Inflammation, genetics, and longevity: further studies on the protective effects in men of IL-10 –1082 promoter  SNP and its interaction with TNF- –308 promoter SNP

Lio, L Scola, A Crivello, G Colonna-Romano, G Candore, M Bonafè, L Cavallone, Marchegiani, F Olivieri, C Franceschi, C Caruso

JMedGenet2003;40:296–299

activity leading to long term tissue damage, and systemic chronic inflammation has been found to be related to mortality risk from all causes in older persons.1 Also, the genetic constitution of the organism interacting with sys- temic inflammation may cause defined organ specific ill- nesses. Thus, age related diseases such as Alzheimer’s disease (AD), Parkinson’s disease, atherosclerosis, type 2 diabetes, sarcopenia, and osteoporosis, are initiated or worsened by sys- temic inflammation, suggesting the critical importance of unregulated systemic inflammation in the shortening of sur- vival in humans.1–3 Accordingly, proinflammatory cytokines are believed to play a pathogenetic role in age related diseases, and genetic variations located within their promoter regions have been shown to influence the susceptibility to age related diseases, by increasing gene transcription and therefore cyto- kine production.3 4

• Many aspects of ageing involve inflammatory proc- esses. We evaluated the association with longevity of um

a, alleles of IL-

and TNF- , known to have opposite func- tions in inflammatory reactions, IL-

acting predomi- a nantly as an anti-inflammatory and TNF- as a proinflammatory factor. • The number of male centenarians homozygous for the –

G genotype, suggested to be associated with high IL-

production, was significantly increased in comparison with younger control subjects. No signifi- cant differences were observed between women and inal controls. The genotypic frequencies of the TNF- promoter SNPs

G and

A, suggested to be asso- a ciated with low and high TNF- production respectively, were not significantly different between centenarians and controls. The evaluation of combined IL-

and _Ea TNF- genotypes showed that there was a significant - increase of the “anti-inflammatory” (IL-

GG/ vis - TNF-

GG) genotype in centenarian men over controls. • Inflammatory markers predict disability and mortality in elderly cohorts and a persistent inflammatory state has been proposed to be involved in the causal pathway of certain age related chronic conditions. Thus, it is intrigu- ing that the possession of an “anti-inflammatory” geno- type is significantly increased in male centenarians.

Conversely, genetic variations determining increased pro- duction of anti-inflammatory cytokines or decreased produc- tion of proinflammatory cytokines have been shown to be associated with successful ageing, suggesting a role for the control of the inflammatory state in the attainment of longev- ity. As recently reported, the distribution of +874Tfi A interferon(IFN)-g, 5 -174C fi G IL-6,6 and –1082Gfi A interleukin(IL)-107 single nucleotide polymorphisms (SNPs) has been shown to be different in centenarians than in younger people.5–7 The +874T allele, involved in high produc- tion of the proinflammatory cytokine IFN-g, was found less frequently in centenarian women than in control women.5 Also, the proportion of subjects homozygous for the G allele at the –174 IL-6 locus, characterised by high serum levels of the proinflammatory cytokine IL-6, was significantly decreased in centenarian men.6 Conversely, the presence of the -1082 GG genotype, suggested to be associated with high production of the anti-inflammatory cytokine IL-10, was significantly increased in centenarian men in comparison with younger male subjects.7 These gender related effects are difficult to explain. However, it is well known that men and women may follow different strategies to reach longevity and that the number of centenarian women always outnumber centenar- ian men, the ratio between women and men ranging from 4/1 to 7/1, with the exception of Sardinia.8 9

tory cytokines and longevity, we investigated the frequency of the -1082G fi A IL-10 promoter SNP in a larger cohort of 72 centenarian men, including 25 typed in a previous study,7 and the interaction of this polymorphism with -308A fi G TNF-a SNP.

MATERIALS AND METHODS

DNA samples were obtained from 72 unrelated centenarian men (25 of whom were part of a previous study)7 and 102 centenarian women from central and southern Italy. DNA samples from healthy unrelated controls (115 men and 112 women, aged 22-60 years), matched for geographical origin, were also collected. Written informed consent for enrolment in the study and for personal data management was obtained from all the subjects according to Italian laws.

It is rather simplistic to examine the influence of a single cytokine in isolation. In fact, cytokines interact in networks in which the functions of one cytokine are modified, modulated, or substituted by another one(s).4 In particular, IL-10 and tumour necrosis factor (TNF-a ), a classical proinflammatory cytokine, have complex and opposing roles,10 11 and an autoregulatory loop appears to exist in which TNF-a stimulates IL-10 production which, in turn, reduces TNF-a synthesis.12 13 Furthermore, their synergistic role in the control of immune-inflammatory responses has been hypothesised.14 To gain further insight into the relation between inflamma-

Blood specimens were collected in tripotassium EDTA ster- ile tubes and immediately stored at -70°C. Genomic DNA extraction was carried out and DNA stored at -20°C for the IL-10 and TNF-a gene analysis. Complete linkage of allele -819C with allele -592C and of allele -819T with allele -592A,

control men were not significantly different. Accordingly, the frequency of SNP –308Gfi A was not significantly different between centenarians and controls (c 2 test). The same was observed in the group of centenarian women (–308G, 0.88 v 0.79, p=NS by c 2 test).