Altered levels of exhaled nitric oxide in rheumatoid arthritis

Exhaled Nitric Oxide Reflects the Immune Reactions of the Airways in Early Rheumatoid Arthritis

Patients with rheumatoid arthritis (RA) have altered levels of exhaled nitric oxide (NO) compared with healthy controls. Here, we investigated whether the clinical features of and immunological factors in RA pathogenesis could be linked to the NO lung dynamics in early disease. A total of 44 patients with early RA and anti-citrullinated peptide antibodies (ACPAs), specified as cyclic citrullinated peptide 2 (CCP2), were included. Their exhaled NO levels were measured, and the alveolar concentration, the airway compartment diffusing capacity and the airway wall concentration of NO were estimated using the Högman-Meriläinen algorithm. The disease activity was measured using the Disease Activity Score for 28 joints. Serum samples were analysed for anti-CCP2, rheumatoid factor, free secretory component, secretory component containing ACPAs, antibodies against Porphyromonas gingivalis (Rgp) and total levels of IgA, IgA1 and IgA2. Significant negative correlations were found between the airway wall concentration of NO and the number of swollen joints (Rho -0.48, p = 0.004), between the airway wall concentration of NO and IgA rheumatoid factor (Rho -0.41, p = 0.017), between the alveolar concentration and free secretory component (Rho -0.35, p = 0.023) and between the alveolar concentration and C-reactive protein (Rho -0.36, p = 0.016), but none were found for anti-CCP2, IgM rheumatoid factor or the anti-Rgp levels. In conclusion, altered NO levels, particularly its production in the airway walls, may have a role in the pathogenesis of ACPA-positive RA.

Exhaled nitric oxide in early rheumatoid arthritis and effects of methotrexate treatment

Patients with established rheumatoid arthritis (RA) and disease modifying treatments have lower nitric oxide (NO) levels in the alveolar compartment (C_ANO) and in the airway wall (C_awNO), but also higher diffusion capacities for NO in the airways (D_awNO) compared to matched controls. The aim of the present study was to investigate the NO lung dynamics in patients with recent onset RA before and after immune suppression with methotrexate therapy. Patients with early RA and antibodies against anticitrullinated peptides (ACPA) were recruited. Measurement of exhaled NO and inflammatory markers in serum were performed. Clinical disease activity was evaluated with Disease Activity Score for 28 joints. Healthy individuals were used as matched controls. Data are presented as median (lower quartile, upper quartile) values. RA patients (n = 44) had lower exhaled NO (F_ENO₅₀) 16 (10–24) ppb compared to controls 21 (15, 29) ppb, p = 0.013. In NO-dynamics, C_ANO was lower in RA patients 1.6 (1.0, 2.2) ppb compared to the control subjects 2.3 (1.3, 3.1) ppb, p = 0.007. C_awNO was also lower in the RA patients 55 (24, 106) ppb compared to control subjects 124 (110, 170) ppb, p < 0.001, but D_awNO was higher 17 (8, 30) mL/s and 9 (5, 11) mL/s respectively, p < 0.001. Methotrexate treatment for three months reduced disease activity, but did not change the NO dynamics. In conclusion, the altered NO dynamics of the lung in ACPA-positive RA patients are already present in the early stages of the disease before any treatments and do not change after methotrexate therapy suggesting a role in the pathogenesis.

Determination of nitric oxide using light-emitting diode-based colorimeter with tubular porous polypropylene membrane cuvette

On the basis of the Griess-Saltzman (GS) reaction, an optical device for nitric oxide (NO) detection in exhaled breath and atmosphere was developed by employing the light-emitting diode (LED, 560 nm) as the light source, light-to-voltage converter (LVC) as the detector, and porous polypropylene membrane tube (PPMT) as the cuvette. The PPMT was filled with GS reagents and covered with a coaxial jacket tube for gas collection and color reaction; two ends of the PPMT were connected with the LED and LVC to detect the change of light transmissivity in the wavelength range of 530 to 590 nm mainly. A gas absorber filled with GS reagents was installed prior to another absorber filled with KMnO₄ solution to eliminate the interference of coexisting NO₂. Under the optimized experimental conditions, the device achieved a limit of detection (3σ/k) of 4.4 ppbv for NO detection. The linearity range of this device was divided into two segments, i.e., 25 to 100 ppbv and 50 to 1000 ppbv, with both coefficients of determination > 0.99. The relative standard deviation was 2.7% (n = 9, c = 100 ppbv), and the analytical time was 5.5 min per detection. The minimum detectable quantity was decreased to 1.18 ng, which was ~ 100 times lower than the original GS method (115 ng). The present device was applied for determination of NO in exhaled breath, vehicle exhaust, and air. In addition to satisfactory spiking recoveries (i.e., 103% and 107%), the analytical results of the present device were in agreement with the results obtained by the standard method. These results assured the practicality of the developed device for NO detection in real environmental samples.

Clinical Values of Nitric Oxide Parameters from the Respiratory System

BACKGROUND

Fractional exhaled nitric oxide (FENO) concentration reliably reflects central airway inflammation, but it is not sensitive to changes in the NO dynamics in the lung periphery. By measuring FENO at several different flow rates one can estimate alveolar NO concentration (C_ANO), bronchial NO flux (J_awNO), bronchial wall NO concentration (C_awNO) and the bronchial diffusivity of NO (D_awNO).

OBJECTIVE

We aimed to describe the current knowledge and clinical relevance of NO parameters in different pulmonary diseases.

METHODS

We conducted a systematic literature search to identify publications reporting NO parameters in subjects with pulmonary or systemic diseases affecting the respiratory tract. A narrative review was created for those with clinical relevance.

RESULTS

Estimation of pulmonary NO parameters allows for differentiation between central and peripheral inflammation and a more precise analysis of central airway NO output. C_ANO seems to be a promising marker of parenchymal inflammation in interstitial lung diseases and also a marker of tissue damage and altered gas diffusion in chronic obstructive pulmonary disease and systemic diseases affecting the lung. In asthma, C_ANO can detect small airway involvement left undetected by ordinary FENO measurement. Additionally, C_awNO and D_awNO can be used in asthma to assess if FENO is increased due to enhanced inflammatory activity (increased C_awNO) or tissue changes related to bronchial remodelling (altered D_awNO).

CONCLUSION

NO parameters may be useful for diagnosis, prediction of disease progression and prediction of treatment responses in different parenchymal lung and airway diseases. Formal trials to test the added clinical value of NO parameters are needed.

Protective effect of Traditional Chinese medicine Shuangwu Zhentong Capsule on collagen-induced arthritis in rats and possible mechanisms

The aim of this study was to investigate the protective effect of Traditional Chinese medicine Shuangwu Zhentong Capsule (SZC) on collagen-induced arthritis (CIA) and the possible mechanisms. Sixty rats were randomly divided into control and model: low-, medium-, and high-dose SZC and prednisone acetate (PA) groups, with 10 rats in each group. The CIA model was established in later 5 groups. The rats in low-, medium-, and high-dose SZC groups were intragastricallly administered with SZC, with dose of 0.5, 1, and 2 g/kg, respectively. The PA group was intragastricallly administered with 5 mg/kg PA. The treatment was performed for 3 weeks. Before treatment and after treatment, the paw swelling degree and polyarthritis index score of rats were measured. At the end of experiment, the serum tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and nitric oxide (NO) levels were determined. The expressions of Ras and Raf-1 protein in synovial tissue were detected. Results showed that, after treatment, compared with model group, in high-dose SZC and PA groups, the paw swelling degree, polyarthritis index score, serum TNF-α, IL-1β and NO levels, and synovial tissue Ras and Raf-1 protein levels were significantly decreased, respectively ( P < 0.05). In conclusion, SZC has obvious protective effects on CIA in rats. The mechanisms may be related to its resistance of inflammatory reaction and down-regulation of Ras and Raf-l protein expressions in synovial tissue.

Malar rash is a predictor of subclinical airway inflammation in patients with systemic lupus erythematosus: a pilot study

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic, auto-immune, multi-organ disease that can affect both the skin and the lungs. Malar rash is a common skin manifestation of SLE and is linked to SLE disease activity, whereas lung involvement is a generally negative prognostic factor for these patients. However, a sensitive and non-invasive screening tool for potential lung involvement in SLE patients is still not available.

METHODS

This study aimed to investigate the relationship between malar rash and airway inflammation in adult SLE patients who were not known to have any lung involvement (clinical or radiologic). The study comprised of the measurement of the concentration of NO in exhaled breath or fraction of exhaled nitric oxide (FeNO) and levels were compared between those with and without malar rash. This tool is considered as a sensitive and non-invasive method that is routinely used in patients with asthma or other respiratory diseases to identify airway inflammation.

RESULTS

A total of 125 patients (100 females, 25 males) were enrolled during the study period from January 2011 to December 2014. Patients with malar rash (N = 35) had a significant decrease in serum levels of C4 (p < 0.05) compared to patients without malar rash (N = 90). The mean levels of FeNO in overall patients were 36.44 ± 8.87 ppb. A statistically significant difference in FeNO₅₀ values between patients with malar rash (43.46 ± 6.72 ppb) and without (29.43 ± 3.64 ppb) was found (p < 0.001). FeNO₅₀ values were inversely correlated only with serum C4 (p < 0.01). However, no correlation between FeNO₅₀ values and SLE clinical disease activity scores was found.

CONCLUSIONS

The presence of a malar rash may predict sub-clinical airway inflammation in SLE patients. Further prospective studies are needed to confirm the usefulness of FeNO measurements in monitoring SLE-associated airway inflammation.