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)

Connexin-protein interactions are believed to be critical for the regulation of gap junctional intercellular communication and for the function of gap junctions formed by these complexes. We have primarily used immunoprecipitation strategies to investigate whether connexin43 binds to selected signaling and cytoskeletal proteins and whether connexin43-protein binding is altered in cultured astrocytes exposed to chemical ischemia/hypoxia, a treatment that resembles ischemia in vivo. Chemical ischemia/hypoxia induced marked dephosphorylation of connexin43, which was accompanied by increased association of connexin43 with c-Src, ERK1/2, and mitogen-activated protein kinase phosphatase-1 and by decreased association between connexin43 and beta-actin. Moreover, we found that endogenous c-Src in normal astrocytes exists primarily in the Triton X-100-soluble membrane fraction, distinct from the Triton-insoluble fraction, which contains gap junctions. After chemical ischemia/hypoxia, c-Src appeared in the Triton-insoluble fraction and was co-immunoprecipitated with connexin43, suggesting that chemical ischemia/hypoxia induced translocation of c-Src to the Triton-insoluble fraction and association with connexin43. Furthermore, the "dephosphorylated" form of connexin43 was immunoprecipitated by a phosphotyrosine antibody, suggesting tyrosine phosphorylation of connexin43 by c-Src. In addition, the association between connexin43 and c-Src was blocked by inhibition of connexin43 dephosphorylation, suggesting that the interaction between connexin43 and c-Src can be regulated by alterations in the phosphorylation state of connexin43. These results identify new binding partners for connexin43 and demonstrate that interactions between connexin43 and protein kinases and phosphatases are dynamically altered as a consequence of connexin43 phosphorylation.
 ...
PMID:Regulation of connexin43-protein binding in astrocytes in response to chemical ischemia/hypoxia. 1561 29

Focal adhesion kinase (FAK) is a 125 kDa protein tyrosine kinase (PTK) associated with focal adhesion in many cells, which plays a major role in the integrity of cytoskeletal structure. Reactive oxygen species produced during ischemia and reperfusion injury has been found to be an important mediator of signal transduction process. We found that low dose H2O2 induced increased FAK production in pulmonary microvascular endothelial cells, which could be blocked by cycloheximide (CHX), a protein synthesis inhibitor. Pulmonary endothelial cells were cultured on DMEM medium till 100% confluent. H2O2 was added at 100 uM for 30 min. The cells were collected and lysed, then immuno-blotted with anti-FAK antibody. After 30 min treatment, we found a 30%+/-6% (N=5) increase of FAK in H2O2 treated endothelial cells. This increase could be blocked by pretreatment of cells with CHX at 5 ug/ml for 60 min. In both groups, increased phosphorylation of ERK was observed. Immuno-fluorescence revealed increased staining of FAK in the peri-nuclear region of the H2O2 treated endothelial cells. These findings suggest that H2O2 activated MAP kinase pathway leading to increased FAK production at the protein level. FAK is a 125 kDa PTK associated with focal adhesion in many cells, and it plays a major role in the integrity of cytoskeletal structure. FAK is discretely localized to focal adhesions via its C-terminal focal adhesion-targeting (FAT) sequence. FAK is regulated by integrin-dependent cell adhesion and can control tyrosine phosphorylation of downstream substrates, like paxillin. The reactive oxygen species produced during ischemia and reperfusion injury has been found to be an important mediator of the signal transduction process. Although the signaling pathways leading to hydrogen peroxide induced endothelial monolayer permeability remain ambiguous, cytoskeletal proteins are known to be essential for maintaining endothelial integrity and regulating solute flux through the monolayer. Recent evidence has shown that H2O2 stimulates cytoskeleton reorganization, cell growth/proliferation, and DNA synthesis in various cells. In our previous study, we found a significantly increased amount of FAK in endothelial cells treated with low doses of H2O2. Mitogen-activated protein (MAP) kinases are a group of 30- to 110-kDa serine/threonine kinases. MAPKs belong to the group of kinases that are rapidly activated in response to growth factor stimulation. This family of MAPKs includes ERK, and ERK2. The activated MAPK can translocate to the nucleus where it can regulate transcription factors. Activation of p44 and p42 extracellular signal-regulated protein kinases (ERK1 and ERK2) is an important step in the cascade leading to cell growth and proliferation. In order to determine the mechanism of increased FAK production, we investigated the relationship of FAK production and ERK activation.
 ...
PMID:Reactive oxygen species increased focal adhesion kinase production in pulmonary microvascular endothelial cells. 1563 12

Reperfusion injury is a complex process involving several cell types (endothelial cells, neutrophils, and cardiomyocytes), soluble proinflammatory mediators, oxidants, ionic and metabolic dyshomeostasis, and cellular and molecular signals. These participants in the pathobiology of reperfusion injury are not mutually exclusive. Some of these events take place during the very early moments of reperfusion, while others, seemingly triggered in part by the early events, are activated within a later timeframe. Postconditioning is a series of brief mechanical interruptions of reperfusion following a specific prescribed algorithm applied at the very onset of reperfusion. This algorithm lasts only from 1 to 3 minutes depending on species. Although associated with re-occlusion of the coronary artery or re-imposition of hypoxia in cell culture, the reference to ischemia has been dropped. Postconditioning has been observed to reduce infarct size and apoptosis as the "end games" in myocardial therapeutics; salvage of infarct size was similar to that achieved by the gold standard of protection, ischemic preconditioning. The cardioprotection was also associated with a reduction in: endothelial cell activation and dysfunction, tissue superoxide anion generation, neutrophil activation and accumulation in reperfused myocardium, microvascular injury, tissue edema, intracellular and mitochondrial calcium accumulation. Postconditioning sets in motion triggers and signals that are functionally related to reduced cell death. Adenosine has been implicated in the cardioprotection of postconditioning, as has e-NOS, nitric oxide and guanylyl cyclase, opening of K(ATP) channels and closing of the mitochondrial permeability transition pore. Cardioprotection by postconditioning has also been associated with the activation of intracellular survival pathways such as ERK1/2 and PI3 kinase - Akt pathways. Other pathways have yet to be identified. Although many of the pathways involved in postconditioning have also been identified in ischemic preconditioning, some may not be involved in preconditioning (ERK1/2). The timing of action of these pathways and other mediators of protection in postconditioning differs from that of preconditioning. In contrast to preconditioning, which requires a foreknowledge of the ischemic event, postconditioning can be applied at the onset of reperfusion at the point of clinical service, i.e. angioplasty, cardiac surgery, transplantation.
 ...
PMID:Postconditioning--A new link in nature's armor against myocardial ischemia-reperfusion injury. 1579 29

We recently reported that Na+/H+ exchanger isoform 1 (NHE1) activity in astrocytes is stimulated and leads to intracellular Na+ loading after oxygen and glucose deprivation (OGD). However, the underlying mechanisms for this stimulation of NHE1 activity and its impact on astrocyte function are unknown. In the present study, we investigated the role of the ERK1/2 pathway in NHE1 activation. NHE1 activity was elevated by approximately 75% in NHE1+/+ astrocytes after 2-h OGD and 1-h reoxygenation (REOX). The OGD/REOX-mediated stimulation of NHE1 was partially blocked by 30 microM PD-98059. Increased expression of phosphorylated ERK1/2 was detected in NHE1+/+ astrocytes after OGD/REOX. Moreover, stimulation of NHE1 activity disrupted not only Na+ but also Ca2+ homeostasis via reverse-mode operation of Na+/Ca2+ exchange. OGD/REOX led to a 103% increase in intracellular Ca2+ concentration ([Ca2+]i) in NHE1+/+ astrocytes in the presence of thapsigargin. Inhibition of NHE1 activity with the NHE1 inhibitor HOE-642 decreased OGD/REOX-induced elevation of [Ca2+]i by 73%. To further investigate changes of Ca2+ signaling, bradykinin-mediated Ca2+ release was evaluated. Bradykinin-mediated intracellular Ca2+ transient in NHE1+/+ astrocytes was increased by approximately 84% after OGD/REOX. However, in NHE1-/- astrocytes or NHE1+/+ astrocytes treated with HOE-642, the bradykinin-induced Ca2+ release was increased by only approximately 34%. Inhibition of the reverse mode of Na+/Ca2+ exchange abolished OGD/REOX-mediated Ca2+ rise. Together, our data suggest that ERK1/2 is involved in activation of NHE1 in astrocytes after in vitro ischemia. NHE1-mediated Na+ accumulation subsequently alters Ca2+ homeostasis via Na+/Ca2+ exchange.
 ...
PMID:Stimulation of astrocyte Na+/H+ exchange activity in response to in vitro ischemia depends in part on activation of ERK1/2. 1590

Mitogen-activated protein kinase (MAPK) 3/MAPK1 (also known as ERK1/ERK2) plays an important role in the signal transduction pathways. To our knowledge, however, its role in the development of testicular ischemia-reperfusion injury has not yet been investigated. Therefore, we studied the pattern of MAPK3/MAPK1 activation in a experimental model of testicular ischemia-reperfusion injury. We also investigated MAPK8 to understand whether an association exists between these two MAPKs. Adult male Sprague-Dawley rats were subjected to 1 h of testicular ischemia followed by 24 h of reperfusion or to a sham testicular ischemia-reperfusion. Animals were randomized to receive PD98059, which is an inhibitor of MAPK3/MAPK1 (10 mg/kg i.p. administered immediately after detorsion), or its vehicle. The time course of MAPK3/MAPK1, MAPK8, and tumor necrosis factor (TNF; also known as TNF alpha) expression and a histological examination in both the ischemic-reperfused testis and the contralateral one were performed. In both testes, MAPK3/MAPK1 and MAPK8 expression appeared following 10 min of reperfusion and reached their highest activation after 30 min. The MAPK levels slowly decreased, and no significant expression of either kinase was observed following 2 h of reperfusion. Expression of TNF was evident after 1 h of reperfusion and reached its maximum increase after 3 h. PD98059 blunted MAPK3/MAPK1 and MAPK8, reduced TNF expression, and improved the testicular damage caused by ischemia-reperfusion injury in both testes. These data emphasize that MAPK3/MAPK1 has a role in testicular damage and that its blockade might have a future therapeutic role for the management of patients with unilateral testicular torsion.
 ...
PMID:Evidence for a role of mitogen-activated protein kinase 3/mitogen-activated protein kinase in the development of testicular ischemia-reperfusion injury. 1594 43

Three subtypes of adenosine receptors (A(1), A(2A) and A(3) ARs) are functionally expressed in cardiomyocytes. Adenosine released during ischemia and ischemia/reperfusion plays a major role in cardioprotection. Phosphatidylinositol 3-kinase (PI-3K)/protein kinase B (PKB) and MEK/ERK1/2 pathways are involved in cell survival. Since the role of these pathways in AR-mediated preconditioning is poorly understood, we have investigated whether PI-3K/PKB and/or MEK1/ERK1/2 pathways are involved in AR-induced cardioprotection in neonatal rat cardiomyocytes. Cells were pre-treated (15 min) with adenosine (non-selective), CPA (A(1)), CGS 21680 (A(2A)) or Cl-IB-MECA (A(3)) before 4 h hypoxia (0.5% O(2)) and 18 h reoxygenation (HX4/R). HX4/R-induced increase in LDH release was significantly reduced by adenosine (70%), CPA (59%) and Cl-IB-MECA (46%). The MEK1 inhibitor PD 98059 suppressed the effects of adenosine, CPA, and Cl-IB-MECA on LDH release, whereas the PI-3K inhibitor wortmannin did not reverse this cardioprotection. Western blotting of phosphorylated ERK1/2 and PKB during HX4/R supported the involvement of ERK1/2 and not PKB in A(1) and A(3) agonist-mediated cardioprotection. In addition, adenosine, CPA and Cl-IB-MECA inhibited HX4/R-induced caspase 3 activity by 75%, 70% and 59%, respectively, and this inhibition was abolished by PD 98059. Interestingly, wortmannin inhibited by 66% the anti-apoptotic response triggered by Cl-IB-MECA but had no effect on adenosine or CPA-induced inhibition of caspase 3. CGS 21680 did not modify cell survival or caspase 3 activity. In conclusion, these data show that the preconditioning effect of adenosine requires A(1) and A(3) but not A(2A) ARs and involves an anti-apoptotic effect via MEK1/ERK1/2 pathway in neonatal rat cardiomyocytes. In addition, A(3)AR-induced preconditioning also involves a PI-3K dependent pathway.
 ...
PMID:Adenosine triggers preconditioning through MEK/ERK1/2 signalling pathway during hypoxia/reoxygenation in neonatal rat cardiomyocytes. 1600 18

In vivo, pathological conditions such as ischemia and ischemia/reperfusion are known to damage the blood-brain barrier (BBB) leading to the development of vasogenic brain edema. Using an in vitro model of the BBB, consisting of brain-derived microvascular endothelial cells (BMEC), it was demonstrated that hypoxia-induced paracellular permeability was strongly aggravated by reoxygenation (H/R), which was prevented by catalase suggesting that H2O2 is the main mediator of the reoxygenation effect. Therefore, mechanisms leading to H2O2-induced hyperpermeability were investigated. N-acetylcysteine and suramin and furthermore usage of a G protein antagonist inhibited H202 effects suggesting that activation of cell surface receptors coupled to G proteins may mediate signal initiation by H2O2. Further, H2O2 activated phospholipase C (PLC) and increased the intracellular Ca2+ release because U73122, TMB-8, and the calmodulin antagonist W7 inhibited H2O2-induced hyperpermeability. H2O2 did not activate protein kinase C (PKC), nitric-oxide synthase (NOS), and phosphatidyl-inositol-3 kinase (PI3-K/Akt). Inhibition of the extracellular signal-regulated kinase (ERK1/ERK2 or p44/42 MAPK), but not of the p38 and of the c-jun NH2-terminal kinase (JNK), inhibited hyperpermeability by H2O2 and H/R completely. Corresponding to H2O2- and H/R-induced permeability changes the phosphorylation of the p44/42 MAP kinase was inhibited by the specific MAP kinase inhibitor PD98059 and by TMB-8 and W7. Paracellular permeability changes by H2O2 correlated to changes of the localization of the tight junction (TJ) proteins occludin, zonula occludens 1 (ZO-1), and zonula occludens 2 (ZO-2) which were prevented by blocking the p44/p42 MAP kinase activation. Results suggest that H2O2 is the main inducer of H/R-induced permeability changes. The hyperpermeability is caused by activation of PLC via receptor activation leading to the intracellular release of Ca2+ followed by activation of the p44/42 MAP kinase and paracellular permeability changes mediated by changes of the localization of TJ proteins.
 ...
PMID:H2O2 induces paracellular permeability of porcine brain-derived microvascular endothelial cells by activation of the p44/42 MAP kinase pathway. 1610 12

Ischemic preconditioning (IPC) is thought to protect by activating survival kinases during reperfusion. We tested whether binding of adenosine receptors is also required during reperfusion and, if so, how long these receptors must be populated. Isolated rabbit hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. IPC reduced infarct size from 32.1 +/- 4.6% of the risk zone in control hearts to 7.3 +/- 3.6%. IPC protection was blocked by a 20-min pulse of the nonselective adenosine receptor blocker 8-(p-sulfophenyl)-theophylline when started either 5 min before or 10 min after the onset of reperfusion but not when started after 30 min of reperfusion. Protection was also blocked by either 8-cyclopentyl-1,3-dipropylxanthine, an adenosine A1-selective receptor antagonist, or MRS1754, an A2B-selective antagonist, but not by 8-(3-chlorostyryl)caffeine, an A2A-selective antagonist. Blockade of phosphatidylinositol 3-OH kinase (PI3K) with a 20-min pulse of wortmannin also aborted protection when started either 5 min before or 10 or 30 min after the onset of reperfusion but failed when started after 60 min of reflow. U-0126, an antagonist of MEK1/2 and therefore of ERK1/2, blocked protection when started 5 min before reperfusion but not when started after only 10 min of reperfusion. These studies reveal that A1 and/or A2B receptors initiate the protective signal transduction cascade during reperfusion. Although PI3K activity must continue long into the reperfusion phase, adenosine receptor occupancy is no longer needed by 30 min of reperfusion, and ERK activity is only required in the first few minutes of reperfusion.
 ...
PMID:Endogenous adenosine protects preconditioned heart during early minutes of reperfusion by activating Akt. 1615 3

Prostanoids in the central nervous system define an important linkage between blood pressure and hormonal responses to hypotension/ischemia. Prostaglandin endoperoxide synthase (PGHS)-2, the inducible isoform of this enzyme, is induced by cerebral hypoperfusion/ischemia. To investigate the mechanism of the PGHS-2 gene expression in response to cerebral hypoperfusion/ischemia in neurons, we used a cell culture model (human SK-N-AS cells) to mimic the oxygen and glucose deprivation (OGD) that usually results from ischemia. Whereas OGD stimulated robust increases in PGHS-2 mRNA abundance, neither oxygen nor glucose deprivation alone was effective. Our data demonstrated that induction of both PGHS-2 mRNA and protein reached peak levels ( approximately 10 fold) after 6 h OGD. This was partially blocked by the inhibition of mitogen-activated protein kinase (MAPK) p38, and was almost completely blocked by the inhibition of extracellular signal-related kinases 1/2 (ERK1/2 or p44/42), another MAPK. These results indicate that PGHS-2 gene expression is induced by oxygen and glucose deprivation synergistically in neurons, and this induction is mediated by one or more members of the MAPK family.
 ...
PMID:Neuronal prostaglandin endoperoxide synthase 2 responses to oxygen and glucose deprivation are mediated by mitogen-activated protein kinase ERK1/2. 1618 70

Apart from its hematopoietic function, erythropoietin (Epo) exerts neuroprotective functions in brain hypoxia and ischemia. To examine the mechanisms mediating Epo's neuroprotective activity in vivo, we made use of our transgenic mouse line tg21 that constitutively expresses human Epo in brain without inducing excessive erythrocytosis. We show that human Epo is expressed in tg21 brains and that cortical and striatal neurons carry the Epo receptor. After middle cerebral artery occlusion, human Epo potently protected brains of tg21 mice against ischemic injury, both when severe (90 min) and mild (30 min) ischemia was imposed. Histochemical studies revealed that Epo induced an activation of JAK-2, ERK-1/-2, and Akt pathways in the ischemic brain. This activation was associated with elevated Bcl-XL and decreased NO synthase-1 and -2 levels in neurons. Intracerebroventricular injections of selective inhibitors of ERK-1/-2 (PD98059) or Akt (wortmannin) pathways revealed that both ERK-1/-2 and Akt were required for Epo's neuroprotective function, antagonization of either pathway completely abolishing tissue protection. On the other hand, ERK-1/-2 and Akt blockade did not reverse the neuronal NO synthase-1/-2 inhibition, indicating that Epo down-regulates these NO synthases in an ERK-1/-2 and Akt independent manner. On the basis of our data, the dual activation of ERK-1/-2 and Akt is crucial for Epo's neuroprotective activity.
 ...
PMID:Brain-derived erythropoietin protects from focal cerebral ischemia by dual activation of ERK-1/-2 and Akt pathways. 1620 20


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>