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IntroductionObesity is associated with a plethora of health complications, including increased susceptibility to infections or decreased vaccine efficacy, partly due to dysregulated immune responses. Monocytes play a crucial role in innate immunity, yet their functional alterations in obesity remain poorly understood.MethodsHere, we employed proteomic and metabolomic analyses to investigate monocyte characteristics in individuals with overweight, obesity, impaired glucose tolerance (IGT), and type 2 diabetes (T2D), compared to lean donors.Results and discussionOur results revealed distinct molecular signatures in monocytes from individuals with obesity, with significant alterations in pathways related to metabolism, cellular migration, and phagocytosis. Moreover, LPS-induced activation of monocytes unveiled heightened metabolic reprogramming towards glycolysis in subjects with obesity accompanied by dysregulated cytokine responses and elevated oxidative stress. Additionally, monocytes from donors with obesity exhibited increased lipid droplet accumulation. These findings shed light on the immunometabolic dysregulation underlying obesity-associated immune dysfunction, highlighting potential targets for therapeutic intervention.

Background: Radiographic axial spondyloarthritis (r-axSpA), formerly known as ankylosing spondylitis (AS), is a chronic, inflammatory rheumatic disease associated with symptoms such as inflammatory back pain, morning stiffness, and arthritis. First-line recommendations for patients with AS include treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) for reducing pain and stiffness. Objectives: The objective of our study is to evaluate the efficacy and short-term NSAID-sparing effect of secukinumab in patients with AS currently treated with NSAIDs. Design: We assessed the clinical Assessment of SpondyloArthritis International Society (ASAS20) response to secukinumab and evaluated the extent to which the use of concomitant NSAID can be reduced between weeks 4 and 12 in r-axSpA patients treated with secukinumab 150 mg compared with placebo. Methods: ASTRUM was a prospective 24-week randomized controlled trial of adult patients with active r-axSpA [Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) ⩾4] who had a documented inadequate response to ⩾2 NSAIDs. Patients were randomized (1:1:1) to initiate treatment with subcutaneous secukinumab 150 mg from either week 0 (group 1), week 4 (group 2), or week 16 (group 3). From week 4 onward, tapering of NSAIDs was allowed in all groups. Results: This study included 211 patients ( n = 71, 70, and 70 in groups 1, 2, and 3, respectively). ASAS20 response at week 12 for pooled groups 1 and 2 versus group 3 was 51.1% versus 44.3% ( p = 0.35). A higher proportion of patients in groups 1 and 2 achieved ASAS40 and BASDAI50 and showed improvements in other secondary clinical outcomes as compared to group 3 at week 16. More patients in groups 1 and 2 versus group 3 stopped their NSAID intake from baseline through week 16. Conclusion: Treatment with secukinumab improved clinical outcomes and showed a short-term NSAID-sparing effect in patients with r-axSpA, even though the primary endpoint was not met. Trial registration: ClinicalTrials.gov; NCT02763046, EudraCT 2015-004575-74.

The calcium-sensing receptor (CaSR) is expressed in many cell types – including immune cells and in particular circulating monocytes. Here, the receptor plays an important physiological role as a regulator of constitutive macropinocytosis. This review article provides an overview of the literature on the role of the calcium sensing receptor in the context of inflammatory processes. Special emphasis is laid upon the importance for monocytes in the context of rheumatoid arthritis. We have shown previously, that stimulation of the receptor by increased extracellular Ca2+ ([Ca2+]ex) triggers a pro-inflammatory response due to NLRP3 inflammasome assembly and interleukin (IL)-1β release. The underlying mechanism includes macropinocytosis of calciprotein particles (CPPs), which are taken up in a [Ca2+]ex-induced, CaSR dependent manner, and leads to strong IL-1β release. In rheumatoid arthritis (RA), this uptake and the resulting IL-1β release is significantly increased due to increased expression of the receptor. Moreover, increased [Ca2+]ex-induced CPP uptake and IL-1β release is associated with more active disease, while CaSR overexpression has been reported to be associated with cardiovascular complications of RA. Most importantly, however, in animal experiments with arthritic mice, increased local calcium concentrations are present, which in combination with release of fetuin-A from eroded bone could contribute to formation of CPPs. We propose, that increased [Ca2+]ex, CPPs and pro-inflammatory cytokines drive a vicious cycle of inflammation and bone destruction which in turn offers new potential therapeutic approaches.

Abstract Inflammation driven by intracellular activation of the NLRP3 inflammasome is involved in the pathogenesis of a variety of diseases including vascular pathologies. Inflammasome specks are released into the extracellular compartment from disrupting pyroptotic cells. The potential uptake and function of extracellular NLRP3 inflammasomes in human coronary artery smooth muscle cells (HCASMC) are unknown. Fluorescently labeled NLRP3 inflammasome particles were isolated from a mutant NLRP3-YFP cell line and used to treat primary HCASMC for 4 and 24 h. Fluorescent and expressional analyses showed that extracellular NLRP3-YFP particles are internalized into HCASMC, where they remain active and stimulate intracellular caspase-1 (1.9-fold) and IL-1β (1.5-fold) activation without inducing pyroptotic cell death. Transcriptomic analysis revealed increased expression level of pro-inflammatory adhesion molecules (ICAM1, CADM1), NLRP3 and genes involved in cytoskleleton organization. The NLRP3-YFP particle-induced gene expression was not dependent on NLRP3 and caspase-1 activation. Instead, the effects were partly abrogated by blocking NFκB activation. Genes, upregulated by extracellular NLRP3 were validated in human carotid artery atheromatous plaques. Extracellular NLRP3-YFP inflammasome particles promoted the secretion of pro-atherogenic and inflammatory cytokines such as CCL2/MCP1, CXCL1 and IL-17E, and increased HCASMC migration (1.8-fold) and extracellular matrix production, such as fibronectin (5.8-fold) which was dependent on NFκB and NLRP3 activation. Extracellular NLRP3 inflammasome particles are internalized into human coronary artery smooth muscle cells where they induce pro-inflammatory and pro-atherogenic effects representing a novel mechanism of cell-cell communication and perpetuation of inflammation in atherosclerosis. Therefore, extracellular NLRP3 inflammasomes may be useful to improve the diagnosis of inflammatory diseases and the development of novel anti-inflammatory therapeutic strategies.

How extracellular calcium can trigger Nlrp3 inflammasome activation has been somewhat controversial and unclear. Here the authors show calciprotein particles are taken up by myeloid cells via calcium-sensing receptor-dependent macropinocytosis in response to high levels of extracellular Ca2+ and this pathway might be critical to inflammatory conditions.

Background: Vaccination rates are known to be low in patients with autoimmune inflammatory rheumatic diseases (AIIRD). We therefore aimed to determine current vaccination rates against influenza, Streptococcus pneumoniae and herpes zoster in a cohort of patients with AIIRD in Germany. Methods: Consecutive adult patients with an AIIRD were recruited from our outpatient clinic during their regular consultations. The individual vaccination status regarding influenza, Streptococcus pneumoniae and herpes zoster was obtained by reviewing the vaccination documents. Results: A total of 222 AIIRD patients (mean age 62.9 ± 13.9 years) were included. In total, 68.5% were vaccinated against influenza, 34.7% against Streptococcus pneumoniae and 13.1% against herpes zoster (HZ). The pneumococcal vaccination was outdated in 29.4% of the vaccinated patients. Vaccination rates were significantly higher in patients ≥60 years old (odds ratio (OR) 2.167, 95% confidence interval (CI) 1.213–3.870, p = 0.008 for influenza, OR 4.639, 95% CI 2.555–8.422, p < 0.0001 for pneumococcal and OR 6.059, 95% CI 1.772–20.712, p = 0.001 for HZ vaccination). Ages > 60 years, female sex, glucocorticoid use and influenza vaccination were all independently associated with a pneumococcal vaccination. Regarding influenza vaccination, only a positive pneumococcal vaccination history remained independently associated. In patients with HZ vaccination, glucocorticoid use and a preceding pneumococcal vaccination were independently associated with HZ protection. Conclusions: The frequencies of vaccinations against influenza, Streptococcus pneumoniae and HZ have increased during recent years. While this can be partly explained by continuous efforts in patient education during the outpatient visits, the COVID-19 pandemic might also have contributed. Nevertheless, the persistently high incidence and mortality of these preventable diseases in patients with AIIRDs mandates further efforts to increase vaccination coverage, particularly in SLE patients.

Reactive oxygen and nitrogen species (ROS/RNS) play an important role in the regulation of cardiac function. Increase in ROS/RNS concentration results in lipid and protein oxidation and is often associated with onset and/or progression of many cardiovascular disorders. However, interplay between lipid and protein modifications has not been simultaneously studied in detail so far. Biomolecule carbonylation is one of the most common biomarkers of oxidative stress. Using a dynamic model of nitroxidative stress we demonstrated rapid changes in biomolecule carbonylation in rat cardiomyocytes. Levels of carbonylated species increased as early as 15 min upon treatment with the peroxynitrite donor, 3-morpholinosydnonimine (SIN-1), and decreased to values close to control after 16 h. Total (lipids+proteins) vs. protein-specific carbonylation showed different dynamics, with a significant increase in protein-bound carbonyls at later time points. Treatment with SIN-1 in combination with inhibitors of proteasomal and autophagy/lysosomal degradation pathways allowed confirmation of a significant role of the proteasome in the degradation of carbonylated proteins, whereas lipid carbonylation increased in the presence of autophagy/lysosomal inhibitors. Electrophilic aldehydes and ketones formed by lipid peroxidation were identified and relatively quantified using LC-MS/MS. Molecular identity of reactive species was used for data-driven analysis of their protein targets. Combination of different enrichment strategies with LC-MS/MS analysis allowed identification of more than 167 unique proteins with 332 sites modified by electrophilic lipid peroxidation products. Gene ontology analysis of modified proteins demonstrated enrichment of several functional categories including proteins involved in cytoskeleton, extracellular matrix, ion channels and their regulation. Using calcium mobilization assays, the effect of nitroxidative stress on the activity of several ion channels was further confirmed. Keywords: Nitroxidative stress, Cardiomyocytes, Lipid oxidation, Protein oxidation, Lipid-protein adducts, Carbonylation

Circulating monocytes can be divided into classical (CM), intermediate (IM), and non-classical monocytes (NCM), and the classical monocytes also contain CD56+ monocytes and monocytic myeloid-derived suppressor cells (M-MDSC). The aim of the study was to evaluate the occurrence of the monocyte subpopulations in human obesity. Twenty-seven normal, 23 overweight, and 60 obese individuals (including 17 obese individuals with normal glucose tolerance and 27 with type 2 diabetes) were included into this study. Peripheral blood mononuclear cells were isolated from human blood, and surface markers to identify monocyte subpopulations were analyzed by flow cytometry. Obese individuals had higher numbers of total monocytes, CM, IM, CD56+ monocytes, and M-MDSCs. The number of CM, IM, CD56+ monocytes, and M-MDSCs, correlated positively with body mass index, body fat, waist circumference, triglycerides, C-reactive protein, and HbA1c, and negatively with high-density lipoprotein cholesterol. Individuals with obesity and type 2 diabetes had higher numbers of IM, NCM, and M-MDSCs, whereas those with obesity and impaired glucose tolerance had higher numbers of CD56+ monocytes. In summary, the comprehensive analysis of blood monocytes in human obesity revealed a shift of the monocyte compartment toward pro-inflammatory monocytes which might contribute to the development of low-grade inflammation in obesity, and immune-suppressive monocytes which might contribute to the development of cancer in obesity.

Monocytes enter sites of microbial or sterile inflammation as the first line of defense of the immune system and initiate pro-inflammatory effector mechanisms. We show that activation with bacterial lipopolysaccharide (LPS) induces them to undergo a metabolic shift toward aerobic glycolysis, similar to the Warburg effect observed in cancer cells. At sites of inflammation, however, glucose concentrations are often drastically decreased, which prompted us to study monocyte function under conditions of glucose deprivation and abrogated Warburg effect. Experiments using the Seahorse Extracellular Flux Analyzer revealed that limited glucose supply shifts monocyte metabolism toward oxidative phosphorylation, fueled largely by fatty acid oxidation at the expense of lipid droplets. While this metabolic state appears to provide sufficient energy to sustain functional properties like cytokine secretion, migration, and phagocytosis, it cannot prevent a rise in the AMP/ATP ratio and a decreased respiratory burst. The molecular trigger mediating the metabolic shift and the functional consequences is activation of AMP-activated protein kinase (AMPK). Taken together, our results indicate that monocytes are sufficiently metabolically flexible to perform pro-inflammatory functions at sites of inflammation despite glucose deprivation and inhibition of the LPS-induced Warburg effect. AMPK seems to play a pivotal role in orchestrating these processes during glucose deprivation in monocytes.

Peripheral CD4CD8 double positive (DP) T cells have been reported to play a role in several autoimmune diseases, virus infections and cancer. In rheumatoid arthritis (RA), both CD4 and CD8 single positive (SP) T cells are known to be involved in the pathogenesis, but the role of peripheral CD4CD8 DP T cells has not been investigated in detail. Anti cyclic citrullinated antibodies (ACPA) positive and ACPA negative RA patients, patients with systemic lupus erythematodes (SLE) and age matched healthy donors (HD) were enrolled in the analysis. The frequencies and phenotype of DP T cells in PBMC were investigated. In addition, DP T cells were quantified in biopsies from rheumatoid synovium. After in vitro restimulation, the cytokine production of DP T cells was investigated in cultures of PBMC. CMV specific cytokine secretion as well as proliferation was analyzed following antigen specific restimulation after an appropriate culture duration. DP T cells were found more frequently in RA patients than in healthy controls or patients with SLE. These DP T cells express αβ TCRs, are of a memory phenotype and share features of both CD4 as well as CD8 SP T cells. Importantly, DP T cells were found to also be present in the rheumatoid synovium. Further characterization of DP T cells from RA patients revealed increased production of IL-21 and IL-4, implying a possible role as T helper cells. In addition, DP T cells in RA seem to contribute to the inflammatory process, because they produce significantly more IFNγ than counterparts from HD and are increased in CMV+ RA patients. Given their capacity to produce a variety of cytokines (IL4, IL21 and IFNγ), their association with ACPA positive RA and their presence in the synovium, we suggest an important role of double positive T cells in the pathogenesis of rheumatoid arthritis.

In rheumatoid arthritis, a significant proportion of cytokine and chemokine synthesis is attributed to innate immune mechanisms. TLR4 is a prominent innate receptor since several endogenous ligands known to activate the innate immune system bind to it and may thereby promote joint inflammation. We generated TLR4 deficient DBA1J mice by backcrossing the TLR4 mutation present in C3H/HeJ strain onto the DBA1J strain and investigated the course of collagen-induced arthritis in TLR4 deficient mice in comparison to wild type littermates. The incidence of collagen- induced arthritis was significantly lower in TLR4 deficient compared to wild type mice (59 percent vs. 100 percent). The severity of arthritis was reduced in the TLR4 deficient mice compared to wild type littermates (mean maximum score 2,54 vs. 6,25). Mice deficient for TLR4 were virtually protected from cartilage destruction, and infiltration of inflammatory cells was reduced compared to wt mice. In parallel to the decreased clinical severity, lower anti-CCP antibody concentrations and lower IL-17 concentrations were found in the TLR4 deficient mice. The study further supports the role of TLR4 in the propagation of joint inflammation and destruction. Moreover, since deficiency in TLR4 led to decreased IL-17 and anti-CCP antibody production, the results indicate a link between TLR4 stimulation and the adaptive autoimmune response. This mechanism might be relevant in human rheumatoid arthritis, possibly in response to activating endogenous ligands in the affected joints.