The Expression of BNP, ET-1, and TGF-β1 in Myocardium of Rats with Ventricular Arrhythmias

Ventricular arrhythmia (VA) is a major component of sudden cardiac death (SCD). To investigate the expression of brain natriuretic peptide (BNP), endothelin-1 (ET-1), and transforming growth factor-beta 1 (TGF-β1) during VA, we established a rat model of VA induced by BaCl₂ solution through a microinjector pump. PD142893 (ET-1 receptor blocker) and SB431542 (TGF-β1 receptor type I blocker) were used to explore the effect of ET-1 and TGF-β1 on BNP expression in the myocardium after VA. BNP, ET-1, and TGF-β1 in rat myocardium were assayed by western blot and immunohistochemical staining for proteins, and real-time quantitative polymerase chain reaction for mRNAs. We found increased expression of BNP and ET-1 in rat myocardium that was associated with the duration of VA. However, TGF-β1 protein expression remained unchanged. Such early increases in BNP and ET-1 may be attributed to fatal arrhythmias associated with SCD, suggesting these may be novel biomarkers of this disease. After intraperitoneal injection of PD142893 and SB431542, respectively, BNP was downregulated in the myocardium of the left ventricle; however, this was abrogated by co-application of the two inhibitors. These results suggested that both ET-1 and TGF-β1, by specifically binding to their receptors, might be involved in the myocardial synthesis of BNP during VA in vivo.

Effect of N-Feruloylserotonin and Methotrexate on Severity of Experimental Arthritis and on Messenger RNA Expression of Key Proinflammatory Markers in Liver

Rheumatoid arthritis (RA) is a chronic inflammatory disease, leading to progressive destruction of joints and extra-articular tissues, including organs such as liver and spleen. The purpose of this study was to compare the effects of a potential immunomodulator, natural polyphenol N-feruloylserotonin (N-f-5HT), with methotrexate (MTX), the standard in RA therapy, in the chronic phase of adjuvant-induced arthritis (AA) in male Lewis rats. The experiment included healthy controls (CO), arthritic animals (AA), AA given N-f-5HT (AA-N-f-5HT), and AA given MTX (AA-MTX). N-f-5HT did not affect the body weight change and clinical parameters until the 14th experimental day. Its positive effect was rising during the 28-day experiment, indicating a delayed onset of N-f-5HT action. Administration of either N-f-5HT or MTX caused reduction of inflammation measured as the level of CRP in plasma and the activity of LOX in the liver. mRNA transcription of TNF-α and iNOS in the liver was significantly attenuated in both MTX and N-f-5HT treated groups of arthritic rats. Interestingly, in contrast to MTX, N-f-5HT significantly lowered the level of IL-1β in plasma and IL-1β mRNA expression in the liver and spleen of arthritic rats. This speaks for future investigations of N-f-5HT as an agent in the treatment of RA in combination therapy with MTX.

Daunorubicin Down-Regulates the Expression of Stem Cell Markers and Factors Involved in Stem Cell Migration and Homing in Rat Heart in Subchronic but not Acute Cardiomyopathy

We tested the hypothesis that daunorubicin (DAU) cardiotoxicity alters expression of cytokines involved in stem cell migration and homing. Male Wistar rats were treated with daunorubicin to induce acute DAU cardiomyopathy (6 × 3 mg/kg, i.p., every 48 hr, DAU-A) or subchronic DAU cardiomyopathy (15 mg/kg, i.v., DAU-C). The left ventricle was catheterized. The animals were killed 48 hr (DAU-A) and 8 weeks (DAU-C) after the last dose of DAU. Expression of foetal genes (Nppa, Nppb), isomyosins (Myh6, Myh7), sources of oxidative stress (Abcb8, gp91phox), cytokines (Sdf-1, Cxcr4, Scf, Vegf, Hgf, Igf-1), markers of cardiac progenitor (c-kit, Atnx-1), endothelial progenitor (CD34, CD133) and mesenchymal (CD44, CD105) stem cells were determined by qRT-PCR in left ventricular tissue. Reduced body-weight, decreased left ventricular weight and function, and elevated Nppa, Nppb, Myh7 were observed in both models. Myh6 decreased only in DAU-C, which had a 35% mortality. Up-regulated gp91phox and down-regulated Abcb8 in DAU were present only in DAU-C where we observed markedly decreased expressions of Scf and Vegf as well as expressions of stem cell markers. Down-regulation of cytokines and stem cell markers may reflect impaired chemotaxis, migration and homing of stem cells and tissue repair in the heart in subchronic but not acute model of DAU cardiomyopathy.

Betaine Increases the Butyrylcholinesterase Activity in Rat Plasma

The physiological function of butyrylcholinesterase (EC 3.1.1.8, BChE) is not clearly understood, but a role was suggested in the fat utilization process, resulting in positive correlation between plasma triglyceride (TG) levels and BChE activity. Consequently we tested the hypothesis that regular intake of betaine, a natural compound intervening in the liver TG metabolism could influence the BChE activity. The BChE activity was estimated spectrophotometrically in plasma of rats fed with betaine enriched standard (B) or high-fat diet (HFB). The results confirmed decreased TG plasma levels after betaine treatment independently on the type of diet (0.15±0.03 (B) vs. 0.27±0.08 (control) mmol/l; p=0.003 and 0.13±0.03 (HFB) vs. 0.27±0.08 (control) mmol/l; p=0.005). The BChE activity increased significantly with betaine administration, however the change was more distinct in the HFB group (0.84±0.34 (HFB) vs. 0.22±0.04 (control) O.D./min/mg; p<0.001 and 0.41±0.11 (B) vs. 0.22±0.04 (control) O.D./min/mg; p=0.001). In conclusion, betaine intake led to elevated BChE activity in plasma and this effect was potentiated by the HF diet. Since betaine is in general used as a supplement in the treatment of liver diseases accompanied by TG overload, its impact on the BChE activity in the role of the liver function marker should be taken into account.

Upregulation of SERCA2a following short-term ACE inhibition (by enalaprilat) alters contractile performance and arrhythmogenicity of healthy myocardium in rat

Chronic angiotensin-converting enzyme inhibitor (ACEIs) treatment can suppress arrhythmogenesis. To examine whether the effect is more immediate and independent of suppression of pathological remodelling, we tested the antiarrhythmic effect of short-term ACE inhibition in healthy normotensive rats. Wistar rats were administered with enalaprilat (ENA, i.p., 5 mg/kg every 12 h) or vehicle (CON) for 2 weeks. Intraarterial blood pressure in situ was measured in A. carotis. Cellular shortening was measured in isolated, electrically paced cardiomyocytes. Standard 12-lead electrocardiography was performed, and hearts of anaesthetized open-chest rats were subjected to 6-min ischemia followed by 10-min reperfusion to examine susceptibility to ventricular arrhythmias. Expressions of calcium-regulating proteins (SERCA2a, cardiac sarco/endoplasmic reticulum Ca(2+)-ATPase; CSQ, calsequestrin; TRD, triadin; PLB, phospholamban; Thr(17)-PLB-phosphorylated PLB at threonine-17, FKBP12.6, FK506-binding protein, Cav1.2-voltage-dependent L-type calcium channel alpha 1C subunit) were measured by Western blot; mRNA levels of L-type calcium channel (Cacna1c), ryanodine receptor (Ryr2) and potassium channels Kcnh2 and Kcnq1 were measured by qRT-PCR. ENA decreased intraarterial systolic as well as diastolic blood pressure (by 20%, and by 31%, respectively, for both P < 0.05) but enhanced shortening of cardiomyocytes at basal conditions (by 34%, P < 0.05) and under beta-adrenergic stimulation (by 73%, P < 0.05). Enalaprilat shortened QTc interval duration (CON 78 ± 1 ms vs. ENA 72 ± 2 ms; P < 0.05) and significantly decreased the total duration of ventricular fibrillations (VF) and the number of VF episodes (P < 0.05). Reduction in arrhythmogenesis was associated with a pronounced upregulation of SERCA2a (CON 100 ± 20 vs. ENA 304 ± 13; P < 0.05) and complete absence of basal Ca(2+)/calmodulin-dependent phosphorylation of PLB at Thr(17). Short-term ACEI treatment can provide protection against I/R injury-induced ventricular arrhythmias in healthy myocardium, and this effect is associated with increased SERCA2a expression.

Discrepant regulation of QT (QTc) interval duration by calcium channel blockade and angiotensin converting enzyme inhibition in experimental hypertension

Antihypertensive treatment may reduce prolonged QT duration in hypertension. Generally, the reductions of blood pressure and/or of cardiac mass are believed to be the responsible factors. However, drugs are not equivalent in QT modulation despite similar antihypertensive and antihypertrophic action. We investigated the effect of a calcium channel blocker, lacidipine and an angiotensin-converting enzyme inhibitor, enalapril on QT duration in rats. Normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were treated with lacidipine (at the dose of 1.5 mg/kg per day for WKY and 3 mg/kg per day for SHR) or enalapril (5 mg/kg per day for WKY and 10 mg/kg per day for SHR) during 8 weeks. Tail-cuff systolic blood pressure (sBP), left ventricular weight (LVW), vascular function of isolated aorta and mesenteric artery and duration of QT (and QTc) interval on Frank electrocardiograms were evaluated. As expected, untreated SHR showed elevated sBP, impaired vascular reactivity, increased LVW and prolonged QT when compared with WKY (p < 0.05). After treatment, both agents markedly improved vascular reactivity and reduced sBP in SHR (p < 0.05). Additionally, enalapril reduced LVW in both hypertensive (by 17%; p < 0.05) and normotensive rats (by 13%; p < 0.05) and, consequently, corrected QT duration in SHR. Interestingly, lacidipine also reduced LVW in SHR (by 9%; p < 0.05), but without influence on prolonged QT. Moreover, lacidipine had no effect on LVW in WKYs but prolonged their QT interval (by 10%; p < 0.05). In conclusion, lacidipine did not reverse a progressive prolongation of QT in SHR, despite sBP lowering and LVW reduction. Thus, the lowering of blood pressure and/or reduction of LVW are not sufficient per se to normalize ventricular repolarization in hypertensive cardiac disease. More likely, modulation of QT prolongation by antihypertensive drugs is a function of their complex action on blood pressure, vascular function, cardiac mass and on reflex neurohumoral activation.