Regulatory Effects of Triptolide on BLyS Expression and Signaling in U937 Cells

Objective: This study aimed to investigate the regulatory effects of Triptolide (TL), a bioactive compound derived from Tripterygium wilfordii , on the expression and signaling of B lymphocyte stimulator (BLyS/BAFF) in the human monocytic cell line U937. Methods: U937 cells were treated with varying concentrations of TL, BLyS, or both. Cell proliferation was assessed using MTT assays, while apoptosis was evaluated via Annexin V/PI flow cytometry and caspase-3 activity analysis. Western blotting and ELISA were performed to measure BLyS protein expression, and quantitative PCR was used to analyze the mRNA levels of BLyS, APRIL, and their receptors (TACI, BCMA, and BAFF-R). Results: BLyS alone promoted U937 cell proliferation and inhibited apoptosis, whereas TL inhibited cell proliferation and induced apoptosis in a dose-dependent manner. When combined with TL, BLyS reversed its anti-apoptotic effect and promoted apoptosis. TL significantly downregulated total BLyS protein levels and membrane-bound BLyS expression, while enhancing the secretion of soluble BLyS at lower concentrations. Additionally, TL treatment downregulated BLyS and TACI mRNA expression while markedly upregulating BCMA and BAFF-R, suggesting altered receptor signaling dynamics. Conclusion: Triptolide disrupts BLyS-mediated signaling by modulating the expression of BLyS and its receptors, leading to enhanced apoptosis in U937 cells. These findings provide new insight into the immunomodulatory mechanism of TL and support its potential use in treating autoimmune diseases and B-cell-related malignancies.