Mireille Drouet

Paraoxonase 1 192/55 Gene Polymorphisms in Alzheimer's Disease

Abstract: An esterase, paraoxonase 1 (PON1), protects against organophosphate neurotoxicity and decreases lipoprotein oxidation. Two polymorphisms of PON1 [192 (R or Q) and 55 (M or L)] exist and are associated with coronary artery disease. We have previously shown that serum PON1 activity (PON1a) is lower in vascular dementia (VaD) than in Alzheimers disease (AD), suggesting that PON1a may distinguish VaD from AD. As PON1 polymorphism modifies PON1a, we determined 192 and 55 PON1 polymorphisms by sequence‐specific primer PCR in 64 healthy subjects (HS; mean age: 79.5 ± 6.3 years; 38 women) and in 72 patients (mean age: 80.2 ± 6.8 years; 51 women) undergoing cognitive evaluations. According to DSM‐IV/NINCDS/ADRDA/NINDS/AIREN criteria, 45 patients (mean age: 80.0 ± 7.2 years, 34 women) had AD and 27 patients (mean age: 79.8 ± 6.6 years, 16 women) had VaD. We also measured serum PON1a by spectrophotometry. No significant differences in phenotype distributions among the three study groups were detected by χ2 test. Among the variables, age, sex, and phenotypes 192 and 55, logistic regression selected only polymorphism 192, but not 55, as a discriminating factor between AD and VaD (p < 0.05). Substitution of serum PON1a for genotype yielded a similar result. PON1 polymorphism 192 appears to be a reliable marker to distinguish patients with AD from patients with VaD and from healthy subjects. Changes in 192 polymorphism distributions in AD and in VaD may at least partially explain the significant difference in PON1a in these two types of dementia.

TCF7L2 Polymorphism Associates with New-Onset Diabetes after Transplantation

New-onset diabetes after transplantation (NODAT) is a serious and frequent complication in transplant recipients. Whether NODAT shares the same susceptibility genes as type 2 diabetes is unknown. In this multicenter study, we genotyped 1076 white patients without diabetes at transplantation for 11 polymorphisms that associate with type 2 diabetes. We defined NODAT as a fasting plasma glucose > or =126 mg/dl on at least two occasions or de novo hypoglycemic therapy. We compared clinical and genetic factors between patients who developed NODAT within 6 mo of transplantation (n = 118; incidence 11%) and patients without diabetes (n = 958). In multivariate analysis, NODAT significantly associated with the following characteristics: TCF7L2 polymorphism (odds ratio [OR] 1.60 per each T allele; P = 0.002), age (OR 1.03 per year; P < 0.001), body mass index at transplantation (OR 1.09 per unit; P < 0.001), tacrolimus use (OR 2.26; P < 0.001), and the occurrence of a corticoid-treated acute rejection episode (OR 2.78; P < 0.001). In summary, our data show that the TCF7L2 rs7903146 polymorphism, a known risk factor for type 2 diabetes in the general population, also associates with NODAT.

Age-associated changes in mitochondrial parameters on peripheral human lymphocytes.

Among theories of aging, mitochondria are believed to be involved in senescence. Alterations of respiratory chain function and accumulation of various mitochondrial DNA mutations have been reported in mammalian postmitotic tissues. Because mitochondria have a central role in apoptosis and in adenosine triphosphate production, alteration of mitochondria function could contribute to immune senescence. We searched for alterations of mitochondrial parameters in peripheral lymphocytes with aging. Comparisons of respiratory chain activities of complex II+III, III, and IV were carried out in two populations of healthy volunteers with average ages of 35.3 +/- 6.7 years and 80.8 +/- 8.7 years. No difference was observed in complex IV activity between each group, whereas a significant decrease of complex II+III and a nonsignificant decrease of complex III activity were observed with aging. Alterations in mitochondrial functions can result from mutations in mitochondrial DNA (mtDNA), the most common being the 4977-bp deletion (mtDNA(-4977)). In either group we observed many deletions of mtDNA on peripheral blood lymphocytes by large-fragment polymerase chain reaction. This result suggests that alterations of respiratory chain activities observed with aging in lymphocytes could be the result of nuclear DNA dysfunction, with consequences on immune function (reduced responsiveness to antigen). Its possible implication on the recent observation of increased apoptosis of CD45RA+ RO- T cells with aging is discussed.

Risk of diarrhoea in a long-term cohort of renal transplant patients given mycophenolate mofetil: the significant role of the UGT1A8*2 variant allele

AIM In renal transplant patients given mycophenolate mofetil (MMF), we investigated the relationship between the digestive adverse events and polymorphisms in the UGT genes involved in mycophenolic acid (MPA) intestinal metabolism and biliary excretion of its phase II metabolites. METHODS Clinical data and DNA from 256 patients transplanted between 1996 and 2006 and given MMF with cyclosporin (CsA, n = 185), tacrolimus (TAC, n = 49) or sirolimus (SIR, n = 22), were retrospectively analysed. The relationships between diarrhoea and polymorphisms in UGT1A8 (2; 518C>G, 3; 830G>A), UGT1A7 (622C>T), UGT1A9 (-275T>A), UGT2B7 (-840G>A) and ABCC2 (-24C>T, 3972C>T) or the co-administered immunosuppressant were investigated using the Cox proportional hazard model. RESULTS Multivariate analysis showed that patients on TAC or SIR had a 2.8 higher risk of diarrhoea than patients on CsA (HR = 2.809; 95%CI (1.730, 4.545); P < 0.0001) and that non-carriers of the UGT1A8 2 allele (CC518 genotype) had a higher risk of diarrhoea than carriers (C518G and 518GG genotypes) (HR = 1.876; 95%CI (1.109, 3.175); P = 0.0192). When patients were divided according to the immunosuppressive co-treatment, a significant effect of UGT1A8 2 was found in those co-treated with CsA (HR = 2.414; 95%CI (1.089, 5.354); P = 0.0301) but not TAC or SIR (P = 0.4331). CONCLUSION These results suggest that a possible inhibition of biliary excretion of MPA metabolites by CsA and a decreased intestinal production of these metabolites in UGT1A8 2 carriers may be protective factors against MMF-induced diarrhoea.

Treatment of ocular cicatricial pemphigoid with the tumour necrosis factor alpha antagonist etanercept.

Sir, Cicatricial pemphigoid (CP) is a rare autoimmune subepithelial blistering disease that predominantly affects the mucous membranes with scarring (1). The disease is characterized by the involvement of muco-cutaneous sites, among them ocular invo-lvement, which can lead to blindness. Mild forms of the disease may be controlled by anti-inflammatory drugs, such as dapsone, whereas severe forms, and particularly ocular involvement, usually require the use of immunosuppressive therapies (2). As tumour necrosis factor (TNF)-α plays a role in the fibrosing process, its targeting strategies are promising in the management of ocular CP. Here we report a case of ocular CP treated successfully with the TNF-α antagonist etanercept.

Age-related alterations of somatic hypermutation and CDR3 lengths in human Vκ4-expressing B lymphocytes

The lower avidity and/or affinity of antibodies generated by an aged immune system could be attributed to two major changes in the antibody repertoire: a shift in germline gene usage and a decrease in the rate of immunoglobulin hypermutation. In an attempt to identify the mechanisms involved in the observed humoral immune deficiency in the elderly, we studied whether differences in the somatic diversity of a particular Vκ region occurred with ageing. By using the polymerase chain reaction and sequencing, we analysed and compared Vκ4–Jκ rearrangements isolated from young (mean age 21 years) and aged (mean age 83 years) healthy adults. Mutations in the Vκ4 gene compared with the germline sequence were determined as well as the length and structure of the CDR3 sequence. We analysed in detail various mechanisms contributing to CDR3 and Vκ variability in rearrangements involving the Vκ4 gene. Our data revealed that, despite strong individual variations, significantly lower levels of somatic mutation were found in the aged group, both for complementarity‐determining regions (CDRs) and framework regions (FRs) encoding Vκ4 sequences. This decrease mostly affected mutations responsible for replacements and thus resulted in a lowered somatic diversification of the encoded Vκ4 proteins in aged individuals. Moreover, comparison of the CDR3 regions of the Vκ4–Cκ cDNA revealed changes in light‐chain junctional diversity that correlated with age. Altogether these data suggest an impaired light‐chain somatic diversity in connection with human senescence.

Modification of HLA expression on peripheral lymphocytes and monocytes during ageing

Immunosenescence involves modifications of humoral and cellular immunity. Here we report the analysis of human leukocyte antigen (HLA) expression on T lymphocytes, B lymphocytes and monocytes of 58 healthy subjects aged 23-95 years old. Using a double staining immunofluorescence and flow cytometry analysis, we have determined the percentages of cells expressing HLA class-I and HLA-DR antigens. The number of antigenic sites expressed per cell were evaluated for HLA-ABCw, HLA-A, HLA-B, HLA-DR locus with a flow cytometry quantification technique. With advancing age, we observed: (i) a significant decrease of the percentage of T cells and B cells expressing HLA-A products; (ii) a decrease of the number of HLA class-I antigenic sites expressed per cell on the three populations tested, predominantly on B cells and in a locus-dependent fashion; (iii) a decrease of the number of HLA-DR molecules expressed per T cell, although the percentage of T cells expressing DR products was increased; (iv) a significant diminution of the percentage of B cells expressing HLA-DR molecules, without changes of the number of HLA-DR antigenic sites per cells. These changes in HLA expression with increasing age could contribute to the decreased level of immunologic responsiveness observed with ageing and contribute to the modification of antigen recognition.

HLA-A and HLA-B transcription decrease with ageing in peripheral blood leucocytes

Immunosenescence involves modifications of humoral and cellular immunity. In a previous study, we have shown a locus‐dependent reduction of HLA class‐I cell surface expression on peripheral lymphocytes and monocytes with advancing age. Here we report the quantitative analysis of HLA‐A and ‐B transcripts from PBL of 54 healthy subjects aged 21–90 years. Using a competitive RT‐PCR method, we observed a significant decrease of HLA‐A (P < 0·0001) and ‐B (P = 0·0025) mRNA contents with increasing age. Secondly, to investigate this locus‐dependent alteration of HLA class‐I transcription, we performed EMSA using nuclear extracts from PBL of five young (24–31‐year‐old) and 5 elderly (58–69 years old) donors with locus A and B sequences of the Enh‐A as probes. No qualitative variation of EMSA profiles appeared between the two groups of donors with 6 and 4 bandshift for the locus A and B, respectively. Quantitatively, we observed a significant increase of B4 intensity in the elderly group compared to the young group (P < 0·05). These results suggest that the variation of DNA binding protein could contribute to the lower transcription of HLA‐A and ‐B with ageing. These alterations of HLA class‐I expression at the transcriptional level could lead to the unresponsiveness of CD8 T cells due to default of antigen presentation with ageing.

PAI-1 donor polymorphism influences long-term kidney graft survival

BACKGROUND The type 1 plasminogen activator inhibitor (PAI-1) is involved in the development of fibrosis, and its intrarenal expression is increased in interstitial fibrosis and tubular atrophy (IFTA). Moreover, a 4G/5G polymorphism of the PAI-1 gene has been described associating 4G haplotype with higher PAI-1 plasma activity. We investigated the relationship between the donor and recipient PAI-1 polymorphism and kidney graft survival. METHODS The PAI-1 genotype was determined for both the 304 donors and the 337 corresponding recipients. In recipients, PAI-1 antigen levels were also determined. We compared 4G/4G donors versus donors with other genotypes. RESULTS Donor or recipient genotype did not influence the PAI-1 plasma level in recipients. Actuarial kidney graft survival was significantly reduced in the 4G/4G donor group (107 months versus 147.5 months, P = 0.013), while recipient PAI-1 genotype did not show any influence on graft survival. Moreover, graft loss due to IFTA proved significantly higher in the 4G/4G donor group (13% versus 6%, P = 0.03). Multivariate analysis showed that the significant independent variables associated with graft loss were the donor 4G/4G genotype, acute clinical rejection and donor age. CONCLUSION Our study suggests that donor PAI-1 polymorphism influences kidney graft survival and that the donor 4G/4G genotype is an independent risk factor for graft loss. Prospective studies are needed to confirm these results.

An elevation in the concentration of HLA class I molecules in human blood due to ageing

The quantification of plasmatic HLA class-I molecules (sHLA-I) was realized by a sandwich ELISA using a monomorphic mAb (W6/32). sHLA-I concentration is significantly increased in the elderly group (>50 years, 0.429+/-0.301 microg ml(-1)) as compared to the young group (<50 years, 0.126+/-0.085 microg ml(-1)). The variation of sHLA-I content could contribute to the unresponsiveness of ageing immune system.