Association of the dihydrolipoamide dehydrogenase gene with Alzheimer's disease in an Ashkenazi Jewish population.

Abundant biochemical evidence links deficient activity of mitochondrial alpha-ketoglutarate dehydrogenase with neuropathologically confirmed Alzheimer's disease (AD). Reduced alpha-ketoglutarate dehydrogenase activity has also been associated with anti-mortem measures of clinical disability. One of the genes encoding this complex, namely, DLD, lies within a chromosome 7 region that is in linkage disequilibrium with AD. We therefore examined the hypothesis that variation in DLD is associated with AD risk. Denaturing HPLC was used to search for sequence variations in the coding and flanking regions of all exons of DLD, but no abundant variants that alter protein sequence were found. However, four common SNPs were identified and genotyped in a case-control series of 297 Caucasians from New York City, including 229 residents of a Jewish nursing home. Logistic regression analysis was performed for the four-locus DLD genotype, sex, and ApoE4 status to determine the association of these independent variables with AD. Significant associations with AD were observed for ApoE4 (P < 10(-6)) and sex combined with DLD genotype (P = 0.013). The association with the DLD genotypes appears only in the male population in both the Caucasian series (P = 0.0009, n = 83) and the Ashkenazi Jewish subseries (P = 0.017, n = 49). The DLD genotype appears to operate independently of APOE in conferring AD risk.     

Insulin degrading enzyme activity selectively decreases in the hippocampal formation of cases at high risk to develop Alzheimer's disease

In this study we report that the membrane-bound, but not cytosolic insulin degrading enzyme (IDE) protein concentration and IDE activity are significantly decreased in the hippocampal formation of cases affected by mild cognitive impairment (MCI) which are at high risk to develop Alzheimer's disease (AD), relative to normal neurological controls. Membrane-bound IDE protein concentrations and activity in the hippocampal formation continued to decrease during the conversion from MCI to mild-severe AD. This selective decrease in hippocampal membrane-bound, but not cytosolic, IDE concentration and activity was tissue specific since no changes in either membrane-bound or cytosolic IDE were found in the occipital cortex of the same cases examined. Most interestingly, the decreased hippocampal membrane-bound IDE protein activity negatively correlated with brain beta-amyloid (Abeta)X-42 content in MCI and in AD brain. The study tentatively suggests that interventions aimed at promoting membrane-bound IDE activities in the brain of MCI cases may help to prevent the onset and possibly the progression into AD through mechanisms involving the clearance of monomeric Abeta from the brain.     

Contribution of cystine-glutamate antiporters to the psychotomimetic effects of phencyclidine.

Altered glutamate signaling contributes to a myriad of neural disorders, including schizophrenia. While synaptic levels are intensely studied, nonvesicular release mechanisms, including cystine-glutamate exchange, maintain high steady-state glutamate levels in the extrasynaptic space. The existence of extrasynaptic receptors, including metabotropic group II glutamate receptors (mGluR), pose nonvesicular release mechanisms as unrecognized targets capable of contributing to pathological glutamate signaling. We tested the hypothesis that activation of cystine-glutamate antiporters using the cysteine prodrug N-acetylcysteine would blunt psychotomimetic effects in the rodent phencyclidine (PCP) model of schizophrenia. First, we demonstrate that PCP elevates extracellular glutamate in the prefrontal cortex, an effect that is blocked by N-acetylcysteine pretreatment. To determine the relevance of the above finding, we assessed social interaction and found that N-acetylcysteine reverses social withdrawal produced by repeated PCP. In a separate paradigm, acute PCP resulted in working memory deficits assessed using a discrete trial t-maze task, and this effect was also reversed by N-acetylcysteine pretreatment. The capacity of N-acetylcysteine to restore working memory was blocked by infusion of the cystine-glutamate antiporter inhibitor (S)-4-carboxyphenylglycine into the prefrontal cortex or systemic administration of the group II mGluR antagonist LY341495 indicating that the effects of N-acetylcysteine requires cystine-glutamate exchange and group II mGluR activation. Finally, protein levels from postmortem tissue obtained from schizophrenic patients revealed significant changes in the level of xCT, the active subunit for cystine-glutamate exchange, in the dorsolateral prefrontal cortex. These data advance cystine-glutamate antiporters as novel targets capable of reversing the psychotomimetic effects of PCP.     

Caspase gene expression in the brain as a function of the clinical progression of Alzheimer disease

BACKGROUND: Caspase gene expression has previously been reported in terminal Alzheimer disease (AD) brain, but, currently, little is known about the temporal pattern of caspase gene expression relative to the onset and clinical progression of AD. OBJECTIVE: To derive a profile of caspase gene expression and proapoptotic indexes as a function of the clinical and neuropathologic progression of AD dementia. SETTING AND PATIENTS: Postmortem survey of nursing home patients characterized clinically by Clinical Dementia Rating (CDR) and neuropathologically by Consortium to Establish a Registry for Alzheimer's Disease criteria. DESIGN AND OUTCOME MEASURES: To assess messenger RNA expression of caspase-1, -2L, -2S, -3, -5, -6, -7, -8, and -9; apoptotic cell death by TUNEL assay; and poly (ADP-ribose) polymerase cleavage in postmortem brain tissue samples from cognitively normal (CDR 0), high risk of developing AD dementia (CDR 0.5), and severe dementia (CDR 5) cases. RESULTS: Compared with CDR 0 cases, elevated messenger RNA expression of caspase-1 and caspase-7 in the entorhinal cortex of CDR 0.5 cases coincided with increased poly (ADP-ribose) polymerase cleavage but not apoptotic cell injury. In the entorhinal cortex of CDR 5 cases, we found elevation of caspase-1, -2L, -3, -5, -6, -7, -8, and -9 and a greater than 4-fold increase in TUNEL-positive cells. Caspase messenger RNA expression was closely associated with neurofibrillary tangle and, to a lesser extent, neuritic plaque density. CONCLUSIONS: Proapoptotic mechanisms may be at play early in the onset of AD (before overt signs of apoptosis) and may be a conditional factor for later apoptotic cell injury or death. These data have relevance to potential therapeutic interventions for AD using selective caspase inhibitors.     

Implications for altered glutamate and GABA metabolism in the dorsolateral prefrontal cortex of aged schizophrenic patients

OBJECTIVE: Pharmacological, clinical, and postmortem studies suggest altered gamma-aminobutyric acid (GABA)-ergic and glutamatergic function in patients with schizophrenia. The dorsolateral prefrontal cortex is one key locus of abnormality. The precise neurochemical mechanisms underlying neurotransmitter alterations, such as hypoglutamatergia or GABA dysfunction, are not well understood. This study investigated key biochemical elements of GABA and glutamate metabolism in brain specimens from schizophrenic patients. The activities of nine principal GABA and glutamate-associated metabolic enzymes were measured concurrently in the dorsolateral prefrontal cortex of antemortem-assessed and neuropathologically characterized schizophrenic and comparison subjects. METHOD: Postmortem dorsolateral prefrontal cortex specimens from schizophrenia, Alzheimer's disease, and normal nonpsychiatric comparison subjects were assayed to determine activities of the principal glutamate and GABA-metabolizing enzymes glutamine synthetase, glutamate dehydrogenase, alpha-ketoglutarate dehydrogenase, phosphate-activated glutaminase, alanine aminotransferase, aspartate aminotransferase, glutamic acid decarboxylase, GABA-transaminase, and succinic semialdehyde dehydrogenase. RESULTS: Glutamic acid decarboxylase activities were twofold greater and phosphate-activated glutaminase activities were fourfold greater in the schizophrenic group than in the comparison group. Differences in postmortem interval, tissue pH, inhibition of phosphate-activated glutaminase, and medication effects could not account for the differences. Differences in phosphate-activated glutaminase and glutamic acid decarboxylase activities in equivalent specimens from Alzheimer's patients were not observed. The activities of the remaining enzymes were unchanged. CONCLUSIONS: Greater phosphate-activated glutaminase and glutamic acid decarboxylase activities, specific to schizophrenia patients, provide additional biochemical evidence that dorsolateral prefrontal cortex glutamate and GABA metabolism is altered in schizophrenic subjects. These greater activities are consistent with models of a dysregulated glutamatergic/GABA-ergic state in schizophrenia.     

Safety and efficacy of epinephrine added to bupivacaine for lumbar epidural analgesia in obstetrics

The effects of epidural bupivacaine with and without 1:300,000 epinephrine on uterine activity, progress of labor, fetal heart rate, maternal blood pressure and heart rate, newborn Apgar scores, neonatal acid-base status, and Neurologic and Adaptive Capacity Scoring System (NACS) were compared in 32 parturients during labor and delivery. Patients in group I (n = 16) received 0.5% bupivacaine with 1:300,000 epinephrine and those in group II (n = 16) received 0.5% bupivacaine alone. Addition of epinephrine to bupivacaine had no significant effects on uterine activity, duration of first or second stages of labor, fetal heart rate and variability, or the incidence of abnormal fetal heart rate patterns. Maternal hypotension occurred less frequently in group I than in group II patients (P less than 0.05). Apgar scores, neonatal acid-base status, and the NACS were equally good in the two groups. Duration of analgesia was significantly longer in group I than in group II (186.8 +/- 11.6 vs 85.3 +/- 6.1 (mean +/- SEM) min, P less than 0.001). It is concluded that adding epinephrine to bupivacaine during epidural anesthesia in the normal parturient has no adverse effects on either mother, fetus, neonate, or the progress of labor; and that it significantly prolongs the duration of anesthesia and decreases the incidence of maternal hypotension.     

Cholinergic modulation of memory in rats

Central cholinergic systems have long been implicated in the modulation of learning and memory processes in animals and man. Drugs that affect the central cholinergic system have been found either to enhance or to hinder performance in tests of learning and memory. Few studies have evaluated the effects of different cholinergic drugs within a single experimental paradigm and with a relatively wide dose range. The studies reported here investigated the effects of cholinergic drugs with diverse modes of action on the retention of a passive avoidance response. Physostigmine, arecoline, oxotremorine, nicotine, and 4-aminopyridine were administered IP immediately following the acquisition of a one-trial passive avoidance task. All of the drugs were found to enhance 72-h retention of passive avoidance; however, the effective doses were different for each of the drugs studied.