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At least 757 records · Page 42Linked to original sources
PubMed2004

Human Claspin works with BRCA1 to both positively and negatively regulate cell proliferation.

Claspin is a homolog of Mrc1, a checkpoint protein required for the DNA replication checkpoint in yeast. In Xenopus, phosphorylated Claspin binds to xChk1 and regulates xChk1 activation in response to replication stress. In this study, we have shown that the human homolog of Claspin is required for resistance to multiple forms of genotoxic stress including UV, IR, and hydroxyurea. Phosphorylation of Claspin was found to depend on the ataxia telangiectasia mutated-Rad3 related (ATR) pathway. DNA damage induces the formation of a complex between Claspin and BRCA1, a second regulator of Chk1 activation. Claspin was found to control BRCA1 phosphorylation on serine 1524, a site whose phosphorylation is controlled by the ATR pathway. These results are consistent with a model in which ATR regulates Claspin phosphorylation in response to DNA damage and replication stress resulting in recruitment and phosphorylation of BRCA1. BRCA1 and Claspin then function to activate the tumor suppressor Chk1. Unexpectedly, we found that Claspin has a second, positive role in control of the cell cycle as Claspin overexpression increased cell proliferation. These results suggest that Claspin has properties of both a tumor suppressor and an oncogene.

Adaptor Proteins, Signal Transducing↗
PubMed1999

Phosphorylation of Ser-20 mediates stabilization of human p53 in response to DNA damage.

Stabilization of p53 in response to DNA damage is caused by its dissociation from Mdm2, a protein that targets p53 for degradation in the proteasome. Dissociation of p53 from Mdm2 could be caused by DNA damage-induced p53 posttranslational modifications. The ATM and ATR kinases, whose activation in response to ionizing radiation (IR) and UV light, respectively, is required for p53 stabilization, directly phosphorylate p53 on Ser-15. However, phosphorylation of Ser-15 is critical for the apoptotic activity of p53 and not for p53 stabilization. Thus, whether any p53 modifications, and which, underlie disruption of the p53-Mdm2 complex after DNA damage remains to be determined. We analyzed the IR- and UV light-induced stabilization of p53 proteins with substitutions of Ser known to be posttranslationally modified after DNA damage. Substitution of Ser-20 was sufficient to abrogate p53 stabilization in response to both IR and UV light. Furthermore, both IR and UV light induced phosphorylation of p53 on Ser-20, which involved the majority of nuclear p53 protein and weakened the interaction of p53 with Mdm2 in vitro. ATM and ATR cannot phosphorylate p53 on Ser-20. We therefore propose that ATM and ATR activate an, as yet unidentified, kinase that stabilizes p53 by phosphorylating it on Ser-20.

Binding Sites↗
PubMed1999

Substrate specificities and identification of putative substrates of ATM kinase family members.

Ataxia telangiectasia mutated (ATM) phosphorylates p53 protein in response to ionizing radiation, but the complex phenotype of AT cells suggests that it must have other cellular substrates as well. To identify substrates for ATM and the related kinases ATR and DNA-PK, we optimized in vitro kinase assays and developed a rapid peptide screening method to determine general phosphorylation consensus sequences. ATM and ATR require Mn(2+), but not DNA ends or Ku proteins, for optimal in vitro activity while DNA-PKCs requires Mg(2+), DNA ends, and Ku proteins. From p53 peptide mutagenesis analysis, we found that the sequence S/TQ is a minimal essential requirement for all three kinases. In addition, hydrophobic amino acids and negatively charged amino acids immediately NH(2)-terminal to serine or threonine are positive determinants and positively charged amino acids in the region are negative determinants for substrate phosphorylation. We determined a general phosphorylation consensus sequence for ATM and identified putative in vitro targets by using glutathione S-transferase peptides as substrates. Putative ATM in vitro targets include p95/nibrin, Mre11, Brca1, Rad17, PTS, WRN, and ATM (S440) itself. Brca2, phosphatidylinositol 3-kinase, and DNA-5B peptides were phosphorylated specifically by ATR, and DNA Ligase IV is a specific in vitro substrate of DNA-PK.

Amino Acid Sequence↗
PubMed2004

DNA replication defects, spontaneous DNA damage, and ATM-dependent checkpoint activation in replication protein A-deficient cells.

Replication protein A (RPA) is a heterotrimeric, single-stranded DNA-binding complex comprised of 70-kDa (RPA1), 32-kDa (RPA2), and 14-kDa (RPA3) subunits that is essential for DNA replication, recombination, and repair in eukaryotes. In addition, recent studies using vertebrate model systems have suggested an important role for RPA in the initiation of cell cycle checkpoints following exposure to DNA replication stress. Specifically, RPA has been implicated in the recruitment and activation of the ATM-Rad3-related protein kinase, ATR, which in conjunction with the related kinase, ATM (ataxia-telangiectasia-mutated), transmits checkpoint signals via the phosphorylation of downstream effectors. In this report, we have explored the effects of RPA insufficiency on DNA replication, cell survival, and ATM/ATR-dependent signal transduction in response to genotoxic stress. RNA interference-mediated suppression of RPA1 caused a slowing of S phase progression, G2/M cell cycle arrest, and apoptosis in HeLa cells. RPA-deficient cells demonstrated high levels of spontaneous DNA damage and constitutive activation of ATM, which was responsible for the terminal G2/M arrest phenotype. Surprisingly, we found that neither RPA1 nor RPA2 were essential for the hydroxyurea- or UV-induced phosphorylation of the ATR substrates CHK1 and CREB (cyclic AMP-response element-binding protein). These findings reveal that RPA is required for genomic stability and suggest that activation of ATR can occur through RPA-independent pathways.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2002

Regulation of cellular and SV40 virus origins of replication by Chk1-dependent intrinsic and UVC radiation-induced checkpoints.

DNA replication is inhibited by DNA damage through cis effects on replication fork progression and trans effects associated with checkpoints. In this study, we employed a combined pulse labeling and neutral-neutral two-dimensional gel-based approach to compare the effects of a DNA damaging agent frequently employed to invoke checkpoints, UVC radiation, on the replication of cellular and simian virus 40 (SV40) chromosomes in intact cells. UVC radiation induced similar inhibitory effects on the initiation and elongation phases of cellular and SV40 DNA replication. The initiation-inhibitory effects occurred independently of p53 and were abrogated by the ATM and ATR kinase inhibitor caffeine, or the Chk1 kinase inhibitor UCN-01. Inhibition of cellular origins was also abrogated by the expression of a dominant-negative Chk1 mutant. These results indicate that UVC induces a Chk1- and ATR or ATM-dependent checkpoint that targets both cellular and SV40 viral replication origins. Loss of Chk1 and ATR or ATM function also stimulated initiation of cellular and viral DNA replication in the absence of UVC radiation, revealing the existence of a novel intrinsic checkpoint that targets both cellular and SV40 viral origins of replication in the absence of DNA damage or stalled DNA replication forks. This checkpoint inhibits the replication in early S phase cells of a region of the repetitive rDNA locus that replicates in late S phase. The ability to detect these checkpoints using the well characterized SV40 model system should facilitate analysis of the molecular basis for these effects.

Animals↗
PubMed2003

A single internal ribosome entry site containing a G quartet RNA structure drives fibroblast growth factor 2 gene expression at four alternative translation initiation codons.

The 484-nucleotide (nt) alternatively translated region (ATR) of the human fibroblast growth factor 2 (FGF-2) mRNA contains four CUG and one AUG translation initiation codons. Although the 5'-end proximal CUG codon is initiated by a cap-dependent translation process, the other four initiation codons are initiated by a mechanism of internal entry of ribosomes. We undertook here a detailed analysis of the cis-acting elements defining the FGF-2 internal ribosome entry site (IRES). A thorough deletion analysis study within the 5'-ATR led us to define a 176-nt region as being necessary and sufficient for IRES function at four codons present in a downstream 308-nt RNA segment. Unexpectedly, a single IRES module is therefore responsible for translation initiation at four distantly localized codons. The determination of the FGF-2 5'-ATR RNA secondary structure by enzymatic and chemical probing experiments showed that the FGF-2 IRES contained two stem-loop regions and a G quartet motif that constitute novel structural determinants of IRES function.

Alternative Splicing↗
PubMed2005

The role of checkpoint kinase 1 in sensitivity to topoisomerase I poisons.

Agents that target topoisomerase I are widely utilized to treat human cancer. Previous studies have indicated that both the ataxia telangiectasia mutated (ATM)/checkpoint kinase (Chk) 2 and ATM- and Rad 3-related (ATR)/Chk1 checkpoint pathways are activated after treatment with these agents. The relative contributions of these two pathways to survival of cells after treatment with topoisomerase I poisons are currently unknown. To address this issue, we assessed the roles of ATR, Chk1, ATM, and Chk2 in cells treated with the topoisomerase I poisons camptothecin and 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan. Colony forming assays demonstrated that down-regulation of ATR or Chk1 sensitized cells to SN-38 and camptothecin. In contrast, ATM and Chk2 had minimal effect of sensitivity to SN-38 or camptothecin. Additional experiments demonstrated that the Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin, which down-regulates Chk1, also sensitized a variety of human carcinoma cell lines to SN-38. Collectively, these results show that the ATR/Chk1 pathway plays a predominant role in the response to topoisomerase I inhibitors in carcinoma cells and identify a potential approach for enhancing the efficacy of these drugs.

Antineoplastic Agents, Phytogenic↗
PubMed2002

Bloom's syndrome protein is required for correct relocalization of RAD50/MRE11/NBS1 complex after replication fork arrest.

Bloom's syndrome (BS) is a rare genetic disorder characterized by a broad range of symptoms and, most importantly, a predisposition to many types of cancers. Cells derived from patients with BS exhibit an elevated rate of somatic recombination and hypermutability, supporting a role for bleomycin (BLM) in the maintenance of genomic integrity. BLM is thought to participate in several DNA transactions, the failure of which could give raise to genomic instability, and to interact with many proteins involved in replication, recombination, and repair. In this study, we show that BLM function is specifically required to properly relocalize the RAD50/MRE11/NBS1 (RMN) complex at sites of replication arrest, but is not essential in the activation of BRCA1 either after stalled replication forks or gamma-rays. We also provide evidence that BLM is phosphorylated after replication arrest in an Ataxia and RAD3-related protein (ATR)-dependent manner and that phosphorylation is not required for subnuclear relocalization. Therefore, in ATR dominant negative mutant cells, the assembly of the RMN complex in nuclear foci after replication blockage is almost completely abolished. Together, these results suggest a relationship between BLM, ATR, and the RMN complex in the response to replication arrest, proposing a role for BLM protein and RMN complex in the resolution of stalled replication forks.

Adenosine Triphosphatases↗
PubMed2003

Anthrax toxin triggers endocytosis of its receptor via a lipid raft-mediated clathrin-dependent process.

The protective antigen (PA) of the anthrax toxin binds to a cell surface receptor and thereby allows lethal factor (LF) to be taken up and exert its toxic effect in the cytoplasm. Here, we report that clustering of the anthrax toxin receptor (ATR) with heptameric PA or with an antibody sandwich causes its association to specialized cholesterol and glycosphingolipid-rich microdomains of the plasma membrane (lipid rafts). We find that although endocytosis of ATR is slow, clustering it into rafts either via PA heptamerization or using an antibody sandwich is necessary and sufficient to trigger efficient internalization and allow delivery of LF to the cytoplasm. Importantly, altering raft integrity using drugs prevented LF delivery and cleavage of cytosolic MAPK kinases, suggesting that lipid rafts could be therapeutic targets for drugs against anthrax. Moreover, we show that internalization of PA is dynamin and Eps15 dependent, indicating that the clathrin-dependent pathway is the major route of anthrax toxin entry into the cell. The present work illustrates that although the physiological role of the ATR is unknown, its trafficking properties, i.e., slow endocytosis as a monomer and rapid clathrin-mediated uptake on clustering, make it an ideal anthrax toxin receptor.

Animals↗
PubMed2006

Spatial organization of the mammalian genome surveillance machinery in response to DNA strand breaks.

We show that DNA double-strand breaks (DSBs) induce complex subcompartmentalization of genome surveillance regulators. Chromatin marked by gamma-H2AX is occupied by ataxia telangiectasia-mutated (ATM) kinase, Mdc1, and 53BP1. In contrast, repair factors (Rad51, Rad52, BRCA2, and FANCD2), ATM and Rad-3-related (ATR) cascade (ATR, ATR interacting protein, and replication protein A), and the DNA clamp (Rad17 and -9) accumulate in subchromatin microcompartments delineated by single-stranded DNA (ssDNA). BRCA1 and the Mre11-Rad50-Nbs1 complex interact with both of these compartments. Importantly, some core DSB regulators do not form cytologically discernible foci. These are further subclassified to proteins that connect DSBs with the rest of the nucleus (Chk1 and -2), that assemble at unprocessed DSBs (DNA-PK/Ku70), and that exist on chromatin as preassembled complexes but become locally modified after DNA damage (Smc1/Smc3). Finally, checkpoint effectors such as p53 and Cdc25A do not accumulate at DSBs at all. We propose that subclassification of DSB regulators according to their residence sites provides a useful framework for understanding their involvement in diverse processes of genome surveillance.

Animals↗
PubMed2002

Arabidopsis cytochrome P450 cyp83B1 mutations activate the tryptophan biosynthetic pathway.

In plants, the tryptophan biosynthetic pathway provides a number of important secondary metabolites including the growth regulator indole-3-acetic acid (IAA) and indole glucosinolate defense compounds. Genes encoding tryptophan pathway enzymes are transcriptionally induced by a variety of stress signals, presumably to increase the production of both tryptophan and secondary metabolites during defense responses. To understand the mechanism of transcriptional induction, we isolated altered tryptophan regulation (atr) mutants in Arabidopsis thaliana with activated transcription of tryptophan genes. One atr complementation group consisted of mutations in the cytochrome P450 gene CYP83B1. Mutant plants had constitutively activated expression of the ATR1 Myb factor gene, which was identified as a positive regulator of tryptophan genes via the atr mutant screen. cyp83B1 mutants were previously characterized as having defects in IAA homeostasis due to perturbation of secondary tryptophan metabolism. Our findings indicate that the upregulation of tryptophan pathway genes might also contribute to the overaccumulation of IAA in mutant plants. Moreover, we show that cyp83B1 mutants have lesion-mimic phenotypes, suggesting that multiple stress pathways are activated by loss of CYP83B1 function.

Arabidopsis↗
PubMed1999

Identification and characterization of nuclear matrix-attachment regions in the human serpin gene cluster at 14q32.1.

Matrix-attachment regions (MARs) are DNA elements that are defined by their abilities to bind to isolated nuclear matrices in vitro. The DNA sequences of different matrix-binding elements vary widely. The locations of some MARs at the ends of chromatin loops suggest that they may represent boundaries of individual chromatin domains. As such, MARs may play important roles in regulating transcription and chromatin structure. As a first step towards assessing the roles of MARs in these processes, we assayed DNA sequences from the human serine protease inhibitor (serpin) gene cluster at 14q32.1 for matrix-binding activity in vitro. This approximately 150 kb region contains the cell-specific genes encoding alpha1-anti-trypsin (alpha1AT) and corticosteroid-binding globulin (CBG), as well as an antitrypsin-related sequence termed ATR. A DNase I-hypersensitive site (DHS) map of the locus has recently been described. We report here that the alpha1AT-ATR-CBG region contains five distinct MARs. There is a strong matrix-binding element approximately 16 kb upstream of alpha1AT; three MARs are between ATR and CBG and one MAR is within the CBG gene itself. These MARs were matrix-associated in all cell types examined. DNA sequencing indicated that the serpin MARs contained predominantly repetitive DNA, although the types of DNA repeats differed among the MARs.

Base Sequence↗
PubMed2002

The effects of atrazine metabolites on puberty and thyroid function in the male Wistar rat.

Recently we reported that atrazine (ATR), a chlorotriazine herbicide, alters the onset of puberty in male Wistar rats. In this study, we examined the same reproductive parameters in the developing male rat following a similar exposure to the primary, chlorinated metabolites of atrazine. Intact male Wistar rats were gavaged from postnatal day (PND) 23 through PND 53 and several reproductive endpoints were examined. The doses selected were the molar equivalents to atrazine in our previous work. Deethylatrazine (DEA), deisopropyl-atrazine (DIA), and diaminochlorotriazine (DACT) were administered by gavage at doses equivalent to the atrazine equimolar doses (AED) of 6.25, 12.5, 25, 50, 100, or 200 mg/kg. Preputial separation (PPS) was significantly delayed by DEA at 25, 100, and 200 AED, by DIA at 25, 100, and 200 AED, and by DACT at 12.5 through 200 AED. When the males were killed on PND 53, DEA (100 and 200 AED), DIA (50 through 200 AED), and DACT (200 AED) treatments caused a significant reduction in ventral prostate weight, while only the highest doses of DIA and DEA resulted in a significant decrease in lateral prostate weight. Seminal vesicle weight was reduced by DEA (25, 100, and 200 AED), DIA (100 and 200 AED), and 100 and 200 AED of DACT. Epididymal weights were reduced in the DEA (200 AED), DIA (200 AED), and DACT (100 and 200 AED) treatment groups. Serum testosterone was reduced only in the males receiving the 2 highest doses of DIA. Serum estrone was increased in the 2 highest doses of the DACT group, while serum estradiol was not different in any group. No differences were observed in any of the thyroid measures. In summary, the metabolites of ATR delay puberty in a manner similar to that observed in the previous study testing atrazine. These data also suggest that the 3 chlorinated metabolites are similar to ATR, by affecting the CNS control of the pituitary/gonadal axis and subsequent development of the reproductive tract.

Animals↗
PubMed2003

Dizocilpine improves beneficial effects of cholinergic antagonists in anticholinesterase-treated mice.

Mice were administered anticholinesterase pesticides dichlorvos (DDVP) or methomyl (MET). Both DDVP and MET induced dose-dependent seizures and lethality in mice. The muscarinic antagonist atropine (ATR, 1.8 mg/kg) did not prevent seizures but diminished the lethality induced by DDVP or MET. The nicotinic antagonist mecamylamine (MEC, 1 mg/kg) affected neither DDVP-induced seizures nor DDVP- and MET-induced lethality, but diminished MET-induced seizures. At a higher dose (10 mg/kg), MEC attenuated seizures produced by MET, but not DDVP, and decreased lethality of both anticholinesterases. The N-methyl-D-aspartate (NMDA) antagonist dizocilpine (MK-801, 1 mg/kg) prevented DDVP-, but not MET-induced seizures. MK-801 did not affect DDVP- or MET-induced lethality. Concurrent administration of ATR and MK-801 prevented the occurrence of DDVP- but not MET-induced seizures. MK-801 coadministered with ATR enhanced its protective effect against DDVP- or MET-induced lethality in mice. Coinjection of MEC (at both doses studied) and MK-801 completely prevented seizures produced by both acetylcholinesterase (AChE) inhibitors. Coadministration of MEC (1 mg/kg) and MK-801 protected mice against DDVP or MET lethality. MK-801 administered along with MEC at 10 mg/kg enhanced antilethal effects of the nicotinic antagonist in DDVP- or MET-treated mice. With respect to the mechanism underlying anticholinesterase-induced neurotoxicity, muscarinic and nicotinic, as well as NMDA receptors, seem to play major roles. The results suggest that combined treatment with cholinergic and NMDA antagonists might be beneficial in anticholinesterase-induced poisonings.

Animals↗
PubMed1986

Blockade of first ovulation in pubertal rats by delta-9-tetrahydrocannabinol: requirement for advanced treatment due to early initiation of the critical period.

Successful blockade of ovulation in pubertal rats by delta-9-tetrahydrocannabinol (THC) required earlier treatment during proestrus than was required in adults under the same conditions. Only 1 of 8 adult rats ovulated after treatment with THC (10 mg/kg body weight, i.p.) at 1400 h proestrus, whereas 77% of pubertal rats released full sets of ova following similar treatment during proestrus of the first or second vaginal cycle. When treatment of pubertal rats was advanced to 1300 h, only 2 of 10 THC-treated rats exhibited full ovulation, an incidence significantly lower than the 80% ovulation rate observed in vehicle-treated animals (p less than 0.05). To determine whether the requirement for earlier THC treatment in pubertal rats was related specifically to THC or reflected possible age-associated differences in timing of the critical period, the ovulation-blocking efficacy of atropine sulfate (ATR) was tested in pubertal rats for comparison with that of THC. The serum concentrations of luteinizing hormone (LH) during the first proestrus (1200-1900 h) were determined in pubertal rats that remained untreated. The incidence of ovulation in rats treated with ATR (350 mg/kg, s.c.) at 1400 h proestrus was not significantly reduced from that in vehicle-treated rats; however, after ATR treatment at 1300 h, only 2 of 11 animals released full sets of ova whereas all vehicle-treated rats ovulated (p less than 0.025). The mean serum LH concentration in untreated pubertal rats was not significantly increased over baseline at 1300 h proestrus, but was markedly elevated by 1400 h (1009 +/- 375 ng/ml; p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Delta-9-tetrahydrocannabinol attenuates luteinizing hormone release induced by electrochemical stimulation of the medial preoptic area.

Despite diverse pharmacological actions, drugs commonly used for blocking ovulation in the rat have not been observed to exert differential effects on the LH response to preoptic stimulation, thus suggesting blocking action above the final hypothalamic GnRH pathway. To determine if ovulatory blockade by delta-9-tetrahydrocannabinol (THC) is consistent with that scheme, LH surges evoked by preoptic stimulation were contrasted with those elicited during blockade by atropine (ATR), a classic ovulation-blocking agent with which other drugs have been compared. THC (10 mg/kg) or ATR (350 mg/kg) treatment before the proestrous critical period uniformly blocked LH release and ovulation in sham-stimulated rats. Preoptic stimulation evoked LH surges after both drug treatments (p less than 0.001), peak levels increasing with the intensity of stimulation (p less than 0.05). However, both maximum LH concentration (p less than 0.05) and total integrated LH release (p less than 0.01) were lower in THC-blocked rats. Inspection of the oviducts revealed no difference in the incidence of ovulation or the number of ova discharged. The reduced LH response during THC blockade was not attributable to variation in the extent or locus of histologically determined stimulation sites. These results distinguish THC from ATR and, by extension, other blocking drugs that do not overtly affect the LH response to preoptic stimulation. Thus, ovulatory blockade by THC may involve a different mechanism, which likely includes inhibitory action within the preoptic-to-tuberal GnRH pathway.

Animals↗
PubMed1999

The costs of intense neuromuscular block for anesthesia during endolaryngeal procedures due to waiting time.

UNLABELLED: The goal of this double-blinded, prospective study was to compare the costs incurred by waiting time of intense neuromuscular block while posttetanic count (PTC) was maintained at 0-2 during jet ventilation. Fifty patients were randomized into five groups to receive atracurium (ATR), mivacurium (MIV), rocuronium (ROC), vecuronium (VEC), and succinylcholine (SUCC). PTC < or =2 was maintained until completion of laryngomicroscopy by administering additional doses of relaxants or by adjusting the speed of the infusion of SUCC. We compared waiting time, i.e., onset time and recovery time, and costs of intense neuromuscular block. The expenses due to waiting time were calculated based on the average costs in the otorhinolaryngological operating room in Tampere University Hospital: FIM 40 (approximately $8) per minute in 1997. MIV and SUCC differ favorably from ATR, ROC, and VEC when waiting time and costs are concerned. The recovery times with MIV and SUCC were considerably shorter than those with ATR, ROC, and VEC (P < 0.001 in all pairwise comparisons). Using the muscle relaxant with the longest waiting time instead of that with the shortest waiting time (difference 21.8 min) cost more than FIM 800 (approximately $160) extra per patient. IMPLICATIONS: In this randomized, double-blinded, prospective study, we evaluated the costs of intense neuromuscular block due to waiting time. Succinylcholine and mivacurium are the most economical muscle relaxants to use when intense neuromuscular block is mandatory. Using intermediate-acting muscle relaxants results in unduly prolonged recovery time and extra costs.

Adult↗
PubMed2001

Homozygosity for angiotensinogen 235T variant increases the risk of myocardial infarction in patients with multi-vessel coronary artery disease.

OBJECTIVE: Molecular variants of the angiotensinogen (AGT) and the angiotensin II type 1 receptor (ATR) genes have been associated with the risk of coronary artery disease (CAD) and myocardial infarction (MI), but data so far available are conflicting. The primary object of the paper is to verify this possible association by a rigorous, angiographically controlled study in a large sample of patients with or without multi-vessel CAD. DESIGN: We designed a large case-control study in Italian patients candidates for coronary artery bypass grafting, with angiographically documented multi-vessel CAD, compared to subjects with angiographically documented normal coronary arteries. METHODS AND RESULTS: AGT M235T and ATR A1166C gene polymorphisms were analysed in 699 subjects; 454 patients were candidates for coronary artery bypass grafting, having angiographically documented (mainly multi-vessel) CAD. An appropriate documentation of previous MI was obtained from 404/454 (89%, 247 with and 157 without MI). Subjects (n = 245) with angiographically documented normal coronary arteries, were included as control group (CAD-free group). CAD patients had a substantial burden of conventional risk factors as compared with controls free of coronary atherosclerosis. Age, gender, smoking habit and number of stenosed vessels were the only differences between patients with or without previous myocardial infarction, who were similarly exposed to the other conventional risk factors (including hypertension). AGT M235T and ATR A1166C allele and genotype frequencies were similar between CAD and CAD-free patients. In the CAD group, AGT 235T allele was found more frequently in subjects with a previous myocardial infarction (0.494 versus 0.414; P < or = 0.05). By logistic regression, homozygosity for AGT 235T variant appeared to confer 1.9-fold increased risk for MI in both the univariate and the multivariate (adjusted for age, gender, smoking habit and number of stenosed vessels) model. CONCLUSIONS: AGT 235 T homozygous patients with multivessel CAD have an increased risk of myocardial infarction as compared with subjects with clinically similar phenotype but different genotype.

Aged↗