroprotective effect of mild hypothermia (33 degrees C), which was induced in the brain during the first 2 hr of reperfusion, we found that the post-ischemic suppression of BER activity is a reversible event. Hypothermic treatment diminished the serine-specific phosphorylation of AP endonuclease and DNA polymerase-beta, promoted BER activities, and attenuated the levels of oxidative DNA lesions after ischemia. These results suggest that the functional impairment of the BER pathway after severe focal cerebral ischemia is due to the loss-of-function post-translational modifications of repair enzymes. Further investigations elucidating the precise mechanism underlying the post-translational regulation of BER enzymes may lead to novel therapeutic strategies for cerebral ischemia.
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PMID:Impaired DNA repair via the base-excision repair pathway after focal ischemic brain injury: a protein phosphorylation-dependent mechanism reversed by hypothermic neuroprotection. 1712 26

Increases in reactive oxygen species and mis-regulation of calcium homeostasis are associated with various physiological conditions and disease states including aging, ischemia, exposure to drugs of abuse, and neurodegenerative diseases. In aged animals, this is accompanied by a reduction in oxidative repair mechanisms resulting in increased methionine oxidation of the calcium signaling protein calmodulin in the brain. Here, we show that oxidation of calmodulin results in an inability to: (1) activate CaMKII; (2) support Thr(286) autophosphorylation of CaMKII; (3) prevent Thr(305/6) autophosphorylation of CaMKII; (4) support binding of CaMKII to the NR2B subunit of the NMDA receptor; and (5) compete with alpha-actinin for binding to CaMKII. Moreover, oxidized calmodulin does not efficiently bind calcium/calmodulin-dependent protein kinase II (CaMKII) in rat brain lysates or in vitro. These observations contrast from past experiments performed with oxidized calmodulin and the plasma membrane calcium ATPase, where oxidized calmodulin binds to, and partially activates the PMCA. When taken together, these data suggest that oxidative stress may perturb neuronal and cardiac function via a decreased ability of oxidized calmodulin to bind, activate, and regulate the interactions of CaMKII.
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PMID:Oxidation of calmodulin alters activation and regulation of CaMKII. 1734 27


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