Effect of HMG-CoA reductase inhibitors on blood pressure in hypertensive patients treated with blood pressure-lowering agents: retrospective study using an anti-hypertensive drug database.

BACKGROUND AND OBJECTIVES: We used a Japanese antihypertensive drug database to investigate the blood pressure-lowering effect of statins in hypertensive patients receiving antihypertensive medication. We also examined the class effect of antihypertensive drugs on blood pressure lowering by statins. MATERIAL AND METHODS: The Risk/Benefit Assessment of Drugs-Analysis and Response (RAD-AR) Council has developed an antihypertensive drug database which contains the results of post-marketing surveillance for various antihypertensive agents from 143,509 antihypertensive users in clinical settings. Antihypertensive patients in the database with concurrent hyperlipidemia were grouped into statin users and non-users, and changes in systolic and diastolic blood pressure over a three-month period were compared. Further, the class effects of antihypertensive drugs on the lipid lowering effects of statins were also investigated. RESULTS: A total of 1070 statin users and 1974 non-users were analyzed. Changes in systolic blood pressure were significantly greater in the statin user than in the non-user group (mean difference: 1.63 mmHg, p = 0.03). In contrast, no significant effect of statin use was observed on the change in diastolic blood pressure (DBP) (0.87 mmHg, p = 0.08). When stratified by antihypertensive class, reductions in blood pressure were greater in statin user groups for all antihypertensive classes without statistical significance, except for a significant change in DBP in those receiving beta-blockers (mean difference: 2.98 mmHg, p = 0.03). DISCUSSION: The present study documented that statin's effect on blood pressure in hypertensive patients with hyperlipidemia in clinical setting is statistically significant but has a minimal significance. With regard to class differences among antihypertensive agents, the decrease was greatest in the DBP of patients treated with beta-blockers. In contrast, no significant changes were seen in the ACE inhibitor or Ca antagonist subgroups. One possible explanation for the differential effects of antihypertensive class in our study might be the lack of a vasodilatation effect.

FebA: a gene for eukaryotic translation initiation factor 4E-binding protein (4E-BP) in Dictyostelium discoideum.

We have identified a gene encoding a eukaryotic initiation factor 4E-binding protein (4E-BP) in the EST database of the Dictyostelium cDNA project. The Dictyostelium 4E-BP, designated febA (four e-binding), showed significant similarity to mammalian 4E-BPs. Northern blot analysis revealed that febA was expressed at a high level in the vegetative growth phase but the level of expression decreased during late development. The gene was shown to be non-essential since disruption of the gene had no severe effect; the null mutant proliferated normally and formed normal fruiting bodies. However, strains overexpressing the gene could not be established, suggesting that an excess of FebA protein may have a lethal effect on the cells.

Total tetra knockout of GP138 multigene family implicated in cell interactions in Dictyostelium discoideum.

The cellular slime mold Dictyostelium discoideum reproduces sexually under submerged and dark conditions. A cell surface glycoprotein gp138 has been identified as a target molecule for cell fusion-blocking antibodies, and is considered to be indispensable for the sexual cell fusion in this organism. Currently, four isoforms of gp138, DdFRP1alpha, DdFRP1beta, DdFRP2, and DdFRP3, are known. Genes encoding the latter three isoforms, GP138C, GP138A, and GP138B, have been isolated, comprising a GP138 multigene family. Here we isolated the fourth GP138 gene, GP138D, encoding DdFRP1alpha. These GP138 genes were found to cluster in a tandem array on chromosome 5, being bordered by two GP138-like sequences highly homologous to them but truncated. To clarify functional relationships among the GP138 family members, the entire GP138 region was deleted by a single knockout. Northern hybridization and western immuno-blotting analyses confirmed complete losses of GP138 mRNA and DdFRPs in the knockout strains, indicating that there are no more GP138 genes. Unexpectedly, however, the GP138-null mutants were fully potent for both sexual cell fusion and subsequent development. In addition, the original fusion-blocking antibodies detected a cell surface protein of close electrophoretic mobility to gp138 in the knockouts, suggesting the possibility that the actual target molecule of the fusion-blocking antibodies was not DdFRPs but this unidentified component. Since GP138-null mutants exhibited no obvious defects either in growth or asexual development, the real function of the GP138 family is unknown. Nevertheless, the expression levels of other developmental genes such as acaA, csaA, cotA-C, and spiA appeared to be altered in the GP138-null mutants. Therefore, it seems to have a non-critical but some role(s) during asexual development.

Spatial expression patterns of genes involved in cyclic AMP responses in Dictyostelium discoideum development.

The spatial expression patterns of genes involved in cyclic adenosine monophosphate (cAMP) responses during morphogenesis in Dictyostelium discoideum were analyzed by in situ hybridization. Genes encoding adenylyl cyclase A (ACA), cAMP receptor 1, G-protein alpha2 and beta subunits, cytosolic activator of ACA (CRAC and Aimless), catalytic subunit of protein kinase A (PKA-C) and cAMP phosphodiesterases (PDE and REG-A) were preferentially expressed in the anterior prestalk (tip) region of slugs, which acts as an organizing center. MAP kinase ERK2 (extracellular signal-regulated kinase-2) mRNA, however, was enriched in the posterior prespore region. At the culmination stage, the expression of ACA, CRAC and PKA-C mRNA increased in prespore cells in contrast with the previous stage. However, no alteration in the site of expression was observed for the other mRNA analyzed. Based on these findings, two and four classes of expression patterns were catalogued for these genes during the slug and culmination stages, respectively. Promoter analyses of genes in particular classes should enhance understanding of the regulation of dynamic and coordinated gene expression during morphogenesis.

Loss of a member of the aquaporin gene family, aqpA affects spore dormancy in Dictyostelium.

We isolated and characterized a gene from Dictyostelium discoideum, which encodes a protein of 279 amino acids (30.6kDa) containing six transmembrane domains with two highly conserved motifs of asparagine-proline-alanine (NPA) found in the aquaporin family of water-channel proteins, although the second motif of the protein has been modified into NPV (asparagine-proline-valine). The deduced amino acid sequence of the gene, which we have named aqpA, is 39% identical to D. discoideum WacA, 26% identical to human Aqp5, 26% identical to Oryza sativa PIP2a, 25% identical to yeast Aqy1 and 24% identical to E.coli AqpZ. Southern analyses indicated that aqpA is present as a single copy in the genome. Northern blot analysis showed that the developmentally regulated 1kb mRNA transcript first appears at the tight mound stage (12h), and is abundant in fingers (16h) and late culminants (20h). In-situ hybridization of slugs revealed that aqpA mRNA accumulated in cells of the prespore region but not in those of the prestalk region. Disruption of aqpA by homologous recombination did not significantly affect growth or developmental morphogenesis. Although mutant spores were viable, when assayed soon after encapsulation, they became permeable to propidium iodide and lost viability after a week on the top of a fruiting body. Thus, AqpA is essential to maintain spore dormancy perhaps through the regulation of water flow.

Developmental changes in the spatial expression of genes involved in myosin function in Dictyostelium.

We analyzed the spatial expression patterns of the genes involved in myosin function by in situ hybridization at the tipped aggregate and early culmination stages of Dictyostelium. Myosin heavy chain II mRNA was enriched in the anterior prestalk region of the tipped aggregates, whereas it disappeared from there and began to appear in both upper and lower cups of the early culminants. Similarly, mRNAs for essential light chain, regulatory light chain, myosin light chain kinase A, and myosin heavy chain kinase C were enriched in the prestalk region of the tipped aggregates. However, expression of these genes was distinctively regulated in the early culminants. These findings suggest the existence of mechanisms responsible for the expression of particular genes.

Identification and characterization of two flavohemoglobin genes in Dictyostelium discoideum.

Flavohemoglobins are being identified in an expanding number of prokaryotes and unicellular eukaryotes. These molecules consist of an N-terminal hemoglobin domain and a C-terminal oxidoreductase domain, and are considered to function in storage or as sensors for O2, and in defense against oxidative stress and/or NO. However, their physiological significance has not yet been determined. Here, we isolated and analyzed two flavohemoglobin genes of Dictyostelium discoideum, DdFHa and DdFHb, which lie close to each other in the genome. DdFHs were induced by submerged conditions, and enriched in the sexually mature cells of D. discoideum. Although they were not essential for growth or development under standard laboratory conditions, disruption of both genes caused an increase in number of large but uninuclear cells, and hypersensitivity to higher concentrations of glucose and to NO releasers. These results indicate that DdFHs are responsible for transducing NO signals to maintain normal cellular conditions against environmental stresses.

The mitochondrial DNA of Dictyostelium discoideum: complete sequence, gene content and genome organization.

We present an overview of the gene content and organization of the mitochondrial genome of Dictyostelium discoideum. The mitochondria genome consists of 55,564 bp with an A + T content of 72.6%. The identified genes include those for two ribosomal RNAs (rn1 and rns), 18 tRNAs, ten subunits of the NADH dehydrogenase complex (nad1, 2, 3, 4, 4L, 5, 6, 7, 9 and 11), apocytochrome b (cytb), three subunits of the cytochrome oxidase (cox1/2 and 3), four subunits of the ATP synthase complex (atp1, 6, 8 and 9), 15 ribosomal proteins, and five other ORFs, excluding intronic ORFs. Notable features of D. discoideum mtDNA include the following. (1) All genes are encoded on the same strand of the DNA and a universal genetic code is used. (2) The cox1 gene has no termination codon and is fused to the downstream cox2 gene. The 13 genes for ribosomal proteins and four ORF genes form a cluster 15.4 kb long with several gene overlaps. (3) The number of tRNAs encoded in the genome is not sufficient to support the synthesis of mitochondrial protein. (4) In total, five group I introns reside in rnl and cox1/2, and three of those in cox1/2 contain four free-standing ORFs. We compare the genome to other sequenced mitochondrial genomes, particularly that of Acanthamoeba castellanii.

LbrA, a protein predicted to have a role in vesicle trafficking, is necessary for normal morphogenesis in Polysphondylium pallidum.

The fruiting body of Polysphondylium pallidum is composed of whorls of branches along the axis of a central stalk. In the course of fruiting body formation, the interval between neighboring whorls, and the number and the spacing of branches in a whorl are highly regulated. In this study, using the REMI (restriction-enzyme-mediated integration) insertional mutagenesis method, we obtained a mutant (strain M2323) with longer branches than those of the wild-type strain PN500. The sequence analyses revealed the presence of an ORF of 206 aa residues (23 kDa) near the vector insertion site. Disruption of the gene, lbrA (long branch A), by homologous recombination causes the same phenotype as that of M2323. A lbrA transcript is expressed maximally at the early aggregation stage in the parental strain, but is not detectable in the REMI mutant. A homology search showed that LbrA is a member of the p24 family proteins, which have been proposed to function as receptors for cargo proteins that are transported by COP I- (coat protein I) and/or COP II-coated vesicles between the endoplasmic reticulum and the Golgi complex. As far as we know, this is the first paper to show that a p24 family member is implicated in morphogenesis.

A new member of the GP138 multigene family implicated in cell interactions in Dictyostelium discoideum.

The cellular slime mold Dictyostelium discoideum reproduces sexually under submerged and dark conditions. Its mating system is polymorphic and particularly interesting with respect to mechanisms of cell recognition. The cell-surface glycoprotein gp138 has been implicated in sexual cell interactions, as it was identified as a target molecule for the antibodies that block sexual cell fusion in D. discoideum. Two mutually homologous genes, GP138A and GP138B, have been cloned, but gene disruption experiments to clarify their functional relationships suggested that there is at least one more gene for gp138. Further protein analysis including peptide mapping also revealed that gp138 exists as three isoforms, DdFRP1, DdFRP2, and DdFRP3. GP138A encodes DdFRP2 and GP138B, DdFRP3, and the presence of a third gp138 gene encoding DdFRP1 was suggested. Here, we isolated and characterized a third GP138 gene, GP138C. Although the deduced amino acid sequences of GP138C matched completely with those of peptide fragments of DdFRP1 in the N-terminal half, the rest did not give complete matches. Overexpression of GP138C caused an increase in the intensity of DdFRP1, but disruption of this gene did not diminish DdFRP1. Our results indicate that GP138C encodes a protein very similar to but distinct from DdFRP1. The GP138 multigene family is thus composed of more members than previously expected, and their functional relationships are of special interest.

A Dictyostelium discoideum homologue to Tcp-1 is essential for growth and development.

Tcp-1 (t-complex polypeptide 1 gene) was first identified in the mouse as relevant for tail-less and embryonic lethal phenotypes. Since then, its homologous sequences have been isolated in several other species, and the yeast Tcp-1 has been shown to encode a molecular chaperon for actin and tubulin. In a random sample of genes expressed in the gamete of Dictyostelium discoideum (Dd), we encountered a sequence containg the TCP1 motifs. The complete ORF of the gene (DdTcp-1) showed more than 60% similarity to TCP-1 of several organisms, including human. DdTcp-1 was found to be expressed in both sexually mature and immature cells at the growth phase. Although the sexual process itself was not affected, antisense interference of this gene resulted in severe retardation of cell growth, leading to the complete cessation of division. In addition, the antisense transformants stopped asexual development at the finger stage. These results suggest an important function of DdTcp-1 in growth and development of this organism.

Characterization of a novel small RNA encoded by Dictyostelium discoideum mitochondrial DNA.

In this study, we analyzed a mitochondrial small (ms) RNA in Dictyostelium discoideum, which is 129 nucleotides long and has a GC content of only 22.5%. In the mitochondrial DNA, a single-copy gene (msr) for the ms RNA was located downstream of the gene for large-subunit rRNA. The location of msr was similar to that of the 5S rRNA gene in prokaryotes and chloroplasts, but clearly different from that in mitochondria of plants, liverwort and the chlorophycean alga Prototheca wikerhamii, in which small-subunit rRNA and 5S rRNA genes are closely linked. THe primary sequence of ms rRNA showed low homology with mitochondrial 5S rRNA from plants, liverwort and the chlorophycean alga, but the proposed secondary structure of ms RNA was similar to that of cytoplasmic 5S rRNA. In addition, ms RNA showed a highly conserved GAAC sequence in the same loop as in common 5S rRNA. However, ms RNA was detected mainly in the mitochondrial 25,000 x g supernatant fraction which was devoid of ribosomes. It is possible that ms RNA is an evolutionary derivative of mitochondrial 5S rRNA.

The Dictyostelium developmental cDNA project: generation and analysis of expressed sequence tags from the first-finger stage of development.

In an effort to identify and characterize genes expressed during multicellular development ill Dictyostelium, we have undertaken a cDNA sequencing project. Using size-fractionated subsets of cDNA from the first finger stage, two sets of gridded libraries were constructed for cDNA sequencing. One, library S, consisting of 9984 clones, carries relatively short inserts, and the other, library L, which consists of 8448 clones, has longer inserts. We sequenced all the selected clones in library S from their 3'-ends, and this generated 3093 non-redundant, expressed sequence tags (ESTs). Among them, 246 ESTs hit known Dictyostelium genes and 910 showed significant similarity to genes of Dictyostelium and other organisms. For library L, 1132 clones were randomly sequenced and 471 non-redundant ESTs were obtained. In combination, the ESTs from the two libraries represent approximately 40% of genes expressed in late development, assuming that the non-redundant ESTs correspond to independent genes. They will provide a useful resource for investigating the genetic networks that regulate multicellular development of this organism.

A site-specific DNA endonuclease specified by one of two ORFs encoded by a group I intron in Dictyostelium discoideum mitochondrial DNA.

The second intron (DdOX1/2.2) of Dictyostelium discoideum cytochrome oxidase subunit 1/2 fused gene has two free-standing ORF genes (Dd ai2a and Dd ai2b) in a loop, which have similar amino acid sequences and are homologous to aI4 DNA endonuclease (I-SceII) of Saccharomyces cerevisiae. To elucidate the functions of these ORFs, we cloned the ORFs into an expression vector and introduced the composite vectors into E. coli. The expression of Dd ai2a in E. coli caused growth inhibition and degradation of the E. coli genomic DNA. To determine whether Dd ai2a protein is a homing type DNA endonuclease, the ability to cleave the homing site of its intron in vivo was examined. Dd ai2a cleaved only one strand of intronless DNA sequence at the site which coincides with the I-SceII cleavage recognition site. We suppose that Dd ai2a functions actually as a homing type DNA endonuclease in D. discoideum mitochondria by virtue of other factors. To obtain further information about the relationship between the existence of introns and the mating system, we carried out in vitro self-splicing assay and polymerase chain reaction analysis using 13 strains of the cellular slime mold.

A mutation in the cAMP signaling pathway affects sexual development of Dictyostelium discoideum.

Amoebae of cellular slime molds have two developmental modes, asexual fruiting body formation and sexual macrocyst formation. How developmental choice is made is an interesting subject of wide importance. Light exposure and dry conditions are favorable for asexual development, while conditions of darkness and high humidity are so for sexual development. In Dictyostelium discoideum, the latter conditions enhance zygote formation, which determines the fate of surrounding cells for sexual development. Here, a mutant (TMC1) defective in the post-fusion aggregation of cells during sexual development is described. This mutant is also aggregationless in asexual development, and the level of cyclic adenosine monophosphate (cAMP) receptor is reduced. Correspondingly, a series of existing mutants with defects in cAMP signaling pathways showed the same sexual phenotype as TMC1. These results suggest that molecular mechanisms of development are shared by the two alternative developmental modes.

Isoforms of gp138, a cell-fusion related protein in Dictyostelium discoideum.

Sexual development of Dictyostelium discoideum is a unique and useful system for the study of sexual phenomena. We have been studying molecular mechanisms of sexual cell fusion in D. discoideum and have identified several relevant cell-surface proteins. One of the proteins, gp138, was identified as a target molecule for fusion-blocking antibodies, and two genes for gp138, GP138A and GP138B, were cloned. The participation of gp138 in the sexual cell fusion was confirmed by antisense RNA mutagenesis, but it is unclear which of the genes encodes gp138. Moreover, the presence of a third gene for gp138 was indicated by gene disruption. In the present study, we generated strains of D. discoideum overexpressing either GP138A or GP138B to investigate the products of these genes. The transformants overexpressing GP138A and GP138B overproduced glycoproteins with molecular masses of 135 and 130 kDa, respectively. Although their molecular masses were different from that of gp138, the results of peptide mapping and amino acid sequencing showed that they are related to proteins, suggesting that the proteins encoded by GP138A and GP138B are isoforms of gp138 protein.

Localization of a DNA topoisomerase II to mitochondria inDictyostelium discoideum: Deletion mutant analysis and mitochondrial targeting signal presequence.

DNA topoisomerase II ofDictyostelium discoideum (TopA), the gene (topA) encoding which we cloned, was shown to have an additional N-terminal region which contains a putative mitochondrial targeting signal presequence. We constructed overexpression mutants which expressed the wild-type or the N-terminally deleted enzyme, and examined its localization by immunofluorescence microscopy and proteinase K digestion experiment. These experiments revealed that the enzyme is located in the mitochondria by virtue of the additional N-terminal region. Furthermore, in the cell extract depleted the enzyme by immunoprecipitation, nuclear DNA topoisomerase II activity was not decreased. These results confirmed that TopA is located in the mitochondria, even through its amino acid sequence is highly similar to those of nuclear type topoisomerase II of other organisms. Thus, this report is the first to establish the location of the mitochondrial targeting signal presequence in DNA topoisomerase II and in proteins ofD. discoideum directly by analyzing deletion mutants.

Choice of partners: sexual cell interactions in Dictyostelium discoideum.

Recognition of mating partners is of central importance in the sexual processes. In consideration that the most important function of sexuality is to shuffle genetic materials to generate wider variation of characters, mating among different genetic backgrounds is preferable. Wild isolates of cellular slime mold Dictyostelium discoideum are predominantly heterothallic, but homothallic ones also exist. In addition, there are bi-sexual strains which are compatible with either mating type of heterothallic strains but are self-incompatible. How cells of these organisms choose proper mating partners may include the essential mechanisms for sexual cell recognition in general. This minireview addresses studies on sexual cell interactions of D. discoideum with special attention to cell recognition and evolution of the mating system.

Protease-sensitive component(s) on the cell surface prevents self-fusion in a bisexual strain of Dictyostelium discoideum.

The sexual cycle of the cellular slime mold Dictyostelium discoideum offers a suitable system to analyze the mechanism of cell recognition during mating. Sexual cell fusion in D. discoideum typically occurs between complementary heterothallic strains. In addition, several bisexual strains are known which undergo sexual cell fusion with heterothallic strains of either mating type, but cannot do so by themselves. In the present study, trypsin digestion of cell surface molecules was found to induce self-fusion in a bisexual strain WS2162, suggesting the presence on the cell surface of a self-recognition molecule whose homophilic interaction interferes with the cell fusion mechanism.