Journal of molecular and cellular cardiology
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J. Mol. Cell. Cardiol. · Dec 2005
Trimetazidine inhibits mitochondrial permeability transition pore opening and prevents lethal ischemia-reperfusion injury.
Trimetazidine (TMZ) affects mitochondrial function during ischemia. Mitochondrial permeability transition is a pivotal event in cardiomyocyte death following acute ischemia. The aim of the present study was to determine whether the anti-ischemic agent TMZ might modulate mitochondrial permeability transition pore (mPTP) opening and limit lethal ischemia-reperfusion injury. ⋯ In controls, Ca(2+) load required for mPTP opening averaged 11 +/- 4 microM mg(-1) mitochondrial protein versus 116 +/- 6 in shams (P<0.0001). Pre-treatment by TMZ or PC attenuated this, with Ca(2+) loads averaging 45 +/- 4 and 46 +/- 4 microM mg(-1) mitochondrial proteins, respectively (P<0.005 versus C). These data suggest that TMZ inhibits mPTP opening and protects the rabbit heart from prolonged ischemia-reperfusion injury.
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J. Mol. Cell. Cardiol. · Oct 2005
Lysozyme binding to endocardial endothelium mediates myocardial depression by the nitric oxide guanosine 3',5' monophosphate pathway in sepsis.
Inflammatory mediators have been implicated as a cause of reversible myocardial depression in septic shock. We previously reported that the release of lysozyme-c (Lmz-S) from leukocytes from the spleen or other organs contributes to myocardial dysfunction in Escherichia coli septic shock in dogs by binding to a cardiac membrane glycoprotein. However, the mechanism by which Lzm-S causes this depression has not been elucidated. ⋯ A guanylyl cyclase inhibitor (ODQ) and a PKG inhibitor (Rp-8-Br-cGMP) also attenuated Lzm-S's depressant effect as did chemical denudation of the endocardial endothelium (EE) with Triton X-100 (0.5%). In EE tissue, we further showed that Lzm-S caused NO release with use of 4,5 diaminofluorescein, a fluorescent dye that binds to NO. The present study shows that the binding of Lzm-S to EE generates NO, and that NO then activates the myocardial guanosine 3',5' monophosphate pathway leading to cardiac depression in sepsis.
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J. Mol. Cell. Cardiol. · Jul 2005
A functional role of the C-terminal 42 amino acids of SUR2A and SUR2B in the physiology and pharmacology of cardiovascular ATP-sensitive K(+) channels.
The ATP-sensitive K(+) (K(ATP)) channel is composed of four pore-forming Kir6.2 subunits and four sulfonylurea receptors (SUR). Intracellular ATP inhibits K(ATP) channels through Kir6.2. SUR is an ABC protein bearing transmembrane domains and two nucleotide-binding domains (NBD1 and NBD2). ⋯ Therefore, C42 modulates the function of not only NBD2 which is close to C42 in a primary structure but NBD1 which is more than 630 amino acid N-terminal to C42. This raises the possibility that in the presence of nucleotides, NBD1 and NBD2 dimerize to induce the conformational change and that the dimerization enables C42 to gain access to both NBDs. Modulation of the nucleotide-NBD1 and -NBD2 interactions by C42 would determine the stability of the nucleotide-dependent dimer and thus, the physiological and pharmacological properties of K(ATP) channels.
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The sulfonylurea receptor SUR is an ATP binding cassette (ABC) protein of the ABCC/MRP family. Unlike other ABC proteins, it has no intrinsic transport function, neither active nor passive, but associates with the potassium channel proteins Kir6.1 or Kir6.2 to form the ATP-sensitive potassium (K(ATP)) channel. ⋯ It constitutes a major pharmaceutical target as it binds numerous drugs, K(ATP) channel openers and blockers, capable of up- or down-regulating channel activity. We here review current knowledge on the molecular basis of the interaction of classical K(ATP) channel openers (cromakalim, pinacidil, diazoxide) with SUR.
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J. Mol. Cell. Cardiol. · Dec 2004
ReviewHypoxic pulmonary vasoconstriction: redox regulation of O2-sensitive K+ channels by a mitochondrial O2-sensor in resistance artery smooth muscle cells.
Hypoxic pulmonary vasoconstriction (HPV) is a widely-conserved mechanism for matching ventilation and perfusion that optimizes systemic PO(2). HPV is elicited by moderate alveolar hypoxia through a mechanism that is intrinsic to the pulmonary circulation, particularly the resistance pulmonary arteries (PA), and is robust even in isolated perfused lungs. Although modulated by the endothelium, HPV persists in denuded PA rings and PA smooth muscle cells (PASMC). ⋯ The role of O(2)-sensitive K(+) channels is conserved in most specialized O(2)-sensitive tissues, including the ductus arteriosus and carotid body. The unique occurrence of hypoxic vasoconstriction in the pulmonary circulation relates to the colocalization of an O(2)-sensor and O(2)-sensitive Kv channels in resistance PAs. HPV has relevance to human physiology, pathophysiology (high altitude pulmonary edema (HAPE) and PHT) and therapy (single lung anesthesia).