Abnormal nitric oxide metabolism in systemic sclerosis: increased levels of nitrated proteins and asymmetric dimethylarginine

Vascular endothelial growth factor as a potential biomarker in systemic sclerosis: a systematic review and meta-analysis

Introduction

Systemic sclerosis (SSc), a chronic autoimmune condition, is characterized by microvascular dysfunction, ineffective angiogenesis, and fibrosis. The identification of robust biomarkers reflecting these processes may assist in clinical management and lead to the discovery of new therapies. We sought to address this issue by conducting a systematic review and meta-analysis of studies investigating one such biomarker, vascular endothelial growth factor (VEGF), in SSc patients and healthy controls and in SSc patients with localized or diffuse disease, different video capillaroscopy patterns (early, active, or late), and presence or absence of complications.

Methods

We searched PubMed, Scopus, and Web of Science from inception to 15 May 2024. We assessed the risk of bias and the certainty of evidence using the JBI checklist for analytical studies and GRADE, respectively.

Results

In 42 eligible studies, compared to controls, patients with SSc had significantly higher plasma or serum VEGF concentrations (standard mean difference, SMD=0.93, 95% CI 0.71 to 1.15, p<0.001; moderate certainty). In further analyses, VEGF concentrations were significantly higher in SSc patients with diffused disease than those with localized disease (SMD=0.30, 95% CI 0.01 to 0.59, p=0.046; very low certainty), in patients with late vs. active video capillaroscopy pattern (SMD=0.35, 95% CI 0.09 to 0.61, p=0.008; very low certainty), and in patients with pulmonary hypertension than those without (SMD=0.93, 95% CI 0.34 to 1.53, p=0.002; very low certainty). By contrast, no significant differences were observed between SSc patients with and without digital ulcers, interstitial lung disease, and telangiectasias, whereas limited evidence was available for alveolitis. Meta-regression and subgroup analysis of studies investigating VEGF in SSc patients and controls showed no significant associations between the effects size and various patient and study characteristics, including SSc duration and use of corticosteroids, immunosuppressors and vasodilators. By contrast, significant associations were observed with the geographical location where the study was conducted.

Discussion

The results of this systematic review and meta-analysis suggest that VEGF can be useful in the assessment and management of SSc and in the identification of novel therapeutic strategies in this patient group.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero, identifier CRD42024552925.

Biomarker analysis from the phase 2b randomized placebo-controlled trial of riociguat in early diffuse cutaneous systemic sclerosis

OBJECTIVE

To examine disease and target engagement biomarkers in the RISE-SSc trial of riociguat in early diffuse cutaneous systemic sclerosis and their potential to predict the response to treatment.

METHODS

Patients were randomized to riociguat (n = 60) or placebo (n = 61) for 52 weeks. Skin biopsies and plasma/serum samples were obtained at baseline and week 14. Plasma cyclic guanosine monophosphate (cGMP) was assessed using radio-immunoassay. α-Smooth muscle actin (αSMA) and skin thickness were determined by immunohistochemistry, mRNA markers of fibrosis by qRT-PCR in skin biopsies, and serum CXC motif chemokine ligand 4 (CXCL-4) and soluble platelet endothelial cell adhesion molecule-1 (sPECAM-1) by enzyme-linked immunosorbent assay.

RESULTS

By week 14, cGMP increased by 94 (78)% with riociguat and 10 (39)% with placebo (P < 0.001, riociguat vs placebo). Serum sPECAM-1 and CXCL-4 decreased with riociguat vs placebo (P = 0.004 and P = 0.008, respectively). There were no differences in skin collagen markers between the two groups. Higher baseline serum sPECAM-1 or the detection of αSMA-positive cells in baseline skin biopsies was associated with a larger reduction of modified Rodnan skin score from baseline at week 52 with riociguat vs placebo (interaction P-values 0.004 and 0.02, respectively).

CONCLUSION

Plasma cGMP increased with riociguat, suggesting engagement with the nitric oxide-soluble guanylate cyclase-cGMP pathway. Riociguat was associated with a significant reduction in sPECAM-1 (an angiogenic biomarker) vs placebo. Elevated sPECAM-1 and the presence of αSMA-positive skin cells may help to identify patients who could benefit from riociguat in terms of skin fibrosis.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT02283762.

Virus-Induced MicroRNA Modulation and Systemic Sclerosis Disease

MicroRNAs (miRNAs) are short noncoding RNA sequences that regulate gene expression at the post-transcriptional level. They are involved in the regulation of multiple pathways, related to both physiological and pathological conditions, including autoimmune diseases, such as Systemic Sclerosis (SSc). Specifically, SSc is recognized as a complex and multifactorial disease, characterized by vascular abnormalities, immune dysfunction, and progressive fibrosis, affecting skin and internal organs. Among predisposing environmental triggers, evidence supports the roles of oxidative stress, chemical agents, and viral infections, mostly related to those sustained by beta-herpesviruses such as HCMV and HHV-6. Dysregulated levels of miRNA expression have been found in SSc patients compared to healthy controls, at both the intra- and extracellular levels, providing a sort of miRNA signature of the SSc disease. Notably, HCMV/HHV-6 viral infections were shown to modulate the miRNA profile, often superposing that observed in SSc, potentially promoting pathological pathways associated with SSc development. This review summarizes the main data regarding miRNA alterations in SSc disease, highlighting their potential as prognostic or diagnostic markers for SSc disease, and the impact of the putative SSc etiological agents on miRNA modulation.

Fractional exhaled nitric oxide in idiopathic pulmonary arterial hypertension and mixed connective tissue disease complicating pulmonary hypertension

BACKGROUND

Fractional exhaled nitric oxide (FeNO) has been extensively studied in various causes of pulmonary hypertension (PH), but its utility as a noninvasive marker remains highly debated. The objective of our study was to assess FeNO levels in patients with idiopathic pulmonary arterial hypertension (IPAH) and mixed connective tissue disease complicating pulmonary hypertension (MCTD-PH), and to correlate them with respiratory functional data, disease severity, and cardiopulmonary function.

METHODS

We collected data from 54 patients diagnosed with IPAH and 78 patients diagnosed with MCTD-PH at the Shanghai Pulmonary Hospital Affiliated to Tongji University. Our data collection included measurements of brain natriuretic peptide (pro-BNP), cardiopulmonary exercise test (CPET), pulmonary function test (PFT), impulse oscillometry (IOS), and FeNO levels. Additionally, we assessed World Health Organization functional class (WHO-FC) of each patient.

RESULTS

(1) The fractional exhaled concentration of nitric oxide was notably higher in patients with IPAH compared to those with MCTD-PH. Furthermore, within the IPAH group, FeNO levels were found to be lower in cases of severe IPAH compared to mild IPAH (P = 0.024); (2) In severe pulmonary hypertension as per the WHO-FC classification, FeNO levels in IPAH exhibited negative correlations with FEV1/FVC (Forced Expiratory Velocity at one second /Forced Vital Capacity), MEF50% (Maximum Expiratory Flow at 50%), MEF25%, and MMEF75/25% (Maximum Mid-expiratory Flow between 75% and 25%), while in severe MCTD-PH, FeNO levels were negatively correlated with R20% (Resistance at 20 Hz); (3) ROC (Receiving operator characteristic curve) analysis indicated that the optimal cutoff value of FeNO for diagnosing severe IPAH was 23ppb; (4) While FeNO levels tend to be negatively correlated with peakPETO2(peak end-tidal partial pressure for oxygen) in severe IPAH, in mild IPAH they had a positive correlation to peakO2/Heart rate (HR). An interesting find was observed in cases of severe MCTD-PH, where FeNO levels were negatively correlated with HR and respiratory exchange ratio (RER), while positively correlated with O2/HR throughout the cardiopulmonary exercise test.

CONCLUSION

FeNO levels serve as a non-invasive measure of IPAH severity. Although FeNO levels may not assess the severity of MCTD-PH, their significant makes them a valuable tool when assessing severe MCTD-PH.

Part I: Epidemiology, pathophysiology, and clinical considerations of primary and secondary Raynaud's phenomenon

Raynaud's phenomenon (RP) is a relatively common disease with both primary and secondary forms. It is well understood as a vasospastic condition affecting the acral and digital arteries, resulting in characteristic, well-demarcated color changes typically in the hands and feet in response to cold or stress. Secondary RP (SRP) has been described in association with a variety of rheumatologic and nonrheumatologic diseases, environmental exposures, and/or medications. While both primary RP and SRP may impact the quality of life, SRP may lead to permanent and potentially devastating tissue destruction when undiagnosed and untreated. It is therefore crucial for dermatologists to distinguish between primary and secondary disease forms early in clinical evaluation, investigate potential underlying causes, and risk stratify SRP patients for the development of associated autoimmune connective tissue disease. The epidemiology, pathogenesis, and clinical presentation and diagnosis of both forms of RP are described in detail in this review article.

Biomarkers in Systemic Sclerosis: An Overview

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by significant fibrosis of the skin and internal organs, with the main involvement of the lungs, kidneys, heart, esophagus, and intestines. SSc is also characterized by macro- and microvascular damage with reduced peripheral blood perfusion. Several studies have reported more than 240 pathways and numerous dysregulation proteins, giving insight into how the field of biomarkers in SSc is still extremely complex and evolving. Antinuclear antibodies (ANA) are present in more than 90% of SSc patients, and anti-centromere and anti-topoisomerase I antibodies are considered classic biomarkers with precise clinical features. Recent studies have reported that trans-forming growth factor β (TGF-β) plays a central role in the fibrotic process. In addition, interferon regulatory factor 5 (IRF5), interleukin receptor-associated kinase-1 (IRAK-1), connective tissue growth factor (CTGF), transducer and activator of transcription signal 4 (STAT4), pyrin-containing domain 1 (NLRP1), as well as genetic factors, including DRB1 alleles, are implicated in SSc damage. Several interleukins (e.g., IL-1, IL-6, IL-10, IL-17, IL-22, and IL-35) and chemokines (e.g., CCL 2, 5, 23, and CXC 9, 10, 16) are elevated in SSc. While adiponectin and maresin 1 are reduced in patients with SSc, biomarkers are important in research but will be increasingly so in the diagnosis and therapeutic approach to SSc. This review aims to present and highlight the various biomarker molecules, pathways, and receptors involved in the pathology of SSc.

Malondialdehyde Serum Levels in Patients with Systemic Sclerosis Relate to Dyslipidemia and Low Ventricular Ejection Fraction

Systemic sclerosis (SSc) is a chronic disease characterized by vasculopathy with the involvement of dysfunctional microcirculatory vessels. Features of the disease include progressive fibrosis of the skin and internal organs and systemic inflammation characterized by the presence of circulating autoantibodies and proinflammatory cytokines. Furthermore, macrovascular disease and atherosclerosis are more common in patients with SSc than in the general population. Oxidative stress plays a crucial role in the development of several processes, including endothelial dysfunction, cancer, inflammation, and atherogenesis. Malondialdehyde (MDA) is a well-established marker of oxidative stress. In this work, we have analyzed the relationship between serum MDA levels and clinical, laboratory, and vascular characteristics in a well-characterized cohort of 53 patients with SSc. A multivariable analysis was performed to study the relationship between circulating MDA and disease characteristics in patients with SSc. Cardiovascular assessment was also performed, including ultrasonography of the carotid and aorta, and echocardiography. MDA showed a significant and positive relationship with the serum levels of lipid profile molecules such as total cholesterol (β coefficient = 0.006 (95% CI: 0.0004 to 0.01), nmol/mL, p = 0.037) and LDL cholesterol (β coefficient = 0.008 (95% CI: 0.001 to 0.01) nmol/mL, p = 0.017). On the contrary, most manifestations of the disease, including skin, lung, and joint involvement, as well as the presence of digital ulcers, were not related to MDA. However, high MDA levels were significantly and independently associated with lower ventricular ejection fraction after adjustment for covariates (β coefficient = -0.04 (95% CI: -0.06 to -0.02), nmol/mL, p = 0.001). In conclusion, serum MDA levels were related to higher levels of total and LDL cholesterol and a lower left ventricular ejection fraction in patients with SSc. MDA could serve as a potential biomarker of dyslipidemia and heart failure in SSc.

Metabolic fingerprinting of systemic sclerosis: a systematic review

Introduction: Systemic sclerosis (SSc) is a chronic autoimmune disease, marked by an unpredictable course, high morbidity, and increased mortality risk that occurs especially in the diffuse and rapidly progressive forms of the disease, characterized by fibrosis of the skin and internal organs and endothelial dysfunction. Recent studies suggest that the identification of altered metabolic pathways may play a key role in understanding the pathophysiology of the disease. Therefore, metabolomics might be pivotal in a better understanding of these pathogenic mechanisms. Methods: Through a systematic review of the literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines (PRISMA), searches were done in the PubMed, EMBASE, Web of Science, and Scopus databases from 2000 to September 2022. Three researchers independently reviewed the literature and extracted the data based on predefined inclusion and exclusion criteria. Results: Of the screened studies, 26 fulfilled the inclusion criteria. A total of 151 metabolites were differentially distributed between SSc patients and healthy controls (HC). The main deregulated metabolites were those derived from amino acids, specifically homocysteine (Hcy), proline, alpha-N-phenylacetyl-L-glutamine, glutamine, asymmetric dimethylarginine (ADMA), citrulline and ornithine, kynurenine (Kyn), and tryptophan (Trp), as well as acylcarnitines associated with long-chain fatty acids and tricarboxylic acids such as citrate and succinate. Additionally, differences in metabolic profiling between SSc subtypes were identified. The diffuse cutaneous systemic sclerosis (dcSSc) subtype showed upregulated amino acid-related pathways involved in fibrosis, endothelial dysfunction, and gut dysbiosis. Lastly, potential biomarkers were evaluated for the diagnosis of SSc, the identification of the dcSSc subtype, pulmonary arterial hypertension, and interstitial lung disease. These potential biomarkers are within amino acids, nucleotides, carboxylic acids, and carbohydrate metabolism. Discussion: The altered metabolite mechanisms identified in this study mostly point to perturbations in amino acid-related pathways, fatty acid beta-oxidation, and in the tricarboxylic acid cycle, possibly associated with inflammation, vascular damage, fibrosis, and gut dysbiosis. Further studies in targeted metabolomics are required to evaluate potential biomarkers for diagnosis, prognosis, and treatment response.

The role of asymmetric dimethylarginine in endothelial dysfunction and abnormal nitric oxide metabolism in systemic sclerosis: results from a pilot study

INTRODUCTION/OBJECTIVES

Systemic sclerosis (SSc) is characterized by generalized vasculopathy affecting mainly small vessels while macrovascular involvement is less investigated. The aim of this study was to examine associations between asymmetric dimethylarginine (ADMA) - a biomarker of atherosclerosis - and assessments of macrovascular endothelial function in patients with SSc.

METHODS

This was a cross-sectional study including consecutive SSc patients attending the Scleroderma Outpatient Clinic. ADMA measurement in serum samples was based on an enzyme immunoassay technique. Participants underwent blood pressure measurement according to 2018 ESC/ESH Guidelines, applanation tonometry for the evaluation of arterial stiffness, and carotid ultrasound for the measurement of the intima-media thickness (cIMT).

RESULTS

Eighty-one Caucasians (82.3% female) SSc individuals with mean age 55.44 ± 13.4 years were included in this analysis. The correlation analysis of ADMA levels (unadjusted and adjusted values) with functional and morphological parameters of atherosclerosis revealed no statistically significant associations. Subgroup analysis based on disease duration (≤ 4 years), immunologic profile (SCL-70 and ACA antibodies), disease type (limited, diffuse), and inflammatory status (erythrocyte sedimentation rate [ESR] > 25 mm/h and C-reactive protein [CRP] > 5 mg/L) showed no associations, except from a significant positive correlation between ADMA levels and cΙΜΤ_mean (r = 0.370, p = 0.044) in individuals with early SSc.

CONCLUSIONS

The results of the study suggest that ADMA may be related with accelerated atherosclerosis in early stages of the disease. However, the lack of association between other morphological and functional parameters of endothelial dysfunction may suggest that other regulators of nitric oxide metabolism may contribute to macrovascular injury in SSc in various phases of the disease. Key Points • ADMA is a biomarker of atherosclerosis and has been linked with microvascular complications of SSc. •ADMA was not correlated with morphological and functional parameters of atherosclerosis in the population of the study. •The demonstrated association between ADMA and cIMT in patients with early SSc may suggest a role of NO/ADMA pathway in the initiation of macrovascular injury in SSc.

Oxidative Stress and Epigenetics: miRNA Involvement in Rare Autoimmune Diseases

Autoimmune diseases (ADs) such as Sjögren’s syndrome, Kawasaki disease, and systemic sclerosis are characterized by chronic inflammation, oxidative stress, and autoantibodies, which cause joint tissue damage, vascular injury, fibrosis, and debilitation. Epigenetics participate in immune cell proliferation and differentiation, which regulates the development and function of the immune system, and ultimately interacts with other tissues. Indeed, overlapping of certain clinical features between ADs indicate that numerous immunologic-related mechanisms may directly participate in the onset and progression of these diseases. Despite the increasing number of studies that have attempted to elucidate the relationship between miRNAs and oxidative stress, autoimmune disorders and oxidative stress, and inflammation and miRNAs, an overall picture of the complex regulation of these three actors in the pathogenesis of ADs has yet to be formed. This review aims to shed light from a critical perspective on the key AD-related mechanisms by explaining the intricate regulatory ROS/miRNA/inflammation axis and the phenotypic features of these rare autoimmune diseases. The inflamma-miRs miR-155 and miR-146, and the redox-sensitive miR miR-223 have relevant roles in the inflammatory response and antioxidant system regulation of these diseases. ADs are characterized by clinical heterogeneity, which impedes early diagnosis and effective personalized treatment. Redox-sensitive miRNAs and inflamma-miRs can help improve personalized medicine in these complex and heterogeneous diseases.

Asymmetric dimethylarginine correlates with worsening peripheral microangiopathy in systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is a connective tissue disease characterized primarily by micro-angiopathy and endothelial dysfunction which stimulate a fibrotic process. Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) inhibitor and represents a novel biomarker for vascular dysfunction. Nailfold video capillaroscopy (NVC) represents a non-invasive and reliable technique for the evaluation of microvasculopathy in SSc.

OBJECTIVES

The aim of this study was to examine the possible association between ADMA and microvascular involvement in patients with SSc.

METHODS

This was a cross-sectional study including consecutive SSc patients attending the Scleroderma Outpatient Clinic. ADMA was measured in serum samples using a commercial enzyme immunoassay. Participants underwent NVC with qualitative and semi-quantitative assessment and all NVC parameters were measured in the distal row of each finger. The findings were classified in one of the three qualitative NVC patterns: early, active, and late.

RESULTS

Eighty-one (92,6 % women) SSc individuals with mean age 55.44 ± 13.4 years were included in this analysis. Within-groups comparisons revealed a trend between higher ADMA levels and progressive micro-vasculopathy (1,29 [2,1] vs 1,57 [1,95] vs 2,41 [3,87]; for early, active and late patterns respectively, p = 0.039). Furthermore, ADMA concentration was significantly associated with the number of capillaries/mm (r = -0.235; p = 0.035).

CONCLUSIONS

Serum ADMA levels were significantly associated with advancing stages of microcirculatory abnormalities suggesting that ADMA may have a role in promoting microvascular endothelial dysfunction in SSc individuals.

Metabolomic profile in patients with primary warm autoimmune haemolytic anaemia

Autoimmune haemolytic anaemia (AIHA) is a rare clinical condition with immunoglobulin fixation on the surface of erythrocytes, with or without complement activation. The pathophysiology of AIHA is complex and multifactorial, presenting functional abnormalities of T and B lymphocytes that generate an imbalance between lymphocyte activation, immunotolerance and cytokine production that culminates in autoimmune haemolysis. In AIHA, further laboratory data are needed to predict relapse and refractoriness of therapy, and thus, prevent adverse side-effects and treatment-induced toxicity. The metabolomic profile of AIHA has not yet been described. Our group developed a cross-sectional study with follow-up to assess the metabolomic profile in these patients, as well as to compare the metabolites found depending on the activity and intensity of haemolysis. We analysed the plasma of 26 patients with primary warm AIHA compared to 150 healthy individuals by mass spectrometry. Of the 95 metabolites found in the patients with AIHA, four acylcarnitines, two phosphatidylcholines (PC), asymmetric dimethylarginine (ADMA) and three sphingomyelins were significantly increased. There was an increase in PC, spermine and spermidine in the AIHA group with haemolytic activity. The PC ae 34:3/PC ae 40:2 ratio, seen only in the 12-month relapse group, was a predictor of relapse with 81% specificity and 100% sensitivity. Increased sphingomyelin, ADMA, PC and polyamines in patients with warm AIHA can interfere in autoantigen and autoimmune recognition mechanisms in a number of ways (deficient action of regulatory T lymphocytes on erythrocyte recognition as self, negative regulation of macrophage nuclear factor kappa beta activity, perpetuation of effector T lymphocyte and antibody production against erythrocyte antigens). The presence of PC ae 34:3/PC ae 40:2 ratio as a relapse predictor can help in identifying cases that require more frequent follow-up or early second-line therapies.

Downregulation of Vascular Hemeoxygenase-1 Leads to Vasculopathy in Systemic Sclerosis

Systemic sclerosis (SSc) is a terminal disease characterized by vasculopathy, tissue fibrosis, and autoimmunity. Although the exact etiology of SSc remains unknown, endothelial dysfunction, oxidative stress, and calcium handling dysregulation have been associated with a large number of SSc-related complications such as neointima formation, vasculogenesis, pulmonary arterial hypertension, impaired angiogenesis, and cardiac arrhythmias. Hemeoxygenase-1 (HO-1) is an antioxidant enzyme involved in multiple biological actions in the cardiovascular system including vascular tone, angiogenesis, cellular proliferation, apoptosis, and oxidative stress. The aim of this work was to investigate the physiological role of HO-1 and its relevance in the cardiovascular complications occurring in SSc. We found that, in early phases of SSc, the expression of HO-1 in dermal fibroblast is lower compared to those isolated from healthy control individuals. This is particularly relevant as reduction of the HO-1/CO signaling pathway is associated with endothelial dysfunction and vasculopathy. We show evidence of the role of HO-1/carbon monoxide (CO) signaling pathway in calcium handling. Using an in vitro model of pulmonary arterial hypertension (PAH) we investigated the role of HO-1 in Ca2+ mobilization from intracellular stores. Our results indicate that HO-1 regulates calcium release from intracellular stores of human pulmonary arterial endothelial cells. We interrogated the activity of HO-1 in angiogenesis using an organotypic co-culture of fibroblast-endothelial cell. Inhibition of HO-1 significantly reduced the ability of endothelial cells to form tubules. We further investigated if this could be associated with cell motility or migration of endothelial cells into the extracellular matrix synthesized by fibroblasts. By mean of holographic imaging, we studied the morphological and functional features of endothelial cells in the presence of an HO-1 activator and selective inhibitors. Our results demonstrate that inhibition of HO-1 significantly reduces cell proliferation and cell motility (migration) of cultured endothelial cells, whilst activation of HO-1 does not modify either morphology, proliferation or motility. In addition, we investigated the actions of CO on the Kv7.1 (KCQN1) channel current, an important component of the cardiac action potential repolarization. Using electrophysiology (whole-cell patch-clamp in a recombinant system overexpressing the KCQN1 channel), we assessed the regulation of KCQN1 by CO. CORM-2, a CO donor, significantly reduced the Kv7.1 current, suggesting that HO-1/CO signaling may play a role in the modulation of the cardiac action potential via regulation of this ion channel. In summary, our results indicate a clear link between: 1) downregulation of HO-1/CO signaling; and 2) pathophysiological processes occurring in early phases of SSc, such as calcium homeostasis dysregulation, impaired angiogenesis and cardiac arrhythmias. A better understanding of the canonical actions (mainly due to the biological actions of CO), and non-canonical actions of HO-1, as well as the interaction of HO-1/CO signaling with other gasotransmitters in SSc will contribute to the development of novel therapeutic approaches.

Clinical significance of endothelial vasodilatory function evaluated by EndoPAT in patients with systemic sclerosis

Endothelial dysfunction is a hallmark of vasculopathy associated with systemic sclerosis (SSc). Reactive hyperemia peripheral arterial tonometry is a rapid and non-invasive technique to assess peripheral microvascular endothelial function by measuring changes in digital pulse volume during reactive hyperemia. Low scores of the reactive hyperemia index (RHI) imply an impaired vasodilatory response and, accordingly, impaired endothelial and vascular health. To investigate the clinical significance of the RHI in SSc patients, RHI values were measured in 43 SSc patients and 10 healthy controls. In diffuse cutaneous SSc (dcSSc) patients, RHI values were significantly decreased compared with healthy controls, and inversely correlated with disease duration. In total SSc patients, there was a significant inverse correlation between RHI values and skin score, and interstitial lung disease was associated with the decrease in RHI values. Among vascular symptoms, the current and past history of digital ulcers was seen more frequently in patients with decreased RHI values than in those with normal RHI values. Although no SSc patients had pulmonary arterial hypertension, an inverse correlation was evident between RHI values and mean pulmonary arterial pressure measured by right heart catheterization. These results indicate that the decrease in RHI values is associated with skin fibrosis, interstitial lung disease, digital ulcers and pulmonary vascular involvement leading to pulmonary arterial hypertension, supporting the canonical idea that endothelial dysfunction is a critical event underlying the development of tissue fibrosis and vascular complications in SSc.

Complementary therapies for patients with systemic sclerosis

Patients with systemic sclerosis often seek information regarding complementary and nutrition-based therapy. Some study results have shown that vitamins D and E, probiotics, turmeric, l-arginine, essential fatty acids, broccoli, biofeedback, and acupuncture may be beneficial in systemic sclerosis care. However, large randomized clinical trials have not been conducted. This review summarizes current data regarding various complementary therapies in systemic sclerosis and concludes with recommendations.

Meta-Analysis of Asymmetric Dimethylarginine Concentrations in Rheumatic Diseases

Raised circulating concentrations of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), have been reported in several rheumatic diseases (RDs). However, the strength of this relationship is unclear. Therefore, the aim of this systematic review and meta-analysis was to evaluate the magnitude and the robustness of the association between ADMA concentrations and RDs. We calculated standardized mean differences (SMD, with 95% confidence intervals, CI). Study heterogeneity was evaluated by meta-regressions and sensitivity analyses according to type of RDs, conventional cardiovascular risk factors, inflammatory markers, and type of ADMA assessment methodology. Thirty-seven studies with a total of 2,982 subjects (1,860 RDs patients and 1,122 healthy controls) were included in our meta-analysis. Pooled results showed that ADMA concentrations were significantly higher in patients with RDs than in healthy controls (SMD = 1.27 µmol/L, 95% CI 0.94–1.60 µmol/L; p < 0.001). However, the between-studies heterogeneity was high. Differences in ADMA concentrations between controls and RDs patients were not significantly associated with inflammatory markers, increasing age, lipid concentrations, body mass index, blood pressure, or methodology used to assess ADMA. Furthermore, subgroup analysis showed no difference across RDs. This meta-analysis showed that, in the context of significant between-study heterogeneity, circulating concentrations of ADMA are positively related to RDs.

Hydrogen Sulfide: A Therapeutic Option in Systemic Sclerosis

Systemic sclerosis (SSc) is a lethal disease that is characterized by auto-immunity, vascular injury, and progressive fibrosis of multiple organ systems. Despite the fact that the exact etiology of SSc remains unknown, oxidative stress has been associated with a large range of SSc-related complications. In addition to the well-known detrimental properties of reactive oxygen species (ROS), gasotransmitters (e.g., nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S)) are also thought to play an important role in SSc. Accordingly, the diverse physiologic actions of NO and CO and their role in SSc have been previously studied. Recently, multiple studies have also shown the importance of the third gasotransmitter H₂S in both vascular physiology and pathophysiology. Interestingly, homocysteine (which is converted into H₂S through the transsulfuration pathway) is often found to be elevated in SSc patients; suggesting defects in the transsulfuration pathway. Hydrogen sulfide, which is known to have several effects, including a strong antioxidant and vasodilator effect, could potentially play a prominent role in the initiation and progression of vasculopathy. A better understanding of the actions of gasotransmitters, like H₂S, in the development of SSc-related vasculopathy, could help to create early interventions to attenuate the disease course. This paper will review the role of H₂S in vascular (patho-)physiology and potential disturbances in SSc. Moreover, current data from experimental animal studies will be reviewed. Lastly, we will evaluate potential interventional strategies.

Oxidative/nitrative stress in the pathogenesis of systemic sclerosis: are antioxidants beneficial?

Systemic sclerosis (SSc) is a multisystem autoimmune disease: characterised from the clinical side by progressive vasculopathy and fibrosis of the skin and different organs and from the biochemical side by fibroblast deregulation with excessive production of collagen and increased expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). The latter contributes to an overproduction of reactive oxygen species that through an autocrine loop maintains NOX4 in a state of activation. Reactive oxygen and nitrogen species are implicated in the origin and perpetuation of several clinical manifestations of SSc having vascular damage in common; attempts to dampen oxidative and nitrative stress through different agents with antioxidant properties have not translated into a sustained clinical benefit. Objective of this narrative review is to describe the origin and clinical implications of oxidative and nitrative stress in SSc, with particular focus on the central role of NOX4 and its interactions, to re-evaluate the antioxidant approaches so far used to limit disease progression, to appraise the complexity of antioxidant treatment and to touch on novel pathways elements of which may represent specific treatment targets in the not so distant future.

The clinical effects of l-arginine and asymmetric dimethylarginine: implications for treatment in secondary Raynaud's phenomenon

Secondary Raynaud's phenomenon (RP) is often the sentinel clinical finding in systemic sclerosis and may precede systemic disease by several years. Altered nitric oxide metabolism plays a critical role in both fibrosis and severe secondary RP phenotypes in these patients. Increased flux through inducible nitric oxide synthase (iNOS) drives cutaneous fibrosis. Failure of flux through endothelial nitric oxide synthase (eNOS) contributes to increased vasoconstriction and decreased vasorelaxation. The underproduction of nitric oxide by eNOS is in part due to increased levels of asymmetric dimethylarginine (ADMA), an endogenous competitive inhibitor of nitric oxide synthase. The inhibitory effects of increased ADMA levels may be counteracted increasing serum l‐arginine, which is often an effective treatment strategy in these patients. As such, l‐arginine‐based therapies should be considered in managing secondary RP, particularly given their favourable safety and tolerability profile. While there is no established dosing regimen, studies of oral l‐arginine in secondary RP suggest that divided dosing may begin at 1–2 g/day and may be titrated up to 10 g/day. Conversely, primary RP is not associated with increased ADMA production which likely accounts for the failure of l‐arginine trials to show benefit in primary RP.

Oxidative stress in the pathogenesis of systemic scleroderma: An overview

Systemic sclerosis (SSc) is a rare disorder of the connective tissue characterized by fibrosis of the skin, skeletal muscles and visceral organs. Additional manifestations include activation of the immune system and vascular injury. SSc causes disability and death as the result of end‐stage organ failure. Two clinical subsets of the SSc are accepted: limited cutaneous SSc (lc‐SSc) and diffuse cutaneous SSc (dc‐SSc). At present, the aetiology and pathogenesis of SSc remain obscure, and consequently, disease outcome is unpredictable. Numerous studies suggest that reactive oxidizing species (ROS) play an important role in the pathogenesis of scleroderma. Over the years, several reports have supported this hypothesis for both lc‐SSc and dc‐SSc, although the specific role of oxidative stress in the pathogenesis of vascular injury and fibrosis remains to be clarified. The aim of the present review was to report and comment the recent findings regarding the involvement and role of oxidative stress in SSc pathogenesis. Biomarkers proving the link between ROS and the main pathological features of SSc have been summarized.

The role of endothelial cells in the vasculopathy of systemic sclerosis: A systematic review

INTRODUCTION

Systemic sclerosis (SSc) is an autoimmune connective tissue disorder characterized by fibroproliferative vasculopathy, immunological abnormalities and progressive fibrosis of multiple organs including the skin. In this study, all English speaking articles concerning the role of endothelial cells (ECs) in SSc vasculopathy and representing biomarkers are systematically reviewed and categorized according to endothelial cell (EC) (dys)function in SSc.

METHODS

A sensitive search on behalf of the EULAR study group on microcirculation in Rheumatic Diseases was developed in Pubmed, The Cochrane Library and Web of Science to identify articles on SSc vasculopathy and the role of ECs using the following Mesh terms: (systemic sclerosis OR scleroderma) AND pathogenesis AND (endothelial cells OR marker). All selected papers were read and discussed by two independent reviewers. The selection process was based on title, abstract and full text level. Additionally, both reviewers further searched the reference lists of the articles selected for reading on full text level for supplementary papers. These additional articles went through the same selection process.

RESULTS

In total 193 resulting articles were selected and the identified biomarkers were categorized according to description of EC (dys)function in SSc. The most representing and reliable biomarkers described by the selected articles were adhesion molecules for EC activation, anti-endothelial cell antibodies for EC apoptosis, vascular endothelial growth factor (VEGF), its receptor VEGFR-2 and endostatin for disturbed angiogenesis, endothelial progenitors cells for defective vasculogenesis, endothelin-1 for disturbed vascular tone control, Von Willebrand factor for coagulopathy and interleukin (IL)-33 for EC-immune system communication. Emerging, relatively new discovered biomarkers described in the selected articles, are VEGF₁₆₅b, IL-17A and the adipocytokines. Finally, myofibroblasts involved in tissue fibrosis in SSc can derive from ECs or epithelial cells through a process known as endothelial-to-mesenchymal transition.

CONCLUSION

This systematic review emphasizes the growing evidence that SSc is primarily a vascular disease where EC dysfunction is present and prominent in different aspects of cell survival (activation and apoptosis), angiogenesis and vasculogenesis and where disturbed interactions between ECs and various other cells contribute to SSc vasculopathy.

Toxic Dimethylarginines: Asymmetric Dimethylarginine (ADMA) and Symmetric Dimethylarginine (SDMA)

Asymmetric and symmetric dimethylarginine (ADMA and SDMA, respectively) are toxic, non-proteinogenic amino acids formed by post-translational modification and are uremic toxins that inhibit nitric oxide (NO) production and play multifunctional roles in many human diseases. Both ADMA and SDMA have emerged as strong predictors of cardiovascular events and death in a range of illnesses. Major progress has been made in research on ADMA-lowering therapies in animal studies; however, further studies are required to fill the translational gap between animal models and clinical trials in order to treat human diseases related to elevated ADMA/SDMA levels. Here, we review the reported impacts of ADMA and SDMA on human health and disease, focusing on the synthesis and metabolism of ADMA and SDMA; the pathophysiological roles of these dimethylarginines; clinical conditions and animal models associated with elevated ADMA and SDMA levels; and potential therapies against ADMA and SDMA. There is currently no specific pharmacological therapy for lowering the levels and counteracting the deleterious effects of ADMA and SDMA. A better understanding of the mechanisms underlying the impact of ADMA and SDMA on a wide range of human diseases is essential to the development of specific therapies against diseases related to ADMA and SDMA.

Exhaled nitric oxide in pulmonary arterial hypertension associated with systemic sclerosis

The fractional exhaled concentration of nitric oxide (FE_NO) has been shown to be reduced in idiopathic pulmonary arterial hypertension (PAH) but has not been adequately studied in PAH associated with systemic sclerosis (SSc). We measured FE_NO at an expiratory flow rate of 50 mL/s in 21 treatment-naive patients with SSc-associated PAH (SSc-PAH), 94 subjects with SSc without pulmonary involvement, and 84 healthy volunteers. Measurements of FE_NO at additional flow rates of 100, 150, and 250 mL/s were obtained to derive the flow-independent nitric oxide exchange parameters of maximal airway flux (J'aw_NO) and steady-state alveolar concentration (CA_NO). FE_NO at 50 mL/s was similar (P = 0.22) in the SSc-PAH group (19 ± 12 parts per billion [ppb]) compared with the SSc group (17 ± 12 ppb) and healthy control group (21 ± 11 ppb). No change was observed after 4 months of targeted PAH therapy in 14 SSc-PAH group patients (P = 0.9). J'aw_NO was modestly reduced in SSc group subjects without lung disease (1.2 ± 0.5 nl/s) compared with healthy controls (1.64 ± 0.9; P < 0.05) but was similar to that in the SSc-PAH group. CA_NO was elevated in individuals with SSc-PAH (4.8 ± 2.6 ppb) compared with controls with SSc (3.3 ± 1.4 ppb) and healthy subjects (2.6 ± 1.5 ppb; P < 0.001 for both). However, after adjustment for the diffusing capacity of CO, there was no significant difference in CA_NO between individuals with SSc-PAH and controls with SSc. We conclude that FE_NO is not useful for the diagnosis of PAH in SSc. Increased alveolar nitric oxide in SSc-PAH likely represents impaired diffusion into pulmonary capillary blood.

Asymmetric Dimethylarginine and Its Relation As a Biomarker in Nephrologic Diseases

It is encouraging to observe that a search for publications on "asymmetric dimethylarginine (ADMA)" in PubMed, as updated on June 2016, yielded >2500 items, 24 years after a splendid paper published by Vallance et al in which the authors proposed that ADMA accumulation could be a cardiovascular risk factor in chronic kidney diseases. ADMA is the endogenous inhibitor of nitric oxide synthase and is related to endothelial dysfunction, which plays an important role in vascular damage elicited by various cardiometabolic risk factors. Although current knowledge suggests that ADMA has critical central roles in renal diseases, there are still unexplained details. The present article aims to provide a review on ADMA and its relation as a biomarker in nephrologic diseases. We aimed to systematize articles in which ADMA levels were assessed in order to clarify its role in many diseases and establish its reference values in different populations.

Clinical relevance of antiphospholipid antibodies in systemic sclerosis: A systematic review and meta-analysis

OBJECTIVE

To evaluate the clinical relevance of antiphospholipid antibodies (aPL) in systemic sclerosis (SSc).

METHODS

A systematic search of EMBASE and PubMed databases from January 1983 to July 2016 was carried out according to PRISMA guidelines whereas Peto׳s odds ratio (OR) for rare events was used for the meta-analysis.

RESULTS

The pooled prevalence of participants positive for IgG and IgM anticardiolipin (aCL) antibodies was higher in SSc than controls (12.8% vs 1.6% and 7.8% vs 0.6%; p < 0.0001 for both) as was that of IgG and IgM anti-beta-2-glycoprotein-I antibodies (aβ₂GPI) (6.1% vs 0.58%, p < 0.0001; 3.5% vs 0.3%, p = 0.001). The pooled prevalence of pulmonary arterial hypertension (PAH) was more common in SSc positive than negative patients for aCL (IgG/IgM combined) (26.5% vs 10.9%, p < 0.0001) whereas the pooled prevalence of renal disease (RD) was more common in IgG aCL positive than negative patients (36.3% vs 10.9%, p = 0.02). The pooled prevalence of thrombosis was higher in IgG aCL, IgM aCL, and IgM aβ₂GPI positive than negative SSc patients (12.6% vs 1.4%, p < 0.0001), (15.1% vs 2.7%, p = 0.002) and (15% vs 0.78%, p = 0.009), respectively. The pooled prevalence of digital infarction/ischemia (DI) was higher in IgG aCL and IgM positive than negative SSc (52.8% vs 39.8%, p = 0.002) and (68.1% vs 29%, p = 0.07).

CONCLUSIONS

A strong relationship exists between aCL and aβ₂GPI of IgG/IgM isotype and SSc; patients positive for these antibodies are more likely to suffer from PAH, RD, thrombosis, and DI. However, data expressed as frequency of aPL positive patients rather than average antibody titers preclude further insight into the relevance of these assumptions.

Exercise-induced brachial artery blood flow and vascular function is impaired in systemic sclerosis

Systemic sclerosis (SSc) is a rare autoimmune disease characterized by debilitating fibrosis and vascular dysfunction; however, little is known about the circulatory response to exercise in this population. Therefore, we examined the peripheral hemodynamic and vasodilatory responses to handgrip exercise in 10 patients with SSc (61 ± 4 yr) and 15 age-matched healthy controls (56 ± 5 yr). Brachial artery diameter, blood flow, and mean arterial pressure (MAP) were determined at rest and during progressive static-intermittent handgrip exercise. Patients with SSc and controls were similar in body stature, handgrip strength, and MAP; however, brachial artery blood flow at rest was nearly twofold lower in patients with SSc compared with controls (22 ± 4 vs. 42 ± 5 ml/min, respectively; P < 0.05). Additionally, SSc patients had an ∼18% smaller brachial artery lumen diameter with an ∼28% thicker arterial wall at rest (P < 0.05). Although, during handgrip exercise, there were no differences in MAP between the groups, exercise-induced hyperemia and therefore vascular conductance were ∼35% lower at all exercise workloads in patients with SSc (P < 0.05). Brachial artery vasodilation, as assessed by the relationship between Δbrachial artery diameter and Δshear rate, was significantly attenuated in the patients with SSc (P < 0.05). Finally, vascular dysfunction in the patients with SSc was accompanied by elevated blood markers of oxidative stress and attenuated endogenous antioxidant activity (P < 0.05). Together, these findings reveal attenuated exercise-induced brachial artery blood flow and conduit arterial vasodilatory dysfunction during handgrip exercise in SSc and suggest that elevated oxidative stress may play a role.

Nailfold capillaroscopy assessment of microcirculation abnormalities and endothelial dysfunction in children with primary or secondary Raynaud syndrome

Raynaud syndrome (RS) manifests as episodes of transient spasms of peripheral blood vessels, most often in response to cold. The reason of that symptom (primary RS (pRS)) usually cannot be found but may be accompanied by some autoimmune diseases (secondary RS (sRS)). In this study, we assessed microcapillary status and serum concentrations of chosen cytokines, adhesive molecules, and nitric oxide (NO) in patients with pRS and sRS in comparison with healthy children. Eighty-six patients with RS were enrolled into the study, including 52 with pRS and 34 with sRS. The control group consisted of 29 healthy children. A decrease in myorelaxative and anticoagulant abilities was observed, with simultaneous prevalence of vasopressor substances and procoagulative activity. Therefore, several important factors such as endothelin-1 (ET-1), E-selectin (E-sel), interleukin-18 (IL-18), and nitrogen oxide (NO) were also analyzed. Two types of capillaroscopy status were determined: normal and microangiopathic. There was a significant relationship between presence of microangiopathy and higher serum ET-1 (p = 0.018) and E-sel (p = 0.021) levels. Similarly, we have found a correlation between presence of ANA and higher ET-1 (p = 0.005), but not E-sel (p = 0.241). In patients with pRS, we found significant relationship between ANA and higher ET-1 (p = 0.008). No such relations were observed in sRS patients. Our data indicates that external factor-induced vasoconstrictive effects dominated in pRS, whereas in sRS in the course of connective tissue diseases, it was accompanied by coexistent vasodilation due to endothelial dysfunction. The latter phenomenon is at least partially dependent on insufficient NO release.

The association between systemic sclerosis, arginine and asymmetric dimethylarginine

Systemic sclerosis (SSc) is a kind of autoimmune disease characterized by inflammatory and endothelial dysfunction. Asymmetric dimethylarginine (ADMA), as an endogenous nitric oxide synthase inhibitor, can cause or contribute to the inflammatory syndrome and endothelial dysfunction. Recently, increased ADMA levels have been demonstrated in SSc, revealing that ADMA might play an important role for the associated manifestations of SSc. Besides, ADMA may play a significant role in the level of NO, which is produced by arginine. In the review, we discuss the role of arginine and ADMA in patients with SSc.

Vasculopathy in scleroderma

Systemic sclerosis (SSc) is a multisystem connective tissue disorder featured by vascular injury and fibrosis of the skin and various internal organs with autoimmune background. Although the pathogenesis of SSc still remains elusive, it is generally accepted that initial vascular injury due to autoimmunity and/or environmental factors causes structural and functional abnormalities of vasculature which eventually result in the constitutive activation of fibroblasts in various organs. Structural alterations consist of destructive vasculopathy (loss of small vessels) and proliferative obliterative vasculopathy (occlusion of arterioles and small arteries with fibro-proliferative change) caused by impaired compensatory vasculogenesis and angiogenesis. Impaired function of SSc vasculature includes the altered expression of cell adhesion molecules predominantly inducing Th2 and Th17 cell infiltration, endothelial dysfunction primarily due to the low availability of nitric oxide, the activated endothelial-to-mesenchymal transition leading to fibro-proliferative vascular change and tissue fibrosis, and the impaired coagulation/fibrinolysis system promoting the formation of intravascular fibrin deposits. Recent new insights into the therapeutic mechanisms of intravenous cyclophosphamide pulse and bosentan and the establishment of a new SSc animal model (Klf5 (+/-);Fli1 (+/-) mice) provide us useful clues to further understand the development of vascular alterations characteristic of SSc. This article overviewed the present understanding of the pathogenesis of SSc vasculopathy.

Endothelial dysfunction in systemic sclerosis

PURPOSE OF REVIEW

Microvascular endothelial cells (MVECs) injury is a critical early event in the pathogenesis of systemic sclerosis (SSc). We aim to provide the reader with an update regarding the role of MVECs in the pathogenesis of SSc and the mechanisms for MVECs dysfunction in the disease.

RECENT FINDINGS

Recent evidence confirms the central role for MVECs in the pathogenesis of SSc, and suggests further mechanisms for MVECs injury. The impact of MVECs perturbations in SSc goes beyond the initiation of the vascular disease to include activation of fibroblasts through the release of cytokines and growth factors like connective tissue growth factor that induce an active and aggressive form of fibroblasts. Moreover, recent studies highlighted a more prominent role for epigenetic factors in the pathogenesis of SSc, and suggested defects in the function of progenitor endothelial cells in SSc. Recent reports helped to shed light on the role of antiendothelial cell antibodies in the pathogenesis of SSc, especially purified subsets of these antibodies like anti-ICAM-1 antibodies, and also reported possible mechanisms for defective vascular endothelial growth factor signaling.

SUMMARY

It is clear that MVECs dysfunction is a key element in the pathogenesis of SSc, but the initial triggers for MVEC dysfunction remain uncharacterized.

Reduced levels of S-nitrosothiols in plasma of patients with systemic sclerosis and Raynaud's phenomenon

Objective

S-Nitrosothiols (RSNOs) are bioactive forms of nitric oxide which are involved in cell signalling and redox regulation of vascular function. Circulating S-nitrosothiols are predominantly in the form of S-nitrosoalbumin. In this study plasma concentrations of S-nitrosothiols were measured in patients with systemic sclerosis (SSc) where NO metabolism is known to be abnormal.

Patients and methods

Venous blood was collected from 16 patients with Raynaud's phenomenon (RP), 45 with systemic sclerosis (SSc) (34 patients had limited SSc (IcSSc) and 11 diffuse cutaneous disease (dcSSc)). Twenty six healthy subjects were used as controls. Plasma S-nitrosothiol concentrations were measured by chemiluminescence. The measurements were related to the extent of biological age, capillary/skin scores and disease duration.

Results

Plasma RSNO levels in patients with Raynaud's phenomenon (RP) and in those with SSc was significantly lower compared to the concentrations in control subjects. In SSc, plasma S-nitrosothiols were often below the level of detection (1nM).

Conclusions

Low S-nitrosothiol concentrations were observed in the blood of patients with SSc and patients with RP indicating a profound disturbance of nitric oxide metabolism.

A PRISMA-driven systematic review for predictive risk factors of digital ulcers in systemic sclerosis patients

Vasculopathy has a major role in the pathogenesis and tissue injury in systemic sclerosis (SSc). Raynaud's phenomenon (RP) is frequently the first clinical manifestation of SSc preceding by years other clinical manifestations. RP in SSc patients is frequent, often very severe and long lasting. The repeated bouts of RP lead to prolonged digital ischemia that may progress to digital ulceration or in extreme to critical digital ischemia with gangrene. Digital ulcers (DU) are a true burden for all patients. They are very painful, with a long and slow healing course, have high risk of infection and are extremely disabling. In adults, up to 40-50% of patients will experience at least one DU in the course of the disease and of these 31-71% will have recurrent ulcers. In order to try to identify predictive risk factors for DU in SSc patients, an extensive literature review was conducted, according to the guidelines proposed at the PRISMA statement. MEDLINE database (PubMed) and Thomson Reuters Web of Knowledge platform were searched for articles published in peer-reviewed journals since 1990 with the last search run on June 2014 and published in English language. The keyword search terms included: digital ulcer/s, systemic sclerosis, scleroderma, digital scars, ischemic complications, autoantibodies, biomarkers, endothelium dysfunction, endothelin-1, vascular endothelial growth factor (VEGF), endostatin, ADMA, endoglin, angiostatin, and capillaroscopy. The following criteria were included: (1) cohorts of SSc patients including patients with DU, (2) endothelium dysfunction and angiogenesis biomarkers compared with a healthy control group, (3) autoantibodies, capillary morphology and distribution, endothelium dysfunction and angiogenesis biomarkers compared between patients with and without digital ulcers, (4) detailed description of the statistical methods used to conclude for predictive factors, and (5) English language. Our search provided a total of 376 citations. Of these, 297 studies were discarded for not meeting the criteria proposed.

Relationship between redox status and cell fate in immunity and autoimmunity

SIGNIFICANCE

The signaling function of redox molecules is essential for an efficient and proper execution of a large number of cellular processes, contributing to the maintenance of cell homeostasis. Excessive oxidative stress is considered as playing an important role in the pathogenesis of autoimmune diseases by enhancing inflammation and breaking down the immunological tolerance through protein structural modifications that induce the appearance of neo/cryptic epitopes.

RECENT ADVANCES

There is a complex reciprocal relationship between oxidative stress and both apoptosis and autophagy, which is essential to determine cell fate. This is especially relevant in the context of autoimmune disorders in which apoptosis and autophagy play a crucial pathogenic role.

CRITICAL ISSUES

In this review, we describe the latest developments with regard to the involvement of redox molecules in the initiation and progression of autoimmune disorders, focusing on their role in cell fate regulation. We also discuss new therapeutic approaches that target oxidative stress in the treatment of these disorders. The administration of antioxidants is scarcely studied in autoimmunity, and future analyses are needed to assess its beneficial effects in preventing or ameliorating these diseases.

FUTURE DIRECTIONS

Deciphering the intricate relationships between oxidative stress and both apoptosis and autophagy in the context of autoimmunity could be critical in elucidating key pathogenic mechanisms and could lead to novel interventions for the clinical management of autoimmune diseases.

Oxidative Stress and Skin Fibrosis

Fibrosis is defined as increased fibroblast proliferation and deposition of extracellular matrix components with potential clinical ramifications including organ dysfunction and failure. Fibrosis is a characteristic finding of various skin diseases which can have life-threatening consequences. These implications call for research into this topic as only a few treatments targeting fibrosis are available. In this review, we discuss oxidative stress and its role in skin fibrosis. Recent studies have implicated the importance of oxidative stress in a variety of cellular pathways directly and indirectly involved in the pathogenesis of skin fibrosis. The cellular pathways by which oxidative stress affects specific fibrotic skin disorders are also reviewed. Finally, we also describe various therapeutic approaches specifically targeting oxidative stress to prevent skin fibrosis. We believe oxidative stress is a relevant target, and understanding the role of oxidative stress in skin fibrosis will enhance knowledge of fibrotic skin diseases and potentially produce targeted therapeutic options.

Amelioration of systemic fibrosis in mice by angiotensin II receptor blockade

OBJECTIVE

Systemic sclerosis (SSc) is characterized by microvascular damage, fibrosis of skin and visceral organs, and autoimmunity. Previous studies have shown that angiotensin II is involved in the synthesis of type I collagen. We investigated whether the blockade of angiotensin II receptor type I (AT1 ) by irbesartan reduces skin and lung fibrosis in 2 murine models of SSc.

METHODS

SSc was induced by daily intradermal injection of HOCl into the backs of BALB/c mice (HOCl-induced SSc). Mice were treated daily with irbesartan by oral gavage.

RESULTS

Irbesartan reduced dermal thickness, collagen concentration, Smad2/3, and α-smooth muscle actin expression, as well as fibroblast proliferation and H-Ras expression in the skin of mice with HOCl-induced SSc. Mice treated with irbesartan also displayed less lung fibrosis, less inflammation, and a lower concentration of collagen in the lungs than untreated mice. Exhaled nitric oxide, inducible nitric oxide synthase, and 3-nitrotyrosine expression in the lungs were decreased following irbesartan treatment. Moreover, irbesartan reduced the number and the proliferation of splenic B and T cells and the serum levels of anti-DNA topoisomerase I autoantibodies.

CONCLUSION

Irbesartan, an AT1 antagonist, prevents fibrosis and inflammation and inhibits nitric oxide production in HOCl-induced models of systemic fibrosis. Our findings extend the indication of an AT1 antagonist to SSc patients with diffuse fibrosis, especially those with lung involvement.

Clinical correlation of brachial artery flow-mediated dilation in patients with systemic sclerosis

OBJECTIVE: To investigate the clinical significance of flow-mediated dilation (FMD) in systemic sclerosis (SSc). METHODS: Thirty-three SSc patients and 12 healthy controls were studied. Ultrasound assessment of the brachial artery FMD was performed on all subjects. The results were expressed as the percentage of increase in brachial artery diameter following hyperemia. RESULTS: Limited cutaneous SSc (lcSSc) patients had significantly lower FMD values than healthy controls (5.3 ± 2.7 versus 7.7 ± 2.0 %, p < 0.05), while the values in diffuse cutaneous SSc (dcSSc) patients (6.7 ± 4.0 %) were comparable to those in lcSSc patients and healthy controls. Although FMD values did not correlate with any clinical features in dcSSc patients, there was an inverse correlation between FMD values and disease duration in lcSSc patients (r = -0.64, p < 0.05). Furthermore, lcSSc patients with decreased FMD values showed significantly higher prevalence of digital ulcers and elevated right ventricular systolic pressure than those with normal values (for each; 75 versus 10 %, p < 0.05). CONCLUSION: The FMD values represent the severity of vascular damages, which progress along with disease duration and lead to digital ulcers and pulmonary arterial hypertension, in lcSSc patients.

Cardiovascular risk in autoimmune disorders: role of asymmetric dimethylarginine

Mounting evidence indicates that cardiovascular events are a main cause of excessive mortality of autoimmune disorders like type I diabetes mellitus and rheumatic diseases. Inflammation and endothelial dysfunction, independent predictors to cardiovascular disease, are hallmarks of autoimmunity. Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, can cause or contribute to the inflammatory syndrome and endothelial dysfunction. Recently, elevated ADMA levels have been demonstrated in many autoimmune diseases, suggesting that ADMA might play an important role for the associated manifestations of cardiovascular disease. In the review, we discuss the role of ADMA in the excessive cardiovascular morbidity and mortality associated with autoimmune diseases.

Alanine-glyoxylate aminotransferase-2 metabolizes endogenous methylarginines, regulates NO, and controls blood pressure

OBJECTIVE

Asymmetric dimethylarginine is an endogenous inhibitor of NO synthesis that may mediate cardiovascular disease. Alanine-glyoxylate aminotransferase-2 (AGXT2) has been proposed to degrade asymmetric dimethylarginine. We investigated the significance of AGXT2 in methylarginine metabolism in vivo and examined the effect of this enzyme on blood pressure.

METHODS AND RESULTS

In isolated mouse kidney mitochondria, we show asymmetric dimethylarginine deamination under physiological conditions. We demonstrate increased asymmetric dimethylarginine, reduced NO, and hypertension in an AGXT2 knockout mouse. We provide evidence for a role of AGXT2 in methylarginine metabolism in humans by demonstrating an inverse relationship between renal (allograft) gene expression and circulating substrate levels and an association between expression and urinary concentrations of the product. Finally, we examined data from a meta-analysis of blood pressure genome-wide association studies. No genome-wide significance was observed, but taking a hypothesis-driven approach, there was a suggestive association between the T allele at rs37369 (which causes a valine-isoleucine substitution and altered levels of AGXT2 substrate) and a modest increase in diastolic blood pressure (P=0.0052).

CONCLUSIONS

Although the effect of variation at rs37369 needs further study, these findings suggest that AGXT2 is an important regulator of methylarginines and represents a novel mechanism through which the kidney regulates blood pressure.

Asymmetric dimethylarginine as a surrogate marker of endothelial dysfunction and cardiovascular risk in patients with systemic rheumatic diseases

The last few decades have witnessed an increased life expectancy of patients suffering with systemic rheumatic diseases, mainly due to improved management, advanced therapies and preventative measures. However, autoimmune disorders are associated with significantly enhanced cardiovascular morbidity and mortality not fully explained by traditional cardiovascular disease (CVD) risk factors. It has been suggested that interactions between high-grade systemic inflammation and the vasculature lead to endothelial dysfunction and atherosclerosis, which may account for the excess risk for CVD events in this population. Diminished nitric oxide synthesis—due to down regulation of endothelial nitric oxide synthase—appears to play a prominent role in the imbalance between vasoactive factors, the consequent impairment of the endothelial hemostasis and the early development of atherosclerosis. Asymmetric dimethylarginine (ADMA) is one of the most potent endogenous inhibitors of the three isoforms of nitric oxide synthase and it is a newly discovered risk factor in the setting of diseases associated with endothelial dysfunction and adverse cardiovascular events. In the context of systemic inflammatory disorders there is increasing evidence that ADMA contributes to the vascular changes and to endothelial cell abnormalities, as several studies have revealed derangement of nitric oxide/ADMA pathway in different disease subsets. In this article we discuss the role of endothelial dysfunction in patients with rheumatic diseases, with a specific focus on the nitric oxide/ADMA system and we provide an overview on the literature pertaining to ADMA as a surrogate marker of subclinical vascular disease.

Nitric oxide inhibits androgen receptor-mediated collagen production in human gingival fibroblasts

Lin S-J, Lu H-K, Lee H-W, Chen Y-C, Li C-L, Wang L-F. Nitric oxide inhibits androgen receptor-mediated collagen production in human gingival fibroblasts. J Periodont Res 2012; 47: 701-710. © 2012 John Wiley & Sons A/S Background and Objective:  In our previous study, we found that flutamide [an androgen receptor (AR) antagonist] inhibited the up-regulation of collagen induced by interleukin (IL)-1β and/or nifedipine in gingival fibroblasts. The present study attempted to verify the role of nitric oxide (NO) in the IL-1β/nifedipine-AR pathway in gingival overgrowth.

MATERIAL AND METHODS

  Confluent gingival fibroblasts derived from healthy individuals (n = 4) and those with dihydropyridine-induced gingival overgrowth (DIGO) (n = 6) were stimulated for 48 h with IL-1β (10 ng/mL), nifedipine (0.34 μm) or IL-1β + nifedipine. Gene and protein expression were analyzed with real-time RT-PCR and western blot analyses, respectively. Meanwhile, Sircol dye-binding and the Griess reagent were, respectively, used to detect the concentrations of total soluble collagen and nitrite in the medium.

RESULTS

  IL-1β and nifedipine simultaneously up-regulated the expression of the AR and type-I collagen α1 [Colα1(I)] genes and the total collagen concentration in DIGO cells (p < 0.05). IL-1β strongly increased the expression of inducible nitric oxide synthase (iNOS) mRNA and the nitrite concentration in both healthy and DIGO cells (p < 0.05). However, co-administration of IL-1β and nifedipine largely abrogated the expression of iNOS mRNA and the nitrite concentration with the same treatment. Spearman's correlation coefficients revealed a positive correlation between the AR and total collagen (p < 0.001), but they both showed a negative correlation with iNOS expression and the NO concentration (p < 0.001). The iNOS inhibitor, 1400W, enhanced IL-1β-induced AR expression; furthermore, the NO donor, NONOate, diminished the expression of the AR to a similar extent in gingival fibroblasts derived from both healthy patients and DIGO patients (p < 0.05).

CONCLUSION

  IL-1β-induced NO attenuated AR-mediated collagen production in human gingival fibroblasts. The iNOS/NO system down-regulated the axis of AR/Colα1(I) mRNA expression and the production of AR/total collagen proteins by DIGO cells.

Endogenous nitric oxide synthase inhibitors in the biology of disease: markers, mediators, and regulators?

The asymmetric methylarginines inhibit nitric oxide synthesis in vivo by competing with L-arginine at the active site of nitric oxide synthase. High circulating levels of asymmetric dimethylarginine predict adverse outcomes, specifically vascular events but there is now increasing experimental and epidemiological evidence that these molecules, and the enzymes that regulate this pathway, play a mechanistic role in cardiovascular diseases. Recent data have provided insight into the impact of altered levels of these amino acids in both humans and rodents, however these reports also suggest a simplistic approach based on measuring, and modulating circulating asymmetric dimethylarginine alone is inadequate. This review outlines the basic biochemistry and physiology of endogenous methylarginines, examines both the experimental and observational evidence for a role in disease pathogenesis, and examines the potential for therapeutic regulation of these molecules.