Asymmetrical dimethylarginine in systemic sclerosis-related pulmonary arterial hypertension

Endothelial Biomarkers of Systemic Sclerosis-Associated Pulmonary Hypertension

OBJECTIVE

Despite efforts at early detection, patients with systemic sclerosis (SSc) pulmonary hypertension (PH) present with advanced disease. We sought to determine whether endothelial biomarkers (asymmetric dimethylarginine [ADMA], soluble endoglin [sEng], and pentraxin-3 [PTX-3]) can determine SSc-PH risk or differentiate between SSc-PH subgroups.

METHODS

ADMA, sEng, and PTX-3 were measured by enzyme-linked immunosorbent assay in four groups: 1) 18 healthy controls, 2) 74 patients with SSc-PH, 3) 44 patients at high risk for PH features, and 4) 10 patients with low risk for PH features. High-risk features included a diffusion capacity (DLco) less than 55% with a forced vital capacity (FVC) greater than 70%, an FVC/DLco ratio of >1.6, or a right ventricular systolic pressure on an echocardiogram greater than or equal to 40 mm Hg. ADMA, sEng, and PTX-3 were compared between these four groups as well as stratified based on the three SSc-PH clinical classification groups (pulmonary arterial hypertension [PAH], left-heart disease, and interstitial lung disease [ILD]).

RESULTS

PTX-3 was significantly lower in subjects with SSc at low risk for PH (median 27.0 pg/ml [interquartile range (IQR) 19.0-47.3]; P < 0.003) than the other groups. The area under the receiver operating characteristic curve was 0.87 (95% confidence interval 0.76-0.98, P = 0.0002) to differentiate low risk from high risk for patients with PH. PTX-3 was significantly lower in SSc-PH from disease of the left side of the heart (57.5 pg/ml [IQR 39.8-79.0]; P < 0.01) compared to SSc-PH from either PAH (85.5 pg/ml [IQR 56.3-104.5]) or ILD (90.3 pg/ml [IQR 74.9-111.0]). Neither ADMA nor sEng differed between the four groups.

CONCLUSION

PTX-3 is a promising biomarker of PH risk status in patients with SSc as well as a possible marker of precapillary PH, which should be validated in an external cohort.

Arginine-NO metabolites are associated with morbidity in single ventricle infants undergoing stage 2 palliation

BACKGROUND

Infants with single ventricle heart disease (SVHD) suffer morbidity from insufficient pulmonary blood flow, which may be related to impaired arginine metabolism. No prior study has reported quantitative mapping of arginine metabolites to evaluate the relationship between circulating metabolite levels and outcomes.

METHODS

Prospective cohort study of 75 SVHD cases peri-Stage 2 and 50 healthy controls. We targeted pre- and post-op absolute serum quantification of 9 key members of the arginine metabolism pathway by tandem mass spectrometry. Primary outcomes were length of stay (LOS) and post-Stage 2 hypoxemia.

RESULTS

Pre-op cases showed alteration in 6 metabolites including decreased arginine and increased asymmetric dimethyl arginine (ADMA) levels compared to controls. Post-op cases demonstrated decreased arginine and citrulline levels persisting through 48 h. Adjusting for clinical variables, lower pre-op and 2 h post-op concentrations of multiple metabolites, including arginine and citrulline, were associated with longer post-op LOS (p < 0.01). Increased ADMA at 24 h was associated with greater post-op hypoxemia burden (p < 0.05).

CONCLUSION

Arginine metabolism is impaired in interstage SVHD infants and is further deranged following Stage 2 palliation. Patients with greater metabolite alterations experience greater post-op morbidity. Decreased arginine metabolism may be an important driver of pathology in SVHD.

IMPACT

Interstage infants with SVHD have significantly altered arginine-nitric oxide metabolism compared to healthy children with deficiency of multiple pathway intermediates persisting through 48 h post-Stage 2 palliation. After controlling for clinical covariates and classic catheterization-derived predictors of Stage 2 readiness, both lower pre-operation and lower post-operation circulating metabolite levels were associated with longer post-Stage 2 LOS while increased post-Stage 2 ADMA concentration was associated with greater post-op hypoxemia. Arginine metabolism mapping offers potential for development using personalized medicine strategies as a biomarker of Stage 2 readiness and therapeutic target to improve pulmonary vascular health in infants with SVHD.

Evaluation of Oxidative Stress and Endothelial Dysfunction in COVID-19 Patients

Background and Objectives: Heat shock proteins (HSPs) are stress proteins. The endogenous nitric oxide (NO) synthase inhibitor asymmetric dimethyl arginine (ADMA) is a mediator of endothelial dysfunction. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus causes endothelial dysfunction and coagulopathy through severe inflammation and oxidative stress. Using these markers, we analyzed the prognostic value of serum ADMA and HSP-90 levels for early prediction of severe coronavirus disease (COVID-19) patients. Materials and Methods: A total of 76 COVID-19 patients and 35 healthy control subjects were included in this case-control study. COVID-19 patients were divided into two groups: mild and severe. Results: Serum ADMA and HSP-90 levels were significantly higher in the COVID-19 patients compared to the control subjects (p < 0.001). Additionally, serum ADMA and HSP-90 levels were determined to be higher in a statistically significant way in severe COVID-19 compared to mild COVID-19 (p < 0.001). Univariable logistic regression analysis revealed that ADMA and HSP-90, respectively, were independent predictors of severe disease in COVID-19 patients (ADMA (OR = 1.099, 95% CI = 1.048-1.152, p < 0.001) and HSP-90 (OR = 5.296, 95% CI = 1.719-16.316, p = 0.004)). When the cut-off value for ADMA was determined as 208.94 for the prediction of the severity of COVID-19 patients, the sensitivity was 72.9% and the specificity was 100% (AUC = 0.938, 95%CI = 0.858-0.981, p < 0.001). When the cut-off value for HSP-90 was determined as 12.68 for the prediction of the severity of COVID-19 patients, the sensitivity was 88.1% and the specificity was 100% (AUC = 0.975, 95% CI= 0.910-0.997, p < 0.001). Conclusions: Increased levels of Heat shock proteins-90 (HSP-90) and ADMA were positively correlated with increased endothelial damage in COVID-19 patients, suggesting that treatments focused on preventing and improving endothelial dysfunction could significantly improve the outcomes and reduce the mortality rate of COVID-19. ADMA and HSP-90 might be simple, useful, and prognostic biomarkers that can be utilized to predict patients who are at high risk of severe disease due to COVID-19.

Idiopathic and connective tissue disease-associated pulmonary arterial hypertension (PAH): Similarities, differences and the role of autoimmunity

Pre-capillary pulmonary arterial hypertension (PAH) is hemodynamically characterized by a mean pulmonary arterial pressure (mPAP) ≥ 20 mmHg, pulmonary capillary wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) > 2. PAH is classified in six clinical subgroups, including idiopathic PAH (IPAH) and PAH associated to connective tissue diseases (CTD-PAH), that will be the main object of this review. The aim is to compare these two PAH subgroups in terms of epidemiology, histological and pathogenic findings in an attempt to define disease-specific features, including autoimmunity, that may explain the heterogeneity of response to therapy between IPAH and CTD-PAH.

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.

Serum Biomarkers in Connective Tissue Disease-Associated Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening complication of connective tissue diseases (CTDs) characterised by increased pulmonary arterial pressure and pulmonary vascular resistance. CTD-PAH is the result of a complex interplay among endothelial dysfunction and vascular remodelling, autoimmunity and inflammatory changes, ultimately leading to right heart dysfunction and failure. Due to the non-specific nature of the early symptoms and the lack of consensus on screening strategies-except for systemic sclerosis, with a yearly transthoracic echocardiography as recommended-CTD-PAH is often diagnosed at an advanced stage, when the pulmonary vessels are irreversibly damaged. According to the current guidelines, right heart catheterisation is the gold standard for the diagnosis of PAH; however, this technique is invasive, and may not be available in non-referral centres. Hence, there is a need for non-invasive tools to improve the early diagnosis and disease monitoring of CTD-PAH. Novel serum biomarkers may be an effective solution to this issue, as their detection is non-invasive, has a low cost and is reproducible. Our review aims to describe some of the most promising circulating biomarkers of CTD-PAH, classified according to their role in the pathophysiology of the disease.

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.

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.

Dysregulation of the Nitric Oxide/Dimethylarginine Pathway in Hypoxic Pulmonary Vasoconstriction—Molecular Mechanisms and Clinical Significance

The pulmonary circulation responds to hypoxia with vasoconstriction, a mechanism that helps to adapt to short-lived hypoxic episodes. When sustained, hypoxic pulmonary vasoconstriction (HPV) may become deleterious, causing right ventricular hypertrophy and failure, and contributing to morbidity and mortality in the late stages of several chronic pulmonary diseases. Nitric oxide (NO) is an important endothelial vasodilator. Its release is regulated, amongst other mechanisms, by the presence of endogenous inhibitors like asymmetric dimethylarginine (ADMA). Evidence has accumulated in recent years that elevated ADMA may be implicated in the pathogenesis of HPV and in its clinical sequelae, like pulmonary arterial hypertension (PAH). PAH is one phenotypic trait in experimental models with disrupted ADMA metabolism. In high altitude, elevation of ADMA occurs during long-term exposure to chronic or chronic intermittent hypobaric hypoxia; ADMA is significantly associated with high altitude pulmonary hypertension. High ADMA concentration was also reported in patients with chronic obstructive lung disease, obstructive sleep apnoea syndrome, and overlap syndrome, suggesting a pathophysiological role for ADMA-mediated impairment of endothelium-dependent, NO-mediated pulmonary vasodilation in these clinically relevant conditions. Improved understanding of the molecular (dys-)regulation of pathways controlling ADMA concentration may help to dissect the pathophysiology and find novel therapeutic options for these diseases.

Non-Invasive Assessment of Endothelial Dysfunction in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is characterised by an increased pressure in the pulmonary arterial circulation, resulting in the elevation of pulmonary vascular resistance. Pulmonary endothelial dysfunction and inflammation, triggered by shear stress and hypoxia, constitute the hallmarks of pulmonary vasculopathy by promoting endothelial and smooth muscle cells proliferation, vasoconstriction, and thrombosis. While research was predominantly focused on pulmonary vasculature, the investigation of peripheral endothelial damage in different vascular beds has attracted the interest over the last years. As a result, effective non-invasive methods that can assess the endothelial function and the architectural integrity have been utilized for the evaluation of pulmonary and peripheral vasculature. Non-invasive plethysmography, pulmonary flow reserve, nailfold videocapillaroscopy, near-infrared spectroscopy, and imaging techniques such as magnetic resonance angiography and perfusion imaging coupled by a number of biomarkers can be used for the assessment of peripheral vascular function in PAH individuals. In this review, we summarise and critically approach the current evidence of more systemic derangement of vascular function in PAH defined by novel, non-invasive methods employed for functional and morphological assessment of endothelium and microcirculation.

Metabolism of asymmetric dimethylarginine in hypoxia: from bench to bedside

Acute hypoxia and chronic hypoxia induce pulmonary vasoconstriction. While hypoxic pulmonary vasoconstriction is a physiological response if parts of the lung are affected, global exposure to hypoxic conditions may lead to clinical conditions like high-altitude pulmonary hypertension. Nitric oxide is the major vasodilator released from the vascular endothelium. Nitric oxide-dependent vasodilation is impaired in hypoxic conditions. Inhibition of nitric oxide synthesis is the most rapid and easily reversible molecular mechanism to regulate nitric oxide-dependent vascular function in response to physiological and pathophysiological stimuli. Asymmetric dimethylarginine is an endogenous, competitive inhibitor of nitric oxide synthase and a risk marker for major cardiovascular events and mortality. Elevated asymmetric dimethylarginine has been observed in animal models of hypoxia as well as in human cohorts under chronic and chronic intermittent hypoxia at high altitude. In lowlanders, asymmetric dimethylarginine is high in patients with pulmonary hypertension. We have recently shown that high asymmetric dimethylarginine at sea level is a predictor for high-altitude pulmonary hypertension. Asymmetric dimethylarginine is a highly regulated molecule, both by its biosynthesis and metabolism. Methylation of L-arginine by protein arginine methyltransferases was shown to be increased in hypoxia. Furthermore, the metabolism of asymmetric dimethylarginine by dimethylarginine dimethylaminohydrolases (DDAH1 and DDAH2) is decreased in animal models of hypoxia. Whether these changes are caused by transcriptional or posttranslational modifications remains to be elucidated. Current data suggest a major role of asymmetric dimethylarginine in regulating pulmonary arterial nitric oxide production in hypoxia. Further studies are needed to decipher the molecular mechanisms regulating asymmetric dimethylarginine in hypoxia and to understand their clinical significance.

Pulmonary Hypertension Subtypes and Mortality in CKD

RATIONALE & OBJECTIVE

Pulmonary hypertension (PH) contributes to cardiovascular disease and mortality in patients with chronic kidney disease (CKD), but the pathophysiology is mostly unknown. This study sought to estimate the prevalence and consequences of PH subtypes in the setting of CKD.

STUDY DESIGN

Observational retrospective cohort study.

SETTING & PARTICIPANTS

We examined 12,618 patients with a right heart catheterization in the Duke Databank for Cardiovascular Disease from January 1, 2000, to December 31, 2014.

EXPOSURES

Baseline kidney function stratified by CKD glomerular filtration rate category and PH subtype.

OUTCOMES

All-cause mortality.

ANALYTICAL APPROACH

Multivariable Cox proportional hazards analysis.

RESULTS

In this cohort, 73.4% of patients with CKD had PH, compared with 56.9% of patients without CKD. Isolated postcapillary PH (39.0%) and combined pre- and postcapillary PH (38.3%) were the most common PH subtypes in CKD. Conversely, precapillary PH was the most common subtype in the non-CKD cohort (35.9%). The relationships between mean pulmonary artery pressure, pulmonary capillary wedge pressure, and right atrial pressure with mortality were similar in both the CKD and non-CKD cohorts. Compared with those without PH, precapillary PH conferred the highest mortality risk among patients without CKD (HR, 2.27; 95% CI, 2.00-2.57). By contrast, in those with CKD, combined pre- and postcapillary PH was associated with the highest risk for mortality in CKD in adjusted analyses (compared with no PH, HRs of 1.89 [95% CI, 1.57-2.28], 1.87 [95% CI, 1.52-2.31], 2.13 [95% CI, 1.52-2.97], and 1.63 [95% CI, 1.12-2.36] for glomerular filtration rate categories G3a, G3b, G4, and G5/G5D).

LIMITATIONS

The cohort referred for right heart catheterization may not be generalizable to the general population. Serum creatinine data in the 6 months preceding catheterization may not reflect true baseline CKD. Observational design precludes assumptions of causality.

CONCLUSIONS

In patients with CKD referred for right heart catheterization, PH is common and associated with poor survival. Combined pre- and postcapillary PH was common and portended the worst survival for patients with CKD.

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.

Clinical Value of Asymmetrical Dimethylarginine Detection in Patients with Connective Tissue Disease-Associated Pulmonary Arterial Hypertension

Objective

To evaluate the clinical value of serum asymmetrical dimethylarginine (ADMA) in patients with connective tissue disease- (CTD-) associated pulmonary arterial hypertension (PAH).

Methods

88 patients with CTD were recruited between December 2017 and August 2018 in Jiangxi Provincial People's Hospital. Patients were further divided into two groups: CTD-without PAH (n = 45 cases) and CTD-with PAH (n = 43 cases), according to the pulmonary systolic blood pressure measured by echocardiography. 40 healthy controls were also included (n = 40 cases). The clinical data, including laboratory examinations, echocardiographic measurements, pulmonary function, and serum ADMA levels determined by enzyme-linked immunosorbent assay, (ELISA) were collected. The correlation between ADMA levels and the occurrence of PAH, pulmonary function, and other laboratory indexes in CTD patients were analyzed. Statistical analyses were performed by SPSS (version 23); P < 0.05 was considered statistically significant.

Results

The serum levels of ADMA in the CTD-PAH group were significantly higher than those of the CTD-without PAH group and healthy control group (P < 0.05); the serum ADMA levels were (0.706 ± 0.153 μmol/L), (1.015 ± 0.122 μmol/L), and (0.661 ± 0.113 μmol/L), respectively. There was no significant difference between the CTD-without PAH group and healthy control group (P < 0.05). Correlation analysis showed that serum ADMA levels were positively correlated with sPAP and NT-proBNP and negatively correlated with DLCO% (r = 0.802, 0.475, −0.585, P < 0.001). Multivariate analysis indicated that elevated serum ADMA levels increased the risk for the appearance of PAH in CTD patients (OR = 57.460, P < 0.001). Using the receiver operating characteristic (ROC) curve analysis, at the cutoff level of 0.810 μmol/L, ADMA showed good diagnostic efficacy as follows: sensitivity was 97.7%, specificity was 75.6%, and the area under the curve (AUC) was 0.947 (P < 0.001).

Conclusion

Increased ADMA levels are independently associated with the presence and severity of PAH in CTD patients. The levels of ADMA in the serum may contribute to be a noninvasive indicator for early diagnosis of CTD-with PAH patients.

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.

Biomarkers for Pulmonary Vascular Remodeling in Systemic Sclerosis: A Pathophysiological Approach

Pulmonary arterial hypertension (PAH) is a severe complication of systemic sclerosis (SSc) associated with high morbidity and mortality. There are several biomarkers of SSc-PAH, reflecting endothelial physiology, inflammation, immune activation, extracellular matrix, metabolic changes, or cardiac involvement. Biomarkers associated with diagnosis, disease severity and progression have been identified, however, very few have been tested in a prospective setting. Some antinuclear antibodies such as nucleosome antibodies (NUC), anti-centromere antibodies (CENP-A/B) and anti-U3-ribonucleoprotein (anti-U3-RNP) are associated with PAH while anti-U1-ribonucleoprotein (anti-U1-RNP) is associated with a reduced PAH risk. Anti-endothelin receptor and angiotensin-1 receptor antibodies might be good markers of SSc-PAH and progression of pulmonary vasculopathy. Regarding the markers reflecting immune activation and inflammation, there are many inconsistent results. CXCL-4 was associated with SSc progression including PAH and lung fibrosis. Growth differentiation factor (GDF)-15 was associated with PAH and mortality but is not specific for SSc. Among the metabolites, kynurenine was identified as diagnostic marker for PAH, however, its pathologic role in the disease is unclear. Endostatin, an angiostatic factor, was associated with heart failure and poor prognosis. Established heart related markers, such as N-terminal fragment of A-type natriuretic peptide/brain natriuretic peptide (NT-proANP, NT-proBNP) or troponin I/T are elevated in SSc-PAH but are not specific for the right ventricle and may be increased to the same extent in left heart disease. Taken together, there is no universal specific biomarker for SSc-PAH, however, there is a pattern of markers that is strongly associated with a risk of vascular complications in SSc patients. Further comprehensive, multicenter and prospective studies are warranted to develop reliable algorithms for detection and prognosis of SSc-PAH.

Plasma L-arginine levels distinguish pulmonary arterial hypertension from left ventricular systolic dysfunction

Pulmonary arterial hypertension (PAH) is a life-threatening condition, characterized by an imbalance of vasoactive substances and remodeling of pulmonary vasculature. Nitric oxide, formed from L-arginine, is essential for homeostasis and smooth muscle cell relaxation in PAH. Our aim was to compare plasma concentrations of L-arginine, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) in PAH compared to left ventricular systolic dysfunction (LVSD) and healthy subjects. This was an observational, multicenter study comparing 21 patients with PAH to 14 patients with LVSD and 27 healthy subjects. Physical examinations were obtained and blood samples were collected. Plasma levels of ADMA, SDMA, L-arginine, L-ornithine, and L-citrulline were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Plasma levels of ADMA and SDMA were higher, whereas L-arginine and L-arginine/ADMA ratio were lower in PAH patients compared to healthy subjects (p < 0.001). Patients with PAH also had lower levels of L-arginine than patients with LVSD (p < 0.05). L-Arginine correlated to 6 min walking distance (6MWD) (r _s = 0.58, p = 0.006) and L-arginine/ADMA correlated to WHO functional class (r _s = -0.46, p = 0.043) in PAH. In conclusion, L-arginine levels were significantly lower in treatment naïve PAH patients compared to patients with LVSD. Furthermore, L-arginine correlated with 6MWD in PAH. L-arginine may provide useful information in differentiating PAH from LVSD.

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.

Endogenous Asymmetric Dimethylarginine Pathway in High Altitude Adapted Yaks

Hypoxia-induced and high altitude pulmonary hypertension are a major problem in the mountain areas of the world. The asymmetric methylarginines (ADMA) inhibit nitric oxide (NO) synthesis by competing with L-arginine, and high levels of plasma ADMA predict adverse outcomes in pulmonary hypertension. However, little is known about the regulation of the ADMA-NO pathway in animals adapted to high altitudes. We measured the plasma ADMA concentration, endothelial NO synthase (eNOS), dimethylarginine dimethylaminohydrolases (DDAH) protein expression, and DDAH activities in the lungs from yaks. Although the yaks are hypoxemic, cardiac function and pulmonary arterial pressures are almost normal, and we found decreased DDAH expression and activity in association with reduced plasma ADMA concentrations. The eNOS expression was significantly higher in yaks. These results indicate that augmented endogenous NO activity in yaks through the ADMA-DDAH pathway and eNOS upregulation account for the low pulmonary vascular tone observed in high altitude adapted yaks.

Acute vasodilator response to vardenafil and clinical outcome in patients with pulmonary hypertension

PURPOSE

Acute vasodilator testing is recommended in patients with pulmonary arterial hypertension to identify individuals who may benefit from long-term treatment with oral calcium channel blockers. The aim of this study was to investigate the use of vardenafil in acute vasoreactivity testing compared to adenosine.

METHODS

A total of 20 patients eligible for right heart catheterisation were enrolled. Acute vasoreactivity testing was carried out with intravenous (iv) adenosine (n = 18) followed by oral vardenafil (n = 20). Haemodynamic responses were recorded at baseline and after 60 min (vardenafil). Responders were defined according to consensus guideline criteria.

RESULTS

Both vardenafil and adenosine significantly decreased mean pulmonary arterial pressure (mPAP, p < 0.001 and p = 0.026, respectively) and pulmonary vascular resistance (p < 0.001 and p > 0.001, respectively), and significantly increased cardiac output (p = 0.001 and p = 0.005, respectively). Vardenafil reduced mPAP more than adenosine (p = 0.044), while adenosine resulted in higher responses of cardiac index (p = 0.009) and pulmonary arterial oxygen saturation (p = 0.042). Acute adverse reactions were common with adenosine, while no side effects were observed after a single oral dose vardenafil. Vardenafil identified five responders (out of 20), while adenosine identified three responders (out of 18). During a 7-year follow-up, vardenafil responders had significantly lower NT-proBNP levels compared to non-responders.

CONCLUSIONS

Vardenafil may be safely used for acute vasoreactivity testing in patients with PH. A single oral dose of vardenafil is better tolerated than iv adenosine and may identify additional responders who could benefit from long-term vasodilator treatment.

Changes in plasma levels of asymmetric dimethylarginine, symmetric dimethylarginine, and arginine after a single dose of vardenafil in patients with pulmonary hypertension

OBJECTIVE

We investigated whether vardenafil, a phosphodiesterase-5 inhibitor, alters plasma levels of asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and arginine.

PATIENTS AND METHODS

ADMA, SDMA, and arginine were measured (0-540 min) in 12 patients with pulmonary hypertension after a single oral dose of vardenafil. Invasive hemodynamic data were collected at baseline and after 60 min.

RESULTS

A reduction in ADMA was observed at 30 and 45 min with a median change of -11.1% (P=0.021) and -12.5% (P=0.002). SDMA decreased with a median -5.3% change (P=0.032) at 45 min. An increase in arginine, median 40.3% (P=0.002), 45.0% (P=0.010), and 77.1% (P=0.008) was observed at 120, 300, and 540 min respectively. An increase in the arginine/ADMA ratio, median 11.7% (P=0.012), 32.5% (P=0.003), 26.5% (P=0.021), 33% (P=0.007), 48.5% (P=0.007), and 63.1% (P=0.008) was observed at 15, 45, 60, 120, 300, and 540 min respectively. There was a positive correlation between vardenafil exposure and the percent change in the arginine/ADMA ratio from baseline to 540 min (r=0.80; P=0.01). A correlation between baseline mean right atrial pressure (mRAP) and baseline ADMA (r=0.65; P=0.023), and baseline SDMA (r=0.61; P=0.035) was observed. A correlation between the baseline arginine/ADMA ratio and baseline cardiac output (CO) (r=0.59; P=0.045) and baseline cardiac index (CI) (r=0.61; P=0.036) was observed. Baseline arginine/ADMA ratio correlated with baseline mRAP (r=-0.79; P=0.002). A correlation between change (0-60 min) in CI and change in arginine (r=0.77; P=0.003) as well as change in the arginine/ADMA ratio (r=0.61; P=0.037) was observed.

CONCLUSIONS

Vardenafil induced changes in ADMA, SDMA, arginine, and the arginine/ADMA ratio in patients with PH. An increase in arginine and the arginine/ADMA ratio was associated with improvement in CI.

Increased levels of asymmetric dimethylarginine are associated with pulmonary arterial hypertension in HIV infection

OBJECTIVE

To examine the relationship between asymmetric dimethylarginine (ADMA) and HIV-associated pulmonary arterial hypertension (PAH).

DESIGN

HIV infection is an independent risk factor for PAH, but the underlying pathogenesis remains unclear. Chronic inflammation resulting in nitric oxide-mediated endothelial dysfunction is a key mechanism underlying other types of PAH. ADMA is an endogenous inhibitor of endothelial nitric oxide synthase. Among uninfected individuals, ADMA is associated with PAH and predicts disease-related mortality.

METHODS

We measured ADMA, high sensitivity C-reactive protein, interleukin-6 (IL-6), D-dimer, and pulmonary artery systolic pressure (PASP) using echocardiography in HIV-infected individuals. Right heart catheterization (RHC) was performed in individuals with a PASP at least 30  mmHg. We performed multivariable analysis to identify factors associated with high PASP by echocardiogram and PAH by RHC.

RESULTS

Among 214 HIV-infected individuals, the median age was 50 years, 82% were men, 71% were on antiretroviral therapy, and 4.2% carried a prior diagnosis of PAH. ADMA and IL-6 were associated with increased values of PASP following multivariable adjustment (7.2% per 0.1 μmol/l, P = 0.0049 and 3.9% per doubling, P = 0.027, respectively). In adjusted analysis among the 85 participants who underwent RHC, ADMA and IL-6 were associated with higher values of mean PAP (14.2% per 0.1 μmol/l, P = 0.0014 and 5.8% per doubling, P = 0.038, respectively). However, only ADMA was associated with PAH (prevalence ratio = 1.74, P = 0.029).

CONCLUSION

Elevated levels of ADMA are independently associated with PAH among HIV-infected individuals. Our findings suggest that chronic HIV-associated inflammation leading to an accumulation of ADMA and subsequent nitric oxide-mediated endothelial dysfunction may represent a novel mechanism for HIV-associated PAH.

Biological functional relevance of asymmetric dimethylarginine (ADMA) in cardiovascular disease

There is growing evidence that increased levels of the endogenous NO synthase inhibitor asymmetric dimethylarginine (ADMA) may contribute to endothelial dysfunction. Studies in animal models as well as in humans have suggested that the increase in ADMA occurs at a time when vascular disease has not yet become clinically evident. ADMA competitively inhibits NO elaboration by displacing L-arginine from NO synthase. In a concentration-dependent manner, it thereby interferes not only with endothelium-dependent, NO-mediated vasodilation, but also with other biological functions exerted by NO. The upshot may be a pro-atherogenic state. Recently, several studies have investigated the effect of various therapeutical interventions on ADMA plasma concentrations.

Correlations of DDAH1 transcript variants with human endothelial asymmetric dimethylarginine metabolizing activity

BACKGROUND

Dimethylarginine dimethylaminohydrolases 1 (DDAH1) is the major enzyme responsible for inactivation of asymmetric dimethylarginine (ADMA). This study seeks to clarify the correlations between mRNA expression levels of DDAH1 transcript variants and the relationship with ADMA metabolizing activity in human.

METHODS

The mRNA expression levels of DDAH1 transcript variants in primarily cultured human umbilical vein endothelial cells (HUVECs) and peripheral blood mononuclear cells (PBMCs) from healthy control subjects and patients suffering from both acute ischemic stroke (AIS) and acute myocardial infarction (AMI) were determined by real-time polymerase chain reaction. ADMA metabolizing activity of the cell lysates from HUVECs was determined by enzyme-linked immunosorbent assay.

RESULTS

A novel DDAH1 transcript variant DDAH1-V3 was identified. DDAH1-V3 mRNA expression correlated significantly with that of both -V2 (R = 0.811; P = 0.000008) and -V1 (R = 0.454; P = 0.04) in HUVECs. In PBMCs from healthy subjects, significant correlation was observed only between DDAH1-V2 and -V3 (R = 0.571; P = 0.001; n = 36). Delta threshold cycle (DCT) values for both DDAH1-V2 and -V3 transcripts were increased significantly in PBMCs from AIS patients (P < 0.05, respectively). In PBMCs from patients suffering from both AIS and AMI, positive pairwise correlations between mRNA levels of DDAH1 transcripts were also observed as analyzed by partial correlation analysis (P < 0.05, respectively). However, only mRNA expression level of the DDAH1-V1 transcript correlated significantly with intracellular ADMA metabolizing activity in HUVECs (R = 0.805; P=0.002).

CONCLUSIONS

This study demonstrated that although there are positive correlations between mRNA expression levels of DDAH1 transcript variants, only the DDAH1-V1 transcript is responsible for ADMA metabolism, and transcript specific primers are recommended to determine DDAH1 mRNA expression.

Serum endothelin-1 and NT-proBNP, but not ADMA, endoglin and TIMP-1 levels, reflect impaired right ventricular function in patients with systemic sclerosis

Background

Heart and pulmonary involvement is a leading cause of systemic sclerosis (SSc)-related deaths.

Objectives

The aim of our study was to assess if biochemical markers of right ventricular (RV) overload, endothelial function and collagen metabolism can predict RV dysfunction assessed by Doppler echocardiography in SSc patients.

Methods

We prospectively studied 111 consecutive patients (101 F, 10 M, age 54.2 ± 13.8 years) with diagnosed SSc (mean disease duration 9.4 ± 11.4 years) and a group of 21 age-matched subjects (18 F, 3 M, age 49.3 + 10.5 years). We performed transthoracic echocardiography (Phillips iE 33) and measured serum endothelin-1 (ET-1), N-terminal pro-brain natriuretic peptide (NT-proBNP), asymmetric dimethylarginine (ADMA), endoglin and human tissue inhibitor of matrix metalloproteinase (TIMP-1) concentration.

Results

Median serum NT-proBNP level in SSc patients was 133.5 (range 21.86–17,670 pg/ml) and was significantly higher than in controls (p = 0.0002). Moreover, the median serum ET-1 level of 1.49 (range 0.26–8.75 pg/ml) was higher in SSc patients (p = 0.002). However, no significant differences in ADMA, TIMP-1 and endoglin serum concentration between SSc patients and controls were observed. Serum NT-proBNP concentration correlated positively with echocardiographic signs of RV overload: tricuspid regurgitation pressure gradient (r = 0.38, p = 0.0004) and RV Tei index (r = 0.25, p = 0.01). ET-1 serum level correlated negatively with tricuspid annular plane systolic excursion (r = −0.4, p = 0.01) and positively with inferior vena cava diameter measured at expiration (r = 0.38, p = 0.0002). The echocardiographic signs of RV overload were significantly more pronounced in the highest NT-proBNP tertile (>195 pg/ml) group than in the lowest one (<88 pg/ml).

Conclusions

Serum ET-1 and NT-proBNP, but not endoglin, ADMA and TIMP-1 levels correlating with the echocardiographic parameters of RV overload, can be considered as noninvasive indicators of RV dysfunction in SSc patients.

Pulmonary hypertension in chronic obstructive and interstitial lung diseases

The purpose of the present review is to summarize the current knowledge on PH in relation to COPD and ILD from a clinical perspective with emphasis on diagnosis, biomarkers, prevalence, impact, treatment, and practical implications. PH in COPD and ILD is associated with a poor prognosis, and is considered one of the most frequent types of PH. However, the prevalence of PH among patients with COPD and ILD is not clear. The diagnosis of PH in chronic lung disease is often established by echocardiographic screening, but definitive diagnosis requires right heart catheterization, which is not systematically performed in clinical practice. Given the large number of patients with chronic lung disease, biomarkers to preclude or increase suspicion of PH are needed. NT-proBNP may be used as a rule-out test, but biomarkers with a high specificity for PH are still required. It is not known whether specific treatment with existent drugs effective in pulmonary arterial hypertension (PAH) is beneficial in lung disease related PH. Studies investigating existing PAH drugs in animal models of lung disease related PH have indicated a positive effect, and so have case reports and open label studies. However, treatment with systemically administered pulmonary vasodilators implies the risk of worsening the ventilation-perfusion mismatch in patients with lung disease. Inhaled vasodilators may be better suited for PH in lung disease, but new treatment modalities are also required.

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.

Protein Arginine Methyltransferases (PRMTs): promising targets for the treatment of pulmonary disorders

Protein arginine methylation is a novel posttranslational modification that plays a pivotal role in a variety of intracellular events, such as signal transduction, protein-protein interaction and transcriptional regulation, either by the direct regulation of protein function or by metabolic products originating from protein arginine methylation that influence nitric oxide (NO)-dependent processes. A growing body of evidence suggests that both mechanisms are implicated in cardiovascular and pulmonary diseases. This review will present and discuss recent research on PRMTs and the methylation of non-histone proteins and its consequences for the pathogenesis of various lung disorders, including lung cancer, pulmonary fibrosis, pulmonary hypertension, chronic obstructive pulmonary disease and asthma. This article will also highlight novel directions for possible future investigations to evaluate the functional contribution of arginine methylation in lung homeostasis and disease.

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.

Increased plasma and salivary nitrite and decreased bronchial contribution to exhaled NO in pulmonary arterial hypertension

BACKGROUND

Conflicting results on exhaled NO in pulmonary hypertension (PH) exist. Therefore, we analysed exhaled NO, as well as systemic and local nitrite, a possible alternative source of NO, in PH with regard to PH aetiology.

METHODS

Exhaled NO at multiple flow-rates, as well as plasma and salivary nitrite and nitrate, was measured in 22 patients with PH and 21 healthy controls. Alveolar NO (Calv(NO) ) and bronchial flux (J'aw(NO) ) were calculated using the slope-intercept model. Patients with PH were subdivided into pulmonary arterial hypertension (PAH) and PH WHO Groups II-IV, according to the WHO clinical classification of PH.

RESULTS

Exhaled NO was reduced at flow-rates in the range of 20-200 mL s(-1) in patients with PAH (n=13) vs. PH WHO Group II-IV (n=9) (P<0·05 all). Patients with PAH had higher Calv(NO) than healthy controls [2·61 (2·23, 3·36) vs. 1.97ppb (1·22, 2·49), P=0·03] and similar to PH WHO Group II-IV (P=0·51). Patients with PAH had lower J'aw(NO) than patients with PH WHO Group II-IV or healthy controls [430 (371, 702) vs. 807 (557, 993) or 731pLs(-1) (580, 818), P<0·05 both]. Subjects with PAH were characterized by higher levels of salivary and plasma nitrite than healthy controls (P<0·05 both).

CONCLUSIONS

Patients with PAH have lower bronchial NO flux compared to healthy controls and patients with PH WHO Group II-IV along with elevated salivary and plasma nitrite compared to controls. This implies reduced bronchial NO synthase-derived NO formation in PAH. Increased alveolar NO levels were found in subjects with PH compared to controls, especially in subjects with PAH. This may reflect NO diffusion disturbances in the alveoli.

Down syndrome patients with pulmonary hypertension have elevated plasma levels of asymmetric dimethylarginine

Down syndrome (DS) patients have an increased risk of developing pulmonary hypertension (PH). Increased plasma levels of asymmetric dimethylarginine (ADMA) may contribute to vascular dysfunction in adults with idiopathic pulmonary hypertension. Our goal was to test the hypothesis that DS patients with PH have higher plasma levels of ADMA than DS patients without PH. DS patients with definitive PH (n = 6) and DS patients with no evidence of PH (n = 12) were studied. Plasma levels of arginine, ADMA, and nitrite/nitrate (NOx; stable metabolites of nitric oxide (NO)) were measured. Plasma arginine concentration was lower (p < 0.05) in PH patients (23 ± 11 μM) versus non-PH patients (46 ± 24 μM). Plasma ADMA concentration was higher (p < 0.005) in PH patients (18.0 ± 4.2 μM) versus non-PH patients (8.6 ± 5.9 μM). Plasma NOx was lower (p < 0.05) in PH patients (4.5 ± 1.7 μM) versus non-PH patients (8.5 ± 7.3 μM). These results are consistent with ADMA contributing to lower NO production in DS patients with PH and suggest that ADMA levels may be a potential biomarker for PH in DS patients.

The autophagic tumor stroma model of cancer: Role of oxidative stress and ketone production in fueling tumor cell metabolism

A loss of stromal Cav-1 in the tumor fibroblast compartment is associated with early tumor recurrence, lymph-node metastasis, and tamoxifen-resistance, resulting in poor clinical outcome in breast cancer patients. Here, we have used Cav-1 (-/-) null mice as a pre-clinical model for this "lethal tumor micro-environment." Metabolic profiling of Cav-1 (-/-) mammary fat pads revealed the upregulation of numerous metabolites (nearly 100), indicative of a major catabolic phenotype. Our results are consistent with the induction of oxidative stress, mitochondrial dysfunction, and autophagy/mitophagy. The two most prominent metabolites that emerged from this analysis were ADMA (asymmetric dimethyl arginine) and BHB (beta-hydroxybutyrate; a ketone body), which are markers of oxidative stress and mitochondrial dysfunction, respectively. Transcriptional profiling of Cav-1 (-/-) stromal cells and human tumor stroma from breast cancer patients directly supported an association with oxidative stress, mitochondrial dysfunction, and autophagy/mitophagy, as well as ADMA and ketone production. MircoRNA profiling of Cav-1 (-/-) stromal cells revealed the upregulation of two key cancer-related miR's, namely miR-31 and miR-34c. Consistent with our metabolic findings, these miR's are associated with oxidative stress (miR-34c) or activation of the hypoxic response/HIF1a (miR-31), which is sufficient to drive authophagy/mitophagy. Thus, via an unbiased comprehensive analysis of a lethal tumor micro-environment, we have identified a number of candidate biomarkers (ADMA, ketones, and miR-31/34c) that could be used to identify high-risk cancer patients at diagnosis, for treatment stratification and/or for evaluating therapeutic efficacy during anti-cancer therapy. We propose that the levels of these key biomarkers (ADMA, ketones/BHB, miR-31, and miR-34c) could be (1) assayed using serum or plasma from cancer patients, or (2) performed directly on excised tumor tissue. Importantly, induction of oxidative stress and autophagy/mitophagy in the tumor stromal compartment provides a means by which epithelial cancer cells can directly "feed off" of stromal-derived essential nutrients, chemical building blocks (amino acids, nucleotides), and energy-rich metabolites (glutamine, pyruvate, ketones/BHB), driving tumor progression and metastasis. Essentially, aggressive cancer cells are "eating" the cancer-associated fibroblasts via autophagy/mitophagy in the tumor micro-environment. Lastly, we discuss that this "Autophagic Tumor Stroma Model of Cancer Metabolism" provides a viable solution to the "Autophagy Paradox" in cancer etiology and chemo-therapy.

Left atrial volume and N-terminal pro-B type natriuretic peptide are associated with elevated pulmonary artery pressure in patients with systemic sclerosis

Early detection of pulmonary hypertension (PH) in patients with systemic sclerosis (SSc) is essential as it leads to substantial morbidity and mortality irrespective of its etiology. The aim of our study was to determine whether noninvasive biochemical and/or echocardiographic indices can predict the presence of PH in these patients. We prospectively studied 66 patients (mean age of 57.7 +/- 12.1 years, 63 women) with SSc without clinical manifestations of heart failure. All patients underwent standard and tissue Doppler echocardiography. Plasma N-terminal pro-B type natriuretic peptide (NT-proBNP) and asymmetric dimethylarginine (ADMA) levels were also measured. In 24 (36%) patients, the diagnosis of PH was established by echocardiography (systolic pulmonary artery pressure value > or =40 mmHg). Left atrial (LA) volume, NT-proBNP, ADMA, ratio of early transmitral filling velocity to early diastolic velocity of the mitral annulus (mitral E/E (m)), and right ventricular myocardial performance index (MPI) were univariate predictors of PH. In multivariate analysis, NT-proBNP, LA volume, and right ventricular MPI were independent predictors of PH in SSc patients. LA volume and NT-proBNP may be useful noninvasive markers for the prediction of elevated pulmonary artery pressure in patients with SSc. These parameters should be considered when assessing this population for risk stratification and for identification of patients demanding further investigation and institution of specific therapy for the disease at the time when it is most likely to be effective.

Early Detection of Cardiac Involvement in Systemic Sclerosis Assessed by Tissue-Doppler Echocardiography: Relationship with Neurohormonal Activation and Endothelial Dysfunction

Objective.

Cardiopulmonary complications are common in patients with systemic sclerosis (SSc). We assessed cardiac involvement in patients with SSc using echocardiography and investigated the association of N-terminal pro-brain natriuretic peptide (NT-proBNP) and asymmetric dimethylarginine (ADMA) with echocardiographic measures of myocardial function in sera of patients with SSc who had no symptoms of heart failure.

Methods.

We prospectively studied 52 patients with SSc (mean age 55.7 ± 10.1 yrs, 51 women), with conventional and tissue-Doppler echocardiography. Plasma NT-proBNP and ADMA levels were measured in all patients. Data were compared with those obtained from 25 healthy controls comparable for age and sex.

Results.

Patients with SSc had impaired left ventricular (LV) and right ventricular diastolic function expressed by inverted ratio of peak early to peak late transmitral (Mit E/A) and transtricuspid velocity and increased left atrial diameter compared with controls. Peak systolic mitral lateral annular motion velocity and peak early diastolic mitral lateral annular motion velocity (LV Em) were lower, while LV E/Em ratio was higher, in patients with SSc compared to controls. ADMA was significantly related with LV Em and E/Em ratio. NT-proBNP was associated with Mit E, Mit E/A ratio and mitral deceleration time. Significant correlation was also observed between NT-proBNP and ADMA levels.

Conclusion.

Depressed cardiac function is common, even in asymptomatic patients with SSc. NT-proBNP and ADMA are significantly correlated with echocardiographic abnormalities, providing a potent link for cardiac function, neuroendocrine derangement, and endothelial dysfunction in patients with SSc who have cardiac disease.

From arginine methylation to ADMA: a novel mechanism with therapeutic potential in chronic lung diseases

Protein arginine methylation is a novel posttranslational modification regulating a diversity of cellular processes, including protein-protein interaction, signal transduction, or histone function. It has recently been shown to be dysregulated in chronic renal, vascular, and pulmonary diseases, and metabolic products originating from protein arginine methylation have been suggested to serve as biomarkers in cardiovascular and pulmonary diseases.

Protein arginine methylation is performed by a class of enzymes called protein arginine methyltransferases (PRMT), which specifically methylate protein-incorporated arginine residues to generate protein-incorporated monomethylarginine (MMA), symmetric dimethylarginine (SDMA), or asymmetric dimethylarginine (ADMA). Upon proteolytic cleavage of arginine-methylated proteins, free intracellular MMA, SDMA, or ADMA is generated, which, upon secretion into the extracellular space (including plasma), directly affects the methylarginine concentration in the plasma. Free methylarginines are cleared from the body by renal excretion or hepatic metabolism. In addition, MMA and ADMA, but not SDMA, can be degraded via a class of intracellular enzymes called dimethylarginine dimethylaminohydrolases (DDAH).

ADMA and MMA are endogenous inhibitors of nitric oxide synthases (NOS) and ADMA has been suggested to serve as a biomarker of endothelial dysfunction in cardiovascular diseases. This view has now been extended to the idea that, in addition to serum ADMA, the amount of free, as well as protein-incorporated, intracellular ADMA influences pulmonary cell function and determines the development of chronic lung diseases, including pulmonary arterial hypertension (PAH) or pulmonary fibrosis. This review will present and discuss the recent findings of dysregulated arginine methylation in chronic lung disease. We will highlight novel directions for future investigations evaluating the functional contribution of arginine methylation in lung homeostasis and disease with the outlook that modifying PRMT or DDAH activity presents a novel therapeutic option for the treatment of chronic lung disease.