Effects of tamoxifen on myocardial ischemia ... - Springer Link

Mol Cell Biochem (2008) 308:227–235 DOI 10.1007/s11010-007-9633-0

Effects of tamoxifen on myocardial ischemia-reperfusion injury model in ovariectomized rats Rauf Onur Ek Æ Yuksel Yildiz Æ Serpil Cecen Æ Cigdem Yenisey Æ Tulay Kavak

Received: 11 June 2007 / Accepted: 18 October 2007 / Published online: 3 November 2007 Ó Springer Science+Business Media, LLC. 2007

Abstract The purpose of this study is to examine the antiarrhythmic and antioxidant effects of tamoxifen, one of the selective estrogen modulators, in ovariectomized rats subjected to myocardial ischemia-reperfusion (I/R) injury. A month after ovariectomy, rats were divided into four groups: (I) ovariectomized controls without any treatment, (II) ovariectomized rats treated with vehicle dimethylsulfoxide (DMSO), (III)–(IV) ovariectomized rats treated with tamoxifen 1 or 10 mg/kg,sc daily for 14 days. To produce arrhythmia, the left main coronary artery was occluded for 7 min, followed by 7 min of reperfusion. The blood pressure (BP), heart rate (HR), electrocardiography (ECG) was recorded before and during the ischemia-reperfusion period. The blood levels of malondialdehyde (MDA), creatine kinase (CK), glutathione (GSH), glutathione peroxidase (GSH-Px), glutathione reductase (GR), and catalase (CAT) were measured after the rats were killed. Tamoxifen reduced the incidence of ventricular tachycardia (VT) on ischemia and reperfusion as well as the incidence and duration of reversible ventricular fibrillation (VF) on reperfusion. I/R injury caused a significant fall in GSH, GSH-Px as well as an increase in MDA and CK levels in the control group when compared to tamoxifen treated groups. The changes in levels of CAT and GR were however, not significant. In conclusion, our findings suggest that tamoxifen has cardioprotective effects against I/R injury in rats, likely its antioxidant properties. R. O. Ek (&) Y. Yildiz S. Cecen Department of Physiology, Medical Faculty, Adnan Menderes University, Aydin 09100, Turkey e-mail: [email protected]; [email protected] C. Yenisey T. Kavak Department of Biochemistry, Medical Faculty, Adnan Menderes University, Aydin, Turkey

Keywords Arrhythmia Antioxidant enzyme Ischemia-reperfusion Ovariectomy Rat Tamoxifen

Introduction Myocardial ischemia develops when the coronary blood supply to the heart is insufficient in relation to the energy demands of the myocardium [1]. During myocardial ischemia oxygen deficiency leads to tissue necrosis, changes in metabolic pattern and cardiac function including depression in contractile activity [2, 3]. Experimental and clinical results suggest that reinstitution of blood flow to the previously ischemic myocardium may contribute to additional tissue injury and structural, functional, and biochemical abnormalities [4–7]. Mechanisms mediating myocardial ischemia-reperfusion (I/R) injury are incompletely defined. However, cytosolic Ca2+ overload [7–9] and oxidative stress [10–14] are postulated as the major mechanisms underlying several manifestations of reperfusion injury. Several studies have confirmed that generation of oxygen-derived free radicals including hydroxyl radical, superoxide anion, and hydrogen peroxide is markedly increased during reperfusion period [7, 10–14]. On the other hand, the endogenous antioxidants, including nonenzymatic antioxidants and the enzymatic free radical scavangers are significantly reduced after myocardial I/R. Hence, it has been suggested that oxidative stress is critically related to impairment of antioxidant defense system in the ischemic myocardial tissue followed by increased formation of reactive oxygen species (ROS) [7, 15, 16]. These ROS have been shown to cause significant myocardial cell damage and heart dysfunction during myocardial I/R injury [17, 18].

123

228

Estrogens exert profound effects on growth, differentiation, and function of many reproductive tissues. They also affect other tissues, including bone, liver, cardiovascular system, and brain. As women undergo menopause, circulating concentrations of estrogen reduce. The relative estrogen loss in postmenopausal women is associated with physiological changes and an increased level of reactive oxygen species as well as the risk of several diseases including cardiovascular disease, osteoporosis and degenerative processes in the nervous system [19–22]. Since estrogen replacement in menopausal women increases the risk of breast cancer [23], newer synthetic drugs designated as selective estrogen receptor modulators (SERMs) (e.g., tamoxifen) which mimic estrogen’s favorable effects on bones but without having carcinogenic activity on breast and other tissues, have been developed. Epidemiological studies of tamoxifen for breast cancer demonstrate a significant reduction in the incidence of cardiovascular disease, such as fatal myocardial infarction in postmenopausal patients [24, 25]. Tamoxifen was also shown to enhance flow-mediated dilation and decrease cardiovascular risk factors in men with advanced atherosclerosis [26]. However, antiarrhythmic and antioxidant activities of tamoxifen are unknown. The purpose of this study was to investigate the effects of tamoxifen on I/R induced arrhythmias and antioxidant parameters in an ovariectomized rat model.

Material and methods Study groups and test drugs Female Wistar Albino rats weighing 250–350 g were used. Bilateral ovariectomies were performed under ether anesthesia. The animals were then allowed to recover for 1 month. The rats were divided into four main groups and following treatments were given for 14 days: (1) ovariectomized controls with no further treatment; (2) ovariectomized rats treated with vehicle dimethyl sulfoxide (DMSO 1 ml/kg/day, sc); (3) ovariectomized rats treated with tamoxifen (1 mg/kg/day, sc); (4) ovariectomized rats treated with tamoxifen (10 mg/kg/ day, sc). The dosage of tamoxifen was selected according to the previous studies [27–29]. Animals were randomly allocated to each drug treatment and vehicle group. All experiments were performed in accordance with the guidelines for animal research from the National Institutes of Health (NIH publication No. 86-23, revised 1985) and were approved by the Committee on Animal Research at Adnan Menderes University. The rats were housed in a room with controlled temperature and

123

Mol Cell Biochem (2008) 308:227–235

humidity under a 12:12 h light–dark cycle. They were allowed free access to food and water. DMSO and tamoxifen citrate salt were purchased from Sigma Chemical Company (St.Louis, MO, USA). Tamoxifen was dissolved in DMSO and given subcutaneously in a final volume of 0.2 ml.

Ischemia-reperfusion protocols Ovariectomized rats were anesthetized with urethane 1.25 g/kg administered intraperitoneally (i.p.). The trachea was cannulated for artificial respiration. Polyethylene catheters (PE-50) were inserted into the common carotid artery for continuous monitoring of heart rate (HR) and blood pressure (BP). A standard lead-I electrocardiogram (ECG) was also recorded by inserting needle electrodes to the extremities of animals. After tracheotomy, the animals were ventilated with room air by a respirator for small rodents (UGO Basile Model 7025, Italy). The chest was opened by a left thoracotomy, followed by sectioning the fourth and fifth ribs, about 2 mm to the left of sternum. Positive-pressure artificial respiration was started immediately with room air using a volume of 1.5 ml/100 g body weight at a rate 60 strokes/min to maintain normal PCO2, PO2, and pH parameters. After the pericardium was incised, the heart was exteriorized by a gentle pressure on the right side of the rib cage. A 6/0 silk suture attached to a 10 mm micro point reverse-cutting needle was quickly placed under the left main coronary artery. The heart was then carefully replaced in the chest, and the animal was allowed to recover for 20 min. Any animal in which this procedure produced arrhythmias or a sustained decrease in blood pressure (BP) to less than 70 mm Hg was discarded. A small plastic snare was threaded through the ligature and placed in contact with the heart. The coronary artery could then be occluded by applying tension to the ligature, and reperfusion was achieved by releasing tension. Successful ligation of the coronary artery was validated by observation of a decrease in arterial pressure and ECG changes (increase in R wave and ST segment elevation). For evaluating the effect of tamoxifen on I/R injury, the coronary artery was occluded for 7 min and then reperfused for 7 min. These durations of I/R injury was used in the same experimental model successfully and it was reported that this protocol produced ectopic activity in optimum number and severity [30–32]. At the end of the reperfusion period animals were killed and blood was collected for biochemical analysis.


Experimental parameters studied Evaluation of arrhythmias Before and during the I/R period, heart rate (HR), blood pressure (BP), and ECG changes were recorded simultaneously on a personal computer with wave form data analysis software (AcqKnowledge, Biopac System, CA, USA). Ventricular ectopic activity was evaluated according to the diagnostic criteria advocated by the Lambeth Convention [33]. ECGs were analyzed to determine incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) in surviving animals. Total glutathione (GSH) determination Total GSH measurements were performed by the method of Tietze [34]. In brief, 0.5 ml sample or standard solution were mixed with 0.25 ml of 1 mol/l sodium phosphate buffer (pH 6.8) and 0.5 ml 5-50 -dithiobis-(2-nitrobenzoic acid) (DTNB, 0.8 g/l in the phosphate buffer) for 5 min. Then, the absorbance was measured at 412 nm using a Shimadzu UV-160 spectrophotometer. The GSH concentration was determined using standard aqueous solutions of GSH. Results were expressed as mg/g hb.

229

was 50 mM phosphate buffer (pH 7.0), 10 mM H202 and erythrocyte lysate. The reduction rate of H202 was followed at 240 nm for 30 s at room temperature. CAT activity was expressed in s-1/g hb.

Determination of glutathione peroxidase (GSH-Px) activity GSH-Px activity was measured by the method described by Paglia and Valentine [38]. To a 1.0 ml cuvette containing 400 ll of potassium phosphate buffer (pH 7.0, 0.25 M), 100 ll of 10 mM GSH, 100 ll of 2.5 mM NADPH, and 100 ll of glutathione reductase (6 U/ml), 200 ll of supernatant and hydrogen peroxide (100 ll of 12 mM) was in succession and change in absorbance was recorded spectrophotometrically at 340 nm for 120 s at an interval of 15 s. GSH-Px activity was expressed as mU/g hb.

Determination of creatine kinase (CK) activity CK activity was measured via an auto analyzer (Abbott Aeroset C-8000) using a commercial kit (7D63-20). The CK activity was expressed as U/l.

Malondialdehyde (MDA) determination

Statistics

The MDA production and hence lipid peroxidation were assessed in the tissues by the method of Ohkowa [35]. MDA forms a colored complex in the presence of TBA, which is detectable by measurement of absorbance at 532 nm. Absorbance was measured with Shimadzu UV160 spectrophotometer. 1,10 ,3,30 -tetraethoxypropane was used as a standard and the results were expressed as lmol/l.

Data were expressed as mean ± standard error of mean (SEM). The database was set up with GraphPad Instat 3.05 (GraphPad Software, San Diego CA, USA). The difference of BP, HR and duration of VT, VF and biochemical parameters among control, vehicle and drug treatment groups were carried out by using analysis of variance (ANOVA) followed by Tukey–Kramer Multiple Comparisons Test. A probability of less than 0.05 was considered to be statistically significant.

Determination of glutathione reductase (GR) activity GR was assayed by following the oxidation of NADPH at 340 nm at 37°C. The reaction was initiated by the addition of 50 ll supernatant to 1 ml of assay mixture containing 50 mmol/l Tris, pH 7.6, 100 lmol/l Na2EDTA, 4 mmol/l GSSG, 120 lmol/l NADPH. A blank cuvette was prepared in which the sample was replaced with water. The reaction was linear for 2–3 min [36]. Determination of catalase (CAT) activity CAT activity measurement in erythrocyte lysate was measured by the method of Aebi [37]. The reaction mixture

Results Effects of tamoxifen on coronary artery occlusion and reperfusion-induced arrhythmias Effects of tamoxifen on coronary occlusion-elicited arrhythmias in rats are shown in Table 1. The incidences of occlusion-induced VTs were reduced from 62.5% in control and vehicle groups to 25% (NS) in groups treated with 1 and 10 mg/kg tamoxifen. Also, the duration of occlusioninduced VT was decreased from 14.3 ± 6.1 s in control group to 3.3 ± 2.2 (P \ 0.05) and 1.5 ± 1.2 s (P \ 0.05) in tamoxifen 1 mg/kg and 10 mg/kg groups, respectively

123

230


Table 1 Effect of tamoxifen on coronary occlusion (7 min) induced arrhythmias in ovariectomized rats n

Ventricular tachycardia

Ventricular fibrillation

Incidence (%)

Duration (s)

Incidence (%)

Duration (s)

Control

8

62.5

14.3 ± 6.1

25

16 ± 4.5

Vehicle (DMSO)

8

62.5

7.8 ± 3.1

25

22 ± 5.5

Tamoxifen (1 mg/kg)

8

25

3.3 ± 2.2*

0

0

Tamoxifen (10 mg/kg)

8

25

1.5 ± 1.2*

0

0

n = number of experiments; values for duration of VT and VF are shown as the mean ± SEM * Statistical difference at the level of P \ 0.05 as compared with control

(Table 1). During occlusion period, irreversible VF and mortality were not observed in any of the animals. Reversible VF occurred in two animals of each control and vehicle groups. On subsequent reperfusion, VT developed in 100% of control and vehicle groups versus 25% (P \ 0.01), 12.5% (P \ 0.001) of tamoxifen at doses of 1 and 10 mg/kg, respectively. The duration of reperfusion-induced VT were also decreased from 142.1 ± 19 s in control and 128.6 ± 19.3 s in vehicle groups to 25.8 ± 14.0 (P \ 0.001) and 24.3 ± 10.9 s (P \ 0.001) in tamoxifen 1 and 10 mg/kg groups, respectively. Tamoxifen caused also significant decreases in the duration and the incidence of reversible VF (P \ 0.01 and P \ 0.001) (Table 2). Although the vehicle for tamoxifen tended to reduce the duration of VT and VF during reperfusion, but these changes did not reach statistical significance when compared to control.

Effects of tamoxifen on antioxidant parameters Tamoxifen treatment (10 mg/kg) markedly reduced lipid peroxidation as evidenced by reduction in MDA levels as compared to control group (1.53 ± 0.08 and 2.88 ± 0.58) (Fig. 1). Tamoxifen treatment with 1 mg/kg and 10 mg/kg also significantly reduced serum CK levels from 6262 ± 986 to 3524 ± 548 and 3542 ± 487 U/l (P \ 0.05) (Fig. 2). During ischemia-reperfusion injury, a significant decrease in GSH and GSH-Px levels were observed in the control group as compared to tamoxifen 10 mg/kg treated group (Table 4). However, tamoxifen treatment resulted in a significant repletion of these biochemical markers compared to control and vehicle groups. During I/R injury, not significant difference in changes of levels of CAT and GR were observed (Table 4).

Discussion Effects of tamoxifen on arterial BP and HR Table 3 summarizes the data showing the effects of tamoxifen (1 and 10 mg/kg) on mean arterial blood pressure and heart rate before and after coronary artery occlusion and reperfusion. No significant difference was observed among control and drug-treated groups.

Although reinstitution of coronary blood flow to the ischemic heart is considered beneficial for the recovery of cardiac pump function, reperfusion after a certain period of ischemia has been shown to further aggravate the cardiac abnormalities [14, 39–41]. Cardiac pump failure and changes in cell ultrastructure due to I/R injury involve a wide variety of complex pathophysiological abnormalities.

Table 2 Effect of tamoxifen on coronary reperfusion (7 min) induced arrhythmias in ovariectomized rats n

Control Vehicle (DMSO)

8 8

Ventricular tachycardia

Ventricular fibrillation

Incidence (%)

Duration (s)

Incidence (%)

Duration (s)

100 100

142.1 ± 19.0 128.6 ± 19.3

100 100

80.3 ± 18.1 58.7 ± 11.9

Tamoxifen (1 mg/kg)

8

25*

25.8 ± 14.0**

25*

8.75 ± 5.7**


8

12.5**

24.3 ± 10.9**

25*

6.25 ± 4.3**

n = number of experiments; values for duration of VT and VF are shown as the mean ± SEM * Statistical difference at the level of P \ 0.01 as compared with control and vehicle ** Statistical difference at the level of P \ 0.001 as compared with control and vehicle

123

Mol Cell Biochem (2008) 308:227–235 Table 3 Summary of mean arterial blood pressure (BP) and heart rate (HR) in control, vehicle and tamoxifen treated groups

231

Groups

End of stabilization

End of ischemia

Reperfusion (min) 1

7

BP (mm Hg) Control

86 ± 3

52 ± 8

68 ± 7

83 ± 5

Vehicle

82 ± 4

48 ± 6

58 ± 5

76 ± 6

Tamoxifen (1 mg/kg)

81 ± 2

49 ± 5

65 ± 6

83 ± 4


83 ± 6

50 ± 4

67 ± 5

79 ± 7

HR (beats/min)

Values are means ± SEM

Control

358 ± 12

328 ± 16

334 ± 17

344 ± 13

Vehicle

338 ± 14

346 ± 21

342 ± 15

354 ± 17

Tamoxifen (1 mg/kg)

334 ± 13

345 ± 19

338 ± 14

364 ± 16


343 ± 10

327 ± 17

335 ± 18

356 ± 15

Fig. 1 Effect of tamoxifen treatment on MDA levels in rats subjected to myocardial ischemia-reperfusion. The values are expressed as mean ± SEM. *P \ 0.05 as compared with control group

Fig. 2 Effect of tamoxifen treatment on serum CK levels in rats subjected to myocardial ischemia-reperfusion. The values are expressed as mean ± SEM. *P \ 0.05 as compared with control group

Neutrophil activation for the generation of different oxidants, such as HOCl [42,43], endothelial dysfunction for the generation of an excessive amount of an oxidant, peroxynitrite [44–47]; and formation of oxyradicals and H2O2 in the ischemic cardiomyoctes [43, 48], are play an important role in promoting oxidative stress and the development of intracellular Ca2+-overload in the I/R hearts. Intracellular Ca2+-overload is considered to play an important role in I/R injury [49–52]. Under oxidative stress conditions, variety of defects in the function and molecular

structure of sarcolemma, sarcoplasmic reticulum, and myofibrils have been shown to occur in I/R hearts [43, 48, 53–60]. Intracellular Ca2+-overload and oxidative stress in ischemic hearts upon reperfusion induce subcellular remodeling in organelles, such as sarcolemma, sarcoplasmic reticulum, extracellular matrix, myofibrils, and mitochondria [61]. Intracellular Ca2+-overload and oxidative stress are major mechanisms for the I/R induced

Table 4 Changes in blood GSH, GSH-Px, GR and CAT levels after ischemia-reperfusion injury in rats Control

Vehicle

Tamoxifen 1 mg/kg

Tamoxifen 10 mg/kg

GSH (mg/g hb)

1.06 ± 0.1

1.25 ± 0.09

1.62 ± 0.17

1,88 ± 0.14*

GSH-Px (mU/g hb)

1183 ± 119

1304 ± 187

1808 ± 265

2451 ± 341*

GR (mU/g hb)

997 ± 190

1100 ± 219

1082 ± 303

1325 ± 163

CAT (s-1/g hb)

0.091 ± 0.008

0.082 ± 0.016

0.090 ± 0.012

0.069 ± 0.011

* Statistical difference at the level of P \ 0.05 as compared with control

123

232

subcellular remodeling, subsequent contractile dysfunction and cardiac arrythmias [17, 61, 62]. The primary source of estrogen is the ovary and levels of estrogen fall profoundly at menopause [63]. Hormone replacement therapy (HRT) has been used to alleviate symptoms for over 50 years. The effects of HRT extend beyond symptom relief and have proved to be very complicated [63, 64]. It has been widely recommended for the prevention and treatment of osteoporosis, improvement of lipid profiles and reduction of the risk of mortality from cardiovascular diseases [65, 66]. However, the potential for cardioprotective effects of HRT after menopausal decline has been extensively studied with controversial and conflicting results. Estrogen administration in postmenopausal women has been shown to lower blood pressure and heart rate, improve the reflex heart rate response to temporary increases in blood pressure, reduce a-adrenoceptor responsiveness and enhance choline acetyltransferase activity at the heart [67–70]. Several investigators also stated that both pre and postmenopausal women on HRT seem to be protected from cardiovascular diseases [64, 71, 72]. Conversely, large human clinical trials suggested that HRT increased cardiovascular disease in postmenopausal women [73, 74]. Lately, it is emerging that HRT may have a ‘critical window’ where early use immediately after menopause has neutral or even cardioprotective effects, whereas once atherosclerosis develops, later HRT use may increase cardiovascular diseases [72, 75]. SERMs represent a class of non-hormonal agents that, similar to estrogen, have receptor agonist effects in bone and lipoproteins, but estrogen antagonistic effects on the breast and endometrial tissues [76–78]. Tamoxifen, a synthetic non-steroidal (a first generation SERM), had beneficial effects in the incidence of cardiovascular disease, such as coronary death [24, 57, 79–82]. Previous experimental studies have shown that acutely added tamoxifen relaxed mammalian blood vessels and inhibited voltagegated Ca2+ channels in vascular smooth muscle cells [83– 85]. Recent studies show that administration of tamoxifen to ovariectomized rats reduced hypercontraction of cerebral arteries [86, 87]. Intima-media thickness of the common carotid artery, an early marker of atherosclerosis, is significantly lower in menopausal women with cancer after taking tamoxifen [88]. Recently, Tsang et al. also showed that tamoxifen attenuated enhanced vascular reactivity induced by estrogen deficiency in rat arteries [89]. In the present study, we provide evidence that in ovariectomized rats the administration of tamoxifen significantly reduced both the incidence and duration of VT and VF during myocardial I/R injury. These results indicate that tamoxifen possesses a robust cardioprotective effect against myocardial I/R injury.

123


It is now established that an explosion of oxygen free radicals occurs immediately after reinstitution of blood flow to a previously ischemic myocardium which may result in enhanced lipid peroxidation as indicated by an increase in MDA levels documented both in clinical and experimental studies in conditions of myocardial I/R injury [90–92]. In the present study, an elevated level of MDA in control I/R group shows increased oxidative stress due to I/R reperfusion generated injury. On the contrary, in the 10 mg/kg/day tamoxifen treated group, they demonstrated decreased levels of lipid peroxidase activity and this could be due to reduced formation of lipid peroxidation from fatty acids. GHH and GSH-Px constitute the major intracellular defenses against damage due to H2O2 and lipid peroxidation during myocardial reperfusion injury [92, 93]. A significant decrease in GSH and GSH-Px in the control group confirms the presence of oxidative stress. In the present study, tamoxifen treatment exhibited significant antioxidant activity as it increased GSH, GSH-Px activity and reduced lipid peroxidation. A significant inhibition of lipid peroxidation evidenced by reduced MDA level and enhanced levels of GSH and GSH-Px indicate the attenuation of oxidative stress associated with I/R injury. Besides antioxidant enzymes and physiological antioxidants, alterations in creatine kinase have been also considered as an important marker of myocardial infarction [94]. In the present study, CK enzyme was estimated in serum and a significant increase in its levels was observed in control and vehicle groups. This observation is consistent with the previous reports and can be attributed to the fact that CK leaked out from the heart tissue to plasma on development of degenerative changes in myocardial cell membranes, due to lipid peroxidation [94]. The observation that tamoxifen treatment significantly restored the activity of CK compared to control I/R suggests the protective effect of tamoxifen on the myocardium. In conclusion, our study presents evidence that tamoxifen could effectively protect myocardium against myocardial ischemia and I/R induced arrhythmia. We can speculate that the beneficial cardioprotective effect of tamoxifen may be due to its antioxidant activity. Therefore, tamoxifen may be beneficial for prevention of cardiovascular system diseases in postmenopausal women. However, further studies are necessary to fully characterize the effects of the tamoxifen on the heart and to predict its potential therapeutic use. Acknowledgments This study was supported by a research grant (TPF-05006) from Adnan Menderes University Research Fund. Authors would like to thank Adnan Menderes University Medical Faculty, Department of Pharmacology for technical assistance during this study.


233

References 1. Weber KT, Janicki JS (1979) The metabolic demand and oxygen supply of the heart: physiologic and clinical considerations. Am J Cardiol 44:722–729 2. Hearse DJ (1990) Ischemia, reperfusion and the determinants of tissue injury. Cardiovasc Drug Ther 4:767–776 3. Harden WR, Barlow CH, Simson MB et al (1979) Myocardial ischemia and left ventricular failure in the isolated perfused rabbit heart. Am J Cardiol 44:741–746 4. Braunwald E, Kloner RA (1985) Myocardial reperfusion: a double-edged sword. J Clin Invest 76:1713–1719 5. Bolli R, Marban E (1999) Molecular and cellular mechanism in myocardial stunning. Physiol Rev 79:609–634 6. Grech ED, Bellamy CM, Jackson MJ et al (1994) Free radical activity after primary coronary angioplasty in acute myocardial infarction. Am Heart J 127:1443–1449 7. Temsah RM, Netticadan T, Dhalla NS (2003) Mechanisms of cellular alterations due to ischemia-reperfusion injury in the heart. In: Dhalla NS, Takeda N, Singh M, Lukas A (eds) Myocardial ischemia and preconditioning. Kluwer Academic Publishers, Boston, pp 149–164 8. Dhalla NS, Panagia V, Singal PK et al (1988) Alterations in heart membrane calcium transport during the development of ischemia-reperfusion injury. J Mol Cell Cardiol 20(suppl 2):3–13 9. Tani M (1990) Mechanisms of Ca2+ overload in reperfused myocardium. Annu Rev Physiol 52:543–559 10. Ceconi C, Curello S, Cargnoni A et al (1988) The role of glutathione status in the protection against ischemic and reperfusion damage: effects of N-acetyl cysteine. J Mol Cell Cardiol 20:5–13 11. Ferrari R, Alfieri O, Curello S et al (1990) Occurrence of oxidative stress during reperfusion of the human heart. Circulation 81:201–211 12. Ferrari R, Ceconi C, Curello S et al (1991) Oxygen free radicals and myocardial damage: protection with thiol containing agents. Am J Med 91:S95–S105 13. Otani H, Engelman RM, Rousou JA et al (1986) Cardiac performance during reperfusion improved by pretreatment with oxygen free-radical scavengers. J Thorac Cardiovasc Surg 91:290–295 14. Dhalla NS, Elmoselhi AB, Hata T et al (2000) Status of myocardial antioxidants in ischemia-reperfusion injury. Cardiovasc Res 47: 446–456 15. Krishenbaum LA, Singal PK (1993) Increase in endogenous antioxidant enzymes protects hearts against reperfusion injury. Am J Physiol 265:H484–H493 16. Vergely C, Perrin C, Laubriet A et al (2001) Postischemic myocardial recovery and oxidative stress status of vitamin C deficient rat hearts. Cardiovasc Res 51:89–99 17. Valko M, Leibfritz D, Moncol J et al (2007) Free radicals and antioxidants in normal physiological functions and human disease. Int J Biochem Cell Biol 39:44–84 18. Kasparova S, Brezova V, Valko M et al (2005) Study of the oxidative stress in a rat model of chronic brain hypoperfusion. Neurochem Int 46:601–611 19. Herrington DM, Klein KP (2001) Effects of SERM’s on important indicators of cardiovascular health: lipoproteins, hemostatic factors, endothelial function. Womens Health Issues 11:95–102 20. Kaya H, Ozkaya O, Sezik M et al (2005) Effects of raloxifene on serum malondialdehyde, erythrocyte superoxide dismutase, and erythrocyte glutathione peroxidase levels in healthy postmenopausal women. Maturitas 50:182–188 21. Stevenson M, Lloyd Jones M, De Nigris E et al (2005) A systematic review and economic evaluation of alendronate, etidronate, risedronate, raloxifene and teriparatide for the

22. 23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33.

34.

35.

36.

37. 38.

39.

40.

41. 42.

prevention and treatment of postmenopausal osteoporosis. Health Technol Assess 9:1–160 Bernardi F, Pluchino N, Stomati M et al (2003) CNS: sex steroids and SERM’s. Ann N Y Acad Sci 997:378–388 Harman SM (2006) Estrogen replacement in menopausal women: recent and current prostective studies, the WHI and The KEEPS. Gend Med 3:254–269 McDonald CC, Stewart HJ (1991) Fatal myocardial infarction in the Scottish adjuvant tamoxifen trial. Scottish Breast Cancer Committee BMJ 303:435–437 Early Breast Cancer Trialists’ Collaborative Group (1992) Systemic treatment of early breast cancer by hormonal, cytotoxic, or immune therapy: 133 randomized trials involving 31000 recurrences and 24000 deaths among 75000 women. Lancet 339:71–85 Clarke SC, Schofield PM, Grace AA et al (2001) Tamoxifen effects on endothelial function and cardiovascular risk factors in men with advanced atherosclerosis. Circulation 103:1497–1502 Li X, Takabashi M, Kushida K et al (1998) The less potent estrogenic effect of tamoxifen on bone in ovariectomized rats with established osteopenia. Calcif Tissue Int 62:502–505 Pham-Dang ML, Clement R, Mercier I et al (2003) Comparative effects of tamoxifen and angiotensin II type-1 receptor antagonist therapy on the hemodynamic profile of the ovariectomized rat. Can J Physiol Pharmacol 81:915–919 Aktug H, Uslu S, Terek MC et al (2006) Effects of ovariectomy and tamoxifen on rat bone tissue: histomorphometric and histopathologic study. Anal Quant Cytol Histol 28:207–212 Guc MO, Boachie-Ansah G, Kane KA et al (1993) Comparison of antiarrhythmic and electrophysiologic effects of diltiazem and its analogue siratiazem. J Cardiovasc Pharmacol 22:681–686 Olmez E, Birincioglu M, Aksoy T et al (1995) Effects of captopril on ischemia-reperfusion-induced arrhythmias in an in vivo rat model. Pharmacol Res 82:37–41 Ozer MK, Sahna E, Birincioglu M et al (2002) Effects of captopril and losartan on myocardial ischemia-reperfusion induced arrhythmias and necrosis in rats. Pharmacol Res 45:257–263 Walker MJ, Curtis MJ, Hearse DJ et al (1988) The Lamberth Conventions: guidelines for the study of arrhythmias in ischemia infarction and reperfusion. Cardiovasc Res 22:447–455 Tietze F (1969) Enzymatic method for quantitative determination of nano gram amounts of total and oxidized glutathione. Applications to mammalian blood and other tissues. Anal Biochem 27:502–522 Ohkawa H, Ohishi N, Yagi, K (1979) Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction. Anal Biochem 95:351–358 Racker E (1955) Glutathione reductase (liver and yeast). In: Colowick SP, Kaplan NO (eds) Methods in enzymology, vol 2. Academic Press, New York Aebi H (1974) Catalase. In: Bergmeyer HU (ed) Methods of enzymatic analysis. Academic Press, New York, pp 673–677 Paglia DE, Valentine WN (1967) Studies on the quantitative and qualitative characterization of erythrocyte peroxidase. J Lab Clin Med 2:158 Dhalla NS, Goffman L, Takeda S et al (1999) Evidence for the role of oxidative stress in acute ischemic heart disease: a brief review. Can J Cardiol 15:587–593 Marczin N, El-Habashi N, Hoare GS et al (2003) Antioxidants in myocardial ischemia-reperfusion injury: therapeutic potential and basic mechanisms. Arch Biochem Biophys 420:222–236 Kim SJ, Depre C, Vatner SF (2003) Novel mechanisms mediating stunned myocardium. Heart Fail Rev 8:143–153 Myers ML, Webb C, Moffat M et al (1991) Activated neutrophils depress myocardial function in the perfused rabbit heart. Can J Cardiol 7:323–330

123

234 43. Kukreja RC, Weaver AB, Hess ML (1989) Stimulated human neutrophils damage cardiac sarcoplasmic reticulum function by generation of oxidants. Biochim Biophys Acta 990:198–205 44. Schulz R, Dodge KL, Lopaschuk GD et al (1997) Peroxynitrite impairs cardiac contractile function by decreasing cardiac efficiency. Am J Physiol Heart Circ Physiol 272:H1212–H1219 45. Xie YW, Kaminski PM, Wolin MS (1998) Inhibition rat cardiac muscle contraction and mitochondrial respiration by endogenous peroxynitrite formation during posthypoxic reoxygenation. Circ Res 82:891–897 46. Oyama J, Shimokawa H, Momii H et al (1998) Role of nitric oxide and peroxynitrite in the cytokine-induced sustained myocardial dysfunction in dogs in vivo. J Clin Invest 101:2207–2214 47. Poderoso JJ, Peralta JG, Lisdero CL et al (1998) Nitric oxide regulates oxygen uptake and hydrogen peroxide release by the isolated beating rat heart. Am J Physiol Cell Physiol 274: C112–C119 48. Xu KY, Zweier JL, Becker LC (1997) Hydroxyl radical inhibits sarcoplasmic reticulum Ca2+ATPase function by direct attack on the ATP binding site. Circ Res 80:76–81 49. Murphy JG, Smith TW, Marsh JD (1988) Mechanisms of reoxygenation-induced calcium overload in cultured chick embryo heart cells. Am J Physiol Heart Circ Physiol 254:H1133–H1141 50. Nayler WG, Panagiotopoulos S, Elz JS et al (1988) Calciummediated damage during post-ischemic reperfusion. J Mol Cell Cardiol 20(Supl 2):41–54 51. Billman GE, Mcllroy B, Johnson JD (1991) Elevated myocardial calcium and its role in sudden cardiac death. FASEB J 5: 2586–2592 52. Lee JA, Allen DG (1991) Mechanisms of acute ischemic contractile failure of the heart. Role of intracellular calcium. J Clin Invest 88:361–367 53. Van Eyk JE, Powers F, Law W et al (1998) Breakdown and release of myofilament proteins during ischemia and ischemia/ reperfusion in rat hearts: identification of degradation products and effects on the pCa-force relation. Circ Res 82:261–271 54. Gao WD, Liu Y, Mellgren R et al (1996) Intrinsik myofilament alterations underlying the decreased contractility of stunned myocardium. A consequence of Ca2+ dependent proteolysis? Circ Res 78:455–465 55. Barbato R, Menabo R, Dainese P et al (1996) Binding of ctyosolic proteins to myofibrils in ischemic rat hearts. Circ Res 78:821–828 56. Foster DB, Noguchi T, VanBuren P et al (2003) C-terminal truncation of cardiac troponin I causes divergent effects on ATPase and force: implications for the pathophysiology of myocardial stunning. Circ Res 93:917–924 57. Canton M, Neverova I, Menabo R et al (2004) Evidence of myofibrillar protein oxidation induced by postischemic reperfusion in isolated rat hearts. Am J Physiol Heart Circ Physiol 286:H870–H877 58. Powell SR, Gurzenda EM, Wahezi SM (2001) Actin is oxidized during myocardial ischemia. Free Radic Biol Med 30:1171–1176 59. Mekhfi H, Veksler V, Mateo P et al (1996) Creatine kinase is the main target of reactive oxygen species in cardiac myofibrils. Circ Res 78:1016–1027 60. Suzuki S, Kaneko M, Chapman DC et al (1991) Alterations in cardiac contractile proteins due to oxygen free radicals. Biochim Biophys Acta 1074:95–100 61. Dhalla NS, Saini HK, Tappia PS et al (2007) Potential role and mechanisms of subcellular remodeling in cardiac dysfunction due to ischemic heart disease. J Cardiovasc Med 8:238–250 62. Hicks JJ, Montes-Cortes DH, Cruz-Dominguez MP et al (2007) Antioxidants decrease reperfusion induced arrhythmias in myocardial infarction with ST-elevation. Front Biosci 12:2029–2037

123

Mol Cell Biochem (2008) 308:227–235 63. Burger HG, Teede HJ (2007) Endocrine changes during the perimenopause. In: Studd J (ed) Treatment of the postmenopausal woman: basic and clinical aspects, 3rd ed. Elsevier, New York 64. Teede HJ (2003) Hormone replacement therapy and the effects on cardiovascular and cerebrovascular disease. Best Pract Clin Endocrinol Metab 17:73–90 65. Grady D, Rubin SM, Petitti DB et al (1992) Hormone therapy to prevent disease and prolong life in postmenopausal women. Ann Intern Med 117:1016–1037 66. Grodstein F, Stampfer MJ, Colditz GA et al (1997) Postmenopausal hormone therapy and mortality. N Engl J Med 336: 1769–1775 67. DeMeersman RE, Zion AS, Giardina E et al (1998) Estrogen replacement, vascular distensibility, and blood pressure in postmenopausal women. Am J Physiol 274:H1539–H1544 68. Sung BH, Ching M, Izzo JL et al (1999) Estrogen improves abnormal norepinephrine-induced vasoconstriction in post-menopausal women. J Hypertens 17:523–528 69. Steptoe A, Fieldman G, Evans O et al (1996) Cardiovascular risk and responsivity to mental stress. The influence of age, gender and risk factors. J Cardiovasc Risk 3:83–93 70. Du XJ, Riemersma RA, Dart AM (1995) Cardiovascular protection by estrogen is partly mediated through modulation of autonomic nervous function. Cardiovasc Res 30:161–165 71. Sourander L, Rajala T, Helenious H (1998) Cardiovascular and cancer morbidity and mortality and sudden cardiac death in postmenopausal women on ERT. Lancet 352:1965–1969 72. Burger HG (2006) Hormone therapy in the WHI era. Aust N Z J Obstet Gynaecol 46: 8–91 73. Hulley S, Grady D, Bush T et al (1998) Randomized trial of estrogen plus progestin for secondary prevention of coronary heart disease in postmenopausal woman. JAMA 288:321–333 74. Rossouw JE, Anderson GL, Prentice RL et al, Writing Group for the Women’s Health Initiative Investigators (2000) Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women’s Health Initiative randomized controlled trial. JAMA 288:321–333 75. Manson JE, Bassuk SS, Harman SM et al (2006) Postmenopausal hormone therapy: new questions and the case for new clinical trials. Menopause 13:139–147 76. Mitlak BH, CohenFJ (1997) In search of optimal long-term female estrogen replacement: the potential of selective estrogen receptor modulators. Hor Res 48:155–163 77. Purdie DW, Beardsworth SA (1999) The selective estrogen receptor modulation: evaluation and clinical application. Br J Clin Pharmacol 48:785–792 78. Mobasseri S, Liebson PR, Klein LW (2004) Hormone therapy and selective estrogen receptor modulators for prevention of coronary heart disease in postmenopausal women. Cardiol Rev 12:287–298 79. Waters DD (2002) Estrogen therapy for unstable angina (editorial). J Am Coll Cardiol 39:238–240 80. Ferrara A, Quesenberry CP, Karter AJ et al (2003) Current use of unopposed estrogen and progestin and risk of acute myocardial infarction among women with diabetes. The Northern California Kaiser Permanente Diabetes Registry, 1995–1998. Circulation 107:43–48 81. McDonald CC, Alexander FE, Whyte BW et al (1995) Cardiac and vascular morbidity in women receiving adjuvant tamoxifen for breast cancer in a randomized trial. BMJ 311:977–980 82. Costantino JP, Kuller LH, Ives DG et al (1997) Coronary heart disease mortality and adjuvant tamoxifen therapy. J Natl Cancer Inst 89:776–782 83. Figtree GA, Webb CM, Collins P (2000) Tamoxifen acutely relaxes coronary arteries by an endothelium-, nitric oxide-, and


84.

85.

86.

87.

88.

estrogen receptor-dependent mechanism. J Pharmacol Exp Ther 295:519–523 Hutchison SJ, Chou TM, Chatterjee K et al (2001) Tamoxifen is an acute, estrogen like, coronary vasodilator of porcine coronary arteries in vitro. J Cardiovasc Pharmacol 38:657–665 Song J, Stanley PR, Zhang F et al (1996) Tamoxifen (estrogen antagonist) inhibits voltage-gated calcium current and contractility in vascular smooth muscle from rats. J Pharmacol Exp Ther 277:1444–1453 Thorin E, Pham-Dang M, Clement R et al (2003) Hyper-reactivity of cerebral arteries from ovariectomized rats: therapeutic benefit of tamoxifen. Br J Pharmacol 140:1187–1192 Tsang SY, Yao X, Chan FL et al (2004) Estrogen and tamoxifen modulate cerebrovascular tone in ovariectomized female rats. Hypertension 44:78–82 Simon T, Boutouyrie P, Simon JM et al (2002) Influence of tamoxifen on carotid intima-media thickness in postmenopausal women. Circulation 106:2925–2929

235 89. Tsang SY, Yao X, Chan HY et al (2007) Tamoxifen and estrogen attenuate enhanced vascular reactivity induced by estrogen deficiency in rat carotid arteries. Biochem Pharmacol 73:1330–1339 90. Sevenian A, Hochstein P (1985) Mechanisms and consequences of lipid peroxidation in biological systems. Annu Rev Nutr 5:365–375 91. Ceconi C, Cargnoni A, Pasini E et al (1991) Evaluation of phospholipid peroxidation as malondialdehyde during myocardial ischemia and reperfusion injury. Am J Physiol 260:H1057–H1061 92. Gao F, Yao CL, Gao E et al (2002) Enhancement of glutathione cardioprotection by ascorbic acid in myocardial reperfusion injury. J Pharmacol Exp Ther 301:543–550 93. Leichtweis S, Ji LL (2001) Glutathionedeficiency intensifies ischemia-reperfusion induced cardiac dysfunction and oxidative stress. Acta Physiol Scand 172:1–10 94. Jennings RB, Murry CE, Steenbergen CJR et al (1990) Acute myocardial ischemia: development of cell injury in sustained ischemia. Circulation 82:3–12

123