Evaluation of Anti-hypertrophic Potential of Enicostemma littorale Blume on Isoproterenol Induced Cardiac Hypertrophy

Inhibition of transglutaminase 2 (TG2) ameliorates ventricular fibrosis in isoproterenol-induced heart failure in rats

AIMS

Transglutaminase (TG) inhibitors represent promising therapeutic interventions in cardiac fibrosis and related dysfunctions. However, it remains unknown how TG inhibition, TG2 in particular, affects the signaling systems that drive pathological fibrosis. This study aimed to examine the effect TG inhibition by cystamine on the progression of isoproterenol (ISO)-induced cardiac fibrosis and dysfunction in rats.

MATERIALS AND METHODS

Cardiac fibrosis was established by intraperitoneal injection of ISO to rats (ISO group), followed by 6 weeks of cystamine injection (ISO + Cys group). The control groups were administered normal saline alone or with cystamine. Hemodynamics, lipid profile, liver enzymes, urea, and creatinine were assessed in conjunction with heart failure markers (serum NT-proANP and cTnI). Left ventricular (LV) and atrial (LA) fibrosis, total collagen content, and mRNA expression of profibrotic markers including TG2 were quantified by Masson's trichrome staining, LC-MS/MS and quantitative PCR, respectively.

KEY FINDINGS

Cystamine administration to ISO rats significantly decreased diastolic and mean arterial pressures, total cholesterol, triglycerides, LDL, liver enzymes, urea, and creatinine levels, while increasing HDL. NT-proANP and cTnI serum levels remained unchanged. In LV tissues, significant reductions in ISO-induced fibrosis and elevated total collagen content were achieved after cystamine treatment, together with a reduction in TG2 concentration. Reduced mRNA expression of several profibrotic genes (COL1A1, FN1, MMP-2, CTGF, periostin, CX43) was also evidenced in LV tissues of ISO rats upon cystamine administration, whereas TGF-β1 expression was depressed in LA tissues. Cystamine decreased TG2 mRNA expression in the LV of control rats, while LV expression of TG2 was relatively low in ISO rats irrespective of cystamine treatment.

SIGNIFICANCE

TG2 inhibition by cystamine in vivo exerted cardioprotective effects against ISO-induced cardiac fibrosis in rats decreasing the LV abundance of several profibrotic markers and the content of TG2 and collagen, suggesting that TG2 pharmacological inhibition could be beneficial to alleviate cardiac fibrosis.

Flaxseed lignans alleviates isoproterenol-induced cardiac hypertrophy by regulating myocardial remodeling and oxidative stress

Cardiovascular diseases, the leading global cause of death, are usually associated with cardiac hypertrophy (CH). CH is an adaptive response of the heart against cardiac overloading, but continuous CH accelerates cardiac remodeling and results in heart failure. Available CH therapies delay the progress of heart failure, but they often fail to control symptoms or restore quality of life. Although flaxseed lignans have been shown to have significant anti-oxidant, anti-hypertensive, anti-inflammatory, and anti-fibrotic effects in various cardiovascular diseases, little is known about their effect on CH. Thus, this study evaluated the therapeutic effect of flaxseed lignans on CH, which was induced by subcutaneous injections with isoproterenol (5 mg/kg b.w) for 14 consecutive days. Flaxseed lignans (200 mg/kg) was given orally for 4 weeks. Cardiac pathological remodeling was evaluated by echocardiography, after which morphometric, biochemical, histological, and ultrastructural analyses were performed. Flaxseed lignans significantly ameliorated CH structural and functional alterations as shown by echocardiography. Lignans also reduced the relative heart weight, significantly decreased the elevated CK-MB and the lipid peroxidation marker malondialdehyde, augmented the myocardial total antioxidant capacity, and ameliorated the histopathological and ultrastructural changes in cardiac tissues and prevented interstitial collagen deposition. The results demonstrate promising anti-hypertrophic effect of flaxseed lignans against isoproterenol-induced cardiac hypertrophy, via regulating myocardial remodeling and oxidative stress. Therefore, lignans could be used as potential pharmacological intervention in the management of CH.

Aloin alleviates pathological cardiac hypertrophy via modulation of the oxidative and fibrotic response

AIMS

Pathological cardiac hypertrophy is a characteristic feature in many cardiovascular diseases (CVDs). Aloin is an anthraquinone glycoside from Aloe species, and the effect of aloin on cardiac hypertrophy and associated fibrotic changes have not been elucidated. This study investigated the effect of aloin against the isoproterenol (ISO)-induced cardiac hypertrophy in rats.

MAIN METHODS

Cardiac hypertrophy experimental model was induced in rats by subcutaneous injection of ISO for 14 days. Meanwhile, the animals were administered orally with aloin at doses of 25 and 50 mg/kg/day. On the 15th day, cardiac echocardiography was performed, the heart was collected and subjected for histopathological, gene expression, and immunoblot studies. Additionally, the effect of aloin on ISO-induced hypertrophic changes in H9c2 cells was investigated.

KEY FINDINGS

Aloin markedly alleviated ISO-induced heart injury, reduced cardiac hypertrophy, improved cardiac function, and histological alterations in the heart. Mechanistically, aloin attenuated ISO-induced fibrosis via inhibition of the levels of collagen I, α-smooth muscle actin (α-SMA), fibronectin, transforming growth factor-β (TGF-β) and pSmad2/3 proteins in the heart. Aloin alleviated ISO-induced myocardial oxidative damage and up-regulated the levels of antioxidant transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) proteins. Moreover, aloin treatment attenuated ISO-induced hypertrophic changes and the generation of reactive oxygen species (ROS) in H9c2 cells in vitro.

SIGNIFICANCE

Our findings demonstrated that aloin alleviated ISO-induced cardiac hypertrophy and fibrosis via inhibiting TGF-β/pSmad2/3 signaling and restoring myocardial antioxidants, and therefore has promising therapeutic potential against cardiac hypertrophy and fibrosis.

Modified citrus pectin prevents isoproterenol-induced cardiac hypertrophy associated with p38 signalling and TLR4/JAK/STAT3 pathway

Modified citrus pectin (MCP) is a specific inhibitor of galectin-3 (Gal-3) that is regarded as a new biomarker of cardiac hypertrophy, but its effect is unclear. The aim of this study is to investigate the role and mechanism of MCP in isoproterenol (ISO)-induced cardiac hypertrophy. Rats were injected with ISO to induce cardiac hypertrophy and treated with MCP. Cardiac function was detected by ECG and echocardiography. Pathomorphological changes were evaluated by the haematoxylin eosin (H&E) and wheat germ agglutinin (WGA) staining. The hypertrophy-related genes for atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and β-myosin heavy chain (β-MHC), and the associated signal molecules were analysed by qRT-PCR and western blotting. The results show that MCP prevented cardiac hypertrophy and ameliorated cardiac dysfunction and structural disorder. MCP also decreased the levels of ANP, BNP, and β-MHC and inhibited the expression of Gal-3 and Toll-like receptor 4 (TLR4). Additionally, MCP blocked the phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), but it promoted the phosphorylation of p38. Thus, MCP prevented ISO-induced cardiac hypertrophy by activating p38 signalling and inhibiting the Gal-3/TLR4/JAK2/STAT3 pathway.

Identification of serum predictors of n-acetyl-l-cysteine and isoproterenol induced remodelling in cardiac hypertrophy

Cardiac hypertrophy (CH), leading to cardiac failure is due to chronic metabolic alterations occurring during cellular stress. Besides the already known relationship between oxidative stress and CH, there are implications of reductive stress leading to CH. This study attempted to develop reductive stress-based CH rat model using n-acetyl-L-cysteine (NAC), a glutathione agonist that was compared with typical isoproterenol (ISO) induced CH model. The main objective was to identify serum metabolites that can serve as potent predictors for seven routine clinical and diagnostic parameters in CH: 3-hydroxybutyrate (3-HB), lactic acid (LA), urea, and ECG-CH parameters (QRS complex, R-amplitude, R-R interval, heart rate) that were hypothesized to underlie metabolic remodelling in this study. CH was assessed using electrocardiography, hypertrophic index and histopathological analysis (H&E stain) in both ventricles after 2 weeks. Gas chromatography mass spectroscopy analysis (GC-MS) identified unique metabolite finger-prints. Correlation and pattern analysis revealed strong relationships between specific metabolites and parameters (Pearson's score > 0.7) of this study. Multiple regression analysis (MRA) for the strongly related metabolites (independent variables) with each of the seven parameters (dependent variables) identified significant predictors for the latter namely fructose, valine, butanoic acid in NAC and cholesterol, erythrose, isoleucine in ISO models, with proline and succinic acid as common for both models. Metabolite set enrichment analysis (MSEA) of those significant predictors (p < 0.05) mapped butyrate metabolism as highly influential pathway in NAC, with arginine-proline metabolism and branched chain amino acid (BCAA) degradation as common pathways in both models, thus providing new insights towards initial metabolic remodeling in the pathogenesis of CH.