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Increased NLRP3-dependent interleukin 1β secretion in patients with familial Mediterranean fever: correlation with MEFV genotype
  1. Alessia Omenetti1,
  2. Sonia Carta2,
  3. Laura Delfino2,
  4. Alberto Martini1,
  5. Marco Gattorno3,
  6. Anna Rubartelli2
  1. 1Pediatrics II Unit, G Gaslini IRCCS and University of Genoa, Genoa, Italy
  2. 2Cell Biology Unit, IRCCS AOU San Martino–IST Istituto Nazionale per la Ricerca sul Cancro, Genoa, Italy
  3. 3Pediatrics II Unit, G Gaslini IRCCS, Genoa, Italy
  1. Correspondence to Dr Anna Rubartelli, Cell Biology Unit, IRCCS Azienda Ospedaliera Universitaria San Martino–IST Istituto Nazionale per la Ricerca sul Cancro, Genoa 16132, Italy; anna.rubartelli{at}istge.it

Abstract

Objectives To define in patients affected by familial Mediterranean fever (FMF) whether or not interleukin (IL)-1β secretion (1) is enhanced, (2) correlates with the type of MEFV mutation and (3) is mediated by NLRP3.

Methods Freshly isolated monocytes from 21 patients with FMF (12 homozygous and 9 heterozygous), 14 MEFV healthy carriers and 30 healthy donors (HDs), unstimulated or after lipopolysaccharide (LPS)-induced activation, were analysed for redox state (production of reactive oxygen species (ROS) and antioxidant responses) and IL-1β and IL-1 receptor antagonist (IL-1Ra) secretion. NLRP3 down-modulation was induced by in vitro silencing of the NLRP3 gene.

Results LPS-stimulated monocytes from patients with FMF displayed enhanced IL-1β secretion, which correlated with number and penetrance of MEFV mutations. Silencing of NLRP3 consistently inhibited IL-1β secretion. As in other autoinflammatory diseases, FMF monocytes produced more ROS than genetically negative cells from HDs. Unlike in cryopyrin-associated periodic fever syndromes (CAPS), however, they were characterised by a conserved and sustained antioxidant response. Consistent with this finding, activated MEFV-mutated monocytes did not exhibit the functional indicators of oxidative stress observed in CAPS, including accelerated IL-1β secretion and deficient production of IL-1Ra.

Conclusions MEFV-mutated monocytes display enhanced IL-1β secretion, which correlates with number of high-penetrance mutations and level of endogenous ROS. Unlike NLRP3-mutated cells, monocytes carrying MEFV mutations withstand oxidative stress and preserve IL-1Ra production, thereby limiting inflammation. Finally, in contrast with that found in the animal model, the increased secretion of IL-1β by LPS-stimulated FMF monocytes is NLRP3-dependent.

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