International Journal of Cardiology 172 (2014) 162–164

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International Journal of Cardiology

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Letter to the Editor

Gusongning reduced the susceptibility of orchidectomized rats toarrhythmias in infarcted myocardium

Lei Yang a,1, Benzhi Cai b,1, RenjunWang b,Weijie Du b, Ying Zhang b, Hongli Shan b, Zhenggang Bi a, Yanjie Lu b,⁎a Department of Orthopedics, The First Affiliated Hospital of Harbin Medical University, Harbin 150001, Chinab Department of Pharmacology, Harbin Medical University, Harbin 150081, China

⁎ Corresponding author. Tel./fax: +86 451 86671354.E-mail address: yjlu86@yahoo.com (Y. Lu).

1 Made equal contribution to this work.

0167-5273/$ – see front matter © 2013 Elsevier Ireland Lhttp://dx.doi.org/10.1016/j.ijcard.2013.12.070

a r t i c l e i n f o

Article history:

Received 9 October 2013Accepted 22 December 2013Available online 28 December 2013

Keywords:ArrhythmiasOrchidectomyIon channel

ed that Asperosaponin VI produced cardioprotective effects on acuteand chronic MI in rats [9]. However, whether the saponins fromDipsacus asper Wall (Gusongning, GSN) have therapeutic effects onheart diseases following androgen deficiency remain unknown. In thisstudy, we aim to explorewhether Gusongning could prevent cardiac ar-rhythmias in infarcted rats with androgen deprivation and its underly-ing mechanisms.

Male Sprague–Dawley (SD) rats (230–280 g) were used in the pres-ent study. Use of the animals was in accordance with the regulations of

Lower levels of androgens increase the risk of heart diseases (IHD)such as arrhythmias and angina besides osteoporosis in men, which isassociated with the loss of cardioprotection of testosterone [1]. Experi-mental studies showed that androgen deficiency affected functional in-tracellular calcium handling and caused the decline of cardiaccontractile functions [2]. Especially, androgen deprivation significantlyslowed down the heart rate and prolonged the duration of QT, QTc in-tervals and QTc-dispersion, which provided the substrate for arrhyth-mias and sudden death [3-4]. Mechanistic studies uncovered therepolarization of ventricular myocardium which was mainly deter-mined by male sex steroid hormone, but not female [4]. Although tes-tosterone replacement therapy has been shown to alleviate symptomsof heart diseases after androgen deficiency inmen and experimental an-imals, its clinical application was restricted by its serious side effectssuch as prostate cancer [5]. Thus, it is necessary to look for new thera-peutic drugs for lethal heart diseases in hypogonadal males.

Dipsacus asper (Xuduan)Wall is one kind of medicinal herb andwellknown as a traditional Chinesemedicine for enhancing bone density [6].The saponin extract of Dipsacus asper wallwas found to enhance osteo-blast maturation and differentiation via increasing BMP-2 and activat-ing p38 and ERK1/2 [6]. One triterpene saponin compound isolatedfrom Dipsacus asper Wall has been shown to attenuate amyloid β-induced cognitive deficits and inflammatory response in rats via regu-lating Akt/NF-κB pathway [7], and also may protect PC 12 cells against

td. All rights reserved.

amyloid β-induced cytotoxicity [8]. In hearts, recent studies also report-

the ethic committees of HarbinMedical University, and confirmed withthe Guide for the Care and Use of Laboratory Animals published by theUS National Institutes of Health (NIH Publication No. 85–23, revised1996). The rats were divided into three groups: MI (myocardial infarc-tion), ORX + MI (myocardial infarction after orchidectomy), andORX + GSN + MI (GSN treated ORX rats before MI). For all groups,the animals were anesthetized with sodium pentobarbital via intraper-itoneally (i.p.) and standard lead II electrocardiograms were continu-ously recorded for a period of 30 min during surgery. The rats wereorchiectomized or sham-operated at the 30 weeks of age. The ratswere then given antibiotics, standard food and water feeding andhoused in separate cages in the laboratory. 24 weeks after surgical pro-cedure, the rats were anesthetized and then underwent ligation of theleft anterior descending coronary artery to induce myocardial infarc-tion. The rats in ORX + MI + GSN group were orally administered byGSN (900 mg/kg) for 7 days before myocardial infarction.

Ventricular cardiomyocytes are acutely isolated, and whole-cellpatch-clamp recordings were performed to record ion currents in car-diomyocyte from the three groups using an Axopatch 200B amplifier(Axon Instruments Inc., Union City, CA, USA). Levels of statistical signif-icance were assessed by Student's t-test. One-way ANOVA was used formultiple comparisons. All data are presented as mean ± SEM. A two-tailed p b 0.05 is considered to be a statistically significant difference.

Firstly, we investigated the effects of GSN on the vulnerability of car-diac arrhythmias during myocardial infarction with androgen depriva-tion. GSN (900 mg/kg) was given orally to ORX rats for 7 days, andthe duration of premature ventricular beat (PVB) and ventricular tachy-cardia (VT) were recorded within 30 min after MI among the threegroups. As shown in Fig. 1, the duration of ventricular arrhythmias in-cluding PVB and VT was significantly prolonged in infarcted rats withandrogen deprivation (1152.1 ± 69.7 ms) compared with infarctedrats (784.0 ± 32.1 ms) (n = 6 for each group, p b 0.05). But, GSNtreatment can significantly shorten the duration of PVB and VT in

Fig. 1. Effects of GSN pretreatment on the vulnerability of ventricular arrhythmias in infarcted hearts with androgen deprivation. (A) The samples of electrocardiograph recorded in heartsamong the three groups. (B) The duration of arrhythmiaswas significantly prolonged inORX + MI group comparedwithMI group. GSN pretreatment significantly shortened thedurationof arrhythmias in ORX + MI rats (*p b 0.05, n = 6).

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infarcted rats with androgen deprivation from 1152.1 ± 69.7 ms to836.8 ± 55.9 ms (Fig. 1B) (n = 6 rats for each group, p b 0.05). Itsuggests that GSN pretreatment can decrease the susceptibility oforchidectomized rats to arrhythmias in infarcted myocardium. Consis-tently, previous studies also reported that androgen deprivation byorchidectomy lengthened theQT in hearts and prone to cardiac arrhyth-mias [4].

Furthermore, we studied the electrophysiological mechanisms un-derlying the prevention of ischemic arrhythmias by GSN in ORX rats. Itis well known that calcium current (ICa) plays an important role inmembrane repolarization and cardiac electrical properties. The increaseor reduction of ICa has been shown responsible for the occurrence of ar-rhythmias. Thus, we employed thewhole-cell patch clamp technique torecord ICa currents in ventricular cardiomyocytes isolated from peri-ischemic zone of hearts. We evaluated the difference of current densityof ICa among the three groups. As shown in Fig. 2, at the voltage of+10 mV, infarcted rats with androgen deprivation displayed a signifi-cant reduction of ICa compared with rats with myocardial infarctionalone. To our knowledge, this is the first study to uncover androgen

Fig. 2. Effects of GSN pretreatment on ICa currents of cardiomyocytes in infarcted rats withcardiomyocytes from the three groups. (B) Infarcted rats with androgen deprivation showedcan attenuate the reduction of ICa in infarcted rats with androgen deprivation (p b 0.05, n = 5

deprivation affected ICa in infarcted rats. But GSN pretreatment can re-verse the reduction of ICa in infarcted heart with androgen deprivation(n = 5 for each group, p b 0.05). It suggests that the restoration of ICaby GSN contributes to decreased susceptibility to arrhythmias duringmyocardial infarction with androgen deprivation.

In rat ventricular myocytes, transient outward potassium currents(Ito) are also responsible for action potential [10]. Thus, we also detectedIto currents in ventricular cardiomyocytes isolated from the threegroups, and evaluated the effects of GSN on Ito currents. Fig. 3A showedthe representative traces of Ito recorded from ventricular cardio-myocytes from the three groups. Compared with cardiomyocytes frominfarcted rats, Ito was not affected in infarcted rats with androgen depri-vation (n = 6 for each group, p N 0.05). It suggests that androgens didnot influence the function of Ito in cardiomyocytes, and the increasedsusceptibility to arrhythmogenesis in infarcted rats with androgen dep-rivation is independent on Ito. Meanwhile, administration of GSN alsodid not impact Ito in infarcted rats with androgen deprivation (n = 6for each group, p N 0.05). This indicates that Ito is not responsible forthe protective effects of GSN on arrhythmias.

androgen deprivation. (A) Representative traces of ICa currents from left ventriculara significant decrease of ICa compared with sham-operated infarcted rats. GSN treatment).

Fig. 3. Comparison of Ito in left ventricular cardiomyocytes from the three groups. (A) The representative traces of Ito recorded from ventricular cardiomyocytes fromMI, ORX + MI, andORX + GSN + MI rats. (B) Ito was not affected by the administration of GSN in infarcted rats with androgen deprivation (p N 0.05, n = 6).

e164 L. Yang et al. / International Journal of Cardiology 172 (2014) 162–164

Taken together, the present study revealed that Gusongningprevented cardiac arrhythmias during myocardial infarction in ORX ratspossibly via acting on L-type Ca2+ currents, which provides the new ev-idence of GSN as a cardioprotective agent for cardiac electrical disorders.

Acknowledgments

This work was supported by the China Postdoctoral ScienceFoundation (2013M531071), Heilongjiang Province PostdoctoralFoundation (LBH-Z12166) and the Scientific Foundation of theFirst Affiliated Hospital of Harbin Medical University (2013B08).

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