The activation of red blood cell transketolase in groups of patients especially at risk from thiamin deficiency

Erythrocyte transketolase activation by thiamin diphosphate has been studied in elderly patients with moderate or severe chronic dementia, acute alcoholic admissions and chronic alcoholics with evidence of brain damage, mostly of the Wernicke-Korsakoff type. Significantly more patients in each group than controls showed abnormal activation of transketolase, not only by 0.3 mM thiamin diphosphate (TDP) but also in further activation by increase to 3 mM. This indicated the presence in a proportion of the alcoholic and the demented patients of an abnormal enzyme variant, similar to that previously found in vitro. The modified transketolase activation test may warn not only of marginal thiamin deficiency but also independently, of susceptibility to brain damage in patients at risk.     

Survey of the Distribution of a Newly Characterized Receptor for Advanced Glycation End Products in Tissues

Advanced glycation end products (AGEs), the final products of nonenzymatic glycation and oxidation of proteins, are found in the plasma and accumulate in the tissues during aging and at an accelerated rate in diabetes. A novel integral membrane protein, termed receptor for AGE (RAGE), forms a central part of the cell surface binding site for AGEs. Using monospecific, polyclonal antibody raised to human recombinant and bovine RAGE, immunostaining of bovine tissues showed RAGE in the vasculature, endothelium, and smooth muscle cells and in mononuclear cells in the tissues. Consistent with these data, RAGE antigen and mRNA were identified in cultured bovine endothelium, vascular smooth muscle, and monocyte-derived macrophages. RAGE antigen was also visualized in bovine cardiac myocytes as well as in cultures of neonatal rat cardiac myocytes and in neural tissue where motor neurons, peripheral nerves, and a population of cortical neurons were positive. In situ hybridization confirmed the presence of RAGE mRNA in the tissues, and studies with rat PC12 pheochromocytes indicated that they provide a neuronal-related cell culture model for examining RAGE expression. Pathological studies of human atherosclerotic plaques showed infiltration of RAGE-expressing cells in the expanded intima. These results indicate that RAGE is present in multiple tissues and suggest the potential relevance of AGE-RAGE interactions for modulating properties of the vasculature as well as neural and cardiac function, prominent areas of involvement in diabetes and in the normal aging process.     

Association of the dopamine receptor D4 (DRD4) gene 7-repeat allele with children with attention-deficit/hyperactivity disorder (ADHD): an update.

Polymorphisms of the dopamine receptor D4 gene DRD4, 11p15.5, have previously been associated with attention-deficit/hyperactivity disorder (ADHD) [Bobb et al., 2005; Am J Med Genet B Neuropsychiatr Genet 132:109-125; Faraone et al., 2005; Biol Psychiatry 57:1313-1323; Thapar et al., 2005; Hum Mol Genet 14 Spec No. 2:R275-R282]. As a follow up to a pilot study [see Castellanos et al., 1998; Mol Psychiatry 3:431-434] consisting of 41 probands and 56 controls which found no significant association between the DRD4 7-repeat allele in exon 3 and ADHD, a greatly expanded study sample (cases n = 166 and controls n = 282) and long term follow-up (n = 107, baseline mean age n = 9, follow-up mean age of n = 15) prompted reexamination of this gene. The DRD4 7-repeat allele was significantly more frequent in ADHD cases than controls (OR = 1.2; P = 0.028). Further, within the ADHD group, the 7-repeat allele was associated with better cognitive performance (measured by the WISC-III) (P = 0.013-0.07) as well as a trend for association with better long-term outcome. This provides further evidence of the role of the DRD4 7-repeat allele in the etiology of ADHD and suggests that this allele may be associated with a more benign form of the disorder.     

Polymorphisms in DNA repair genes as risk factors for spina bifida and orofacial clefts

Repairing DNA damage is critical during embryogenesis because development involves sensitive periods of cell proliferation, and abnormal cell growth or death can result in malformations. Knockout mouse experiments have demonstrated that disruption of DNA repair genes results in embryolethality and structural defects. Studies using mid-organogenesis rat embryos showed that DNA repair genes were variably expressed. It is hypothesized that polymorphisms that alter the functionality of DNA repair enzymes may modify the risk of malformations. We conducted a case-control analysis to investigate the relationship between DNA repair gene polymorphisms and the risk of spina bifida and oral clefts. Newborn screening blood spot DNA was obtained for 250 cases (125 spina bifida, 125 oral clefts) identified by the California Birth Defects Monitoring Program, and 350 non-malformation controls identified from birth records. Six single nucleotide polymorphisms of five DNA repair genes representing three distinct repair pathways were interrogated including: XRCC1 (Arg399Gln), APE1 (Asp148Glu), XRCC3 (Thr241Met), hOGG1(Ser326Cys), XPD (Asp312Asn, Lys751Gln). Elevated or decreased odds ratios (OR, adjusted for race/ethnicity) for spina bifida were found for genotypes containing at least one copy of the variant allele for XPD [751Gln, OR = 1.62; 95% confidence interval (CI) = 1.05-2.50] and APE 148 (OR = 0.58; CI = 0.37-0.90). A decreased risk of oral clefts was found for XRCC3 (OR = 0.62; CI = 0.39-0.99) and hOGG1 (326 Cys/Cys, OR = 0.22; CI = 0.06-0.78). This study suggested that polymorphisms of DNA repair genes, representing different major repair pathways, may affect risk of two major birth defects. Future, larger studies, examining additional repair genes, birth defects, and interaction with exposures are recommended.     

102T/C polymorphism of serotonin receptor type 2A gene is not associated with schizophrenia in either Chinese or British populations

Several pieces of evidence implicate serotonin receptors in the aetiology of schizophrenia, and recently a number of studies have reported a genetic association between the 102T/C polymorphism of serotonin receptor type 2A gene and schizophrenia. Unfortunately a number of failures to replicate these positive associations in both Caucasian and Chinese populations have also been reported. We have examined the 102T/C polymorphism by PCR amplification and restriction analysis of DNA from: 202 schizophrenics and 202 controls from Shanghai; 112 schizophrenics and 224 parents from Chengdu, Cina; and 253 schizophrenics and 244 controls from the the UK. We find no evidence of association or transmission disequilibrium between the 102T/C polymorphism and schizophrenia in any of the groups we have examined. We conclude that either the original positive reports occurred by chance or any effect must be minimal, and urge caution in interpreting small positive results derived using data from different centres.     

Mercury (II) alters mitochondrial activity of monocytes at sublethal doses via oxidative stress mechanisms

The perennial controversy about the safety of mercury in dental amalgams has adversely affected the availability and the quality of dental care. Chronic Hg(II) blood concentrations above 300 nM are known to alter function of the nervous system and the kidney. However, the effects of blood concentrations of 10 to 75 nM, far more common in the general population, are not clear and mechanisms of any effects are not known. The monocyte is an important potential target of Hg(II) because of its critical role in directing inflammatory and immune responses. In the current study we tested the hypothesis that concentrations of Hg(II) of 10 to 300 nM alter monocyte activity via a redox-dependent mechanism. Mitochondrial activity was used to establish inhibitory concentrations of Hg(II) following 6 to 72 h of exposures to THP1 human monocytic cells. Then subinhibitory concentrations were applied, and total glutathione levels and reactive oxygen species (ROS) were measured. Antioxidants [N-acetyl cysteine, (NAC); Na2SeO3, (Se)] and a pro-oxidant (tert-butylhydroquinone, tBHQ) were used to support the hypothesis that Hg(II) effects were redox-mediated. After 72 h of exposure, 20 microM of Hg(II) inhibited monocytic mitochondrial activity by 50%. NAC mitigated Hg(II)-induced mitochondrial suppression only at concentrations of greater than 10 microM, but Se had few effects on Hg-induced mitochondrial responses. tBHQ significantly enhanced mitochondrial suppression at higher Hg(II) concentrations. Hg(II) concentrations of 75 and 300 nM (0.075 and 0.30 microM, respectively) significantly increased total glutathione levels, and NAC mitigated these increases. Se plus Hg(II) significantly elevated Hg-induced total cellular glutathione levels. Increased ROS levels were not detected in monocytes exposed to mercury. Hg(II) acts in monocytic cells, at least in part, through redox-mediated mechanisms at concentrations below those commonly associated with chronic mercury toxicity, but commonly occurring in the blood of some dental patients.     

CD154-CD40-induced reactivation of latent HIV-1 infection

Reservoirs of latent HIV-1 in T cells and macrophages pose one of the major obstacles that hamper final eradication of HIV-1 from infected patients. Targeting costimulatory molecules expressed on cell types harboring latent HIV-1 to achieve reactivation may provide a new approach to overcome this problem. One such molecule is CD40, a member of the tumor necrosis factor (TNF)-receptor family. Using THP89GFP cells as a model for latently infected macrophages, we demonstrate that trimeric forms of recombinant CD154 allow for the direct reactivation of latent HIV-1 infection. Reactivation is augmented by the release of TNF-alpha. The presence of TNF-alpha is also crucial for the expression of late structural genes such as p24 Gag. In addition, levels of secreted TNF-alpha are sufficiently high to reactivate latent HIV-1 in a latently HIV-1-infected T-cell line (J89GFP). Taken together, our results demonstrate that costimulatory molecules may be attractive targets to reactivate latent HIV-1 in infected patients.