The impact of antigen expression in antigen-presenting cells on humoral immune responses against the transgene product.

Treatment of genetic diseases by gene therapy is hampered by immune responses against the transgene product. Promoter choice has been shown to be an important parameter of the presence or absence of antibodies against the transgene product after gene transfer. Here, the generality of some of these observations was tested by comparing different murine strains and different transgene products. We show immunological unresponsiveness for human apolipoprotein (apo) A-I in six murine strains after transfer with E1E3E4-deleted adenoviral vectors containing hepatocyte-specific expression cassettes. However, differences in the induction of a humoral immune response against human apo A-I after gene transfer with vectors driven by the major histocompatibility complex class II Ebeta promoter and the ubiquitously active cytomegalovirus promoter were not consistent in these six murine strains. Furthermore, use of a potent hepatocyte-specific expression cassette did not prevent a humoral immune response against human plasminogen in C57BL/6 mice. In contrast, human microplasminogen transfer resulted in stable expression in the absence of an immune response against the transgene product. Taken together, the molecular design of strategies to abrogate or induce an immune response against the transgene product may be hampered by the multitude of parameters affecting the outcome, thus limiting the external validity of results.

Apolipoprotein A-I and lecithin:cholesterol acyltransferase transfer induce cholesterol unloading in complex atherosclerotic lesions.

Plasma levels of high-density lipoprotein (HDL) cholesterol and its major apolipoprotein (apo), apo A-I, are inversely correlated with the incidence of ischemic cardiovascular diseases. Reverse cholesterol transport is likely the main mechanism underlying the atheroprotective effects of HDL. Here, we investigated whether increased HDL cholesterol following hepatocyte-directed adenoviral rabbit apo A-I (AdrA-I) or rabbit lecithin-cholesterol acyltransferase (LCAT) (AdrLCAT) transfer may induce cholesterol unloading in complex atherosclerotic lesions in heterozygous low-density lipoprotein receptor-deficient rabbits fed a 0.15% cholesterol diet for 420 days before and for 120 days after transfer. HDL cholesterol levels increased 2.0-fold (P<0.001) and 1.9-fold (P<0.001) in the 120 days after transfer with AdrA-I and AdrLCAT, respectively, compared to levels just before transfer whereas non-HDL cholesterol remained unchanged. Increased HDL cholesterol following AdrA-I and AdrLCAT transfer resulted in a 31% (P<0.05) reduction of the intima/media ratio in comparison with the control progression group. Compared to the baseline group killed after 420 days of cholesterol diet, AdrA-I and AdrLCAT transfer reduced the percentage of Oil Red O area 1.6-fold (P<0.001) and 1.4-fold (P<0.001), respectively. In conclusion, increased HDL cholesterol after AdrA-I and AdrLCAT transfer inhibits progression of atherosclerosis and induces cholesterol unloading in complex lesions in rabbits.

Direct comparison of hepatocyte-specific expression cassettes following adenoviral and nonviral hydrodynamic gene transfer.

Hepatocytes are a key target for treatment of inborn errors of metabolism, dyslipidemia and coagulation disorders. The development of potent expression cassettes is a critical target to improve the therapeutic index of gene transfer vectors. Here we evaluated 22 hepatocyte-specific expression cassettes containing a human apo A-I transgene following hydrodynamic transfer of plasmids or adenoviral transfer with E1E3E4-deleted vectors in C57BL/6 mice. The DC172 promoter consisting of a 890 bp human alpha(1)-antitrypsin promoter and two copies of the 160 bp alpha(1)-microglobulin enhancer results in superior expression levels compared to constructs containing the 1.5 kb human alpha(1)-antitrypsin promoter, the 790 bp synthetic liver-specific promoter or the DC190 promoter containing a 520 bp human albumin promoter and two copies of the 99 bp prothrombin enhancer. The most potent expression cassette consists of the DC172 promoter upstream of the transgene and two copies of the hepatic control region-1. Minicircles containing this expression cassette induce persistent physiological human apo A-I or human factor IX levels after hydrodynamic transfer. In conclusion, in this comparative study of 22 hepatocyte-specific expression cassettes, the DC172 promoter in combination with two copies of the hepatic control region-1 induces the highest expression levels following hydrodynamic and adenoviral transfer.

PINK1-induced mitophagy promotes neuroprotection in Huntington's disease.

Huntington's disease (HD) is a fatal neurodegenerative disorder caused by aberrant expansion of CAG repeat in the huntingtin gene. Mutant Huntingtin (mHtt) alters multiple cellular processes, leading to neuronal dysfunction and death. Among those alterations, impaired mitochondrial metabolism seems to have a major role in HD pathogenesis. In this study, we used the Drosophila model system to further investigate the role of mitochondrial damages in HD. We first analyzed the impact of mHtt on mitochondrial morphology, and surprisingly, we revealed the formation of abnormal ring-shaped mitochondria in photoreceptor neurons. Because such mitochondrial spheroids were previously detected in cells where mitophagy is blocked, we analyzed the effect of PTEN-induced putative kinase 1 (PINK1), which controls Parkin-mediated mitophagy. Consistently, we found that PINK1 overexpression alleviated mitochondrial spheroid formation in HD flies. More importantly, PINK1 ameliorated ATP levels, neuronal integrity and adult fly survival, demonstrating that PINK1 counteracts the neurotoxicity of mHtt. This neuroprotection was Parkin-dependent and required mitochondrial outer membrane proteins, mitofusin and the voltage-dependent anion channel. Consistent with our observations in flies, we demonstrated that the removal of defective mitochondria was impaired in HD striatal cells derived from HdhQ111 knock-in mice, and that overexpressing PINK1 in these cells partially restored mitophagy. The presence of mHtt did not affect Parkin-mediated mitochondrial ubiquitination but decreased the targeting of mitochondria to autophagosomes. Altogether, our findings suggest that mitophagy is altered in the presence of mHtt and that increasing PINK1/Parkin mitochondrial quality control pathway may improve mitochondrial integrity and neuroprotection in HD.

Continuous administration of the glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylate produces striatal lesion.

This study examined the effects of chronic intrastriatal infusion of L-trans-pyrrolidine-2,4-dicarboxylate (PDC), a selective competitive inhibitor of high affinity glutamate transport systems, via osmotic minipumps in rats. Injection of PDC at the rate of 25 nmol/h for 14 days caused striatal lesion. Histological evaluation on frontal striatal sections showed that the lesion was circumscribed to a circular area showing a dramatic neuronal loss accompanied by gliosis and representing 30% of the whole striatal surface at the level of the injection site. A total loss of neurons expressing glutamate decarboxylase (GAD67), enkephalin or substance P mRNA was observed on a similar circular area, suggesting degeneration of the two populations of striatal efferent neurons. In the whole striatum outside the region devoided of hybridization signal, a selective 27% decrease in enkephalin mRNA expression occurred, suggesting a higher sensitivity of enkephalin neurons versus substance P neurons to glutamate uptake-mediated alterations. Injection of PDC at the rate of 25 nmol/h for 3 days produced striatal lesion of similar extent. In contrast, PDC at the rate of 5 nmol/h did not produce neuronal damage when administered over 14 days. This study provides new in vivo evidence that defective glutamate transport is one of the critical conditions that may give rise to toxicity of an endogenous transmitter system in the striatum, and may underlie neuronal death in neurodegenerative diseases.

Direct analysis of phthalate ester biomarkers in urine without preconcentration: method validation and monitoring.

Phthalates, which are ubiquitous in the environment, are readily metabolized in human bodies to their respective monoesters. These phthalate monoesters are non-persistent with short half-lives, which make them the ideal biomarkers of human exposure to phthalates. In this study a direct analysis method without preconcentration was developed and validated for the following phthalate ester metabolites in urine: mono-(2-ethylhexyl) phthalate, mono-(2-ethyl-5-hydroxyhexyl) phthalate, mono-(2-ethyl-5-oxohexyl)phthalate, monobenzyl phthalate, mono-isobutylphthalate, mono-n-butyl phthalate and monoethyl phthalate. The recovery of the phthalate ester metabolites varied between 97% and 104%. The intraday precision for the replicate analysis (n=10) of a urine sample did not exceed 5% for most of the compounds. The coefficient of variance amounted to 2-3%. The limit of quantification was set equal to 0.5µg/L for the majority of the compounds. A comparison between the direct analysis method and a foregoing solid phase extraction (SPE) of the urine sample was made. Finally, the applicability of the direct analysis method was tested in three interlaboratory comparisons.

Species differences in transgene DNA uptake in hepatocytes after adenoviral transfer correlate with the size of endothelial fenestrae.

Sinusoidal fenestrae may restrict the transport of gene transfer vectors according to their size. Using Vitrobot technology and cryo-electron microscopy, we show that the diameter of human adenoviral serotype 5 vectors is 93 nm with protruding fibers of 30 nm. Thus, a diameter of fenestrae of 150 nm or more is likely to be sufficient for passage of vectors from the sinusoidal lumen to the space of Disse and subsequent uptake of vectors in hepatocytes. The average diameter of fenestrae in New Zealand White rabbits (103+/-1.3 nm) was 1.4-fold (P<0.0001) lower than in C57BL/6 mice (141+/-5.4 nm). The percentage of sinusoidal fenestrae with a diameter larger than 150 nm was 10-fold (P<0.01) lower in rabbits (3.2+/-0.24%) than in C57BL/6 mice (32+/-5%), and this resulted in 8.8-fold (P=0.01) lower transgene DNA levels in hepatocytes in rabbits after adenoviral transfer. Injection of N-acetylcysteine combined with transient liver ischemia preceding intraportal transfer in rabbits increased the percentage of sinusoidal fenestrae above 150 nm 2.0-fold (P<0.001) and increased transgene DNA levels in hepatocytes 6.6-fold (P<0.05). In conclusion, species differences in transgene DNA uptake in hepatocytes after adenoviral transfer correlate with the diameter of fenestrae.

Interethnic marriage: bringing in the context through multilevel modelling.

PIP: "This article deals with the underlying causes of interethnic marriages of Turks and Moroccans living in Belgium.... Higher odds [of interethnic marriage] are generally found for the second generation and at higher levels of age at marriage and educational attainment. Interethnic marriage is further promoted by a small size of the ethnic group, by low ethnic heterogeneity and by low correlation between the ethnic and the socio-economic dimension. Interethnic marriages are generally more prevalent in districts where the common language is French and where the majority of immigrants originate from urban regions in the country of origin." (EXCERPT)^ieng

Mortality following conjugal bereavement, Belgium 1991-96: the unexpected effect of education.

This paper examines excess mortality following spousal bereavement by time since bereavement, sex, age, and education. The main hypothesis challenged is that higher education buffers the harmful effects of spousal loss. Using a log-rate model, death-rate ratios (widowed/married) are estimated for 49,849 and 126,746 Belgian widowers and widows and an equal number of non-bereaved controls matched to the bereaved on their socio-demographic characteristics. The hypothesis that the more educated suffer less excess mortality is not supported. Although higher educational levels are associated with lower mortality in general, they do not alleviate the effects of bereavement. On the contrary, in the period immediately following spousal loss, the more highly educated seem to have more, rather than less, excess mortality. Three possible arguments are suggested to account for this: education-related differences in the partner-relationship, structural differences in the availability of appropriate social support, and cultural differences in potential support networks.

Differential effects of corticostriatal and thalamostriatal deafferentation on expression of the glutamate transporter GLT1 in the rat striatum.

This study compared the effects of the disruption of the two main presumably glutamatergic striatal inputs, the corticostriatal and thalamostriatal pathways, on GLT1 expression in the rat striatum, using in situ hybridization and immunohistochemistry. Unilateral ibotenate-induced thalamic lesion produced no significant changes in striatal GLT1 mRNA labeling and immunostaining as assessed at 5 and 12 days postlesion. In contrast, significant increases in both parameters were measured after bilateral cortical lesion by superficial thermocoagulation. GLT1 mRNA levels increased predominantly in the dorsolateral part of the striatum; there, the increases were significant at 5 (+84%), 12 (+101%), and 21 (+45%) but not at 35 days postlesion. GLT1 immunostaining increased significantly and homogeneously by 17-26% at 12 and 21 days postlesion. The increase in GLT1 expression at 12 days postlesion was further confirmed by western blot analysis; in contrast, a 36% decrease in glutamate uptake activity was measured at the same time point. These data indicate that striatal GLT1 expression depends on corticostriatal but not thalamostriatal innervation. Comparison of our results with previous data showing that cortical lesion by aspiration downregulates striatal GLT1 expression further suggests that differential changes in GLT1 expression, and thus presumably in glial cell function, may occur in the target striatum depending on the way the cortical neurons degenerate.

Characterization of striatal lesions produced by glutamate uptake alteration: cell death, reactive gliosis, and changes in GLT1 and GADD45 mRNA expression.

This study investigated the time course of the striatal lesions produced by continuous local injection of the glutamate uptake inhibitor, L-trans-pyrrolidine-2,4-dicarboxylate (PDC) at the rate of 25 nmol/h in rats. The extent of the neurodegeneration area (defined as the lesion area) did not significantly vary with the duration of the PDC treatment between 3 and 14 days, but was markedly reduced 3 months after cessation of the 14-day treatment, probably reflecting striatal atrophy. After the 3-day treatment, the lesion zone showed calcium precipitates and marked microglial reaction contrasting with the reduction of astroglial labeling and loss of the glutamate transporter GLT1 mRNA expression; however reactive astrocytes were observed around the lesion. After the 14-day treatment, the lesion zone presented reactive astrocytes and microglia without calcification, and a partial recovery of GLT1 mRNA expression. Interestingly, the growth arrest DNA damage-inducible GADD45 mRNA expression was induced around the lesion after 3 days but inside the lesion after 14 days of treatment. Three months after the 14-day treatment, the astroglial reactivity persisted within the lesion whereas most of the other markers examined tended to normalize. These data suggest that defective glutamate transport induces primary death of neurons and dysfunction of astrocytes. They strongly implicate reactive astrocytes with GLT1 and GADD45 transcripts in preventing secondary neuronal death.

Nigrostriatal denervation does not affect glutamate transporter mRNA expression but subsequent levodopa treatment selectively increases GLT1 mRNA and protein expression in the rat striatum.

There is growing evidence that the loss of the nigrostriatal dopaminergic neurones induces an overactivity of the corticostriatal glutamatergic pathway which seems to be central to the physiopathology of parkinsonism. Moreover, glutamatergic mechanisms involving NMDA receptors have been shown to interfere with the therapeutical action of levodopa. Given the key role played by uptake processes in glutamate neurotransmission, this study examined the effects of nigrostriatal deafferentation and of levodopa treatment on the striatal expression of the glutamate transporters GLT1, GLAST and EAAC1 in the rat. No significant changes in striatal mRNA levels of these transporters were detected after either levodopa treatment (100 mg/kg; i.p., twice a day for 21 days) or unilateral lesion of the nigrostriatal pathway by intranigral 6-hydroxydopamine injection. In contrast, animals with the lesion subsequently treated with levodopa showed a selective increase (36%) in GLT1 mRNA levels in the denervated striatum versus controls. These animals also showed increased GLT1 protein expression, as assessed by immunostaining and western blotting. These data provide the first evidence that levodopa therapy may interfere with striatal glutamate transmission through change in expression of the primarily glial glutamate transporter GLT1. We further suggest that levodopa-induced GLT1 overexpression may represent a compensatory mechanism preventing neurotoxic accumulation of endogenous glutamate.

Serotonin depletion produces long lasting increase in striatal glutamatergic transmission.

The ability of serotonin (5-HT) to influence striatal glutamatergic transmission was examined by determining changes over time in glutamate extracellular levels, transporter expression and synaptosomal uptake in rats with lesion of serotonergic neurones. By 8 days after intraraphe injections of 5,7-dihydroxytryptamine, producing 80% decreases in striatal tissue 5-HT levels, no changes were observed in the glutamatergic transmission. When 5-HT depletion was almost complete (21 days post-lesion), high affinity glutamate uptake in striatal synaptosomal preparations was significantly increased (156% of control), although no changes in striatal GLT1, GLAST and EAAC1 mRNAs, and GLT1 protein were detected by in situ hybridization and immunohistochemistry. Meanwhile, the serotonin lesion produced large increases in basal extracellular levels of glutamate and glutamine (364% and 259%, respectively) determined in awake rats by in vivo microdialysis, whereas no change was observed in dopamine levels as compared with control rats. High potassium depolarization as well as L-trans-pyrrolidine-2,4-dicarboxylate, also induced larger increases in extracellular levels of glutamate in lesioned rats than in controls. Finally, similar changes in glutamate transmission were observed by 3 months post-lesion. These results suggest that 5-HT has a long lasting and tonic inhibitory influence on the striatal glutamatergic input, without affecting the basal dopaminergic transmission.

Impaired glutamate uptake in the R6 Huntington's disease transgenic mice.

Huntington's disease (HD) is a late-onset neurodegenerative disease for which the mutation is CAG/polyglutamine repeat expansion. The R6 mouse lines expressing the HD mutation develop a movement disorder that is preceded by the formation of neuronal polyglutamine aggregates. The phenotype is likely caused by a widespread neuronal dysfunction, whereas neuronal cell death occurs late and is very selective. We show that a decreased mRNA level of the major astroglial glutamate transporter (GLT1) in the striatum and cortex of these mice is accompanied by a concomitant decrease in glutamate uptake. In contrast, the expression of the glutamate transporters, GLAST and EAAC1, remain unchanged. The mRNA level of the astroglial enzyme glutamine synthetase is also decreased. These changes in expression occur prior to any evidence of neurodegeneration and suggest that a defect in astrocytic glutamate uptake may contribute to the phenotype and neuronal cell death in HD.

The size of sinusoidal fenestrae is a critical determinant of hepatocyte transduction after adenoviral gene transfer.

The hepatotropism and intrahepatic distribution of adenoviral vectors may be species dependent. Hepatocyte transduction was evaluated in three rabbit strains after transfer with E1E3E4-deleted adenoviral vectors containing a hepatocyte specific alpha1-antitrypsin promoter-driven expression cassette (AdAT4). Intravenous administration of 4 x 10(12) particles/kg of AdAT4 induced human apo A-I levels above 40 mg/dl in Dutch Belt, but below 1 mg/dl in New Zealand White and Fauve de Bourgogne rabbits. Diameters of sinusoidal fenestrae were significantly (P=0.0014) larger in Dutch Belt (124+/-3.4 nm) than in New Zealand White (108+/-1.3 nm) and Fauve de Bourgogne (105+/-2.6 nm) rabbits, suggesting that a smaller size constitutes a barrier for hepatocyte transduction. Indeed, intraportal transfer preceded by intraportal injection of sodium decanoate, which increases the diameter of sinusoidal fenestrae to 123+/-3.4 nm (P<0.01) in New Zealand White rabbits, increased human apo A-I levels 32- and 120-fold in New Zealand White and Fauve de Bourgogne rabbits, respectively, but did not affect expression in Dutch Belt rabbits. In conclusion, size of sinusoidal fenestrae appears to be a critical determinant of hepatocyte transduction after adenoviral transfer.