Maria Celeste Lechner

Transcriptional regulation of the human CYP46A1 brain-specific expression by Sp transcription factors

Brain defective cholesterol homeostasis has been associated with neurologic diseases, such as Alzheimer’s and Huntington’s disease. The elimination of cholesterol from the brain involves its conversion into 24(S)‐hydroxycholesterol by CYP46A1, and the efflux of this oxysterol across the blood–brain barrier. Herein, we identified the regulatory elements and factors involved the human CYP46A1 expression. Functional 5′deletion analysis mapped a region spanning from nucleotides ‐236/‐64 that is indispensable for basal expression of this TATA‐less gene. Treatment of SH‐SY5Y cells with mithramycin A resulted in a significant reduction of promoter activity, suggesting a role of Sp family of transcription factors in CYP46A1 regulation. Combination of Sp1, Sp3, and Sp4 over‐expression studies in Drosophila SL‐2 cells, and systematic promoter mutagenesis identified Sp3 and Sp4 binding to four GC‐boxes as required and sufficient for high levels of promoter activity. Moreover, Sp3 and Sp4 were demonstrated to be the major components of the protein‐DNA complexes observed in primary rat cortical extracts. Our results suggest that the cell‐type specific expression of Sp transcription factors – substitution of Sp1 by Sp4 in neurons – is responsible for the basal expression of the CYP46A1 gene. This study delineates for the first time the mechanisms underlying the human CYP46A1 transcription and thereby elucidates potential pathways underlying cholesterol homeostasis in the brain.

Association of A313 G polymorphism (GSTP1*B) in the glutathione-S-transferase P1 gene with sporadic Parkinson's disease.

Genetic predisposition, environmental toxins and aging contribute to Parkinsons disease (PD) multifactorial etiology. Weak environmental neurotoxic factors may accumulate over time increasing the disease risk in genetically predisposed subjects. Polymorphic genes encoding drug‐metabolizing‐enzymes (DMEs) are considered to account for PD susceptibility by determining individual toxic response variability. In this work, the allelic distributions and genotype associations of three major brain‐expressed DMEs were characterized, in sporadic PD cases and controls. No significant association was found between CYP2D6 genotype and PD, but subjects with extensive metabolizer (EM) CYP2D6 phenotype, and the variant GSTP1*B genotype were at significantly higher PD risk than the corresponding poor or intermediary metabolizers (CYP2D6 poor metabolizer phenotype+intermediary metabolizers). A significant association was observed between the GSTP1*B allele and zygosity with PD (GSTP1*A/*B– 51.58%/34.37%, odds ratio (OR) = 2.29; 95% confidence interval (95% CI) = 1.25–4.18; *B/*B– 6.32%/1.05%, OR = 10.67; 95% CI = 1.19–94.79). This association was particularly strong in the elder patients group (≥69 year) who showed double PD risk for GSTP1*B heterozygous, whilst GSTP1*B/*B homozygous were exclusively found amongst patients. An interaction between GSTM1 and GSTP1 was observed in this late onset PD group. The present results suggest that native GSTP1 encoding the fully active transferase variant should play a relevant role in dopaminergic neuroprotection.

Association of metabolic gene polymorphisms with tobacco consumption in healthy controls.

Polymorphisms in genes that encode for metabolic enzymes have been associated with variations in enzyme activity between individuals. Such variations could be associated with differences in individual exposure to carcinogens that are metabolized by these genes. In this study, we examine the association between polymorphisms in several metabolic genes and the consumption of tobacco in a large sample of healthy individuals. The database of the International Collaborative Study on Genetic Susceptibility to Environmental Carcinogens was used. All the individuals who were controls from the case‐control studies included in the data set with information on smoking habits and on genetic polymorphisms were selected (n = 20,938). Sufficient information was available on the following genes that are involved in the metabolism of tobacco smoke constituents: CYP1A1, GSTM1, GSTT1, NAT2 and GSTP1. None of the tested genes was clearly associated with smoking behavior. Information on smoking dose, available for a subset of subjects, showed no effect of metabolic gene polymorphisms on the amount of smoking. No association between polymorphisms in the genes studied and tobacco consumption was observed; therefore, no effect of these genes on smoking behavior should be expected.

GSTpi expression in MPTP-induced dopaminergic neurodegeneration of C57BL/6 mouse midbrain and striatum.

MPTP-induced dopaminergic neurotoxicity involves major biochemical processes such as oxidative stress and impaired energy metabolism, leading to a significant reduction in the number of nigrostriatal dopaminergic neurons. Glutathione S-transferase pi (GSTpi) is a phase II detoxifying enzyme that provides protection of cells from injury by toxic chemicals and products of oxidative stress. In humans, polymorphisms of GSTP1 affect substrate selectivity and stability increasing the susceptibility to parkinsonism-inducing effects of environmental toxins. Given the ability of MPTP to increase the levels of reactive oxygen species and the link between altered redox potential and the expression and activity of GSTpi, we investigated the effect of MPTP on GSTpi cellular concentration in an in vivo model of Parkinson’s disease. The present study demonstrates that GSTpi is actively expressed in both substantia nigra pars compacta and striatum of C57BL/6 mice brain, mostly in oligodendrocytes and astrocytes. After systemic administration of MPTP, GSTpi expression is significantly increased in glial cells in the vicinity of dopaminergic neurons cell bodies and fibers. The results suggest that GSTpi expression may be part of the mechanism underlying the ability of glial cells to elicit protection against the mechanisms involved in MPTP-induced neuronal death.

Cerebral hemorrhage and apoE

Abstract The ɛ4 allele of apolipoprotein E (apoE) is found more commonly among patients with Alzheimer’s disease (AD) than in the normal population. ApoE is associated with brain amyloid, a component of cerebral amyloid angiopathy (CAA), which is both a pathological feature of AD and a frequent cause of lobar intracerebral hemorrhage (ICH). We hypothesized that the frequency of ɛ4 allele is higher in patients with CAA-related ICH than in hypertensive ICH and in the normal population. To test this hypothesis we compared the frequency of apoE alleles in four populations: 24 patients with lobar ICH, 24 matched patients with hypertensive ICH, 24 matched normal controls, and 173 population controls. Although there was a tendency to a higher frequency of apoE ɛ4 in lobar ICH patients, we found no significant differences in the frequency of this allele between the four studied populations. In addition we did not confirm the finding of some authors of a higher frequency of apoE ɛ2 in patients with lobar ICH than in the normal population. Previous studies on the subject are discussed. The relationship between apoE polymorphism and lobar CAA-related ICH remains to be clearly defined.

Apolipoprotein E genotype of a Portuguese control population and Alzheimer's disease patients

The present work first describes the frequency of APOE alleles and genotypes in Portuguese populations in relation to AD pathology. We genotyped a group of late onset sporadic AD cases, their pairwise controls and a larger group of randomly selected individuals, to assess the distribution pattern of APOE alleles in the Portuguese population. APOE ɛ4 relative frequency may significantly vary among different populations—a fact which should be taken into consideration for the correct evaluation of the cossegregation of this allele with AD pathology. We observed a frequency of 0.087 ± 0.029 of the APOE ɛ4 and 0.043 ± 0.021 of the APOE ɛ2 allele in the Portuguese random population which as expected showed a marked prevalence of the APOE ɛ3 form (0.870 ± 0.035). In the AD patients the APOE ɛ4 allele frequency was significantly higher (0.360 ± 0.081) than in the controls (χ2 = 31.000, p < 0.00001, df = 2). Consistently APOE ɛ3 allele frequency (0.640 ± 0.081) was significantly lower than in the controls while APOE ɛ2 was absent in the studied AD population. Taken together our results demonstrate that the Portuguese population is characterized by a relatively low frequency of the APOE ɛ4 allele, in good agreement with previous observations of a gradient of ɛ4 allele frequency in Europe, decreasing from North to South. Several lines of evidence point at APOEɛe4 allele as a major genetic susceptibility factor in AD. The APOE ɛ4 allele was significantly higher [odds ratio (OR) = 5.93, 95% CI 3.55–9.91] in the Portuguese AD patients than in the random non‐demented population. The genotype analysis of the Portuguese AD patients here described reveals a marked, increased frequency of ɛ4 homo‐ and heterozygous individuals consistent with an APOE ɛ4 zigosity effect as a further genetic trait predisposing to AD development.