The Autophagy Level Is Increased in the Synovial Tissues of Patients with Active Rheumatoid Arthritis and Is Correlated with Disease Severity

Li Zhu, Huaizhou Wang, Yu Wu, Zhengwen He, Yanghua Qin, Qian Shen, Li Zhu, Huaizhou Wang, Yu Wu, Zhengwen He, Yanghua Qin, Qian Shen

Abstract

Rheumatoid arthritis (RA) is a complex and not fully understood autoimmune disease associated with multijoint damage. The main effector cells, the synovial fibroblasts, are apoptosis resistant and hyperplastic which indicate that autophagy level is high in synovial tissue. Real-time PCR, immunocytochemistry, and western blotting were used in this paper to study the autophagy status of the synovial tissues obtained from RA and OA patients at the time of joint replacement surgery. We further evaluated the correlation between autophagy levels with RA activity-associated serum markers with SPSS. The results showed that the expression levels (both in mRNA and in protein level) of autophagy-related proteins (belcin1, Atg5, and LC3) in the synovial tissue of patients with active rheumatoid arthritis (n = 20) were significantly higher than those in OA patients (n = 16). We further showed that the LC3-II/β-actin relative gray value was strongly correlated with the serum levels of several RA activity-related markers: CRP, ESR, CCP, and RF. Our results indicate that evaluating the autophagy level of synovial biopsies might be a useful way to diagnose RA and to estimate the disease activity. Reducing the expression level of autophagy-related genes might become a new therapeutic target for active rheumatoid arthritis.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
The relative expression levels of beclin1, Atg5, and LC3 mRNA in synovial tissue. The levels of beclin1, Atg5, and LC3 mRNA expression in synovial tissue from RA (n = 20) and OA (n = 16) patients. ∗∗p < 0.01; the error bars indicate standard deviation.
Figure 2
Figure 2
Localization and expression level of beclin1, Atg5, and LC3 in RA synovial tissues. Immunohistochemical analyses of beclin1, Atg5, and LC3 localization in RA synovium. Synovial tissues from RA and OA patients were stained with anti-beclin1 antibodies (a and b), anti-Atg5 antibodies (c and d), anti-LC3 antibodies (e and f), H&E staining (g and h), or anti-rabbit IgG antibodies as a nonimmune control (i and j). Magnification 200x.
Figure 3
Figure 3
The autophagy-related proteins beclin1 and LC3-II show enhanced expression in RA and OA synovial tissues. Western blotting was used to determine the expression level of autophagy-related proteins beclin1 and LC3-II in RA and OA synovium. The expression of beclin1 and LC3-II was quantified, compared with the expression of actin.
Figure 4
Figure 4
Correlation between the LC3-II/β-actin relative gray value and disease activity parameters in RA patients. The correlation between the LC3-II/β-actin relative gray value and the serum CRP level (a), ESR level (b), serum CCP level (c), or serum RF level (d). n = 20; p < 0.05 is considered statistically significant.

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