Abstract:

Objective To investigate the effect of cornus officinalis glycosides on bone injury and osteoarthritis in rats exposed to cadmium based on the long non coding RNA deleted in lymphocytic leukemia 2（lncRNA DLEU2）/microRNA-655（miR-655）/Mothers against decapentaplegic homolog 7（SMAD7） signaling pathway. Methods Animal experiments were conducted from June to December 2023 in the animal room of Qinhuangdao First Hospital. Forty rats were divided into a normal group，a cadmium exposure model group，a low-dose cornus officinalis glycosides group，and a high-dose cornus officinalis glycosides group. Except for the control group，the femoral osteoarthritis model of cadmium-exposed rats was established by continuous intragastric exposure to cadmium dichloride（CdCl₂） in all other groups. During the CdCl₂ exposure period，rats in the low-dose and high-dose cornus officinalis glycosides groups（2 000 and 4 000 mg/kg） were intragastrically administered with the corresponding dose of cornus officinalis glycosides daily，and the normal group and the cadmium exposure model group were intragastricly administered with an equal volume of normal saline. After the experiment，SkyScan 1076 Bruker-Micro CT scanner was used to measure the femoral bone density（BMD），trabecular number，trabecular thickness，and trabecular dispersion of the rats. The thermal stimulation latency，femoral osteoarthritis score，and toe volume of the rats were measured. Real-time fluorescence reverse transcription and Western blotting were used to measure the levels of lncRNA DLEU2，miR-655，and SMAD7 in the femur of the rats. And enzyme-linked immunosorbent assay was used to measure the levels of interleukin-1β（IL-1β），tumor necrosis factor-α（TNF-α），and cysteinyl aspartate specific proteinase-3（caspase-3） proteins in the femur of the rats. Results The cadmium exposure model group had higher levels of femoral trabecular dispersion，femoral joint inflammation area，toe volume，femoral miR-655 mRNA，and femoral IL-1β，TNF-α，and caspase-3 protein than those of the normal group，while BMD，trabecular number，trabecular thickness，paw withdrawal thermal latency（PEL），lncRNA DLEU2 mRNA（0.95±0.17 vs 4.32±0.16），SMAD7 mRNA（0.42±0.29 vs 4.82±0.10） and protein（0.32±0.06 vs 1.52±0.16） levels were lower than those of the normal group，and the differences were statistically significant（all P<0.05）. The trabecular dispersion，joint inflammation area，toe volume，femoral miR-655 mRNA，femoral IL-1β，TNF-α，and caspase-3 protein levels in the low-dose cornus officinalis glycosides groups and high-dose cornus officinalis glycosides groups were lower than those in the cadmium exposure model group，while BMD，trabecular number，trabecular thickness，PEL，lncRNA DLEU2 mRNA（1.72±0.11，2.87±0.07 vs 0.95±0.17），SMAD7 mRNA（1.11±0.20，2.89±0.17 vs 0.42±0.29） and protein levels（0.74±0.12，0.95±0.11 vs 0.32±0.06） were higher than those in the cadmium exposure model group，and the differences were statistically significant（all P<0.05）. The trabecular dispersion，femoral osteoarthritis area，toe volume，femoral miR-655 mRNA， femoral IL-1β，TNF-α，and caspase-3 protein levels in the high-dose cornus officinalis glycosides group were lower than those in the low-dose cornus officinalis glycosides group，while BMD，trabecular number，trabecular thickness，PEL，lncRNA DLEU2 mRNA（2.87±0.07 vs 1.72±0.11），SMAD7 mRNA（2.89±0.17 vs 1.11±0.20） and protein levels（0.95±0.11 vs 0.74±0.12） were higher than those in the low-dose cornus officinalis glycosides group（all P<0.05）. Conclusion Cornus officinalis glycosides have a significant therapeutic effect on bone injury and osteoarthritis in cadmium exposed rats. The mechanism is related to the activation of lncRNA DLEU2/miR-655/SMAD7 signaling pathway in the femur of cadmium exposed rats，thereby inhibiting inflammation and apoptosis of femoral cells.

Key words: lncRNA DLEU2, miR-655, SMAD7, Cornus officinalis glycosides, Cadmium, Bone injury, Osteoarthritis