Abstract-Our previous study demonstrated that periostin, an extracellular matrix protein, plays an important role in left ventricular remodeling through the inhibition of cell-cell interactions. Because the gene regulation of periostin has not yet been examined, we focused on the effects of angiotensin (Ang) II and mechanical stretch, because Ang II and mechanical stretch are related to cardiac remodeling after myocardial infarction. First, we examined the effects of Ang II on periostin in myocytes and fibroblasts in vitro. Ang II significantly increased periostin through phosphatidylinositol 3-kinase, c-Jun N-terminal kinase, p38, and extracellular signal-regulated kinase 1/2 pathways in myocytes and fibroblasts (PϽ0.05). On the other hand, mechanical stretch also significantly increased periostin expression (PϽ0.05). This increase was inhibited partially, but significantly, by an Ang II receptor blocker, valsartan, and inhibited almost completely by valsartan with the neutralization antibodies for transforming growth factor-␤ and platelet-derived growth factor-BB (PϽ0.05). Therefore, we further examined periostin expression in vivo. Periostin expression was significantly increased in infarcted myocardium (PϽ0.05), and treatment with valsartan significantly attenuated it at 4 weeks after myocardial infarction (PϽ0.05), accompanied by a significant improvement in cardiac dysfunction (PϽ0.05). Overall, the present study demonstrated that Ang II, as well as mechanical stretch, stimulated periostin expression in both cardiac myocytes and fibroblasts, whereas valsartan significantly attenuated the increase in periostin expression. The inhibition of periostin by valsartan might especially contribute to its beneficial effects on cardiac remodeling after myocardial infarction. Key Words: angiotensin II type 1 receptor blockers Ⅲ myocardial infarction Ⅲ adhesions Ⅲ fibrosis Ⅲ ventricular remodeling C ardiac remodeling after myocardial infarction (MI) results in ventricular dysfunction, which contributes to a poor outcome and high mortality. 1 The use of angiotensin (Ang)-converting enzyme inhibitors in patients with MI has improved survival and reduced the rates of major cardiovascular events, 2 and Ang II receptor blockers (ARBs) were expected to prevent cardiac remodeling, like Ang-converting enzyme inhibitors. The Valsartan in Acute Myocardial Infarction Trial demonstrated that an ARB, valsartan, was as effective as a proven regimen of an Ang-converting enzyme inhibitor captopril in improving survival and reducing cardiovascular mortality in patients who suffered an MI. 3,4 Treatment with captopril or valsartan resulted in similar changes in cardiac volume and ejection fraction after MI, 3 whereas treatment with captopril after MI significantly reduced left ventricular (LV) enlargement. 2 On the other hand, periostin is a novel secreted and putative soluble extracellular matrix protein 5 and is known to be expressed in bone and to a lesser extent in lung, kidney, and heart valves but is not found in normal blood vess...

The molecular regulatory mechanisms and the characterization of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in hypoxia were studied in a mouse brain capillary endothelial cell line, MBEC4. Activation of GAPDH gene expression by hypoxia was suppressed by an intracellular Ca(2+) chelator and inhibited by a non-selective cation channel blocker or a Na(+)/Ca(2+) exchanger (NCX) blocker. Sequencing of reverse transcription-PCR products demonstrated that MBEC4 expressed an mRNA encoding NCX3, which functions even under cellular ATP-depleted conditions, in addition to mRNAs encoding NCX1 and NCX2. The inhibition of Ca(2+)/calmodulin-dependent protein kinases or c-Jun/AP-1 activation caused a significant decrease in the activation of GAPDH mRNA by hypoxia. These results suggest that hypoxia stimulates Ca(2+) influx through non-selective cation channels and causes the reverse operation of the three NCX isoforms, and consequently, increased intracellular Ca(2+) up-regulates GAPDH gene expression through an AP-1-dependent pathway. Furthermore, subcellular fractionation experiments showed that hypoxia increased GAPDH proteins not only in the cytosolic fraction, but also in the nuclear and particulate fractions, in which GAPDH should play no roles in glycolysis. However, the GAPDH activity did not rise in proportion to the increase of GAPDH protein by hypoxia even in the cytosolic fraction. These results suggest that not all hypoxia-induced GAPDH molecules contribute to glycolysis.

Lysophosphatidic acid (LPA) is an endogenous lipid growth factor that is thought to play important roles in cell proliferation and antiapoptosis and therefore may have roles in the development and progression of benign prostatic hyperplasia (BPH). CYR61 (CCN1), on the other hand, is a growth factor-inducible immediate early gene that functions in cell proliferation, differentiation, and extracellular matrix synthesis. Here we show the close relationship between LPA-induced expression of CYR61 and prostate enlargement. CYR61 mRNA and protein were dramatically up-regulated by 18:1 LPA (oleoyl-LPA) within 1 and 2 h, respectively, in both stromal and epithelial prostatic cells. G protein-coupled receptors, i.e. Edg-2, Edg-4, and Edg-7, for LPA were also expressed in both stromal and epithelial prostatic cells. Furthermore, on DNA microarray analysis for normal and BPH patients, CYR61 was found to be related to the development and progression of BPH, regardless of symptoms. Although CYR61 mRNA was synthesized in hyperplastic epithelial cells, in many cases of BPH, CYR61 protein was detected in both the epithelial and stromal regions of BPH patient tissues. The functional contribution of CYR61 to prostatic cell growth was demonstrated by recombinant CYR61 protein and anti-CYR61 neutralizing antibodies, which inhibited CYR61-dependent cell spreading and significantly diminished cell proliferation, respectively. In conclusion, these data support the hypothesis that LPAs induce the expression of CYR61 by activating G proteincoupled receptors and that CYR61 acts as a secreted autocrine and/or paracrine mediator in stromal and epithelial hyperplasia, demonstrating the potential importance of this signaling mechanism in the disease.

Angiopoietin-1 (Ang1) binds to and activates Tie2 receptor tyrosine kinase. Ang1-Tie2 signal has been proposed to exhibit two opposite roles in the controlling blood vessels. One is vascular stabilization and the other is vascular angiogenesis. There has been no answer to the question as to how Tie2 induces two opposite responses to the same ligand. Our group and Dr. Alitalo's group have demonstrated that trans-associated Tie2 at cell-cell contacts and extracellular matrix (ECM)-anchored Tie2 play distinct roles in the endothelial cells. The complex formation depends on the presence or absence of cell-cell adhesion. Here, we review how Ang1-Tie2 signal regulates vascular maintenance and angiogenesis. We further point to the unanswered questions that must be clarified to extend our knowledge of vascular biology and to progress basic knowledge to the treatment of the diseases in which Ang1-Tie2-mediated signal is central.

HIF-1␣ is originally identified as a transcription factor that activates gene expression in response to hypoxia. In metazoans, HIF-1␣ functions as a master regulator of oxygen homeostasis and regulates adaptive responses to change in oxygen tension during embryogenesis, tissue ischemia, and tumorigenesis. Because Hif-1␣-deficient mice exhibit a number of developmental defects, the precise role of HIF-1␣ in early cardiac morphogenesis has been uncertain. Therefore, to clarify the role of HIF-1␣ in heart development, we investigated the effect of knockdown of HIF-1␣ in Xenopus embryos using antisense morpholino oligonucleotide microinjection techniques. Knockdown of HIF-1␣ resulted in defects of cardiogenesis. Whole mount in situ hybridization for cardiac troponin I (cTnI) showed the two separated populations of cardiomyocytes, which is indicative of cardia bifida, in HIF-1␣-depleted embryos. Furthermore, the depletion of HIF-1␣ led to the reduction in cTnI expression, suggesting the correlation between HIF-1␣ and cardiac differentiation. We further examined the expression of several heart markers, nkx2.5, gata4, tbx5, bmp4, hand1, and hand2 in HIF-1␣-depleted embryos. Among them, the expression of nkx2.5 was significantly reduced. Luciferase reporter assay using the Nkx2.5 promoter showed that knockdown of HIF-1␣ decreased its promoter activity. The cardiac abnormality in the HIF-1␣-depleted embryo was restored with co-injection of nkx2.5 mRNA. Collectively, these findings reveal that HIF-1␣-regulated nkx2.5 expression is required for heart development in Xenopus. Hypoxia inducible factor-1 (HIF-1)2 is a transcriptional factor that has the fundamental function in mammalian development and homeostasis, and is considered to become a target for therapy in cancer and cardiac ischemia (1). In response to localized tissue hypoxia, HIF-1 is activated to regulate the transcription of hypoxia-inducible genes that mediate angiogenesis, erythropoiesis, vasodilation, and anaerobic metabolism (2). Under normoxic conditions, the ␣ subunit of HIF-1 (HIF-1␣) undergoes rapid decay via a ubiqutin-proteasome degradation pathway involving the von Hippel-Lindau tumor suppressor gene product (pVHL) (3-5). Hypoxia prevents ␣ subunit from ubiquitination, thereby allowing HIF-1␣ to escape from proteolysis, to dimerize with constitutively expressed HIF-1␤ (6), and to translocate into the nucleus with HIF-1␤.In the early development of mammals, the natural progression of organogenesis involves hypoxia. Diffusion of oxygen in the embryo is limited by its size shortly after gastrulation. In turn, molecular responses to oxygen gradients by HIF-1 are responsible for proper differentiation and maintenance of the cardiovascular system (7). Null mutation of either Hif-1␣ or Hif-1␤ in mice leads to midgestational lethality of embryos, accompanied with phenotypes that include defects in the vasculature, placenta, and heart at embryonic day 10.5 (E10.5) (2, 8, 9). Thus, improper response to low oxygen in the embryo leads to abnormal cardiovascular m...