Phosphodiesterase: overview of protein structures, potential therapeutic applications and recent progress in drug development

Phosphodiesterases (PDEs) are essential regulators of cyclic nucleotide signaling with diverse physiological functions. Because of their great market potential and therapeutic importance, PDE inhibitors became recognized as important therapeutic agents in the treatment of various diseases. Currently, there are seven PDE inhibitors on the market, and the pharmacological and safety evaluations of many drug candidates are in progress. Three-dimensional (3D) structures of catalytic domains of PDE 1, -3, -4, -5 and -9 in the presence of their inhibitors are now available, and can be utilized for rational drug design. Recent advances in molecular pharmacology of PDE isoenzymes resulted in identification of new potential applications of PDE inhibitors in various therapeutic areas, including dementia, depression and schizophrenia. This review will describe the latest advances in PDE research on 3D structural studies, the potential of therapeutic applications and the development of drug candidates.Received 30 November 2004; received after revision 24 January 2005; accepted 5 February 2005     

模拟5000米低氧大鼠脑内信息物质含量变化初探

利用减压舱模拟海拔５０００米低氧并采用放射免疫的方法，观察了大鼠大脑皮层和小脑内信息物质浓度的变化，并比较了两部位间的含量差异。以西宁地区海拔２２６０米作为对照，发现：高海拔低氧可引起大鼠脑内ｃＡＭＰ含量升高尤以小脑显著。     

Isoprenaline-like effects of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine on mechanical,biochemical and electrophysiological parameters in the mammalian heart

Summary The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) mimicked the effects of isoprenaline on the force of contraction, the cAMP content and the slow Ca⁺⁺ inward current (I_si) in isolated guinea pig papillary muscles. The results support the hypothesis that phosphodiesterase inhibitors and -adrenoceptor agonists exert their positive inotropic effects by increasing I_si via the common mediator cAMP.Acknowledgment. This work was supported by the Deutsche Forschungsgemeinschaft.     

磁场对AMI心肌的保护作用──磁场对大鼠实验性AMI血浆cAMP cGMP,血清Mg~( )含量变化的影响

本实验将大鼠随机分为五组：空白对照组、磁作用对照组、AMI组、AMI药物（心得安）治疗组。AMI磁场治疗组。采用放射免疫方法和原子分光光度法测定各组大鼠血浆cAMP、cGMP，血清Mg 含量。结果表明：AMI磁场治疗组血浆cAMP、cGMP，含量及cAMP／cGMP比值均明显低于AMI组（P＜0．05），与药物治疗组近似，略高于空白对照组和磁作用对照组空白对照组和磁作用对照组最低、两组间无显著差异。AMI磁场治疗组血清Mg＋．含量明显高于AMI组（P＜0．05），与药物治疗组近似。略低于空白对照组、磁作用对照组，空白对照组和磁作用对照组最高，两组间无显著差异。证实了磁场对动物实验性AMI，心肌的保护作用，为磁场用于AMI的治疗提供实验依据。     

Evaluation of signal transduction pathways mediating the nuclear exclusion of the androgen receptor by melatonin

The intracellular signaling pathways mediating the nuclear exclusion of the androgen receptor (AR) by melatonin were evaluated in PC3 cells stably transfected with the AR. The melatonin-induced nuclear exclusion of the AR by melatonin (100 nM, 3 h) was blocked by LY 83583 (an inhibitor of guanylyl cyclases). 8-Bromo-cGMP (a cell-permeable cGMP analog), mimicked the effect of melatonin, as did ionomycin (a calcium ionophore) and PMA [an activator of protein kinase C (PKC)], and their effects were blocked by GF-109203X (a selective PKC inhibitor). BAPTA (an intracellular calcium chelator) blocked the effects of melatonin and 8-bromo-cGMP but not of PMA. Inhibition or activation of the protein kinase A pathway did not affect basal or melatonin-mediated AR localization. We conclude that the melatonin-mediated rise in cGMP elicits AR nuclear exclusion via a pathway involving increased intracellular calcium and PKC activation. These results define a novel signaling pathway that regulates AR localization and androgen responses in target cells. Received 31 July 2001; received after revision 18 September 2001; accepted 30 October 2001     

四种单核苷酸的毛细管区带电泳分离分析

报道了４种单核苷酸（ｃＡＭＰ、ｃＧＭＰ、ＡＭＰ、ＧＭＰ）的毛细管区带电泳分离及含量测定方法．方法的线性范围：ｃＡＭＰ为２－７５０ｍｇ·Ｌ－１,ｃＧＭＰ为２－６５０ｍｇ·Ｌ－１,ＡＭＰ为２－２５０ｍｇ·Ｌ－１,ＧＭＰ为２－３００ｍｇ·Ｌ－１;当浓度为１００ｍｇ·Ｌ－１,其δ（相对标准偏差）为２３０％（ｃＡＭＰ）、２．５０％（ｃＧＭＰ）、０．６８％（ＡＭＰ）和２．２７％（ＧＭＰ）．     

Acetylcholine receptors in the gastrulating chick embryo

Summary Muscarinic acetylcholine receptors are present in the gastrulating chick embryo.     

Stomatal guard cell responses to kinetin and natriuretic peptides are cGMP-dependent

Immunological evidence suggests that plants contain natriuretic peptides (NPs) and furthermore (3- [¹²⁵I]iodotyrosol²⁸) rat atrial NP (rANP) binds specifically to plant membranes. rANP and immunoaffinity-purified plant NP analogues also promote concentration-dependent stomatal opening. Here we report that kinetin, a synthetic cytokinin, and rANP induce stomatal opening in Tradescantia albiflora and that the effect of rANP is critically dependent on the secondary structure of the peptide hormone. The native circular molecule is active, whereas the linearized molecule shows no biological activity. Furthermore, kinetin- and rANP-induced stomatal opening is reversibly inhibited by two in hibitors of guanylate cyclase, LY 83583 and methylene blue. Stomatal opening is also induced in a concentration-dependent manner by the cell-permeant cyclic guanosine-3′,5′-monophosphate (cGMP) analogue 8-Br-cGMP, and this effect is prevented by the stomatal closure promoting plant hormone abscisic acid (ABA). We conclude that in guard cells kinetin and rANP pathways operate via guanylate cyclase upregulation, and we propose that ABA-induced closure is not cGMP-dependent. Received 1 October 1997; received after revision 2 December 1997; accepted 6 January 1998     

Icariin on relaxation effect of corpus cavernosum smooth muscle

NO-cGMP pathway in penile corpus cavernosal smooth muscle plays an important role in penile erection. The level of cGMP is regulated by a balance between the rate of synthesis by guanylate cyclase and the rate of hydrolytic breakdown to guanosine 5′ monophosphate (GMP) by phosphodiesterase 5(PDE5). Icariin is isolated from natural drug Epimedii herba, it is shown to have the relaxation effect on corpus cavernosal smooth muscle of rabbit (IC50: 4×10⁻⁴ mol/L), and the mechanism of the relaxation effect of Icariin on corpus cavernosum believed to have the inhibiting effect on PDE5 and activation of NO-cGMP pathway to enhancing penile erection.     

The role of calcium in aggregation and development ofDictyostelium

Changes in cytosolic Ca²⁺ play an important role in a wide array of cell types and the control of its concentration depends upon the interplay of many cellular constituents. Resting cells maintain cytosolic calcium ([Ca²⁺]_i) at a low level in the face of steep gradients of extracellular and sequestered Ca²⁺. Many different signals can provoke the opening of calcium channels in the plasma membrane or in intracellular compartments and cause rapid influx of Ca²⁺ into the cytosol and elevation of [Ca²⁺]_i. After such stimulation Ca²⁺ ATPases located in the plasma membrane and in the membranes of intracellular stores rapidly return [Ca²⁺]_i to its basal level. Such responses to elevation of [Ca²⁺]_i are a part of an important signal transduction mechanism that uses calcium (often via the binding protein calmodulin) to mediate a variety of cellular actions responsive to outside influences.