Acute and chronic caffeine administration differentially alters striatal gene expression in wild-type and adenosine A(2A) receptor-deficient mice

In order to assess for the respective involvement of adenosine A(1) and A(2A) receptors (A(2A)-R) in the consequences of short- and long-term caffeine exposure on gene expression, the effects of acute caffeine administration on striatal, cortical, and hippocampal expression of immediate early genes (IEG), zif-268 and arc, and the effects of long-term caffeine or 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) exposure (once daily for 15 days) on striatal gene expression of substance P, enkephalin, and glutamic acid decarboxylase isoforms, GAD65 and GAD67, were evaluated in wild-type and A(2A)-R-deficient (A(2A)-R(-/-)) mice. In situ hybridization histochemistry was performed using oligonucleotides followed by quantitative image analysis. Our results demonstrated that a biphasic response of IEG expression to acute caffeine observed in the wild-type striatum was resumed in a monophasic response in the mutant striatum. In the cerebral cortex and hippocampus, the effect of caffeine was weak in wild-type, whereas in mutant mice it induced a 2-3-fold increase in the IEG expression to restore a level similar to the wild-type basal expression. Chronic caffeine and DPCPX-mediated regulation in neuropeptide and GADs striatal gene expression typically showed the mimicking of alterations resulting from the A(2A)-R genetic deficiency in 25 mg/kg caffeine-treated wild-type mice as well as the dose-dependent normalization of substance P and enkephalin expression in A(2A)-R(-/-) mice. These results indicate that, depending on the dose, the blockade of A(2A)-R or A(1) receptors by caffeine is preferentially revealed leading to highly differential alterations in striatal gene expression and they also suggested the central role of these two receptors on the control of dopaminergic functions.     

Antagonism of NMDA receptors as a potential treatment for Down syndrome: a pilot randomized controlled trial

Down syndrome (DS) is the most common genetic cause of intellectual disability. The N-methyl-D-aspartate (NMDA) receptor uncompetitive antagonist, memantine hydrochloride (memantine), has been shown to improve learning/memory and rescue one form of hippocampus synaptic plasticity dysfunction in the best-studied mouse model of DS available, the Ts65Dn mouse. Given the status of memantine as a treatment for Alzheimer''s disease (AD) approved by the Food and Drug Administration, the preclinical evidence of potential efficacy in Ts65Dn mice, and the favorable safety profile of memantine, we designed a study to investigate whether the findings in the mouse model could be translated to individuals with DS. In this pilot, proof-of-principle study we hypothesized that memantine therapy would improve test scores of young adults with DS on measures of episodic and spatial memory, which are generally considered to be hippocampus dependent. Accordingly, in this randomized, double-blind, placebo-controlled trial, we compared the effect of 16-week treatment with either memantine or placebo on cognitive and adaptive functions of 40 young adults with DS using a carefully selected set of neuropsychological outcome measures. Safety and tolerability were also monitored. Although no significant differences were observed between the memantine and placebo groups on the two primary outcome measures, we found a significant improvement in the memantine group in one of the secondary measures associated with the primary hypothesis. Only infrequent and mild adverse events were noted.     

大鼠GAD65基因慢病毒载体的构建及其在MSCs中的表达

目的构建谷氨酸脱羧酶65(glutamic acid decarboxylase 65,GAD65)重组慢病毒表达载体,感染间充质干细胞(mesenchymal stem cells,MSCs)并进行鉴定。方法 PCR法扩增GAD65基因,构建LV5-GFP-GAD65慢病毒载体;与包装质粒共转染293T细胞包装病毒;将慢病毒感染大鼠MSCs,荧光显微镜鉴定转染率,Western blot检测GAD65的表达。结果双酶切及测序结果表明LV5-GFP-GAD65慢病毒载体构建成功;包装病毒产生的病毒液滴度为5×107TU/ml;慢病毒感染大鼠MSCs的转染率高于90%,Western blot结果显示GAD65蛋白表达比对照组明显升高。结论 GAD65重组慢病毒载体构建成功,包装得到高浓度病毒液,感染大鼠MSCs能稳定过表达GAD65蛋白,为进一步探索侧脑室注射基因化的MSCs治疗癫痫奠定实验基础。     

Identification of aspartic acid-203 in human thymidine phosphorylase as an important residue for both catalysis and non-competitive inhibition by the small molecule “crystallization chaperone” 5′-O-tritylinosine (KIN59)

Thymidine phosphorylase (TP) is a catabolic enzyme in thymidine metabolism that is frequently upregulated in many solid tumors. Elevated TP levels are associated with tumor angiogenesis, metastasis and poor prognosis. Therefore, the use of TP inhibitors might offer a promising strategy for cancer treatment. The tritylated inosine derivative 5′-O-tritylinosine (previously designated KIN59) is a non-competitive inhibitor of TP which was previously found to be instrumental for the crystallization of human TP. A combination of computational studies including normal mode analysis, automated ligand docking and molecular dynamics simulations were performed to define a plausible binding site for 5′-O-tritylinosine on human TP. A cavity in which 5′-O-tritylinosine could fit was identified in the vicinity of the Gly405-Val419 loop at a distance of about 11 Å from the substrate-binding site. In the X-ray crystal structure, this pocket is characterized by an intricate hydrogen-bonding network in which Asp203 was found to play an important role to afford the loop stabilization that is required for efficient enzyme catalysis. Site-directed mutagenesis of this amino acid residue afforded a mutant enzyme with a severely compromised catalytic efficiency (V_max/K_m of mutant enzyme ∼50-fold lower than for wild-type TP) and pronounced resistance to the inhibitory effect of 5′-O-tritylinosine. In contrast, the D203A mutant enzyme kept full sensitivity to the competitive inhibitors 6-aminothymine and 6-amino-5-bromouracil, which is in line with the kinetic properties of these inhibitors. Our findings reveal the existence of a previously unrecognized site in TP that can be targeted by small molecules to inhibit the catalytic activity of TP.     

Peptide from glutamic acid decarboxylase similar to coxsackie B virus stimulates IFN-γ mRNA expression in Th1-like lymphocytes from children with recent-onset insulin-dependent diabetes mellitus

At the clinical onset of insulin-dependent diabetes mellitus (type 1 diabetes), inflammation within the pancreatic islets of Langerhans causes insulitis. CD4+ or Th-lymphocytes will be activated after stimulation resulting in interferon-gamma (IFN-γ) production by Th1-like lymphocytes and/or interleukin-4 (IL-4) secretion from Th2-like lymphocytes. The antigens responsible for this activation are unknown, but studies have suggested glutamic acid decarboxylase (GAD) to be a possible candidate. One peptide from this enzyme (amino acid 247–279) with a similar amino acid sequence to coxsackie B virus may cause lymphocyte proliferation in diabetic patients. In this study we have shown that this peptide activates Th1-like lymphocytes which produce increased amounts of IFN-γ mRNA, but seldom mRNA for IL-4. Lymphocytes from healthy HLA-matched controls (DR3/4) did not respond with an upregulated mRNA expression for these cytokines when stimulated by the GAD-peptide (P<0.05). A low or absent expression of IFN-γ mRNA was significantly correlated to a high fasting C-peptide at 3 months' duration (P<0.05). In conclusion, we suggest that GAD₆₅ is involved in the development of type 1 diabetes and that the Th1-response may play a role in the destruction of β cells. Received: 3 October 1997 / Accepted in revised form: 24 June 1998     

Effects of tetracycline on the absorption of 65Zinc in rats

Summary The effects of tetracycline on the absorption of orally ingested ⁶⁵Zn was studied on rats by whole body counting assay. ⁶⁵Zn was given as a single dose to groups of rats, five in each, which were started on tertracycline. Tetracycline was given in daily doses of 25 mg, 50 mg, 100 mg, and 200 mg for 10 days. From the 6th day of the study, ⁶⁵Zn retention when plotted against time in a semilog plot, approximated linearity. The net absorption of ⁶⁵Zn in the various groups was determined by extrapolating to zero time the linear curve segment of individual retention curves. Except for the lowest tetracycline dosage, tetracycline significantly impaired ⁶⁵Zn absorption. The elimination rate of retained ⁶⁵Zn from the 6th day was significantly higher in the group receiving 200 mg tetracycline as compared with the control group.     

Caspase-cleaved tau accumulation in neurodegenerative diseases associated with tau and α-synuclein pathology

Alzheimers disease (AD), Picks disease (PiD), progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and dementia with Lewy bodies (DLB) are diseases associated with the accumulation of tau or -synuclein. In AD, -amyloid (A)-associated caspase activation and cleavage of tau at Asp⁴²¹ (Tau) may be an early step in neurofibrillary tangle (NFT) formation. To examine whether Tau accumulates in other diseases not characterized by extracellular A accumulation, we examined PiD, PSP, and CBD cases in comparison to those without extensive tau accumulation including frontotemporal lobar degeneration without Pick bodies (FTLD) and control cases. Additionally, we studied Tau accumulation in DLB cases associated with intracellular -synuclein. Tau was observed in all disease cases except non-PiD FTLD and controls. These results demonstrate that the accumulation of Tau may represent a common pathway associated with abnormal accumulation of intracellular tau or -synuclein and may be relatively less dependent on the extracellular accumulation of A in non-AD dementias.