Abstract:

Objective To discuss the regulatory effect of lutein on the phosphatidylinositol-3-kinase （PI3K）/protein kinase B （AKT） signaling pathway and chondrocyte autophagy in mandibular joint cartilage tissue of rabbits with traumatic temporomandibular joint ankylosis （TMJA）， and to clarify its mechanism. Methods Thirty-two male New Zealand white rabbits were divided into sham operation group， model group， lutein group， and 3-MA （PI3K/AKT signaling pathway inhibitor） + lutein group， and there were 8 rabbits in each group. The rabbit model of TMJA was established in model group， lutein group， and 3-MA+lutein group， while the rabbits in sham operation group only underwent tissue exposure without surgery. The rabbits in lutein group were administered 10 mg·kg^-1 lutein， and those in 3-MA+lutein group were administered 15 mg·kg^-1 3-MA and 10 mg·kg?1 lutein. All the drugs were injected via the marginal ear vein starting 24 h after surgery， once a week for 3 consecutive months. After completion， the cartilage tissue on the surgical side was collected. HE staining was used to evaluate the patho morphology of the mandibular joint cartilage tissue of the rabbits in various groups； Western blotting method was used to detect the expression levels of PI3K， AKT， phosphorylated AKT （p-AKT）， Beclin-1， autophagy-related protein 5 （ATG5）， microtubule-associated protein 1 light chain 3-Ⅰ （LC3-Ⅰ）， microtubule-associated protein 1 light chain 3-Ⅱ（LC3-Ⅱ）， autophagy receptor protein （P62）， matrix metalloproteinase 13 （MMP-13）， a disintegrin and metalloproteinase with thrombospondin motifs-5 （ADAMTS-5）， aggrecan， and type Ⅱ collagen （Col Ⅱ） proteins in temporomandibular joint cartilage tissue of the rabbits in various groups； transmission electron microscopy was used to detect the numbers of autophagosomes in temporomandibular joint cartilage tissue of the rabbits in various groups. Results Compared with sham operation group， the pathological score of mandibular joint cartilage tissue of the rabbits in model group was increased （P<0.05）. The Western blotting results showed that compared with sham operation group， the expression levels of PI3K， p-AKT， aggrecan， and Col Ⅱ proteins in mandibular joint cartilage tissue of the rabbits in model group were decreased （P<0.05）， while the expression levels of Beclin-1， ATG5， P62， MMP-13， ADAMTS-5 proteins and ratio of LC3-Ⅱ/LC3-Ⅰ were increased （P<0.05）. Compared with model group， the expression levels of PI3K， p-AKT， aggrecan， and Col Ⅱ proteins in mandibular joint cartilage tissue of the rabbits in lutein group were increased （P<0.05）， while the expression levels of Beclin-1， ATG5， P62 protein and ratio of LC3-Ⅱ/LC3-Ⅰ were decreased （P<0.05）. Compared with lutein group， the expression levels of PI3K， p-AKT， Beclin-1， ATG5， and ratio of LC3-Ⅱ/LC3-Ⅰ， and P62 proteins in mandibular joint cartilage tissue of the rabbits in 3-MA+ lutein group were decreased （P<0.05）， while the expression levels of MMP-13 and ADAMTS-5 proteins were increased （P<0.05）， and the expression levels of aggrecan and Col Ⅱ proteins were decreased （P<0.05）. The transmission electron microscope observation results showed that compared with sham operation group， the number of autophagosomes in temporomandibular joint cartilage tissue of the rabbits in model group was increased （P<0.05）； compared with model group， the number of autophagosomes in temporomandibular joint cartilage tissue of the rabbits in lutein group was decreased （P<0.05）； compared with lutein group， the number of autophagosomes in temporomandibular joint cartilage tissue of the rabbits in 3-MA+lutein group was decreased （P<0.05）. Conclusion Lutein improves the mandibular joint cartilage tissue damage in the TMJA rabbits by regulating the PI3K/AKT signaling pathway and chondrocyte autophagy.

Key words: Lutein, Phosphatidylinositol 3-kinase, Protein kinase B, Temporomandibular joint ankylosis, Chondrocyte autophagy