The study on methotrexate therapy in collagen induced arthritis rats / 中华风湿病学杂志

ABSTRACT

Objective To explore the circadian rhythm of interleukin (IL)-6 in collagen induced arthritis (CIA) rats and investigate the effectiveness and safety of methotrexate (MTX) administered according to IL-6 rhythm.Methods Serum IL-6 concentrations of CIA and normal rats at different time points were measured by enzyme-linked immunosorbent assay (ELISA).CIA rats were randomly divided into the experimental group A,experimental group B and control group.MTX (1/7 mg·kg-1 ·d-1) was administered once a day when the IL-6 level began to increase or decrease in the experimental group,while MTX (1 mg/kg) administered once a week in the control group.Arthritis scores and leukocyte counts were observed.The production of IL-6 and C reactive protein (CRP) levels in the serum were measured.Moreover,histological changes in the ankle joint were examined.One-way analysis of variance (ANOVA),two independent sample t test were used to evaluate the experimental data.Results The plasma IL-6 levels in CIA rats were different at different time points,which began to increase at 1800 and decrease at 600.Arthritis score in the experimental group A (4.8±0.7)was lower than that in the control group (5.8±1.0,t=2.256,P=0.0406) and experimental group B (5.5±0.5,t=2.393,P=0.0313).The levels of TNF-α [(185±21) ng/L],IL-6 [(99±6) ng/L],IL-1β[(20.1±1.6) ng/L] and CRP[(1251±282) μg/L] in the experimental group A were significantly lower than those in control group [TNF-α(207±10) ng/L,t=2.726,P=0.016 4;IL-6(100±6) ng/L,t=2.669,P=0.0183;IL-1β(22.0±1.3) ng/L,t=2.814,P=0.0138;CRP(1 417±278) μg/L,t=2.369,P=0.0327].The level of IL-6 in the experimental group A[(93±6) ng/L] was lower than that in the experimental group B [(99±6) ng/L,t=2.323,P=0.0358].Compared with the control group [(9650±1062)/μl],the counts of leukocyte in the experimental group A [(4595±603)/μl,t=3.841,P=0.0064] and experimental group B [(3833±585)/μl,t=4.442,P=0.003] were significantly lower.Compared with the control group (9.1 ±2.0),histopathology scores in the experimental group A (6.6±1.3,t=2.606,P=0.015) and experimental group B (7.4±1.3,t=3.857,P=0.0007) were significantly lower.Conclusion The plasma IL-6 levels in CIA rats have shown evident circadian rhythm.There-fore,once a day administration is better than once a week.The therapeutic effect of RA may be improved by administering MTX at the time points according to the circadian rhythm of IL-6.