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Damage-associated molecular pattern molecules, such as heat shock proteins and S100 proteins, represent tissue danger signals, which mediate inflammatory responses after being released from activated or necrotic cells. These danger signals, and their receptors, could be targets for novel approaches in the treatment of rheumatic diseases, as discussed in this article. Innate immunity achieves our primary host defense by recognizing invading microorganisms through pathogen-associated molecular patterns (PAMPs) and by reacting to tissue damage signals called damage-associated molecular patterns (DAMPs). DAMP molecules, including high mobility group box 1 protein (HMGB-1), heat-shock proteins (HSPs), uric acid, altered matrix proteins, and S100 proteins, represent important danger signals that mediate inflammatory responses through the receptor for advanced glycation end-products (RAGE, also known as AGER) and Toll-like receptors, after release from activated or necrotic cells. The terms 'alarmins' and 'endokines' have also been proposed for DAMP molecules. A prototypic DAMP molecule, the nuclear protein HMGB-1, is either passively released by necrotic cells or actively secreted with delay by activated cells. S100A8, S100A9, and S100A12 are calcium-binding proteins expressed in the cytoplasm of phagocytes. They are rapidly secreted by activated monocytes or neutrophils, which are abundant in inflamed synovial tissue. HSPs are involved in the crosstalk between innate and adaptive immune systems, and primarily mediate immune regulatory functions. Multiple positive feedback loops between DAMPs and PAMPs and their overlapping receptors temporally and spatially drive these processes and may represent the molecular basis for the observation that infections, as well as nonspecific stress factors, can trigger flares in rheumatic diseases. Key Points The innate immune system, as well as the adaptive immune system, has a key role in initiating and perpetuating synovial inflammation by responding to groups of macromolecules that represent a recognition pattern for potential threats to the host Owing to their similarities to cytokines and their release by activated or damaged cells under conditions of cell stress, the terms 'endokines', 'alarmins', or 'danger signals' have been used as synonyms for proinflammatory damage-associated molecular pattern molecules (DAMPs) DAMPs include high mobility group box 1 protein (HMGB-1), heat-shock proteins, uric acid, altered matrix proteins, S100 proteins, and a growing number of molecules associated with cell stress and necrosis As opposed to pathogen-associated molecular patterns (PAMPs), comprised of pathogen-derived factors, DAMPs represent endogenous molecules that are also ligands for pattern recognition receptors (PRRs) The multiligand receptor for advanced glycation end-products (RAGE) and Toll-like receptors are PRRs, which are involved in transducing signals after binding DAMP molecules The overlapping receptor systems of DAMPs and PAMPs may represent the molecular basis for the well-known link between nonspecific inflammatory triggers like infections and disease flares in autoimmune disorders

The receptor for advanced glycation end products (RAGE) is a multiligand receptor involved in a number of processes and disorders. While it is known that RAGE-signaling can contribute to toxic liver damage and fibrosis, its role in acute inflammatory liver injury and septic multiorgan failure is yet undefined. We examined RAGE in lipopolysaccharide (LPS) induced acute liver injury of D-galN sensitized mice as a classical model for tumor necrosis factor alpha (TNF-α) dependent inflammatory organ damage. Mice ( and C57BL/6) were intraperitoneally injected with D-galN (300 mg/kg) and LPS (10 μg/kg). Animals were monitored clinically, and cytokines, damage associated molecular pattern molecules (DAMPs) as well as liver enzymes were determined in serum. Liver histology, hepatic cytokines as well as RAGE mRNA expression were analyzed. Cellular activation and functionality were evaluated by flow cytometry both in bone marrow- and liver-derived cells. Genetic deficiency of RAGE significantly reduced the mortality of mice exposed to LPS/D-galN. Hepatocyte damage markers were reduced in mice, and liver histopathology was less severe. mice produced less pro-inflammatory cytokines and DAMPs in serum and liver. While immune cell functions appeared normal, TNF-α production by hepatocytes was reduced in mice. We found that RAGE deletion attenuated the expression of pro-inflammatory cytokines and DAMPs in hepatocytes without affecting cellular immune functions in the LPS/D-galN model of murine liver injury. Our data highlight the importance of tissue-specific RAGE-signaling also in acute inflammatory liver stress contributing to sepsis and multiorgan failure.

S100A12 is overexpressed during inflammation and is a marker of inflammatory disease. Furthermore, it has been ascribed to the group of damage-associated molecular pattern molecules that promote inflammation. However, the exact role of human S100A12 during early steps of immune activation and sepsis is only partially described thus far. We analyzed the activation of human monocytes by granulocyte-derived S100A12 as a key function of early inflammatory processes and the development of sepsis. Circulating S100A12 was determined in patients with sepsis and in healthy subjects with experimental endotoxemia. The release of human S100A12 from granulocytes as well as the promotion of inflammation by activation of human monocytes after specific receptor interaction was investigated by a series of in vitro experiments. S100A12 rises during sepsis, and its expression and release from granulocytes is rapidly induced in vitro and in vivo by inflammatory challenge. A global gene expression analysis of S100A12-activated monocytes revealed that human S100A12 induces inflammatory gene expression. These effects are triggered by an interaction of S100A12 with Toll-like receptor 4 (TLR4). Blocking S100A12 binding to TLR4 on monocytes or TLR4 expressing cell lines (HEK-TCM) abrogates the respective inflammatory signal. On the contrary, blocking S100A12 binding to its second proposed receptor (receptor for advanced glycation end products [RAGE]) has no significant effect on inflammatory signaling in monocytes and RAGE-expressing HEK293 cells. Human S100A12 is an endogenous TLR4 ligand that induces monocyte activation, thereby acting as an amplifier of innate immunity during early inflammation and the development of sepsis.

Familial Mediterranean fever (FMF) is caused by mutations within the Mediterranean fever ( ) gene. Disease severity depends on genotype and gene dose with most serious clinical courses observed in patients with M694V homozygosity. Neutrophils are thought to play an important role in the initiation and perpetuation of inflammatory processes in FMF, but little is known about the specific characteristics of these cells in FMF patients. To further characterize neutrophilic inflammatory responses in FMF and to delineate gene-dose effects on a cellular level, we analyzed cytokine production and activation levels of isolated neutrophils derived from patients and subjects with distinct genotypes, as well as healthy and disease controls. Serum levels of interleukin-18 (IL-18) (median 11,485 pg/ml), S100A12 (median 9,726 ng/ml), and caspase-1 (median 394 pg/ml) were significantly increased in patients with homozygous M694V mutations. Spontaneous release of S100A12, caspase-1, proteinase 3, and myeloperoxidase (MPO) was restricted to cultured neutrophils derived from patients with two pathogenic mutations. IL-18 secretion was highest in patients with two mutations but also increased in neutrophils from healthy heterozygous MEFV mutation carriers, exhibiting an gene-dose effect, which was formerly described by us in patients' serum. CD62L (l-selectin) was spontaneously shed from the surface of cultured neutrophils [median of geometric mean fluorescence intensity (gMFI) after 5 h: 28.8% of the initial level]. While neutrophils derived from healthy heterozygous mutation carriers again showed a gene-dose effect (median gMFI: 67.1%), healthy and disease controls had significant lower shedding rates (median gMFI: 83.6 and 82.9%, respectively). Co-culture with colchicine and/or stimulation with adenosine triphosphate (ATP) and lipopolysaccharide (LPS) led to a significant increase in receptor shedding. Neutrophils were not prevented from spontaneous shedding by blocking IL-1 or the NLRP3 inflammasome. In summary, the data demonstrate that cultured neutrophils derived from FMF patients display a unique phenotype with spontaneous release of high amounts of IL-18, S100A12, MPO, caspase-1, and proteinase 3 and spontaneous activation as demonstrated by the loss of CD62L. Neutrophilic activation seems to be independent from IL-1 activation and displays a gene-dose effect that may be responsible for genotype-dependent phenotypes.

Background Analysis of myeloid-related protein 8 and 14 complex (MRP8/14) serum concentrations is a potential new tool to support the diagnosis of systemic-onset juvenile idiopathic arthritis (SJIA) in the presence of fever of unknown origin. Objective To test the ability of MRP8/14 serum concentrations to monitor disease activity in patients with SJIA and stratify patients at risk of relapse. Methods Serum concentrations of MRP8/14 in 52 patients with SJIA were determined by a sandwich ELISA. The monitoring of therapeutic regimens targeting interleukin 1 and tumour necrosis factor α, and methotrexate treatment was analysed and diagnostic power to predict flares was tested. Results MRP8/14 levels were clearly raised in active disease and decreased significantly in response to successful treatments. Serum concentrations of MRP8/14 increased significantly (p<0.001) (mean±95% CI 12.030±3.090 ng/ml) during disease flares compared with patients with inactive disease (864±86 ng/ml). During clinical remission MRP8/14 serum levels of >740 ng/ml predicted disease flares accurately (sensitivity 92%, specificity 88%). MRP8/14 levels correlated well with clinical disease activity, as assessed by physician's global assessment of disease activity (r=0.62), Childhood Health Assessment Questionnaire (r=0.56), active joint count (r=0.46) and with C-reactive protein (r=0.71) and erythrocyte sedimentation rate (r=0.72) (for all p<0.001). Conclusion MRP8/14 serum concentrations correlate closely with response to drug treatment and disease activity and therefore might be an additional measurement for monitoring anti-inflammatory treatment of individual patients with SJIA. MRP8/14 serum concentrations are the first predictive biomarker indicating subclinical disease activity and stratifying patients at risk of relapse during times of clinically inactive disease.

Prediction of inflammatory bowel disease relapse has important implications for therapeutic strategies. Fecal S100A12 has been reported as a novel marker of intestinal inflammation. The objective was to investigate the utility of S100A12 as a marker for the confirmation of stable remission and prediction of relapses.MethodsWe consecutively included 147 adults and 34 children with Crohn’s disease (n = 61) or ulcerative colitis (n = 120). Over a 3-year period, we collected 686 stool samples and 861 serum samples during regular follow-up visits. S100A12 and calprotectin levels were measured by an enzyme-linked immunoassay.ResultsFecal S100A12 correlated with S100A12 serum levels, other laboratory markers, as well as disease activity, location, and behavior. Fecal S100A12 levels in the relapse group differed significantly from those of the nonrelapse group. A baseline fecal S100A12 level of >0.5 mg/kg was significantly associated with disease relapse within 18 months. Time course analysis of fecal S100A12 before and after relapse showed a clear increase of S100A12 concentrations up to 6 months before clinical relapse. At 0.43 mg/kg, the sensitivity and specificity of S100A12 for predicting relapse already 8 to 12 weeks earlier were 70% and 83%, respectively.ConclusionsRegular measurements of fecal S100A12 levels reliably detect inflammatory bowel disease relapse at an early stage, which makes the test a promising noninvasive tool for monitoring and optimizing therapy, and may reduce the need for invasive investigations during disease follow-up.

Background Systemic juvenile idiopathic arthritis (SJIA) is an autoinflammatory disease associated with chronic arthritis. Early diagnosis and effective therapy of SJIA is desirable, so that complications are avoided. The PRO-KIND initiative of the German Society for Pediatric Rheumatology (GKJR) aims to define consensus-based strategies to harmonize diagnostic and therapeutic approaches in Germany. Methods We analyzed data on patients diagnosed with SJIA from 3 national registries in Germany. Subsequently, via online surveys and teleconferences among pediatric rheumatologists with a special expertise in the treatment of SJIA, we identified current diagnostic and treatment approaches in Germany. Those were harmonized via the formulation of statements and, supported by findings from a literature search. Finally, an in-person consensus conference using nominal group technique was held to further modify and consent the statements. Results Up to 50% of patients diagnosed with SJIA in Germany do not fulfill the International League of Associations for Rheumatology (ILAR) classification criteria, mostly due to the absence of chronic arthritis. Our findings suggest that chronic arthritis is not obligatory for the diagnosis and treatment of SJIA, allowing a diagnosis of probable SJIA. Malignant, infectious and hereditary autoinflammatory diseases should be considered before rendering a diagnosis of probable SJIA. There is substantial variability in the initial treatment of SJIA. Based on registry data, most patients initially receive systemic glucocorticoids, however, increasingly substituted or accompanied by biological agents, i.e. interleukin (IL)-1 and IL-6 blockade (up to 27.2% of patients). We identified preferred initial therapies for probable and definitive SJIA, including step-up patterns and treatment targets for the short-term (resolution of fever, decrease in C-reactive protein by 50% within 7 days), the mid-term (improvement in physician global and active joint count by at least 50% or a JADAS-10 score of maximally 5.4 within 4 weeks) and the long-term (glucocorticoid-free clinically inactive disease within 6 to 12 months), and an explicit treat-to-target strategy. Conclusions We developed consensus-based strategies regarding the diagnosis and treatment of probable or definitive SJIA in Germany.

The inflammasome has been recognized as one of the key components of innate immunity. Gain-of-function mutations in the exon 3 of gene have been implicated in inflammatory diseases suggesting the presence of functionally important sites in this region. Q703K (c.2107C>A, p.Gln703Lys, also known in the literature as Q705K) is a common variant of , that has been considered to be both clinically unremarkable or disease-causing with a reduced penetrance. We aimed to investigate the potential genetic impact of the variant Q703K in patients with recurrent fever presenting with two autoinflammatory diseases: PFAPA (periodic fever, aphthous stomatitis, pharyngitis and cervical adenitis) and CAPS (cryopyrin-associated periodic syndrome), as well as with undefined autoinflammatory disease (uAID). This is an international multicentric observational retrospective study characterizing the clinical phenotype of patients presenting with recurrent fever suspected to be of auto-inflammatory origin and where the Q703K variant was found. Monocytes of parents of 6 Q703K+ PFAPA patients were studied and levels of pro-inflammatory cytokines produced by monocytes of Q703K+ and Q703K- parents have been compared by ELISA. We report 42 patients with the Q703K genetic variant: 21 were PFAPA patients, 6 had a CAPS phenotype, and 15 had an uAID. The phenotypes of PFAPA, CAPS and uAID were quite similar between Q703K positive and negative patients with the exception of increased prevalence of pharyngitis in the Q703K positive CAPS population compared to the negative one. The production of IL-1β was not significantly different between Q703K+ and Q703K- monocytes from asymptomatic parents. The evidence we report in our study shows an increased prevalence of Q703K in patients with autoinflammatory diseases, suggesting an association between the Q703K variant and the risk of PFAPA, CAPS and uAID syndromes. However, we did not show a functional effect of this mutation on the inflammasome basal activity.

Objectives To assess the sensitivity of the phagocyte-specific molecules myeloid-related protein (MRP) 8 and MRP14 (calprotectin) for monitoring disease activity during anti-interleukin (IL)-1 therapies in patients with cryopyrin-associated periodic syndromes (CAPS), including familial cold autoinflammatory syndrome (FCAS), Muckle–Wells syndrome (MWS) and chronic infantile neurological, cutaneous and articular (CINCA) syndrome. Methods A total of 39 patients with CAPS, including 5 FCAS, 16 MWS and 18 CINCA syndrome, received anti-IL-1 therapy. All patients with CINCA and 12 with MWS were treated with IL-1Ra (anakinra), 14 patients with MWS with a monoclonal anti-IL-1β antibody (canakinumab) and patients with FCAS received IL-1 Trap (rilonacept). During serial clinical visits serum amyloid A, C-reactive protein, erythrocyte sedimentation rate and MRP8/14 serum levels were analysed. Results Untreated patients with CAPS had significantly elevated MRP8/14 values. In response to treatment there was a significant reduction of MRP8/14 levels in CINCA (2,830 (range 690 – 8,480) ng/ml to 670 ng/ml, p < 0.001) and MWS patients (anakinra-treated: 4,390 (1790 – 9780) ng/ml to 1,315 ng/ml (p = 0.003); canakinumab-treated: 3,000 (500 – 13060) ng/ml to 630 ng/ml (p=0.001)). However, in many patients with CAPS, MRP8/14 levels were still elevated compared with healthy individuals, reflecting residual disease activity. However, canakinumab-treated patients with CAPS showed normalised MRP8/14 levels, suggesting control of phagocyte activation. Conclusions Monitoring of cellular systems involved in inflammatory cascades of the innate immunity was successfully applied to the IL-1-driven CAPS diseases. This is the first study illustrating different states of subclinical disease activity in all types of CAPS depending on the type of anti-IL-1 therapy. MRP8/14 is a sensitive biomarker for monitoring disease activity, status of inflammation and response to IL-1 blockade in patients with CAPS.

Background The objective of this initiative was to develop a treat-to-target (T2T) approach for the management of patients with Familial Mediterranean Fever (FMF), including the definition of a complex treatment target, and establish strategies that improve patient care and long-term outcome. Methods An initial set of statements as well as a flow chart visualising the proposed concept was developed. To adapt the preliminary statements to the current state of knowledge, a systematic literature search was performed and the modified statements were subject to a Delphi approach. To ensure the applicability of the statements in daily practice, an online survey was conducted among paediatric rheumatologists in Germany. In addition, data from the national AID-NET registry were analysed with respect to therapeutic response. Results This T2T initiative yielded a total of 26 statements guiding FMF management with respect to diagnosis, treatment targets, treatment strategies and monitoring. The online survey identified cut-off values for inflammatory markers indicating treatment intensification and appropriate measures in case of colchicine intolerance or non-adherence. The analysis of data derived from the national AID-NET showed that colchicine therapy was successfully terminated in 61% of patients (27 out of 44) with heterozygous MEFV mutations. Multidimensional treatment targets incorporating objective and subjective reported outcome measures were developed. These provide the basis for stratifying patients into the following treatment paths: continue colchicine, persisting attacks / inflammation, colchicine intolerance, persisting arthritis, colchicine reduction and adjustment/reduction of biologics. Conclusions The proposed consensus treatment plan for the management of FMF incorporates multidimensional targets allowing transparent treatment decisions, which will promote personalised disease management and increase adherence to therapy.