Are advanced glycation end-product-modified proteins of pathogenetic importance in fibromyalgia?

Long COVID and the Neuroendocrinology of Microbial Translocation Outside the GI Tract: Some Treatment Strategies

Similar to previous pandemics, COVID-19 has been succeeded by well-documented post-infectious sequelae, including chronic fatigue, cough, shortness of breath, myalgia, and concentration difficulties, which may last 5 to 12 weeks or longer after the acute phase of illness. Both the psychological stress of SARS-CoV-2 infection and being diagnosed with COVID-19 can upregulate cortisol, a stress hormone that disrupts the efferocytosis effectors, macrophages, and natural killer cells, leading to the excessive accumulation of senescent cells and disruption of biological barriers. This has been well-established in cancer patients who often experience unrelenting fatigue as well as gut and blood–brain barrier dysfunction upon treatment with senescence-inducing radiation or chemotherapy. In our previous research from 2020 and 2021, we linked COVID-19 to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) via angiotensin II upregulation, premature endothelial senescence, intestinal barrier dysfunction, and microbial translocation from the gastrointestinal tract into the systemic circulation. In 2021 and 2022, these hypotheses were validated and SARS-CoV-2-induced cellular senescence as well as microbial translocation were documented in both acute SARS-CoV-2 infection, long COVID, and ME/CFS, connecting intestinal barrier dysfunction to disabling fatigue and specific infectious events. The purpose of this narrative review is to summarize what is currently known about host immune responses to translocated gut microbes and how these responses relate to fatiguing illnesses, including long COVID. To accomplish this goal, we examine the role of intestinal and blood–brain barriers in long COVID and other illnesses typified by chronic fatigue, with a special emphasis on commensal microbes functioning as viral reservoirs. Furthermore, we discuss the role of SARS-CoV-2/Mycoplasma coinfection in dysfunctional efferocytosis, emphasizing some potential novel treatment strategies, including the use of senotherapeutic drugs, HMGB1 inhibitors, Toll-like receptor 4 (TLR4) blockers, and membrane lipid replacement.

Metal-induced oxidative stress level in patients with fibromyalgia syndrome and its contribution to the severity of the disease: A correlational study

BACKGROUND

Fibromyalgia syndrome (FMS) is an extra-articular rheumatological disease characterised by widespread chronic musculoskeletal pain. Metal-induced oxidative stress contributes to the severity of FMS.

AIMS

First, this study evaluated the association between plasma levels of toxic heavy metals and essential metals with oxidative stress (OS) markers. Second, the OS markers and metal contents were correlated with the disease severity by assessing the Fibromyalgia Impact Questioner Revised (FIQR) and tender points (TP).

METHOD

A total of 105 FMS patients and 105 healthy controls of similar age and sex were recruited. OS parameter such as lipid peroxidation (LPO), protein carbonyl group (PCG), nitric oxide (NO) and essential metals such as zinc (Zn), magnesium (Mg), manganese (Mn), copper (Cu) and toxic heavy metals such as aluminium (Al), arsenic (As), lead (Pb) were estimated.

RESULTS

Levels of LPO, PCG, NO (p< 0.001) and Cu, Mn, and Al (p< 0.001), were significantly higher, and Mg (p< 0.001) and Zn (p< 0.001) were significantly lower in patients compared to controls. A positive association was observed between OS parameters, FIQR and TP with Cu, Al and Mn. A significant negative association was observed between Zn and Mg with FIQR, TP and OS parameters.

CONCLUSION

Heavy metals such as Al induce OS parameters and decrease the levels of essential trace elements such as Mg and Zn, which may be responsible for the severity of FMS.

The Glycation Products Before and After Therapy for Acute and Chronic Pain

Pain increased the number of free radicals in the body. Previously, we studied changes mainly in oxygen and nitroxide free radicals and described these changes relative to the lipids and saccharides. In this article we focus on changes relative to proteins. Assessment of AGE products (advanced glycation end-products) was carried out by measuring fluorescence. Patients were divided into two groups: 15 patients with acute pain and 17 patients with chronic pain. Acute pain was associated with a variety of surgical procedures and patients were examined before and after surgical procedures. The group of patients with chronic pain suffered from various types of chronic pain, but mainly back pain. In patients with acute pain, total protein (TP) decreased after surgery, as did the level of AGE and the AGE/TP ratio. Nonetheless, post-operative pain increased. In patients with chronic pain, neither total protein, AGE, or AGE/TP changed, despite significant pain relief being reported after treatment. Changes in proteins, as biochemical markers, before and after pain treatment did not show any significant changes. In patients with acute pain, the recorded changes only lasted for 3-5 days after the operation. While in chronic pain, there were no significant changes at all. The assumption that changes in proteins, as biomarkers, would have the same importance as changes in lipids and saccharides was not proven.

Potential Mediators between Fibromyalgia and C-Reactive protein: Results from a Large U.S. Community Survey

BACKGROUND

Fibromyalgia, a potentially debilitating chronic pain syndrome of unknown etiology, may be characterized by inflammation. In this study, we investigated the relation of FMS to serum C-reactive protein (CRP) in a large population of adults (18+) and investigated the influence of other factors on this relationship, including BMI, comorbidities, as well as mood and sleep disturbance.

METHODS

Participants were 52,535 Ohio Valley residents (Fibromyalgia n = 1125). All participants completed a comprehensive health survey (2005-2006) part of the C8 Health Project; serum levels of CRP were obtained, as was history of Fibromyalgia physician diagnosis. Logistic and linear regressions were used for this cross-sectional analysis.

RESULTS

Mean CRP was higher among participants reporting Fibromyalgia than those without (5.54 ± 9.8 vs.3.75 ± 7.2 mg/L, p < .0001)). CRP level showed a strong, positive association with FMS (unadjusted odds ratio (OR) for highest vs. lowest quartile = 2.5 (CI 2.1,3.0;p for trend < .0001)); adjustment for demographic and lifestyle factors attenuated but did not eliminate this association (AOR for highest vs. lowest quartile = 1.4 (CI 1.1,1.6;p for trend < .0001)). Further addition of body mass index (BMI) and comorbidities to the model markedly weakened this relationship (AORs, respectively, for highest vs lowest CRP quartile = 1.2 (CI 1.0,1.4) and 1.1 (CI 0.9,1.3). In contrast, inclusion of mood and sleep impairment only modestly reduced the adjusted risk estimate (AORs for highest vs. lowest quartile = 1.3 (CI 1.1,1.5) for each)).

CONCLUSIONS

Findings from this large cross-sectional study indicate a significant positive cross-sectional association of Fibromyalgia to serum C-reactive protein may be explained, in part, by BMI and comorbidity. Prospective research is needed to confirm this, and clarify the potential mediating influence of obesity and comorbid conditions on this relationship.

Microfluidic-based non-enzymatic glycation enhances cross-linking of human scleral tissue compared to conventional soaking

We evaluated nano-structural and chemical changes in human scleral collagen caused by non-enzymatic glycation using AFM, Raman spectroscopy, and microfluidics. Twenty 8 × 2 mm² scleral strips (n = 5, each) were divided into four groups of pure sclera tissues (control group) and sclera tissues with incubation (1 hr in BSS and ribose) and preservation (23 hr in 90% ethanol) for 7 days (BSS + DR₇ group) and 30 days (BSS + DR₃₀ group) at room temperature, and 7 days in a microfluidic chip (BSS + DR + µF₇ group). The BSS + DR₇ and BSS + DR₃₀ groups were incubated in a mixture of balanced salt solution (BSS) and 0.2 M D-ribose in PBS, pH 7.4 containing 0.1% sodium azide, while the BSS + DR + µF₇ group was incubated in the same solutions supplied by two inlet reservoirs from a microfluidic chip. The scleral tissues incubated in the microfluidic environment showed a clear irregular parallel arrangement of collagen fibrils with tangled fibrils. A Raman shift was observed at 919 cm^-1 in the glycation groups. Non-enzymatic glycation led to an increased in the density of scleral stromal collagen. Our method using non-enzymatic glycation in a microfluidic environment successfully induced collagen cross-linking. These in vitro results suggested that glycation can be used to strengthen connective tissues. SCANNING 38:421-426, 2016. © 2016 Wiley Periodicals, Inc.

A monoclonal antibody against the receptor for advanced glycation end products attenuates inflammatory and neuropathic pain in the mouse

BACKGROUND

The receptor for advanced glycation end products (RAGE) is a multi-ligand receptor in the immunoglobulin superfamily. RAGE is localized throughout ascending sensory pathways (skin, peripheral nerve, dorsal root ganglion, spinal cord), and in cell types interacting with sensory neurons (endothelial cells, smooth muscle cells, monocytes and macrophages). Neuronal RAGE expression increases in pathological pain states in humans and rodents, and soluble RAGE attenuates thermal hypoalgesia in diabetic mice. The objective of the present study was to investigate whether pharmacological modulation of RAGE could attenuate mechanical allodynia in rodent pain models.

METHODS

We developed an anti-RAGE monoclonal antibody (11E6) that binds to the C2 immunoglobulin domain of human RAGE, binds to mouse RAGE, and presumably to the same domain in mouse RAGE. The antinociceptive activity of 11E6 was investigated in mouse models of inflammatory (complete Freund's adjuvant) and neuropathic (chronic constriction injury of the sciatic nerve) pain. Mice were dosed intraperitoneally with 11E6 or IgG (negative control).

RESULTS

Increased mechanical thresholds were observed following a single dose of 11E6 in both inflammatory and neuropathic pain models. Similar treatment with IgG did not alter nociceptive sensitivity. Repeated dosing with 11E6 significantly attenuated established mechanical hypersensitivity in a neuropathic pain model in a dose-related fashion.

CONCLUSIONS

These data demonstrate that specific modulation of RAGE effectively attenuates nociceptive sensitivity associated with chronic inflammatory and neuropathic pain states.

An intricate relationship between pain and depression: clinical correlates, coactivation factors and therapeutic targets

INTRODUCTION

An apparent clinical relationship between pain and depression has long been recognized, which makes an enormous impact on the individual health care. At present, the practical implication of such overlapping symptomatology between pain and depression is not clear, but the prevalence estimates for depression are substantially inflated among patients with chronic pain and vice versa. This interaction has been labeled as the depression-pain syndrome or depression-pain dyad.

AREAS COVERED

This article discusses the neurobiological substrates and neuroanatomical pathways involved in pain-depression dyad along with newer therapeutic targets.

EXPERT OPINION

Several key themes emerged from our review of the relationship between depression and pain. First, the diagnosis of depression in pain or vice versa is particularly challenging, and the development of better diagnostic framework that involves both pain and depression is particularly required. Secondly, the entwined relationship between pain and depression supports the possibility of common coactivating factors that results in their neurophysiological overlap. A broad understanding of the role played by the central nervous system (CNS) in the processing of pain and depression may eventually lead to the introduction of triple reuptake inhibitors, agomelatine, vilazodone and ketamine with novel mechanism of action, hence appear to be of promising potential for pain with depression.

Curcumin ameliorates reserpine-induced pain-depression dyad: behavioural, biochemical, neurochemical and molecular evidences

An apparent clinical relationship between pain and depression has long been recognized. Depression and pain are often diagnosed in the same patients. The emerging concept for pain-depression pathogenesis is the dysfunction of biogenic amine-mediated pain-depression control and the possible involvement of nitrodative stress-induced neurogenic inflammation. The present study was designed to investigate the effect of curcumin on reserpine-induced pain-depression dyad in rats. Administration of reserpine (1mg/kg subcutaneous daily for three consecutive days) led to a significant decrease in nociceptive threshold as evident from reduced paw withdrawal threshold in Randall Sellitto and von-Frey hair test as well as significant increase in immobility time in forced swim test. This behavioural deficit was integrated with decrease in the biogenic amine (dopamine, norepinephrine and serotonin) levels along with increased substance P concentration, nitrodative stress, inflammatory cytokines, NF-κβ and caspase-3 levels in different brain regions (cortex and hippocampus) of the reserpinised rats. Curcumin (100, 200, 300mg/kg; ip) dose dependently ameliorated the behavioural deficits associated with pain and depression by restoring behavioural, biochemical, neurochemical and molecular alterations against reserpine-induced pain-depression dyad in rats.

[Mitochondrial dysfunction in fibromyalgia and its implication in the pathogenesis of disease]

Fibromyalgia (FM) is a chronic pain syndrome with unknown etiology. Recent studies have shown evidence demonstrating that oxidative stress may have a role in the pathophysiology of FM, however it is still not clear whether oxidative stress is the cause or the effect of the abnormalities documented in FM. Furthermore, it is also controversial the role of mitochondria in the pathophysiology of FM, however signs associated with mitochondrial dysfunction have been observed in FM. Mitochondria are also known to be strong producers of ROS, so have been related with the pathogenic mechanism of numerous diseases including FM. To this respect, it has been observed antioxidants therapies might be beneficial to improve the mitochondrial performance. Therefore, the dysfunction mitochondrial opens a great field of therapeutic research, for what it should start considering in the clinical medicine the boarding of the FM by means of therapy with antioxidant and drugs related to the mitochondrial biogenesis.

Mitochondrial dysfunction and mitophagy activation in blood mononuclear cells of fibromyalgia patients: implications in the pathogenesis of the disease

Introduction

Fibromyalgia is a chronic pain syndrome with unknown etiology. Recent studies have shown some evidence demonstrating that oxidative stress may have a role in the pathophysiology of fibromyalgia. However, it is still not clear whether oxidative stress is the cause or the effect of the abnormalities documented in fibromyalgia. Furthermore, the role of mitochondria in the redox imbalance reported in fibromyalgia also is controversial. We undertook this study to investigate the role of mitochondrial dysfunction, oxidative stress, and mitophagy in fibromyalgia.

Methods

We studied 20 patients (2 male, 18 female patients) from the database of the Sevillian Fibromyalgia Association and 10 healthy controls. We evaluated mitochondrial function in blood mononuclear cells from fibromyalgia patients measuring, coenzyme Q₁₀ levels with high-performance liquid chromatography (HPLC), and mitochondrial membrane potential with flow cytometry. Oxidative stress was determined by measuring mitochondrial superoxide production with MitoSOX™ and lipid peroxidation in blood mononuclear cells and plasma from fibromyalgia patients. Autophagy activation was evaluated by quantifying the fluorescence intensity of LysoTracker™ Red staining of blood mononuclear cells. Mitophagy was confirmed by measuring citrate synthase activity and electron microscopy examination of blood mononuclear cells.

Results

We found reduced levels of coenzyme Q₁₀, decreased mitochondrial membrane potential, increased levels of mitochondrial superoxide in blood mononuclear cells, and increased levels of lipid peroxidation in both blood mononuclear cells and plasma from fibromyalgia patients. Mitochondrial dysfunction was also associated with increased expression of autophagic genes and the elimination of dysfunctional mitochondria with mitophagy.

Conclusions

These findings may support the role of oxidative stress and mitophagy in the pathophysiology of fibromyalgia.

Low plasma levels of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNFalpha), and vascular endothelial growth factor (VEGF) in patients with alpha1-antitrypsin deficiency-related fibromyalgia

Abnormalities in blood inflammatory markers have been associated with clinical manifestations and the pathogenesis of the fibromyalgia syndrome (FMS); a relationship between inherited alpha1-antitrypsin deficiency (AATD) and FMS has also been recently raised. In this study, plasma levels of inflammatory markers in FMS patients with and without AATD have been investigated. Blood samples from 138 age-matched females (79 FMS) and 59 general population (GP), with normal MM [n = 82 (59.4%)] and with MS, MZ, SZ, and ZZ AATD genotypes [n = 56 (40.6%)], were analyzed by ELISA for monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-alpha (TNFalpha), soluble TNFalpha receptors I and II, interleukin-8, and vascular endothelial growth factor (VEGF). Plasma levels of MCP-1, VEGF, and TNFalpha were significantly lower in FMS and GP subjects with AATD compared with those with normal MM-AAT genotypes. Moreover, plasma levels of MCP-1, VEGF, and TNFalpha were lower in AATD subjects with FMS than in those without FMS (P = 0.000, 0.000, and 0.046, respectively). No statistical differences were found for the other substances measured. Furthermore, a logistic regression model based on plasma MCP-1 cutoff value of <or=130 pg/ml allowed us to discriminate between FMS and GP subjects with a sensitivity of about 93% and a specificity of 79%. Low plasma levels of MCP-1, VEGF, and TNFalpha are related to AATD, although more markedly in FMS patients. Thus, hypotheses considering FMS as an inflammatory condition related to high plasma levels of inflammatory biomarkers cannot be supported.

Detection of elevatedNε‐carboxymethyllysine levels in muscular tissue and in serum of patients with fibromyalgia

OBJECTIVES

To compare levels of the advanced glycation end product (AGE) N(epsilon)-carboxymethyllysine (CML) present in the muscle tissue and in the serum of patients with fibromyalgia (FM) vs. healthy controls.

METHODS

The serum levels of CML were measured in 41 patients with FM and 81 healthy controls. The presence of CML, nuclear factor kappa B (NF-kappaB), the AGE receptor (RAGE), collagen types I, II, VI, and CD68-positive monocytes/macrophages in muscle tissue of 14 patients with FM was investigated by immunohistochemistry.

RESULTS

Patients with FM showed significantly increased serum levels of CML in comparison to healthy controls. The immunohistochemical investigation revealed a stronger staining for CML and NF-kappaB and more CD68-positive monocytes/macrophages in the muscle of FM patients. The collagens and CML were co-localized, suggesting that the AGE modifications were related to collagen. RAGE was absent in controls but a faint and patchy staining was seen in FM.

CONCLUSIONS

In the interstitial connective tissue of fibromyalgic muscles we found a more intensive staining of the AGE CML, activated NF-kappaB, and also higher CML levels in the serum of these patients compared to the controls. RAGE was only present in FM muscle. AGE modification of proteins causes reduced solubility and high resistance to proteolytic digestion of the altered proteins (e.g. AGE-modified collagens). AGEs can stimulate different types of cells by activation of the transcription factor NF-kappaB, mediated by specific receptors of AGEs (e.g. RAGE) on the cell surface. Both mechanisms may contribute to the development, perpetuation, and spreading of pain characteristic in FM patients.

Bio-ecological control of chronic liver disease and encephalopathy

Minimal encephalopathy was originally associated with chronic liver disease but is increasingly associated with most other chronic diseases and particularly with diabetes and also chronic disorders in other organs: kidneys, lungs, thyroid and with obesity. It is increasingly with dramatically increased and more or less permanent increase in systemic inflammation, most likely a result of Western lifestyle. Frequent physical exercise and intake of foods rich in vitamins, antioxidants, fibres, lactic acid bacteria etc in combination with reduction in intake of refined and processed foods is known to reduce systemic inflammation and prevent chronic diseases. Some lactic acid bacteria, especially Lb paracasei, lb plantarum and pediococcus pentosaceus have proven effective to reduce inflammation and eliminate encephalopathy. Significant reduction in blood ammonia levels and endotoxin levels were reported in parallel to improvement of liver disease. Subsequent studies with other lactic acid bacteria seem to demonstrate suppression of inflammation and in one study also evidence of clinical improvement.

Antioxidant status, lipid peroxidation and nitric oxide in fibromyalgia: etiologic and therapeutic concerns

We proposed to assess the oxidant/antioxidant status, lipid peroxidation and nitric oxide (NO) in untreated fibromyalgia (FM) patients and controls. The effect of amitriptyline (A, 20 mg daily) and sertraline (S, 100 mg daily) treatment on patients' superoxide dismutase (SOD), xanthine oxidase (XO), adenosine deaminase (ADA) enzyme activities, thiobarbituric acid reactive substances (TBARS) and NO levels was investigated. Thirty female patients with primary FM and age-matched 16 healthy female controls were included. Patients received an 8-week course of treatment with either A or S. FM patients had higher serum levels of TBARS (particularly malondialdehyde) and lower levels of nitrite compared to controls whereas enzyme activities were similar. A and S significantly improved Fibromyalgia Impact Questionnaire (FIQ) pain scores, Hamilton anxiety and depression rating scales. But neither A nor S had significant effects on measured oxidative stress parameters, except SOD activity that was significantly reduced after S treatment. Total myalgic scores negatively correlated with XO activity, and depression scales negatively correlated with levels of TBARS. Our results indicate that patients with FM are under oxidative stress. These findings represent a rationale for further research assessing the effect of free radical scavengers or antioxidant agents like vitamins and omega-3 fatty acids on peripheral and central mechanisms in FM.

The RAGE pathway in inflammatory myopathies and limb girdle muscular dystrophy

Oxidative stress and nuclear factor-kappaB (NF-kappaB) activation are linked to the pathogenesis of many metabolic, degenerative, and chronic inflammatory diseases. Activation of the receptor for advanced glycation end products (RAGE) by its specific ligand N(epsilon)-carboxymethyllysine (CML) results in the activation of NF-kappaB and the production of proinflammatory cytokines. To determine whether engagement of RAGE contributes to the pathogenesis of inflammatory myopathies, we performed immunohistochemical studies on the presence of CML-modified proteins, RAGE and activated NF-kappaB in muscle biopsies of patients with polymyositis (PM, n=10), dermatomyositis (DM, n=10), limb girdle muscular dystrophy (LGMD, n=10) and in 10 controls with normal muscle biopsy results. In inflammatory myopathies CML, RAGE and NF-kappaB were detected in mononuclear cells and in regenerating muscle fibers. CML, NF-kappaB and, to a lesser extent, RAGE were also found in degenerating muscle fibers, but colocalization of CML, RAGE and NF-kappaB was only seen in infiltrating mononuclear cells and regenerating muscle fibers. Immunofluorescence double labeling demonstrated an expression of CML, RAGE and NF-kappaB in CD4-, CD8-, CD22- and CD68-positive mononuclear cells. Western blot analysis showed an increased immunoreactivity for CML-modified proteins in PM and DM. In LGMD, CML, RAGE and NF-kappaB were found in regenerating muscle fibers and less frequently in degenerating muscle fibers, and with lower staining intensities than in inflammatory myopathies. Our data suggests that the CML-RAGE-NF-kappaB pathway is an evident proinflammatory pathomechanism in mononuclear effector cells in PM and DM. RAGE-mediated NF-kappaB activation may be involved in muscle fiber regeneration in inflammatory myopathies and LGMD.

α1-Antitrypsin and fibromyalgia: new data in favour of the inflammatory hypothesis of fibromyalgia

alpha1-Antitrypsin (AAT) circulates in high serum concentrations, and impregnates most body tissues. AAT has a broad anti-inflammatory spectrum, and modulates most inflammatory reactions occurring in human body. Recently, a possible relationship between AAT deficiency (AAT-D) and fibromyalgia (FM) has been raised, with the finding that intravenous infusions of purified human AAT efficiently controlled FM symptoms in two patients with severe hereditary AAT-D. On the other hand, functional magnetic resonance imaging has detected a significant greater activity in pain sensitive areas of the brain in patients with FM, in response to cutaneous stimuli, providing further evidence for a physiological explanation for FM pain. In recent studies abnormal profiles of inflammation markers in serum and biopsies have been found in FM patients. Since most of these inflammation mediators can be inhibited by AAT, these observations would suggest that at least a subset of the FM syndrome could be related to an inflammatory process, possibly due to an imbalance between inflammatory and anti-inflammatory substances, in the soft body tissues. Future directions of research would be: (1) to develop epidemiological studies to determine the gene frequency of AAT deficiency alleles in FM patients; (2) implementation of a double-blind placebo-controlled clinical trial to determine the specific role of AAT augmentation therapy in AAT-D patients with FM; (3) identification of specific laboratory markers for diagnostic and clinical evaluation purposes in FM; (4) application of the newest medical imaging techniques for diagnosis; and (5) identification of genetic, familial, and environmental risk factors suspected to participate in the FM syndrome development.

The advanced glycation end product pentosidine correlates to IL-6 and other relevant inflammatory markers in rheumatoid arthritis

OBJECTIVE

Oxidative stress and inflammatory processes accelerate the formation of advanced glycation end products (AGE), e.g. of pentosidine. The aim of this study was to investigate the relationships between levels of pentosidine in serum and synovial fluid, proinflammatory cytokines, other markers of inflammatory activity, and the state of radiologically visible bone destruction in patients with rheumatoid arthritis (RA).

OBJECTIVES

One hundred thirty-three nondiabetic RA patients and 56 age-matched, healthy subjects were included. Serum and synovial fluid pentosidine, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and rheumatoid factor levels were determined. In 30 patients, the proinflammatory cytokines interleukin (IL)-1beta, IL-6, and TNF-alpha and the soluble receptors sIL-2R, sIL-6R, sTNF-alpha, and RI/RII were also measured.

RESULTS

Serum levels of pentosidine were on average significantly higher in RA patients than in healthy subjects and correlated significantly to ESR, CRP, and serum levels of IL-6. Serum and synovial fluid pentosidine did not show any differences. Rheumatoid factor-positive RA patients had higher pentosidine levels in the synovial fluid than rheumatoid factor-negative patients. Correlations could not be found between pentosidine and the other cytokines or cytokine receptors measured.

CONCLUSION

The binding of AGE on cell receptors induces activation of nuclear factor kappa B, resulting in enhanced synthesis of proinflammatory cytokines. Moreover, AGE generation may also lead to the formation of new, immunologically relevant epitopes at synovial proteins. Both mechanisms could contribute to initiation and perpetuation of the inflammatory and destructive processes in RA.