Morinda Officinalis Polysaccharides Inhibit Osteoporosis in Rats via the P2X7R/NLRP3 Pathway

OBJECTIVE To investigate the mechanism of Morinda officinalis polysaccharides inhibiting osteoporosis, especially its regulatory effect on P2X7R/NLRP3 inflammasome pathway.

METHODS The 100 female SD rats were randomly divided into 10 groups, including sham group, model group, low, medium and high doses of Morinda officinalis polysaccharides groups(50, 100, 200 mg·kg⁻¹, oral), diethylstilbestrol positive group(0.1 mg·kg⁻¹, oral), Coomassie brilliant blue G group(75 mg·kg⁻¹, intraperitoneal injection), Coomassie brilliant blue G co-administration group(Morinda officinalis polysaccharides 100 mg·kg⁻¹+Coomassie brilliant blue G 75 mg·kg⁻¹ administered in combination), fluoromethyl ketone group(0.15 mg·kg⁻¹, intravenous), fluoromethyl ketone co-administration group(Morinda officinalis polysaccharides 100 mg·kg⁻¹+fluoromethyl ketone 0.15 mg·kg⁻¹ administered in combination), 10 rats in each group. Osteoporosis model was established by bilateral ovariectomy. Each treatment group was given drugs according to the corresponding dose, and the sham group and model group were given a gavage of an equal volume of saline. After 6 weeks of continuous administration, the rats of each group were sacrificed. Bone microstructural parameters(bone mineral density, trabecular number, trabecular separation, trabecular thickness, and bone volume/tissue volume) were measured by Micro-CT. Serum levels of bone metabolism related factors(BMP-2, BALP, OC, CTX-I) and inflammatory factors(TNF-α, IL-6, IL-1β, IL-18) were measured by ELISA kit. Expression of P2X7R, NLRP-3, Caspase-1, GSDMD-N, OPG, RANKL and other proteins were detected by Western blotting. Finally, HE staining was used to observe the pathological changes of bone tissue in each group.

RESULTS After the treatment of Morinda officinalis polysaccharides, osteoporosis healed obviously, bone mineral density, trabecular number, trabecular thickness and bone volume/tissue volume increased significantly, trabecular separation decreased significantly; pathological results showed that the number of trabecular bone increased, the average trabecular bone area increased, trabecular bone gap decreased significantly, inflammatory cell infiltration decreased; meanwhile, BMP-2, BALP, OC levels increased, CTX-I, TNF-α, IL-6, IL-1β, IL-18 levels decreased in serum. MOP also up-regulated OPG protein expression and down-regulated P2X7R, RANKL, NLRP3, Caspase-1 and GSDMD-N protein expression in bone tissue. Coomassie brilliant blue G and fluoromethyl ketone could enhance the promoting effect of Morinda officinalis polysaccharides on osteoporotic healing.

CONCLUSION Morinda officinalis polysaccharides can regulate the inflammatory factor level in osteoporosis by inhibiting P2X7R-NLRP3 inflammasome pathway, so as to play an anti-osteoporosis role.