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Functional consequences of pathogenic variant c.61G>C in the inflammasome gene NLRP3 underlying keratitis fugax hereditaria
  1. Sabita Kawan1,2,
  2. Michael Paul Backlund1,
  3. Annamari Tuulia Immonen1,2,
  4. Tero Tapani Kivelä2,
  5. Joni Antero Turunen1,2
  1. 1Eye Genetics Group, Folkhälsan Research Center, Helsinki, Finland
  2. 2Department of Ophthalmology, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
  1. Correspondence to Dr Joni Antero Turunen, Ophthalmology, Helsinki University Central Hospital, Helsinki, 00280, Finland; joni.turunen{at}helsinki.fi

Abstract

Aims To elucidate the effect of NLRP3 variant c.61G>C on interleukin-1β (IL-1β) secretion in keratitis fugax hereditaria (KFH), a cryopyrin-associated periodic syndrome limited to the eye, and to probe the potential modifying role of prednisolone.

Methods Peripheral blood mononuclear cells (PBMCs) isolated from whole blood of patients with KFH and healthy controls were grown under steady-state conditions or primed with lipopolysaccharide (LPS) with or without prednisolone, and subsequently activated with ATP. Cell lysates and proteins precipitated from the cell culture media were separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. NLRP3, procaspase-1, and IL-1β were visualised by western blotting. The concentration of secreted IL-1β in the culture media was quantified by ELISA.

Results Following priming of the NLRP3 inflammasome with LPS, a lower threshold for IL-1β secretion was observed in patient-derived PBMCs, compared with healthy controls (median, 124 vs 10 pg/mL, respectively). Interestingly, in PBMCs derived from patients with frequent KFH symptoms, LPS priming alone was able to trigger substantial IL-1β secretion (median, 522 pg/mL), whereas those of patients experiencing occasional KFH attacks showed a subtler release of IL-1β (median, 85 pg/mL). NLRP3 expression was significantly enhanced with LPS stimulation (p=0.03) whereas procaspase-1 expression was not affected. LPS and ATP treated PBMCs from patients with KFH showed significantly diminished IL-1β secretion with prednisolone treatment (p=0.04).

Conclusions PBMCs from patients with KFH are more prone to secrete IL-1β, confirming the presumption that the c.61G>C is a gain-of-function variant. Furthermore, prednisolone is confirmed as a potent drug to reduce IL-1β secretion in KFH.

  • Cornea
  • Experimental – laboratory
  • Drugs
  • Immunology
  • Inflammation

Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

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Data availability statement

All data relevant to the study are included in the article or uploaded as supplementary information.

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Footnotes

  • Twitter @joniturunen

  • Contributors Contributors: JAT conceptualised and designed the study with SK. ATI recruited patients and had full access to patient’s data. SK carried out all the experiments. SK and MPB analysed and interpreted the data. SK, MPB and ATI take responsibility for the integrity and accuracy of data analysis. SK and MPB drafted the manuscript. Critical revision of the manuscript for important intellectual content was given by TK, JAT and MPB. The guarantor: JAT. All authors commented on the manuscript.

  • Funding The study received support from The Jane and Aatos Erkko Foundation, Finland (grant number: N/A); The Eye and Tissue Bank Foundation, Finland (grant number: N/A); The Eye Foundation, Finland (grant number: N/A); The Mary and Georg C. Ehrnrooth Foundation, Finland (grant number: N/A); The Paulo Foundation, Finland (grant number: N/A); The Evald and Hilda Nissi Foundation, Finland (grant number: N/A); The Finnish Cultural Foundation, Finland (grant number: N/A); and The Helsinki University Hospital Research Fund (grant number: TYH2019323).

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.