Anti-Inflammatory Heat Shock Protein 70 Genes are Positively Associated with Human Survival

R. Singh*, S. Klvraa, P. Bross, K. Christensen, L. Bathum, N. Gregersen, Q. Tan and S. I. S. Rattan

FCMB, Vejle, Denmark; Department of Clinical Genetics, Vejle Hospital, Denmark; Research Unit for Molecular Medicine, Aarhus University Hospital, Denmark; Institute of Public Health, University of Southern Denmark, Denmark; Department of Epidemiology, Odense University Hospital, Denmark; Department of Clinical Biochemistry and Genetics, Odense University Hospital, Denmark; Department of Molecular Biology, Aarhus University, Denmark

Abstract: A positive relationship between stress tolerance and longevity has been observed in several model systems. That the same correlation is applicable in humans and that it may be open to experimental manipulation for extending human lifespan requires studies on the association of stress genes with longevity. The involvement of heat shock protein 70 (Hsp70) in cellular maintenance and repair mechanisms, including its role as an anti-inflammatory protein, makes it a suitable candidate for studying such associations. We have studied the association of three single nucleotide polymorphisms (SNPs), HSPA1A (-110A>C), HSPA1B (1267A>G), and HSPA1L (2437T>C), present in the three HSP70 genes with human survival in a cohort of individuals born in the year 1905. This population cohort is a part of the longitudinal study of Danish nonagenarians. Since DNA samples were already collected in 1998, this gave us the opportunity to perform survival analysis on these subjects. Haplotype relative risk and genotype relative risk were calculated to measure the effects of haplotypes and genotypes on human survival in a sex-specific manner. A significant association of HSPA1A-AA (RR=3.864; p=0.016) and HSPA1B-AA (RR=2.764; p=0.039) genotypes with poor survival was observed in female subjects. Also, female carriers of haplotype G-C-T had longer survival than the non-carriers (HRR=0.550; p=0.015). On average, female carriers of the G-C-T haplotype live about one year longer than non-carriers. This result corroborates our previous observations from heat shock response (HSR) study where we had shown that after heat stimulation, mononuclear cells from the carriers of genotype HSPA1L-TT had better Keywords: HSP70, HSR, aging, longevity, survival, haplotype, polymorphisms.

INTRODUCTION

Association studies, where the frequencies of alleles and genotypes generated from a single locus candidate marker are compared between old cases and young controls [19,20], have been widely used to identify genes involved in human longevity. This approach has certain drawbacks and is prone to false positive results due to sampling bias and potential secular trend in gene-environment interaction [21]. An alternative to this approach is the cohort-based human survival study, where a group of individuals are genotyped for a candidate gene and then followed-up over the years to analyze their survival. This approach, though ideal, is expensive in terms of time and money and hence rare. However, with the increase in the number of elderly, particularly in the developed world and with the well-established and extensive population-based registries, it has been possible to perform cohort-based survival studies in old individuals [22].

At the cellular level, all organisms respond to stress by synthesizing specific stress proteins, the so-called heat shock proteins (Hsp), at the expense of other proteins. This phenomenon known as the heat shock response (HSR) protects the cells from subsequent damage and aids them to counteract the adverse effects of the stress [1-4]. Hsp are ubiquitous, cytoprotective, highly conserved chaperone proteins, which are a part of cellular safety and rescue mechanisms, preventing proteins from misfolding, permitting unfolded proteins to cross biological membranes, and then allowing them to fold properly [1], or targeting the damaged proteins for degradation and removal through proteolytic pathways [5]. Furthermore, Hsp are also known to have anti-inflammatory effects by acting on NF-(cid:1)B pathways [6-8].

Another drawback in the conventional genes-for-longevity studies is that single locus markers are tested for their association with human longevity. Since lifespan is a complex trait where, along with the environment, a network of genes and genetic variables play a critical role, it is prudent to study genetic variations in a group (haplotype), rather than single polymorphisms for mapping longevity determinant genes. In this context, recently a lot of attention has been focused on the effects of haplotypes on human longevity [23,24].

This ability tocognitive parameters were also measured in these individuals.

RESULTS

Gene and genotype frequencies of the three SNPs are given in Table 1. Fig. (1) and Table 2 show that female carriers of genotypes HSPA1A-AA (RR=3.864; p=0.016) and HSPA1A-AC (RR=2.577; p=0.056) had a shorter survival duration than carriers of HSPA1A-CC. Genotyping was done using real-time (RT) PCR on the LightCycler system (Roche Applied Sciences), which monitors the amplification of PCR product in real-time using fluorescent labelled oligonucleotide probes and primers specific for:

1. Gene/Genotypic Frequency Distribution of the Three SNPs in 1905 Cohort Individuals

HSPA1A (- AA AC CC A C 110A>C) M F M F M F M F M F 
25 41.9 65 47 10 11.1 57.5 65.3 42.5 34.6 
(10) (49) (26) (55) (4) (13) (46) (153) (34) (81) 

HSPA1B AA AG GG A G (1267A>G) M F M F M F M F M F 
25 38 62.5 47.9 12.5 14 56.2 61.9 43.7 38.1 
(10) (46) (25) (58) (5) (17) (45) (150) (35) (92) 

HSPA1L TT TC CC T C (2437T>C) M F M F M F M F M F 
62 57.7 35.1 37.9 2.7 4.3 79.7 76.7 20.2 23.2 
(23) (67) (13) (44) (1) (5) (59) (178) (15) (54) 

M = male; F = female. Data are presented as a percentage with the number of individuals given in parentheses.