Blood levels of inflammatory IL-6 not tied to lung involvement in SSc

Easier way of predicting interstitial lung disease with scleroderma needed

Patricia Inácio, PhD avatar

by Patricia Inácio, PhD |

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Blood levels of interleukin (IL)-6, a pro-inflammatory signaling molecule, do not link with a risk of pulmonary involvement in people with systemic sclerosis (SSc), a study reports.

As a result, IL-6 “could not be regarded as a potential therapeutic target,” the researchers wrote in the study, “Serum interleukin-6 level and its association with pulmonary involvement in progressive systemic sclerosis; a case-control study,” published in the journal Clinical and Molecular Allergy.

“Due to the high prevalence of lung disease” in these people and diagnostic tests that can be difficult, “there is a clear need for a less costly and invasive diagnostic technique with an acceptable level of sensitivity and specificity to diagnose the lung disease in an earlier stage and prevent the irreversible complications,” the researchers noted.

Significant differences, however, were not seen in IL-6 blood levels between groups of SSc patients with and without lung involvement in the study.

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ILD seen to increase risk of death for scleroderma patients in study

Levels of IL-6 known to rise with more severe skin scarring

SSc, also known as scleroderma, is an autoimmune disease characterized by the accumulation of scar tissue that affects the skin and possibly internal organs.

Lung involvement is the leading cause of death among people with SSc and may occur as interstitial lung disease (ILD) — a group of conditions marked by scarring of the lungs that makes it difficult to breathe.

The release of IL-6 by inflammatory cells previously has been linked with more severe skin scarring in SSc patients. A research team with Kashan University of Medical Sciences, in Iran, investigated whether blood levels of IL-6 correlated with lung involvement in these patients.

In total, the researchers analyzed 60 SSc patients followed at their clinic between 2015 and 2016. Participants were divided in two groups of 30 patients each — those with ILD (73.4% women) and those without ILD (60% women), who served as controls.

Control group patients were significantly younger (mean age, 43.9 vs. 52.5 years). Disease duration was significantly longer in the SSc-ILD group (mean of 11.6 years vs. 7.4 years), as was the frequency of active disease, 70% versus 20%, according to EUSTAR (European Scleroderma Trials and Research) scores.

Blood work showed that levels of IL-6 were higher in SSc-ILD patients than in controls, but this difference was not statistically significant, meaning it could be due to chance.

Men in the SSc-ILD group had a significantly higher mean IL-6 level than those in the control group, a mean 141.7 versus 14.3 picograms (pcg)/ml, but no such differences were seen in women.

Also, no significant differences were seen when comparing patients with active disease between the two groups, or those with inactive disease.

Analysis stratifying by age — younger than 50 or age 50 and older — also showed no differences in IL-6 levels between the two groups. A similar lack of significant differences was found when stratifying by disease duration — less than 10 years or 10 and more years.

Heart involvement was seen in about one in every four SSc-ILD patients (eight people; 26.7%) and in none of the controls. Five patients (16.7%) in the SSc-ILD group and six (20%) in the control group had other rheumatologic diseases.

Levels of C-reactive protein, a marker of inflammation, were significantly higher in SSc-ILD patients relative to controls. The same was seen for pulmonary artery pressure (PAP), a measure of blood pressure in the arteries supplying blood to the lungs. PAP was normal in 83.3% of controls and in 13.3% of the SSc-ILD patients.

Overall, since a significant difference in blood IL-6 levels was seen only in men with SSc, a minority patient group in this study, a correlation between IL-6 levels and lung disease in this group should be the focus of future research, the team concluded.