Folate-modified triptolide liposomes target activated macrophages for safe rheumatoid arthritis therapy.DOI: 10.1039/D1BM01520F

TP was obtained from Pufei De Biotech Co., Ltd (Chengdu,China). Cholesterol and egg phosphatidylcholine (EPC) wereobtained from Avanti Polar Lipids, Inc. (Alabaster，AL,USA).DSPE-PEG2000 and 1,2-distearoyl-sn-glycero-3-phosphoethanol-amine-N-[amino (polyethylene glycol)-2000] (DSPE-PEG2000-NH2) were purchased from NOF Corp. (Tokyo, Japan). Chickentype II collagen, complete Freund adjuvant,and incompleteFreundadjuvant were obtained from Chondrex,Inc.(Redmond, WA,USA). RANKL was purchased from PeproTechInc. (Cranbury, NJ, USA). M-CSF and lipopolysaccharide (LPS)were provided by Meilun Co.，Ltd (Dalian,China). 4',6-Diamidino-2-phenylindole (DAPI) and 1,1-dioctadecyl-3,3,3,3-tetramethylindotricarbocyanine iodide (DiR) were obtainedfrom Kaiji Biological Technology Development Co.，Ltd(Nanjing,China).ELISA kits were purchased from SolarbioCo.,Ltd (Beijing, China). MMP-2 and MMP-9 antibodies werepurchased from Abcam Co.，Ltd (Cambridge,MA，USA). Allother reagents used were of analytical grade.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by synovial joint hyperplasia, joint inflammation, cartilage erosion and bone destruction. Macrophages play an essential role in the pathogenesis of RA, and folate receptor β (FR-β) is highly expressed on the surface of activated synovial macrophages in RA patients. Triptolide (TP) has anti-inflammatory properties, and it can protect the cartilage matrix, but its clinical application has been limited due to poor solubility, low bioavailability and systemic toxicity. Therefore, we constructed folate-modified triptolide liposomes (FA-TP-Lips) to target macrophages, thereby treating RA in a safe and effective way. The experiments indicated that FA-TP-Lips had properties of small particle size, uniform particle size distribution, high drug encapsulation and long circulation. Furthermore, FA-TP-Lips showed reduced cytotoxicity, increased cellular uptake and significant anti-inflammatory effects in vitro. It also inhibited osteoclastogenesis. In vivo experiments revealed that liposomes could prolong the circulation of TP in the body, as well as exhibit significant cartilage-protective and anti-inflammatory effects with lower toxicity compared with the free TP group, thereby providing a promising new approach for the treatment of RA.

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