Brain Natriuretic Peptide mRNA Levels Research Articles

Involvement of phosphatase and tensin homolog-induced putative kinase 1/Parkin-mediated autophagy in angiotensin II-induced cardiac hypertrophy in C57BL/6 mice.

ObjectiveTo study the role of autophagy in angiotensin II-induced cardiac hypertrophy in C57BL/6 mice.MethodsWe randomly assigned 10 C57BL/6 mice into the control and angiotensin II (Ang II) groups (n = 5 in each group). Ang II group mice were injected with Ang II (3 mg/kg/day). Cardiac structure, myocardial pathological changes, mitochondrial structure, autophagosomes, mitochondrial membrane potential (MMP), and myocardial apoptosis were examined. Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1), Parkin, and microtubule-associated protein1A/1B-light chain 3 (LC3) II protein expression levels and mRNA expression of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were examined.ResultsThe heart weight/body weight ratio, posterior wall of the left ventricle, myocardial apoptosis (%), relative number of autophagosomes, ANP and BNP mRNA levels, and PINK1, Parkin, and LC3 II protein levels were significantly higher in the Ang II group than in the control group. The MMP and left ventricular ejection fraction were significantly lower in the Ang II group than in the control group. There was disordered arrangement of cardiomyocytes and mitochondria, and obvious mitochondrial swelling, cardiomyocyte hypertrophy, and fibrosis in the Ang II group.ConclusionPINK1/PARKIN-mediated autophagy is involved in Ang II-induced cardiac hypertrophy by affecting myocardial apoptosis and mitochondrial function.

Si-Miao-Yong-An decoction ameliorates cardiac function through restoring the equilibrium of SOD and NOX2 in heart failure mice

Si-Miao-Yong-An decoction (SMYAD), a Chinese herbal formula, has been used in treating ischemic cardiovascular diseases. However, the cardioprotective mechanism of SMYAD treating heart failure (HF) remains unclear. Herein we investigated the effect of SMYAD on isoprenaline (ISO)-induced HF in C57BL/6 mice. Cardiac function and pathological changes in myocardial tissue were evaluated as well as A-type natriuretic peptide (ANP) and brain natriuretic peptide (BNP) expression. The underlying mechanism of SMYAD was deciphered using UHPLC MS/MS coupled with bioinformatics and was verified. SMYAD treatment significantly ameliorated cardiac function, reduced collagen deposition and cardiomyocyte apoptosis, reversed cardiac hypertrophy and down-regulated the expression levels of ANP and BNP mRNA compared with those in HF mice. Decipherment analyses based on 138 ingredients prompted that anti-oxidation was the key mechanism of SMYAD treating HF. In vitro and in vivo, SMYAD showed antioxidant activity, significantly up-regulated superoxide dismutase (SOD)-1 and SOD-2 mRNA expression levels and reduced NADP/NADPH ratio. Moreover, the increased expression levels of NADPH oxidase 2 (NOX2), p47phox and Rac family small GTPase 1 (Rac1) were obviously ameliorated after SMYAD treatment. Together, this study reveals that SMYAD can apparently improve heart function of ISO-induced HF mice by inhibiting the myocardial oxidative stress through restoring the equilibrium of SOD and NOX2.

NLRP3 inhibition improves heart function in GPER knockout mice

The molecular mechanisms of postmenopausal heart diseases in women may involve the loss of estrogen-deactivation of its membrane receptor, G-protein coupled estrogen receptor (GPER), and subsequent activation of the cardiac NLRP3 inflammasome, a component of the innate immune system. To study the potential effects of cardiac GPER on NLRP3-mediated inflammatory pathways, we characterized changes in innate immunity gene transcripts in hearts from 6-month-old cardiomyocyte-specific GPER knockout (KO) mice and their GPER-intact wild type (WT) littermates using RT2 Profiler™ real-time PCR array. GPER deletion in cardiomyocytes decreased %fractional shortening (%FS) and myocardial relaxation (e′), and increased the early mitral inflow filling velocity-to-early mitral annular descent velocity ratio (E/e′), determined by echocardiography, and increased the mRNA levels of atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP), determined by real-time PCR. Of the 84 inflammasome-related genes tested, 9 genes were upregulated, including NLRP3 and IL-18, while 1 gene, IL-12a, was downregulated in GPER KO when compared to WT. The importance of NLRP3 upregulation in GPER KO-induced heart failure was further confirmed by an in vivo study showing that, compared to vehicle-treated KO mice, 8 weeks of treatment with a NLRP3 inhibitor, MCC950 (10 mg/kg, i.p., 3 times per week), significantly limited hypertrophic remodeling, defined by reductions in heart weight/body weight, and improved systolic and diastolic functional indices, including increases in %FS and e′, and decreases E/e′ (P < 0.05). Both ANF and BNP mRNA levels were also significantly reduced by chronic MCC950 treatment. The findings from this study point toward a new understanding for the increased occurrence of heart diseases in women following loss or absence of estrogenic protection and GPER activation that involves cardiac NLRP3 inflammatory pathways.

Chronic low‐intensity exercise training prevents coronary artery stiffness via inhibiton of perivascular adipose‐secreted advanced glycation end products in aortic‐banded mini‐swine

Previous findings from our laboratory have shown increased coronary artery stiffness is associated with increased vascular advanced glycation end product (AGE) levels from aortic‐banded (AB) mini‐swine. Perivascular adipose tissue (PVAT) promotes arterial stiffness, yet the mechanisms underlying PVAT‐related arterial stiffening and whether exercise is therapeutically efficacious in preventing this phenomenon are unknown. We hypothesized that both chronic low‐intensity continuous and interval exercise training (LICT and LIIT, respectively) would prevent PVAT‐related AGE secretion and coronary arterial stiffening in AB mini‐swine. Male Yucatan mini‐swine (8 mo. old) were divided into 4 groups (n=7/group): sedentary control (CON), sedentary AB heart failure (HF), AB plus LICT (HF+LICT), and AB plus LIIT (HF+LIIT). Significance was set at P &lt; 0.05 using one way ANOVA. Following the development of left ventricular (LV) hypertrophy (2 mo. post‐AB), animals began LICT or LIIT consisting of treadmill running 3 days/wk, 55 min/day, for 15 weeks. Only animals in the HF group showed both increased lung weight and LV brain natriuretic peptide mRNA levels, suggestive of heart failure. Coronary artery mechanical stiffness was assessed via a DMT Myograph system, and protein levels in arterial and PVAT samples was examined by immunohistochemistry. HF compared to CON had a significantly lower coronary elastin elastic modulus (EEM) (284.3±27.58 vs. 444.35±37.55 kPa) associated with reduced elastin content. Both LICT and LIIT prevented the decreases in the EEM (474.2±37.83 and 510.6±55.98 kPa, respectively) and coronary elastin content observed in the HF group. Compared to CON, HF animals had significantly increased AGE levels in both the coronary artery and PVAT, along with increased AGE secretion from isolated PVAT samples conditioned in media. Increased PVAT secretion and coronary AGE accumulation were prevented by both LICT and LIIT. To determine if PVAT contributes to arterial stiffness, aortas from young healthy mice exposed to PVAT‐conditioned media were mechanically tested. Aortas exposed to HF‐conditioned media had a significant decrease in the EEM (368.47±20.34 vs. 582.41±28.99 kPa) and decreased elastin content compared to CON, which was prevented when treated with PVAT‐conditioned media from LICT and LIIT animals (542.84±58.09 and 517.8±22.03 kPa, respectively). The AGE inhibitor, aminogunadine (AMG), prevented decreases in the EEM (368.47±20.34 vs. 642.58±35.32 kPa), arterial elastin content, and increases in arterial AGE accumulation observed after exposure to PVAT‐conditioned media from the HF group. In summary, both LICT and LIIT prevent coronary artery stiffness and preserve normal elastin levels via inhibition of PVAT‐derived AGE in a pre‐clinical model of pressure overload‐induced heart failure.Support or Funding InformationR01 HL112998 (Emter, PI)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

MicroRNA-10-5p regulates differentiation of bone marrow mesenchymal stem cells into cardiomyocytes by targeting TBX5.

The purpose of the study was to investigate the regulatory effect of microRNA-10-5p on TBX5 during myocardial differentiation of bone marrow mesenchymal stem cells (BMSCs) in rats. Rat BMSCs were first isolated, cultured and identified by flow cytometry. Expression levels of BNP (Brain Natriuretic Peptide), α-actinin, and Islet-1 in BMSCs co-cultured with rat cardiomyocytes were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Dual-luciferase reporter gene assay was conducted to verify the binding condition between microRNA-10-5p and TBX5. Subsequently, we detected TBX5 expression after overexpression or knockdown of microRNA-10-5p in BMSCs. Rescue experiments were conducted by overexpression of both microRNA-10-5p and TBX5 in BMSCs, and then, the expression levels of BNP, α-actinin, and Islet-1 were detected by qRT-PCR and Western blot. Flow cytometry results showed positive-CD73 (99.3%), positive-CD90 (95.4%), and negative-CD34 (4.2%), which were consistent with immunophenotypic characteristics of BMSCs. TBX5 overexpression or microRNA-10-5p knockdown increased mRNA levels of BNP, α-actinin, and Islet-1 in BMSCs co-cultured with rat cardiomyocytes. Dual-luciferase reporter gene assay confirmed that microRNA-10-5p could bind to TBX5. Both mRNA and protein expressions of TBX5 were negatively regulated by microRNA-10-5p. The inhibited expression levels of BNP, α-actinin, and Islet-1 by microRNA-10-5p overexpression in BMSCs were partially reversed by TBX5 overexpression. MicroRNA-10-5p regulates BMSCs differentiation into cardiomyocytes by binding to TBX5.

Involvement of brain natriuretic peptide signaling pathway in the cardioprotective action of sitagliptin.

The current study is focusing on the role of brain natriuretic peptide (BNP), a substrate of dipeptidyl peptidase-4 (DPP-4) enzyme, and its signaling survival pathway in the cardioprotective mechanism of sitagliptin, a DPP-4 inhibitor. Male Wistar rats were randomized into 7 groups, sham, I/R, KT-5823 (selective protein kinase (PK) G inhibitor), 5-HD (selective mito-KATP channel blocker), sitagliptin (300mg/kg, po), sitagliptin+KT-5823, and sitagliptin+5-HD. Sitagliptin was administered for 3 days prior to induction of coronary I/R, while either KT-5823 or 5-HD was administered intravenously 5min before coronary ligation. Pretreatment with sitagliptin provided significant protection against I/R injury as manifested by decreasing, percentage of infarct size, suppressing the elevated ST segment, reducing the increased cardiac enzymes, as well as DPP-4 activity and elevating both heart rate (HR) and left ventricular developed pressure (LVDP). However, the addition of either blocker to sitagliptin regimen reversed partly its cardioprotective effects. Although I/R increased BNP content, it unexpectedly decreased that of cGMP; nevertheless, sitagliptin elevated both parameters, an effect that was not affected by the use of the two blockers. On the molecular level, sitagliptin decreased caspase-3 activity and downregulated the mRNA levels of BNP, Bax, and Cyp D, while upregulated that of Bcl2. The use of either KT-5823 or 5-HD with sitagliptin hindered its effect on the molecular markers tested. The results of the present study suggest that the cardioprotective effect of sitagliptin is mediated partly, but not solely, through the BNP/cGMP/PKG survival signaling pathway.

VEGFB-VEGFR1 ameliorates Ang II-induced cardiomyocyte hypertrophy through Ca2+ -mediated PKG I pathway.

In response to assorted stimuli, the heart will develop into cardiomyocyte hypertrophy, but sustained cardiomyocyte hypertrophy will finally lead to heart failure. This research is aimed to examine the effect of VEGFB on cardiomyocyte hypertrophy by using the cardiomyocyte-derived cell line H9C2 of cultured rates. It turns out that VEGFB can positively prevent the Ang II-induced rising in the size of cardiomyocyte as well as reduce Ang II-induced mRNA and protein levels of β-MHC (β-myosin heavy chain), BNP (brain natriuretic peptide), and ANP (atrial natriuretic peptide). Moreover, VEGFB can regulate the decline of the Ang II-induced rising in Ca2+ . After VEGFR1 knockdown, these effects of VEGFB were partially reversed. Moreover, VEGFB attenuated the suppression of PKG I, p-VASP, and RGS2 caused by Ang II; whereas VEGFR1 knockdown partially abolished the indicated effect of VEGFB. In a word, the effect of VEGFB on relevant downstream targets and the pathways of PKG I by VEGFR1 may explain its efficacy on cardiomyocyte hypertrophy. Thus, it can be suggested that it is feasible to apply VEGFB-VEGFR1 for reducing the symptoms of cardiomyocyte hypertrophy.

Urocortin attenuates myocardial fibrosis in diabetic rats via the Akt/GSK-3β signaling pathway

ABSTRACTObjective: Urocortin, a novel identified corticotropin-releasing factor-related endocrinal peptide, has been shown to play an essential role in cardioprotection. Until recently, whether urocortin can protect the heart against diabetic cardiomyopathy (DCM) remained unclear. Herein, we evaluated the cardioprotective effect of urocortin on cardiac dysfunction, inflammation, and fibrosis and demonstrated the potential mechanism in a diabetic rat model. Methods: Diabetic rats were randomly divided into 4 groups: diabetic control group, urocortin, urocortin + astressin (a selective CRF receptor 2 antagonist) and urocortin + triciribine (an Akt pathway blocker). Cardiac catheterization was performed to evaluate cardiac function. The levels of creatine phosphokinase isoenzyme (CK-MB), plasma brain natriuretic peptide (BNP), myocardial collagen volume fraction (CVF) and left ventricular mass index (LVWI) were measured. Inflammatory factors (transforming growth factor beta 1, TGF-β1; connective tissue growth factor, CTGF) and activation of signaling proteins (Akt, GSK-3β) were also detected using western blot. Results: DCM was successfully induced by the injection of streptozotocin (STZ) as evidenced by abnormal heart mass and cardiac function as well as the imbalance of extracellular matrix homeostasis. Rats in the DCM group showed increased mRNA and protein levels of LVWI, BNP, CK-MB, CVF, TGF-β1 and CTGF compared to the control group, which were accompanied with diminished phosphorylation of Akt and GSK-3β. Interestingly, myocardial dysfunction, cardiac fibrosis, and inflammation were suppressed by urocortin in the heart of diabetic rats. Moreover, inhibition of phosphorylation of Akt and GSK-3β was also reversed by urocortin. These effects of urocortin were suppressed by astressin. In addition, triciribine partially reduced the effects of urocortin on myocardial dysfunction, inflammation, and cardiac fibrosis. Conclusions: These results suggest that urocortin exhibits a therapeutic benefit in the treatment of DCM by attenuating fibrosis and inflammation. Furthermore, inhibition of the Akt/GSK-3β signaling pathway may be partially responsible for these effects.

Aspirin Attenuates Angiotensin II-induced Cardiomyocyte Hypertrophy by Inhibiting the Ca(2+)/Calcineurin-NFAT Signaling Pathway.

In this study, we examined whether aspirin could inhibit cardiac hypertrophy. We utilized cultured neonatal mouse cardiomyocytes and mice for the study and subjected to cardiomyocyte immunochemistry, qRT-PCR, and immunoblotting analysis. The cardiac function was measured using M-mode echocardiography. Ten μM aspirin significantly inhibited Ang II-induced increase in cardiomyocyte size, the mRNA, and protein levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (β-MHC) (P < 0.05). Meantime, consistent with the result in vitro, the increase in HW/BW ratio, the mRNA, and protein levels of ANP, BNP, and β-MHC could be reduced by aspirin in vivo (P < 0.05). Analysis of cardiac function revealed that mouse hearts treated with Ang II displayed thickening of the ventricular walls, left ventricular end-diastolic dimensions, and left ventricular end-systolic dimensions were significantly decreased (P < 0.05), whereas interventricular septal thickness at end-diastole, interventricular septal thickness at end-systole, posterior wall thickness in diastole, and posterior wall thickness in systole were markedly increased (P < 0.05), which could be reversed by aspirin (P < 0.05). Moreover, aspirin blunted the increase inCa(2+) and inhibited the calcineurin activity and NFAT dephosphorylation caused by Ang II (P < 0.05). Aspirin inhibited cardiac hypertrophy in vitro and in vivo through inhibition of the Ca(2+)/calcineurin-NFAT signaling pathway. Therefore, these findings suggested that aspirin might become a therapeutic option to reduce cardiac hypertrophy.

Qiliqiangxin Attenuates Phenylephrine-Induced Cardiac Hypertrophy through Downregulation of MiR-199a-5p

Background/Aims: Qiliqiangxin (QL), a traditional Chinese medicine, has long been used to treat chronic heart failure. Previous studies demonstrated that QL could prevent cardiac remodeling and hypertrophy in response to hypertensive or ischemic stress. However, little is known about whether QL could modulate cardiac hypertrophy in vitro, and (if so) whether it is through modulation of specific hypertrophy-related microRNA. Methods: The primary neonatal rat ventricular cardiomyocytes were isolated, cultured, and treated with phenylephrine (PE, 50 µmol/L, 48 h) to induce hypertrophy in vitro, in the presence or absence of pretreatment with QL (0.5 µg/ml, 48 h). The cell surface area was determined by immunofluorescent staining for α-actinin. The mRNA levels of hypertrophic markers including atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (MYH7) were assayed by qRT-PCRs. The protein synthesis of cardiomyocytes was determined by the protein/DNA ratio. The miR-199a-5p expression level was quantified in PE-treated cardiomyocytes and heart samples from acute myocardial infarction (AMI) mouse model. MiR-199a-5p overexpression was used to determine its role in the anti-hypertrophic effect of QL on cardiomyocytes. Results: PE induced obvious enlargement of cell surface in cardiomyocytes, paralleling with increased ANP, BNP, and MYH7 mRNA levels and elevated protein/DNA ratio. All these changes were reversed by the treatment with QL. Meanwhile, miR-199a-5p was increased in AMI mouse heart tissues. Of note, the increase of miR-199a-5p in PE-treated cardiomyocytes was reversed by the treatment with QL. Moreover, overexpression of miR-199a-5p abolished the anti-hypertrophic effect of QL on cardiomyocytes. Conclusion: QL prevents PE-induced cardiac hypertrophy. MiR-199a-5p is increased in cardiac hypertrophy, while reduced by treatment with QL. miR-199a-5p suppression is essential for the anti-hypertrophic effect of QL on cardiomyocytes.

Gender differences in the expression of genes involved during cardiac development in offspring from dams on high fat diet.

Previously we have demonstrated that maternal high fat diet (HF) during pregnancy increase cardiovascular risk in the offspring, and pharmacological intervention using statins in late pregnancy reduced these risk factors. However the effects of maternal HF-feeding and statin treatment during pregnancy on development of heart remain unknown. Hence we measured expression of genes involved in cell cycle progression (cyclin G1), ventricular remodelling brain natriuretic peptide (BNP), and environmental stress response small proline-rich protein 1A (SPRR 1A) in the offspring left ventricle (LV) from dams on HF with or without statin treatment. Female C57 mice were fed a HF diet (45% kcal fat) 4 weeks prior to conception, during pregnancy and lactation. From the second half of the pregnancy and throughout lactation, half of the pregnant females on HF diet were given a water-soluble statin (Pravastatin) in their drinking water (HF + S). At weaning offspring were fed HF diet to adulthood (generating dam/offspring dietary groups HF/HF and HF + S/HF). These groups were compared with offspring from dams fed standard chow (C 21% kcal fat) and fed C diet from weaning (C/C). LV mRNA levels for cyclin G1, BNP and SPRR 1A were measured by RT-PCR. Heart weights and BP in HF/HF offspring were higher versus C/C group. Maternal Pravastatin treatment reduced BP and heart weights in HF + S/HF female offspring to levels found in C/C group. LV cyclin G1 mRNA levels were lower in HF/HF versus both C/C and HF + S/HF offspring. BNP mRNA levels were elevated in HF/HF females but lower in males versus C/C. BNP gene expression in HF + S/HF offspring was similar to HF/HF. SPRR 1A mRNA levels were similar in all treatment groups. Statins given to HF-fed pregnant dams reduced cardiovascular risk in adult offspring, and this is accompanied by changes in expression of genes involved in adaptive remodelling in the offspring LV and that there is a gender difference.

Dual agonism of peripheral cannabinoid CB1/CB2 receptors suppresses cardiac myocyte hypertrophy (652.9)

The development of endocannabinoid‐based therapies is hindered by psychoactive side effects mediated by central CB1 receptors. We determined the effect of CB‐13, a peripherally‐restricted agonist of CB1/CB2 receptors, on cardiac myocyte hypertrophy. Endothelin‐1 (ET‐1, 0.1 μM) induced hypertrophy of rat cardiac myocytes as measured by cell enlargement (122±4%), protein synthesis ([3H]‐leucine incorporation; 147±13%), and fetal gene expression (brain natriuretic peptide mRNA levels; 426±88%) (p&lt;0.05 vs. controls). CB‐13 attenuated all hypertrophic indicators and activated two anti‐hypertrophic signals: AMP‐activated protein kinase (AMPK) and eNOS through phosphorylation at Thr172 and Ser1177, respectively. eNOS activation was ablated by shRNA knockdown of AMPK, and disruption of signaling through AMPK (knockdown) or eNOS (L‐NIO, 1 μM) blocked the anti‐growth effects of CB‐13. CB‐13 also improved mitochondrial function by trafficking through AMPK and PGC‐1α (a driver of mitochondrial biogenesis). ET‐1‐induced mitochondrial depolarization, as assessed by subcellular compartmentalization of the potential‐sensitive dye, JC‐1, was inhibited by CB‐13. In conclusion, dual agonism of peripheral CB1/CB2 receptors is protective in the context of cardiac myocyte hypertrophy and mitochondrial dysfunction vis‐à‐vis crosstalk between AMPK, eNOS and PGC‐1α.

Mechanical Stretch Increases Brain Natriuretic Peptide Production and Secretion in the Human Fetal Membranes

Brain natriuretic peptide (BNP) is synthesized by human fetal membranes, both the amnion and chorion. This locally produced BNP inhibits the contraction of the human myometrium, contributing to the maintenance of myometrial quiescence during pregnancy. We tested the hypothesis that BNP production is increased by fetal membrane stretching, which is predicted to occur in the expanding uterus, and inhibited by epidermal growth factor (EGF), whose production in the fetal membranes increases in late pregnancy. Term fetal membranes were obtained during elective cesarean delivery before labor. Sections of membranes were placed in an isolated chamber containing DMEM: F12 medium (37°C) and stretched with a 35 g weight. Medium and tissue samples were collected at 0, 3, 6, 18, and 24hours for measurement of messenger RNA (mRNA) and BNP levels in the presence/absence of EGF (2 × 10(-9)mol/L). Inducible nitric oxide synthase (iNOS) and β-actin were also evaluated to discard a nonspecific effect of mechanical stretch on protein expression. We found that amnion and chorion stretching increased the BNP mRNA (reverse transcription-polymerase chain reaction [RT-PCR]) and protein (radioimmunosorbent assay [RIA]) levels from 18 hours onward. The effect of stretching was inhibited by EGF (2 × 10(-9) mol/L). Stretch did not increase iNOS or β-actin protein levels. We concluded that chorion and amnion stretching may increase BNP expression in the fetal membranes during pregnancy, while increasing biological activity of EGF may decrease BNP production in the chorion and amnion late in pregnancy. We postulate BNP is an important regulator of myometrial contractility during pregnancy, and its production is modulated by both stretch and progressive increase in EGF levels during pregnancy.

Activation of GPR30 attenuates diastolic dysfunction and left ventricle remodelling in oophorectomized mRen2.Lewis rats

GPR30 is a novel oestrogen receptor expressed in various tissues, including the heart. We determined the role of GPR30 in the maintenance of left ventricular (LV) structure and diastolic function after the surgical loss of ovarian hormones in the female mRen2.Lewis rat, a model emulating the cardiac phenotype of the post-menopausal woman. Bilateral oophorectomy (OVX) or sham surgery was performed in study rats; the selective GPR30 agonist, G-1 (50 µg/kg/day), or vehicle was given subcutaneously to OVX rats from 13-15 weeks of age. Similar to the cardiac phenotype of sham rats, G-1 preserved diastolic function and structure relative to vehicle-treated OVX littermates independent of changes in blood pressure. G-1 limited the OVX-induced increase in LV filling pressure, LV mass, wall thickness, interstitial collagen deposition, atrial natriuretic factor and brain natriuretic peptide mRNA levels, and cardiac NAD(P)H oxidase 4 (NOX4) expression. In vitro studies showed that G-1 inhibited angiotensin II-induced hypertrophy in H9c2 cardiomyocytes, evidenced by reductions in cell size, protein content per cell, and atrial natriuretic factor mRNA levels. The GPR30 antagonist, G15, inhibited the protective effects of both oestradiol and G-1 on this hypertrophy. These data show that the GPR30 agonist G-1 mitigates the adverse effects of oestrogen loss on LV remodelling and the development of diastolic dysfunction in the study rats. This expands our knowledge of the sex-specific mechanisms underlying diastolic dysfunction and provides a potential therapeutic target for reducing the progression of this cardiovascular disease process in post-menopausal women.

Interpretation of elevated plasma visfatin concentrations in patients with ST-elevation myocardial infarction

Visfatin is a cytokine that is expressed in many tissues, including the heart, and has been proposed to play a role in plaque destabilization leading to acute myocardial injury. The present study evaluates plasma levels of visfatin in acute ST-elevation myocardial infarction (STEMI) patients and examines the temporal changes in visfatin levels from the acute period to the subacute period to determine a correlation with the degree of myocardial ischemia. We evaluated 54 patients with STEMI. Circulating levels of visfatin and brain natriuretic peptide (BNP) were measured by ELISA. In addition, local expression of visfatin and BNP were detected by quantitative real-time polymerase chain reaction and immunohistochemical (IHC) analysis of left ventricular myocytes in a mouse model of myocardial infarction (MI). Plasma levels of visfatin were significantly increased in patients with STEMI on admission, relative to controls (effort angina patients and individuals without coronary artery disease). The visfatin levels reached a peak 24h after percutaneous coronary intervention (PCI) and then decreased toward the control range during the first week after PCI. The basal plasma visfatin levels were found to correlate with peak troponin-I, peak creatine kinase-MB, total white blood cell count, and BNP levels. Trend analyses confirmed that visfatin levels correlated with the number of diseased coronary arteries. Further, in MI mice, mRNA levels of visfatin and BNP were found to be higher than in sham-treated mice. IHC analysis showed that visfatin and BNP immunoreactivity was diffusely observable in left ventricular myocytes of the MI mice. This study indicates that plasma visfatin levels are significantly higher in STEMI patients and that these higher visfatin levels correlate with elevated levels of cardiac enzymes, suggesting that increased plasma visfatin may be closely related to the degree of myocardial damage.

Early and late effects of the DPP-4 inhibitor vildagliptin in a rat model of post-myocardial infarction heart failure

BackgroundProgressive remodeling after myocardial infarction (MI) is a leading cause of morbidity and mortality. Recently, glucagon-like peptide (GLP)-1 was shown to have cardioprotective effects, but treatment with GLP-1 is limited by its short half-life. It is rapidly degraded by the enzyme dipeptidyl peptidase-4 (DPP-4), an enzyme which inhibits GLP-1 activity. We hypothesized that the DPP-4 inhibitor vildagliptin will increase levels of GLP-1 and may exert protective effects on cardiac function after MI.MethodsSprague-Dawley rats were either subjected to coronary ligation to induce MI and left ventricular (LV) remodeling, or sham operation. Parts of the rats with an MI were pre-treated for 2 days with the DPP-4 inhibitor vildagliptin (MI-Vildagliptin immediate, MI-VI, 15 mg/kg/day). The remainder of the rats was, three weeks after coronary artery ligation, subjected to treatment with DPP-4 inhibitor vildagliptin (MI-Vildagliptin Late, MI-VL) or control (MI). At 12 weeks, echocardiography and invasive hemodynamics were measured and molecular analysis and immunohistochemistry were performed.ResultsVildagliptin inhibited the DPP-4 enzymatic activity by almost 70% and increased active GLP-1 levels by about 3-fold in plasma in both treated groups (p < 0.05 vs. non-treated groups). Cardiac function (ejection fraction) was decreased in all 3 MI groups compared with Sham group (p < 0.05); treatment with vildagliptin, either early or late, did not reverse cardiac remodeling. ANP (atrial natriuretic peptide) and BNP (brain natriuretic peptide) mRNA levels were significantly increased in all 3 MI groups, but no significant reductions were observed in both vildagliptin groups. Vildagliptin also did not change cardiomyocyte size or capillary density after MI. No effects were detected on glucose level and body weight in the post-MI remodeling model.ConclusionVildagliptin increases the active GLP-1 level via inhibition of DPP-4, but it has no substantial protective effects on cardiac function in this well established long-term post-MI cardiac remodeling model.

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

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.

Ischemia‐Reperfusion Induces Transcriptional Activation of Brain Natriuretic Peptide Gene via ERK1/2 in H9c2 cells.

Brain natriuretic peptide (BNP) is a cardiac hormone released from heart ventricular cells in response to myocyte stretch. Although BNP has recently been shown to be cardioprotective during myocardial ischemia/reperfusion (IR), mechanism of BNP gene expression by IR has not been clarified yet. Here, we show the mechanism underlying IR‐induced BNP gene expression in H9c2 rat cardiomyocytes.IR induced expression of BNP mRNA and transactivation of BNP promoter in H9c2 cells. Activation of MAP kinase family members such as ERK1/2 and p38 MAPK was triggered by IR. U0126, an inhibitor of MEK, but not SB203580, an inhibitor of p38 MAPK, completely prevented increase of IR‐induced BNP gene expression. In addition, antioxidants such as DMSO and TEMPO diminished induction of BNP and phosphorylation of ERK1/2. To investigate whether increase in free intracellular calcium [Ca2+]i has a role in expression of BNP by IR, calcium chelator BAPTA‐AM was treated before reperfusion. BAPTA‐AM strongly reduced induction of BNP by IR. Moreover, calcium ionophore A23187 increased levels of BNP mRNA and phosphorylation of ERK1/2. Taken together, IR‐mediated BNP gene expression may be due to calcium‐ and ROS‐mediated activation of ERK1/2 in H9c2 cells. This research was supported by MRC from cell death disease research center funded by KOSEF.

Mineralocorticoid Receptor Antagonism Attenuates Cardiac Hypertrophy and Prevents Oxidative Stress in Uremic Rats

Chronic renal failure causes left ventricular hypertrophy, but the molecular mechanisms involved remain unknown. We, therefore, investigated whether the mineralocorticoid receptor is implicated in the cardiac hypertrophy observed in uremic rats and whether mineralocorticoid receptor blockade could be protective in chronic renal failure. Experimental groups were: control rats, uremic rats (NPX) with 5/6 nephrectomy (5 weeks), and NPX rats fed with spironolactone for 5 weeks. Systolic blood pressure was increased in both NPX rats and NPX rats fed with spironolactone for 5 weeks. Echocardiography revealed concentric left ventricular hypertrophy in uremia, which was attenuated by spironolactone. Enlarged cardiomyocyte size was observed in both left and right ventricles of NPX rats, an effect that was prevented by spironolactone. Mineralocorticoid receptor antagonism attenuated the increase of ventricular brain natriuretic peptide mRNA levels induced by nephrectomy. Left ventricular gene expressions of aldosterone synthase, mineralocorticoid receptor, and hydroxysteroid dehydrogenase type 2 were the same in the 3 groups, whereas gene expression of the glucocorticoid receptor was significantly diminished in chronic renal failure rats. No significant differences in cardiac aldosterone were observed between control rats and NPX rats, although NPX rats fed with spironolactone for 5 weeks showed increased plasma aldosterone levels. However, a significant increase in serum and glucocorticoid-inducible kinase-1 mRNA expression and protein was present in the NPX group; spironolactone treatment significantly reduced serum and glucocorticoid-inducible kinase-1 mRNA and protein in the left ventricle. Uremic rats exhibited a significant increase of superoxide production and reduced nicotinamide-adenine dinucleotide phosphate oxidase subunits expression (NOX-2, NOX-4, and p47(phox)) in the left ventricle, which was prevented by the mineralocorticoid receptor antagonist. Our findings provide evidence of the beneficial effects of spironolactone in cardiac hypertrophy and cardiac oxidative stress in chronic renal failure.

Myocardial Gene Expression in Heart Failure Patients Treated With Cardiac Resynchronization Therapy: Responders Versus Nonresponders

We studied whether functional improvement after cardiac resynchronization therapy (CRT) is associated with reversal of the heart failure (HF) gene program. Cardiac resynchronization therapy improves exercise tolerance and survival in patients with advanced congestive HF and dyssynchrony. Twenty-four patients referred for CRT underwent left ventricular (LV) endomyocardial biopsies immediately before CRT implantation (baseline). In addition, 17 of them underwent LV endomyocardial biopsy procurement 4 months later (follow-up). In 6 control patients with normal LV function, LV biopsies were obtained at the time of coronary artery bypass grafting. The LV messenger ribonucleic acid (mRNA) levels of contractile and calcium regulatory genes were measured by quantitative real time polymerase chain reaction and normalized for glyceraldehyde 3-phosphate dehydrogenase (GAPDH). The HF patients showing an improvement in New York Heart Association (NYHA) functional class by >1 score and a relative increase in LV ejection fraction ≥25% at 4 months after CRT were considered as responders. The HF patients were characterized by lower LV mRNA levels of α-myosin heavy chain (α-MHC), β-myosin heavy chain (β-MHC), sarcoplasmic reticulum calcium ATPase 2α (SERCA), phospholamban (PLN), and higher brain natriuretic peptide (BNP) mRNA levels as compared with control subjects. Responders to CRT (n = 11) showed an increase in LVEF (p < 0.001), a decrease in left ventricular end-diastolic diameter (p = 0.003), and NYHA functional class (p = 0.002), and a reduction in N-terminal proBNP levels (p = 0.032) as compared with baseline. This was associated with an increase in mRNA levels of α-MHC (p = 0.035), SERCA (p = 0.032), a decrease in BNP mRNA levels (p = 0.002), and an increase in the ratio of α-/β-MHC (p = 0.018) and SERCA/PLN (p = 0.012). No significant changes in molecular profile were observed in nonresponders. In HF patients with electromechanical cardiac dyssynchrony, functional improvement related to CRT is associated with favorable changes in established molecular markers of HF, including genes that regulate contractile function and pathologic hypertrophy.