Familial Mediterranean fever mutations are hypermorphic mutations that specifically decrease the activation threshold of the Pyrin inflammasome.

FMF is the most frequent autoinflammatory disease and is associated in most patients with bi-allelic MEFV mutations. MEFV encodes Pyrin, an inflammasome sensor activated following RhoGTPase inhibition. The functional consequences of MEFV mutations on the ability of Pyrin variants to act as inflammasome sensors are largely unknown. The aim of this study was to assess whether MEFV mutations affect the ability of Pyrin to detect RhoGTPase inhibition and other inflammasome stimuli. IL-1β and IL-18 released by monocytes from healthy donors (HDs) and FMF patients were measured upon specific engagement of the Pyrin, NLRP3 and NLRC4 inflammasomes. Cell death kinetics following Pyrin activation was monitored in real time. Monocytes from FMF patients secreted significantly more IL-1β and IL-18 and died significantly faster than HD monocytes in response to low concentrations of Clostridium difficile toxin B (TcdB), a Pyrin-activating stimulus. Monocytes from patients bearing two MEFV exon 10 pathogenic variants displayed an increased Pyrin inflammasome response compared with monocytes from patients with a single exon 10 pathogenic variant indicating a gene-dosage effect. Using a short priming step, the response of monocytes from FMF patients to NLRP3- and NLRC4-activating stimuli was normal indicating that MEFV mutations trigger a specific hypersensitivity of monocytes to low doses of a Pyrin-engaging stimulus. Contrary to the NLRP3 mutations described in cryopyrin-associated periodic syndrome, FMF-associated MEFV mutations do not lead to a constitutive activation of Pyrin. Rather, FMF-associated mutations are hypermorphic mutations that specifically decrease the activation threshold of the Pyrin inflammasome without affecting other canonical inflammasomes.

Jamilloux Y ，Lefeuvre L ，Magnotti F ，Martin A ，Benezech S ，Allatif O ，Penel-Page M ，Hentgen V ，Sève P ，Gerfaud-Valentin M ，Duquesne A ，Desjonquères M ，Laurent A ，Rémy-Piccolo V ，Cimaz R ，Cantarini L ，Bourdonnay E ，Walzer T ，Py BF ，Belot A ，Henry T ... -  《-》

Fast diagnostic test for familial Mediterranean fever based on a kinase inhibitor.

Familial Mediterranean fever (FMF) is the most frequent hereditary autoinflammatory disease. Its diagnosis relies on a set of clinical criteria and a genetic confirmation on identification of biallelic pathogenic MEFV variants. MEFV encodes pyrin, an inflammasome sensor. Using a kinase inhibitor, UCN-01, we recently identified that dephosphorylation of FMF-associated pyrin mutants leads to inflammasome activation. The aim of this study was to assess whether quantifying UCN-01-mediated inflammasome activation could discriminate FMF patients from healthy donors (HD) and from patients with other inflammatory disorders (OID). Real-time pyroptosis and IL-1β secretion were monitored in response to UCN-01 in monocytes from FMF patients (n=67), HD (n=71) and OID patients (n=40). Sensitivity and specificity of the resulting diagnostic tests were determined by receiver operating characteristic curve analyses. Inflammasome monitoring in response to UCN-01 discriminates FMF patients from other individuals. Pyroptosis assessment leads to a fast FMF diagnosis while combining pyroptosis and IL-1β dosage renders UCN-01-based assays highly sensitive and specific. UCN-01-triggered monocytes responses were influenced by MEFV gene dosage and MEFV mutations in a similar way as clinical phenotypes are. UCN-01-based inflammasome assays could be used to rapidly diagnose FMF, with high sensitivity and specificity.

Magnotti F ，Malsot T ，Georgin-Lavialle S ，Abbas F ，Martin A ，Belot A ，Fauter M ，Rabilloud M ，Gerfaud-Valentin M ，Sève P ，Duquesne A ，Hot A ，Durupt S ，Savey L ，Giurgea I ，Grateau G ，Henry T ，Jamilloux Y ... -  《-》

Increased NLRP3-dependent interleukin 1β secretion in patients with familial Mediterranean fever: correlation with MEFV genotype.

Omenetti A ，Carta S ，Delfino L ，Martini A ，Gattorno M ，Rubartelli A ... -  《-》

Dysregulated production of interleukin-1β upon activation of the NLRP3 inflammasome in patients with familial Mediterranean fever.

Familial Mediterranean fever (FMF) is caused by mutations in pyrin, a protein expressed in innate immune cells that interacts with caspase-1 and other inflammasome components to regulate interleukin (IL)-1β maturation. Since NLRP3 inflammasome represents major source of IL-1β, we studied its protein expression and function in FMF. We isolated peripheral white blood cells (WBCs) from 20 symptoms-free FMF patients and 21 healthy individuals. Intracellular protein expression of NLRP3, caspase-1, IL-1β at baseline and after LPS/ATP sequential treatment for NLRP3 activation was assessed by immunoblotting. Secreted IL-1β was quantified by ELISA. THP-1 cells were transfected with wild-type or mutant pyrin and IL-1β secretion was measured. FMF WBCs exhibited lower NLRP3 and active caspase-1 protein expression compared to healthy individuals, and LPS/ATP treatment resulted in significantly lower intracellular IL-1β levels in FMF patients. Likewise, LPS/ATP induced caspase-1-dependent IL-1β release at significantly lower amounts in the FMF group (1182±192 versus 2134±245pg/mL in controls, p=0.004). Consistently, THP-1 cells transfected with FMF-associated M694V mutant pyrin displayed lower LPS/ATP-induced IL-1β compared with wild-type pyrin-transfected cells. FMF WBCs demonstrate reduced NLRP3-mediated IL-1β production. Additional studies are needed to define whether this finding represents a compensatory mechanism to control inflammation or is directly linked to disease pathogenesis.

Repa A ，Bertsias GK ，Petraki E ，Choulaki C ，Vassou D ，Kambas K ，Boumpas DT ，Goulielmos G ，Sidiropoulos P ... -  《-》

Familial Mediterranean fever mutations lift the obligatory requirement for microtubules in Pyrin inflammasome activation.

Van Gorp H ，Saavedra PH ，de Vasconcelos NM ，Van Opdenbosch N ，Vande Walle L ，Matusiak M ，Prencipe G ，Insalaco A ，Van Hauwermeiren F ，Demon D ，Bogaert DJ ，Dullaers M ，De Baere E ，Hochepied T ，Dehoorne J ，Vermaelen KY ，Haerynck F ，De Benedetti F ，Lamkanfi M ... -  《-》