Overexpression of the growth arrest and DNA damage-induced 45alpha gene contributes to autoimmunity by promoting DNA demethylation in lupus T cells.
OBJECTIVE
Demethylation of CD11a and CD70 regulatory regions in CD4+ T cells contributes to the development of autoreactivity and overstimulation of autoantibodies. Because growth arrest and DNA damage-induced 45alpha (GADD45alpha) reduces epigenetic silencing of genes by removing methylation marks, this study examined whether the gadd45A gene could contribute to autoimmunity by promoting DNA demethylation in T cells from patients with systemic lupus erythematosus (SLE).


METHODS
Levels of GADD45alpha, CD11a, and CD70 messenger RNA (mRNA) and protein were detected by real-time reverse transcription-polymerase chain reaction and Western blotting or flow cytometry. Global DNA methylation was evaluated using Methylamp global DNA methylation quantification kits. Detection of CD4+ T cell proliferation and autologous B cell IgG antibodies was performed using commercially available kits. CD11a and CD70 promoter methylation was determined with bisulfite sequencing.


RESULTS
Elevated gadd45A mRNA expression and global DNA hypomethylation were observed in CD4+ T cells from SLE patients. The levels of gadd45A mRNA were inversely proportional to the levels of DNA methylation. Positive correlations were found between gadd45A and CD11a/CD70 mRNA levels. Expression of gadd45A mRNA was increased in CD4+ T cells following ultraviolet B irradiation, and this was accompanied by increased levels of CD11a and CD70 mRNA. Moreover, increased expression of gadd45A, CD11a, and CD70 mRNA was accompanied by increased autoreactivity and excessive B cell stimulation in gadd45A-transfected CD4+ T cells. CD11a promoter methylation was also significantly reduced in transfected cells. Transfection of gadd45A small interfering RNA inhibited the autoreactivity of SLE CD4+ T cells and led to significant increases in the methylation levels of the CD11a and CD70 promoter regions.


CONCLUSIONS
These findings indicate that gadd45A may contribute to lupus-like autoimmunity by promoting DNA demethylation in SLE CD4+ T cells.
Li
Yaping
Y
Second Xiangya Hospital and Central South University, Changsha, China.
Zhao
Ming
M
Yin
Heng
H
Gao
Fei
F
Wu
Xiaoyan
X
Luo
Yongqi
Y
Zhao
Sha
S
Zhang
Xiujuan
X
Su
Yuwen
Y
Hu
Nan
N
Long
Hai
H
Richardson
Bruce
B
Lu
Qianjin
Q
D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000276:immunology; D015551:Autoimmunity / Q000235:genetics* / Q000276:immunology; D040881:CD11a Antigen / Q000235:genetics; D053282:CD27 Ligand / Q000235:genetics; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology* / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000235:genetics*; D004249:DNA Damage / Q000276:immunology; D019175:DNA Methylation / Q000276:immunology* / Q000528:radiation effects; D005260:Female; D005786:Gene Expression Regulation / Q000276:immunology / Q000528:radiation effects; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000235:genetics* / Q000276:immunology*; D008297:Male; D009687:Nuclear Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D014466:Ultraviolet Rays / Q000009:adverse effects; D055815:Young Adult; D000097642:GADD45 Proteins
D001323:Autoantibodies; D040881:CD11a Antigen; D053282:CD27 Ligand; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C505771:CD70 protein, human; C439070:GADD45A protein, human; D000097642:GADD45 Proteins