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This study aimed to investigate the therapeutic effects of Morinda officinalis iridoid glycosides(MOIG) on paw edema and bone loss of rheumatoid arthritis(RA) rats, and analyze its potential mechanism based on ultra-high performance liguid chromatography-guadrupole time-of-flight tandem mass spectrometry(UPLC-Q-TOF-MS) serum metabolomics. RA rats were established by injecting bovin type Ⅱ collagen. The collagen-induced arthritis(CIA) rats were administered drug by gavage for 8 weeks, the arthritic score were used to evaluate the severity of paw edem, serum bone metabolism biochemical parameters were measured by ELISA kits, Masson staining was used to observe the bone microstructure of the femur in CIA rats. UPLC-Q-TOF-MS was used to analyze the alteration of serum metabolite of CIA rats, principal component analysis(PCA) and partial least squares-discriminant analysis(PLS-DA) were used to screen the potential biomarkers, KEGG database analysis were used to construct related metabolic pathways. The results demonstrated that the arthritic score, serum levels of IL-6 and parameters related with bone metabolism including OCN, CTX-Ⅰ, DPD and TRAP were significantly increased, and the ratio of OPG and RANKL was significantly decreased, the microstructure of bone tissue and cartilage were destructed in CIA rats, while MOIG treatments could significantly reduce arthritis score, mitigate the paw edema, reverse the changes of serum biochemical indicators related with bone metabolism, and improve the microstructure of bone tissue and cartilage of CIA rats. The non-targeted metabolomics results showed that 24 altered metabolites were identified in serum of CIA rats; compared with normal group, 13 significantly altered metabolites related to RA were identified in serum of CIA rats, mainly involving alanine, aspartate and glutamate metabolism; compared with CIA model group, MOIG treatment reversed the alteration of 15 differential metabolites, mainly involving into alanine, aspartate and glutamate metabolism, D-glutamine and D-glutamate metabolism, taurine and hypotaurine metabolism, valine, leucine and isoleucine biosynthesis. Therefore, MOIG significantly alleviated paw edema, improved the destruction of microstructure of bone and cartilage in CIA rats maybe through involving into the regulation of amino acid metabolism.

Excessive and persistent inflammatory responses are a potential pathological condition that can lead to diseases of various systems, including nervous, respiratory, digestive, circulatory, and endocrine systems. Cannabinoid type 2 receptor(CB2R) belongs to the G protein-coupled receptor family and is widely distributed in immune cells, peripheral tissues, and the central nervous system. It plays a role in inflammatory responses under various pathological conditions. The down-regulation of CB2R activity is an important marker of inflammation and and CB2R modulators have been shown to have anti-inflammatory effects. This study explored the relationship between CB2R and inflammatory responses, delved into its regulatory mechanisms in inflammatory diseases, and summarized the research progress on CB2R modulators from plants other than cannabis, including plant extracts and monomeric compounds, in exerting anti-inflammatory effects. The aim is to provide new insights into the prevention and treatment of inflammatory diseases.