PKA phosphorylates multiple molecules involved in calcium (Ca 2+ ) handling in cardiac myocytes and is considered to be the predominant regulator of β-adrenergic receptor-mediated enhancement of cardiac contractility; however, recent identification of exchange protein activated by cAMP (EPAC), which is independently activated by cAMP, has challenged this paradigm. Mice lacking Epac1 (Epac1 KO) exhibited decreased cardiac contractility with reduced phospholamban (PLN) phosphorylation at serine-16, the major PKA-mediated phosphorylation site. In Epac1 KO mice, intracellular Ca 2+ storage and the magnitude of Ca 2+ movement were decreased; however, PKA expression remained unchanged, and activation of PKA with isoproterenol improved cardiac contractility. In contrast, direct activation of EPAC in cardiomyocytes led to increased PLN phosphorylation at serine-16, which was dependent on PLC and PKCε. Importantly, Epac1 deletion protected the heart from various stresses, while Epac2 deletion was not protective. Compared with WT mice, aortic banding induced a similar degree of cardiac hypertrophy in Epac1 KO; however, lack of Epac1 prevented subsequent cardiac dysfunction as a result of decreased cardiac myocyte apoptosis and fibrosis. Similarly, Epac1 KO animals showed resistance to isoproterenol-and aging-induced cardiomyopathy and attenuation of arrhythmogenic activity. These data support Epac1 as an important regulator of PKA-independent PLN phosphorylation and indicate that Epac1 regulates cardiac responsiveness to various stresses.

BackgroundAortic aneurysm is a common but life-threatening disease among the elderly, for which no effective medical therapy is currently available. Activation of prostaglandin E2 (PGE2) is known to increase the expression of matrix metalloproteinase (MMP) and the release of inflammatory cytokines, and may thus exacerbate abdominal aortic aneurism (AAA) formation. We hypothesized that selective blocking of PGE2, in particular, EP4 prostanoid receptor signaling, would attenuate the development of AAA.Methods and FindingsImmunohistochemical analysis of human AAA tissues demonstrated that EP4 expression was greater in AAA areas than that in non-diseased areas. Interestingly, EP4 expression was proportional to the degree of elastic fiber degradation. In cultured human aortic smooth muscle cells (ASMCs), PGE2 stimulation increased EP4 protein expression (1.4±0.08-fold), and EP4 stimulation with ONO-AE1-329 increased MMP-2 activity and interleukin-6 (IL-6) production (1.4±0.03- and 1.7±0.14-fold, respectively, P<0.05). Accordingly, we examined the effect of EP4 inhibition in an ApoE−/− mouse model of AAA infused with angiotensin II. Oral administration of ONO-AE3-208 (0.01–0.5 mg/kg/day), an EP4 antagonist, for 4 weeks significantly decreased the formation of AAA (45–87% reduction, P<0.05). Similarly, EP4+/−/ApoE−/− mice exhibited significantly less AAA formation than EP4+/+/ApoE−/− mice (76% reduction, P<0.01). AAA formation induced by periaortic CaCl2 application was also reduced in EP4+/− mice compared with wild-type mice (73% reduction, P<0.001). Furthermore, in human AAA tissue organ cultures containing SMCs and macrophages, doses of the EP4 antagonist at 10–100 nM decreased MMP-2 activation and IL-6 production (0.6±0.06- and 0.7±0.06-fold, respectively, P<0.05) without increasing MMP-9 activity or MCP-1 secretion. Thus, either pharmacological or genetic EP4 inhibition attenuated AAA formation in multiple mouse and human models by lowering MMP activity and cytokine release.ConclusionAn EP4 antagonist that prevents the activation of MMP and thereby inhibits the degradation of aortic elastic fiber may serve as a new strategy for medical treatment of AAA.

Abstract-We reported previously that ATP2B1 was one of the genes for hypertension receptivity in a large-scale Japanese population, which has been replicated recently in Europeans and Koreans. ATP2B1 encodes the plasma membrane calcium ATPase isoform 1, which plays a critical role in intracellular calcium homeostasis. In addition, it is suggested that ATP2B1 plays a major role in vascular smooth muscle contraction. Because the ATP2B1 knockout (KO) mouse is embryo-lethal, we generated mice with vascular smooth muscle cell-specific KO of ATP2B1 using the Cre-loxP system to clarify the relationship between ATP2B1 and hypertension. The KO mice expressed significantly lower levels of ATP2B1 mRNA and protein in the aorta compared with control mice. KO mice showed significantly higher systolic blood pressure as measured by tail-cuff method and radiotelemetric method. Similar to ATP2B1, the expression of the Na 1 In the Millennium Genome Project 2 we identified single nucleotide polymorphisms located upstream or within the ATP2B1 gene as strong susceptible polymorphisms for hypertension in Japanese. Some of these findings have been replicated in individuals of European descent in the Global Blood Pressure Genetics sample and have also been validated in other studies in individuals of European descent, 3 Koreans, 4-6 and Japanese. 7 The single nucleotide polymorphisms of ATP2B1 identified in these studies showed a significant association with hypertension in various large-scale study populations with different methods, genome-wide association study in the Cohorts for Heart and Aging Research in Genomic Epidemiology Consortium and the Korean study and candidate gene analysis in our previous study. However, the functional roles of ATP2B1 in blood pressure control have not yet been proven in vivo. The ATP2B1-null mutant mouse has been reported to be embryolethal 8 ; thus, we need to make a conditional knockout (KO) mouse model of ATP2B1 using the Cre-loxP system to reveal the function of the gene. Because the ATP2B1 gene encodes one of the calcium pumps and plays an important role in contraction of bladder smooth muscle, 9 we selected vascular smooth

Polyglycolic acid (PGA), a biodegradable aliphatic polyester, has only been produced in small quantities as an extremely expensive, high value-added product because no technology has existed to permit inexpensive mass production. PGA is a novel biodegradable resin that offers high mechanical strength and high gas-barrier performance. To mass-produce high-molecularweight PGA on an industrial scale, Kureha Corporation has developed a process to obtain large yields of the intermediate glycolide (GL) with high levels of purity. Using the obtained GL, we developed a method to polymerize high-molecular-weight PGA continuously. A commercial production plant is now in operation. Because high-molecular-weight PGA can be produced at a lower cost than previously possible, we have also developed various applications that utilize its characteristics. The use of PGA in shale gas and oil exploration is of interest because PGA can supply ultra-strong and biodegradable materials.