Advanced glycation endproducts are increased in rheumatoid arthritis patients with controlled disease

Correction for tissue optical properties enables quantitative skin fluorescence measurements using multi-diameter single fiber reflectance spectroscopy

BACKGROUND AND OBJECTIVE

Fluorescence measurements in the skin are very much affected by absorption and scattering but existing methods to correct for this are not applicable to superficial skin measurements.

STUDY DESIGN/MATERIALS AND METHODS

The first use of multiple-diameter single fiber reflectance (MDSFR) and single fiber fluorescence (SFF) spectroscopy in human skin was investigated. MDSFR spectroscopy allows a quantification of the full optical properties in superficial skin (μa, μs' and γ), which can next be used to retrieve the corrected - intrinsic - fluorescence of a fluorophore Qμa,x(f). Our goal was to investigate the importance of such correction for individual patients. We studied this in 22 patients undergoing photodynamic therapy (PDT) for actinic keratosis.

RESULTS

The magnitude of correction of fluorescence was around 4 (for both autofluorescence and protoporphyrin IX). Moreover, it was variable between patients, but also within patients over the course of fractionated aminolevulinic acid PDT (range 2.7-7.5). Patients also varied in the amount of protoporphyrin IX synthesis, photobleaching percentages and resynthesis (>100× difference between the lowest and highest PpIX synthesis). The autofluorescence was lower in actinic keratosis than contralateral normal skin (0.0032 versus 0.0052; P<0.0005).

CONCLUSIONS

Our results clearly demonstrate the importance of correcting the measured fluorescence for optical properties, because these vary considerably between individual patients and also during PDT. Protoporphyrin IX synthesis and photobleaching kinetics allow monitoring clinical PDT which facilitates individual-based PDT dosing and improvement of clinical treatment protocols. Furthermore, the skin autofluorescence can be relevant for diagnostic use in the skin, but it may also be interesting because of its association with several internal diseases.

Oxidative stress markers are increased in patients with mastocytosis

BACKGROUND

Mastocytosis is characterized by clonal proliferation of mast cells limited to the skin (cutaneous mastocytosis: CM and mastocytosis in the skin: MIS) and/or involving internal organs (systemic mastocytosis: SM). Oxidative stress occurring in various inflammatory and neoplastic disorders causes molecular damage with the production of advanced oxidation protein products (AOPPs) and advanced glycation end products (AGEs). We evaluated these markers of oxidative stress in patients with CM/MIS and SM and correlated their levels with the presence of symptoms related to mast cell activation.

METHODS

Serum levels of AOPPs and AGEs in 34 patients with mastocytosis (23 CM/MIS and 11 SM) and 27 healthy controls were measured by spectrofluorimetric and spectrophotometric methods. Serum tryptase levels were measured by immunofluorescence.

RESULTS

Serum AOPPs, but not AGEs, were significantly higher in patients with mastocytosis as compared to healthy controls. While serum tryptase levels were higher in patients with SM as compared to those with CM/MIS, there was no difference in AOPP and AGE concentrations between these two groups of patients. Patients with recurrent mediator-related symptoms had lower AOPPs and AGEs as compared to patients without symptoms. AOPPs and AGEs were inversely correlated with the severity of symptoms, and in patients with symptoms, AOPPs correlated with tryptase levels.

DISCUSSION

Our data show that mastocytosis is associated with a state of increased oxidative stress that, in patients with mediator-related symptoms, correlates with mast cell burden as assessed by tryptase. Patients with symptoms presumably have an adaptive response resulting in lower blood levels of AOPPs and AGEs.

Roles of claudin-5 and von Willebrand factor in patients with rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disorder that affects approximately 1% of the world's population. The pathogenesis of RA is not understood fully. It is assumed that endothelial function is associated with the proinflammatory state of RA. Endothelial dysfunction/activation reflects the increased level of von Willebrand factor (vWF) and a shift toward prothrombotic activity of the endothelium. The present study was performed to investigate the possible relationships between vWF and claudin-5 and the level of disease activity in patients with RA. The study population was divided into four groups according to the disease activity score in 28 joints (DAS28): remission group (RG), 18 patients (DAS28 < 2.6); low disease activity group (LDAG), 23 patients (DAS28 > 2.6-3.2); moderate disease activity (MDAG), 23 patients (DAS28 > 3.2-5.1); high disease activity group (HDAG), 14 patients (DAS28 > 5.1); and control group (CG), 10 healthy subjects. Claudin-5 and vWF assessment were derived from serum samples gathered from the patients known to have RF and anti-CCP titers in the normal ranges. A high positive association of claudin-5 and vWF with the MDAG was observed (P < 0.001). The results of our study indicated that the relationship between vWF and claudin-5, which are indicators of endothelial cell dysfunction and tight junction activity, may be a predictor of disease activity. Further studies are required to investigate these pathways to shed light on the roles of claudin-5 and vWF in the progression of inflammation and other vascular conditions.

Assessment of the usefulness of skin autofluorescence as an indicator of disease activity and of the risk of developing diabetes in patients suffering from rheumatoid arthritis

Objectives

Diabetes develops much more often in patients suffering from rheumatoid arthritis (RA) than in healthy population. One of the parameters which allow to evaluate the risk of developing diabetes and cardiovascular diseases (CVD) is the level of advanced glycation end products (AGE) in the skin. In patients suffering from RA, an increase in AGE level may be also linked with the course of the underlying disease. The aim of the study was to evaluate the correlation between the AGE level and the course of RA as well as other risk factors for the development of diabetes and CVD.

Material and methods

The study included 148 patients divided into three groups: group I – patients with RA (n = 102, 79 F/23 M), group II – patients with RA and diabetes (n = 21, 14 F/7 M), group III – healthy individuals (n = 25, 16 F/9 M). Each patient underwent a skin autofluorescence signal (SAF) examination with an AGE Reader, which allows the assessment of AGE level, as well as being subjected to the laboratory tests panel. Additionally, patients from group I and II have had their DAS28 (ESR) indicator calculated.

Results

In groups I, II, and III, the respective mean SAF values, expressed in arbitrary units [au], were to 2.54, 2.74, and 1.96 au. Between-group differences in terms of mean SAF values were statistically significant (p < 0.05).

Conclusions

Significantly higher mean SAF values in groups I and II as compared to group III suggest that the increase in the AGE level in patients with RA is linked with the underlying disease and does not have to correspond with the real risk of diabetes and CVD. In conclusion, despite the known limitations of the technique, measuring AGE levels allows for closer monitoring of RA patients who are at a higher risk of developing diabetes.

Vascular effects of advanced glycation endproducts: Clinical effects and molecular mechanisms

The enhanced generation and accumulation of advanced glycation endproducts (AGEs) have been linked to increased risk for macrovascular and microvascular complications associated with diabetes mellitus. AGEs result from the nonenzymatic reaction of reducing sugars with proteins, lipids, and nucleic acids, potentially altering their function by disrupting molecular conformation, promoting cross-linking, altering enzyme activity, reducing their clearance, and impairing receptor recognition. AGEs may also activate specific receptors, like the receptor for AGEs (RAGE), which is present on the surface of all cells relevant to atherosclerotic processes, triggering oxidative stress, inflammation and apoptosis. Understanding the pathogenic mechanisms of AGEs is paramount to develop strategies against diabetic and cardiovascular complications.

Skin autofluorescence relates to soluble receptor for advanced glycation end-products and albuminuria in diabetes mellitus

The aim of this study was to compare skin autofluorescence caused by advanced glycation end-products (AGEs) with biochemical markers of endothelial dysfunction and soluble receptor for AGEs (sRAGE) in patients with diabetes. Skin autofluorescence (AF) assessed by AGE-Reader was evaluated with sRAGE and other biochemical parameters in 88 patients with diabetes (47 Type 1/T1DM/ and 41 Type 2/T2DM/) and 20 controls. Skin AF was significantly higher in T1DM and T2DM in comparison to controls (2.39 ± 0.54, 2.63 ± 0.73 versus 1.96 ± 0.33 AU; P < 0.0001). Positive correlation of AF with sRAGE was detected in T1DM and T2DM (r = 0.37, P < 0.02 and r = 0.60, P < 0.0001), but not in controls. Significantly higher AF values were found in patients with positive albuminuria as compared to those with normal albuminuria. Similarly, higher AF was detected in patients with endothelial dysfunction expressed by vWF, ICAM-1, and VCAM-1. Multiple regression analysis revealed independent association of skin AF with age, sRAGE, and albumin-creatinine ratio in patients with diabetes (R (2) = 0.38). Our study confirms that AF is elevated in patients with diabetes, especially with positive albuminuria and endothelial dysfunction. The strong and independent relationship between AF and sRAGE supports the idea that AF may reflect AGEs/RAGE interactions. The exact mechanism remains to be established.