Functional consequences of pathogenic variant c.61G>C in the inflammasome gene <i>NLRP3</i> underlying keratitis fugax hereditaria.

Abstract

To elucidate the effect of <i>NLRP3</i> 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. 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. 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). 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.