Sinomenine inhibits the expression of PD‑L1 in the peripheral blood mononuclear cells of mesangial proliferative nephritis patients.

: Sinomenine has been used to treat autoimmune diseases for centuries. However, little is known about its exact mechanisms of action. Whether sinomenine has an effect on programmed death‑1 (PD‑1) ligands (PD‑Ls) in vivo remains unclear. The present study aimed to determine the effect of sinomenine on the expression of PD‑L1 and PD‑L2 in peripheral blood mononuclear cells (PBMCs). A total of 25 patients with mesangial proliferative nephritis (MsPGN) were treated with sinomenine and followed up for 3 months. The expression of PD‑L1 and PD‑L2 was studied by using real‑time RT‑PCR and flow cytometric analysis, and recorded at months 0, 1 and 3 within the PBMCs. The intra‑renal expression of PD‑L1 and PD‑L2 was studied by immunohistochemistry. The results revealed that the PBMCs from the MsPGN patients expressed high levels of PD‑L1 at the mRNA and protein levels compared with the healthy donors. Immunohistochemistry revealed an increased PD‑L1 expression in the renal tissues from the MsPGN patients. Sinomenine was observed to have a significant effect in decreasing the PD‑L1 expression in the PBMCs. The present study therefore suggests a novel mechanism for the therapeutic effects of sinomenine on MsPGN in vivo.