Rebeccah J Mathews

Vitamin D3 down-regulates intracellular Toll-like receptor 9 expression and Toll-like receptor 9-induced IL-6 production in human monocytes

OBJECTIVE To determine whether vitamin D(3) modulates monocytic expression of intracellular Toll-like receptors (TLRs) 3, 7 and 9. METHODS Human monocytes were isolated from peripheral blood and cultured with 100 nM vitamin D(3) for 24, 48 and 72 h. Expression of CD14 and TLR2, TLR3, TLR4, TLR7 and TLR9 were examined by flow cytometry. Monocytes exposed to vitamin D(3) for 48 h were then stimulated with a TLR9 agonist for a further 24 h. The level of IL-6 secretion was measured by ELISA. RESULTS CD14 was up-regulated, whereas TLR2, TLR4 and TLR9 expression was down-regulated by vitamin D(3) exposure in a time-dependent manner. TLR3 expression was unaffected by vitamin D(3) and there was no measurable expression of TLR7 on the monocytes. TLR9-induced IL-6 production was impaired in monocytes treated with vitamin D(3) compared with untreated cells. CONCLUSION The intracellular TLRs are differentially regulated by vitamin D(3), with TLR9 being down-regulated by vitamin D(3) exposure whereas TLR3 was unaffected. This decreased TLR9 expression in monocytes had a downstream functional effect as these cells subsequently secreted less IL-6 in response to TLR9 challenge. This may have significant biological relevance and may be a factor in the association of vitamin D deficiency with susceptibility to autoimmune disease.

Evidence of NLRP3-inflammasome activation in rheumatoid arthritis (RA); genetic variants within the NLRP3-inflammasome complex in relation to susceptibility to RA and response to anti-TNF treatment

Background The NLRP3-inflammasome, implicated in the pathogenesis of several inflammatory disorders, has been analysed in rheumatoid arthritis (RA). Methods Relative gene expression of NLRP3-inflammasome components was characterised in PBMCs of 29 patients receiving infliximab. A total of 1278 Caucasian patients with RA from the Biologics in Rheumatoid Arthritis Genetics and Genomics Study Syndicate (BRAGGSS) cohort receiving tumour necrosis factor (TNF) antagonists (infliximab, adalimumab and etanercept) were genotyped for 34 single nucleotide polymorphisms (SNPs), spanning the genes NLRP3, MEFV and CARD8. Regression analyses were performed to test for association between genotype and susceptibility and treatment response (disease activity score across 28 joints (DAS28) and EULAR improvement criteria) at 6 months, with secondary expression quantitative trait loci (eQTL) analyses. Results At baseline, gene expression of ASC, MEFV, NLRP3-FL, NLRP3-SL and CASP1 were significantly higher compared with controls whereas CARD8 was lower in the patients. Caspase-1 and interleukin-18 levels were significantly raised in patients with RA. SNPs in NLRP3 showed association with RA susceptibility and EULAR response to anti-TNF in the BRAGGSS cohort, and in monocytes but not B cells, in eQTL analysis of 283 healthy controls. CARD8 SNPs were associated with RA susceptibility and DAS28 improvement in response to anti-TNF and eQTL effects in monocytes and B cells. Conclusions This study found evidence of modulation of the NLRP3-inflammasome in patients with RA prior to receiving infliximab and some evidence of association for SNPs at NLRP3 and CARD8 loci with RA susceptibility and response to anti-TNF. The SNPs associated with susceptibility/response are not the main eQTL variants for either locus, and the associations with treatment response require replication in an independent cohort.

Magnetic resonance imaging with hyperpolarized [1,4-(13)C2]fumarate allows detection of early renal acute tubular necrosis.

Acute kidney injury (AKI) is a common and important medical problem, affecting 10% of hospitalized patients, and it is associated with significant morbidity and mortality. The most frequent cause of AKI is acute tubular necrosis (ATN). Current imaging techniques and biomarkers do not allow ATN to be reliably differentiated from important differential diagnoses, such as acute glomerulonephritis (GN). We investigated whether 13C magnetic resonance spectroscopic imaging (MRSI) might allow the noninvasive diagnosis of ATN. 13C MRSI of hyperpolarized [1,4-13C2]fumarate and pyruvate was used in murine models of ATN and acute GN (NZM2410 mice with lupus nephritis). A significant increase in [1,4-13C2]malate signal was identified in the kidneys of mice with ATN early in the disease course before the onset of severe histological changes. No such increase in renal [1,4-13C2]malate was observed in mice with acute GN. The kidney [1-13C]pyruvate/[1-13C]lactate ratio showed substantial variability and was not significantly decreased in animals with ATN or increased in animals with GN. In conclusion, MRSI of hyperpolarized [1,4-13C2]fumarate allows the detection of early tubular necrosis and its distinction from glomerular inflammation in murine models. This technique may have the potential to identify a window of therapeutic opportunity in which emerging therapies might be applied to patients with ATN, reducing the need for acute dialysis with its attendant morbidity and cost.

Immune complexes stimulate CCR7-dependent dendritic cell migration to lymph nodes

Antibodies are critical for defense against a variety of microbes, but they may also be pathogenic in some autoimmune diseases. Many effector functions of antibodies are mediated by Fcγ receptors (FcγRs), which are found on most immune cells, including dendritic cells (DCs)—important antigen-presenting cells that play a central role in inducing antigen-specific tolerance or immunity. Following antigen acquisition in peripheral tissues, DCs migrate to draining lymph nodes via the lymphatics to present antigen to T cells. Here we demonstrate that FcγR engagement by IgG immune complexes (ICs) stimulates DC migration from peripheral tissues to the paracortex of draining lymph nodes. In vitro, IC-stimulated mouse and human DCs showed greater directional migration in a chemokine (C-C) ligand 19 (CCL19) gradient and increased chemokine (C-C) receptor 7 (CCR7) expression. Using intravital two-photon microscopy, we observed that local administration of IC resulted in dermal DC mobilization. We confirmed that dermal DC migration to lymph nodes depended on CCR7 and increased in the absence of the inhibitory receptor FcγRIIB. These observations have relevance to autoimmunity because autoantibody-containing serum from humans with systemic lupus erythematosus (SLE) and from a mouse model of SLE also increased dermal DC migration in vivo, suggesting that this process may occur in lupus, potentially driving the inappropriate localization of autoantigen-bearing DCs.

NOD-like receptors and inflammation

The nucleotide-binding and oligomerization domain, leucine-rich repeat (also known as NOD-like receptors, both abbreviated to NLR) family of intracellular pathogen recognition receptors are increasingly being recognized to play a pivotal role in the pathogenesis of a number of rare monogenic diseases, as well as some more common polygenic conditions. Bacterial wall constituents and other cellular stressor molecules are recognized by a range of NLRs, which leads to activation of the innate immune response and upregulation of key proinflammatory pathways, such as IL-1β production and translocation of nuclear factor-κB to the nucleus. These signalling pathways are increasingly being targeted as potential sites for new therapies. This review discusses the role played by NLRs in a variety of inflammatory diseases and describes the remarkable success to date of these therapeutic agents in treating some of the disorders associated with aberrant NLR function.

Rilonacept in the management of cryopyrin- associated periodic syndromes (CAPS)

Cryopyrin-associated periodic syndromes (CAPS) are a subgroup of the hereditary periodic fever syndromes, which are rare autoinflammatory and inherited disorders, characterized by recurrent inflammation and varying degrees of severity. CAPS are thought to be driven by excessive production of interleukin-1β (IL-1β), through over-activation of the inflammasome by gain of function mutations in the gene encoding cryopyrin (NLRP3). This conclusion is supported by the remarkable efficacy of IL-1β blockade in these conditions. Rilonacept (ArcalystTM; Regeneron) is the first us Food and Drug Administration-approved treatment for familial cold autoinflammatory syndrome and Muckle–Wells syndrome and the first in a new line of drugs designed for longer-acting IL-1 blockade. Rilonacept has been associated with a decrease in disease activity, high-sensitivity C-reactive protein (hsCRP) and serum amyloid A (SAA) in the treatment of CAPS. The clinical safety and efficacy of rilonacept in CAPS and non-CAPS populations will be summarized in this review. Rilonacept is also beneficial for patients who tolerate injections poorly, due to an extended half-life over the unapproved CAPS treatment, anakinra, requiring weekly rather than daily self-administration. Other autoinflammatory disorders may also benefit from rilonacept treatment, with clinical trials in progress for systemic onset juvenile idiopathic arthritis, gout and familial mediterranean fever.

Differential effects of infliximab on absolute circulating blood leucocyte counts of innate immune cells in early and late rheumatoid arthritis patients

Anti‐tumour necrosis factor (TNF) biologics have revolutionized therapy of rheumatoid arthritis (RA). We compared the effects of infliximab on numbers of circulating leucocyte subsets in early RA (disease/symptom duration of ≤1 year) and late RA patients (>1 year). A control group consisted of early RA patients treated with a combination of methotrexate (MTX) and methylprednisolone. Blood samples were obtained at baseline (pre‐therapy) from all RA patients, divided into three groups: (i) late RA receiving infliximab/MTX, (ii) early RA–infliximab/MTX, (iii) early RA–steroid/MTX, and also from follow‐up patients at 2 and 14 weeks. Significant differences in absolute counts of monocytes and granulocytes were observed between healthy controls and RA patients. At baseline CD14bright monocytes and CD16+ granulocytes were increased in both early RA and late RA patients. CD4+ T cells, CD8+ T cells and B cells were all increased at baseline in early RA, but not in late RA. At 2 weeks following infliximab treatment decreased granulocytes were observed in both early and late RA and decreased natural killer (NK) cells in late RA. CD16+ granulocytes and NK cells were also decreased at 14 weeks post‐infliximab in early RA. Biotinylated infliximab was used to detect membrane‐associated TNF (mTNF)‐expressing leucocytes in RA patients. CD16+ granulocytes, NK cells and CD14dim monocytes all expressed higher levels of mTNF in RA patients. In summary infliximab is associated with decreased CD16+ granulocyte and NK cell counts, possibly through binding of mTNF. Differential effects of infliximab between early and late RA suggest that pathogenic mechanisms change as disease progresses.

Fifth International Congress on Familial Mediterranean Fever and Systemic Autoinflammatory Diseases

The Fifth International Congress on Familial Mediterranean Fever and Systemic Autoinflammatory Diseases (Rome, Italy, 4–8 April, 2008) reviewed developments in the field of innate immunity and discussed their relevance to the pathogenesis of associated diseases. The meeting gathered over 300 participants from 32 countries. New modes of inheritance of autoinflammatory diseases, animal models, novel related genes and the remarkable efficacy of IL-1β blockage in most of these diseases were emphasized.