Background Toll-like receptor 9 (TLR-9) can recognize nucleic acids especially DNA segments, plays an important role in innate immunity. Recently, it has been found that TLR-9 also involves in the recognition of self DNA fragments, initiates the autoimmune response with the production of interferon-alfa (IFN-α) which is the central cytokine in Systemic lupus erythematosus (SLE). Anti-malarial drugs such as Hydroxychloroquine (HCQ) and quinacrine (Qn) are commonly used in the treatment of SLE, with the combination of glucocorticoid. However, their mechanisms are still unclear. Recent studies imply that these drugs may influence TLR pathway.

Objectives To evaluate the influence of anti-malarial drugs ( HCQ and Qn ) on the initiation of IFN-α production through TLR-9 pathway, with or without combination with glucocorticoid.

Methods Freshly isolated PBMCs of healthy donors were stimulated with the TLR-9 agonist CpG oligodeoxynucleotides (CpG-A ODN)-2216, then incubated with different kinds of anti-malarial drugs ( HCQ and Qn or both) and / or different doses of glucocorticoid (hydrocortisone). The changes in the expression of IFN-α were detected by real time PCR.

Results (1). Hydroxychloroquine or quinacrine alone or combined together significantly reversed the elevation of IFN-α caused by ODN 2216 (Qn (p=0.047), HCQ (p=0.047), Qn and HCQ (p=0.046)). (2). When combined with low (10-5 M) or middle (10-4 M) dose of hydrocortisone, HCQ or Qn or both significantly revised the elevation of IFN-α caused by ODN 2216 ((low dose: Qn (p=0.034), HCQ (p=0.032), Qn and HCQ (p=0.036), middle dose: Qn (p=0.028), HCQ (p=0.024), Qn and HCQ (p=0.028)), which could not be revised by glucocorticoid alone (each p>0.05). (3). When combined with high dose (10-3 M) hydrocortisone which could significantly promote the expression of IFN-α (p=0.032<0.05), only HCQ could significantly revise the elevation of IFN-α caused by ODN 2216 (p<0.05).

Conclusions (1). Anti-malarial drugs (HCQ Qn) hamper the critical pathogenesis of lupus that TLR-9 recognition of nucleotides (ODN 2216) elevates the IFN-α expression in PBMCs.(2). The combination with anti-malarial drugs (HCQ Qn) seem to be a good choice to help low or middle dose glucocorticoid to achieve a better disease control by inhibiting IFN-α, which cannot be decreased by glucocorticoid alone. (3). Only HCQ could revise the elevation of IFN-α caused by ODN 2216 in case of using high dose glucocorticoid.

Acknowledgements This study was supported by the grant for the scientific research foundation of ministry of education in China (20090171120090).

Disclosure of Interest: None Declared