Mu Hsin Chang

Eccentric cardiac hypertrophy was induced by long‐term intermittent hypoxia in rats

It is unclear whether cardiac hypertrophy and hypertrophy‐related pathways will be induced by long‐term intermittent hypoxia. Thirty‐six Sprague–Dawley rats were randomly assigned into three groups: normoxia, and long‐term intermittent hypoxia (12% O2, 8 h per day) for 4 weeks (4WLTIH) or for 8 weeks (8WLTIH). Myocardial morphology, trophic factors and signalling pathways in the three groups were determined by heart weight index, histological analysis, Western blotting and reverse transcriptase‐polymerase chain reaction from the excised left ventricle. The ratio of whole heart weight to body weight, the ratio of left ventricular weight to body weight, the gross vertical cross‐section of the heart and myocardial morphological changes were increased in the 4WLTIH group and were further augmented in the 8WLTIH group. In the 4WLTIH group, tumour necrosis factor‐α(TNFα), insulin‐like growth factor (IGF)‐II, phosphorylated p38 mitogen‐activated protein kinase (P38), signal transducers and activators of transcription (STAT)‐1 and STAT‐3 were significantly increased in the cardiac tissues. However, in the 8WLTIH group, in addition to the above factors, interleukin‐6, mitogen‐activated protein kinase (MEK)5 and extracellular signal‐regulated kinase (ERK)5 were significantly increased compared with the normoxia group. We conclude that cardiac hypertrophy associated with TNFα and IGF‐II was induced by intermittent hypoxia. The longer duration of intermittent hypoxia further activated the eccentric hypertrophy‐related pathway, as well as the interleukin 6‐related MEK5–ERK5 and STAT‐3 pathways, which could result in the development of cardiac dilatation and pathology.

Lipopolysaccharide upregulates uPA, MMP-2 and MMP-9 via ERK1/2 signaling in H9c2 cardiomyoblast cells

Upregulation of urokinase plasminogen activator (uPA), tissue plasminogen activator (tPA), and matrix metallopeptidases (MMPs) is associated with the development of myocardial infarction (MI), dilated cardiomyopathy, cardiac fibrosis, and heart failure (HF). Evidences suggest that lipopolysaccharide (LPS) participates in the inflammatory response in the cardiovascular system; however, it is unknown if LPS is sufficient to upregulate expressions and/or activity of uPA, tPA, MMP-2, and MMP-9 in myocardial cells. In this study, we treated H9c2 cardiomyoblasts with LPS to explore whether LPS upregulates uPA, tPA, MMP-2, and MMP-9, and further to identify the precise molecular and cellular mechanisms behind this upregulatory responses. Here, we show that LPS challenge increased the protein levels of uPA, MMP-2 and MMP-9, and induced the activity of MMP-2 and MMP-9 in H9c2 cardiomyoblasts. However, LPS showed no effects on the expression of tissue inhibitor of metalloproteinase-1, -2, -3, and -4 (TIMP-1, -2, -3, and -4). After administration of inhibitors including U0126 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor), CsA (calcineurin inhibitor), and QNZ (NFκB inhibitor), the LPS-upregulated expression and/or activity of uPA, MMP-2, and MMP-9 in H9c2 cardiomyoblasts are markedly inhibited only by ERK1/2 inhibitors, U0126. Collectively, these results suggest that LPS upregulates the expression and/or activity of uPA, MMP-2, and MMP-9 through ERK1/2 signaling pathway in H9c2 cardiomyoblasts. Our findings further provide a link between the LPS-induced cardiac dysfunction and the ERK1/2 signaling pathway that mediates the upregulation of uPA, MMP-2 and MMP-9.

Histone Acetylation Is Essential for ANG-II-Induced IGF-IIR Gene Expression in H9c2 Cardiomyoblast Cells and Pathologically Hypertensive Rat Heart

The IGF‐II/mannose 6‐phosphate receptor (IGF‐IIR/Man‐6‐P) up‐regulation correlates with heart disease progression and its signaling cascades directly trigger pathological cardiac hypertrophy, fibrosis, and cardiomyocytes apoptosis. IGF‐IIR gene expression/ suppression is able to prevent myocardial remodeling. However, the regulating mechanisms for the IGF‐IIR gene remain unclear. This study performed reverse transcriptase PCR (RT‐PCR) and methylation‐specific PCR (MS‐PCR) to detect expression and DNA methylation of CpG islands within the IGF‐IIR genomic DNA region. Our finding revealed that the IGF‐IIR gene was up‐regulated both in H9c2 cells treated with tumor necrosis factor‐alpha (TNF‐α), lipopolysaccharide (LPS), angiotensin II (ANGII) and inomycin, and age‐dependently in spontaneously hypertensive rat (SHR) heart. For the DNA methylation study, although there were four CpG islands within IGF‐IIR genomic regions, the DNA methylation distribution showed no change either in cells treated with ANGII or in the SHR heart. Using chemical inhibitors to individually block histone acetyltransferase (HAT) and histone deacetylase (HDAC) activity, we found that histone acetylation was essential for ANGII‐induced IGF‐IIR gene expression using RT‐PCR and luciferase assay. The Chromatin immuno‐precipitation assay indicated that acetyl‐Histone H3 and acetyl‐Histone H4 associated with the IGF‐IIR promoter increased in the presence of ANGII, otherwise methyl‐CpG binding domain protein 2 (MeCP2) is disassociated with this. Taken together, this study demonstrates that histone acetylation plays a critical role in IGF‐IIR up‐regulation during pathological cardiac diseases and might provide a targeting gene in transcriptional therapies for the failing heart. J. Cell. Physiol. 227: 259–268, 2012.

Cardiac Contractile Dysfunction and Apoptosis in Streptozotocin-Induced Diabetic Rats Are Ameliorated by Garlic Oil Supplementation

Previous studies have suggested that garlic oil could protect the cardiovascular system. However, the mechanism by which garlic oil protects diabetes-induced cardiomyopathy is unclear. In this study, streptozotocin (STZ)-induced diabetic rats received garlic oil (0, 10, 50, or 100 mg/kg of body weight) by gastric gavage every 2 days for 16 days. Normal rats without diabetes were used as control. Cardiac contractile dysfunction examined by echocardiography and apoptosis evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay were observed in diabetic rat hearts. Additionally, a shift in cardiac myosin heavy chain (MHC) gene expression from α- to β-MHC isoform, decreased levels of superoxide dismutase-1 (SOD-1) and cardiac α-actin, and elevated cardiac thiobarbituric acid reactive substances (TBARS) and caspase- and p38-NFκB-leading apoptosis signaling activities were demonstrated in diabetic hearts. However, these diabetes-related cardiac dysfunctions were almost dose-dependently ameliorated by garlic oil administration. In conclusion, garlic oil possesses significant potential for protecting hearts from diabetes-induced cardiomyopathy.

IGF-II/mannose 6-phosphate receptor activation induces metalloproteinase-9 matrix activity and increases plasminogen activator expression in H9c2 cardiomyoblast cells

The IGF-II/mannose 6-phosphate receptor (IGF2R) function in extracellular matrix (ECM) remodeling is known to occur as a result of transforming growth factor-beta (TGF-beta) activation and plasmin in the proteolytic cleavage level caused by the interaction between latent TGF-beta and urokinase plasminogen activator receptor (uPAR) respectively. In one of our previous studies, we found IGF-II and IGF2R dose-dependently correlated with the progression of pathological hypertrophy remodeling following complete abdominal aorta ligation. However, how this IGF2R signaling pathway responds specifically to IGF-II and regulates the myocardial ECM remodeling process is unclear. We found that IGF2R was aberrantly expressed in myocardial infarction scars. The matrix metalloproteinase-9 (MMP-9) zymographic activity was elevated in H9c2 cardiomyoblast cells treated with IGF-II, but not IGF-I. Treatment with Leu27IGF-II, an IGF2R specifically binding IGF-II analog, resulted in significant time-dependent increases in the MMP-9, tissue-type plasminogen activator (tPA), and urokinase plasminogen activator (uPA); and a reduction in the tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) protein expression. Furthermore, IGF2R expression inhibition by siRNA blocked the IGF-II-induced MMP-9 activity. We hypothesize that after IGF-II is bound with IGF2R, the resulting signal disrupts the balance in the MMP-9/TIMP-2 expression level and increases plasminogen activator (PAs) expression involved in the development of myocardial remodeling. If so, IGF2R signaling inhibition may have potential use in the development of therapies preventing heart fibrosis progression.

Second-hand smoke-induced cardiac fibrosis is related to the Fas death receptor apoptotic pathway without mitochondria-dependent pathway involvement in rats.

Exposure to environmental tobacco smoke has been epidemiologically linked to heart disease among nonsmokers. However, the molecular mechanism behind the pathogenesis of cardiac disease is unknown. In this study, we found that Wistar rats, exposed to tobacco cigarette smoke at doses of 5, 10, or 15 cigarettes for 30 min twice a day for 1 month, had a dose-dependently reduced heart weight to body weight ratio and enhanced interstitial fibrosis as identified by histopathologic analysis. The mRNA and activity of matrix metalloprotease-2 (MMP-2), representing the progress of cardiac remodeling, were also elevated in the heart. In addition, we used reverse-transcriptase polymerase chain reaction and Western blotting to demonstrate significantly increased levels of the apoptotic effecter caspase-3 in treated animal hearts. Dose-dependently elevated mRNA and protein levels of Fas, and promoted apoptotic initiator caspase-8 (active form), a molecule of a death-receptor–dependent pathway, coupled with unaltered or decreased levels of cytosolic cytochrome c and the apoptotic initiator caspase-9 (active form), molecules of mitochondria-dependent pathways, may be indicative of cardiac apoptosis, which is Fas death-receptor apoptotic-signaling dependent, but not mitochondria pathway dependent in rats exposed to second-hand smoke (SHS). With regard to the regulation of survival pathway, using dot blotting, we found cardiac insulin-like growth factor-1 (IGF-1) and IGF-1 receptor mRNA levels to be significantly increased, indicating that compensative effects of IGF-1 survival signaling could occur. In conclusion, we found that the effects of SHS on cardiomyocyte are mediated by the Fas death-receptor–dependent apoptotic pathway and might be related to the epidemiologic incidence of cardiac disease of SHS-exposed non-smokers.

Leu27IGF2 plays an opposite role to IGF1 to induce H9c2 cardiomyoblast cell apoptosis via Gaq signaling

This study examines the role of IGF2/mannose 6-phosphate receptor (IGF2R) signaling in the signaling transduction regulation and cell apoptosis in H9c2 cardiomyoblast cells. However, it is difficult to recognize the distinct activation of IGF2 signaling without interfacing with IGFI receptor (IGF1R) after exposure to IGF2. Leu27IGF2, an analog of IGF2 that interacts selectively with the IGF2R, was used to specifically activate IGF2R signaling in this study. DNA fragmentation and TUNEL assay revealed that in contrast to IGF1 treatment preventing angiotensin II and AG1024-induced cell apoptosis, Leu27IGF2 appears to synergistically increase apoptosis in those cells. We further found cell apoptosis induction and an increase in the active form of caspase 3 in the treatment of cells with Leu27IGF2, but not IGF1. To detect the interaction between IGF2R and Galphaq using the immunoprecipitation assay, we found that IGF2R could directly interact with Galphaq and after treatment with Leu27IGF2 the binding ability of Galphaq to IGF2R had increased. This sequentially resulted in the phosphorylation of phospholipase C-beta, a key downstream modulator of Galphaq, on serine 537. Moreover, disruption of the Galphaq protein by small interferon RNA reduced the cell apoptosis induced by Leu27IGF2. Our findings demonstrate that IGF2R activation appears to induce cell apoptosis via Galphaq-deriving signaling cascades and its effect is completely different from IGF1R survival signaling.

Anti-inflammatory effects of probiotic Lactobacillus paracasi on ventricles of BALB/C mice treated with ovalbumin.

Lactic acid bacteria (LAB) are microorganisms that benefit animals with allergic diseases and intestinal disorders such as inflammatory bowel disease. We propose that LAB can prevent cardiomyocytes inflammation and apoptosis in BALB/c mice using an ovalbumin (OVA)-induced allergy. Thirty-nine male BALB/c mice were divided into five groups: normal control, allergy control and three allergy groups each treated with Kefir I (Kefir I), Kefir II (Kefir II) or GM080 products (GM080). The myocardial architecture and apoptotic molecules in the excised left ventricle from these mice were investigated and post-treatment effects were evaluated. The inflammatory pathway, including toll-like receptor 4 (TLR4), phospholate-Jun-N-terminal kinase (p-JNK), JNK1/2 and tumor necrosis factor- alpha (TNF-α) and the mitochondria-dependent apoptosis phospholate-p38 (p-p38), Bcl-2 associated agonist of cell death (Bad), Bcl-2 associated X (Bax) and activated caspase 3, were found to be significant- ly increased in the hearts of allergy mice. The expression of phospholate-nuclear factor-κB (p-NFκB), TNF-α, p-p38 and Bad protein products were reduced or retarded in the Kefir I- or II-treated allergy group. The GM080-treated allergy group exhibited significantly lower p-JNK, JNK1/2, phospholate- Ikappa B (p-IκB), Bax and Bad protein products than the Kefir I and Kefir II allergy groups. These results indicate that LAB can reduce inflammation and prevent apoptosis of cardiomyocytes in the heart of OVA-induced allergy mice.

Dung-shen (Codonopsis pilosula) attenuated the cardiac-impaired insulin-like growth factor II receptor pathway on myocardial cells.

Previous studies from our lab showed that increase in AngII in H9c2 cells causes elevated IGFII and IGFIIR through MEK and JNK, leading to rise in intracellular calcium, calcineurin activation by PLC-β3 via Gαq, insertion into mitochondrial membranes of Bad, and apoptosis via caspases 9 and 3. Codonopsis pilosula is traditionally used to lower blood pressure. The purpose of our study is to investigate if C. pilosula attenuates AngII plus Leu(27)-IGFII-induced calcium influx and apoptosis in H9c2 cardiomyoblasts. C. pilosula significantly attenuated AngII induced IGFIIR promoter activity. Leu(27)-IGFII was applied to enhance the AngII effect. C. pilosula also reversed Ca(2+) influx, MOMP and apoptosis increased by AngII plus Leu(27)-IGFII. Molecular markers in IGFIIR apoptotic pathway (IGFIIR, calcineurin, etc.) and IGFIIR-Gαq association were downregulated by C. pilosula. However, p-Bad(Ser136) and Bcl-2 were increased. Therefore, C. pilosula suppresses AngII plus Leu(27)-IGFII-induced IGFII/IGFIIR pathway in myocardial cells.

Garlic oil attenuates the cardiac apoptosis in hamster-fed with hypercholesterol diet.

Hypercholesterolemia is a well established risk factor for cardiac cell apoptosis. The purpose of this study is to evaluate the effects of garlic oil on cardiac apoptosis induced by a hypercholesterol diet. Twenty-four male Golden-Syrian hamsters at 3 months of age were randomly divided into three groups, control, cholesterol and garlic oil groups received a chow diet, chow diet with 2% cholesterol, and chow diet with 2% cholesterol and 1% garlic oil for 8 weeks, respectively. The TUNEL-positive apoptotic cells, and several apoptotic proteins were significantly induced in the excised left ventricle in cholesterol group, whereas significant reduction was observed in cholesterol plus garlic oil group. The IGFI receptor dependent survival pathway was inhibited in cholesterol group whereas it was obviously reversed in cholesterol plus garlic oil group. Our results suggest that administration of garlic oil shows protective effects on cardiac apoptosis in rats with high cholesterol intake.