Undetectable mannose binding lectin and corticosteroids increase serious infection risk in Rheumatoid Arthritis

Background: Infection is the leading cause of death in rheumatoid arthritis (RA). Corticosteroid (CS) use is a known and important risk factor for serious infections (SIs). Mannose binding lectin (MBL) is a genetically determined component of the innate immune system implicated in neonatal infections. Objective: Our aim was to determine whether MBL deficiency is a risk factor for SIs in RA and to compare it with CS use and also synthetic and biologic disease-modifying antirheumatic drug (DMARD) therapy. Methods: Data on 228 patients with RA were collected for up to 7 years (median = 5.9 years). Serum MBL concentrations were determined in all patients receiving synthetic (n = 96) or biologic (n = 132) DMARD therapy. Results: High rates of SIs were observed in RA irrespective of treatment (17%). Similar rates of SIs were observed in synthetic and biologic DMARD users. The rates of single and multiple Sis were similar, irrespective of the use of a biologic agent. Undetectable MBL (\u3c56 ng/mL) concentrations and maintenance prednisolone at 10 mg per day or higher were associated with an increased risk for an SI, with incident risk ratio of 4.67 (P = .001) and 4.70 (P \u3c .001), respectively. Conclusions: Undetectable MBL and prednisolone confer a high risk for an SI. The use of biologic DMARDs did not confer substantial SI risk in this observational study. MBL deficiency is hitherto an unrecognized risk factor for an SI in RA

Therapeutic targeting of cathepsin C::from pathophysiology to treatment

Cathepsin C (CatC) is a highly conserved tetrameric lysosomal cysteine dipeptidyl aminopeptidase. The best characterized physiological function of CatC is the activation of pro-inflammatory granule-associated serine proteases. These proteases are synthesized as inactive zymogens containing an N-terminal pro-dipeptide, which maintains the zymogen in its inactive conformation and prevents premature activation, which is potentially toxic to the cell. The activation of serine protease zymogens occurs through cleavage of the N-terminal dipeptide by CatC during cell maturation in the bone marrow. In vivo data suggest that pharmacological inhibition of pro-inflammatory serine proteases would suppress or attenuate deleterious effects of inflammatory/auto-immune disorders mediated by these proteases. The pathological deficiency in CatC is associated with Papillon-Lefèvre syndrome. The patients however do not present marked immunodeficiency despite the absence of active serine proteases in immune defense cells. Hence, the transitory pharmacological blockade of CatC activity in the precursor cells of the bone marrow may represent an attractive therapeutic strategy to regulate activity of serine proteases in inflammatory and immunologic conditions. A variety of CatC inhibitors have been developed both by pharmaceutical companies and academic investigators, some of which are currently being employed and evaluated in preclinical/clinical trials

ATP modulates Ca2+ uptake by TRPV6 and is counteracted by isoform-specific phosphorylation

Ca2� homeostasis requires balanced uptake and extrusion, and dysregulation leads to disease. TRPV6 channels are homeostasis regulators, are upregulated in certain cancers, and show an unusual allelespecific evolution in humans. To understand how Ca2� uptake can be adapted to changes in metabolic status, we investigate regulation of Ca2�-influx by ATP and phosphorylation. We show that ATP binds to TRPV6, reduces whole-cell current increments, and prevents channel rundown with an EC50 of 380 �M. By using both biochemical binding studies and patch-clamp analyses of wild-type and mutant channels, we have mapped one relevant site for regulation by ATP to residues within the ankyrin repeat domain (ARD) and identify an additional C-terminal binding region. Stimulation of PKC largely prevented the effects of ATP. This regulation requires PKC�II and defined phosphorylation sites within the ARD and the C-terminus. Both regulatory sites act synergistically to constitute a novel mechanism by which ATP stabilizes channel activity and acts as a metabolic switch for Ca2� influx. Decreases in ATP concentration or activation of PKC�II disable regulation of the channels by ATP, rendering them more susceptible to inactivation and rundown and preventing Ca2� overload.—Al-Ansary, D., Bogeski, I., Disteldorf, B. M. J., Becherer, U., Niemeyer, B. A. ATP modulates Ca2� uptake by TRPV6 and is counteracted by isoformspecific phosphorylation