PGP and systemic lupus erythematosus: In the present study, we aimed to investigate the effect of PNS on reversing SR in lupus mice and determine whether PNS reverses P-gp-mediated SR via SIRT1/FoxO1/MDR1 signalling in lymphocytes of lupus mice, which may be the major mechanism underlying the SR reversal potential of PNS in lupus.