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P2X7-mediated alteration of membrane fluidity is associated with the late stages of age-related macular degeneration

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Abstract

We have shown deficits in monocyte phagocytosis from patients with age-related macular degeneration (AMD). Cell membrane fluidity is known to affect phagocytic capacity and leucocyte functionality more generally. Therefore, we examined membrane fluidity of peripheral blood leucocytes in human patients with AMD and in the P2X7 null mouse model of AMD using flow cytometry with a fluorescent probe for fluidity, TMA-DPH. The results showed that membrane fluidity was decreased in all leucocyte types of late AMD relative to healthy controls (HC) including monocytes, neutrophils and lymphocytes but this was not apparent in earlier stages of AMD. Further analysis of factors contributing to membrane fluidity indicated that pre-treatment of monocytes and lymphocytes with ATP greatly increased membrane fluidity in humans and mice. Evidence from P2X7 null mice and P2X7 antagonists confirmed that these ATP-driven increases in membrane fluidity were mediated by P2X7 but were not associated with the classic P2X7 functions of pore formation or phagocytosis. Analysis of P2X7 expression indicated that receptor levels were elevated in classic monocytes of late AMD patients, further suggesting the P2X7 may contribute to altered plasma membrane properties. Our findings identified a novel biological function of P2X7 in modulating membrane fluidity of leucocytes and demonstrated reduced membrane fluidity in cellular changes associated with the late stage of AMD.

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All records, raw data and analysis are stored in compliance with the institutions’ requirements and are available upon approved request. This manuscript does not have supplemental information.

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Acknowledgements

We thank Mrs. Melinda Cain for her help in blood collection.

Funding

This work was supported by ARC Future Fellowship (BG, FT120100581) and NHMRC Project Grant (1048082, 1061419, 1120095), Principal Research Fellowship (RG, 1103013), Macular Disease Foundation Australia Project Grant (2014–2016), Macular Society Grant USA (2015), BrightFocus Foundation Project Grant (M2016061) and the Victorian Government’s Operational Infrastructure Support Grant to the Florey Institute.

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Authors and Affiliations

  1. The Florey Institute, The University of Melbourne, 30 Royal Parade, Parkville, VIC, 3052, Australia

    Candace Drysdale, Keunha Park, Xin Huang, Yihan Li, Joelyn Wong, James S. Wiley & Ben J. Gu

  2. Department of Anatomy & Physiology, The University of Melbourne, Melbourne, VIC, Australia

    Kirstan A. Vessey & Erica Fletcher

  3. Centre for Eye Research Australia, Department of Surgery (Ophthlamology), University of Melbourne, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia

    Emily Caruso & Robyn H. Guymer

  4. National Clinical Research Center for Aging and Medicine, Huashan Hospital of Fudan University, Shanghai, China

    Ben J. Gu

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  1. Candace Drysdale
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  2. Keunha Park
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  4. Xin Huang
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Correspondence to Ben J. Gu.

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The authors declare no competing interests.

Ethical approval

The study was approved by the Royal Victorian Eye and Ear Hospital human ethics committee (AMDRF95/283H/20) and by the Eastern Health human ethics committee (E05/1011). The animal work was approved by the Florey Institute Animal Ethics Committee (13–053-FNI).

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The research adhered with the Declaration of Helsinki, and written informed consent was obtained from all participants.

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Robyn H. Guymer and Ben J. Gu are co-senior authors.

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Drysdale, C., Park, K., Vessey, K.A. et al. P2X7-mediated alteration of membrane fluidity is associated with the late stages of age-related macular degeneration. Purinergic Signalling 18, 469–479 (2022). https://doi.org/10.1007/s11302-022-09894-y

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