Both the human pregnane X receptor (hPXR) and constitutive androstane receptor (hCAR) are capable of regulating CYP3A4 and CYP2B6 gene expression. However, the majority of currently identified CYP3A4 and CYP2B6 inducers are confirmed activators of hPXR but not hCAR. To compare these receptors with respect to their chemical selectivities, 16 drugs known to induce CYP3A4 and/or CYP2B expression were evaluated for relative activation of hPXR versus hCAR. Because of the high basal but low chemical-induced activation of hCAR in immortalized cells, alternative methods were used to evaluate hCAR activation potential. Thirteen of the 16 compounds were classified as moderate to strong hPXR activators. In contrast, carbamazepine (CMZ), efavirenz (EFV), and nevirapine (NVP) were classified as negligible or weak hPXR activators at concentrations associated with efficacious CYP2B6 reporter or endogenous gene induction in primary human hepatocytes, suggesting potential activation of hCAR. Subsequent experiments demonstrated that these three drugs efficiently induced nuclear accumulation of in vivo-transfected enhanced yellow fluorescent protein-hCAR and significantly increased expression of a CYP2B6 reporter gene when hCAR was expressed in CAR Ϫ/Ϫ mice. In addition, using a recently identified, chemically responsive splice variant of hCAR (hCAR3), the hCAR activation profiles of the 16 compounds were evaluated. By combining results from the hPXR-and hCAR3-based reporter gene assays, these inducers were classified as hPXR, hCAR, or hPXR/hCAR dual activators. Our results demonstrate that CMZ, EFV, and NVP induce CYP2B6 and CYP3A4 preferentially through hCAR and that hCAR3 represents a sensitive tool for in vitro prediction of chemical-mediated human CAR activation.CYP3A4 and CYP2B6 are induced at the mRNA, protein, and activity levels by the same compounds, including rifampin, phenobarbital, clotrimazole, cyclophosphamide, calcium channel antagonists, HMG-CoA reductase inhibitors, and thiazolidinediones (Drocourt et al., 2001;Kocarek et al., 2002;Lindley et al., 2002;Sahi et al., 2003;Faucette et al., 2004). Coinduction of these enzymes is mediated through transcriptional activation of the corresponding genes by the nuclear receptors pregnane X receptor (PXR) and constitutive androstane receptor (CAR), which are capable of binding to the same response elements in the promoter regions of the CYP3A4 and CYP2B6 genes (Goodwin et al

Abstract-In response to stress signals, postnatal cardiomyocytes undergo hypertrophic growth accompanied by activation of a fetal gene program, assembly of sarcomeres, and cellular enlargement. We show that hypertrophic signals stimulate the expression and transcriptional activity of myocardin, a cardiac and smooth muscle-specific coactivator of serum response factor (SRF). Consistent with a role for myocardin as a transducer of hypertrophic signals, forced expression of myocardin in cardiomyocytes is sufficient to substitute for hypertrophic signals and induce cardiomyocyte hypertrophy and the fetal cardiac gene program. Conversely, a dominant-negative mutant form of myocardin, which retains the ability to associate with SRF but is defective in transcriptional activation, blocks cardiomyocyte hypertrophy induced by hypertrophic agonists such as phenylephrine and leukemia inhibitory factor. Myocardin-dependent hypertrophy can also be partially repressed by histone deacetylase 5, a transcriptional repressor of myocardin. These findings identify myocardin as a nuclear effector of hypertrophic signaling pathways that couples stress signals to a transcriptional program for postnatal cardiac growth and remodeling. (Circ Res. 2006;98:1089-1097.)Key Words: cardiac hypertrophy Ⅲ cardiac myocytes Ⅲ cardiac transcription factors Ⅲ myocardin Ⅲ serum response factor Ⅲ transcription factors Ⅲ transcriptional regulation C ardiac myocytes proliferate rapidly during embryogenesis but lose their proliferative capacity soon after birth. 1 However, adult cardiac myocytes retain the ability to respond to mechanical, hemodynamic, hormonal, and pathologic stimuli by hypertrophic growth, defined by an increase in myocyte size or myofibrillar volume without a change in myocyte number. 2 Whereas cardiac hypertrophy allows the myocardium to adapt functional performance to alterations in workload associated with developmental maturation, physiological challenge, or injury, prolonged hypertrophy in response to stress signaling frequently progresses to heart failure with consequent sudden death attributable to cardiac arrythymias. 2 Cardiac hypertrophy is accompanied by the activation of a set of fetal cardiac genes that are normally expressed in the heart only before birth. 1,3 The reactivation of cardiac fetal genes in postnatal cardiomyocytes in response to hypertrophic signals suggests that the transcriptional program that controls cardiac gene expression during development may be redeployed to regulate hypertrophic cardiac growth. The MADS (MCM1, Agamous, Deficiens, SRF)-box transcription factor myocyte enhancer factor-2 (MEF2) and the zinc finger transcription factor GATA4 play important roles in cardiac development and in hypertrophic growth in response to stress, although the signaling pathways and underlying molecular mechanisms that modulate their activities are distinct. 4 -6 We have shown that MEF2 activity is stimulated by the signal-dependent dissociation from class II histone deacetylases (HDACs), which act as repressors...

Vascular endothelial growth factor A (VEGF-A) is a pivotal player in angiogenesis. It is capable of influencing such cellular processes as tubulogenesis and vascular smooth muscle cell (VSMC) proliferation, yet very little is known about the actual signaling events that mediate VEGF-A induced VSMC phenotypic switch. In this report, we describe the identification of an intricate VEGF-A-induced signaling cascade that involves VEGFR2, STAT3, and Myocardin. We demonstrate that VEGF-A promotes VSMC proliferation via VEGFR2/STAT3-mediated upregulating the proliferation of markers like Cyclin D1 and PCNA. Specifically, VEGF-A leads to nitrosylation of Myocardin, weakens its effect on promoting the expression of contractile markers and is unable to inhibit the activation of STAT3. These observations reinforce the importance of nitric oxide and S-nitrosylation in angiogenesis and provide a mechanistic pathway for VEGF-A-induced VSMC phenotypic switch. In addition, Myocardin, GSNOR and GSNO can create a negative feedback loop to regulate the VSMC phenotypic switch. Thus, the discovery of this interactive network of signaling pathways provides novel and unexpected therapeutic targets for angiogenesis-dependent diseases.

In this paper, a strain HZ1 which was isolated in our former works was classified as Lactobacillus Casei (L. Casei) by 16S rDNA sequence analysis. The results of angiotensin-converting enzyme (ACE) inhibitory assay showed that this novel stain was able to produce ACE inhibitory components when it was used to fermented milk. Applying the methods of membrane filtration and anion-exchange chromatography with fast protein liquid chromatography (FPLC) system, nine fractions with remarkable ACE inhibitory activity were obtained, and two bioactive fractions, recorded as ACEI-2 and ACEI-5, exhibited the highest ACE inhibitory rate of 60.55% and 71.71%, respectively. Furthermore, seven fractions proteins/polypeptides, which exhibited ACE inhibitory rate higher than 50% were separated from ACEI-2 and ACEI-5 by using sephadex gel filtration chromatography. These works might provide a foundation for the following study of L. Casei HZ1 and its probiotics functions, and contribute to the development of functional foods or drugs that provide health benefits to patients suffering from hypertension.