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Abstract  Leucine-zipper and sterile-alpha motif kinase (ZAK) is the key intra-cellular mediator protein in cardiomyocyte hypertrophy induction by transforming growth factor beta 1 (TGF-β1) which has also been identified as a profibrotic cytokine involved in cardiac fibrosis progression. We hypothesized whether ZAK over-expression causes cardiac scar formation due to the extra-cellular matrix (ECM) degraded enzyme regulation in this paper. Using immuno-histochemical analysis of the human cardiovascular tissue array, we found a positively significant association between ZAK over-expression and myocardial scars. ZAK over-expression in H9c2 cardiomyoblast cells increases the metalloproteinase tissue inhibitor 1/2 (TIMP-1/2) protein level, which reduces matria metalloproteinase-9 (MMP-9) activity and also activates c-JNK N-terminal kinase 1/2 (JNK1/2) and p38 signaling, which induces MMP-2, possibly resulting in cardiac fibrosis. Taken together, ZAK activity inhibition may be a good strategy to prevent the cardiac fibrosis progression. [ABSTRACT FROM AUTHOR]

RhoGDIβ, a Rho GDP dissociation inhibitor, induced hypertrophic growth and cell migration in a cultured cardiomyoblast cell line, H9c2. We demonstrated that RhoGDIβ plays a previously undefined role in regulating Rac1 expression through transcription to induce hypertrophic growth and cell migration and that these functions are blocked by the expression of a dominant-negative form of Rac1. We also demonstrated that knockdown of RhoGDIβ expression by RNA interference blocked RhoGDIβ-induced Rac1 expression and cell migration. We demonstrated that the co-expression of ZAK and RhoGDIβ in cells resulted in an inhibition in the activity of ZAK to induce ANF expression. Knockdown of ZAK expression in ZAK-RhoGDIβ-expressing cells by ZAK-specific RNA interference restored the activities of RhoGDIβ. [ABSTRACT FROM AUTHOR]

We found that overexpression of RhoGDIβ, a Rho GDP dissociation inhibitor, induced hypertrophic growth and suppressed cell cycle progression in a cultured cardiomyoblast cell line. Knockdown of RhoGDIβ expression by RNA interference blocked hypertrophic growth. We further demonstrated that RhoGDIβ physically interacts with ZAK and is phosphorylated by ZAK in vitro, and this phosphorylation negatively regulates RhoGDIβ functions. Moreover, the ZAK-RhoGDIβ interaction may maintain ZAK in an inactive hypophosphorylated form. These two proteins could negatively regulate one another such that ZAK suppresses RhoGDIβ functions through phosphorylation and RhoGDIβ counteracts the effects of ZAK by physical interaction. Knockdown of ZAK expression in ZAK- and RhoGDIβ-expressing cells by ZAK-specific RNA interference restored the full functions of RhoGDIβ. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The chemopreventive property of garlic is related in part to its induction of phase II detoxification enzymes. In the present study, we investigated the modulatory effect of 3 garlic organosulfur compounds, i.e., diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), which differ in their number of sulfur atoms, on the gene expression of the π class of glutathione S-transferase (GSTP). Hepatocytes isolated from male Sprague-Dawley rats were cultured with 50-200 μmol/L of DAS, DADS, or DATS for 24 h. DADS and DATS increased GST activity toward ethacrynic acid by 40 and 66%, respectively (P < 0.05). Moreover, both garlic allyl sulfides dose dependently induced GSTP mRNA and protein expression. DATS increased the protein level more than DADS (P < 0.05). In contrast, DAS did not affect the activity or the protein or mRNA levels of this phase II drug-metabolizing enzyme. In Clone 9 liver cells, the pTA-luciferase reporter assay showed that luciferase activity in DADS- and DATS-treated cells was 2.8- and 3.9-fold higher than that in control cells, respectively (P < 0.05). Again, luciferase activity was not affected by treatment with DAS. Deletion of -2.7 to -2.6 kb in the GSTP promoter region, which contains the GSTP enhancer (GPE) I element, abolished the upregulation of GSTP transcription by DADS and DATS. Deletion of GPE II, however, did not affect the induction of reporter activity. In conclusion, the effectiveness of 3 garlic allyl sulfides on GSTP expression was related to the number of sulfur atoms in the molecules, and GPE I was responsible for this upregulation. [ABSTRACT FROM AUTHOR]

The regulation of genes by amino acids is attracting increasing attention. In the present study, we investigated the restriction of expression of the π class of glutathione S-transferase (GST Yp) by sulfur amino acids. Hepatocytes isolated from male Sprague­Dawley rats were cultured with L-15-based medium containing low (LSAA; 0.1 mmol/L L-methionine and 0.1 mmol/L L-cysteine) or high (HSAA; 0.5 mmol/L L-methionine and 0.2 mmol/L L-cysteine) amounts of sulfur amino acids for up to 6 d. Cellular protein contents did not differ between LSAA- and HSAA-treated cells over the entire period. In contrast, glutathione concentrations were suppressed by the LSAA medium and on d 6 were only 20% of those of HSAA-treated cells (P < 0.05). As shown by immunoblot analysis, GST Yp protein levels were greater in LSAA-treated cells than in HSAA-treated cells (P < 0.05). The induction of GST Yp by L-methionine and L-cysteine restriction was not affected by insulin and dexamethasone, but the latter suppressed GST Yp expression (P < 0.05). LSAA increased GST Yp mRNA levels and GST activity toward ethacrynic acid (P < 0.05). GST Vp induction occurred only in cells with a limited supply of L-methionine; restriction of L-isoleucine, L-leucine, L-lysine, and L-phenylalanine had no significant effect. In contrast with the induction of GST Yp, the expression of the GST isoforms Ya and Yb was not changed by amino acid restriction. In conclusion, hepatic GST Vp gene expression is upregulated by a limited availability of sulfur amino acids. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the individual and combined effects of dietary fat and garlic oil on cytochrome P[sub450] 2B1 and the placental form of glutathione S-transferase in rat liver. Materials and methods; Effect of garlic oil on the body and liver weights of rats fed with low and high corn oil; Fatty acid profiles in hepatic phospholipids in rats fed with low and high corn oil.

β-Tricalcium phosphate (β-TCP) is an osteoconductive material in clinical. In this study, we have doped silica (Si) into β-TCP and enhanced its bioactive and osteostimulative properties. To check its effectiveness, a series of Si-doped with different ratios were prepared to make new bioactive and biodegradable biocomposites for bone repair. Formation of the diametral tensile strength, ions released and weight loss of cements was considered after immersion. In addition, we also examined the behavior of human dental pulp cells (hDPCs) cultured on Si-doped β-TCP cements. The results showed that setting time and injectability of the Si-doped β-TCP cements were decreased as the Si content was increased. At the end of the immersion point, weight losses of 30.1%, 36.9%, 48.1%, and 55.3% were observed for the cement doping 0%, 10%, 20%, and 30% Si into β-TCP cements, respectively. In vitro cell experiments show that the Si-rich cements promote human dental pulp cell (hDPC) proliferation and differentiation. However, when the Si-doped in the cement is more than 20%, the amount of cells and osteogenesis protein of hDPCs was stimulated by Si released from Si-doped β-TCP cements. The degradation of β-TCP and osteogenesis of Si gives a strong reason to believe that these Si-doped β-TCP cements may prove to be promising bone repair materials. [ABSTRACT FROM AUTHOR]