Matrix Metalloproteinase‐2 Activity is Associated with Divergent Regulation of Calponin‐1 in Conductance and Resistance Arteries in Hypertension‐induced Early Vascular Dysfunction and Remodelling

Matrix metalloproteinase (MMP)‐2 participates in hypertension‐induced maladaptive vascular remodelling by degrading extra‐ and intracellular proteins. The consequent extracellular matrix rearrangement and phenotype switch of vascular smooth muscle cells (VSMCs) lead to increased cellular migration and proliferation. As calponin‐1 degradation by MMP‐2 may lead to VSMC proliferation during hypertension, the hypothesis of this study is that increased MMP‐2 activity contributes to early hypertension‐induced maladaptive remodelling in conductance and resistance arteries via regulation of calponin‐1. The main objective was to analyse whether MMP‐2 exerts similar effects on the structure and function of the resistance and conductance arteries during early hypertension. Two‐kidney, one‐clip (2K‐1C) hypertensive male rats and corresponding controls were treated with doxycycline (30 mg/kg/day) or water until reaching one week of hypertension. Systolic blood pressure was increased in 2K‐1C rats, and doxycycline did not reduce it. Aortas and mesenteric arteries were analysed. MMP‐2 activity and expression were increased in both arteries, and doxycycline reduced it. Significant hypertrophic remodelling and VSMC proliferation were observed in aortas but not in mesenteric arteries of 2K‐1C rats. The contractility of mesenteric arteries to phenylephrine was increased in 2K‐1C rats, and doxycycline prevented this alteration. The potency of phenylephrine to contract aortas of 2K‐1C rats was increased, and doxycycline decreased it. Whereas calponin‐1 expression was increased in 2K‐1C mesenteric arteries, calponin‐1 was reduced in aortas. Doxycycline treatment reverted changes in calponin‐1 expression. MMP‐2 contributes to hypertrophic remodelling in aortas by decreasing calponin‐1 levels, which may result in VSMC proliferation. On the other hand, MMP‐2‐dependent increased calponin‐1 in mesenteric arteries may contribute to vascular hypercontractility in 2K‐1C rats. Divergent regulation of calponin‐1 by MMP‐2 may be an important mechanism that leads to maladaptive vascular effects in hypertension.     

The CD147/MMP‐2 signaling pathway may regulate early stage cardiac remodelling in spontaneously hypertensive rats

Previous studies have reported that decreased matrix metalloproteinase‐2 (MMP‐2) is associated with early stage (age 8–16 weeks) ventricular remodelling in spontaneously hypertensive rats (SHR). We hypothesized that inhibited CD147/MMP‐2 signalling might down‐regulate MMP‐2 expression and augment remodelling in spontaneously hypertensive rats. Twenty‐nine male SHR (8 weeks) were randomly assigned to SHR, CD147, and CD147+DOX groups. The control group included eight age‐matched WKY rats. CD147 and CD147+DOX groups received recombinant human CD147 (600 ng/kg in 1.5 mL saline, weekly). The SHR and WKY groups received the vehicle. The CD147+DOX group also received doxycycline, an inhibitor of MMPs (daily, 30 mg/kg in 1.5 mL saline, iG). On day 56 echocardiography and left ventricular mass index (LVWI) measurements were collected and histological sections were stained for cell and collagen content. Myocardium MMP‐2, TIMP‐1, CD147, and collagens types I and III were estimated by western blot. CD147 and the ratio of MMP‐2/TIMP‐1 were lower in SHR than WKY rats (P<.05). Myocyte hypertrophy, partial fibre breaks, plasmolysis, necrosis and collagen content (collagen volume fraction [CVF], I and III) in SHR were above control levels (P<.05). CD147 rats showed CD147, MMP‐2 and MMP‐2/TIMP‐1 were increased (P<.05), CVF, LVWI, and collagen I and III were decreased (P<.05) and myocyte morphology was improved. CD147 levels did not differ between CD147+DOX and CD147 groups, CVF, collagens type I and III and partial fiber breaks were more abundant in CD147+DOX (P<.05). In summary, an inhibited CD147/MMP‐2 pathway was associated with early stage cardiac remodelling, and CD147 supplementation may attenuate this response.     

Asiatic acid alleviates cardiovascular remodelling in rats with L‐NAME‐induced hypertension

A previous study demonstrated the antihypertensive effect of asiatic acid. The current study investigates the effect of asiatic acid on cardiovascular remodelling and possible mechanisms involved in N_ω‐nitro‐L‐arginine methyl ester hydrochloride (L‐NAME)‐induced hypertensive rats. Male Sprague–Dawley rats were treated with L‐NAME (40 mg/kg per day) for 3 weeks in order to induce hypertension. Hypertensive rats were administered asiatic acid (20 mg/kg per day) or vehicle for a further 2 weeks. It was found that hypertensive rats showed high systolic blood pressure, left ventricular (LV) hypertrophy, increases in LV fibrosis, aortic wall thickness and aortic collagen deposition (P < 0.05). Moreover, decreased plasma nitrate and nitrite (NOx) and increased plasma tumor necrosis factor alpha (TNF‐α) were observed in hypertensive rats (P < 0.05). This was consistent with downregulation of endothelial nitric oxide synthase (eNOS) expression and upregulation of inducible nitric oxide synthase (iNOS) expression in heart and aortic tissues (P < 0.05). Levels of malondialdehyde (MDA) in plasma, aortic and heart tissues were significantly increased in hypertensive rats (P < 0.05). Asiatic acid markedly reduced blood pressure, alleviated cardiovascular remodelling, and restored plasma NOx and TNF‐α as well as eNOS/iNOS expression in heart and aortic tissues (P < 0.05). Additionally, there was a significant reduction of MDA levels in the tissues of treated hypertensive rats. In conclusion, this study demonstrates the therapeutic effects of asiatic acid on blood pressure and cardiovascular remodelling, which is possibly related to the restoration of eNOS/iNOS expression, and the resulting anti‐inflammatory and antioxidant activities.     

l‐Carnitine Attenuates Cardiac Remodelling rather than Vascular Remodelling in Deoxycorticosterone Acetate‐Salt Hypertensive Rats

Abstract: l ‐Carnitine is an important co‐factor in fatty acid metabolism by mitochondria. This study has determined whether oral administration of l ‐carnitine prevents remodelling and the development of impaired cardiovascular function in deoxycorticosterone acetate (DOCA)‐salt hypertensive rats (n = 6–12; #p < 0.05 versus DOCA‐salt). Uninephrectomized rats administered DOCA (25 mg every 4th day s.c.) and 1% NaCl in drinking water for 28 days developed cardiovascular remodelling shown as systolic hypertension, left ventricular hypertrophy, increased thoracic aortic and left ventricular wall thickness, increased left ventricular inflammatory cell infiltration together with increased interstitial collagen and increased passive diastolic stiffness and vascular dysfunction with increased plasma malondialdehyde concentrations. Treatment with l ‐carnitine (1.2% in food; 0.9 mg/g/day in DOCA‐salt rats) decreased blood pressure (DOCA‐salt 169 ± 2; + l ‐carnitine 148 ± 6# mmHg), decreased left ventricular wet weights (DOCA‐salt 3.02 ± 0.07; + l ‐carnitine 2.72 ± 0.06# mg/g body‐wt), decreased inflammatory cells in the replacement fibrotic areas, reduced left ventricular interstitial collagen content (DOCA‐salt 14.4 ± 0.2; + l ‐carnitine 8.7 ± 0.5# % area), reduced diastolic stiffness constant (DOCA‐salt 26.9 ± 0.5; + l ‐carnitine 23.8 ± 0.5# dimensionless) and decreased plasma malondialdehyde concentrations (DOCA‐salt 26.9 ± 0.8; + l ‐carnitine 21.2 ± 0.4# μmol/l) without preventing endothelial dysfunction. l ‐carnitine attenuated the cardiac remodelling and improved cardiac function in DOCA‐salt hypertension but produced minimal changes in aortic wall thickness and vascular function. This study suggests that the mitochondrial respiratory chain is a significant source of reactive oxygen species in the heart but less so in the vasculature in DOCA‐salt rats, underlying the relatively selective cardiac responses to l ‐carnitine treatment.     

Recombinant Human Matrix Metalloproteinase‐2 Impairs Cardiovascular β‐Adrenergic Responses

Growing evidence supports the involvement of matrix metalloproteinases (MMPs) in the pathogenesis of many cardiovascular diseases. Particularly, imbalanced MMP‐2 activity apparently plays a critical role in cardiovascular remodelling. While some studies have suggested that MMP‐2 may affect the vascular tone and impair β‐adrenoreceptor function, no previous study has examined the acute haemodynamic effects of MMP‐2. We examined the effects of recombinant human MMP‐2 (rhMMP‐2) administered intravenously to anaesthetized lambs at baseline conditions and during β₁‐adrenergic cardiac stimulation with dobutamine. We used 26 anaesthetized male lambs in two study protocols. First, rhMMP‐2 (220 ng/kg/min. over 60 min.) or vehicle was infused in the lambs, and no significant haemodynamic changes were found. Therefore, we infused dobutamine at 5 μg/kg/min. i.v. (or saline) over 180 min. in lambs that had received the same rhMMP‐2 infusion preceded by doxycycline i.v. at 10 mg/kg (or saline). Plasma and cardiac MMP‐2 levels were assessed by gelatin zymography, and gelatinolytic activity was assessed by spectrofluorimetry. Dobutamine decreased systemic vascular resistance index, and this effect was attenuated by rhMMP‐2 infusion. Moreover, dobutamine increased the cardiac index and left ventricular dP/dt_max, and these effects were attenuated by rhMMP‐2. The previous administration of doxycycline blunted rhMMP‐2‐induced changes in dobutamine responses. While the infusion of rhMMP‐2 did not increase plasma and cardiac MMP‐2 levels, it increased cardiac gelatinolytic activity, and doxycycline blunted this effect. Our findings show that rhMMP‐2 exerts no major haemodynamic effects in lambs. However, rhMMP‐2 impairs the responses elicited by activation of β‐adrenoreceptors.     

Metoprolol Treatment Lowers Thrombospondin‐4 Expression in Rats with Myocardial Infarction and Left Ventricular Hypertrophy

Abstract: Thrombospondins are matrix proteins linked to extracellular matrix remodelling but their precise role in the heart is not known. In this study, we characterised left ventricular thrombospondin‐1 and ‐4 expression in rats treated with a beta‐blocker metoprolol during the remodelling process in response to pressure overload and acute myocardial infarction. Left ventricular thrombospondin‐1 and thrombospondin‐4 mRNA levels increased 8.4‐fold (p < 0.001) and 7.3‐fold (p < 0.001) post‐infarction, respectively. Metoprolol infusion by osmotic minipumps (1.5 mg/kg/hr) for 2 weeks after myocardial infarction decreased thrombospondin‐1 and thrombospondin‐4 mRNA levels (55% and 50%, respectively), improved left ventricular function, and attenuated left ventricular remodelling with reduction of left ventricular atrial natriuretic peptide and brain natriuretic peptide gene expression. Thrombospondin‐1 and ‐4 mRNA levels correlated positively with echocardiographic parameters of left ventricular remodelling as well as with atrial natriuretic peptide and brain natriuretic peptide gene expression. Moreover, there was a negative correlation between left ventricular ejection fraction and thrombospondin‐1 mRNA levels. In 12‐month‐old spontaneously hypertensive rats with left ventricular hypertrophy, metoprolol decreased left ventricular thrombospondin‐4 levels and attenuated remodelling while thrombospondin‐1, atrial natriuretic peptide and brain natriuretic peptide mRNA levels as well as left ventricular function remained unchanged. In metoprolol‐treated spontaneously hypertensive rats, thrombospondin‐4 gene expression correlated with parameters of left ventricular remodelling, while no correlations between thrombospondins and natriuretic peptides were observed. These results indicate that thrombospondin‐1 expression is linked exclusively to left ventricular remodelling process post‐infarction while thrombospondin‐4 associates with myocardial remodelling both after myocardial infarction and in hypertensive heart disease suggesting that thrombospondins may have unique roles in extracellular matrix remodelling process.     

l‐Arginine Attenuates Cardiac Dysfunction,But Further Down‐Regulates α‐Myosin Heavy Chain Expression in Isoproterenol‐Induced Cardiomyopathy

In view of previously reported increased capacity for nitric oxide production, we suggested that l ‐arginine (ARG), the nitric oxide synthase (NOS) substrate, supplementation would improve cardiac function in isoproterenol (ISO)‐induced heart failure. Male Wistar rats were treated with ISO for 8 days (5 mg/kg/day, i.p.) or vehicle. ARG was given to control (ARG) and ISO‐treated (ISO+ARG) rats in water (0.4 g/kg/day). ISO administration was associated with 40% mortality, ventricular hypertrophy, decreased heart rate, left ventricular dysfunction, fibrosis and ECG signs of ischaemia. RT‐PCR showed increased mRNA levels of cardiac hypertrophy marker atrial natriuretic peptide, but not BNP, decreased expression of myosin heavy chain isoform MYH6 and unaltered expression of pathological MYH7. ISO increased the protein levels of endothelial nitric oxide synthase, but at the same time it markedly up‐regulated mRNA and protein levels of gp91phox, a catalytical subunit of superoxide‐producing NADPH oxidase. Fibrosis was markedly increased by ISO. ARG treatment moderately ameliorated left ventricular dysfunction, but was without effect on cardiac hypertrophy and fibrosis. Combination of ISO and ARG led to a decrease in cav‐1 expression, a further increase in MYH7 expression and a down‐regulation of MYH6 that inversely correlated with gp91phox mRNA levels. Although ARG, at least partially, improved ISO‐impaired basal left ventricular systolic function, it failed to reduce cardiac hypertrophy, fibrosis, oxidative stress and mortality. The protection of contractile performance might be related to increased capacity for nitric oxide production and the up‐regulation of MYH7 which may compensate for the marked down‐regulation of the major MYH6 isoform.     

Contribution of different Nox homologues to cardiac remodeling in two-kidney two-clip renovascular hypertensive rats: effect of valsartan.

Growing evidences have shown that hypertension, cardiac hypertrophy and fibrosis were associated with an overactivity of NAD(P)H oxidase. It is unknown, however, which isoform of NAD(P)H oxidase yields O(2)*(-) formation in heart and aorta in two-kidney, two-clip (2K2C) hypertensive rats in vivo and thus is responsible for the development of cardiac remodeling. We examined the pathological change of NAD(P)H oxidase homologues and tested the effect of valsartan on the cardiac remodeling in 2K2C renovascular hypertensive rats. Four weeks after male Sprague-Dawley rats accepted 2K2C or sham operation, 2K2C hypertensive (>160 mmHg) rats were divided into vehicle-treated (2K2C) and valsartan (30 mg kg(-1) per day, for 6 weeks)-treated (2K2C+Val) groups, which were compared with sham-operated controls (Sham). At week 10, 2K2C hypertensive rats showed increased serum level of angiotensin II (Ang II), MDA and blood pressure (BP), obvious cardiac hypertrophy and fibrosis, increased O(2)*(-) production and NAD(P)H oxidase activity and expression in aorta and heart. The heart in 2K2C hypertensive rats preferred to use NADH as substrate while the aorta used both NADH and NADPH. Valsartan treatment decreased BP, ameliorated cardiac hypertrophy and fibrosis, decreased O(2)*(-) production and NAD(P)H oxidase activity in aorta and heart. Nox2 and Nox4 protein expression increased in heart, while Nox1 and Nox4 increased in aorta in 2K2C hypertensive rats, which were all normalized after valsartan treatment. In conclusion, these data indicate that different Nox expression might account for substrate preference and the formation of O(2)*(-) by NAD(P)H oxidase resulting from elevated Ang II in the 2K2C model contributes to the development of renovascular hypertension and subsequent cardiac remodeling.     

Antihypertensive and vascular remodelling effects of the imperatorin derivative OW1 in renovascular hypertension rats

OW1 is a novel imperatorin derivative that exhibits vasodilator activity. In the present study, the antihypertensive effect of and inhibition of vascular remodelling by OW1 were investigated in two‐kidney, one‐clip (2K1C) renovascular hypertensive rats. Rats were subjected to the 2K1C procedure and treated with OW1 (40 or 80 mg/kg per day) for 8 weeks. Blood pressure was measured in conscious rats. Microalbumin (mALB) and total protein (U‐TP) concentrations were determined in the urine, as were plasma concentrations of angiotensin (Ang) II, calcitonin gene‐related peptide (CGRP) and angiotensin‐converting enzyme 1 (ACE). The unclipped kidney was stained with haematoxylin and eosin and Masson trichrome, whereas aortic sections were stained with Masson trichrome. In addition, OW1‐induced vasodilatation was evaluated in vitro in rat mesenteric and renal arteries. Immunohistochemical analysis was used to quantify collagen I and III expression. OW1 relaxed rat mesenteric and renal arterial rings in vitro. Treatment of 2K1C hypertensive rats with OW1 (40 and 80 mg/kg per day) for 8 weeks significantly decreased blood pressure. In addition, OW1 reduced plasma AngII and ACE concentrations and increased plasma CGRP concentrations. At 80 mg/kg per day, OW1 decreased blood urea nitrogen, mALB and U‐TP levels. Histological analysis revealed that OW1 reduced renal arteriolar thickness and relieved the structural hypertrophic arteries. Moreover, OW1 had an inhibitory effect on vascular remodelling and renal lesions in hypertensive rats. In conclusion, the results suggest that OW1 could potentially be a novel candidate for hypertension intervention.     

Attenuation of the LPS‐induced,ERK‐mediated upregulation of fibrosis‐related factors FGF‐2, uPA,MMP‐2, and MMP‐9 by Carthamus tinctorius L in cardiomyoblasts

Severe and potentially fatal hypotension and cardiac contractile dysfunction are common symptoms in patients with sepsis. LPS was previously found to dramatically upregulate expression of fibrosis‐related factors FGF‐2, uPA, MMP‐2, and MMP‐9 in primary cardiac fibroblasts. MMPs are capable of denaturing and degrading fibrillar collagens and other components of the extracellular matrix (ECM). Studies have shown that dysregulation of expression of MMPs is associated with development of myocardial extracellular matrix remodeling and cardiac fibrosis, which contribute to progression of heart failure. In this study, H9c2 cells and cardiac fibroblasts were divided into five treatment groups: control, LPS (1 μg/mL) and three concentrations of FC_EtOH (Carthami Flos ethanolic extract) (31.25, 62.5, and 125 μg/mL). Phosphorylation of ERK‐1/2 was observed to be rapidly induced upon treatment with LPS. In contrast, it was significantly suppressed by the administration of FC_EtOH (125 μg/mL). Effects of FC_EtOH on LPS‐induced MMP‐2 and MMP‐9 expression in H9c2 cells occurred directly through ERK1/2 were determined. H9c2 cells were therefore pretreated with EGF‐R to activate ERK pathway. Both protein levels of MMP‐2 and MMP‐9 and immunefluorescent signals of MMP‐9 were significantly enhanced by EGFR. In contrast, MMP‐2 and MMP‐9 were significantly reduced after FC_EtOH administration. Based on these findings, the authors concluded that FC_EtOH elicits a protective effect against LPS‐induced cardio‐fibrosis through the ERK1/2 pathway. Carthamus tinctorius L may potentially serve as a cardio‐protective agent against LPS‐ induced cardiac fibrosis. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 754–763, 2017.     

Specific α7 nicotinic acetylcholine receptor agonist ameliorates isoproterenol‐induced cardiac remodelling in mice through TGF‐β1/Smad3 pathway

It is well‐accepted that inflammation plays an important role in the development of cardiac remodelling and that therapeutic approaches targeting inflammation can inhibit cardiac remodelling. Although a large amount of evidence indicates that activation of α7 nicotinic acetylcholine receptor (α7nAChR) causes an anti‐inflammatory effect, the role of α7nAChR in cardiac remodelling and the underlying mechanism have not been established. To investigate the effect of the specific α7nAChR agonist, PNU282987, on cardiac remodelling induced by isoproterenol (ISO 60 mg/kg per day) in mice, the cardiomyocyte cross‐sectional area (CSA) and collagen volume fraction were evaluated by hematoxylin and eosin (HE) and Masson staining, respectively. Cardiac function and ventricular wall thickness were measured by echocardiography. The protein expressions of collagen I, matrix metalloproteinase 9 (MMP‐9), transforming growth factor β1 (TGF‐β1), and Smad3 were analyzed by Western blot. ISO‐induced cardiac hypertrophy, characterized by an increase in the heart weight/body weight ratio, CSA and ventricular wall thickness. Moreover, cardiac fibrosis indices, such as collagen volume fraction, MMP‐9 and collagen I protein expression, were also increased by ISO. PNU282987 not only attenuated cardiac hypertrophy but also decreased the cardiac fibrosis induced by ISO. Furthermore, PNU282987 suppressed TGF‐β1 protein expression and the phosphorylation of Smad3 induced by ISO. In conclusion, PNU282987 ameliorated the cardiac remodelling induced by ISO, which may be related to the TGF‐β1/Smad3 pathway. These data imply that the α7nAChR may represent a novel therapeutic target for cardiac remodelling in many cardiovascular diseases.     

Exacerbated cardiac fibrosis induced by β‐adrenergic activation in old mice due to decreased AMPK activity

Senescent hearts exhibit defective responses to β‐adrenergic receptor (β‐AR) over‐activation upon stress, leading to more severe pathological cardiac remodelling. However, the underlying mechanisms remain unclear. Here, we investigated the role of adenosine monophosphate‐activated protein kinase (AMPK) in protecting against ageing‐associated cardiac remodelling in mice upon β‐AR over‐activation. 10‐week‐old (young) and 18‐month‐old (old) mice were subcutaneously injected with the β‐AR agonist isoproterenol (ISO; 5 mg/kg). More extensive cardiac fibrosis was found in old mice upon ISO exposure than in young mice. Meanwhile, ISO treatment decreased AMPK activity and increased β‐arrestin 1, but not β‐arrestin 2, expression, and the effects of ISO on AMPK and β‐arrestin 1 were greater in old mice than in young mice. Similarly, young AMPKα2‐knockout (KO) mice showed more extensive cardiac fibrosis upon ISO exposure than that was observed in age‐matched wild‐type (WT) littermates. The extent of cardiac fibrosis in WT old mice was similar to that in young KO mice. Additionally, AMPK activities were decreased and β‐arrestin 1 expression increased in KO mice. In contrast, the AMPK activator metformin decreased β‐arrestin 1 expression and attenuated cardiac fibrosis in both young and old mice upon ISO exposure. In conclusion, more severe cardiac fibrosis is induced by ISO in old mice than in young mice. A decrease in AMPK activity, which further increases β‐arrestin 1 expression, is the central mechanism underlying the ageing‐related cardiac fibrosis induced by ISO. The AMPK activator metformin is a promising therapeutic agent for treating ageing‐related cardiac remodelling upon β‐AR over‐activation.     

Different regulation of miR‐29a‐3p in glomeruli and tubules in an experimental model of angiotensin II‐dependent hypertension: potential role in renal fibrosis

The aim of this study was to evaluate the role of the angiotensin II (Ang II) induced‐differential miRNA expression in renal glomerular and tubulo‐interstitial fibrosis in an experimental model of Ang II‐dependent hypertension. To clarify this issue, Sprague Dawley rats were treated with Ang II (200 ng/kg per minute, n = 15) or physiological saline (n = 14) for 4 weeks. Systolic blood pressure and albuminuria were measured every 2 weeks. At the end of the experimental period, renal glomerular and tubulo‐interstitial fibrosis was evaluated by histomorphometric analysis, after Sirius‐Red and Masson's trichrome staining. Ang II increased systolic blood pressure (P < 0.0001), albuminuria (P < 0.01) and both glomerular and tubulo‐interstitial fibrosis (P < 0.01). Using laser capture microdissection and miRNA microarray analysis this study showed that miR‐29a‐3p was down‐regulated in renal tubules and up‐regulated in glomeruli. Real‐time polymerase chain reaction (PCR) experiments confirmed in Ang II‐treated rats a down‐regulation of miR‐29a‐3p in tubules (P < 0.01), while no significant changes were observed in glomeruli. Matrix metalloproteinase‐2 (MMP‐2) was identified as putative miR‐29a‐3p target (by TargetScan, miRanda, Tarbase software) and functionally confirmed by luciferase activity assay. These data demonstrate that the effects of Ang II on miR‐29a‐3p expression in renal tubules is different from the one exerted in the glomeruli and that miR‐29a‐3p targets MMP‐2. These results suggest that the development of renal fibrosis at glomerular and tubulo‐interstitial level depends on different molecular mechanisms.     

Berberine attenuates adverse left ventricular remodeling and cardiac dysfunction after acute myocardial infarction in rats: Role of autophagy

The present study aimed to test the hypothesis that berberine, a plant‐derived anti‐oxidant, attenuates adverse left ventricular remodelling and improves cardiac function in a rat model of myocardial infarction (MI). Furthermore, the potential mechanisms that mediated the cardioprotective actions of berberine, in particular the effect on autophagy, were also investigated. Acute MI was induced by ligating the left anterior descending coronary artery of Sprague‐Dawley rats. Cardiac function was assessed by transthoracic echocardiography. The protein activity/levels of autophagy related to signalling pathways (e.g. LC‐3B, Beclin‐1) were measured in myocardial tissue by immunohistochemical staining and western blot. Four weeks after MI, berberine significantly prevented cardiac dysfunction and adverse cardiac remodelling. MI rats treated with low dose berberine (10 mg/kg per day) showed higher left ventricular ejection fraction and fractional shortening than those treated with high‐dose berberine (50 mg/kg per day). Both doses reduced interstitial fibrosis and post‐MI adverse cardiac remodelling. The cardioprotective action of berberine was associated with increased LC‐3B II and Beclin‐1 expressions. Furthermore, cardioprotection with berberine was potentially related to p38 MAPK inhibition and phospho‐Akt activation. The present in vivo study showed that berberine is effective in promoting autophagy, and subsequently attenuating left ventricular remodelling and cardiac dysfunction after MI. The potential underlying mechanism is augmentation of autophagy through inhibition of p38 MAPK and activation of phospho‐Akt signalling pathways.     

Enhanced vasorelaxation effect of endogenous anandamide on thoracic aorta in renal vascular hypertension rats

Emerging evidence has indicated that anandamide (AEA) is able to stimulate vasorelaxation in both spontaneously hypertensive rats (SHRs) and L‐NAME‐induced hypertensive rats. Yet it remains unknown whether AEA modulates vasomotion of the aorta in renovascular hypertensive (RVH) rats. The aim of present study is to explore the effect of AEA on the relaxation of thoracic aortas in two‐kidney one‐clip (2K1C)‐induced RVH rats. It is demonstrated that AEA stimulates a pronounced relaxation in the aortas of 2K1C rats compared with sham rats. The enhanced relaxation caused by AEA in aortas from 2K1C rats was diminished in the presence of the cannabinoid receptor‐1 (CB₁) antagonist AM251 and the CB₂ receptor antagonist AM630. Likewise, the vasodilation action of AEA was blocked in L‐NAME‐treated or endothelium‐denuded aortas. The Western blot results revealed that the expression of CB₁ and CB₂ receptors was increased in the 2K1C rat aortas compared with sham rats. The phosphorylation of endothelial nitric oxide synthase (p‐eNOS) at the activation site Ser1177 was enhanced in AEA‐treated rings from 2K1C rats in both time‐dependent and dose‐dependent manners. The augmented p‐eNOS expression was inhibited by the co‐treatment with AM251 or AM630. Taken together, the present study demonstrated that AEA enhanced endothelium‐dependent aortic relaxation through activation of both CB₁ and CB₂ receptors and P‐eNOS/NO pathway in 2K1C rats.     

Tanshinone IIA prevents cardiac remodeling through attenuating NAD (P)H oxidase-derived reactive oxygen species production in hypertensive rats

Tanshinone IIA is one of major constituents of Salvia miltiorrhiza Bunge known as Danshen. Our and others' studies have shown that Tan IIA could protect cardimyocyte against apoptosis; however the effect of Tan IIA on cardiac remodeling disease is still unknown. In this study, we investigated the effects of Tan IIA on cardiac hypertrophy and fibrosis in two-kidney, two-clip (2K2C) hypertensive rats and by which, if any, mechanisms. Administration of 2K2C hypertensive rats with Tan IIA attenuated cardiac dysfunction and fibrosis. However Tan IIA treatment had no effects on BP control. Further studies revealed that Tan IIA inhibited the increased NAD(P)H oxidase activity and expression as well as O2*- production in 2K2C hypertensive rats. Our results indicated that Tan IIA significantly improved cardiac function and attenuated fibrosis in 2K2C hypertensive rats. The protective action of Tan IIA is likely mediated by its antioxidant effect, independent of BP control, partially via inhibiting NADPH oxidase.     

Icariin attenuates cardiac remodelling through down-regulating myocardial apoptosis and matrix metalloproteinase activity in rats with congestive heart failure

Objectives In this study, the anti‐heart failure effect of icariin, a natural flavonol glycoside, and the underlying mechanisms were investigated. Methods Heart failure was induced by isoproterenol in male Sprague–Dawley rats. Matrix metalloproteinase activity was determined by gelatin zymography assay. The mRNA expression was determined by real‐time PCR. The protein expression was determined by Western bolt. Mitochondria structure was examined by transmission electron microscopy. Key findings Isoproterenol administration resulted in a severe heart failure, as shown by the increased levels of left ventricular weight index, heart rate, left ventricular end diastolic pressure, maximal rate of left ventricular pressure decline (dp/dt_min), decreased levels of left ventricular systolic pressure and maximal rate of left ventricular pressure rise (dp/dt_max). Against these, icariin dose‐dependently reversed the changes of these cardiac morphometric and haemodynamic parameters. In addition, icariin significantly inhibited serum levels of tumour necrosis factor‐α, noradrenaline, angiotensin II and brain natriuretic peptide in rats with congestive hear failure and improved the histological changes, including cardiocyte hypertrophy, cardiocyte degeneration, inflammatory infiltration and cardiac desmoplasia. Furthermore, the expression and activity of matrix metalloproteinase (MMP)‐2 and MMP‐9, which regulate collagen production, were also blocked by icariin. Moreover, myocardial apoptosis was remarkably attenuated by icariin through regulating Bcl‐2/Bax axle. Conclusions Icariin ameliorates left ventricular dysfunction and cardiac remodelling through down‐regulating matrix metalloproteinase‐2 and 9 activity and myocardial apoptosis in rats with congestive heart failure.     

Metalloproteinase Inhibition Protects against Reductions in Circulating Adrenomedullin during Lead‐induced Acute Hypertension

Intoxication with lead (Pb) results in increased blood pressure by mechanisms involving matrix metalloproteinases (MMPs). Recent findings have revealed that MMP type two (MMP‐2) seems to cleave vasoactive peptides. This study examined whether MMP‐2 and MMP‐9 levels/activities increase after acute intoxication with low lead concentrations and whether these changes were associated with increases in blood pressure and circulating endothelin‐1 or with reductions in circulating adrenomedullin and calcitonin gene‐related peptide (CGRP). Here, we expand previous findings and examine whether doxycycline (a MMPs inhibitor) affects these alterations. Wistar rats received intraperitoneally (i.p.) 1st dose 8 μg/100 g of lead (or sodium) acetate, a subsequent dose of 0.1 μg/100 g to cover daily loss and treatment with doxycycline (30 mg/kg/day) or water by gavage for 7 days. Similar whole‐blood lead levels (9 μg/dL) were found in lead‐exposed rats treated with either doxycycline or water. Lead‐induced increases in systolic blood pressure (from 143 ± 2 to 167 ± 3 mmHg) and gelatin zymography of plasma samples showed that lead increased MMP‐9 (but not MMP‐2) levels. Both lead‐induced increased MMP‐9 activity and hypertension were blunted by doxycycline. Doxycycline also prevented lead‐induced reductions in circulating adrenomedullin. No significant changes in plasma levels of endothelin‐1 or CGRP were found. Lead‐induced decreases in nitric oxide markers and antioxidant status were not prevented by doxycycline. In conclusion, acute lead exposure increases blood pressure and MMP‐9 activity, which were blunted by doxycycline. These findings suggest that MMP‐9 may contribute with lead‐induced hypertension by cleaving the vasodilatory peptide adrenomedullin, thereby inhibiting adrenomedullin‐dependent lowering of blood pressure.