Elsevier

European Journal of Pharmacology

Volume 762, 5 September 2015, Pages 293-298
European Journal of Pharmacology

Cardiovascular pharmacology
Pre-treatment with LCZ696, an orally active angiotensin receptor neprilysin inhibitor, prevents ischemic brain damage

https://doi.org/10.1016/j.ejphar.2015.05.059Get rights and content

Abstract

Angiotensin II receptor blockers (ARBs) are known to prevent ischemic brain damage after stroke. Natriuretic peptides, which are increased by a neprilysin inhibitor, are also reported to protect against brain damage. Therefore, we investigated the possible protective effect of valsartan (VAL) compared with LCZ696 (VAL+ neprilysin inhibitor; 1:1) after middle cerebral artery (MCA) occlusion. Eight-week-old male C57BL/6J mice were treated with VAL (3 mg/kg per day) or LCZ696 (6 mg/kg per day) for 2 weeks before MCA occlusion. Blood pressure and heart rate were measured by telemetry. Cerebral blood flow (CBF) was determined by laser-Doppler flowmetry. Ischemic area was evaluated by triphenytetrasodium chloride staining, and oxidative stress was determined by dihydroethidium staining. Blood pressure and heart rate were not significantly different before and after treatment. Pre-treatment with LCZ696 or VAL reduced the ischemic area, and this effect of LCZ696 was more marked than that of VAL pre-treatment. The decrease in CBF in the peripheral region of the ischemic area was significantly attenuated by pre-treatment with LCZ696 or VAL, without any significant effect on CBF in the core region. VAL or LCZ696 pre-treatment significantly decreased the increase of superoxide anion production in the cortex on the ischemic side. However, no significant difference in CBF and superoxide anion production was observed between VAL and LCZ696 pre-treatment. The preventive effect of LCZ696 on ischemic brain damage after stroke was more marked than that of VAL. LCZ696 could be used as a new approach to prevent brain damage after stroke. (246 words)

Introduction

Stroke is one of the leading causes of disability and death in the industrialized world, and post-stroke disabilities markedly impair quality of life. The renin angiotensin system is well known to play a role in the pathogenesis of ischemic brain damage, and has been evaluated in various studies such as in mouse models of brain infarction induced by middle cerebral artery (MCA) occlusion (Iwai et al., 2004, Saavedra et al., 2006, Walther et al., 2002). Angiotensin II type 1 (AT1) receptor blockers (ARBs) were shown to attenuate ischemic brain damage in these studies. Regarding the clinical relevance of the protective effects of ARBs against brain damage after stroke, Fuentes et al. reported that patients taking antihypertensive drugs at stroke onset had a lower rate of a poor outcome than those not on antihypertensive treatment, and those taking an ARB had better outcomes than those without an ARB, while analysis of other antihypertensive drugs showed no difference (Fuentes et al., 2010).

Inhibition of neutral endopeptidase (NEP) has been investigated as a potential novel therapeutic target, because of its ability to increase the plasma concentrations of natriuretic peptides (NPs), since NPs have potent natriuretic and vasodilator properties, inhibit the activity of the renin–angiotensin–aldosterone system, lower sympathetic drive, and exert antiproliferative and antihypertrophic effects (Mangiafico et al., 2013). LCZ696 is a novel single molecule in which the molecular moieties of valsartan and the molecular moieties of an NEP inhibitor prodrug, AHU377, are present in a 1:1 M ratio (Gu et al., 2010). LCZ696 provides a complementary and fully additive reduction of BP compared with valsartan (Ruilope et al., 2010). In heart failure patients with preserved ejection fraction, LCZ696 reduced NT-proBNP to a greater degree than did valsartan alone, and LCZ696 showed beneficial effects on symptoms independent of its BP-lowering effect (Solomon et al., 2012), suggesting that LCZ696 leads to cardiovascular benefits over and above the effect on BP lowering (Bloch and Basile, 2010).

In the acute phase of ischemic stroke, NP level is frequently elevated and has been shown to be an independent predictor of mortality (Estrada et al., 1994, Iltumur et al., 2006, Nakagawa et al., 2005). These results suggest that NPs could play a role in the prevention of ischemic brain damage at least in part due to hemodynamic regulation during the acute phase of stroke. Accordingly, we tried to explore the beneficial effects of LCZ696 on focal brain ischemia induced by MCA occlusion in mice and its possible mechanisms in comparison with valsartan.

Section snippets

Animals and treatment

All procedures were reviewed and approved by the Animal Studies Committee of Ehime University. An ARB, valsartan (VAL), was purchased from LKT Laboratories, Inc. (St. Paul, MN). LCZ696 was provided by Novartis Pharma AG (Basel, Switzerland). Mice were treated with VAL (3 mg/kg per day) or LCZ696 (6 mg/kg per day) orally as powder in gelatin mini-capsules (Torpac, Inc., Fairfield, NJ) daily for 2 weeks before MCA occlusion. Body weight was measured after VAL or LCZ696 pre-treatment for 2 weeks.

Focal ischemic injury of brain after MCA occlusion

Focal brain ischemia was induced by MCA occlusion using the intraluminal filament technique. VAL (3 mg/kg/day) or LCZ696 (6 mg/kg/day) was administered for 2 weeks before MCA occlusion. Systolic blood pressure, diastolic blood pressure and heart rate were not significantly different in each group (Fig. 1). Pre-treatment with VAL or LCZ attenuated the ischemic area, and quantitative analysis of the average ischemic ratio showed a significant reduction of approximately 41% and 55% in the VAL and

Discussion

In the present study, we demonstrated that both valsartan and LCZ696 pre-treatment significantly decreased the ischemic area after stroke, at least in part by increasing CBF in the penumbra and inhibiting oxidative stress. Moreover, we observed that LCZ696 pre-treatment was more effective than VAL pre-treatment in reducing the ischemic area, independent of BP.

In spite of their apparent similar effects to increase CBF and decrease superoxide anion production after stroke, LCZ696 was more

Sources of funding

This study was supported by JSPS KAKENHI Grant numbers 25293310 (M.H.) and 25462220 (M.M.), and research grants from pharmaceutical companies: Astellas Pharma Inc., Bayer Yakuhin, Ltd., Daiichi-Sankyo Pharmaceutical Co. Ltd., Nippon Boehringer Ingelheim Co. Ltd., Shionogi & Co. Ltd., and Takeda Pharmaceutical Co. Ltd.

Disclosure

None.

Acknowledgment

This study was partially funded by Novartis Pharma K.K and the material was provided by Novartis Pharma AG.

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