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Introduction: CD38 is a multifunctional enzyme with a potent Ca2+ mobilizing effect, cyclic ADP-ribose (cADPR), and nicotinic acid adenine dinucleotide phosphate (NAADP). Here, we aimed to demonstrate the role of CD38 in platelets via protein kinase C (PKC)-mediated internalization and activation. Methods: Mouse platelets were used in this study. Thrombin, an agonist of platelet function, provoked a prompt and long-lasting increase in intracellular Ca2+ concentration ([Ca2+]i), resulting from an interplay of multifold Ca2+ mobilizing messengers.The signaling pathway was delineated using different inhibitors and techniques such as platelet aggregation assay, intracellular calcium measurements, immunoprecipitation, immunoblotting, and flow cytometry. Results: We observed a sequential formation of cADPR and NAADP through CD38 activation by PKC of non-muscle myosin heavy chain IIA (MHCIIA), resulting in phospholipase C (PLC) activation in the thrombin-stimulated platelets. These findings reveal that PKC is fundamental in activating CD38 and elicits a physiological response in the murine platelets. Conclusion: PKC is involved in many signaling pathways. Specifically, PKC is involved in the internalization of CD38 via MHCIIA in CD38+/+ wild-type (WT) and CD38-/- knockout mice (KO). CD38 generates calcium-mobilizing agents that act on specific receptors of the calcium stores. Calcium triggered platelet aggregation while serving as a secondary messenger. [ABSTRACT FROM AUTHOR]

Angiotensin-(1-7) [ANG-(1-7)], one of the bioactive peptides produced in the renin-angiotensin system, plays a pivotal role in cardiovascular physiology by providing a counterbalance to the function of ANG II. Recently, it has been considered as a potential candidate for therapeutic use in the treatment of various types of cardiovascular diseases. The aim of the present study is to explain the modulatory role of ANG-(1-7) in atrial natriuretic peptide (ANP) secretion and investigate the functional relationship between two peptides to induce cardiovascular effects using isolated perfused beating rat atria and a cardiac hypertrophied rat model. ANG-(1-7) (0.01, 0.1, and 1 [micro]M) increased ANP secretion and ANP concentration in a dose-dependent manner at high atrial pacing (6.0 Hz) with increased cGMP production. However, at low atrial pacing (1.2 Hz), ANG-(1-7) did not cause changes in atrial parameters. Pretreatment with an antagonist of the Mas receptor or with inhibitors of phosphatidylinositol 3-kinase (PI3K), protein kinase B (Akt), or nitric oxide synthase blocked the augmentation of high atrial pacing-induced ANP secretion by ANG-(1-7). A similar result was observed with the inhibition of the [Na.sup.+]/[H.sup.+] exchanger-1 and [Ca2.sup.+]/ calmodulin-dependent kinase II (CaMKII). ANG-(1-7) did not show basal intracellular [Ca2.sup.+] signaling in quiescent atrial myocytes. In an in vivo study using an isoproterenol-induced cardiac hypertrophy animal model, an acute infusion of ANG-(1-7) increased the plasma concentration of ANP by twofold without changes in blood pressure and heart rate. A chronic administration of ANG-(1-7) increased the plasma ANP level and attenuated isoproterenol-induced cardiac hypertrophy. The antihypertrophic effect was abrogated by a cotreatment with the natriuretic peptide receptor-A antagonist. These results suggest that 1) ANG-(1-7) increased ANP secretion at high atrial pacing via the Mas/PI3K/Akt pathway and the activation of [Na.sup.+]/[H.sup.+] exchanger-1 and CaMKII and 2) ANG-(1-7) decreased cardiac hypertrophy which might be mediated by ANP. atrial natriuretic peptide; cardiac hypertrophy; atrial myocyte; Mas; signal transduction: phosphatidylinositol 3-kinase doi: 10.1152/ajpheart.00608.2009.

The role of ADP-ribosyl cyclases (ADPR-cyclases) in diabetic nephropathy was investigated. ADPR-cyclases synthesize cADP-ribose (cADPR), a [Ca.sup.2+]-mobilizing second messenger, and are stimulated by G protein-coupled receptors. We have previously reported that ADPR-cyclases can be activated by ANG II and showed that a specific kidney ADPR-cyclase inhibitor, 4,4'-dihydroxyazobenzene (DHAB), can protect ANG H-mediated mesangial cell growth (Kim SY, Gul R, Rah SY, Kim SH, Park SK, Im MJ, Kwon HJ, Kim UH. Am J Physiol Renal Physiol 294: F982-F989, 2008). In this study, we examined the preventive effect of DHAB on glomerular injury in streptozotocin (STZ)-induced diabetic mice. Male mice were randomly assigned to normal control and diabetic groups of comparable age. A diabetic group received 45 [micro]g/kg of DHAB for 6 wk via daily intraperitoneal injections. Several nephropathy parameters were improved in the DHAB-treated diabetic group compared with the diabetic group, including urinary albumin (diabetic, 44.6 [+ or -] 5.1 vs. treated, 33.9 [+ or -] 3.9 [micro]g/day), creatinine clearance (diabetic, 0.72 [+ or -] 0.03 vs. treated, 0.83 [+ or -] 0.04 ml*[min.sup.-1]*100 [g.sup.-1]), ratio of kidney to body weight (diabetic, 2.5 [+ or -] 0.04 vs. treated, 1.4 [+ or -] 0.04), and mesangial matrix expansion (diabetic, 13.9 [+ or -] 2.2 vs. treated, 8.5 [+ or -] 2.0%). These results indicate that kidney function in STZ-induced diabetes was improved by DHAB administration. Furthermore, DHAB inhibited phosphorylation of Akt and nuclear factor of activated T cell 3 nuclear translocation, as well as ADPR-cyclase activity and cADPR production, which were increased in the kidneys of the diabetic group. In addition, DHAB trealxnent decreased fibrosis marker protein expression and glomerular hypertrophy in the diabetic kidney. These findings indicate a crucial role that ADPR-cyclase signaling plays in the renal pathogenesis of diabetes and provide a therapeutic tool for the treatment of renal diseases. angiotensin; cADP-ribose; 4,4'-dihydroxyazobenzene

ADP-ribosyl cyclase (ADPR-cyclase) produces a [Ca.sup.2+]-mobilizing second messenger, cADP-ribose (cADPR), from NA[D.sup.+]. In this study, we investigated the molecular basis of ADPR-cyclase activation in the ANG II signaling pathway and cellular responses in adult rat cardiomyocytes. The results showed that ANG II generated biphasic intracellular [Ca.sup.2+] concentration increases that include a rapid transient [Ca.sup.2+] elevation via inositol trisphosphate (IP3) receptor and sustained [Ca.sup.2+] rise via the activation of L-type [Ca.sup.2+] channel and opening of ryanodine receptor. ANG II-induced sustained [Ca.sup.2+] rise was blocked by a cADPR antagonistic analog, 8-bromo-cADPR, indicating that sustained [Ca.sup.2+] rise is mediated by cADPR. Supporting the notion, ADPR-cyclase activity and cADPR production by ANG II were increased in a time-dependent manner. Application of pharmacological inhibitors and immunological analyses revealed that cADPR formation was activated by sequential activation of Src, phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (Akt), phospholipase C (PLC)-[gamma]1, and I[P.sub.3]-mediated [Ca.sup.2+] signal. Inhibitors of these signaling molecules not only completely abolished the ANG II-induced [Ca.sup.2+] signals but also inhibited cADPR formation. Application of the cADPR antagonist and inhibitors of upstream signaling molecules of ADPR-cyclase inhibited ANG II-stimulated hypertrophic responses, which include nuclear transitcation of [Ca.sup.2+]/calcineurin-dependent nuclear factor of activated T cells 3, protein expression of transforming growth factor-[beta]1, and incorporation of [[sup.3]H]leucine in cardiomyocytes. Taken together, these findings suggest that activation of ADPR-cyclase by ANG II entails a novel signaling pathway involving sequential activation of Src, PI 3-kinase/Akt, and PLC-[gamma]1/I[P.sub.3] and that the activation of ADPR-cyclase can lead to cardiac hypertrophy. angiotensin II; calcium ion, adenosine 5'-triphosphate-ribosyl cyclase; cardiomyocytes

ADP-ribosyl cyclase (ADPR-cyclase) produces a [Ca.sup.2+]-mobilizing second messenger cyclic ADP-ribose (cADPR) from NA[D.sup.+]. In this study, we investigated the molecular basis of ADPR-cyclase activation and the following cellular events in angiotensin II (ANG II) signaling in mouse mesangial cells (MMCs). Treatment of MMCs with ANG II induced an increase in intracellular [Ca.sup.2+] concentrations through a transient [Ca.sup.2+] release via an inositol 1,4,5-trisphosphate receptor and a sustained [Ca.sup.2+] influx via L-type [Ca.sup.2+] channels. The sustained [Ca.sup.2+] signal, but not the transient [Ca.sup.2+] signal, was blocked by a cADPR antagonistic analog, 8-bromo-cADPR (8-Br-cADPR), and an ADPRcyclase inhibitor, 4,4'-dihydroxyazobenzene (DHAB). In support of the results, ANG II stimulated cADPR production in a time-dependent manner, and DHAB inhibited ANG II-induced cADPR production. Application of pharmacological inhibitors revealed that activation of ADPR-cyclase by ANG II involved ANG II type 1 receptor, phosphoinositide 3-kinase, protein tyrosine kinase, and phospolipase C-[gamma]1. Moreover, DHAB as well as 8-Br-cADPR abrogated ANG II-mediated Akt phosphorylation, nuclear translocation of nuclear factor of activated T cell, and uptake of [[sup.3]H]thymidine and [[sup.3]H]leucine in MMCs. These results demonstrate that ADPR-cyclase in MMCs plays a pivotal role in ANG II signaling for cell proliferation and protein synthesis. cyclic ADP-ribose; intracellular [Ca.sup.2+] concentration