Calcium-sensing receptor-mediated NLRP3 inflammasome response to calciprotein particles drives inflammation in rheumatoid arthritis.

Increased extracellular Ca2+ concentrations ([Ca2+]ex) trigger activation of the NLRP3 inflammasome in monocytes through calcium-sensing receptor (CaSR). To prevent extraosseous calcification in vivo, the serum protein fetuin-A stabilizes calcium and phosphate into 70-100 nm-sized colloidal calciprotein particles (CPPs). Here we show that monocytes engulf CPPs via macropinocytosis, and this process is strictly dependent on CaSR signaling triggered by increases in [Ca2+]ex. Enhanced macropinocytosis of CPPs results in increased lysosomal activity, NLRP3 inflammasome activation, and IL-1ß release. Monocytes in the context of rheumatoid arthritis (RA) exhibit increased CPP uptake and IL-1ß release in response to CaSR signaling. CaSR expression in these monocytes and local [Ca2+] in afflicted joints are increased, probably contributing to this enhanced response. We propose that CaSR-mediated NLRP3 inflammasome activation contributes to inflammatory arthritis and systemic inflammation not only in RA, but possibly also in other inflammatory conditions. Inhibition of CaSR-mediated CPP uptake might be a therapeutic approach to treating RA.

Tofacitinib or adalimumab versus placebo in rheumatoid arthritis.

BACKGROUND: Tofacitinib (CP-690,550) is a novel oral Janus kinase inhibitor that is being investigated for the treatment of rheumatoid arthritis. METHODS: In this 12-month, phase 3 trial, 717 patients who were receiving stable doses of methotrexate were randomly assigned to 5 mg of tofacitinib twice daily, 10 mg of tofacitinib twice daily, 40 mg of adalimumab once every 2 weeks, or placebo. At month 3, patients in the placebo group who did not have a 20% reduction from baseline in the number of swollen and tender joints were switched in a blinded fashion to either 5 mg or 10 mg of tofacitinib twice daily; at month 6, all patients still receiving placebo were switched to tofacitinib in a blinded fashion. The three primary outcome measures were a 20% improvement at month 6 in the American College of Rheumatology scale (ACR 20); the change from baseline to month 3 in the score on the Health Assessment Questionnaire-Disability Index (HAQ-DI) (which ranges from 0 to 3, with higher scores indicating greater disability); and the percentage of patients at month 6 who had a Disease Activity Score for 28-joint counts based on the erythrocyte sedimentation rate (DAS28-4[ESR]) of less than 2.6 (with scores ranging from 0 to 9.4 and higher scores indicating greater disease activity). RESULTS: At month 6, ACR 20 response rates were higher among patients receiving 5 mg or 10 mg of tofacitinib (51.5% and 52.6%, respectively) and among those receiving adalimumab (47.2%) than among those receiving placebo (28.3%) (P<0.001 for all comparisons). There were also greater reductions in the HAQ-DI score at month 3 and higher percentages of patients with a DAS28-4(ESR) below 2.6 at month 6 in the active-treatment groups than in the placebo group. Adverse events occurred more frequently with tofacitinib than with placebo, and pulmonary tuberculosis developed in two patients in the 10-mg tofacitinib group. Tofacitinib was associated with an increase in both low-density and high-density lipoprotein cholesterol levels and with reductions in neutrophil counts. CONCLUSIONS: In patients with rheumatoid arthritis receiving background methotrexate, tofacitinib was significantly superior to placebo and was numerically similar to adalimumab in efficacy. (Funded by Pfizer; ORAL Standard ClinicalTrials.gov number, NCT00853385.).

Identification and characterization of "pathoadaptive mutations" of the cadBA operon in several intestinal Escherichia coli.

The dysenteric Shigella spp. and enteroinvasive Escherichia coli (EIEC) have evolved from commensal E. coli by the acquisition of a virulence plasmid and inactivation of genes of the cad locus encoding lysine decarboxylase (LDC) by so-called pathoadaptive mutation. As horizontal gene transfer and recombination occurs frequently in E. coli we were interested to see if similar pathoadaptive mutations are commonly present in other intestinal pathotypes. Therefore, we examined 140 intestinal E. coli strains of various pathotypes and the ECOR collection for their ability to decarboxylate lysine, and identified 25 strains that were unable to do so. Complementation of a Shiga toxin-producing E. coli and two enteropathogenic E. coli strains, both LDC-negative, with the intact cad locus restored LDC activity and resulted in a reduction in adherence to tissue culture cells. We investigated the cad locus for possible alterations by using hybridization and PCR techniques and compared the results with the alterations reported for Shigella spp. and EIEC strains. Interestingly, the alterations of the cad genes were similar to those previously reported, pointing towards a parallel evolution of LDC silencing in different intestinal E. coli pathotypes.

Description of a 111-kb pathogenicity island (PAI) encoding various virulence features in the enterohemorrhagic E. coli (EHEC) strain RW1374 (O103:H2) and detection of a similar PAI in other EHEC strains of serotype 0103:H2.

Human infections with enterohemorrhagic E. coli (EHEC) strains of serotype O103:H2 are of increasing importance in Germany. As bovines are the principal EHEC reservoir behind the occurrence of human infections, we analyzed a pathogenicity island (PAI I(RW1374)) of bovine O103:H2 strain RW1374 to identify putative virulence features. This PAI I(RW1374) harbors a functional 34-kb locus of enterocyte effacement (LEE) core region and has a total length of 111 kb. About 43 kb upstream of the LEE core a gene cassette consisting of efa1/lifA gene and flanking IS elements suggests another putative transposon within the PAI(IRW1374). In addition, the ent gene, encoding a Shigella ShET-2 enterotoxin homologue, is present about 57 kb upstream of the LEE core. This PAI is therefore a complex assembly of various virulence determinants including the efa1/lifA and the ent gene resembling O157:H7 PAI OI-122/SpLE3 as well as the LEE core region. An integrase gene on the very left end of PAI I(Rw1374) is disrupted by an IS629 homologue. In an attempt to mobilize the LEE core we performed conjugation, transformation and transduction experiments. We were, however, unable to mobilize the whole or even single regions of PAI I(RW1374). Comparative studies with other strains of serotype O103:H2 isolated from humans, bovines and food showed that they all harbored a similar phe V-inserted PAI including the virulence genes ent and lifA/efa1 as well as the large virulence-associated plasmid encoding the EHEC hemolysin. This combination of several virulence factors confirms the complex virulence of O103:H2 EHEC and may at least partly explain the high virulence of this EHEC serotype in humans.