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Interleukin-6-gene C/G 174 polymorphism in nonagenarian and octogenarian subjects in the BELFAST study. Reciprocal effects on IL-6, soluble IL-6 receptor and for IL-10 in serum and monocyte

Irene M. Rea , Owen A. Ross *, Marilyn Armstrong , Susan McNerlan , d b b Denis H. Alexander , Martin D. Curran , Derek Middleton

a Department of Geriatric Medicine, Queens University of Belfast, Whitla Medical Building, 97, Lisburn Road, Belfast, UK b Northern Ireland Histocompatability and Immunogenetics Centre, Belfast City Hospital, Belfast BT9 7TS, UK c Immunology and Microbiology Department, Royal Trust Group, Queens University of Belfast, Belfast, UK d

Received 1 July 2002; received in revised form 3 October 2002; accepted 20 December 2002

Abstract

In this study, we have assessed any change in the frequency of the GG homozygotes of the 174 IL-6 polymorphism with increasing age, arguing that if IL-6 tracks with functional disability and age-related diseases, then there may be attrition or reduction in the frequency of homozgyous subjects, who produce higher levels of IL-6 in serum, in older survivors in a population. We have tested this hypothesis in a large group of free-living, mentally competent, nonagenarian and octogenarian subjects from the Belfast Elderly Longitudinal Ageing Study*BELFAST study and found that the frequency of GG homozygotes with IL-6-174C/G polymorphism / decreases with age by about 10%, compared with young controls. In addition we find that CC homozygotes have higher serum levels of IL-6 levels compared with GG (P(cid:2)0.055), with reciprocal and significant changes in the anti-inflammatory IL-10 (P(cid:2)0.05). / / Both IL-6 and IL-10 were spontaneously produced from separated mononuclear cell monolayers in elderly subjects, with significantly higher levels of secreted IL-10 supernatant levels (P(cid:2)0.05) at 20 h, for G allele subjects carrying the IL-6-174C/G / polymorphism. In conclusion, in the BELFAST study, there appears to be a reduction in the frequency of GG homozygotes in the octo/nonagenarian age group and a higher serum IL-6 level associated with CC homozygotes with reciprocal changes for the anti- inflammatory cytokine IL-10.

Keywords: Interleukin-6-gene; Nonagenarian and octogenarian subjects; BELFAST study

1. Introduction

also increased in a range of age-related disorders such as autoimmune disease (O’Shea et al., 2002), atherosclero- sis (van der Meer et al., 2002), congestive cardiac failure (Wollert and Drexler, 2001), hypertension (Humphries et al., 2001) as well as in acute infection (Suffredini et al., 1999). Recently a promotor C/G 174 polymorphism of IL-6 has been identified which has functional activity with some groups reporting an increase in serum IL-6 associated with GG homozygotes compared with CC homozygotes (Fishman et al., 1998), though lately other groups have found an increase associated with CC homozygosity (Brull et al., 2001, 2002; Olivieri et al., 2002; Jones et al., 2001; Kiplinen et al., 2001). This

IL-6, an important cytokine at the centre of the immune response, is increased in serum in elderly people (Ershler, 1993a; Bruunsgaard et al., 2001). Although the cause is unknown, it has been associated with functional disability, cognitive decline and stroke in older people (Reuben et al., 2002; Ershler and Keller, 2000; Revilla et al., 2002). Elevation of IL-6, an acute phase reactant, is

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dichotomy of results in relation to IL-6-174C/G poly- morphism and IL-6 levels remains unresolved with a few

2.2.1. IL-6 promotor polymorphism

In this study, we have assessed any change in the frequency of the GG homozygotes of the 174 IL-6 polymorphism with increasing age, arguing that if IL-6 tracks with functional disability and age-related dis- eases, then there may be attrition or reduction in the frequency of homozgyous subjects, who produce higher levels of IL-6 in serum, in older survivors in a popula- tion. We have tested this hypothesis in a large group of free-living, mentally competent, nonagenarian and oc- togenarian subjects from the Belfast Elderly Long- itudinal Ageing Study*BELFAST study (Rea et al., / 2000). In addition we have assessed the effect of the C/G polymorphism on IL-6 levels in serum in a proportion of these elderly subjects. Additionally, we looked at the effect of the IL-6 polymorphism on soluble IL-6 receptor (sIL-6R) and on IL-10, important anti-inflam- matory cytokines, to assess if there was any functional effect of these anti-inflammatory cytokines which might explain serum IL-6 increases in ageing. Although we have previously demonstrated that IL-6 can be pro- duced from stimulated CD3(cid:3) lymphocytes by intracel- / lular cytokine methodology and more readily in older compared with young subjects (McNerlan et al., 2002), a good deal of evidence suggests that the increased IL-6 is produced by other cells such as monocytes (Fagiola et al., 1993; Ershler et al., 1993b). In this study, we have therefore looked for IL-6 and its anti-inflammatory partner IL-10, in monocyte supernatants separated and set up ‘in vitro’ and assessed any differential effect of the C/G 174 IL-6 polymorphism on IL-6 and IL-10 secre- tion.