Fig. 1: Illustration of the Spirulina platensis (SP)-based therapeutic to remodel bone homeostasis in rheumatoid arthritis (RA) by suppressing synovial inflammation and osteoclast activation.

A Schematic illustration of the targeting delivery of macrophage cell membranes-engineered SP (SP@M) toward inflammatory arthritis, which acts as a targeted therapeutic to remodel bone homeostasis in RA by relieving synovial inflammation and independently suppressing osteoclast activation. The SP accelerates the protein degradation of Kelch-like ECH-associated protein 1 (KEAP1) via microtubule-associated protein 1 light chain 3 (LC3)-mediated autophagy and ubiquitin-mediated proteasome degradation. Following the KEAP1 inactivation, the nucleus translocation of transcription factor nuclear factor-erythroid 2 p45-related factor 2 (NRF2) is increased, leading to the mitigation of synovial inflammation and amelioration of RA in collagen-induced arthritis (CIA) mouse models. B The bright-field microscopic image of SP cells. C The scanning electron microscopy image of the single SP cell. D The fluorescence image of SP cells. E UV–vis absorption spectrum of SP cells. For B–E, three independent experiments were repeated.