Paraoxonase 1 Activity Is Modulated by the rs662 Polymorphism and IgG Anti-High-Density Lipoprotein Antibodies in Patients With Rheumatoid Arthritis: Potential Implications for Cardiovascular Disease

Anti-apolipoprotein A-1 IgG, incident cardiovascular events, and lipid paradox in rheumatoid arthritis

Objective

To validate the prognostic accuracy of anti-apolipoprotein A-1 (AAA1) IgG for incident major adverse cardiovascular (CV) events (MACE) in rheumatoid arthritis (RA) and study their associations with the lipid paradox at a multicentric scale.

Method

Baseline AAA1 IgG, lipid profile, atherogenic indexes, and cardiac biomarkers were measured on the serum of 1,472 patients with RA included in the prospective Swiss Clinical Quality Management registry with a median follow-up duration of 4.4 years. MACE was the primary endpoint defined as CV death, incident fatal or non-fatal stroke, or myocardial infarction (MI), while elective coronary revascularization (ECR) was the secondary endpoint. Discriminant accuracy and incidence rate ratios (IRR) were respectively assessed using C-statistics and Poisson regression models.

Results

During follow-up, 2.4% (35/1,472) of patients had a MACE, consisting of 6 CV deaths, 11 MIs, and 18 strokes; ECR occurred in 2.1% (31/1,472) of patients. C-statistics indicated that AAA1 had a significant discriminant accuracy for incident MACE [C-statistics: 0.60, 95% confidence interval (95% CI): 0.57-0.98, p = 0.03], mostly driven by CV deaths (C-statistics: 0.77; 95% CI: 0.57-0.98, p = 0.01). IRR indicated that each unit of AAA1 IgG increase was associated with a fivefold incident CV death rate, independent of models' adjustments. At the predefined and validated cut-off, AAA1 displayed negative predictive values above 97% for MACE. AAA1 inversely correlated with total and HDL cholesterol.

Conclusions

AAA1 independently predicts CV deaths, and marginally MACE in RA. Further investigations are requested to ascertain whether AAA1 could enhance CV risk stratification by identifying patients with RA at low CV risk.

Humoral responses against HDL are linked to lipoprotein traits, atherosclerosis, inflammation and pathogenic pathways during early arthritis stages

OBJECTIVE

Chronic inflammation and immune dysregulation are crucial mechanisms for atherosclerosis in RA. Recent evidence suggests a link via humoral responses against high-density lipoproteins (HDL). This study aimed to characterize the specificity, clinical relevance and emergence of humoral responses against HDL along disease course, especially during the earliest phases of arthritis.

METHODS

IgG and IgM serum levels of antibodies against HDL (anti-HDL) and apolipoprotein A1 (anti-ApoA1) were measured in 82 early RA patients, 14 arthralgia individuals and 96 controls. Established RA patients (n = 42) were included for validation. Atherosclerosis and vascular stiffness were measured by Doppler ultrasound. Lipoprotein content, particle numbers and size were measured by H-NMR. Cytokines were measured by immunoassays. A cardiometabolic-related protein panel was evaluated using high-throughput targeted proteomics.

RESULTS

Anti-HDL and anti-ApoA1 responses were increased in early RA compared with controls (both P < 0.001) and were comparable to established disease. Only anti-ApoA1 antibodies were increased in arthralgia. IgG anti-HDL and anti-ApoA1 were associated with unfavourable lipoprotein traits in RA and arthralgia, respectively. A similar picture was observed for inflammatory mediators. No associations with clinical features or risk factors were found. IgG anti-HDL were independently associated with atherosclerosis occurrence in early RA, and outperformed patient stratification over conventional algorithms (mSCORE) and their anti-ApoA1 counterparts. Anti-HDL antibodies correlated with proteins involved in immune activation, remodelling and lipid metabolism pathways in early RA.

CONCLUSION

Humoral responses against HDL particles are an early event along the arthritis course, although quantitative and qualitative differences can be noticed among stages. These differences informed distinct capacities as biomarkers and underlying pathogenic circuits.

Diagnosis and management of cardiovascular risk in rheumatoid arthritis: main challenges and research agenda

INTRODUCTION

Rheumatoid arthritis (RA) exhibit a cardiovascular (CV) risk that is 1.5-2.0 times higher compared to the general population. This CV risk excess is likely caused by the involvement of chronic inflammation and immune dysregulation. Therefore, conventional algorithms and imaging techniques fail to fully account for this risk excess and provide a suboptimal risk stratification, hence limiting clinical management in this setting.

AREAS COVERED

Compelling evidence has suggested a role for adaptations of conventional algorithms (Framingham, SCORE, AHA, etc) or the development of RA-specific algorithms, as well as the use of a number of several, noninvasive imaging techniques to improve CV risk assessment in RA populations. Similarly, in-depth analyses of atherosclerosis pathogenesis in RA patients have shed new light into a plethora of soluble biomarkers (such as inflammatory cytokines, vascular remodeling mediators or autoantibodies) that may provide incremental value for CV risk stratification.

EXPERT OPINION

Extensive research has demonstrated a lack of performance of chart adaptations in capturing real CV risk in RA population, as well as for RA-specific algorithms. Similarly, limitations have been detected in the use of soluble mediators. The development of a novel, RA-specific algorithm including classical and non-traditional risk factors may be advisable.

Association between Paraoxonase/Arylesterase Activity of Serum PON-1 Enzyme and Rheumatoid Arthritis: A Systematic Review and Meta-Analysis

Background: A decrease in serum paraoxonase (PON-1) and arylesterase (ARE) activity has been reported in rheumatoid arthritis (RA) patients and linked to chronic inflammation and impaired antioxidant defense. Methods: A systematic review and meta-analysis were performed to critically appraise the current evidence on plasma/serum concentrations of PON-1 and ARE activity in RA patients and healthy controls. The Web of Science, PubMed, Scopus, and Google Scholar databases were searched from inception to November 2021. We used random-effects meta-analysis. The risk of bias was estimated using the Joanna Briggs Institute Critical Appraisal Checklist tool. The certainty of the evidence was assessed with GRADE. The study complied with the PRISMA statements and was registered in PROSPERO (CRD42022345380). Results: Seventeen studies reported PON-1 activity (1144 RA patients, 797 controls) and ten reported ARE activity (1367 RA patients, 1037 controls). RA patients had significantly lower PON-1 (SMD = −1.32, 95% CI −1.94 to −0.70; p < 0.001) and ARE activity (SMD = −0.91, 95% CI −1.37 to −0.46; p < 0.001). There was substantial heterogeneity (PON, I2 97%; ARE, 95.7%, p < 0.001 for both). There was no publication bias. The pooled SMD values did not significantly change after sensitivity analysis. The certainty of the evidence was very low due to the observational nature of the studies and the large heterogeneity. Conclusion: Our meta-analysis has shown that both serum PON-1 and ARE activity are significantly lower in RA patients, suggesting a deficit in antioxidant defense mechanisms in this disease.

A systematic review and meta-analysis of paraoxonase-1 activity in asthma

Human serum paraoxonase-1 (PON-1) is a critical antioxidant defence system against lipid oxidation. Decreased PON-1 activity has been associated with systemic oxidative stress in several disease states. We conducted a systematic review and meta-analysis of plasma/serum concentrations of PON-1 in asthma, a chronic inflammatory airway disease. The electronic databases PubMed, Web of Science, Scopus and Google Scholar were searched from inception to February 2022. In total, 8 studies in 355 asthmatic patients and 289 healthy controls were included in the meta-analysis. Serum PON-1 concentrations were significantly lower in asthmatic patients (SMD = −1.58, 95% CI −2.53 to −0.63; p = 0.001). The pooled SMD values were not substantially altered in sensitivity analysis. There was no publication bias. There were non-significant differences in PON-1 concentrations in patients with severe vs. mild-to-moderate asthma (SMD =  − 0.39, 95% CI − 1.00 to 0.22, p = 0.21). Our meta-analysis has shown that serum PON-1 concentrations are significantly lower in patients with asthma, suggesting the presence of an impaired antioxidant defense in this group.

Novel Surrogate Markers of Cardiovascular Risk in the Setting of Autoimmune Rheumatic Diseases: Current Data and Implications for the Future

Patients suffering from rheumatologic diseases are known to have an increased risk for cardiovascular disease (CVD). Although the pathological mechanisms behind this excess risk have been increasingly better understood, there still seems to be a general lack of consensus in early detection and treatment of endothelial dysfunction and CVD risk in patients suffering from rheumatologic diseases and in particular in those who haven't yet shown symptoms of CVD. Traditional CVD prediction scores, such as Systematic Coronary Risk Evaluation (SCORE), Framingham, or PROCAM Score have been proposed as valid assessment tools of CVD risk in the general population. However, these risk calculators developed for the general population do not factor in the effect of the inflammatory burden, as well as other factors that can increase CVD risk in patients with rheumatic diseases, such as glucocorticoid therapy, abnormal lipoprotein function, endothelial dysfunction or accelerated atherosclerosis. Thus, their sole use could lead to underestimation of CVD risk in patients with rheumatic diseases. Therefore, there is a need for new biomarkers which will allow a valid and early assessment of CVD risk. In recent years, different research groups, including ours, have examined the value of different CVD risk factors such as carotid sonography, carotid-femoral pulse wave velocity, flow-mediated arterial dilation and others in the assessment of CVD risk. Moreover, various novel CVD laboratory markers have been examined in the setting of autoimmune diseases, such as Paraoxonase activity, Endocan and Osteoprotegerin. Dyslipidemia in rheumatoid arthritis (RA) is for instance better quantified by lipoproteins and apolipoproteins than by cholesterol levels; screening as well as pre-emptive carotid sonography hold promise to identify patients earlier, when prophylaxis is more likely to be effective. The early detection of subtle changes indicating CVD in asymptomatic patients has been facilitated through improved imaging methods; the inclusion of artificial intelligence (AI) shows promising results in more recent studies. Even though the pathophysiology of coronary artery disease in patients with autoimmune rheumatic diseases has been examined in multiple studies, as we continuously gain an increased understanding of this comorbidity, particularly in subclinical cases we still seem to fail in the stratification of who really is at risk—and who is not. A the time being, a multipronged and personalized approach of screening patients for traditional CVD risk factors, integrating modern imaging and further CV diagnostic tools and optimizing treatment seems to be a solid approach. There is promising research on novel biomarkers, likewise, methods using artificial intelligence in imaging provide encouraging data indicating possibilities of risk stratification that might become gold standard in the near future. The present review concentrates on showcasing the newest findings concerning CVD risk in patients with rheumatologic diseases and aims to evaluate screening methods in order to optimize CVD risk evaluation and thus avoiding underdiagnosis and undertreatment, as well as highlighting which patient groups are most at risk.

Osteoprotegerin and MTHFR gene variations in rheumatoid arthritis: association with disease susceptibility and markers of subclinical atherosclerosis

We aimed to explore whether the rs2073618 variant (G1181C) of the osteoprotegerin (OPG) gene and the methylenetetrahydrofolate reductase (MTHFR) rs1801131 (A1298AC) and rs1801133 (C677T) gene polymorphisms contribute to rheumatoid arthritis (RA) susceptibility and RA related subclinical atherosclerosis. Overall 283 RA patients and 595 healthy controls (HC) were genotyped for common variants of the OPG and MTHFR genes using PCR based assays. Clinical and laboratory parameters were recorded following thorough chart review. Surrogate markers of subclinical atherosclerosis (Carotid/Femoral intima media thickness/plaque formation) along with traditional risk factors for atherosclerosis were assessed in all RA patients and 280HC. Increased prevalence of the CC genotype of the rs2073618 variant was detected in RA patients vs HC (42.4% vs. 33%, p-value: 0.04). RA patients with high serum titers of rheumatoid factor (RF) or anti-cyclic citrullinated peptide (CCP) antibodies displayed increased prevalence of the CC genotype of the rs2073618 variant of the OPG gene compared to HC (48.6% and 47.5 vs 33.3%, p-values: 0.0029and 0.0077 respectively). Of interest, this genotype turned to be associated with higher carotid IMT scores (0.872 ± 0.264 vs 0.816 ± 0.284, p-value: 0.01) and marginally with higher rates of carotid plaque formation (66% vs 54.1%, p = 0.06). The MTHFR 1298CC genotype was more prevalent only in the anti-CCP positive group compared to HC, with no associations detected with markers of subclinical atherosclerosis, following adjustment for traditional cardiovascular (CVD) risk factors. Reduced rates of carotid/femoral plaque formation were detected among RA patients harboring the MTHFR TT genotype (52.4 vs 72.7, p-value: 0.009, respectively). This association remained significant following adjustment for classical CVD risk factors (OR [95% CI 0.364 [0.173-0.765], p-value: 0.008). Genetic variations of the osteoprotegerin and MTHFR genes seem to increase susceptibility for seropositive RA and potentially contribute to subclinical atherosclerosis linked to RA. Larger studies are needed to confirm these findings.

Paraoxonase and arylesterase activity of serum PON-1 enzyme in psoriatic patients: a systematic review and meta-analysis

Human serum paraoxonase-1 (PON-1) is a critical antioxidant defense system against lipid oxidation. Decreased PON-1 activity has been associated with systemic oxidative stress in several disease states. We conducted a systematic review and meta-analysis of plasma/serum concentrations of PON-1 paraoxonase and arylesterase activity in psoriasis, a chronic immune-mediated and inflammatory skin disease. The electronic databases PubMed, Web of Science, and Scopus were searched from inception to November 2021. In total, 14 studies in 691 psoriatic patients and 724 healthy controls were included in the meta-analysis. Serum paraoxonase activity was significantly lower in psoriatic patients (SMD = - 2.30, 95% CI - 3.17 to - 1.42; p < 0.001); however, no significant between-group differences were observed in serum arylesterase activity (SMD = - 0.34, 95% CI - 0.11 to 0.80; p = 0.14). The pooled SMD values were not substantially altered in sensitivity analysis. There was no publication bias. In conclusion, our meta-analysis has shown that serum paraoxonase, but not arylesterase, activity is significantly lower in psoriasis, suggesting an impaired antioxidant defense in these patients.

Clinicopathological Characteristics and Influencing Factors of Renal Vascular Lesions in Anti-neutrophil Cytoplasmic Autoantibody-Related Renal Vasculitis

The purpose of this study was to evaluate the clinicopathological features of different degrees of extraglomerular renal vascular lesions (RVLs) in patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated renal vasculitis and explore their clinical determinants. This is a retrospective study of 186 patients with ANCA-associated renal vasculitis diagnosed at the First Affiliated Hospital of Zhengzhou University from January 2014 to April 2019. The patients who met the inclusion criteria were divided into non-renal RVLs, mild RVLs, moderate RVLs, and severe RVLs. It was found that there were significant differences in serum creatinine (SCR), estimated glomerular filtration rate (eGFR), erythrocyte sedimentation rate (ESR), high-density lipoprotein (HDL), systolic blood pressure (SBP), the prevalence rate of hypertension, the proportion of normal glomeruli, and the proportion of sclerotic glomeruli and interstitial fibrosis integral. SCR and ESR are independent risk factors for RVLs. The participants were followed up for 1 year, and the progression to end-stage renal disease (ESRD) and death was defined as endpoint events. We found that the survival rate of patients without RVLs was significantly higher than that of patients with RVLs and that the RVLs were an independent risk factor for ESRD or death. Early intervention in the progression of RVLs can improve the prognosis.

Cardiovascular Disease in Rheumatoid Arthritis: Risk Factors, Autoantibodies, and the Effect of Antirheumatic Therapies

Objective:

To scope the current published evidence on cardiovascular risk factors in rheumatoid arthritis (RA) focusing on the role of autoantibodies and the effect of antirheumatic agents.

Methods:

Two reviews were conducted in parallel: A targeted literature review (TLR) describing the risk factors associated with cardiovascular disease (CVD) in RA patients; and a systematic literature review (SLR) identifying and characterizing the association between autoantibody status and CVD risk in RA. A narrative synthesis of the evidence was carried out.

Results:

A total of 69 publications (49 in the TLR and 20 in the SLR) were included in the qualitative evidence synthesis. The most prevalent topic related to CVD risks in RA was inflammation as a shared mechanism behind both RA morbidity and atherosclerotic processes. Published evidence indicated that most of RA patients already had significant CV pathologies at the time of diagnosis, suggesting subclinical CVD may be developing before patients become symptomatic. Four types of autoantibodies (rheumatoid factor, anti-citrullinated peptide antibodies, anti-phospholipid autoantibodies, anti-lipoprotein autoantibodies) showed increased risk of specific cardiovascular events, such as higher risk of cardiovascular death in rheumatoid factor positive patients and higher risk of thrombosis in anti-phospholipid autoantibody positive patients.

Conclusion:

Autoantibodies appear to increase CVD risk; however, the magnitude of the increase and the types of CVD outcomes affected are still unclear. Prospective studies with larger populations are required to further understand and quantify the association, including the causal pathway, between specific risk factors and CVD outcomes in RA patients.

The role of high-density lipoprotein cholesterol, apolipoprotein A and paraoxonase-1 in the pathophysiology of neuroprogressive disorders

Lowered high-density lipoprotein (HDL) cholesterol has been reported in major depressive disorder, bipolar disorder, first episode of psychosis, and schizophrenia. HDL, its major apolipoprotein component, ApoA1, and the antioxidant enzyme paraoxonase (PON)1 (which is normally bound to ApoA1) all have anti-atherogenic, antioxidant, anti-inflammatory, and immunomodulatory roles, which are discussed in this paper. The paper details the pathways mediating the anti-inflammatory effects of HDL, ApoA1 and PON1 and describes the mechanisms leading to compromised HDL and PON1 levels and function in an environment of chronic inflammation. The molecular mechanisms by which changes in HDL, ApoA1 and PON1 might contribute to the pathophysiology of the neuroprogressive disorders are explained. Moreover, the anti-inflammatory actions of ApoM-mediated sphingosine 1-phosphate (S1P) signalling are reviewed as well as the deleterious effects of chronic inflammation and oxidative stress on ApoM/S1P signalling. Finally, therapeutic interventions specifically aimed at improving the levels and function of HDL and PON1 while reducing levels of inflammation and oxidative stress are considered. These include the so-called Mediterranean diet, extra virgin olive oil, polyphenols, flavonoids, isoflavones, pomegranate juice, melatonin and the Mediterranean diet combined with the ketogenic diet.

Inhibitory role of long non-coding RNA OIP5-AS1 in rheumatoid arthritis progression through the microRNA-448-paraoxonase 1-toll-like receptor 3-nuclear factor κB axis

NEW FINDINGS

What is the central question of this study? What are the functions of long non-coding (lnc) RNA OIP5-AS1 in development of rheumatoid arthritis inflammation and what is the molecular mechanism? What is the main finding and its importance? LncRNA OIP5-AS1 mitigates rheumatoid arthritis progression through the competitive endogenous RNA network involving the miR-448-paraoxonase 1 axis and through the inactivation of the toll-like receptor 3-nuclear factor κB signalling pathway. This study may offer new ideas for molecularly based control of rheumatoid arthritis.

ABSTRACT

Rheumatoid arthritis (RA) is an autoimmune disorder with dysregulation of long non-coding RNAs (lncRNAs) possibly involved. This study aimed to inquire into the roles of lncRNA OIP5-AS1 in RA progression. A rat model of RA was induced. Overexpression of OIP5-AS1 was introduced in the model rats, and the changes in paw swelling, RA severity and the inflammatory factors interleukin (IL)-1β, IL-10, IL-6 and tumour necrosis factor α were measured. Fibroblast-like synoviocytes (FLSs) from RA patients were collected for in vitro experiments. A gain- and loss-of function study of OIP5-AS1, miR-448 and paraoxonase 1 (PON1) was performed to explore their roles in RA-FLS growth, apoptosis and inflammation. A toll-like receptor 3 (TLR3)-specific agonist, polyinosine-polycytidylic acid, or a nuclear factor κB (NF-κB)-specific antagonist, QNZ, was administrated in RA-FLSs. Consequently, overexpression of OIP5-AS1 reduced the symptom severity and the levels of inflammatory factors in RA rats. OIP5-AS1 could bind to miR-448 to up-regulate PON1 expression. Further overexpression of miR-448 reversed the effects of OIP5-AS1, while overexpression of PON1 inhibited RA-FLS growth and inflammation. In addition, TLR3 activation promoted RA progression. To conclude, this study evidenced that lncRNA OIP5-AS1 may mitigate RA progression through the miR-448-PON1 axis and through the inactivation of the TLR3-NF-κB signalling pathway.

Oxidative Stress Biomarkers and Peripheral Endothelial Dysfunction in Rheumatoid Arthritis: A Monocentric Cross-Sectional Case-Control Study

Previous studies have suggested that oxidative stress may heighten atherosclerotic burden in rheumatoid arthritis (RA), but direct evidence is lacking.

OBJECTIVE

To evaluate the relationship between established plasma oxidative stress biomarkers and peripheral endothelial dysfunction (ED), a marker of early atherosclerosis, in RA.

METHODS

Paroxonase-1 (PON-1), protein-SH (PSH), and malondialdehyde (MDA) were measured in 164 RA patient s and 100 age- and sex-matched healthy controls without previous cardiovascular events. Peripheral ED, evaluated by flow-mediated pulse amplitude tonometry, was defined by log-transformed reactive hyperemia index (Ln-RHI) values < 0.51.

RESULTS

PON-1 activity and PSH concentrations were significantly reduced in RA patients compared to controls. In regression analysis, increased plasma MDA levels were significantly associated with reduced Ln-RHI [B coefficient (95% CI) = -0.003 (-0.005 to -0.0008), p = 0.008] and the presence of peripheral ED (OR (95% CI) = 1.75 (1.06-2.88), p = 0.028). Contrary to our expectations, increased PON-1 activity was significantly associated, albeit weakly, with the presence of ED (OR (95% CI) = 1.00 (1.00-1.01), p = 0.017).

CONCLUSIONS

In this first evidence of a link between oxidative stress and markers of atherosclerosis, MDA and PON-1 showed opposite associations with peripheral vasodilatory capacity and the presence of ED in RA. Further studies are needed to determine whether this association predicts atherosclerotic events in the RA population.

PON-1 haplotype (-108C>T, L55M, and Q192R) modulates the serum levels and activity PONase promoting an atherogenic lipid profile in rheumatoid arthritis patients

INTRODUCTION/OBJECTIVE

Paraoxonase 1 (PON1) promotes antioxidant and antiatherogenic activity related to the hydrolysis of oxidized lipids of low-density lipoproteins. In rheumatoid arthritis (RA) patients, it has been reported that low PON1 activity is related to an impaired lipid profile, increasing cardiovascular risk (CVR). The goal of this study was to analyze the effect of common PON1 polymorphisms and haplotypes on enzymatic activity, PON1 serum levels (PON1s), and lipid parameters related to atherogenic profile in RA patients.

METHODS

A cross-sectional study was carried out on 250 Mexican patients with RA. The lipid profile was determined by colorimetric tests. The PON1 activity (CMPAase) was measured by spectrophotometry. The levels of PON1s were determined by ELISA, and the polymorphisms in the PON-1 gene (-108C>T, L55M, and Q192R) were genotyped by the PCR-RFLP method. The haplotypes were estimated and statistical analysis was performed.

RESULTS

The median of the CMPAase activity and PON1 levels was 13.91 U/mL and 24.75 ng/mL, respectively. The CMPAase activity was significantly lower in carriers of -108TT and 192QQ genotypes (β = - 4.09, P = 0.001 and β = - 3.73, P = 0.002, respectively); moreover, the PON1 levels were lower in 192Q allele carriers (P < 0.01). The TLQ haplotype was associated with CMPAase activity < 13.91 U/mL (OR = 2.29, P < 0.001), as well as with levels of PON1s < 24.75 ng/mL (OR = 1.65, P = 0.017). In this study, the CMPAase activity (< 13.91 U/mL) showed a positive association with lower levels of high-density lipoprotein cholesterol (HDL-c; < 40/50 mg/dL), and with a triglycerides/HDL-c ratio > 3%, and a total cholesterol/HDL-c ratio > 4.5/5%, all representatives of an atherogenic risk lipid profile.

CONCLUSIONS

PON1 polymorphisms modulate the CMPAase activity and PON1 levels in Mexican patients with RA. The CMPAase activity < 13.91 U/mL is associated with an atherogenic lipid profile, independently of inflammation markers and treatment with anti-rheumatic drugs. Key Points •The haplotype TLQ is a marker for low PONase activity in rheumatoid arthritis. •The haplotype TLQ is a marker for low PON1 serum levels in rheumatoid arthritis. •The enzymatic PON1 activity represents the best marker for an atherogenic lipid profile in rheumatoid arthritis, in comparison with PON1 levels. •The haplotype TLQ is a marker of low PON1 activity, levels of PON1s, and atherogenic lipid profile, independent of treatment therapy in rheumatoid arthritis.

Humoral Immunity Against HDL Particle: A New Perspective in Cardiovascular Diseases?

BACKGROUND

Autoimmune diseases are closely associated with cardiovascular diseases (CVD). Over the last decades, the comprehension of atherosclerosis, the principal initiator of CVD, evolved from a lipidcentered disease to a predominant inflammatory and immune response-driven disease displaying features of autoimmunity against a broad range of auto-antigens, including lipoproteins. Among them, high density lipoproteins (HDL) are important actors of cholesterol transport and bear several anti-atherogenic properties, raising a growing interest as therapeutic targets to decrease atherosclerosis and CVD burden, with nevertheless rather disappointing results so far. Reflecting HDL composition complexity, autoimmune responses and autoantibodies against various HDL components have been reported.

RESULTS

In this review, we addressed the important complexity of humoral autoimmunity towards HDL and particularly how this autoimmune response could help improving our understanding of HDL biological implication in atherosclerosis and CVD. We also discussed several issues related to specific HDL autoantibody subclasses characteristics, including etiology, prognosis and pathological mechanisms according to Rose criteria.

CONCLUSION

Finally, we addressed the possible clinical value of using these antibodies not only as potential biomarkers of atherogenesis and CVD, but also as a factor potentially mitigating the benefit of HDL-raising therapies.

IgG Anti-High Density Lipoprotein Antibodies Are Elevated in Abdominal Aortic Aneurysm and Associated with Lipid Profile and Clinical Features

High-density lipoproteins cholesterol (HDLc) levels are decreased in abdominal aortic aneurysm (AAA), which is hallmarked by autoimmunity and lipid aortic deposits. To investigate whether IgG anti-HDL antibodies were present in AAA and their potential association with clinical features, IgG anti-HDL and total IgG along with HDLc plasma levels were measured in 488 AAA patients and 184 controls from the Viborg Vascular (VIVA) study, and in tissue-conditioned media from AAA intraluminal thrombus and media layer samples compared to control aortas. Higher IgG anti-HDL levels were found in AAA compared to controls, even after correcting for total IgG, and after adjusting for potential confounders. IgG anti-HDL levels were correlated with aortic diameter in univariate and adjusted multivariate analyses. IgG anti-HDL antibodies were negatively associated with HDLc levels before and after correcting for potential confounders. Increased anti-HDL antibodies were identified in tissue-conditioned media from AAA samples compared to healthy aortas, with higher levels being observed in the media layer. In conclusion, increased IgG anti-HDL levels (both in plasma and in tissue) are linked to AAA, associated with aortic diameter and HDLc levels. These data suggest a potential immune response against HDL in AAA and support an emerging role of anti-HDL antibodies in AAA.

Functional implications of single nucleotide polymorphisms rs662 and rs854860 on the antioxidative activity of paraoxonase1 (PON1) in patients with rheumatoid arthritis

BACKGROUND

Atherosclerosis leading to cardiovascular disease (CVD) is the main cause of mortality and morbidity in patients with rheumatoid arthritis (RA). Paraoxonase1 (PON1) is the best understood member of plasma paraoxonases with anti-atherogenic properties.

PATIENTS AND METHODS

Spanish RA (n = 549) consecutively recruited from 1 single center and 477 ethnically matched healthy controls were included in a case-control study. The concentration of PON1 was evaluated by means of an enzyme-linked immunosorbent sssay (ELISA). An arylesterase/paraoxonase assay kit was used to evaluate PON1 activity. Sample genotyping was performed by using TaqMan assays-on-demand. All results were expressed as medians ± interquartile range. One-way ANOVA comparisons were done using a nonparametric Kruskall-Wallis test. P values under 0.05 were considered to be significant.

RESULTS

The concentration of PON1 in the RA group was higher than in control group (p = 0.0003), although the differences were not significant when PON1 activities were compared between both groups. No significant differences were found related to distributions of rs662 genotypes in RA patients compared to healthy controls. Among rs854860 polymorphisms, overall genotype was widely distributed between RA patients and controls. Overall PON1 concentration in plasma was not significantly different between individuals carrying any of rs662 (p = 0.8501) or rs854860 (p = 0.2741) polymorphisms. Although PON1 levels were not associated with any of the SNPs in the study, differences appear when enzyme activities are compared for each SNP separately. CVD in RA patients correlate with increased PON1 levels and lower PON1 activity.

CONCLUSIONS

Although protective role of PON1 against oxidative damage in vivo could be related to other activities, in our study arylesterase activity was useful to identify phenotypic differences with emphasis placed on two SNPs coding for nonconservative amino acid changes in the functional protein.

Correlation of High-Density Lipoprotein-Associated Paraoxonase 1 Activity With Systemic Inflammation, Disease Activity, and Cardiovascular Risk Factors in Psoriatic Disease

OBJECTIVE

To compare the activity of high-density lipoprotein (HDL)-associated paraoxonase 1 (PON1) in patients with psoriasis (PsO) and patients with psoriatic arthritis (PsA), and to evaluate the association of PON1 activity with the extent of disease activity and severity of the cardiovascular disease (CVD) burden in these patients.

METHODS

Serum levels of paraoxonase and arylesterase activity (both measures of PON1 function in humans) were measured in patients with PsA (n = 198, 51.0% male) and patients with PsO (n = 145, 50.3% male) who were enrolled in a longitudinal psoriatic disease biorepository. Data on PsA disease activity (using the Disease Activity Score in 28 joints [DAS28], Clinical Disease Activity Index, and painful/swollen joint counts), preexistent CVD and CVD risk factors (including diabetes, dyslipidemia, hypertension, and smoking), Framingham Risk Scores for CVD, quality of life measures, and laboratory test findings (erythrocyte sedimentation rate, C-reactive protein level, and lipid profiles) were recorded.

RESULTS

Serum arylesterase activities were significantly lower in patients with PsO and patients with PsA (mean ± SD 111.1 ± 25.5 μmoles/minute/ml and 124.4 ± 33.4 μmoles/minute/ml, respectively) compared to healthy controls (144.3 ± 33.4 μmoles/minute/ml) (each P < 0.001 versus healthy controls). Serum arylesterase activity decreased in parallel with increasing levels of disease activity (DAS28 scores, P = 0.012), older age (P = 0.013), higher body mass index (P = 0.042), greater incidence of metabolic syndrome (P = 0.004) and hypertension (P = 0.014), and worsening Framingham Risk Scores (P = 0.001). However, no correlation was seen between serum arylesterase activity and the extent of disease activity or CVD burden in patients with PsO. Serum paraoxonase activity trended lower both in patients with PsO and in patients with PsA (each P = 0.073 versus healthy controls). However, no association was seen between serum paraoxonase activity and the extent of disease activity or CVD burden in either of the patient cohorts.

CONCLUSION

PON1 activity is decreased in psoriatic diseases. In the PsA cohort, decreases in arylesterase activity correlated with increasing severity of joint disease and CVD burden. Arylesterase activity, as compared to paraoxonase activity, appeared to serve as a more sensitive predictor of preexisting CV risk factors in the PsA cohort. However, this correlation was not observed in the PsO population.

Increased cardiovascular risk in rheumatoid arthritis: mechanisms and implications

Rheumatoid arthritis is a systemic autoimmune disease characterized by excess morbidity and mortality from cardiovascular disease. Mechanisms linking rheumatoid arthritis and cardiovascular disease include shared inflammatory mediators, post-translational modifications of peptides/proteins and subsequent immune responses, alterations in the composition and function of lipoproteins, increased oxidative stress, and endothelial dysfunction. Despite a growing understanding of these mechanisms and their complex interplay with conventional cardiovascular risk factors, optimal approaches of risk stratification, prevention, and treatment in the context of rheumatoid arthritis remain unknown. A multifaceted approach to reduce the burden posed by cardiovascular disease requires optimal management of traditional risk factors in addition to those intrinsic to rheumatoid arthritis such as increased disease activity. Treatments for rheumatoid arthritis seem to exert differential effects on cardiovascular risk as well as the mechanisms linking these conditions. More research is needed to establish whether preferential rheumatoid arthritis therapies exist in terms of prevention of cardiovascular disease. Ultimately, understanding the unique mechanisms for cardiovascular disease in rheumatoid arthritis will aid in risk stratification and the identification of novel targets for meaningful reduction of cardiovascular risk in this patient population.

Anti-High-Density Lipoprotein Antibodies and Antioxidant Dysfunction in Immune-Driven Diseases

Introduction

Impaired high-density lipoprotein (HDL) levels and antioxidant functionality of HDL, mainly attributed to a decreased paraoxonase-1 (PON1) functionality, have been described in autoimmune conditions. In this setting, a role for humoral response in cardiovascular disease is emerging. This study evaluates the role of immunoglobulin G (IgG) antibodies against HDL and disease-related autoantibodies on HDL dysfunction in immune-driven diseases.

Methods

Serum IgG anti-HDL antibodies, PON1 activity, and total antioxidant capacity (TAC) were quantified in 381 patients with different immune-driven diseases [18 mixed connective tissue disease (MCTD), 35 primary Sjögren syndrome (pSS), 38 systemic sclerosis (SSc), 33 ANCA-associated vasculitis (AAV), 60 diabetes mellitus 1, 29 autoimmune B12 deficiency/pernicious anemia, 29 primary biliary cirrhosis, 46 IBD/Crohn, 54 IBD/UC, and 39 celiac disease (CD)] and 138 healthy controls.

Results

IgG anti-HDL antibodies were increased in MCTD, pSS, AAV, and inflammatory bowel disease (IBD) [Crohn and ulcerative colitis (UC)], even after correcting for total IgG levels, but not in organ-specific autoimmune diseases. Anti-HDL antibodies were negatively associated with PON1 activity in MCTD (r = −0.767, p < 0.001) and AAV (r = −0.478, p = 0.005), whereas both anti-HDL and anti-neutrophil cytoplasm antibod levels were related to an impaired PON1 activity and TAC in IBD/UC. In SSc, anti-centromere antibodies correlated PON1 activity. anti-Saccharomyces cerevisiae antibodies levels were negatively associated with PON1 activity (r = −0.257, p = 0.012) and PON1/TAC ratio (r = −0.261, p = 0.009) in IBD/Crohn. HDL dysfunction in CD was only related to anti-transglutaminase levels.

Conclusion

IgG anti-HDL antibodies and HDL dysfunction are common hallmarks of systemic autoimmunity. Anti-HDL and disease-related autoantibodies account for the HDL antioxidant dysfunction in immune-driven conditions, mainly in systemic autoimmune disorders.

Correlation of PON1 polymorphisms with ankylosing spondylitis susceptibility: A case-control study in Chinese Han population

Paraoxonase 1 (PON1) modulates the oxidative stress and inflammatory response, thus, it might relate to the risk of ankylosing spondylitis (AS). The aim of present study was to discover the correlation of PON1 polymorphisms (rs662 and rs854560) with PON1 activity and AS risk.Around 128 AS patients and 146 healthy controls were recruited in this case-control study. PON1 polymorphisms were genotyped by direct sequencing. Serum PON1 activity was detected and compared by nonparametric test in different genotypes of PON1 polymorphisms. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to present the relative risk for AS.GG genotype and G allele of rs662 polymorphism were closely correlated with enhanced AS risk (P = .034, OR = 2.318, 95%CI = 1.051-5.113; P = .032, OR = 1.485, 95%CI = 1.033-2.135). PON1 activity was obviously higher in controls than that in AS patients. Significant difference of PON1 activity has been discovered in the different rs662 genotypes (P < .01). rs662 GG genotype carriers had the lowest PON1 activity, followed by AG carriers and the AA carriers. Besides, no significant relationship existed between rs854560 genotypes and AS risk.PON1 rs662 polymorphism is significantly correlated with increased AS risk via inhibiting PON1 activity.

Antibodies to paraoxonase 1 are associated with oxidant status and endothelial activation in rheumatoid arthritis

Anti-paraoxonase 1 (PON1) antibodies could be a potential missing link between oxidative status, inflammation and cardiovascular disease (CVD) in rheumatoid arthritis (RA) patients. Therefore, they could represent an emerging clinical biomarker of CV risk in this condition.

ApoA1 and ApoA1-specific self-antibodies in cardiovascular disease

Apolipoprotein A1 (ApoA1) is a main protein moiety in high-density lipoprotein (HDL) particles. Generally, ApoA1 and HDL are considered as atheroprotective. In prooxidant and inflammatory microenvironment in the vicinity to the atherosclerotic lesion, ApoA1/HDL are subjected to modification. The chemical modifications such as oxidation, nitration, etc result in altering native architecture of ApoA1 toward dysfunctionality and abnormality. Neutrophil myeloperoxidase has a prominent role in this mechanism. Neo-epitopes could be formed and then exposed that makes them immunogenic. Indeed, these epitopes may be recognized by immune cells and induce production of proatherogenic ApoA1-specific IgG antibodies. These antibodies are biologically relevant because they are able to react with Toll-like receptor (TLR)-2 and TLR4 in target cells and induce a variety of pro-inflammatory responses. Epidemiological and functional studies underline a prognostic value of ApoA1 self-antibodies for several cardiovascular diseases, including myocardial infarction, acute coronary syndrome, and severe carotid stenosis.