Molecular Psychiatry (2002) 7, 110–112 2002 Nature Publishing Group All rights reserved 1359-4184/02 $15.00 www.nature.com/mp ORIGINAL RESEARCH ARTICLE Codon 311 (Cys → Ser) polymorphism of paraoxonase-2 gene is associated with apolipoprotein E4 allele in both Alzheimer’s and vascular dementias Z Janka1, A Juha´sz1,A´ Rimano´czy1, K Boda2,JMa´rki-Zay3 and J Ka´lma´n1 1Department of Psychiatry; 2Medical Informatics, Albert Szent-Gyo¨rgyi Center for Medical and Pharmaceutical Sciences, Faculty of Medicine, University of Szeged, Semmelweis u. 6, H-6725 Szeged, Hungary; 3Central Laboratory, Be´ke´s County Hospital, PO Box 46, H-5701, Gyula, Hungary Keywords: paraoxonase; apolipoprotein E; genetic mark- Table 1 Frequency distribution of PON2 and apoE geno- ers; Alzheimer’s disease; vascular dementia; DNA polymor- types and alleles in the control, Alzheimer’s and vascular phism dementia populations The gene of an esterase enzyme, called paraoxonase (PON, EC.3.1.8.1.) is a member of a multigene family that Control Alzheimer’s Vascular comprises three related genes PON1, PON2, and PON3 dementia dementia with structural homology clustering on the chromosome 7.1,2 The PON1 activity and the polymorphism of the PON2 genotype PON1 and PON2 genes have been found to be associa- CC 4 (8%) 2 (4%) 3 (6%) ted with risk of cardiovascular diseases such as hyper- CS 20 (39%) 23 (43%) 19 (34%) cholesterolaemia, non-insulin-dependent diabetes, coron- SS 27 (53%) 28 (53%) 33 (60%) ary heart disease (CHD) and myocardial infaction.3–8 The PON2 allele importance of cardiovascular risk factors in the patho- C (cys) 28 (27%) 27 (25%) 25 (23%) mechanism of Alzheimer’s disease (AD) and vascular S (ser) 74 (73%) 79 (75%) 85 (77%) dementia (VD)9–13 prompted us to examine the genetic ApoE genotype effect of PON2 gene codon 311 (Cys→Ser; PON2*S) 22 – – – polymorphism and the relationship between the PON2*S 2 3 6 (12%) 3 (6%) 6 (11%) allele and the other dementia risk factor, the apoE poly- 2 4 – – 1 (2%) morphism in these dementias. The PON2*C and PON2*S 3 3 38 (74%) 32 (60%) 32 (58%) allele frequencies were similar in both AD (25% and 3 4 6 (12%) 15 (28%) 14 (25%) 75%) and VD groups (23% and 77%), respectively, com- 4 4 1 (2%) 3 (6%) 2 (4%) pared with the controls (27% and 73%). The ratio of the ApoE allele PON2*S carriers was significantly higher among the 2 6 (6%) 3 (3%) 7 (6%) apoE4 allele carrier AD (27%) and VD (25%) groups than 3 88 (86%) 82 (77%) 84 (76%) in the control (12%). Our results indicate that the PON2*S 4 8 (8%) 21 (20%) 19 (17%) and apoE4 alleles have interactive effect on the develop- ment of the two most common forms of dementias AD and VD, and further support the hypothesis that cardio- vascular factors contribute to the development of AD. quencies is different in the normal Hungarian popu- Molecular Psychiatry (2002) 7, 110–112. DOI: 10.1038/ lation from that in the Asian Indian, the only available sj/mp/4000916 examined group from the literature.14 The Hungarians have less CC (8%) and more SS (53%) genotypes than Until now there were no data available about the PON2 the Asian Indians have, 17.5% and 40.2% respectively. codon 311 polymorphism in the normal Hungarian In the Hungarian sample the PON*S allele was more population (Table 1). On the other hand significant frequent (73%) than in the Asian Indian group exam- inter-racial variability in the allelic distribution of ined (61%).14 other PON-like genes (PON1 and PON2) and risks asso- The human genome contains three PON-like genes ciated with CHD were reported.14–16 Since the Hung- close to each other, but the function of these enzymes arian population is considered to be genetically and is still not clear.2 Recently PON1 has emerged as an linguistically different from the other European ethnic independent risk factor for cardiovascular disease. groups and genetic differences have been reported in Despite the lack of its natural substrate there is growing other lipid metabolism related genes such as the apoE evidence suggesting that as well as catalysing the polymorphism,17,18 it is also important to examine the hydrolysis of nerve toxic organophosphates, when inter-ethnic differences of other genetic risk factors PON1 is associated with high density lipoprotein such as the PON2 mutation. Our results indicate that (HDL), it may protect against LDL oxidation and pre- the distribution of the PON2 genotype and allele fre- vent atherosclerosis formation by hydrolysing lipid Paraoxonase-2 gene polymorphism in Alzheimer’s and vascular dementias Z Janka et al 111 peroxides, leukotriene-like compounds and therefore Table 2 PON2 allele frequencies among the apoE4 allele car- inhibiting the oxidation of HDL and low density lipo- riers and non-carriers protein (LDL).19,20 Furthermore, reduced PON1 activity has been found in patients with the risk of cardiovascu- PON2 Controls Alzheimer’s Vascular lar diseases such as hypercholesterolaemia, non-insu- allele dementia dementia lin-dependent diabetes, coronary heart disease and myocardial infarction.3–5 On the other hand, not only C E2 or E3 26 (25%) 20 (19%) 18 (16%) PON1 activity, but also the polymorphism of the PON1 E4 2 (2%) 7 (7%) 7 (6%) a and PON2 genes has been found to be associated with S E2 or E3 62 (61%) 50 (47%) 58 (53%) b c the same cardiovascular risk factors and diseases.6–8 E4 12 (12%) 29 (27%) 27 (25%) Among the two common genomic variations of the a ␹2 = = Ͻ PON1 gene, the codon 148 (Ala→Gly) mutation was probe 8.523; df 4; P 0.014. b ␹2 probe = 8.18; df = 1; P Ͻ 0.006. reported to be associated with non-insulin-dependent c ␹2 probe = 5.166; df = 1; P Ͻ 0.027. diabetes21 and might worsen glycaemia and lipidaemia in diabetic patients. The codon 192 mutation of the same gene was associated with the risk of coronary no interactive effect was examined with the apoE4 heart disease and had a synergistic effect with the allele. Our results indicate that atheroclerosis-related codon 311 (Cys→Ser) polymorphism of another gene, genetic risk factors might have importance in the the PON2 from the PON gene family.14 It is pertinent to development of the two most frequent dementing dis- mention here that alterations of the serum PON activity orders, AD and VD. Therefore, besides the reported have been described in AD recently,22 but the PON1 lipid metabolism-related risk factors such as the apoE gene polymorphism was not associated with either the polymorphism and the apo A-IV codon 360 mutation,24 severity of the atherosclerosis or the AD-like neuro- the PON2 codon 311 (Cys→Ser) mutation might have pathology in a different AD population.23 Here we had an interactive effect together with the apoE4 allele on similar results with the polymorphism of the PON2 the development of dementia. gene and found that the frequencies of the PON2*S allele were 75% and 77% in the AD and VD groups, Methods respectively, and no significant differences were found compared with controls (73%) (Table 1). Our results Case ascertainment and diagnosis indicate that it is unlikely that the codon 311 One hundred and fifty-nine Caucasian probands par- (Cys→Ser) polymorphism of the PON2 gene alone has ticipated in our study. The 51 normal control persons an impact on the development of AD and VD. Further- (mean age ± SD, 71.8 ± 7 years; male/female 24/27; more another cardiovascular disease and AD-related Mini-Mental State Exam (MMSE) score ± SD, 28 ± 1.3 risk factor, the apoE polymorphism, was also deter- points) were spouses of the AD and VD probands and mined in the present study. It was found that the apoE none of them had verified symptoms of dementia. The 3/4 genotype was more frequent, 28% and 25% in the 53 AD (mean age ± SD, 66.3 ± 10 years; male/female AD and VD groups, than in the control group (12%) 17/36; MMSE score ± SD, 19 ± 2.2 points) and 55 VD (Table 1). The E4 allele was over-represented in both (mean age ± SD, 72.9 ± 10.8 years; male/female 23/32; dementia groups (20% AD and 17% VD) compared MMSE score ± SD, 22 ± 3.5 points) patients were selec- with the controls (8%). One limitation of our study was ted from the outpatients of the local Memory Clinic. that the dementia cases were only clinically diagnosed The clinical diagnosis of late onset sporadic AD was as AD and VD, and no autopsy data are available. based on the DSM-III-R and NINCDS-ADRDA criteria. Therefore we can not exclude the possibility that our The AD probands were considered sporadic type, VD group may include a substantial portion of mixed because none of them had a family history of dementia. AD and VD cases. This potential diagnostic inaccuracy The probable VD cases were diagnosed according to might explain the similarity of the E4 allele frequencies the criteria of ICD-10 and NINDS-AIREN for research reported here in the AD and VD groups. studies. All patients underwent CT, MRI and SPECT To investigate whether the PON2*S and apoE4 studies in order to exclude any other neurological dis- alleles are interactive regarding the dementia risk, the order. None of the probands had diabetes mellitus PON2 allele frequencies were calculated among the according to their blood sugar examination.