WRN polymorphisms affect expression levels of plasminogen activator inhibitor type 1 in cultured fibroblasts.

Background: Recessive mutations in WRN gene eliminate WRN protein function (helicase) and cause Werner syndrome. One of the most important clinical features of Werner syndrome patients are the premature onset and accelerated atherosclerosis process. Studies carried out on polymorphic WRN locus have shown that the alleles 1367R and 1074L confer protection for cardiovascular disease. Given that the levels of plasminogen activator inhibitor type 1 (PAI-1) were found to be significantly increased in Werner syndrome patients, is quiet possible that PAI-1 expression could be under regulation of WRN helicase. Therefore the purpose of this work was to evaluate the role of WRN polymorphism in modulating the expression of PAI-1.

Methods: In order to accomplish our aim, an array of primary cultured fibroblasts from normal adult donors was genotyped for polymorphisms of both the WRN and PAI-1 loci. In addition, steady state levels of WRN and PAI-1 were measured by semi-quantitative RT-PCR assays in such cultures. To search for the potential relationship between the lack of WRN protein and PAI-1 expression, heterozygous cultures of fibroblasts (1367RC/1074LF; WRN genotype) were treated with a molecule of interference RNA against WRN messenger RNA (mRNA).

Results: We found that, carriers of 1367R and 1074L alleles of WRN shown to have low amounts of PAI-1 in plasma (7.56 +/- 5.02), as compared with carriers of 1367C and 1074F alleles (16.09 +/- 6.03). Moreover, fibroblasts from carriers with these alleles had low expression levels of PAI-1 mRNA. The treatment of heterozygous primary fibroblast cultures (1367RC/1074LF; WRN genotype) with iRNA against WRN mRNA caused PAI-1 overexpression. Treatment with normal PAI-1 inducers (TGFbeta, TNFalpha, or insulin) in these cultures and from those with genotypes 1367CC/1074FF and 1367RR/1074FL resulted in a genotype-dependent PAI-1 expression level.

Conclusion: Our results suggest that polymorphisms in the WRN gene might have a significant role regulating PAI-1 levels in healthy individuals and "normal states" as well as acute or chronic stress, obesity, aging, acute inflammation, among others, where characteristic high levels of insulin, TNF alpha and TGFbeta, could favor PAI-1 high levels in carriers with polymorphic variants (C and F alleles), beyond the levels reached by carriers with other alleles (R and L alleles).