Relationships between single nucleotide polymorphisms of antioxidant enzymes and disease

The presence and progression of numerous diseases have been linked to deficiencies in antioxidant systems. The relationships between single nucleotide polymorphisms (SNPs) arising from specific antioxidant enzymes and diseases associated with elevated oxidative stress have been studied with the rationale that they may be useful in screening for diseases. The purpose of this narrative review is to analyse evidence from these studies. The antioxidant enzyme SNPs selected for analysis are based on those most frequently investigated in relation to diseases in humans: superoxide dismutase (SOD2) Ala16Val (80 studies), glutathione peroxidise (GPx1) Pro197Leu (24 studies) and catalase C-262T (22 studies). Although the majority of evidence supports associations between the SOD2 Ala16Val SNP and diseases such as breast, prostate and lung cancers, diabetes and cardiovascular disease, the presence of the SOD2 Ala16Val SNP confers only a small, clinically insignificant reduction (if any) in the risk of these diseases. Other diseases such as bladder cancer, liver disease, nervous system pathologies and asthma have not been consistently related to this SOD SNP genotype. The GPx1 Pro197Leu and catalase C-262T SNP genotypes have been associated with breast cancer, but only in a small number of studies. Thus, currently available evidence suggests antioxidant enzyme SNP genotypes are not useful for screening for diseases in humans.     

Brain Amino Acids Measured by Intracerebral Dialysis in Portacaval Shunted Rats

Changes in brain amino acid uptake and metabolism have been proposed as a possible etiological factor in hepatic encephalopathy. By use of a brain dialysis technique (a thin tube implanted in the brain of the living animal), the extracellular amino acid concentrations in the striatum of portacaval (PC)-shunted and sham-operated rats were measured. Leucine, phenylalanine, methionine, and glutamine were increased two- to sixfold in the PC-shunted rats, whilst no changes were seen for GABA, valine, glutamate, or isoleucine, confirming previous reports. Aspartate levels were 350% higher in the PC-shunted rats, and this rise, as well as that of phenylalanine, was significantly correlated with the lower motor activity observed in the PC-shunted rats, suggesting a possible importance of these amino acids in the etiology of hepatic encephalopathy. The amino acid concentrations measured in whole blood demonstrated the well-known pattern of low levels of branched-chain amino acids and increased concentrations of phenylalanine, glutamine, and histidine.     

Formation of heterodimers between wild type and mutant trp aporepressor polypeptides of Escherichia coli

Availability of the three-dimensional structure of the trp repressor of Escherichia coli and a large group of repressor mutants has permitted the identification and analysis of mutants with substitutions of the amino acid residues that form the tryptophan binding pocket. Mutant aporepressors selected for study were overproduced using a multicopy expression plasmid. Equilibrium dialysis with 14C-tryptophan and purified mutant and wild type aporepressors was employed to determine tryptophan binding constants. The results obtained indicate that replacement of threonine 44 by methionine (TM44) or arginine 84 by histidine (RH84) lowers the affinity for tryptophan approximately two- and four-fold, respectively. Replacement of arginine 54 by histidine (RH84) or glycine 85 by arginine (GR85) results in complete loss of tryptophan binding activity. Purified mutant and wild type aporepressors were used in in vitro heterodimer studies. The trp repressor of E. coli functions as a stable dimer. A large number of trp repressor mutants produces defective repressors that are transdominant to the wild type repressor in vivo. The transdominance presumably results from the formation of inactive or slightly active heterodimers between the mutant and wild type polypeptide subunits. An in vitro assay was developed to detect and measure heterodimer formation. Heterodimer formation was thermally induced, and heterodimers were separated on nondenaturing polyacrylamide gels. Aporepressors readily formed heterodimers upon treatment at 65 degrees C for 3 minutes. Heterodimer formation was significantly retarded by the presence of the corepressor, L-tryptophan. Indole-3-propionic acid, 5-methyl tryptophan, and other analogs of tryptophan, as well as indole, also inhibited heterodimer formation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stereoselective protein binding of ketoprofen: Effect of albumin concentration and of the biological system

Equilibrium dialysis was used to study in vitro the enantioselective binding of R, S, and racemic ketoprofen at physiological pH and temperature in human serum albumin (HSA) (1, 20, and 40 g/liter) and in plasma. The binding of enantiomers in a racemic mixture was studied to see the effect of each isomer on the other's interaction with the protein. The free fractions were determined by high-performance liquid chromatography. The binding of ketoprofen enantiomers to albumin was enantioselective, depending on both drug and protein concentrations. Enantioselectivity was observed in plasma too but was the opposite of that in HSA at 40 g/liter. The percentage of each isomer unbound was higher in the racemic mixture than with the isomer alone. The displacement of probes specific for HSA sites I and II, studied by spectrofluorimetry, suggests that all three preparations of ketoprofen are bound mainly to site I and secondarily to site II. © 1993 Wiley-Liss, Inc.     

Effects of reserpine on dopamine metabolite in the nucleus accumbens and locomotor activity in freely moving rats

The effect of reserpine (2 mg/kg i.p.) on both locomotor activity and the turnover of dopamine metabolite in the rat nucleus accumbens was estimated by using an activity monitor (Animex) and by in vivo brain microdialysis. Three to five hours after reserpine administration locomotor activity was reduced and there was a concomitant increase in the level of the dopamine metabolite, homovamillic acid. These findings suggest that depletion of dopamine from the nucleus accumbens may result in decreased locomotor activity. The data support the notion that dopamine in this tissue contributes to the control of locomotion.     

Brain Dialysis: In Vivo Metabolism of Dopamine and Serotonin by Monoamine Oxidase A but Not B in the Striatum of Unrestrained Rats

A dialysis cannula was implanted into rat striatum while the animals were anesthetized, and the area was perfused with Ringer solution while the animals were unanesthetized after at least 3 days following surgery. Concentrations of the metabolites of 3,4-dihydroxyphenylethylamine (DA) and 5-hydroxytryptamine (5-HT) in the perfusate were determined by HPLC with electrochemical detection. Levels of the DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the perfusate significantly decreased after pargyline administration (50 mg/kg i.p.), which may inhibit not only monoamine oxidase (MAO)-B but also MAO-A in these high doses. The level of the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) also decreased after pargyline treatment, although change in the relative level of 5-HIAA was less than that of DOPAC or HVA. To clarify the mechanisms for the metabolism of monoamines in rat striatum, highly specific MAO-A and -B inhibitors were used in the following experiments. Treatment with l-deprenyl (10 mg/kg), a specific inhibitor for MAO-B, did not cause any statistically significant change in DOPAC, HVA, and 5-HIAA levels. No significant change was found in rat striatal homogenates at 2 h after the same treatment with l-deprenyl. In contrast, low-dose treatment (1 mg/kg) with clorgyline, a specific inhibitor for MAO-A, caused a significant decrease in levels of these three metabolites in both the perfusates and tissue homogenates. In addition to the above three metabolites, the level of 3-methoxytyramine, which is an indicator of the amount of DA released, greatly increased after treatment with a low dose (1 mg/kg) of clorgyline.(ABSTRACT TRUNCATED AT 250 WORDS)     

Macromolecular interactions with cadmium and the effects of zinc,copper, lead,and mercury ions

Interactions of cadmium (Cd) ions with bovine serum albumin (BSA), bovine hepatic metallothionein (MT), calf thymus histone and deoxyribonucleic acid (DNA), and bovine hepatic chromatins were studied in the presence and absence of divalent zinc (Zn), copper (Cu), mercury (Hg), or lead (Pb) ions, using equilibrium dialysis at pH 7 and at 37°C. The BSA had 3.5 Cd-binding sites with an apparent affinity constant of 1×10⁵. The other metal ions inhibited the binding by reducing the affinity constant and the number of Cd-binding sites in BSA. There were 6 high affinity and 13 low affinity Cd-binding sites in the MT. Zinc ions had poor efficacy in reducing the binding of Cd to the MT. However, the Cu²⁺ and Hg²⁺ ions inhibited the Cd binding to a considerable extent, the former ions being more potent in this respect. Histone did not bind Cd. There were two kinds of Cd-binding sites in DNA: One mole of Cd per four moles DNA-phosphorus at low affinity sites, and one mole of Cd per 6.7 moles DNA-phosphorus at high affinity sites. Their apparent association constants were 8.3×10⁵ and 4.4×10⁶ M, respectively. The other metal ions had inhibitory effects on the binding of Cd to DNA. Histone reduced the Cd-DNA interactions to only a minor extent. The other metal ions reduced the binding of Cd to DNA-histone complex to a small extent. Cadmium binds to the euchromatin (Euch), heterochromatin (Het), and Euch-Het mixture almost equally. The other metal ions reduced the binding maximally in Euch-Het followed next in order by Het and Euch. Cupric ions were the most potent inhibitors of the interactions of Cd with the nuclear materials.     

The three-dimensional structure of β2 microglobulin: Results from X-ray crystallography

β2-microglobulin, the light chain component of the major histocompatibility complex I, is involved in the development of DRA, an amyloid deposition disease occurring in man. Specifically, the β2-microglobulin component, dissociated form the complex heavy chain, gives rise to amyloidogenic deposits in the joints of patients exposed to long dialysis periods. β2-microglobulin three-dimensional structure is based on an antiparallel β?barrel fold, with immunoglobulin domain topology, displaying structural flexibility in the crystal and NMR structures so fare determined. The structural bases of amyloidogenic potential in β2-microglobulin can be related to local unfolding, to the tendency to aggregate laterally through non-compensated β-strands, and partly also to its trend towards N-terminal proteolytic degradation. Such trends emerge quite clearly from inspection of a limited number of crystal structures of β2-microglobulin as an isolated chain, separated form the major histocompatibility complex I heavy chain.     

维持性腹膜透析患者并发真菌性腹膜炎的易感因素和结局分析

目的分析腹膜透析相关性真菌性腹膜炎(FP)发生率、致病菌、治疗情况和预后。方法回顾性分析2010年1月至2019年10月陆军军医大学第二附属医院腹膜透析中心发生的18例FP,选择与同期收治非真菌性腹膜炎113例比较,记录所有FP患者的临床资料,治疗方法和转归,分析FP发生的易感因素和结局。结果腹膜透析相关性腹膜炎共389例次,FP 18例次,占4.6%。其中白念珠菌6例(33.3%)、近平滑念珠菌5例(27.8%)、无名念珠菌3例(16.7%)、光滑念珠菌2例(11.1%)、热带念珠菌1例(5.6%)和克柔念珠菌(5.6%)1例。与非真菌性腹膜炎相比较,FP组腹透时间更长(P<0.001)、既往抗生素使用率高(P<0.001)、血浆白蛋白(ALB)更低(P<0.001)、C反应蛋白(CRP)更高(P<0.001)、甲状旁腺激素(PTH)和血磷(P)水平更高(P<0.001)。Logistic回归分析结果显示腹透时间越长、1个月内使用抗生素、低ALB和高CRP是发生FP的危险因素(P<0.05)。18例次FP中,14例患者拔管转血透(77.8%),4例患者死亡(22.2%),FP组腹膜透析技术失败率和死亡率明显高于BP组。结论腹透时间越长、既往使用抗生素、低ALB和高CRP是FP的易感因素。FP是腹膜透析的严重并发症,是导致技术失败的主要原因,确诊后早期拔管可降低死亡率。