Acupuncture regulates PI3K/Akt/mTOR signaling and up-regulates cell autophagy to protect sy-novial tissue of adjuvant arthritis rats

Abstract

To observe the effect of acupuncture of "Yinlingquan"(SP9) and "Sanyinjiao"(SP6) on expression of phosphatidylinositol-3 kinase/protein kinase B/mammalian target protein of rapamycin (PI3K/Akt/mTOR) signaling in adjuvant arthritis (AA) rats, so as to explore its mechanism underlying improvement of AA. Forty-eight male Wistar rats were randomly divided into normal control, AA model, acupuncture and medication (tripterygium wilfordii) groups, with 12 rats in each group. The AA model was established by putting the rats in a windy, cold and wet environment for 12 h, once every day for 21 days and injection of Freund's complete adjuvant (CFA) into the sole of the right hindlimb on the 21st day. Manual acupuncture stimulation was applied at SP9 and SP6 for 30 min/time, once a day for 21 days. Rats of the medication group received gavage of tripterygium wilfordii tablets solution (8 mg/kg), once a day for 21 days, and those of the normal control group and model group received gavage of the same amount of normal saline, once a day for 21 days. The degree of joint swelling and arthritis index (AI) were detected 1 day before modeling, 3 days after modeling, and 21 days after the treatment. Twenty-four hours after the last treatment, the contents of serum cytokines interleukin (IL)-17, IL-6 and tumor necrosis factor (TNF)-α were detected by enzyme-linked immunosorbent assay (ELISA); and changes of synovial ultrastructure were observed under electron microscope. Western blot was used to detect the expression levels of PI3K, Akt, phosphorylated protein kinase B (p-Akt), phosphorylated mammalian rapamycin target protein (p-mTOR), mTOR, microtubule associated protein 1 light chain 3B (LC3-Ⅱ) and mammalian atg6 homologous protein (Beclin-1) in the synovial membrane tissue. Compared with the normal control group, the joint swel-ling degree and AI, contents of serum TNF-α, IL-6 and IL-17, and the expression levels of PI3K, Akt, p-Akt, mTOR and p-mTOR in the synovium were increased in the model group (P<0.05), while the expression levels of LC3-Ⅱ and Beclin-1 proteins in the synovium were significantly decreased (P<0.05). Compared with the model group, the joint swelling degree and AI, contents of serum TNF-α, IL-6 and IL-17, and the expression levels of PI3K, Akt, p-Akt, mTOR and p-mTOR were significantly decreased in the acupuncture and medication groups (P<0.05), while the expresion levels of LC3-Ⅱ and Beclin-1 proteins were significantly increased （P<0.05）. Comparison between the two treatment groups showed that the therapeutic effects of acupuncture were obviously weaker than those of medication in down-regulating TNF-α and IL-6, Akt, p-Akt and mTOR levels (P<0.05) and in up-regulating Beclin-1 expression (P<0.05). Outcomes of electron microscope displayed widened nuclear membrane space, some fractured mitochondrial cristae with vacuoles, expanded rough endoplasmic reticulum, reduction of autophagosomes in the cytoplasm and ruptured synovial cell membrane in the model group, and increase of autophagosomes, deformed organelles in the acupuncture and medication groups. Acupuncture can relieve the inflammatory reactions and joint synovial injury of the affected joint in AA rats which may be associated with its effects in inhibiting PI3K/Akt/mTOR signaling and increasing the auto-phagy level of synovial cells.