The salivary glands of children with oligoarticular-type juvenile idiopathic arthritis may be targets of inflammatory, oxidative stress-mediated injury, a study has shown.

In an investigation of the salivary gland involvement and saliva and serum antioxidant profiles in patients with juvenile idiopathic arthritis (JIA), Dr. Riva Brik of Meyer Children's Hospital in Haifa, Israel, and colleagues observed a major increase in antioxidant enzyme activity in the serum and saliva of children with systemic, polyarticular, and oligoarticular-type disease, as well as significant and specific damage to the salivary glands in those children with oligoarticular JIA.

Although there is a scarcity of data on salivary gland involvement or alterations in JIA, previous studies in adults with rheumatoid arthritis have shown direct relationships between disease severity and increased levels of antioxidant enzymes in secreted saliva and serum, suggesting that saliva—which is easier and less invasive to collect—might be suitable as a window into serum composition in children. Because adult studies also have identified oxidative stress as a major contributing factor to the chronic inflammatory process within the inflamed joint, the ability to measure such changes in saliva could have therapeutic implications in JIA (J. Rheumatol. 2006;33:2532–7).

Toward this end, the investigators studied the salivary composition and the saliva and serum antioxidant profiles of 22 children with JIA according to the American College of Rheumatology criteria and 15 healthy controls. Of the children with JIA, 10 had oligoarticular, 7 had polyarticular, and 5 had systemic-type disease. The mean age of the 15 girls and 7 boys with JIA was 12.2 years and the mean durations of follow-up and disease activity were 5.8 years and 5.1 years, respectively.

Saliva and serum samples were obtained concomitantly from each study participant. Saliva was analyzed for flow rate (volume of saliva secreted per minute), chemistry (pH, calcium, phosphate, magnesium, total protein, albumin, lactate dehydrogenase, and amylase), total antioxidant status, peroxidase activity, and uric acid. Serum was analyzed for total antioxidant status, peroxidase activity, uric acid, total protein, and albumin.

The analyses showed that the median salivary flow rates of the JIA patients as a whole were within normal range and were similar to those of the healthy controls. The median flow rate of children with oligoarticular arthritis was 33% lower than that of the control group. The difference did not reach statistical significance, however, due to the large standard error values, according to the authors.

Sialochemistry analysis findings indicated the saliva composition in children with oligoarticular JIA contained significantly lower levels of magnesium, total protein, amylase, and lactate dehydrogenase compared with the other JIA subtypes. Additionally, levels of salivary calcium and phosphate were low, bordering on a statistically significant difference. Compared with controls, there were no significant differences between the total JIA group and the healthy controls in measures of salivary calcium and albumin; however, patients with systemic disease showed increased levels of salivary total protein and polyarticular patients had significantly increased levels of amylase. Salivary pH was higher in all of the JIA patients compared with controls, and was highest in the oligoarticular group.

The salivary antioxidant analyses showed that salivary peroxidase activity was significantly higher (8.5%) in the JIA group as a whole compared with controls, and most notably among the polyarticular group, whose levels were 17% higher than controls. The antioxidant enzyme superoxide dismutase was significantly increased in the JIA patients, particularly in those with systemic-type disease in whom a 74% increase was noted, the authors wrote. Measures of salivary uric acid and total antioxidant status in the JIA patients were not statistically different from those of the controls. The results of the serum analyses showed significantly higher levels of serum peroxidase activity in the JIA group, with the maximal increase of 17% observed in the polyarticular subgroup. All of the JIA subgroups showed nonsignificant reductions in uric acid concentrations compared with controls and nonsignificant differences in total antioxidant status. A significant increase in serum albumin concentrations was seen in all three JIA subgroups, with a mean 9.3% increase in the total group compared with the control group.

“Our main finding was significant alterations in the saliva of patients with oligoarticular JIA compared to controls and also to other patients with JIA,” the authors wrote. “Whereas the total group of patients showed increased levels of antioxidant enzyme activity both in serum and in saliva, presumably as a result of the ongoing inflammatory process, only the patients with oligoarticular-type disease showed evidence of specific injury to the salivary glands, as reflected by a reduced salivary flow rate, low levels of amylase and LDH activity, and lower concentrations of total proteins.” The changes observed in the saliva of the children with oligoarticular-type disease “may designate the salivary glands [in similarity to joints] as target organs of inflammatory, oxidative stress-mediated injury,” they stated.

“We also showed that saliva is a reliable representative of serum composition and can be used for pertinent testing in children,” they noted.

One JIA Type Involves Injury to Salivary Glands