SLCO1B1 variants as predictors of methotrexate-related toxicity in children with juvenile idiopathic arthritis.

Objectives: Methotrexate (MTX) administered at the dose 10-15 mg/m2 is currently recommended as the first line therapy in most juvenile idiopathic arthritis (JIA) subtypes. Gastrointestinal side effects and hepatotoxicity are the most prevalent manifestations of MTX intolerance, frequently leading to discontinuation of otherwise effective treatment. Genetic variability within solute carrier organic anion transporter family member 1B1 (SLCO1B1), encoding a hepatic MTX membrane transporter, has been associated with high-dose MTX efficacy and toxicity in paediatric patients with acute lymphoblastic leukaemia. The aim of our study was to determine the association between single-nucleotide polymorphisms in the SLCO1B1 gene (rs4149056, rs2306283) on the disease activity and presence of side effects of MTX therapy in patients with JIA.Method: The study recruited 100 children with JIA of all subtypes treated with MTX. Demographic and clinical parameters were collected at the baseline of MTX therapy and on a control visit 4-6 months after starting MTX. Genotyping was performed using genomic DNA isolated from peripheral blood samples.Results: In comparison to wild-type allele, SLCO1B1 rs4149056 CT/CC variant was significantly associated with higher odds ratio of MTX gastrointestinal side effects occurrence (OR=4.55, 95%CI 1.37-15.13; p=0.013). SLCO1B1 rs4149056 TT subjects were more likely than CT/CC individuals to develop hepatotoxicity (17.86% vs 4.76%, p = 0.046).Conclusion: SLCO1B1 rs4149056 may serve as a determinant of MTX treatment toxicity in children with JIA.

Distribution and clinical significance of blood dendritic cells in children with juvenile idiopathic arthritis.

BACKGROUND: A role for dendritic cells (DC) in the development of adult rheumatoid arthritis has been suggested. To date, this problem has been poorly explored in juvenile idiopathic arthritis (JIA). OBJECTIVE: To analyse distribution and maturation status of blood DC (BDC) in JIA. METHODS: Absolute BDC counts were assessed by the "single platform" method in peripheral blood (PB) of 47 untreated children with JIA and 32 healthy controls. Moreover, BDC were investigated in JIA synovial fluid (SF). When the panel of monoclonal antibodies against BDC antigens (BDCA) was used, three BDC subpopulations were determined: myeloid type 1 (mDC1; BDCA-1+/HLA-DR+/CD19-), myeloid type 2 (mDC2; BDCA-3+/HLA-DR+/CD14-) and plasmacytoid (pDC; BDCA-2+/HLA-DR+/CD123+). RESULTS: A considerable deficiency of all subtypes of BDC was found in the PB of children with JIA. BDC counts in JIA SF were significantly higher than in PB both from children with JIA (p<0.001) and healthy children (p<0.001). SF BDC, especially mDC1 and mDC2 subtypes, had significantly higher expression of maturation markers (CD40, CD80, CD86 or CD83 antigens) than those from PB. A smaller number of PB BDC at diagnosis correlated significantly with poor response to treatment. CONCLUSIONS: A deficiency of BDC in PB is accompanied by enrichment of SF with those cells. Probably, circulating BDC migrate to joints where they undergo maturation and help to mediate and maintain the local immune response. Interestingly, the level of PD BDC deficiency seems to influence the outcome in children with JIA.

Regulation of peripheral blood and synovial fluid lymphocyte apoptosis in juvenile idiopathic arthritis.

OBJECTIVE: Complex regulatory mechanisms are involved in the induction of apoptosis. Their impairment may play a role in the pathogenesis of several autoimmune diseases. Recently, we have described higher incidences of spontaneous apoptosis of peripheral blood (PB) lymphocytes in children with juvenile idiopathic arthritis (JIA). This study aimed to evaluate the regulatory mechanisms that may be responsible for this phenomenon. METHODS: Thirty-four JIA children were examined and compared with 20 healthy children of similar ages. Expression of regulatory proteins p53, Bax and Bcl-2 in lymphocytes isolated from PB and synovial fluid (SF) was assessed. Serum and SF levels of interleukin-15 (IL-15) were also evaluated. RESULTS: The study showed significantly decreased Bcl-2 expression in JIA PB lymphocytes, compared to both healthy control (p = 0.03) and JIA SF lymphocytes (p = 0.005). There were no significant differences found in Bax expression between groups or compartments examined. However, the Bax/Bcl-2 ratio was nearly two-fold higher in PB lymphocytes than in SF of JIA patients (p = 0.001). p53 expression in PB lymphocytes from both JIA and control children did not statistically differ. In JIA, however, p53 was significantly higher in PB than SF lymphocytes (p = 0.016). IL-15 levels were about 20-fold higher in JIA SF than in serum from either JIA or healthy children (p < 0.0001). CONCLUSION: The results suggest that a higher incidence of apoptosis of PB lymphocytes observed in JIA may be associated with down-regulation of Bcl-2, rather than with changes in expression of Bax and p53. In contrast, the low p53 expression and elevated IL-15 appear to provide mechanisms responsible for suppression of apoptosis in SF cells from JIA patients.

Apoptosis of peripheral blood lymphocytes in patients with juvenile idiopathic arthritis.

BACKGROUND: Recent data suggested that abnormalities in mechanisms regulating apoptosis may have a role in the development of the rheumatoid process. OBJECTIVE: To evaluate different aspects of apoptosis in children with juvenile idiopathic arthritis (JIA). METHODS: The frequency of TUNEL positive peripheral blood (PB) lymphocytes (apoptotic index (AI)), as well as serum CD95 (APO1/Fas) antigen expression and serum levels of sFas and interleukin 15 (IL15), were examined in 44 cases of JIA. Results were correlated with type of onset, activity of JIA, and acute phase indicators. RESULTS: The AI of lymphocytes was significantly higher in patients with JIA than in controls (p=0.020). The mean AI of lymphocytes was increased in JIA with systemic type of onset and high activity (p=0.001). Moreover, IL15 levels in systemic disease were higher than in controls (p=0.012). An increased AI correlated with raised IL15 (p=0.046), erythrocyte sedimentation rate (p=0.005) and C reactive protein (CRP; p=0.017). Additionally, correlation was found between IL15 and CRP levels (p=0.039). CD95 and sFas levels were unchanged compared with controls. CONCLUSION: PB lymphocytes of children with JIA have an increased tendency to undergo apoptosis. The degree of apoptosis depends on the type of onset and activity of JIA and correlates with serum levels of IL15. Further studies are needed to explain whether this is an epiphenomenon of the disease activity or is related to the pathogenesis of JIA.