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)

To mimic the effect of ischemia on the integrity of airway epithelium and expression of cystic fibrosis transmembrane conductance regulator (CFTR), we induced an ATP depletion of the respiratory epithelium from upper airway cells (nasal tissue) and human bronchial epithelial 16HBE14o- cell line. Histological analysis showed that 2 h of ATP depletion led to a loss of the epithelium integrity at the interface between basal cells and columnar cells. The expression of connexin 43 (Cx43, subunit of the gap junctions) and desmoplakins 1 and 2 (DPs 1 and 2, major components of the desmosomes) proteins was inhibited. After 90 min of ATP depletion, a significant decrease of the transepithelial resistance (25%) was observed but was reversible. Similar results were obtained with the 16HBE14o- human bronchial epithelial cell line. ATP depletion led to actin filaments depolymerization. The expression of the mature CFTR (170 kDa) and fodrin proteins at the apical domain of the ciliated cells was down-regulated. The steady-state levels of CFTR, Cx43, DPs 1 and 2 mRNAs, semiquantified by RT-polymerase chain reaction kinetics, remained constant throughout ATP depletion in nasal tissue as in the homogeneous cell population of 16HBE14o- human bronchial epithelial cell line. This suggests that the down-regulation of these proteins might be posttranscriptional. The intercellular diffusion through gap junctions of Lucifer dye was completely inhibited after 90 min of ATP depletion but was reversible. The volume-dependent and the cAMP-dependent chloride secretion were inhibited in a nonreversible way. Taken together, these results suggest that an ATP depletion in human airway epithelium, mimicking ischemia, may induce a marked alteration in the junctional complexes and cytoskeleton structure concomitantly with a loss of apical CFTR expression and chloride secretion function.
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PMID:ATP depletion induces a loss of respiratory epithelium functional integrity and down-regulates CFTR (cystic fibrosis transmembrane conductance regulator) expression. 934 29

Gap junctions are conductive channels that connect the interiors of coupled cells. In the hippocampus, GABA-containing hippocampal interneurons are interconnected by gap junctions, which mediate electrical coupling and synchronous firing and thereby promote inhibitory transmission. The present study was undertaken to examine the hypothesis that the gap junctional proteins connexin 32 (Cx32; expressed by oligodendrocytes, interneurons, or both), Cx36 (expressed by interneurons), and Cx43 (expressed by astrocytes) play a role in defining cell-specific patterns of neuronal death in hippocampus after global ischemia in mice. Global ischemia did not significantly alter Cx32 and Cx36 mRNA expression and slightly increased Cx43 mRNA expression in the vulnerable CA1, as assessed by Northern blot analysis and in situ hybridization. Global ischemia induced a selective increase in Cx32 and Cx36 but not Cx43 protein abundance in CA1 before onset of neuronal death, as assessed by Western blot analysis. The increase in Cx32 and Cx36 expression was intense and specific to parvalbumin-positive inhibitory interneurons of CA1, as assessed by double immunofluorescence. Protein abundance was unchanged in CA3 and dentate gyrus. The finding of increase in connexin protein without increase in mRNA suggests regulation of Cx32 and Cx36 expression at the translational or post-translational level. Cx32(Y/-) null mice exhibited enhanced vulnerability to brief ischemic insults, consistent with a role for Cx32 gap junctions in neuronal survival. These findings suggest that Cx32 and Cx36 gap junctions may contribute to the survival and resistance of GABAergic interneurons, thereby defining cell-specific patterns of global ischemia-induced neuronal death.
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PMID:Global ischemia-induced increases in the gap junctional proteins connexin 32 (Cx32) and Cx36 in hippocampus and enhanced vulnerability of Cx32 knock-out mice. 1156 43

Rat cortical astrocytes in pure culture are functionally coupled to neighboring cells via connexin (Cx) 43 gap junctions under ordinary conditions. Small fluorescent molecules such as Lucifer yellow (LY) pass between cell interiors via gap junctions, but do not enter the cells when externally applied. Subjecting rat and mouse cortical astrocytes to "chemical ischemia" by inhibition of glycolytic and oxidative metabolism induced permeabilization of cells to Lucifer yellow and ethidium bromide before loss of membrane integrity determined by dextran uptake and lactate dehydrogenase release. The gap junction blockers octanol and 18alpha-glycyrrhetinic acid markedly reduced dye uptake, suggesting that uptake was mediated by opening of unapposed hemichannels. Extracellular La(3+) also reduced dye uptake and delayed cell death. The purinergic blocker, oxidized ATP, was ineffective. Astrocytes isolated from mice with targeted deletion of the Cx43 coding DNA exhibited greatly reduced dye coupling and ischemia-induced dye uptake, evidence that dye uptake is mediated by Cx43 hemichannels. Dye coupling was reduced but not blocked by metabolic inhibition. Blockade of lipoxygenases or treatment with free radical scavengers reduced dye uptake by rat astrocytes, suggesting a role for arachidonic acid byproducts in hemichannel opening. Furthermore, permeabilization was accompanied by reduction in ATP levels and dephosphorylation of Cx43. Although hemichannel opening would tend to collapse electrochemical and metabolic gradients across the plasma membrane of dying cells, healthy cells might rescue dying cells by transfer of ions and essential metabolites via Cx43 gap junctions. Alternatively, dying astrocytes might compromise the health of neighboring cells via Cx43 gap junctions, thereby promoting the propagation of cell death.
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PMID:Metabolic inhibition induces opening of unapposed connexin 43 gap junction hemichannels and reduces gap junctional communication in cortical astrocytes in culture. 1175 80

In cardiac myocytes of new-born rats, the degree of intercellular communication through gap junctional channels closely depends on the metabolic state of the cells. In contrast, in stably transfected HeLa cells expressing rat cardiac connexin43 (Cx43, the main channel-forming protein present in ventricular myocytes), a major part of junctional communication persisted in ATP-depleted conditions, in the presence of a metabolic inhibitor (KCN) or of a broad spectrum inhibitor of protein kinases (H7). However, another metabolic inhibitor, antimycin A, which like cyanide inhibits electron transfer in the respiratory chain, totally interrupted cell-to-cell communication between Cx43-HeLa cells, even in whole-cell conditions, when ATP (5 mM) was present. Antimycin A caused a modest increase in cytosolic calcium concentration; however, junctional uncoupling still occurred when this rise was prevented. Conditions of ischemic insult (e.g. ischemia or chemical hypoxia) frequently cause the activation of protein kinases, particularly of Src and MAP kinases, and such activations are known to markedly disrupt gap junctional communication. Antimycin-induced junctional uncoupling occurred even in the presence of inhibitors of these kinases. Antimycin A appears able to cause junctional uncoupling either through the ATP depletion it induces as a metabolic poison or via a direct action on gap junction constituents.
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PMID:The metabolic inhibitor antimycin A can disrupt cell-to-cell communication by an ATP- and Ca(2+)-independent mechanism. 1450 27

Recent studies have demonstrated that electrical uncoupling at gap junctions during ischemia is associated with cardiac Connexin-43 (Cx43) dephosphorylation. Whether oxidative stress is involved in this phenomenon still remains unclear. In the present study, we examined the influence of selenium intake on reperfusion-induced Cx43 dephosphorylation. Male Wistar rats were fed a diet containing either 0.05 mg/kg (Low-Se, n = 13) or 1.5 mg/kg (High-Se, n = 11) selenium for 8 weeks. At the end of this diet, hearts were isolated and subjected to 10 min regional ischemia followed by 10 min reperfusion. The level of dephosphorylated Cx43 was determined in tissue samples from ischemic/reperfused and non-ischemic regions of the hearts. At the end of the experiemental diet, the activity of the antioxidant enzyme glutathione peroxidase (GSH-Px) was increased in high-Se hearts compared with low-Se hearts (+ 13%; p < 0.05). After ischemia/reperfusion, in low-Se hearts, Cx43 dephosphorylation appeared significantly increased in the left ventricle compared to the non-ischemic right ventricle (+ 149%; p < 0.05). The high-Se diet significantly reduced Cx43 dephosphorylation in the left ventricle (p < 0.05 vs. low-Se diet). In conclusion, our results suggest that oxidative stress may be involved in Cx43 dephosphorylation during myocardial ischemia/reperfusion, thereby contributing to arrhythmogenesis.
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PMID:Selenium status as determinant of connexin-43 dephosphorylation in ex vivo ischemic/reperfused rat myocardium. 1624 Jun 71

The carboxyl-terminal domain of connexin43 (Cx43CT) is involved in various intra- and intermolecular interactions that regulate gap junctions. Here, we used phage display to identify novel peptidic sequences that bind Cx43CT and modify Cx43 regulation. We found that Cx43CT binds preferentially to peptides containing a sequence RXP, where X represents any amino acid and R and P correspond to the amino acids arginine and proline, respectively. A biased "RXP library" led to the identification of a peptide (dubbed "RXP-E") that bound Cx43CT with high affinity. Nuclear magnetic resonance data showed RXP-E-induced shifts in the resonance peaks of residues 343 to 346 and 376 to 379 of Cx43CT. Patch-clamp studies revealed that RXP-E partially prevented octanol-induced and acidification-induced uncoupling in Cx43-expressing cells. Moreover, RXP-E increased mean open time of Cx43 channels. The full effect of RXP-E was dependent on the integrity of the CT domain. These data suggest that RXP-based peptides could serve as tools to help determine the role of Cx43 as a regulator of function in conditions such as ischemia-induced arrhythmias.
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PMID:Identification of a novel peptide that interferes with the chemical regulation of connexin43. 1669 Aug 83

Coordinated contractile activation of the heart and resistance to ischemic injury depend, in part, on the intercellular communication mediated by Cx43-composed gap junctions. The function of these junctions is regulated at multiple levels (assembly to degradation) through phosphorylation at specific sites in the carboxyl terminus (CT) of the Cx43 protein. We show here that the selective permeability of Cx43 junctions is regulated through protein kinase C (PKC)-dependent phosphorylation at serine 368 (S368). Selective permeability was measured in several Cx43-expressing cell lines as the rate constant for intercellular dye diffusion relative to junctional conductance. The selective permeability of Cx43 junctions under control conditions was quite variable, as was the open-state behavior of the comprising channels. Coexpression of the CT of Cx43 as a distinct protein, treatment with a PKC inhibitor, or mutation of S368 to alanine, all reduced (or eliminated) phosphorylation at S368, reduced the incidence of 55- to 70-pS channels, and reduced by 10-fold the selective permeability of the junctions for a small cationic dye. Because PKC activation during preischemic conditioning is cardioprotective during subsequent ischemic episodes, we examined no-flow, ischemic hearts for Cx43 phosphorylated at S368 (pS368). Consistent with early activation of PKC, pS368-Cx43 was increased in ischemic hearts; despite extensive lateralization of total Cx43, pS368-Cx43 remained predominantly at intercalated disks. Our data suggest that the selectivity of gap junction channels at intercalated disks is increased early in ischemia.
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PMID:Selectivity of connexin 43 channels is regulated through protein kinase C-dependent phosphorylation. 1670 97

This study is to explore whether the protective effect of resveratrol on ischemia-reperfusion injury is correlated with the structural and functional association between M3 receptor (M3 subtype of muscarinic acetylcholine receptor) and Cx43 (connexin 43 gap junction proteins). Immunoprecipitation, immunoblotting and immunofluorescence were applied to investigate whether resveratrol has an effect on structural and functional association between M3 and Cx43. The effect of resveratrol on electrocardiogram Lead II ex vivo in rats, SOD (superoxide dismutase) activity and MDA (malondialdehyde) content was also observed in order to evaluate the protective effect of resveratrol on ischemia-reperfusion injury. Resveratrol could restore the structural and functional association between M3 receptor and Cx43 gap junction proteins that was partially destroyed under ischemia-reperfusion injury. The phosphorylation and spatial distribution disturbances in Cx43 expression caused by ischemia-reperfusion injury were also restored. Also, the QRS duration, SOD activity and MDA content were restored. Resveratrol could restore the structural and functional association between M3 receptor and Cx43 gap junction proteins.
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PMID:[Resveratrol restored the structural and functional association between M3 receptor and connexin 43 gap junction proteins in ischemia-reperfusion injury of isolated rat heart]. 1752 Aug 2

Phosphorylation at unspecified sites is known to regulate the life cycle (assembly, gating, and turnover) of the gap junction protein, Cx43. In this paper, we show that Cx43 is phosphorylated on S365 in cultured cells and heart tissue. Nuclear magnetic resonance structural studies of the C-terminal region of Cx43 with an S365D mutation indicate that it forms a different stable conformation than unphosphorylated wild-type Cx43. Immunolabeling with an antibody specific for Cx43 phosphorylated at S365 shows staining on gap junction structures in heart tissue that is lost upon hypoxia when Cx43 is no longer specifically localized to the intercalated disk. Efficient phosphorylation at S368, an important Cx43 channel regulatory event that increases during ischemia or PKC activation, depends on S365 being unphosphorylated. Thus, phosphorylation at S365 can serve a "gatekeeper" function that may represent a mechanism to protect cells from ischemia and phorbol ester-induced down-regulation of channel conductance.
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PMID:Phosphorylation at S365 is a gatekeeper event that changes the structure of Cx43 and prevents down-regulation by PKC. 1808 22

In normal brain, neurons, astrocytes, and oligodendrocytes, the most abundant and active cells express pannexins and connexins, protein subunits of two families forming membrane channels. Most available evidence indicates that in mammals endogenously expressed pannexins form only hemichannels and connexins form both gap junction channels and hemichannels. Whereas gap junction channels connect the cytoplasm of contacting cells and coordinate electric and metabolic activity, hemichannels communicate the intra- and extracellular compartments and serve as a diffusional pathway for ions and small molecules. A subthreshold stimulation by acute pathological threatening conditions (e.g., global ischemia subthreshold for cell death) enhances neuronal Cx36 and glial Cx43 hemichannel activity, favoring ATP release and generation of preconditioning. If the stimulus is sufficiently deleterious, microglia become overactivated and release bioactive molecules that increase the activity of hemichannels and reduce gap junctional communication in astroglial networks, depriving neurons of astrocytic protective functions, and further reducing neuronal viability. Continuous glial activation triggered by low levels of anomalous proteins expressed in several neurodegenerative diseases induce glial hemichannel and gap junction channel disorders similar to those of acute inflammatory responses triggered by ischemia or infectious diseases. These changes are likely to occur in diverse cell types of the CNS and contribute to neurodegeneration during inflammatory process.
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PMID:Modulation of brain hemichannels and gap junction channels by pro-inflammatory agents and their possible role in neurodegeneration. 1881 86


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