Ornithine Aminotransferase versus GABA Aminotransferase: Implications for the Design of New Anticancer Drugs

Ornithine aminotransferase (OAT) and γ‐aminobutyric acid aminotransferase (GABA‐AT) are classified under the same evolutionary subgroup and share a large portion of structural, functional, and mechanistic features. Therefore, it is not surprising that many molecules that bind to GABA‐AT also bind well to OAT. Unlike GABA‐AT, OAT had not been viewed as a potential therapeutic target until recently; consequently, the number of therapeutically viable molecules that target OAT is very limited. In this review the two enzymes are compared with respect to their active‐site structures, catalytic and inactivation mechanisms, and selective inhibitors. Insight is offered that could aid in the design and development of new selective inhibitors of OAT for the treatment of cancer.     

Renal elimination of organic anions in cholestasis

The disposition of most drugs is highly dependent on specialized transporters. OAT1 and OAT3 are two organic anion transporters expressed in the basolateral membrane of renal proximal tubule cells, identified as contributors to xenobiotic and endogenous organic anion secretion. It is well known that cholestasis may cause renal damage. Impairment of kidney function produces modifications in the renal elimination of drugs. Recent studies have demonstrated that the renal abundance of OAT1 and OAT3 plays an important role in the renal elimination of organic anions in the presence of extrahepatic cholestasis. Time elapsed after obstructive cholestasis has an important impact on the regulation of both types of organic anion transporters. The renal expression of OAT1 and OAT3 should be taken into account in order to improve pharmacotherapeutic efficacy and to prevent drug toxicity during the onset of this hepatic disease.     

Assessment of seminal YKL-40 in infertile men with varicocele

Several studies attempted to explain the negative impact of varicocele on spermatogenesis and fertilisation processes. YKL-40 is a novel glycoprotein biomarker that had been associated with several diseases. This quasi-interventional study aimed to assess the seminal levels of YKL-40 in infertile men with varicocele before and after varicocelectomy. Overall, 50 men were included in this study divided into 20 healthy fertile men and 30 infertile oligoasthenoteratozoospermic (OAT) men with varicocele that underwent varicocelectomy. All participants were subjected to history taking, clinical examination and scrotal Doppler. Also, semen analysis and seminal YKL-40 assessment were carried out in the start and 6 months after varicocele surgical repair. The results showed a significant increase in the mean seminal YKL-40 level in infertile OAT men with varicocele compared with the healthy fertile men. Six months post-varicocelectomy, the mean seminal KYL-40 level exhibited significant decreases correlated with improved sperm parameters. Overall, seminal levels of YKL-40 showed significant negative correlations with sperm concentration, total sperm motility and sperm normal morphology. It could be concluded that seminal YKL-40 is elevated in infertile OAT men with varicocele where varicocelectomy induces decreased seminal YKL-40 levels correlated with improved semen parameters.     

Assessing outcome measures of oral anticoagulation management in children

The complexities of managing oral anticoagulation therapy in children have been well described and various management strategies have been designed to optimise clinical outcomes within this challenging population. To date, outcome measurements used within paediatric studies investigating oral anticoagulant management have focused upon achieving therapeutic range and examining the incidence of medication-related adverse events. Whilst the reporting of such data is a priority, the relatively small number of children participating in clinical studies of oral anticoagulant management and the difficulties associated with conducting multi-centre interventional trials in such populations limit the ability of researchers to measure the significance of interventions made. This review examines current methods of reporting outcomes for paediatric oral anticoagulation management and identifies how the inclusion of quality of life as an outcome measure may strengthen the methodology of research aimed at measuring the impact of management interventions within the field of paediatric oral anticoagulant therapy.     

Inhibition of human organic anion transporter 3 mediated pravastatin transport by gemfibrozil and the metabolites in humans

Coadministration of gemfibrozil (600?mg, b.i.d., 3 days) with pravastatin (40?mg/day) decreased the renal clearance of pravastatin by approximately 40% in healthy volunteers. To investigate the mechanism of this drug–drug interaction in the renal excretion process, we undertook an uptake study of pravastatin using human organic anion transporters (hOATs)-expressing S2 cells. hOAT3 and hOAT4 transported pravastatin in a saturatable manner with Michaelis--Menten constants of 27.7?µM and 257?µM respectively. On the other hand, hOAT1 and hOAT2 did not transport pravastatin. Gemfibrozil and its glucuronide and carboxylic metabolite forms inhibited the uptake of pravastatin by hOAT3 with IC₅₀ values of 6.8?µM, 19.7?µM and 5.4?µM, respectively. Considering the plasma concentrations of gemfibrozil and its metabolites in humans, the inhibition of hOAT3-mediated pravastatin transport by gemfibrozil and its metabolites would lead to a decrease in the renal clearance of pravastatin in clinical settings.     

OATP1B1/1B3 activity in plated primary human hepatocytes over time in culture

Primary human hepatocytes are widely used as an in vitro model for evaluation of drug metabolism and transport. However, it has been shown that the gene expression of many drug-metabolizing enzymes and transporters change in culture. The aim of the present study was to evaluate the activity of organic anion-transporting polypeptide 1B1 (OATP1B1) and 1B3 (OATP1B3) in plated primary human hepatocytes over time in culture. The uptake kinetics of the OATP1B1/1B3 substrate [³H]-estradiol-17β-d-glucuronide was determined in cells from five donors. An extensive and variable decrease in OATP1B1/1B3 activity and/or increase in passive diffusion was observed over time. Already after 6 h in culture, the OATP1B1/1B3 activity was not possible to determine in liver cells from one donor, while after 24 h, the uptake activity was not measurable in one additional donor. In the other three, the decrease in CL_int (V_max/K_m) values ranged from 15% to 86% after 24 h in culture compared to the values measured at 2 h. Visual examination of OATP1B1 protein expression by confocal microscopy showed localization to the plasma membrane as expected, and an extensive decrease in OATP1B1 expression over time in culture supported the decline in activity. The significant reduction in SLCO1B1 and SLCO1B3 gene expression over time determined by RT-PCR also supported the loss of OATP1B1/1B3 activity. In conclusion, plated primary human hepatocytes are useful as an in vitro model for OATP1B1/1B3-mediated uptake studies, but the culture time may substantially change the uptake kinetics.     

Cognitive endophenotypes in OCD: A study of unaffected siblings of probands with familial OCD

Background

Impairments in executive functions and non-verbal memory are considered potential endophenotype markers of obsessive–compulsive disorder (OCD). For the neuropsychological deficits to be considered endophenotypes, they should be demonstrable in unaffected family members.

Aim

To compare the neuropsychological performance in unaffected siblings of probands with familial OCD with that of individually matched healthy controls.

Methods

Twenty-five unaffected siblings of OCD probands with familial OCD, and 25 individually matched healthy controls were assessed with tests of attention, executive function, memory and intelligence.

Results

Unaffected siblings showed significant deficits in tests of decision making and behavioural reversal i.e., the Iowa Gambling Task (IGT) and the Delayed Alternation Test (DAT) respectively, but performed adequately in other tests.

Conclusions

Our study suggests that the deficits in decision making and behavioural reversal could be potential endophenotypes in OCD. These deficits are consistent with the proposed neurobiological model of OCD involving the orbitofrontal cortex. Future studies could couple cognitive and imaging strategies to identify neurocognitive endophenotypes in homogenous samples of OCD.     

Incomplete nuclear transformation of human spermatozoa in oligo-astheno-teratospermia: characterization by indirect immunofluorescence of chromatin and thiol status

BACKGROUND Sperm heterogeneity in the human, as observed in oligo-astheno-teratozoospermia (OAT), is associated with hypospermatogenesis. METHODS The chromatin of sperm from OAT and normospermic males was characterized with antibodies specific for nucleosomes, the histone H3.1/H3.2 isoform, histone TH2B, apoptosis-associated H4 acetylation (KM-2) and protamines. Subsequently, sperm samples were stained with the thiol-specific fluorochrome monobromobimane (mBBr) before and after reduction with dithiotreitol (DTT) as most thiol groups reside in the cysteine-rich protamines. We also used fluorescence-activated cell sorter (FACS) for sperm histograms and sorting for high or low free and total thiol levels. These fractions were further analysed for DNA damage with the TdT-UTP nick end-labelling (TUNEL) assay. RESULTS OAT sperm nuclei stained higher for nucleosomes and KM2-epitopes, and lower for TH2B. For free, and total, thiol groups, OAT sperm were characterized by biphasic distributions, reflecting incomplete thiol oxidation as well as overoxidation, and possibly reduced protamine contents. The TUNEL assay on sperm subfractions, for both control and OAT sperm, revealed that a lower level of free thiol groups is associated with a higher TUNEL incidence, and this relationship was also found for total thiol levels. Hence, both overoxidation and a low total number of thiol groups predestine for sperm apoptosis. CONCLUSIONS Chromatin characteristics reflecting an incomplete nucleosome to protamine remodelling were found in subfertile males. Sperm apoptosis is related to both incomplete remodelling and protamine overoxidation.     

水蛭素对高尿酸血症大鼠尿酸盐转运体OAT1、URAT1、GLUT9表达的影响

目的 探究水蛭素对高尿酸血症大鼠的作用及机制。方法 雄性Wistar大鼠随机分为对照组、模型组、别嘌醇（30 mg/kg）组和水蛭素低、中、高剂量（0.2、0.4、0.8 g/kg）组。大鼠ig氧嗪酸钾（0.75 g/kg）,1次/d,连续5周,建立高尿酸血症模型;同时各给药组分别ig相应剂量的药物,1次/d,连续5周。采用生化法检测大鼠血清和尿液中的尿酸水平;免疫组化法测定肾组织中有机阴离子转运蛋白1（organic anion transporter 1,OAT1）水平;Western blotting法测定肾组织中葡萄糖转运体9（glucose transporter 9,GLUT9）、OAT1、尿酸盐转运体1（urate transporter 1,URAT1）蛋白表达;qRT-PCR检测肾组织中GLUT9、OAT1、URAT1 mRNA表达。结果 模型组大鼠血清和尿液中尿酸水平显著升高（P<0.01）,GLUT9、URAT1 mRNA和蛋白表达水平明显升高（P<0.01）,OAT1 mRNA和蛋白表达水平明显降低（P<0.01）;与模型组比较,水蛭素可显著降低大鼠血清和尿液中尿酸水平（P<0.01）,显著下调GLUT9、URAT1 mRNA和蛋白表达水平（P<0.01）,显著上调OAT1 mRNA和蛋白表达水平（P<0.01）。结论 水蛭素可通过调控高尿酸血症大鼠肾脏尿酸盐转运体OAT1、URAT1、GLUT9的表达,从而发挥降尿酸作用。