Association study of polymorphisms in the receptor for advanced glycation end-products (RAGE) gene with susceptibility and prognosis of heart failure

Background

Functional polymorphisms in the receptor for advanced glycation end-products (RAGE) gene have been implicated in several vascular diseases. However, to date, no study investigated the association of RAGE polymorphisms with heart failure (HF).

Objective

In this study we tested the hypothesis that the 63-bp insertion/deletion, the − 374T > A (rs1800624) and the − 429T > C (rs1800625) polymorphisms in the RAGE gene might be associated with susceptibility to HF and could predict all-cause mortality in Brazilian outpatients with left ventricular systolic dysfunction.

Methods

A total of 273 consecutive HF patients (196 Caucasian- and 77 African-Brazilians) and 334 healthy blood donors (260 Caucasian- and 74 African-Brazilians) were enrolled in a tertiary care university hospital. Genotyping of RAGE polymorphisms was done by polymerase chain reaction (PCR) or PCR followed by enzyme restriction analysis.

Results

The allele, genotype and haplotype frequencies of − 374T > A and − 429T > C polymorphisms were not significantly different between HF patients and healthy blood donors in both ethnic groups. However, among African-Brazilians, the frequency of carriership of the del allele was lower in HF patients than in blood donors (2.6% vs 12.2%, respectively, p = 0.008). Patients were followed-up for a median of 38 months and the survival analysis did not reveal a consistent association between RAGE polymorphisms and all-cause death in both ethnic groups.

Conclusion

The − 374T > A and − 429T > C polymorphisms in the RAGE gene were not associated with the susceptibility and prognosis of HF. Notwithstanding, the 63-bp ins/del polymorphism might be involved in the susceptibility to HF in African-Brazilians.     

Effect of homomeric P450-P450 complexes on P450 function

Previous studies have shown that the presence of one P450 enzyme can affect the function of another. The goal of the present study was to determine if P450 enzymes are capable of forming homomeric complexes that affect P450 function. To address this problem, the catalytic activities of several P450s were examined in reconstituted systems containing NADPH-POR (cytochrome P450 reductase) and a single P450. CYP2B4 (cytochrome P450 2B4)-, CYP2E1 (cytochrome P450 2E1)- and CYP1A2 (cytochrome P450 1A2)-mediated activities were measured as a function of POR concentration using reconstituted systems containing different concentrations of P450. Although CYP2B4-dependent activities could be explained by a simple Michaelis-Menten interaction between POR and CYP2B4, both CYP2E1 and CYP1A2 activities generally produced a sigmoidal response as a function of [POR]. Interestingly, the non-Michaelis behaviour of CYP1A2 could be converted into a simple mass-action response by increasing the ionic strength of the buffer. Next, physical interactions between CYP1A2 enzymes were demonstrated in reconstituted systems by chemical cross-linking and in cellular systems by BRET (bioluminescence resonance energy transfer). Cross-linking data were consistent with the kinetic responses in that both were similarly modulated by increasing the ionic strength of the surrounding solution. Taken together, these results show that CYP1A2 forms CYP1A2-CYP1A2 complexes that exhibit altered catalytic activity.     

QTLs for agronomic traits in the Mediterranean environment identified in recombinant inbred lines of the cross 'Arta' × <Emphasis Type="Italic">H. spontaneum</Emphasis> 41-1

A genetic linkage map has been developed for recombinant inbred lines (RILs) of the cross 'Arta' × Hordeum spontaneum 41-1. One hundred and ninety four RILs, randomly chosen from a population of 494 RILs, were mapped with 189 markers including one morphological trait (btr = brittle rachis locus). The linkage map extended to 890 cM. Agronomic traits such as grain yield, biological yield, days to heading, plant height, cold tolerance and others were evaluated at the ICARDA research stations Tel Hadya and Breda during the years 1996–97 and 1997–98. QTLs for agronomic traits related to drought resistance were localized. For the most-important character 'plant height under drought stress', QTLs on 2H, 3H and 7H were detected. The 'plant height' QTLs, specially the one on 3H, showed pleiotropic effects on traits such as days to heading, grain yield and biological yield. QTLs were also identified for other traits associated with adaptation to the Mediterranean environment such as cold tolerance, days to heading and tiller number. The identification of QTLs for agronomic traits is a first step to analyze and to dissect complex characters such as adaptation to drought tolerance.Comunicated by R. Hagemann     

Proinflammatory cytokine responses induced by influenza A (H5N1) viruses in primary human alveolar and bronchial epithelial cells

Background

Fatal human respiratory disease associated with influenza A subtype H5N1 has been documented in Hong Kong, and more recently in Vietnam, Thailand and Cambodia. We previously demonstrated that patients with H5N1 disease had unusually high serum levels of IP-10 (interferon-gamma-inducible protein-10). Furthermore, when compared with human influenza virus subtype H1N1, the H5N1 viruses in 1997 (A/Hong Kong/483/97) (H5N1/97) were more potent inducers of pro-inflammatory cytokines (e.g. tumor necrosis factor-a) and chemokines (e.g. IP-10) from primary human macrophages in vitro, which suggests that cytokines dysregulation may play a role in pathogenesis of H5N1 disease. Since respiratory epithelial cells are the primary target cell for replication of influenza viruses, it is pertinent to investigate the cytokine induction profile of H5N1 viruses in these cells.

Methods

We used quantitative RT-PCR and ELISA to compare the profile of cytokine and chemokine gene expression induced by H5N1 viruses A/HK/483/97 (H5N1/97), A/Vietnam/1194/04 and A/Vietnam/3046/04 (both H5N1/04) with that of human H1N1 virus in human primary alveolar and bronchial epithelial cells in vitro.

Results

We demonstrated that in comparison to human H1N1 viruses, H5N1/97 and H5N1/04 viruses were more potent inducers of IP-10, interferon beta, RANTES (regulated on activation, normal T cell expressed and secreted) and interleukin 6 (IL-6) in primary human alveolar and bronchial epithelial cells in vitro. Recent H5N1 viruses from Vietnam (H5N1/04) appeared to be even more potent at inducing IP-10 than H5N1/97 virus.

Conclusion

The H5N1/97 and H5N1/04 subtype influenza A viruses are more potent inducers of proinflammatory cytokines and chemokines in primary human respiratory epithelial cells than subtype H1N1 virus. We suggest that this hyper-induction of cytokines may be relevant to the pathogenesis of human H5N1 disease.     

Effects of ionic strength on the functional interactions between CYP2B4 and CYP1A2

The presence of one P450 can influence the catalytic characteristics of a second enzyme through the formation of heteromeric P450 complexes. Such a complex has been reported for mixed reconstituted systems containing NADPH-cytochrome P450 reductase, CYP2B4, and CYP1A2, where a dramatic inhibition of 7-pentoxyresorufin-O-dealkylation (PROD) was observed when compared to simple reconstituted systems containing reductase and a single P450 enzyme. The goal of the present study was to characterize this interaction by examining the potential of the CYP1A2-CYP2B4 complex to be formed by charge-pair interactions. With ionic interactions being sensitive to the surrounding ionic environment, monooxygenase activities were measured in both simple systems and mixed reconstituted systems as a function of ionic strength. PROD was found to be decreased at high ionic strength in both simple and mixed reconstituted systems, due to disruption of reductase-P450 complexes. Additionally, the inhibition of PROD in mixed reconstituted systems was relieved at high ionic strength, consistent with disruption of the CYP2B4-CYP1A2 complex. When ionic strength was measured as a function of CYP1A2 concentration, a shift to the right in the inflection point of the biphasic curve occurred at high ionic strength, consistent with a loss in CYP1A2 affinity for CYP2B4. When this analysis was applied to the same systems using a different substrate, 7-EFC, evidence for a high-affinity complex was not observed, demonstrating that the characteristics of the CYP1A2-CYP2B4 complex are influenced by the substrates present. These results support the role for a substrate specific electrostatic interaction between these P450 enzymes.     

Kinetics of cytochrome P-450 reduction: evidence for faster reduction of the high-spin ferric state

Results are presented that support our hypothesis [Backes, W. L., Sligar, S. G., & Schenkman, J. B. (1980) Biochem. Biophys. Res. Commun. 97, 860-867] that the multiphasic reduction kinetics of cytochrome P-450 are, in part, due to the spin equilibrium of the ferric hemoprotein. The disappearance of the high-spin charge-transfer band at 650 nm during reduction of the hemoprotein by NADPH was fast, exhibiting a rate constant greater than that of the fast phase of reduction measured by formation of the carbon monoxide adduct. In contrast, the disappearance of the ferric low-spin form of the cytochrome was at a considerably slower rate. A mathematical expression of the fractional content of high-spin cytochrome P-450 was obtained by comparing the ratio of the initial rate of change in the fraction of total oxidized cytochrome remaining to the initial rate of change in the fraction of high-spin ferric P-450 remaining. Results supporting the model were obtained by using both microsomes and purified cytochrome P-450 RLM5. The calculation from experimental data yielded results that were similar to those obtained by different extrapolation methods used for estimation of the amount of high-spin cytochrome P-450, supporting further the proposed relationship between the spin equilibrium and the reduction kinetics of this hemoprotein.     

Reduction kinetics of purified rat liver cytochrome P-450. Evidence for a sequential reaction mechanism dependent on the hemoprotein spin state

The anaerobic reduction kinetics of purified rat liver ferric cytochrome P-450 from phenobarbital-treated rat liver microsomes, reconstituted with saturating NADPH-cytochrome P-450 reductase, have been investigated and were shown not to be monophasic. From experiments correlating changes in the rate of fast-phase reduction with the spin state of the heme iron existing at preequilibrium, data were obtained consistent with a model for spin-state control of cytochrome P-450 reduction wherein the high-spin form of the hemoprotein is more rapidly reduced than the low-spin form. In addition, the temperature dependence of the reduction process in the presence of the substrate benzphetamine was studied. From the results obtained it is suggested that the endothermic nature of the low- to high-spin transition largely accounts for the apparent activation energy observed for the reduction of high-spin cytochrome P-450 being relatively temperature insensitive when compared to the rate constant for reduction of the membrane-bound form of the hemoprotein.     

The role of site-specific N-glycosylation in secretion of soluble forms of rabies virus glycoprotein

Rabies virus glycoprotein is important in the biology and pathogenesis of neurotropic rabies virus infection. This transmembrane glycoprotein is the only viral protein on the surface of virus particles, is the viral attachment protein that facilitates virus uptake by the infected cell, and is the target of the host humoral immune response to infection. The extracellular domain of this glycoprotein has N- glycosylation sequons at Asn37, Asn247, and Asn319. Appropriate glycosylation of these sequons is important in the expression of the glycoprotein. Soluble forms of rabies virus glycoprotein were constructed by insertion of a stop codon just external to the transmembrane domain. Using site-directed mutagenesis and expression in transfected eukaryotic cells, it was possible to compare the effects of site-specific glycosylation on the cell-surface expression and secretion of transmembrane and soluble forms, respectively, of the same glycoprotein. These studies yielded the surprising finding that although any of the three sequons permitted cell surface expression of full-length rabies virus glycoprotein, only the N-glycan at Asn319 permitted secretion of soluble rabies virus glycoprotein. Despite its biological and medical importance, it has not yet been possible to determine the crystal structure of the full-length transmembrane form of rabies virus glycoprotein which contains heterogeneous oligosaccharides. The current studies demonstrate that a soluble form of rabies virus glycoprotein containing only one sequon at Asn319 is efficiently secreted in the presence of the N-glycan processing inhibitor 1-deoxymannojirimycin. Thus, it is possible to purify a conformationally relevant form of rabies virus glycoprotein that contains only one N-glycan with a substantial reduction in its microheterogeneity. This form of the glycoprotein may be particularly useful for future studies aimed at elucidating the three-dimensional structure of this important glycoprotein.