Association of Serum Soluble Transferrin Receptor Concentration With Markers of Inflammation: Analysis of 1001 Patients From a Tertiary Rheumatology Center

OBJECTIVE

Soluble transferrin receptor (sTfR) is considered to be a useful biomarker for the diagnosis of iron deficiency, especially in the setting of inflammation, as it is thought to not be affected by inflammation. We analyzed the relationship between sTfR levels and inflammatory markers in patients with known or suspected inflammatory rheumatic disease (IRD).

METHODS

Blood samples of 1001 patients with known or suspected IRD referred to a tertiary rheumatology center were analyzed. Study participants were classified as patients with active IRD and patients with inactive IRD or without IRD. Correlation analyses were used to explore the relationship between sTfR levels and inflammatory markers (ie, C-reactive protein [CRP], erythrocyte sedimentation rate [ESR]). We applied multiple linear regression analysis to evaluate the predictive value of CRP levels for sTfR concentrations after adjustment for potential confounding factors.

RESULTS

There were positive correlations between inflammatory markers (CRP, ESR) and serum sTfR levels (ρ 0.44, ρ 0.43, respectively; P < 0.001), exceeding the strength of correlation between inflammatory markers and the acute phase reactant ferritin (ρ 0.30, ρ 0.23, respectively; P < 0.001). Patients with active IRD demonstrated higher serum sTfR levels compared to patients with inactive or without IRD (mean 3.99 [SD 1.69] mg/L vs 3.31 [SD 1.57] mg/L; P < 0.001). After adjustment for potential confounding factors, CRP levels are predictive for serum sTfR concentrations (P < 0.001).

CONCLUSION

The study provides evidence against the concept that sTfR is a biomarker not affected by inflammation.

Medically Unexplained Symptoms Are Linked to Chronic Inflammatory Diseases: Is There a Role for Frontal Cerebral Blood Oxygen Content?

INTRODUCTION

Patients often go to the physician with medically unexplained symptoms (MUS). MUS can be autonomic nervous system-related "unspecific" symptoms, such as palpitations, heart rhythm alterations, temperature dysregulation (hand, feet), anxiety, or depressive manifestations, fatigue, somnolence, nausea, hyperalgesia with varying pains and aches, dizziness, etc. Methods: In this real-world study, we investigated MUS in a cohort of unselected outpatients from general practitioners in Italy. It was our aim to increase the understanding of MUS by using principal component analyses to identify any subcategories of MUS and to check a role of chronic inflammatory diseases. Additionally, we studied cerebral blood oxygen (rCBO2) and associations with MUS and chronic inflammatory disease.

RESULTS

Participants included 1,597 subjects (50.6 ± 0.4 years, 65%/35% women/men). According to ICD-10 codes, 137 subjects had chronic inflammatory diseases. MUS were checked by a questionnaire with a numeric rating scale and cerebral blood flow with optical techniques. The analyses of men and women were stratified. Psychological symptom severity was higher in the inflamed compared to the non-inflamed group (fatigue, insomnia in women and men; recent mood changes, daytime sleepiness, anxiety, apathy, cold hands only in women; abnormal appetite and heart rhythm problems only in men). Principal component analysis with MUS provided new subcategories: brain symptoms, gut symptoms, and unspecific symptoms. Brain and gut symptoms were higher in inflamed women and men. Chronic inflammatory diseases and pain were tightly interrelated in men and women (p < 0.0001). In women, not in men, average frontal rCBO2 content was higher in inflamed compared to non-inflamed subjects. In men, not in women, individuals with pain demonstrated a lower average frontal rCBO2 content compared to pain-free men. MUS did not relate to rCBO2 parameters.

CONCLUSION

This study shows close relationships between MUS and chronic inflammatory diseases but not between MUS and rCBO2 parameters.

Heat of the night: sleep disturbance activates inflammatory mechanisms and induces pain in rheumatoid arthritis

Sleep has a homeostatic role in the regulation of the immune system and serves to constrain activation of inflammatory signalling and expression of cellular inflammation. In patients with rheumatoid arthritis (RA), a misaligned inflammatory profile induces a dysregulation of sleep-wake activity, which leads to excessive inflammation and the induction of increased sensitivity to pain. Given that multiple biological mechanisms contribute to sleep disturbances (such as insomnia), and that the central nervous system communicates with the innate immune system via neuroendocrine and neural effector pathways, potential exists to develop prevention opportunities to mitigate the risk of insomnia in RA. Furthermore, understanding these risk mechanisms might inform additional insomnia treatment strategies directed towards steering and reducing the magnitude of the inflammatory response, which together could influence outcomes of pain and disease activity in RA.

[Role of the sympathetic nervous system in chronic inflammation]

In this review article the current model of the interaction between the sympathetic nervous system (SNS) and the immune system in the context of chronic inflammation is presented. Mechanisms in the interaction between the SNS and the immune system are shown, which are similar for all disease entities: 1) the biphasic effect of the sympathetic system on the inflammatory response with a proinflammatory, stimulating effect before and during the activation of the immune system (early) and a more inhibitory effect in late phases of immune activation (chronic). 2) The interruption of communication between immune cells and the brain by withdrawal of sympathetic nerve fibers from areas of inflammation, such as the spleen, lymph nodes or peripheral foci of inflammation. 3) The local replacement of catecholamines by neurotransmitter-producing cells to fine-tune the local immune response independently of the brain. 4) Increased activity of the SNS due to an imbalance of the autonomic nervous system at the systemic level, which provides an explanation for known disease sequelae and comorbidities due to the long duration of chronic inflammatory reactions, such as increased cardiovascular risk with hypertension, diabetes mellitus and catabolic metabolism. The understanding of neuroimmune interactions can lead to new therapeutic approaches, e.g., a stimulation of beta-adrenergic and even more an inhibition of alpha-adrenergic receptors or a restoration of the autonomic balance in the context of arthritis ) can make an anti-inflammatory contribution (more influence of the vagus nerve); however, in order to translate the theoretical findings into clinical action that is beneficial for the patient, controlled interventional studies are required.

[Energy metabolism of the immune system : Consequences in chronic inflammation]

BACKGROUND

Energy is the currency of life. The systemic and intracellular energy metabolism plays an essential role for the energy supply of the resting and activated immune system and this also applies to chronic inflammatory diseases.

OBJECTIVE

This presentation examines both components of the systemic and cellular energy metabolism in health and chronic inflammation.

MATERIAL AND METHODS

A literature search was conducted using PubMed, Embase and the Cochrane Library. The information is presented in the form of a narrative review.

RESULTS

A chronically activated immune system acquires large amounts of energy-rich substrates that are lost for other functions of the body. In particular, the immune system and the brain are in competition. The consequences of this competition are many known diseases, such as fatigue, anxiety, depression, anorexia, sleep problems, sarcopenia, osteoporosis, insulin resistance, hypertension and others. The permanent change in the brain causes long-term alterations that stimulate disease sequelae even after disease remission. In the intracellular energy supply, chronic inflammation typically involves a conversion to glycolysis (to lactate, which has its own regulatory functions) and the pentose phosphate pathway in disorders of mitochondrial function. The chronic changes in immune cells of patients with rheumatoid arthritis (RA) lead to a disruption of the citric acid cycle (Krebs cycle). The hypoxic situation in the inflamed tissue stimulates many alterations. A differentiation is made between effector functions and regulatory functions of immune cells.

CONCLUSION

Based on the energy changes mentioned, novel treatment suggestions can be made in addition to those already known in energy metabolism.

Chronic Effects of the Sympathetic Nervous System in Inflammatory Models

The immune system is embedded in a network of regulatory systems to keep homeostasis in case of an immunologic challenge. Neuroendocrine immunologic research has revealed several aspects of these interactions over the past decades, e.g., between the autonomic nervous system and the immune system. This review will focus on evidence revealing the role of the sympathetic nervous system (SNS) in chronic inflammation, like colitis, multiple sclerosis, systemic sclerosis, lupus erythematodes, and arthritis with a focus on animal models supported by human data. A theory of the contribution of the SNS in chronic inflammation will be presented that spans these disease entities. One major finding is the biphasic nature of the sympathetic contribution to inflammation, with proinflammatory effects until the point of disease outbreak and mainly anti-inflammatory influence thereafter. Since sympathetic nerve fibers are lost from sites of inflammation during inflammation, local cells and immune cells achieve the capability to endogenously produce catecholamines to fine-tune the inflammatory response independent of brain control. On a systemic level, it has been shown across models that the SNS is activated in inflammation as opposed to the parasympathetic nervous system. Permanent overactivity of the SNS contributes to many of the known disease sequelae. One goal of neuroendocrine immune research is defining new therapeutic targets. In this respect, it will be discussed that at least in arthritis, it might be beneficial to support β-adrenergic and inhibit α-adrenergic activity besides restoring autonomic balance. Overall, in the clinical setting, we now need controlled interventional studies to successfully translate the theoretical knowledge into benefits for patients.

The PMN-MDSC - A key player in glucocorticoid resistance following combined physical and psychosocial trauma

Stress-associated somatic and psychiatric disorders are often linked to non-resolving low-grade inflammation, which is promoted at least in part by glucocorticoid (GC) resistance of distinct immune cell subpopulations. While the monocyte/macrophage compartment was in the focus of many clinical and preclinical studies, the role of myeloid-derived suppressor cells (MDSCs) in stress-associated pathologies and GC resistance is less understood. As GC resistance is a clear risk factor for posttraumatic complications in patients on intensive care, the exact interplay of physical and psychosocial traumatization in the development of GC resistance needs to be further clarified. In the current study we employ the chronic subordinate colony housing (CSC) paradigm, a well-characterized mouse model of chronic psychosocial stress, to study the role of myeloid cells, in particular of MDSCs, in innate immune activation and GC resistance following combined psychosocial and physical (e.g., bite wounds) trauma. Our findings support the hypothesis that stress-induced neutrophils, polymorphonuclear (PMN)-MDSCs and monocytes/monocyte-like (MO)-MDSCs get primed and activated locally in the bone marrow as determined by toll-like receptor (TLR)2 upregulation and increased basal and lipopolysaccharide (LPS)-induced in vitro cell viability. These primed and activated myeloid cells emigrate into the peripheral circulation and subsequently, if CSC is accompanied by significant bite wounding, accumulate in the spleen. Here, PMN-MDSCs and monocytes/MO-MDSCs upregulate TLR4 expression, which exclusively in PMN-MDSCs promotes NF-κB hyperactivation upon LPS-stimulation, thereby exceeding the anti-inflammatory capacities of GCs and resulting in GC resistance.

The transition between acute and chronic infections in light of energy control: a mathematical model of energy flow in response to infection

Background: Different parts of an organism like the gut, endocrine, nervous and immune systems constantly exchange information. Understanding the pathogenesis of various systemic chronic diseases increasingly relies on understanding how these subsystems orchestrate their activities. Methods: We started from the working hypothesis that energy is a fundamental quantity that governs activity levels of all subsystems and that interactions between subsystems control the distribution of energy according to acute needs. Based on physiological knowledge, we constructed a mathematical model for the energy flow between subsystems and analysed the resulting organismal responses to in silico infections. Results: The model reproduces common behaviour in acute infections and suggests several host parameters that modulate infection duration and therapeutic responsiveness. Moreover, the model allows the formulation of conditions for the induction of chronic infections and predicts that alterations in energy released from fat can lead to the transition from clearance of acute infections to a chronic inflammatory state. Impact: These results suggest a fundamental role for brain and fat in controlling immune response through systemic energy control. In particular, it suggests that lipolysis resistance, which is known to be involved in obesity and ageing, might be a survival programme for coping with chronic infections.

Sympathectomy aggravates subchondral bone changes during osteoarthritis progression in mice without affecting cartilage degeneration or synovial inflammation

OBJECTIVE

Osteoarthritis (OA) pathogenesis involves the interaction of articular cartilage with surrounding tissues, which are innervated by tyrosine hydroxylase-positive (TH+) sympathetic nerve fibers suggesting a role of the sympathetic nervous system (SNS) during OA progression. We analyzed the effects of sympathectomy (Syx) in a murine OA model.

METHODS

Peripheral Syx was generated by 6-hydroxydopamine (6-OHDA) injections in male C57BL/6 mice. OA was induced in wild-type (WT) and Syx mice by destabilization of the medial meniscus (DMM). TH+ fibers and splenic NE were analyzed to evaluate Syx efficiency. OA progression was examined by OARSI and synovitis scores and micro-CT. Expression of TH, α2A- and β2-adrenergic receptors (AR), and activity of osteoblasts (ALP) and osteoclasts (TRAP) was investigated by stainings.

RESULTS

Syx resulted in synovial TH+ fiber elimination and splenic NE decrease. Cartilage degradation and synovitis after DMM were comparably progressive in both WT and Syx mice. Calcified cartilage (CC) and subchondral bone plate (SCBP) thickness and bone volume fraction (BV/TV) increased in Syx mice due to increased ALP and decreased TRAP activities compared to WT 8 weeks after DMMWT and Syx mice developed osteophytes and meniscal ossicles without any differences between the groups. AR numbers decreased in cartilage but increased in synovium and osteophyte regions after DMM in both WT and Syx mice.

CONCLUSION

Peripheral dampening of SNS activity aggravated OA-specific cartilage calcification and subchondral bone thickening but did not influence cartilage degradation and synovitis. Therefore, SNS might be an attractive target for the development of novel therapeutic strategies for pathologies of the subchondral bone.

β2-Adrenoceptor Deficiency Results in Increased Calcified Cartilage Thickness and Subchondral Bone Remodeling in Murine Experimental Osteoarthritis

Purpose

Recent studies demonstrated a contribution of adrenoceptors (ARs) to osteoarthritis (OA) pathogenesis. Several AR subtypes are expressed in joint tissues and the β2-AR subtype seems to play a major role during OA progression. However, the importance of β2-AR has not yet been investigated in knee OA. Therefore, we examined the development of knee OA in β2-AR-deficient (Adrb2^-/-) mice after surgical OA induction.

Methods

OA was induced by destabilization of the medial meniscus (DMM) in male wildtype (WT) and Adrb2^-/- mice. Cartilage degeneration and synovial inflammation were evaluated by histological scoring. Subchondral bone remodeling was analyzed using micro-CT. Osteoblast (alkaline phosphatase - ALP) and osteoclast (cathepsin K - CatK) activity were analyzed by immunostainings. To evaluate β2-AR deficiency-associated effects, body weight, sympathetic tone (splenic norepinephrine (NE) via HPLC) and serum leptin levels (ELISA) were determined. Expression of the second major AR, the α2-AR, was analyzed in joint tissues by immunostaining.

Results

WT and Adrb2^-/- DMM mice developed comparable changes in cartilage degeneration and synovial inflammation. Adrb2^-/- DMM mice displayed elevated calcified cartilage and subchondral bone plate thickness as well as increased epiphyseal BV/TV compared to WTs, while there were no significant differences in Sham animals. In the subchondral bone of Adrb2^-/- mice, osteoblasts activity increased and osteoclast activity deceased. Adrb2^-/- mice had significantly higher body weight and fat mass compared to WT mice. Serum leptin levels increased in Adrb2^-/- DMM compared to WT DMM without any difference between the respective Shams. There was no difference in the development of meniscal ossicles and osteophytes or in the subarticular trabecular microstructure between Adrb2^-/- and WT DMM as well as Adrb2^-/- and WT Sham mice. Number of α2-AR-positive cells was lower in Adrb2^-/- than in WT mice in all analyzed tissues and decreased in both Adrb2^-/- and WT over time.

Conclusion

We propose that the increased bone mass in Adrb2^-/- DMM mice was not only due to β2-AR deficiency but to a synergistic effect of OA and elevated leptin concentrations. Taken together, β2-AR plays a major role in OA-related subchondral bone remodeling and is thus an attractive target for the exploration of novel therapeutic avenues.

Differential inflammation-mediated function of prokineticin 2 in the synovial fibroblasts of patients with rheumatoid arthritis compared with osteoarthritis

Prokineticin 2 (PK2) is a secreted protein involved in several pathological and physiological processes, including the regulation of inflammation, sickness behaviors, and circadian rhythms. Recently, it was reported that PK2 is associated with the pathogenesis of collagen-induced arthritis in mice. However, the role of PK2 in the pathogenesis of rheumatoid arthritis (RA) or osteoarthritis (OA) remains unknown. In this study, we collected synovial tissue, plasma, synovial fluid, and synovial fibroblasts (SF) from RA and OA patients to analyze the function of PK2 using immunohistochemistry, enzyme-linked immunosorbent assays, and tissue superfusion studies. PK2 and its receptors prokineticin receptor (PKR) 1 and 2 were expressed in RA and OA synovial tissues. PKR1 expression was downregulated in RA synovial tissue compared with OA synovial tissue. The PK2 concentration was higher in RA synovial fluid than in OA synovial fluid but similar between RA and OA plasma. PK2 suppressed the production of IL-6 from TNFα-prestimulated OA-SF, and this effect was attenuated in TNFα-prestimulated RA-SF. This phenomenon was accompanied by the upregulation of PKR1 in OA-SF. This study provides a new model to explain some aspects underlying the chronicity of inflammation in RA.

Increased Serum Levels of soluble ST2 as a Predictor of Disease Progression in Systemic Sclerosis

OBJECTIVE

Interleukin-33 (IL-33) has been investigated as a mediator in the pathogenesis of fibrosis in lung, liver, and heart. There is accumulating evidence for the involvement of the IL-33/IL-33 receptor ST2L signalling pathway in systemic sclerosis (SSc). Little is known about the role of serum sST2 in SSc, which is the subject of the present investigation.

METHOD

Serum levels of sST2 were measured in 49 patients with SSc, recruited prospectively between November 2017 and March 2019. Patients were divided into those with progressive and those with stable disease. Receiver operating characteristics (ROC) curve analysis was applied to study sST2 as a marker for identifying patients with progressive disease. We used multivariate logistic regression analysis to evaluate the predictive value of sST2 for progressive disease after adjustment for potential confounding factors.

RESULTS

Serum sST2 levels in patients with progressive disease were significantly elevated compared with patients with stable disease (mean ± sem: 50.4 ± 4.7 ng/mL vs 29.2 ± 2.97 ng/mL, p < 0.001). ROC curve analysis identified an sST2 cut-off value of 37.8 ng/mL as optimal for discriminating patients with progressive disease from those with stable disease (sensitivity 80.0%, specificity 79.3%, area under the curve 0.80). After controlling for potential confounding factors (age, gender, C-reactive protein, pro-brain natriuretic peptide, and sum of internal medicine comorbidities), sST2 remained predictive of progressive disease (odds ratio 1.070, 95% confidence interval 1.017-1.126, p < 0.009).

CONCLUSION

In the present study, sST2 serum levels were predictive of disease progression in patients with SSc.

Anti-Inflammatory Effects of Endogenously Released Adenosine in Synovial Cells of Osteoarthritis and Rheumatoid Arthritis Patients

Exogenous adenosine and its metabolite inosine exert anti-inflammatory effects in synoviocytes of osteoarthritis (OA) and rheumatoid arthritis (RA) patients. We analyzed whether these cells are able to synthesize adenosine/inosine and which adenosine receptors (ARs) contribute to anti-inflammatory effects. The functionality of synthesizing enzymes and ARs was tested using agonists/antagonists. Both OA and RA cells expressed CD39 (converts ATP to AMP), CD73 (converts AMP to adenosine), ADA (converts adenosine to inosine), ENT1/2 (adenosine transporters), all AR subtypes (A₁, A_2A, A_2B and A₃) and synthesized predominantly adenosine. The CD73 inhibitor AMPCP significantly increased IL-6 and decreased IL-10 in both cell types, while TNF only increased in RA cells. The ADA inhibitor DAA significantly reduced IL-6 and induced IL-10 in both OA and RA cells. The A_2AAR agonist CGS 21680 significantly inhibited IL-6 and induced TNF and IL-10 only in RA, while the A_2BAR agonist BAY 60-6583 had the same effect in both OA and RA. Taken together, OA and RA synoviocytes express the complete enzymatic machinery to synthesize adenosine/inosine; however, mainly adenosine is responsible for the anti- (IL-6 and IL-10) or pro-inflammatory (TNF) effects mediated by A_2A- and A_2BAR. Stimulating CD39/CD73 with simultaneous ADA blockage in addition to TNF inhibition might represent a promising therapeutic strategy.

Increased extracellular water measured by bioimpedance analysis and increased serum levels of atrial natriuretic peptide in polymyalgia rheumatica patients : Signs of volume overload

BACKGROUND

Water retention is a typical feature of acute inflammatory episodes, chiefly implemented by the sympathetic nervous system (SNS) and the hypothalamic-pituitary-adrenal (HPA) axis. This is an important compensatory mechanism counteracting expected water loss, e.g., due to sweating. Both the SNS and HPA axis are activated in polymyalgia rheumatica (PMR). As retention mechanisms may similarly apply in this disease, we hypothesized increased water retention in PMR.

METHODS

Using bioimpedance analysis body composition was investigated in 64 healthy controls and 32 treatment-naive PMR patients. All PMR patients satisfied the 2012 EULAR/ACR classification criteria for PMR. 32 PMR patients were tested before and after 7 days of glucocorticoid-based therapy. Serum levels of pro-atrial natriuretic peptide (proANP) were investigated in all PMR patients and 15 healthy controls.

RESULTS

Extracellular water (ECW) was markedly higher in PMR patients than in controls (mean ± SD: 49.1 ± 6.0% versus 36.3 ± 2.5% of total body water, p < 0.001). Patients with PMR demonstrated significantly higher serum levels of proANP compared to controls. Even before glucocorticoid treatment was initiated, systolic and diastolic blood pressure were higher in PMR patients compared to controls. Extracellular water levels did not change in PMR patients upon 7 days of intensified treatment.

CONCLUSION

This study demonstrated increased extracellular water and elevated serum levels of proANP as signs of fluid overload in patients with PMR. Volume changes are imprinted as long-lasting mechanisms as water distribution is not affected by short-term anti-inflammatory therapy.

Sex steroids and autoimmune rheumatic diseases: state of the art

In autoimmune rheumatic diseases, oestrogens can stimulate certain immune responses (including effects on B cells and innate immunity), but can also have dose-related anti-inflammatory effects on T cells, macrophages and other immune cells. By contrast, androgens and progesterone have predominantly immunosuppressive and anti-inflammatory effects. Hormone replacement therapies and oral contraception (and also pregnancy) enhance or decrease the severity of autoimmune rheumatic diseases at a genetic or epigenetic level. Serum androgen concentrations are often low in men and in women with autoimmune rheumatic diseases, suggesting that androgen-like compounds might be a promising therapeutic approach. However, androgen-to-oestrogen conversion (known as intracrinology) is enhanced in inflamed tissues, such as those present in patients with autoimmune rheumatic diseases. In addition, it is becoming evident that the gut microbiota differs between the sexes (known as the microgenderome) and leads to sex-dependent genetic and epigenetic changes in gastrointestinal inflammation, systemic immunity and, potentially, susceptibility to autoimmune or inflammatory rheumatic diseases. Future clinical research needs to focus on the therapeutic use of androgens and progestins or their downstream signalling cascades and on new oestrogenic compounds such as tissue-selective oestrogen complex to modulate altered immune responses.

Learned Immunosuppressive Placebo Response Attenuates Disease Progression in a Rodent Model of Rheumatoid Arthritis

OBJECTIVE

Patients with chronic inflammatory autoimmune diseases benefit from a broad spectrum of immunosuppressive and antiproliferative medication available today. However, nearly all of these therapeutic compounds have unwanted toxic side effects. Recent knowledge about the neurobiology of placebo responses indicates that associative learning procedures can be utilized for dose reduction in immunopharmacotherapy while simultaneously maintaining treatment efficacy. This study was undertaken to examine whether and to what extent a 75% reduction of pharmacologic medication in combination with learned immunosuppression affects the clinical outcome in a rodent model of type II collagen-induced arthritis.

METHODS

An established protocol of taste-immune conditioning was applied in a disease model of chronic inflammatory autoimmune disease (type II collagen-induced arthritis) in rats, where a novel taste (saccharin; conditioned stimulus [CS]) was paired with an injection of the immunosuppressive drug cyclosporin A (CSA) (unconditioned stimulus [US]). Following conditioning with 3 CS/US pairings (acquisition), the animals were immunized with type II collagen and Freund's incomplete adjuvant. Fourteen days later, at the first occurrence of clinical symptoms, retrieval was started by presenting the CS together with low-dose CSA as reminder cues to prevent the conditioned response from being extinguished.

RESULTS

This "memory-updating" procedure stabilized the learned immune response and significantly suppressed disease progression in immunized rats. Clinical arthritis score and histologic inflammatory symptoms (both P < 0.05) were significantly diminished by learned immunosuppression in combination with low-dose CSA (25% of the full therapeutic dose) via β-adrenoceptor-dependent mechanisms, to the same extent as with full-dose (100%) pharmacologic treatment.

CONCLUSION

These results indicate that learned immunosuppression appears to be mediated via β-adrenoceptors and might be beneficial as a supportive regimen in the treatment of chronic inflammatory autoimmune diseases by diminishing disease exacerbation.

The memory of the fatty acid system

Mental memory system has sensory memory, short-term memory, working memory, and long-term memory. Working memory "keeps things in mind in parallel" when performing complex tasks. Similar aspects can be found for immunological memory. However, there exists another one, the memory of the fatty acid system. This article shows sensory memory of the fatty acid system, which is the perception apparatus of small intestine enterocytes (CD36, SR-B1, FATP4, FABP1, FABP2) and hepatocytes. In these cells, the fatty acid short-term memory is located, consisting of a cytoplasmic lipid droplet cycle. Similar like a working memory in the brain, the short-term memory of enterocytes and hepatocytes use parallel processing and recourse to long-term fatty acid memory. The fatty acid long-term memory is far away from these primary points of uptake. It is located in the adipocyte and in cellular membranes. The process of building a fatty acid memory is described with constructs like sensing environmental material, encoding, consolidation, long-term storage, retrieval, re-encoding, re-consolidation, and renewed long-term storage. The article illustrates the dynamics of building a fatty acid memory, the information content of fatty acids including the code, the roles of fatty acids in the body, and a new understanding of the expression "you are what you eat". The memory of the fatty acid system, plays a decisive role in integrating environmental signals over time (diet and microbiome).

Norepinephrine Inhibits the Proliferation of Human Bone Marrow-Derived Mesenchymal Stem Cells via β2-Adrenoceptor-Mediated ERK1/2 and PKA Phosphorylation

Bone marrow-derived mesenchymal stem cells (BMSCs) represent an alternative to chondrocytes to support cartilage regeneration in osteoarthritis (OA). The sympathetic neurotransmitter norepinephrine (NE) has been shown to inhibit their chondrogenic potential; however, their proliferation capacity under NE influence has not been studied yet. Therefore, we used BMSCs obtained from trauma and OA donors and compared the expression of adrenergic receptors (AR). Then, BMSCs from both donor groups were treated with NE, as well as with combinations of NE and α1-, α2- or β1/2-AR antagonists (doxazosin, yohimbine or propranolol). Activation of AR-coupled signaling was investigated by analyzing ERK1/2 and protein kinase A (PKA) phosphorylation. A similar but not identical subset of ARs was expressed in trauma (α2B-, α2C- and β2-AR) and OA BMSCs (α2A-, α2B-, and β2-AR). NE in high concentrations inhibited the proliferation of both trauma and OA BMCSs significantly. NE in low concentrations did not influence proliferation. ERK1/2 as well as PKA were activated after NE treatment in both BMSC types. These effects were abolished only by propranolol. Our results demonstrate that NE inhibits the proliferation and accordingly lowers the regenerative capacity of human BMSCs likely via β2-AR-mediated ERK1/2 and PKA phosphorylation. Therefore, targeting β2-AR-signaling might provide novel OA therapeutic options.

Absence of α-calcitonin gene-related peptide modulates bone remodeling properties of murine osteoblasts and osteoclasts in an age-dependent way

Mice with an overall deletion of the sensory neuropeptide α-calcitonin gene-related peptide (α-CGRP) develop an age-dependent osteopenic bone phenotype. Underlying molecular mechanisms of how αCGRP affects bone cell metabolism are not well understood. This study aims to characterize differences in metabolic parameters of osteoblast-like cells (OB) and differentiated bone marrow-derived macrophages (BMM)/osteoclast (OC) cultures isolated from 3 month (3 m) and 9 month old (9 m) α-CGRP-deficient mice (-/-) and age-matched WT controls. All WT bone cell cultures endogenously produced and secreted α-CGRP. We found higher BMM but reduced OB numbers and reduced OB vitality after isolation from 9 m compared to 3 m mice, independent of genotype. Absence of α-CGRP reduced cell spreading, increased apoptosis rate throughout osteogenic differentiation, and reduced ALP activity during late osteogenic differentiation in 9 m OB-/- cultures, whereas minor effects were found in 3 m OB-/- cultures. Cathepsin K activity was reduced in 3 m OC-/- cultures. On the contrary, 9 m OC-/- cells demonstrated increased proliferation and caspase3/7 activity. The absence of α-CGRP influenced bone formation and resorption rate differently in bone cells from 3 and 9 m old mice. In summary we suggest, that an increase of dysfunctional mature osteoblasts might occur during aging and contribute to the development of the osteopenic bone phenotype in mature adult (9 m) α-CGRP-deficient mice.

Fatigue in inflammatory rheumatic disorders: pathophysiological mechanisms

Today, inflammatory rheumatic disorders are effectively treated, but many patients still suffer from residual fatigue. This work presents pathophysiological mechanisms of fatigue. First, cytokines can interfere with neurotransmitter release at the preterminal ending. Second, a long-term increase in serum concentrations of proinflammatory cytokines increase the uptake and breakdown of monoamines (serotonin, noradrenaline and dopamine). Third, chronic inflammation can also decrease monoaminergic neurotransmission via oxidative stress (oxidation of tetrahydrobiopterin [BH4]). Fourth, proinflammatory cytokines increase the level of enzyme indoleamine-2, 3-dioxygenase activity and shunt tryptophan away from the serotonin pathway. Fifth, oxidative stress stimulates astrocytes to inhibit excitatory amino acid transporters. Sixth, astrocytes produce kynurenic acid that acts as an antagonist on the α7-nicotinic acetylcholine receptor to inhibit dopamine release. Jointly, these actions result in increased glutamatergic and decreased monoaminergic neurotransmission. The above-described pathophysiological mechanisms negatively affect brain functioning in areas that are involved in fatigue.

Proinflammatory α-Adrenergic Neuronal Regulation of Splenic IFN-γ, IL-6, and TGF-β of Mice from Day 15 onwards in Arthritis

INTRODUCTION

In arthritic mice, a sympathetic influence is proinflammatory from the time point of immunization until the onset of disease (days 0-32), but reasons are unknown. Disruption of the major anti-inflammatory pathway through Gαs-coupled receptors probably play a role. For example, noradrenaline cannot operate via anti-inflammatory β2-adrenoceptors but through proinflammatory α1/2-ad-renoceptors. This might happen, first, through a loss of sympathetic nerve fibers in inflamed tissue with low neurotransmitter levels (noradrenaline only binds to high-affinity α-adrenoceptors) and, second, through an alteration in G-protein receptor coupling with a predominance of α-adrenergic signaling. We hypothesized that both mechanisms play a role in the course of collagen type II-induced arthritis (CIA) in the spleen in mice.

METHODS

In CIA mice, nerve fiber density in the spleen was quantified by immunohistochemistry techniques. The functional impact of sympathetic nerve fibers in the spleen was studied by a micro-superfusion technique of spleen slices with a focus on the secretion of IFN-γ and IL-6 (proinflammatory) and TGF-β (anti-inflammatory).

RESULTS

During CIA, sympathetic nerve fibers get increasingly lost from day14 until day 55 after immunization. The influence of electrically released noradrenaline diminishes in the course of arthritis. At all investigated time points (days 14, 32, and 55), only proinflammatory neuronal α-adrenergic effects on cytokine secretion were demonstrated (i.e., stimulation of IFN-γ and IL-6 and inhibition of TGF-β).

CONCLUSION

Sympathetic nerve fibers are rapidly lost in the spleen, and only proinflammatory α-adrenergic neuronal regulation of cytokine secretion takes place throughout the course of arthritis. These results support a predominance of a proinflammatory α-adrenergic sympathetic influence in arthritis.

A thyroid hormone network exists in synovial fibroblasts of rheumatoid arthritis and osteoarthritis patients

While patients with rheumatoid arthritis (RA) sometimes demonstrate thyroidal illness, the role of thyroid hormones in inflamed synovial tissue is unknown. This is relevant because thyroid hormones stimulate immunity, and local cells can regulate thyroid hormone levels by deiodinases (DIO). The study followed the hypothesis that elements of a thyroid hormone network exist in synovial tissue. In 12 patients with RA and 32 with osteoarthritis (OA), we used serum, synovial fluid, synovial tissue, and synovial fibroblasts (SF) in order to characterize the local thyroid hormone network using ELISAs, immunohistochemistry, imaging methods, tissue superfusion studies, cell-based ELISAs, flow cytometry, and whole genome expression profiling. Serum/synovial fluid thyroid hormone levels were similar in RA and OA (inclusion criteria: no thyroidal illness). The degradation product termed reverse triiodothyronine (reverse T3) was much lower in serum compared to synovial fluid indicating biodegradation of thyroid hormones in the synovial environment. Superfusion experiments with synovial tissue also demonstrated biodegradation, particularly in RA. Cellular membrane transporters of thyroid hormones, DIOs, and thyroid hormone receptors were present in tissue and SF. Density of cells positive for degrading DIOs were higher in RA than OA. TNF increased protein expression of degrading DIOs in RASF and OASF. Gene expression studies of RASF revealed insignificant gene regulation by bioactive T3. RA and OA synovial tissue/SF show a local thyroid hormone network. Thyroid hormones undergo strong biodegradation in synovium. While bioactive T3 does not influence SF gene expression, SF seem to have a relay function for thyroid hormones.

Increased pain and sensory hyperinnervation of the ligamentum flavum in patients with lumbar spinal stenosis

Nociceptive sensory nerve fibers have never been investigated in the ligamentum flavum (LF) of patients with LSS. The aim was to analyze nociceptive sensory nerve fibers in the ligamentum flavum (LF) of patients with LSS. A prospective study in patients with lumbar spinal stenosis (LSS) undergoing invasive surgical treatment for lumbar spinal stenosis (LSS) with flavectomy was performed. Patients with LSS were subjected to flavectomy and density of sensory and sympathetic nerve fibers, macrophages, vessels, activated fibroblasts, and cells were investigated by immunostaining techniques. A group of patients with acute disc herniation served as control group. We found a higher density of sensory nerve fibers in LSS patients versus controls. These findings support the role of LF in associated low back pain. Density of sensory nerve fibers in LSS, was positively correlated with typical markers of clinical pain and functional disability, but not with LF density of activated fibroblasts. Inflammation as estimated by macrophage infiltration and higher vascularity does not play a marked role in LF in our LSS patients. In the present study, compared to men with LSS, women with LSS demonstrate more pain and depression, and show a higher density of sensory nerve fibers in LF. This study shed new light on nociceptive nerve fibers, which are increased in LSS compared to controls. The findings speak against a strong inflammatory component in LSS. A higher pain levels in women compared to men can be explained by a higher density of nociceptive nerve fibers. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1-7, 2019.

Substance P modulates bone remodeling properties of murine osteoblasts and osteoclasts

Clinical observations suggest neuronal control of bone remodeling. Sensory nerve fibers innervating bone, bone marrow and periosteum signal via neurotransmitters including substance P (SP). In previous studies we observed impaired biomechanical and structural bone parameters in tachykinin (Tac) 1-deficient mice lacking SP. Here, we aim to specify effects of SP on metabolic parameters of bone marrow macrophage (BMM)/osteoclast cultures and osteoblasts isolated from Tac1-deficient and wildtype (WT) mice. We demonstrated endogenous SP production and secretion in WT bone cells. Absence of SP reduced bone resorption rate, as we found reduced numbers of precursor cells (BMM) and multinucleated osteoclasts and measured reduced cathepsin K activity in Tac1-/- BMM/osteoclast cultures. However, this might partly be compensated by reduced apoptosis rate and increased fusion potential of Tac1-/- precursor cells to enlarged "super" osteoclasts. Contrarily, increased ALP enzyme activity and apoptosis rate during early osteoblast differentiation accelerated osteogenesis and cell death in the absence of SP together with reduced ALP activity of Tac1-/- osteoblasts during late osteogenic differentiation resulting in reduced bone formation at later stages. Therefore, we suggest that absence of SP presumably results in a slight reduction of bone resorption rate but concomitantly in a critical reduction of bone formation and mineralization rate.

[Research consortium Neuroimmunology and pain in the research network musculoskeletal diseases]

BACKGROUND

The research consortium Neuroimmunology and Pain (Neuroimpa) explores the importance of the relationships between the immune system and the nervous system in musculoskeletal diseases for the generation of pain and for the course of fracture healing and arthritis.

MATERIAL AND METHODS

The spectrum of methods includes analyses at the single cell level, in vivo models of arthritis and fracture healing, imaging studies on brain function in animals and humans and analysis of data from patients.

RESULTS

Proinflammatory cytokines significantly contribute to the generation of joint pain through neuronal cytokine receptors. Immune cells release opioid peptides which activate opioid receptors at peripheral nociceptors and thereby evoke hypoalgesia. The formation of new bone after fractures is significantly supported by the nervous system. The sympathetic nervous system promotes the development of immune-mediated arthritis. The studies show a significant analgesic potential of the neutralization of proinflammatory cytokines and of opioids which selectively inhibit peripheral neurons. Furthermore, they show that the modulation of neuronal mechanisms can beneficially influence the course of musculoskeletal diseases.

DISCUSSION

Interventions in the interactions between the immune system and the nervous system hold a great therapeutic potential for the treatment of musculoskeletal diseases and pain.

Selective Activation of Tumor Necrosis Factor Receptor II Induces Antiinflammatory Responses and Alleviates Experimental Arthritis

OBJECTIVE

Treg cells modulate immune responses and can suppress the development of autoimmune diseases. Tumor necrosis factor receptor II (TNFRII) has been recognized as a key receptor on these cells that facilitates expansion and stabilization of CD4+ Treg cells. The purpose of the present study was to investigate the therapeutic activity of a novel TNFRII agonist in experimental arthritis as well as the role of different Treg cell subsets.

METHODS

A novel mouse TNFRII-selective fusion protein (EHD2-sc-mTNF_R2 ) was generated by genetic engineering. Mouse T cells were incubated together with interleukin-2 and/or EHD2-sc-mTNF_R2 , and the effects on Treg cells were analyzed by flow cytometry. Mice with collagen-induced arthritis (CIA) were treated with EHD2-sc-mTNF_R2 or saline, and the therapeutic effects were monitored and characterized.

RESULTS

Selective activation of TNFRII was found to expand both CD4+ and CD8+ Treg cells. Moreover, TNFRII activation elevated the number of CD4+CD25+ and CD8+CD25+ Treg cells and increased the number of FoxP3-expressing cells in CD8+, but not CD4+, Treg cells, indicating different mechanisms of TNFRII-induced expansion of diverse T cell subsets with suppressive activity. In the CIA model, we demonstrated that administration of the TNFRII agonist EHD2-sc-mTNF_R2 led to the expansion of both CD4+ and CD8+ Treg cells in vivo and induced antiinflammatory responses that alleviated arthritis.

CONCLUSION

Our findings support the use of TNFRII-selective therapeutics as an effective approach to the treatment of arthritic disease and possibly other inflammatory and autoimmune diseases.

Stimulation of TNF receptor type 2 expands regulatory T cells and ameliorates established collagen-induced arthritis in mice

Tumor necrosis factor (TNF) and its receptors TNF receptor type 1 (TNFR1) and type 2 (TNFR2) have a central role in chronic inflammatory diseases. While TNFR1 mainly confers inflammation, activation of TNFR2 elicits not only pro-inflammatory but also anti-inflammatory effects. In this study, we wanted to investigate the anti-inflammatory therapeutic potential of selective activation of TNFR2 in mice with established collagen-induced arthritis. Mice with established arthritis induced by immunization with bovine collagen type II were treated with six injections of the TNFR2-specific agonist TNCscTNF80, given every second day. Two days after treatment cessation, the cell compositions of bone marrow, spleen and lymph nodes were analyzed. Mice were visually scored until day 30 after the start of therapy and the degree of joint inflammation was determined by histology. Treatment with TNCscTNF80 increased arthritis-induced myelopoiesis. Little effect was seen on the infiltration rate of inflammatory immature myeloid cells and on the reduction of lymphoid cells in secondary lymphoid organs. Upon treatment, frequency of regulatory T (Treg) cells in the CD4⁺ T-cell population was increased in both spleen and inguinal lymph nodes. In addition, the expression of TNFR2 on Treg cells was enhanced. The clinical score started to improve 1 week after cessation treatment and remained lower 30 days after initiation of therapy. The histological score also revealed amelioration of joint inflammation in TNCscTNF80-treated versus control mice. Activation of TNFR2 might provide a suitable therapeutic strategy in autoimmune arthritis by increasing the numbers of regulatory cell types, in particular Treg cells, and by attenuation of arthritis.

A Promising New Approach for the Treatment of Inflammatory Pain: Transfer of Stem Cell-Derived Tyrosine Hydroxylase-Positive Cells

OBJECTIVES

The appearance of endogenous tyrosine hydroxylase-positive cells (TH+ cells) in collagen-induced arthritis was associated with an anti-inflammatory effect. Here we investigated putative anti-inflammatory and antinociceptive effects of the transfer of induced, bone marrow stem cell-derived TH+ cells (iTH+ cells) on murine antigen-induced arthritis (AIA).

METHODS

Bone marrow-derived stem cells were differentiated into iTH+ cells. These cells were transferred to mice immunized against methylated bovine serum albumin (mBSA) 2 days before AIA was induced by injection of mBSA into one knee joint. In AIA control mice and iTH+-treated mice the severity of AIA, pain-related behavior, humoral and cellular responses, and the invasion of macrophages into the dorsal root ganglia were assessed.

RESULTS

The intravenous transfer of iTH+ cells before AIA induction did not cause a sustained suppression of AIA severity but significantly reduced inflammation-evoked pain-related behavior. The iTH+ cells used for transfer exhibited enormous production of interleukin-4. A major difference between AIA control mice and iTH+-treated AIA mice was a massive invasion of the dorsal root ganglia by iNOS-negative, arginine 1-positive macrophages corresponding to an M2 phenotype. The differences in other cellular and humoral immune parameters such as release of cytokines from stimulated lymphocytes between AIA control mice and iTH+-treated mice were small.

CONCLUSIONS

The transfer of iTH+ cells may cause a long-lasting reduction of arthritis-induced pain even if it does not ameliorate inflammation. The invasion of M2 macrophages into the dorsal root ganglia is likely to be an important mechanism of antinociception.

The brain and immune system prompt energy shortage in chronic inflammation and ageing

Sequelae frequently seen in patients with chronic inflammatory diseases, such as fatigue, depressed mood, sleep alterations, loss of appetite, muscle wasting, cachectic obesity, bone loss and hypertension, can be the result of energy shortages caused by an overactive immune system. These sequelae can also be found in patients with chronic inflammatory diseases that are in remission and in ageing individuals, despite the immune system being less active in these situations. This Perspectives article proposes a new way of understanding situations of chronic inflammation (such as rheumatic diseases) and ageing based on the principles of evolutionary medicine, energy regulation and neuroendocrine-immune crosstalk. A conceptual framework is provided to enable physicians and scientists to better understand the signs and symptoms of chronic inflammatory diseases and long-term disease consequences resulting from physical and mental inactivity.

Inflammation Is an Important Covariate for the Crosstalk of Sleep and the HPA Axis in Rheumatoid Arthritis

Rheumatoid arthritis (RA) patients have sleep problems, and inflammation influences sleep. We demonstrated that sleep quality improves during intensified treatment with methotrexate (MTX) or etanercept (ETA). Since the hypothalamic-pituitary-adrenal (HPA) axis is involved in sleep regulation, this study investigated the interrelation between sleep parameters, inflammation as objectified by C-reactive protein (CRP), and serum cortisol and adrenocorticotropic hormone (ACTH) levels. Thirty-one eligible patients (disease activity score, DAS28CRP ≥3.2) participated in a 16-week, open, prospective study of HPA axis outcomes. MTX was initiated in 15 patients (female-to-male ratio 9/6) and ETA in 16 patients (14/2). Clinical, laboratory (after polysomnography [PSG] between 8 and 9 a.m.), sleep (PSG), and HPA axis outcome parameters (after PSG between 8 and 9 a.m.) were recorded at baseline and week 16. Clinical characteristics of patients markedly improved throughout the study (e.g., DAS28CRP: p < 0.001; CRP: p < 0.001). Sleep efficiency and wake time after sleep onset markedly improved in the ETA group. Serum cortisol and ACTH did not change during observation. At baseline, serum cortisol levels were negatively correlated to sleep efficiency; this may depend on inflammation, because controlling for CRP eliminated this negative correlation. After ETA treatment, serum cortisol had a high positive correlation with total sleep time, sleep efficiency, and a negative correlation with wake time before and after sleep onset, which was not eliminated by controlling for CRP. In RA patients, the data indicate that inflammation is an important covariate for the crosstalk of sleep and the HPA axis.

Effects of treatment with etanercept versus methotrexate on sleep quality, fatigue and selected immune parameters in patients with active rheumatoid arthritis

OBJECTIVES

To compare sleep quality, disease activity and patient-reported outcomes such as fatigue and immune parameters in patients with rheumatoid arthritis treated with etanercept (ETA) or methotrexate (MTX).

METHODS

Of 36 patients (28-joint Disease Activity Score, DAS28CRP≥3.2) in this 16-week (w), open, prospective study, 19 (11 women) received MTX 12.5-17 mg/w, and 17 (14 women) received ETA 25 mg x 2/w, alone or in combination with MTX. Clinical (DAS28CRP, visual analogue scale), laboratory (C-reactive protein [CRP]), sleep (polysomnography), functional (Multidimensional Fatigue Inventory; Health Assessment Questionnaire-Disability Index (HAQ-DI); 36-item Short-Form Health Survey (SF-36), immunological (humoral/cellular) and neuroendocrine (hormonal) parameters were recorded at baseline (BL), w8 and w16.

RESULTS

BL characteristics did not differ significantly between the ETA and MTX groups except disease duration: mean age (years): 48.6±8.8 vs. 49.4±16.6; mean disease duration (months): 19.6±46.3 vs. 81.2±79.2; and DAS28CRP: 4.4±0.9 vs. 4.4±1.7, respectively. DAS28CRP, SF-36, and HAQ-DI improved significantly in both groups from BL to w16 (p≤0.05). The DAS28CRP improvements at w16 (mean changes -1.8 in the ETA group, and -1.4 in MTX group), were not statistically significant from each other. The absolute values of sleep efficiency, total sleep time, and stage 2 sleep duration increased significantly in the ETA group, but no significant changes were reported in the MTX group.

CONCLUSIONS

Both therapies improved disease activity, CRP, SF-36 and HAQ-DI, with faster, more pronounced changes in DAS28CRP in the ETA group, which alone had significantly improved sleep parameters.

α-MSH modulates cell adhesion and inflammatory responses of synovial fibroblasts from osteoarthritis patients

INTRODUCTION

The synovium is a target for neuropeptides. Melanocortins have attained particular attention as they elicit antiinflammatory effects. Although synovial fluid from patients with rheumatic diseases contains α-melanocyte-stimulating hormone (α-MSH) it is unknown whether synovial fibroblasts generate α-MSH and respond to melanocortins.

METHODS

Synovial tissue was obtained from osteoarthritis (OA) patients. Cells were isolated and prepared either as primary mixed synoviocytes or propagated as synovial fibroblasts (OASFs). Melanocortin receptor (MC) and proopiomelanocortin (POMC) expression were investigated by endpoint RT-PCR, immunofluorescence and Western immunoblotting. Functional coupling of MC1 was assessed by cAMP and Ca(2+) assays. Cell adhesion was monitored by the xCELLigence system. Secretion of α-MSH, tumour necrosis factor (TNF), interleukin (IL)-6 and IL-8 was determined by ELISA.

RESULTS

OASFs in vitro expressed MC1. MC1 transcripts were present in synovial tissue and appropriate immunoreactivity was detected in synovial fibroblasts in situ. OASFs contained truncated POMC transcripts but neither full-length POMC mRNA, POMC protein nor α-MSH were detectable. In accordance with this only truncated POMC transcripts were present in synovial tissue. α-MSH increased cAMP dose-dependently but did not alter calcium in OASFs. α-MSH also enhanced adhesion of OASFs to fibronectin and reduced TNF, IL-6 and IL-8 secretion in primary mixed synoviocyte cultures. In OASFs, α-MSH modulated basal and TNF/IL-1β-mediated secretion of IL-6 and IL-8.

CONCLUSION

Synovial fibroblasts express MC1in vitro and in situ. α-MSH elicits biological effects in these cells suggesting an endogenous immunomodulatory role of melanocortins within the synovium. Our results encourage in vivo studies with melanocortins in OA models.

Sex hormones influence on the immune system: basic and clinical aspects in autoimmunity

Sex hormones seem to play an important role as modulators of the autoimmune disease onset/perpetuation. Generally, steroid hormones are implicated in the immune response, with estrogens as enhancers at least of the humoral immunity and androgens and progesterone (and glucocorticoids) as natural immunosuppressors. Synovial fluid levels (SF) of proinflammatory estrogens relative to androgens are significantly elevated in both male and female rheumatoid arthritis (RA) patients, as compared to controls, which is most probably due to increase of local enzymatic aromatase activity. Serum levels of estrogens have been found altered in RA patients, particularly estradiol in man. Thus, available steroid prehormones are rapidly converted to proinflammatory estrogens in the synovial tissue in the presence of inflammatory cytokines (i.e., TNFa, IL-1, IL-6). The increased estrogen concentrations observed in RA SF of both sexes are characterized mainly by the hydroxylated forms, in particular, 16a-hydroxyestrone, showing a mitogenic tumor growth stimulating role. Altered serum hydroxylated estrogens have been found also in serum of systemic lupus erythematosus (SLE) patients. As a matter of fact, our recent studies indicate that 17-b estradiol (E2) clearly enhanced the expression of markers of cell growth and proliferation, whereas testosterone (T) induced an increase of markers indicating DNA damage and apoptosis. In particular, our data further shows that the enhancing role of estrogens on immune/inflammatory response is exerted by activating the NFkB complex pathway. In conclusion, locally increased estrogens (i.e., synovial tissue in RA or skin in SLE) might exert activating effects on cell proliferation, including macrophages and fibroblasts, suggesting new roles for estrogens in autoimmunity.

The synthetic cannabinoid WIN55,212-2 mesylate decreases the production of inflammatory mediators in rheumatoid arthritis synovial fibroblasts by activating CB2, TRPV1, TRPA1 and yet unidentified receptor targets

Background

In rheumatoid arthritis (RA), synovial fibroblasts (SF) secrete large amounts of IL-6, IL-8 and matrix metalloproteinases (MMPs) which are crucial for cartilage destruction. RASFs are sensitive to the action of cannabinoids and they not only express cannabinoid receptors type I and II (CB₁ and CB₂) but also transient receptor potential channels type vanilloid (TRPV1) and ankyrin (TRPA1). The synthetic cannabinoid WIN55,212-2 mesylate (WIN) demonstrated strong anti-inflammatory effects in monocytes and synovial fibroblasts only in high concentrations in a non-cannabinoid receptor dependent manner. In this study we assessed the ability of WIN to modulate cytokine and MMP-3 production in SFs over a wide concentration range and identified specific receptor targets that mediate the effects of this synthetic cannabinoid.

Methods

MMP-3, IL-6 and IL-8 were determined by ELISA. Adhesion was measured by the XCELLigence system. Proliferation was assessed by cell titer blue assays.

Results

WIN significantly reduced TNF-induced IL-6, IL-8 and MMP-3 production in concentrations below 2 μM, while higher concentrations completely inhibited production of IL-6 and IL-8 but increased extracellular MMP-3 levels. The inhibitory effect at low concentrations (<2 μM) was independent on activation of either CB₁ or CB₂ but was attenuated by TRPV1 or TRPA1 inhibition in OASFs and RASFs. The effects of high concentrations of WIN on cytokine and MMP-3 production were decreased by the calcium chelating agent BAPTA, the AMPK activator metformin, the TRPA1 antagonist A967079 and the CB₂ antagonist COR170. Furthermore, fetal calf serum content in culture media strongly influenced the efficacy of WIN at high concentrations. In addition, high concentrations of WIN also diminished SF adhesion and proliferation without altering cell viability whereas low concentrations promoted SF adhesion without any influence on proliferation.

Conclusion

The synthetic cannabinoid WIN in low concentrations exhibits anti-inflammatory effects in synovial fibroblasts independent of CB₁ and CB₂ while CB₂ and yet unidentified receptor targets are responsible for WIN effects in micromolar concentrations. Our results indicate a TRPV1/TRPA1 dependent mechanism of SF regulation that might be coupled to cellular energy status and calcium content.

Peripheral elimination of the sympathetic nervous system stimulates immunocyte retention in lymph nodes and ameliorates collagen type II arthritis

OBJECTIVES

In collagen type II-induced arthritis (CIA), early activation of the sympathetic nervous system (SNS) is proinflammatory. Here, we wanted to find new target organs contributing to proinflammatory SNS effects. In addition, we wanted to clarify the importance of SNS-modulated immunocyte migration.

METHODS

A new technique termed spatial energy expenditure configuration (SEEC) was developed to demonstrate bodily areas of high energy demand (to find new targets). We studied homing of labeled cells in vivo, lymphocyte expression of CCR7, supernatant concentration of CCL21, and serum levels of sphingosine-1-phosphate (S1P) in sympathectomized control/arthritic animals.

RESULTS

During the course of arthritis, SEEC identified an early marked increase of energy expenditure in draining lymph nodes and spleen (nowhere else!). Although early sympathectomy ameliorated later disease, early sympathectomy increased energy consumption, organ weight, and cell numbers in arthritic secondary lymphoid organs, possibly a sign of lymphocyte retention (also in controls). Elimination of the SNS retained lymph node cells, elevated expression of CCR7 on lymph node cells, and increased CCL21. Serum levels of S1P, an important factor for lymphocyte egress, were higher in arthritic than control animals. Sympathectomy decreased S1P levels in arthritic animals to control levels. Transfer of retained immune cells from draining lymph nodes of sympathectomized donors to sympathectomized recipients markedly increased arthritis severity over weeks.

CONCLUSIONS

By using the SEEC technique, we identified draining lymph nodes and spleen as major target organs of the SNS. The data show that the SNS increases egress of lymphocytes from draining lymph nodes to stimulate arthritic inflammation.

Increased extracellular water measured by bioimpedance and by increased serum levels of atrial natriuretic peptide in RA patients-signs of volume overload

The aim of the study is to investigate water compartments in patients with rheumatoid arthritis (RA). Acute inflammatory episodes such as infection stimulate water retention, chiefly implemented by the sympathetic nervous system (SNS) and hypothalamic-pituitary-adrenal (HPA) axis. This is an important compensatory mechanism due to expected water loss (sweating etc.). Since SNS and HPA axis are activated in RA, inflammation might be accompanied by water retention. Using bioimpedance analysis, body composition was investigated in 429 controls and 156 treatment-naïve RA patients between January 2008 and December 2014. A group of 34 RA patients was tested before and after 10 days of intensified therapy. Levels of pro-atrial natriuretic peptide (proANP) and expression of atrial natriuretic peptide in synovial tissue were investigated in 15 controls and 14 RA patients. Extracellular water was higher in RA patients than controls (mean ± SEM: 49.5 ± 0.3 vs. 36.7 ± 0.1, % of total body water, p < 0.0001). Plasma levels of proANP were higher in RA than controls. RA patients expressed ANP in synovial tissue, but synovial fluid levels and synovial tissue superfusate levels were much lower than plasma levels indicating systemic origin. Systolic/diastolic blood pressure was higher in RA patients than controls. Extracellular water levels did not change in RA patients despite 10 days of intensified treatment. This study demonstrates signs of intravascular overload in RA patients. Short-term intensification of anti-inflammatory therapy induced no change of a longer-lasting imprinting of water retention indicating the requirement of additional treatment. The study can direct attention to the area of volume overload.

Predominance of synovial sensory nerve fibers in arthrofibrosis following total knee arthroplasty compared to osteoarthritis of the knee

BACKGROUND

So far, there exists no golden standard for the treatment of arthrofibrosis (AF) following total knee arthroplasty (TKA). Although pain is a hallmark of AF, nociceptive nerve fibers have never been investigated in affected joint tissue.

METHODS

A total of 24 patients with osteoarthritis (OA) of the knee (n = 12) and post-TKA AF of the knee (n = 12) were included. Along evaluation of typical clinical signs and symptoms by using the Knee Society Clinical Rating System (KSS), the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC index), the innervation of joint tissue was studied by semiquantitative immunofluorescence of nerve fibers.

RESULTS

Patients with AF compared to OA had a lower KSS and lower KOOS. In all compartments (anterior, medial, and lateral recesses), the density of synovial sympathetic nerve fibers was significantly higher in OA compared to AF, which was also true for the density of sensory nerve fibers in the medial and lateral recesses. In synovial tissue of the anterior recess of patients with AF compared to OA, the density of nociceptive sensory nerve fibers was significantly higher relative to sympathetic nerve fibers. This was similarly observed in the neighboring infrapatellar fat pad of the knee.

CONCLUSIONS

Similar as in many painful musculoskeletal diseases, this study indicates that patients with arthrofibrosis of the knee after TKA demonstrate a preponderance of profibrotic sensory nerve fibers over antifibrotic sympathetic nerve fibers. This could serve as a starting point for AF therapy with specific antifibrotic pain medication or regional anesthetic techniques.

Chronic inflammatory systemic diseases: An evolutionary trade-off between acutely beneficial but chronically harmful programs

It has been recognized that during chronic inflammatory systemic diseases (CIDs) maladaptations of the immune, nervous, endocrine and reproductive system occur. Maladaptation leads to disease sequelae in CIDs. The ultimate reason of disease sequelae in CIDs remained unclear because clinicians do not consider bodily energy trade-offs and evolutionary medicine. We review the evolution of physiological supersystems, fitness consequences of genes involved in CIDs during different life-history stages, environmental factors of CIDs, energy trade-offs during inflammatory episodes and the non-specificity of CIDs. Incorporating bodily energy regulation into evolutionary medicine builds a framework to better understand pathophysiology of CIDs by considering that genes and networks used are positively selected if they serve acute, highly energy-consuming inflammation. It is predicted that genes that protect energy stores are positively selected (as immune memory). This could explain why energy-demanding inflammatory episodes like infectious diseases must be terminated within 3–8 weeks to be adaptive, and otherwise become maladaptive. Considering energy regulation as an evolved adaptive trait explains why many known sequelae of different CIDs must be uniform. These are, e.g. sickness behavior/fatigue/depressive symptoms, sleep disturbance, anorexia, malnutrition, muscle wasting—cachexia, cachectic obesity, insulin resistance with hyperinsulinemia, dyslipidemia, alterations of steroid hormone axes, disturbances of the hypothalamic-pituitary-gonadal (HPG) axis, hypertension, bone loss and hypercoagulability. Considering evolved energy trade-offs helps us to understand how an energy imbalance can lead to the disease sequelae of CIDs. In the future, clinicians must translate this knowledge into early diagnosis and symptomatic treatment in CIDs.

Anti-inflammatory effects of N-acylethanolamines in rheumatoid arthritis synovial cells are mediated by TRPV1 and TRPA1 in a COX-2 dependent manner

Introduction

The endocannabinoid system modulates function of immune cells and mesenchymal cells such as fibroblasts, which contribute to cartilage destruction in rheumatoid arthritis (RA). The aim of the study was to determine the influence of N-acylethanolamines anandamide (AEA), palmitoylethanolamine (PEA) and oleylethanolamine (OEA) on several features of arthritic inflammation in vitro (human material) and in vivo (a mouse model).

Methods

Immunofluorescence and western blotting were used to detect cannabinoid receptors and related enzymes. Cytokines and MMP-3 were measured by ELISA. Intracellular signaling proteins were detected by proteome profiling. Proliferation was quantified by CTB reagent. Adhesion was assessed by the xCELLigence system. After onset of collagen type II arthritis, mice were treated daily with the FAAH inhibitor JNJ1661010 (20 mg/kg) or vehicle.

Results

IL-6, IL-8 and MMP-3 (determined only in synovial fibroblasts (SFs)) were downregulated in primary synoviocytes and SFs of RA and OA after AEA, PEA and OEA treatment. In SFs, this was due to activation of TRPV1 and TRPA1 in a COX-2-dependent fashion. FAAH inhibition increased the efficacy of AEA in primary synoviocytes but not in SFs. The effects of OEA and PEA on SFs were diminished by FAAH inhibition. Adhesion to fibronectin was increased in a CB₁-dependent manner by AEA in OASFs. Furthermore, elevation of endocannabinoids ameliorated collagen-induced arthritis in mice.

Conclusions

N-acylethanolamines exert anti-inflammatory effects in SFs. A dual FAAH/COX-2 inhibitor, increasing N-acylethanolamine levels with concomitant TRP channel desensitization, might be a good candidate to inhibit the production of proinflammatory mediators of synovial cells and to reduce erosions.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0845-5) contains supplementary material, which is available to authorized users.

Mimicking disruption of brain-immune system-joint communication results in collagen type II-induced arthritis in non-susceptible PVG rats

The brain-immune system-joint communication is disrupted during collagen type II (CII) arthritis in DA rats. Since PVG rats are not susceptible to arthritis induction, comparison of hypothalamic and peripheral neuro-endocrine and immune responses between immunized DA and PVG rats might help to explain their different susceptibility to develop the disease. PVG and DA rats were immunized with CII. Corticosterone, neurotransmitters, anti-CII antibodies, and cytokine concentrations in plasma, and hypothalamic neurotransmitters and cytokines were determined by ELISA, Luminex, HPLC and RT-qPCR. Adrenalectomy or sham-operation was performed in PVG and DA rats 14 days before immunization. Basal plasma corticosterone and adrenaline concentrations were significantly higher, and plasma cytokines and hypothalamic noradrenaline were lower in PVG rats than in DA rats. While DA rats developed severe arthritis upon immunization (maximum score 16), only 12 out of 28 PVG rats showed minimal symptoms (score 1-2). The density of sympathetic nerve fibers in arthritic joints of DA rats markedly decreased, but it remained stable in immunized PVG rats. The ratio corticosterone to IL-1β levels in plasma was markedly higher in immunized PVG rats than in arthritic DA rats. Adrenalectomy resulted in severe arthritis in PVG rats upon immunization with CII. While DA rats show an altered immune-brain communication that favors the development of arthritis, PVG rats express a protective neuro-endocrine milieu, particularly linked to the basal tone of the HPA axis. Mimicking disruption of this axis elicits arthritis in non-susceptible PVG rats.

Proinflammatory receptor switch from Gαs to Gαi signaling by β-arrestin-mediated PDE4 recruitment in mixed RA synovial cells

OBJECTIVE

In chronic inflammation, prevention of cAMP degradation by phosphodiesterase-4 (PDE4) inhibition can be anti-inflammatory therapy. However, PDE4 inhibition was uneffective in rheumatoid arthritis (RA). Recent studies demonstrated that PDE4/β-arrestin interaction at β-adrenoceptors resulted in switching from Gαs to Gαi signaling and ERK1/2 activation. Such a switch in signaling might elicit proinflammatory effects. We aimed to investigate this possible Gαs to Gαi signaling switch in RA and osteoarthritis (OA) mixed synoviocytes.

METHODS

Synoviocytes were treated alone or with combinations of adrenergic, dopaminergic, and adenosinergic drugs, rolipram (PDE4 inhibitor), inhibitors of Gαi signaling (pertussis toxin), and blockers of protein kinase A (PKA). Under normoxic or hypoxic conditions, proinflammatory TNF was the readout-parameter. We investigated co-expression and interaction of PDE4 and β-arrestin by imaging techniques. Expression of pERK1/2 was analyzed by western blotting.

RESULTS

Mixed synoviocytes in RA and OA possessed all major Gαs-coupled neurotransmitter receptors. Under hypoxia, particularly in RA cells, Gαs-coupled receptor agonists unexpectedly increased TNF and respective antagonists decreased TNF. Under hypoxia, rolipram alone or rolipram plus Gαs agonists increased TNF, which was reversed by pertussis toxin or PKA inhibition. Co-localization and interaction of PDE4 and β-arrestin in synovial tissue and cells was demonstrated. Gαs agonists or rolipram plus Gαs agonists increased pERK1/2 expression.

CONCLUSIONS

This study in human arthritic synovial tissue presents an unexpected proinflammatory switch from Gαs to Gαi signaling, which depends on PDE4/β-arrestin interaction. This phenomenon is most probably responsible for reduced efficacy of PDE4 inhibitors and Gαs agonists in RA.