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CARDIOVASCULAR
-Opioid Receptor Stimulation on Ca2+ Homeostasis in Rat Ventricular Myocytes Subjected to Ischemic Insults
Department of Physiology and Institute of Cardiovascular Sciences and Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, China
Received March 3, 2004; accepted March 26, 2004.
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Abstract |
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-opioid receptor agonist)] on viability and injury, HSP70 expression, and [Ca2+]i in ventricular myocytes subjected to metabolic inhibition and anoxia (MI/A), with blockade of HSP70 synthesis. In myocytes with vehicle pretreatment, the percentage of dead cells determined by trypan blue exclusion, the injury reflected by release of lactate dehydrogenase, and the resting [Ca2+]i measured by spectrofluorometry significantly increased, whereas the amplitude of electrically induced [Ca2+]i transient decreased, after 10 min with 10 mM 2-deoxy-D-glucose and 10 mM sodium dithionite, known to cause MI/A. However, when myocytes were subjected for 30 min to either 20 mM lactate and 10 mM 2-deoxy-D-glucose (MIP) or 30 µM U50,488H (UP) 20 h before MI/A, the changes in viability and injury, and [Ca2+]i responses were significantly attenuated. These were accompanied by a significantly increased HSP70 expression. Furthermore, blockade of HSP70 synthesis with selective antisense oligonucleotides abolished the beneficial effects of MIP or UP. This study provides first evidence that activation of HSP70 induced by preconditioning, which conferred delayed cardioprotection, restored partially the [Ca2+]i homeostasis altered by ischemic insults.
-opioid receptor (-OR) with a -OR agonist, U50,488H (UP), has been shown to confer delayed cardioprotection (Wu et al., 1999
; Zhou et al., 2001). The protective effect of MIP or UP was accompanied by an enhanced expression of a stress-inducible heat shock protein 70 (HSP70) and blockade of the HSP70 synthesis with a selective antisense (AS) oligonucleotides abolished the protection, indicating that HSP70 mediated the delayed cardioprotection of MIP or UP (Zhou et al., 2001). However, the signaling transduction mechanisms of activation of HSP70 leading to cardioprotection are far from clear.
Intracellular Ca2+ ([Ca2+]i) overload is widely believed to be a precipitating cause of myocardial injury upon ischemia and reperfusion (IR) based on the observation that [Ca2+]i overload is always associated with myocardial injury upon IR. In support of the notion, a host of experimental studies have shown that calcium channel antagonists limited the infarct size induced by IR (Przyklenk et al., 1999). In a recent study, we found that administration of a calcium chelator, BAPTA-2AM, reduced the injury caused by myocardial IR (our unpublished data). This observation is convincing evidence in support of [Ca2+]i overload being a precipitating factor of injury upon IR. A previous study in our laboratory also showed that ischemia-induced myocardial injury was accompanied by [Ca2+]i overload, and pretreatment with U50,488H a day before attenuated the injury, accompanied by reduced [Ca2+]i overload (Chen et al., 2003).
Therefore, the purpose of the present study was to test the hypothesis that activation of HSP70 by preconditioning reduced the [Ca2+]i overload induced by IR. We used an isolated ventricular myocyte preparation preconditioned with metabolic inhibition or pretreated with U50,488H, both of which have been shown to confer delayed cardioprotection against ischemic insults, namely, metabolic inhibition and anoxia (MI/A) (Ho et al., 2002). In addition to resting [Ca2+]i, we also determined the electrically induced [Ca2+]i transient, which represents the influx of Ca2+ via the L-type Ca2+ channel and the release of Ca2+ from sarcoplasmic reticulum induced by Ca2+ entry (Janczewski and Lakatta, 1993). We first correlated the HSP70 expression with [Ca2+]i responses after MI/A in ventricular myocytes subjected to preconditioning. We then determined [Ca2+]i responses upon blockade of HSP70 synthesis with a selective antisense oligonucleotides in ventricular myocytes after UP or MIP. Results showed for the first time that activation of HSP70 induced by preconditioning, which conferred delayed cardioprotection, restored partially the [Ca2+]i homeostasis altered by ischemic insults. This finding also suggests that HSP70 may mediate the delayed cardioprotection of preconditioning by restoring calcium homeostasis.
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Materials and Methods |
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). After isolation, they were allowed to stabilize for at least 30 min before experiments. The procedure described by Wu et al. (1999) was adopted. As shown in Fig. 1, myocytes were first subjected to 30-min pretreatment with either a selective -OR agonist, 30 µM U50,488H (UP) or metabolic inhibition (MIP) with a glucose-free Krebs' buffer at pH 6.5 containing 20 mM lactate and 10 mM 2-deoxy-D-glucose (2-DOG), an inhibitor of glycolysis, in the presence or absence of a selective -OR antagonist, 5 µM nor-binaltorphimine (nor-BNI), administered at 5 min before and throughout the pretreatment period. In the control group, cells were subjected to pretreatment with normal Krebs' (vehicle pretreatment, VP) for 30 min. After incubation in culture medium for 20 h, myocytes were then subjected to severe MI/A with glucose-free Krebs' solution for 10 min containing 10 mM 2-DOG, an inhibitor of glycolysis, and 10 mM sodium dithionite (Na2S2O4), an oxygen scavenger (Ho et al., 2002). Finally, the myocytes were transferred back to normal Krebs' solution for 10-min reperfusion. To determine the effects of blockade of HSP70, AS or sense (S) oligonucleotides (10 µM) of HSP70 were delivered into the culture medium during the 20-h incubation period.
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Trypan Blue Exclusion. Trypan blue exclusion was used to determine the viability of myocytes. At the end of reperfusion, ventricular myocytes were incubated with 0.4% trypan blue dye for 3 min. About 200 cells in each group were counted in a hemocytometer chamber under a light microscope. Live cells are able to exclude the dye and look nonblue. So, the percentage of nonblue cells over total cells was used as an index of viability.
Lactate Dehydrogenase (LDH) Assay. LDH was released from injured cells and was used as an index of cell injury. The activity in the cultured medium represents the LDH release from the cultured ventricular myocytes. A spectrophotometric enzyme activity assay was performed with a UV-Rate assay kit (Stanbio Laboratory, San Antonio, TX). LDH specially catalyzes the oxidation of lactate to pyruvate with the subsequent reduction of NAD to NADH. The rate at which NADH forms is proportional to LDH activity. At the end of the experiments, NADH absorbance increase per minute at 340 nm (
A/min) of the supernatant was determined from each experimental group. Then LDH activity (units per milliliter) was calculated according to the formula A/min*3.376.
Polyacrylamide Gel Electrophoresis and Western Blotting. At the end of experiments, cells were harvested and lysed in 0.5 ml of lysis buffer [50 mM Tris·HCl (pH 7.4), 1% Nonidet P40, 150 mM NaCl, 1 mM EDTA, 1 mM phenylmethylsulfonyl fluoride, 1 mg/ml of aprotinin, and 1 mg/ml of leupeptin] at 4°C and then sonicated (Sonic and Materials, Danbury, CT) with three 15-s bursts on ice. The cytosolic fraction was obtained by centrifugation at 12,000g for 5 min at 4°C. Protein concentration was determined by the Bio-Rad (Hercules, CA) protein assay based on the Bradford dye-binding procedure with bovine serum albumin as the standard. Protein (60 µg) was loaded on the lane of SDS-polyacrylamide gel and separated by electrophoresis in 5% acrylamide stacking gel and 12% acrylamide separating gel initially at 100 V for 2 h. The separated proteins were transferred electrophoretically from the gel onto nitrocellulose membrane (0.45-µm pore size; Hybond-C) at 100 V in 4°C for 1.5 h in a buffer containing 25 mM Tris-base, 192 mM glycine, and 20% methanol. After the membranes had been washed in buffer (TBS pH 7.4, containing 0.1% Tween 20 and 5% skimmed milk power) for 60 min at room temperature to block nonspecific binding sites, they were probed at 4°C overnight with a mouse anti-HSP70 monoclonal antibody at 1:2000. After washing for 30 min with TBS (0.1% Tween 20 solution), the membranes were then incubated for 1 h with a secondary antibody solution conjugated to horseradish peroxidase-conjugated rabbit anti-mouse at 1:2000 dilution. Then, the membranes were washed for 30 min with TBS. Detection was performed using an enhanced chemiluminescence detection system.
Measurement of [Ca2+]i in the Single Ventricular Myocyte. A spectrofluorometric method with Fura-2/AM as the Ca2+ indicator was used for measurement of [Ca2+]i. Ventricular myocytes were incubated with 5 µM Fura-2/AM for 30 min. Fluorescent signals obtained at 340 nm (F340) and 380 nm (F380) excitation wavelengths were recorded and stored in the computer for data processing and analysis. The F340/F380 ratio was used to represent cytosolic [Ca2+]i in the ventricular myocyte. To induce [Ca2+]i transients, myocytes were electrically stimulated at 0.2 Hz. The amplitude of the electrically induced [Ca2+]i transients was determined as the difference between the diastolic and the peak [Ca2+]i levels.
Drugs and Chemicals. Joklik's modified Eagle's medium, U50,488H, type I collagenase, insulin, HEPES, bovine serum albumin, 2-DOG, lactate acid, sodium dithionite, and Fura-2AM were purchased from Sigma-Aldrich (St. Louis, MO). Nor-BNI was from Tocris Cookson Ltd. (Ellisville, MO), and LDH assay kit was from Stanbio. Concentrations of U50,488H, nor-BNI, 2-DOG, and sodium dithionite used were based on previous studies (Wu et al., 1999; Zhou et al., 2001). Rainbow-colored protein markers (RPN-756), Hybond-P (polyvinylidene difluoride transfer membrane RPN303F), enhanced chemiluminescence (RPN-2106), and Kodak Biomax Light-1 film were from Amersham Biosciences UK Ltd. (Little Chalfont, Buckinghamshire, UK); the primary antibody of mouse anti-HSP70 monoclonal antibody (SPA-810) from StressGen (Victoria, BC, Canada); secondary antibody of peroxidase-conjugated rabbit anti-mouse immunoglobulins-horseradish peroxidase was from DakoCytomation Denmark A/S (Glostrup, Denmark); and the Quantity 1 software for imaging and quantitative analysis of relative density of HSP70 was from Bio-Rad. HSP70 AS oligonucleotides (TGTTTTCTTGGCCAT) and HSP70 S oligonucleotides (ATGGCCAAGAAAACA) were synthesized from sequences complementary to the initiation codon and four downstream codons of rat HSP70 mRNA (Invitrogen, Carlsbad, CA) as described previously (Kim et al., 1997).
Statistical Analysis. All data were expressed as means ± S.E. One-way analysis of variance followed by Newman-Keuls multiple comparison tests was carried out to test for differences between the mean values within the same study. A difference of P < 0.05 was considered significant.
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Results |
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-OR antagonist, was administered before and during the pretreatments, the protective effects of both UP and MIP were abolished, indicating that the effects were -OR-mediated. Similarly, UP or MIP significantly lowered the LDH activity compared with the VP group, and the effects were abolished in the presence of 5 µM nor-BNI (Fig. 2B).
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Effects of UP or MIP on HSP70 Expression in Ventricular Myocytes Subjected to MI/A. There was no detectable HSP70 expression without MI/A (data not shown). After 10-min MI/A, there was visible HSP70 expression in all groups. The expression was significantly greater in UP (Fig. 3A) and MIP groups (Fig. 3B). This was directly related to the changes in percentage of nonblue cells but inversely related to the release of LDH (Fig. 2). These enhancing effects of UP and MIP on HSP70 expression were significantly attenuated in the presence of nor-BNI.
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Effects of UP or MIP on Resting [Ca2+]i and Electrically Induced [Ca2+]i Transient in Ventricular Myocytes Subjected to MI/A. As shown in Figs. 4A and 7A, the resting [Ca2+]i increased gradually during MI/A; the elevation was 16.3% at the end of the period. The elevation was significantly attenuated by UP or MIP, an effect abolished in the presence of nor-BNI. Immediately after reperfusion, the resting [Ca2+]i further increased, reaching a peak within the first 2 to 3 min, and then gradually declined to a level lower than that at the end of MI/A, but still higher than that before MI/A. The increases in resting [Ca2+]i at the peak in UP and MIP groups were significantly lower than that of the VP group and were abolished in the presence of nor-BNI (Figs. 4B and 7A). There was, however, no difference in resting [Ca2+]i at the end of reperfusion between treatment and control groups (data not shown).
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The amplitude of electrically induced [Ca2+]i transient, representing the release of Ca2+ during E-C coupling and shown to directly correlate with contraction (Yu et al., 1998), was markedly reduced during MI/A. At the end of MI/A, the amplitude was only 12% of that before MI/A in the VP group. After reperfusion, the amplitude was gradually and partially restored and stabilized at a certain level. At the end of 10-min reperfusion, the amplitude was 28% of that before MI/A. Like the change in [Ca2+]i, the decreases in amplitude were significantly attenuated by UP or MIP (Figs. 5 and 8A).
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Effects of UP or MIP on HSP70 Expression, Viability, and Injury in Ventricular Myocytes Subjected to MI/A after Blockade of HSP70 Synthesis. In groups incubated with the AS oligonucleotides, but not S oligonucleotides, to HSP70, the elevated HSP70 expression induced by UP or MIP (Fig. 6A) was abolished. This was accompanied by abolition in increased percentage of nonblue cells (Fig. 6B) and reduced LDH release (Fig. 6C) induced by UP or MIP.
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Effects of UP or MIP on Resting [Ca2+]i and Electrically Induced [Ca2+]i Transient in Ventricular Myocytes Subjected to MI/A After Blockade of HSP70 Synthesis. As shown in Fig. 7, UP and MIP significantly attenuated the elevation of resting [Ca2+]i during MI/A and reperfusion induced by 10-min MI/A. However, these ameliorating effects of both treatments were completely abolished by AS oligonucleotides to HSP70 administered during the incubation period. On the other hand, coincubation with S oligonucleotides failed to alter the [Ca2+]i responses to either UP or MIP.
Similar to the changes in resting [Ca2+]i, the reductions in amplitude of the electrically induced [Ca2+]i transient were restored by UP and MIP; and the AS, but not S oligonucleotides, to HSP70, abolished the effects of both UP and MIP (Fig. 8).
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Discussion |
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-OR agonist, U50,488H, conferred delayed cardioprotection and attenuated [Ca2+]i overload accompanied by increased HSP70 expression, and blockade of HSP70 synthesis abolished the effects of preconditioning/pretreatment in ventricular myocytes subjected to MI/A. The observations confirm the role of HSP70 in delayed cardioprotection. More importantly, they are the first evidence that HSP70 activated by preconditioning is responsible for the restoration of [Ca2+]i homeostasis altered by ischemic insults. Because [Ca2+]i overload is generally believed to be a harbinger of cell death, this finding suggests that HSP70 may mediate the delayed cardioprotection of preconditioning by restoring calcium homeostasis.
The novel finding of the present study is the causal relationship between enhanced HSP70 expression and attenuated [Ca2+]i overload after preconditioning in the ventricular myocytes subjected to ischemic insults and reperfusion. This is consistent with similar observations made in other tissues. In rat C6 glioma cells, recovery of impaired Ca2+ mobilization mediated by 5-hydroxytryptamine-2A receptor after heat stress was shown to coincide with increased HSP70 expression, and blockade of HSP70 synthesis with its inhibitor quercetin abolished the recovery (Kagaya et al., 2000). A similar observation on the inositol-1,4,5-trisphosphate-mediated Ca2+ mobilization and HSP70 after heat stress has also been found in NG 108-15 cells (Katayama et al., 1994). These observations indicate a causal relationship between HSP70 and calcium handling.
Proteins such as L-type Ca2+ channel and Na+/Ca2+ exchangers in the sarcolemmal membrane and Ca2+-ATPase in the membrane of sarcoplasmic reticulum are involved in maintaining [Ca2+]i homeostasis. It is very likely that HSP70 may stabilize or facilitate the activities of these proteins as a molecule chaperone, thus restoring the [Ca2+]i homeostasis impaired by ischemic insults, as it does on steroid receptors (Tsai and O'Malley, 1994). In support of this notion, a previous study showed that HSP70 overexpression attenuated the NaCN-induced [Ca2+]i increase, and this was accompanied by a reduction of Vmax of the Na+/Ca2+ exchangers (Kiang et al., 1998). Further studies are still needed.
Heat shock proteins are the first proteins to be proposed as effectors of late ischemic preconditioning (IP), based on the assumption that an unknown protein was needed to carry the memory of preconditioning (Downey et al., 1994). It was reported that exposure of intact rat hearts to hyperthermia decreased the infarction induced by left coronary artery occlusion, and this was correlated with marked HSP70 expression (Donnelly et al., 1992). Ischemic preconditioning was also shown to minimize both infarction and arrhythmias, which was accompanied by increased HSP70 expression in conscious rabbits (Yang et al., 1996). This observation suggests that activation of HSP70 may confer cardioprotection. Furthermore, HSP70 overexpression in transfected myocytes (Cumming et al., 1996) or intact transgenic animals (Trost et al., 1998) produced protective effects. This is evidence demonstrating the ability of HSP70 to confer cardioprotection (Latchman, 2001). There were, however, controversies on the role of HSP70 in preconditioning based on the lack of enhanced expression of the protein in rabbits preconditioned with adenosine (Bernardo et al., 1999) or a time lag between HSP70 expression and cardioprotection (Yamashita et al., 1997). In a previous study in our laboratory (Zhou et al., 2001) and in the present study, we observed that -OR stimulation conferred delayed cardioprotection and enhanced HSP70 expression, and blockade of the synthesis of HSP70 with a selective AS oligonucleotide abolished the protection. The results provide unequivocal evidence that HSP70 mediates cardioprotection of preconditioning.
Ischemia and reperfusion results in a depression of myocardial contractility as well as infarction, whereas IP could improve this contractile dysfunction (Cohen et al., 1991; Bolli et al., 1997) besides reducing infarct size. In the present study, we showed that MI/A decreased the amplitude of electrically induced [Ca2+]i transient, known to correlate directly with the contraction of ventricular myocytes (Yu et al., 1998), and the reduction was attenuated by MIP or UP via HSP70 activation. The finding suggests that HSP70 also restored cardiac contractility reduced by MI/A. The observation is compatible with a previous observation that in conscious pigs, late IP attenuated myocardial stunning and increased expression of HSP70 at the same time (Sun et al., 1995). Because the electrically induced [Ca2+]i transient represents the influx of Ca2+ via the L-type Ca2+ channel and release of Ca2+ from the sarcoplasmic reticulum (Janczewski and Lakatta, 1993), improvement of cardiac contractility is also a result of the restoration of [Ca2+]i homeostasis.
We found in the present study that resting [Ca2+]i rose progressively during 10-min MI/A, an observation reported previously in both whole hearts (Field et al., 1994; Hotta et al., 1998) and isolated myocytes (Seki and MacLeod, 1995) subjected to ischemia, MI/A, or hypoxia. [Ca2+]i increased even further into reperfusion, reaching its peak at reperfusion 2 to 3 min, and then declined, but not to the preischemia level. In myocytes exposed to 15-min anoxia, there was also a further increase in [Ca2+]i, reaching the peak at 2 to 3 min into reperfusion (Seki and MacLeod, 1995). Moreover, in the isolated perfused hearts exposed to 30 min low-flow ischemia, similar further increase in [Ca2+]i was observed, reaching a plateau at about 1 min into reperfusion (Seki et al., 2001). Interestingly, when the hearts were subjected to 10-min low-flow ischemia, there was no further elevation in [Ca2+]i during reperfusion (Seki et al., 2001). So the pattern of [Ca2+]i overload during reperfusion may vary in different preparations and after different durations of ischemia.
In our previous studies, we showed that -OR stimulation with a selective -OR agonist, U50,488H, produced the same cardioprotection as did preconditioning with MI or ischemia and that blockade of the -OR with a selective -OR antagonist abolished the protective effects of both -OR stimulation and preconditioning (Wu et al., 1999; Zhou et al., 2001; Chen et al., 2003). The observations are unequivocal evidence that -OR mediates cardioprotection of preconditioning. In the present study, we showed that -OR stimulation produced the same effect on Ca2+ homeostasis as did MIP. The finding is in agreement with the notion that -OR mediates cardioproteciton of preconditioning.
In conclusion, the novel finding of this study is the demonstration of a causal relationship between enhanced HSP70 expression and attenuated [Ca2+]i overload after preconditioning. Because [Ca2+]i overload is the precipitating cause of cell injury/death, our finding suggests that HSP70 may mediate the delayed cardioprotection of preconditioning by restoring calcium homeostasis altered by ischemic insults.
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Acknowledgements |
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Footnotes |
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ABBREVIATIONS: MIP, preconditioned with metabolic inhibition; -OR, -opioid receptor; UP, preconditioned with U50,488H; HSP70, heat shock protein 70; AS, antisense; [Ca2+]i, cytosolic calcium; IR, ischemia and reperfusion; BAPTA-2AM, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-2 acetoxymethyl ester; AM, acetoxymethyl ester; MI/A, metabolic inhibition and anoxia; 2-DOG, 2-deoxy-D-glucose; nor-BNI, nor-binaltorphimine; VP, vehicle pretreatment; S, sense; RE, reperfusion; LDH, lactate dehydrogenase; TBS, Tris-buffered saline; IP, ischemic preconditioning; U50,488H, trans-(+)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzeneacetamide.
Address correspondence to: Prof. T. M. Wong, Department of Physiology, Faculty of Medicine, the University of Hong Kong Special Administrative Region, China. E-mail: wongtakm{at}hkucc.hku.hk
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References |
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|---|
Bernardo NL, Okubo S, Maaieh MM, Wood MA, and Kukreja RC (1999) Delayed preconditioning with adenosine is mediated by opening of ATP-sensitive K(+) channels in rabbit heart. Am J Physiol 277: H128–H135.
Bolli R, Bhatti ZA, Tang XL, Qiu Y, Zhang Q, Guo Y, and Jadoon AK (1997) Evidence that late preconditioning against myocardial stunning in conscious rabbits is triggered by the generation of nitric oxide. Circ Res 81: 42–52.
Chen M, Zhou JJ, Kam KW, Qi JS, Yan WY, Wu S, and Wong TM (2003) Roles of KATP channels in delayed cardioprotection and intracellular Ca(2+) in the rat heart as revealed by kappa-opioid receptor stimulation with U50488H. Br J Pharmacol 140: 750–758.[CrossRef][Medline]
Cohen MV, Liu GS, and Downey JM (1991) Preconditioning causes improved wall motion as well as smaller infarcts after transient coronary occlusion in rabbits. Circulation 84: 341–349.
Cumming DV, Heads RJ, Watson A, Latchman DS, and Yellon DM (1996) Differential protection of primary rat cardiocytes by transfection of specific heat stress proteins. J Mol Cell Cardiol 28: 2343–2349.[CrossRef][Medline]
Donnelly TJ, Sievers RE, Vissern FL, Welch WJ, and Wolfe CL (1992) Heat shockprotein induction in rat hearts. A role for improved myocardial salvage after ischemia and reperfusion? Circulation 85: 769–778.
Downey JM, Cohen MV, Ytrehus K, and Liu Y (1994) Cellular mechanisms in ischemic preconditioning: the role of adenosine and protein kinase C. Ann NY Acad Sci 723: 82–98.[Medline]
Field ML, Azzawi A, Styles P, Henderson C, Seymour AM, and Radda GK (1994) Intracellular Ca2+ transients in isolated perfused rat heart: measurement using the fluorescent indicator Fura-2/AM. Cell Calcium 16: 87–100.[CrossRef][Medline]
Ho JC, Wu S, Kam KW, Sham JS, and Wong TM (2002) Effects of pharmacological preconditioning with U50488H on calcium homeostasis in rat ventricular myocytes subjected to metabolic inhibition and anoxia. Br J Pharmacol 137: 739–748.[CrossRef][Medline]
Hotta Y, Fujita M, Nakagawa J, Ando H, Takeya K, Ishikawa N, and Sakakibara J (1998) Contribution of cytosolic ionic and energetic milieu change to ischemia- and reperfusion-induced injury in guinea pig heart: fluorometry and nuclear magnetic resonance studies. J Cardiovasc Pharmacol 31: 146–156.[CrossRef][Medline]
Janczewski AM and Lakatta EG (1993) Buffering of calcium influx by sarcoplasmic reticulum during the action potential in guinea-pig ventricular myocytes. J Physiol (Lond) 471: 343–363.
Kagaya A, Okada A, Jitsuiki H, Tawara Y, Inagaki M, Takebayashi M, Saeki T, Nishida A, Nakata Y, and Yamawaki S (2000) Effect of heat stress on serotonin-2A receptor-mediated intracellular calcium mobilization in rat C6 glioma cells. J Neural Transm 107: 919–929.[CrossRef]
Katayama S, Shuntoh H, Matsuyama S, and Tanaka C (1994) Effect of heat shock on intracellular calcium mobilization in neuroblastoma x glioma hybrid cells. J Neurochem 62: 2292–2299.[Medline]
Kiang JG, Ding XZ, and McClain DE (1998) Overexpression of HSP-70 attenuates increases in [Ca2+]i and protects human epidermoid A-431 cells after chemical hypoxia. Toxicol Appl Pharmacol 149: 185–194.[CrossRef][Medline]
Kim YM, de Vera ME, Watkins SC, and Billiar TR (1997) Nitric oxide protects cultured rat hepatocytes from tumor necrosis factor-alpha-induced apoptosis by inducing heat shock protein 70 expression. J Biol Chem 272: 1402–1411.
Latchman DS (2001) Heat shock proteins and cardiac protection. Cardiovasc Res 51: 637–646.
Przyklenk K, Simkhovich BZ, Bauer B, Hata K, Zhao L, Elliott GT, and Kloner RA (1999) Cellular mechanisms of infarct size reduction with ischemic preconditioning. Role of calcium? Ann NY Acad Sci 874: 192–210.[CrossRef][Medline]
Seki S, Horikoshi K, Takeda H, Izumi T, Nagata A, Okumura H, Taniguchi M, and Mochizuki S (2001) Effects of sustained low-flow ischemia and reperfusion on Ca2+ transients and contractility in perfused rat hearts. Mol Cell Biochem 216: 111–119.[CrossRef][Medline]
Seki S and MacLeod KT (1995) Effects of anoxia on intracellular Ca2+ and contraction in isolated guinea pig cardiac myocytes. Am J Physiol 268: H1045–H1052.
Sun JZ, Tang XL, Knowlton AA, Park SW, Qiu Y, and Bolli R (1995) Late preconditioning against myocardial stunning. An endogenous protective mechanism that confers resistance to postischemic dysfunction 24 h after brief ischemia in conscious pigs. J Clin Investig 95: 388–403.
Trost SU, Omens JH, Karlon WJ, Meyer M, Mestril R, Covell JW, and Dillmann WH (1998) Protection against myocardial dysfunction after a brief ischemic period in transgenic mice expressing inducible heat shock protein 70. J Clin Investig 101: 855–862.[Medline]
Tsai MJ and O'Malley BW (1994) Molecular mechanisms of action of steroid/thyroid receptor superfamily members. Annu Rev Biochem 63: 451–486.[CrossRef][Medline]
Wu S, Li HY, and Wong TM (1999) Cardioprotection of preconditioning by metabolic inhibition in the rat ventricular myocyte. Involvement of kappa-opioid receptor. Circ Res 84: 1388–1395.
Yamashita N, Hoshida S, Nishida M, Igarashi J, Aoki K, Hori M, Kuzuya T, and Tada M (1997) Time course of tolerance to ischemia-reperfusion injury and induction of heat shock protein 72 by heat stress in the rat heart. J Mol Cell Cardiol 29: 1815–1821.[CrossRef][Medline]
Yang XM, Baxter GF, Heads RJ, Yellon DM, Downey JM, and Cohen MV (1996) Infarct limitation of the second window of protection in a conscious rabbit model. Cardiovasc Res 31: 777–783.[CrossRef][Medline]
Yu XC, Li HY, Wang HX, and Wong TM (1998) U50,488H inhibits effects of norepinephrine in rat cardiomyocytes-cross-talk between kappa-opioid and betaadrenergic receptors. J Mol Cell Cardiol 30: 405–413.[CrossRef][Medline]
Zhou JJ, Pei JM, Wang GY, Wu S, Wang WP, Cho CH, and Wong TM (2001) Inducible HSP70 mediates delayed cardioprotection via U-50488H pretreatment in rat ventricular myocytes. Am J Physiol 281: H40–H47.
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