Little is known about interactions between environmental and genetic risk factors for osteoarthritis (OA). Genetic factors include variation or mutation in genes involved in parathyroid hormone signalling. Exposure to the endocrine disrupting chemicals perfluoro-octanoic acid (PFOA) or perfluorooctane sulfonate (PFOS) have been suggested as potential environmental contributors, although evidence to support this association is conflicting. In this study, the authors test the hypothesis that PFOA and PFOS may alter the mRNA expression of genes in the parathyroid signalling cascade to provide evidence on possible pathways between these chemicals and OA. The relationship between PFOA or PFOS serum levels and the in vivo expression of the Parathyroid hormone 1 and 2 genes (PTH, PTH2), Parathyroid hormone 1 and 2 receptor genes (PTH1R, PTH2R) and the parathyroid hormone-like (PTHLH) gene in peripheral blood were measured from a cross-sectional population study designed to assess the potential health effects of these chemicals. Multivariate linear regression models were used and it was found that PFOA or PFOS was inversely correlated with parathyroid hormone 2 receptor (PTH2R) expression (coefficients=-0.43 and -0.32, p=p=0.017 and 0.006 for PFOA and PFOS respectively) in 189 female subjects. The levels of PTH2 transcripts encoding the ligand of PTH2r, were also found to be lower in women with OA (median 2.08) compared with controls (median 3.41, p=0.046). As the parathyroid signalling cascade is a known candidate for osteoarthritis risk and the findings raise the possibility that exposure to these chemicals may contribute to the pathogenesis of OA in some individuals.
Authors: Galloway TS, Fletcher T, Thomas OJ, Lee BP, Pilling LC, Harries LW. ;Full Source: Chemosphere. 2015 Feb;120:555-62. doi: 10.1016/j.chemosphere.2014.09.066. Epub 2014 Oct 17. ;