Effects of Hydroxychloroquine on the Metabolism of Fas ligand of T cells

Min, Jun Ki; Lee, Hee Jin; Lee, Won Sun; Park, Sang Hee; Min, So Youn; Cho, Mi La; Cho, Chul Soo; Kim, Ho Youn

Abstract

OBJECTIVE
Hydroxychloroquine (HCQ) is a drug that has been used to treat autoimmune disorders such as rheumatoid arthritis and systemic lupus erythematosus. However, the specific mechanism for its pharmacologic action has been largely unknown. It has been reported that dysregulation of lymphocytic apoptosis mediated by Fas ligand (FasL) and Fas is associated with the development of autoimmune diseases and HCQ induces apoptosis in peripheral blood lymphocytes. These reports suggest that HCQ may exert its pharmacologic effects through the modulation of FasL and Fas. Therefore, we are intended to investigate the effects of HCQ on the regulation of FasL and Fas. Jurkat cells or peripheral blood mononuclear cells (PBMNC) were treated with varying concentrations of HCQ. Semiquantative reverse transcription- polymerase chain reaction, Western blotting, flow cytometry, and ELISA were used for this study. HCQ at nontoxic concentrations( 50~150 micrometer) caused a dose dependent increase of FasL mRNA expression and FasL in cell lysates. HCQ inhibited the release of intracellular 40 kDa FasL by Jurkat cells which were pulse-stimulated with PHA (50 microgram/ml). Jurkat cells activated with PHA increased membrane bound FasL (mFasL) expression (24.5+/-4.3%), however Jurkat cells pretreated with HCQ(150 micrometer) followed by PHA administration did not further increase mFasL expression (26.8+/-1.6%). Addition of different concentrations of HCQ to the cultured PBMNC stimulated with PHA for 24 hours showed increase of soluble FasL (sFasL). The levels of sFasL treated with HCQ zero, 50, 150 and 300 micrometer for 24 hours were 38.6+/-3.0, 43.4+/-5.1, 77.0+/-3.6(P<0.05) and 72.3+/-8.1pg/ml(P<0.05) respectively. However, fas metabolism was not affected by HCQ.
CONCLUSION
These results suggest that HCQ may exhibit its pharmacological effects by upregulation of FasL gene expression and increased production sFasL without any influence on the Fas metabolism of T cells.