Proton pump inhibitors inhibit PHOSPHO1 activity and matrix mineralisation in vitro

Katherine Staines, Katherine Myers, Kirsty Little, Stuart Ralston, Colin Farquharson

    Research output: Contribution to journalArticlepeer-review


    Proton pump inhibitors (PPIs) have been associated with an increased risk of fragility fractures in pharmaco-epidemiological studies. The mechanism is unclear, but it has been speculated that by neutralising gastric acid, they may reduce intestinal calcium absorption, causing secondary hyperparathyroidism and bone loss. Here we investigated that hypothesis that the skeletal effects of PPI might be mediated by inhibitory effects on the bone-specific phosphatase PHOSPHO1. We found that the all PPIs tested inhibited the activity of PHOSPHO1 with IC50 ranging between 0.73 µM for esomeprazole to 19.27 µM for pantoprazole. In contrast, these PPIs did not inhibit TNAP activity. We also found that mineralisation of bone matrix in primary osteoblast cultures was inhibited by several PPIs in a concentration dependent manner. In contrast, the histamine-2 receptor antagonists (H2RA) nizatidine, famotidine, cimetidine and ranitidine had no inhibitory effects on PHOSPHO1 activity. Our experiments show for the first time that PPIs inhibit PHOSPHO1 activity and matrix mineralisation in vitro revealing a potential mechanism by which these widely used drugs are associated with the risk of fractures.

    Original languageEnglish
    Pages (from-to)696-705
    Number of pages10
    JournalCalcified Tissue International
    Issue number6
    Publication statusPublished - 2 Jul 2021

    Bibliographical note

    This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit

    Funding Information: We are grateful to Medical Research Scotland for a Vacation Scholarship (KM) and the Society for Endocrinology for a Summer Studentship (KL). We are also grateful to the Biotechnology and Biological Sciences Research Council (BBSRC) for Institute Strategic Programme Grant Funding BB/J004316/1.


    • Histamine-2 receptor antagonists
    • Mineralisation
    • PHOSPHO1
    • Proton pump inhibitors
    • TNAP


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