Primary Study Of The Role Of TRAIL In The Pathogenesis Of Graves' Disease

TRAIL (Apo-2L) is one of members of the TNF super-family. Just like TNF-a and FasL, it belongs to type II membrane-bound protein, and has both membrane-bound and soluble forms and acts through type I membrane receptors that signal apoptosis through a cytoplasmic death domain, as the apoptosis plays an pivotal role in maintaining homeostasis of tissues. Autoimmune thyroid disease (AFTD) includes Graves' disease and Hashimoto' thyroiditis, while apoptosis has an important role in the pathogenesis of this kind of disease. Objects(1)To observe the expression of TRAIL in PBMCs. (2) To investigate the level of serum soluble TRAIL in Graves' patients. (3).To investigate the expression of TRAIL on lymphocytes, and (4).To understand the effect of Triiodothyronine (T3) in different concentrations on the apoptosis of lymphocyte in vitro. MethodsThe TRAIL immunoreactive substance was observed in PBMCs hnmunohistochemically. Expression of TRAIL and apoptosisof lymphocytes were tested by Flow cytometric analysis. Serumsoluble TRAIL was measured with sandwich enzyme-linked immunosorbent assay in patients with Graves' disease (n=50), Prim ary hypothyroidism (n=22) and controls(n=40). At the same time,T3, T4, TSH, TGAb and TPOAb were examined in all patients.Results1. The expression of TRAIL on PBMC :The immunoreactive positive substance distributed in cytoplas ma, while it was negative on nuclei. The percentage of lymphoc yte and monocyte among PBMC were 97.48?.43% and 3.15 + 0.83 % respectively. The ratio of TRAIL immunoreactive lymphoc yte was 26.31+3.18)%, while that of monocytes was 1.04+0.132. The Effect of T3 in different concentrations on the expressi on of TRAIL in peripheral blood lymphocytesThe percentage of TRAIL positive lymphocyte were 16.78+3.8 4%, 18.11+3.04 %, 23.03+2.28 %, 28.01 + 1.37%, 32.43+3.96 % respectively when the lymphocyte were cultured in different c oncentrations of T3 (1X 10-12mol/L, 1X 10-11mol/L, 1X 10-10mol/L,lX10-9mol/L, 1X10-8mol/L ). There were significant difference between all concentrations(P <0.05), except 10-12mol/L and 10-11m ol/L (P=0.605) .3. The Effect of T3 in different concentrations on apoptosis of peripheral blood lymphocytes.With the increasing of T3 hormone concentrations, the amou nt of apoptotic cells raised. The percentages of apoptotic cell w ere 5.1 + 0.89% , 12.53 + 2.00%, 15.51 + 2.45%, 18.66+1.02%, 22. 76+2.43%, 28. 76+3. 32% when T3 in different concentrations (0 mol/L, 1X 10-12mol/L, 1 X 10-10mol/L, 1X 10-10mol/L, 1 X 10-9mo 1/L, 1X 10-8mol/L ) were added into the culture media. There we re significantly different among groups. (P <0.01).4. Serum sTRAIL level in thyroid diseasesThe serum sTRAIL in the patients with GD were significantly higher than those in healthy controls(2.23+0.46ng/ml vs 0.80 + 0.07ng/ml , p<0.05) and those of hypothyroidism (1.02+1.45 ng/ ml, p<0.05) . The levels of serum soluble DR4 and DR5 in the patients with GD, hypothyroidism and healthy controls weren't di fferent. Conclusion:The immunohistochemical work of this experiment indicated that TRAIL protein expressed in part of PBMC, especially in human peripheral blood lymphocytes, and T3 can up-regulate the expression of TRAIL and increase the apoptosis of lymphocytes in vitro when T3 is in certain extent of concentrations. As the clinic study, the level of sTRAIL was higher in Graves' disease than in hypothyroidism and control. All this data showed that TRAIL system may play an important role in the pathogenesis of Graves' disease. Further investigations are necessary to evaluate the significance of our results.