Taxol, a microtubule stabilizer, improves cardiac functional recovery during postischemic reperfusion in rat in vitro.
OBJECTIVE
Microtubule disruption contributes to cellular and organic dysfunction, and is implicated in ischemia/reperfusion (I/R) injury. The purpose of this study was to explore the effects of taxol, a microtubule stabilizer, on cardiac functional recovery during reperfusion.


METHODS
Left ventricular developed pressure, left ventricular end-diastolic pressure, maximal time derivatives of pressure and the severity of ventricular arrhythmias were analyzed in isolated rat heart. Microtubule structure was immunohistochemically measured. Apoptosis and necrosis was identified with TUNEL or TTC staining, respectively. Mitochondrial permeability transition pore (mPTP) mRNA expression was examined by real-time polymerase chain reactions. mPTP opening, reactive oxygen species (ROS), and oxidative enzyme activities were measured with fluorometric or spectrophotometric techniques. Intracellular calcium concentration ([Ca(2+) ](i) ) and Ca(2+) transients were examined by Fura-2-AM and Fluo-3-AM, respectively. Cytosolic cytochrome c, sarcoplasmic reticulum Ca(2+) -ATPase (SERCA2), ryanodine receptors (RyR), phospholamban (PLB), and PLB phosphorylation were analyzed by Western blot. Effective refractory period (ERP) and afterpotential-mediated activity were detected using microelectrode.


RESULTS
Taxol improved the functional recovery of post-I/R. Taxol preserved the intact microtubule structure in reperfusion. mPTP mRNA expression was unchanged while the mPTP opening was reduced by taxol, and this effect was accompanied by the decreased ROS level caused by oxidative enzymes activities' changes. Taxol reduced apoptosis and the level of cytosolic cytochrome c in reperfusion. Taxol also promoted rapid recovery of [Ca(2+) ](i) , prevented reduction of the amplitude of Ca(2+) transients and shortened the decay time of Ca(2+) transients. The protein expression of SERCA2, RyR, and PLB remained unchanged in reperfusion. Taxol prevented the increase of Phospho-Thr17-PLB and Phospho-Ser16-PLB in reperfusion. In addition, taxol facilitated rapid recovery of ERP and counter-acted afterpotential-mediated activity.


CONCLUSIONS
Taxol may effectively improve cardiac functional recovery during reperfusion via inhibiting mPTP opening, ameliorating abnormal calcium homeostasis, and reducing the substrates associated with arrhythmias.
Xiao
Junjie
J
Department of Cardiology, East Hospital, Tongji University School of Medicine, Shanghai, China.
Liang
Dandan
D
Liu
Ying
Y
Zhang
Hong
H
Liu
Yi
Y
Zhao
Hong
H
Li
Jun
J
Peng
Luying
L
Zhou
Zhaonian
Z
Chen
Yi-Han
YH
D000200:Action Potentials; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001145:Arrhythmias, Cardiac / Q000209:etiology / Q000517:prevention & control; D020013:Calcium Signaling / Q000187:drug effects; D002135:Calcium-Binding Proteins / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D033681:Mitochondrial Membrane Transport Proteins / Q000187:drug effects / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D009200:Myocardial Contraction / Q000187:drug effects*; D015428:Myocardial Reperfusion Injury / Q000150:complications / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D009336:Necrosis; D018384:Oxidative Stress / Q000187:drug effects; D017239:Paclitaxel / Q000494:pharmacology*; D010477:Perfusion; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D020127:Recovery of Function; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D013997:Time Factors; D050257:Tubulin Modulators / Q000494:pharmacology*; D016277:Ventricular Function, Left / Q000187:drug effects*; D017725:Ventricular Pressure / Q000187:drug effects; D000099211:Phospholamban
D002135:Calcium-Binding Proteins; D045304:Cytochromes c; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017239:Paclitaxel; D017382:Reactive Oxygen Species; D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D050257:Tubulin Modulators; D000099211:Phospholamban; C506948:Atp2a2 protein, rat