Therapeutic effects of the artemisinin analog SM934 on lupus-prone MRL/lpr mice via inhibition of TLR-triggered B-cell activation and plasma cell formation

We previously reported that SM934, a water-soluble artemisinin derivative, was a viable treatment in murine lupus models. In the current study, we further investigated the therapeutic effects of a modified dosage regimen of SM934 on lupus-prone MRL/lpr mice and explored its effects on B cell responses, a central pathogenic event in systemic lupus erythematosus (SLE). When orally administered twice-daily, SM934 significantly prolonged the life-span of MRL/lpr mice, ameliorated the lymphadenopathy symptoms and decreased the levels of serum anti-nuclear antibodies (ANAs) and of the pathogenic cytokines IL-6, IL-10 and IL-21. Furthermore, SM934 treatment restored the B-cell compartment in the spleen of MRL/lpr mice by increasing quiescent B cell numbers, maintaining germinal center B-cell numbers, decreasing activated B cell numbers and reducing plasma cell (PC) numbers. Ex vivo, SM934 suppressed the Toll-like receptor (TLR)-triggered activation and proliferation of B cells, as well as antibody secretion. Moreover, the present study demonstrated that SM934 interfered with the B-cell intrinsic pathway by downregulating TLR7/9 mRNA expression, MyD88 protein expression and NF-κB phosphorylation. In human peripheral blood mononuclear cells (PBMCs), consistent with the results in MRL/lpr mice, SM934 inhibited TLR-associated B-cell activation and PC differentiation. In conclusion, a twice daily dosing regimen of SM934 had therapeutic effects on lupus-prone MRL/lpr mice by suppressing B cell activation and plasma cell formation.