Pyroptosis by NLRP3/caspase-1/gasdermin-D pathway in synovial tissues of rheumatoid arthritis patients

We investigated the potential involvement of pyroptosis, a proinflammatory form of regulated cell death, in rheumatoid arthritis (RA). Synovial fluid, synovial tissues and/or serum were compared among 32 patients with RA, 46 patients with osteoarthritis (OA) and 30 healthy controls. Samples were assayed for interleukin (IL)-1β, IL-18 and lactate hydrogenase (LDH). Synovial expression of NLRP3, caspase-1 and cleaved gasdermin D (GSDMD) was assayed using immunohistochemistry and multiplex immunohistochemistry. Patients with RA showed significantly higher levels of IL-1β and IL-18 in synovial fluid than patients with OA, and significantly higher levels of both cytokines in serum than healthy controls. RA was associated with higher levels of LDH in synovial fluid than OA. Among patients with RA, levels of IL-1β, IL-18 and LDH were significantly higher in synovial fluid than in serum, and the levels in synovial fluid positively correlated with disease activity and inflammation. Synovial cells, particularly macrophages, showed upregulation of NLRP3, caspase-1 and cleaved GSDMD in RA compared to OA. Our results implicate pyroptosis in the pathogenesis of RA, perhaps as a driver of local inflammation in joints.     

Gene polymorphisms and serum levels of TL1A in patients with rheumatoid arthritis

Recent findings showed elevated expression of tumor necrosis factor (TNF)-like ligand 1A (TL1A) in rheumatoid arthritis (RA) patients and arthritis mice. However, whether TL1A gene polymorphisms may correlate with RA susceptibility needs to be discussed. This case-control study was performed on 350 RA patients and 556 healthy subjects to identify TL1A genetic variants (rs3810936, rs6478109, and rs7848647) and their possible association with TL1A levels, susceptibility to and severity of RA. Odds ratio and 95% confidence interval were calculated to represent the correlation between TL1A polymorphisms and RA. The TL1A serum levels were evaluated. Results showed that frequencies of TC, TT + TC genotypes of rs3810936, rs7848647 in RA patients were significantly lower in RA patients compared with controls. Patients with C allele showed more severe disease course (disease activity index: erythrocyte sedimentation rate, rheumatoid factor) than in carriers of T allele. However, the allele or genotype frequencies of rs6478109 were not associated with RA. In addition, TL1A genetic variants conferred higher TL1A levels in RA patients compared with controls. In conclusion, these findings indicated an association between TL1A rs3810936, rs7848647 variation and the susceptibility of RA in a sample of Chinese individuals, and TL1A may correlate with severity of RA.     

Elevated levels of serum antibodies against alpha-1, 6-glucan in patients with systemic lupus erythematosus or rheumatoid arthritis

This study was undertaken to investigate whether levels of anti-alpha-1, 6-glucan antibodies in human sera correlate with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Serum samples were collected from patients with SLE (n = 30), RA (n = 30) and healthy adult volunteers. IgG, IgA and IgM levels against alpha-1, 6-glucan were measured using enzyme linked immunosorbent assays. Anti-alpha-1, 6-glucan IgG prevalence was raised in patients with active SLE (73.3%) and RA (60%) compared with healthy controls (13.3%). Strong correlation between anti-alpha-1,6-glucan-IgG levels and anti-perinuclear factor (r = 0.642; p<0.05) in RA patients or anti-nuclear antibodies (r = 0.675; p<0.05) in SLE patients was observed. No significant differences in anti-alpha-1,6-glucan-IgA or-IgM levels were noted between different groups. We conclude that anti-alpha-1,6-glucan-IgG levels were significantly elevated in patients with SLE or RA and positively correlated with disease activity.     

Matrix metalloproteinases MMP-3 and MMP-1 levels in sera and synovial fluids in patients with rheumatoid arthritis and osteoarthritis

OBJECTIVES: To investigate whether serum levels of matrix metalloproteinases (MMP-3, stromelysin) and (MMP-1, collagenase) are specifically elevated in joint disease as rheumatoid arthritis (RA) compared to osteoarthritis (OA), and to assess how these markers reflect the clinical activity of RA compared to circulating cytokine as tumor necrosis factor-alpha (TNF-alpha) as well as established variables as [C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR)]. SUBJECTS AND METHODS: This study included 22 patients with RA, 10 patients with OA and 10 healthy control subjects matched for age and sex. Patients with superimposed infection were excluded. Serum levels of MMP-3, MMP-1, TNF-alpha and CRP were assayed. Synovial fluid (SF) levels of MMP-3 and MMP-1 were also assayed. RESULTS: Serum levels of TNF-alpha and CRP in RA patients were significantly higher than normal subjects. Serum MMP-1 was significantly elevated in patients with RA and OA, compared to healthy controls but there were no significant differences between patients with RA and those with OA. Serum MMP-3 levels did not differ between OA patients and normal sera. However, RA patients displayed significantly elevated levels of this enzyme, compared to OA and control sera. Levels of MMP-3 and MMP-1 in the SF of RA patients were significantly higher than in OA fluids. CRP, ESR, TNF-alpha and MMP-3 correlated significantly with the swollen joint count. The strongest positive correlations existed between rheumatoid activity as assessed by the levels of CRP and circulating levels of MMP-3. Similar correlations between TNF-alpha concentration and CRP, MMP-1 and MMP-3 were observed in RA patients. Serum levels of MMP-3 correlated significantly with serum concentrations of MMP-1 in RA patients (r = 0.487, p < 0.05). There was close correlation between serum and SF concentrations of MMP-3 in RA patients (r = 0.619, p < 0.01). In the same patients there was highly significant correlation between SF concentrations of MMP-3 and MMP-1 (r = 0.732, p < 0.001). CONCLUSIONS: Our data suggested that elevated MMP-3 levels reflected disease activity of RA better than cytokine levels. However, MMP-3 levels do not exceed the association of CRP with clinical activity.     

Investigation of protein oxidation and lipid peroxidation in patients with rheumatoid arthritis

We aimed to determine the importance of neutrophil activation and the source of oxidative stress in the pathogenesis of rheumatoid arthritis (RA) by quantification of advanced oxidation protein products (AOPP) and total thiol levels as markers of oxidative protein damage, malondialdehyde (MDA) levels as a marker of lipid peroxidation and myeloperoxidase (MPO) activity as a marker of neutrophil activation in patients with RA. Fifty-seven rheumatoid arthritis patients were included in the study and sub-grouped according to disease activity (active, n = 31; inactive, n = 26) and compared with healthy controls (n = 25). Serum MPO activity, AOPP, MDA, and thiol levels were measured by an enzymic spectrophotometric method. Serum MPO activity (p < 0.001), AOPP (p < 0.001), MDA (p < 0.001) and levels of thiol (p < 0.002), were higher in the patient group than the controls. Active and inactive RA groups were compared with the control group and there were significant differences between each parameter. MPO activity, AOPP, MDA and thiol levels were significantly higher in both active and inactive RA patients than the controls. On the other hand, when a comparison was made between active and the inactive stage, a statistically significant difference was present only in MDA (p < 0.05) and AOPP levels (p < 0.05). There was also a significant positive correlation between all parameters. These data strongly suggest that neutrophils, which constitute the most important source of chlorinated oxidants due to their high MPO content, may be involved in serum AOPP formation and therefore the production of a novel class of pro-inflammatory mediators of oxidative stress in RA patients and that protein oxidation could play an important role in the pathogenesis of RA as does lipid peroxidation.     

Medication persistence over 2 years of follow-up in a cohort of early rheumatoid arthritis patients: associated factors and relationship with disease activity and with disability

Introduction

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is a tumour necrosis factor (TNF) family member capable of inducing apoptosis in many cell types.

Methods

Using immunohistochemistry, terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) and real-time PCR we investigated the expression of TRAIL, TRAIL receptors and several key molecules of the intracellular apoptotic pathway in human synovial tissues from various types of arthritis and normal controls. Synovial tissues from patients with active rheumatoid arthritis (RA), inactive RA, osteoarthritis (OA) or spondyloarthritis (SpA) and normal individuals were studied.

Results

Significantly higher levels of TRAIL, TRAIL R1, TRAIL R2 and TRAIL R4 were observed in synovial tissues from patients with active RA compared with normal controls (p < 0.05). TRAIL, TRAIL R1 and TRAIL R4 were expressed by many of the cells expressing CD68 (macrophages). Lower levels of TUNEL but higher levels of cleaved caspase-3 staining were detected in tissue from active RA compared with inactive RA patients (p < 0.05). Higher levels of survivin and x-linked inhibitor of apoptosis protein (xIAP) were expressed in active RA synovial tissues compared with inactive RA observed at both the protein and mRNA levels.

Conclusions

This study indicates that the induction of apoptosis in active RA synovial tissues is inhibited despite stimulation of the intracellular pathway(s) that lead to apoptosis. This inhibition of apoptosis was observed downstream of caspase-3 and may involve the caspase-3 inhibitors, survivin and xIAP.     

Anti-inflammatory cytokines in gingival crevicular fluid in patients with periodontitis and rheumatoid arthritis: a preliminary report

Cytokines which are produced by host cells play an important role in pathogenesis both rheumatoid arthritis (RA) and chronic periodontitis (CP). In this study, we aim to investigate the levels of Interleukin (IL)-4 and IL-10 in gingival crevicular fluid (GCF). Seventeen patients with CP, 17 patients with RA and 17 healthy controls (HC) were included. The RA group was divided into two groups according to gingival sulcus depths (RA-a: PD < or =3mm, (n=12), RA-b: PD>3mm, (n=5)). For each patient, clinical parameters were recorded. The GCF samples were evaluated by enzyme-linked immunosorbent assay (ELISA) for IL-4 and IL-10 levels. IL-4 levels in the RA-a, RA-b and CP subjects were significantly lower compared to the HC subjects (p<0.05). The mean level of IL-4 in RA-b group was significantly higher than that in CP group (p<0.05). IL-10 mean level in the HC group was higher than those in the other groups (p<0.05). In the RA-a group, higher IL-10 level was found compared to the CP patients (p<0.05). Within the limitations of this preliminary report, it can be concluded that the initiation and progression of periodontal inflammation may be due to a lack or inappropriate response of the anti-inflammatory cytokines in both CP and RA.     

Follistatin-like protein 1 is elevated in systemic autoimmune diseases and correlated with disease activity in patients with rheumatoid arthritis

Introduction

Follistatin-like protein 1 (FSTL1) is a proinflammation mediator implicated in arthritis in rodent animal models. The present study is aimed at assessing FSTL1 levels in systemic autoimmune diseases and correlating them with disease activity in patients with rheumatoid arthritis (RA).

Methods

Serum FSTL1 levels from 487 patients with systemic autoimmune diseases and 69 healthy individuals were measured by enzyme-linked immunosorbent assay (ELISA). FSTL1 expression in synovial fluid (SF) and synovial tissues (STs) was determined by ELISA, immunohistochemistry, real-time polymerase chain reaction (RT-PCR) and western blot analysis in RA patients and trauma controls. FSTL1 levels in fibroblast-like synoviocytes (FLSs) from RA patients were determined by real-time PCR and western blot analysis.

Results

Serum FSTL1 levels were significantly elevated in patients with RA, ulcerative colitis, systemic lupus erythematosus, Sjögren's syndrome (SS), systemic sclerosis and polymyositis/dermatomyositis. Serum FSTL1 levels in the RA and secondary SS patients were substantially higher than those in other patients. Serum FSTL1 levels were increased in early RA, rheumatoid factor (RF)- and anti-cyclic citrullinated peptide antibody (ACPA)-negative patients compared to healthy controls. Moreover, serum FSTL1 concentrations were significantly higher in long-standing RA patients than in early RA patients and in the RF- and ACPA-positive RA patients than in RF- and ACPA-negative RA patients. Elevated FSTL1 levels in the STs and SF of RA patients were also observed. FSTL1 levels in serum were markedly higher than those in SF in RA patients. The strongest FSTL1 staining was detected in the cytoplasm of synovial and capillary endothelial cells from RA synovium. Furthermore, FSTL1 was induced in FLSs by inflammatory mediators. Importantly, serum FSTL1 levels were correlated with several important biologic and clinical markers of disease activity, including erythrocyte sedimentation rate, C-reactive protein, RF, ACPA, swollen joint count, patient global visual analogue scale score and Disease Activity Score 28 in the adult RA patient population. Notably, serum FSTL1 levels were significantly diminished following successful treatment and clinical improvement.

Conclusions

Elevated FSTL1 levels reflect not only joint diseases but also inflammation and tissue degradation in systemic autoimmune diseases. Serum FSTL1 levels may thus serve as a serological inflammatory marker of disease activity in RA patients.     

Cholinergic anti-inflammatory pathway activity and High Mobility Group Box-1 (HMGB1) serum levels in patients with rheumatoid arthritis

High Mobility Group Box-1 (HMGB1) is a cytokine implicated in the pathogenesis of rheumatoid arthritis (RA) and other inflammatory diseases. The cholinergic anti-inflammatory pathway, a vagus nerve-dependent mechanism, inhibits HMGB1 release in experimental disease models. Here, we examine the relationship between vagus nerve activity and HMGB1 in patients with RA. We compared RR interval variability, an index of cardiac vagal modulation, HMGB1 and hsCRP serum levels, and disease activity scores in thirteen RA patients and eleven age- and sex-matched controls. In RA patients, serum levels of HMGB1 and hsCRP were elevated as compared with controls (HMGB1=71 ng/mL [45-99] vs. 18 ng/mL [0-40], P<0.0001; hsCRP=14.5 mg/L [0.7-59] vs. 1 mg/L [0.4-2.9], P<0.001). RR interval variability in RA patients was significantly decreased as compared with controls (HF=38 msec2 [14-80] vs. 288 msec2 [38-364], P<0.0001; rMSSD=20.9+/-9.79 msec, 52.6+/-35.3 msec, P<0.01). HMGB1 levels and RR interval variability were significantly related (rho=-0.49, P<0.01). HMGB1 serum levels significantly correlated with disease activity scores (DAS-28) in patients with RA (P=0.004). The study design does not enable a determination of causality, but the results are consistent with the hypothesis that decreased cholinergic anti-inflammatory pathway activity is associated with increased HMGB1 levels in patients with RA.     

Expression of ID family genes in the synovia from patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by aggressive proliferation of synovial tissue leading to destruction of cartilage and bone. To identify molecules which play a crucial role for the pathogenesis, we compared mRNA expression pattern of RA synovium with that of osteoarthritis (OA), using the differential display. From the panel of differentially expressed genes, ID1 (inhibitor of differentiation 1) was considered to be particularly relevant to the pathogenesis of RA, because Id family genes have been shown to play a role in cell proliferation and angiogenesis. To examine whether the up-regulation of these genes is consistently observed in the patients with RA, mRNA levels of ID1 and ID3 in the synovial tissues from 13 patients with RA and 6 patients with OA were semi-quantitatively analyzed by RT-PCR. Mean mRNA levels of ID1 and ID3 were significantly elevated in RA synovia compared with OA by 8.6-fold (P = 0.0044) and 3.3-fold (P = 0.0085), respectively. Immunohistochemistry revealed striking staining of Id1 and Id3 in the endothelial cells, suggesting a possible role of Id in severe angiogenesis observed in RA. The expression of Id family genes in the synovium constitutes a new finding of particular interest. Their functional role as well as their contribution to the genetic susceptibility to RA requires further investigation.     

A Potential Role of Myeloid DAP12-Associating Lectin (MDL)-1 in the Regulation of Inflammation in Rheumatoid Arthritis Patients

The pathogenic roles of myeloid DAP12-associating lectin-1(MDL-1) and DAP12 in human rheumatoid arthritis (RA) remain unknown. Frequencies of MDL-1-expressing monocytes in 22 active RA patients, 16 inactive RA patients, 12 osteoarthritis (OA) patients and 10 healthy controls (HC) were determined by flow-cytometry analysis. The mRNA expression levels of MDL-1 and DAP12 on PBMCs were evaluated by quantitative PCR, and their protein expression levels in the synovium were examined by immunohistochemistry. Significantly higher median percentages of circulating MDL-1-expressing monocytes were observed in active RA patients (53.6%) compared to inactive RA patients (34.1%), OA patients (27.9%), and HC (21.2%). Levels of MDL-1 and DAP12 gene expression in PBMCs and their protein expression in the synovium were significantly higher in active RA patients than in inactive RA or OA patients. MDL-1 levels were positively correlated with parameters of disease activity, articular damage, and levels of proinflammatory cytokines. MDL-1 activator (Dengue virus type 2 antigen) stimulation on PBMCs resulted in significantly enhanced levels of proinflammatory cytokines in RA patients compared to those in OA patients or HC, indicating that MDL-1 activation is functional. Frequencies of MDL-1-expressing monocytes and levels of MDL-1 and DAP12 gene expression significantly decreased after effective therapy. Concordant overexpression of MDL-1 and DAP12 were correlated with increased production of proinflammatory cytokines in RA patients, suggesting their roles in regulating articular inflammation.     

Failure of catecholamines to shift T-cell cytokine responses toward a Th2 profile in patients with rheumatoid arthritis

To further understand the role of neuro-immunological interactions in the pathogenesis of rheumatoid arthritis (RA), we studied the influence of sympathetic neurotransmitters on cytokine production of T cells in patients with RA. T cells were isolated from peripheral blood of RA patients or healthy donors (HDs), and stimulated via CD3 and CD28. Co-incubation was carried out with epinephrine or norepinephrine in concentrations ranging from 10(-5) M to 10(-11) M. Interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, interleukin (IL)-4, and IL-10 were determined in the culture supernatant with enzyme-linked immunosorbent assay. In addition, IFN-gamma and IL-10 were evaluated with intracellular cytokine staining. Furthermore, basal and agonist-induced cAMP levels and catecholamine-induced apoptosis of T cells were measured. Catecholamines inhibited the synthesis of IFN-gamma, TNF-alpha, and IL-10 at a concentration of 10(-5) M. In addition, IFN-gamma release was suppressed by 10(-7) M epinephrine. Lower catecholamine concentrations exerted no significant effect. A reduced IL-4 production upon co-incubation with 10(-5) M epinephrine was observed in RA patients only. The inhibitory effect of catecholamines on IFN-gamma production was lower in RA patients as compared with HDs. In RA patients, a catecholamine-induced shift toward a Th2 (type 2) polarised cytokine profile was abrogated. Evaluation of intracellular cytokines revealed that CD8-positive T cells were accountable for the impaired catecholaminergic control of IFN-gamma production. The highly significant negative correlation between age and catecholamine effects in HDs was not found in RA patients. Basal and stimulated cAMP levels in T-cell subsets and catecholamine-induced apoptosis did not differ between RA patients and HDs. RA patients demonstrate an impaired inhibitory effect of catecholamines on IFN-gamma production together with a failure to induce a shift of T-cell cytokine responses toward a Th2-like profile. Such an unfavorable situation is a perpetuating factor for inflammation.     

Increased adiponectin is negatively linked to the local inflammatory process in patients with rheumatoid arthritis

Adiponectin has been shown to exert insulin-sensitizing, anti-atherogenic, and anti-inflammatory properties in metabolic diseases. It has been suggested that adiponectin may play a role in rheumatoid arthritis (RA). To assess adiponectin in serum and synovial fluid from patients with RA and osteoarthritis (OA), and in serum from healthy controls. Adiponectin and CRP levels were analyzed by ELISA. The clinical activity of RA patients was assessed according to the 28 joint count Disease Activity Score. Synovial fluid adiponectin was significantly higher in RA than in OA patients (p<0.001). Adiponectin was negatively associated with the leukocyte count in RA synovial fluid (r=-0.45, p<0.05). Serum adiponectin was higher in RA compared to healthy controls (p<0.02), however comparable to OA patients. Serum adiponectin was higher than in synovial fluid in both diseases (p<0.001). In general, women had higher adiponectin levels than men. Adiponectin was not related to age, disease duration, body mass index, or disease activity of RA patients. Adiponectin is decreased in synovial fluid compared to serum indicating that peripheral fat stores are major producers of adiponectin into the blood stream. However, increased synovial fluid adiponectin in RA patients may counterpart the local inflammatory process.     

HLA-DRB1*04 gene polymorphisms and expressions profiles of interleukin-18 and interleukin-18 binding protein following in vitro stimulation in human peripheral blood mononuclear cells of healthy individuals and patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic arthritic condition that can lead to deformities and disabilities. Interleukin-18 (IL-18) is a proinflammatory cytokine known to play a role in the acute and chronic inflammatory phases of RA. IL-18 binding protein is the natural antagonist of IL-18 protein. We aim to identify the effect of HLA-DRB1*04 gene polymorphisms on IL-18 and IL-18BP gene expressions profiles as well as the time-course profiles following in vitro stimulation with mitogens. Peripheral blood mononuclear cells from 16 RA patients and 21 healthy controls were cultured for 1, 4, 8, 12, 24, 48 and 72 h following stimulation with either LPS or PHA. mRNA expression of IL-18 and IL 18BP were determined by quantitative real-time PCR using a comparative Ct (threshold cycle) method. IL-18 levels in supernatants were measured by enzyme-linked immunosorbent assay. Basal mRNA (4.5-fold) and protein levels of IL-18 were increased and IL-18BP mRNA expression was decreased (8-fold) in RA patients when compared to controls. Similarly, increased IL-18 levels were observed in active RA patients, whereas IL-18BP expression was increased in inactive patients. There was an increase in mRNA and protein levels of IL-18 in RA patients that peaked at 4 h and 8 h respectively following LPS stimulation. A similar profile was observed for IL-18BP; however, the expression level was higher in controls than RA patients. Persistent high production of IL-18 in RA is associated with disease progression and IL-18 BP seems to inhibit this activity.     

Determination of oxidant stress in plasma of rheumatoid arthritis and primary osteoarthritis patients

Determination of oxidant stress in plasma of rheumatoid arthritis (RA) and primary osteoarthritis (POA) patients is important in understanding the pathogenesis of these diseases. In this study, we examined the relationship between oxidant stress and inflammation by measuring protein carbonyl content, thiol levels and plasma protein fractions as the oxidation markers and erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) tests as inflammation markers. Protein carbonyls content was higher in RA and POA patients, as compared to controls (p<0.0001), while the plasma thiol levels in both groups of patients were significantly lower than controls (p<0.0001). Increased levels of proteins under 40 kDa molecular mass were detected in the RA and POA patients compared to that of controls (p<0.0001) both in HPLC and SDS-PAGE analysis. Total protein concentration in plasma of RA patients was higher than the controls (p<0.001), while in POA patients was lower than that of controls (p<0.001). ESR and CRP levels were higher in both the patient groups than the normal group (p<0.001). These results suggested that alterations in the oxidant stress markers could be the cause of inflammation in these diseases. Thus, while working for RA/POA treatment strategies, consideration of the relationship between oxidant stress and inflammation would be worth evaluating.     

Association between autophagy and inflammation in patients with rheumatoid arthritis receiving biologic therapy

Background

Increasing evidence indicates a pathogenic role of deregulated autophagy in rheumatoid arthritis (RA). We examined the relationship between autophagy and inflammatory parameters in patients with RA receiving biologic therapy.

Methods

In 72 patients with RA and 20 healthy control subjects (HC), autophagosome levels were determined by the mean fluorescence intensity (MFI) of autophagosomotropic dye incorporated into circulating immune cells, and p62 expression levels in immune cells were measured by flow cytometry. We used immunoblotting to examine protein expression of LC3-II and p62 in peripheral blood mononuclear cells.

Results

Patients with RA had significantly higher levels of autophagosome reflected by MFI of Cyto-ID in circulating lymphocytes, monocytes, and granulocytes (median values, 3.6, 11.6, and 64.8, respectively) compared with HC (1.9, 6.0, and 35.8; respectively) (all p?<?0.001). p62 MFI levels in lymphocytes and granulocytes from patients with RA (17.1 and 8.6, respectively) were significantly lower than those in the corresponding cells from HC (20.2, p?<?0.05; and 13.1, p?<?0.001, respectively). Significantly higher levels of LC3-II protein expression in contrast to lower p62 protein levels were observed in patients with RA than in HC. The autophagosome levels in immune cells were significantly correlated with inflammatory parameters in patients with RA, and they were significantly decreased with disease remission after treatment with tumor necrosis factor-α inhibitors or interleukin-6 receptor inhibitor.

Conclusions

Elevated autophagy with significant correlation to inflammation suggests the involvement of autophagy in RA pathogenesis. The effectiveness of biologic therapy might be partly related to the downregulation of autophagy expression.

     

Reactive oxygen species, lipid peroxides and essential fatty acids in patients with rheumatoid arthritis and systemic lupus erythematosus

We studied free radical generation, lipid peroxidation and the levels of essential fatty acids and of their metabolites in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Both superoxide and hydrogen peroxide generation by peripheral leukocytes but not malondialdehyde levels, as measured by thiobarbituric acid assay, were found to be significantly enhanced both in RA and SLE. Fatty acid analysis of the plasma PL fraction revealed that both LA and ALA metabolites are significantly decreased in RA and SLE compared to controls. These results suggest that essential fatty acid metabolism is altered in RA and SLE.     

Extracellular mitochondrial DNA and oxidatively damaged DNA in synovial fluid of patients with rheumatoid arthritis

We investigated whether plasma and synovial fluid (SF) samples from patients with rheumatoid arthritis (RA) contained extracellular mitochondrial DNA (mtDNA) or the oxidatively damaged DNA adduct 8-hydroxy-2'-deoxyguanosine (8-oxodG). Moreover, we correlated the laboratory findings of the patients with RA with their levels of mtDNA and 8-oxodG. SF and plasma samples from 54 patients with RA, SF from 30 non-arthritic control subjects, and plasma from 22 healthy volunteers were collected. The samples were subjected to polymerase chain reaction (PCR) using mitochondrial genomic primers, and the products were analyzed by SDS–polyacrylamide-gel electrophoresis. The intensities of the PCR-amplified bands were quantified and normalized to a reference sample. Furthermore, the SF samples were assayed by enzyme-linked immunosorbent assay for 8-oxodG. Extracellular PCR-amplifiable mtDNA was detected in the SF of 38 of 54 (70%) patients with RA, but not in any of the SF controls. PCR-amplifiable mtDNA was detected in the plasma of 30 of 54 (56%) of patients with RA and in 6 of 22 (27%) of the healthy volunteers. The levels of mtDNA in the plasma and SF samples of patients with RA were significantly higher (P < 0.0001) than in the respective control samples. The presence of both mtDNA and 8-oxodG in SF was significantly correlated with the presence of rheumatoid factor in the patients with RA. Extracellular mtDNA and oxidized DNA were detected in the SF of the great majority of patients with RA, but were absent or present at low levels in the control SF. These findings indicate that endogenous nucleic acid compounds might participate in joint inflammation by activating immune cells in the joints to produce proinflammatory cytokines.     

Increased levels of serum myeloperoxidase in patients with active rheumatoid arthritis

Aims

The clinical significance of myeloperoxidase (MPO) has been the focus of investigation because it may contribute to the chronic, non-microbial inflammatory process in various diseases. Here, we determined serum MPO levels in rheumatoid arthritis (RA) and other autoimmune or inflammatory conditions, and investigated the associations between MPO levels and disease activity indicators in RA.

Main methods

The distribution of MPO was determined in serum samples from patients with RA, systemic lupus erythematosus (SLE), primary Sjögren's syndrome (pSS), dermatomyositis (DM), or ankylosing spondylitis (AS) and from healthy controls using commercial ELISA kits. Associations of serum MPO levels with the disease variables of RA patients were evaluated.

Key findings

All patient samples analyzed showed higher serum levels of MPO than healthy controls. Furthermore, MPO levels in RA were significantly higher than those in the other diseases with the exception of DM. Higher MPO levels were observed in RA patients with increased C-reactive protein (p = 0.005) or neutrophil percentage (p < 0.001), as well as in those with highly active disease (p < 0.001). Moderate positive correlations between MPO levels and IgM (r = 0.334, p = 0.001), C-reactive protein (r = 0.293, p = 0.003), erythrocyte sedimentation rate (r = 0.240, p = 0.016), or DAS28 (r = 0.350, p < 0.001) were also demonstrated.

Significance

The MPO concentration is likely to increase in patients with chronic inflammation. The associations between MPO and the disease variables of RA patients support a role for MPO in the inflammatory process of the disease.